Can I fit 3 x9 speed crankset to 3 x 8 speed cartridge

Question: I have a Merida hybrid cycle fitted with Shimano XT Deore 3 x 8 speed (42/32/24T). The crank has a few worn teeth and I would like to replace with Shimano XT Deore (48/36/26T). The seller states this is for 3 x 9 speed gear set, can I fit to my cycle?
Answer: Yes, there are no complications with running a 9 speed crankset on an 8 speed drivetrain. You can see image below that some 9 speed cranks are even listed as being 9/8 speed cranks. You shouldn't encounter any problems, but you will have you readjust your front dérailleur to make room for the larger ring, and double check your chain length on big rings after it's installed.
Answer: Strictly speaking, one crankset will have been manufactured for an 8-speed chain, the other will have been manufactured for a 9-speed chain. That is basically the difference between the two.
The external widths of an 8-speed chain and a 9-speed chain differ by something like a few tenths of a millimetre. It is arguable whether this amount makes any practical difference to your shifting experience.
On the one hand, the bike companies will say that it does. Everything that is part of the chainset will have been manufactured precisely, based upon a certain chain width, and anything different will give you an "imperfect" experience. But then the bike companies also have a vested interest in selling you components.
On the other hand, the difference is so small that many people happily run this setup without reporting any ill-effects.
Aside from this, I agree entirely with @ShemSeger's answer, but I did think it was important to emphasise to you that there will be a difference, albeit slight, between the two cranksets.
Answer: The front is effectively independent of the back - a triple which is "9 speed" should work fine if you replace it with a triple "8 speed" and vice versa (the speeds for the rear when marketing front cranksets are marketing). Similar with derailleurs in the front vs whats going on in the back.
You will probably need a new chain, and you need to see if the front derailleur is even rated to take a 48t (which I suspect it probably isn't). This can be done by checking the spec sheet for the front derailleur. If not, you need a FD which has the same cable pull as your shifters which has the capacity.
Also, on a Deore XT crankset, you can buy replacement chainrings and install them, so you could save a decent amount of money this way.
Comment: As @PeterH noted above the chain starts getting narrower overall as the number of rear cogs it is designed to support increases ([Wikipedia article on Bicycle Chain](https://en.wikipedia.org/wiki/Bicycle_chain#Width)). I think I've read that this leads to tighter spacing between the chainrings of an "optimal" crankset. I doubt if this would make much difference between 8 and 9 speeds where the difference is ~0.5mm, but it might start being significant going to 10 or 11 speeds.


Which forecasting method should be selected in case of contradictory results from different accuracy measures?

Question: I'm comparing some forecasting methods using four accuracy measures: Mean Absolute Error (MAE), Mean Squared Error (MSE), Mean Absolute Percentage Error (MAPE), Mean Absolute Scaled Error (MASE). The results are contradictory according to these different measures; which method finally should be selected? Is there any solution in this case?
Comment: Do you have any measure/estimate of the consequences of being out by a given amount in your forecast?
Comment: NO, I don't have any measure for that end, Just I do the forecast using some methods (like SES, Theta, Naive,..) and I compare their accuracy using the mentioned measures
Answer: Disagreement among these measures is actually a natural thing, as they target different objectives. Suppose you'd know the true probability distribution of the random variable (call it $Y$) of interest. Then, in order to minimize the MSE, you'd state the mean of $Y$ as a forecast. In order to minimize the MAE, however, you'd state the median of $Y$, which is different from the mean if the distribution of $Y$ is skewed.
Hence it is easily possible that method A gives better forecasts of the mean, whereas method B is better for the median, which makes the measures disagree. In order to choose an accuracy measure, you should think about which concept (mean vs median vs ...) you're interested in.
PS: MAPE and MASE seem to target more exotic objectives which are less popular than the mean and median. See http://arxiv.org/pdf/0912.0902.pdf for details on this.
Comment: +1. Note that the expected absolute percentage error (APE) is minimized by the (-1)-median of the future distribution, see p. 752 in [the published version of Gneiting's paper](http://www.tandfonline.com/doi/abs/10.1198/jasa.2011.r10138). The MASE actually doesn't target anything exotic at all. It's a scaled version of the MAE - scaled by the in-sample error of the random walk forecast, which is a scaling factor that is *independent of the forecast and the future distribution*. Thus, the expected MASE is minimized by the same quantity as the expected MAE, namely the median.
Answer: It's quite common to have conflicting values for different error metrics like MAE, ME, RMSE, MAPE. There are two main reasons behind that
1) The way the formulas for those metrics are defined.
2) The nature of your data itself.
While you can't do much with regard to first reason.You should really examine the nature of your data, to decide on selecting the error metrics to compare different models.
Lets take a very basic example, suppose your data series has few values which are zero or very small ( close to zero), In that case MAPE( Mean Absolute Percentage Error) would not be a correct metric to compare your mode.Even though your forecast might be reasonably good, MAPE(both in sample /out of sample) could be very high due to those zero values.
Bottom Line : Examine your data.
The Problems I deal with : The previous approach works quite good if we have handful of time series. But what if we are dealing with selecting forecasting models for 300-500 time series ( a common case in supply chain, retail, manufacturing). Well the best approach is to calculate all the metrics for every model like ME, RMSE, MAPE, MPE, MAE, MASE( Mean Absolute Scaled Error) or any other metrics which is used in your domain.
Select the model which gives low values for most of the error metrics.
This process can be automated.
For a list of modern error metrics you can refer
[here](http://robjhyndman.com/papers/mase.pdf "


How to get debug information from a c++ application which is shipped to customer?

Question: I am not sure if it is possible but assume that I have a c++ application and I am sendimng to our customers. The application may have bugs and hence it fails, but I can not get any information about the place that it failed. Is there any way that I can get debug information from such application?
I am using visual studio for development.
Comment: Logging, logging and even more logging.
Comment: @JoachimPileborg any library? any documentation or tutorial?
Comment: In addition, look into crash dumps, writing your own minidump using functions found in WinDbg.dll, etc.
Answer: Use a lot of logging:

log start and end of every important action you are doing, of course
make sure it doesn't effect application performance too much.

log any errors from API calls or other failures from your routines.

And finally you can automatically generate crash dumps and allow user to submit this dump or lets say crash report including your application logs. This article will help you on how to catch you application crash and generate dump file: http://www.codeproject.com/Articles/1934/Post-Mortem-Debugging-Your-Application-with-Minidu#_Writing_a_Minidump_with MiniDumpWri


Error while implementing oauth provider using oauth-plugin(pelle)

Question: I want to secure my web application's API using oauth. I searched a lot & finally decided to try following link http://stakeventures.com/articles/2007/11/26/how-to-turn-your-rails-site-into-an-oauth-provider.
I followed the steps & I am able to register new application successfully.
I am using devise for authentication & the pelle's oauth-plugin is compatible with acts_as_authenticated, restful_authentication or restful_openid_authentication as mentioned in the above post.
So I am getting following error when I try to run http://localhost:3000/oauth/autherize
<code>NameError (undefined local variable or method `login_required' for #<OauthController:0xc410490>):
</code>
I searched for the solution & I got following link http://groups.google.com/group/oauth-ruby/browse_thread/thread/3656e3904050fd9a.
Now is there any alternate solution other than mentioned in above link. If yes then please guide me about that & if not then please tell me how to actually implement the solution.
Where actually the oauth_controller_spec.rb file resides? Do I need to fork & edit the plugin for that?
Answer: You may want to have a look here: authlogic and oauth-plugin. Maybe this answer is helpful.


Why always the number of arbitrary constant is equal to order of a Differential Equation?

Question: Why always the number of arbitrary constant is equal to order of a Differential Equation?
Comment: An $n$th order differential equation will have $n$ arbitrary constants in its solution.
Comment: I think you will need to elaborate a little on the context and scope of your question before you can get a good answer. But briefly: there are as many constants as there are derivatives.
Answer: In general, the number of arbitrary constants of an ordinary differential equation (ODE) is given by the order of the highest derivative.
e.g. $$y\color{red}'=f(x)$$ has $\color{red}{\text{one}}$ constant of integration, $$y\color{red}{''}+y'=f(x)$$ has $\color{red}{\text{two}}$, $$y\color{red}{'''}+y''=f(x)$$ has $\color{red}{\text{three}},$ etc..
To generalise, suppose we've an ODE of the form $$a_ny^{(\color{green}{n})}+a_{n-1}y^{^{(n-1)}}+\cdots+a_2y''+a_1y'+a_0y=f(x), $$ where $a_i$ is a function of $x$.
Then the number of arbitrary constants in the general solution to this equation is $\color{green}{n}.$

Notation: $y^{(n)}=\frac{d^ny}{dx^n}$
Comment: Can we show this fact from an algebraic point of view. I mean, since the solution of a linear (homogeneous) ODE of order $n$ is a vector space whose dimension is $n$, if $y_i$ is each of this element, then any linear combination of these $y_i$, say, $y = \sum_i \alpha_i y_i$ where $\alpha_i$ are arbitrary constants $\neq 0$, spans the set of all possible solutions of the ODE. Am I write?


How to bind SP list to Spfx extension as dropdown

Question: I have a SP List with 5 items and Url to it. So now I would like to add this SP list as dropdown to SPFX extension. I was wondering how to achieve this as I know how to add as an WebPart but not to SPFX extn.
Answer: According to my research and testing, we can bind dropdown list from a SharePoint Online list using react and PnP in the SharePoint Framework (SPFx). Please refer to the following document to bind dropdown list from SharePoint list:
https://www.enjoysharepoint.com/spfx-bind-dropdown-list-from-sharepoint-list/
Note: Microsoft is providing this information as a convenience to you. The sites are not controlled by Microsoft. Microsoft cannot make any representations regarding the quality, safety, or suitability of any software or information found there. Please make sure that you completely understand the risk before retrieving any suggestions from the above link.
Hope it can help you. Thanks for your understanding.
Comment: Thank you for your suggestion, which means it is possible to bind them in spfx extension


Can compound relative pronoun be omitted?

