What star would cause a planet to have white plants?

Question: Okay, I'm trying to make a planet that has at least part of its surface, or at least part of its underground, habitable for humans (breathable atmosphere at a suitable pressure, a suitable level of gravity and radiation, and a suitable temperature). The plants here are white in color. What kind of star(s) will it need to orbit, in order for white plants to evolve there?
Comment: There are [white plants](https://www.google.com/search?q=white+plant&tbm=isch) and [white flowers](https://www.google.com/search?q=white+flowers&tbm=isch) on Earth. Could you elaborate on how your plants would be different?
Comment: "White" is a human concept, it's basically "all the light frequencies we've evolved to see". So the question isn't really what would cause plants to be white, it's "what would cause plants and people to co-evolve so the latter don't see any of the frequencies plants use to power their photosynthesis"
Answer: As @L.Dutch pointed out in his answer, white is not a single wavelength, but a mixture of all the colours in the spectrum of visible light.
However there is a way you can get white, or atleast, very pale plants. A plant, as pointed out, absorbs most of the light that falls on it (excluding the green part of the spectrum). However, if by chance, you managed to make the parent star extremely bright, then the plant would have to reflect off most of the sunlight, so as to prevent it from getting damaged. There is even a real life example of this. Earth plants have been known to turn pale and die upon exposure to too much sunlight. So, if you had a star that was extremely bright, then that would cause your evolving plants to be very pale, almost white and form an analogue to chlorophyll for energy harvesting.
However there is a massive drawback to this. Really bright stars, especially above F-type spectral class stars, have a nasty reputation for releasing a b***load of UV-rays. (Let's ignore UV flares from smaller stars like M-type and K-type stars for now, these are only rare events). So the planet's water would have been already have been disintegrated into hydrogen and oxygen and blown away before you even got simple bacterial life. I do not know for how bright would it have for your plants to be really pale, so as to reflect nearly all starlight that falls on it, but a certain-something tells me that you would need something like a A-type star for your plants to appear pale.
Even if you managed to keep the water to the surface (thanks to ozone shenanigans blah-blah), you would face a big problem. Life is rather slow, like hella lot slow. It took nearly 3 billion-something for life to evolve from simple bacteria to walking bald apes who waste life making memes- no, we are getting off-topic.
Anyways, the point is the same. Since our Sun is a long-lived star (As of 5th May 2023, it has about 7 billion years before it goes on steroids and expands into a red giant), life has a ton of time to spend to grow. But, boy, if you want white plants, then you have got only a trickle of time left (Ranging from a few million years to nearly just 1 billion years), because you need a bright star, and well, bright stars' lives aren't, well, very "bright". So you have got very little time for your white plants to quickly evolve.
So, although you can get "white" plants, the possibility of getting them is very, very low. Your star will go supernova in just a few million years (Yes, a "supernova"), and life has got only that much time to quickly evolve into "white" plants. So, no white plants for you :(
Comment: Can "very bright" not simply be replaced by "closer to the planet", removing the drawbacks about short life and UV?
Comment: The other option is to go the other direction: a red dwarf puts out most of its energy in the infrared.  Since there isn't much selective pressure driving plants to absorb in the visible spectrum, you could get white plants entirely as an accidental side effect of optimizing for infrared absorption.
Comment: That's exactly what I'm thinking.
Comment: Leafs actually absorb most green light. They just absorb *even more* red and blue light. See here (note this goes into the infrared): https://link.springer.com/chapter/10.1007/978-3-030-33157-3_14.
This does not include transmittance but transmitted light can be absorbed by other leaves.
Comment: @wimi: look at Venus for example for what closer to the planet might do to planets.
Comment: @infinitezero If Venus had a smaller core, then it could have a weaker EM field, lose  atmosphere faster to solar wind and as a consequence be a cooler, more Earth like world despite more sunlight.
Comment: Don't forget that a more massive planet, at least 6G at the surface, could hold on to it's atmosphere even with the UV light.
Comment: Yellow stars produce the most light in the visible spectrum for how much energy they transfer.  So, this answer would actually work a lot better if you stuck with a yellow sun, but placed the planet closer to the star than Earth.  An F-type star could burn up all life on a planet with UV rays, even at ranges where the RGB light is less intense than it is on Earth.
Answer: None. White is not the color of a single wavelength. It's just the impression of all the perceived frequencies at the same time.
A white plant would absorb very little light, which is what a plant needs to be a plant.
Comment: The visible spectrum is a tiny tiny piece of the entire electromagnetic spectrum. Being white would only mean that it could absorb little light from that tiny slice of wavelengths. That would matter little to a plant that absorbed light from the ultraviolet, infrared, or any of the many other frequency bands that aren't visible.
Comment: Mostly true. A star that provided a great deal of light might require the plants to develop highly reflective coloration in order to avoid chromosomal damage. This would also probably result in a planet that was too hot for water, but maybe the planet had a naturally high albedo for other reasons? Planet of chalk?
Comment: This seems convincing but it's not true. You can get white from just blue and yellow. The plants could be absorbing everything else.
Comment: That makes a lot of sense.
Comment: It could also be a response to a change in the planets atmosphere, or a flare heavy star.
Comment: Your second phrase is true for most colors in daily life: Most colors are not the color of a single wavelength. Pure/spectral colors are the exception, not the rule. This is important, e.g. because a pure red light would not illuminate a pure brown wall.
Comment: From Wikipedia on the color White: "Many of the light sources that emit white light emit light at almost all visible wavelengths... [which] has led to the notion that white light can be defined as a mixture of "all colors" or "all visible wavelengths". This widespread idea is a misconception, and might originally stem from the fact that Newton discovered that sunlight is composed of light with wavelengths across the visible spectrum. Concluding that since "all colors" produce white light then white must be made up of "all colors" is a common logical error."
Answer: A Red or Brown Dwarf
Red and Brown dwarfs produce very little light in the visible spectrum meaning that plants would get most of thier energy from infrared light.  Since visible light is not a major factor, plants don't really have a reason to specialize in the visible spectrum.  That said, low exposure to visible light can also lead to a low resistance to it. Just like Earth life has a limited resistance to UV and greater, your world's sensitivity to short wavelength EM radiation may start in the visible spectrum.
So plants, especially those that live in the brighter parts of the world, will evolve to reflect harmful RGB radiation making white a dominant color on your world.
