Mount a network drive when windows starts up without being logged in

Question: Current Scenario: I have a NAS Box, and a Windows 2003 Server that our recording software is on (Security Cameras).  The software stores the data on the NAS box.  Currently someone has to be logged in with valid credentials in order to keep the drive mounted (e.g. domain admin).  I know you can mount the drive with a batch file, but this stores credentials in clear text and is not a good solution.  I am looking for another way to get the drive to mount on startup without someone having to be logged in.  I do have a generic account setup that has access to read/write to the drive but can't log-in interactively, this is the account I would like to use to mount it if any.  Any suggestions?
Answer: What is the reason that you need to map a drive? Is it just so that you can store the user credentials? If the security PC can save to a UNC path (\\servername\share), then you could try running the service as a different user, one that has permission to access the share.
Let me know if I am on the right track here:
\\nasbox\SecurityFootage is where the files must be saved to, but they do not permit anonymous read/write access. So, at the moment, you map a network drive, (let's say M:), using credentials, and tell the security cameras to record there.
Because the security software runs as a service, you would prefer it if could just start automatically with the system, and write to the M: - but at the moment it can't because there's no anonymous access to \\nasbox\SecurityFootage
IF the scenario I've just described is accurate, then there is workaround:

Leave the NAS box alone, with all its security intact
Change the account that the service runs under to the non-interactive user you mentioned in your question

To do this, Right-click on the service, go to Properties, Log On, and choose "This Account", and enter the domain credentials in there

This will mean that when the recording service starts it will be run under the account specified, and will thus have permissions to save to \\nasbox\SecurityFootage
Comment: Yes, while running as a service and using that service account as the authenticated user works.  Thanks
Comment: Excellent. Glad we could be of service!
Comment: "we"? Do you have Schizophrenia? =)
Comment: "we" being the community of serverfault.
Answer: Wesley, I suggest you learn the actual meaning of the word 'Schizophrenia' before you so loosely use it in a sentence.
Answer: If the NAS box supports iSCSI, you could mount the remote storage as a local drive.
Have you tried telling the software to store on a UNC path instead of a drive letter?
Use the batch file and a scheduled task.  Protect the batch file with NTFS permissions and the scheduled task using permissions as well.


How to "LIMIT 50000,1"?

Question: So, LIMIT 50000,1 won't work well? Then, how come? What to do if rows after several rows are required?
I read it at http://www.mysqlperformanceblog.com/2006/09/01/order-by-limit-performance-optimization/
Answer: If you specify a LIMIT, MySQL will process the query without the limit, and then just read ahead until it gets to the limit point.
In other words, if you specify LIMIT 50000,1, the database will have to read 50001 records just to get the one you're interested in.
If the limit is low, this doesn't really matter, but with a high limit, it'll add a significant amount of time to the query.
All of this is covered in the link you provided (which seems to be quite a good resource).
If you're doing this kind of thing and need performance over a large number of pages, you may be better off doing a more direct query, for example querying where the sort column is greater than the last entry on the previous page. There are pitfalls to this approach as well, of course, but the one thing it will be is quicker than LIMIT 50000,1 (as long as you have an index, of course)
Answer: It says nowhere that it wont work, only that performance may suffer. As you can see, the writer suggests that you may remember the last id and do a where id > last_id limit 20 instead of just limit 5000, 20.

Beware of large LIMIT Using index to
  sort is efficient if you need first
  few rows, even if some extra filtering
  takes place so you need to scan more
  rows by index then requested by LIMIT.
  However if you're dealing with LIMIT
  query with large offset efficiency
  will suffer. LIMIT 1000,10 is likely
  to be way slower than LIMIT 0,10. It
  is true most users will not go further
  than 10 page in results, however
  Search Engine Bots may very well do
  so. I've seen bots looking at 200+
  page in my projects. Also for many web
  sites failing to take care of this
  provides very easy task to launch a
  DOS attack - request page with some
  large number from few connections and
  it is enough. If you do not do
  anything else make sure you block
  requests with too large page numbers.
For some cases, for example if results
  are static it may make sense to
  precompute results so you can query
  them for positions. So instead of
  query with LIMIT 1000,10 you will have
  WHERE position between 1000 and 1009
  which has same efficiency for any
  position (as long as it is indexed)

How to "LIMIT 50000,1"?


What does happen to electrons in the weak force decay?

Question: What happen with the Electrons produced in Stars due to the weak force decay? Do they combine with other atoms? Are they just pushed out of the Sun? Do they help with the electron degenerative pressure? OR they are used again to produce another neutron? Or Physicist are not sure yet?
Comment: If the question is about fusion products in the sun then you are mostly talking about positrons (anti-electrons), and that makes a big difference.
Comment: @dmckee, no, I am most interested to understand what happen with the electron produced during the decay of neutron or weak force interaction.
Comment: They are part of the plasma , see my answer here https://physics.stackexchange.com/questions/302370/plasma-and-stars
Comment: @ ann v see this comment: do you believe that partially answers my question, or solar winds have nothing to do with weak force decay?
https://physics.stackexchange.com/questions/13582/is-solar-wind-positively-charged
Answer: Short Answer: Electrons are not bound in the plasma of the star, so they roam around freely after any decay process with two exceptions.

If they are at the core.
When a star is undergoing collapse.

At the core, fusion is taking place so any free electrons/protons will fuse together to create heavier elements thereby keeping the pressure of the fusion matched with the gravitational pull.
If the fusion pressure is not enough, the star undergoes a collapse. When a star is undergoing collapse, and if the gravitational attraction is great enough to pass the electron degeneracy pressure, the compressed electrons with protons will form neutrons. If the neutron degeneracy pressure is greater than the gravitational attraction, this is how you obtain a neutron star. If the gravitational attraction is greater still, the neutron degeneracy pressure fails and you obtain a black hole.
Comment: thanks for your reply, but maybe my question is not clear. I am most interested to understand where  electrons produced during a beta decay or W and Z bosons decays end up. Meaning, sure, a neutron can decay and produce a proton, electron and anti-electronneutrino, but what happen with electron, what is its new function? Does it keep floating around? Is it required to combine with the proton?
Comment: Ahh I see. Sorry, should have elaborated a bit more. The electrons are in a plasma so the beta decay, or W/Z decay products are not bound inside the star. So most of the time, the electron floats around, yes. However, this changes when you enter the core where fusion is actually taking place. So at the core, the electron is not free.
Comment: Just another addendum, this [**wiki**](https://en.wikipedia.org/wiki/Proton%E2%80%93proton_chain_reaction) might help.
Comment: thanks, so electrons can exist without being attached to an nucleus. In this case, per heavier densities of other objects, is it fair to concluded that electrons would be pushed out of the crust of the Sun into the corona?
Comment: Her Ernesto, I've edited the answer to be clearer.

To answer your most recent question, the electron is free within the star. Theoretically it would make its way to the corona, just like photons, but its more likely to remain within the star. This is because, while the electron is not bound, there is still a significant electromagnetic force produced by the star on the electron. The E&M force won't cause photons to escape from the star, but it will effectively trap the electrons inside the star. The exception being that for high velocity, electrons could bounce around until they escape.
Comment: thanks, so it is possible that the electrons would form the corona then? And if the electrons escape, have we ever detected an income electron from the Sun?
Comment: Hi Ernesto, if I have answered the question, please let me know. With regards to your most recent questions, the corona is still actively being studied but there are undoubtedly electrons, protons, and hydrogen particles near the corona. The detection of incoming electrons is verified from solar winds.


Preferred Wordpress video format?

Question: I'm developing a Wordpress blog for a client who needs to embed their own video files. Flash video was our format of choice until recently, but is there a preferred format for Wordpress? One that easily integrates?
Answer: The Codex lists several core-supported oEmbed sites (including a few being added in 3.5):

YouTube (only public videos and playlists - "unlisted" and "private" videos will not embed)
Vimeo (note older versions of WP have issues with https embeds, just remove the s from the https to fix)
DailyMotion
blip.tv
Flickr (both videos and images)
Viddler
Hulu
Qik
evision3
Scribd
Photobucket
PollDaddy
WordPress.tv (only [http://videopress.com/ VideoPress]-type videos for the time being)
SmugMug (WordPress 3.0+)
FunnyOrDie.com (WordPress 3.0+)
Twitter (WordPress 3.4+)
Instagram (WordPress 3.5+)
SlideShare (WordPress 3.5+)
SoundCloud (WordPress 3.5+)
Comment: So there is no native way to embed your own videos directly into a blog post?
Comment: oEmbed **is** the way to embed videos manually into a blog post. Please read the linked Codex entry.

Preferred Wordpress video format?


Vector fonts with UTF-8 support?

Question: In fact the situation I find myself in is a bit more complicated than the question might suggest. I need to typeset a document with various accented characters and would like some hyphenation support for that. I know I need T1 font encoding for that. Unfortunately, then I have to use a bitmap font by default, which is quite ugly... Can I force Computer Modern with T1 or is there no way around? In the latter case, which vector fonts would you suggest? I am only marginally interested in XeTeX or LuaTeX solutions.
Comment: type1 version of T1-encoding cm-font exist now for already a long time. Install either the cm-super fonts or use the the lmodern fonts. Beside this: The font encoding (T1) has nothing to do with the input encoding (utf-8).
Comment: @UlrikeFischer: Thanks for the clarification! I am aware that font encoding and input encoding are different things. Maybe the title of the post was misleading. I just wanted to say that I use UTF-8 input encoding and would like a vector font with appropriate font encoding to support all facilities offered by UTF-8. By the way: I see there is a `cm-unicode` font also. Wouldn't that be a better option than `cm-super`?
Comment: UTF-8 encodes each of the 1112064 code points in the Unicode character set. So do you really want a font which supports *all* facilities of utf8? If yes you should use xetex/luatex along with a large unicode font. Covering such a large number of glyphs with the standard TeX-fonts with 256 glyphs per font is (as you can see in the CJK packages) rather tiresome. — `cm-unicode` is as far as I can see meant for engines like xetex/luatex.
Comment: @UlrikeFischer: Ok, I'm not that greedy! :D Why don't you make your first comment an answer? I'd surely upvote it.
Answer: I strongly suggest Latin Modern fonts instead of CM.
See the post: Latin Modern vs cm-super?
If you also want to have UTF8 encoding mapping in the pdf file (for copy-pasting and accessibility) you can add some line to your preamble assuming you are using pdfTeX (pdfLaTeX).
The minimal code below I have prepared for another post show you how to do this:
\documentclass[]{article}

