Cron wont save python script to txt file

Question: I've got a problem with my python script. I'd like to save data from serial, with python script to txt file every 5 minutes.
My Cron script:
*/5 * * * * root /home/user/temperature.py >> /home/user/temperature.txt

My python script:
#!/usr/bin/env python
# -*- coding: utf-8 -*-
# pytemp.py

import serial
import time

ser = serial.Serial('/dev/ttyACM0',9600, timeout=10)
read = ser.read(5)
comp = read.split()
ser.close();
print time.strftime("%Y-%m-%d %H:%M:%S"), comp[0]

Cron creates file temperature.txt but it's empty.
If I'm runing script with command python temperature.py it works fine showing me date and temperature.
Can anyone help me with it?
//EDIT:
Hey,
I found error - my folder with python's script wasn't chmoded correctly. I changed destination of script and now it's ok, but I see something wrong in my script. Temperature is shown as:
2013-03-16 13:40:01 166.8
2013-03-16 13:41:02 1617.

and it should look like:
20013-03-16 13:40:01 16.68

for example.
How can I edit my python script?
Answer: Have you tried
*/5 * * * * root python /home/user/temperature.py >> /home/user/temperature.txt

?


What US customs procedures must the pilot of a private aircraft follow when traveling in and out of the country?

Question: As the Pilot In Command of a private aircraft, what are the customs procedures that must be complied with before leaving, before returning, and upon arrival to the USA?
Answer: General

Each person leaving the country must be authorized to return to the US.  (ie. they are a US citizen or their visa allows them to leave and return to the US.)
Ensure that you have all required paperwork

Pilot license
Medical
Aircraft Registration
The aircraft must have a current customs decal.

Ensure that the aircraft is properly equipped

12" Registration Numbers
Transponder

Before Leaving the US

File eAPIS

eAPIS is required to be filed at least 60 minutes prior to your departure.
Other third party services (ie. FlightPlan.com, etc.) may make this easier if you do it a lot.

File an international flight plan

May be an instrument or a defence VFR flight plan

Before Returning to the US

File eAPIS (see above)
File a flight plan (see above)
Notify customs and obtain permission at least one hour prior to landing in the US.  Record the initials of the customs officer that you spoke to just in case they misplace your notification.

Note that if you are coming from locations "south of the US" (for the specific definition, see here), you must stop at the designated airport closest to your point of border crossing to clear customs (unless you have an overflight permit).

Upon Arrival in the US

You must land at an airport of entry.
Report immediately to the designated customs location
Do not allow anybody or anything to leave/enter the aircraft until the customs official gives your permission

The only exception that I know of to this are the South Florida airports where you are expected to take all people and belongings into the customs facility for inspection.

Discard any international garbage in the approved manner.
Provide required paperwork

A Customs Declaration for each arriving family

Wait for customs to specifically tell you that you are cleared before you attempt to leave.

Notes
This is not all-encompassing, please help add to and expand this list so that others may learn from our experience!
A TON of useful information is made available by the FAA in the Guide for Private Flyers.
Answer: The FAA outlines the procedures on their website.
In short, you'll need proper documentation for the airplane, flight plans, passports for everyone on board, and more.
Comment: I am looking for specific procedures to follow, such as notification requirements, etc.  The site that you link to is a good start, but does not include everything.


How to get user's permission sets in Data Repeaters filters

Question: I have custom field (multiselect picklist) on Question object, which we use to filter the displayed records in accordance with his permissoin sets. On visualforce pages it's implemented using SOQL filtering.
But also we use salesforce community and site.com pages in our project, where Question records are displayed with Data Repeaters. And I want to implement similar filtering functionality here. Maybe someone know how can I get access to current user's permission sets in Data Repeaters filters or how can I implement this in other ways?
Answer: Unfortunately, there seems to be no way of referencing a User's permission set in filters (and thus Data Repeaters).
What I'd do in this situation is leverage a hierarchy-custom setting. This would allow you to specify a certain value, based on the user's profile, while you can add exceptions pretty easily for certain users.
In the filter (formula only) you can then simply evaluate the custom setting value as <code>{!$Setup.CustomSettingName__c.CustomFieldName__c}</code> and it'll return the current user's specific value.
Would that be a viable option for you?


Facebook wall Image blur Issue

Question: I am trying to copy and paste my website's link on Facebook's wall. But with website's Image it also fetch some Javascript code and show it on Facebook page. This is not happen's when I type that url manually.
Here is that code,
<code>$("#target").append(''); // iterate through all the elements and create UL
options.each(function(){
    $("#target dd ul").append('' + $(this).text() + '' + $(this).val() + '');
}); // remove the select
$('#quicklink_form').hide(); // backup
</code>
I tried but not able to find the solution. Could anyone help me to get through this.
Answer: Run your URL through Facebook's Debug Tool and see if you've got the correct Meta Tags present on your page for Facebook's crawler - if not, fix them

Facebook wall Image blur Issue


Rotating multiple objects in animation

Question: I am trying to animate a drone with 6 spinning propellers in version 2.79b. I can make the props spin in object mode by selecting them and choosing individual origins for pivot center, however when I try to animate the spinning props only 1 prop spins. How do I animate all 6 props spinning at the same time? I have tried grouping, parenting and joining and still only 1 prop spins.
Comment: I managed to get all 6 props to spin, but I had to animate each prop individually. Is this normal behavior for animation? Is there any way to duplicate the parent child relationship for animation?
Comment: Can you submit a screenshot of your Blender workspace to start?
Answer: See that pretty record button by the keys at the bottom of the screen? Click that button. That's the Automatic Keyframe Button.
You also want to open up the action editor to actually see the keyframes.
So open up that editor, select all of the blades. Press, I, which iirc is insert keyframe. It should insert a keyframe for all of the blades, if not, you will just need to do it individually. This will make blender store the pose for those different blades at that frame in time. Now all you need to do to animate is go to a different point in time, and just rotate all of the blades. You can do them all at the same time if you've shift selected them before rotating, and you have 'individual center' selected for the transform origin, which is what you seem to have set, judging by the two circles between your shading and widget option.
You can extrapolate on the animation, which will make Blender continue the animation that you already started, further down the timeline. You can also just duplicate the keyframes of the final position of the blade, drag it to say, +60 frames, then at +30 frames, insert another keyframe where it's 50% of the animation to cause it to loop. You can also edit the curve of the animation in the IPO editor.
If you have any more questions, feel free to comment on this answer.
Comment: This looks like what I was looking for. Haven't had a chance to play with it today, things blew up at work. I will piddle with it as soon as I can. Thanks!
Comment: Cool. You might get a weird rotational error where at some point the animation might rotate the wrong way. You might be able to solve this by inserting a keyframe on the very last frame of the animation before it restarts, or using Quaternions. If you run into this issue LMK, so that I can look into it.
Answer: You may want to add a custom property to the drone object, and then keyframe the number value of the custom property.
For each prop, you could add a driver to its Z-axis rotation. In the driver settings, you'd add the custom property number to the current Z-axis value.
I found a video that explains the process a bit better than I can at the moment:
https://youtu.be/Ht4m5txvWos
Thus by animating the custom property value, you animate all six props at once. Why go through all the trouble of repeating steps?
You may also want to look into animation F-curve modifiers, function or cyclic in particular. Thus with one of those applied to the custom property, you'd be able to keep the props spinning at a constant rate with only a single animation keyframe. The slope on the animation F-curve then correlates to the speed and direction of movement.
This could be more in-depth and complicated, but that gets more into rigging and scripting. Yes, that is more complicated. But if you use the same model more than once, it saves a lot of extra work in animating later on. (This is why rigging is an art/science in itself.)
Comment: Thanks for the pointers. I was adjusting the rotation and F-curves for each individual prop. 3 spin cw and 3 spin ccw. It was a lot of work and I was looking for a way of simplifying the process. This looks like a better way, I just have to wrap my head around the process. Thanks for the help.

Rotating multiple objects in animation


What kind news or information would make the price of a stock go up?

Question: So I'm just trying to get as much information as I can before I start trading but what kind news is guaranteed or at least has a great chance to push the price upward? the reason is because I've seen moments when news that you would think would push the stock up but instead it either plummeted downward or just stayed the same any advice would be most appreciated. :)
Comment: If we had an answer, do you think we'd give it away for free? Think about that for a moment as more than a few market timing newsletters exist that claim to know what will go up.
Comment: "Penny stocks" is *often* taken to imply more of speculation (for example, swing trading) than longer-term investing (whether you are a "value investor", "dividend investor", or some other variant). If you need to ask this type of question, you should ask yourself if you have the knowledge to outsmart people who do this for a living.
Answer: There is a highly related question which is much easier to answer: what normally value-increasing news about a company would cause that company to fall in value in the public stock market? By answering that, we can answer your question by proxy.
The answer to that question being: anything that makes investors believe that the company won't be able to maintain the level of profit.
For example, let's say a company announces a 300% profit growth compared to the previous year. This should push the stock upwards; maybe not by 300%, but certainly by quite a bit. Let's also say that this company is in the business of designing, manufacturing and selling some highly useful gadget that lots of people want to buy.
Now suppose that the company managed such an profit increase by one of:

firing its engineering department,
selling off its manufacturing machinery,
or by their product being named Product Of The Year in an applicable category