Also of note: Red and Brown Dwarfs are very long lived, stable stars.  As a general rule of thumb, you don't really want a star bigger than a Type F Main Sequence star if you want to give life any chance of evolving into anything plant life.
Comment: @fluffysheap Technically, Dwarves also emit light that is mostly in the infrared spectrum...
Comment: @FuriousArcturus You are assuming an orbit of 1 AU.  A closer to star orbit could still receive the exact same amount of total EM energy as a plant on Earth, but very little of that radiation would be in the visible light spectrum by comparison.  A primary producer will generally make chemicals to target the sweet spot of where the energy of a wavelength corresponds to its predominance in the spectrum.  If plants need to make a separate chemical just to capture a tiny bit of visible light, then it's a waste of resources
Comment: Dwarves are little men with beards.  Dwarfs is the right term for stars.
Comment: Wrong. the answer is quite the opposite. A plant growing on a planet orbiting a red dwarf would be completely dark, as they would have to absorb as much light as possible.
This answer is in all aspects totally inaccurate, and the fact that this inaccurate answer was accepted kinda makes me deeply disturbed.
Answer: I'm interpreting your question to be equivalent to "what kind of light would cause white plants to evolve on a planet?" I make this distinction from that of the star because my understanding is that this is mostly a question of the atmosphere—most stars produce light across a very broad range of the electromagnetic spectrum, but atmospheres absorb pieces of the spectrum. Our atmosphere absorbs most light outside the visible spectrum and so (one can hypothesize that) plants on our planet have evolved to use light in the visible spectrum for photosynthesis.
White plants would reflect light across the visible spectrum. This is a very small fraction of the total electromagnetic spectrum, so that shouldn't necessarily matter as long as there is enough usable light for photosynthesis outside of the visible spectrum. If the planet's atmosphere absorbs most visible light and lets pass a substantial amount of light outside the visible spectrum, then (one can hypothesize that) anything photosynthetic that were to evolve would be likely to use non-visible light for photosynthesis while reflecting visible light. This all requires hypothesizing that a photosynthetic mechanism could evolve that uses non-visible light; for what it's worth, I do not personally find this to be a very big leap for a science fiction world.
Unfortunately, I don't have the expertise to tell you precisely what gases (or gas plus particulate) are needed to block visible light while letting pass other parts of the electromagnetic spectrum, but whatever the atmosphere was made of, it would almost certainly look black on account of its absorbing visible light.
Comment: This is along the lines of what I was thinking.  White is simply stimulating all the receptors pretty much equally, In fact, since our plants generally reflect Green, all you'd have to do is get them to reflect Red and Blue for us to see it as white.  Perhaps a dim star and the planet's atmosphere combine to put the most energy in the infrared part of the spectrum and plants are not interested in most of the visible spectrum because it is too low-energy.
Answer: A plant on earth converts CO2 and H20 + sunlight to food.
The earths atmosphere blocks much of the energy that is outside of the visible spectrum (ozone < 300nm, H20 and C02 > 750 nm).
Ozone doesn't block radiation < 200nm, ultraviolet.  So a star that emits a lot of ultraviolet (bluer) that had plant life that evolved to use ultraviolet for photosynthesis could conceivably produce plants that are white to us.
Answer: It isn't the star, but biology. You should be able to achieve purely white plants with our sun.
Chlorophyl is green, absorbing both blue and red while reflecting green, giving that color to plants. Yes, plants are throwing the most abundant light away for some reason - I have no idea why. Getting white color requires reflecting at least two wavelengths - check CIE color chart and drag any line that goes through the white spot and those are the two wavelengths you require.
For example, your plants reflect blue/violet and yellow. They would want to get rid of blue and lower to limit UV damage (perhaps there is little to no ozone?); reflecting yellow for those white plants and green of our plants seems about the same (= I have no idea why, but ...)
Note that while light reflected off plants looks white, anything illuminated by it will look weird. Say green stuff will look kind of grey, red stuff will look grey and similar. Perhaps that is desirable.
Comment: Chlorophyl does not so much "reflect" green as it just absorbs red and blue better.  Chlorophyl still absorbs up to 80% of green light, but its better efficiency in the high and low ranges make it look green.  As for why the importance of green is neglected, most of the total energy from the sun comes from infrared and red light; however, shortwave light plays an import part in the production of resin and root growth apart from any benefit it may have for energy production.  In otherwards, green absorption is slightly  neglected because Red and Blue are more important.
Answer: As mentioned in other answers and comments, greater sunlight intensity could result in plants developing pale colorations to protect themselves from excessive light. Brighter stars are an unlikely mechanism due to their short lifetimes, but a closer orbit will have the same effect, and a close binary would allow you to double the luminosity without shortening the lifespan of the stars. However it's achieved, it would need to be a pretty fine-tuned system to produce pale colored plants but not just overheat the planet beyond being capable of supporting complex life.
One thing that helps: the stress of excessive sunlight will be stronger toward the equator. There might be more colorful life toward the poles, "bleached" varieties being able to spread closer to the equator. Or there might be a strong axial tilt, with the "bleached" varieties being able to grow further into the hot season, and winter life perhaps being more colorful.
Also, yellow stars become more luminous as they age, swelling into red giants. A very old system might have a much brighter star, the plant life having had plenty of time to adapt to the increasing luminosity, and the light-colored plant life might actually be the only thing keeping the planet cool enough to support life.
Answer: Probably: any.
It is a misconception that Earth plants are green.  They come in red, green, and brown.
It is really just a matter of what energy process or processes evolve in the plants.  So it is all a matter of luck.
Answer: As so far everyone has mentioned, earth based plants are mostly green because there has been evolutionary pressure that lead to green being a dominant color. For earth this is mostly due to the spectrum of light (a lot of orange and red) but there are other colors in plants and these plants have survived the evolutionary pressure, so they are possible.
What if there is another source of pressure that made these plants white? What if there is a reason that the other colors no longer exist?
Maybe there was a plant-based disease that killed all non-white plants? Perhaps there was a mass extinction event that made all plant-eaters that saw color disappear and white plants are (or were) harder to see? Maybe white offered better camouflage for pollinators? Maybe there was a science experiment gone wrong by a (previous) intelligent inhabitant that made white the dominant plant color? Or the previous inhabitant had religious reasons to strongly prefer white plants and remove all others?