%PdfTeX settings for a correct UTF 8 Mapping
%------------------------------------------------------
\usepackage{ifpdf}
\ifpdf    \input{glyphtounicode.tex}    %Part of modern distribution
      %%%\input{glyphtounicode-cmr.tex}     %Additionnal glyph: You must grab it from pdfx package
      \pdfgentounicode=1
\else  %Place here the settings for other compilator
\fi

%Encoding + cmap (to get proper UTF8 mapping)
%------------------------------------------------------
\usepackage{cmap}
\usepackage[utf8]{inputenc}
\usepackage[T1]{fontenc}

%NB: CHANGE lmodern AND fourier TO SEE THE PROBLEM OF MISSING UNICODE CHARACTERS
%     You can see this on Acrobat Pro with acessibility checking or simply by copy-pasting the content.
%     Of course copy paste is not perfect in both case but it is better with lmodern
%------------------------------------------------------
\usepackage{lmodern}
%%\usepackage{fourier}

%AMS Math + UTF8 mapping of ams symbols
%------------------------------------------------------
\usepackage{amsmath}
\usepackage{amssymb} % I load it after Fourier else I have more incorrect utf8 mapping (with \geqslant for example)
%Correct UTF8 mapping for ams fonts
\ifdefined\pdffontattr% \ifdefined is part of the e-TeX extension, which is part of any modern LaTeX compiler.
    \immediate\pdfobj stream file {umsa.cmap}
    {\usefont{U}{msa}{m}{n}\pdffontattr\font{/ToUnicode \the\pdflastobj\space 0 R}}
    \immediate\pdfobj stream file {umsb.cmap}
    {\usefont{U}{msb}{m}{n}\pdffontattr\font{/ToUnicode \the\pdflastobj\space 0 R}}
\fi

%Start document
%------------------------------------------------------
\begin{document}

All these examples work fine with Latin Modern but not with Fourier Font (and Palatino and maybe others).

\bigskip
Issue with mapsto : ${\mathcal F} : \boldsymbol{\eta} \in {\mathbb{R}}^{np}\ \mapsto {\mathcal F}\left(\boldsymbol{\eta} \right)\in \mathbb{R}$

\bigskip
Issue with sqrt : $\sqrt{X}$

\bigskip
Issue with parenthesis : $X \geqslant \left(\frac{1}{2}\right)^2$

\bigskip
Issue with sum : $\sum_{n=0}^\infty X^n$

\end{document}

Vector fonts with UTF-8 support?


Do we really need a review tab on a wizard pattern?

Question: I saw some wizard flow patterns have a Review on the last part, is it really necessary?
Answer: The Review stage is generally useful for verifying the data keyed in by the user in the previous steps.
Best used in scenarios where the user cannot  roll back the changes after confirming like, transferring funds to someone.
However in less severe cases this step is redundant.
Note that the over all goal is to give an opportunity to trace back and rectify instead of penalizing the user.
Comment: A good example of this is pretty much any ecommerce cart, most will assure you that you'll have a chance to review the order before you confirm it.
Answer: Good usability requires that you minimize cognitive load, and having to remember information increases this load.
On the last screen of a wizard the user is clicking a button to confirm / submit the details they have entered on all the previous screens. If there is no "review" screen presented at this point, the user has to remember what they have entered on each screen. Even if they can go back through all the screens to review and double check their entries, they still have to remember things that are on previous screens.
If the amount of information entered is minimal then you could argue that a review screen is not necessary, but in general developers choose the wizard pattern precisely because they have a lot of information that needs entered and they want to break it up into manageable chunks (long forms are intimidating).
Answer: The answer, as always, is "It depends."
Reviewing the data we've entered is important in certain scenarios like shopping-cart checkouts (where we're spending money and shipping to an address) and multi-step data entry (where we've entered info in several prior steps and checking it all together would be useful).
In other scenarios, like formatting a drive or setting up some bit of our system, we might not find reviewing everything we've done to be useful because "Who cares?"
Answer: IMHO, this review step is nice to confirm before saving permanently into the DB and to prevent user type errors.


Why is it important to prove that a problem is NP-complete?

Question: Am I correct in understanding that proving a problem NP complete is a research success? If so why?
Answer: Ali, good question.
Suppose you want to show that some problem P is computationally hard.  Now, you could conjecture that P is hard just based on the fact that we don't have any efficient algorithms for it yet.  But this is rather flimsy evidence, no?  It could be that we have missed some nice way to look at P which would make it very easy to solve.  So, in order to conjecture that P is hard, we would want to accumulate more evidence.  Reductions provide a tool to do exactly that!  If we can reduce some other natural problem Q to P, then we have shown P is at least as hard as Q.  But Q could be a problem from some completely different area of mathematics, and people may have struggled for decades to solve Q also.  Thus, we can view our failure to find an efficient algorithm for Q to be evidence that P is hard.  If we have lots of such Q's from many different problem domains, then we have a huge body of evidence that P is hard.
This is exactly what the theory of NP-completeness provides.  If you prove your problem to be NP-complete, then you have tied its hardness to the hardness of hundreds of other problems, each of significant interest to various communities.  Thus, morally speaking, you can be assured that your problem is indeed hard.
Comment: @Ali: I definitely recommend you to read [Garey and Johnson](http://en.wikipedia.org/wiki/Computers_and_Intractability:_A_Guide_to_the_Theory_of_NP-Completeness).  The famous cartoon in the book is a must-see!
Comment: So the initial aim is to find an efficient algorithm for P but since that appears unachievable one assumes that P is computationally hard and then your answers explains the rest?
Comment: We want to show that our problem P is computationally hard, but we don't want to assume that P is hard to prove that P is hard :) Instead, if you prove P to be NP-complete (or even NP-hard but let's ignore the distinction here), you've shown that if any one out of hundreds of already-well-scrutinized problems is hard, then P is also hard.  This is because if there were an efficient algorithm for P, there would also be efficient algorithms for each of the hundreds of problems.
Answer: Proving a problem NP-Complete is a research success because it frees you from having to search for an efficient and exact solution for the general problem you are studying.  It proves that your problem is a member of a class of problems so difficult that nobody has been able to find an efficient and exact algorithm for any of the problems, and such a solution for any of the problems would imply a solution for all of the problems.
It is usually a stepping stone, because your problem is still there - you simply have to relax your requirements. Usually people try and figure out how to relax one or more of "efficient", "exact", or "general".  Inefficient-and-exact-and-general is the attempt to find better and better constants in the exponent for these algorithms.  Efficient-and-inexact-and-general is the study of approximation algorithms.  Efficient-and-exact-but-not-general is the study of fixed-parameter tractability and the search for subclasses of input for which efficient algorithms can be found.
Comment: Nice point for three ways to relax the problem! I guess randomized algorithms falls in the "efficient-and-inexact-and-general" category.
Comment: Really?  Not all randomized algorithms are inexact.
Comment: And of course you are right, JeffE. Also, I understand you are (or were) instructing a former student of mine in algorithms!  As to Hsien-Chih's point, I don't think randomized algorithms fit well in this scheme.  Certainly some randomized algorithms (genetic algorithms and neural nets come to mind) are inexact yet efficient and general, but some randomized algorithms are quite exact - consider the algorithm for verifying a number is prime!  It's a random algorithm, but I am quite confident that nobody has ever gotten a non-prime out of any reasonable implementation.
Answer: Let's see two different cases why two different persons would like to prove a problem $NP-complete$:
a) You are working on a software project. Having specified your system , you are starting to define the architecture of your application. This includes breaking down the large problem/need the application serves to smaller problems. Let's say that you have been given the task to find an efficient (we don't want our application to be slow!) algorithm for one of those smaller problems. After struggling for some time, you cannot find a polynomial algorithm. Then you might think: maybe this problem is very hard, so it's very difficult (or even impossible) to find an efficient algorithm. By proving that the problem is $NP-complete$, you have some evidence for this conjecture of yours and you should start considering an alternative approach (e.g. altering the problem so it becomes easier).
b) You are researching complexity theory. By definition, you want to characterize problems (or classes of problems) according to the number of resources needed , i.e. the difficulty to solve them. By proving that a certain problem is $NP-complete$, you gain some insights:
i) You know have a vast knowledge of the problem. Instead of working on a single problem, you can work with the class of $NP-complete$ problems, which might lead you to new insights.
ii) You allow researches that want to prove $P=NP$ another way to do that. Maybe your problem is easier to attack than $3-SAT$.
iii) On the reverse direction, you can use your new problem as a representative of $NP-complete$ problems. By studying it, you can perhaps understand why this problem is so difficult to solve (= does not have an efficient algorithm) and apply this knowledge to all other problems in the class. (that's what Deolalikar tried to do with the $CLIQUE$ problem)
Summarizing, characterizing a problem allows you to use common techniques. By studying the class it is related to, you can think in an abstract level, without bothering about the specifics of this particular problem, which is common in mathematics and science in general. Working with classes instead of individual members allows you to use known techniques and furthermore, apply your insights to a larger number of objects, instead of only one.
Comment: Many people solve NP-complete problems in practice, even if they're NP-hard to approximate. In the average case many problems turn out to be much easier, although this can be hard to show; it is even harder to prove anything about heuristic algorithms that work well in practice. I suggest the software architect to ask someone whether the problem is "really" difficult before giving up and changing her design.
Comment: I am not saying that the design needs to change. Using a heuristic or approximation algorithm seems to me (falsely?) like changing the problem... since know you are asking for less precise solutions (are those acceptable? it depends on the application!).
Answer: I see that previous answers explain why it is important to know if a problem is or is not NP-complete, but none seems to directly address the question: The proof of "$p$ is NP-complete" is not considered a research success for all $p$. It depends on various things, such as whether $p$ is interesting, whether the proof has new techniques, whether "$p$ is NP-complete" has interesting consequences, etc.
Comment: I've heard that there was a time when you proved some problems are NP-complete, you would have your PhD thesis. Is that true?
Comment: @Hsien-ChihChang張顯之: I can't comment on that, but those results certainly used to be much more popular a few decades ago. It seems increasingly difficult these days to publish a paper in which you "only" prove a hardness result (with the exception of "famous problems" of course), whereas that would not have been a problem in the 70's-80's, judging from the abundance of this kind of papers during that period.
Answer: Each problem has several connections with other problems. In addition, there are relations between a problem and complexity classes.
Therefore, classifying one problem as NPC usually gives us insight into other problems, as well as complexity classes.
For instance, take the graph isomorphism (GI) problem. In the following paper:

Uwe Schöning, Graph isomorphism is in the low hierarchy, Proceedings of the 4th Annual Symposium on Theoretical Aspects of Computer Science, 1987, 114–124; also: Journal of Computer and System Sciences, vol. 37 (1988), 312–323.

it is proven that if GI ∈ NPC, then the polynomial hierarchy (PH) collapses to its second level; which will be a major breakthrough in structural complexity theory.


