In what way are Minecraft Resource Packs (Texture Packs) hardware intensive?

Question: If I want to run an HD texture resource pack, but it lowers my framerate; is there a specific or general upgrade I would need to off-set the problem? I.e., do HD packs only use RAM to load and run, or is it a combination of RAM and processor?
Comment: @dlras2 It doesn't. It has built-in textures, that you can *select* in the resource pack view, but they're built-in. Since "it lowers my framerate" is in the question, you can safely assume that they're using a pack that has higher-res textures than the default ones it's replacing.
Comment: @dlras2 The way the game seems to work, I don't believe so. Both ways it has to go into a compressed archive to fetch the textures, since it doesn't use an uncompressed texture folder on-disk like some games do/can.
Comment: You'll have to dig into what the program is using more of; more RAM (I've never had this be the bottleneck for MC), more CPU, more GPU?
Comment: @SevenSidedDie I had assumed they were distributed as a resource pack, and not actually built in. Dunno if it makes a performance difference, but good to know.
Comment: @dlras2 They're inside the version.jar. Using a 16x16 replacement pack won't make a performance difference since it's a 1:1 replacement, but a 32x32 pack or up will impact performance. I've heard of players who don't realise that the default is so low-res and gleefully installed a 128x pack, without realising they were doing a 64-fold increase in texture size!
Comment: @SevenSidedDie Do you think the 1:1 replacement would affect performance by having the images reside outside the .jar? Obviously increased texture size means increased resource usage, as you pointed out.
Answer: Resource packs that provide high-resolution textures ("HD texture packs") require your GPU to fetch, store, and render exponentially more pixels every frame. Every 2x texture size step (16 to 32, 32 to 64, etc.) involves 4x the GPU processing* than the previous step. This is all also stored in RAM too, but your RAM is rarely the performance bottleneck when increasing texture size.
So what this math means is that if your GPU is using (for example) 20MB of its onboard VRAM for storing the textures for a particular scene (i.e., looking at a particular forest) using a default 16x16 resolution texture pack, going up to a 32x32 texture pack will require 80MB of VRAM for looking at that spot from that angle, and the card has to spend proportionately more time to render it all.* Jumping up to a 64x64 texture pack will increase it again to 320MB of texture memory needed. Now if you step up to a 128x128 texture pack, that's going to (for that particular angle on that particular forest) load 20MB*4*4*4 of texture data over the 16x16 version, for 1.28GB of VRAM needed... which is a pretty big jump! And note that, every time you swing your view around to something with completely different textures (say, from a forest to the desert behind you) the video card will have to either already have those textures cached (which is less likely the more space each needs) or have to load them from RAM or disk, which introduces camera lag.
So what's the take-home message? That VRAM is the most important bottleneck for high-res texture packs, and the more you're asking the GPU to deal with bigger and bigger textures, the less of its data storage and processing capacity it may have left over for other tasks* such as scratch processing storage and caching other textures so that it doesn't have to reload them from RAM/disk when you move around your world.
To offest this, you want to do two things: not get too ambitious with your texture pack sizes, and install a mod like Optifine (the Standard or Lite editions that don't add fancy graphics) that improves and streamlines Minecraft's inefficient default rendering code. Remember that the size comparisons go exponentially backwards, too: if you're finding 64x64 to be a heavy load and laggy, the drop down to 32x32 will give you somewhere around a 4x performance increase!*

* This is a vast simplification. Modern GPUs do a bunch of pipelining and parallel processing, and have separate dedicated modules for textures verses vertex versus shader processing, and the 20MB of textures might leave a bunch of that capacity idle, so it may not be a perfect 4x increase. However, at higher loads that already saturate the processing capacity of a video card, the comparison will be closer to the simplification.
Comment: @Ender Give it a week, maybe. It's been a while since my discrete electronics education, so someone could easily come along and school me with corrections or a better answer. ;)
Comment: I'm strongly considering putting this answer up for bounty, thanks much!
Comment: Since Minecraft uses [mipmaps](https://en.wikipedia.org/wiki/Mipmap) (at least the latest version with default settings), increasing texture size shouldn't affect performance at all until the machine runs out of VRAM and starts storing textures in RAM.
Answer: Normally more GPU and RAM. However, things like Optifine and MCPatcher can make it easier on your GPU. However, it's a bit of a worse story for the RAM with those programs.
Comment: Has MCPatcher added rendering improvements? I haven't used it for a while.
Comment: @SevenSidedDie I think it has, I'm not sure though.
Comment: Luckily RAM is very rarely a bottle neck for minecraft
Comment: @DCA- When you're running a 512x it sure is ;) I give MC 4GBs (I've got 16) and it **still** uses a bunch of the page file.


Distance parallax and cosmological distance in universe in expansion

Question: I know that we cannot measure cosmological distances with parallax, but this is more a philosophical question. Am I correct in assuming that if we could measure distances using parallax (like stellar parlax used for nearby stars) the distance we would measure would correspond to the "angular diameter distance" ? https://en.wikipedia.org/wiki/Angular_diameter_distance
Answer: Yes, exactly. The angular diameter distance is defined such that it is compatible with "regular" trigonometric rules, just as the luminosity distance is compatible with regular relations between flux, distance, and luminosity.
Only for at flat and non-expanding universe would these distances coincide with each other, and with the "true" distance, which is what you would measure if you lay out meter sticks (after freezing the Universe in time, so it doesn't expand more before you're done).


"president-elect" grammatically correct?

Question: Why is "president-elect" grammatically correct? Shouldn't it be "president-elected" or "elected president"?
Comment: I suggest that there's no grammar involved, because grammatically it's a single (compound) word.  We might expect that the hyphen would gradually disappear over time, as seems to happen with other originally hyphenated words.
Comment: @jamesqf Not sure I can see the hyphen disappearing in this case. The usual transition is that two separate words become one hyphenated word, which later becomes one unhyphenated word. But "presidentelect" looks extremely clumsy.
Answer: President-elect is correct.
The word elect was appropriated to the English language in the 15th century from the Latin electus, the past participle of the verb eligere. In this form it acted as a noun or adjective designating the person chosen for an office, and that old use established the pattern reflected in President-elect.
Our verb elect arose about a hundred years later as a recategorization of the noun/adjective; if we had been concerned to return to the Latin root the verb would have been elige (which is reflected in the adjective eligible).
This, by the way, is very common in English etymologies. Many English verbs are formed on Latin past participles—almost all of our -ate words, for instance, such as demonstrate, aggregate, complicate, arbitrate.
Answer: Try to think of it as a stock phrase.
Some phrases of Latin or French origin 'require' the adjective to be placed after the noun.
I can give several additional examples here: secretary general, court martial, battle royal, heir apparent, devil incarnate, etc.
However, these uses are quite restricted. You'll have to learn them by rote.
Answer: The phrase president elect/president-elect is grammatical.
In the phrase, elect is a postpositive adjective; it's always placed after the person who has been elected by voting to a particular position,  but he has not yet started work such as president elect, prime minister elect.
Comment: *President elected* is features a [participal clause](http://learnenglish.britishcouncil.org/en/quick-grammar/participle-clauses), while *president-elect* is simply a noun --- Contrast *The president elected in 2016* with \**The president-elect in 2016*; The first one is grammatical but the second one is not.
Comment: Why isn't it "President elected"? After all the following is grammatical: *She is the newly-elected President/Prime Minister* It's not "newly-elect", or is it?
Comment: Am I the only one who finds it a bit ironic that my comment about ungrammaticality contains an ungrammatical sentence (\*"*President elected* is features...")? --- I should stop checking SE late at night...
Answer: Other phrases that may show the range of structure might include:

District champion
Preseason favorite [can be used later in the season, and we still use favorite instead of favorited/favored]
Husband-to-be
Manager-in-waiting
Expected graduate

So the focus can be on what was done, the continuing current quality (as having completed the action), or what the future expectation/consequence will be.  There are some better examples, I am sure, of each.
But I believe we tend towards using "president-elect" rather than "future president" or "elected president" because the attention is on the current.  Future president would put the attention down the road more, and perhaps also fail to give a measure of the learning process needed in transitioning into being the president (and it also goes against a common superstition/respect of not claiming something until it actually is true, due to any unforeseen potholes and to allow the current office to complete their job).  Elected beckons back more to the election than the person now or the challenge at hand.  So it seems sharpest to say "president elect" rather than the just-as-legitimate "future president" or "elected president".


Can mushrooms spontaneously die?

Question: These are called mushrooms I believe, had been growing on my door for a few weeks. It's monsoon here. Last night I took a picture of it and it looked like this . Today when I woke up it became like this: . All this within 12 hours. I'm pretty sure nobody touched the fungus so I'm inclined to believe this was spontaneous.
Comment: nice door! if you want to prevent mould on a door, the least you can do is infuse it with bleach. I imagine the TV has moss on it and the bath has ducks in it.
Comment: Of the thousands of shaggy manes I have seen ( and eaten most) , I never saw one growing directly on wood , nearly always they grow in grass .
Comment: Those shaggy manes are very fast rotting mushrooms
Answer: There are several fungi that autodigest  their lamellae  to release spores. Yours seems to be one of them. Due to the black liquid they release during autodigestion, they have the common name inkcap.
As an example, read this Wikipedia article about Coprinus for more details.
Comment: Actually "shaggy mane" is the common name in US ; inkys and micas are other closely related species.
Comment: It is said the mushrooms deliquesce when they liquify fairly suddenly. Note that the edible version of that mushroom is always nice until the first gray tones appear in the gills, at which stage they are past their prime and way less palatable... they are only worth picking when completely white and when the mushroom is completely closed, otherwise you have to cut the dark bits off. And there are unpleasant copy cats of the same mushroom so you must ID them well. take the spores of shaggy ink caps, mix them with flour and water in a blender, and throw them around some overturned decayed ground
Comment: Actually the coprinus comatus ( pictured) , gets pinkish before grey. I have eaten them with traces of pink, no problem.

