What is the altitude required to bypass Russia's airspace restrictions for airlines?

Question: Given that Russia charges a lot for flights over Siberia from Europe to Asia, would flying above the
Kármán line (100km)
effectively bypass this restriction (from legal perspective) ?
If not, what is that altitude ?
Comment: Related: [Is there a height limit to national airspace?](https://aviation.stackexchange.com/q/43439/14897)
Answer: The Kármán line is considered to be the upper limit of airspace and the lower limit of outer space. According to the Outer Space Treaty of 1967 outer space cannot be appropriated by nations (nations cannot claim ownership of parts of outer space).
In that sense, one would be able to fully legally avoid navigation (and other) fees and bureaucracy imposed by any country one was to fly over if it was done above the Kármán line, but since the stunt would require a spacecraft, it hardly would pay off...
Comment: The [Kármán line](https://en.wikipedia.org/wiki/K%C3%A1rm%C3%A1n_line) is an *attempt* at a definition. For instance the USAF and FAI have different definitions for it. The cost-effectiveness part of your answer is good, but the rest may give the wrong impression that all countries agree to where space starts.
Comment: Any aircraft that must generate net downlift in order to not gain altitude, can be safely considered to be orbiting rather than flying.
Comment: You are correct @ymb1 FAI and space trieties use Kármán line, while for example US consideres space to begin 20km lower. I might have to improve the wording of my answer. What I was after is that Kármán line is the "safe" option with not much of anyone claiming you to be in their airspace. For cost, the aforementioned 20k difference hardly makes, well, a difference.


N channel MOSFET as high side switch

Question: How to make high side switch using N channel mosfet? Supply (drain) voltage is 24V and so its source voltage is also goes to 24V when mosfet is fully turn on. I'm not using any PWM to gate of the mosfet. How to turn on the mosfet continuously?
Comment: What is your required load current?
Comment: Maximum load current will be 10A.
Comment: There are integrated charge pump circuits for this use case or do you need a solution with discrete components?
Comment: thanks for reply, i don't have any charge pump circuit. yes need a solution with discrete components.
Comment: The 9V battery can ensure a supplying. For on/off signal transfer use an optocoupler. You can use a small transformer or small isolated smps instead battery.
Comment: You can check this old thread too: https://electronics.stackexchange.com/questions/487819/can-a-n-channel-mosfet-used-as-a-highside-switch
Answer: A simple solution is to use photovoltaic driver, like VOM1271, from Vishay.
You need to supply 10 mA to the diode, from 24 V or any output, and typical open circuit voltage is 8.4 V, but only 15 uA. In case your MOSFET needs more gate voltage, you can use 2 in serial connection. The switching on will be slow, but for low speed application is Ok.
Answer: To fully enhance ("turn on") an n-channel power MOSFET, the gate must be more positive than the source.  Many devices are specified for their minimum Rdson with Vgs = 10 V, and a max allowed Vgs of 20 V.  Since you are not driving the FET with a PWM signal and you don't say anything about a maximum turn-on time, there are several ways to do this.
One is to use a gate-driver IC.  This has a charge pump in it, a form of switching power supply that is a low-current boost converter.  The output can be either added to the supply voltage, so in a 24 V circuit the gate drive signal would be 34 V (-ish), or isolated.  In that case, the driver IC could be running on 12 V, but the output can be floating on 400 V.  This works well in things like motor drives and high-power switching power supplies.
Depending on the application and the rest of the circuit, you can grow your own charge pump driver from scratch
Another approach is to use an optocoupler that has a small, isolated, floating voltage output.  The drive signal is relatively slow, especially with large FETs.  The input capacitance of a large FET can be something like 10 nF.  Driven by a current source of 15 uA, the turn-on time would be around 6 or 7 milliseconds.  That would be a real problem if the FET were being driven with a 1 kHz square wave,, but for a static switch application it should be fine.  A possible issue is the power level required.  While the static current into a MOSFET gate is almost 0, The current to drive the LED in this type of device is often 10mA to 20 mA.  If the control signal is coming from something like a CMOS gate that is rated for only 3 or 4 mA, you will have to add a driver transistor.
Answer: With a small transformer in flyback mode you can provide an isolated gate voltage. The important aspect is here to provide fast rising and falling gate signals to keep the transition time between on and off short.
The shown circuit has rise and fall times below 40 us, which is a bit faster than the typical photovoltaic couplers. This may be helpful with 10 A load current.
The combination of V5, R1, M3 and V4 just simulates a fast PWM, enabled and disabled with 1 kHz, coming from a uC. So we can see the switching transitions in the simulator.

simulate this circuit – Schematic created using CircuitLab
Comment: OP says `I'm not using any PWM to gate of the mosfet. How to turn on the mosfet continuously?` Also M1 will probably die because of the spikes. Better to tie one end of the pri to ground and drive from a totem-pole as the pri will never be floating.
Comment: @RohatKılıç If the 100 kHz PWM is present the FET is continuously on.
Comment: I know how the circuit works. What I'm saying is that your circuit requires a pulse generator yet the OP doesn't have any, as far as I understood, otherwise he/she could have gone for a charge pump or something similar already.
Comment: The pulse generator for this can be as simple as a two-transistor oscillator or a TLC555, so I think this is a valid answer. Rohat has a point that you may want a snubber to protect M1 though.
Comment: Well, I understood the "not using PWM" as a hint, that no fast load switching is required, not that no PWM would be available at all. And yes, a snubber network on the primary side should be there.

N channel MOSFET as high side switch


Unwrap model with UVs at proper size?

Question: I have the model of house with seams on it.

When I'm trying to unwrap it (U > unwrap) It unwraps wrong.

Some polygons are bigger then others, and I don't know what to do.
How do I unwrap it proportional?
Comment: the easy way (but with less control) is to use some automatic unwrap method (cube projection, smart unwrap or lightmap) in the U menu. Learning more about UV mapping could help you in the future : http://cgcookie.com/blender/2011/01/21/intro_uvmapping/
Answer: this happens because either :

have edited the mash after unwrapping
have scaled the object after unwrapping

to resolve this :

apply scale :  Ctrl+A and select scale
unwrap the mesh again
Comment: notice that he has a seam on every edge? if he was to doo smart UV project, he'd get proportional, but it would be a mess. My guess is the thought process went like this. "Hmmm... unwrap it like a teddy bear... (that's how I learned.) Well, this doesn't even look like a teddy bear. so I guess I can [A] > [Ctrl]+[E] > mark seam. hey! there we go!
Comment: I don't thionk he unwrapped rright in the first place. that's the problem.
Comment: @ARadish he seems to be using seams ,so i think he knows how to unwrap

Unwrap model with UVs at proper size?


Is "invoke" synonymous with "have" in this sentence?

Question: I'm confused about the sentence below, is it correct? Please help me clear the confusion. I don't understand the meaning of Invoke; is it synonymous with have?

I invoke the right of parley = I have the right of parley.
Answer: No, to invoke something is to make use of it. It's a lot more effective to invoke a right if you do in fact have that right, but one can invoke a right one doesn't have, or have a right that one does not invoke.
It's sort of like "I own an apple" versus "I eat an apple". If you're eating an apple, it's beset that you own it, but you can eat an apple you don't own, and you can own an apple you don't eat. They're not synonymous.
Answer: What you have written on the left side of your '=' is correct as to the meaning of invoke. That would imply a claim that what is on the right side of the '=' is true.
Macmillan Dictionary: invoke
These definitions from Macmillan dictionary are apt:
1: to use a law or rule in order to achieve something
1a: to mention a law, principle, or idea in order to support an argument or to explain an action.
The dictionary reference also has example sentences.
Answer: Let's look at the definition of the word, "invoke":

to use a law in order to achieve something, or to mention something in order to explain something or to support your opinion or action. (Cambridge)

Police can invoke the law to regulate access to these places.

another definition: If you invoke a law, you state that you are taking a particular action because that law allows or tells you to. (collins dictionary)

so invoke can be used when someone uses, applies or implements a law. also it can be used to explain the fact that someone has the right to take an action because the law allows them to or tells them to.
So have the right to do something and invoke the right to do something can be synonymous in a sense.
Answer: No, they're not the same.  You could have the right to parley but not invoke it.  Imagine for example the famous "you have the right to remain silent".  The person being arrested has the right not to talk, but they might talk anyway.  If they do not talk, they are invoking their right to remain silent.


What is the difference between horloge and pendule?

Question: What's the difference between horloge and pendule? All I know so far is what is given on Collins English-French dictionary: https://www.collinsdictionary.com/dictionary/english-french/clock.
Answer: The most common word for "clock" is horloge (une horloge). Any device whose purpose is to tell the time can be called an horloge, except for small ones that fit in a pocket or are worn around the wrist: those are called "watches" in English and montres in French (une montre). An alarm clock is un réveil; you'd only refer to it as horloge if you were using it to display the time and you weren't using its alarm functionality.
The word horloge is also used for a part of a device that tells the time, for example for the clock on a video recorder or a kitchen appliance, or a clock application on a computer. A device whose purpose is to keep the time (but not directly display it) is also called une horloge, for example une horloge atomique (an atomic clock), or the clock of a circuit in electronics.
Une pendule is a particular type of clock that uses a pendulum (a pendulum clock). A pendulum is un pendule (masculine), a pendulum clock is une pendule (feminine), originally short for "une horloge à pendule". More rarely, the word pendule can be used for any kind of horloge in the sense of a device whose sole purpose is to tell the time. You can use pendule for an electric clock, but not for the time display on an appliance.
The characterisation of horloge as "large" and pendule as "small" in the Collins dictionary makes no sense at all. If anything, a pendule would tend to be bigger; the less a clock looks like a pendulum clock, the less likely people are to call it pendule.
Answer: Both display the time.
A pendule (feminine) is an increasingly rare kind of horloge which works thanks to a pendule (pendulum: masculine).
On the other hand, horloges can use anything like springs or electricity to operate.
Answer: Techniquement, une pendule est une catégorie d'horloge qui fonctionne à l'aide d'un pendule, ou balancier, un objet qui pend et qui oscille.

