mobileconfig file with mdm payload, is invalid profile

Question: I'm trying to install .mobileconfig file that was created through IPCU.
but when I click on an  attached .mobileconfig file in mail.
It occured error message as "invalid profile".
what is problem ?
if the certificate is problem, please let us know how to make.
Below is the procedure I created the certificate.

in keychain, After navigate Keychain Access/Certifiate Assistant/Certificate generate,
I have generated Certificate. and exported .p12 file
.p12 file is used to Credentials setting in IPCU
Answer: You could be having any number of problems, but the one I've seen most often is that you're trying to install an encrypted profile and the device can't find the appropriate private key (which must be on the device prior to receiving the profile, and is required for decryption).
Your best bet is to get more information on the problem, which you can do by connecting the device to your Mac or PC, selecting its entry in iPCU (in the left-hand column—the entry that only shows-up once you connect the device) and clicking on the Console tab. This will give you access to the device's system log file, which generally contains a lot more info on what the real issue is.
The process you used to create the certificate seems reasonable enough and isn't likely the reason you're getting the error; I couldn't say much more than that without knowing what you're using the certificate for.
Answer: Did you sign the mobileconfig file? If yes, have you tried not to sign it?
Answer: Usually this error message pops up if you are trying to download iOS from macOS. So tap that same link from an iPad instead of on macOS, or choose the iTunes-based download method (iOS Restore Images), and upgrade from iTunes.
https://forums.developer.apple.com/message/234381#234381


.htaccess 301 Redirect that Works for http and https cases, .com and localhost

Question: I need to do a 301 redirect on a single page. If I just wanted it to work from www.example.com, I would have:
redirect 301 /urisegment1/urisegment2/urisegment3 http://www.example.com/urisegment1/urisegment2/NEWURISEGMENT3

The problem is, users may access http://www.example.com/urisegment1/urisegment2/urisegment3  or sometimes https://www.example.com/urisegment1/urisegment2/urisegment3/ if they have been logged in and access SSL-protected pages. Also I have the site set up locally so I can access it through http://www.example.local/urisegment1/urisegment2/urisegment3
How can I get this to work for all cases?

(That's the end of the question, my current .htaccess file below in case it is relevant. Note it's mostly not my own work, it is drawn from various sources).
<IfModule mod_rewrite.c>

RewriteEngine on
RewriteBase /

#Removes trailing slashes (prevents SEO duplicate content issues)
#RewriteCond %{REQUEST_FILENAME} !-d
#RewriteRule ^(.+)/$ $1 [L,R=301]

#forces www.
RewriteCond %{HTTP_HOST} !^www\.
RewriteRule ^(.*)$ http://www.%{HTTP_HOST}/$1 [R=301,L]

#force homepage to http from https
RewriteCond %{HTTP_HOST} ^www\.example\.com$
RewriteCond %{HTTPS} on
RewriteRule ^$ http://www.example.com/ [R=301,L]

#If a controller can't be found - then issue a 404 error from PHP
ErrorDocument 404 /404.html

#Removes access to the system folder by users.
#Additionally this will allow you to create a System.php controller,
#previously this would not have been possible.
#'system' can be replaced if you have renamed your system folder.
RewriteCond %{REQUEST_URI} ^sys.*
RewriteRule ^(.*)$ /index.php/$1 [L]

# Checks to see if the user is attempting to access a valid file,
# such as an image or css document, if this isn't true it sends the
# request to index.php. The first condition allows access to assets, css, js and the robots file
RewriteCond $1 !^(index\.php|assets|css|js|robots\.txt)
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule ^(.*)$ index.php?/$1 [L]

RewriteCond %{THE_REQUEST} ^.*/index.php
RewriteRule ^(.*)index.php$ http://www.example.com/$1 [R=301,L]

# Removes access to the system folder by users.
# Additionally this will allow you to create a System.php controller,
# previously this would not have been possible.
# 'system' can be replaced if you have renamed your system folder.
RewriteCond %{REQUEST_URI} ^system.*
RewriteRule ^(.*)$ /index.php/$1 [L]

</IfModule>

<IfModule !mod_rewrite.c>

# Without mod_rewrite, route 404's to the front controller
ErrorDocument 404 /index.php

</IfModule>

Answer: I just tried the following rule
RewriteCond %{REQUEST_URI} !newvalue/?$
RewriteRule ^(.*)/[^/]+/?$ /$1/newvalue [L,R=301]

which should keep everything but the last URI segment, so it should work with http(s) and different domains.
You have to update the newvalue in both lines to avoid endless redirects.
Comment: Thanks for the reply. However let's say my 'urisegment3' was something like 'example-directory-about-computers' and my new 'urisegment3' was 'computer-directory', how would the rewrite rule you posted redirect from old to new? 'newvalue' is on both lines? I tried it without success unfortunately


Remote location management copy and install large software updates to 50 LAN

Question: Initially posted to Stack Overflow and was directed here. I'm new to programming and am trying to write a powershell script to manage software updates.
I'm in a windows domain environment with over 50 remote offices. Each office has 4 computers. One computer, "Computer A," has dropbox installed that we use for backups, and now software updates. I want to execute a script from my local machine that copies a folder (~1 GB) to the other computers in that LAN, and runs the setup.exe file in the directory to update software on these computers.
As far as I can tell in order to use the Enter-pssession cmdlet & run a copy-item and start process, I have to:

On remote machine enable winrm by: enable-psremoting -force
On remote machine enable CredSSP authentication by: enable-smancredssp -role server -force
On local machine enable CredSSP authentication by: enable-SmanCredSSP -role
client -force

From here I can enter the Power shell session and begin the copy and install. Here is the code I'm running:
<code>#Allow my computer to send credentials to remote computers
Enable-WSManCredSSP -Role Client -DelegateComputer * -Force
$credential = Get-Credential -Credential domain\user
#Getting Content
$path = "C:\computernames.csv"
Import-Csv -path $path |
foreach-object {
    $computername = $_.Name
    if (Test-Connection -cn $_.Name -quiet) {
        #copy the batch file that allows remote powershell access
        $source = "c:\"
        $destination = "\\$computername\c$\install files\remoteaccess"
        robocopy $source $destination
        #open file to allow remote PS access
        & psexec \\$computername -a runas -u domain\user -p password -c -f -h "\\$computername\c$\install files\remoteaccess\remoteaccess.bat"
    #Initiates Power Shell session with remote computer
    Enter-PSSession -cn $_.Name -Credential $credential -Authentication Credssp
    #begin copy
        #be sure to refine destination
    copy-item -path $_.Source -Destination $_.Destination -force -verbose -recurse | out-file c:\copylog.txt
    #begin silent install
        #code here
    #stop wsmancredssp accep
    disable-wsmancredssp -role server
    #close pssession
    exit-pssession
    } else {
        "$computername is not online"
    }
}
Disable-wsmancredssp -role client
</code>
The computernames.csv has the headers: Name, Source, Destination with UNC directories for each LAN's computer with dropbox and where to copy the file.
The "remoteaccess.bat" file contains the following two lines of code:
<code>powershell.exe enable-psremoting -force >>c:\remotelog.txt
powershell.exe Enable-WSManCredSSP -role Server -force >>c:\remotelog.txt
</code>
The powershell window freezes after initiating the psexec session with the remote computer and sends the first powershell command to enable remoting. No error is generated, or input requested. The output of this command is saved in the remotelog text file:
 "WinRM has been updated to receive requests.
WinRM service started.
WinRM already is set up for remote management on this machine."
It appears the powershell command to enable wsmancredssp is never received. When I run the batch file on the remote computer from remote access software, both commands execute and are logged successfully. Where is my psexec command going wrong, or how can I setup these computers to allow remote sessions with a remote command without using GPO?
Answer: The code is off in a number of ways:

If you are in a Windows Domain environment, why don't you just enable Powershell remoting via GPO?
Enter-PSSession is a command for interactive remote sessions, what
you are looking for is New-PSSession and Invoke-Command with the
session parameter
CredSSP is only required if you want to access remote systems from
the remote system that you're connected to
Why do you copy 1GB of data over to the branch offices? Is the connection to the main office too unstable?
the robocopy command is copying all contents of C:\ to a remote
destination, that is definitely not want you want (pagefile.sys,
    bootmgr, etc).


How to explain that leave-one-out cross-validation doesn't need stratification in the context of classification?

Question: Stratification is usually defined as training data and testing data having the same distribution of  class values. In leave-one-out cross-validation, each fold only has 1 instance. I know that it's impossible and unnecessary to apply stratification the way we do it for k-fold cross-validation. However, I don't know how to explain it. How do you explain that the single instance in the test data has the same distribution as the training data?
Answer: Maybe the difficulty is:

that in some cases stratification would be needed, but
due to leaving out exactly one instance at at time, it is impossible to achieve it.

In these situations, LOO is known to have a particularly large pessimistic bias. Textbook example is a majority vote classifer with two classes and the same number of cases in each class: the tested instance always comes from the minority class in the training data.


Contract question

Question: If you sign a contract, and the person asking you to sign explains nothing, but there is a part you totally miss (Maybe it's in a tiny font at the bottom of a page, or hidden somewhere.), you sign the contract, and that hidden part is held against you, can you sue the person who wrote it for misleading you? Or is it totally your responsibility to read the whole thing thoroughly?
Comment: What you mean "hidden"?
Answer: As a general rule you are bound by all terms of a contract, even those that you do not read. I can imagine a case where the print is sufficiently fine or hidden to not be considered part of the contract - indeed, some statutes expressly require certain kinds of language in certain kinds of contracts to be in "conspicuous" print to be enforceable and define that term, and if the relevant language (even if readable) is not in the proper typeface or size as defined in the statute, it cannot be enforced.
Generally speaking, you would not have a valid cause of action to sue someone who presented you with the contract for misleading you as a fraud tort, but one could imagine some fact pattern where that was true (e.g. if the person presenting you with the contract to sign specifically held it in such a way is to actually prevent you from reading the language in question, knowing that this would conceal an important term from you that might have been different, for example, from the term that was discussed during the course of contract negotiations and that you would rely on the lack of an ability to see that term to their detriment). This kind of fraud, when it happens, is called "fraud in factum".
Fraud in factum would very rarely arise in a contract of adhesion. Normally, it would arise in a contract drafted for an individual transaction.

Contract question


Can cider go bad?