Can mushrooms spontaneously die?


How to control LED monitor (desktop) brightness and contrast through an program in UBUNTU 12.04?

Question: Is there any application available which can control LED Monitor (desktop) brightness and contrast? Ideally, it should be configurable and can be made to adjust with day-night settings according to system current time? Or it should have configurable profiles which can be used as and when required.
Answer: With the current technology, no. Both vga and dvi (im assuming thats what you are using) do not have a "brightness pin" that can control the backlight of your monitor.


Is it possible for this tweakable block cipher scheme to be secure for more than $2^\frac{n}{2}$ blocks? $2^{n}$ blocks?

Question: In the title, $n$ is the block size in bits and will not be used to denote it in the body of this question unless otherwise stated. Imagine that we have $\mathbb{K} \in \{0, 1\}^{\ell_{K}}$, $\mathbb{T} \in \{0, 1\}^{\ell_{T}}$, and $\mathbb{X} \in \{0, 1\}^{\ell_{X}}$, $E(K, T, X): \mathbb{K} \times \mathbb{T} \times \mathbb{X} \rightarrow \mathbb{X}$, and $D(K, T, X): \mathbb{K} \times \mathbb{T} \times \mathbb{X} \rightarrow \mathbb{X}$. We have a tweakable block cipher where the encryption of a block of data is returned by $E(K, T, X)$, the decryption of a block of data is returned by $D(K, T, X)$, $K$ is the secret key, $T$ is the tweak, and $X$ is the block of data. Suppose that this tweakable block cipher is meant to be used in such a way that $T$ is equal to the block number. If $\ell_{T}$ is sufficiently large, then will the maximum number of blocks that can be encrypted under this scheme be equal to or possibly even greater than $2^{\frac{\ell_{X}}{2}}$ or even $2^{\ell_{X}}$?
Answer: Abstractly, there is no $2^{l_X/2}$ limit on the security of a block cipher. The security claim is that the block cipher is indistinguishable from a random permutation which it may remain even after the adversary has seen all its inputs and outputs (for a particular key). Similarly, there is no reason a tweakable block cipher needs to become insecure after a certain number of blocks are encrypted.
In practice the security of a block cipher depends on the mode of operation you use and most of those break down one way or another after $2^{l_X/2}$ blocks.
Practical ciphers also do not claim perfect security. AES-128 security claim is only "128-bit security". If you construct a tweakable block cipher from AES-128 the security bound is even lower. E.g. XEX/XTS security proof adds a term that is proportional to the square of the number of encryptions. So you should not use it more than AES itself, but in fact a small factor fewer times.
If you have a tweakable block cipher that is not constructed from another block cipher, its security claim may or may not depend on its block size. So using it like you describe may or may not be secure for more than $2^{l_X/2}$ blocks.
Comment: Is every tweakable block cipher that is constructed from a normal block cipher going to be insecure for more than $2^{0.5 \times \ell_{X}}$ encryptions?
Comment: @Melab using XTS, yes. Other constructions, maybe not. I don't think they have to.
Comment: @otus I would intuitively guess that it may _not_ be possible to avoid the birthday bound, because you're trying to get $2^{\ell_T}$ independent choices of PRP out of a single PRP.  Under a single key, there's only one permutation, not $2^{\ell_T}$ independent ones, and a lack of collisions in the outputs for different tweaks might reveal something; if you try to pick different subkeys for each tweak, the subkeys themselves might collide.  (This is nowhere near a formal argument, of course, just a hazy intuition!)
Comment: @SqueamishOssifrage you are probably right when considering simple (efficient) constructions with a single key and no rekeying. However, when you use [more than one key](https://eprint.iacr.org/2012/450.pdf) the birthday bound can be avoided. Likely also with constructions that somehow mix the tweak into the key input (which is slow with AES).


High accuracy 3-D scanners for outdoor scene reconstruction at long-ranges

Question: We are looking for a 3-D scanner for a project which is mounted at a distribution center where trucks are monitored. The trucks are viewed from the top and the goal is to estimate the 3-D pose of the truck.
We tried with the ZED stereo camera first, but they are terrible in long range accuracy. I'm looking now for suggestions for stereo cameras that can perform well at a longer range, around 15 meters at an accuracy of +/- 5 cm in the pose.
Other options include lidars, but it would be great if the community can help us choose the model that can fit this requirement.
Answer: Stereo cameras perform well at short distances, indeed: when using binocular vision, it is much harder to determine whether the object is, say, 50 meters away or 50.1 meters away, than to know whether it's 1 meter away or 1.1 meter away, despite the difference of 10 cm. in both cases. Here's a diagram which may help; the bigger the difference between α1 and  α2, the easier it is to determine the distance Δ1.

In order to make it easier, you should increase the distance between the "eyes."

In other words, instead of using a stereo camera, where the distance between the sensors is usually just a few centimeters, you can use two ordinary cameras put at a distance of a few meters from each other.
Then, you can use, for instance, OpenCV in order to create a 3D scene. The terms you may look at are disparity map and 3D reconstruction.
Comment: Thanks @Arseni for the answer. We have some stereo cameras with bigger baseline also under consideration. Any other reconstruction methods other than stereo, (like SFM, TOF) as suggestions? Or LIDAR ? Should be ideal for outdoor (high illumination) and long range applications.


Feature Layer (Polygon) Rendering issue in ArcGIS Server 10.1

Question: I have a feature layer consisting of 96,000 features, but we are displaying a maximum of 13,000 features in our map application. There is an issue that for some zoom levels the features are visible and for other, intermediate zoom levels the features are not visible. I have deleted the feature class and restarted the service in case there is issue with the feature class, but that also did not help.Thank you in advance and any kind of help will be appreciated.
Answer: Have you tried clearing the ArcGIS server rest cache?
http://blogs.esri.com/esri/arcgis/2010/10/08/clearing-the-arcgis-services-directory-cache-the-easy-way/
Also you cleared the browser cache/tried a different browser?
Comment: I guess it is for Arcgis server 10.0 and not for 10.1...
Comment: Its still possible to clear the rest cache at 10.1, although it does say it should be automatically cleared "automatically updates the REST cache when you add, update or remove services and folders". I'd try it anyway: http://[host]/arcgis/admin/system/handlers/rest/cache/clear via http://servicesbeta2.esri.com/arcgis/sdk/rest/clearcache.html


Audio line-in feature

Question: Does anyone know if any of the latest smartphones provide a audio line-in support? Am aware that this question has been addressed earlier as well but it has been a while since the last query on this and also the smartphones has evolved so much.
Comment: in some headphones there are 4 wires and the 4th one is for a mic so just search up on youtube how to add line input and then yeh
Answer: For the sake of completion, I will answer my own query. After googling for few days, I conclude that none of the existing Android phones in the market provide line-in support. This is more of a hardware restriction.

Audio line-in feature


Is it ok to screw into a steel door?

Question: I am looking to hang some blinds over the window on my front door.  Is ok to screw the mounting hardware directly into the door?
Comment: You could always replace the door with one that has blinds inside it. No dusting required :)
Answer: It's definitely not a problem.  As @ChrisF mentioned, the best way is to drill a small pilot hole (1/8" would probably be about right) and use a self-tapping screw.
"Self tapping screws" suggest that you don't need a pilot hole, but they're really meant for sheet metal.  They'll never get started in the steel skin of your door.  A small hole will let them engage.
Drilling steel is not like drilling wood.  Please forgive me if this is too basic, but someone else might find it useful.
To drill the hole, first locate where you want it with a pencil.  Then use a center punch with a hammer to tap a small indent right where you want the hole.  If you don't have a center punch use a nail.  If you don't tap a center mark, your drill will skate right across the surface of the door and scratch the paint.
Then drill at the full speed applying some pressure directly behind the drill motor, in line with the twist drill.(1)  If you're used to drilling wood you might be surprised how much pressure it takes.

(1) A bit (ha ha) of anal-retentive vocabulary: the thing that you plug in is the "drill motor".  The thing that actually drills, which most people call the "bit", is not a bit, it's a drill, usually a "twist drill".  I only bring this up because the the anonymity of the interwebs makes me bold.
Comment: drill1    [dril]  Show IPA
–noun
1.
Machinery, Building Trades .
a.
a shaftlike tool with two or more cutting edges for making holes in firm materials, esp. by rotation.
b.
a tool, esp. a hand tool, for holding and operating such a tool.

Looks like the "Drill motor" can also be called a drill.  So you would put the drill in the drill and drill a hole.
Comment: Darn you, evolving English language!
Comment: @Tester101 re: lubrication - Apologies for a stunted humor gland if you're poking fun at me - but IMO lubrication isn't important for a job like this but the lack of a center punch will ruin the job by scratching the door paint.
Comment: No lubrication?
Comment: Not poking fun just wanted to know if you would use lubrication while drilling the door.
Comment: I know you're right about the terminology but I find it funny that the language has evolved so much in this case that saying "apply pressure to the drill motor in line with the twist drill" actually *sounds wrong* (to me anyway, and I suspect to most) vs. "apply pressure to the drill in line with the bit."
Answer: Should be fine, just be careful not to poke a dent in the exterior skin when you pre-drill.
Answer: I'd use self tapping screws with a very small pilot hole.
Answer: Another approach is to avoid drilling at all and use a magnetic curtain rod.  These are reasonably priced and stick well to the steel door without damaging it.
Comment: and Neodymium magnets aren't technically that expensive - at least ones that would hold up well enough for this.

Is it ok to screw into a steel door?


open source job/process management/monitoring/control system

Question: I'm looking for an open source solution for the following:
I have jobs that need to run continuously.  The jobs are applications or scripts.  If they fail, they need to be restarted.  If they fail, say 10 times consecutively or within a certain time period, say 1 hour, they need to be cancelled and notification issued to a central repository.  If the jobs start heating up (using CPU or memory etc.) warnings should be issued and then killed if they get too hot.  The jobs could be optionally scheduled to run only during certain hours.
I know there must be open source, platform independent, high-level-language (i.e. implemented in python, etc.) full-service, sophisticated solutions for this, but I'm not even sure what to look for or what such a system is called.  I've done a lot of googling but have yet to find something that does all this.
Answer: Supervisor (written in Python) will do most of what you want out of the box.  It can be extended with the other bits of functionality using the XML-RPC API.