In scenario 1 (firing the engineering department), it is highly unlikely that the company will be able to come up with, manufacture and sell a Next Generation Gadget. Hence, while profit is up now, it is highly likely to go down in the months and years coming up. Because stock market investors are more interested in future profits than in past profits, this should push the value of the company down.
In scenario 2 (selling off the machinery), the company may very well be able to come up with a Next Generation Gadget, and if they can manufacture it, they might very well be able to sell it. However, no matter how you slice it, the short-term costs for manufacturing either their current generation Gadget, or the Next Generation Gadget, are bound to go up because the company will either need to rent machinery, or buy new machinery. Neither is good for future profits, so the value of the company again should go down in response.
In scenario 3 (their product getting a large boost), the company still has all the things that allowed them to come up with, produce and sell Gadgets. They also have every opportunity to come up with, manufacture and sell Next Generation Gadgets, which implies that future profits, while far from guaranteed, are likely. In this case, the probability remains high that the company can actually maintain a higher level of profit. Hence, the value of the company should rise.
Now apply this to a slightly more realistic scenario, and you can see why the value of a company can fall even if the company announces, for example, record profits.
Hence, you are looking for news which indicate a present and sustained raised ability to turn a profit. This is the type of news that should drive any stock up in price, all else being equal.
Obviously, buyer beware, your mileage may vary, all else is never equal, nothing ever hits the average, you are fighting people who do this type of analysis for a living and have every tool known available to them, etc etc. But that's the general idea.
Comment: I wish those people downvoting this answer would leave a comment explaining what they think is wrong with the answer. It's hard to fix it when there's no indication of what to fix.
Answer: You should not trade based on what news is just released, if you try you will be too slow to react most of the time. In many cases the news is already priced into the stock during the anticipation of the news being released. Other times as soon as the news is released the price will gap up or down in response to the news.
Some times when you think that the news is good, like new record profits have been achieved, but the share price goes down instead of up. This may be due to the expectation of the record profits by analysts to be 20% more than last year, but the company only achieves 10% more than last year. So the news is actually seen as bad because, even though record profits, it hasn't met expectations. The same can happen in the other direction, a company may make a loss and the share price goes up. This may be because it was expected to make a 50% loss but only made a 20% loss due to cost cutting, so this is seen as a good thing and the price can shoot up, especially if it had been beaten down for months.
An other example is when the Federal Reserve in the USA put up interest rates earlier this month. Some may have seen this as bad news and expected share prices to fall, but instead prices rallied. This was actually seen as good news, firstly because it had been expected for a long time, and secondly and more importantly because a small rise in interest rates after many years of near zero rates is a sign of the economy finally starting to improve. If the economy is improving, that means more people will have jobs, more people will be spending more money, companies will start to make higher revenues and start to expand, which means higher profits and higher share prices.
A better way to trade is to have a written trading plan and use technical analysis to develop a set of buy and sell criteria that you follow to the tea. Then back test your trading plan through various market conditions to make sure you get a positive expectancy.


Chrome extension to make page is reloading more visible

Question: If you have a good number of tabs they will be narrow enough you can't see the page loading indicator in the tab and there's absolutely nothing in a browser page to indicate it is currently reloading. Is there something to make it better visible?
Answer:
there's absolutely nothing in a browser page to indicate it is currently reloading

I usually have very narrow tabs.
The top left corner of my Chrome browser screen looks like this:

When I reload a page, the circular arrow symbol changes to an "X" until the reload has finished.
(If it is taking too long, clicking the "X" cancels the reload request.)
Comment: Ray means the circular arrow symbol next to the address bar. This might be self evident to those who reload the page by pressing that button but I always use the keyboard so I didn't even realize that button survived (most buttons from early browsers didn't).


Disabling all older versions of ssl in Apache 2 to force authentication over TLS 1.2?

Question: I read here that all (older?) versions of SSL need to be disabled in order to force TLS 1.2 authentication.  How does one do this on Apache 2?
Comment: http://httpd.apache.org/docs/current/mod/mod_ssl.html#sslprotocol
Answer:
I read here that all (older?) versions of SSL need to be disabled in order to force TLS 1.2 authentication.

That's not what it says! It says all versions of SSL need to be disabled to force use of TLS - not to force use of TLSv1.2.
SSL/TLS comes in a number of versions, in increasing order of age and security:

SSLv2
SSLv3
TLSv1
TLSv1.1
TLSv1.2

SSLv1 was never made available to the public and TLSv1.3 is currently being worked on.
In theory the browser should use the strongest available which both it and the server support, but there are downgrade attacks which cause lower versions to be used which can then be broken so best to turn off ones you don't want used so they simply cannot be used.
It's generally accepted that SSLv2 and SSLv3 are now insecure due to a combination of flaws found in them and increases in compute power meaning they can be broken. So you should definitely disable them using the following:
SSLProtocol all -SSLv2 -SSLv3

Note SSLv2 is usually off by default now but no harm being explicit.
TLSv1 is interesting. PCI Compliance standard (used when you accept payments by cards on your website) has recently mandated turning off TLSv1 too but it's still needed for some browsers still in use so that may well hurt some of your users (e.g. IE8 users on XP - yes even though XP is officially retired and unsupported it's still in use). Personally I think we're almost ready to turn that off but not quite yet.
TLSv1.1 is another interesting one. TLSv1.2 came out shortly after and nearly every browser that supports 1.1 also supports 1.2 so usage of 1.1 is tiny. So if you're looking to firm up your SSL/TLS config then might be just as well to skip that one and go straight to TLSv1.2 only rather than both which will save you turning it off later when some vulnerability is found later. On the flip side it is still secure and maybe that tiny subset of browsers are some of your visitors.
So if you want just TLSv1.2 (with option of TLSv1.3 in future) then you can use this config:
SSLProtocol all -SSLv2 -SSLv3 -TLSv1 -TLSv1.1

Or alternatively just this (though limiting you to just TLSv1.2 no matter what come along later):
SSLProtocol TLSv1.2

You can also measure your current usage using a custom log format, so you can see how many of your visitors still use TLSv1 for example: http://httpd.apache.org/docs/current/mod/mod_ssl.html#logformats
However that's not the whole story for having a strong https setup.
For a start it depends heavily on the version of OpenSSL you have installed and/or the version it was compiled with. That might mean TLSv1.2 is not even available to you - there are many OpenSSL 0.9.8 installs still out there!
Next up is the CipherSuite you use within that version of SSL/TLS. Some are more secure than others and some have more performance hit than others. You also should specify that the server should specify the order so your strongest suite is used. This is (at the time of writing) a strong suggestion with still good legacy support:
SSLHonorCipherOrder on
SSLCipherSuite "EECDH+AES128:EECDH+AES256:+SHA:DHE-RSA-AES256-SHA:DHE-RSA-AES128-SHA:RSA+3DES:!DSS"

Then there's other options like compression, HSTS, CT, HPKP and OCSP Stapling but they really are specialist subjects and beyond the scope of this question (blogged about them here if interested in further reading: https://www.tunetheweb.com/security/https/ )
The best option for testing your https set up is the online https://www.ssllabs.com/ssltest tool. Just plug your website address in and a couple of minutes later you're have a report on how good your setup is. IMHO there is no good reason not to get an A grade here unless you are on old hardware/software (in which case why are you not upgrading?). If looking after a website I'd strongly suggest re-running that test once a quarter to check on any new developments and config changes that you might need to do to stay on top of your config.
Comment: Oh so it is all!  I thought maybe it was a typo...glad I asked, and thanks for letting me know.
Answer: It is not correct, using only TLSv1.2 will remove some browser compatibilities, and will not fix all SSL breach.
If SSL is not more used, it is because some breach of securities has been found.
But that's not solve all trouble.
To be effective, you need to update your OpenSSL version, and use an Apache configuration to remove other vulnerabilities
Here the configuration to secure your SSL, incrase the browser compatibilities  without being vulnerable to attack :
SSLEngine on
SSLOptions +StrictRequire
SSLProxyEngine on

# Prevent Beast attack
SSLHonorCipherOrder on

# SSL Compression (CRIME attack)
SSLCompression off

# HSTS
Header always set Strict-Transport-Security "max-age=63072000; includeSubdomains; pr$

# PROTOCOL
SSLProtocol -all +TLSv1 +TLSv1.1 +TLSv1.2
SSLCipherSuite EECDH+AESGCM:EDH+AESGCM:AES256+EECDH:ECDHE-RSA-AES128-SHA:DHE-RSA-AES128-GCM-SHA256:AES256+EDH:ECDHE-RSA-AES256-GCM-SHA384:ECDHE-RSA-AES128-GCM-SHA256:DHE-RSA-AES256-GCM-SHA384:ECDHE-RSA-AES256-SHA384:ECDHE-RSA-AES128-SHA256:ECDHE-RSA-AES256-SHA:DHE-RSA-AES256-SHA256:DHE-RSA-AES128-SHA256:DHE-RSA-AES256-SHA:DHE-RSA-AES128-SHA:ECDHE-RSA-DES-CBC3-SHA:EDH-RSA-DES-CBC3-SHA:AES256-GCM-SHA384:AES128-GCM-SHA256:AES256-SHA256:AES128-SHA256:AES256-SHA:AES128-SHA:DES-CBC3-SHA:HIGH:!aNULL:!eNULL:!EXPORT:!DES:!MD5:!PSK:!RC4

After that you can test your SSL security level on this site https://www.ssllabs.com/ssltest
Comment: It is not my fault if they have noobies administrators, i tested some banks SSL, and they show vulnerabilities. Removing all up to TLS 1.1 will not make it more secure if their server are bad configured. Not all browsers are TLS1.2 compatible
Comment: Separately from cipher suite vulnerabilities, there is now a drive in financial sector to completely eliminate TLS1.1 and all below by half-2016.
Answer:
Update to the most recent version of Apache 2.
Update to the most recent version of OpenSSL 1.0.1+.
Edit Apache ssl.conf or httpd.conf

Add
# only use TLSv1.2 and above, to have SHA-256 and GCM
SSLProtocol all -SSLv2 -SSLv3 -TLSv1 -TLSv1.1

Restart Apache.


Will neurons live after the death of a human? If so, how long?