Question: The sentence "we can do to keep them down is great", which I used the grammar webpage to check. The grammar webpage is showing it is correct. But I think the more correct sentence would be "whatever we can do to keep them down is great".  It is means "whatever" can be omitted, right?
Comment: Whatever the webpage says, the sentence does not make sense. It needs a subject such as _whatever_ or _anything_.
Comment: _Cost_ is singular, so it should be _keep it down_ (or use _costs_ instead). You still need a subject for the main clause. We're not supposed to do proofreading, but I'll just mention that the first part needs to be _Concerning the cost(s)_, or _As concerns the cost(s)_.
Comment: @Kate Bunting. thank you for replying.
let me modify this sentence
1.  "we concern the cost, whatever we can do to keep them down is great."
2.  "we concern the cost, we can do to keep them down is great."
which one is correct? thank you again.
Answer: "Whatever" is necessary, because the sentence requires an object of "can do."


Is the phrase "parking garage" redundant?

Question: Is there an instance in which the use of the word "garage" as opposed to "parking garage" would imply something other than a structure where vehicles are parked?
Comment: When you get your car fixed, you can take it to a *garage* which isn't a parking garage.
Comment: many many types of garages in the states.
Comment: an *appliance garage*...  https://goo.gl/images/QU7tqC
Comment: Also [this is a ***parking*** garage](https://goo.gl/images/9ZnHxF)  whereas [this is just a garage](https://goo.gl/images/ob6vwq)
Answer: Even though one parks in the garage in one's own house, it isn't referred to as a "parking garage", only as a garage. "Parking garage" refers to a large garage with many parking places, such as a public one or one belonging to an office building. It's the covered equivalent of a parking lot.
Answer: No, its not.
Garage can mean where a car may be serviced or fuelled.
Answer: In my opinion there are cases where it is and isn't redundant.
According to the Wikipedia disambiguation page a garage may refer to:

"Automobile repair shop, where vehicles are serviced and
  repaired."

It would be very strange to say that your car is parked inside the repair shop. Especially if it's on a car hoist with its wheels removed. Therefore I claim it is not a parking garage at all.

"Bus garage, a building or complex used for storage of buses when not
  in use."

The buses at this garage, or maybe (depot more commonly) is for the parking of buses. If you use the word "garage" as the place where the buses are kept when not operating, then parking garage in this sense is redundant because you are parking them in this garage(place where buses are parked).

"Garage (residential), a building or part of a building for storing
  one or more vehicles."

If you keep your car in your residential garage, it's a garage where you park your car, so parking garage would be redundant. However some people have a garage in which they don't park their cars, they might keep only tools or equipment, then it's not a parking garage, it's just a part of the house or outbuilding that may been designed to hold cars and repurposed for something else.

"Multi-storey car park, a building serving as a public parking
  facility."

If a "garage" means the area where cars are parked, then parking garage here is redundant.

"Filling station, where vehicles take on fuel or recharge"

This is a tricky one. I don't call a filling/service/gas station a garage at all. Here you would be parking your car. If a filling station is a garage and you park your car, even temporarily while you get fuel or buy a donut. Then maybe it could be redundant, but I'm not sure about this.

Is there an instance in which the use of the word "garage" as opposed
  to "parking garage" would imply something other than a structure where
  vehicles are parked?

Yes, see my explanation of a repair shop and residential garage.
Also, just because a term is redundant (can also be called tautologous), doesn't necessarily make it wrong or frowned upon.

"They filed through the doorway one by one."

Any ordinary doorway would most likely only accommodate a single person at a time, so "one by one" seems tautologous. However as a matter of style it's fine, at least I argue.
Wikipedia meanings of garage


Capturing UDID using mobile browsers

Question: Is there a way we can capture UDID using mobile browsers.
I have been working on a application  which needs to capture a mobile's UDID/ IMEI information when I'm using the application over my mobile phones and this needs to capture IMEI. Please help :)
Answer: No. It is not possible to get a unique identifier such as the UDID or the IMEI on mobile browsers.
If you want to "identify" your users, you will have to use a cookie (but these can be deleted by your user). Another approach which is interesting can be ssen at http://panopticlick.eff.org/ - they "identify" browsers by their capabilities.

Capturing UDID using mobile browsers


How to send a document from a document library as an attachment in an email?

Question: I need to add a column to a document library that will have the text "Send in email" for each document in the library. If a user clicks on it, it should open a new Outlook email and automatically add that document as an attachment. The user can then type in a subject and a receiver and a message and so on, but the important thing is that the document must be added as an attachment to the email.

Is this possible?
And if it is, how could I achieve this with just JavaScript? I figured out how to create the column and add the text "Send in email" to it and I can fetch the path of the document too, and in an anchor I added a Mailto and it works fine (opens a new email) but it doesn't add an attachment. From what I've read this is not possible due to security reasons. Is there an alternative to this, where I can still add the document as an attachment to an email?

On a side note, everyone in our company has Outlook installed on their machine and they all have permissions to access the SharePoint site (it's an intranet site).
If the attachment can't be added, could it perhaps be possible to download the document to a temp directory, then add it to a new email? Or is this also impossible?

I'd really prefer this in JavaScript since I'm not that advanced with C# yet.
Answer: as you mentioned due the security you can't add attachment in new email.
All that you can it is create "mailto:" link with pre-filled fields (to, subject, body), but it also might not work, if client has specific settings or he hasn't outlook.
As workaround I may suggest you have a look at using workflows, the basic scheme may looks as follows:
An user click on the link (custom action) and run workflow "Send email".
The workflow get current item data, attachment links and send email with attachments.
In my case exist a nuance, out of the box SharePoint workflow doesn't allow you to send email with attachments, but you can extend their functionality using 3rd party solutions, I would recommend you to use Plumsail Workflow Actions Pack, and "Send e-mail with attachments" workflow action for this.
P.S.: I'm one of the developer of this product and know it as very good product for such purposes.
Comment: I know I could use a workflow but the thing is that the person who sends the email with the document as an attachment has to be able to fill in the body of the email. So the email can't be one that is automatically sent, it has to open in the client email program so that he/she can add some more text and then send the email. All our employees have Outlook installed.
Answer: After serious investigation I fear there is no such option when limited to JavaScript. An attachment cannot be added directly to an e-mail. An alternative would be to add the URL of the document you want to send to the body of the e-mail.


Noise and Blur in Cuda

Question: I'm trying to add noise and blur functions to my project in Cuda and after quite some research i've hit a bit of a stumbling block, I've read up on the Gaussian blur matrix but i'm still having trouble getting a working piece of code which would be able to blur certain parts of an image, I've managed to get a form of noise to show.
If anyone could give a bit of help in either explaining how to implement a Gaussian or a simpler blur method or even providing a bit of code which implements blurring.
Gratefully appreciated!!
Answer: Gaussian blur is a separable filter, so you can apply the 1D kernel first to all the rows in your ROI and then to the columns of the blurred rows.
The tricky part with CUDA is that this is a neighbourhood operation, so typically you will need to have each block overlap by half the kernel size in order to get the required neighbourhood pixels into shared memory.
Answer: FYI, these are two separate questions and should be asked separately in this site.
Regarding the blur - for large blur kernels (strong blurs) the best approach is to use the FFT on the image and on a Gaussian noise kernel image then multiply the results using the complex multiplication and inverse FFT that result. You will have to implement a FFT-Shift function yourself and if you are using color images, you will have to split the image into a separate buffer per channel.
For small blur kernels (gentile blurs) the simplest approach is for each pixel in the result image, sum nearby pixels in the source image (with a Gaussian weight function).
Regarding the noise - test easiest approach is to load a pre-generated pseudo-random generator's result image into CUDA after transforming it from uniformly distributed random numbers to normal distributed random numbers. E.g. this question.
The a correctly size region in the random image should be multiplied by the noise sigma and added to the source image to receive the result.
Last time I checked there was no random buffer generation solution for CUDA, however, that was a few years ago.
Update: CUDA now has cuRand so you should be able to generator random numbers instead of using a pregenerated random buffer.
Comment: On the random buffer comment - NVIDIA now ship a dedicated random number generator library for CUDA. See [cuRAND](http://developer.nvidia.com/curand) if you are interested.

Noise and Blur in Cuda


If I use Weight of Evidence to transform categorical variables, do I still need to inform their indexes to Catboost

Question: I'm using Weight of Evidence (WOE) to encode my categorical features. Do I still need to inform Catboost that they are categorical features by using cat_features parameter?
Answer: The goal to encoding is to transform categorical into numerical so that an algo can learn on them. So the general answer would be no, after encoding into numerical you shouldn't declare them as categorical anymore.
However, as its name suggest it, catboost is designed to handle categorical... so for catboost you probably want to use categorical. In this case you shouldn't need to encode categorical at all... There are some very specific exceptions (over-fitting), and even in that case you might want to start with other parameters - min data in leaf for exemple before getting into relatively complex encoding. WoE encoding makes sense for simpler models (basically it should work well with logistic regression by design).


Will NVME SSD speed up heavy queries, e.g. selects at large offsets / table scans etc?

Question: If the database data will be on NVME SSD which let's assume is 4x faster than an ordinary SSD will queries like SELECT something OFFSET 100000 and the like typically also be much faster (of course when they are not cached/buffered etc)?
Comment: This will only help if disk is what your queries are actually waiting on.
Answer: It is quite obvious, is it not?
If the IO side of the database is the bottleneck, then having a better IO side will speed things up.
Now, most of the time - outside of data warehouses - IO should not bottleneck that bad once you leave the really low IOPS side of Hard discs. A proper database server will have enough RAM (again, outside of data warehouses) hat a lot is cached - which means that no, you may not really need THAT much database bandwidth and it will likely NOT get you 4x the throughput.
But if you have like 5gb RAM and a 100GB table and you make a table scan, then yes, faster IO means faster query processing. Obviously.
Also Note: NVM does not necessarily mean the SSD is also faster. Not sure they are any, but you better make sure your NVM SSD is up to the task. There are some really cheap ones that are a: not optimized for the write performance needed and b: just too slow to use up the NVM ports.
Answer: I am in the process of provisioning for an NVME RAID. Before committing to purchase, I wanted to try and benchmark how queries requiring a scan would benefit from better transfer speeds.
I currently have an SSD RAID with read speeds in the neighbourhood of 900MBps, and an HDD RAID with read speeds in the neighbourhood of 100MBps. Wanting a quick and dirty metric, I've tested on only 2 tasks:
(1) pulling all records (less than 100) matching an unindexed column
(2) pulling one record offset by 100 000 000.
Times are:

Time to execute (1): 82s on SSD vs 780s on HDD
Time to execute (2): 49s on SSD vs 480s on HDD

Differences in time to execute are very close to read speed differences. I'll update with results on NVME RAID when it is operational
[EDIT]
I've been able to run similar queries on an NVME system (2100 MBps vs 900 MBPS on our SSD array). Queries execute 30% faster, not twice as fast. Clear signs that CPU is becoming an issue.


