Have you ever wondered do animals also think like we humans do?

Question: this question always pop in my mind that what my pets would be thinking or do they also think like we do. i know animals also feel emotions but i dont know if they also have ability to think or not. Have you ever wondered what goes on in an animal's mind? What kinds of thoughts it has, or whether it can be sad or happy? Do they think like people do?
Comment: lots of people do wonder about this and pets can be sad-happy-frustrated.but i do not think it is possible to answer what they do think about.i am not even sure how people think or if all people do think in the same way,pets can often show the owner what they want(by walking to the door they can comunicate that they wants to go outside)but the reason a pet do have for this is unknown but we can guess.
Comment: Related https://psychology.stackexchange.com/questions/4037/what-if-anything-sets-humans-apart-from-other-species
Comment: Have a look at this [TED talk about what animals are thinking and feeling](https://www.youtube.com/watch?v=-wkdH_wluhw)
Answer: Yes, they do think in a way that is similar and comparable, but not quite the same.

Life is very vivid to animals. In many cases they know who they are.
  They know who their friends are and who their rivals are. They have
  ambitions for higher status.  They compete. But many animals express
  empathy for each other. There are documented stories of elephants
  finding people who were lost. In one case, an old woman who couldn't
  see well, got lost and was found the next day with elephants guarding
  her. They had encased her in sort of a cage of branches to protect her
  from hyenas. That's seems extraordinary to us but it comes naturally
  to elephants.

https://news.nationalgeographic.com/2015/07/150714-animal-dog-thinking-feelings-brain-science/

... Grandin examines the surprising similarities between an animal's mind and an autistic mind—her own. "Autistic people," she writes, "are closer to animals than normal people are." This may sound like a cruel judgment, the sort of thing a cold-hearted clinician would say, but it isn't. It's an acute observation, all the more important because it comes from an autistic person. Her autism, Grandin suggests, puts her somewhere between normal human mentality and animal mentality, not as a matter of IQ but as a matter of perception and emotion. Being closer to animals isn't necessarily a bad thing. After all, that's what makes Grandin such an uncanny translator of animal behavior.

http://discovermagazine.com/2005/may/what-do-animals-think

"These data suggest that not only do some animals have a subjective take on the suitability of the option they are evaluating for their goal, they possess a subjective, internal signal regarding their confidence in this take that can be deployed to select amongst different options," he wrote.

https://www.sciencedaily.com/releases/2017/11/171101151206.htm


Am I able to replace the bolt in the hub to be quick release on a back wheel?

Question: I have this wheel and want to replace the skewer that it is tightened with to a quick release fitting is this possible?
Comment: Yes, but it's a bit of a project. You will need to remove the axle and transfer the hardware to a new axle that has a hole through it for the quick release skewer.
Answer: The 'bolt' through the hub is actually an axle that is threaded along its length The wheel bearings are sandwiched between 'cup' surfaces in the hub and 'cones' that thread onto the axle.
The axle in this type of hub can be replaced if they get bent or damaged, they can also be replaced with a quick release type. The quick release type has a hole though it that accepts a quick release skewer shaft.
Replacing the axle is fairly straightforward, but requires making sure you get the correct length axle and re-assembling the bearings.
Here's a video from RJ the Bike Guy showing how to replace the axle.
Comment: You want to make sure you order an axle to fit your frame and will be shorter than the bolt on axle.
Comment: Here's a [quick release axel assembly](https://www.amazon.com/GEEDIAR-Mountain-Release-Bicycle-Skewer/dp/B01L1B80FS) that's for sale. Not a product endorsement but an example of what you'll need to replace that solid axle with a quick release set up.
Comment: wow, this is long winded, this bike is a bit of a heap of crap to be honest. My ribble got stolen in London, then when I moved to Madrid just wanted a bike so got this thinking it would be decent, should have spent extra. I have spent to much modifying it now. Think its time to invest in something better again. It's just really annoying as I always have to ride around with a 15" spanner in case I get a puncture


Draw busbars in qelectrotech

Question: In qelectrotech how can I draw a busbar?
Comment: Your first sentence seems unrelated to the question.
Comment: In electronics the buses length is equal wires. but in power buses are a little longer than wires I think.
Comment: I am an eletronics engineer but I can't see what you are talking about. "Bus length is equal wire" equal in what ? Impedance ? Physical length ? Electrical length ?
Comment: What does electrical length mean?
Or impedance is not same in meaning as length I think;

I meant length in appearance in diagram.

You know that bus in power, is a bar for example copper bar for make connection to other lines. it is a little like a wire. without any rectangle or circle.

Anyway I think I should make it myself or import this component to qelectrotech.
Comment: @Blup1980: Thanks.
I red it again and red more about busbars.

You are right.

I edited my question.
Answer: Finally I found how to draw a bus.
One way is to make a bus element and then use it.
Making an element is very easy. first select the "new element button and choose the required options.

You can change the size of background from edit menu "size and hotspot"
Now should draw a rectangle and put several terminals on it. to change the orientation of the terminals just select it and from information at left change the orientation. Also add a textfild to beside your element for naming. You can put "bus_" for the default.

After select the save button you can use the element "bus".
You can also save your element to a file from file menu.
To use your element select it from elements panel and drag it to the drawing area.
Answer: Alternative approach a busbar element:

It's a black rectangle with a centre pin to attach wires, and two side contacts to stack them side by side.
When you compose them, you get this (all signals are connected):

The symbol is set as terminal, so that the three terminals share the same signal.
Code:
<code><definition hotspot_y="15" hotspot_x="34" orientation="dyyy" version="0.60" width="70" link_type="terminal" type="element" height="20">
    <uuid uuid="{d35ce3f4-2a25-4e52-9dcf-8d2d2adc872f}"/>
    <names>
        <name lang="it">Busbar</name>
    </names>
    <informations></informations>
    <description>
        <rect width="60" y="-13" style="line-style:normal;line-weight:normal;filling:black;color:black" antialias="false" x="-30" height="6"/>
        <rect width="0" y="-10" style="line-style:normal;line-weight:normal;filling:none;color:black" antialias="false" x="15" height="5"/>
        <input size="9" text="_" y="-25" tagg="label" rotate="true" x="10"/>
        <line x1="0" y1="-4" x2="0" end1="none" end2="none" length1="1.5" style="line-style:normal;line-weight:normal;filling:none;color:black" antialias="false" length2="1.5" y2="-8"/>
        <terminal orientation="w" y="-10" x="-30"/>
        <terminal orientation="e" y="-10" x="30"/>
        <terminal orientation="s" y="0" x="0"/>
    </description>
</definition>
</code>
If you paste it to a text file and save it as busbar.elmt you should get a working component.

Draw busbars in qelectrotech


Test suites for utilities (cat, cp etc) Linux or BSD?

Question: Are there any test suites available for the small programs usually shipped with the operating system? Specifically, programs like cp, cat, dd etc (anything in /bin/) on Linux or BSD; OpenBSD being the preferred option.
I know that md5 has a testing script built in however I can't find any others.
The regression testing suite from OpenBSD doesn't have tests for all the utilities.
Comment: What is it you'd like to test?
Comment: I'm writing custom versions of a few coreutils with the same interface.
Answer: The POSIX test suites provide full coverage of the standard utilities, which won't be everything in /bin on most systems. It will cover all of the tools you list, however. As well as only covering the standard utilities, the suite will only cover their specified behaviours, and any extensions above POSIX would be ignored (at best).
You would want the VSC suite, "for Shell and Utilities", rather than the one for system interfaces. These are available for a fee to trademark licensees, but you can get a time-limited licence as an open-source project implementing the standard for free with what doesn't appear to be an onerous licence agreement.
There are open suites for much of the system interfaces, but I'm not aware of one for the utilities (and the ones I know of are quite dated as well).
Comment: The POSIX test suite seems like a good fit. Also FreeBSD ships with a test suite and it might be closest to the utilities for OpenBSD (https://wiki.freebsd.org/TestSuite/).
I'm trying to figure out how I can pull that into OpenBSD.
Comment: The issue with the VSC suite is that I'd need to contact the Open group for the test suite. I ended up using the GNU coreutils tests and the test suite from busybox.
Answer: On GNU/Linux, these utilities are a part of the coreutils, the test suite can be found in the source repository under tests.
Note: Linux is just the kernel, the rest of the system is developed by different entities, such as GNU.

GNU is an operating system that is free software...consists of GNU packages (programs specifically released by the GNU Project) as well as free software released by third parties.

On BSD, the whole operating system is developed together in one repository.
For OpenBSD, there do not appear to be any tests for these utilities in their source repository.
Comment: https://github.com/openbsd/src/tree/master/regress
They do have regression tests for a few of the utilities.
Comment: Per the Makefile, `# To run full regression tests you just need one step:
# make regress`. Note that you will probably need to use `bmake` if running on Linux.
Comment: I was actually asking about the coreutils since it doesn't seem to work easily without having first built coreutils but it is possible with a few modifications. The OpenBSD regression suite is easier to run as you noted but it doesn't cover all the utilities. I ended up using a combination of tests from GNU coreutils, busybox and the OpenBSD regression tests.
Comment: Any idea how to run the tests? I need the tests to run on OpenBSD using my custom coreutils implementation.


Can a corporation run for office?

Question: Under the notion of corporate personhood, what prevents a corporation from running for or holding political office?
Comment: The background:  I was writing a comic that was meant to be absurd about a rock band running for President.  Then I started wondering how absurd this actually is.  For example, could a group of people run for a single office?  Then I imagined a group trying to justify this and reaching for "corporate personhood" as a justification... possibly leading to the demise of corporate personhood by forcing the issue.
Comment: Can a group of people run for or hold a political office collectively?
Comment: @DrunkCynic: Worldwide, people have definitely attempted to job share, and there is  a school of thought that it might help diversify politics: https://www.theguardian.com/politics/1999/apr/20/scotlanddevolution.devolution2, so the concept certainly isn't as crazy as you might think.
Comment: At least to me, it's hard to see why you would imagine that corporate personhood would allow a firm to run for office.  Is there some background to this question?
Answer: Corporate personhood isn't exactly what it says on the tin. It doesn't grant a corporation all the rights of the person.
Historically, corporate personhood was created to allow corporations to enter into contracts (for example, to hire employees or purchase services).
The United States Supreme Court has extended other rights to corporations also, but none of them include running for office. I don't know of an official compendium of the rights of businesses, but Mother Jones summarizes some in this article:

The right to sue in federal court
Corporations are citizens for the purposes of court jurisdiction
Although not generally protected by the Constitution, corporations do enjoy equal protection under the law
Corporations are also protected from unreasonable search and seizure
Corporations are also protected from double jeopardy.