How to demonstrate ability to operationalize research during interview

Question: One of the feedback I received after my PhD interview failure was that " there is not enough evidence of ability to operationalize the research". So how can I clarify my capability of carrying out a research for my next interview. During my failed interview, I was ask to talk about my prior research, therefore I mentioned my master thesis used SPSS. However it seems that my response was not compelling enough.
Answer: Mentioning your skills with SPSS is great but statistical analysis is just a part of research. (And if we speak about this part, I would be more interested in which statistical methods you used and why (who selected these methods, you or your supervisor?, did you consider other methods?, etc.) to see how well you understand statistical analyses.)
More relevant would be your research question, design and contribution to the whole process (Did you come up with these on your own or was it given to you? What was your contribution in designing the study? Did you collect the data? Did you apply for ethical permission (if applicable) on your own? Do you plan to publish your thesis?)
If you are asked a similar question at the next interview, try to give a brief summary of your thesis (topic, design, methods, results, your contribution).
Also: please do not be discouraged that you have not been selected this time! Being invited for an interview means that you are a good candidate. It is just that there are many good candidates out there and limited number of places. Learn from this experience, do not give up and good luck with the next interview!
Comment: Thank you for your enlightening answer. I found out I haven't covered all the aspects of your suggestion. During my previous interview, I figured out I was too overwrought to even being stuttering when answer such question. Furthermore, I want to ask, if I have multiple research projects, which one should I pick to exhibit my research ability?
Comment: You are very welcome. I was also nervous during my first interviews so I can relate to that. Later ones were easier because you learn what to expect and how to respond. I would very briefly mention each project but focus on one. Something like: "I have worked on projects A, B and C but C was my main project." and then tell about C. Choose the project you know best and/or the one that shows your abilities best.
Comment: It is very valuable advice. Yeah it was my first interview also, so I was super on edge the whole time. When the interview was over, I found out I answered the questions not as I practiced. As I don't have any publication yet, I wonder whether it would be one of major deficiency of my research skill? My master thesis was done in 2015 therefore the regression was straightforward however I encounter some problems of data issues that I eventually overcome. Should I mention it?
Comment: This could be different in some countries/institutions but usually publication experience is not a requirement. It can be a big advantage, though. From my understanding, your experience could be given as an example of "overcoming difficulties" if you get such a question. However, I would advise against going into defensive mode with regard to your master project or your lack of publication. Try to emphasise your strengths and achievements.
Answer: One of the best ways to demonstrate skills and ability to carry out a research project is to ask intelligent and relevant questions about the project as part of your interview. When I interview students, that is one of the ways I find out about their ability to understand and put new information in context.
So for instance, a student who will be running experiments might ask about current protocols related to lab work during COVID and then discuss how they might make sure to get the work done under those conditions. Someone doing data analysis might ask about the structure of the data to be analyzed and the packages or libraries used most by the group. They might then comment on how they would approach the analysis or other packages they have found helpful for similar data.
When you treat the interview as a collaborative conversation you can most easily demonstrate your ability to carry out the work successfully.
Comment: Thank you for your constructive comment to my query. During my first interview, they only asked me about my prior research experience without adding further questions in relation to them. Therefore, should I be more proactive when answering such question in order to convey my research skill?
Comment: Did they ask you, usually at the end of the interview, if you had any questions for them? You can proactively ask questions earlier, but if you have not had the opportunity, then this is the place to begin such questions/ discussions.
Comment: Yeah, they asked me do I have any questions for them. At first, I stuttered giving my questions and probably it was my first interview, I was too edgy to recall what I needed to do, even for the sake of clarifying my proposal or asked them why they didn't ask me much about the methodology even though it was a funded project.


Ultimaker 2 ticking sound coming from feeder

Question: Recently, the ticking sounds started to come from feeder of my UM2. Inspecting it I have noticed that once in a while stepper motor jumps back for few steps. I have an idea of what can be the reason, but I just want to hear what you can think of. That is the video of feeder during the printing :)
https://youtu.be/z6CzudMOeD0 First tick at 10sec
Comment: please refer to this topic
http://3dprinting.stackexchange.com/questions/904/teflon-tubing-in-nozzle-throat-coming-out
Answer: Ultimately, your stepper motor is unsuccessful in driving the filament through the extruder. A couple potential reasons:

extruder temperature isn't high enough. This could either be operator error from not setting the temperature correctly or your machine is getting a false reading. Typically, for ABS/PLA, you can get away with a low extruding temperature of about 210c.
filament tension is too high. This happens if, say, your spool of filament gets kinked or wrapped around the spool spindle.
your nozzle is clogged. I've encountered where I had back flow coming out of the nozzle (filaments oozed around from the hotend at the threads). This was a result of not putting the hotend back together correctly. There was a enough hardened plastic backed up in the hotend that when I threaded the nozzle back on, it technically didn't fit back on all the way.
Comment: For the record, and for people interested, I believe this is a feature of the Ultimaker 2's firmware, whereby the voltage to the stepper motor that drives filament is regulated to prevent the feeder gear from grinding into the filament when the filament can't move enough. This causes the stepper motor to jump backwards.
Comment: When you add a nozzle to a heater  block, especially a block with melted filament, it needs to be tightened with the block hot.
Answer: I had the same issue. It can happen for number of reasons.
One of them is too low print temperature as stepper cant push the filament through. Also you could have partially blocked nozzle or if you print with PLA and have left it out for a while its diameter can enlarge and get stuck in the bowden tube.
Answer: So, problem was too low printing temperature. It was 200c. For PLA I have it was too low. Now I'm confused, for PLA the temperature range for printing is given from 180-210 (It is even written on particular coil). Does it mean that even printing in this range I should adjust temperature for each of plastics I have?
Update: I have researched a bit about phenomena I had. According to RepRap wiki http://reprap.org/wiki/Hot_End_Design_Theory the flow of material dependent on many parameters, starting with softening point of plastic and ending with environmental conditions. I can conclude that in my conditions temperature of 200c did't give enough material flow (but feeder still tried to push it as much as it required). And ticking was one of indicators of it.
Answer: Oh yeah that is way too low for the ultimaker.
That temp is a general "this is what PLA melts at" so if you took plastic, heated it up to that temp it would melt.
However, you don't heat all the plastic at once. Your hotend it at that temp and if you let it sit it would heat up (fairly quickly). Printers like the ultimaker are fast, and well designed. They have a very small heat melt zone. So the plastic only has a fraction of time to heat up.
Solution? Higher temps!
(do not do this example. Not liable if you hurt yourself) You know how you can take a lighter and almost slowly wave your finger thought it without getting burned? You know if you let it stay even a full second you would regret it. Same thing here. It is going too fast to heat up.


Do you have to hold note or is pedal sufficient?

Question: In the following measure of Air in D major by Bach, do I have to keep pressing A (and play around with thumb on A) or can I let go (with sustain pedal)?
Answer: I think it's better to hold the note. Using a sustain pedal would also sustain the notes in the bass as well as the upper treble notes. It's difficult to sustain only the single note, even using the sostenuto pedal (which would normally sustain the first D chord in measure 9.)
Answer: This would completely mess up the bass pattern, so press A and hold.  That's not really much of a stretch: this arrangement of the orchestra suite #3 movement is for typical keyboard instruments.  As a note aside, I play this thing from the orchestra score on a chromatic button accordion and for a lack of skills at tasteful reduction of polyphonic music, I just play the violins and the bass, leaving out the viola.  That actually requires you to span a 2-octave range at one point of time.
So if you get a piano version of an orchestra piece that seems awkward rather than impossible, chances are that you already have a version that the arranger considered playable as-is.
As a note aside, I remember some piano menuet by Mozart apparently requiring the use of the nose for a note in the middle with other keyboard action left and right.


Why must swap partition be nested when created as an extended partition?

Question: I did not want to use up my last primary partition so I created my new swap partition as an extended partition.  However, somewhat redundantly, it is created under sda4.  This makes little sense as sda5 is the only partition in ext4.  Why is it forced to be nested?  Why can it not be created at the same level as the primary partitions, but it must be made a "child" partition?  Do you understand what I am saying?  This is an unnecessary distinction, as it is the only partition occupying the extended partition.  I'd rather my swap be called sda4 and not be subordinated as sda5...
Answer: You're mixing up logical and extended partitions. Go and read about PC partition structure.
You can have up to 4 primary-or-extended partitions, and at most one of it may be extended¹. An extended partition is a container for logical partitions¹. A primary partition or a logical partition is a container for a filesystem (or an LVM volume or some swap space or a BSD partition or other kind of volume that isn't a PC-style partition). The swap partition is nested in the extended partition because that's what it means to be a logical partition.
In your case, making the swap partition a logical partition rather than a primary partition won't change anything regarding the primary partition quota, since you don't otherwise have an extended partition. If you wanted to free one primary partition slot, you'd need to have at most two primary partitions in addition to one extended partition.
Note that Linux doesn't care whether it's installed on primary or logical partitions. You could make both your system partition and your swap partition logical. Or you could create one partition that's an LVM physical volume and create two LVM logical volumes, one for the root filesystem and one for swap. LVM gives you easier management within Linux at the expense of other OSes seeing the LVM physical volume as an opaque blob.
¹  That's not strictly required, but you'd have to go through hoops to circumvent that, and your fellow administrators will curse you.
Answer: Nothing says that it has to be.  In your configuration, the swap partition is at the end of the disk, which is covered by the extended partition space.  On my Ubuntu system, I have my root filesystem in the first 60GB partition, then a 4GB swap partition, then the extended partition.  It depends on how you wish to have the system set up.
The architecture of the drives being used these days has a limitation of only three (3) physical partitions and one extended partition.  Since you have two ntfs and one ext4 partition, any additional partition (swap) would need to go inside the extended partition.
Comment: The limitation is from the msdos partition table, not the drives, and the limit is 4 primary partitions.  If you use a primary partition as an extended partition, that leaves 3 left.  If you get rid of the extended partition then you can use the 4th partition for the swap.
Answer: Unix is all about transparency and power and programmer's convenience, and not so big on making things look nice if it sacrifices those things even a little bit.  So if there's a partition entry on the disk, there's a partition device to go with it.  (The only exceptions are empty partition slots, but then, since there's no reserved space, there's nothing to write to.)
So when dealing with DOS partition tables, Linux reserves partition numbers 1 through 4 for the primary partitions, leaving 5 and up for logical partitions.  Because the structure of the partition tables make it easier that way, because it's nice to know you're working with a primary partition if the number is 1-4, and because who am I to know that you won't want to write directly to the extended partition at some point?
(You think that's bad... Sun systems reserve partition 2 as a "whole disk" partition.  Partition 2 must reserve the entire disk, and it must overlap with the other partitions on the disk.)