Question: I don't know if this is correct or not, but I have heard this from a friend and I want to get a clear explanation about this.I hope there is some one who can help me.
Comment: This is called "necrobiosis".
Comment: isn't brain death the definition of death in many medical cases?
Comment: Yes, brain death is what medical professionals [generally] use to define death, as modern medicine is often able to keep a human body physiologically functioning for an extended period of time through technology and medication - and it is often possible to do this well past where the body would have originally died on its alone.  This is done when there remains hope that the body will recover and consciousness will return.  However, if additionally cerebral function is also convincingly lost (discussion of how we test for that is another topic), the concept of medical futility comes into play.
Answer: I think that depends somewhat on how the human dies - in particular on the conditions. If they die in a very cold environment (say at the top of some icy mountain range), they'll freeze and metabolic processes will slow down considerably, and so will cell death. But such hypothermia-based slowing down is a special case. Normally, if your heart stops or you are not getting oxygen to your brain (perhaps due to a stroke), your neurons will start dying pretty quickly. Within many minutes there will certainly be considerable permanent cell loss - certainly within hours. If oxygen is significantly depleted, ATP production will also significantly drop. If this happens, the various ATP-dependent processes will slow to a crawl (including the Na/K ATPase and other ion pumps and channels that are needed for maintaining and changing the voltage difference between the inside and outside of the cell). This in itself is bad enough as a lot of the enzymes and mechanisms that are dependent on the voltage difference will fail (and probably enough of a reason for many cells to start dying), but one of the effects of this is apparently an increase in the extracellular glutamate, which ultimately leads to (via NMDA receptors for example) an influx of calcium ions into the neurons. Too much of the calcium ions is once again toxic for a variety of the processes inside the cell and is an additional and big reason for neuronal cell death.
In short, as far as I know, neurons don't have a good time living without sufficient oxygen and therefore after a typical human death.


asp.net mvc C# file upload value persistance

Question: i am using file upload on the user front. is there any way if some exception occurs the html file control is able to persist its value on post back(i know it can't) but any work around?.  i am using server side validations.
Comment: What kind of exception are you talking about? The file upload is handled in the web server I believe and then handed to the MVC stack, not sure what exception you might imagine occurring and what you'd have to persist.
Comment: i am talking about if textbox value is empty or not
Comment: i want to persist the file selected by the user if some exception occurs and he had selected the file as well
Answer: This could get messy.
Just a couple of points,
If an exception occurs do you really think it is wise to save the file?
By its nature an exception is telling you an error has occurred and processing should not continue. I would think the only time you should save the file is when you can recover or handle the exception without any side affects.
In which case you have to ask yourself, can you not just prevent the exception in the first place?
Always, always do validation on BOTH client and server side.
Why? Well to prevent this sort of thing, at least as much as possible. Let the user know there is a problem before posting, much better experience for them.
It terms of the problem, the best thing you could do is potentially keep the file path, and if an error occurs put that value back into the input box.
This wont be pretty, the input type for files is one of those special cases where the browser is responsible for a lot of the user interaction.
Remember in most cases what is happening is the browser is collection the byte information from the file and passing that around as part of the request, this is not something you are going to be able to manipulate easily.


What is the nature of the Key, Value, and InputFormat types passed to Spark's StreamingContext.fileStream[K, V, F]("directory")

Question: From what I understand, streaming text files from a directory requires a key of type LongWritable, a value of Text, and a format of TextInputFormat. These are passed automatically in the textFileStream() method.
Is the key in that case the line number, with the value being the text on that line?
What should the key and value types be for ParquetInputFormat - and more generally, how can I figure this out for myself regarding other file types?
Also, how do these types relate to the DStream that is returned by the method? If I pass a parquet file which has rows of, say, 100 columns, how will this be parsed into RDDs and DStreams by spark?
Answer: For ParquetInputFormat I think the key type must be Void, and the value type an object representing your data.
ssc.fileStream[Void, YourObject, ParquetInputFormat[YourObject]]("hdfs:...")


Learning C# in Mono

Question: How solid is Mono for C# development on Linux and OS X?  I've been thinking about learning C# on the side, and was wondering if learning using Mono would suffice.
Answer: I have been using mono for upwards of 2 years now.  Work is windows and .Net, home is mono on GNU/Linux.  I have been able to run both GUI and ASP.NET apps with no problems from the same SVN repository.  The only changes I had to make were in connection strings.  ASP.NET works well under mod_mono for apache and xsp2.  Some of the .NET 3.5 pieces are not there but definitely works for .NET 2.0 and earlier.
Monodevelop is coming along nicely and I believe the debugger is working well too.
Answer: It should be just fine. It supports C# 3.0 now. I usually try to stick with targeting 2.0 though and it is very stable.
Winforms and ASP.NET have both worked fine for me. The only thing to consider is there is currently no support for WPF.
Answer: .NET 2.0 is fully implemented and if you are planning to use only .NET 2.0 it's almost guaranteed that it will work properly (even WinForms) :) Other versions are still under heavy development so you have to check the Mono's website.
Answer: I can't speak to Mono's OSX support, but it is used for some pretty big projects in Linux, such as Banshee and F-Spot. Monodevelop is a pretty decent IDE available for it.
Comment: OSX support has advanced significantly since this post, Monodevelop is now officially released for the platform, and Banshee for OSX is in beta I believe.
Answer: Mono is very solid on OSX. The only part of the stack that's lacking is GUI, neither Gtk# or Winforms work as well as on linux.
Answer: I think it is very viable to learn C# using mono. I don't have hands-on experience with mono but the platform seems very stable and Mono is used in many commercial and open source applications.
Answer: Mono has just recently announced that it has full support for .NET 3.5 and overall Mono handles the majority of things well. A lot of the work is done by volunteers so you will still hit corner cases that will cause problems but they are very responsive on bugzilla and mailing lists.
Another great feature they've just added is the ability to attach to a process running on Linux/Mac from Visual Studio in Windows remotely. This gives you the ability to debug any system specific problems you could be having.
Answer: To learn the language, you will be just fine. There are some libraries missing in mono, but that would not prevent you from learning the language. You can find more information at the Mono Project Page: FAQ.
Answer: Mono is de facto .NET for Unix.
I don't suggest but I encourage you learn C# using Mono. In this way you'll put a feet in .NET cross-platform approach.
Now using Xamarin Mono Tools (http://xamarin.com/) you can also design cross-platform mobile apps sharing code between Android, iOS and WindowsPhone (and more).

Learning C# in Mono


Engineered hardwood install has gaps at and and sides where I can see underlayment and staples respectively & floor is very squeaky

Question: I have a high quality engineered hardwood floor with a 3-4 mm wear layer and at least 7 layers of good solid wood below. It's installed on a wooden subfloor over a basement or crawl space. My problem is, I think the contractor didn't set the boards closely enough to each other because they hurried. The gaps at the end of row or in between the sides of the boards is wide enough that I can see the underlayment at the ends and I can see the staples in the tongue and groove on the sides. It has been this way since they installed it.
The floor squeaks a lot. It flexes in some places. The gaps are in about 25% of the joints of the boards throughout the floor. The solution they are offering is to cut some of the boards up and then gluing down a new board cut a little longer and set more centered to try and split the gap between the two sides/ edges. They are also trying to putty some of the gaps with an acrylic (I think they said) putty that they try to match the color. They are then trying to make up for the flex (that was caused because they didn't properly screw down the subfloor to the joists where it squeaked before installation) by going into the basement and screwing up through the subfloor into the bottom of the flooring.
Any suggestions or reality checks can you provide to make sure I am being reasonable but also am getting a floor that is going to last and look good for years? Should I accept a putty solution or make them replace the board to tighten it up. Should I demand a new install done correctly?
Comment: Post a photo with a ruler showing.
Here we can only comment on the technical aspects, not your looming legal fight.
Comment: That all sounds terrible, both in workmanship and your experience, but it's not a question for us. It's a subjective and contractual (legal) one. We don't do either of those here. I suggest that you review your contract and consult an attorney, if necessary.
Comment: Sounds like the fix they're proposing is a hack.  I would not accept that.
Answer: I would want them to fix it right.If it meant pulling up the planks and installing them correctly, then so be it. You purchased a quality flooring with a good wear layer and good wood under that. None of that will matter with a putty fix. "Try to fix the gap .... try to match the color", those are scary phrases. Hopefully, you haven't paid them in full yet. you contracted for a professional installation, not a hack job.
Comment: I'm sure you'll get a bunch of votes for your likely popular opinion, but the question should be closed. It's clearly off topic.
Comment: Do you think it would be possible to pull up the flooring without damaging it?   Assuming they only used crown staples to install and didn't use tongue and groove glue.  Given the install would you even want them to try again?
Comment: @FreshCodemonger  If they didn't use glue, I imagine they have a tool for removing the staples.  and you're probably right, once a hacker, always a hacker.


Can I automatically change the desktop wallpaper everytime I log on

Question: I have learned how to change the background via the terminal but can I get the terminal to change to a different background every time I log on?
Comment: See these: http://askubuntu.com/questions/66914/how-to-change-desktop-background-from-command-line-in-unity, http://askubuntu.com/questions/270049/how-to-run-a-command-at-login
Comment: Thank you for your advice, I will read carefully and learn :D
Comment: possible duplicate of https://askubuntu.com/questions/134/how-do-i-create-a-desktop-wallpaper-slideshow
Answer: Introduction
The script below takes a directory as argument ( preferably only containing images ) , selects random item form its contents, and sets the item as wallpaper. It is intended to be started on user's login, although can be used by itself just as well.
Setting up and Usage
First of all, the script must be stored somewhere on the system. Preferably, it should be placed into your ~/bin directory. If you don't have bin directory in your home directory, then just create one.
Next,ensure the script has executable permissions. You can use either chmod +x ~/bin/set_random_wallpaper.py or do it the GUI way by right clicking on the file and checking Allow executing file as program in the Permissions tab of the Properties menu.
The script requires a directory as argument. Preferably, you should give it full path. For example:
set_random_wallpaper.py /home/JohnDoe/Pictures/wallpapers/

If you are doing it via command-line, then you can give relative path, Pictures/wallpapers/ , but for setting it up to run upon login automatically , use full path.
To make the file run upon every login, open Startup Applications program and click "Add" button. Use full path to command and to folder:
/home/JohnDoe/bin/set_random_wallpaper.py /home/JohnDoe/Pictures/wallpapers/