(crédit: "By Ivan2010 [CC BY-SA 4.0 (https://creativecommons.org/licenses/by-sa/4.0)], from Wikimedia Commons")


Integer to NSInteger And Save To Core Data

Question: I have a integer named marbles, and am trying to save it into an array using the following code:
[records setValue:marbles forKey:@"marbles"];

With this code, I get the warning:
warning: Semantic Issue: Incompatible integer to pointer conversion sending 'int' to parameter of type 'id'
So, How do I set the value for an NSInteger.
Next Question, How do re-upload the array into core data? I fetch the array, make changes, and how do I apply those changes back to Core Data?
Thanks
Answer: Initialize an NSNumber (which is what CoreData is expecting) with your integer:
NSNumber *marbleNumber = [NSNumber numberWithInt:marbles];
[records setObject:marbleNumber forKey@"marbles"];

Or:
[records setMarbles:[NSNumber numberWithInt:marbles]];

To persist your changes, you save your context:
NSError *error;
[myManagedObjectContext save:&error];

//handle your error

Answer: NSArrays will only take objects, so the first step is to turn your NSInteger into a NSNumber using this method:
+ (NSNumber *)numberWithInt:(int)value

so:
NSNumber *myNumber = [NSNumber numberWithInt:marbles];

and then you can do:
[records setValue:myNumber forKey:@"marbles"];

Basically once you fetch the data, you get a managedObjectContext, think of it as a drawing board, and any changes (including adding or deleting new objects), you make to this objects may be saved again to CoreData using something like this:
NSError *error;
        if (![context save:&error]) {
            // Update to handle the error appropriately.
            NSLog(@"Unresolved error %@, %@", error, [error userInfo]);
            exit(-1);  // Fail
        }

Where context is the context you would get with your NSFetchedResultsController. Which you can get like this:
NSManagedObjectContext *context = [fetchedResultsController managedObjectContext];

I would recommend taking a look at the Core Data programming guide
Answer: - (id)primitiveValueForKey:(NSString *)key;
- (void)setPrimitiveValue:(id)value forKey:(NSString *)key;

use NSNumber in place of (id)value


DS18B20 reading double after long use

Question: I installed two DS18B20s on a pi almost a year ago. They have worked great until the last couple months. I am doing a bit of a stress test on them and have been polling them every second for almost a year. One day I checked them and both of their temperatures were way over what they should be. I thought it was strange so I rebooted the pi and they still read very high. I didn't look into it at the time but about the next day I checked and they were reading normally. They read normally for over a month. Now they are doing it again so I looked at the data coming in and indeed they are about double the actual temperature. I'm just wondering if this is a failure mode or if something else could be going on. I'm going to replace them as soon as new ones come in. Has anyone else experienced this? Any ideas on fixing them?
Comment: Experienced what?  You haven't told us the temperatures being returned or the ambient temperature.
Comment: The temperatures are double the actual temperature. So if the ambient is 21c then the return is 42c
Comment: It sounds like the design is on the edge. How long are the leads. Check the clock timing.
Answer: DS18B20s are cheap sensors that are useful for setting up and testing.  They are prone to failure after extended use.  If you are fine with simply replacing them with new ones then do this - they are cheap and a few bucks worth will keep you going for years.
Otherwise, if you want longer-term reliability (and more accuracy) then invest in a higher quality sensor.

DS18B20 reading double after long use


How to have a hash function that maps any binary string of size n to binary string of size n?

Question: I am implementing certificateless cryptography from this research paper in python language. Essentially, I want to have the following hash function mapping. This hash function is mentioned in the setup algorithm in section 2.4 of the paper. Here n is the bit-length of plaintexts.
$$\begin{align}
H_4: \{0, 1\}^n\to\{0, 1\}^n\\
\end{align}$$
Is there any inbuilt hash function in hashlib python library? Or how can I construct this hash function in python?
Comment: It's specified [here](https://docs.python.org/3.9/library/hashlib.html#shake-variable-length-digests) - there since 3.6, which is the oldest still supported lib version. The API is so simple that there is really not much to it. It would maybe require a *bit* more work if your *n* is not a multiple of 8, but that's about it. Try it and ask on [so] when stuck.
Comment: This question contains two separate parts: which (kind of) hash algorithms can I use and which ones are available in the hashlib python library. It seems to focus on the later one, and that's off topic on this site, strictly speaking.
Comment: I didn't answer because it is probably a somewhat better fit on SO, but can honestly not be buggered to convert that formula to an image. ashizz, please do react on answers you're getting here and on [so].
Answer: Probably the best algorithm to use is SHAKE specified for Keccak, which is the winner of the SHA-3 competition. You can use either SHAKE128 or SHAKE256 depending on the security and performance balance you wish to achieve.
For Python, the algorithm is specified here and should be available since 3.6, i.e. all supported versions. You can just create the hash (or rather XOF) algorithm, call update as many times you want on the binary input and then retrieve the result using digest(digestSize) call, where digestSize is in bytes.

If you require an $n$ that is not a multiple of 8 (i.e. the input / output is not byte aligned) you may need to perform some tricks, e.g. prefixing zeros to the input and removing the leftmost bits from the output afterwards. Of course, that assumes that $n$ doesn't vary, or you may get input message collisions. Most practical protocols have been designed with byte-aligned input/output parameters though.


Best practices for performance benchmarking test

Question: I have a J2EE web-application running on Sun hardware with OpenSolaris/Glassfish stack. We're starting our performance bench-marking tests, to prepare for our scalability requirements later.
Any guidelines/best practices would be very useful..
Answer: For a free Open Source tool I've found Apache's Jmeter pretty good:
http://jmeter.apache.org/
As Joe said you'll need to figure out how to model user behaviour and simulate user load.
Answer: If you are using JUnit? For simple Time Measurement in JUnit there is JUnitPerf which also supports LoadTests. JUnit 4 is not supported very well but it works for me. ContiPerf is an alternative which also supports annotations for easy configuration. I use this before using JMeter.
Answer: I'm sure there is many generic ways to test server performance to be found on the web.
But have you thought that perhaps this an opportunity to gather stories and write a test tuned to exactly how your users will use the server? Even if it doesn't perfectly reflect the way that the server will ultimately work, it will let you start learning something rather than being only formal exercise. I think this is the spirit of agile development.


How to insulate register boot?

Question: The county inspector dinged me on a couple of things for my bonus room renovation.  One of these things is wrapping the register boots (endpoints) in insulation.  I've seen registers with this insulation already installed, but he mentions that batted insulation is fine.  The reason for this is to supposedly reduce the condensation leaking outside the boot and onto the wooden frame, joist, and sheetrock.  Any idea what you folks do to accomplish this?  I have some old R-6 flex duct insulation and some foil tape and was planning to wrap the batt around the boot and tape it up with foil tape.
Answer: You're thinking about this too much. The goal is to reduce air contact with the metal. Simply get yourself some R-11 or R-13 fiberglass batts and pack the joist or ceiling space loosely around each vent component. Condensation is greatly reduced by doing so, and your obligation is fulfilled.
Comment: Thanks.  I tried doing this and it looks damn ugly and I'm not sure if I'm packing it too tight and losing the insulating quality of the batts.  Do inspectors usually care if you use insulating ductboard or something similar to this?  Would be much easier and I can easily assure no air between the boot and foamboard.
Comment: I doubt you could reduce the R value of an R-11 batt to below the R-6 that insulated ducting would have even if you jammed it tight. That's not a concern. What does "ugly" have to do with it? I appreciate craftsmanship as much as anyone, but... it's insulation. :)
Answer: you have to understand the dynamics involved.  the goal is not just insulation, but intactness of the vapour barrier.  you can have all the insulation in the world and it will do you no good if you allow nice warm air to enter into the insulation pocket.  the warm air cools as it permeates the batt and eventually starts to cool.  once it drops to the dewpoint of the air, the trapped moisture in the air precipitates out and now you have wet insulation.  when  the cold air in the uninsulated space reaches the wet insulation you are going to get ice.  then the cycle repeats, ever closer to your inner heated space.  if it warms up, the ice melts and now you have wet insulation.  gravity and capillary action draw the moisture through the batt and eventually you have moisture up against the wood and drywall.  if you use batting and don't ensure the air barrier is intact, you will make a problem for yourself.  you can do it with batting and very careful use of sealing tape and caulking.  why bother?  polyurethane foam is used for a reason.  its a great insulator that doesn't lose r-value over time and its airtight right out of the gate.  just foam it.  the foam blocking or forming i described is just to minimize the amount of liquid foam you have to use.  you can use straight spray foam if you want as well, its just more costly.  your time and money.
Answer: its a little hard to tell what you have going on.  i am assuming these are ceiling hot air vents in a room below an insulated attic space.  use 2" styrofoam board to build a "form" aroun the register termination (tighter the better to use as little foam as possible).  you want to do it so the adjacent joists and the foam act like a box around the ductwork.  then inject sprayfoam into all the places you can get it.  this way you have an r7 or higher (depends on the foam) box that is not only insulated but airtight.  this is the best way to do it and here in ontario (and it meets the new revised code specs) we have lots of these types of reno special heating systems that run insulated ducts through an attic.
Comment: Inspector actually specifically mentioned using batted.  Not the pink stuff but that silvery stuff you find inside R-6 or R-8 flex duct.  He also told me that he didn't want to see construction screws connecting joists to rafters but whatever.  Have you tried using batted to cover the boot before?
Comment: The material in flex duct insulation is also fiberglass, in most cases. It's just typically a coarser variety, which I assume is cheaper to produce. Batts are a finer fiber to reduce itching and discomfort during install.

How to insulate register boot?