normalization of probabilities in predicting a poly-neuron output in neural nets

Question: When predicting a poly-neuron output in neural nets, say, predicting multiple handwritten digits and giving an output neuron vector (0.1,...,0.9,0.1,...), many use sth like softmax (or sth like the energy dependent probability exponential formula in statistical mechanics) to normalize the output vector such that all the components of the output vector sum up to 1, and that the normalized output vector becomes a probability vector. I doubt the necessity of this normalization, for without which I can equally well predict as per the biggest vector component. Is there anything I overlooked?
Answer: You are correct, but this is not called normalization. You can simply use the highest probability output for category. This is what softmax does for you. For example 2 output neurons can have 0.1 for dog and 0.9 for cat as the loss. Softmax will it just convert it to [0,1] meaning no dog but a cat is on the image.
Comment: What I mean by normalization is that softmax makes the components of the probability vector sum up to 1, which I don't deem a must. That's clear, I won't use softmax for this sheer aesthetic piece of pleasure.
Comment: You can do that as well. But if your loss is for example categorical_crossentropy then a softmax is needed because crossentropy requires a one-hot output.
Comment: @ Manngo Sorry I don't get what you mean by categorical. If I have several digits to recognize, is that what you mean?
Comment: categorical_crossentropy loss requites data encoded as on-hot method as categories like [0,0,0,0,1,0,0,0]. This is what softmax does.
Answer: Yes, you have overlooked something. Let me explain this with an example:
When training a neural network, you use the loss function as a signal to backpropagation. Now let us say that you have a network which outputs three categories: Cat, Dog, and Toad. Let's say the prediction of the network in an iteration is [0.7, 0.6, 0.3], although the data is, in fact, an image of a dog, meaning the truth is: [0 1 0].
Without a softmax layer, you cannot really tell much the network got the prediction wrong. In this example you might think the difference is 0.7 - 0.6 = 0.1, however after running a softmax, you realize that it is in fact 0.03, since the network was very strong in differentiating between the Toad category vs. Dog and Cat, so the loss is not as big as it seems.
Now as an experiment, run a neural network without the softmax layer and see for yourself, how severe it can affect the training. Not only that, but normalization of the input batches also makes a huge difference in training a network.
Comment: i got ur point. but i think whether it b softmax or my original idea of outputting a vector tag of 3 scalar components, the magnitude of the numbers or the relative differences between numbers are all artificially controllable or tunable? as long as i keep this in mind, i wont really care about, in ur softmax case, how big 0.7-0.6=0.1 is. if i stick to outputting a trinary vector tag, i'll train the network so that the contrasts between the numbers r huge enough. would u agree?


What is good modern book/resource on advanced experiments?

Question: I am looking for resources (doesn't have to be a single book) that would cover some of the more challenging cases of experimental design and statistical analysis. Some of the cases I would like to be covered:
1. Cases where units of randomization are different from units of analysis
Example: I run an ecommerce platform with M sellers and N buyers I want to introduce a treatment on seller level, but interested in the probability of a buyer making a purchase. A typical buyer will visit several stores in a session.
2. The outcome variable is highly skewed
Example: I run a call center and I want to try prompting the customer to enter their customer ID before reaching the agent. I hope to reduce the average duration of a phone calls. The phone calls distribution is extremely skewed.
3. A treatment group has differently shaped distribution
Example: Same call center, but now my treatment works much better for shorter calls and slightly worse for longer calls. What's the correct way of analyzing this?
4. The treatment itself makes my groups unbalanced
Example: The same ecommerce platform as in 1. but now I want to experiment with different ranking mechanisms. By being assigned to a more favorable ranking position a seller might want to raise prices, increase its inventory, change marketing strategies, etc. in a way that will make some of those variables systematically different for different treatments.
Comment: Nice question!!
Answer: Some of your problems had been studied in the literatures. Specially on works on ECOLOGY. The song of the dodo by David Quammen is one which is more like stories. But another ones Ecological Diversity and Mathematical Ecology by Pielou had been studied mathematically. Also there is a book by Stephen P. Hubbell name The unified neutral theory of biodiversity and biogeography which had both. Then you may recall those concepts appear in the books and translate to the ones that you asked.


What's the difference between 仕事 and 働く?

Question: Apart from 働く being a verb, and 仕事 being a (suru) noun, what is the difference between the two?
Answer: They(仕事する and 働く) mean "to work in a company or as a one-person operation" and also "to do something".
However 働く has some meanings besides like 作用する(act on). For example, 地球では重力が働く(Gravity acts on the earth) http://dictionary.goo.ne.jp/jn/176758/meaning/m0u/%E5%83%8D%E3%81%8F/
Answer: Putting parts of speech problem aside, 働く stands for "labor", the activity you put some effort to do something, while 仕事 is "job", or what you put your effort to do. Both are common words and applicable when you describe people working at office.
It's not so easy to find situations only either one makes sense because the two are usually pairing up, but for example:

○ 百人力の働き
  × 百人力の仕事

百人力 means "100-people worth of power" or "Herculean strength" (not Herculean task) to express how you are efficient to get works over with. It can only modify 働き and not 仕事, because the job is the same job.

× 急な働き
  ○ 急な仕事

急 means "sudden, urgent". What comes suddenly isn't your performance but the task.
Below listed some extra definitions each word particularly have, for your information:

働く: to commit (a crime), to function
働き: function, performance
仕事: profession, work (of physics)
Comment: @Earthliŋ https://en.wikipedia.org/wiki/Work_(physics)
Comment: By "work (physics)" do you mean "(physical) work"?
Answer: Not much. You can see it as "working" and "doing your job" in English.
There are quite a few of those, just like in English.

話す->talk
  話+する->have a talk
Answer: As you see the Japanese word "働く" consists of the Chinese character "働" and Japanese character, Hiragana "く." On the other hand, "仕事" consists of two Chinese characters. You can almost always use both words for the same situation.
"I hate working on Sundays."
Correct: "日曜日に働くのは嫌だ"
Correct: "日曜日に仕事するのは嫌だ", "日曜日の仕事は嫌だ"
However there is a slight difference between the two words. A word consisting of a Chinese character and a Japanese character Hiragana gives us a soft impression.
So if you give a title for the TV program for children about the vehicles like cement mixer truck, Fire Truck, Police Car and Ambulance, etc. In this case "働くくるま" is a little bit better than "仕事のくるま." There is almost slight difference but when you come right down to it "働く" is rather casual and "仕事" is rather formal.
Comment: Strictly speaking 働 is not a *Chinese* character, https://ja.wikipedia.org/wiki/%E5%92%8C%E8%A3%BD%E6%BC%A2%E5%AD%97.
Comment: @AndrewGrimm I think that "Chinese character" could be understood in a more restrictive sense of "character used in some form of Chinese", although in the context of the Japanese language it is sometimes used as a synonym for *kanji*.
Comment: @Earthlin Does "Chinese character" usually mean the same thing as "kanji"?
Comment: I used "Chinese character" as "Kanji."


Can one use a 26" tube in a 27.5" tire or a 27.5" tube in a 29" tire?

Question: I upgraded my bike but have a bunch of old tubes lying around. Can I use them?
Comment: OK for 'track side' get you home repairs, but i would not leave the wrong sized tube in. Me and mates some times 'share' spared and tools to save weight, We carry a  couple of spare 27.5" in the group to which covers the 26 and 29ers.
Comment: If you want to get use out of old tubes donate them to a local bike coop, bikes for kids or similar charity, or list 'em for free on Craigslist or your local Facebook bike marketplace.
Comment: Note that tube width is also an issue.  A tube of say 1.25 inch width will usually work up to maybe 1.75 inch, but you get much more difference than that and you will have problems.  And fitting a wide tube in a narrow tire will often result in tube failure due to the tube folding up on itself.
Answer: yes I'm pretty sure it should work. have not tried it myself but when you pump up a tube outside of the tire the diameter increases quite a lot (so the change in diameter from 26-27.5 or from 27.5-29") should not be an issue imo.
Comment: +1. A slightly smaller MTB tube in a bigger MTB tire will work. There is a limit to it, of course. I recently tried to fit a tube marked as 27.5" × 2.4" into a fatbike tire of 26"×4.8" dimensions. I managed to inflate it and everything looked fine when I left it for the night. In the morning the tube was split in shreds. Silly me.
Comment: @GrigoryRechistov yes indeed when you put a bigger tube into a smaller tire the tube will fold over onto itself which usually results in a blown tube when riding
Comment: @GrigoryRechistov that might be a decent related but new question - your 26" fatbike tyre is asking a lot to go from 2.4" to 4.8"


to trace shares from folio number?