What factors determine whether wind resistance will have an important effect?

Question: What factors determine whether or not wind resistance will have an
important effect on the trajectory of a projectile?
Comment: I think this will help: http://demonstrations.wolfram.com/ProjectileWithAirDrag/
Answer: As a general rule of thumb, you can often assess the importance of air resistance by considering the mass of the air swept out by an object compared to the mass of the object itself. Though if you are being a little more accurate, you should estimate the ratio of the drag force to a relevant force for your problem.
Air Drag
To start, let's first try to figure out what the form of air resistance is. By understanding the form it takes, we'll have a better intuition about its importance.  By dimensional analysis, we expect the form of the drag force to be
$$ F \sim \rho_{\text{air}} A v^2 $$
which agrees well with the canonical form
$$ F = \frac 12 C_D \rho_{\text{air}} A v^2 $$
here $\frac 12 C_D$ taking the place of the unspecified dimensionless constant. Being a dimensionless constant, we should expect $C_D/2$ to be of order ~1. Typical values for $C_D/2$ are closer to ~0.1. The details of the value of $C_D$ depends on the shape and speed of the object, in particular the Reynold's number, but typical values are around 0.5 for smooth spheres, or 0.3 for most cars or so, wikipedia lists several values, and nasa has values for a baseball between 0.5 and 0.2 depending on speed. But we will not be too worried about the particular coefficient in front since we are going for a rough rule of thumb at this point.
We can additionally understand this form for the air drag with a simple model.  In a very simple model, we could treat all of the air molecules at rest, wherein an object moving through the air will experience a drag force because it will continuously come into contact with the air molecules.  Imagine that the air has density $\rho_{\text{air}}$ and each molecule has mass $m_{\text{air molecule}}$, as our object moves through the air, with velocity $v$, every time it collides with an air molecule it will have to transfer some momentum $\sim 2 m_{\text{air molecule}} v$ to each molecule it collides with.  Each air molecule occupies on average a volume $m_{\text{air molecule}}/\rho_{\text{air}}$, and if our object moves with velocity $v$ and cross section $A$, in a small amount of time it will trace out a volume $ v A \Delta t$, so in total, the momentum we must transfer is
$$ \Delta p = \left( \text{ momentum transferred per molecule } \right)  \times \\  \left( \text{ molecules per volume } \right) \times \left( \text{ volume traced in a small time } \right) $$
$$ \Delta p =  \left( 2 m_{\text{air molecule}} v \right) \left( \frac{ \rho_{\text{air}} }{ m_{\text{air molecule}} } \right) \left( A v \Delta t \right) \sim \rho_{\text{air}} A v^2 \Delta t $$
which gives us a force of
$$ F \sim \frac{\Delta p}{\Delta t} \sim \rho_{\text{air}} A v^2 $$
which agrees in form to both the dimensional analysis and the known formula.
To be clear, I'll point out as a small aside that these arguments only apply to air drag in the limit of large Reynold's number (which is totally applicable to everyday objects in air), where we can treat the air as turbulent.  Stoke's Drag ( $ F \propto v $) occurs in the low Reynold's number limit.  For more on Reynold's number, see this answer .
Importance
In physics, we cannot really say whether any dimensionful quantity is by itself big or small.  By changing units one could always change the form of the number.  1 meter sounds like a regularly sized number, but it is $10^9$ nm, or $10^{-16}$ light years.  But, dimensionless numbers we can really say something about.  So, let's try to determine whether air resistance is important by taking its ratio with another force.  If that ratio is small, we are probably safe in ignoring the impact of air resistance.  As our other force, let's take gravity, since we most often are interested in the effects of air resistance when it comes to ballistic problems.  We are interested in the ratio
$$ \epsilon = \frac{ \rho_{\text{air}} A v^2 }{ m g } $$
This ratio is a dimensionless number, and so should reveal whether air resistance is important or not in a real, quantifiable sense.  If you were doing another sort of problem, you should instead determine the ratio of the air drag force to whatever force you thought was relevant.
But, if we are interested in a decent rule of thumb, we can simplify further.  In a ballistic problem, the scale for the velocity of the object can be taken to be $ v \sim \sqrt{ g L } $, where $L$ is something like the range of the projectile, on purely dimensional grounds, at which point, our ratio becomes
$$ \epsilon = \frac{ \rho_{\text{ air }} A g L }{ m g } = \frac{ \rho_{\text{air}} A L }{ m } = \frac{ \text{ mass of air swept out }} { \text{ mass of object }} $$
wherein we recover the rule of thumb I gave at the top.
Another interesting way to rework the rule of thumb (though less accurate) would be to express the mass of the object in terms of it's own density.
$$ \frac{ \rho_{\text{air}} A L }{ m } = \frac{ \rho_{\text{air}} A L }{\rho A R } = \frac{ \rho_{\text{air}} }{ \rho } \frac{ L }{ R} \sim \frac{ L }{ 100 R } $$
Where in the last step, I've taken the typical densities of solid objects to be $\sim 1 \text{ g/cm}^2 $, a factor of 1000 less than air, and tried to be slightly more accurate by putting back in another factor of 0.1 for the $C_D/2$ we dropped.  This last rule of thumb suggests that air resistance is important when an object moves 100 times its own size through air, but is the most inaccurate form we have, and assumes the object under consideration has a density near to water, or said another way, that it nearly either floats or sinks, but this form is easy to do in your head.  This form is reminiscent of Newton's approximation for the impact depth.
Example
Let's demonstrate this rule of thumb with a simple example.  I'll try to simulate throwing a baseball at different speeds, both with and without air resistance taken into account and compare the effect it has on the range the ball travels.  For my baseball, I'll use
$$ m = 145 \text{ g} \quad A = \frac{\pi}{4} \left( 9 \text{ in} \right)^2 \quad \rho_{\text{air}} = 1.2 \text{ kg/m}^3 \quad g= 9.8 \text{ m/s}^2 \quad \theta_0 = 20^{\circ} \quad y_0 = 2 \text{ m} \quad C_D = 0.3 $$
Here I show the results of the simulation.  The darker lines are with air resistance taken into account, and the lighter lines are without.  The colors correspond to different initial speeds.

And here is a table summarizing the distances travelled with ($L'$) and without ($L$) air resistance, the percent error you would have gotten in the range if you ignored air resistance $\Delta L/L$, and our estimates for the relative importance of air resistance from above.
$$
\begin{array}{c|lllll}
v_0 (\text{mph}) & L (\text{ft}) & L' (\text{ft}) & \Delta L/L & \frac{\frac 12 C_d \rho A v_0^2 }{ m g } & \frac{\rho A L}{m} \\
\hline
5 & 4.96 & 4.77 & 0.03 & 0.03 & 0.51 \\
10 & 11.2 & 10.3 & 0.08 & 0.10 & 1.2 \\
15 & 18.8 & 16.5 & 0.12 & 0.23 & 1.9 \\
20 & 28.1 & 23.3 & 0.17 & 0.42 & 2.9 \\
25 & 38.9 & 30.2 & 0.22 & 0.65 & 4.0
\end{array}
$$
So, in particular, notice that when the ratio of the mass of air swept out to the mass of the object is small, air resistance isn't that important.  And furthermore, if you actually calculate the ratio of the air resistance force to the other relevant force, this gives you a more accurate measurement of whether air resistance is important, and in particular, if the value is small, it gives you an quantitative estimate of the expected deviation of your answer.
Further Reading

Introductory physics: The new Scholasticism. Hogg and Mahajan arXiv:physics/0412107
Air Resistance. David Hogg arXiv:physics/0609156
Real World Ballistics: A dropped bucket. David Hogg arXiv:0709.0107
Comment: If I'm considering the mass of the air swept out, doesn't that imply a linear relationship with the velocity and not a quadratic one?
Comment: Great answer. One comment: When you first define $\epsilon$ you leave out the dimensionless factor $C_D/2$. Any chance you could mention typical order of magnitudes of $C_D$ at that point? Otherwise I don't know how small $\epsilon$ really needs to be in order for the ratio of the forces to be small.
Comment: @JerrySchirmer not sure what you're referring to.  The fact that drag is $\propto v^2$ has one $v$ from sweeping and another $v$ from momentum imparted.  The air swept out is $\propto L$, and as a simple scaling argument for a projectile $v \sim \sqrt{ gL }$.  These are all consistent with one another.  Drag $\propto v$ is only for low Reynold's number, in which the simple model is flawed.
Comment: @BMS tried to clarify.  being dimensionless we expect $C_D \sim 1$ or so.  Typical values are closer to ~0.1.  Included links to wiki and nasa for some values.
Answer: The drag force [1] is proportional to the square of the velocity, the density of the surrounding medium and the product of the cross section of the projectile and the drag coefficient [2] of your projectile. You need to compare this force to other forces involved to determine if you can omit it in your calculations.
[1]https://en.wikipedia.org/wiki/Drag_%28physics%29
[2]https://en.wikipedia.org/wiki/Drag_coefficient
Answer: The forces which a fluid through which a solid body is moving can be separated on the basis of their direction: the force along the body's direction of motion is a drag. The force perpendicular to the direction of motion (assuming for simplicity the body to be rotationally symmetric with respect to the velocity axis) is called lift.
The drag comprises various terms, called respectively skin friction, form drag, interference drag, induced drag and wave drag. The total drag on an object depends on which of these components dominates. For streamlined objects, total drag decreases at first with increasing air speed, so that the total drag has a minimum at some intermediate speed, then increases as airspeed increases further. For non-streamlined objects, the law discussed elsewhere ($\vec F\propto -\vec v$) is roughly correct.
For compact and dense bodies like a bullet, neglect of the lift is easily justifiable, leaving only the resistance term. For less dense, and elongated bodies the lift can become the dominant (though by no means the only force). The ratio of the two can be expressed in terms of a coefficient called $L/D$, which is the major term influencing the efficiency of streamlined bodies like wings, fuselage, whole airplanes, and so on.
Wikipedia has good discussions of all of these terms.