Question: This is my first try at making cider. I had great results from fermentation. I was short of some things like a hrdometer so it was reacted off into 2 car boys and sealed with airlocks stored in a dark place with a very constant temperature +/- 3 degs. For 3 years. It is a nice clear amber color. What SG should I be looking for or reading my new toy refactor meter Opinions Please ?
Answer: First to answer the title of your question. Yes cider can certainly go bad! It will go bad the same way as other wines:

If the alcohol is below an ABV of ~12% then oxygen can activate acetobacters which will turn your brew into vinegar.
Any contamination from bacteria (e.g. if you stirred the cider with an unsanitized spoon) can of course cause problems.

Luckily spoiled brews almost always taste extremely awful, so you'd never be in doubt if your brew has been spoiled.
SG is starting gravity, so it seems a bit late for your 3 year old brew. But given the typical ABV of ciders I'd say a typical SG would be in the range of 1.040-1.070; that would give you an ABV of 5-9% if all the sugars fermented out.
A note to remember regarding refractometers is that they are nice and easy to use with SG, but when there is alcohol in the solution you need to do some calculation on your reading to get the true value.
Comment: Maybe I should have written 'cloudy, or opaque'. Often with green slime a bit like a 'vinegar mother' if you have ever seen one. There were legends that farmers would toss into the vat lumps of meat (horses heads!), dead rats, etc. Tough guys would prove they were tough by drinking it when it was 'evil'. Often caused incontinence of the brown kind. There is less rough cider drunk now, I think, compared to the 1970s when I was a young man. A local pub used to serve 'snakebite' - half cider, half beer, but only in half pints because if not drinkers would start fights.
Comment: Living as I do near Somerset (England) I am familiar with 'scrumpy', or 'rough cider' which is traditional for the area. Farmers charge you by the gallon to fill up your own containers.  Often completely unofficial and unregulated.  I have seen plenty of stomach upsets from that stuff. One rule of thumb was to discard it when it gets hazy.
Comment: That sounds both fun and scary at the same time! One issue with your hazy evaluation would be that young cider would already be hazy so you'd be scared every time you go get a cup
Answer: Measuring specific gravity can tell you when fermentation has finished, but after several years you can already be quite confident that it has! SG measurements are of no use at all in determining if the product is safe to drink.
The good news is that cider is quite low pH and contains a fair amount of alcohol, so it's not friendly to many pathogens.
If the airlock ran dry, allowing significant oxygen ingress, you will likely find the product has undergone another fermentation process and turned to vinegar. An aerobic (oxygen-requiring) family of microbes called Acetobacter will convert ethanol to acetic acid if enough oxygen is present.
If the product has escaped oxygen ingress, has dropped clear, and doesn't have have a pellicle on the surface or any sign of mould, it is quite likely to be OK. Probably somewhat oxygen damaged as an airlock and bung are not 100% effective at excluding permeation, but drinkable.
If the product had been stored in glass carboys with a proper lid I would be very confident that it would be in good condition.
Your best tool here is your nose, and if your nose leaves you confident, your sense of taste.

Can cider go bad?


Difference between Tensor product, dot product and the action of dual vector on a vector

Question: In the book Schutz on general relativity, I have come across the dot product between vectors, the action of a dual vector on a vector (or also a tensor on vectors) and the tensor product between dual vectors and vectors. I am not able to understand the difference between the three distinctively. Kindly help. Try to keep it simple and not too mathematical. Still a beginner.
Comment: Related: https://physics.stackexchange.com/q/32011/2451 , https://physics.stackexchange.com/q/105347/2451 and links therein.
Answer: Unfortunately this is mathematical because it is linear algebra. Still, I'll try to make it as simple as possible.
Dot Product, also known as Inner Product
The dot product is the usual product from basic geometry. Let us work on $\mathbb{R}^3$, the euclidean three-dimensional space. Given two vectors sitting on the origin, $v,w\in \mathbb{R}^3$ we define the dot product between them to be:
$$v\cdot w = v_xw_x+v_yw_y+v_zw_z$$
The reason is that this gives information about lengths and angles. First, the length of a vector, which is the distance between the origin and the point it reaches, is simply $|v|=\sqrt{v\cdot v}$ the angle between two vectors is characterized by $v\cdot w = |v| |w| \cos\theta$.
The inner product ends up being the name of the generalization of this. First one can readily generalize to an euclidean space of arbitrary dimension $\mathbb{R}^n$ by creating the inner product between $v,w\in \mathbb{R}^n$ as
$$\langle v,w\rangle=\sum_{i} v_i w_i$$
and defining the length and angle by the corresponding formulas. The inner product can be further abstracted. One can define it by axioms: saying what properties it is expected to have. And this generalizes even further to more abstract spaces. The bottom line is: the inner product gives geometric information such as angles and lengths of vectors.
Important to understand also, the inner product gives you the idea of projecting one vector in the direction of the other. Actually, if $w$ is a unit vector, $|w|=1$, then $\langle v,w\rangle$ is the projection of $v$ in the direction of $w$. You can check this in $\mathbb{R}^3$ to be according to our intuition.
The action of a covector on a vector
Now, forget $\mathbb{R}^n$. Consider instead one vector space $V$ over the real numbers. Associated to every such vector space, there is the so-called dual space denoted $V^\ast$. It is defined as the space of all linear functions that takes vectors and delivers numbers. In symbols, a member of $V^\ast$ is a function $f : V \to \mathbb{R}$, it takes an element of the set to the left of the arrow and gives one element to the right of the arrow. Furthermore, $f$ is linear, meaning that $f(\alpha v + \beta w) = \alpha f(v) + \beta f(w)$. All such functions comprises $V^\ast$.
It turns out that if $V$ has an inner product $\langle,\rangle$ defined on it, you can build elements of $V^\ast$ with it. You just fix one arbitrary vector $w\in V$, and define $f_w : V\to \mathbb{R}$ to be
$$f_w(v)=\langle v,w\rangle$$
What is $f_w$? It is a function that takes a vector and dots it with the fixed $w$, so it projects. Actually, independently of the existence of an inner product we can think of all elements of $V^\ast$ as things that takes vectors and extract projections. This is the way to understand $V^\ast$ and covectors in general.
By the way, if $V$ is finite dimension and has one inner product, as it will be in general relativity, this works the other way around to. All covectors are of this form: the inner product with a certain vector.
Importantly enough, if $\{e_i\}$ is a basis for $V$, there is one special basis for $V^\ast$ called dual basis of $\{e_i\}$ defined as all elements $\varphi^i : V\to \mathbb{R}$ such that $\varphi^i(e_j)=\delta^i_j$.
The Tensor Product
The tensor product is altogether different. There is one very general and abstract definition which depends on the so-called universal property. It states basically the following: we want the most general way to multiply vectors together and manipulate these products obeying some reasonable assumptions.
We won't follow this route. For differential geometry (which is the language of general relativity), there is another definition which ends up being equivalent to this one for the case of interest.
Given a vector space $V$, we know $V^\ast$ the space of all linear functions $f : V\to \mathbb{R}$. We also know the inner product, which is a function that takes two vectors and delivers a number. We symbolicaly write $\langle,\rangle : V\times V\to \mathbb{R}$ because it takes two vectors to a number.
Furthermore, if we fix a vector $w\in V$ into either entry of $\langle,\rangle$, the other slot is linear. Such a map is called bilinear. It is linear in each entry with the others held fixed with something in them.
We define a tensor of type $(r,0)$ to be the generalization to $r$ vectors. It takes $r$ vectors to a number, and is linear in each entry with the others held fixed. We write $T : V\times\cdots \times V \to \mathbb{R}$ with $r$ copies of $V$. The space of tensors of type $(r,0)$ is denoted $T_r^0 (V)$ and obviously $T_1^0(V)=V^\ast$.
Now, if you have $f,g\in V^\ast$ it is quite obvious that $T(v,w)=f(v)g(w)$ is an element of $T_2^0(V)$. If $f\in V^\ast$ and $h\in T_2^0(V)$ for example, we also have $T(v_1,v_2,v_3)=f(v_1)h(v_2,v_3)$ one element of $T_3^0(V)$.
The generalization is the tensor product. It is one operation that concatenates together two tensors in this way. It can be written as $\otimes : T_r^0(V)\times T_s^0(V)\to T_{r+s}^0(V)$ and is defined so that if $T\in T_r^0(V)$ is a $(r,0)$ type tensor and $S\in T_s^0(V)$ is an $(s,0)$ type tensor, then
$$T\otimes S(v_1,\dots,v_r,w_1,\dots,w_s)=T(v_1,\dots,v_r)S(w_1,\dots,w_s).$$
Now a theorem says that given a basis $\{e_i\}$ of $V$ and the dual basis $\{\varphi^j\}$ of $V^\ast$, then for every $r\in \mathbb{N}$, the set of all products of $r$ elements $\varphi^j$ is a basis of $T_r^0(V)$. For example, $\{\varphi^i\otimes \varphi^j\}$ is a basis of $T_2^0(V)$.
Differences and relations
Each product has its use. Inner products give geometric ideas like projections, angles and lengths. Covectors when applied to vectors can also be thought to be giving some sort projections, but they don't give alone a notion of angles and lengths. While inner products must be postulated (a vector space can carry an inner product or not), all vector spaces comes with covectors together in the dual.
The tensor product is a more general multiplication of vectors that allows one to build a tensor algebra. But for differential geometry, tensors are to be thought as multilinear maps of a number of vectors. In this setting the tensor products allow us to build higher types of tensors by putting together other ones of lower types.
Interestingly, since the inner product itself is a $(2,0)$ tensor, and since we can form a basis for $T_2^0(V)$ using covectors and the tensor product, we see that the inner product ends up being a linear combination of products of covectors. It is, thus, built out of covectors really.
Answer: The tensor product combines two lower rank tensors into a higher rank one. For example, you can put two vectors $v^a$ and $w^b$ together to create a rank-2 tensor $v^aw^b$, which can be thought as a matrix. In this particular example, the tensor product is essentially the direct product of two vectors. You can generalize this idea to higher rank tensors straightforwardly.
The dot product combines two vectors into a scalar (a number). It is actually the inner product. You need a metric $g_{ab}$ to do so.
The action of a dual vector $\omega_a$ on a vector $v^a$ also results in a scalar. The difference is that the metric tensor is not needed.
If a metric tensor $g_{ab}$ exists, the above two operations are related. If a vector field $w^a$ is given, you can construct a dual vector $\omega_a=g_{ab}w^b$, and the action of $\omega_a$ on a vector $v^a$ is actually the inner product between $v^a$ and $w^a$: $\omega_av^a=g_{ba}w^bv^a$.
Comment: Thanks a lot...was very helpful...just one more thing...is the tensor product anything similar to the cross product between vectors?
Comment: @NamanAgarwal The cross product creates a new vector, so the rank does not change. So the tensor product is very different from the cross product. In 3 dimensions, the cross product can be realized by applying the exterior derivative on the 1-form, followed by the Hodge dual operation. If you do not know differential form or the Hodge dual, just ignore this part.