With Indian e-visa, can I do 2nd entry from Nepal back to India through Banbasa border crossing?

Question: My situation is that I'm already in India. I entered India with tourist e-visa. First entry has to be through one of designated air/sea ports. I did enter through Delhi airport and I got visa stamp to my czech passport. Stamp says I have multiple entries, 90 days continuous stay in India and visa is valid for 1 year. Now I used up almost 90 days and I want to travel to Nepal for shortest time possible and return to India to get another 90 days of continuos stay. I'm in Rishikesh so closest and most cheap option seems to be by bus traveling to Banbasa (land) boarder crossing. Can I return back on my e-visa also through Banbasa (which is not designated 1st entry port)? And how long do I need to stay in Nepal?
Answer: Yes it is possible with e-visa to travel out and back in to India through Banbasa border crossing. I just tried today :). But you can not return same day (as I wanted). You need to stay in Nepal for 1 night and return next day. You need to pay 2400 Inr at Nepali border and they give you 15 days Nepali Visa. They also need 1 passport photo.
Basically you shall end up with 4 passport stamps. 1st stamp for leaving India. 2nd stamp for entering Nepal. 3rd stamp for leaving Nepal. 4th stamp for entering India.


Approximation of derivatives in the finite volume method

Question: I am looking into the finite volume method and I have come to a problem with discritisation. Suppose I am looking at a particular cell(I'm dealing) with cartesian grid. at the points $(X_{i},Y_{j}),(X_{i+1},Y_{j}),(X_{i+1},Y_{j+1}),(X_{i},Y_{j+1})$. Call the edges of the call $e,n,w,s$ using the usual notation for FVM. Suppose I need to find out $$\frac{\partial\varphi}{\partial X}\Bigg|_{n}.$$ How do I find the approximation from the cell centres?
Comment: Are you rather interested in parabolic flux approximations?
Answer: The main idea behind the finite volume method is rather based on approximating the conservation laws in integral weak form (Divergence theorem)
\begin{equation}
  \frac{d}{dt}\int_{x_L}^{x_R} u(x,t) dx = f(u(x_L,t)) - f(u(x_R,t)),
\end{equation}
rather than in differential form
\begin{equation}
  u_t + f(u)_x =0,
\end{equation}
where spatial derivatives never occure. The goal is more in finding accurate numerial flux functions.
One way to improve the approximation is based on a reconstruction procedure, which at least needs derivatives in the cell centers.
Comment: Here, the function is $f(u,u_{x})$.
Comment: @MatthewHunt Green-Gauss or Least-Squares maybe an option.
Answer: The fluxes for this problem are evaluated on the cell boundaries rather than the cell centres. So for cells small enough, you can use a simple arithmetic average:
$$\frac{\partial \varphi}{\partial X}\Bigg|_{n}=\frac{1}{2}\left(\frac{\partial \varphi}{\partial X}\Bigg|_{Y+\delta Y/2}+\frac{\partial \varphi}{\partial X}\Bigg|_{Y-\delta Y/2}\right)$$
That is the average of the value at the cell centres above and below. Then I simply use central differencing to find the value of $\partial_{X}\varphi$ at the cell centres. Does this seem reasonable?
Comment: I think your main confusion are the tangential gradients on the cell faces. These are generally approximated including cell values from diagonal elements. With this you can calculate mean values on the cell corners.
Comment: They're just derivatives. So I have the LHS evaluated at the point $(X+\delta X/2,Y)$, and I need to approximate this.
Comment: Your replies are extremly careless. Can you please stick to the formula above or give more details? Actually you want to calculate a gradient in x-direction on a face parallel to the x-axis. This is not possible using cell averages from direct neighbor elements only.
Comment: I think that you're not understanding the question. I've figured out the issue.
Answer: In a normal finite volue method you interpolate your profile by piecewise constant functions, so that in every cell you assume a constant value of amplitude for all points lying in that region. This makes it very easy to integrate the volume of that cell! The downside is, that at the borders between your cells you introduce a discontinuity of your amplitude and consequently of your derivative. Naively you would have to assume that the derivatives are zero within your cells, and infinite or null exactly at your border.
Now, no one is stopping you to model the derivative at your cell boundaries in a plausible way, and that is exactly what is being done. You define the derivative at your cell boundary as the difference in amplitude of your two cells divided by the distance of their centerpoints. This has the advantage, that any consequent flux you calculate through that border is identical when evaluated from both sides. The mass flowing out of one cell is exactly the mass flowing into the other. That leads to the nice conservation properties of finite volume methods.
Comment: I can compute the derivatives of $\partial_{X}\varphi$ on the east and west sides, but I don't know how to do it on the north and south faces. I've seen how it's done for finite differences, I wondered if there was an equivalent way of doing it for finite volume.


What is the difference between artifact and evidence

Question: I am reading about the incident response. I cannot able to understand exactly the terms artifact and evidence. When i searched in google so many resources are using these terms generally. How can i find out standard definitions for these two terms? and what is the difference between them?
Comment: Please provide example context. Such as a sentence where these terms are used in the IT Security realm.
Comment: If you want to get formal re. what is "evidence" is, evidence is something that is or would be admissible in some sort of legal proceeding (including  civil, criminal, administrative, etc. adjudication) or dispute resolution. An artifact is a trace you believe may have (Maybe? More likely than not? Could have been? Guess depends on your standard of proof.)  left by an adversary in a system. If you don't want to get formal re. "evidence"...well, there's really not a difference that matters beyond semantics. (Source: law degree.)
Answer: Artifact: A piece of data that may or may not be relevant to the investigation / response. Examples include registry keys, files, time stamps, and event logs.  You can see many defined in the ForensicArtifacts project on github.
Evidence: A piece of data (artifact) that is relevant to your investigation because it supports or refutes a hypothesis.
With our incident response software, we talk about collecting artifacts from remote hosts and analyzing them to determine if they are evidence.
Answer:
Artifact: Something observed in a scientific investigation or experiment that is
  not naturally present but occurs as a result of the preparative or
  investigative procedure.

If you pull a hard drive the data is evidence.
If someone had to take ownership of a file to break into some encryption then that person will show as last updated by.  That is an artifact.
Comment: Also, don't forget that to be useful, evidence has to be handled in a specific way in order to maintain its usefulness. You have to be able to demonstrate that it cannot have been tampered with at any point. The so-called "chain of evidence".
Comment: @Julian Knight  That would depend on the legal (or, in some instances, private) rules that govern whatever court or adjudication institution you're trying to introduce the "evidence" into. You are right that some courts, under some sources of law, in some areas of  the world (for eg. a federal criminal proceeding in the U.S.) might require proof of "chain-of-evidence" re. how the drive was collected, examined, and stored. Many other institutions might require lesser or essentially no such proof to let it into consideration. All depends on what type of proceeding, where, under what laws/rules.
Comment: @halfinformed I did litigation support in the US for a while and that artifact would be noted in the chain of evidence.
Answer: Artifacts would be something supporting such as an SOP or guidelines explaining the process to be followed.
Evidence would be something that proves the process is being followed.
Comment: Do you have any references for these definitions? They appear to be very wrong in general, but specifically wrong in terms of Incident Response.


Was this a high IGBT gate current?

Question: I'm controlling an IGBT inverter with a DSP. I'm pretty sure I turned on two IGBT's at the same time which made a short circuit. The PCB I'm using to step up the PWM signal to drive the IGBT's let the smoke out and I'm trying to figure what my problem is. If the IGBT did get turned on to cause a short then is it possible that the currents going into the IGBT driver got massive? Thanks
Comment: Could you post some sort of schematic or diagram? It's hard to know without more details. As a rough guess, I would not expect IGBTs being shorted to affect the board driving the IGBTs.
Answer: When you are designing inverters with IGBTs there are a few key things to worry about. You already discovered the big one, which is the timing of the high side and low side IGBTs on the same output leg. If you turn them on at the same time, or turn one on while the other is still in the process of turning off, you get a very high current through the two of them. This is called "shoot-through" and is definitely something you want to avoid.  Remember that IGBTs have resistance measured in tenths of Ohms and your capacitor bank and the traces/wires between it and the IGBTs will be very low impedance by design... That's a lot of energy with an ideal short-circuit path.  On a 208V inverter design you might have a 340V bus and a half an ohm IGBT on-resistance ... you get the idea.
If you are using a DSP with any kind of motor control enhancements, there will be a few extra settings to play with on the PWM peripheral. You'll see options for tuning how much dead time there is between PWM outputs, tuning the delay before and after the midpoint of the PWM pulse, and there may also be additional inputs to detect things like de-sat or excessive current.
In my own inverter designs I tended to put the de-sat detection in hardware, as my almost two decades of experience has taught me not to trust software. :-)
Another very critical thing, and one that is not quite as critical anymore with the more advanced PWM controllers, is that the high-side driver and the low-side driver must be balanced.  If it takes 500us for a gate fire signal to propagate to the IGBT on the high side, you must add additional delay to the low side (the low side driver is generally a simpler and thus faster circuit). As I said, high-end PWM controllers allow fine-grained control over each PWM output and can unbalance the firing so the hardware side is simpler, but being the old fart that I am, I still think it's good design to have the timing on both sides matched.
When testing, I strongly suggest some kind of fast fusing and even reduced current on the bench. IGBTs can be damned expensive, the magic smoke they let out isn't good for your lungs and the noise they make isn't good for your ears.  Wear proper protection equipment and always be fully aware of the lighting that lurketh in a fully charged capacitor bank. Inverter design mandates that you minimize impedance, which just makes the accidents all that more spectacular and dangerous.
Answer: From your question, it sounds like the IGBT drivers themselves failed. Like most things, failure can be due to overvoltage, or due to overpower. Overvoltage is possible, but would probably be due to an sub-optimal circuit design.
Overpower might indicate very high switching frequencies, an undersized driver for the IGBT you're running, or that the IGBT gate-emitter has gone to a dead short.