All of these cases have to do with legal process. However, two recent cases (since 2010) have changed the general notion of corporate personhood a bit:

Corporations enjoy a right to free speech (2010)
Corporations enjoy a right to freedom of religion (2014)

These are extensions of civil rights to corporations. However, nothing in them either explicitly or implicitly includes the ability to run for office. In fact, prior Supreme Court rulings include the determination that corporations do not generally enjoy Constitutional protections or privileges (such as the ability to run for certain offices).
Answer: Requirements for different political offices are different. So you would need to look at the exact requirements for a political office to tell if it might theoretically be open to legal persons. For example, Article 2 of the US constitution says about the requirements of being the president:

No person except a natural born citizen, or a citizen of the United States, at the time of the adoption of this Constitution, shall be eligible to the office of President;

No matter how broad your definition of "person" or "citizen": A corporation is founded, not naturally born, so this already disqualifies a legal person from presidency.
However, a final judgment in this matter would be up to the US Supreme Court, just like they did in many other matters where it was questionable if a company enjoys the same constitutional rights as a natural person. For example, the SCOTUS ruled that the 1st amendment applies, but the 5th amendment does not. So if HyperMegaCorp Ltd. would insist that they as a company (as opposed to their current CEO as a person) can run for sheriff of Someplace County, a court would have to decide in that matter.
By the way, keep in mind that political parties are also legal persons. So if an office which is supposed to be personalized would be open to legal people, then a whole political party as a legal person could run for that office, too.

Can a corporation run for office?


Should I sign NDA without legal consultation?

Question: If a client wants to get NDA signed before they can share any proprietary data for small project. Should I sign without getting a legal consultation? If so should I include this cost in the invoice? If I am providing the service via a freelancing website isn't their data already protected by terms of service of the site? I am talking about fiverr.com specifically.
Comment: It depends on how simple and how punitive the NDA is...
Comment: The only person who can tell you whether or not to sign the NDA, is a lawyer. (If the job doesn't pay enough for you to comfortably consult with a lawyer before signing a document, DON'T ACCEPT IT.)
Comment: Have they shared that NDA with you yet? You're right to be careful. Do not accept a contract without seeing that NDA first. And do not let them assume that you will sign it without having a lawyer look at it. Until you can see it first, you can't tell if it's reasonable, or if you'll need to have a lawyer look at it. The terms of services of the site are designed to protect the site itself. Do not assume they're designed to protect the client, or you.
Comment: @Erik: that's a truly absurd comment. Tons of non-lawyer types can give a reasonable opinion on whether OP should sign a particular NDA, based on what clauses are in it, whether they seem reasonable, how far-reaching it is, whether it looks like it was drafted by an idiot or people who know what they're doing, etc. Of course if the OP themselves hasn't seen the NDA, first they need to ask the client to send it (duh) so they can read it, think about it, *if necessary* consult with a lawyer, etc.
Answer: A quick sniff test is whether the NDA is mutual or not. If the NDA makes no distinction whatsoever between the obligations of both parties, there's little chance it'll contain inane language. So at first pass it's usually a good idea to pull out your own (attorney-vetted) mutual NDA and offer to use that instead when the NDA you're being handed is not.
If the NDA is not mutual and you don't have your own, then yeah, it's best to check with an attorney. NDAs can contain language and gotchas that slap you with all sorts of asinine obligations and ludicrous penalties if you fail to comply with them. Particularly so when attorneys engage in what's probably best described as legal pissing contests. (Don't stress too much about it though, because actually enforcing NDAs is hard - particularly across jurisdictions - and collecting is harder still.)
With respect to your other questions:

No, the cost of having an attorney read the NDA before you sign is on you.
Yes, Fiverr's ToS does contain language related to ownership and confidentiality.

The latter doesn't say much besides the fact that your client basically owns what you deliver and that you should stay professional and keep confidential information to yourself. Freelancing sites invariably have similar language.
It's also worth stressing that if confidentiality really is a concern for them, they probably shouldn't be using a mostly anonymous online gig site or sharing information so sensitive that signing an NDA is in order before disclosing it.
Lastly, it's not hard to come across information on how to read and interpret an NDA. See for instance this Quora question for a whirlwind tour.


Algebraic number theory topics for undergrads

Question: What are some interesting topics or problems in algebraic number theory which could be presented to students in a first undergraduate algebra course (which covers some elementary number theory, groups, and rings)?
Comment: How much does the course cover? Is it possible you can explain quadratic reciprocity? If so, there is an extremely nice group theoretic proof of it.
Comment: As with Asvin's suggestion, this depends on what the course covers, and how advanced the students are. If the students are a bit more experienced, then you might consider introducing basic class field theory. This might be a bit challenging for your audience (depending on their background), and you probably can't cover it very deeply, but I think it's one of the most beautiful topics in algebraic number theory, and could be a very good teaser for a student who thinks he is interested in algebraic number theory.
Answer: Sounds very much like our first course in algebraic structures. Examples that might or might not fit the bill (I have only tried a few of these, but will get a chance to do so soon):

Pell equations. May be while looking for units of the ring $\Bbb{Z}[\sqrt2]$? Start by observing that $u=1+\sqrt2$ is a unit because $(1+\sqrt2)(1-\sqrt2)=-1$. Because the units of a ring form a group, its powers
$$u^n=(1+\sqrt2)^n=a_n+b_n\sqrt2$$ will also be units. Because $\sqrt2\mapsto-\sqrt2$ extends to a ring automorphism, the inverse is $(-1)^n(a_n-b_n\sqrt2)$. This also yields a sequence of good rational approximations to $\sqrt2$, so one can build some purely computational exercises out of this as well (in my experience the weaker students appreciate those). The fact that the unit group is $C_\infty\times C_2$ must wait :-)
Fields of size $p^2$ as quotients of rings of integers of number fields. $\Bbb{Z}[i]/\langle p\rangle$ is such a field when $p=3$ (compute the inverses), but with $p=5$ its is not. Why? May try quotients of other rings as well?
If you cover fields of fractions, you can also make basic exercises about the rings of rational $p$-adic integers. Interesting subrings of $\Bbb{Q}$?

This is a bit of a stretch - sorry about that.
Comment: This is a great answer, and the first one is a classic. As far as the second goes, it might also be interesting to present the ramification of primes in $\mathbb{Z}[i]$, which one can do with relatively basic algebra and very basic number theory.
Answer: I am reading this delightful paper by Harald Helfgott Growth and Generation in $\mathrm{SL}_2(\mathbb{Z}/p\mathbb{Z})$ where he explores the Cayley graphs whose vertices are $2\times 2$ invertible matrices with entries in the finite fiele $\mathbb{F}_p$.  Two edges are connected if they are joined by elements of a generating set.
$$ A = \left\{ \left(\begin{array}{cc} 1 & 1 \\ 0 & 1\end{array}\right)  , \left(\begin{array}{cc} 1 & 0 \\ 1 & 1\end{array}\right) \right\}$$
He asks for the diameter of this graph - the length of the longest path between two elements.  The result was known using difficult spectral methods for the above generating set and unknown for the generating set below.  Basically change 1 into 3.
$$ A = \left\{ \left(\begin{array}{cc} 1 & 3 \\ 0 & 1\end{array}\right)  , \left(\begin{array}{cc} 1 & 0 \\ 3 & 1\end{array}\right) \right\}$$
This would be a great chance for to explore the interplay between groups and generators, graphs and eigenvalues.
The full results of the paper are certainly out of reach for an intro algebra class, however this is for the better.  The statement of the problem should be enough; partial result lead to meaningful exploration on a modern research-type problem.
Answer: I would like to see:

Fermat's Last Theorem
Quadratic Residues
Quasigroups

, all of which have undergone major transformations recently, and offer some form of 'closure' (my word - they all have results, not just conjectures).
Comment: first undergraduate algebra course having FLT?  WTF!
Comment: http://en.wikipedia.org/wiki/Fermat%27s_Last_Theorem; it's going on 400years old, Hardhy & Wright ItToN covers it - 100years old, it is no longer unproved, so defines a necessary and sufficient aim for undergraduates, **AND** I have proved $x^3+y^3\ne z^3$ using only modular arithmetic! @Squirtle
Comment: Sure.... sure.  I thought that you meant you want them to include the study of elliptic curves and other deep results from algebra that only specialists know
Comment: when i grew up, nothing was real...


How can I convert a .m2ts to .mkv?

Question: Does anyone know of an application that allows me to convert an m2ts file to mkv or some other format? Preferably something that allows me to convert it directly, rather than convert the whole Blu-ray disc. hddump didn't work because it doesn't convert only the m2ts file, and the contents are on a .iso that I mounted virtually.
Answer: ffmpeg
I think ffmpeg will do the job it's quite simply copy all the streams and output them in an mkv container. No information is lost/re-encoded.
ffmpeg -i input.mt2s -scodec copy -acodec copy -vcodec copy -f matroska input.mkv

Answer: With Handbrake you can convert all kinds of files:

Supported Sources:

Any DVD or Bluray-like source: VIDEO_TS folder, DVD image, real DVD or bluray (unencrypted -- removal of copy protection is not supported), and some .VOB, .TS and M2TS files
Most any multimedia file it can get libavformat to read and libavcodec to decode.

Outputs:

File format: MP4(M4V) and MKV
Video: MPEG-4(ffmpeg), H.264(x264), or Theora(libtheora)
Audio: AAC, CoreAudio AAC (OS X Only), MP3, or Vorbis. AC-3 pass-through, DTS pass-thorugh (MKV only)"
Comment: Thank you, this will also be nice to have in the future.
Comment: You can also convert for ipods and similar. It's really great :)
Comment: Note that Handbrake will re-encode the video, whereas ffmpeg will simply copy the internal stream to the new MKV container.  This will be much faster and not change the quality.
Comment: Except the PPA doesn't work (404). I had to manually add it to my softare sources.
Answer: The easiest tool to use is mkvmerge, which is part of the mkvtoolnix package. To convert your file:
sudo apt-get install mkvtoolnix
mkvmerge -o output.mkv input.m2ts

Example output:
mkvmerge v6.1.0 ('Old Devil') built on Mar  4 2013 20:24:55
'input.m2ts': Using the demultiplexer for the format 'MPEG transport stream'.
'input.m2ts' track 0: Using the output module for the format 'AVC/h.264'.
'input.m2ts' track 1: Using the output module for the format 'AC3'.
'input.m2ts' track 2: Using the output module for the format 'PGS'.
The file 'output.mkv' has been opened for writing.
'input.m2ts' track 0: Extracted the aspect ratio information from the MPEG-4
 layer 10 (AVC) video data and set the display dimensions to 1920/1080.
Progress: 100%
The cue entries (the index) are being written...
Muxing took 4 minutes 20 seconds.