Origin of the term "eating your own dog food"

Question: I'm trying to find the first usage of the term "eating your own dogfood", as a reference to companies, especially software companies, using their own products in house in order to more effectively troubleshoot.  I'm fairly certain it originated with Microsoft, but I'd like to find out which year they first used it, if possible.
Comment: Now also a verb: to dogfood, dogfooding.
Answer: The Wikipedia article on the topic has a whole section on the origin of this phrase:

The editor of IEEE Software recounts that in the 1970s television advertisements for Alpo dog food, Lorne Greene pointed out that he fed Alpo to his own dogs. Another possible origin is the president of Kal Kan Pet Food, who was said to eat a can of his dog food at shareholders' meetings.
In 1988, Microsoft manager Paul Maritz sent Brian Valentine, test manager for Microsoft LAN Manager, an email titled "Eating our own Dogfood", challenging him to increase internal usage of the company's product. From there, the usage of the term spread through the company.

So the phrase didn't originate with Microsoft, but the first (known) use of the phrase in this context was indeed in 1988.
Comment: For reference, the citations on those sections of the Wikipedia article: The first paragraph cites [the IEEE Magazine article "Eating Your Own Dog Food" by Warren Harrison](https://www.computer.org/csdl/magazine/so/2006/03/s3005/13rRUygBwg0). The second paragraph cites *Inside Out: Microsoft—In Our Own Words* (ISBN 0446527394) and the article ["VMworld 2009: Virtualization, controversy and eating your own dog food" by John Brodkin](https://www.arnnet.com.au/article/317315/vmworld_2009_virtualization_controversy_eating_your_own_dog_food/).
Answer: I seem to recall that tech companies were using "Eating our own cooking" prior to 1988. I also vaguely recall that some wag had changed that to "Eating your own dogfood", possibly as a jab at Microsoft.  So it would be interesting to know if Maritz picked it up from the trade press or coined the phrase by morphing the Alpo claim with "Eating our own cooking".  And in either case was "Eating our own dogfood" a bit of self-deprecating humor or was he oblivious to the negative implications of the transformed version?
By the way, Warren Buffett uses "Eating our own cooking" frequently.  However, Buffett didn't meet Bill Gates until 1991. If Gates introduced this phrase into Microsoft, it was either because it was common marketing/sales jargon or he was reading Buffett shareholder letters.
Answer: I remember Larry Ellison at Oracle as the first to say this. They were using the Sybase database internally and they decided to force themselves to design it around the business needs of their own company which was at the time similar to many of their customers..
Answer: I believe this was a reaction to the Democratic party trying to make the point about poor or elderly people not having enough money to make ends meet and were left with eating dog food. As a response I think it was the president of Alpo got on TV and ate dog food. Hence the term. I may be a little inaccurate, but it was something along those lines.
Comment: This would be greatly improved with a reference/link to a source.


Control web interface on Raspberry Pi with GPIO inputs

Question: I know that there are a lot of articles about controlling Raspberry Pi outputs via web interfaces, but there is nothing about doing the opposite. I would like to control web interfaces that runs on Raspberry Pi with GPIO inputs. For example, if I press the button connected to the Pi then the button in the web interface would be pressed too. I just want to understand tha concept that should be used to get a bi-direcrectional communication. Thanks!
Answer: What you would need to do is utilise a socket. A socket allows a server and client to communicate directly with an ongoing connection.
The advantage of this is fairly high. Let's say you want a user interface on the Raspberry Pi, you'll find most interfaces are fairly lacking. Except on of course: HTML. This pretty much sounds like what you want. You have a server which presents a UI, as well as a socket that can communicate directly with the pages. Then you can even allow the pages to give feedback to the server, or simply allow the server to react to physical elements like a button push and then inform the sockets of a state change.
Comment: The node.js based Socket.IO might seem a misleading and poor choice of terms since a network [socket](https://en.wikipedia.org/wiki/Network_socket) is a fundamental entity of *all* networking (read: you cannot do anything on a computer network without the use of a socket), although it is abstracted away at the web programming level. Anyway, it is based on [WebSockets](https://en.wikipedia.org/wiki/WebSocket) (see [here](https://en.wikipedia.org/wiki/WebSocket)) which is the more general (i.e., not confined to node.js) approach used in contemporary web programming.
Comment: That's why I gave you a link in my explanation. It's probably also why 2 other people have +1'd this answer.
Comment: No, the link in the answer obfuscates this -- it makes it sound like this is a special thing not used for normal http stuff.  That's true of *websockets*,  it is **not** true of "sockets".  Really that module should have been called Websocket.IO.  I'm just pointing this out lest someone down the road become confused and believe that normal web stuff *and all other forms of network communication* are not socket based.  So it would make more sense to say "a socket allows a server and client to communicate", period, no qualifications, if it were not for the poor choice of names ("Socket.IO").
Comment: Put another way, this is not really a problem of your answer but one derived from the Socket.IO docs.


Isaiah 33:6b-The fear of the LORD is His treasure - what entails "fear of the LORD," and what "His treasure" specifically means?

Question:
And, how relevant is "fear of the LORD" to US?

Text: Isaiah 33:6b (NKJV)
"The fear of the LORD is His treasure."
Answer: The Hebrew word Strong 3374 יִרְאָה yirah, used in Isaiah 33:6, is the same as the word used in Genesis 20:11 by Abraham :

Surely the fear of God is not in this place and they will slay me for my wife's sake. [KJV]

So it would appear to be a general word for humanity being in fear of deity. It is a fear which restrains men (clearly from the way in which Abraham uses it) from outright bloodthirsty and bestial behaviour.
Moreover, humanity is exhorted, generally, together with its rulers to :

Serve the Lord with fear and rejoice with trembling [Psalm 2:11, KJV]

God, himself, is involved in this :

I will put a fear in the land of Egypt [Ezekiel 30:13, KJV]

Natural events can cause such a fear as we see in Jonah, after the sea was stilled when the sailors cast Jonah into it :

Then the men feared the Lord exceedingly [Jonah 1:16, KJV]

But all of this is not, necessarily, combined with a personal knowledge of God or with a personal interest in the salvation of God or with the intimacy of heart worship towards God.
Not necessarily, it would seem from the various contexts.
There is general exhortation for humanity to be aware of Deity, to reverence Deity and to be afraid, for so they should be. It is only reasonable.
And if the fear of the Lord 'is his treasure' then he values it. It is worth something even if, initially, it only restrains humanity from excessive evil upon earth.

In the New testament scriptures the Greek word phobos is used to describe both the fear of God and the fear of men, the disciples gathering 'for fear of the Jews' [John 20:19 KJV] and the gathered company of believers being affected when 'fear came upon every soul'
[Acts 2:43, KJV], as they 'continued steadfast in the apostles' doctrine and fellowship,  and in breaking of bread, and in prayers.
To us (as the question asks) that is to say, if we believe in Jesus Christ and gather with others who do so, this fear is enjoined by the apostles. It is to be experienced.
Paul exhorts the Corinthian Christians :

... let us cleanse ourselves from all filthiness of the flesh and spirit, perfecting holiness in the fear of God. [1 Corinthians 7:1, KJV]

The fear of God in this verse is the context in which one would 'perfect' holiness. One would begin with such a fear and one would, within it, perfect that holiness which is the holiness with which God is holy.

Because it is written, Be ye holy; for I am holy. [1 Peter 1:16, KJV]

Without the fear of God, one would not be able to even start such a process of 'perfecting holiness'.
Answer: The most famous verse on the fear of the Lord is Proverbs 1:7:

The fear of the Lord is the beginning of knowledge,
  but fools despise wisdom and instruction. (NIV)

This is what the New Bible Dictionary says about fear:

[Holy Fear] comes from the believer's apprehension of the living God. According to Luther, the natural man cannot fear God perfectly; according to Rudolf Otto, he is 'quite unable even to shudder or feel horror in the real sense of the word'. Holy fear, on the other hand, is God-given, enabling men to reverence God's authority, obey his commandments and hate and shun all form of evil (Je. 32:40; cf. Gn 22:12; Heb 5:7).It is, moreover, the beginning (or principle) of wisdom (Ps. 111:10); the secret of uprightness (Pr. 8:13); a feature of the people in whom God delights (Ps. 147:11); and the whole duty of man (Ec. 12:13). It is also one of the divine qualifications of the Messiah (Is. 11:2-3).[1]

It goes on to make the point that in the OT, "true religion is often regarded as synonymous with the fear of God".
In terms of how this is related specifically to Isaiah, this is what Alec Motyer says about this verse:

Yahweh has treasured up the fear of himself to bestow on his people, this being the beginning of wisdom and the foundation of every other blessing. (Isaiah by the Day, p. 159)

In short, you could say the fear of the Lord is true spirituality. Is is a holy reverence for God which causes us to love him, respect him, honour and obey him. As the passage in Isaiah says, God's blessings come to us through the fear of the Lord:

Taste and see that the Lord is good;
  blessed is the one who takes refuge in him.
Fear the Lord, you his holy people,
  for those who fear him lack nothing. (Psalm 34:8-9)
Answer: The problem with "the fear of the Lord", or, "the fear of God" (equivalent in this context) is the idea is not explicitly defined anywhere in Scripture.  However, we may glean much from the likes of W E Vine, "Expository Dictionary of NT Words".  The Entry under "Fear" reads (in part):

...  "reverential fear," (1) of God, as a controlling motive of the
life, in matters spiritual and moral, not a mere "fear" of His power
and righteous retribution, but a wholesome dread of displeasing Him, a
"fear" which banishes the terror that shrinks from His presence,
Romans 8:15 , and which influences the disposition and attitude of one
whose circumstances are guided by trust in God, through the indwelling
Spirit of God, Acts 9:31 ; Romans 3:18 ; 2 Corinthians 7:1 ; Ephesians
5:21 (RV, "the fear of Christ"); Philippians 2:12 ; 1 Peter 1:17 (a
comprehensive phrase: the reverential "fear" of God will inspire a
constant carefulness in dealing with others in His "fear"); 3:2,15;
the association of "fear and trembling," as e.g., in Philippians 2:12
, has in the Sept. a much sterner import, e.g., Genesis 9:2 ; Exodus
15:16 ; Deuteronomy 2:25 ; 11:25 ; Psalm 55:5 ; Isaiah 19:16 ...