My cars wheel makes kla klak when driving 60 to 80 kms per hour,but the outer cv and wheel bearing is changed

Question: inside of wheel not sure if this could be the problem
Comment: What is the year/make/model/engine of the car in question?
Answer: That link circled is part of the steering system.  Its a link that connects the steering rack to the outer hub.  That should be tight with absolutely no free play. It's a part of the system that steers your car when you turn your steering wheel.  The part you've circled is called the "outer tie rod end" in the image below.  Note, if your outer tie rod is loose, its a major safety issue.  Do NOT drive the car until it's fixed.

With that said, my guess is somebody did some maintenance on your car and forgot to re-install the stabilizer/sway bar links.  If they are just hanging free, you will definitely hear a irregular rattle noise at different vehicle speeds.  Terminology Note: Sway bar = Stabilizer Bar = Stabar  The stabilizer bar helps drive performance by reducing the body roll of a vehicle during fast cornering or over road irregularities.
Typically the sway bar has short links to connect between the lower control arm and the front struts.  In the image below, the sway bar link is the dog bone shaped thing on the right.

I'm guessing yours isn't correctly attached at both ends, or its loose..  Looking at your photo, the sway bar link is that small silver colored round bar that is just peeking out from behind the rubber CV joint boot in the photo. Its oriented up and down. Crawl under the car a bit, grab that bar and shake it hard.  Do this on both sides of the car.  Is it tight and secured?  Make sure vehicle is in secure before you do that.  Safety first.
Comment: Thanks so much for your feedback appreciate it so much,no that klak klak sound was before the outer cv joint and wheelbearing was replaced,after that parts was replaced the car made that sound again on that exact same speed as i mentioned above
Comment: When you got under the car and shook the silver staybar links on both sides of car were they tight?


Transformer short circuit test

Question: Why is the power factor obtained by performing a short circuit test on a transformer higher than the power factor obtained in an open circuit test?
Answer: In an open circuit test you can be sure that about 90% of the current taken is to magnetize the transformer's core. That current taken is due to the inductance of the primary (as if it were an inductor with no secondary). There are some resistive effects due to eddy current losses in the laminates and hysterisis loss too but these are relatively small compared to the dominant current of the magnetization inductance.
This means the dominant component is an inductor and this makes the power factor quite small.
In a short circuit test, it is the leakage components in the windings that are measured and, these can be quite similar in impedance i.e. dc resistance of secondary is of the same order as leakage reactance of secondary and ditto for the primary. This roughly (and with some hand-waving) makes the power factor round about 0.5 but could be as low as 0.2 and as high as 0.9.
The open circuit test will show a power factor that is likely to be below 0.5 and probably in the realms of 0.3 or less.
I am generalizing here and clearly some transformers (especially those used in flyback converters) have very low magnetization inductance but, for the average 50Hz/60Hz power transformer, the above will be the case.
Comment: I want to know if this reason is right or wrong--> that in open circuit there is current flowing ie magnitizing current in a single coil but when the transformer is short circuited the current now flows from both the coils ( primary and secondary) making power factor more lagging??
Comment: No that isn't true - the current that flows on a short circuit test is more balanced between the reactive leakage in the windings and the dc resistance of the windings.
Answer: Answer by friend @Andy is nice. Just to brief it:

Short Circuit

In short circuit test we have to pass rated current through the short circuited side.
Therefore we select High Voltage (HV) side normally for short circuiting, because it's rated current is less and therefore it is easy to short.
Since the winding are short circuited it takes very less voltage to let the rated current flow through the secondary side, i.e., short circuited winding
When the voltage is less, the flux produced due to it, is less
Therefore, flux linking with core, 'phi' is very less
Hence, cos(phi), that is the power factor, is more. This is also the reason for "When we connect watt-meter in SC test it gives us approximately Copper loss only and Iron loss is negligible."

Since, flux linkage is negligible therefore, iron loss is negligible and hence whatever power is consumed, almost all of that is used to meet Copper loss.

Open Circuit

In open circuit test we have to apply rated secondary voltage
Therefore, we generally select Low Voltage side for secondary
In Transformer, Primary Current Ip, is the sum of no load current I0 and the current due to effect of 'load on secondary' I2".
I0 is primary no load current and is approximately 5% of rated primary current, which is very small value
I2" is dependent on secondary current I2 and since, secondary is open circuited, therefore I2 = 0 and this implies I2" = 0
Thus Ip, which is sum of I0 and I2", is very small
Therefore, Copper loss is negligible.
And since we have applied rated voltage, therefore normal flux linkage takes place and inductance of circuit increases.
This gives low power factor and also Iron loss is shown on the watt-meter (approx.)

Transformer short circuit test


Methods for using the Golden Ratio in fluid application UI design?

Question: I have seen a bit about leveraging the Golden Ratio in traditional web design applications, however I've not found much in the way of thoughts on utilizing it within fluid desktop application design.  That is to say, when given an application that has potentially infinite possibilities in resize, how does one go about conceptually using the Golden Ratio in such scenarios?
Comment: Square peg, round hole. In other words, you don't. The golden ratio isn't all that amazing of a tool anyways. Useful if you're building a roman temple, perhaps, but otherwise not as magical as some make it out to be.
Comment: Ratio is independent from resizing.
Comment: Mostly mumbo-jumbo: http://graphicdesign.stackexchange.com/questions/272/how-often-is-the-golden-ratio-actually-used-in-modern-design
Answer: Using percentage widths in your CSS can maintain column or element ratios:
width: 61.8%;
Just make sure you're aware of how CSS treats percentage widths and heights:
http://www.impressivewebs.com/width-100-percent-css/
Comment: Well, was asking about application UI design vs web css based apps, but still relevant.  When I was thinking about this I was caught up in the moment and didn't consider just reverting to percentage amounts across the board.  Thanks, will play with that.