Is there a "URL-Structure" for Users and Groups I can access via Hyperlink?

Question: I have a Custom WebPart which gets credentials from the site into a GridView-Table. The result (user and credential) is shown as strings. I want to create a Hyperlink to the users e.g. mysite, instead using strings. Is this possible?
Answer: There are built in web-parts for this, but I always feel they aren't quite right.
So what you need to access is:
SPWeb > SPGroupCollection > ForEach SPGroup > ForEach SPGroup.Users > SPUser.OwnedGroups
Then display out your tree like:
Users > Groups
or
Groups > Users
The code for getting the properties is:
<code>SPServiceContext serviceContext = SPServiceContext.GetContext(SPSite);
UserProfileManager manager = new UserProfileManager(serviceContext);
UserProfile profile = manager.GetUserProfile(oUser.ToString());
ProfileValueCollectionBase FirstName = profile.GetProfileValueCollection("FirstName");
ProfileValueCollectionBase LastName = profile.GetProfileValueCollection("LastName");

if (profile["PictureURL"].Value != null)
{
    ProfileValueCollectionBase baseVal = profile.GetProfileValueCollection("PictureURL");
}
else
{
     //Default image
}

var userUrl = profile.PersonalUrl
</code>
Comment: Hi Hugh, thanks for your answer. I have the URL as a string in a Datatable and want to create a Hyperlink out of the URL. I tried to build a html in the datatable. But the datatable does not accept html, only Content :) Do you know how I can make a string-url in a datatable(gridview) into a Hyperlink?
Comment: From code behind, you would have to override the renderer. Or have it print out in some sort of pseudo tags that a javascript function updates on page? The two things that instantly come to mind for fixing that.


When did Higgs particles first appear in the early universe?

Question: When did Higgs particles first appear in the early universe? For example, did they first appear during the electroweak epoch, the quark epoch, or...?
Answer: The Higgs boson gains mass by "eating" the Goldstone mode corresponding to spontaneous electroweak symmetry breaking, so it appeared at the end of the electroweak epoch.  Before the electroweak epoch, all particles were completely massless and travelled exactly at the speed of light.
Comment: Actually it is still not quite right. The Higgs scalar field (not the "Higgs boson") contains 4 degrees of freedom. After electroweak symmetry breaking three of these become the massless Goldstone bosons which are eaten by the *gauge fields* to give masses to the W and Z bosons. The remaining degree of freedom of the Higgs field becomes the massive Higgs boson.
Comment: Now you've lost me. I thought Goldstone bosons are massless. The Higgs boson is massive as we all know. Right?
Comment: @flippiefanus You're absolutely right.  Sorry about that, I've corrected my answer.  See the last line of page 3 of http://home.fnal.gov/~lykken/Physics_Today.pdf
Comment: @flippiefanus I'm not an expert on the matter, but it sounds like you are - you should answer the OP's question yourself! :-)
Comment: When it comes to what happened during the early universe, I'm not an expert either. :-)


Why is application deployed on Amazon Elastic Beanstalk not accessible?

Question: I have deployed Spring MVC & MySQL based application on Amazon Elastic Beanstalk. The RDS instance of MySQL is working perfectly. I deployed my application war on Beanstalk using Tomcat 6 (which is referring to RDS instance) and the EC2 instance is running successfully as per the AWS Management Console intimation but while accessing application URL I am facing the following issue
<code>Error 324 (net::ERR_EMPTY_RESPONSE): The server closed the connection without sending any data.
</code>
Note: Availing free services of AWS. I have defined instance type as small for RDS and medium for web application and do have S3 instance with 36mb data.
Could any one suggest me what would be the problem?
Answer: I resolved the issue by creating EC2 security Groups to the DB instance.


What is the literal meaning of the scientific name for the cactus wren?

Question: What does the scientific name Campylorhynchus brunneicapillum mean? I simply want to find a way to decipher the meaning of scientific names. In the past I had to translate the names syllable by syllable using an abbreviated Latin dictionary to get a rough idea of the meaning. I can not find an on-line Latin translator that works - and not all scientific names are Latin.
Answer: According to the Helm Dictionary of Scientific Bird Names:

Kampylos, καμπúλος (Greek): curved, bent;
Rhynchos, ῥύγχος (Greek): bill.

Also, for the specific epithet:

Brunneus (late Latin): brown;
Capillus (Latin): hair.

Page with the Genus name: https://books.google.com.au/books?id=-RfSBAAAQBAJ&lpg=PP1&pg=PA87#v=onepage&q&f=false
Page with the specific epithet: https://books.google.com.au/books?id=-RfSBAAAQBAJ&lpg=PP1&pg=PA78#v=onepage&q&f=false
Comment: PS: I already knew this by heart because I studied Ancient Greek (and Latin is quite obvious to me because I speak a Romanic language), but I linked that "birds names dictionary" so you can have another source to search. Also, have in mind that it's complicated to use a regular Latin or Greek dictionary as you use an English one because you have to know the declension and the nominative form of the word. For instance, *androgen*: if you look for *andros* in a Greek dictionary you're not gonna find it, because that's the genitive. You have to look for *aner*, which is the nominative.


$k[{X_1},\cdots,{X_m}]$ is not isomorphic to $k[{X_1},\cdots,{X_n}]$ if $m\neq{n}.$

Question: I am trying to prove this. Assume that $k$ is a field and that $k[{X_1},\cdots,{X_r}]$ denotes the ring of polynomials in $r$ variables with coefficients in $k$. If ${\phi}:k[{X_1},\cdots,{X_m}]\rightarrow{k[{X_1},\cdots,{X_n}]}$ is a ring isomorphism such that ${{\phi}|_k}={({\rm{}id})_k}$, (the restriction of $\phi$ to $k$ is the identity mapping), then it must be the case that $m=n$.
Not sure how to approach this because I don't know if anything can be said about the set $\{{\phi{(X_1)}},\cdots,{\phi{(X_m)}}\}.$ Does the image of this set be contained in $\{{X_1},\cdots,{X_n}\}$? If so, then $\phi$ being a bijection will force $m=n$. Thanks!
Comment: Do you know about *dimension* of commutative Noetherian rings?
Comment: I don't know the dimension of a commutative ring!
Comment: $\phi(X_1), \dots \phi(X_m)$ can be any polynomials whatsoever, so you'll have to work harder than that.
Answer: There are lots of ways to do this by formalizing the intuitive idea that the spectrum $\text{Spec } k[x_1, \dots x_n]$, also known as affine $n$-space $\mathbb{A}^n$, has dimension $n$. For example, you can

compute that the transcendence degree of the field of fractions over $k$ is $n$.
compute that the Krull dimension is $n$ (somewhat harder).
compute that the dimension of the Zariski tangent space at any $k$-point is $n$ (easier).

These are all isomorphism invariants.
You can also work very directly on the level of polynomials by assuming that $m > n$ and showing that $\phi : k[x_1 \dots x_m] \to k[x_1, \dots x_n]$ cannot be injective by finding a nonzero polynomial in the kernel. The argument is a generalization of this math.SE answer.
Comment: Similarly to 3, the global $\Omega^1_{k[x_1,\ldots,x_n] / k}$ is a free $k[x_1,\ldots,x_n]$-module of rank $n$.
Comment: @student: yes. The volume for $n$ variables is $\frac{D^n}{n! d_1 d_ 2 \dots d_n}$.
Comment: @Daniel: yes, that's also very nice! And it implies 3).
Comment: Awed by your insights! I am struggling to learn the basics of algebraic curves, so I will revisit these useful comments when I have learned more. The last (direct) approach is very elegant. Trying to generalize your argument  "this math.SE answer" above. in the case of two variables, am wondering whether the "volume" of the $m$-dimensional simplex formed can be evaluated by a multiple integral. (The calculation would have to give your answer for the two variable case obviously!)
Answer: HINT:
Consider a $k$-morphism from $k[x_1, \ldots,x_m]$ to $k[x_1, \ldots, x_n]$,  $x_i\mapsto a_i(x_1, \ldots, x_n)$, $i=1,\ldots, m$.
Assume that the map is surjective. Then there exist $P_1$, $\ldots$, $P_n$ polynomials in $m$ variables $a_1$, $\ldots$, $a_m$ so that $$P_j(a_1(x_1,\ldots, x_n), \ldots, a_m(x_1, \ldots, x_n)) = x_j$$ Using the chain rule we obtain for the jacobians
$$\frac{\partial P}{\partial a}(a(x)) \cdot \frac{ \partial a}{\partial x}(x)=(\delta_{ij})\  (=I_n) $$
and so the rank of both matrix factors must be $n\le m$.
Comment: @student: if you specialize the Jacobians to a point they become linear maps on Zariski tangent spaces, and this becomes an elaboration of the third proof I suggest in my answer.
Comment: @student:  Assume that $m<n$. On the left hand side the determinant is $0$ (something that is not hard to check), on the right hand side is $1$. No need to look at ranks.
Comment: @student: Check out the second answer here https://math.stackexchange.com/questions/2787362/show-the-determinant-of-a-product-of-non-square-matrices-equals-zero-if-multipli
Comment: One can regard the Jacobian matrices as linear transformations ${K^{m}}\rightarrow{K^{n}}$ where $K=k({X_1},\cdots,{X_n})$ the field of rational functions in $m$ indeterminates. The rank then has the usual definition. I suppose we work in the ring directly, and think in terms of modules over the ring $k[{X_1},\cdots,{X_n}]$, but in this case I am not sure about the notion of dimension.
Comment: I will struggle to understand your three proofs. I have a feeling I will learn a lot!!
Comment: Really nice! Sorry! But am missing why the determinant on the left hand side must be 0! This determinant can only be worked out for the matrix that is the product of the two factors, because each of the two Jacobians is not a square matrix.
Comment: Adding in rows and columns of 0s makes it work. The argument is general enough to work for matrices over an arbitrary field-useful! Thanks.