Comment: You're right, mosu's tools support this for a while now. I recommend subscribing to the RSS feed of [his blog](http://www.bunkus.org/blog/) and installing updated versions from his repository, which are updated every one to two months. I recently found that they don't seem to support lpcm though.

How can I convert a .m2ts to .mkv?


Disable Mini-Map Rotation in Battlefield 3

Question: Is there a way to disable the mini-map rotation in Battlefield 3? I would rather North on the map was always facing up.
Answer: The only way that I've been able to find to do this, is to press N twice.
The (extremely big) downside to this, is that it means your map is at minimum zoom level, showing the entire map at once.
Comment: @KyleBrandt I use N twice with M whenever I'm in a vehicle. The only downside is that you lose the ability to see who owns what objectives, and what the ticket count is. The upside is if someone's spotted anywhere on the map, you can track them at all times, and you can see when a vehicle becomes empty anywhere on the map too.
Comment: Too bad I can't window it and stick it on a second monitor. But thanks, I never noticed it did this, maybe I can just get used to the N twice with the bigger mode M
Comment: Also, a lot of us are on maybe 8pm-ish EST on the SE Bf3 server (http://s.tk/bf3) ;-)
Comment: @KyleBrandt Would love to play on there with you guys, but being in Aus, my ping doesn't even show up because it's too high (just get the little dash -ms)


How is transactionIndex decided in a block?

Question: I'm using web3py and web3js to send transactions on the Harmony EVM chain using sendRawTransaction, and i noticed that once my transaction is sent, the transactionIndex value will always be between 0 and 3. Why is that? And is there a way to set a specific index for my transactions?
Answer: transactionIndex will be set by miner. each block has many transactions which are ordered to mine. your transaction's index is 0 when the block goes to mine the transaction was first tx in that block. maybe you are using local dev node because in real networks a user cant get his/her tx all the time at first place in a block
Comment: it's about gas price, miners will mine those txs with higher gas price first, at your block, your gas price was 0.00000405 then you reached 2 index, 0 index had more gas price: 0.0000054 and 4 index has lower than gas price as you : 0.00000002
Comment: It's not always 0, but it's always a low number between 0 and 3. Here is an example https://explorer.harmony.one/tx/0x1852ba3fac03d7e02529fc7d4da53301610410ae3d96740beefe47f3c2063b17
Comment: Damn i didn't notice that. Thank you a lot!


Munin: do not notify state changes to OK

Question: Munin-limits seems to trigger notifications for any state change (OK->CRITICAL, OK->WARNING, WARNING->CRITICAL) bidirectionally. Is there a way to prevent Munin from notifying returns to "OK"?
Answer: I freely concede this question is about munin rather than NAGIOS.  However, the two tools live hand-in-glove, and NAGIOS's notification engine is sophisticated and configurable, whilst munin's isn't.  So instead of asking munin to notify you, have it inform NAGIOS and let NAGIOS do the notifying.  Then you can set restrictions on time of day, use service escalations to notify management if problems persist, craft the form of the notification so as to be more appropriate to the medium (SMS and email notifications shouldn't look like each other), and, yes, control whether notification is sent on recovery.
In the contact template, or wherever this is defined for you, change
service_notification_options    w,u,c,r,f,s
host_notification_options       d,u,r,f,s

to eg
service_notification_options    w,u,c,f,s
host_notification_options       d,u,f,s

That is to say, remove the r for recovery from both service and host notification options.  Or you can override this on a contact-by-contact basis, in the contact's definition.
I must apologise to the author of this question because I am so habituated to having munin notify via NAGIOS - all my munin installations, and there are quite a few of them, do that - that I didn't originally notice that the question was munin-specific.  However, my answer stands: if you want a notification engine that you can make configuration changes to, use a configurable engine.
Comment: aag, see my added comments above, and please accept my apologies!  As for the downvote, mouse over the down arrow; the popup says "*This question does not show any research effort; it is unclear or not useful*".  Downvotes without comment may be presumed to be for at least one of those reasons.
Comment: thank you for your useful and correct answer which has solved my problem. As usual, the Thought Police at serverfault has downvoted my question. I will not delete though, since I am quite convinced that it will be helpful to others as well.
Comment: I spoke too soon. The advice to change 'service_notification_options' seems to relate to Nagios. The question, however, is how to change the behavior of Munin notifications (direct, not via Nagios).


neo4j (cypher) is very slow

Question: I am trying to build a graph of different entities liked by people on Facebook to create a basic cross domain recommendation engine.
I have got data for different entities (movies, books, music, etc). Nodes are created for each item with properties as name of the item (name of the movie, book, etc) and entity type of the item (movie, book, etc). Any two nodes have relationships between them called "affinity". This relationship also has a "strength" property, which is equal to the no. of people who have liked these two items.
I use FB users to connect these nodes. FB users also are nodes in the graph with properties as name of the person and type as person. The relationship between these nodes and item nodes is called 'likes'. Now if a person has liked a movie, I would like to recommend him books or music by traversing the graph. This is the cypher query I am trying to traverse the graph:
START root = node(<LIKED_MOVIE_NODE_ID>)
MATCH p = root-[rel1:affinity*..3]-(movies)<-[rel2:likes]-(persons)-[rel3:likes]->(books)
WHERE HAS(movies.type) and movies.type = "movies" and HAS(persons.type) and persons.type = "person" and HAS(books.type) and books.type = "books"
RETURN books

This runs very slow, sometimes taking upto 500 secs. I have got some 13000 movies, 2000 books and 3000 music nodes. Connecting them are 16000 people. All together there are some 300,000 relationships.
My questions are :

Am I doing something wrong? Is there a better way to do this?
I am new to neo4j. I have tried some of the techniques for tuning the neo4j graphDB. I have increased the min heap size to 4 GB and am running it on a 8 core machine with 32 GB RAM.
I want to know the strength of the relationships rel1 and number of rel2 and rel3. Rel1 has got a property strength. I am not able to find it out,

Please advise as I am on the verge of giving up neo4j and going back to SQL. Atleast it works. :(
Regds,
Paritosh
Answer: Cypher is slow. Actually very slow when compare to the traversal and core API (http://java.dzone.com/articles/get-full-neo4j-power-using)
That said, you could try to limit the amount of nodes neo4j processes, by splitting up your Match into different WITH clauses. Depending on your usecase you could for example put the
root-[rel1:affinity*..3]-(movies) in a seperate clause, and filter out the distinct movies. Else neo4j will process all combinations of paths which lead to a movie.
PS:
WHERE HAS(movies.type) and movies.type = "movies" and HAS(persons.type) and persons.type = "person" and HAS(books.type) and books.type = "books"

can be rewritten as
WHERE movies.type! = "movies" and persons.type! = "person" and books.type! = "books"

Or if you are using neo4j 2.0.0M4 you can just skip the HAS()

neo4j (cypher) is very slow


How early can you enter USA after H1B visa extension

Question: My H1-B visa is already expired , however I have a valid I797A until Feb 2020 and have also applied for my extension. I would like to travel to my home country in December and understand that would need to get a new visa stamp in order to re-enter USA. I intend to apply for new H1-B visa with the H1B-extension I797A , can I re-enter the USA in JAN-2020 10 days prior to the start date on my new I797A which will be March 2020, or should I get a visa with the old I797A ( Feb 2020 ) ?
Answer: US visas do not have a start date. You can enter the US the same day as the visa is stamped in your passport. Remember that it is the visa which allows you to travel to the US.


Why are heavy things harder to lift?

Question: According to multiple websites, any object in free-fall (no air resistance) on earth will accelerate towards the Earth at 9.8 m/s. If all objects fall towards the Earth at the same rate, regardless of their mass, then why is it harder to push a heavier object away from the Earth, than a lighter object?
Comment: Note that both current answers contain the same (small) error as this question: the acceleration is 9.8 m/s^2. m/s is the unit of speed, m/s^2 is the unit of acceleration.
Answer: When you are lifting an object, you are exerting a force that balances the force of gravity on the object. By $$ F = m g$$ where g is the acceleration due to gravity, you see that a greater mass causes a greater gravitational force that has to be balanced by the force you apply to the object by holding it or lifting it at a constant velocity.
Using the more general Newtonian law of gravitation, $$F = G \frac{M m}{r^2}$$
with $G$ being the gravitational constant, $r$ the separation and $M$ and $m$ two masses, we can rearrange for an object in the gravitational pull of Earth: $$F = G \frac{M_{Earth}}{r^2} m$$
If we approximate this by saying that the object is very close to Earth and its mass is nearly zero, the first part of the formula depends only on Earth's physical properties and therefore becomes a constant: $$g = G \frac{M_{Earth}}{r^2}$$
We see that $$g = 6.67 \times 10^{-11} \frac{5.97 \times 10^{24}}{(6.37\times 10^6)^2} \frac{N m^2}{kg^2} \frac{kg}{m^2} = 9.81 \frac{N}{kg} = 9.81 \frac{m}{s}$$
So, the acceleration due to gravity only depends on the mass and the radius of the planet (with our assumptions), but the force that you need to exert in order to balance gravity depends on the mass of the object you are trying to hold.
Answer: The acceleration of any object due to gravity is $g = 9.8m/s$ and this constant does not depend on the mass of the object (or the speed of the object or anything else for that matter, as long as you're on/near earth). Pushing an object away from the earth is another story. While the acceleration of objects towards earth does not depend on their masses, their weight does, $Weight=F=mg$. Two balls, one made of steel and one made of cotton, falling towards the ground will be accelerating at the same rate, but they will both hit on your head with different effects. In short, it's harder to push ($W=F=mg$) a heavier object because it has a larger mass, but acceleration is always just $g=9.8m/s$. The acceleration, together with the mass, causes weight.
Answer: The falling object actually creates an equal and opposite gravitational force pulling up on our mother earth. The effect is invisible because the earth is so massive, and the earth doesn't complain verbally the way the rest of us do. You will even see massive objects doing some work on her during impact.

Why are heavy things harder to lift?


How can a developer break into a system administration career? Is it a good idea?