Such an idea/concept is best understood by the first occurrence of the term "fear of God" (or similar) in Gen 22:11, 12, where we have part of the story about Abraham sacrificing Isaac but being stopped by the angel of the LORD.

Just then the Angel of the LORD called out to him from heaven,
"Abraham, Abraham!"
"Here I am," he replied.
"Do not lay a hand on the boy or do anything to him," said the angel,
"for now I know that you fear God, since you have not withheld your
only son from me."

This suggests that to fear God or fear the LORD is to have such reverential respect that the person has a genuine fear of displeasing God.  As such, Abraham was will to forgo that which was most precious to him other than serving God; in other words, serving God was more important to Abraham that even the love for his closest and most precious family and only son, Isaac.
Put another way, Abraham loved God more than all else and thus "feared God".
The Bible lists numerous advantages of fearing the LORD/God such as prosperity, delivering just government, having eternal life, and much else.  Isa 33:6 eulogizes this idea by simply saying that Zion's greatest asset was their fear of the LORD -

He will be the sure foundation for your times, a storehouse of
salvation, wisdom, and knowledge.  The fear of the LORD is Zion's
treasure.

Thus, if Israel had been faithful in serving God and "fearing God" they would have been "a storehouse of salvation, wisdom, and knowledge."  Briefly this was true under Solomon  as described in 1 Kings 4:20, 21 -

The people of Judah and Israel were as numerous as the sand on the
seashore, and they were eating and drinking and rejoicing. And Solomon
reigned over all the kingdoms from the Euphrates to the land of the
Philistines, as far as the border of Egypt. These kingdoms offered
tribute and served Solomon all the days of his life.
Answer: The relevance of "the fear of the LORD" to us should become clear when the biblical meaning of that phrase – 'the fear of the LORD' – is opened up. The God of the Bible is so awesome, only fools would not give him due reverence - which is the biblical meaning of the fear of God. Proverbs chapter 9 is an invitation to Wisdom's 'house' and those who heed it come under the instruction of the Lord God Almighty (vs. 10). Knowing that "it is a fearful thing to fall into the hands of the living God" (Hebrews 12:28-29 & 10:31), there can be no chummy attitude to prayer or worship. The Almighty will not become the 'all-matey'. To have that reverent fear is the beginning of wisdom. "The knowledge of the holy is understanding" Proverbs 9:10 continues. That's a plural 'holy [things]'.
It includes reverence of his majesty, and dread of his wrath. Yet those who are his children know Him as their loving heavenly Father, for the very reason that they have a holy fear of God which leads them to obedience and love, and adoption into God's family. Those who belong to God by faith know the fear of the Lord - an awesome thing, because God is holy.
I've started by working backwards with your questions, so will continue. How is this fear of the Lord "his treasure"? Well, treasure is often priceless, fabulous wealth.  Let me now quote the Isaiah verse from Youngs' Literal Translation of the Bible (YLT), starting with verse 5 to get the start of the sentence:

"Set on high is Jehovah, for He is dwelling on high. He filled Zion
[with] judgment and righteousness, and hath been the steadfastness of
thy times, the strength of salvation, wisdom, and knowledge, fear of
Jehovah – it is His treasure."

Wisdom is this immense, incalculable treasure, leading to salvation, and God lavishes it upon those who reverently fear him. His righteous judgment is appreciated and experienced by those who fear him, for they are given the wisdom from above to grasp how God's righteous judgment was poured out on Jesus when He was bearing the punishment for sin on the cross. They see Jesus, high and lifted up – the epitome of all treasure. There is no greater gift God could give to humanity than his beloved Son, and that is the gift bestowed freely upon those who have reverent fear of the Lord.
Finally, your first query. Again, let me quote from YLT, this time turning to Ezekiel chapter 1, the vision of the awesome, fiery lightning cloud, with four living creatures with wheels within wheels governing their supernatural movements. Do read the whole chapter. Now, here is the relevant verse (18) regarding those wheels:

"As to their rings, they are both high and fearful, and their rings
[are] full of eyes round about them four."

The word 'fearful' is sometimes translated as 'awesome', and that is the point. Such a vision would make anyone tremble, and when we are admonished in scripture to have holy "fear of the Lord", a sense of awesomeness should grip us and make us tremble, for this is the living, Almighty God we are considering, and we are his creatures, the work of his hands.  We give him all due reverence, or we are fools who have spurned his gracious invitation to sit in Wisdom's house.


Mix two audio tracks - stretch one to sync with other

Question: I have two music tracks of the exact same music (I have rights to it) but each is incomplete.  One is missing the start, the other is missing the end.
Both were recorded from the same source, except due to inconsistencies with the recording hardware at the time, one was recorded just slightly faster than the other and so the overlapping parts are at slightly different speeds and pitches - otherwise they are identical.
I want to merge them together, effectively overlap them, into one complete version of the song, but need to adjust the speed and pitch of one to match the other.  (Then I can simply line up the overlapping parts and fade one in and the other out to get the result - good enough).
Of course, computers can adjust pitch and speed independently by applying clever algorithms, etc. (although sometimes this results in some quality loss) - unlike say speeding up or slowing down an analog tape or record player where changing the speed changes the pitch as well. This "non-clever" analog-type outcome is fine - in fact preferred (to avoid that potential quality loss) - because knowing that the original source for both tracks is the same, getting the speed right this way should get the pitch right anyway, and vice versa.
What app, if any, on Mac can help me achieve this (stretch/shrink an entire track uniformly, both pitch and speed, to sync with another), and what functionality or steps or whatever do I need to understand to do it?
I've tried GarageBand, but if that can do it, I can't figure out how. I'm probably missing something.  Or perhaps GB isn't the app for this...?  Perhaps Logic Pro can do this, but this project isn't worth the cost of that app, and surely some free or inexpensive app can do just this (simple?) task?
Any advice/direction/help most welcome. Thanks!
Answer: I suggest you try Audacity, which has very powerful audio editing tools, including the duration stretch/compress and pitch change functions. I've used it many times for a variety of audio tasks over the past 10 years or so. I cannot recommend it more highly. Catalina is not currently supported, however.
If you need to save to .mp3 and other formats, you will need the FFmpeg library (links on download page) for these functions.


Is gravitational energy released when a body contracts?

Question: Kelvin stated that gravitational energy released due to contraction was responsible for the energy radiated in the stars. Although the theory was wrong, was the assumption practically right? If it's right, how does contraction take place?
Answer: It is correct. Contracting stars heat up due to their own contraction. This justifies the initial temperature raise in a star, before fusion begins in earnest.
Kelvin was not 100% wrong, it's just that fusion, over the life time of the star, makes much, much more energy than contraction. The collapse heats up the star at the very beginning, then fusion takes over and makes essentially all the heat you observe.
This is also true of gas giant planets. Even a tiny amount of contraction may raise their temperature measurably. E.g., Jupiter radiates more energy than it receives from the Sun - this is due to contraction, at a rate of 2 cm / year (diameter).
TLDR: Gravitational energy becomes heat.
Comment: "may raise their temperature measurably". Not really. The core gets a little hotter, but what we measure - the temperature at the surface is getting lower all the time. See slide 26 https://www.cps-jp.org/~pschool/pub/2011-01-10/08_Fortney/pub/20110113_fortney_01.pdf
Answer: Gravitational contraction will always release gravitational potential energy. In most systems, where this happens slowly, you can apply the virial theorem to say that half the released energy is radiated and half is used to heat the contracting gas.
The real question is whether the release of gravitational PE is significant compared with other sources. In most stars it is not. Nuclear fusion is responsible for extending their lives way beyond the Kelvin-Helmholtz timescale - the amount of GPE divided by their luminosity.
In some stars GPE is hardly released at all though. The capability to contract depends on the behaviour of gas's pressure as a function of temperature. If pressure is independent of temperature then no contraction of an object is possible even as it radiates away its energy and even if it has no other energy sources.
This is the case for white dwarfs supported by electron degeneracy pressure. They cannot contract further and will simply cool down at constant radius.
Jupiter is an interesting intermediate case. Yes it is contracting, but not at the rate you would expect for a perfect gas. Eventually, its contraction will slow right down and it will just cool.
Answer: In addition to the answers by Florin and Rob, I'd like to point out that the gravitational energy in the end dominates over all other sources, like fusion, at least for massive stars.
When a massive star eventually collapses to a neutron star, the gravitational pressure is so strong that protons and electrons are pressed into neutrons and all heavy nuclei are destroyed. In other words, the energy gained by fusion was merely a credit payed back with huge interest.
The situation is even more dramatic when the star collapses to a black hole. Such objects release an energy of $\epsilon M c^2$ with efficiency $\epsilon\sim0.1$ depending on the details (e.g. the spin of the black hole). This is far more than the $\epsilon<0.01$ from Hydrogen fusion and by far the most efficient natural energy source. The energy emitted from the formation of supermassive black holes equals (approximately) the binding energy of their host galaxies.


Can my xubuntu installation be converted to standard Ubuntu?

Question: I currently have xubuntu installed on my netbook, and I'm considering converting it to the standard vanilla Ubuntu. Is this possible? If so, how do I start?
Answer: You'll simply need to install the ubuntu-desktop meta-package. This installs all the nessisary packages for a "Vanilla" Ubuntu Desktop. sudo apt-get install ubuntu-desktop Once this has been completed you can restart your computer. At the login screen you can switch from XFCE to Ubuntu Desktop under the Session dropdown. Doing so will load the Gnome desktop.
If you're satisfied with Ubuntu Desktop and wish to remove xubuntu you can always remove the meta package xubuntu-desktop which will remove the meta-package. If you wish to remove all the packages from the xubuntu-desktop meta package you'll have to remove those by hand. An updated list of all the packages by distrobution is available simply copy the line for your version of Ubuntu
Comment: What about upgrades? Will they work properly, too?
Comment: Would there be any conflicting daemons or startup scripts by having both ubuntu-desktop and xubuntu-desktop (regarding 14.04) installed?
Comment: Would it be better to use autoremove instead of remove since autoremove will also remove the orphaned dependencies?
Comment: @Jasper `xubuntu-desktop` isn't considered orphaned since you can have multiple Desktop Environments on one installation. However, if you remove `xubuntu-desktop` meta-package it should take out all packages that aren't inner-dependent for packages outside of the meta-package. One may need to run autoremove after removing `xubuntu-desktop` if there are any orphaned packages though.
Comment: Removing the xubuntu-desktop meta-package will not remove the Xfce desktop. It will only remove the xubuntu-desktop package itself. You will need to remove all the xfce and xubuntu specific packages individually to remove Xubuntu.
Comment: @charlie-tca You're right, it only remove the meta package unless xubuntu-desktop was installed with aptitude which isn't available in the distribution anymore. I've updated my answer to reflect that and the "proper" way to remove all the xubuntu packages
Answer: You can simply install all standart ubuntu package with apt
sudo apt install ubuntu-desktop

Then when you feel good with your new environement
sudo apt purge xubuntu-desktop
sudo apt autoremove

And don't forget to reconfigure GDM3 login
sudo dpkg-reconfigure gdm3

Also you may want to change Ubuntu loading screen. It is realy easy, check this answer.
Finally reboot
sudo reboot

Answer: Install ubuntu-desktop.
To uninstall xubuntu, follow these guidelines: (select the right ubuntu version first)
http://www.psychocats.net/ubuntu/puregnome
Since xubuntu-destkop is a metapackage removing it will not remove the other underlying packages. The link above tells you which ones you need


Are trained abilities passed to offspring via breeding?