That's it !
Script Source
The script is also available on GitHub:
#!/usr/bin/env python3
"""
Author: Serg Kolo , <firstname.lastname@example.com>
Date: December, 21,2016
Purpose: Sets random wallpaper from a given directory
Written for: https://askubuntu.com/q/851705/295286
"""
from gi.repository import Gio
import os,sys,random

def gsettings_set(schema, path, key, value):
    """Set value of gsettings schema"""
    if path is None:
        gsettings = Gio.Settings.new(schema)
    else:
        gsettings = Gio.Settings.new_with_path(schema, path)
    if isinstance(value, list):
        return gsettings.set_strv(key, value)
    if isinstance(value, int):
        return gsettings.set_int(key, value)
    if isinstance(value,str):
        return gsettings.set_string(key,value)

def error_and_exit(message):
    sys.stderr.write(message + "\n")
    sys.exit(1)

def select_random_uri(dir_path):

    selection = random.choice(os.listdir(dir_path))
    selection_path = os.path.join(dir_path,selection)
    while not os.path.isfile(selection_path):
        selection = random.choice(os.listdir(dir_path))
        selection_path = os.path.join(dir_path,selection)

    selection_uri = Gio.File.new_for_path(selection_path).get_uri()
    return selection_uri

def main():
    """ Program entry point"""
    if len(sys.argv) != 2:
       error_and_exit('>>> Script requires path to a directory as single argument')
    if not os.path.isdir(sys.argv[1]):
       error_and_exit('>>> Argument is not a directory')
    img_dir = os.path.abspath(sys.argv[1])
    uri = select_random_uri(img_dir)
    try:
        gsettings_set('org.gnome.desktop.background',None,'picture-uri',uri)
    except Exception as ex:
       error_and_exit(ex.repr())

if __name__ == '__main__': main()

Technical details and theory of operation
The script itself works in pretty simple way, but I spiced it up with a few functions of my own. The main function checks if there is an argument and if that argument is a directory - otherwise it quits. If everything is OK, we proceed to get absolute path of the directory, and give it to set_random_uri() function.
As you may or may not know, the wallpaper is set in dconf database, which can be accessed and altered with gsettings command. The simple command line way is
gsettings set org.gnome.desktop.background picture-uri file:///home/JohnDoe/Pictures/cool_wallpaper.jpg

The file://... part is the file's URI (which is essentially a encoded path of the file, and is quite useful if your system uses different locale than English). First, we need to select random file and get its URI. That's simple - we use random.choice() to select from list and os.listdir() to get list of items in directory. What if our random selection happens to be a directory and not a file ? Well, that's what while loop is for in select_random_uri. Once we're happy with the selection, we get its
Well, from there that is pretty much the same thing that is happening in gsettings set command, but I'm using custom-written gsettings_set() function, avoiding the need to call an external command, and it has been useful for other projects, such as Launcher List Indicator.
That's it ! Have fun coding and enjoy Ubuntu responsibly !
Additional resource

Bash version of such script has been implemented before, see: https://askubuntu.com/a/744470/295286


What type of fork is Litecoin?

Question: Is Litecoin classified as either a hard fork or soft fork? If neither, what is considered as?
Comment: It's an altcoin. A fork implies that a _split_ occurs, they thus have a shared transaction _history_. Litecoin, afaik, started with a completely new genenesis block.
Answer: It's considered a source code fork, or an altcoin, neither a hard fork nor soft fork of bitcoin. To be classified as a soft/hard fork, it should share some of the same chain from the genesis block. LN has a completely different chain right from the start so it's not a fork of the bitcoin chain.
Note that even coins sharing the same chain as bitcoin from the genesis block, e.g. BCH, are not considered hard forks by most people because they are not "bitcoin". They are generally termed "forkcoins"
Comment: Appreciate the explanation--just to check on the last point--does that essentially mean 'forkcoin' potentially synonymous with something being a soft or hard fork depending on who you ask?
Comment: @jlw yes I'm sure some hardcore BCH supporters would call it a hardfork rather than an altcoin, but to most people it's clear it's an altcoin
Answer: Litecoin is neither a hard or a soft fork. The codebase is a fork from Bitcoin codebase but it by no means share any history with the Bitcoin blockchain and thus considered as a separate alternative cryptocurrency to Bitcoin.
It is now trading at $179 https://www.coingecko.com/en/price_charts/litecoin/usd

What type of fork is Litecoin?


Is $GCT$ necessarily a negative result program?

Question: $GCT$ is a candidate program to separate permanent and determinant through symmetries. If indeed permanent and determinant can be handled in similar complexity class would $GCT$ be a program which can provide the insight? Is so how would the hypothetical demonstration be?
Comment: There is an abusive moderator.
Comment: I don't really understand the downvotes. I'd encourage the people who did so to leave a constructive comment, but my guess is that they downvoted and then unfortunately won't ever visit the question again.
Comment: I agree with @JoshuaGrochow's comment and I'd also encourage more upvoting. That said, people are free to vote up and down content they like or do not like, I believe such are still the rules on this site. In any case, this is about users voting and not about moderators as far as I can see.
Answer: It depends a little what you mean exactly by "GCT". If you mean it more generally, the answer is certainly yes. If you mean it more specifically about multiplicity obstructions, this is a bit more of an open question.
If you mean GCT generally as applying algebraic geometry to complexity theory, or perhaps even slightly more specifically using geometry to cross the GCT chasm, as in this quote:

By geometric complexity theory, we mean henceforth any approach to cross the GCT chasm using asynthesis of geometry and complexity theory. -Mulmuley, GCT V arXiv

Then the answer is that algebraic geometry can certainly prove positive results in complexity theory. First in principle: $\mathsf{VNP} \nsubseteq \overline{\mathsf{VP}}$ if and only if there is a polynomial vanishing on the latter but not on the former - this is very basic algebraic geometry. Similar results hold whenever one considers the approximative/border/closure of a complexity class. Second, in history: border-rank methods are algebro-geometric, and have yielded new algorithms for matrix multiplication, as well as results relating the complexity of a polynomial to those of its factors Bürgisser (arXiv)
If, on the other hand, you mean more specifically separating complexity classes using multiplicity obstructions, then your question gets at the "converse" question in GCT: that is, it is a theorem that a multiplicity obstruction implies a separation of complexity classes, but is the converse true? In general for $G$-varieties this is almost certainly false (that is, given a reductive algebraic group $G$ like $GL_n$ acting algebraically on a vector space $V$, and two varieties $X,Y \subseteq V$ that are each unions of $G$-orbits, is it the case that $X \subseteq Y$ iff there are no multiplicity obstructions?). But for the particular varieties of interest in GCT, there is some chance that the converse might hold. A first indication of this is that the polynomials studied are characterized by their symmetries, which already tells you that the group action here is telling you more about these particular varieties than it would be for general $G$-varieties.
If the converse held, then one could in principle get a collapse of complexity classes by proving that there were no multiplicity obstructions. On the one hand, this seems quite hard. On the other hand, Bürgisser-Ikenmeyer-Panova (arXiv) proved that there were no occurrence obstructions (multiplicty zero in one class and nonzero in the other).
However, even if the converse didn't hold, knowing that there were no multiplicity obstructions would still, I think, yield significant insight into the relationship between these problems. Each representation of $GL_{n^2}$ appearing in the ring of (meta)polynomials (a polynomial ring in a number of variables that is equal to the number of monomials of degree $n$ in $n^2$ variables) corresponds to a $GL_{n^2}$-invariant property of (ordinary) polynomials. The isomorphism type of such a representation tells you how its defining equations transform under the action of $GL_{n^2}$. The multiplicity of a given isomorphism type (isotype) in the coordinate ring of one of these varieties $X$ thus tells you how many properties of that isotype the polynomials in $X$ have. Knowing that there were no multiplicity obstructions would still imply that these complexity classes share many more properties than one might initially think.


B2 visa valid for a year, but passport got WT/WB stamp at airport?

Question: In September I entered the US with a B2 Visa that is valid for one year. I was told when my visa was approved at my interview I am able to enter and renter the US as many times as I like for this year. However at immigration when I arrived here my passport got a stamp saying WT/WB so now I am worried I have to leave at the end of December?
Comment: Did you check your [I-94](https://i94.cbp.dhs.gov/) online?
Answer: You should do one of the following before the December date that I assume is stamped or written into your passport:

Get your entry record corrected.  You were admitted under the visa waiver program, but you should not have been because you have a B-2 visa.
leave and re-enter the US.

When you enter the US in the future with a visa, open your passport to the page bearing your visa before handing it to the immigration officer.  This will reduce the chance of an incorrect admission record.
To get your entry record corrected,  you can present yourself at a deferred inspection site.  These sites are for those who "believe that the documentation and corresponding endorsements issued at the port of entry require review and possible correction" (among others):

The Deferred Inspection Site staff is also available to review and issue the necessary documents to remedy errors recorded on arrival documents issued at the time of entry to the United States relating to improper non-immigrant classification, inaccurate biographical information or incorrect period of admission, if appropriate. Any designated deferred inspection location or CBP office located within an international airport should be able to assist you, regardless of where the actual document was issued.
Travelers are encouraged to contact sites not located within an international airport to establish an appointment, if necessary. In many instances, the location of your final destination where the discrepancy will be resolved may not be the port of your first arrival into the United States. Mail-in procedures are generally not available.
The Deferred Inspection Sites will only correct errors made at the time of entry. You must contact U.S. Citizenship and Immigration Services (USCIS) if you wish to: replace a lost, stolen, or mutilated Crewman's Landing Permit, CBP Form I-95; apply to extend your stay in the United States; or, change your immigration status. Specific information can be found on the USCIS website.

If instead you decide on a quick trip to Canada, Mexico, or the Caribbean, you should mention explicitly to the officer that you were admitted under the VWP even though you had a valid visa.  Otherwise, the officer might readmit you for the balance of your initial admission period, since that is the usual procedure for VWP travelers who make quick trips to Canada, Mexico, or the Caribbean.
You should also be aware that a 1-year visa does not entitle you to remain in the US for a year.  The duration of admission for B-2 visitors is normally six months.  If you are planning to spend more than six months in the US in total, you may well have some explaining to do.
Also note that your last visit to the US need not end before the expiration date of your visa: the period of admission is independent from that.  For example, if your visa were valid from 1 September 2019 until 31 August 2020, you could in theory begin a six-month stay on 31 August 2020.  The likelihood of this being permitted depends in part on how much time you've spent in the US in the recent past.
As an example of someone who did understand that the visa's period of validity doesn't dictate the duration of each stay, yet who nonetheless got into fairly serious trouble, you may be interested in the story of Baxter Reid.  Even the journalist reporting the linked story repeats his misunderstanding of the visa rules:

Sydney man Baxter Reid, 26, was in the US on a five-year visa and had travelled to Canada as part of a requirement for him to exit and re-enter America every six months to keep his visa valid.