LaTeX Error: File `scrpage2.sty' not found

Question: Can someone explain how to solve this problem: LaTeX Error: File `scrpage2.sty' not found? I read all the answers but didn't understand what to do. Today I install miktex 2.9 and winedt 10.3.
Comment: scrpage2.sty is obsolete, and is moved. Read the documentation. Use ` scrlayer-scrpage` instead, see [message at CTAN](https://ctan.org/pkg/scrpage2) from the author.
Comment: See also https://komascript.de/faq_scrpage2_en (English) and https://komascript.de/faq_scrpage2 (German).
Answer: The author has declared the package scrpage2 obsolete. It is no longer included in TeX live and MikTeX. The package is still available on CTAN (https://ctan.org/pkg/scrpage2, https://ctan.org/pkg/koma-script-obsolete), but it would have to be installed manually from the .dtx source. See also https://komascript.de/faq_scrpage2_en.
Users are advised to switch to the successor package scrlayer-scrpage. If you have
\usepackage[<options>]{scrpage2}

in your preamble, replace it with
\usepackage[<options>]{scrlayer-scrpage}

Apparently all commands and options of scrpage2 are also recognised by scrlayer-scrpage, so a switch should be possible. But users are strongly encouraged to double check the results and consult the .log file as well as the manual for hints about deprecated, obsolete or otherwise outdated commands.
(Just to be clear, scrlayer-scrpage is part of the regular KOMA-Script bundle and can be installed as the package koma-script in both MiKTeX and TeX live if it isn't installed already.)
If some code/package beyond your control loads scrpage2, contact the author and look into alternatives (scrpage2 has been up for deprecation for quite a while [about six years; it has thrown warnings for at least two years according to https://komascript.de/faq_scrpage2_en], so if the code author hasn't reacted until now, that suggests they might not follow the development of their code that closely any more). If you must use external code that uses scrpage2, you can try the workaround suggested at https://komascript.de/faq_scrpage2_en:
Add
\RequirePackage{scrlfile}
\ReplacePackage{scrpage2}{scrlayer-scrpage}

to your preamble before the \documentclass line. That will load scrlayer-scrpage when any code requests scrpage2.
Comment: Thank you! Finally it works!
Comment: @Silva I'm glad it works for you. But don't just make the changes, actively look at the `.log` files and the documentation to make sure you are not using outdated commands/options. If this is not code you wrote yourself, tell the author about the deprecation and be wary of its overall quality.
Comment: Thank you! This worked seamlessly.
Comment: +1: I ran into the exact same problem today!
Answer: If anyone (like me) is using Overleaf and gets the scrpage2.sty error, you can choose to work on your document with a previous version of TeXLive that still supports the obsolete package (see here).
On the long run this will create problems to your doc, but it works for me when need a quick fix to a non-important file.
Comment: Welcome to TeX.SE!
Comment: Thanks a lot @Mensch!
Answer: This is meant as a comment to the first reply, but I don't have enough "reputation" yet. (just linked my account with tex.stackexchange), but I think it's important to note.
I use documentclass scrreprt and the solution by moewe (replacing scrpage2 with scrlayer-scrpage) worked for me, although I got new errors and had to include definitions for the layout of \section etc. to fix them:
\begin{document}

\titleformat{\section}{\Large\sffamily\bfseries}{\thesection}{1em}{}
\titleformat{\subsection}{\large\sffamily\bfseries}{\thesubsection}{1em}{}
\titleformat{\subsubsection}{\large\sffamily\bfseries}{\thesubsubsection}{1em}{}

\sffamily makes text sans-serif, \bfseries makes it bold.
This might help others struggling with this unexpected deprecation of an otherwise stable system ....
Comment: Welcome to TeX.SE!


In CiviEvent, can the answer to one question reveal additional questions?

Question: We are setting up conference registration using CiviEvent and are wondering if the answer to one question reveal additional questions. For instance, in our old system, you could select "on-site" or "off-site" accommodations and related questions would then be revealed. So this is really a dependency question—can one question showing be dependent upon the selection the user makes for another question. Please take into consideration that we are CiviEvent newbies!
Answer: This feature is called "conditional visibility". Standard CiviEvent registration does not have this feature. There are several ways to accomplish this, but unfortunately most aren't really newbie-friendly.
The Profile Conditionals extension adds this feature but it's difficult to configure - you have to configure it by hand in civicrm.settings.php.
FormBuilder will be the successor to the current CiviEvent pages when complete. It has conditionals in the CiviCRM 5.69+.  However, it doesn't currently process payments, so is only suitable (for now) on free events.
If you're on Drupal or Backdrop, the Webform module has conditionals, and with Webform-CiviCRM, will do what you need.  This is my recommendation if you use one of those CMSes.
WordPress has the "Caldera Forms" plugin with CiviCRM integration.  I don't know the current status of it - there was a meeting yesterday I didn't attend.  Hopefully if you're on WordPress someone can speak to whether that's feasible.
Comment: I was able to get Profile Conditionals working with some trial and error. It will be nice once CiviEvent is using FormBuilder and can use FB's conditionals. This works for now. Thanks for the suggestion!


A word that means education away from self reliance

Question: What is a word that means: To deliberately educate the masses away from knowledge of self sustainability/self reliance. I heard this word some 10 years ago and can't remember what it was..
Comment: Capitalism.  (Seriously -- think about it.)
Answer: Close, but no cigar:
disenfranchise

Disfranchisement is also termed to the revocation of power or control of a particular individual, community or being to the natural amenity they are abound in; that is to deprive of a franchise, of a legal right, of some privilege or inherent immunity. –Wiki

Usually, it has to do with voting:
dis·en·fran·chise /ˌdisənˈfran(t)SHīz/ verb –Google

deprive (someone) of the right to vote.
"the law disenfranchised some 3,000 voters on the basis of a residence qualification"
deprived of power; marginalized.
"a hard core of kids who are disenfranchised and don't feel connected to the school"
deprive (someone) of a right or privilege.
  "a measure that would disenfranchise people from access to legal advice"

North Korea disenfranchises its citizens from just about everything.
Answer: Doublespeak (most likely coined by George Orwell in his book Nineteen Eighty-Four) is one such method of doing that which you've described. Here is the Wikipedia definition:

Doublespeak is language that deliberately disguises, distorts, or
  reverses the meaning of words.

In many cases, doublespeak effectively amounts to feeding the masses trivia-masquerading-as-fact so as to deter them from educating themselves — or, as Edward S. Herman is quoted (from the same Wikipedia entry),

"What is really important in the world of doublespeak is the ability to
  lie, whether knowingly or unconsciously, and to get away with it; and
  the ability to use lies and choose and shape facts selectively,
  blocking out those that don't fit an agenda or program."

Note that obfuscation, or the act of purposely confusing someone or -thing, is a key component of doublespeak.
Also of note is disinformation, which (again, as defined by Wikipedia) is

"intentionally false or inaccurate information that is spread
  deliberately. It is an act of deception and false statements to
  convince someone of untruth."
Answer: I suppose you could use the word "domesticate" since one definition is:

domesticate: to breed or train (an animal) to need and accept the care of human beings [1]

Use of this word would, however, have a derogatory connotation in this context.


Avoiding snails around potted greenery?

Question: I had an idea about snail trap. I was wondering if placing a plastic ring in a form of a brush around a pot with needles pointing down would serve the purpose. Using very tiny spaced needles (i.e. low density per cm2) would force the hungry snail to fall down due to a small contact area, right? (See picture).
Comment: No idea, but I would love to see the results of the experiment!
Comment: Shallow containers ( saucers) of beer is the typical snail trap. I never used it as I see no problem caused by snails.
Answer: If you made it out of copper, it would work even better, but that will be more expensive.
Snails do not like to touch copper.
A chemical reaction happens when they crawl over the metal, which causes unpleasant feelings on their skin.
Al-tough not everyone will agree with me about this and I have seen snails just crawling over the copper, but most of them really hate it.

Avoiding snails around potted greenery?


What happens if I exceed Steam's transaction threshold?

Question: I know that you have to put in billing information for Steam Community market once you make over 200 transactions in a year or $20,000 in USD, and if you exceed the $20k threshhold you get income taxed. But what about the transaction threshold? What do I have to do if I cross it?
Comment: I disagree that this is a legal question or off topic. It's framed in those terms because of a misconception on the part of the asker (which I addressed in my answer). At its core however, the question is simple: What is the significance of Steams collection of personal information after crossing the 200 transaction threshold. The fact that it's a legal requirement is actually immaterial. What matters is that *both* thresholds must be met for Steam to send a 1099. (And that if you're bringing in significant revenue, you should consult an accountant.)
Answer: So, to be clear, crossing either threshold is not what makes your income via the steam community market taxable. That is something that will vary wildly from jurisdiction to jurisdiction, and across a variety of financial circumstances. You should know, however, that in many cases, income from the Steam community market is taxable well before you have conducted twenty thousand dollars in transactions. Consult a qualified tax professional or accountant in your area if you are doing any significant amount of business through Steam and have any concerns about this matter.
What you're referring to is a practice by valve, in which, once you have both sold 200 items and exceeded 20,000 dollars in transaction value, you will receive an IRS form 1099 declaring that income at the end of the year. Valve requests the information neccesary to do this when you have crossed either one threshold, to keep them on file and use them as neccesary.
From Valve's FAQ on the subject:

Will you be providing 1099's based on my transactions in the Community Market?
  The United States Internal Revenue Service requires us to report gross sales for, and provide IRS Form 1099's to, only those subscribers who are U.S. citizens or residents and who exceed 200 sales transactions in a calendar year and also exceed $20,000 in gross sales proceeds from those sales transactions in that same calendar year, from all of the subscriber's accounts. If you are a U.S. citizen or resident and exceed both of these thresholds, we will report the amount of gross sales to the IRS and provide you with Form 1099.
Do I have to pay income taxes on the proceeds of sales I make in the Community Market?
  Different countries have different rules relating to the taxation of digital transaction. For U.S. citizens and residents, as discussed above, we are obligated to collect certain taxpayer identifying information from those who engage in more than 200 transactions in a calendar year, but no information is reported to the U.S. Internal Revenue Service unless your gross revenues from such sales exceed $20,000. Ultimately, the responsibility for determining any income tax liabilities, which you may or may not have, rests with you. If you are concerned about your liability, you should consult a tax advisor.
Answer: If you do over sell over $20,000 worth of products, you are legally required to pay taxes for it. This isn't a requirement by Steam, but one by Internal Revenue Service under Internal Revenue Code section 6050W.
If you pass 200 transactions in sales in a Calender Year, you'll be asked to fill a 1099 tax form, again required by IRS. Once you pass $20,000, your sales will be reported to IRS if you are a USA citizen or resident (and you may be taxed for it, if you want a total clarification, consult a qualified tax professional or accountant in your area as LP_MF stated).
Comment: In the context of American taxes, residency is often irrelevant. *Citizenship* is sufficient.
Comment: @LessPop_MoreFizz ah, thanks for clarifying. editing.
Comment: @LessPop_MoreFizz "only those subscribers who are U.S. citizens or residents" turns out it is both.
Comment: Yeah, I wasn't saying that residents weren't taxed - non-citizen residents most certainly are! - but that citizens abroad are also on the hook. Apologies for the lack of clarity.