Question: My concerns. It generally does not seem to pay nearly as much as developer positions without prior experience. It also seems there are a lot of people who do not advance to decent paying jobs. Whats a good route to take and is it worth it?
Answer: One way to gain the requisite experience while still pulling in a decent wage is to get a developer position with a small development shop or small firm. When I was in college, I got a programming internship with a small development shop and witihn the first couple of weeks I was building and running cable, doing server management, and ensuring the backups kicked off and ran. I also became first level hardware/workstation support. Now I previously had some experience working on PCs, but nothing at the level of a company that requires. I know others who were professional programmers who went a similar path.
But one caution: if you really like development, this may not be a switch you want to make. You may find yourself longing for days when you can sit down and code heads down. As a system administrator, those days will be rare and subject to interruption with the latest real world problem.
Answer: My career path went from the operations side into the business side. It looked like this:
IT Support --> Network Admin --> System Admin --> Developer --> ETL/Data Warehouse
You will have to content with crappy hours and carrying a pager with the first three positions. I really love this stuff, but I don't live being woken up at 3 AM for some idiot manager wanting help because they have deleted some system files in a server (true story!).
I've spent my career in the US SouthWest region, away from the coasts. Things may be different in other regions. Here are some of the things in the operations side of computing:

Certs are king. It's mostly about knowing specific combinations of hardware and OS. It's very easy to get pidgen-holed into a specific hardware/OS combination.
Most companies treat operations folks as second class citizens. Good working environments are very rare. I spend 6 years here, and never had one.
You will get interrupted continually. You'll rarely have the chance to get into the "zone."
The pay is not very good when starting. It's a lot harder to get into high salary fast. I topped out at around $35K, before I got tired of being yanked around. I got to $80-$100K very quickly with programming and data warehousing.

This type of work is fulfilling, if you like working with your hands, and hate sitting at one place all the time. Otherwise, you will hate it with a passion. I'm one of those people that need 8 hours of uninterrupted sleep, so getting out was a good move for me. :)
Comment: Usually the way to go up in the system administrator career field is to go towards the high-end stuff that can't go down... clustering, directory services, etc., and become tier 3 level. Another approach is to go infrastructure architecture. But it can be a while as you pay your dues. Certs I have found to be not as big a deal if your resume/c.v. shows your experience.
Answer: I started out my professional career as a programmer. My degree is in Computer Information Systems, and I was all set to be an application programmer. In my first job out of college, I was doing the standard junior level development - QA, testing, scripting, converting projects between languages, programming web sites, etc. Then it turned out the guy the company hired to be the sysadmin fit the programming/development needs better than I did (they really needed a higher level person), and I was well suited to system administration. After all, I'd been doing that for years as a hobby anyway, and I preferred it to code.
Over the years, I've been primarily a system administrator ever since, though in the last year, I've seen my job role change back to programming. Lots of QA and acceptance testing with automation tools, because of configuration management. Every book I've read on system adminstration harps on automation. You have to automate any task you do more than once, they say. It's true. Automation of course requires ... programming.
So, I think you might find yourself coming full circle.
The system administration field really is leaning toward programming as a required discipline with the increasing number of API and frameworks used to configure and manage servers, instances, and tools.
For example, Puppet really broke the sysadmin space by bringing an excellent automation tool to mainstream usage. Sure, cfengine has been around for awhile, but even in 10 years of system administration, I never touched it. Instead, like many other system administrators, I cobbled together my own tools from various glue scripts and components. A new tool, Chef, is an even bigger breakthrough because it offers not only a declarative configuration language, but a RESTful API with which to program nodes and resources.
These practices bring performance and scalability to the forefront of the system administrators task list. Instead of spending hours (or weeks, or more) figuring out how to glue your monitoring tool with your system management webui, you can focus on analyzing the data the monitoring tool presents, so you can improve performance and business metrics.
Plus I find it a lot more fun than installing and configuring Nagios ;).
Answer: Your best bet is to get some kind of technical support role, ideally with a computer shop that looks after small businesses. Working in a single role won't give you very much exposure to the kind of real-world challenges that the high-paid system administrators face.
You need to pick a career that you enjoy, if you're not going to enjoy 5+ years of underpaid sysadmin work being on call 24/7 then you'll never get to the cushy end where you'll only do a few all nighters a month, and have a lot of spare time the rest.
Answer: You might be able to do both at the same time, that is work mainly as a developer and start doing administration of the development environment as well as SCM. You will start to gain knowledge about installing and configuriong software tools and machines related to your environment. Build up experience that way and then move slowly but steady into more mature sys admin work.
I have travelled the developer to sys admin road like this.


Origin of Azide's Name

Question: Today, I learned that  $\ce{N_3^-}$ is referred to as azide. I was wondering why $\ce{N_3^-}$ is referred to as azide. I checked Wikipedia for an answer, but I didn't find one. Does anyone know why this ion is assigned this name?
Comment: Speaking of which, azidoazide azide, unsurprisingly has only Nitrogen and explodes upon any stimulus (including a bright light). [unrelated but a cool fact]
Comment: dictionary.com says it's azo- + -ide.
Answer: Nitrogen was originally called 'azote' by Lavoisier. This name persists in many nitrogen containing species such as azide, hydrazine, diazonium etc.
The '-ide' ending is the standard ending for anions of a single element such as carbide, oxide, sulfide etc.
Answer: Bon explains in their answer that

Nitrogen was originally called 'azote' by Lavoisier.

And it was called 'azote' because living things cannot survive in the gas.

From Greek a- "not, without" [...] + zoion "a living being;" [...] coined in French by Lavoisier & de Morveau because living things cannot survive in the gas.
http://www.etymonline.com/index.php?term=azo-&allowed_in_frame=0
Answer: We look here at the "-ide" part. It ultimately derives from the French word for "acid".
When the agent that supports combustion was identified as an acid former ("oxygène"), the products of such combustion came to be called "oxygène acides", contracted to "oxides".
The spread of the suffix to compounds of other nonmetals may have been promoted by the fact that several other nonmetals also form acidic products, such as "chlorine acids" ("chlorides") produced when that element combines with hydrogen, sulfur or phosphorus.

Origin of Azide's Name


Can I post email correspondence between myself and my apartment community Property Manager online?

Question: I live in a fairly upscale apartment community in a major city in Florida. I've been having major issues concerning building security and another matters that I tried to address with our property manager. Her response was dismissive, rude, argumentative and did not even address most of the issues that I brought up.  I followed up with her again and her reply was even more dismissive and arrogant.  Currently I'm trying to take my problems with our property manager with the management company ( You're very large and on apartment communities around the Southeast).  In case this doesn't go anywhere, I would like to warn another people in a review about living here.  I would like to post the emails in the review, redacted for privacy and removing any personal information to provide receipts and backup my claims.  If I did so, would that be illegal in any way?
Answer:
would that be illegal in any way?

No, since you are taking the precaution of redacting for privacy and removing third-parties' personal/identifying information.
In fact, publishing records that support your assertions is likelier to discourage the landlord about filing a defamation lawsuit. That is because you are pre-emptively disclosing evidence that your assertions are truthful, and truth is an absolute defense in claims of defamation. An analogous rationale applies to other forms of retaliation that the landlord might be tempted to incur.
Comment: Agree on the conclusion, but unless there were something unusual about their contents, I don't think there would be anything illegal about publishing even if the e-mails were unredacted.
Comment: @bdb484 Maybe, but in any case it is better to err on the safe side. For instance, if another tenant is a victim of stalking/harassment, that tenant will not appreciate the publishing [on the Internet] of information that can facilitate the harasser's purpose of figuring out the tenant's home address.


Suppress Overset text alert for InDesign CS6

Question: Is there anyway I can set up a rule to not allow overset text in a text frame? I want to print without getting the "Overset text" alert for an specific text frame.
Comment: Delete the text. Add a text frame off the page and let your text flow into that....
Answer: Object → Text Frame Options → Auto-Size (tab) → Auto-Sizing = Height Only (or both)
This solves your issue.
If you want hide a part of the text, just put it into a frame (Paste Into). This frame became a mask for a text box.
You can setup such behavior for any new text box as default. This can be done from 'Objects Styles' panel.


What is the frequency distribution of the electromagnetic wave emitted by a charge accelerating along a given trajectory?

Question: Charged particles radiate when accelerated. From a few other Physics.SE answers like
What is the frequency of a photon emitted by an accelerated charged particle? and
How electromagnetic waves are created? it is understood that the accelerated charge emits a frequency spectrum, not a single frequency.
Most physics literatures on classical electrodynamics solve the problem only for synchrotron radiation or bremsstrahlung.
What is the general procedure for finding the frequency spectrum if the particle moves in a given trajectory r(t)?  For example, if the charged particle is accelerated in a straight line (constant acceleration along x-axis) then how can we calculate the frequency distributions of the EM waves?
Answer: This is in standard texts. For example,
in J.D. Jackson, Classical electrodynamics, third edition, Eq. 14.67
\begin{equation}
\frac{d^2I}{d\omega d\Omega} = \frac{e^2\omega^2}{4\pi^2 c}
\left | \int_{-\infty}^\infty \hat n \times (\hat n \times \vec \beta)
e^{i\omega(t-\hat n \cdot \vec r(t)/c)} dt \right |^2
\end{equation}
as the intensity distribution as a function of frequency and direction.
Here $\vec r(t)$ is the particle trajectory,
$c\vec \beta = \frac{d\vec r(t)}{dt}$,
and $\hat n = \hat x \sin\theta \cos\phi+\hat y \sin\theta\sin\phi
+\hat z \cos\theta$ is the unit vector in the direction of radiation. Jackson's result is in Gaussian units.
Jackson discusses when this is valid. Essentially when the radiation
is localized in space and time (for example, no radiation before the big bang.
Your example of a constant acceleration is a well known
badly behaved trajectory.)
A standard way to derive the result is to start with an arbitrary
localized in space and time current and charge density. Plug these into
the Lorenz gauge retarded coulomb's law equations for the vector and
scalar potentials. Fourier transform the potentials in time to get their
frequency components, take the large distance limit to separate the
radiation fields which go like $r^{-1}$. The result is that the
radiation fields are proportional to the component of the space-time Fourier transform of the
current density evaluated at $\vec k = \frac{\hat n\omega}{c}$, and $\omega$ which is
transverse to the radiation direction.
Calculating the time integral of the
Poynting vector then gives the intensity (i.e.
the energy radiated per unit frequency and solid angle).
You can see that the integral in Jackson's result is proportional to
the Fourier transform of the current density at this $\vec k$ value.
That is
\begin{equation}
\begin{split}
\vec J(\vec k,\omega) &= \int d^3r' dt'  ec\vec \beta
\delta^3(\vec r'-\vec r(t')) e^{-i \vec k\cdot \vec r'+i\omega t' }
\\
&= ec \int dt' \vec \beta(t') e^{-i\vec k \cdot \vec r(t') +i\omega t'}
\end{split}
\end{equation}
with $\vec k = \hat n \frac{\omega}{c}$. Taking $- \hat n \times (\hat n \times \vec J(\vec k,\omega))$ gives the transverse component.
Comment: Can you give references to where the frequency spectrum "well known badly behaved trajectory" of constant acceleration has been treated?
Comment: One place is section 8.1 of Rudolf Peierls "Surprises in theoretical physics." It is titled "Radiation in hyperbolic motion." He discusses the problem of uniform acceleration (in the rest frame) and the paradoxes and solutions along with references.