Question: I am in receipt of KYC updating reminder for my father. He has passed away in 2013 and these the two letter where only FOLIO number is written and number of shares. How to know more details and get the same transferred on mothers demat account who is the legal heir too.
Comment: The letters are sent by LINK intime
Answer: Write to Link or visit their Branch if in your city. They should be able to guide you with the procedure.
Search through your dad's old documents to see if there is any physical share certificate.
If the share certificate is lost; there will be some process [that link or the company who's shares you hold] will be able to guide you. Generally involves creating notarized document on stamp paper in prescribed format. This along with death certificate, etc should enable you to get the shares transferred to your mothers demat account
Answer: Check the letter sender name properly. The Sender will have something as "LinkIntime-CompanyName " or department name as the company name.
Write to them or visit their office & they will guide you with the procedures.

to trace shares from folio number?


Frame Or Paint Crack (Cannondale Super Six Carbon)

Question: I am about to pull the trigger on a used 2012 Cannondale SuperSix bike. This would be my first bike and I'm very excited.  However I am a bit concerned about some cracks.   Seller claims paint is cracked and not the carbon frame but I have my doubts.  I wanted to see what you guys think of this picture.
Comment: Wait a little to hear what others say. My thinking is that you'd need to take the forks, and probably the headset bearings out to see the if the inside of the headtube is cracked. If I already owned it, I would try some repairs, but the *good deal* aspect adds to the worries. Whenever a deal seems too good to be true, it usually is.
Comment: Welcome to [bicycles.se] @Juan. The cracks around the top headset bearing look cosmetic to me, the one at the bottom headset bearing looks structural. Don't be surprised if people want to close the question as *opinion based*, because everyone *can* have an opinion. Look for answers that are well explained. In the end, like with many questions of the *is this Ok* type, my advice is *don't do it*.
Comment: @JuanGutierrez: The "coin test" isn't going to be useful on these edges of the frame where the sound will anyway differ.  The carbon is cracked or it isn't, and the only way to know is to look carefully.  Personally I'd not buy this bike.
Comment: The crack at the bottom of the head tube is serious enough that I wouldn't trust the frame without an ultrasound inspection. Even removing the fork and checking the inside of the head tube may not be definitive, although it is a good first step.  Unfortunately, ultrasound inspections are costly, and not practical on bikes not already owned.  This bike is one to pass on in my opinion.
Comment: Thanks Andy for the fast response.    I am going to check out the bike tomorrow,  Is there away to test for structural damage?   if is cosmetic i dont care since the bike seems to be a pretty good deal but if is structural i wont bother.   Just want to make sure is structural
Comment: i read about the coin test by tapping the frame with coin and listening to the sound.  whats ur take on that?
Comment: Sounds good, but I haven't done it. I try to only recommend things I have seen work :-) BTW, a) to reply to other people, use @theirname, and b) this thread of comments is getting a bit long - at some stage soon we could be told to go to the chatroom.
Comment: @JuanGutierrez the coin test or tap test is crap.  I can't even find studs in the wall at home by doing a tap test.   I doubt anyone can hear the difference between   *tink* and *tiink*
Answer: Since it's a few seconds with an allen key to pop the stem off and have a look at the inside of the head tube, I suggest doing that. Strongly suggest. If there's any damage to the fibres, or the cracks go deeper than the gel coat, don't buy the bike. If you don't know what that means, or the seller won't let you look, don't buy the bike. Exposed fibres or cracks on the inside of the frame might be fixable, but not by you (or you'd know enough that you wouldn't need to ask your question here, you'd be answering it instead). But they are probably not fixable.
The failure mode here is most likely that the head tube will break, probably when you're braking heavily. That's not a good crash to have, you can easily end up with severe dental trauma and that can never be fixed. Break an arm, grind half the skin off your face or hand, it hurts but those things grow back. Teeth don't. My partner has an expensive bridge where her front teeth used to be, and when we can spare $20,000 we will get them fixed better. Not fixed properly, because no-one can currently do that for any price, but something better than the "temporary bridge" that has been there for 10 years.
The trouble with buying something when you don't have a close relationship with the seller is that you have no idea whether it's really a good deal (if so, why doesn't the seller have any friends that will take the good deal?), or whether you're the gimp. Especially with carbon fibre and other materials that can fail in non-obvious ways, a common reason to sell is that the bike has failed in some way that's not going to be easy for the buyer to tell before they buy it.
The other obvious reason for a "good deal" is stolen property. Grab the serial number and search online for it, including the various stolen bike registries. You might be surprised at what comes up.
Comment: @andy256 true. I guess my expectations for people who own expensive bikes are probably inflated. Our shop attracted people who did a lot of their own maintenance, as well as people who tired and failed :)
Comment: What's a few seconds for you becomes a half hour job for many. Allen key? Oh yeah, I have some somewhere. What size is it? Yikes, it's metric! And so on ...
Answer: Frankly, it's going to be hard for random strangers on the internet to determine the extent of damage to carbon fiber from a picture.
Be upfront with the seller - tell him you're uncomfortable and would like to have a bike shop take a look at it. Be prepared before hand - find a local, reputable shop, explain the situation and ask them if they'll do the inspection & how much they'd charge. Be willing to pay them $20, $30, $50 for their work. For the shop it is probably just a few minutes work to disassemble and inspect.
If they determine it's cracked carbon, not just paint, you've saved yourself the purchase price and the potential of an expensive hospital bill. If they say it looks good, you're probably OK, and the few bucks for peace of mind is probably worth it.
In any case, don't let the emotion of pursuing a good deal override your gut feeling about it. If you don't think it's safe, pass, no matter how good the deal is. After all, it's your body on the line should it fail on you.
Comment: Thanks this is a great idea.  I will ask the seller about a bike-shop reinspection.  I told him im concern about that bottom crack and He keeps saying if i dont trust him i dont have to buy it.  Really bad sing lol ( why would i trust someone on craigslist)  If he desnt agree to a bike shop inspection then i will pass on it.
Answer: I personally have no experience with carbon fibre.  However there are carbon repair specialists who can tell you the damage.  Find one of these specialists locally, and ask the seller to get it checked.
You should share the results with seller, even if you paid for the testing youself.
On no account would I buy the bike and then get it tested.  Right now its the seller's property, but once cash has changed hands its yours, and previous owner is under no obligation to refund you should the test results be unsatisfactory.
Comment: Backing off is a better option than attempting to have a carbon-frame repaired, especially if the damage appears to be in this section of the frame. The damage is of the kind that suggests a frontal shock. The fork and the steerer may be damaged as well.
Comment: Thank you guys.  You have been very helpful.  I have decided to keep on looking.
Answer: I'm going to answer a question posed in the comments about how well the tap test works. Basically, you take a coin (or a really small mallet) and you tap gently around an area where there's suspected to be a structural flaw like an internal fracture. There may be a change in pitch around the flaw (for carbon bikes, that would typically be a something delamination, which is where two layers of carbon get separated because of an impact).
Unfortunately, it turns out that the tap test is generally unreliable on bikes, and on an area this small I wouldn't expect it to work at all. Raoul Luescher repairs carbon bikes and has extensive prior experience in aerospace composites. Per an article by Luescher, in aerospace, tap testing be used as a secondary method to test composite parts, but it works best on flat panels that are not laminated. Carbon fiber is a laminate (multiple sheets of carbon are suspended in resin and then baked at high temperature and pressure). Aircraft, it seems, often have large flat panels that have a metal or composite skin with some sort of honeycomb core, which are not laminated. The tap test is less reliable in laminated parts.
In addition, most of the surfaces on bikes are curved, like the suspected damaged areas in the photo were curved. My reading of Luescher is that curvature affects the pitch when you tap the area.
In sum, the aerospace industry mainly relies on ultrasonic scanning, especially for mission critical areas. We do not have the expertise or the equipment to conduct widespread ultrasonic inspections in the bike industry. The suggestion in one of the answers to take the fork out and look at the inside of the steerer tube was a good one. Unfortunately, this is one of the limitations of buying carbon bikes. Carbon is much stronger and more reliable than some people give it credit for - otherwise it would be unusable in the aerospace industry. Moreover, it's very repairable, although the repairer does need to know what they're doing (e.g. have equipment and experience in ultrasound scanning, be able to clean the damaged area sufficiently for the resin to bond, choose correct resin and fiber, etc). However, when we encounter surface defects like this, the uncertainty affects the resale value. It could be that most flaws like this are just paint scratches, and in fact I bet that most times they are, but neither the buyer, nor the seller, nor the average bike store has any way to verify that.
Comment: This might be better as a stand-alone question of "how well does the coin test work for detecting damage to carbon fibre frames?"


English speakers inserting R in French words

Question: I teach French to people from various background and first languages, but one thing that most English speakers do (even very proficient ones sometimes) is adding R sounds in words. Saying 'droi' for "doigt", 'par' for 'pas', 'mitroyen' for "mitoyen".
Other speakers don't do this at all. Any idea why this happens?
Comment: Many English dialects have a rounded /r/, which is sometimes reduced to /w/. Since initial /dr/ is common in English, while initial /dw/ is rare, _droi_ for _doigt_ may be a case of mishearing the French. To an English speaker, French /r/'s are very strange animals.
Comment: What sort of English do your English speakers speak? British? American? Irish?
Comment: When you say an 'r' sound, do you mean an English [ɻʷ] or a French [ʀ]? In two of your examples, note that you have a dental followed by [wa], of which [w] is a velarised consonant. If you're concentrating on correctly producing the foreign (and to many people quite difficult) velar/uvular trill [ʀ], the velar narrowing in [w] could perhaps end up getting so narrow that it becomes actual friction – but of course only if you're talking about the French r sound. As for _pas_, English doesn't have short [ɑ] and wouldn't allow short [a] in an open monosyllable, so [ɑː] would be closest.
Answer: This is conjecture, but it's conjecture that's too long to put into the comments.