Grails (On App Engine) - Basic Search Functionality

Question: What I need is Search Scaffolding but in its absence I was wondering if you could point me in the direction of any really simple examples for adding search to a domain.
I can't use the searchable plugin as it conflicts with the AppEngine plugin (Unless someone has got this to work?). I just need to be able to filter the scaffold list to contain only the results which match the query. I don't need a pure text box solution, I imagine it too look exactly like the 'create' form except when you submit you get a list of matching objects.
I hope this makes sense, thanks in advance!
Gav
Answer: Google App Engine - Full Text Search


Car motor heat to drive a steam engine

Question: Why wouldn't be able to place a car motor inside a water tank or another liquid to be heated by the motor, instead of wasting the heat and then use the steam generated, to drive a steam engine, which itself would be submerged in the same liquid to not let any heat escape from the system?
Comment: This has been done (though not exactly as you describe).  I recall articles about such (experimental) setups ca 1970 in Mechanics Illustrated.  The generated power was posited to power AC and accessories.
Answer: BMW is actually working on something similar - they call it the turbosteamer concept.
It is a combined cycle where a heat exchanger captures heat from the engine and uses it to drive a steam circuit, recovering some mechanical energy.
There are more details at this SAE article. There are apparently issues to be worked out in getting the system small enough to fit in a passenger vehicle before it will reach the market.
Clearly, surrounding a car engine with a fluid that could be boiled and have the enthalpy to do useful work would be prohibitive in size and weight. Thus a practical system would have to be based on capturing heat from, say, exhaust gases.
Similar combined cycle techniques have been tried at power stations and in shipboard engines, with some success. Examples include combined cycle power plants with gas turbines fired by natural gas, with some of the waste heat being captured by heat exchangers and driving a steam turbine to generate additional power.
You can do a search on Google for "combined cycle power generation" and find much material, although I can't post it here as it is probably copyrighted.
As has been pointed out, there is a definitive limit to the amount of heat energy that can be recovered to do useful work, the Carnot efficiency. It will never be 100% of the heat energy. This is an inevitable consequence of the second law of thermodynamics.
Answer: Yes definitively.
Is it practical?Maybe.
Any temperature difference can be used to run an engine in principle.
However that does imply that heat will not escape the system.
If you can convert all the Heat into work then you violate the second law.
The limitation imposed by Carnot is still valid.
Comment: https://en.wikipedia.org/wiki/Automotive_thermoelectric_generator
Comment: It just seems counterproductive to try and get rid of heat, which is energy wasted. Not just the motor, but the wheels and every other moving part in the car could be shielded with materials to not let any heat escape, but rather cool those parts with some liquid running all around the car and then have a steam engine turn that heat into useful energy as far as possible. A calculation on how much we could actually get out of this would be nice.

Car motor heat to drive a steam engine


How to backup POA based ethereum private blockchain and restore it in a fresh new environment

Question: Is there a way to backup the POA based ethereum private block-chain [created from microsoft azure POA template] and also restore it in a all new environment with out loosing any transactions & accounts?
Answer: Zip/tarball the whole directory that has chain instance. This will include :
Accounts (keystore)
Block+Transactions (chaindata)
You can then start a node on any other machine with this directory.
In addition to the directory, there would be a genesis json, create a backup of that as well.
Answer: I think you should ask an azure expert or post your question on azure website.I propose you explore the possibility of exporting the template as described here :
https://docs.microsoft.com/en-us/azure/azure-resource-manager/resource-manager-export-template
then backup and restore your VMs as described here
https://docs.microsoft.com/en-us/azure/backup/quick-backup-vm-portal


SVN upgrade from 1.6.9 to 1.7.9?

Question: I am going to be performing a server migration for our SVN repos hosted on Enterprise Linux 6.2 using SVN 1.6.9 over svnserve (svn://) and mod_dav_svn (http://).  I will be using the svnbackup.pl (svnadmin dump) and svnrestore.pl scripts to make backups from one server, create the repos on the new server and restore to the new repos.  I would like to install SVN 1.7.9 (latest stable) on the new server and wanted to know if anyone has experience with this, or if anyone has encountered any issues with restoring backups from a 1.6.9 repo to a 1.7.9 repo.  Thanks in advance!  Centos 6.4 on destination server.
Comment: Why are you migrating, exactly? The RHEL (or CentOS) package might have an old version number, that doesn't mean it has all the bugs of that version. Installing random stuff _will_ break your setup.
Comment: I am moving to an entirely new server.  The old server has the version from the repos, and I was considering downloading and installing the latest stable (1.7.9) from the web and installing it to the new server before migrating the repo data over.
Answer: I did svn 1.5 to svn 1.6, so, this is what I did:

I left the production running on svn 1.5 as is. My repos are in /opt/repos/svn/
I installed svn 1.6 + https and relative modules on another host. The location of the repo is exactly the same, i.e. /opt/repos/svn.
I svnhotcopy or svndump all repos to its own files and scp-ed over to /opt/repos/svn on the machine running svn 1.6. If no one is using svn, you can even rsync it. svnhotcopy is a great tool, it will create a copy of a repo while it is in use, to avoid any data corruption.
Then I pointed my svn client to the new host, checked out repo I have access to. Updated some files, checked it in, I could view my files on https as we used cvsweb. This was my test that it works.
For my maintenance, I had everyone exit out of svn, after hours, I removed all repos on the new host, rsync-ed repos from old host to the new host. Change DNS to point svn CNAME to the new host. The new host became my production host and the old host, I upgraded to 1.6 and is now my standby host.

Do not upgrade it without any backup. Backup all repos and upgrade it on another host. SVN is an important tool, you must have a standby host just in case your production goes down.
Good luck.
Comment: Also, let me know if you have any questions. Plus, make sure the developers are onboard with it and they have upgraded their clients to use the new server.
Comment: I was curious about that.  We mostly use Windows clients, TortoiseSVN.  Does the client version need to match the server version of SVN?  Will the working copies that are checked out from 1.6 be compatible/in-sync with the 1.7 backend?
Comment: we had an issue with someone using Subversion 1.6 client with Subversion 1.5 server on Linux. What happened was that the guy using 1.6 client, when he checked out the code, everything was fine. When he checked code in using 1.6 client, everything worked for him. The developer who was using 1.5 subversion client, when he did svn update, at some point he got segmentation fault. The client died while trying to checkout the code. So, I upgraded his client to subversion 1.6. We don't have any windows client but I don't see any issues with someone using TortoiseSVN.

SVN upgrade from 1.6.9 to 1.7.9?


How to choose participants for a study?

Question: I want to know how can I get some participants for an empirical research study I would be conducting. Does universities have systems in place to call/recruit participants or do I have to find them myself?
Comment: By participants, do you mean people to be subjects in your experiments? In that case, you have to arrange it with your advisor.
Comment: You've mentioned elsewhere that you're a Masters student moving into a Ph d program.

As far as I know, universities do not make arrangements for this kind of work(recruiting from other universities/asking other Professors to collaborate). Lecturers can however, put up a notice asking students to register for an independent study under them.

Alternatively you could look for online collaborators. However, this can be an extremely time-consuming thing to do.
Comment: What do you mean by "participants"? If it is about a psychological experiment, try asking on http://cogsci.stackexchange.com/.
Answer: You will almost certainly have to recruit study participants yourself. As others have suggested, speak with your advisor to out whether there are any participant pools he's used in the past. If you find others that he hasn't used before it's a good idea to make sure he's OK with the pool before you dive in, so to speak.
Note that, in some fields, the pool of participants can be a significant limiting factor to the generalizability of the study results. Think very carefully about exclusionary criterion before settling on something. Note also that your IRB may require you to provide justification for exclusion/inclusion of certain populations (i.e., children, pregnant women, drug users). Try to make sure your population sample is as inclusive as possible.
Comment: *"he's OK with the pool before you dive in"* — we see what you did there!
Answer: I am not aware of any university run participant pools. I am aware of many departmental run and research group run participant pools. Some charities and companies also run participant pools.
It is quite possible that you will not have to recruit the participants yourself. Your supervisor and/or colleagues would be a good place to start asking about participant pools. Failing that, all universities have an institutional review board (IRB) or independent ethics committee that might be aware of participant pools in your research area.
Answer: At the universities I've worked in North America, human-subject studies (esp. those funded by taxpayer-funded research) must be approved by a research ethics committee. The ways to recruit participants is something that must be stated and approved. Over the years, committee members have offered lots of advice about how to recruit subjects, as they have seen many projects and many experiments. A professor has to submit a project for approval, so you'd have to coordinate it with an adviser. You can probably consult with committee members before you submit the request.
The studies I've managed have recruited participants in simple and effective ways: e-mail lists, university newspapers, facebook, flyers posted on campus, etc. As others have pointed out, the means of recruitment will affect the generalizability of the study results.
I saw one project that had trouble finding enough participants via the declared means (flyers), but it was not possible (because of the ethics committee re-approval) to use another means to recruit (e.g., last-minute facebook campaign) to try to find more participants. Be careful not to lock yourself into a way that's too limited.