How do you spawn ONLY zombies in Singleplayer?

Question: I'm making a maze where you have to fight zombies and get to the end, but all these other mobs start showing up and I can't figure out how to spawn only zombies. Also, I can't use dispensers.
Comment: What are you using to spawn them at the moment? Mob spawners, summon command, spawn eggs? Do you just want to turn off natural spawning of other mobs?
Comment: @xXPikminXx It absolutely would spawn them. First of all, mob spawners check for valid spawning spaces before doing anything; they never spawn mobs inside blocks because that is not a valid spawning space. Secondly, spawners spawn mobs in a space that is 8 blocks wide, 8 blocks wide, and 3 blocks wide by default, centered on the spawner. So spawners placed flush with the floor will spawn mobs on the level of the floor, and spawners placed inside a wall will spawn mobs outside that wall.
Comment: I'm not using anything (yet) because I cant figure out how without using dispensers. Mob spawners also wont work because they'd have to be underground. If there's a way to do it with command blocks, that would be great
Comment: @xXPikminXx I fail to see how mob spawners underground is unworkable. You have a maze. Just put them underneath or inside the walls of the maze. Mapmakers do that all the time.
Comment: @Unionhawk if I put a mob spawner underground, it wouldnt spawn them because they would just suffocate in the ground .-.
Answer: Here are the brief steps to ensure only zombies and players live.
(Thanks Unionhawk for pointing out my mistake in the first answer and providing suggestions on this answer!)

Make a redstone clock.
Connect 4 command blocks into the redstone clock.
Insert these commands into the command blocks:
kill @e[type=Skeleton]

kill @e[type=Creeper]

kill @e[type=Enderman]

kill @e[type=Spider]

3.5 If you are in a superflat world you may want to add a kill Slime command.
Remember to activate these command blocks at the same time.
Activate the redstone clock.
Done.

You can also make the super fast command block clock but you have to change the doTileDrops gamerule to false.

Here are the brief steps to spawn a zombie.

Place a command block on the ground.
set the following command:
summon Zombie ~ ~2 ~

Activate it.

This will make the zombie spawn 2 blocks on top of the command block.
Comment: You may want to rethink your commands; `/kill @e[type=!Zombie]` will kill the player.
Comment: Hmm. Forgot that. Thanks for reminding. Maybe I should use the scoreboard to do this?
Comment: You *could*, but the easier way would be to use 3 separate commands; `/kill @e[type=Creeper]` etc.
Comment: So I should make a command block for every mob...?
Comment: You only really need 4 to cover natural hostile mob spawns. Creepers, skeletons, and endermen, and spiders.
Answer: To spawn a zombie with a command block, type in the command:
/summon Zombie X Y Z

Replace X Y Z with the coordinates of where you want to spawn the zombie.
Comment: when I do that it just says "Unable to summon object". Do I need to do "x=(x) y=(y) and z=(z)"?
Comment: @xXPikminXx Yes, replace X Y Z with the coordinates of where you want to spawn the zombie.
Comment: Actually the syntax is normally `~x ~y ~z` for coordinates. If you left it blank (`~ ~ ~`) it would summon them right on top of the location of origin (i.e. if you executed the command, it would appear in your block, or on top of a command block if that was the point of origin)
Comment: @Ben ~ makes the coordinates relative, rather than normal coordinates. Just replacing X Y Z with the coordinates will work.
Answer: Setup:
/scoreboard objectives add selector dummy

Clock(20tps)
/scoreboard players set @e selector 1
/scoreboard players set @e[type=<Type>] selector 0//One of these per entity type, in this case one for zombie and one for players
/tp @e[x=<X>,y=<Y>,z=<Z>,r=<Range>,score_selector_min=1] ~ ~-600 ~

First it marks all entites, then unmarks the selected entite(s), and finally teleports the marked entites down into the void so there is no dying animation and no items drop.
Answer: Use a command block to set certain gamerules. If you program one with this command,

/gamerule doMobSpawning false

then mobs can only spawn if you spawn them in with /summon, a spawn egg, a dispenser, etc.
Answer: Method #1:
You can do this by auto-killing all hostile mobs that are not Zombies - Plug in Command blocks with these commands into a fast Redstone clock (or use the 1.9 Command Block fetures):

/kill @e[type=Spider]
/kill @e[type=Enderman]
/kill @e[type=Creeper]
/kill @e[type=Skeleton]
/kill @e[type=CaveSpider]
/kill @e[type=Witch]
/kill @e[type=Slime]
/kill @e[type=Guardian]

Method #2 (the hardcore one):
When a non-Zombie hostile mob spawns, replace it with a Zombie - Again, on a fast RS clock plug Command blocks with these commands:

/execute @e[type=Spider] ~ ~ ~ summon Zombie ~ ~ ~
/execute @e[type=Enderman] ~ ~ ~ summon Zombie ~ ~ ~
/execute @e[type=Creeper] ~ ~ ~ summon Zombie ~ ~ ~
/execute @e[type=Skeleton] ~ ~ ~ summon Zombie ~ ~ ~
/execute @e[type=CaveSpider] ~ ~ ~ summon Zombie ~ ~ ~
/execute @e[type=Witch] ~ ~ ~ summon Zombie ~ ~ ~
/execute @e[type=Slime] ~ ~ ~ summon Zombie ~ ~ ~
/execute @e[type=Guardian] ~ ~ ~ summon Zombie ~ ~ ~

And, if any of these Command blocks has a positive output, trigger a Command block with this command (using a Comparator):

/execute @e[type=Zombie] ~ ~ ~ kill @e[type=!Zombie, r=2]

Note: the r=2 is important, because if the mob would move when spawned and the command would be r=1, it wouldn't get killed, just moved - many mobs would spawn.
Note: You can redo this to the 1.9 Command block structure.


Public webserver with Apache Tomcat (OS X Lion)

Question: I just find out that it is possible to create public webserver through "preference". Is it possible to make this "webserver" to a Apache Tomcat server? I develop in Java/Jsp/Servlet..
I use Lion and I'm new to Mac
Answer: No. The System Preferences setting only activates Apache HTTP Server.
You can set up Tomcat stand-alone yourself, or configure Apache to use mod_jk to connect to Tomcat as described e.g. here.
Answer: Yes of course. But the firewall doesn't make it simple nowadays. In earlier versions of OSX you could add a port exception to the firewall, which isn't possible AFAICS. You can install the Waterroof firewall frontend.
http://www.hanynet.com/waterroof/
Another option is to use apache as frontend to tomcat, using Mod_JK.
https://tomcat.apache.org/connectors-doc/webserver_howto/apache.html
A third option, if you don't need Apache, is to make Tomcat listen to port 80, and disable Apache. Enabling the webserver in the firewall does make OSX start the webserver. So you probably should make Apache use another port as well, say port 9090. Then apache starts, when the firewall starts it, and you start tomcat manually.
TOMCAT
Open server.xml
<Connector connectionTimeout="20000" port="8080"

Should be: port="80"
See https://stackoverflow.com/questions/5544713/starting-tomcat-on-port-80-on-centos-release-5-5-final
APACHE
Edit httpd.conf
listen 80

should be: listen 9090
See https://httpd.apache.org/docs/2.0/bind.html


Requesting police report and criminal applications

Question: I am in Massachusetts and I got a criminal traffic citation. How can I request police report and criminal citations?
Comment: How long ago was this ticket made.  As the defendent in this case, the government must turn over all relevent documentation.  A call to records would likely suffice.
Comment: Three weeks ago.
Comment: Criminal? As in not just a ticket, but misdemeanor charge?
Comment: True. Some charge.
Comment: "A call to records." Would you be a bit of specific?
Answer: The citation itself is on file in the court where you'll have charges. Obtaining it should be as easy as walking in to the clerk's office and asking for it.
The incident report may be different. In some courts, it will just be filed with the citation, which should make it easy to get. And in some places, police will just give you a copy if you ask for it, though I'm not sure what Massachusetts' laws are on that. If you can't get it either of those ways, you may be able to access it in the discovery phase of your case. Especially if it gets that far, you should definitely get an attorney to help you out.


Practical Interpretation of PCAs for a supplier analysis

Question: I am using PCA to validate and research a set of 13 suppliers of products against a set of about 50 variables and performance indicators against an ideal "wish"-Supplier, mostly based on G. Jankers Book on Factor Analysis for Supplier a Rating System.
While using R Studio I use my data to perform the PCA with prcomp.
My question is regarding practical statements of the outcomes of the PCA and its factors.
My Goal is to identify the perfomance indicators, in which a supplier needs to improve, in order to improve another outcome. For example, maybe a supplier needs to improve reaction speed in order that the amount of price requests rise as well. Or to identify groups of suppliers with similar performance indicators.
PC1 accounts for about 50% of all variances, PC2 for 15%, PC3 for 10% and so on.
If I now have a look on PCAs against the loadings for each of the 50 performance indicators and check the PCAs against the Suppliers, I result in having a few questions. Also to make sure I did understand correctly.

Lets say Supplier 1 loads really low on PC1, like -6,23569. PC1 loads really high on the first 5 performance indicators. Can it be said that: "Supplier 1 does move against PC1"? So Supplier 1 would have really low loadings on the first 5 Performance indicators? Anything that loads high on PC1 would turn negative on Supplier 1 and vice versa?

If a certain group of Performance indicators load significantly high on a PC, can it be said that a Supplier, that loads high on that PC as well does generally move with the PC and has generally higher emphasis on that group of performance indicators?

PC1 is said to count for 50% of the information. If a performance indicator loads REALLY LOW on PC1, does that mean that this one performance indicator holds significantly more value in the whole spectrum because PC1 has such a high emphasis on it, which also means that this performance indicator might be the most important one in the specturm? Going further down the PCs, if PC10 has a very high loading on another one which didnt stand out on any of the PCs before, does this mean this indicator has just less value overall?