Derivation of an RC Low Pass Filter's Cutoff Frequency

Question: I can't seem to figure out how to derive an RC low pass filter's cutoff frequency. I'm doing so an exercise because I want to find out the cutoff frequency of a more complex low pass filter, because I can't figure out that either. What I really need is a step by step solution for the RC LPF's cutoff frequency. I can write the equation for an RC filters transfer function but I don't understand how to find the magnitude of the transfer function. All the resources I'm finding do not show the steps. They have the transfer function, then show the magnitude of the transfer function on the next line.
Answer: Remember from mathematics that a complex number can be written as: \$z=a+j\,b\$.
Ok, once you know that, the magnitude of this number is easily calculated as \$\left|z\right| = \sqrt{a^2 + b^2}\$. Plug it into your transfer function and you'll find that \$\left|1+j\omega RC\right| = \sqrt{1^2 + (\omega RC)^2 }\$.
For the cutoff frequency of your RC low-pass filter, the cutoff frequency is the one when the output power has been reduced to half the passband power, which means a 3dB decrease in gain, thus : \$\implies \frac{\left|V_{out}\right|}{\left|V_{in}\right|} = \frac{1}{\sqrt{2}}\left|H(j0)\right|\$ where \$\left|H(j0)\right|\$ is the gain in the passband of your RC low-pass filter, which in this case is equal to 1.
Set this value equal to the transfer function value and you'll find the cutoff frequency to be \$\omega = \frac{1}{RC}\$
Comment: This works if the gain in the passband is 0dB. If the gain in the passband is other than 0dB, then instead of 1/sqrt(2) you have to use Ao/sqrt(2) where Ao is the gain in the passband. Or something like that.
Comment: @mkeith you are right, my bad I forgot that. Edited!
Answer:
I can't seem to figure out how to derive an RC low pass filter's
cutoff frequency

This occurs when the resistance has the same magnitude as the capacitive reactance: -
$$R = \dfrac{1}{\omega C} \hspace{1cm}\text{ or  }\hspace{1cm} \omega = \dfrac{1}{RC}$$
For the magnitude of the TF: -
$$H(j\omega) = \dfrac{1}{1 + j\omega RC} = \dfrac{1-j\omega RC}{1^2 + \omega^2R^2C^2}$$
So,
$$|H(j\omega)| = \dfrac{\sqrt{1^2 + \omega^2R^2C^2}}{1+\omega^2R^2C^2} = \dfrac{1}{\sqrt{1^2 + \omega^2R^2C^2}}$$


Website & Web Application

Question: what is the difference between the Website and Web application? For eg: facebook, twitter, myntra, onlinesbi etc...this are all website are web application.
Comment: Already answered: http://stackoverflow.com/questions/8694922/whats-the-difference-between-a-web-site-and-a-web-application
Comment: That might seem like it, but that's actually not an off-topic reason, even if they were the same question. And although the content is the same (actually, that one is fleshed out much more thoroughly) this is tagged with [tag:manual-testing] which makes me assume Mahesh is looking at this from a testing perspective instead of a terminology perspective. If anything, it's a close for "unclear what you're asking" because how it relates to testing isn't clear in the question.
Comment: This question appears to be off-topic because it is a duplicate of a question on Stack Overflow: http://stackoverflow.com/questions/8694922/whats-the-difference-between-a-web-site-and-a-web-application
Answer: The difference is in an individual's perception. It all depends on what you think. Many would say that Facebook is a web application, whereas others would say it is a website.
For example services like the ATM software, payment gateway, email service can all be thought of a web application. But if you really get into the depth you will see that they have webpages built which execute in web browsers and run on technology that is used for developing and executing web services, which by definition according to me makes them a website.
So, the true answer is IT DEPENDS on how you look at it... ;)
Answer:
what is the difference between the Website and Web application?

From a QA point of view, there is no difference.
Some application development tools/environments have these as different choices, depending on the tasks involved in the project (see: http://msdn.microsoft.com/en-us/library/dd547590(v=vs.110).aspx)
Comment: @NielsvanReijmersdal - I've never seen testing be about anything other than whether a user can do what's needed. Was the Amazon of 10 years ago a web site or a web application? Did anyone care as long as they could get what they wanted there?
Comment: I dare to differ. Websites are mainly about content and web-applications about user specific functionallity. Testing a website would focus on can the user find what he needs, where a web-application focuses on can the user do what he needs.
Answer: I would say the website is what the user sees and can interact with in the browser.
The web application is the thing that handles those interactions and tells the browser what to display.
The user doesn't interact with the application directly, only with the website.
Comment: I understand somewhat...can you elaborate......
Answer: A very basic explanation

Website is just a web page where most of the time testing will be of broken links and broken images and more if SEO is being processed on/for that website
Web application is a application where there has to be more work from the testing point of view for example applying various types of testing
Comment: This is really too simplistic for this site - we tend to prefer more substantive answers that include reasons for the decisions and definitions.

Website & Web Application


How to apply damage to entities without instant damage effect?

Question: I want to be able to give an entity damage for a command I'm making, but instant damage effect is way too much, how do I apply other amounts of damage with command blocks?
Comment: I am working on something that should be done either today or tomorrow. It requires a data pack for ease of use and for multiplayer friendliness although is not required. Would a data pack work?
Answer: 1.16+
Note: This data pack is in beta, and is in the works.  If you have any bugs please let me know, and I'll add it to the known bugs list.  Also, this is not tested in any version other then 1.16.4
I created a data pack that allows you to set health and  deal damage to a player(for mobs use data modify instead).  First off, you can get the data pack here.  After installing it, make sure it says in chat that it was installed.
How To Use
Dealing Damage
To damage a player, set that player's damage scoreboard to how much damage you want to apply(negatives heal players), then run the function editor:deal_damage as the player you want to damage and you are done.
Setting Health
To set the health of a player, set that player's sethealth scoreboard to what health you want that player to have, then run the function editor:set_health as the player you want to edit health and you are done.
Remember: 1 heart is 2 HP, and a half a heart is 1 HP, default max health is 20 HP(10 hearts)
The Commands
To damage players:
scoreboard players set <selector> damage <value>
execute as <selector> run function editor:deal_damage