Was this a high IGBT gate current?


Are the states in the convex decomposition of a density matrix necessarily orthogonal?

Question: In Nielsen and Chuang's QC&QI, I do not see a statement one way or another. In Steeb and Hardy's Problems and Solutions, orthogonality is asserted. If the $p_i$ in $\sum_i p_i |\psi_i\rangle\langle\psi_i|$ were guaranteed to be distinct, then the eigenvalues would be distinct and orthogonality would be assured. In the general case, I don't know, and I wonder if this question is important given that the $\psi_i$ are not uniquely determined.
Comment: You can use `|\psi_k\rangle` to write a ket.
Answer: No. In the ensemble interpretation of a density matrix
$$
\rho=\sum_k p_k|\psi_k\rangle\langle \psi_k|
$$
the states $|\psi_k\rangle$ are not necessarily orthogonal. Also, the probabilities $p_k$ are not necessarily eigenvalues.
Ensembles vs eigendecomposition
A density matrix $\rho$ encodes multiple ensembles $\{p_k, |\psi\rangle_k\}$, see theorem $2.3$ on page $103$ in Nielsen & Chuang about the unitary freedom. Eigendecomposition of $\rho$ is one of those ensembles - one with orthogonal states $|\psi_k\rangle$ - but generally not the only one.
Example
In fact, Nielsen & Chuang give an explicit example on page $103$
$$
\rho=\frac12|a\rangle\langle a|+\frac12|b\rangle\langle b| = \frac34|0\rangle\langle 0|+\frac14|1\rangle\langle 1|\tag{2.165}
$$
where $|a\rangle\equiv\sqrt{\frac34}|0\rangle+\sqrt{\frac14}|1\rangle$ and $|b\rangle\equiv\sqrt{\frac34}|0\rangle-\sqrt{\frac14}|1\rangle$ are not orthogonal. Note that even though $\rho$'s eigenvalues $\frac34$ and $\frac14$ are distinct the ensemble it represents is not unique (unlike eigendecomposition which is unique when eigenvalues are distinct).
Comment: To be precise, the freedom is really a partial isometry (or isometry, when starting from the eigenvalue decomposition) rather than a unitary.
Comment: The issue with the "unitary + padding" characterization rather than the "(partial) isometry" characterization is that it does *not* specify the relation of two given ensemble decomposition, but only of ensemble decompositions up to padding.
Comment: I agree, but "unitary freedom" is what Nielsen & Chuang call it in the book.
Comment: Wasn't meant as a criticism, I just felt it might be good to point this out. "Conceptually", memorizing this as a unitary DoF is indeed fine (and also correct when allowing to pad ensemble decompositions with zeros).
Comment: Yeah, padding the ensembles is exactly what they do.
Answer: To build on the other answer, we can in fact characterise the set of coefficients that can fit into a convex decomposition of a density matrix.
Given $\rho$, we can write
$$\rho = \sum_k a_k |u_k\rangle\!\langle u_k|$$
for some set of (not necessarily orthogonal) states $\{|u_k\rangle\}$ if and only if $\mathbf a\preceq \boldsymbol{\lambda}(\rho)$, meaning that the vector of coefficients $\mathbf a\equiv(a_1,a_2,...)$ is majorised by the vector of eigenvalues of $\rho$.
See e.g. Watrous' book for a proof (section 4.3, page 245).


Generation of medical institution names: training corpora?

Question: My question is quite similar to this one: Generation of institution names. I need to be able to produce 'fake' names of medical institutions, specifically to create data for unit tests. Unfortunately, simple tools like Faker do not work well for this task, so I am interested in a more sophisticated solution, possibly involving some NER model(s). My question here is where can I get text corpora for training the model? The texts must contain (human-)recognizable names of medical institutions, preferably in a number of languages. I have seen allusions that this might be done by scraping PubMed or other Web sources - are there possibly some concrete examples or howtos?
Answer: I can think of a couple options to collect a sample of medical institutions:

Wikipedia has a list of hospitals by country (isn't Wikipedia amazing?)

Many countries have some kind of national directory of medical institutions, but that would probably be difficult to scrap and specific to each country.

UMLS has a category ("semantic group") for "Health Care Related Organization" (T093, see here), which means that a list of such organizations can be directly collected from the UMLS data. I thought this would be a good option, but I did a quick test and it appears to contain only names of departments, no proper nouns, for example:
<code>Community occupational therapy clinic
Abortion Center
Area Health Education Center
</code>

Given that UMLS is closely related to PubMed, my guess is that it's not a very good direction, but maybe I didn't dig deep enough. Fair warning: Processing the whole PubMed/PMC is quite a lot of work in my experience.
Comment: Thanks Erwan, both suggestions are helpful! In the mean time, I have found a way to directly request the NCBI RESTful API, as in this [link](https://dataguide.nlm.nih.gov/eutilities/utilities.html). I am writing more about this in my answer below
Comment: I will write a Python script to mine these data, if someone is interested, feel free to contact me.
Comment: BTW, the wikipedia list of hospitals is far from complete. I checked for the two areas I know well, and the coverage is certainly less than 20% of what there is.
Answer: I have found a way to create the corpus of potentially medical institutions by requesting the NCBI RESTful server, following the description in this link.
First, you send an ESearch request containing some searching criteria (e.g. 'radiology', 'dicom', 'segmentation' - or whatever). As a response you obtain an XML document with a list of PubMed Ids.
Then you can send a EFetch request containing the IDs, and as a response you will obtain an XML document with an  tag for each author. That data can then be used to build the corpus (in the 1st approximation)


Measure and metric

Question: What, in simple terms, is the difference between a measure and a metric, and what applications require a measure rather than a metric, and vice versa? Examples would be great.
Comment: Maybe looking at a book like Royden would immediately satisfy you?
Answer: A metric measures the distance between two things. For instance, the usual metric in $\mathbb{R}^2$ is the one for which the distance between $(a,b)$ and $(c,d)$ is $\sqrt{(a-c)^2+(b-d)^2}$.
A measure measures sizes of sets. For instance, with respect to the Lebesgue measure on $\mathbb R$, the measure of an interval $[a,b]$ is equal to $b-a$.
Answer: Let $X$ be some set.
A metric is a function $d: X \times X \rightarrow [0, \infty)$ that describes the distance between the two input values. A function $d$ of this type is a metric, if it is positive definite, symmetric and fulfils the triangular inequality. Examples are the Euclidean distance on $X = \mathbb{R}^n:$ $d(x,y)= \sqrt{\sum_{i=1}^n (x_i - y_i)^2}$. Or the discrete metric $d(x,y)$ that is $0$, if $x=y$ and $1$ otherwise.
A measure is defined on subsets of $X$, a so-called $\sigma$-algebra, say $\mathcal{A}$. This $\sigma$-algebra is a subset of the power set of $X$. While a metric measures distance, a measure typically measures area or volume of a set. In a  1D example, also sort of a distance. The Lebesgue measure in 2D for instance assigns each rectangle in $\mathbb{R}^2$ the area of the rectangle. Starting from this, one can show that it can be used to measure the area of most subsets of $\mathbb{R}^2$.

Measure and metric


Raster processing and query PostGIS

Question: I have around 2000 raster file in TIFF format of 4.5Gb size. I want to store them in a PostGIS DB in order to do some mapalgebra operation between them and than query the results of the calculation with a vector of polygons doing zonal statics, in particular mean value. I'll like to do this operation in the quickest way possible. can you lease suggest me an SQL query do so in the fastest way, or other possible solutions?
Comment: Can you point out what you already did yourself? Are there specific issues that you are encountering? It always helps when you provide people with a clear question instead of a generic one.
Answer: The typical query for zonal statistics over a raster table looks like this:
<code>SELECT polyid,
       sum(ST_Area((gv).geom) * (gv).val) / sum(ST_Area((gv).geom)) AS meanval
FROM (SELECT polyid,
             ST_Intersection(rast, geom) AS gv
      FROM tiled_raster_table, polygon_table
      WHERE ST_Intersects(rast, geom)) foo
GROUP BY polyid;
</code>
Your raster table has to be tiled (e.g. 32x32) and indexed (on the rast column) for best performance.
You might also have to project your polygon table to the same coordinate system as your raster table (not the opposite) if it's not already the case.
This tutorial show the whole process but it is a bit outdated.

Raster processing and query PostGIS


Why does fructose reduce Tollen's reagent and Fehling's solution?

Question: Even though fructose is a ketohexose (ketone-containing hexose, a six-carbon monosaccharide), it reduces Tollen's reagent and Fehling's solution. Generally, a ketone does not reduces Tollen's reagent and Fehling's solution. So, why is this possible in the case of fructose?
Answer: The presence of the hydrogen atom in the aldehyde group gives reducing properties to the aldehyde molecule. Aldehydes are easily oxidized by mild oxidizing agents such as Tollens' reagent ($\ce{Ag+}$ in aqueous ammonia), Fehling's reagent ($\ce{Cu^2+}$ complexed with tartrate), or Benedict's reagent ($\ce{Cu^2+}$ complexed with citrate). Ketones do not have such reducing properties and are not oxidized under similar conditions. Therefore, Tollens' reagent, Fehling's reagent, or Benedict's reagent can be used to distinguish aldehydes from ketones.
However, fructose reduces such reagents even though it contains no aldehyde group. Reduction occurs because the reagents are basic solutions and fructose is readily isomerized to a mixture of aldoses (glucose and mannose) under basic conditions.