AC in van is blowing hot air but condensation is dropping

Question: Is there a reason why condensation would be dripping from a van that isn't blowing cold when the AC is set to Max and recirculate? It's a 99 Chrysler Town and Country. It is a manual temp control unit.
Comment: Bad blend door motor may be. Whats the YMM? Auto or manual AC?
Comment: I've seen bad blend door motors or the control module for the temp. control unit.    How's the engine temp gauge?  There's a chance it could be thermostat related if that's high, as well.
Comment: The temp gauge is in the normal range.
Comment: The heater may also have a tap/solenoid and that may be bad as well. Also, have the system leak checked and the original charge restored. Might be the time if it has never been done. Low charge makes the evaporator freeze and then thaw in a cycling fashion and that gives lots of condensation dripping and no vent airflow (which can be interpreted as hot air since the cabin temperature can't be affected by such a low airflow; the cooling performance also decreases per se).
Comment: My friend said that the AC was working and then suddenly started blowing hot. She turned it off and back on assuming that it would come back to cool but it didn't.
Comment: Sign of a low charge making the evaporator freeze up, if the AC resumes cooling after leaving the system off for a long time and then turning it back on. If the AC never comes on again, the compressor clutch coil may also have failed. AC diagnosis is complicate stuff.
Comment: Don't think about charging it with cans though. The proper way of charging is recovering whatever's left, vacuuming thoroughly and then reinserting the proper refrigerant charge for the vehicle (inside the high pressure side and in liquid form) and the quantity of refrigerant oil that the machine pulled out of the lines.
Answer: most automotive a/c units have a low pressure sensor on or near the dryer ,so if it go low the unit will not engage so im saying its the door in the unit that switches from hot to cold or visa versa ..it is usually controlled by a cable or vacuum operated switch the door and or cable connect usually on the passenger side under the dash you may have to pull the glove box to access or  get a flashlight and look under the passenger side while moving the switch on the controls a cable will sometimes work lose if so is an easy fix usually put it back on by hand sometime requires a screwdriver of a lose screw holding clamp that holds cable in place ,,if it is vacuum operated then you have to find the leak and replace hose could be under the hood for vacuum hose broken or came lose   hope this helps
Comment: Can be a lot more subtle than no operation at all. If you're on low charge it might be enough for the LP switch to actually sense enough pressure, but not for the whole evaporator coil/coils to be sprayed thoroughly with semiliquid refrigerant by the OT or TXV. That way, the beginning of the evaporator will soon coat with ice, and that ice will then begin developing across the whole evaporator, progressively restricting airflow and reducing cooling capacity until the LP switch trips and the compressor stops operating.
Answer: My vote is for the blend door.  If its a manual AC system, the blend door should be directly connected to the temp nob - on my Early 2000 and later 1990s Chyrsler it was a cable.   On 2000 Durango, the cable came off and the blend door was stuck in one position.  Cable was accessible just above glove box (I think I had to remove the glove box).  There was noticeably less tension on the control knob.


Sql server 2012 grant role permission to just validate view but not select data from it

Question: Is there a permission in SQL server 2012 to just validate/ existence an object (in my case it's a view) but not a select permission? Idea is if a usergroupA try select a view it just should not fail and return no records. Thanks in advance!
Comment: Since you're a new member I wanted to make sure you knew about pressing the little check mark on the answer which resolves your question just to the left of it to tag it as the accepted answer . . . see [Accepting An Answer](http://meta.stackexchange.com/questions/5234/how-does-accepting-an-answer-work) for more detail on this if needed.
Answer:
Is there a permission in SQL server 2012 to just validate/ existence
  an object (in my case it's a view) but not a select permission?

Consider granting VIEW DEFINITION  permission as defined in the below quoted reference; this still applies to SQL Server 2012 as well.

VIEW DEFINITION
The VIEW DEFINITION permission lets a user see the metadata of the
  securable on which the permission is granted. However, VIEW DEFINITION
  permission does not confer access to the securable itself. For
  example, a user that is granted only VIEW DEFINITION permission on a
  table can see metadata related to the table in the
  sys.objects
  catalog view. However, without additional permissions such as SELECT
  or CONTROL, the user cannot read data from the table. For more
  information about viewing metadata, see GRANT
  (Transact-SQL).

Creating a per Database Role for VIEW DEFINITION permissions
<code>/* CREATE A NEW ROLE  -- View Definition */
-- Database specific
CREATE ROLE db_All_ViewDefinition
GRANT VIEW DEFINITION TO db_All_ViewDefinition
</code>
Members of this role in the database you create it on should only have access to the applicable metadata as long as they don't have other permissions to database objects such as explicit SELECT access to the a table or a member of the db_datareader fixed database role.

Granting VIEW DEFINITION permissions explicitly per object
<code>USE [DatabaseName];
GRANT VIEW DEFINITION ON dbo.tablename
TO [domain\username]
</code>
The above TSQL will grant explicit VIEW DEFINITION access to the specific DB object and to the specific security principal as specified in the applicable TSQL logic

Further Resources

GRANT Object Permissions (Transact-SQL)
CREATE ROLE (Transact-SQL)
VIEW DEFINITION
Comment: Will this allow the user to select from the view and return no rows?
Comment: @DanGuzman There's an option [**Granting VIEW DEFINITION permissions explicitly per object**] listed in my answer to assign the explicit `VIEW DEFINITION` permission on a per-DB-object basis. Without over analyzing this simple question too much, word-for-word for the part of the OP's question which I answered, and quoted in the top of my answer, this is what I would consider, test, confirm, and all other relevant aspects to ensure it works as expected before rolling out into a production environment.
Comment: Granting View Definition explicitly per object doesn't allow user to select from the view and return no rows. Is there any other way we can achieve this?
Answer: As far as I know, you can achieve that with Row-Level Security. Available only in SQL Server 2016 though.
Comment: Have you found another way to do that? View definition permission just give you the ability to see the structure of the object.
Comment: Unfortunately no Dan there's no inbuilt feature as you said up until 2016 but came up with a work around to altered view to have a clause which filters out what users can see based on group membership using the IS_MEMBER function.


What is the difference between Rule Utilitarianism and Act Utilitarianism?

Question: Based on the definitions given by Wikipedia , Rule Utilitarianism and Act Utilitarianism both seems to imply the same meaning
Rule Utilitarianism

Action is right as it conforms to a rule that leads to the greatest
  good, or that "the rightness or wrongness of a particular action is a
  function of the correctness of the rule of which it is an instance."

Act Utilitarianism

Person's act is morally right if and only if it produces at least as
  much happiness as any other act that the person could perform at that
  time

The supposed difference between Rule Utilitarianism and Act Utilitarianism

For rule utilitarians, the correctness of a rule is determined by the
  amount of good it brings about when followed. In contrast, act
  utilitarians judge an act in terms of the consequences of that act
  alone