To set player health:
scoreboard players set <selector> sethealth <value>
execute as <selector> run function editor:set_health

How It Works
What the data pack does is set the max health of the player to what health you want to set, and gives the player the instant health effect so it will update the player health, setting the player's health to max, then it sets the max health to be what it originally was.
Known Bugs

A bug that shows the player as dead, even though they are not. (Its a Minecraft bug)

Incompatibilities
All Incompatibilities are being worked on to be compatible

An existing helmet/item in the helmet slot with the max health attribute

Finding Bugs/Issues
Bugs
If you find any bugs, please report it.  Also add how you found the bug, so I can recreate it, and fix it, videos/screenshots of bugs are preferred.
Issues
If you have any performance issues while running the data pack, please report it.  Also add what performance issues you are getting, low tps, low fps, etc.  Videos/screenshots and computer specs do help!
Where to report
To report bugs/issues, use either comments on this answer, or the issues page on the GitHub download link.
Terms of Use
If you use this in a data pack to publish, I would like for you to put the GitHub link to the data pack somewhere for others who may want it, Thanks.  You are welcome to edit the data pack to whatever you want, just don't break it! :)
Comment: Is your solution complex enough to warrant a data pack? Why can't you just run the `/attribute` and `/effect` commands on your own?
Comment: @ExpertCoder14 the datapack is supposed to be for simplicity and for wide use.  If you did it with `/attribute` and `/effect`, you would have to know what to set the max health attribute back to, which in some circumstances, is not easy.  If you really wanted to, you could recreate this with command blocks instead, but it would take a while, and would need some workarounds.
Comment: Ah, great explanation that fills in the missing part. Yes, setting the `maxHealth` attribute back to the correct value definitely requires some more trickery. I'm worried that you might have reinvented the wheel though, did you check for a "standard" or more widely used data pack out there before going off to make your own? I had to learn that the hard way with the previous answer when we were talking about player inventory modification, turns out there was an "industry standard" data pack out there that I changed the link in your answer to reference, rather than our own.


Friction and a sphere on an inclined plane

Question: If I have a stationary sphere on an inclined plane such that friction is sufficient to prevent the sphere from sliding down the incline. Then about the centre of sphere frictional force is the only force that will create a torque. So shouldn't the sphere keep rotating at one place instead of being still?
Answer: First, we assume that all bodies are rigid and rolling friction is absent.
The type of friction most important here is static friction. Static friction between two surfaces acts only when no relative motion is present, and has variable direction and a maximum possible magnitude. Both can be determined by a simple rule:
Static friction opposes the direction of impending relative motion between two surfaces and has the least possible magnitude which will prevent said relative motion.
According to the question, the value of coefficient of friction is sufficiently high, so we will not worry about it.
When the sphere is placed at some height on the incline and then released, the following will happen:

Component of gravity normal to the incline will get balanced by normal force.
Component of gravity along the incline would induce downward sliding in the absence of static friction.

This might make us think that the frictional force should act in a direction upward the incline to balance gravity with a magnitude equal to $mg\sin\theta$ where $m$ is the mass of the sphere, and $\theta$ is the angle of the incline. But if that were the case it would induce rotation of the sphere at the same spot, which would lead to relative motion between the two surfaces. That does not agree with the earlier rule.
So, static friction will in fact act in the direction upward the incline with a magnitude equal to $(2/7)mg\sin\theta$ (this is the value is particular for a solid rigid sphere).
We can easily arrive at this value using: 1. the value of moment of inertia of a solid sphere, 2. The condition for pure rolling angular acceleration = linear acceleration divided by radius.
Pure rolling will occur because this is the only case where the surfaces have no relative motion between them.
Answer: If you want, then you may make the friction coefficient ($\mu$) as large as you want, but still the sphere will roll. Why? Because the frictional force will not exceed the force of gravity acting on the sphere.
See, the friction arises to stop any relative motion between two surfaces. But when the ball is rolling, there is no relative motion between the sphere and the inclined plane. So the friction would be just enough to stop slipping, and this value comes out to be lesser than the force due to gravity on the sphere. If you want then you can rigorously prove this by drawing a free body diagram and finding the torque about the COM to find the anguoar acceleration. I leave it up to you as an exercise.
Also, the claim that the sphere will rotate at a single place can be rejected by energy considerations. If a sphere keeps on rotating at the same place, then the friction is surely going to do some negative work on it. Also there is no source of energy for the sphere. So eventually the rotation must stop. In fact, the rotation shouldn't even start because you require energy to rotate something. Where will you get that from?
Comment: Understood. Thank you.
Comment: So it means a ball can never stay at rest on any inclined plane of nonzero angle of inclination?
Comment: @EmileyS. It can, if you put a fixed obstacles on the inclined plane.
Comment: @EmileyS See [this](https://i.stack.imgur.com/aICdE.jpg). This kind of arrangement can also help keep a hollow sphere static. For a solid sphere, you might have to change the density of the sphere and make it a non uniform sphere such that its COM lies exactly above the point of contact of the sphere with the plane.
Answer: Assume that sphere is in equilibrium then the net forces and net torque should be zero.

Net forces are equal then mgsinθ=friction
Net torque about centre should be zero then torque of mgsinθ is zero ,also torque of friction should be zero for equilibrium.

From second Friction equal to zero but you say friction is sufficient.
Both statement are contradict each other.
Hence, sphere should roll over the incline plane.


What happens if a Cognito Form cannot connect to SharePoint?

Question: We would like to connect our Cognito Forms to our local SharePoint system. In the scenario that our SharePoint system becomes unavailable, will Cognito Forms attempt to re-send the data at a later time if a successful connection is not made?
Answer: I'm a developer with Cognito Forms. Unfortunately, Cognito Forms will not re-send the data if the SharePoint system is down when the integration is triggered. However, Cognito Forms does provide a way to re-submit an entry. In order to do this, you will need to enable "Save & Resume" on your form. Once "Save & Resume" is enabled, you will be able to set the status of an entry to "Incomplete" on the Entries page. When you edit an "Incomplete" entry, you will have the option to "Submit" the entry. Please keep in mind that all notifications or integration configured to run when an entry is submitted will be triggered. For example, a email notification configured to be sent when an entry is submitted will go out.