How to choose participants for a study?


Difference in Meaning between Стой, Хватит, Перестань, and Прекрати?

Question: What is the difference in meaning between the various ways to say 'stop?' Namely, 'стой,' 'хватит,' 'перестань,' and 'прекрати?' Also, can they be used interchangeably and in all cases when one wants to say 'stop?'
Answer: Стой means stay still, stop going. It could be either an order like "Stop! Don't move" or just asking similar to "Hey, stop! Wait for me" or even "Hey, stop. Let me think". The latter two especially in soft forms like "постой", "постой-ка". But you cannot translate, say, "Stop kidding me" with "Стой".
Хватит = enough. It could be an order similar to stop just the way Enough! in English is.
Перестань, прекрати are essentially the same in imperative. You may think that перестать = leave off, and прекратить = cease, put an end.
Comment: Перестань is a request: *cut it out*, *enough!*.
Answer: When asking somebody to cease some activity, those do have slightly different meanings.
"Стой" is an imperative (a command) to [temporarily] halt any advancement, supposedly to evaluate the situation and decide whether it's worth continuing.
"Хватит" is not an imperative, it's an advice, a statement of fact, "what you've done up until now should suffice, you'd be wise to cease at this point".  It is softer than "стой".  Of course, it can be said with much force to sound like a command, yet grammatically it's indicative mood.
Both "перестань" and "прекрати" are imperatives.  Both are commands, both mean "put an end to it", "cease".  Between those two, "прекрати" is stronger, to my ear.
Answer: Стой
It literally means you should stop. Examples:

Freeze! Freeze or I'll shoot! -- Стой! Стой, стрелять буду!
Hold on, we need to get back and lock the door. -- Стой, нам надо вернуться и запереть дверь.

Хватит
It is closest in meaning to "that's enough":

-Would you like more whisky? - No, thanks, that's enough for me. -- Не хотите ли еще виски? - Нет, спасибо, мне хватит.
That's enough fooling around! -- Хватит дурачиться!
That's enough lies! -- Хватит лгать!

Перестань и Прекрати
These two are interchangeable, in my opinion. Moreover, these are sometimes interchangeable with "хватит", but not always:

Stop fooling around! -- Перестань (прекрати) дурачиться!
Stop lying! -- Перестань (прекрати) лгать!

I couldn't come up with a situation when you cannot substitute "перестань" or "прекрати" with "хватит" (looks like you always can). However, like with the whisky example, you can't always substitute "хватит" with "перестань" or "прекрати".
Also note that I am translating "перестань" and "прекрати" with an actual verb "stop", while "хватит" with a full sentence "that's enough".


System-wide Copy (not Paste) without formatting

Question: Is there any way to copy text (not paste) without copying the accompanying formatting? In some programs, you may have an option to paste just the text to strip off any formatting copied with the text, but in other programs there is no such option - it's just a straight paste (with any formatting coming along with it).  I want to know if there is any way to copy only the text so there is no formatting to have to worry about.
Answer: No, but there are ways to remove formatting from the text in the Clipboard, so that pasting will be format-free.
I use this Terminal sequence:
<code>pbpaste | pbcopy
</code>
which takes the existing clipboard text and 'rinses' it through raw text.
I have this in a shell script, which I can call from the scripts menulet.
Or you can paste into a plain text editor, like BBEdit, and then copy again.
Comment: @JesseP. What apps are these?
Comment: @JesseP. Office 2016 and 2021 both have Paste and Match Style, which ignores formatting on the pasteboard. There's also a Paste Raw Text menu item, which you can configure to have a shortcut. MacOS Services are also definitely available in Office. If you update your question with reference to Office, I'll explain how it's all done in my answer.


How to find my forgotten Firefox master password

Question: I don't remember my Firefox master password. I changed it several days ago and now I'm  restricted on several functions.
Answer: I don't remember my Firefox master password
There are two options:

Use FireMaster to recover your password, or
Reset your Master Password.

See below for instructions.

Option 1: Use FireMaster to recover your password
About FireMaster

FireMaster is the First ever tool to recover the lost Master Password
  of Firefox.
Master password is used by Firefox to protect the stored
  login/password information for all visited websites. If the master
  password is forgotten, then there is no way to recover the master
  password and user will lose all the passwords stored in it.
However you can now use FireMaster to recover the forgotten master
  password and get back all the stored Login/Passwords.
FireMaster supports Dictionary, Hybrid, Brute-force and advanced
  Pattern based Brute-force password cracking techniques to recover from
  simple to complex password. Advanced pattern based password recovery
  mechanism reduces cracking time significantly especially when the
  password is complex.
FireMaster is successfully tested with all versions of Firefox
  starting from 1.0 to latest version v47.0

...

License  : Freeware Platform : Windows XP, 2003, Vista, Windows 7,
  Windows 8, Windows 10

Source FireMaster - The Firefox Master Password Recovery Tool
See the source link for complete instructions

Option 2: Reset your Master Password

Using the Master Password feature, you can protect all of your locally
  stored usernames and passwords with a master password. If you have
  forgotten your master password, you must reset it.
Warning: Resetting your master password will remove all of your saved
  usernames and passwords.

In the Firefox location bar, enter the following location:
<code>chrome://pippki/content/resetpassword.xul
</code>
Press Enter.
The "Reset Master Password" page will appear. Click the Reset button, to reset your master password.

Source Reset your Master Password if you've forgotten it


What is the best cross-browser solution for browser based document signing (w/ digital signature)?

Question: I need to implement a browser based component (most likely java applet since it needs to be cross-browser) that will allow us to digitally sign and verify data in the XadES format. What options are available and what is the best solution?
Answer: The best solution I would think would be to build a web service or if applicable build it right into your application. Unless you want to provide more details on how you plan to implement it or any other platform / business constraints then finding the best solution is a shot in the dark at this point.
So here is how I would start
Google this: XadES jar library
 Try a link and then see if it does everything you need.
If it doesn't try the next link and see if that works better.
The best way to ensure it works on all browsers is to perform the work on the server via a web service instead of an applet.
Answer: I found one that seems to work, but is still in development and has some bugs:
http://projectestic.uji.es/pr/cryptoapplet/


Technological challenges in substituting EO Satellites X-band downlinks with laser downlinks?

Question: The majority of Earth Observation satellites, whether for meteorology or land analysis, downlink their data in the X-Band to either government-run or privately-owned ground stations. In Europe, the company Tesat has developed laser terminals that have been successfully tested in orbit, from one EO satellite to one geostationary communications satellite, with TerraSAR-X and recently with Sentinel-1A. Apart from the obvious - all types of lasers interact with the atmosphere (absorption, attenuation and scattering) - and the pointing accuracy required, what would be the main technological challenges in using lasers for direct downlinks to the ground?
Comment: Atmospheric attenuation is already a very good reason to avoid LEO-ground laser links: you need to have a cloudless sky and you need to be high above the horizon (>30°) for it to work, which severly restricts your access time.

Note that the planned European Data Relay System is advertised for LEO-GEO laser links and for UAV-GEO links. The UAVs envisionned are the large ones, which fly above the cloud cover.
Answer: The technical challenges aren't the main barrier; several demonstration missions have demonstrated laser downlink to the ground.
The main obstacles are:

Operational: Clouds necessitate ground stations on mountain tops and in deserts, which generally means expensive + poor backhaul for the data as well as making it difficult to achieve 99% uptime without many spare stations all over the world
Regulatory: All currently planned systems rely on a powerful laser uplink "beacon" for the satellite to lock onto; that can be a hazard for aircraft and potentially to other satellites, requiring permission to be obtained days in advance of each comm session from the Laser Clearing House
Necessity: X-band works pretty well!


Is Jupiter made entirely out of gas?

Question: I heard that Jupiter is made out of gas. But in school I learned that Jupiter has gravity which is 2.5 times that of Earth (Gravity that can tear apart a comet) and gravity is proportional to mass.
So if Jupiter is made out of gas alone, how does it have such high gravity and maintain so many moons around it?
Comment: Jupiter has a **lot** of gas. Don't sit next to him in the theater.
Comment: Jupiter is made (mostly) out of elements that are gases *at standard conditions for temperature and pressure (STP, 0-20 °C, 1 atm)*. Jupiter is mostly *not* at STP--the pressures are so great throughout the majority of these giants that these "gases" are compressed into liquids and solids to give overall densities comparable to water (1.33 g/mL for Jupiter, 0.68 g/mL for Saturn).
Comment: @Nick T. Hot Jupiter exoplanets can have densities similar to lead. They are still *gas* giants. The *gas* at the centre of the Sun is 160 times denser than water.
Comment: @Nick T No, it is not subjective. Gas particles have no (or at least little) interaction energy compared with their kinetic energies. The material at the centre of the Sun behaves (almost) like an ideal gas.
Comment: Strikers - please don't add new questions as an edit. The comet struck Jupiter - the images are online. It probably didn't 'strike' the core as such - it would have fallen in until densities matched, so that may be at the surface of liquid.
Comment: @RobJeffries you're already 4 orders of magnitude up on hydrogen at 1 atm (or dozens if you're talking about it as a nebula), so what's another few? I was mostly alluding to how "gas" is subjective.
Comment: @RobJeffries fine, "biased" by what we experience on earth.
Comment: @Nick T Biased? Gases and liquids and solids are quite different things. The changes between them - phase changes - occur, not at certain densities, but at loci in the pressure versus temperature plane. If it walks like a duck and quacks like a duck, it is a duck. The gas in the centre of the Sun is an ideal gas and behaves like one, even though it is 160 times as dense as water. There could be solids and probably are liquids inside Jupiter but we would already know it all if all it depended on was the density - which is reasonably well known - at the core, about 70 times that of water.
Answer: Comet Shoemaker–Levy 9 crashed into Jupiter a few years back.

As well as these molecules, emission from heavy atoms such as iron, magnesium and silicon was detected, with abundances consistent with what would be found in a cometary nucleus.