Question: If I train a dweller's abilities, then breed them, is the boosted ability considered for offspring? From how the game mechanics work, I feel the answer is "yes", but it goes against how real-world breeding works so I am curious if someone can confirm this.
Answer: The two parent dwellers do have an effect on the offspring's stats but not significantly. Common dwellers' starter stat threshold is 2 points so the child will inherit the most common high stats of each parent but only to a max of 2. You have to train them to increase their stats further after they've grown up.
e.g. If the two parents have high stats in perception and different stats in other fields, then the child will grow up and have the max threshold in perception, two. Think of it as a child inheriting a family name and continuing family profession.
Comment: Ugh I should have read this more closely. I was the up vote. This answer is factually wrong. Please ignore the trivial edit I attempted. I would post my own, correct answer but the question is a duplicate.
Comment: My apologies, my fault for putting more faith than I should have in the fallout community on reddit.


Can money be refunded after order cancellation in HDFC multicurrency forex card?

Question: I ordered something online on Amazon while in US using my HDFC multicurrency forex card. A day later the payment was processed and the amount got deducted from my forex card. I had to cancel the order later on due to some reason. Amazon said they'll refund any deducted amount in 1-2 days but how are they supposed to do that since it is a prepaid card and there is no bank account associated it.
Answer: The refund will be made to the multi-currency card. There is no need for an associated bank account. Consider how did you load currency into your card? In the same way, the refund will happen.
Comment: I don't think the refund will happen in the currency the card was loaded in - I presume the refund will occur in the currency that Amazon received, whether the rate has  gone up or down, and the card itself will show the receipt as its base currency, which may be higher or lower than what was originally loaded in that currency.


SSH ing in one terminal and duplicating it

Question: I usually have the habit of working with different terminal pointing to the same directory by opening different files. I sshed an server from one of my terminal from ubuntu and I had to do the same for all my terminals, is there a way where I can duplicate the terminals so that I don't need to connect on every terminal? Thanks, sorry if this is a duplicate, seems like an very common question.
Answer: You can use Linux Screen to do what you need. It's a good tool to work with :)
Here is a good tutorial
Comment: I tried Screen, its really good.... But I guess I kinda want to duplicate the image in different windows at the same time, i.e want to see all windows at the same time.
Answer: Just install byobu, screen or tmux on the server. byobu is recommended since it is a wrapper script around screen (or tmux).
These are "command-line window managers" - with one SSH session you can open a lot of "windows", each window containing a shell, you can switch between them and all the software you are running still running even if you disconnect.
Try this on server:
sudo apt-get install byobu

then execute byobu, press <F2> to create more one window and <F3> and <F4> to navigate between windows. Press <Ctrl> + a + d to deattach your session (all your windows will keep running) - if byobu asks something to you, answer that you want to use screen-like keyboard shortcuts. Then, if you disconnect, reconnect and execute byobu again, you'll be in your last session, with all that windows.
Obviously, you can also use byobu locally and open only one terminal window (instead of tabs in your terminal application, like gnome-terminal, you'll have windows inside byobu).
Comment: I guess, byobu will create another screen. For Example, I ssh an server and then create an window using byobu/screen, then the window which I have right now will disappear, behind screen. But what I was looking for is,I SSH an server and then need to duplicate the window I have right now into antoher window in the client, So I will have two windows in the client and I can avoid sshing in another window to the same server. I usually work with 6-7 terminal windows open just to see the control flow, in case of C++. Thanks for your help.
Answer: You can clone your SSH session using the ControlMaster option in OpenSSH 4.0 (older versions does not support it). Check out this straight-forward tutorial.
Comment: this looks to be a good answer but the link is dead
Comment: Updated the link accordingly
Answer: Tmux/screen is fine, but it's kind of uncomfortable to have multiple terminals in a window manager in a terminal in a window manager, the inner window manager being tmux/screen.
What I do for this is having keybindings that launch terminals that ssh to the systems I most commonly connect to. So, for example, pressing Super+F5 would execute urxvt -e ssh common-server-1.
Because I got keys set up for these systems, I only need to input my key decryption password for the first terminal, and it stays cached long enough to launch other terminals that immediately go to the remote system's shell prompt.
To quickly get them all on the same directory, I make use of shell history. The directory I want is typically the last one I went to, so I just cd Ctrl+pEnter and I'm there.


Sum of rank-one matrices equals identity

Question: Let $v_1,\dots,v_n\in \mathbb{C}^n$ be vectors satisfying
$$
v_1v_1^* + \dots + v_n v_n^* = I
$$where $I$ is the identity matrix and $v^*$ denotes the conjugate transpose. These vectors are clearly linearly independent. Is it necessarily the case that the $v_i$'s are orthonormal?
Answer: Yes, it is.
Considered as linear transformations one has
$\,vv^*=v\,\langle v\mid\cdot\,\rangle$,
assuming the scalar product to be conjugate-linear in its first slot.
Choose an ONB $\{\beta_k\}\subset\mathbb C^n$ and let $\,T\,$ be the linear transformation from that ONB to the given basis $\{v_1,\dots,v_n\}$, so that
$T\beta_k = v_k\,$ for $\,k=1,2,\dots,n$. Then
$$I\:=\:v_1v_1^*+\ldots + v_n v_n^*
 \:=\:\sum^n_{k=1} T\beta_k\langle T\beta_k\mid\cdot\,\rangle
 \:=\:\sum^n_{k=1} T\beta_k\langle\,\beta_k\mid T^*\cdot\,\rangle
 \:=\: TT^*,$$
hence $\,T\,$ is unitary and
$\,\{v_1,\dots,v_n\}\,$ is an ONB as well.


How inject dependency in custom TelemetryInitializer?

Question: We are using Autofac 4 for DI and I started experimenting with AI a short while ago. Now I created a IdentityTelemetryInitializer class which needs and IIdentityProvider to be able to get the ID of the current authorized user and set it add it to the context. I cannot find a way in which to inject dependencies into a TelemetryInitializer. If I define a contructor that takes an IIdentityProvider, the custom initializer is skipped altogether.
Any ideas are welcome. I was thinking of having the user ID also set as the Thread Principal so that we can access it this way, but I was hoping I could use DI for this?
Comment: What do youm ean by "the custom initializer is skipped altogether" ? do you mean that the base ctor is not called ?
Answer: You cannot inject dependencies using a constructor as the initializer initialized internally using the default (empty) constructor. When you explicitly defined a new ctor you've actually 'removed' the default one, thus the initializer was skipped altogether, as you've mentioned.
Therefore, the only way is to resolve the dependencies during the 'Initialize' method, after registering them on application startup.
<code>ctx.RegisterType<MyService>().As<IService>().AsSelf(); // on application startup
ctx.Resolve<IService>(); // during initializer 'Initialize' method
</code>
Comment: Thanks for the answer. I tried it out, however, the dependency is registered in Autofac via .InstancePerRequest(). The telemetry initializer class seems to live in a different (longer lifetime) scope and has no access to per-request dependencies :-(
Comment: @ParaJaco can't you use the HttpContext to resolve the dependency? from Autofac documentation - [How do I work with per-request lifetime scope?](http://docs.autofac.org/en/latest/faq/per-request-scope.html): "If you have application startup code or a background thread in an ASP.NET MVC app trying to use DependencyResolver.Current - the AutofacDependencyResolver requires a web context to resolve things. When you try to resolve something from the resolver, it's going to try to spin up a per-request lifetime scope and store it along with the current HttpContext"
Comment: I would not know how to do that, would you have an example of how this could be done?
Comment: @yonisha (and others) : even if this works, it breaks somehow the promise of DI , or am I wrong somewhere ?  What is wrong here ? is this the TelemetryInitializer API that is not good enough ? I guess this use case if very common and right now I don't see a practical solution to solve it
Answer: You might look at the question I asked here
How to have "Request" events with authenticated user id ?
because I had managed to have the TelemetryInitializer working, passing user id via the HttpContext as suggested by @yonisha.
Off course it's not as lean as what you try to achieve.
The Telemetry Initializer is called each time you instanciate a Telemetry class, so really depending of how you manage them. Btw I am looking for good advice/best pratice on that : for the moment I have one private instance on each Controller that need to track something, but that does not smell good due to lifetime of Controller.
Comment: Indeed with some step back, my answer is not an answer to the question, but a workaround to solve the problem.


i want to know about reference of hadith about the skys in which there is zikar of 7 skys

Question: please share referance of hadith on your web at this link The size of each sky
Answer: As Salaamu 3laykum,
This site goes into details regarding the specific words of the size of the earth compared to the first heaven, etc. here
https://www.islamweb.net/en/fatwa/340636/size-of-each-heaven-compared-to-one-above-it

However, there is a narration that states the following:

Abu Dharr al-Ghifāri (may Allah be pleased with him) reported that the Prophet (may Allah's peace and blessings be upon him) said: "The Kursi in comparison to the Throne is only like an iron ring thrown in a desert on earth."  Sahih/Authentic. - [Ibn Abi Shaybah in Al-'Arsh]