What are the equivalents of millionnaire, multimillionaire and billionaire in Japanese?

Question: I'm talking about the "cultural" ones, because with the yen currency the scale is completely different (millionnaire with yen is only about having approximately 10 000 usd so I don't think it's the real equivalent).
Answer: 億万長者【おくまんちょうじゃ】 is the best-known word. Actually there is also a word 百万長者, but it's not commonly used for the obvious reason.
ミリオネア is at least understood because of this TV program, but it's not used in daily conversations.
Comment: @Jirei I assume an 億万長者 has at least 100M yen, but basically it vaguely refers to a super-rich person. Bill Gates is still safely an 億万長者, too.
Comment: 億万長者 is a word that just means " rich person" without referring especially to an amount of money ?
Answer: There is also the word [大富豪]{だい・ふ・ごう}, but I don't know if it's commonly used other than for the card game.
Comment: It is definitely used in the 'extremely rich person' meaning.  I don't think it's *terribly* uncommon, though my intuition might not be reliable on that point.  At any rate, I learned in context with that meaning, and you can find plenty of examples in [BCCWJ](http://www.kotonoha.gr.jp/shonagon/).


What is the worst scenario, if the hard disk or motherboard don't support the `hddparm -s`?

Question: I have a desktop PC, that dubs as a RAID-6 server. When I don't need the RAID-related stuff, I'd like to spin off all the hard drives involved in RAID (I hate the noise). Unfortunately, even if everything is stopped, the system probes the drives from time to time causing the hard drives to spin up.
From the hdaparm man page one can read, that issuing commands like hddparm -s /dev/sdc can prevent the disk from ever spinning up again... unless the motherboard supports it:
   -s     Enable/disable  the power-on in standby feature, if supported by
          the drive.  VERY DANGEROUS.  Do not use  unless  you  are  abso‐
          lutely  certain  that both the system BIOS (or firmware) and the
          operating system kernel (Linux >= 2.6.22)  support  probing  for
          drives  that  use this feature.  When enabled, the drive is pow‐
          ered-up in the standby mode to allow the controller to  sequence
          the  spin-up of devices, reducing the instantaneous current draw
          burden when many drives share a power supply.  Primarily for use
          in  large RAID setups.  This feature is usually disabled and the
          drive is powered-up in the active mode  (see  -C  above).   Note
          that  a  drive may also allow enabling this feature by a jumper.
          Some SATA drives support the control of this feature by  pin  11
          of the SATA power connector. In these cases, this command may be
          unsupported or may have no effect.

I still don't understand, what is the worst scenario if the hard drive or motherboard don't support it. Does it mean, that the hard drive will be bricked?
Or will it be enough to take the hard drive to a friend, who happens to have compatible motherboard which would map the spinned-down hard drives, to re-enable it?

Another question: What exactly features should my hard drive support? My hard drive seems to support Power-Up In Standby feature set, which may not be the same as power-on in standby feature mentioned by the man.
How can I check necessary features it in for motherboard? What name does this feature have?
The hdparm -I /dev/sdc:
Enabled Supported:
   *    SMART feature set
        Security Mode feature set
   *    Power Management feature set
   *    Write cache
   *    Look-ahead
   *    Host Protected Area feature set
   *    WRITE_BUFFER command
   *    READ_BUFFER command
   *    NOP cmd
   *    DOWNLOAD_MICROCODE
        Power-Up In Standby feature set
   *    SET_FEATURES required to spinup after power up
        SET_MAX security extension
   *    48-bit Address feature set
   *    Device Configuration Overlay feature set
   *    Mandatory FLUSH_CACHE
   *    FLUSH_CACHE_EXT
   *    SMART error logging
   *    SMART self-test
   *    General Purpose Logging feature set
   *    64-bit World wide name
   *    {READ,WRITE}_DMA_EXT_GPL commands
   *    Segmented DOWNLOAD_MICROCODE
   *    Gen1 signaling speed (1.5Gb/s)
   *    Gen2 signaling speed (3.0Gb/s)
   *    Gen3 signaling speed (6.0Gb/s)
   *    Native Command Queueing (NCQ)
   *    Host-initiated interface power management
   *    Phy event counters
   *    NCQ priority information
   *    DMA Setup Auto-Activate optimization
   *    Software settings preservation
   *    SMART Command Transport (SCT) feature set
   *    SCT Write Same (AC2)
   *    SCT Features Control (AC4)
   *    SCT Data Tables (AC5)
        unknown 206[12] (vendor specific)
        unknown 206[13] (vendor specific)

Answer: RAID combines the existing drives into a "superdrive". There aren't "drives that can be turned off because they aren't being used" (unless the RAID is a separate set from the drive from which the machine boots/with the operating system).
Comment: I know. But sometimes I don't need any part of the array. And this is what I write about. The array is on completely separate set of hdds than the rest of the system.


where android backup its data?

Question: For some reason, I had to reset my nexus5. Thankfully, I had "Backup my data" on. So, most of my settings are back. But I need to access the backup to change the wallpaper position (it has reset my last wallpaper, but I need to slide it). I have checked google drive and g+ auto-backup which backs up the pictures, but the wallpaper is not there.
Any idea where I can found the data backed up?
Comment: Also related: [What info does Google backup?](http://android.stackexchange.com/q/15434/16575) / [Is there any way to check the backup that android does?](http://android.stackexchange.com/q/21888/16575) / [Can I manually download my wifi settings to my Android device from my Google account?](http://android.stackexchange.com/q/26193/16575)
Answer: The data backed up using "Back up my data to Google's servers" aren't user-accessible. Each app has access to its own backup data. That's the only access available without hacking into the backup service.
This is a deliberate design decision. Android protects app data from being seen or modified by users or other apps, making it easier for apps to rely on the integrity of their data. (That is, unless you have root, in which case you're on your own.) Allowing users to intercept and maybe modify the backup data would defeat that protection, making it harder to write robust apps and harder for apps to restrict how you use their data (e.g. for movie rental apps).
You can learn more by reading my detailed answer about Google backup and how you can interact with it.

where android backup its data?