Those heavy elements are consistent with the comet being at least being partially composed of rock. So Jupiter is known to contain at least some rock. In fact, gas giants are thought to form around an initial small rocky or metallic core, which has sufficient gravity to draw in hydrogen, helium, water etc. from the protoplanetary nebula. By 'small rocky core' something with the mass of two or more earths is usually implied. The gravity field of such a body makes it difficult for even hydrogen to achieve escape velocity.
Comment: Ah, sorry, I misunderstood you. I see what you're saying now. Since Shoemaker–Levy is *part* of Jupiter now, Jupiter therefore contains iron, magnesium, and silicon. :)
Comment: @MatthewPiziak Sure, I didn't mean to imply otherwise. But now they're rock, *and* part of Jupiter. For Jupiter to be entirely non-rocky, as was asked, you'd have to come up with a mechanism to exclude passing dust grains and asteroids from the death grip of the planet's gravity well.
Comment: The source that you give seems to be ambiguous as to whether the heavy atoms originate from Shoemaker–Levy or from Jupiter itself. Since Jupiter is suspected to be solid only to 78% of its radius (ISBN 0816051968) and since the outer layers of its solid core are predicted to be metallic hydrogen, I find it incredibly unlikely that heavy atoms like iron, magnesium, and silicon exist in such concentrations that they would be described as comet-like. The emissions must have been from the disintegration of the comet itself.
Answer: It doesn't matter if the body is made of gas, rocks, liquid or plasma, the four states of matter all have mass. So, as we know, mass create a gravitational field, and the more mass the stronger the gravity - and Jupiter has 317x Earth mass.
Comment: Metallic hydrogen, as we've seen it, has a density around 0.6g/cc: https://astronomy.stackexchange.com/questions/8251/is-jupiter-made-entirely-out-of-gas/8256#8256 rocks run from about 2 to 7 or more per cubic cm. Unless there's a phase change in solid hydrogen down near the core, those rocks are going to want to sink. They've had a *long* time to do so.
Comment: strikers - the core is almost certainly liquid (hydrogen and helium, mostly), but even if there was solid in there it wouldn't be rock. Gravity is entirely down to mass. It doesn't care what form that mass is in.
Comment: you mean to say needless of having rock on it jupiter is having gravity due to the mass of gas.
Answer: I concur with everyone else here (of course) that the gravity at the "surface" of Jupiter is entirely determined by the mass contained within that surface. The composition makes no difference.
However I differ with some on the answer to the headline title question. We simply do not know whether Jupiter has a rocky core.
A popular theory for the formation of giant planets is that they must begin by forming a rocky/icy core with perhaps a mass of 10-20 times the mass of the Earth. This then slowly accretes for a few million years until it grows massive enough for a runaway short period of gas accretion that builds its entire mass. See  http://blog.planethunters.org/tag/core-accretion/ for another popular account.
If Jupiter formed like this then it should have a core. However, this is not the only game in town. Planets could also form in the protoplanetary disk by collapsing directly, in which case there would be no rocky/icy core. The recent discoveries of possible planet formation around the $<1$ million-year old HL Tau has led to a resurgence of this idea - it is difficult to form gas giants by core-accretion so quickly.
The answer may come reasonably soon. In July 2016, NASA's Juno spacecraft will arrive in orbit around Jupiter. One of its prime mission objective is to gather more information on how massive the core is at the centre of Jupiter using a battery of instruments including an experiment very sensitive to tiny gravitational field variations.
http://en.wikipedia.org/wiki/Juno_(spacecraft) http://www.nasa.gov/mission_pages/juno/overview/index.html#.VI9PuiusVSg
Comment: So, did the answer come?
Answer: According to Newton's Law of Universal Gravitation, you simply need interacting masses in order to generate a gravitational force between them.  Gases have mass and they therefore can contribute to gravity.  So even if Jupiter is entirely gaseous, it is so incredibly massive besides (so much gas!), that it has a much stronger gravitational pull than Earth.  The Sun is gaseous too, after all.
Be cautious, however, when someone compares gravitational forces so simply as "2.5 times".  There is always a hidden assumption/reference in this because the force depends on more than just mass (e.g. distance).  Earth's gravity is way stronger where I sit!  In your teacher's case, it is probably meant that the gravitational force felt at the surface of Jupiter is 2.5 times what you would feel on the surface of Earth.  To choose a "surface" for a gaseous planet, you need to make more assumptions.
Anyhow, for the titled question, it is highly likely that Jupiter is not entirely gaseous.  With all of that matter (not just hydrogen and helium, but everything else everything in our solar system is made of) and all of that gravitational pull, you are bound to have precipitated solids that condense into a solid planetary core.

Is Jupiter made entirely out of gas?


Is there online data on asteroid axial tilts?

Question: I am hoping to find axial tilts for asteroids and also their spring and fall equinox. Some of the asteroids I'm interested in are:
4 Vesta, 1 Ceres, 24 Themis, 65 Cybele, 153 Hilda, 624 Hektor
Answer: From this article, http://hubblesite.org/pubinfo/pdf/2010/33/pdf.pdf, here's the rotation axis for 4 Vesta: RA=307.5°±3.1°, Dec=43.1°±1.2°. Update, per TildalWave's comment: RA=305.8°±3.1°, Dec=41.4°±1.5°
Rotational motion of Ceres.
An old article (1986): Magnusson, P., Distribution of spin axes and senses of rotation for 20 large asteroids, Icarus 68:1 1-39 http://www.sciencedirect.com/science/article/pii/0019103586900722


Deployment of separate layers to Azure

Question: Let's say I have 3 instances in the Azure. Each is running separate layer of the application, as I described in this question Independent deployment of separate layers to Azure. For independent deployment of each layer (read Role) a separate Azure deployment project is created. The question is, what instance will be replaced, when I will be deploying, for example business layer? Can I be sure that the instances with UI and Data Access will stay untouched? How the instance to be replaced is found, based on name of the role?
Answer: To clarify, you have 3 layers, each hosted in a different windows azure role (not instance). If you have each role in a seperate deployment (seperate hosted services), then when you deploy, you are only going to be upgrading that layer. The other layers will not be impacted.
However if there are any signature differences, a dependent layer may break if the service its trying to call changes. Its for this reason that you want t omake sure any services support versioning and are always backwards compatible at least one version.
I've created a quick blog post with some screen shots of doing a single role upgrade. Note that the silverlight portal issued an exception for me while doing this and I've reported that error and will update the blog post if we find out what it was about.
Updated: There is bug in the silverlight management portal that currently prevents the performance of a single role upgrade. The Windows Azure team is aware of this and will be addressing it in a future update. No ETA for that update at this time. However, you can still perform the single role update/upgrade via the management API.
Comment: these role can be in the same hosted service? what is the principle of finding instances that belong to specific layer? is it name of the role?
Comment: Yes, you can host the roles in the same service. If you use RoleEnvironment, you can iterate through the roles and their specific instances. But this isn't really for a service upgrade, more for internal discovery and direct connectivity. Using a manual upgrade, you can actully have single deployment package for the service, but only upgrade specific role (I think, never tried it).
Comment: I'll try to shave out some time tonight to do a blog on the role upgrade for you. :)
Answer: As Brent said, it is definitely possible to do a Single Role upgrade. It used to be that if you made any changes to the ServiceDefinition (change VM size, added new Config settings, updated Role Name or changed the instance count from the service definition that is currently deployed) when you upgraded that role, Azure Fabric Controller would not allow you to do in-place upgrade. Now, that is also possible. So you can do an in-place upgrade on Role and bump up the VM size. As always, you at least want to have 2 instances to ensure that you don't experience any downtime.
Ranjith
http://www.opstera.com

Deployment of separate layers to Azure


Red text for confirmation message

Question: I'm working on a site which has its main colors as a dark red and carbon fiber as main colors. After an email is sent, a confirmation message is displayed. Would it be acceptable to make this confirmation message in red to match the site colors, or would it confuse people as generally success messages are green and error messages are in red?
Comment: Very similar: http://ux.stackexchange.com/questions/38479/how-can-i-highlight-errors-when-bright-red-is-the-main-color-of-the-brand
Answer: User interfaces have over the years established standards to help users recognize common situations. We have come to associate messages with red text, red background or other red elements with warnings about something that has gone wrong.
If you were to present positive messages using the standard presentation of a negative message, in stead of communicating with your users in a way they'll understand, you create for them a Stroop effect test.
Regardless of your site's style, in a user interface you need to be able to communicate failure, success and other messages in an easily understandable way.
Answer: If one person including yourself is in doubt, then the solution is not ideal. So it might be better if you used another color. Is carbon fiber (dark gray?) not an option?

Red text for confirmation message


MAC OS X - screencast

Question: what can I use to record an screencast at os x leopard?
Freeware are prefered.
Regards
Answer: If you really can't spend any money, take a look at ScreenCastle.  It's a web-based (uses Java) tool that works cross platform.
That said, on a mac, some of the greatest screencasts I have seen have been made with ScreenFlow ($99).  It is very easy to use, has built in editing ability, and has great high end features.  But it is not free.
Comment: ScreenFlow trial I think solves my current need. Thank you
Answer: I have been impressed with Jing.  It allows you to take screencasts and screenshots and share them easily.
Answer: Another reason to hold off on investing in a screen recording tool right now, OS X 10.6 (Snow Leopard) has one built-in:  Screen Recording in Snow Leopard's Quicktime X
Answer: iShowU HD is well worth the $30.
Answer: If you've configured the Podcast Producer service on your OS X Server then the obvious answer would be to use Podcast Capture on the client since it already comes with Mac OS.
See: http://www.apple.com/server/macosx/features/podcasts.html

MAC OS X - screencast


How does this field multiplication in libsecp256k1 work?