A visitor visa does not authorize someone to stay in the US for the duration of the visa on the condition that they leave and return every six months; rather, it authorizes them to apply for entry during the duration of the visa.  At each application for entry, the immigration officer determines whether the applicant is in fact a temporary visitor.  Someone who is spending more time in the US than out of it is likely to be seen as not a temporary visitor.
If a visitor is admitted in B-1 or B-2 status, the immigration officer grants a period of admission of six months to one year (8 CFR 214.2(b)(1) and 8 CFR 214.2(b)(2)).  This can be extended without leaving the country by filing an application with USCIS, but that option is not available for VWP visitors.
Comment: Thank you thank you thank you!! You have cleared up every question I've had since arriving here! I was aware of the need to re enter every 6 months and the expiration date being separate from the entry date. Thank you!
Comment: @Harper you're welcome.  As suggested by Michael Hampton, you might also want to check your I-94 online just in case the record there reflects B-2 admission.  It's possible that you were admitted correctly but that the officer wrote the incorrect status and date in your passport.  I don't suppose it's likely, however.
Comment: Ok thank you to both of you. I think it has been stamped with the incorrect label. I just checked my I-94 (which I didn't even know existed so thank you!) and it says I was admitted under my B2 visa and have until March 2020 to stay here before I have to leave. And then I assume I can re enter sincerely my actually visa will still be valid and finish the program I am in here which ends in May.
Comment: @Harper in that case you might consider calling CBP just to get explicit confirmation from them that you can rely on the online I-94 over the annotation in your passport, or alternatively whether you need to get your passport updated to reflect the online record.  I suspect they'll tell you not to worry about it, or perhaps to print a copy of the I-94 and keep it with your passport.  If you call them, please post an answer to let us know what happened.
Comment: @Harper, phoog  wouldn't the immediate reentry in March to remain until May be problematic? Having some proof of leaving in May might be helpfull, otherwise they may suspect a form of border hopping.
Comment: @MarkJohnson it could be problematic, yes.  Perhaps more problematic is the existence of a "program," the significance of which didn't quite impress itself upon me before now, and suggests that there actually should be a student visa or exchange visitor visa.  On the other hand, B-2 visitors can be admitted for up to one year although that is rather unusual.  If the reason for staying would have justified an 8-month initial entry, the return shouldn't be a problem.
Comment: @Harper what program?  Did you tell the immigration officer about it when you entered?
Answer: UPDATE. I call the LAX cup office and a very helpful man helped me understand the situation.  It is basically what you guys said (thank you!!), that I can stay here for as long as my I94 allows and the stamp on my passport isn't as issue. I will bring a copy of the I94 when I leave just incase. Thank you to everyone to helped me understand this!
Comment: You may want to [merge](https://travel.stackexchange.com/help/merging-accounts) your accounts.  This will enable you to edit your question and to comment on it and its answers even if you have too little reputation to edit and comment elsewhere.  It might also be a good idea to merge your two answers into one.  The confirmation from CBP is valuable information.  Just to be clear: did they tell you that there was no need to go to a deferred inspection office?
Answer: Hi and sorry for my absence. I called and emailed the CBP but am waiting for a response. Tomorrow I will call again to see if anything has been done. I am here for a ballet program that runs until the end of May. It does not culminate in any degree or qualification, so I cannot get a student visa, and I am also not being paid to dance here and instead have to pay fees myself. All the international dancers here are on the same visa as me. Some have had issues re entering the US as you have seen yourself how the program can be misleading and cause authorities to second guess our intentions here. However I have a confirmed flight home and proof of ties to Australia to prove I do not plan to try and fool the system! My plan is to bring all these documents with me for when I re enter after a few days in Canada in March, as well as my 1-94 form saying I was in fact admitted under my B2 visa in September. I told the people at LAX that I was coming here to dance for 9 months, and they didn't ask any more questions.


Short story about an alien named Ushtu(?) coming from a future Earth, when ours was destroyed by a nuclear explosion

Question: I'm looking for a short story about an alien from a future Earth (from an age after a nuclear explosion destroys ours). IIR he was part of a group mind and was named (?) Ushtu
Comment: Hi there. That's some info already, but still, a bit terse - could you please take a look at [these guidelines](https://scifi.meta.stackexchange.com/a/9337/98028) on story-ID, see if they trigger any more memories you could [edit] in? For instance, when did you read that? Was it in a magazine, like say _Analog_ or F&SF?
Answer: I suspect this is "Courier of Chaos" by Poul Anderson.

The world of the far past was a terrible
  one to Ushtu — but no more terrifying
  than Ushtu himself was to Earthlings ...

Found with a search for "Ushtu" future Earth.
Comment: If this is correct, you can accept it by clicking on the checkmark by the voting buttons.
Answer: You are absolutely correct! It was indeed "Courier of Chaos" by Poul Anderson. It appears to have been one of his earlier pieces (I did not discover his work until much later on--it's odd that this one stayed with me for such a long time).
I found the book it was published in and read the piece. There's more to it than what I remembered--but I did get the jist of it--an investigation as to the cause of a worldwide extinction and change in the planet that ends up preventing this event (and obliterates source of the investigators).
That said I was rather taken by the (sketchy) depiction of this future Earth with its hive-mind inhabitants. They seemed interesting and it's a shame they vanished. I wonder if the author used bits of them in later works.


In RuneScape, will my Adventurer's Log include my F2P game time if I ever start membership later?

Question: I'm looking to get membership but I also want to see how long I've been playing RuneScape all in all.
Answer: It probably won't.
The Aventures' Log is a members-only feature, and thus does not appear if you are F2P. So your hours probably aren't counted while F2P.
If you're interested in how long you've played, talk to Hans. He will tell you how long you are close to your 5/10 year veteran cape. Then find some calculator which will figure out 10 (or 5) years minus the days Hans tells you. This will be the day you crated the account though, and won't actually tell you the amount of time you've played RuneScape.
Comment: That's too bad. I wanted to see how much time I'm putting into this game.
Answer: I'm pretty sure it won't. As when I used to play this game several months ago when my membership would run out I would maybe play f2p for a couple days as I was too lazy to go to the store and buy a card.
In that small time period my log did not track my f2p progress. Even though I was only f2p for maybe 5 days I still completed a lot in game such as boss fights leveling up and finding rare drops.


Access user information based on list

Question: I've created a List with a 'Person' column to manage favourite people.  So the operator will add a few favourite people to the list. It appears that the person column can only return a single attribute.
Then I want to display the favourite people on the home page with other details like phone number, email address.
So I guess I need to create a webpart that reads the list and then fetches the email address and phone number from user profile and finally displays the info. I've been reading that SharePoint also has a hidden list (_layouts/users/details.aspx) but this only gets populated once a user accesses the site, so this wont work. Hence I think User Profiles is the option here.
Any ideas how I can achieve this?
Thanks
Comment: just a heads up. do not use the user information hidden list for this because there are many complications in that. Even if you delete a user from your AD, the user information list will not be updated. therefore your webpart will not show the correct information.
Answer: Go to Visual Studio and create a new project, look under SharePoint and click on the version you're using. I'm presuming 2010. You should see some options and for you, you can click on Visual Webpart. Give it a meaningful name and click ok.
Go to Solution Explorer and then expand VisualWebPart1 and double click on the .cs file to start coding. The ascx is the front end (visual) part where you can add controls ect. If you expand that you have a codebehind for that ascx where you can also add code, but in this case we're not adding code within the ascx but rather inheriting by adding it to the .cs codebehind.
The following code has not been tested and I just made it so more than likely would need fine tuning or amending to work properly! You need to amend the list name that you want to pull out to your one. I am missing some checks for the user that you might want to do to see if they exist rather than throwing a not found exception!
As noted it's not properly done so could be cut down and made better. The getUser method could be expanded to cut the main body code down so that it returns a list of data rather than the spuser object but I will leave that for you.
    // Visual Studio might automatically update this path when you change the Visual Web Part project item.
    private const string _ascxPath = @"~/_CONTROLTEMPLATES/showUsers/VisualWebPart1/VisualWebPart1UserControl.ascx";
    private UserProfileManager upm;
    protected override void CreateChildControls()
    {
        Control control = Page.LoadControl(_ascxPath);
        Controls.Add(control);

        //get your custom list and populate all the items into a collection to iterate over
        SPList myFavList = SPContext.Current.Web.Lists["myFavList"];
        SPListItemCollection items = myFavList.Items;

        upm = new UserProfileManager(SPServiceContext.Current);

        //list view to contain all the values and to display on the webpart!
        Microsoft.SharePoint.WebControls.ListView lv = new Microsoft.SharePoint.WebControls.ListView();

        Random rnd = new Random();

        //iterate through each list item
        foreach (SPListItem item in items)
        {
            //get the user from the list item
            //I don't know what your list looks like so I'm presuming that you have a list of users(people) that you want to iterate to get their details from????
            SPUser user = getUser(item["people"].ToString());

            if (user != null)
            {
                //make sure its not a service account or system account
                if (user.LoginName.ToString() != "NT AUTHORITY\\LOCAL SERVICE" && user.LoginName.ToString() != "SHAREPOINT\\system")
                {
                    //get the profile object for that user
                    UserProfile profile = upm.GetUserProfile(user.LoginName);

                    //display the data to page any way you like!!:

                    Label lbl = new Label();
                    lbl.ID = rnd.Next().ToString();
                    //an example of what it would look like: "ali sharepoint's workemail : email@example.com"
                    //you can do what you like, this example is wacking the data into a label which isnt great. You can create its visual container within the ascx or change the label to a gridview or table
                    lbl.Text = user.LoginName + "'s workemail : " + (string)profile["WorkEmail"].Value;
                }
            }
        }
    }

    //getUser needs to be domain\username
    private SPUser getUser(string getUser)
    {
        SPUser user = null;
        try
        {
            // Chek if user exists
            if (upm.UserExists(getUser))
            {
                // The user exists
                user = SPContext.Current.Web.AllUsers[getUser];
            }
            else
            {
                // The User doesn't exists
            }

        }
        catch(Exception a)
        {
            //user doesn't exist// catch exception here and carry on
        }

        return user;
    }

Access user information based on list


Does the private beta have community wiki?