The justification of action for the above rule mentioned are about  the greater good of the society , How are Act Utilitarianism and Rule Utilitarianism different from each other ???
Answer: A rule utilitarian thinks, before acting, about the consequences of people following that rule. If the outcome is regarded as positive, she might decide that it's good to follow that rule in general, and will apply it in future.
An act utilitarian doesn't generalise the act, but regards it as a single action with a single outcome. She will have to weigh the possible consequences each and every time she acts.
Therefore, rule utilitarianism is considered to be more practicable, countering the anti-utilitarian argument that weighing each and every possible outcome each and every time is just not the way we want to (or can) spend our time.
On the other hand, act utilitarians consider rule utilitarians somewhat dull-witted, for a smart person might think of herself to be able to decide what to do without just applying rules time and time again. Also, blindly applying rules to specific situations can have unforeseen negative consequences that might have been averted by somebody who paid more attention instead of executing a programme.
At the same time, act utilitarians are criticised for their double standards, for they think it is useful if everybody follows "good" rules while they take for themselves the right to decide whether or not it is clever to stick to those rules in a specific situation.
An example: A rule utilitarian drives at night and sees a red intersection light. Thinking "it would have good consequences if people would stick to the rule and not cross red lights, so everyone is safe while waiting for a short while", she would apply that rule to herself and wait for it to turn green. Meanwhile, the act utilitarian might think "well, I certainly hope that people, who aren't me, in general follow that rule and stay put, but as there's no one around who might get influenced by my act, since there's no police around to fine me, and since I would see an approaching car as it's dark, I might as well cross right now."
Sources: There is a paper by Smart which you can find here; I'm pretty sure that's what we read in the seminar where I learned what I wrote. Smart's the act utilitarian.
Comment: Your example of the street light perfectly illustrates the difference(s) for me. Thank you for such an intelligible response. With there now being over 100k views of this post, I'm quite surprised you've only received [a net of] 10 upvotes (mine now included)!
Comment: Hi there, thanks! But the link seems to be broken, any chance you could update it, or tell us the title of the paper?
Comment: [Here's a paper](http://personal.lse.ac.uk/robert49/teaching/mm/articles/Smart_1956Utilitarianism.pdf) by Smart that is linked on the [Rule Utilitarianism wikipedia article](https://en.wikipedia.org/wiki/Rule_utilitarianism)
Answer: Originally, I was going to comment on iphigenie's answer, but I decided there were enough parts I wanted to comment on that it's worth supplying a second answer -- even though the other one is good as it is.
John Stuart Mill's Utilitarianism seeks to maximize happiness (something he inherits from Jeremy Bentham and his father). Contemporary versions are usually a bit more nuanced in what they are trying to do and are probably better called consequentialism.  There are several flaws in Mill's original idea for utilitarianism which center on two pairs of epistemic concerns.
First, there's a question about whether we are to do what we expect would maximize happiness or whether we are to in fact maximize happiness. If we are expected to really maximize happiness, we face an impossible task, because we can get it completely wrong (maybe the cake I baked for your birthday contains an allergen that kills you and depresseds thousands of people). But then if we are just maximizing what we expect will make people happy, then we need to have some rules in place to balance how hard we need to be learning about this or else its just as good to cut off your hand (if I mistakenly believe this will make you happy) as it is to sing you a song. To some extent, rule utilitarians and act utilitarians disagree about the degree to which we need rules to overcome this problem with Mill's approach.
Second, there's a worry about how adaptive our ethical theory should be. Do we adopt principles that would maximize happiness (e.g. R.M. Hare) or do we adjust continuously towards what will maximize happiness? If you answer the former, then it is rule utilitarianism. Otherwise, it is act utilitarianism. I take it the two worries that need to be balanced here are this. On the one hand, if you wind up with rules and complex considerations of when you can amend them, you sound a lot like like a deontologist -- something other than utility by itself is guiding you. On the other hand is the worry you raise about the concerns of calculation joined with an anti-theory position and a haphazard reality.
Answer: utilitarianism is an ethical theory that holds the belief that  all moral actions should be decided on the basis that they cause "the greater happiness for the greater number". A teleological approach is one which is based on consequences, and deontological approach is based on a set of rules or absolutes.
utilitarianism can be divided into two classes: Act utilitarianism and rule utilitarianism.
Act utilitarianism is linked to Jeremy Bentham, moral decisions are decisions that are based upon consequences of each individual situation in relation to the total amount of happiness that they produce.
Rule utilitarianism is associated with Mill, example can be roads rules, you must drive on the left hand side of the road, this applies to everyone that drives and it is the rules and it must be or should be followed in all situation, even if we were stuck in traffic jam. This is because the rule is to keep order on the road
The main differences between act and rule utilitarianism is the fact that one is teleological and the other is mainly deontological. for example our world is governed by rules, either implied or implemented, and we are taught to live by the these rules. The society expects us to act in a such a way that will conform to these rules in order to live happy.
Act utilitarianism beliefs that an action becomes morally right when it produces the greatest good for the greatest number of people, while Rule utilitarianism beliefs that the moral correctness of an action depends on the correctness of the rules that allows it to achieve the greatest good.
Act utilitarianism is the belief that it is alright to break a rule as long as it brings greater good.
Answer: Act utilitarianism's main question, with a quote from https://www4.uwsp.edu/philosophy/dwarren/IntroBook/ValueTheory%5CConsequentialism%5CActVsRule%5CActVsRule.htm, is "does this specific action maximize happiness more than any other that could be performed at the time?" Act utilitarianism is basically a specific interest that is justifiable if, and only if, it makes others happy, too.
Rule utilitarianism is a more general form. It's main question is "what general rule would this action follow, and would it maximize happiness if generally followed?" So if this action was made a universal law, would it create good? Such as lying; lying, under certain conditions, could be justifiable. However, the rule utilitarian would say that lying, if followed as a general law/rule, would not create good.
Act=specific interest that is able to be justified to maximize happiness.
Rule=general happiness that would be maximized and is able to create maximized happiness if followed as a general rule. :)
Answer: Rule utilitarianism looks at the consequences of actions on society, rather than the effects on just a subset.
Consider the following scenario. A surgeon has the option of saving one persons life, or the option of letting them die and saving the lives of seven people who all need organ transplants. By sacrificing one person, seven can live. Act utilitarianism says that you should do the action that leads to the most amount of good. The surgeon should sacrifice his patient. Murder is acceptable, as long as the outcome is positive for a greater number of people.
Rule based utilitarianism looks at the consequences of individual actions for everyone, all of society rather than just the group of people immediately affected. In the previous example, act utilitarianism tried to maximise the total good for the patient and the seven people needing organ transplants. If instead looking at the consequences for everyone, doctors killing patients to save lives would lead to a breakdown in trust between patients and doctors, patients would refuse to be operated on and more people would die of treatable conditions. The net outcome would be bad. Thus it would be preferable to have doctors follow a rule "Never sacrifice one patient to save many", rather than have them try to maximise utility on a case by case basis.
Of course there's nothing stopping an act based utilitarian from considering the consequences to all of society when trying to determine how to maximise total good. In which case their actions would be exactly the same as a rule based utilitarian. However act based utilitarianism doesn't explicitly say that they must, so it allows people to categorise certain actions as good which rule based utilitarians would categorise as bad.
Comment: `Rule utilitarianism is similar to Kantian ethics` seems like a bit of an overstatement or at least unclear in a rather infelicitous way. (1) there's nary a categorical imperative in sight. (2) Kantian ethics as normally formulated does not look at consequences.
Comment: Kantian ethics isn't categorised as consequentialist but at its core it is. The categorical imperative looks for a logical contradiction in a rule, it looks at the consequences of that rule when applied universally to see if a contradiction occurs (and if so it cannot be a moral law). What would be the result if everyone acted this way? Is the same question asked in rule based utilitarianism and Kantian ethics, although Kantian ethics is looking for a contradiction while rule based utilitarianism is trying to determine the net good or bad. So there are differences, which i should havementioned
Comment: The contradictions the CI looks for are not in "consequences" as normally understood. Instead, it's looking for that which is either logical contradictory or that which would produce contradiction in conjunction with the "laws of nature" (which for Kant does not mean what it means for most other thinkers).
Comment: Traditional interpretations of Kant see him as squarely anti-consequentialist, squarely accepting that the moral course of action may produce very negative consequences but that it should be done because it is moral.
Comment: true, but only because he's looking at consequences on a large scale "What would occur if everyone did this?" rather than the consequences for the individual in their particular context.
Comment: No, it's not a matter of scale. It's a matter of kind. He's not looking at "consequences" in any normal sense of the word there. He's looking at the merely logical consequences and then those in conjunction with "laws of nature." He might be wrong; he might be incoherent, but he's not trying to weight and measure outcomes for better or worse.
Comment: no not in a normal sense, but a logical contradiction is a consequence. And it just so happens that a lot of the contradictions match what rule based utilitarianism would classify as a bad outcome. Because "tragedy of the commons" style scenarios always lead to a contradiction.
Comment: I think you're confusing outcomes with theories there. Just because two theories both condemn murdering your neighbors doesn't mean the two theories concluded this for the same reason. A *logical contradiction* is the consequence of an **argument** which can be presented outside of time -- not an outcome in the world. Utilitarian views work temporal consequences.
Comment: It's not really worthwhile to argue this here. If you removed the reference to Kant in the first paragraph you'd be dandy. As it is, you're stating something that's basically wrong by most interpretive standards but could be "right" if we take Kant to be completely wrong about what he thought he was doing.
Comment: Removed the reference to kant - but disagree that a contradiction could be presented outside of time or outside of the world.
Comment: Okay, that means you disagree with Kant, which is a completely legitimate thing to do.
Answer: just to help thought I would upload an essay which isn't perfect but offers a comparative over rule and act utilitarianism and evaluative for those who are stuck, if anyone can suggests some improvements please say so ....
The two types of theory: rule utilitarianism(mill) and act utilitarianism (Bentham)come under the same ethical theory of utilitarianism which questions the rights of individuals or a minority to a majority, using the justification of 'the greater good' or 'greatest happiness for the greatest number'. It is strictly a teleogical theory concerned with the outcome as the deciding factor over an actions' 'goodness' or 'badness'. It seeks to create the greatest well being produced. It opposes all deontological theories that concentrate on moral rules like natural moral law or Kantian ethics, it aligns quite similarly to Fletcher's situation ethics. Bentham's act utilitarianism also referred to as hedonic utilitarianism, can ne seen through important parts. Motivation (for Bentham it was either pleasure or pain), principle of utility (the usefulness of the right/wrong action). Whilst mills rule utilitarianism, came after Bentham's as a backlash from the problems within the theory. It rejects the hedonic calculus, creates a new understanding of happiness (state of mind from the application of principles: liberty and freedom). States that humans must constantly be progressing to be truly happy, but not all pleasures are of equal value and that happiness is not just based hedonistic desires. Mills theory also questioned the intrinsic part of utilitarian with the concept being purely quantative, he asked what would stop one a single person being destroyed by the majority. Overall, I agree that rule utilitarianism is an improvement on act utilitarianism as it is far more progressive to a more equal society.
Act utilitarianism judges every situation individually and in isolation from the community, Bentham and others applying it would ask: what action would bring about the greatest good. Looks at the consequences of each individual act and calculates utility each time the act is performed. rule utilitarianism attempted to re-define utilitarianism in a way that made it practical to use when creating rules for society. Mill argued there needed to be generally agreed rules in order for a happy society to function. Looks at the consequences of having everyone follow a particular rule and calculates the overall utility of accepting or rejecting the rule.
The individual theories have their own problems as highlighted by either side, act utilitarianism doesn't accommodate to real life problems with the inconvenient time-consuming hedonic calculus. Also in particular cases, act utilitarianism can justify disobeying important moral rules and violating individual rights. When referring to levels of higher and lower pleasures rule utilitarianism becomes socially exclusive to those who cannot experience higher pleasures. It is argued that rule utilitarianism becomes rule-worship when they refuse to break a rule : If the consequences demand it, we should violate the rule.
One of the reasons I find rule utilitarianism an improvement to act utilitarianism is because I believe it has higher social benefit to moral decision making, mill aimed to Mill's offer more protection towards minorities passed over by the masses, and less subject to abuse. Whilst Bentham's seems to only enable unethical behaviour and allow society to be complacent with the discrimination over minorities. Although the idea over higher and lower pleasures can be elitist as the higher pleases are only available to a select, but it could be argued that mill here was advocating cultural reform to make them available to others. Mill made his point of higher and lower pleasures in the quote "It is better to be a human being dissatisfied than a pig satisfied; better to be Socrates dissatisfied than a fool satisfied. And if the fool, or the pig, is of a different opinion, it is only because they only know their own side of the question." , higher pleasures being :literature, theatre, reading and lower :sleeping, eating. For this point I find Bentham's level ground over pleasure levels being non-existent and any happiness is valid I find a strength in act utilitarianism. The problem with act utilitarianism in terms of social benefit in moral decision making is that, Bentham's hedonic approach clearly is overly more self-serving. For him it is about the individual's search for pleasure, not the greatest good for the advancement of society and all members of society. It can easily be twisted to serve whatever desire the person making the decision decides. For example a serial killer could use this to argue that is alright for him to kill specific people who bring pain into the world (like a thief). The action and out come of death is wrong but the happiness of the killer and the happiness of potential future victims of theft overcomes the pain from his death.
Rule utilitarianism is an improvement with its practicality in application. act utilitarianisms' hedonic calculus (the system used for calculating the amount of pain or pleasure created) is overly cumbersome and make rule utilitarianism's generalised rules far superior and easy to apply. The Hedonic Calculus takes all available options in a scenario then weighs up the pain and pleasure generated by each in order to decide which option to follow. These are purity, remoteness, extent, duration, intensity, certainty. This drawn out process becomes frivolous the extent it goes to doesn't make it realistic for everyday use in situations
In conclusion although rule Utilitarian appears to be rather discriminatory in relation to the level of pleasures I see it more as mill highlighting this so that a better more free society could sustain itself making the higher pleasures available to all. And similar to Mill himself I see Bentham's approach to be too rigid for everyday life, and too self-serving with its hedonistic.