Under basic conditions, the proton alpha to the carbonyl group (aldehyde or ketone) is reversibly removed. If the resulting enolate ion reprotonates on the oxygen, an enediol intermediate results. Thus, the base-catalyzed enediol rearrangemet can move the carbonyl group up and down the chain.
Furthermore, in the enolate ion, the affected carbon atom is no longer asymmetric. Reprotonation can occur on either face of the enolate, giving either configuration. Thus, the base-catalyzed epimerization results in a mixture of stereoisomers.
Therefore, under strongly basic conditions, the combination of enediol rearrangements and epimerization leads to a complex mixture of sugars (see also: Lobry de Bruyn–van Ekenstein transformation).
Comment: However, everywhere, it is written only 'alpha-hydroxy ketones'. Not all alpha-hydroxy ketones are fructose, that is, not all alpha hydroxy ketones can double tautomerization to form an aldehyde.
Comment: [This answer](https://chemistry.stackexchange.com/a/73333/5026) nicely elaborates the mechanism stated in words in this answer.
Answer: In the presence of very dilute alkalis, glucose, for example, is converted into a mixture of glucose, mannose and fructose. It is explained by the presence of an intermediate enodiol, and is also called epimerization, since a mixture of epimers is obtained. All monosaccharides are oxidized with Benedict, Fehling and Tollens reagents, also giving aldonic acids. These reactions do not serve to distinguish aldoses from ketoses, as occurred with aldehydes and ketones, since the latter also reduce the previous reagents, since, under the conditions of the tests, the ketoses equilibrate with the aldoses through an ene diol, as just seen. The carbohydrates that test positive for these tests are
called reducing sugars.


Is the following sequence $x_{n}=\frac{1 +(-1)^n}{n}$ Cauchy?

Question: Is the following sequence $x_{n}=\frac{1 +(-1)^n}{n}$ Cauchy? I got not Cauchy, but would appreciate someone to check this. Thank you!
So I got the sequence is bounded by 2 and that $abs(x_n-x_{n+1})<=2$ then if we pick $\epsilon=1/2$ then the sequence is not Cauchy... is my proof sufficient?
Comment: 1) If $\epsilon = \frac 12$ and $n,m> 4$ then $|x_n-x_m| < \frac 12 = \epsilon$ so nothing you said makes any sense and 2) you can't show something for *one* epsilon; you must show it for all.
Comment: Well, show us your work where you got "not Cauchy", then we can check for it for you.
Comment: @ZeroXLR just edited my question, check please. Thanks
Comment: Ok, how does being bounded above by $2$ prevent the sequence elements from not get any closer than $\epsilon = 1 / 2$? To conclude that, you will need a lower bound not an upper bound
Comment: It converges,  so it is Cauchy.
Answer: Hint: Recall that a convergent sequence is automatically Cauchy. Next, note that the triangle inequality yields
$$
|x_n| \leq \frac{1 + |(-1)^n|}{n} =\frac{2}{n}.
$$
From here can you show that $\lim{x_n}$ exists?
Answer: $|x_n-x_m| \leq \frac 1 n +\frac 1 n +\frac 1 m +\frac 1 m <\epsilon $ whenever $n, m \geq \frac 4 {\epsilon}$.
Answer: If $n$ is even then $x_n = \frac {1+1}n = \frac 2n$ and if $n$ is odd then $x_n = \frac {1-1}n = 0$.
It should be well known that $\frac 1n \to 0$ so $\frac 2n\to 0$ and, of course $0\to 0$ so $x_n \to 0$ and converging sequences are Cauchy so this should be Cauchy.
Just as we prove that $b_n = \frac 1n$ is a cauchy sequence by saying for any $\epsilon > 0$ then if we let $N = \frac 2{\epsilon}$ then if $n,m > N$  then $\frac 1n < \frac 1N = \frac \epsilon 2$ and $\frac 1m <\frac \epsilon 2$ so $|b_n - b_m|=|\frac 1n - \frac 1m| \le |\frac 1n| + |\frac 1n| < \frac \epsilon 2 + \frac \epsilon 2$...
We prove $x_n$ is cauchy by pointing out for any $\epsilon > 0$ if we let $N = \frac 4\epsilon$ then if $n,m > N$ then if $n$ is even then $x_n =\frac 2{n}< \frac 2N = \frac 12\epsilon$ and if $n$ is odd then $x_n = 0 < \frac 12 \epsilon$ so either way $x_n < \frac 12 \epsilon$.
Same thing for $x_m$ and $|x_n - x_m| \le |x_n| + |x_m| < \frac 12 \epsilon + \frac 12 \epsilon = \epsilon$.


ArcGIS Server 10.2.2 - Map Export Sometimes Returns Blank Image

Question: I've run into a fun little issue with ArcGIS Server 10.2.2 to end my week with...  I have discovered today that the export operation (the one that renders map layer images) is randomly returning blank images.  As in - I enter a export url into the browser, hit F5, get expected image.  Hit F5 again - get blank image.  Hit F5 again - get expected image.  None of the parameters are changing - its exact same url.  There is no observable pattern - sometimes I got to hit F5 multiple times before I get expected image.
I remember facing a similar bug back at 10.1 - where every other GET query failed (How does that make it through testing???).  This seems awfully similar to that.  I starting search GeoNet - and have seen similar posts.  Does anyone know if there is any official NIM for this issue - and more importantly a solution or workaround?
Answer: The solution on the JavaScript API side is to intercept the request to export map by passing a handler function to esriRequest.setRequestPreCallback like explained here
https://developers.arcgis.com/javascript/jsapi/esri.request-amd.html#esrirequest.setrequestprecallback
Check if ioArgs.url ends with "MapServer/export"
If yes, then set ioArgs.content.random to Math.random()


ECO 36 on 200 amp panel

Question: I want to install an ECO 36 36kW electric water heater which requires 150 amps max. My house panel is 200 amp and is out of space. What are my best options?
Comment: Can you post a photo of your panel? Also, what make/model/size is your current hot water heater, where are you on this planet, and *why* are you interested in a tankless heater?
Answer: I have installed similar water heaters and because of the large amp draw you will need a larger service a sub panel alone is not enough. Several homes I was able to use a 30/40 service panel 300 amps continuous / 400 peak I think some call these 320 amp services. In one large all electric home I had to install a 400 amp panel. From either of these you can feed your existing main that would become a sub panel (some rewiring may be needed to isolate the neutral from ground) a 2nd sub could be added to power your water heater and any additional loads for future use. Because of the size of this load it is not as simple as just adding a sub from your existing main panel. The service drop and usually the meter base will also required to be changed. I would first check with the power company to verify your service can be upgraded without you having to purchase a larger transformer. Most customers making this change have been ok with the costs and results but I had 1 customer that after spending +10k or more had the tankless removed because he liked the 80 gallon electric better.
Comment: +1 - I would vote for a second main breaker just for the water heater and keep the stress of that heavy load away from the rest of the house panel. You are allowed more than one main and it makes sense to wire the water heater separate.
Answer: First, I would think about a load calculation for your house to make sure adding 150A of load does not justify adding additional service capacity.  I can think of two facilities with 200A panels where it would be perfectly reasonable within their service.  However, the result of this load calculation may be that you just need bigger service.  If you can get 400 (320) amp service, that is typically handled by installing two 200A panels.  You could retain your first panel and fit a second panel right next to it.
If the load calculation supports staying at 200A, then you have a simple matter that the "full panel" situation is absolutely intolerable. Again the answer is another 200A panel right next to it, but in this case you feed it as a subpanel, fitting a 60-100A breaker (60A breakers have the advantage of being $9) in the main panel.  Then move a bunch of smaller branch circuits to the subpanel, freeing up slots in your main panel.  You will need to free up 6 spaces to accommodate the three 2-pole breakers the water heater will require.
Make sure to lay out the subpanel so you could trivially convert the setup to 400A/dual main panels.  That way you don't have to do any work if you go that way later.

Getting a water heater that is large enough is a Very Correct Thing To Do. I would even say that a 150A heater is not excessive, you will get about the same BTU as my gas unit.
Here is what is the mistake, however: shipping on-demand hot water all over a large house.   For instance my friend has a sprawling ranch house, with bedrooms and those bathrooms clustered at one end of the house, and kitchen, laundry and the guest bathroom clustered at the other.  Between them is a very long hot water pipe, which causes endless waiting for the water to heat up.  This also wastes a lot of energy, because after filling the long pipe with hot water, that hot water is then abandoned in the pipe.  Having one single huge tankless, in that house, would be a great design waste.
Getting rid of that long wait is often a design goal of switching to tankless. Fitting the tankless in the same place as the tanked heater will not solve it.
The beauty of electric hot water is it has no flue.  It can be sited almost anywhere.  The ideal place is 6 inches from the shower's hot water faucet, but I'll settle for under that bathroom's sink.
So don't carry the heat long distances in copper pipe.  Carry it in copper wire. Heat carried via wire moves at the speed of light and has no wastage, no electrons abandoned in the wire at the end of the shower.  In other words, that calls for smaller tankless units distributed around the house as needed.
This impacts load calculations, because you don't necessarily need to factor for all the units being on at the same time.
Answer: You need to vacate 2 slots in you CB panel or replace the panel with another 200amp panel with more slots.
Do an amperage survey with an amp probe. Turn on everything you would use at the same time on any one breaker and see how much amperage is loading the circuit with your clamp on amp probe. Consolidate circuits if you can.

ECO 36 on 200 amp panel


Is there any way to rename app name in lauchpad?

Question: I have 3 eclipses installed on my mac eclipse jee, eclipse for android and eclipse for php.
all three eclipses are cooming in launchpad with the name eclipse.
Is there any way i can rename app name like
eclipse jee, eclipse php, eclipse android in launchapad?
Answer: You can by using an Administrator account and renaming the apps in Finder. LaunchPad will show the changed name accordingly.
There also is this app, which seems to make renaming items and other operations in LaunchPad possible. Unfortunately, it seems to be discontinued, so try it at your own risk.
Finally, if you are comfortable with SQLite databases and SQL, you could manually make the necessary changes in the LaunchPad database. I'd advise you to first back up your database before you start tinkering with it. You can use the built-in sqlite3 command-line client to manipulate this database. You'll want to find the appropriate records in the apps table, and update their title field.
Comment: Hi, I can't rename the application itself. Is there a way to rename the LaunchPad shortcut only? Are there any alternatives to the application you linked? Thank You.
Comment: yeah actually that's my next question. I have a doubt if i rename the .app file, i think some features may not work.
Comment: That shouldn't be a problem, but the easiest way to find out is test it. You can always change the name back.
Comment: hmmmm i have renamed .app files. i will updated when i will get any prob.
Comment: @Vivart, I added some alternative solutions if just renaming the apps does not work for you.
Answer: Fer's answer works perfectly without the danger of renaming the apps. Perhaps it was misunderstood by some.
The easiest way to do this is to open Terminal, type ln -s (included trailing space) and drag the App to be "renamed" into the Terminal window twice. You should have the full path to the app in your command twice, modify the second path to rename the app, just keep the path the same.
For example, to rename "Microsoft Remote Desktop" to just "Remote Desktop":
ln -s /Applications/Microsoft\ Remote\ Desktop.app /Applications/Remote\ Desktop.app
You don't even need to hide the original icon for the app in LaunchPad, as the new one replaces it.
Comment: important to note that you need to make sure the new symlink has the ".app" extension to it in order for it to show up in launchpad, even though it works fine without that extension when clicked in finder.
Answer: Create a symbolic link of your Launchpad app:
ln -s Launchpad.app Launchpad_renamed.app

Comment: The question is about how to rename apps *on* the Launchpad, not the Launchpad app itself.