My Goal is to identify which performance indicators actually make a difference and then check which supplier needs to improve which area or which are the ones that needs to be focussed on.
Just imagine you are in a shoe store and sell addidas, nike, puma etc, and you want to figure out which of those is your times worth and you get the best out of and how to push them to become your ideal supplier.
Some Inputs of PCA Savy people are appreciated.
Supplier vs. PCs
Performance Indicators vs. PCs
Edit:
Ok so I understood Question 1 and 2.
Am I correct in assuming that if a Factor loads high very early in the ranks of PCs that this must be something of bigger importance towards the whole factor spectrum?
I have analysed the accumulation of explanation per indicator. (Sum of the Squareroots of the loadings per PC). Why am I not reaching 100% on the last PC on neither factor? highest I did get was 76% Explanation.
Comment: Okay I have understood Question 1 and 2 now. Since PC1 = Loading1 * Performance indicator1 + Loading2 * performance indicator2... and so on.
Answer: Principal Component Analysis (PCA) is not very useful for that type of interpretation.

Just imagine you are in a shoe store and sell addidas, nike, puma etc, and you want to figure out which of those is your times worth and you get the best out of and how to push them to become your ideal supplier.

It would be more useful to frame it as a supervised learning problem and find the feature and instances that are most associated with the target values.


What happens to Colombian beans that do not make Supremo or Extra?

Question: I'm learning about Colombian coffee and its national grading standards of Supremo (highest) and Extra (second highest). Does anyone know what percentage of all beans produced falls into those two categories? What happens to the beans that don't make one of those two grades?
Answer: They get sold for less money as "standard export" grade coffee.  Because of NFC's marketing campaign, ANY sort of Colombian coffee ends up with higher brand recollection than most other coffee.  There is a slightly slanted view of the matter here.  The writers are coffee aficionados who prize distinctive origin flavors in their coffee, which is rarely present in NFC graded coffee since they are more often than not mixed batches of beans from different growers.  That isn't to say that the NFC's work doesn't ensure high standards for Colombian exports, but it isn't favorable to some sectors of the coffee market who prize distinct coffee from a single origin.
Comment: Cool thanks! Your picture does indeed speak a thousand words. In your link, I was surprised to read that the Supremo and Extra grades are not about quality but about bean size.
Comment: There is a lot of variation in the coffee market.  Lots of beans that look uniform will sell better to some customer segments than beans with size and shape irregularities (peaberries left in) and a higher cupping score.


Tablet as a secondary monitor

Question: Do I have any option to use my Samsung Galaxy Note 10.1 (2014 edition) as a secondary screen?
I want to use it for Photoshop, which runs on the PC, but I control it on the tablet. I know I can draw with the tab, and there are apps for drawing, and I've already used Sketchbook (Autodesk) but it has a lot of limits with the layers and brushes.
I have already tried applications like "Splashtop" via the internet but it was very laggy, and I also gave a chance to "Slide" (because of the USB connection) but the installation didn't work.
I don't really trust apps which work via the internet because it might be very slow and laggy, and it's a big deal in computer drawing, so I look for a solution which works via HDMI or USB cable.
Does anyone have an idea how can I make it work?
Answer: You can try :

Air Display by Avatron
iDisplay
Splashtop

Tablet as a secondary monitor


data matching multiple columns with fuzzy matching criteria

Question: I'm doing a similar project to this: Data matching algorithm
Where, I have one data frame (dataset1) with customer details, without a special unique ID, which is then matched against data frame 2 (dataset2) which has the same fields along with a special unique ID.
Example:
Dataset1 columns include:
Title, Last name,  First name, Middle/other name, address,  DOB, sex, health care number
dataset2 columns include:
Unique ID, Title, Last name,  First name, Middle/other name, address,  DOB, sex, health care number
My plan:
My data set 1 is ~500,000 rows w/ 11 or so columns - the row count can be split if required. Data set 2 is ~2,000,000
Based on matching criteria from the business eg. >5 columns must match, and potentially a fuzzy component eg names that are hyphenated (inc. other special characters) in one data set but not in the other.
Based on the approximate match, this ID, and the fields from data set 2 is copied into data set 1 in adjacent columns, along with an overall match %.
Then overall match % ranges can be extracted and inspected by the business.
I plan on using Panda with Fuzzywuzzy.
I'm having trouble planning my technical approach on the logic of my code.
SHould I look through the first field for matches, then filter down on the next column, and so on? I think so, but how does the loop operate moving across the columns in the two comparative data sets?
do I need to write each operation of comparison back into the data set for storage or can it be kept else where?
the alternative that might work, is that I concatenate all the columns into a single column, and those are matched, and returned with the matched ID, other fields and the matching %.
I'm looking for the best direction to head into, along with general logic on the best way to do it.
Answer: In general: try, observe, adjust and repeat.
It may be worth exploring any small adjustments to standardize and make data as consistent as possible before using Fuzzywuzzy.

Some data sets could use 555-555-5555, 0, or - for an empty phone number or Jan 1, 1970 for blank DOB.  Dataframe.replace({column:{to_replace:replace_val}) can help clean those up.
Python's dateutil.parser is helpful with standardizing a variety of date formats.
Try wrapping the fuzz ratio and removing punctuation from last name before analyzing.
Addresses: Pandas.column.str.upper() can be used to apply consistent case.  Try without punctuation, too.
Concatenating all fields may be a good first pass for exact matches.  2nd pass could evaluate less important fields like Sex and Title for missing data.

In general, you may want to approach in layers, remove direct matches followed by the most certain matches, reevaluate until the amount of effort required for the next wave approaches what you consider diminishing returns for this project.
If you approach by column, you may want to remove the certain matches then start with last name and then create a list of choices of the next most deterministic column and use fuzzywuzzy's process.extract to assist with the decision tree. There may also be a better approach that I'm not aware of!


Can the output of a logic gate be split to serve as input for other logic gates?

Question:

In the textbook picture, they use 5 NOT gates, repeatedly splitting the R input only to have it go into a different NOT gate. Are you allowed to put the input of R into a single NOT gate, and split the output twice? In this case, allowing you to have a total of 3 NOT gates, and 3 AND gates?
Comment: It depends on the logic tech. Check fan-out of logic devices. Having said that, one logic gate output will drive two logic gate inputs pretty much 100% of the time.
Comment: In theory: yes. In practice: as long as drive strengths, frequencies, capaticance and so on allow it, then yes.
Comment: @Puffafish Ok great thanks!
Comment: @Andyaka Thanks for the clarification!
Comment: @greybeard This is for an introductory Discrete Math class where we aren't allowed to simplify the equation or use NAND gates yet, but that approach is what I was thinking too
Answer: Having a logic output driving multiple logic input is normal. In ideal logic diagrams, a single logic output could drive an infinite amount of logic inputs, and on many occasions, a clock output will be used on all logic gates that need to run on that clock.
If a logic output could only drive one logic input, it would need a logic device which can internally split a logic signal into two, which again would be paradoxal - inside the chip you would still need to be able to split a logic signal into two.
In real world logic gates, depending on logic family, an output can drive somewhere around 4 to 20 inputs.
Buffers can be used to take a signal in and drive multiple inputs which allows to split a signal into multiple ones that can again drive multiple inputs. But each logic gate or buffer will also add a delay to the signal.


How to tell it is a relativistic kugelblitz instead of other photonic attack?

Question: Set in a quite distant future, intergalactic war is brewing and it is important to tell what form of attacks the enemy ship is using otherwise the battle will quickly become one sided. Anyway imagine a torpedo in the form of a kugelblitz is being deployed in battle, the micro blackhole is then accelerated to close to speed of light so that the spaces between itself and target becomes small granting it enough time to evaporate into deadly Gamma. But from the enemy frame of reference how can they tell? What technology and methods can be used to establish the nature of the attack?
Answer: An object between an observer and a light source will affect light coming from the source.
https://en.wikipedia.org/wiki/Kugelblitz_(astrophysics)

In simpler terms, a kugelblitz is a black hole formed from radiation
  as opposed to matter. (Such a black hole would nonetheless have
  properties identical to one of equivalent mass and angular momentum
  formed in a more conventional way, in accordance with the no-hair
  theorem.)

https://en.wikipedia.org/wiki/No-hair_theorem

The no-hair theorem states that all black hole solutions of the
  Einstein–Maxwell equations of gravitation and electromagnetism in
  general relativity can be completely characterized by only three
  externally observable classical parameters: mass, electric charge, and
  angular momentum.

A Kugelblitz is coming fast.   Light is faster.

The Kugelblitz will be a darkened area against stars behinds it.  This is true also for an incoming meteor.
Unlike the meteor, the Kugelblitz will intercept radiation from an area greater than its profile because its gravity will bend in and capture photons that otherwise would pass near it and on to the observe.  It might appear as a meteor larger in diameter than the Kugelblitz is.
The Kugelblitz (by virtue of its gravity) will bend light near it that it does not intercept.  The relative positions of stars on the far side of the incoming Kugelblitz will appear to change.  This is actually true for normal masses also but by a trivial amount.

These effects would be noticed immediately by a computer whose job it was to watch the stars in all directions.  If a fixed distant star blinks out or appears to move, something is in between you and the star.  Observation over a period of a second will allow the trajectory of the incoming object to be calculated.
You will move out of the way and wonder how much it cost to throw that very expensive rock.
Comment: @Ryan_L Doesn't have to be stars. could be something looking at background radiation. Fairly uniform all around, except for that small dead pixel in the middle... god I hope that's a dead pixel... *end transmission*
Comment: I don't disagree with your answer, but I feel like I need to point out that this is no easy feat.  A kugelblitz needs to be small, so it evaporates in a reasonable amount of time, in order to be used as a weapon.  Certainly microscopic, maybe about the size of an atom.  This is going to be difficult to see even in the best of conditions.  In practice, you may not always have stars in the right places in the background to get any occlusions or lensing effects at all.
Comment: One problem is that you need to detect the black hole and then evade it before you watch it pop into gamma radiation. A BH with mass 10^6 kg has radius $10^{-21}$m and pops in 84 seconds. 10^5 kg in 0.08 seconds. These are TINY, much smaller than an electron. Also remember that gravity from a meteor is equivalent to gravity from an equal-mass black hole (outside the meteor's radius).
Answer: A micro-sized black hole will be a powerful source of intense gamma rays and interesting particle radiation; that's just the nature of Hawking radiation. A hole which evaporates in a second is emitting zettawatts of EM and particle radiation. A shorter-lived hole will be proportionally brighter, and even if it were travelling at highly relativistic speeds the journey will not be instantaneous and radiation will be emitted and so can be observed.
Because of the sheer speed of the emitter, observers who are watching it fly towards them will see the radiation strongly blueshifted, and observers watching it fly away from them will see it strongly redshifted. This will make it obvious to everyone involved that the projectile was a highly radiant relativistic object. The spectrum and types of emitted radiation will show that it is not merely an extremely hot blackbody, but clearly something that's pulling a wide variety of particles out of the quantum vacuum. To me, at least, this seems trongly suggestive of a black hole, but perhaps there are other phenomena that could do this too.
It will not be possible to distinguish a kugelblitz from any other kind of black hole, due to the no-hair theorem mentioned by Willk.