How to permanently disable region-folding in Visual Studio 2008

Question: Anyone know how to turn off code folding in visual studio 2008? Some of my colleagues love it, but I personally always want to see all the code, and never want code folded out of sight. I'd like a setting that means my copy of Visual Studio never folds #regionsor function bodies.
Answer: Edit: I recommend this other answer
Go to the Tools->Options menu.
Go to Text Editor->C#->Advanced.  Uncheck "Enter outlining mode when files open".
That will disable all outlining, including regions, for all c# code files.
Comment: Unchecking this option disables outlining completely however. Is there another setting somewhere that will just display all regions in the code expanded when a file is opened?
Comment: I think you have to use Macros to do that, but I don't know the code to accomplish it.
Comment: Option location moved in [VS 2013](http://stackoverflow.com/questions/20820358/visual-studio-2013-c-outlining-collapsing-if-else-while-code-regions): Text Editor -> C# -> View, Outline Statement Blocks.
Comment: Can anyone explain what outlining mode is PLEASE?
Comment: This works in VS 2015 as well, which I'm grateful for!
Answer: The accepted answer turns off ALL code folding.  If you want to disable #region folding but  collapse comments, loops, methods, etc I wrote a plugin that does this for you.
Make #regions suck less (for free):
http://visualstudiogallery.msdn.microsoft.com/0ca60d35-1e02-43b7-bf59-ac7deb9afbca

Auto Expand regions when a file is opened
Optionally prevent regions from being collapsed (but still be able to collapse other code)
Give the #region / #end region lines a smaller, lighter background so they are less noticeable (also an option)
Works in C# and VB (but only in VS 2010/2012, not supported for 2008)
Comment: Hoping for VS 2017.
Comment: @NickPainter I appreciate that this comment comes about 4 years too late, but you can get it to install on VS2017 by modifying the extension.vsixmanifest file in the DisableRegions.vsix (which is just a renamed zip file) to include additional supported versions. Please bear in mind I only tested this for like 2 mins on 1 install of VS so YMMV, but it appears to work for me. I take no responsibility if you kill your VS install though.
Comment: Any plans for a VS 2013 version? Is the source available? I'm sure someone would be willing to add 2013 support.
Answer: You can also disable region-wrapping on generated code (like when you use the Visual Studio shortcut to auto-implement an interface).
alt text http://dusda.com/files/regionssuck.png
Comment: I found this at *Tools > Options > Text Editor > C# > Advanced > Implement Interface*. Uncheck *Surround generated code with #region*. Thanks again.
Answer: Options / Text Editor / C# / Advanced / Enter outlining mode when files open
Answer: It's not permanent, but the keystrokes Ctrl-M Ctrl-L expand the regions in a file
Answer: Also, a quick way to toggle expand/collapse of all regions is: CTRL + M + L
Answer: I've posted an answer in a related-but-not-duplicate thread that may help some people here.  I detailed how to create macros that will deactivate a single unit's #regions by commenting out the #region and #endregion directives, with a companion for reactivating them.  With the #regions deactivated the Ctrl+M+O / Collapse to Definitions function does exactly what I want it to.  I hope this is useful for someone beside myself.
Shortcut to collapse to definitions except regions
Answer: This option seem to be available only in C# and not in C/C++ (Visual Studio 2005). To disable outlining in C/C++ files you need to make a trick by changing the outlining color to editor's background color. To do this go to Tools > Options > Environment > Fonts and Colors > Collapsible Text > Change "Item Foreground" color to White (or whatever your background color is).
Comment: This!  This is what I've been looking for!  Really appreciate this insight into an annoying "feature" that I've been looking to kill off for months (if not years)!
Comment: @jerhewet by using this solution you might go into trouble if you click that white area by mistake and region folds, then to unfold it you need to aim click at an invisible area.
Answer: i resolved the problem for me with an environmentevent:

start macroeditor (alt+f11)
open macroproject / EnvironmentEvents
paste the follwing code:

    Private Sub DocumentEvents_DocumentOpened(ByVal Document As EnvDTE.Document) Handles DocumentEvents.DocumentOpened
        If (Not Document Is Nothing) Then
            If (Document.FullName.ToLower().EndsWith(".cs")) Then
                Try
                    DTE.ExecuteCommand("Edit.ExpandAllOutlining")
                Catch ex As Exception
                End Try
            End If
        End If
    End Sub

    Private Sub WindowEvents_WindowActivated(ByVal GotFocus As EnvDTE.Window, ByVal LostFocus As EnvDTE.Window) Handles WindowEvents.WindowActivated
        If (Not GotFocus Is Nothing) Then
            If (Not GotFocus.Document Is Nothing) Then
                If (GotFocus.Document.FullName.ToLower().EndsWith(".cs")) Then
                    Try
                        DTE.ExecuteCommand("Edit.ExpandAllOutlining")
                    Catch ex As Exception
                    End Try
                End If
            End If
        End If
    End Sub

Greetings
Tobi


Data Retrival from the GenBank?

Question: When I go to NCBI & Select nucleotide option there and in search box write For Example CNGA3 gene the page shows that there are 553 items.I know the method of downloading or retrieving the One item's or record's FASTA format but "if I have to download the FASTA Format of all the 553 items simultaneously without opening each link then what options should I use..?" If you know it then please help me.. ?
Answer: I think that using NCBI Gene would be a better option here:

Go to NCBI Gene http://www.ncbi.nlm.nih.gov/gene/
Enter your gene of interest, in this case CNGA3 (and optionally the species)
Click the species of interest (I'm assuming you are looking for human, the first search result)
On the information page scroll down and click on FASTA which will provide the sequence for the gene of interest.
Answer: It is easy and possible. I will use steps which you already used and add additional steps to answer your question.

Go to Pubmed
Select nucleaotide from list
Enter gene of interest
In format option choose 'FASTA'

Click on send and then complete record

Click create file and you are ready to go !

Data Retrival from the GenBank?


First TDD, Simple 2-tier C# Project - what do I unit test?

Question: This is probably a stupid question but my googling isn't finding a satisfactory answer.  I'm starting a small project in C#, with just a business layer and a data access layer - strangely, the UI will come later, and I have very little (read:no) concept / control over what it will look like.
I would like to try TDD for this project.  I'm using Visual Studio 2008 (soon to be 2010), I have ReSharper 5, and nUnit.
Again, I want to do Test-Driven Development, but not necessarily the entire XP system.  My question is - when and where do I write the first unit test?
Do I only test logic before I write it, or do I test everything? It seems counter-productive to test things that have no reason to fail (auto-properties, empty constructors)...but it seems like the "No new code without a failing test" maxim requires this.
Links or references are fine (but preferably to online resources, not books - I would like to get started ASAP).
Thanks in advance for any guidance!
Answer:
It seems counter-productive to test
  things that have no reason to fail
  (auto-properties, empty
  constructors)...

It is...There's no logic in an empty constructor or auto-property to test.

when do I write the first
  unit test?

Before you write your first line of testable code.  Think about the behavior you want your method to perform.  Write your test based on the desired behavior.  That test (and all the others that follow) embody your program's specifications.

where do I write the first unit test?

In the first Test Class you create.
This is probably the best online resource:
Introduction to Test Driven Design (TDD)
http://www.agiledata.org/essays/tdd.html
Comment: Yes, essentially. After you write the test, then you write the code to pass the test, the test remains as a *regression test* to prove that the method still meets the requirement, in case you refactor. Also, *there can be more than one test* that specifies the overall requirements for the method.
Comment: Okay. So it's not writing a test to check the code I've already planned to write...it's writing a test, sort of, AS the plan for the code I'm about to write?
Answer: There is a shift in mindset that you have to dive into with TDD.  If you're not doing TDD, you'd usually write some code, then write a unit test to make sure the code does what you expect, and handles a few different corner cases.  With TDD, you actually write a test first, that typically uses classes and methods that you haven't even written yet.
Once you write your test, and you're satisfied that the test is a good example of how your code should be used, you start to write the actual classes and method to make the test pass.
It's kind of hard at first, because you won't have intellisense help, and your code won't build until you actually implement the production code, but by writing the test first, you are forced to think about how your code will be used before you even write it.
Answer:
It seems counter-productive to test
  things that have no reason to fail
  (auto-properties, empty
  constructors)...

It may seem counter productive, but if you have code that depends upon the defualt state of your newly constructed objects, then it's worthwhile testing. Someone can come in and change the default values for fields, and your code breaks.
It can be helpful to remember that your tests are not just for finding things that fail, but verifying that your code lives up to its advertised contract. You could argue that you don't need to worry - if the contract breaks then the code depending on that will also break. This is true, but creates tests that fail from "remote" problems. Ideally, a problem with a class should cause failure in it's own unit test first, and rather than in the unit tests of it's clients.
Doing TDD without any kind of requirements or design to work from is hard. With traditional coding where you sit down and bang out something that does what you want, the requirements evolve as the code evolves - requirements almost come from the code, as you dig deeper and discover in more detail what you need. But with TDD, the tests are embodiments of the requirements, and so you have to have these up front, crystal clear in your mind. If you're starting from an empty sheet, then you're having to requirements analysis, test design, and code design all at once.
Answer: One way to bootstrap TDD is to write an integration test first -- that is, before any unit tests. This integration test is oriented toward proving that your application works as expected in an end-to-end sense.
Obviously, the application is not written yet, so your initial integration test would not check very many things. For example, suppose you were writing a data-crunching program that is supposed to analyze a flat file and produce a summary report. A simple end-to-end test would invoke the program and then confirm that a file was produced in the expected location. That test will fail because your app doesn't do anything yet.
Then you write a minimal version of your app to satisfy the simple integration test. For example, the app will run and write a hard-coded title of the summary report to the file. In its current form, your application is sometimes referred to as a walking skeleton -- the thinnest possible slice of somewhat realistic functionality.
From that point, you add meat to the skeleton -- of course, writing a test before each new bit of functionality is written. Once you start doing this, the "What to test first" question becomes a bit more tractable and many of your new tests will be unit-oriented (rather that integration-oriented).


bitcoin core, deleted receiving address?

Question: Hi I set an address on bitcoin core and after I just downloaded it for mac. It was taking a crazy amount of time to synchronise which I realised was normal. I sent some $200 to the adress and whilst mucking around with the settings i hit the reset button which at the time I thought would fix the synchronisation issue. Anyway I've searched many .dat files and the receiving address is deleted from my bitcoin core app. Will I still receive my funds? If not, can I recover them?
Comment: Did you make a backup of the wallet, or make a note of the private key, before hitting that reset button?
Comment: If your node is syncing from scratch, the payment won't be shown in the wallet until your node gets to that point in the network history. The 'fix' is likely to just wait until the sync is complete, and then all will be well. Your funds are at no risk in the meantime, as long as you keep the wallet file / backup safe.
Comment: Unless you deleted anything, the Settings Reset button won't change anything except some node settings. It does not effect any transactions in your wallet. It does not effect any of your addresses.
Comment: If , at some time in the past, you had changed the directory containing your wallet.dat file, resetting options might cause the wallet to not know where your wallet.dat file was.
Answer: Did the same thing as you. In BitCoin Core, made a receive address.. then removed it. Then sent 5k worth of BTC to that removed address. Luckly.... Bitcoin Core has your back. Just don't close the wallet and wait till the transaction confirms, and sync the wallet 100%. It will eventually show incoming transaction and combine them into your main wallet. Search your wallet address you sent the transaction to with blockchain.com, see if its confirmed. Now its just a waiting game. Keeps your hair standing up
Comment: This makes no sense; you cannot delete receiving addresses in Bitcoin Core.