Tl:dr
French /dʀw/ and /tʀw/ are likely to be analysed as /dw/ or /tw/ by English speakers. Because the realisations of /ʀ/ and  /w/ in such words are co-articulated and therefore overlap, they mimic what would be analysed as a single /w/ in English. Some English speakers will therefore replicate this pronunciation for all /dw/ and /tw/ sequences.

Full answer
Doigt and mitoyen
Firstly in a word like droit, there is nothing resembling what an English speaker would recognise as an (English) /r/, the sound [ɹ]. The French /ʀ/, often realised as [ʁ], is unusual enough  for English speakers to recognise it in those environments where we would have no comparable sound. However, the [ʁ]  in a word like droit is very similar to a sound that many English speakers sometimes encounter when they hear a word-initial /w/ in English, especially if this word is particularly stressed.
English /w/ is a co-articulated consonant. In other words, it involves two strictures (narrowing obstructions of the airflow through the vocal tract). The first is labial, caused by the narrowing and rounding of the lips. The second is velar, cause by the back of the tongue raising towards the velum.  In English, it is the labialisation of /w/ which is most prominent, because this stricture is the narrowest. In a language like Spanish, the velar stricture for Spanish /w/ is narrower. It would be fair to say that English speakers find their /w/ more like the vowel /u:/ and Spanish speakers their /w/ more like the velar consonant /g/. However, occasionally, when an English speaker hears an accented or stressed word beginning with /w/ they will hear frication caused by the back of the tongue getting very close to the velum and causing there to be frication, turbulence in the air stream. This is caused by the air from the lungs becoming disturbed as it is forced through the narrow space between the raised back of the tongue and the velum, the soft skin covering the back of the roof of the mouth. In other words the velar aspect of the /w/ will become much more prominent.
Why does this matter? Well, when an English speaker hears a word like droit, they don't hear the beginning of the word as /dʀwɑ/ but just as /dwɑ/. When we speak, our articulators, our mouths, are always preparing for the forthcoming sounds and the articulations necessary to produce them. A French speaker saying droigt will already be rounding and narrowing their lips during the production of the [d] in anticipation of the [w]. In other words the [d] will be labialised. This lip rounding will continue through the /ʀ/, or rather [ʁ], segment. At this point the co-articulation of the French /ʀ/ and the French /w/, will mimic a hyper-articulated English /w/. An English speaker will not recognise the frication as a separate phoneme.
My semi-educated guess (and that's what this is) is that an English speaker's phonological and phonetic brain, when they hear droit, interprets it as /dwɑ/ but detects what they feel to be a specially French articulation of the /w/. They then carry this pronunciation through to all /dwɑ/ sequences they encounter.
One may wonder why an English speaker would interpret a uvular fricative [ʁ] with that component of a hyper-articulated English /w/, the velar fricative [ɣ]. The reason is simply that English has no uvular sounds made at the very back of the mouth. So any fricative made at the back of the mouth counts as the same single type of noise for an English listener (there is no differentiation between velar and uvular sounds).

Pas
The case with pas is completely different. There are two possibilities that come to mind. The first is that French /ɑ/, [ɑ], is a sound which, in English is associated with words with an orthographic R. For rhotic speakers [those that pronounce English /r/, even when there is no following vowel], it may be that they include an /r/ there because it would be present in English. For non-rhotic speakers [those that only pronounce English /r/ when there is a following vowel], they may be inserting an /ʀ/ in the French word when the following word begins with a non-high vowel. This mimics what non-rhotic English speakers do in English with English /r/.
Comment: English doesn't permit /vw/ and /vr/? Perhaps not in inherited, lexical words, but loan words like _voyeur_ /vwɑˈjɜːr/ and onomatopoetic words like _vroom_ /vruːm/ definitely do have those clusters initially. And of course English definitely permits /dw/ and /tw/, so if speakers perceive French /Tʀw/ clusters as a sort of 'special' /Tw/ cluster, it's because they recognise them as different from their own /Tw/ clusters – but they should then still find it easy enough to distinguish these from French /Tw/ clusters, which are like the English ones.
Comment: @JanusBahsJacquet Point taken re *vroom* and *voyeur*, but I do think such cases are exceedingly rare, and as you point out are both exceptional in other ways. However, I don't agree with your second point there. These two pronunciations would be allophonic in English for English speakers [and hence the words *droit* and *doigt* would appear to be homophones]. The ones that are the same as the English ones won't stick out or sound particularly French for them and they'll pass unnoticed. However, the "French-sounding" ones will be more noticeable and  prominent. ...
Comment: @JanusBahsJacquet You conjecture English speakers should find it easy to tell French /tʀw/ clusters from /tw/ ones (and I believe that if you gave them minimal pairs, they'd be able to consistently pick up on which one had that particularly French sound). However, problem is that as evidenced by the question, (which I assume to be in good faith), they *don't* seem to be able to on their own. And then we'd need a better explanation of why. There almost definitely *is* a better or fuller explanation, including why they find *droit* and *doight* homophonesbut I'm stuffed if I can think of it ;-)


How to make meatball style food that keeps its shape

Question: How to preserve shape of meatballs and mince-meat shami kebabs? What ingredients help these items keep their shape? We tried chicpea flour, eggs but the bodies do not keep their shape but some chefs make it so solid that you can literally throw it to someone to catch and it will not loose its shape?
Comment: I am not an expert on this but the chance are you using a whole egg and a fatty mince. Fat shrink when deep fried. And egg white can get aerated. So when you deep they shrink. Only use egg yolk. I think flour is not the problem. Lastly, slam meat against the bowl so it remove all the air. And if you have vacuum sealer machine. Use it to remove the air. And let's see what happen
Comment: Chickpea flour might be too fine to do what you're trying to do.  Breadcrumbs (thickener) and eggs (binding agent) should be fine for most applications of this type.  It's common in American meatloaf, for instance.
Comment: I shape them first, then nuke until about 3/4 done. They stay stable and round since they're not stirred in the microwave. Finish in a regular fry pan. -An egg, regular flour is enough.
Answer: Overworking the meat is generally what you want to avoid for a burger, but in the case of kebab meat it may help. It will give it a denser and bouncier texture.
To do this, when mixing in the other ingredients, just mix for a bit longer than you normally would, especially with your hands as the heat will probably melt the fat slightly and help to bind it. Keep working it until the texture is smooth.
Answer: For meatballs, you can take 1/2 to 1/3 of the meat and process it in a food processor to make it almost gluey. Mix this with the flavourings/herbs and process again if you want the meat to homogenized or keep the herbs with the unprocessed part if you want chunky herbs. It also gives the meat a springier texture. You can achieve the same effect by working the meat with your hands by mashing and rubbing vigorously as the other answer and comment said.
Shami Kababs are traditionally made with boneless beef. The chunkier/thready texture of meat helps the kabab hold their shape. Ground beef mince is also used instead if you like it mild. To achieve a balance, you can use half meat cubes and half ground mince.
The trick to a good shami kabab is not just in choosing meat with enough fat to keep it juicy and moist but also in the proportion of chana daal cooked with the mince to hold it together, ideally 1kg meat and 250g daal. More the chana daal, softer the texture will be.
It's very important to cook the mixture of meat and daal until all the water has completely and absolutely evaporated out of the mixture before you take it off the heat. If the mixture is too wet, the kebabs will not hold their shape and will disintegrate while frying.
Adding an egg in the cooked mixture (of meat, chana daal, spices and herbs) and mixing it in with your hand also helps to retain the shape. You can also place the shaped kababs on a flat tray/platter and put them in the freezer for some time to settle. This will help them hold their shape while frying.
If the shami kebab mixture is a bit too sticky or loose and feels difficult to hold together while shaping or frying, as a last resort you can add 1-2 tbsp of roasted gramflour to the mixture but that's not recommended as it interfers with the authentic taste of shami kababs.
Dip the shami kabab in whisked egg and shallow fry using minimal oil. This gives them a nice golden crust preventing any disintegration.
Answer: Kneading salt into the meat should denature some proteins to make it more sticky. This can result in a heavy product, as you have alluded to.
(I will add a link, a laboratory exercise from a Southern USA university about food science and meat preservation, if I can find it)
То lighten the product it is typical in western cooking to add breadcrumbs, but as these decrease the strength, eggs are often added to compensate.


How did Python implement the built-in function pow()?

Question: I have to write a program to calculate a**b % c where b and c are both very large numbers. If I just use a**b % c, it's really slow. Then I found that the built-in function pow() can do this really fast by calling pow(a, b, c).
 I'm curious to know how does Python implement this? Or where could I find the source code file that implement this function?
Comment: The cpython source repo is at http://hg.python.org/cpython/
Comment: ...under _Objects/longobject.c:long_pow()_ (as JimB had already commented).
Answer: If a, b and c are integers, the implementation can be made more efficient by binary exponentiation and reducing modulo c in each step, including the first one (i.e. reducing a modulo c before you even start).  This is what the implementation of long_pow() does indeed. The function has over two hundred lines of code, as it has to deal with reference counting, and it handles negative exponents and a whole bunch of special cases.
At its core, the idea of the algorithm is rather simple, though. Let's say we want to compute a ** b for positive integers a and b, and b has the binary digits b_i. Then we can write b as
b = b_0 + b1 * 2 + b2 * 2**2 + ... + b_k ** 2**k

ans a ** b as
a ** b = a**b0 * (a**2)**b1 * (a**2**2)**b2 * ... * (a**2**k)**b_k

Each factor in this product is of the form (a**2**i)**b_i. If b_i is zero, we can simply omit the factor. If b_i is 1, the factor is equal to a**2**i, and these powers can be computed for all i by repeatedly squaring a. Overall, we need to square and multiply k times, where k is the number of binary digits of b.
As mentioned above, for pow(a, b, c) we can reduce modulo c in each step, both after squaring and after multiplying.
Comment: @BenSandler: Because _a_ ≡ _a'_ (mod _c_) and _b_ ≡ _b'_ (mod _c_) imply _ab_ ≡ _a'b'_ (mod _c_), or in other words, it doesn't matter whether you first reduce _a_ and _b_ modulo _c_ and then multiply them, or multiply them first and then reduce modulo _c_.  See [the Wikipedia article on modular arithmetic](https://en.wikipedia.org/wiki/Modular_arithmetic#Integers_modulo_n).
Comment: Why can we reduce by modulo c in each step?
Comment: @JohanC I've updated the link to include the commit hash, so it doesn't get out of date anymore.
Comment: Note that `long_pow` is now defined at another line in that file: https://github.com/python/cpython/blob/master/Objects/longobject.c#L4246
Answer: You might consider the following two implementations for computing (x ** y) % z quickly.
In Python:
def pow_mod(x, y, z):
    "Calculate (x ** y) % z efficiently."
    number = 1
    while y:
        if y & 1:
            number = number * x % z
        y >>= 1
        x = x * x % z
    return number