As a footnote though, consider that if you can accelerate non-trivial masses to high relativistic speeds, there's absolutely no reason to fire anything other than boring, regular matter. The kinetic energy of the projectile is such that the contribution of its mass-energy to the total amount of boom becomes increasingly uninteresting. This is why there's no point making an antimatter particle beam, for instance.
The amount of energy released by a black hole in its final moments cannot exceed the mass energy of the hole. At speed of .9c, more than half of the energy released at the end is the kinetic energy of the projectile. AT .99c, the kinetic energy is more than 22x the mass energy.
You haven't specified how fast your "torpedo" is travelling, but there's a reasonable chance that you've simply made things much more complex and awkward than they need to be.  Take the energy you would have thrown into the kugelblitz, and use it to shoot a bigger or faster projectile, or make several shots. Saves carrying all those dumb, heavy, power-hungry, massively hot gamma ray lasers nailed to a fiddly and probably delicate mount, too.
Answer: The sensor blitz.
The other answers are pretty good, but just for fun variety, when a ship arrives in a destination that they think is dangerous and might get attacked, they could launch cluster bombs that each contain thousands of micro-sensors, the size of a penny or whatever.  They fill the entire surrounding space for thousands of miles with these, which signal the ship when they detect a kugelblitz heading in.  Either by radio, which is still faster but don't give a huge heads up, or by quantum entangled communications, which would be instantaneous (if not entirely in keeping with our current understanding of physics).


Time of Paul's Conversion in Acts 9:1-9

Question: Can we know from the Bible how much time passed from Jesus' ascension in Acts 1:9 to His appearance to Saul / Paul on the road to Damascus?
Answer: Based on the NT books of [Acts, Luke, John] the 'Resurrection-Ascension' timeline generates the following events :
Day-1 [Luke 24:1-3, John 20:1] Resurrection Sunday :

17th of Aviv (three days after Pesach, based on Luke 23:54) during Chag HaMatsot.

Day-8 [John 20:26] Doubting Thomas Monday :

25th of Aviv; four days after Chag HaMatsot)

Day-28 : undocumented Pesach for unclean disciples (14th of Ziv זִ֗ו , the redo of Pesach based on Numbers 9:11-12)

Day-40 [Acts 1:3] Ascension Friday :

26th of Ziv זִ֗ו (second month) : "being seen by them during forty days" ἡμερῶν τεσσαράκοντα ὀπτανόμενος αὐτοῖς

Day-49 [Acts 2:1] Pentecost/Shavuot Sunday :

6th of Sivan (third month) celebration of Shavuot "7-Weeks" (based on Deuteronomy 16 verses 9-10)

The Remainder of Acts 3-9 gives no definitive timeline leading up to Saul's conversion.
After Saul's vision [Acts 9:1-9], we are only told he developed his own understanding of Jesus the Nazarene - after three years [Galatians 1:18].
Comment: But, Paul's time spent learning of Jesus after his conversion is beyond the time frame.  I've read several guesses of the time from the ascension to Stephen's stoning, but nothing I can see in scripture confirms.  Others seeming to speculate it was about 3-1/2 years.
Answer: There is very little chronological information in the book of Acts.  I can see none between the ascension and diaspora of Acts 8:1.  However, it was probably about 3 years, based on very little data.

Jesus ascended 40 days after the His crucifixion, Acts 1:3, 9
Pentecost was 50 days after the crucifixion
Acts 1:8 appears to suggest that the apostles were to evangelize Jerusalem and Judea before going further to the Gentiles.  This might have taken some time and all the events between Acts 1:9 and 8:1 are confined to this area.

Specifically, following Pentecost in Acts 2, we have the following events before the Philip is sent to Samaria:

Peter & John heal the beggar and then answer for their actions to the Sanhedrin, Acts 3, 4
Annanias and Sapphira incident, Apostles heal many and the apostles persecuted, Acts 5
Seven deacons appointed, Acts 6:1-7.  This marks the end of the incidents in Jerusalem.
Following the appointment of the seven deacons, Stephen's ministry expanded greatly and came to the attention of the Sanhedrin after the two parties developed - some of whom were from some distance away, Cyrene, Alexandria, Celicia and Asia (Acts 6:9).  So some time was required for Stephen's reputation to have spread that far.  After this, Stephen is tried, condemned and executed by the Sanhedrin.

This, and the material I placed in the appendix below suggest that there were a "few years" between Acts 1:9 and 9:1, but we cannot be precise.
The only other thing we can observe is the that in addition to the material in the appendix below, the material in the early part of Acts appears to be arranged to document the focus of Gospel preaching moving from Jews to gentiles, possibly in filfilment of some of the OT prophecies such as Dan 9:

Acts 7:51, 57, 58:  Stephen stoned, Jews (at least the leaders) reject Jesus as Messiah, finally.  Stephen recognizes that Jesus is now in the heavenly sanctuary, Acts 7:48, 49, 55, 56, seated at the right hand of God.
Acts 8:1:  Church scattered from Jerusalem
Acts 8:26, 27:  First missionary to gentiles, Philip & the Ethiopian
Acts 9:11, 12, 15:  Paul the apostle to gentiles is called and appointed
Acts 10:11, 12:  Peter's vision to go to the gentiles
Acts 11:17, 18, 26:  Gentiles become Christians and called such
Acts 11:19-21:  Church headquarters moved from Jerusalem to Antioch

Again, there is little hard chronological data here so we cannot be too precise.
APPENDIX - Book of Acts Outline
The book of acts reads like a church report of progress at various stages beginning with Jesus sending out the disciples until the Gospel reached Rome.  Each section concludes with a summary of the progress of the Gospel that naturally divides the book into six sections.  The table below summarizes this.

Reference
Progress
Summary

1:1 – 6:7
Gospel preached in Jerusalem
6:7 So the word of God spread. The number of disciples in Jerusalem increased rapidly, and a large number of priests became obedient to the faith.

6:8 – 9:31
Gospel spreads from Jerusalem to Samaria
9:31 Then the church throughout Judea, Galilee and Samaria enjoyed a time of peace and was strengthened. Living in the fear of the Lord and encouraged by the Holy Spirit, it increased in numbers.

9:32 – 12:24
Gospel spreads to Antioch and 1st Gentile convert, Cornelius
12:24 But the word of God continued to spread and flourish.

12:25 – 16:5
Gospel spreads to Asia Minor including Galatia
16:5 So the churches were strengthened in the faith and grew daily in numbers.

16:6 – 19:20
Gospel spreads to Europe
19:20 In this way the word of the Lord spread widely and grew in power.

19:20 – 28:31
Gospel spreads to Rome
28:31 He proclaimed the kingdom of God and taught about the Lord Jesus Christ--with all boldness and without hindrance!
Comment: Thank  you.  I keep seeing God's patterns repeat.  Jesus' 3-1/2 yr ministry to the Jews; maybe it was another 3-1/2 yrs to the grafting in of the nations; that would make a 7 year span of preaching the gospel to Jerusalem & the lost sheep of Israel.
Comment: @Gina - that is the likely time frame but I cannot prove it.
Answer: How long would it take for a well educated Roman/Pharisee, a zealot of God's word and the heresy of the Nazarene; to run out of Messianic Jews in all of Jerusalem to lock up and bond? He felt his work in Jerusalem was done and had heard of diaspora Yeshua believers in Damascus and had developed a reputation and was known throughout the area. Ananias in Damascus reminded God's voice of who he was when asked to restore his sight. I've studied this for a while and my best guess is Saul, not a big guy and not pleasing to look at either, about the same age as Yeshua was confronted by the Man he was persecuting about 7 years after the passion. That's my story and I'm sticking to it. If Christ Jesus had to pick a sufficient time for the 12 to make some headway instead of still hiding out, and He did pick a time; don't you think it would be 7.
Comment: Your answer could be improved with additional supporting information. Please [edit] to add further details, such as citations or documentation, so that others can confirm that your answer is correct. You can find more information on how to write good answers [in the help center](/help/how-to-answer).
Comment: Your thoughts are welcome, but this site requires scripture for the basis.  Any scripture you can add that would support your answer?

Time of Paul's Conversion in Acts 9:1-9


Storage nightmare

Question: I've known my phone's been pretty full for a while (mainly music, which is seemingly impossible to save to my SD card), but the equalizer on the music app I use recently started acting up. I went onto Google Play to give it a shit review, but then realised it needed an update. When I tried the update, it told me I had insufficient storage space, so I decided to delete the app to see if it would have been updated if I downloaded it again. Insufficient storage space. I've now deleted four fairly large apps from my phone, and guess what my phone told me when I tried to download the music app again? Yep... Insufficient storage space! Still. And now I've got no apps either... Is there anything I can do about this?
Comment: Welcome to the Android Enthusiasts! Wow, looks you've got some "shitty downvotes" (hint: 1. if something "acts up", before giving bad ratings at Playstore better check if it's not your fault; 2. have you used our nice search function to check for similar issues?). To get you started nevertheless, I've re-tagged your question. Please check our [insufficient-memory tag-wiki](http://android.stackexchange.com/tags/insufficient-memory/info) for first aid and useful links. Good luck!
Answer: your storage issue is widely encountered within the android devices users.Although you didn't mention your device name and android version,you should look for your microSD card if it is mounted read/write or read only and see your internal SD card too.Google has restricted the ability to write to the SD card for Android KitKat and above so you have to try to use Kitkat SDFix from Play Store to restore this great feature.If this doesn't work you might try to root your device and install the Xposed framework and then download a module called "HandleExternalStorage" from within the Xposed installer,activate it and reboot your phone or tablet.

Storage nightmare


IOS Push notification using Flash (AIR 2.5)

Question: Has anybody used the IOS push notification using the lastest AIR 2.5 SDK for mobile? Could somebody please send me to any tutorial or example on implementing it. Thanks in advance.
Answer: I don't think it's possible to send push notifications using the iPhone packager for Adobe Flash at this moment.
Although the Adobe team did some nice work with AIR 2.6; APNS implementation isn't one of them.
I hope they'll be able to implement APNS support in any future AIR update, that would be welcome feature especially with multiplayer gaming.