Why is my computer out of battery when I wake it from hibernation?

Question: I use hibernate, I don't know what happens, with other modes. Sometimes (not always) when I turn the computer on, it says, that battery is too low (like 4% or something). I use the computer mostly with the charger, it should be fully charged, when I turn it off.
The computer somehow turns itself on. I don't know why or how, but several times I have heard the "error noise", and it's warm in the morning.
I checked, taht the maintenance time is not set to night and not allowed to wake the computer, I checked, that the computer is not allowed to restart, when some error happens.
I am using windows 10
Comment: After asking the machine to hibernate, do you unplug it from the power?
Comment: yes, I do. I had hibernation issues in the past in that it wouldn't hibernate, but it does now
Comment: And you shut the lid before it finishes hibernating?
Comment: I hibernate by shutting the lid (it's set to hibernate when the lid closes)
Answer: From the comments, it would seem that the machine isn't fully entering hibernation, thus leaving the power active to the machine. Since you unplug the machine, the battery drains as it's still in use.
The causes for this could be :-

A Windows Error popping up, preventing completion of the process
An in the hiberfil.sys file (where windows stores all the memory information)
Another timer or setting which sends the machine to sleep or standby (two states which are low power, but still require power)

To diagnose or resolve this, set the power options to do nothing with the lid closes, and then ensure there is a good timer on other power options such as sleep and standby. Set the machine to hibernate only from your action (start menu). Observe the hibernating process until the power switches off, then remove the power from the screen. If it hibernates properly, you know that it's the other timers causing the issue. If it doesn't you'll get an error message which you can act on, and further diagnose the issue.
One other cause of hibernation problems is available disk space on the root drive (usually C:). You need at LEAST the total amount of RAM, as available disk space. If you are close to the limit, then that may account for the unpredictability of hibernation.
Answer: Could be some BIOS option, normally called something like Charge USB devices even when laptop is powered off.
I've seen it waste 10% overnight on a ThinkPad just trying to detect if something was plugged in USB. Could be that if you are leaving something plugged to the laptop.
Answer: If you have a Lenovo Thinkpad or Yoga, there are two options which can cause this: 1) fast startup is enabled, or 2) power off charging
Full details with screenshots are available at https://pcsupport.lenovo.com/us/en/products/laptops-and-netbooks/yoga-series/yoga-3-pro-1370-laptop-lenovo/solutions/ht509457-battery-may-discharge-when-laptop-is-powered-off-or-in-a-sleep-state-thinkpad-ideapad


Geowebcache 900913

Question: I am trying to create a wms tile cache in 900913 projection using Geoserver's Geowebcache extension. My data is  in a PostgreSQL database in 4326 projection. Do I have to reproject my data to 900913(a.k.a. 3857) prior to seeding my tile layer in 900913?
Answer: No, but it will be faster if you do. And please use 3857 instead of 900913 which has been deprecated for a while now.
Comment: feel free to submit a pull request to fix it
Comment: GeoServer's integrated GWC has a predefined gridset EPSG:900913 but not EPSG:3857 gridset. Perhaps GWC/GeoServer projects could show good example here.

Geowebcache 900913


Worth reworking a nodeJS server to use Connect (mainly for everyauth)?

Question: For the past 6 months, I've been working on my own nodeJS app, where I've built everything myself from the ground up. There are only a couple things that my server does, since most of the work in my app is done on the front-end.
One thing I'm currently looking at implementing is a user log-in + facebook authentication system for the app. It seems like every-auth is a much more robust framework for this than anything else out there. However, you need to have Express or Connect to use that.
As such, I'm considering reworking my code to use ConnectJS for (mainly) this purpose. That said, I really like having a really simple server that does only what it needs to do and nothing beyond that. Are there any other modules for authentication that are as robust as every-auth that don't need Connect that anybody would recommend?
And for those of you that do use Connect - how handy are the other features that it offers? Is it worth gzipping data that would be returned by the server? Is the static file server faster or any different than regular nodejs code that does the same thing?
I'm really on the fence right now and would appreciate any thoughts from people who've had experience programming nodejs apps both with and without Connect.
Best,Sami
AMMENDMENT - if each request that my server receives will at some point involve connecting to MongoDB using node-mongodb-native driver, does this change anything at all? I'm a little confused as to whether or not I can essentially have the code I've already written as a module of sorts that acts as one of the middleware items that I can add to connect. If this sentence showcases that I have a complete misunderstanding of what connect does, I'd appreciate any clarification.
Answer: Connect is a middleware framework. This means it's all about separation and implementation of third party (read: yours and everyone else's) middleware. Connect has no overhead compared to a straight node server.
Connect and Express are both very useful. I've also been working with Everyauth and I can say it's a lot easier than setting up all of your OAuth implementations separately(which I've done).
Here are some links:
http://howtonode.org/connect-it
http://tjholowaychuk.com/post/664516126/connect-middleware-for-nodejs
The Express guide: http://expressjs.com/guide.html
and a similar, but not duplicate, stack question: What is Node.js' Connect, Express and "middleware"?
Comment: @thisissami Yes, that is right.

Instead of calling http.createServer(...), you call connect.createServer().  The object returned from connect.createServer() works identically to that returned from the http module, but also has an additional use() function which applies middleware to each incoming request.
Comment: haha the transition was pathetically simple. just had to change my 3 different instances of "http" to "connect" and add a "next" in the callback to the server.
Comment: Thanks for this response Chris. In that case, just so I make sure I understand how it works, I can essentially replace the http module with the connect module and my code should work identically? And then it's just a matter of adding more modules before it gets to my code to add more functionality? If that's the case, then I feel silly for not using it already.
Comment: Well, you're not replacing the http module, connect extends the http server, but yes, you will be replacing your http code with connect code and it just adds some additional functionality.
Answer: Without knowing the implementation details of your app, and what its functionality is, it is hard to give an accurate assessment about the benefits Connect would bring to your app, as well as how difficult it would be to make the transition.
That being said, I highly recommend using the Connect/Express combo when developing apps.  There is a healthy middleware ecosystem developing around Connect, which makes it very easy to drop needed modules into an application, such as logging, compression, and authentication.  As you application matures and more features are implemented, having a flexible architecture in place will allow it to evolve more smoothly.
Since your evaluating authentication frameworks, I'll also mention that I'm the developer of Passport, which is an alternative to everyauth that aims to be more modular and unobtrusive.  Passport is built on top of Connect as well.  However, it is written to be extensible as to the context it operates in (Connect by default), so it should be possible to adapt to other, even home-grown, frameworks.


How to avoid unregistering of mscoree 2.4 during 2.0 installation?

Question: I've an application that depend on a reference to mscoree 2.0 (from .net 2.0-3.5).
I know that it isn't a good practice, but I've to live with it for now.
The app is installed with standard msi (generated by Visual Studion setup project).
My issue is that I've .net 4.0 on the box with mscoree 2.4 installed and each time I'm installing my little app the mscoree 2.4 get unregistered and I need to repair .net 4.0 installation in order to get it back in order.
Do anyone faced similar behaviour with .net COMs?
Is there an easy way / workaround to avoid mscoree 2.4 unregistration?
Comment: I have the same problem with mscoree.dll . How did you managed with this issue ?
Answer: I would check out:
Mailbag: Should I re-install the versions of the .NET Framework in a specific order?
Aaron says this is to avoid a couple setup bugs and yours may or may not be in that list. ( You have to follow the links to find out. )


Install OS 10.13 without iTunes 12.7

Question: I need ability to manage my apps but not the app Store. Can OS 10.13 be installed without installing iTunes 12.7. Where can I download OS 10.13 that does not include iTunes?. I will be installing on a Mac Book Pro - Mid 2014.
Answer: You can install install iTunes 12.6.3 on top of / over iTunes 12.7 for all OS that support iTunes 12.7 and both are compatible with iOS 11.
Apple KB: Deploy apps in a business environment with iTunes
You need the direct link, it apparently does not appear as an update.
Mac link.
Windows 32 bit link.
Windows 64-bit Link.
If you've already been using 12.7 you may have luck importing your 12.7 lib  to a clean 12.6.3 Library, as outlined on MacRumors, but I had no joy.
I ended up restoring a backup of my Library [just the catalog not all the tunes] from a time before i updated to 12.7.

Install OS 10.13 without iTunes 12.7


MatLab fmin function

Question: I have an .m file in matlab named PowerMinimiser and two functions in it
function PowerMinimiser
    PowerOut = fmin(minFunction,0,100);
    display(PowerOut)
end

and
function PowerOut = minFunction(varargin)
    RunMode = 2;
    ThresholdValue = 10;
    if nargin > 0
        ThresholdValue  = varargin{1};
    end
    %Receive PowerOut value from .main file and pass in ThresholdValue and
    %RunMode values:
    [PowerOut] = main(ThresholdValue,RunMode);
end

Now what I would like to do is use the matlab fmin function so that I can find a value for the variable ThresholdValue which will give the lowest value possible for the variable PowerOut. The value for ThresholdValue is a number between 1 and 100, and is passed into a function in the main.m where a number of calculations are done and then a value for PowerOut is outputted.
Using the minFunction function I am able to receive and pass the variable fine, using the line
     [PowerOut] = main(ThresholdValue,RunMode);

but I am not sure how to use the fmin function to get the value of ThresholdValue that gives the lowest value for PowerOut. I would like the ThresholdValue value to be shown once the fmin has done the necessary calculations. How can I do this? Any help would be greatly appreciated.
Thanks
Answer: You should use function fminbnd, which replaced fmin function in newer versions of Matlab. To pass function as an argument to fminbnd use @ in front of the function name, like this:
PowerOut = fmin( @minFunction, 0, 100 );

MatLab fmin function


Entropy change in mixing a gas at constant temperature and pressure

Question: The expression given on Wikipedia is (https://www.google.co.in/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&cad=rja&uact=8&ved=0ahUKEwj-_pDA2IfSAhUFto8KHa2kBAwQygQIIDAA&url=https%3A%2F%2Fen.wikipedia.org%2Fwiki%2FEntropy_of_mixing%23Mixing_of_ideal_materials_at_constant_temperature_and_pressure&usg=AFQjCNFVf8mAoquhiL05HeVXC1H3cw54xA)
But If I evaluate it as following I get a different answer .
$$\Delta S=\int q_{rev}/T=\int pdV/T $$
as p and T are constants $$p(V_1+V_2)/T $$
What is wrong with my method ?
Answer: The reference you gave involves mixing two different chemical species together at constant temperature and pressure.  The problem you seem to be solving is mixing the same chemical species with itself at constant temperature and pressure.  For that process, the change in entropy is zero.  If you really intended to determine the entropy of mixing two different chemical species, then the path you identified is not a reversible path for transitioning between the initial and final states of the system.