In C:
#include <stdio.h>

unsigned long pow_mod(unsigned short x, unsigned long y, unsigned short z)
{
    unsigned long number = 1;
    while (y)
    {
        if (y & 1)
            number = number * x % z;
        y >>= 1;
        x = (unsigned long)x * x % z;
    }
    return number;
}

int main()
{
    printf("%d\n", pow_mod(63437, 3935969939, 20628));
    return 0;
}

Comment: @Fabiano My function is not supposed to be used. It is simply an explanation of how Python works behinds the scenes without referring to its source in C. I was trying to answer **wong2's** question about how `pow` was implimented.
Comment: Can anyone explain why this solution works? I am having trouble understanding the logic behind this algorithm.
Comment: @NoctisSkytower, what would be the benefit of this considering the native python `pow()` builtin function supports this as well and seems faster?
`>>> st_pow = 'pow(65537L, 767587L, 14971787L)
>>> st_pow_mod = 'pow_mod(65537L, 767587L, 14971787L)'
>>> timeit.timeit(st_pow)
4.510787010192871
>>> timeit.timeit(st_pow_mod, def_pow_mod)
10.135776996612549`
Comment: @Noctis, I tried running your Python implementation and got this:TypeError: ufunc 'bitwise_and' not supported for the input types, and the inputs could not be safely coerced to any supported types according to the casting rule ''safe''  ---- As I'm learning Python right now, I thought you might have an idea about this error (a search suggests it might be a bug but I'm thinking that there's a quick workaround)
Comment: @stackuser: It appears to be working fine in the following demonstration: http://ideone.com/sYzqZN
Answer: I don't know about python, but if you need fast powers, you can use exponentiation by squaring:
http://en.wikipedia.org/wiki/Exponentiation_by_squaring
It's a simple recursive method that uses the commutative property of exponents.
Answer: Python uses C math libraries for general cases and its own logic for some of its concepts (such as infinity).
Answer: Line 1426 of this file shows the Python code that implements math.pow, but basically it boils down to it calling the standard C library which probably has a highly optimized version of that function.
Python can be quite slow for intensive number-crunching, but Psyco can give you a quite speed boost, it won't be as good as C code calling the standard library though.
Comment: `math.pow()` does't have the modulo argument, and isn't the same function as the builtin `pow()`. Also FYI, Psyco is getting pretty stale, and no 64-bit support. NumPy is great for serious math.
Answer: Implement pow(x,n) in Python
def myPow(x, n):
        p = 1
        if n<0:
            x = 1/x
            n = abs(n)

        # Exponentiation by Squaring

        while n:
            if n%2:
                p*= x
            x*=x
            n//=2
        return p

Implement pow(x,n,m) in Python
def myPow(x,n,m):
            p = 1
            if n<0:
                x = 1/x
                n = abs(n)
            while n:
                if n%2:
                    p*= x%m
                x*=x%m
                n//=2
            return p

Checkout this link for explanation


What are the records for highest 1 year span performance rating?

Question: I've heard that Bobby Fischer had a 2892 performance in 1971. If this is true, it's probably the highest performance, but I don't know if this is true. Does anyone have any information about this?
Answer: Given Carlsen's 2882 current rating and the fact that he also reached this rating in 2014, it seems likely that at some point he had a year with a performance rating higher than your 2892 figure. (I calculated Carlsen's 2013 performance rating as 2890 [47 points in 69 games against an average opponent of 2757] but it's tedious enough to calculate that I don't want to do it for every year.)
However, if you use current FIDE rules on how to calculate performance rating, Fischer's performance rating in 1971 was even higher than the number you specified.
In 1971, Fischer participated in three official matches that I know of:
Fischer - Taimanov Candidates Quarterfinal
Fischer - Larsen Candidates Semifinal
Fischer - Petrosian Candidates Final
(He also played some blitz and simul games, but I assume those don't count.)
Taimanov was rated 2620, Larsen was rated 2660, and Petrosian was rated 2640 at the times of the matches. Fischer scored 6/6 in the first two matches and 6.5/9 in the third, for a total of 18.5/21 and an average opponent rating of 2640.
18.5/21 corresponds to a fractional score of 0.88. According to FIDE regulations, this in turn means that the performance rating is 336 points higher than the opponent's average rating. 2640 + 336 = 2976 performance rating.
It's hard to say whether that's the highest ever, but it very well might not be, even setting aside powerhouses like Carlsen. Since a 100% score results in a performance rating 800 points above the average opponent, anyone whose record for a particular year consisted solely of a 100% match score against a 2200 player would have a performance rating of 3000. I'm guessing that has happened to someone at least once.
Answer:
I've heard that Bobby Fischer had a 2892 performance in 1971. If this
  is true, it's probably the highest performance, but I don't know if
  this is true. Does anyone have any information about this?

According to the Olimpbase site FIDE produced 2 rating lists covering 1971, one in July 1971 covering January 1971 through June 1971 and one in July 1972 covering July 1971 through June 1972.
According to this his ratings over this period were -
(Unofficial) January 1971 list - 2740
July 1971 list - 2760
July 1972 list - 2785
As you can see 2785 was the highest his rating ever reached. He was never anywhere near 2892.
Comment: Rating is not the same as performance rating, though. I had a performance rating of 2041 in one tournament even though my rating has never been more than 1800.


In IDA, why are the addresses of instructions different from the corresponding locations in the original file? How do I find the file locations?

Question: I noticed that if I found an instruction in IDA, the address shown to its left would be wildly different from where it appears in the actual file. I wanted to know why this was the case and how I can find the offset in the file that each instruction corresponds to. Thanks!
Comment: Did you expect that a file is loaded *unmodified* into memory? Starting at address #0? It has not been that way since ... well, even though mid-1980's COM files under DOS *were* loaded and executed unmodified, they *still* could not load at address #0 -- it would overwrite the system!
Comment: @usr2564301 Well... I honestly didn't expect the disassembler would handle relocating the code, but it makes sense that it does. I'm fairly new to RE so forgive me for my naivety. I would still like to find out what parts of the static file the disassembly corresponds to. Is there a way to do that in IDA?
Comment: IDA by default tries to load a PE at the preferred load address as supplied in the PE header. But even if you force it to relocate to `0` (I wonder if it allows that), then the code would still not correspond to the file. Whole sections may not load at all, be discarded, or moved to another address.
Answer: The file offset of the current location is displayed in the disassembly (IDA View) status bar together with the address.
Comment: When opening a binary, does IDA load it to the same place within the Ida process and then just show you the address that you've selected to load the segments as if it's at that address. I cannot see any allocation within ida64.exe at the address that IDA claims the binary is at
Answer: IDA is displaying the Relative Virtual Address based on the base address of the binary (or on that you supply before loading the binary). The reason this is different from the actual address is because it is mapped into memory. The Relative Virtual Address (RVA) is BaseAddress + Offset, if you find the offset address and add it to your at rest binary base address you will find the same point within the binary.
Answer: Igor gave the answer for Ida. A more general possibility, very simple and working everywhere, would be just to write down a sequence of immutable bytes from the disassembler (i.e. avoiding changing addresses), then load the file into a Hex Editor and let it search for that sequence. If it is long enough there will mostly be only a single hit within the file.


Does an increase in inlet temperature affect fuel flow and power output?

Question: The fuel flow rate decreases as the inlet temperature of the air entering the engine increases. Will the engine produce same amount of power as when the fuel flow was higher?
Comment: Are you sure the fuel flow rate *always* decreases as the inlet temperature increases, and why? PS. Is this from a quiz, and which one?
Answer: Most civil aircraft engines are "flat rated". See What is a flat rated engine?

That means, the thrust (power) produced is constant (flat), as ambient temperature increase, up to a certain temperature, and then the turbine inlet temperature limit is reached, and fuel flow and thrust is reduced as the ambient temperature continues to increase.
So, thrust is initially constant as inlet temperature increases, then decreases. It's a bit harder to predict what fuel flow will need to do to achieve this behaviour. It will certainly reduce in the temperature range where thrust is reducing, but in the cooler temperatures before that, it is probably increasing to keep thrust constant. As the chart shows, in this region EGT and N1 rpm are increasing. I expect fuel flow is probably showing the same behaviour as N1.
Thrust cannot actually be measured in flight, so most engines use either N1 rpm, or engine pressure ratio, (turbine exit perssure/engine inlet pressure) as a way to predict thrust. GE typically uses N1, whereas Pratt & Whitney and Rolls Royce usually use EPR. Using EPR is technically better, beacuse it will account for engine deterioration, where as using N1 assumes the fan mass flow remains the same for a given rpm as the engine degrades. But EPR requires 2 pressure measurements, which are less reliable, so most engines that use EPR have N1 control as a backup mode.  See
What is the difference between EPR and rotor speed as thrust setting parameter?


Where does Lightroom keep changes?