How do I craft in Assassin's Creed 3?

Question: I have been playing AC3 for a while, and wondering how to craft and upgrade? I'm at sequence 9
Comment: It's explained as part of a story mission. You can't craft or upgrade any sooner than that anyways.
Comment: I removed the Wii-U tag. Crafting is available and is the same in all version of the game as far as I am aware.
Answer: Info about crafting taken from Assassin's Creed Wiki

Crafting in Assassin's Creed III involves raw materials that can be purchased from the Davenport Homestead, gathered from looting, or found in chests. Crafting could be done at the "Accounting Book" which could be found in the Homestead, or in any of the general stores in Colonial America, by selecting an artisan followed by a resource.

So, in addition to smitty69's answer, crafting can also be performed at the Homestead.
You'll need to complete Homestead missions, in order to gain more artisans and increase their levels, which will enable you to craft more items.
Answer: To craft items, you need to have the correct ingredients to what you wish to make and bring them to a store in which you buy weapons and what not, there will be a book next to the merchant in which you can craft several things, providing you have the correct ingredients.
Answer: An addition to the answers mentioned above: various crafted items require a recipe as well. These are obtained by looting the various chests scattered throughout Boston, New York, the Frontier and the homestead.
An easier way to craft the items is to select the recipe itsself: select crafting, press A or Square and select the item you wish to craft. Required ressources as well as the artisan required are then automatically placed in the respective fields.
The inventions require plans, which are obtained by collecting all almanac pages of a certain set. It is possible to by maps for these almanac pages as well from the general stores.

How do I craft in Assassin's Creed 3?


Cracking WI-FI password offline at distance, is that possible?

Question: Let's suppose I was able to get a handshake from my target's network and I got the .CAP file (containing the handshake), but I would like to crack the password from another location (away from the target network location). Would it be possible, or do I have to be nearby the target network to do that?
Comment: btw - distance doesn't matter - you are asking about cracking a static key, which doesn't require a connection to the AP
Comment: there's quite a lot on this topic online. Have you tried "crack wifi password offline"?
Comment: @schroeder I just found a website with a lot of information about it, thanks. I guess I searched the wrong terms.
Comment: @BinaryMatrix please share your sources in comments to help others with the same question.
Comment: @Baron this helped with my question http://www.howtogeek.com/202441/your-wi-fi%E2%80%99s-wpa2-encryption-can-be-cracked-offline-here%E2%80%99s-how/
Answer: You can be anywhere you like.
Once you have the handshake you can crack the password anywhere you like.
The handshake is as if you have a "hashed" password and you want to crack it.
One method of doing this is using aircrack-ng which tries to crack the handshake using a dictionary attack (This is a passive attack on your captured packets). You can view the full tutorial here.
Comment: @BinaryMatrix No problem =]
Answer: Deauthenticate the wifi clients with aireplay-ng (from aircrack-ng suite) or wifite. Make sure your rx quality is as good as possible. Use two adapters, and sniff with one using airodump-ng (fix the ivs_only var in airodump-ng.c and recompile) --output-format=csv,pcap or kismet. Inject with the other one. Depending on the type, you may need airmon-ng to set rfmon. Once you have a bunch of handshakes, use pyrit to crack them. You need a GPU or several for this (you can use client mode, and connect it to other machines in server mode over IP). CPU cracking is dead, forget about it. I have some old scripts which use aireplay-ng to deauth widely (every wlan, a few different modes of deauthentication), but I suppose wifite is more userfriendly.
Comment: I have to assert that CPU cracking is well and truly dead. Still works somewhat for password hashes, but IIRC the wpa psks are rolled 16k times, and you will never get as efficient cracking with cpu as with gpu. E.g.: my core i5 can do ~1700 c/s, but my gpu can do ~70000 c/s. And it is a cheap, old gpu. google hashcat-ocl, hashcat-cuda.


We found this is it mold?

Question:
We had a water leak about two months ago and since then I have been sick. We have a mold specialist coming out but they couldn't come for two weeks. We peeled the carpet back to find this...
Comment: Hello, and welcome to Stack Exchange. It's hard to say from one picture, and I'm no expert, but that doesn't look like mold to me, as it's granular.
Answer: That appears to just be the broken down remains of rubberized carpet padding. If you look on the tack strip (the little strip with the nails in it that holds the carpet in place), there appear to be larger pieces of it still embedded on the strip, probably from a previous carpet installation that was removed sloppilly years ago. That's not to say you don't have mold somewhere, but that's not mold.

We found this is it mold?


Force whatsapp to upload backup

Question: My whatsapp is uploading backup every week so the backup system is working .
But i want to backup the chat right now so i tried to press the big green "BACK UP" button. A pop up appeared "Backing up messages , please wait a moment (%)" .
It goes from 0% to 100% , but after 100% , the popup just disappear and no backup was made .
How do i force whatsapp to upload backup right now ?

I log out from my whatsapp account and relogin , the back up button works after relogin . I don't know why this happen , maybe a bug in whatsapp.
Answer: By backup do you mean backup to Google Drive or local backup of messages?
The Whatsapp backup process consists of two distinct phases:

Local backup: saving all messages inside the phone memory.
Backup to Google Drive: it happens only after the local backup and only if a Google account is selected. This backup includes all messages and media (you can choose whether to include videos or not).

If you get a pop-up saying: "Backing up messages", it means that it's only completing the local backup of messages, which seems to be successful in your case.
If you want to force a backup to Google Drive you have to first select the Google account in Settings > Chat > Chat Backup > Google Drive Settings > Google Account, then click the green "Back Up" button and Whatsapp will automatically backup both locally and to Google Drive.