Should I use a fan or fume extractor for soldering?

Question: I have been starting to solder about once every two weeks. I haven't used any sort of fume extraction or fan, but reading about the health risks, I now understand how important it is to get those fumes away from you. I have some 120mm computer fans lying around that could scatter the fumes and blow them away. Is this adequate for soldering, or should I really just get a fume extractor? I really don't want to spend 50 dollars one one, so I want people's opinions on this. If I only solder occasionally, and use a fan to blow the fumes, do I need a fume extractor?
Answer: Personally, I would always go for a fume extractor. For irregular soldering, most people don't use one, but really if you want to reduce the long term health risks then it is always better to get an extractor rather than just try to blow the fumes away. You could never be sure where the fans are actually blowing the fumes, the harmful chemicals could still be in the air. However, you can use all those fans to build your own fume extractor.
There are lots of tutorials on YouTube and Google on how to build your own fume extractor for soldering that don't cost much money! This is the best way to do it in my opinion! Saves money and gives you a bit of a project to work on too
Comment: [Link for the lazy](https://www.youtube.com/watch?v=z64-RwxSztU). Could be quite a fun project.
Comment: The DIY Perks video said to vent the air outside using ducting. Should I actually do that or should I use a carbon filter like most other fume extractors you can buy?
Comment: Either really. Stick a vent to the outside to get rid of it or use a filter if there is no convenient window nearby
Comment: I built mine myself. Quite enjoyed doing it too!


A/C frozen Suction line

Question: MIS called me, as I'm a Bulidings and grounds TECH. Limited A/C knowledge.
 He said the server rooom was getting hot. Servers put out some heat.
There are 2 units in the room. A Reem and a Rudd unit. The room has no fresh air only room air. Each unit takes room air and for the bottom which blows over the evaporation coils. The condensers are on the roof 2 of them. The filters at bottom of the room units were very clean. I went to the roof and found on the Reem unit a frozen Suction line. As well as a frozen Evapoator coil. I live in syracuse NY. Where the nights get cold. I remember a Contracor many years ago when it was 29 degrees out went to the roof units and overrided something electronically. Because the same thing happened.Low refrigerant will do this i think. 410A
Comment: Please revise your post into the form of a question. The backstory isn't necessarily applicable, but if you leave it, keep it short and separate it for readability. Then as it appears you did, explain what you've checked. Then ask a question.  Based on what you are suggesting, age of the units and the actual model #'s will help. Also, since there are filters in-line, you'll need a licensed tech to evacuate the system to service the filter & oil (most likely)
Comment: The evaporator is inside where you want the cold. The condenser is outside and it gets warm, not cold.  It should be impossible for the condenser to freeze. Even if it was frozen in a block of ice, it would just melt the ice.  Now, the A/C unit may have an interlock to shut down the A/C system when it is too cold... That's not a problem with the condenser, but rather, to protect the evaporator from too-cold outside air.  And seeing no point to run an air conditioner when it is cold out.
Answer: Frozen suction line and evaporator coils can be caused by a few different items.  But basically the A/C unit is making more cooling than the air flow can dissipate. Dirty filters is the first place to look.  They will restrict air flow.  Not enough air flow means inability to dissipate cooling to the room, means freeze-up. If the filters are good, look at the coil itself.  Is it dirty?  Shut the system down, defrost the coil then you can inspect it.  If it is dirty, you have to clean it.  dirt on the coil face will restrict air flow.  Lack of air flow can mean freeze-up. Now check to make sure the blower wheel is clean.  A dirty blower wheel cannot mover air like it should.  If it is dirty, you have to pull that blower wheel and clean it.  Not very much dirt on those fins can reduce the efficiency of the wheel a lot.  Not enough air movement across the coil means freezing. Now think about it this way, you want to direct as much warm air across those coils as you possibly can.  Is there any way to augment the flow of the warm air in the room across those cooling coils? If the room thermostat is calling for cooling those compressors are going to run.  When they run they are going to produce a certain amount of cooling regardless of other conditions in the room.  If you can't dissipate that cooling off the coils they will over cool and freeze.  With a frozen coil, not enough air flow across the coil is 95% of the time the problem.  Either move more air or shut the units for a short period of time to let the warm air catch up.  This is a good start. Good Luck.
Answer: Low charge and low air flow will cause freezing of the suction line. Usually only part of the coil will be frozen if it is low on refrigerant. If it is very cold outside and it is a normal air conditioner it will freeze up. Air conditioners are designed to work when it is hot outside. When the temperature drops so does the head pressure. The head pressure drives the suction pressure. If there is not enough pressure the coil goes below freezing and starts to ice up. Usually units designed to be used while cold outside would have some sort of head pressure control. Once it has frozen all you can do is defrost it and see if it still freezes. If it froze because it was too cold out all will be well once it warms up. Check for anything restricting the air flow such as closed dampers or a dirty coil.
Answer: After you check out all the items that Paul Logan and User76730 suggested, if the coils still freeze you can do the following. 1) Have the HVAC service contractor that services your A/C units install a head pressure control device as user 76730 suggested. I used them on any A/C unit that ran when the outside air temperature was below 60 degrees F. 2) If you need cooling  when the weather is very cold, Have a contractor install a fresh air cooling system that brings in cold outside air and exhausts the hot ceiling air. This type system is rather inexpensive to operate does a good job of reducing the rooms temperature.

A/C frozen Suction line


What is a Heavenly Father? What is spirit-possession in a human being?

Question: If the language of the God-family is disagreeable with the understandings or dogma of Muslim belief, how can I understand the belief that it is possible for a non-human being to possess or inhabit a human being, but it is not possible or true that the Creator of both non and human beings cannot possess or inhabit one of or all of His creatures whenever and however He so wills. Does Islam mean Allah will not inhabit His human being and all of His human beings? How does Islam know the Will of Allah? Is it possible to understand Allah as a and The Heavenly Father, as in the Father of all things and beings?
Answer: The term 'Father' is a Christian rather than an Islamic term as in 'Our Father in Heaven' in the Lord's Prayer.
In the sense that the father is a creator, that it his seed that seeds new life, this is simply understood in Islam as al-Khaliq, the Creator and is one of the attributes of Allah, who is beyond all description. As in Sura al-An'am 6:102

This is Allah - Your Lord! There is no god  worthy of worship except Him. He is the Creator of all things, so worship him alone. And He is the Maintainer of everything.

As for spirit possession, there is possession by jinns.
Comment: Father is also a concept before it is ascribed to a religious expression and therefore can be understood outside of religious expressions. Therefore, I am certain that the Muslim understands Fatherhood. I almost understand that because it is a term embraced in both Judaism and Christianity, Islam will not agree to look at the same thing in the same way. It is clear though to any reasonable person that God as Spirit is therefore the Father of spirits, all spirits and everything spiritual, including Islam. It is ultimately admirable that the Muslim does not venture too far from the term Allah.
Comment: Jinns...if the Muslim concedes that spirit can possess a human body, it seems likely that were it not for religion, the idea that the Father of Spirit can 'take' (or give) possession of a human body would be conceivable and acceptable.


Definition of Bilinear maps.

Question: Please I need a layman's definition of the bilinear map.
Wikipedia has a brilliant one, I however don't seem to make anything of it.
Answer: Loosely speaking, a bilinear map satisfies:
$B(x+y,z) = B(x,z) + B(y,z)$ (additive in the first "coordinate"),
$B(x,y+z) = B(x,y) + B(x,z)$ (additive in the second "coordinate"),
$B(cx,y) = cB(x,y) = B(x,cy)$ (preserves scaling in each "coordinate").
Think about $B$ as multiplication of real numbers for example: $B(a,b) = a\cdot b$
$B(x+y,z) = (x+y)\cdot z = x\cdot z + y\cdot z = B(x,z) + B(y,z)$
$B(x,y+z) = x\cdot (y+z) = x\cdot y + x\cdot z = B(x,y) + B(x,z)$.
$B(cx,z) = (cx)\cdot z = c\cdot(xz) = x\cdot(cz) = B(x,cz)$
Comment: This is a great answer, it contains a simple but detailed example to illustrate the definition. The definition is broke down into legible pieces without the use of jargon that the layman may not understand.
Comment: Draw the graph of it and you'll understand why it is called bi-linear.
Answer: As RobertIsrael already mentioned, a bilinear map is just a mapping which is linear in two variables.
If you have a linear map $L$ which maps a vector space $X$ into another space $Y$ then you can write,
$$ L( a \vec{u} + b \vec{v} ) = a L( \vec{u} ) + b L (\vec{v}) $$.
With a bilinear map you are mapping from a cartesian product of vector spaces to some other vector space. So let $B: X \times Y \rightarrow Z$ be a bilinear map. Then we can write,
$$ B(a \vec{u} + b \vec{v},c \vec{s} + d \vec{t}) = ac B(\vec{u},\vec{s}) + ad B(\vec{u},\vec{t}) + bc B( \vec{v}, \vec{s}) + bd B(\vec{v},\vec{t}),$$
A simple example of such a map is the mapping $f:\mathbb{R} \times \mathbb{R} \rightarrow \mathbb{R}:(x,y)\rightarrow x\cdot y$. Where we consider the real numbers to be a vector space over the real field.
Another example of such a mapping is the inner product (when its restricted to only have real values).
Comment: Souldn't it be *ad B(u, t)* instead of *ad B(u,s)*?
Comment: @PouriyaZarbafian, yes I apparently made a typo. Thanks for catching that!
Answer: Do you know what a linear map is?  A bilinear map is a map in two variables (each of which could take values in some vector space) that is linear in each separately.  That is,  $B(x,y)$ is a bilinear map if for each $x$, the map taking $y$ to $B(x,y)$ is linear and for each $y$, the map taking $x$ to $B(x,y)$ is linear.

Definition of Bilinear maps.