Physics of Fireworks

Question: This evening I saw the 4th July classic Fireworks in San Diego, and I was wondering about the most physical picture of what was happening. Does anyone have a good way to explain the detailed physical features of the phenomenon?
Answer: It's "just" plasma physics. The "fire" part heats up atoms to the point where they lose electrons. When those ions regain electrons, the electron undergoes transition in energy state from free to bound. This energy is released as a photon (since electrons are bound electromagnetically to atoms). The energy of the photon is tied to the electrical energies of the bound electron state, which in turn is determined by the number of protons in the nucleus.
Comment: Most of the commentators on http://physics.stackexchange.com/questions/23469/is-fire-plasma don't seem to believe that ordinary flames are plasma.
Comment: Do you know if is there any more specific reference to the fireworks applications of the plasma processes?
Comment: @dmckee: I'd agree with those comments; for a regular fire that's probably the case. But fireworks use selected metals (e.g. Potassium, Lithium, Calcium) to achieve the desired colors, and those ionize far easier. See also http://www.chemicalforums.com/index.php?topic=3553.msg15479#msg15479

Physics of Fireworks


Can triggers tell if a Workflow invoked them?

Question: Is there anything available to us in Apex that can be used to determine if a trigger was fired by Workflow/Process Builder?
Comment: As far as I know: no.
Comment: What kind of workflow? Triggers require initiation of DML activity for them to be activated. Off-hand, I can't think of any time-based workflow that causes DML to occur. In an execution context, Workflow and Process Builder aren't called until After a trigger is fired at least once, after which the workflow or process builder activity could cause it to be called again (i.e. recursion); something a Boolean variable can be used to detect.
Comment: @crmprogdev how can a boolean (maybe more like a static counter?) be used when the same trigger runs twice before WF gets to run? e.g. user inserts an Account > AccountTrigger runs > updates Contacts > ContactTrigger runs > updates another set of Accounts (different from user Account) > AccountTrigger runs again > WF runs > etc
Comment: @Mossi. It depends on trigger design whether static or non-static var would be used to prevent recursion. I've written some triggers that required static boolean and others where a static boolean would cause issues with other instances of the same class. In the situation you cite where Contacts are updated by an Account trigger, I'd expect there to be two instances of the Account trigger. A 2nd instance would begin after update of the Contacts that creates a diff `Trigger.new` and a 2nd rel execution instance of trigger for those Accts gets spawned. NOT operating on same records any longer.
Comment: Exactly. But in that case how can a boolean (or any other variable) tell whether or not a WF caused the 2nd Account trigger to run?
Answer: Triggers (which represent the domain layer in a Separation of Concerns architecture) should not have to know how they were invoked as they could be invoked via

Web or REST service DML
VF controller
Standard controller
Data Loader
AJAX Toolkit
Asynchronous process
...
Comment: But they *can* detect if they've been re-run in the same transaction by using a static variable. Usually, this doesn't matter for a well-written trigger, but it can avoid extra queries/DML statements by doing so.
Comment: I agree with @sfdcfox. I always feel soiled if I code trigger.isExecuting as that usually means I haven't structured my separation of concerns properly.  There is no Workflow.isExecuting.
Comment: But I believe the trigger context in SF does allow partial detection of the caller, using the `isExecuting` flag check. Isn't it so?
Comment: @Mossi a workflow could include an additional field update to an sobject field isinWorkflowContext__c that would be useful to a before insert or before update trigger as those triggers can switch it off
Comment: Yes. But I was just trying to point out that SF may not be completely following the SoC architecture as they are partially exposing how triggers were invoked via the `isExecuting` flag. As for the custom field solution; that can definitely be applied to one-off scenarios. But it fails in bigger designs.
Answer: I was searching the same some time ago and it looks like the answer is NO. There is also an idea posted 6 years ago on that but yet not implemented. So it is an old one.
Comment: Static variables can detect if a trigger re-fires a second time, which is probably why that idea was never seriously considered. However, I would say that the ability to detect if the trigger happened from a particular context (API versus UI) would be pretty convenient.
Comment: @sfdcfox I'm not agitating to vote for that idea:) I'll better edit my post.
Answer: Now salesforce released new ENUM called 'Quiddity', by using this you can easily know what invoked your code. Read here and here you can find example code.
Comment: Yes and no... Quiddity tells you what started the entire transaction. If someone edited a record in an Aura component, provoking a workflow rule, which in turn provoked a trigger... the quiddity will be Aura.


what are the main advantages of using a Double Stereo projection?

Question: I'm not per say a GIS guru, I'm more of a user of the technology. On a recent project we were asked to analyze, provide, and submit all our analysis using a Double Stereo projection. What are the main advantages of using it vs. UTM, or any other projection.
Comment: The best resource I know of on Map Projections is by Carlos Furuti. His work us knowledgeable, well presented, understandable and comprehensive. A rarely found combination. You can begin at the end with the [Map Projections Summary](http://www.progonos.com/furuti/MapProj/Normal/ProjTbl/projTbl.html). Your answer is certainly there, but will take some digging.
Comment: @mattwilkie that link is dead currently, here is another resource with some archived links to the original source matt linked https://map-projections.net/properties.php
Comment: Thank you for the link to the Map Projections Summary. +100, if it were possible.
Answer: As far as I can tell, "Double Stereographic" is identical to stereographic.  Stereographic projections are favored for work around the poles because the meridians radiate in straight lines around the projected pole.  The projection is conformal, implying the meridians also have the correct relative directions, too.
In the stereographic projection, all geodesics on the sphere are projected either to portions of lines or portions of circles in the plane.  (This is because the formula for the projection is particularly simple.)  A rotation of the sphere can be computed as a fractional linear transformation of the plane, which is the fundamental operation of inversive geometry.  Thus, certain natural operations on the sphere are easily and directly computed and visualized in a stereographic projection.
In mathematics the stereographic projection is a fundamental tool: it creates a conformal one-to-one correspondence between the sphere and the plane with a "point at infinity".  This unifies many aspects of complex analysis and algebraic geometry.
Answer: Double Stereographic vs Stereographic.
Mathematically a stereographic projection is directly projecting the sphere to the plane.  A double projection is projecting to another mathematical spheroid first (Guassian Spheroid).  Both projection centers are located on opposite the tangent point of the plane (ie on the other side of the planet).
Why use either of these methods?  The Canadian Province of New Brunswick uses a unique projection (NB Double Stereographic) because of the unique shape of NB (almost a square) this projection allows for minimal distortion around a circle with a scale factor of 1.  Basically it is used in this case because NB straddles multiple UTM zones and it is convenient to use NB Double given the shape and population distribution in the province.  It wouldn't be an ideal projection for a long skinny jurisdiction, as for say in Chile or Japan etc.


Security Log Analyze

Question: is there any tools that I give it web server log (like Apache web server) and analyze it if there was any attack or not?
I don't want to use SIEM.
Answer: There is benefit to using a full-cycle platform that allows SIEM Engineering (e.g., Splunk ES) and Security Automation (e.g., Splunk Phantom), but these can also be performed using open-source platforms (e.g., HELK for SIEM engineering and Rundeck for Security Automation).
There are many benefits to ATT&CK detection, which may be platform-dependent. For example, Microsoft Sysmon is great for Windows and Windows Server, but no use on Linux or macOS. osquery has many configurations for all 3, but ATT&CK coverage tends to be Windows-only as well. auditd is Linux-only. xnumon is macOS-only, but there's a lot going on there, which even this forum has covered.
It sounds like what you are asking for in this question is not only going to be OS-dependent, but also perhaps Web Server or even Application Dependent. However, there are some standards, such as the NCSA Common Web Server Log format, and loose guidelines.
After-the Fact, there isn't much you can do, but I have seen a few articles cover tools such as apache-scalp. For Apache httpd web server, the access log file(s) are usually in /var/log/apache2/access.log, but can be anywhere (even the config can be anywhere). For Windows Server IIS web server, the log files are usually in \WINDOWS\system32\LogFiles\W3SVC1, but again, can be configured elsewhere. Most databases and other integration points for web applications do not log by default, or their logs are uninteresting for security purposes (but this is not always the case).
If you can install tools or run Python scripts, etc, then you may be off to a good start. If not, then you may be able to bring the logs elsewhere, but then you end up right back at the original Not-Using Splunk problem that brought you here in the first place. Microsoft has a more-official tool for web server / web app log analysis named LogParser which can do cool things, such as:

logparser.exe -i:iisw3c -o:Datagrid -rtp:100 "select date, time, c-ip, cs-uri-stem, cs-uri-query, time-taken, sc-status from C:wwwlogsW3SVCmyserver*.log where cs-uri-query like '%UNION%'"

Apache, Nginx, and IIS web servers tend to only log HTTP GET requests and their associated server response codes. If you want more, then you'll  need to turn to additional bolt-on utilities and/or configurations.
For example, for Apache, mod_dumpio has been around since 2009, and mod_security and others were added later to support HTTP POSTs and lengthy server response collection.
proxy_pass or fastcgi_pass lines can be configured for the Nginx web server in order to leverage the $request_body variable.
The Advanced Logging Extension for IIS can be added to Microsoft IIS Server to achieve the same, or better.
Comment: https://www.apacheviewer.com/unlock/
Comment: https://github.com/kitabisa/teler

Security Log Analyze


Change key icon keyboard: Drawable return int?