Question: Coming from this comment: is it possible to create a community wiki during the private beta?
Answer: Yes, it is possible to create a community wiki answer. But there is rarely any case for it. Community wiki was primarily useful in the old days when there was a minimum reputation requirement to edit posts. Now, anyone can suggest an edit (which will be reviewed if the editor doesn't have enough reputation), so community wiki has lost most of its use. FAQ-type posts have also been replaced by tag wikis to a large extent. You may want to use it on an answer to encourage others to contribute to it actively, but that's very rare.
It is not possible to create a community wiki question. The possibility used to exist, but was removed because there was no good use for it. On Stack Overflow, it used to be a way to tolerate bad questions, but this is no longer done.
Community wiki answers are still used on meta sites, which don't have suggested edits, for things like FAQs.
Comment: In summary: there is no restriction on CWs specific to private beta.


Adding an EV Charging Station to an AC Circuit

Question: We just had a air conditioner compressor installed last week. The contractor installed a new 240V 30Amp circuit to the compressor. We are also wanting to install a new EV Charging Station (which is also 240V 30A). Can we ask an electrician to install the EV Charging Station (or to add a 240V NEMA outlet) on the same circuit as the Air Conditioner or do we need to have an entirely new circuit run from the main box for the EV Charging Station?
Comment: will you ever want to charge and use AC at the same time?
Comment: Do you have space in your panel for more circuits?  Is the air conditioning compressor near where you'd want to plug the EV charger in?
Answer: I believe you'll need a new circuit.  Fixed appliances generally require dedicated circuits.  But from a more practical view, how would you plan on not using both at the same time?   If both being used at the same time would almost surely trip the breaker.
Comment: Thanks for the info. I figured that was going to be the case. I don't have any more space at the main panel (it's 200A service). They put a lot of circuits in when they redid the electrical (the house is 112 years old, but the entire house was rewired about 15 years ago). Seems like the best option might be a subpanel and a new circuit). It's too bad because the AC is right next to where I would want the EV charging station.
Comment: @Justin -- what's the Minimum Circuit Ampacity on the air conditioner nameplate? Also, does your EV charger *actually draw 30A*? Or does it *plug into a 30A receptacle*? Finally, do you know what size wire was run for the new air conditioner circuit?
Comment: in some places it's allowed to fit a switch that affords choosing between two loads.
Answer: Nope. EVSE's need to be on a dedicated circuit.  That's a Code requirement.
The amps of the service don't decide how many spaces are in the panel. "spaces" and "amps" are totally different numbers, you can have 12-space 200A or 42-space 100A. It sounds like you need to add a subpanel somewhere convenient.  I recommend counting the spaces (not circuits) you now have, subtract that from 50, and get a subpanel with about that many spaces.


Can you clarify what an 1NO1NC switch is?

Question: I've come across multiple mentions of switches described as 1NO1NC.
They often described as having 2 options: ON/(OFF) and (ON)/OFF and from what I gather they have 3 terminals for wires: a NO terminal, a NC terminal and a C (?) terminal.
Can you explain what these mean?
When would you use an NO or an NC switch?
Answer: NO = Normally open (open = open circuit = not creating a path for the current)
NC = Normally closed (closed = short circuit = creating a path for the current)
C = Common

(The drawings show the state in the absence of force.)
When you press a normally-open pushbutton, you provide a path for the current.
When you press a normally-closed pushbutton, you impede the current from flowing.
In a relay, when the coil is not energized, C and NC are connected. When the coil is energized, the magnetic field attracts the movable metal, and C and NO are connected instead.
Uses:

NC pushbuttons are used in emergency stop buttons. You press them when an accident has occurred, or may occur, and you need to immediately stop some machine, whose action could damage someone or something. Normally-closed buttons are preferred for two reasons:
a) they don't rely on creating a good contact, to signal something. They just have to open a circuit, which is much easier. An NC is more robust and therefore safer.
b) they react quicker. For an NO button, the signal event happens at the end of the movement (when the movable part makes contact). For an NC button, the signal event happens at the beginning of the movement (when the movable part stops making contact).
Comment: Thanks for the clear explanations, that's awesome. Also nice uses examples
Comment: oops, forgot I hadn't accepted an answer here. All great answers. I'll go with the people's choice :)
Answer: NO is normally open i.e. the contacts are normally open and close when the switch is actuated.
NC is normally closed i.e. the contacts are normally closed and open when the switch is actuated.
1NO1NC is generally used to describe contactors (industrial power relays) and manual switches like emergency stop buttons. It means that there is one pair of normally closed and one pair of normally open contacts with their own terminals i.e. there will be four terminals.
The switch you describe with 3 terminals would normally be called SPDT or single pole, double throw.
Generally normally open contacts are used in most electronics especially for momentary contact push buttons- it is more intuitive to work with switches like this.
You will find normally closed contacts in a lot of industrial applications as logic is entirely implemented by switches and contactors. The NC contacts are used on an emergency stop button to interrupt the current holding the contactor coil energised, for example.
Comment: Thanks to you too. Great reference on the SPDT terminology
Answer: The abbreviation "NO" means "Normally Open".  The abbreviation "NC" means "Normally Closed".
These switches are usually of a momentary type rather than latching.  "Momentary" means that they're only on while you're pushing them like a key on your keyboard, rather than latching, which means that they stay where you put them like a light switch.  This might be a spring-loaded toggle switch, or they might be a pushbutton.  It may also be a pair of switches or contactors sharing a single activation lever.
"C" almost certainly stands for "Common", which would be the terminal that is shared between both switches.  When the switch body itself has a common terminal, that's usually known as an"SPDT" or "Single-pole Double-Throw" switch.  The single pole is the common terminal, and the switch can be "thrown" in either direction.
Here's a simple schematic diagram of a 1NC1NO switch.  Imagine that the <--- is a spring pulling the center lever to the left:
    <---|
        |
NC-|    |     |-NO
   |----|--|
   |    O     |
C1-|          |-C2

In this default setup, the left-side terminal "NC" is closed; it is connected to C1.  There is a break in the "NO" switch; it is open or not connected to C2.  When actuated, the situation changes:
    <- - - |
           |
NC-|       |  |-NO
      |----|--|
   |       O  |
C1-|          |-C2

Now the "NC" terminal is an open, while the "NO" terminal is closed. When released, it will spring back to the left and be in the original configuration.
You could use an individual NC or NO switch in many situations.  For example, a reset button is commonly used for a reset circuit:

Normally, the resistor R1 keeps the output wire high.  When the button is pressed, the line is pulled to ground and the output is low.  You could reverse the positions and use an NC button, but that would draw power continuously through the resistor.
One application for a 1NC1NO combination switch is in emergency shut-off devices, like the 'red mushrooms' common on industrial equipment.  By using both switch types, the system can go into a shut-down state in most failure modes:

The button is pressed: NC becomes open and NO becomes closed.
The cable is severed cleanly: NO remains open (because the wires are disconnected) but NC becomes open.
The cable is severed and shorted out: NC remains closed but NO becomes closed.

This type of switch is commonly available with the mushroom and each switch available as separate parts, later assembled like this:

The three units at the back of the switch are individual units with their own actuators.
Comment: @KevinVermeer: I would expect "1NO1NC" to describe a switch with two pairs of terminals, with the terminals of the first pair being shorted when the switch is "pushed", the terminals of the second pair being shorted when the switch is not, and neither of the terminals in the first pair being connected to either terminal of the second pair in any situation.  It seems odd to apply such terminology to a 3-terminal device, which would more typically be described as "SPDT".
Comment: @KevinVermeer I don't think that latching/non-latching is the distinction between 1NC1NO and SPDT. Microswitches with 3 contacts are always described as SPDT, whereas industrial switches and contactors are always 1NO1NC or 1NO2NC etc. I can't find any examples of a correctly described SPDT as 1NO1NC, only badly described switches on ebay.
Comment: Thanks for the clarifications on SPDT vs 1NO1NC.  I've learned something today and edited accordingly.
Comment: @KevinVermeer Thanks for your input too. Nice illustrations too :)


CSS: How do you change the color of the "check" within an HTML checkbox?

Question: How do you change the color of the "check" within an HTML checkbox?
By default, on WinXP Firefox/Chrome/IE - the check is green. I would like to change the check within an INPUT type="checkbox" to orange
Answer: There's no way to do this consistently with stock inputs. Safari, for one, will never respect your tweaks.
You can use JavaScript to present styled elements that function as checkboxes. Here's one plugin that uses jQuery.
Comment: +1 for right answer and suggesting workarounds; I believe checkbox color is an OS setting, rather than an HTML or CSS or even browser setting.
Comment: Not in all browsers, they're not.
Comment: Scrollbars are also OS objects, but they're stylable.
Answer: As others have said, this isn't particularly easy to do in a cross-browser way.
But another possibility is jQuery UI which is highly customizable.  You can even design a theme on their site.  And along with all that you can use the jQuery UI Checkbox.
You could potentially roll your own lighter-weight version of all this with a combination of Javascript and CSS.  But I imagine you'd run into a lot of compatibility issues that have already been figured out by the jQuery guys.
Answer:
<input type="checkbox" CHECKED>

This is not a cross-browser solution (hey, IE!). Here's a more portable one:

<input type="checkbox" class="checkbox" CHECKED>


Maximize power to RL with LM741 output

Question: I have to design a circuit that maximizes power to RL which is a resistance representing a speaker attached to the end of a LM741 op-amp. This is a non-inverting op amp in the circuit, and I just need a generalized explanation of what to do to get the maximum power to (or dissipated in) RL.
Answer: You need to make the [closed loop] output impedance equal RL. If the speaker is inductive, as in real life, it gets more complicated as you want power factor correction essentially by having an output impedance that is the complex conjugate of the load. See http://en.wikipedia.org/wiki/Maximum_power_transfer_theorem

Maximize power to RL with LM741 output


Any way to link to a time slice of Twitter posts?