CentOS 5.6 Update Version Of Tar

Question: I am running CentOS 5.6 and for some ungodly reason, the version of tar is from 2004, and not compatible with the node package manager (NPM). How in the world can I update it? Is there an additional yum repository I can add, so I can simply execute yum update tar.
Comment: What version is your current tar and what version do you require?
Comment: Also, tar is an old piece of software and isn't updated often, why do you need a new version?
Comment: @MikeyB Looking at the the CentOS 5.6 FTP site (which seems to be the closest rpm-based distros get to a `packages.` site), it looks like 5.6 has 1.15.1.  My guess is that in 2006 when 1.15.91 changed file globbing to require `--wildcard`, RHEL/CentOS kept the old version rather than changing their programs.
Answer: The CentOS6 package fails dependencies on 5.6, so, you probably will need to build it yourself, either nicely packaged or not.  I don't seen an updated "tar" package up at Dag or Karan.
Comment: glibc, so you're not going to be able to easily work around that one.  I just tried a "rpmbuild" on the RHEL6 tar src rpm (GNU tar 1.23), and it's failing because it needs a newer autoconf version.  If you want a packaged installation, your best bet might be to grab the 5.6 SRPM, open it up, and modify the .spec file to use a more recent tar distribution.  Or, you can just do the usual "configure; make install" thing and put the new one in /usr/local/bin.
Comment: Which dependencies?
Answer: Yes, on my RHEL 5.x system, the package is called tar.x86_64. So yum update tar will fetch the update if there is one available.
Comment: Yeah that version is way old, I need a newer version, do I have to build from source?
Comment: No, the package from yum will have the same name. Use `yum info tar` to see the new version that will be available. Also remember that RHEL and Centos are conservative with their package selection, as a result, they don't ship the most recent packages.

CentOS 5.6 Update Version Of Tar


Difference between a skiplist and an Indexable skiplist

Question: Can someone please help me understand the main differences between a simple skiplist and an indexable skiplist? How does an indexable skiplist work in comparison to a normal skiplist (maybe a little example?), I can only find so little about it online.
Thanks.
Comment: (Please add *what contents* found *here* you think should have helped, and *how* it didn't.)
Answer: An Indexable Skiplist is a skiplist with the added property that it can quickly lookup the $m$th entry (in order) in a skiplist in $O(\log n)$ time in a skiplist of $n$ entries.  In other words, it takes a skiplist that is not an indexable skiplist $O(n)$ time, on average, to find the $m$th element in order in a skiplist, while an ordered skiplist can do this in logarithmic time.
It does this by keeping track of the width of the links in the skiplist.


How did Parashurama, a Vishnu Avatar, appear alongside the next two Avatars of Rama & Krishna?

Question: Why if Lord Parashurama is a Vishnu Avatar appear with Rama in the Ramayana and with Krishna in the Mahabharata?
Comment: @Creator Yes he did: http://www.sacred-texts.com/hin/m05/m05096.htm I discuss it in this answer: http://hinduism.stackexchange.com/a/2395/36
Comment: first of all parshurama didn't appear directly in front of krishna.
Comment: I don't understand your question. Maybe you need to explain better what exactly you are looking for.
Comment: I will tell you simple answer.
Because God parshurama is one of the seven Chiranjeevies (not exactly Immortals but Lives Long).
he was born in Tretya Yug.
and he will be one of the Saptrishis in 8th manavtar. Currently we live in 7th manavtar 28th Chaturyug.
Answer: There are only 7 Cheerenjivi's (the eternal Beings) out of which one is lord Parshurama.
See following for all names
अश्वत्थामाबलिर्व्यासोहनुमांश्च विभीषण:कृपश्चपरशुरामश्च सप्तैतेचिरंजीविन:
Also Lord Parshurama is an Avatar of Lord Vishnu and his every avatar has a specified work to do in it's whole life span out of which Parshurama was the one with a life upto the Chaturyuga so he had a large amount of work to do for a long time in Coming Yugas (after Treta Yuga(his birth Yuga)).
Lord Parshurama is the one which is Bramhin as well as a Warrior it means he is a Bramhin Warrior a perfect Guru for every being, he also has all the magical weaponry traning (astra vidya) with him. Because of this qualities he has been casted as a guru of lot of characters that too very Important like Bhishma Pitamaha, Karna,Kalki(see kalki purana for refrence).Also he Supplies all knowlegde to the Important Characters at Right time for sake of the God's will and planning.
Cases when he appeared and why

In TretaYuga
In case of Ramayana in Sita Swayamvar after the Breaking of the Pinak Dhanush of Lord Shiva ,Lord Parshuram who was in medetation on Mahendra Parwat became angry and due to his sattvic anger he came to Lord Rama and tested him for his patience and most importantly he Gave his Bow the Sharang Dhanush to Lord Rama as it was nessesary for Ravan Vadh
refrences:Wiki
In DwaparYuga
In case of Mahabharata he was the mentor and guru of Bhishma Pitamaha ,Karna.
Lord Parshurama was all aware of the future incidents as he was himself   Vishnu he knew Karna would be a obstacle in Dharmsanstapan Path (In path of Dharma) so to ensure his death he cursed him (for his lie of being Bramhin in order to become his disciple) of losing all his falsely gained knowlegde at the time when he needed it most and it happened to be the fighting time in mabharata war and he died for the same reasons due to his death Pandava's win,this answer tells the story of meeting of Lord Krishna and Lord Parshurama
Future Appearance in Kaliyuga
In future i.e. Kaliyuga it is said that Lord Parshurama will be the Guru of Lord Kalki The Kalki Purana writes that he will reemerge at the end of Kali Yuga to be the martial and spiritual guru of Kalki, the tenth and final avatar of Vishnu. It is foretold that he will instruct Kalki to perform a difficult penance to Shiva, and receive the celestial weaponry needed to bring about end time. source Kalki.

In these all lilas(Games/Actions) of Lord Shri Hari Vishnu he played a role for a long time as Lord Parshurama to help himself in tasks that he had to accomplish himself.
Comment: You should probably replace Wikipedia sources with actual scriptures.


Common Causes of Operating System Crashes

Question: I am interested to learn: what are the most common technical causes (from the perspective of operating system programming) of an operating system crash (not limited to Windows crashes)?  I'm looking for an answer not like "too many apps open", but what specifically happens when too many apps are open that causes the crash.
Answer: In my opinion

Bad drivers
Kernel bugs
Hardware failure
End of resources

A modern operating system will not let a mere application crash it.
Comment: Nice list, however "end of resources" should not cause a crash unless there is a bad driver, or bad kernel. Good code should handle all resource allocation failures gracefull. It is however true that this is quite common type of driver bug.
Comment: I was thinking about "fork bombs" and root file system full
Answer: It's Buggy Drivers that cause OS crashes. Only the OS itself and drivers are able to harm the system.
To your suggestions:

No OS has problems if an application accesses the same memory as the OS. Either the memory is accessible or it is not. If an application tries to access memory that it should not the CPU generates a segmentation-fault. The OS hands this over to the application and the problem is solved. (in 99% the app will crash afterwards, but that's not the fault of the OS).
You're suggesting that slower programs are more safe. That's not true. The OS does not need to know what exactly your program is doing.
Comment: 1. "Segmentation fault" (or GPF in Windows land) is the term you are looking for when an application tries to access memory that it's not allowed to. "Page fault" refers to when a section of memory is accessed but it's been swapped out to virtual memory.
Answer: In modern OS, application code and OS code run in separate address spaces. The application code cannot crash the operating system. See here:
http://en.wikipedia.org/wiki/Ring_(computer_security)
The most common readon for a crash is code that is acting as part of the OS interfearing with other code that is acting as part of the OS. A common cause is poorly written device drivers that live in the OS's address space.
Less often, crashes are caused by hardware faulures.
Answer: Any OS crash can occur due to either of the two main reasons:

Hardware Problem.
Software Problem.