Question: I'm trying to change a key icon on press in run time:
@Override
public void onPress(int primaryCode) {
    Keyboard currentKeyboard = KbView.getKeyboard();
    List<Keyboard.Key> keys = currentKeyboard.getKeys();
    KbView.invalidateKey(primaryCode);
    keys.get(primaryCode).label = null;
    keys.get(primaryCode).icon = R.drawable.image;
}

However, the last line says:
Incompatible types.
Required: android.graphics.drawable.Drawable
Found: int

If I use instead: keys.get(ponto).icon = getResources().getDrawable(R.drawable.image);
says that getDrawable(int) is deprecated.
(It works, but when I press a key, change the icon  of other key)
(I'm using API level 8)
Answer: I also had that problem. Try this:
Keys.get(primaryCode).icon = ContextCompat.getDrawable(Context, R.drawable.image);

You need to have the support lib in your project.


Honda Oil Pan in winter cold

Question: Does anyone know if Hondabond gasket sealant can be applied in low temperatures?  I have to replace my Honda 3.5l oil pan due to cracking and cannot wait until temps moderate.
Comment: Welcome to Motor Vehicle Maintenance & Repair!
Answer: Read the label for any specific warnings about application temperatures.
Answer: It ultimately depends on how cold it is. As jwh20 said, the label will likely say.
That said, I couldn't find an exact temp marked on the packaging for the HT stuff. However, it's a little anecdotal, but DAP 100% silicone sealant can be applied as low as -35F and as high as 140F. Since these sealants are "partial drying" types, it would be best not to go that cold.
I'll see if I can get something more specific.

Honda Oil Pan in winter cold


Greasepencil render only renders half of the frames

Question: I'm fairly new to blender but I've been making animations with Greasepencil for a while and haven't had this issue yet. I'm rendering a large video as a png sequence (5000+ frames) with eevee. About 2800 frames were rendered perfectly, but the rest of them showed up as completely blank transparent images.
I thought the problem might be the storage on my computer, but after deleting plenty of other animation files and resetting my computer, the same images failed to render. From what I can tell, there's no difference between the frames that rendered and the frames that didn't.
Here's an image of my settings.
Comment: just a question: if you render png anyway, why don't you render "just" the rest of your failed png? or just one to check whether the reason is your setup or your computer? It's just a waste of time to render everything again if you already have rendered (+saved) pngs
Comment: Hi, I didn't render everything again. I don't know if it was clear, but I have tried rendering just the failed parts and nothing will work, but everything is fine if it's one of the frames that already rendered.
Answer: Alright, I figured it out and am posting the answer in here in case anyone has the same problem.
I think Blender had some kind of limit on how many frames I could render at a time in a project. I'm not sure why, but I was able to render the broken frames by copying the project, deleting the keyframes for what I had already rendered, and then rendering the broken parts.
I put those PNG files in a separate folder, then went back to my original Blend project and added the frames to the video editor.


How to add Case as an option in the "Related To" drop down of emails in SFDC?

Question: Users send emails from Cases often and found that when they click on an email address anywhere in SFDC, the email editor pops open and they can relate it to any record/object except for Case for some reason. I'm not sure where this setting is, if there is one to designate what objects are available to related to the email. Does anyone know how to get Case available?
Answer: There are 2 fields on the EmailMessage object which links the email to other objects
<code>ParentId : This field relates to only ***Cases***

RelatedToId : This field related to objects other than cases
</code>
Docked Email Composer feature came out in Winter 20, which allows us to write emails in the composer, but seems like the composer doesn't have "parentId" field on it. This is a potential Idea.
Release notes : https://help.salesforce.com/s/articleView?id=release-notes.rn_cases_popout_to_docked_email_composer.htm&type=5&release=222
EmailMessage doc : https://developer.salesforce.com/docs/atlas.en-us.object_reference.meta/object_reference/sforce_api_objects_emailmessage.htm
Answer: As per Send Email Action Considerations for Cases:

The Related To field can't be set to Cases in the global Send Email action.


Discrete convolution

Question: please can I ask a bit stupid question? Let say I need to solve an equation in a form
$\frac{\partial X}{\partial t}=\sum_k M_k * X_{n-k}$
How can I do the discrete convolution numerically? I will say I will expand X into series (FFT) and then, please?
I have a layer of free surfaces on the top and bottom and from the sides the material can inflow/outflow..
Many thanks
Comment: In principle you are right. The details of the method depend on the details of the problem (especially boundary treatment). You may add more details to get a good answer.
Answer: In the continuous case on the whole real line, the convolution of two functions is equal to the inverse Fourier transform of the pointwise product of their Fourier transforms.
In the finite (discrete) case, it depends on the how you define the behavior of the convolution at the end points (as Dirk pointed out), since $n-k$ can be outside the range of indices for your vectors. There are two possibilities to prevent this (but since you didn't specify limits for your sum, I don't know which one you need):

You can "wrap around" the indices, i.e., for $n<k$ take $X_{N+n-k}$, where $N$ is the length of $X$ and $M$. This is the cyclic convolution, defined as
$$ (M*X)_n = \sum_{k=1}^N M_k X_{(n-k)\ \textrm{mod}\, N},\qquad 1\leq n\leq N.$$
In this case, you can compute the convolution as in the continuous case:
$$ M*X = FFT_N^{-1}\left(FFT_N(M)FFT_N(X)\right), $$
where $FFT_N$ is the (fast) discrete Fourier transform of length $N$.
You can "truncate" the indices, i.e., take $\max(1,n-k)$ instead of $n-k$. Without going into details, you now need to sum over a larger range; the linear convolution is defined as
$$ (M*X)_n = \sum_{k=\max(1,n-N)}^{\min(n,N)} M_k X_{n-k}\qquad 1\leq n\leq 2N-1.$$
Note that the linear convolution of two vectors of length $N$ has therefore length $2N-1$. To compute this using the FFT, you need to pad the vectors: Let $(X;0_m)$ denote the vector $X$ padded by $m$ zeros. Then,
$$ (M*X;0_1) = FFT_{2N}^{-1}\left(FFT_{2N}((M;0_N))FFT_{2N}((X;0_N))\right).$$
Comment: If one is computing a linear convolution of a Fourier series, then it can be advantageous to put the origin in the middle of the array, in which case the array of added zeroes need only be half the length of the input data.

The library fftw++ (fftwpp.sf.net) provides some convolution routines which take care of the padding for you, which might be worth checking out.

Discrete convolution


Blender 2.8 rig not fully updating on render

Question: I know 2.8 is still in beta mode so I was just wondering if anyone else is having this same issue and if it will be fixed at some point. My rig has lots of drivers attached to it. For some reason the 2.8 version of blender is really slow at updating the location of the mesh around the armature when it moves. Sometimes I have to double click the time line for it to fully update dependencies. When I go to do a render, it can forget sometimes also. Like I said, I know it's a beta, but has anyone else noticed a slow armature registry and is this a known issue? If so, I hope they fix it because my rig works great in 2.79 Didn't they do a full rebuild of the bone system?
Answer: The problem is caused by collision, if you have multiple collision on a armature it causes this problem. normally the armature should have priority but something gets mixed up there.
As soon as I remove all collisions it worked like expected.


Why is it that T-tails want to climb like on a PA-44? It seems like it always wants to climb

Question: I'm having a little difficulty understanding the aerodynamics of a t-tail and how it affects climb.
Comment: Can you elaborate on what is it that you find unusual or don't understand? At first glance that sounds like the aircraft is pitching up because it is not trimmed.
Answer: Because of the location of the horizontal stabilizer, it isn't as affected by the power setting. Thus, it's likely that you are trimming to compensate for power reductions when you don't need to. I would make sure you trim well, and ensure you are trimming based on what the airplane needs rather than what you would put in on a Cessna.
Answer: It's important to remember that airplanes trim to a speed.  If the trim control and tab is at position X, the airplane will seek a speed of Y, pitching up or down as required until it's at its trim speed.  The trim control is effectively a speed setting dial, in terms of what the airplane wants to do if left on its own.  If the airplane wants to climb, it's because it has surplus thrust at its trim speed, T tail or no.  If you are trimmed at 120 kt in the Seminole and it wants to climb, it means you have too much power for level flight at 120 kt.  If you don't want it to climb, either reduce power or trim to an airspeed that gives level flight at that power setting.
Normally located horizontal tails in tractor airplanes are subjected to trim speed changes when thrust is changed, because the thrust changes modify tail down force, the tail being in the propellers wash.  Adding power increases the downforce and reduces the airplane's trim speed.  If you're trimmed at 90 kt in a 172 at a certain power setting and add more power, the airplane will pitch up as it seeks to maintain its 90 kt trim speed.  But the stronger slipstream from the prop "fools" the tail into thinking its still too fast even when at 90kt, and will seek a slightly slower speed, say 87 kt.  Opposite happens when reducing power.
A T tail, being up mostly out of the propeller stream, is much less affected by power changes, only to the extent that there are pitching moments due to the prop's thrust line; in this they they are more like a jet with tail mounted engines (add thrust without touching the controls and it pitches down slightly due to the thrust increase, accelerates, than starts to pitch up and go about seeking its trim speed while climbing).
So when you add power to climb with a T tail, there isn't the immediate up pitching tendency from the propeller wash "blowing harder" on the tail; there is only the pitching tendency from the increased airspeed itself as the airplane initially accelerates from the added thrust, and the increased free stream airspeed "blows harder" on the tail.  So overall there is a much more mild response to power changes and the airplane has a stronger tendency to accelerate a bit before pitching up.
In a normal tail you add throttle and it pitches up almost right away, but once you've stabilized in the climb, you may find your trimmed speed is a bit lower than before and you have to add a bit of nose down trim to keep the same trim speed as when you started.
With a T tail you add throttle and initially there is little pitch change until the airplane accelerates and then starts to pitch up.  You can help it along with a bit of up elevator minimize the initial speed overshoot and hunt that results. However, when it's all settled down in the climb and everything's back in equilibrium, you should still be pretty much as the same trim speed as you started.  If the trim speed changed it's only to the extent that the engine's thrust line increased or decreased the thrust line's pitching tendency, if there is one.
The other effects of T tails are related to its location that takes it in and out of the stronger downwash flow coming from the wings.  When the airplane is pitched up on takeoff for example, the tail starts off high enough to be minimally affected by the wing's downwash, but then as the tail comes down at rotation, it descends into the downwash and suddenly sees more negative angle-of-attack and therefore more downforce than before.  This results in the phenomenon common on T tails where you have to pull fairly hard to lift the nose but then relax some of the pull as soon as the airplane lifts off to keep from overpitching.