Question: I am interested in linking to a sequence of tweets by a single user - starting and ending with specific tweets. Basically, due to the constraints, people often tweet a series of short posts that are best viewed together. I wonder if there is a way to refer to them as such (for example by providing starting and ending tweet IDs).
Answer: You can't choose the start and end message IDs, but you can use a date range.
<code>from:codinghorror since:2014-10-01 until:2014-10-05
</code>
The above search will give you all of the tweets from Jeff Atwood from October 1 to October 5.
(Twitter Advanced Search Operators)
Answer: If you have TweetDeck you can create a timeline or collection of tweets. You'll select the tweets you want to show together and then have a URL that you can tweet out or post elsewhere that will show the tweets you've grouped.
You can also use something like Storify which does the same thing, but in addition, allow you to include relevant posts from other sites and social networks if you wanted some other context.


How anti-inflammatory are nsaids?

Question: So I currently have some bad tonsillitis and an infection in one of my ears. My doctor at school gave me ibuprofen (for pain and anti-inflammation) and penicillin. I was just wondering if higher doses (doc told me 2x 200mg tablets) would reduce inflammation even further. Is there a point where the nsaid can't help anymore, even in higher doses? (Ex. If I take 3 200mg pills will it reduce inflammation even more than 2 pills would?)
Comment: @Lucky - This walks a fine line, I'll agree. Without the personal details, the basic question is "If X dose reduces inflammation, would X*2 dose reduce it even further?" which is on topic. But, the intent behind it makes it personal. As with you, I will wait (Since my close vote is like a presidential veto :p)
Comment: Welcome to health SE :-). I'm not sure that this is on topic (personal medical advice isn't), but I,m not going to vote to close just yet. In general, it is unwise to ignore your doctor's advice **especially** regarding the increase of a dose. Such a large increase should not be done by yourself or by following advice on the internet. You can read the patient information leaflet that comes with the medicine, and look at the section *adverse effects*.
Answer: You're asking if there is a dose response relationship for ibuprofen, and what does it look like. For most people the analgesic effect (surrogate for inflammation) flattens out at 400 mg, but 20% might get a better response with a higher dose. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2000723/
Comment: Good answer. It's also important to point out that while higher doses could have incremental benefit, they may also cause adverse effects. Taking more than 400 mg of ibuprofen at a time may not be safe for certain individuals, including the elderly, people with high blood pressure, or people with kidney disease.
Comment: We routinely use 1600 mg of slow release Ibuprofen for arthritis patients.
Comment: As I'm sure you're aware, those slow release tablets will have different pharmacokinetics vs. the regular ones; higher doses can be tolerated because the compound is released over a longer period of time. In general, 3200 mg / 24h is the maximal safe dosage of ibuprofen for healthy adults. The maximal safe dosage would be much less in children or in people with comorbid disease.
Comment: Sure, I was just pointing out that drugs can be formulated in different ways to reduce the toxicity.

How anti-inflammatory are nsaids?


When should I end a sentence?

Question: I like to write long sentences, but people complain that I move from thought to thought in the same sentence, and that it ought to be split into multiple sentences. Although I'd like to correct this problem, I'm not sure how to define a complete thought. Can someone please define it for me? Thank you.
Comment: There isn't a perfect guide for this, but if you have more than three commas, two m-dashes, or two semicolons, your sentence is a little out of control. Can you think how the sentence would be stated as two separate sentences? Try that, and see if it still flows the same in your head. If it does, it actually will flow BETTER as two. If there is an and, see if it works better as two sentences (especially if there is more than one and).
Comment: As long as each sentence is a grammatically correct, complete sentence, you are fine.
Answer: Err on the side of brevity. As a rule of thumb, short (but grammatically complete) sentences are preferable to long sentences because they are easier to read. If a sentence can be easily split into two, then you should usually do so. Where this would leave you with a very short sentence or a lack of context, it may be preferable to keep the independent clauses together and throw in a coordinating conjunction instead, but this should not be the default.
Another helpful rule of thumb is to count the number of commas and conjunctions (and, or, but) in a single sentence. Unless a sentence contains an embedded list, you should rarely have more than two or three of each in a sentence. For most sentences, you should have one or zero of each.
Finally, take into account stylistic considerations. If you are intentionally writing in a "stream of consciousness" style to evoke a particular creative effect, then run-on sentences are an entirely legitimate and appropriate technique.
Answer: Consider reading your sentences out loud after you type them.  If you feel like you just ran a sprint, it probably needs shortening.

When should I end a sentence?


How did Denisov reappear in Leo Tolstoy's War and Peace?

Question: In 1807 Major Denisov got court-martialed for stealing food, threatening and insulting chief quartermaster, and thrashing two officials even dislocating the arm of one of them. All of this happens near the end of Book VI. Denisov's actual fate is not presented, but in my understanding it meant he was sent to Siberia if not worse and won't appear in the novel again. Yet much later, in 1812 and middle of Book IX he reappears as Lieutenant Colonel, a rank higher than that of Major. How did that happen? It feels like there's no continuity in what happened to him.
Answer: While I didn't find an explicit explanation in the book, it's possible to speculate about it. The simplest solution is as follows.
Vasily Denisov has a clear historical prototype: Denis Vasilyevich Davydov, one of the most popular heroes of the 1812 war. They have similar names, stature, personal traits and so on (for a proper statement see an article in the Russian magazine «Дилетант» (Dilettante) – claiming that ''every school kid knows" that).
In 1812, Davydov was a Lieutenant-Colonel and led guerrilla warfare against the French. Russian readers were aware of these connections, so when Denisov reappears, it doesn't come as a surprise.
Of course, if the hero is sent to Siberia, this explanation doesn't work. But this doesn't follow from the text or historical sources.
In the novel we only have:

The adjutant told them that the affair was likely to take a very bad
turn: that a court-martial had been appointed, and that in view of the
severity with which marauding and insubordination were now regarded,
degradation to the ranks would be the best that could be hoped for.

Historian Natan Eidelman in his book «Грань веков» (The edge of the centuries) studied the verdicts of the supreme audit military court (which tried the nobility). He found out that while under the rule of Paul I the share of harsh sentences was significant, the penalties became softer after his son Alexander I succeeded him in 1801:

More than 70% of the sentences are short–term arrest, treatment of
production, demotion for short periods, imputation of the court as
punishment, arrest for two weeks.

So Siberia doesn't seem inevitable (note that Denisov is an officer and nobleman). In 1807, Denisov receives some punishment, then in 1812, when Russia is invaded, his military skills grow higher in demand, and he goes to lead a guerrilla detachment.


Is it possible to store edge data layers?

Question: Something that I do frequently in blender is use a UV map for coordinates to map an otherwise procedural texture, such as when texturing a snake. I don't always know where the best seams would be beforehand, so I like to try putting them in a different places and create multiple UV layers. So I was wondering, in the same way as one can switch between multiple UV maps, is it possible to store edge data sets, for example, save multiple sets of UV seams or edge creases and toggle between them?
Answer: You can save "edge data" like that in the form of seams on UV maps.  Use "seams from islands" operation in UV editor to select what your seams would have been for that UV map.
Can also maintain multiple copies of your model, and use a data transfer modifier to copy seam status (or all sorts of other edge statuses.)


What is a Domain Model

Question: I have read the wikipedia definition of a domain model. I still don't get it. I have been reading alot of posts for NHibernate and almost in every post I read I see the term Domain Model. What exactly is it and does any one have an example of a domain model.
Answer: Basically, it's the "model" of the objects required for your business purposes.
Say you were making a sales tracking website - you'd potentially have classes such as Customer, Vendor, Transaction, etc.  That entire set of classes, as well as the relationships between them, would consititute your Domain Model.
Comment: Thank you for not using the phrase in the definition. The "domain is the problem domain." Totally unhelpful. Your answer is what I was looking for.
Answer: A domain model is a visual representation of real situation objects in a domain.
A domain is an area of concern. Its used to refer to the area you are dealing with.
The model is a diagram, for domain models the class diagram UML is mostly used. The class diagram is only used for the notation.
The term domain model does not mean a set of diagrams describing software classes.
So for example imagine a store. For that store you want to build a brand new Point Of Sale system (lets call it POS system). A POS system is a computerized application used to record sale and handle payments. So you focus on the domain of the POS system.
Now you will conceptualize the objects that will be used for this system.
So you will get objects like: Sale, Payment, Register, Item etc.
In a domain model you model these objects and draw associations between them so that you have an high level idea how this system will work.
An example of the POS domain model will be like this:
Comment: You nailed it. Domain is actually the problem that we are solving, and modelling is the abstract representation of higher level objects and its association with each other.
Answer: If you were to take your program and strip away the gui and the DBMS, and replace it with a command line interface, and a MySQL server instance, then port the whole thing to a different platform with different system calls and file system access api calls, the part that you didn't change in that process is the domain model.
Answer: This article might help:
https://dddcommunity.org/learning-ddd/what_is_ddd/
The basic idea is that the Domain is the problem domain and the model is... well the model of it. The above article is puts it far more eloquently than I would and there are plenty of other resources there if you want to go down the rabbit hole.
Answer: Answering from perspective of Eric Evans's "Domain-Driven Design: Tackling Complexity in the Heart of Software" book:

[A domain] model is a system of abstractions that describes selected aspects of a domain and can be used to solve problems related to that domain.