HARDWARE PROBLEMS:

Power Related problems:
              Improper functioning of the System Power Supply can lead to immediate shutting down of the System.
Overheating of RAM: Overheating RAM could lead to corruption of data in it.This can lead to definite crash where reset is a must.
Improper Overclocking: Causes Overheating. Certain Hardware Components are sensitive to heat. When Overheating occurs automatically the system shuts down.
Bad Sectors in Hard Drive:
                The Hard disk is divided into sectors where data is stored. Some sectors become Bad sectors.
        Reasons:
                    a. Prolonged usage - many writes and reads.
                    b. Manufacturing defect.
If sectors in the hard disk, where important system information is stored, becomes a bad sector then it is difficult to load those files, thus leading to a crash.
RAM Issues: Cause: Data retrieval not possible. This is very important as this leads to Fatal Exception Error

Major Misconception: An application crash in your system does not always lead to a system crash. Generally "Nothing" happens to the OS. It just sends you a report saying so and so application has crashed.
SOFTWARE PROBLEMS:

Corrupt Registry: Before starting any application, the OS looks into its registry. Registry is a small Database where all the information about kernel, drivers and information about applications are stored. Registry can get corrupted due to improper uninstallation of applications, careless editing of registry, too many installed applications etc.
More causes of Corrupt Registry. This leads to routine applications refusing to start thus causing the Blue Screen of Death to be displayed.
Improper Drivers : In order to use additional hardware, we need drivers, generally downloaded from the internet. These drivers might contain bugs. These bugs cause the OS to crash. Modern operating systems are released with the option of "Safe Mode Boot". Safe Mode Boot loads only important drivers (minimum) and not all. Safe Mode Boot is used for diagnostic purposes to find the driver with bugs.
Virus and Trojan: Common reasons for OS crash. Viruses and Trojans corrupt the system files, "eat up" the memory not allowing OS to retrieve it when a programs stops, changes administrative settings, frequent rebooting without any sign etc
Thrashing: Deadlock occurs when two programs running require control over a particular resource. Sometimes during a deadlock, the OS tries to switch back and forth between the two programs. This eventually leads to Thrashing where the hard drive is being overworked by moving information between the system memory and virtual memory excessively causing a system crash.
Answer: No you are way off. Typically there is nothing an application can do that can cause the OS to crash. OS crashes are generally caused by buggy device drivers and hardware failures.
Answer: Two different sources trying to access a locked area is one problem. Getting all mutexes, monitors and locks to work 100% is not trivial.
Comment: I am voting this up because deadlocks and livelocks *are* a very common cause of operating system failure.
Answer: If we use Vista as an example - drivers ... NVidia in particular http://arstechnica.com/news.ars/post/20080325-vista-capable-lawsuit-paints-picture-of-buggy-nvidia-drivers.html. It's the OS that dictates memory allocation, not applications. Well, that's the theory.
Answer: os crash may also cause due to some sectors crash in harddisk this is because i all pcs os presents in primary drive in the hardidsk.


Grace Design Spacebar SB-30

Question: I'd liked to get input on the Grace Design Spacebar SB-30 for potential use in a compact spaced omni nature recording rig? Is 30cm too close together for a good spaced image? Can you angle the omni's outward? Thanks!
Answer: I think you'll find 30cm spaced omnis will provide too narrow an image for nature recording. Placing the omnis at an angle will do very little (if anything) to widen the image, since by very nature, omnis aren't directional. The larger 66cm spacebar would work better for this application, but even then, you're probably better off mounting the mics on separate stands for greater control of the stereo width. The only way to work with Omnis in a more compact setup would be to use a Jecklin Disc.
Comment: The simple answer: directionality of the pickup pattern. The complicated answer, read this:

http://www.reddingaudio.com/downloads/Rycote%20Technical/The%20Stereophonic%20Zoom.pdf

DPA microphones also has a lot of great info on their website in the "microphone university" section.
Comment: Thanks @Justin, forgive the ignorance but how do cardioids provide a wide image in an ORTF set up but omnis at the same angle don't? Feel free to just link me if there are websites out there with this info. Thanks!
Comment: Great link Justin, thanks. On my "to read thoroughly" list.

Grace Design Spacebar SB-30


C# AttributeUsage for Specific Class

Question: Is it possible to have something like AttributeUsage to restrict the use of an attribute to a specific class (not just AttributeTargets.Class - that would be any class)?
Answer: One way to accomplish this, if you have access to the specific class, is detailed by Marc Gravel here: http://marcgravell.blogspot.com/2009/06/restricting-attribute-usage.html.  Basically you implement the attribute as a protected class of the specific type.  Then it can only be used by that type.
Answer: No.  There is nothing in the framework that would do this.
However, the code that uses the attribute in question could always check to make sure that the class's type is the specific class (or one of its subclasses).
Attributes, by themselves, do nothing - so this should have the same effect.
Answer: Make all data in the Attribute accessible only by a public static method which takes the class you want in question and checks to see if it has the given attribute.

C# AttributeUsage for Specific Class


Only first 10 layers of Geoserver WMS layers of enabled in ArcGIS

Question: I can see only first 10 wms layers of Geoserver is enabled while opening with ArcMap. Is there anyway, I can make all layers enabled?
Answer: This is a limitation of ArcMap to stop the (unwanted) loading of hundreds of layers. See the documentation, last paragraph: "ArcGIS automatically turns on the first 10 layers in any WMS service you add to a map or preview in ArcCatalog."
Nevertheless, you could write a Python script for ArcMap to enabled all the layers - if really necessary. Here's an link to a script.
Comment: @NannanSatish: great. I edited my answer, you can accept it, if it solved your problem. I also deleted my comments to avoid misunderstandings.
Comment: Thanks for reply Greg; No, my question is not that one,. mine is about the layer not enabled; if you look closed,. only first 10 layers enabled,. rest are disabled..
Comment: Thanks Greg,. Python script for ArcGIS,. or to Geoserver WMS Layer?


How to add Minecraft.jar to Steam in Ubuntu

Question: I have created a bin folder in my home directory and put my minecraft.jar in that folder. I then used Steam's "add non-steam game" option and added the minecraft.jar, but when I click play nothing happens. I can run the .jar manually but I would like to get all my games on steam so it's all nice and organized.
Answer: This best way to enable it from steam is to create a .desktop shortcut to run the jar package.   This will also allow you to provide name, description and icon to steam, as well as providing the full command line, including attributes.
Answer: I've used the following wrapper script for Minecraft back when I used to play it:
#! /bin/bash

# Minecraft launcher script

# Enable if using Oracle Java
#export LD_LIBRARY_PATH="/usr/lib/jvm/j2re1.7-oracle/lib/amd64/"

# Allow a heap size of 512M to 4096M
java -Xmx4096M -Xms512M -cp $HOME/bin/Minecraft/minecraft.jar net.minecraft.LauncherFrame

Just place it in a text file named minecraft in your bin folder, in my case I made a folder named Minecraft and put the minecraft.jar file in there to keep things clean. Please note your filesystem is case sensitive; unlike in Windows minecraft and Minecraft can coexist without causing problems.
Remember to change the permissions of the script to allow it to be executed. In the file explorer, right click and select Properties, then click the Permissions tab and check the Allow executing file as program checkbox. If you instead would prefer using the command line the command is chmod 755 ~/bin/minecraft.
The script allows for some tweaking, by default it allows Minecraft to use up to 4GB of RAM. To change this, adjust the -Xmx4096M parameter; for example 8GB will be -Xmx8192M.


(Got an error reading communication packets) but no error on client

Question: i've search a lot about this thread without results.
we don't know how to resolve this:
DB : mariaDB
SERVER: Microsoft Azure
enviroment: Nodejs with Knex (pool connections, min 0 max 300)

our client app stop to catch db response, without an error, except for (Got an error reading communication packets)

if we try to connect to mysql through Navicat/TablePlus/MysqlWorkbench (or even our app in local) during the error we still receive the data from db.
we don't know how to resolve it, since wednesday.

any idea about it?
Answer: Try to increase your connection pool min size 5 instead of 0.
From DB side, verify the timeout variables  and connection pool variables like
<code>wait_timeout & interactive_timeout >=  app connection pool timeouts.  (db timeouts should not be less than app timeouts).    And check to make sure the value of max_allowed_packet is high enough. Lastly increase enough net_read and net_write timeouts from DB side.
</code>


Are there benefits to having a SQL-like read only database layer over a Blockchain distributed ledger?

Question: Distributed Blockchain datastores provide inmutability to recorded transactions and only allow to add records accepted by a consensus algorithm in sequence.  You could store data on the blockchain or have references to where data might live in other data stores.  The blockchain does not seem to me like an ideal data structure to execute aggregate queries (assuming a client would allow for it) which a SQL-like database is good for.  For example, if I want to know yearly income for a certain address in the ledger, one way to do it would be to create a flatten structure for all the elements in the transactions list field and execute a group by operation by address and year, and finally sum the amount field.  A flattened structure would fit in a denormalized table.  Also, there are ledgers that could record complex fields for each transaction, for instance, IoT device data.  Is it absurd to think read-only SQL-like layers would be a good solution for making queries to extract data insight? What other benefits or disadvantages I am missing?
Comment: I do not think there is a point considering the entire block chain is basically one table. So there is nothing relational about it.  A stream seems a more appropriate model.
Comment: @KJP  I cannot say, do not know what insights are in this context, not after reading your update either. The whole question is starting to look pointless to me. Whenever I read up on block chain to learn what the fuss is about I end up thinking to myself it is all a useless unscalable load of bull that has even more political issues than technical ones. So until I see the light I think it is best for me to retreat from this discussion.
Comment: the update statement?
Comment: @Ewan if I understand your statement let me add that the Relational layer should not allow for updating of previous records.  It should strictly allow read type queries.
Comment: @MartinMaat if it is a big table then would you agree there is a benefit to adding a SQL like query language to obtain insights?  Also, do you have a reference to what you mean by the stream model?  I update my question to have more context of what I had in mind.
Answer: Yes, and I believe you have already identified the benefits.
A blockchain structure is not a good structure for looking up data - you often have to search the entire chain. If you will be doing lookups, it is a very good idea to have some type of auxiliary indexing. One way to do so would be to copy all of the data from the blockchain into an SQL database.
Answer: There comes caveat in setting up an SQL-Like read-only DB for the blockchain ledger. To begin with, I am not a blockchain expert but I do have the basic knowledge to tell you in terms of data design how this would be a nightmare.
Firstly, an SQL-Like database requires a sorted data, for your distributed ledger fetching all of the blocks in a blockchain to set up a read-only DB would be the most expensive task.
Secondly, you won't be updating that readOnly DB per transaction, if you do that there would arise a problem of sorting the data. Thirdly, the information per account's identity is encrypted, usually in 34 characters (for BTC case) and having to sort things up or even a "group by" query to group the string oriented data would be a the addition to the evil witch hanging upside down from your ceiling fan.
You could get better results with NoSQL just because, even if the data is sort of organized, in the long run it is highly unorganized, and thus if you could just save the data based upon blockchain-user-account-id and add in values accordingly or perhaps a 'history' object, that could turn out to be a better option for you.
So far I can see the complexity of such solution through your spectacles as n^2. Perhaps NoSQL could squeeze things for you in this scenario.
The rest is all your choice.
Have a nice day. :)