Question: I've imported some raw images from camera and made changes. When I close and reopen LR I can still see the changes, but my original important RAW file is intact. So I'm curious, where/how LR keeps my changes on top of RAW file? Can I make my changes on imported RAW file? Say want to crop imported file and keep just cropped version.
Answer: Lightroom does not make changes to the original file. It stores the actions of each edit in the LR catalog. When you Export an image to, say a JPEG, LR performs each of those actions, creating a new file, in this case a JPEG. It never alters the original.  The RAW file isnt really an image, but data that was recorded by the sensor. You see an image in preview because the RAW file actually stores a small JPEG preview image within the file. So 'cropping' the RAW isn't meaningful. You instead use the RAW data to create an image that you can crop as your final output. The output can be JPEG, TIFF, PSD, DNG, etc.
The catalog location can be found by looking under Catalog Settings.
You can also ask Lightroom to store these same edit actions in a 'sidecar' file, which will be stored alongside (in the same directory) of your RAW image, by selecting "Automatically write changes to XMP" in the Metadata tab of Catalog settings.
Comment: @Michael: "Thus by having sidecar file I can migrate to another PC and have the same action history for each RAW file?" - no, the XMP file only stores the current settings for the file, not the complete history (i.e. as seen in the History panel in Lightroom). The history is stored in the catalog, regardless of whether you use sidecar files or not.
Comment: "It never alters the original." is not fully true - there are exceptions. When you change the capture time then LR writes new time directly into original file, even into RAW file. JPEG's get also modified directly(i.e. the Exif data) , for example with keyword, caption, title, etc.
Comment: Thus by having sidecar file I can migrate to another PC and have the same action history for each RAW file?
Comment: Theoretically yes. However, there are not many programs that can consume this XMP data, even though it is standardized.  You can do this within LR of course, but I find exporting the images and their catalog simpler (a function in LR)
Comment: I mean only LR of course and for the situations when I want to backup my image corrections. Say I dropped my Macbook accidentally from window but having sidecar and raw will give my efforts back.
Comment: Backup in 3s my friend, that includes your RAWs and your LR catalog. [3 copies: 1 ea two different media, 1 stored offsite]
Comment: @Mark: yes, I understand that backing up catalog file will keep me safe.

Where does Lightroom keep changes?


TekPub Feedback

Question: Following on from a previous thread that had a link to TekPub, I have just had a quick look and I think it looks pretty impressive.  Are any of you guys subscribers and if so would you recommend it?  I am mainly interested in general software design and, as a language, C# and it's features.  Is there much content posted on a regular basis along these lines to warrant the outlay?
Answer: Yes, I would get it.  For the small amount of money a month that it costs, you really can't beat what's on there. They have top notch people making the videos, and there is a load of content.  What's nice is that

They add new content (they just add Mastering C# by Jon Skeet).
If at some point in time you don't get any more value, you can always cancel.

We use it where I work to get people to pick up things they need to learn (we have several people who are just starting out on C# etc.).  It honestly makes my life a lot easier, because I can have them watch it instead of creating presentations to teach them things they need to know.  This sounds lazy, but I can honestly say from experience that it takes a lot of time to create a presentation to show a topic which gets people to understand concepts like programming.
This isn't also just for beginning people, they have a number of more advanced topics as well (multithreading etc.).
Answer: You don't have to get a recurring subscription if you're not satisfied with the amount of new material produced. You can always purchase the productions you are interested in individually.
Answer: They go to great lengths to ensure customers are satisfied with the content. If you don't like the content, you can tell them at any time and they will give you a refund.
I was a monthly subscriber for about 6 months, then upgraded to a yearly subscription b/c it's really worth it. The content is good, fresh, and new stuff is coming out on a regular basis. Plus, every single episode is done by well-known experts of the topic. I can't think of many other training sites where I recognize almost every video author's name (except maybe Pluralsight).
Answer: I subscribe to TekPub. I like it very much as I travel a lot, and carrying books is heavy and is expensive. Having access to videos to watch/download is super awesome. I totally recommend them.
The quality of the videos have been pretty good. I've gone through Git, Rails 3, and started a few others recently. They come out with new series and/or add to an existing one almost every month. You can follow them on twitter too at: @tekpub to follow updates almost in real time.
Other services you may want to look at are:

PeepCode (their library of videos is bigger than TekPub's)
ontwik (they do push out quite a few videos a month)

TekPub Feedback


Does a current originates a magnetic force against itself?

Question: If electric current creates a magnetic field, and if magnetic field exerts a force in charged particles in movement, is that correct that when a current (in a coil, or something) creates magnetic field, there is also a force against the coil?
Comment: This is how inductors work.
Answer: Yes, the magnetic field produced by a coil does exert forces on the coil.
Every element of the coil exerts a force on every other element which is not perpendicular to it. It exerts a repulsive force on parallel elements in which the current is flowing in the opposite direction. And it exerts an attractive force on elements in other loops of the coil which are adjacent and parallel to it, in which the current is flowing in the same direction. These are just the familiar forces between parallel/anti-parallel current-carrying wires.
There are also forces of intermediate value between elements which are inclined at different angles other than parallel or perpendicular.
As a result there is a resultant outward force on the coil, tending to increase its area, and at the same time a contracting force between adjacent loops, tending to shorten the length of a solenoid.
However, no element of the wire exerts a magnetic force on itself.
Answer: You can think of a magnetic field as an electric field from a different frame of reference (thanks to the help of special relativity).
This video explains it well.
So it all depends on the situation and of the frame of reference. This might give further info.
Hope this helps.
Answer: For a really simple example of a circuit exerting a force on one of it's elements, it's worth nothing that this idea is the principle behind a railgun:
https://en.wikipedia.org/wiki/Railgun


Create Lead using DeveloperForce toolkit for .Net

Question: I am wondering how to use toolkit for .net to create new leads, because most examples I can find on the net are created using wsdl. I want to know what do I need to do before defining lead, hot to define it and how to update it on application.
Answer: There are examples of creating records using the Force.com Toolkit for .NET in Nothing But .Net – Implementing CRUD Operations.
You will want something like:
<code>public class Lead {
    public string Id { get; set; }
    public string LastName { get; set; }
    public string Company { get; set; }
}

// ...

// Get the client based on your chosen authentication method
ForceClient client = new ForceClient(instanceUrl, accessToken, apiVersion);

Lead lead = new Lead() { LastName = "Doe", Company = "Acme" };

string newLeadId = await client.CreateAsync("Lead", lead);
</code>
Comment: I am using auth.UsernamePasswordAsync(_consumerKey, _consumerSecret, _username, _password + _securityToken).Wait(); to authenticate, but it crashes saying it has issue with mscorlib.dll, do you have any suggestons?
Comment: @Vilius I'd suggest raising a new question with sample code the reproduces the issue. Ideally you should be using the `await` keyword rather than `.Wait()`


Why did the pound sterling lose its reserve status to USD?

Question: Why did the pound sterling lose it reserve status to USD? Was this due to some agreement during the Bretton Woods negotiations?
Comment: This is a big question, depending on how one interprets "why". The mechanical reason was that the UK's gold reserves were emptied during WWII. The Bretton Woods system made the USD the reserve currency to reflect the fact that the US had most of the world's monetary gold. Beyond that, the explanation is a book-length history. It would help if you clarify how narrow you want the question to be.
Answer: As written, this question has an extremely wide scope, and an answer would be the length of a book. I will attempt a narrow answer.
People use "reserve currency" at present in a very loose manner. In the context of this question, it had a very specific meaning. Currencies were pegged, ultimately to gold. Currencies that had inadequate gold reserves used "strong" gold-backed currencies as extra backing for their pegs. Hence, the strong currencies were used as reserves.
Britain lost almost all of its gold reserves in World War II, in order to finance the war effort. (The process started earlier, with large losses in World War I.) Without adequate gold reserves of its own, the pound was not a credible backing for another country's gold peg. Hence, it lost reserve status.
The Bretton Woods agreement enshrined the financial reality of the post-war system: the U.S. has accumulated almost all of the official gold reserves as a result of supplying the warring countries. The system was set so that the US dollar was gold-backed, and other currencies were backed by the USD.
Anything beyond this outline turns into a financial history of 1910-1950, for which there are many choices.


KVM graphical tools and employment

Question: I saw a job classified asking for a Linux admin who could administer KVM based vm's.  I can do so if I use virt-manager or some form of graphical tool, but I'm not really familiar with all of the command line material.  I also cant really find a good tutorial on it, as most sites say to use the graphical stuff.  My question is, for a position like this is my understanding satisfactory to apply?
Answer: The newer versions of virt-manager are pretty decent but it still doesn't expose all the options and control that the underlying system has.  At this point it's pretty usable for the most common operations though.  In addition to the extra options that are exposed at the command line it also lends itself to better automation and scripting.
If you want to learn about the command line options then read the following man pages.

kvm or qemu these normally point to the same manpage.
virsh

To explore virsh you can also type virsh to start a shell and then type help.
Also keep in mind that managing KVM is more than just knowing KVM.  You also need to have a good bit of networking and storage skills.  It could also involve setting up and configuring the virtual machines as well.
If the position is a Junior position I would go for it.  Nothing to lose by trying.
Answer: For the sake of having a job and also a place to learn through experience, yes apply for the job. If you get to the interview stage you could always tell them that you have knowledge of managing it through virt-manager and you prefer to use that to the command line tools. For all you know, maybe just knowing that libvirt exists is enough to put you ahead of the rest.
However, for the completeness of your knowledge, you should really learn how to do it via the command line interface. For all you know, you may some day need to write an application wrapper or library service to do things that the GUI tools may not be able to handle completely.
Moreover, you will actually learn more about computers and networking in general if you are forced to do things without relying on the magic of GUI tools and wizards. In fact, you may start to understand why virt-manager has those options that it has.
Answer: even if you always use a front-end, if you can't handle the tool itself, it doesn't count as 'administer' in my book.
Answer: libvirt is just one option. Besides the commercially supported RHEV, there are quite a few additional management platforms, ways of clustering, storage and everything else.
Administering virtualization means you have to know about clustering, load balancing, server and storage hardware management, networking and quite possibly several OS types.
virt-manager only is a drop in the ocean :)

KVM graphical tools and employment