Practically it means the following. On the input we have domain experts, domain knowledge sources and requirement for a software product. Modeling would mean eliciting the relevant [for the software under the development] part of that domain knowledge and representing it somehow. If I understood the author correctly, the model can be represented in many ways: as a text, as diagrams, as a code, in form of oral communication. The model is updated in parallel with iterative software development, being reworked for the need of the software development.
So a domain model is a selective and structured representation of domain knowledge relevant for a given software development project.
Comment: Perfect ! Thank you for elucidating this point. I was just about to put a question here about What is domain model as per DDD ? But you just answered my question.
Answer: Domain model is a collection of constructs that accurately models one particular business domain. Simply put, it's a collection of entities, enumerations, value objects, exceptions/custom exceptions, interfaces, services, etc. All of that represents the domain model. Anything that has any impact in describing the business domain. On the other hand, any construct that doesn't take part in this description; the UI code, infrastructure related code, persistence objects, various tools, etc; are considered as third-party/outer concerns in the context of DDD.
Check out this short article
https://fiseni.com/posts/what-is-a-domain-model/
Answer: in a super simple sentence I can say:

Domain model is an abstraction of domain, expressed as code
implementation which is a view not reality of business use case.

What is a Domain Model


For attackers looking to launch arp spoof on a target, does the attack have to happen in real time?

Question: I was surfing the web at 3 in the morning and I got a warning which seems to indicate a MITM attack. Does this mean the attacker was able to passive sniff my activity in real-time in order to launch the attack?
Comment: Did you get the SSL certificate warning message when browsing the HTTPS site ?
Comment: Where did the warning come from?
Comment: Yes! I did get a certificate warning with the yellow badge and man in the hat.It was an https site!  It came from my student loan page where I have to login to view my account.  So did an attack happen in real time?
Answer: I think Yes, it has to be in real time.

As I understand the attack, it poisons the cache of arp entries in your OS using arp replies, and due to ARP protocol standards, it updates the cache of the OS immediately even if the entries is not expired.
After the attack is finished, the OS updates the ARP cache after multiple 'futile' requests using the poisoned cache.


Freelancing to UK company from India

Question: I am freelancing to UK clients from India and get paid in pounds. Please could someone suggest a suitable setup for this. I know I have to pay taxes in India , which  I am fine with. Can I raise invoice as an individual and get paid in Indian Bank account ? Should I include VAT in the invoice ?
Answer: You can raise invoices as individual and get paid in an Indian Bank Account. You would need to check with your client in UK if he is comfortable with this. Normally on cross border payments, when you are quoting for your work, its best to add that any tax obligation of this transaction in UK will be borne by UK company and any tax obligation in India by you. This way you would not be worried about other taxes.
Even as a free lancer individual , you can deduct cetrain items as expenses[for example phone calls to UK company, purchase of a Laptop etc]. Consult an accountant and he would help you. Ofcouse you have to pay tax yourself in advance.
If the amounts start to become large or there are partners whom you have to pay, then it would become advisable to register a company.
Related Questions:
As a freelancer, how to receive money from overseas company to my individual bank account in India?
Indian citizen wants to work as a freelancer for Europe. How to pay tax in India?
Answer: Getting paid
There are various way to get paid:
1. If you have credit card, you can use it to open a PayPal account.
You can invoice the client and client can pay you using their Credit Card or their PayPal account. Later you should transfer the amount to you bank account.
2. Your client can directly transfer to you account, in this case you need to tell you account details with bank's SWIFT code to you client.
3. There is few other services available where your client can pay using Credit Card and other methods and you get final payment in India's bank account. They charge some fee for their service.  Please beware that there some fraud services available so you should trust wisely.
Paying Tax
Whatever way you choose, the money comes to your account and you need to calculate your income and pay tax accordingly. You should consult Income Tax consultant and they can do Income Tax Return calculation for you.

Freelancing to UK company from India


Memory in sequential circuit

Question:
In sequential circuit block diagram ,it is said that some outputs are again feedbacked to inputs,after storing them in memory.
But,where is that memory in sr latch.In sr latch ,it is seen that the output is directly taken to the inputs,and their is no memory.
Comment: Welcome to EE.SE. There is a schematic button on the editor toolbar. It's easy to use and makes professional looking schematics to replace your Paint schematics.
Answer: Some of the inputs are taken from the outputs in your drawing, not the other way around.  Left/Right direction in the drawing doesn't matter, signals always flow from outputs to inputs.
Since some of the inputs (one input from each NAND gate) are depending on the outputs of the NAND gates, it is sequential and with this particular configuration it has memory.

Memory in sequential circuit


Does combining the Gusting and Wall infusions on kinetic blast result in a wall that gusts for the duration?

Question: The Gusting infusion can be given a duration of 1 round for either a cost of 2 Burn or having the blast do no damage, and the Wall infusion has an innate duration of 1 round per point of the Kineticist's Con modifier--so what if you combined the two on an air blast and chose to have it do no damage? Would that result in an air wall that forces a DC 15 Strength check to cross it (as per Gust of Wind) for the wall's duration?
Answer: You can combine one form infusion and one substance infusion on any blast without issues. From the Kineticist's Infusion ability:

By using infusions along with her kinetic blasts, a kineticist can alter her kinetic blasts to suit her needs. Infusions come in two types, each of which changes a kinetic blast differently: a substance infusion causes an additional effect, while a form infusion causes the kinetic blast to manifest in a different way. Each infusion can alter only certain kinds of kinetic blasts, which are listed in its Associated Blasts entry. Each time the kineticist uses one of her kinetic blast wild talents, she can apply up to one associated form infusion and up to one associated substance infusion.

If we check the Gusting infusion, we will see it is a substance infusion:

Gusting Infusion
Element(s) air; Type substance infusion; Level 1; Burn 1

While the Wall infusion is a form infusion:

Wall
Element(s) universal; Type form infusion; Level 5; Burn 3

Since both infusions can change the damage of your Blast (if you accept extra Burn from Gusting), you have to apply the substance infusion first, then apply the form infusion. Gusting reduces the damage to 0, and form reduces the damage to half since Air generates physical blasts (but 0/2 is still 0).

If a kineticist's form and substance infusions both alter the kinetic blast's damage, apply the substance infusion's alteration first.

This means you have three options:

An instantaneous blast that will hit a single target for normal damage and hold/push him away. This costs 1 Burn.
A lasting wall-shaped blast that causes half the damage of your blast and will hold/push enemies away from it. This costs 4 Burn.
A one-round lasting line-shaped blast that causes no damage but will hold/push enemies away. This costs 1 Burn.


Bluetooth keyboard with jumbled keys

Question: I bought a bluetooth keyboard (which works perfectly fine on windows) and all the keys are either jumbled or not working at all.
It worked fine on ubuntu as well until I pressed the num lock key and ever since then it stopped working. I even tried to reset the keyboard by removing the battery but nothing helps.
The keys that do work are the num pad keys with the fn key, backspace, = (which is mapped under the - key) and the special function keys (such as volume mute/up/down (F10,F11 and F12 respectively), brightness (F5 and F6) etc (all of which are not in accordance with the hardware layout)
Does anyone know how to fix this?
It's a maxxter act-kb-bt-001 keyboard that requires a pin to be typed upon connecting.
I can connect with bluetoothctl and it shows me this info but the jumbled keys problem persist.
[Bluetooth 3.0 Keyboard]# info
Device 16:07:02:00:0E:A2
    Name: Bluetooth 3.0 Keyboard
    Alias: Bluetooth 3.0 Keyboard
    Class: 0x002540
    Icon: input-keyboard
    Paired: yes
    Trusted: yes
    Blocked: no
    Connected: yes
    LegacyPairing: yes
    UUID: Service Discovery Serve.. (00001000-0000-1000-8000-00805f9b34fb)
    UUID: Human Interface Device... (00001124-0000-1000-8000-00805f9b34fb)
    UUID: PnP Information           (00001200-0000-1000-8000-00805f9b34fb)
    Modalias: usb:v05ACp0239d011B

ps xev and xinput don't register input from any unmapped keys
Answer: Default for ubuntu sessions is numlock on.
To make the default numlock off so your keyboard works:
sudo apt-get install numlockx

...then go to Startup Applications Preferences and add a new entry:
Comment: Thanks mate but it was the keyboard. I switched it for another model and it works perfectly now.

Bluetooth keyboard with jumbled keys


Can somebody explain SDF and MACE to me?

Question: I can't find any information on SDF and MACE save for a vague exert in Kinser's Image Operators books. Therefore I am dumbfounded. I can't understand what they do and what's their role in composite filters. Can somebody please explain them to me? Thanks.
Answer: Your question is allusive at that point: explanation of acronyms (SDF, MACE), need for composite filters... A starting point is  matched spatial filter (MSF). To overcome its limitations, several versions have been proposed. David Casasent is a common denominatoir of the ones you consider.
For the SDF filer, my reference is:

C. F. Hester and David Casasent, "Multivariant technique for multiclass pattern recognition," Applied Optics, 1980

A technique for multiclass optical pattern recognition of different
  perspective views of an object is described. Each multiclass
  representation of an object is described as an orthonormal basis
  function expansion, and a single averaged matched spatial filter is
  then produced from a weighted linear combination of these functions.
  The technique is demonstrated for a terminal missile guidance
  application using IR tank imagery.

with comment in:

J. B. Nelson, "Multivariant technique for multiclass pattern recognition: comment"

In a recent article, Hester and Casasent discussed an interesting
  technique in multiclass pattern recognition. They mentioned that other
  approaches to the construction of an orthonormal basis function set
  were possible and specifically suggested the possibility of using a
  Karhunen-Loéve expansion as an alternative to their own Gram-Schmidt
  procedure. It is the purpose of this Letter to recommend yet another
  alternative, the singular value decomposition (SVD), which has very
  convenient conceptual and numerical advantages, and to show how it may
  serve as a foundation for future extensions of the theory. The scope
  of the present discussion is restricted solely to the digital
  processing aspects of Ref. 1. It will begin with a brief review of the
  problem in the slightly modified matrix notation that is more
  compatible with the SVD technique that follows.

Abhijit Mahalanobis, B. V. K. Vijaya Kumar, and David Casasent, Minimum average correlation energy filters, Applied Optics, 1987

The synthesis of a new category of spatial filters that produces sharp
  output correlation peaks with controlled peak values is considered.
  The sharp nature of the correlation peak is the major feature
  emphasized, since it facilitates target detection. Since these filters
  minimize the average correlation plane energy as the first step in
  filter synthesis, we refer to them as minimum average correlation
  energy filters. Experimental laboratory results from optical
  implementation of the filters are also presented and discussed