Android system partition image on pc or sdcard

Question: I want to take raw image of my android system partition either on sdcard or on my pc using adb or any other way.. if their is way please help
Comment: I think we need more details here. What problem are you trying to solve?
Comment: Martyn I tried your link but it gives me permission denied error. I need a dump of android OS of my galaxy mini, I want to check it for something at raw level so em new to android so please any good idea..
Comment: Upvoting because I have this issue and not sure why it was downvoted in the first place.
Answer: Here's how to get a system dump from Android:
Prepare Your PC

Ensure that your computer has the most recent version of the Java Development Kit installed. If it doesn't, download and install the most recent JDK from Oracle's Java SE Downloads page.
Navigate to the Download the Android SDK page on the Android Developers website in a Web browser and download the installer package to your computer. Double-click the downloaded file and follow the installation prompts.
Navigate in Windows Explorer to the location where you installed the SDK. By default, this is C:\Program Files\Android\android-sdk.
Double-click the SDK Manager to launch it. In the left pane file tree, check the box next to "Android SDK Platform-tools." Click "Install Packages." A confirmation window appears. Click the radio button next to "Accept All." Click "Install." A progress bar appears.

Prepare Your Phone

Press your phone's menu button from the Home screen. Tap "Settings." The Settings menu appears.
Tap "Applications." In the Application Settings menu, tap "Development."
Check the box next to "USB Debugging" in the Development menu.

Get a System Dump

Press "R" and the Windows key simultaneously on your PC keyboard to bring up the Run box. Type "cmd."
Type the following into the command window:
cd C:\Program Files\Android\android-sdk\platform-tools
Type "adb.exe shell."
Type su dd if=/dev/block/stl6 of=/sdcard/factoryfs.rfs at the ABD shell prompt. Replace "/sdcard/factoryfs.rfs" with the location to copy the file to if you don't want it on the phone's SD Card.

Reproduced in full from this site


Prove the matrix of an orthogonal linear transformation relative to an orthonormal basis is orthogonal.

Question: Let $V$ be an $n$-dimensional inner product space (not necessarily the standard inner product), and let $L:V \rightarrow V$ be an orthogonal linear transformation. Let $B=\{v_1,...,v_n\}$ be an orthonormal basis for $V$. Let $A$ be the matrix of $L$ relative to this basis. Prove that $A$ is orthogonal.
My attempt:
To prove that $A$ is orthogonal, I could prove that $A^TA=I$, or I could prove that the inner product of any two columns of $A$ is zero and the length of any column of $A$ is one. (I  use standard the inner product for the first proof but not the second, right?)
I know how to prove that $A$ is orthogonal if $V= \mathbb R^n$, but I am not sure how to generalize to any orthogonal basis. This is how I would do it for $V= \mathbb R^n$:

Column $i$ of $A$ is simply $T(e_i)$, where $e_i$ is the $i$th vector in the $n$-dimensional standard basis.
Since $T$ is an orthogonal transformation and therefore preserves length, $||T(e_i)||=||e_i||=1$ since the basis is orthogonal.
Since $T$ is an orthogonal transformation, for all $x,y$ in $V$, $<Tx,Ty>=<x,y>$. Moreover, Since the basis $B$ is orthogonal, the inner product of any two basis vectors is $0$. Therefore, the inner product of any two columns of $A$ is $0$.
Since the length of every column of $A$ is $1$ and the inner product of any two columns of $A$ is $0$, $A$ is orthogonal.

My problem with generalizing to any $V$ is step 1: Specifically, what would $A$ look like for an arbitrary $V$?
Answer: Hint: For a general $\ V\ $:
$$
T\left(v_j \right)= \sum_{i=1}^na_{ij}v_i\ ,
$$
so
$$
\left\langle v_j, v_k\right\rangle= \left\langle T\left(v_j\right), T\left(v_k\right)\right\rangle
= \left\langle \sum_{i=1}^na_{ij}v_i, \sum_{l=1}^na_{lk}v_l\right\rangle\ .
$$
What happens if you use the bilinearity of the inner product to pull the coefficients of $\ v_i\ $ and $\ v_l\ $ in the rightmost term of these equations out of it?
Comment: How can $a_{ij}$ be factored out if it depends on $i$? Same for $a_{lk}$.
Comment: Linearity of the inner product in its first argument implies that
$$
\left\langle \sum_{i=1}^na_{ij}v_i,\sum_{l=1}^na_{lk}v_l\right\rangle= \sum_{i=1}^na_{ij} \left\langle v_i,\sum_{l=1}^na_{lk}v_l\right\rangle\
$$
and then linearity in its second argument implies that
\begin{align}
\left\langle \sum_{i=1}^na_{ij}v_i,\sum_{l=1}^na_{lk}v_l\right\rangle&= \sum_{i=1}^na_{ij} \sum_{l=1}^na_{lk} \left\langle v_i,v_l\right\rangle\\
&=  \sum_{i=1}^n\sum_{l=1}^n a_{ij}a_{lk} \left\langle v_i,v_l\right\rangle\ .
\end{align}


Anet A8 with Marlin firmware: Auto Home is crashing into bed

Question: I got things moving from the answer to a previous question. Now, since the base-video I'm following is non-English, I want the next phase fixed: Probing failed
Auto Homing showing failing Z-homing

After the final adjusted firmware upload, and bringing the sensor up, I see that the extruder pushes the bed down a bit when I auto home and then the LCD screen says probing failed.
If compare to the latest (v1.1.9) Configuration.h file from GitHub, here are the changes:
#define FIX_MOUNTED_PROBE // Line #0719, Uncommented

#define X_PROBE_OFFSET_FROM_EXTRUDER 16  // Line # 0779, Was 0
#define Y_PROBE_OFFSET_FROM_EXTRUDER 58  // Line # 0780, Was 0

#define Z_HOMING_HEIGHT 5 // Line # 0870, Was 4

// #define MIN_SOFTWARE_ENDSTOP_Z // Line # 0907 Commented

#define AUTO_BED_LEVELING_LINEAR // Line # 0977, Uncommented

#define LEFT_PROBE_BED_POSITION  (X_PROBE_OFFSET_FROM_EXTRUDER + MIN_PROBE_EDGE) // Line # 1027, Uncommented
#define RIGHT_PROBE_BED_POSITION (X_BED_SIZE                   - MIN_PROBE_EDGE) // Line # 1028, Uncommented
#define FRONT_PROBE_BED_POSITION (Y_PROBE_OFFSET_FROM_EXTRUDER + MIN_PROBE_EDGE) // Line # 1029, Uncommented
#define BACK_PROBE_BED_POSITION  (Y_BED_SIZE                   - MIN_PROBE_EDGE) // Line # 1030, Uncommented

#define Z_SAFE_HOMING // Line # 1144, Uncommented

From the above changeset, lines 1027-1030 are from the other SO question I mentioned above, the remaining are following the video.
After completing the steps up to the point where I push the firmware and have to lift the ROKO up I followed instructions in this video, my "Auto Home" operation is failing.
Update 1
I used Pronterface as recommended by @dgrat in comments below and got this result:
>>> M119
SENDING:M119
Reporting endstop status
x_min: open
y_min: open
z_min: TRIGGERED

I did not get the Probing failed message this time.
What's next?
Update 2
I also went ahead and tried out the second answer, where @0scar is recommending to uncomment #define MIN_SOFTWARE_ENDSTOP_Z.
The results are exactly the same: The head hits the hotbed and goes back and then comes down slowly hitting and compressing the spring a bit before stopping. I did not get the Probing failed message this time.
Comment: There is a command for that. http://marlinfw.org/docs/gcode/M119.html. I use it now and then with http://www.pronterface.com/. You are not the first one with such problems. I suggest to always test the switches before using the machine to avoid damage.
Comment: Does the endstop trigger?
Comment: @dgrat How do I detect that trigger?
Comment: @dgrat please check update to thread
Comment: I also tested that raising the z-axis by just 2 nm makes the A4 paper on the bed move with an acceptable resistance. Have I hardcoded the Z position somehow?
Answer: You should un-comment the following line to get rid of the Probing failed error message:
// #define MIN_SOFTWARE_ENDSTOP_Z // Line # 0907 Commented

to
#define MIN_SOFTWARE_ENDSTOP_Z

You have basically disabled the use of the minimum Z endstop, while in fact you are using one, the difference is that it is a sensor now, not a mechanical switch.
Please note the distance of the sensor to the bed, it looks as though it is pretty far away. Before sending an auto home command, it is better to test the endstop triggering beforehand; an external application (e.g. Pronterface, Repetier-Host, OctoPrint, etc.), USB cable and a laptop/computer can be used to send G-code commands through the terminal of the external application. Code M119 will output the endstop trigger status to the terminal.
Comment: I'll make this change and push firmware again. Will get back on this. I do not know why the guy in the video commented this out.
Comment: @HassanGulzar Have you fixed this, if not update your question so that other people may answer, or an update can be made.
Comment: Not yet. I have to redo the setup to verify if I've done anything wrong
Comment: I tried with the line uncommented but the result is the same. The head still pushed down on the hot plate such that the springs are a bit compressed.
Comment: @HassanGulzar As far as can be seen the configuration is fine, to be sure add a link to your configuration.h file. What you describe now is that it works correctly, but it is not tuned correctly.


Quick release skewer installation help

Question: I was wondering if I could easily install a quick release skewer on my Kent 700c Mens roadtech bike that I got from Walmart. If not what would i need to do in order to do so.
Comment: The work to do this would probably cost a good portion of the bike itself. Theres a product called Axle Release which you can install pretty quickly yourself though, which does quick release-like functionality.
Comment: Also consider that money spent on a wallyworld bike is money you're not saving for a nice bike.
Comment: Also remember QRs are somewhat less secure when locked in a rack because there's no-tool removal compared to an axle with nuts.
Comment: Follow the link to the answer Batman provided at the top here. It goes into more detail about the issues you will face if you decide to swap out the axles to use a quick release. (width of frame etc)
Answer: The correct answer is 'no', you cannot "easily install a quick release skewer" on this bike.
The easiest way would be to buy a different front wheel that is already built with a QR skewer and swap the whole wheel out (make sure to check for correct size and hub spacing before you purchase). Alternatively, you could buy just a new hub that uses a QR skewer, but to swap-out your hubs you'd essentially be re-building your wheel (spoke by spoke) which requires a lot of expertise and specialized tools.
As an alternative, you might consider finding some vintage winged-nuts. If you can find some that fit your current axles, they will serve the same/similar function as a quick-release skewer (that is, they'd allow you to quickly remove your front wheel without the use of a tool).
Comment: Assuming you can find the right hollow axle to fit the existing hub, replacing just the axle of a standard design hub would be MUCH MUCH easier than replacing the hub.  With the right part a front axle can be replaced in about 5 minutes.  A rear axle would take 10-20, as you have to first get the cluster out of the way.  Of course there are fancy hubs that require a post-doc course to deal with, but they're likely already QR.

Quick release skewer installation help