Question: I'm looking at libsecp256k1's codebase, for learning reasons (doubt I can contribute with anything useful there). While looking at the field implementation, the implementation of secp256k1_fe_mul_inner in both 10x26 and 5x52 is a little strange to me. I know some multiplication algorithms, like Karatsuba and Toom's algorithms, but this one doesn't look like one of them, at least I couldn't relate.
Looking at the source and git history, I only see a reference to Peter Dettman, but I was unable to find any paper authored by him. Is this algorithm inspired by a public paper? Any reference would be helpful, as I'm unable to follow reason about the code itself. I understand what it is doing, but I don't know exactly how.
Comment: @JulioDiEgidio I would recommend posting an answer with links and a summary of details from the first link.
Comment: I am not sure whether I should post this as an answer (can I just answer with a couple of links?), anyway have a look at this: https://free-cy.blogspot.com/2020/04/mathematics-behind-secp256k1femulinner.html , which I have found from here: https://bitcointalk.org/index.php?topic=5425925
Answer:
Is this algorithm inspired by a public paper?
Any reference would be helpful, as I'm unable
to follow reason about the code itself.

I am not sure about "papers", but more or less formal articles on modular multiplication in fact abound: indeed, the implementation in question "simply" leverages known properties of modular arithmetic.
As to the specifics, the following is the link to a post about an older and somewhat simpler version of secp256k1_fe_mul_inner than the current one, but it might be enough to support further exploration/reverse-engineering:

@cycheng, "Mathematics behind secp256k1_fe_mul_inner", 2020
https://free-cy.blogspot.com/2020/04/mathematics-behind-secp256k1femulinner.html

That article also contains a link to the relevant modular arithmetic, in a nice and compact series of slides, which I will repost here:

Peter Schwabe, "Efficient implementation of finite-field arithmetic," 2013
https://cryptojedi.org/peter/data/pairing-20131122.pdf

(There could be some added value in explaining the present implementation of secp256k1_fe_mul_inner, since it adds few more optimizations on top of the basic modular arithmetic.  But I think that would require a level of detail and formality that is well beyond the scope of the present question.)


Green's functions and delta initial conditions

Question: The Green's function of the $Lu=u_t-u_{xx}=0$ differential equation is a Gaussian distribution with variance $t/2$ and mean $0$, which is also the solution to the differential equation itself, for a $\delta$ initial condition at $x=0$. The general solution here is a convolutional product $G*f$ for initial $u(0,x)=f(x)$. For the wave equation $Lu=u_{tt}-u_{xx}-u_{yy}-u_{zz}=0$, Green's function is a spherical wavefront with a $\delta$ distribution, exactly what you'd expect from a $\delta$ initial condition. The 1st differential equation here is a parabolic, the 2nd hyperbolic, so they're quite different. I understand how Green's function is used to solve inhomogeneous differential equations using a convolutional product; if $LG=\delta$, $L(f*G)=f*(LG)=f*\delta=f$, so $y=f*G$ solves $Ly=f$. But that is not what seems to be going on here. So I don't understand, what is the relationship between Green's function and $\delta$ initial conditions? To what extent does this $y=G*f$ trick for initial conditions $f$ work? Why does this look so similar to solving an inhomogeneous equation?
Answer: Note first that for the heat equation and for the wave equation we have a "special" coordinate $t$, which we associate with time. Therefore, for these problems it is natural to consider "initial value problems," whereas for your second example there is no such thing as the initial condition, so the analogy is not that straightforward as you describe.
Second (and to answer your question), for any inhomogeneous linear problem of the form
$$
Lu=f(t,x),\quad u(0,x)=0,\tag{1}
$$
with a special coordinate $t$, one can consider a family of the initial value problems
$$
Lv=0,\quad v(\tau,x)=f(\tau,x),\quad \tau\geq 0.\tag{2}
$$
If you can solve the second problem, then the solution to the original problem is simply given as
$$
u(t,x)=\int_{0}^t v(t,x;\tau)d\tau,
$$
where $v(t,x;\tau)$ is the solution of $(2)$ for $t_0=\tau$. That is, for the linear problems the initial value problem for the homogeneous equation and solution to an inhomogeneous equation are very much related (this is called  Duhamel's principle).
Comment: This is what I was looking for. I was so confused because I noticed the similarity but just could not figure out what was going on. They should teach us physicists this!


How does Stack Overflow work for posts?

Question: When I post something, it moves down the pages fast. Does it jump back to the top on an edit, comment or answer?
Answer: You can bump a question when editing it. Search for questions here on meta using "bumping" (here), some considerations have to be taken for it as it is easily abused. It is also considered editing when you retag a question. Commenting does not bump the question, but answering does. Other than that Coyote already pointed out the community crawler.
Comment: so what your saying is i shouldn't reedit my posts so much? or that the measures in place are just a background feature
Comment: Does the bumping actually happen on Stack Overflow now? Didn't the rules change? The answer may be in *[Recent feature changes to Stack Exchange](http://meta.stackexchange.com/questions/59445/recent-feature-changes-to-stack-exchange)*.
Answer: Most people find questions they would like to answer based off of the tags your question has rather than it's position on the page.
If you question is good and upvoted, it will appear farther up some pages such as the "Unanswered" section.  Also the community crawler will occasionally bump questions.

How does Stack Overflow work for posts?


Why wasn't Kruge aware of the size of the Enterprise crew?

Question: In Star Trek III: The Search For Spock, why didn't Kruge know there were only five people on the Enterprise bridge? Could't the Bird of Prey scan to know how many life signs were aboard the Enterprise? Has there been any in universe answer to this in films books etc?
Comment: It probably COULD scan for lifesigns, but I don;t think Kruge would have had any reason to order them to do so.
Answer: A real-life modern warship could operate (badly, and for a short time) with a crew of three: one person on the bridge, one person in the combat control center, and one person in engineering. However, were you to come upon a modern destroyer cruising by, checking to see how many crewmembers you could see would likely not be the first thing on your mind because the assumption would be that it's fully crewed, not that there's only three people trying to operate it.
Kruge came across a well-known starship of a known class not knowing that it had been stolen by a handful of people. There's no reason for him not to have simply assumed it was crewed by the normal complement.


What does Provider mean in asp.net?

Question:
I've got confused . We hear a lot about Provider in ASP.NET . Membership-Provider , Role Provider , XmlDataProvider ,CustomProvider, ....
What are those and why we need them in ASP.NET ?
Comment: See http://stackoverflow.com/questions/2287596/what-is-a-dot-net-provider/2287662#2287662.
Answer: Provider is a synonyme with "Supplier" which means:

Someone whose business is to supply a
  particular service or commodity

Just as in real life, a provider is someone / something that helps you solve communicaiton with a certain service or help you solve a problem.
For instance, the Membership Provider in .NET is used to handle Membership such as Authentication, Registering new Users and many more options comes with this.
The Role Provider goes hand in hand with the above, because it helps you handle Roles attached to users that you have in ( They have Memberships! ).
You might want to read this: Microsoft ASP.NET 2.0 Provider Introduction from MSDN
Answer: Using the Provider model means that if you don't like the way something in ASP.NET works or you want/need to extend it, you can write your own. As long as it supports the core functionality that ASP.NET needs to work as part of the platform i.e. it inherits from MemrbershipProvider/RoleProvider/WhateverProvider, you can do what you want in the internals.
You can then swap out the default Provider and use yours in it's place e.g. say you don't use SQL Server, you use CouchDB for all your data storage. You can't use the SqlMembershipProvider, but you can write a CouchDBMembershipProvider* - as long as you inherit from MembershipProvider and override its' methods to work with CouchDB you're good to go.
* I'm not saying you should do this, I'm just saying you can :-)

What does Provider mean in asp.net?


What is the word for a scenario in which all choices lead to the same outcome

Question: Does such a word even exist?  If not, what should I use as an alternative?
Comment: The phrase "Damned if you do, damned if you don't" refers to a situation in which no matter which action you take, you get a negative result, but they are not necessarily the same outcome.
Comment: This actually has a surprising amount of possible answers. As you can see by the wealth of very different answers posted already. I have to put this on hold pending additional clarification from you on how exactly you intend to use it. For example, is it a good thing or a bad thing? Do you need an everyday idiom, a scientific term, a proverb? An example sentence would be nice.
Comment: saying something *is a wash* might be what you're looking for. though the examples out there seem to cast it as a competitive parity phrase, i've always heard and used it to mean the paths that lead from picking any one thing out of a bunch of given choices is just a featureless plain with nothing to differentiate the choices (a wash).
Answer: "Hobson's choice" may be appropriate, ie. the outcome is utterly inevitable despite the illusion of choice, the allusion being to one Thomas Hobson who had a (ie. just one) horse for sale, in spite of the appearance that he gave to his customers of having more than 40: https://en.wikipedia.org/wiki/Hobson%27s_choice
As to if one word exists to fulfill the requirement, beyond words such as inevitable/inevitability, and phrases such as convergent-evolution, I'm realy not sure anything directly fits. I should say that perhaps doom/doomed is the closest but has rather sinister overtones in modern English. Ordained, predestined, predetermined, others - but still none reference choice in the way the Hobson's choice does. https://www.merriam-webster.com/dictionary/doom
Comment: If you are truly looking at "illusion of choice", wouldn't Morton's Fork be more related to this?
Comment: @Keeta I'd not heard of that, makes sense - why not write an answer?
Answer: Not a single word but a common saying is:
all roads lead to Rome:

said to mean that all the methods of doing something will achieve the same result in the end.

(Cambridge Dictionary)
Answer: It might be a Catch-22.

There was only one catch and that was Catch-22, which specified that a concern for one's own safety in the face of dangers that were real and immediate was the process of a rational mind. Orr was crazy and could be grounded. All he had to do was ask; and as soon as he did, he would no longer be crazy and would have to fly more missions. Orr would be crazy to fly more missions and sane if he didn't, but if he was sane, he had to fly them. If he flew them, he was crazy and didn't have to; but if he didn't want to, he was sane and had to. Yossarian was moved very deeply by the absolute simplicity of this clause of Catch-22 and let out a respectful whistle.