What is the proper beracha on granola bars

Question: According to Halacha what is the proper beracha to be made on granola bars? Is it mezonot  or maybe something else? Is this question  a machloket amongst the  poskim?
Comment: What are they made of and how are they processed?
Comment: This is one of those ask your local Orthodox Rabbi questions. You'll get different answers depending on who you ask.
Comment: If the individual oats are visible, some may recommend shehakol.
Comment: @NT If you ask my rabbi, he'll tell you to only eat them during a bread meal. YMMV.
Answer: This is the epitome of a safek brachos. Whenever a maggid shiur wants to give an example of a modern day food that is a real debate on the bracha, they use granola and granola bars (two very distinct issues). As far as granola bars goes, besides the ingredients, the process is also a key factor.
From the OU:

If one does not understand the process involved in creating a granola bar, one could study the ingredient panel a hundred times and still not be able to answer the above question. However, through our access to the companies that produce these bars we are privy to information that is important in resolving this issue

In the late nineteenth century "Granola" was a trademark for foods consisting of whole grains that were crumbled and baked until crispy. Today, granola bars are made from whole grain oats that are first cooked until softened and then rolled into flat flakes. They are then combined with sugars, oils and syrups and baked. The Mishna Berura (Orach Chaim 208:3) states that if grains are reduced and broken down in the cooking process, even if they were introduced whole, one should recite Mezonos. The granola bar grains appear to remain whole. The Shulchan Aruch (Orach Chaim 208:4) says that on whole toasted grains the proper Beracha is Borei Pri Hoadoma. In many granola bars the oats actually comprise less than fifty percent of the volume of the bar. The majority of the ingredients are those on which one would recite a Shehakol. Never the less, Rabbi Belsky and Rabbi Schachter have said that the proper Beracha Rishona to be recited when eating a granola bar is Borei Pri Haodoma. The oats (granola) are clearly considered the ikar, and all the other ingredients are considered tofel. We should therefore follow the regular rules of ikar vitofel and recite Hoadoma. Some poskim, however, consider the cooking process together with the subsequent baking to be a maiseh kideira. They posit that through all the cooking and baking, the grains must be partially broken down, and the proper beracha to be recited, as per the above mentioned Mishna Berura, would be Mezonos. Whether one recites Haodoma or Mezonos either way one would be yotzai bidieved. The disagreement is as to which beracha should be recited lichatchila.
Comment: "Whether one recites Haodoma or Mezonos either way one would be yotzai bidieved. The disagreement is as to which beracha should be recited lichatchila." But for bracha acharona it matters a lot more.
Comment: Yes. But the op asked about the bracha rishona.


What does "Got to own your own, you have to got to own your own" mean (song lyric)?

Question: I'm trying to understand what "Got to own your own, you have to got to own your own" means, it could interpreted as something you can use like a motivational phrase or is translated literally like "you have to be on command of yourself"?
Comment: It would be very very hard to say without knowing the full context. Please provide the surrounding lyrics as well as the name of the song and the artist who sings it. A youtube link to a recording of the song would be helpful as well, especially if you share a link to the exact time in the song where you hear the lyric (there is an option for this if you click the "share" button under the youtube video).
Comment: Oh I see, here is the song: https://www.youtube.com/watch?v=ZHTA-c4VX10 and the lyrics: https://www.musixmatch.com/es/letras/Yazmin-Lacey-2/Own-Your-Own Thank you so much for replaying
Answer: There are plenty of scenarios where you could legitimately say "own your own", due to the fact that there are multiple meanings of the word 'own'. For example, it is fairly common to say "I own my own home", in which the first use of the word is a verb for ownership, and the second instance works as a determiner to indicate whose home it is.
Without the full lyrics of your song I can't be overly specific about the meaning but it's pretty clear your quotation is the same format as my example, using the word firstly as a verb and then as a determiner. "Own", in the sense of ownership, has a common modern usage which means to accept or embrace some aspect of your life. My assumption, without further context, would be that "got to own your own" means you should accept or embrace who you are, or accept what you have and enjoy / appreciate it.
Comment: Or that there's some material object that's referenced in the surrounding context, such that the subject of what "own your own [thing]" is supposed to be obvious.


Can replacing wires fix a display

Question: I dropped my laptop on the ground.  For about 7 days the display would not work though the hard drive was fine.  I could use the computer with a different display.  The display has magically started working again but it has flickered off for a few seconds twice over a period of ten minutes.  Perhaps the only thing that is wrong is that some wires went ajar during the dropping and they just need to be replaced.   Can one purchase wires and easily replace them?  I have a Macbook Pro Retina Mid 2015.
Answer: No, on the newer MBPs, the display cable is basically integral to the "Display Assembly" part, even if it is just the cable that was damaged it is not replaceable on its own, not "easily" by any reasonable standard.
Realistically if the display cable is seriously damaged you need to replace the entire display half of the laptop.
If it is only the display connector that is damaged, it may be possible to repair but the smt soldering needed for such a job means it would not be easy either, though you might be able to find a third party repair shop that could do it for you without replacing half the laptop.
Though I don't think it is likely, if the problem is that the display cable connector simply came loose, then that would be an easy fix. But I feel that would just be wishful thinking.
Answer:
Can one purchase wires and easily replace them?

The "wires" is called a flex cable and it can be purchased.
Easily?  That depends on your level of technical skill.
Typically, wires don't "go ajar;" connectors break.  You may have broken solder joints, a connector my be damaged connector on the logic board.  Without putting hands on, it is impossble to know what's wrong.  At present all you have is symptoms:

dropped MacBook
Intermittent display

There's a myriad of causes for those symptoms so until it's opened up and properly diagnosed, everything is speculation.

Can replacing wires fix a display


How much can we compute with one single qubit?

Question: This might be a little stupid question, but I was just talking with some friends who are working in neuroscience and I tried to explain them quantum computing. When I explained them the bloch sphere and the infinite number of points on that sphere, they asked me why we actually do use more than one qubit for computation, since we could store in principle an infinite amount of bits in one qubit (not speaking about reading that out!).
So, what I was wondering is the following:
Would it be possible in principle by angular manipulation of two qubits - one input and one working qubit to solve any computational problem, like a sat problem, conditioned of course that any operation could be implemented as an angular manipulation?
Answer: I think you have answered your own question when you say "not speaking about reading that out!" It doesn't matter if the answer to a problem is encoded in a qubit if that information isn't accessible to us. In fact, it can be shown that measuring a qubit never reveals more than one classical bit of information, the so called "Holevo bound." Exercise for the reader: go look up "superdense coding" and sort through the initial apparent contradiction.
Answer: Quantum computers can be simulated by classical computers with a time which is exponentially big in the number of qubits (and linear in the time used by the quantum computer).  Thus, if you run a circuit on two qubits which takes time $T$, this can be simulated by a classical computer which uses a time which is $T$ times an exponential function of 2, i.e., a constant: This is, we can do no more with a two-qubit quantum computer efficiently than we can do with a classical computer.
Answer: 1: quantum calculus is for the moment a theoretical game, there is no existing maching doing it for real.
2: quantum calculus has something very special: you won't get the q-bits back. So you have to think of algorithms and problems with huge combinatory of intermediate calculus based on short data and short output (probably more than 1 bit, still).  Not all problems are like that, and algorithms are pretty different.
3: in theory you can have an infinite number of superimposed states in a qbit. But the real world and technologies are about constraints (did you notice that cars not yet roll at the speed of light ? ;-) ) : how long can you keep the states, how precisely can you manage the interactions, how to you inject a data and get a result, etc.


Any open source alternative to MyHDL?

Question: Is there any open source alternative to MyHDL? I have started learning but finding it very difficult.
Comment: You might be better off learning the underlying VHDL first, then you can see what MyHDL is doing.
Answer: If you're planning to actually use it (e.g. to program an FPGA), GEZEL might be a good choice.
But if you're just starting out and only looking to learn, have a look at the first few chapters/projects of nand2tetris. They have a custom HDL which is easy to understand and introduced step by step.

Any open source alternative to MyHDL?


Disable IK then re-enable with different pose

Question: So first of all I'm very-very beginner in Blender. Previously I have used Source Filmmaker. In SFM you had an option to apply IK rig to models and after that detach it. Now in Blender I have a model (not own) which has standard IK rig in it. My goal is to pose the model with FK only and after that re-enable IK rigs to that newly created pose (similar like in SFM). I can't do that because if I'm re-enabling IK it always puts back the actual body-part to its default position. Am I missing something? Thank you in advance for your help!
Comment: You can apply an IK-deformed pose with CTRL+A (ie. burn it into the rest pose), but this step is irreversible. You can not go back to the first pose afterwards and the armature will no longer deform your model correctly unless you apply the pose the the model first. This is probably not the IK-FK-switch you want. I don't think such a thing is possible in vanilla blender, and may be impossible even with scripts. Posing bones in IK chains gives funky results.
Answer: You may be able to achieve something similar to this with the auto ik setting, but I'm not sure as I don't really use it.
IK/FK switching while preserving pose is difficult in blender as it currently stands.
The only way I've seen it done is by having 3 sets of bones, one for the FK pose, one for the IK and one to actually deform the mesh. A driver is then created to determine which chain controls the deform chain. Scripts are then provided to snap the FK chain to the IK chain's position and vice versa.
The above technique is used in the Rigify rig that comes as an addon with blender.
Also as an aside, why do you want to enable IK after posing? This will cause the rig to use IK interpolation(straight line between poses) between poses rather than FK? Most of the time you will actually want FK interpolation(arcs between poses), the only time you normally want IK if the end of the chain is explicitly fixed (e.g. a foot planted on the ground), and in these cases it is often easier to pose by IK anyway.
Answer: What i usually do when I need to keep the transform but lose the ik is one of two things.
Thing 1: use the 3D cursor to place dummy objects in place of where you want the bones to be, and then move them in to position manually one by one, or... (since this can get a bit cumbersome if you have a lot of IK/constraints going on)
Thing 2: Keyframe all the bones to whatever poses you need and export an FBX. Upon export It will convert everything to FK. All you need to do then is either bring it into a new project and go from there, or if you absolutely must have it applied to the object in the original project you exported it from, you can import the FBX back into your project and then transfer (copy/paste) its animation/action keyframes back over to the original model via the dope sheet.