(Heller's Catch-22)
It's used in situations where there appears to be a choice but because of rules and regulations, there isn't actually a choice, therefore all outcomes are identical regardless of any choices made.
Answer: Predestination means that the outcome has already been decided, but the dictionaries are rather theological about their definitions.
Macmillan says

the belief that people have no control over events because God or
  another force has arranged everything that is going to happen

Oxford says

the belief that people have no control over events because these
  things are controlled by God or by fate

Cambridge says

the doctrine that God has ordained all that will happen . . .

So I prefer inevitable — certain to happen. Some examples:
Macmillan has

You must face the inevitable and try to deal with it.

Oxford has

Everybody is always trying to hide children from the horrors of life
  when it is inevitable that they will find them out in the near future.

Cambridge has

When you're working such long hours, it's inevitable that your
  marriage will start to suffer.
Answer: Another relevant quotation rather than a single word is Henry Ford's famous maxim which is generally quoted as "You can have any colour you want as long as it's black", but is actually "Any customer can have a car painted any color that he wants so long as it is black".
Answer: Not a 'single word', but one idiomatic phrase possibility would be "six of one, half a dozen of the other":

The alternatives are equivalent or indifferent; it doesn't matter which one we choose.
from wiktionary.com


Is there such as thing as acoustic windshield tint/film?

Question: I was wondering if there was a product like this. Also, here in Canada (and other countries too), tinting the windshield is illegal. What if the film is clear? Would it still be illegal?
Comment: There is such a thing as an [acoustic windshield](http://carlite.com/product/acoustic-glass/) that Ford currently uses in several vehicles.  Ford uses the SoundScreen® brand - there may be other manufacturers.  Not sure.
Comment: @JPhi1618   This is the whole windshield?
Comment: @DucatiKiller Yes.  I'm not sure if it's an arrangement where Ford is the only company that buys from the manufacturer (SoundScreen® looks like a Ford trademark), or if they make windshields for other cars as replacements.  Here is an [article](http://glassmagazine.com/article/auto/acoustic-windshields-the-quiet-revolution) about the tech.
Comment: @JPhi1618  I love tech.  Great link, great info.  TY
Answer: I've never heard of an acoustic tint (could be out there..), but there is a windshield material manufacturer (Saflex) that makes an acoustic layer for use inside a windshield.

They market it as "Saflex Q Series", and one of their biggest clients is Ford (via Carlite), which puts it in several of their vehicles under the SoundScreen® trademark.  This PDF from Carlite (OEM windshield manufacturer for Ford) shows the many Ford cars with the tech in 2013.
Another article describing the technology: http://glassmagazine.com/article/auto/acoustic-windshields-the-quiet-revolution

More recently, PVB suppliers have developed vinyls with improved acoustic-damping qualities. These new interlayers are particularly efficient in the 1,500 Hz to 5,000 Hz frequency range.
The decibel reduction typically is 2-3 dB overall. Although not large, it results in a quieter vehicle interior that allows people to converse without shouting.
Acoustic vinyl also enables vehicle designers to decrease the thickness of the windshield without negatively affecting noise levels. This is particularly important as automotive engineers try to shave weight off vehicles to make them more fuel efficient. Acoustic vinyl windshields meet all of the same federal safety specs as regular vinyl.
Answer: S-LEC is one worth looking into, cost is unknown to me, or how effective it is as treatment.
Locally in Hawaii we have a tint that can be put on the windshield. Its purely a UV film, as it has no help on "tinting" the light transmission any darker than factory. You could perhaps put a few layers on there.
Thats probably about the thickest anyone is going to allow anything to be put on the windshield. Not sure how much it would help any acoustics. Maybe a last option to have one more layer of any kind, protect that nice car dash, or more rigidity up front.


Installing yum packages by pattern

Question: I want to install all openoffice packages. Passing openoffice* obviously wouldn't work, because it'd look at file system. How can I do that?
Answer: You can use shell globbing patterns as package names:

If no package matches the given package name(s), they are assumed to be a shell glob and any matches are then installed.

(from yum(8))
But you have to make sure that your shell does not consume your glob:
# yum install 'openoffice*'

Without the single quotes the shell expands the glob if your directory contains files whose filenames begin with 'openoffice'.
Alternative (inspect package list)
You can query all installable package that match openoffice* via:
$ yum list available 'openoffice*'

To extract those package names you can use repoquery:
$ repoquery --qf='%{name}' --pkgnarrow=available 'openoffice*'

Thus you could install those packages via:
# xargs yum install < output_from_prev_command.log

(Those steps give you the chance to inspect the list of all 'openoffice*' matching packages, e.g. to remove obvious unwanted packages.)
Comment: @JamesAntill, thanks for the hint, updated the answer accordingly.
Comment: Note that instead of using "yum list available" (which is meant to be UI and not necessarily usable from sed) you are _much_ better off using repoquery --pkgnarrow=available.
Answer: Hmmm... I've checked it and
yum install openoffice*

works properly (wildcard is accepted)
Comment: The * should be escaped, or it could match a file in the current directory containing "openoffice" in its name.
Comment: also works with `yum update a* b* c*`

Installing yum packages by pattern


Xcode 4 installation:

Question: I just got a Mac OS X 10.7 and was all set to install Xcode 4 and the iOS SDK onto it, but as it turns out, it will not let me do this because the installer reads this:
iPhone SDK requires MAC OS X 10.6.6 (To install iOS SDK you  must quit the installer and upgrade).
What does the SDK mean I should upgrade, my Mac pro is a higher level, it's a 10.7 !!! Do they mean I should downgrade ??? (pun intended!)
Anybody with similar problems and have a way around this?
:(
Parijat Kalia!
Answer: Lion requires XCode 4.1 at minimum.

Xcode 4 installation:


What does zero heat capacity mean?

Question: What is the physical meaning of 0 heat capacity? Does it mean that no matter how much heat I put in, I cannot raise the temperature? If so, does this means that if a system is at absolute zero, it cannot be raised in temperature?
Answer: Zero heat capacity means an infinitesimally small amount of energy will increase the temperature by an infinitely large amount.
An object has a non-zero heat capacity because it has internal degrees of freedom that it can channel absorbed energy into. The more internal degrees of freedom the higher the heat capacity.
Zero heat capacity emerges as the zero temperature limit of an Einstein solid. We get this limit because the energy spacing of quantum states has to be less than $kT$ for those states to be excited and participate in determining the specific heat. As $T \rightarrow 0$ the spacing is greater than $kT$, and the end result is the solid has no accessible degrees of freedom and therefore a zero heat capacity.
However the moment you add the smallest amount of heat the temperature increases, some states become accessible and the specific heat becomes non-zero. The zero specific heat is more of an idealised limit than a real phenomenon.
Comment: Another way to say the same thing is that if $C=0$, when you raise the temperature the energy remains constant, because $kT$ is still less than $\epsilon$, where $\epsilon$ is the energy difference between the first excited and ground state. Therefore, as John correctly said, no transition can occur and the system stays in the ground state. This is a purely quantum phenomenon: classical systems have $C>0$ at $T=0$ (es. the Dulong-Petit model).
Comment: @John Rennie: Minor correction: Your first sentence should read: "Zero heat capacity means an infinitesimally small amount of energy will increase the temperature by a *finite amount*."
Comment: So does this mean that no physical system can have zero heat capacity at $T>0$?
Comment: Any system undergoing an isothermal change with associated heat transfer?
Comment: @Pirx Depends what you mean by "infinitesimal" and which infinitesimals you use, really :)

What does zero heat capacity mean?


Isn't "there're" a contraction for "there are"?

Question: Aw, don't be silly. Well, I think so. So we'll say, "There're books in the library." We can also say, "We know there're not lots of foods or drinks in the library, but only books."
Comment: @Clare - That's different.  It's distributing "is" over a list.  And "there're" is used all the time by native English speakers.  (And "they're" is also used, but it means something entirely different.)
Comment: Most English speakers use *there's* instead of *they're* nowadays, even when referring to multiple things. "There's a pen, a book and a compass on the table." Search this site for *there is* or *there's*.
Comment: Your second sentence would more properly be "We know there's not a lot of food or drinks in the library, only books."
Answer: This seems to be used in spoken English at times (especially in North America), but I never see it in writing.


To say that I did something with a software: in [SW Name] / on [SW Name]

Question: I drew it on AutoCAD or I drew it in Matlab.
Answer: Generally when talking about software, you're going to use the word, "in."
You might work "on" a project "in" AutoCAD.
Also, when talking about a single piece software installed on a computer, generally English speakers will call it a program.  The word software is used more often when talking about software in general or software plural.
"My computer is having a software issue.  I have lots of software installed on my computer, but the program that's causing the problem is AutoCAD.  When I'm working in AutoCAD my screen keeps turning a strange purple color and then everything freezes up.  This only happens while I'm working in AutoCAD, so it has to be a software problem and not a hardware problem."
Additionally, to address the verb "drew" in your example, while you might create a drawing on a piece of paper, in AutoCAD, you're still working within a computer program, so the word "in" is still correct.  You might draw a plan in AutoCAD or draw a picture in Photoshop, or view a drawing in Paint.  All of those things are done in a program on your computer.
If you said your three year old child drew something on your computer, then I would expect to see some kind of drawing on the case of your computer.
Comment: I agree, but you should address the example verb "drew". I think people might say "drew it **on**" because drawing occurs on a flat surface. Even in software it is on a flat screen. Or, just to be safe, "using".
Comment: @user3169 - Moreover, I wouldn't characterize the use of _on_ in this context as "wrong" or "incorrect" or "ungrammatical" – even if it wasn't using tablet technology. I think _in_ is probably the safer preposition to use, but _on_ isn't overly jarring.
Comment: Addressed the verb "drew."  Thanks user3169.
Comment: @user3169 - I agree. "On" isn't wrong.  And there are situations where I'd use "on" to refer to a program - especially if it connects to something outside your local computer.  "I'm on Citrix," or "I'm on Facebook."  I'm guessing that how rigid the usage is depends who is using language.  An IT professional may need to be more rigid in their usage than a general computer user.
Answer: We (Programmers) use in while talking about software.
Exp :
Write a program in java that should display only digits.
Design a 3D image in AutoCAD.