Force whatsapp to upload backup


Electromagnetic field around a conductor with current

Question: According to this video https://www.youtube.com/watch?v=bHIhgxav9LY I have a question: If the glowing of a light bulb is the result of energy supplied from the electromagnetic field around a conductor, Why does the electricity not hurt me when I touch the cord from the turned on vacuum cleaner?
Comment: Also, to make questions more accessible and guard against [link rot](https://en.wikipedia.org/wiki/Link_rot), please include at least author and title of resources you link in your question so the content can be reconstructed if the link rots away.
Comment: The light bulb (and the wire connected to it) is a good conductor, you're not - how are the two situations supposed to be comparable? See also https://physics.meta.stackexchange.com/q/13917/50583 for an overview of already extant questions about this veritasium video - perhaps one of them already clears up your confusion here.
Comment: Please clarify your specific problem or provide additional details to highlight exactly what you need. As it's currently written, it's hard to tell exactly what you're asking.
Answer: The intuitive understanding of electric current as similar to water flow is very persuasive, and hard to quit. In spite of the efforts of the video makers, it is tempting  to view the energy flow as a kind of a material flow. In this case we could be hurt by the fields if we are in the way.
But what the Pointyng vector only shows is that the battery is a source of electrical energy (from chemical reaction). The lamp is a sink of electrical energy (transformed in heat and light). But it is required a conductor wire connecting this components to get this energy flow.
If something touches the wire, and the striking example is a bird in a high voltage transmission line, the electric energy is negligible through its body.
Answer: Your hand is a conductor, surrounded by insulating stuff, for that reason electric field is zero inside your hand, so also Poynting-vectors are zero inside your hand, so there is no energy flow inside your hand.
As there is an energy flow to the upstream and to the downstream of your hand, the flowing energy must make some turns when flowing around your hand. I mean when you are grabbing the cord.
(Maybe if you moved the hand to the downstream direction, you could steal some energy from the wire? From the space around the wire, I mean. :)   )
For the sake of completeness, let's say your hand is an insulator, then same amount of Poynting-vectors are pointing into your hand from the upstream direction as are pointing out of your hand into the downstream direction, so your hand is nor absorbing any of the energy flowing through your hand, so it can not feel any effect of the energy.


Dynamically loading a native library inside Java applet

Question: I am trying to write a Java applet that will read from a user's serial port. For this I am using the Java Comm API in conjuction with the RXTX library. I've successfully managed to read data through a local Java application but I can't seem to do the same from within an applet. The problem is that the RXTX library is a native library and I haven't found a way to load this library inside the Java applet. I've found two interesting articles (Using JNI in Applets which references to this article), but both are over 10 years old and I am wondering if there is a newer solution. Or if you can suggest an alternative, I would love to hear it!
Answer: Use Java Web Start. You can include the native library as a signed jar and everything should work.
1) put the native librarys in  a jar in the ROOT directory
2) sign ALL the jars
3) write a JNLP referencing all the jars (go do a search on how to write jnlp's)
after that it should work
Answer: Firstly I'd suggest doing that in an Applet is probably a bad idea.
If you do go ahead anyway, JNLPAppletLauncher may help.
Answer: I don't know about applets, other than they're locked down heavily wrt. security/accessing the machine's resources etc.
If you need a web-deployable solution, have you looked at Java Web Start ? See in particular this FAQ entry
Answer: Frankly, trying to access devices from a Java applet is a bad idea even if you could make it work, and loading a dynamic library into the conventional applet is an even worse idea; in fact, I'd be astounded if you could find a way to trick a modern browser into doing it.  (Consider the possible security implications.)
You're better off, as suggested on other questions, building an app that can be launched with Web Start.
Comment: The current Java PlugIn runs the applet outside of the browser process. These neatly circumvents Vista' "Low Integrity" security restrictions.
Comment: So are you saying that Vista un-sandboxes the applet?  That's possibly even more of a security horror than loading a dll -- it would violate the Java security policy as well as being a Real Bad Idea.
Answer: I'd be real interested in the answer here also.  My suggestion would be to install the .jar and .dll for RXTX into the \program files\java\ tree.  You could install them on the target system before trying to use the applet.  I like the idea of using Java Web Start.  If you sign the applet, can't you read/write any file on the machine?  So you could install the .jar and .dll and then use them afterward?
For windows, I suggest using "Windows Java Serial Com Port Driver" rather than rxtx.
You can download it from http://www.engidea.com/blog/informatica/winjcom/winjcom.html
I've found it much easier to install and use and much more bug-free.
I was unable to use RXTX with USB serial devices because RXTX would crash when the USB port was unplugged.  winjcom solved these problems for me, and more.
I'm still trying to decide how to deploy the DLL, but I'm not sweating it because I don't expect the DLL for "Windows Java Serial Com Port Driver" to change.
-Stosh


The adjoint representation and irreducibility of the Clifford group

Question: Let $ P $ be the Pauli group and $ Cl $ (the Clifford group) be the normalizer of $ P $ in the unitary group $ U_d $ . Consider the representation given by acting the unitary group $ U_d $ on the Lie algebra $ \mathfrak{su}_d $ by conjugation (essentially the adjoint representation)
$$
\text{ad}: U_d \to \text{End}(\mathfrak{su}_d)
$$
Since the Clifford group is a subgroup of $ U_d $ we can restrict $ \text{ad} $ to get a representation
$$
\text{ad}:Cl \to  \text{End}(\mathfrak{su}_d)
$$
Is this representation of the Clifford group an irreducible representation?
Comment: I think you can argue from the fact that the adjoint representation of U is irreducible that the adjoint representation of the Clifford group is also irreducible, since the Clifford group is a 2-design.
Comment: Ya that sounds right but I was curious to see if someone had an easier/different perspective/ or how they would work out the details of the 2-design argument
Answer: The 2-design proof is exactly about proving that this is an irrep since these are equivalent statements. I think that this is about the simplest proof that you can find.
Let me elaborate. Let $\tau^{(2)}(U):= U\otimes U$ be a representation of $U(d)$. Then, a subgroup $G\subset U(d)$ is a unitary 2-design if and only if $\tau^{(2)}|_{G}$ decomposes into the same irreps as $\tau^{(2)}$. This is because the 2-design definition reads
$$
 \int_G U^{\otimes 2} (\cdot) (U^{\otimes 2})^\dagger \,dU = \int_{U(d)} U^{\otimes 2} (\cdot) (U^{\otimes 2})^\dagger \,dU.
$$
These are both projectors onto the commutant of $\tau^{(2)}$ and $\tau^{(2)}|_{G}$, respectively. Since the dimension of the commutant is the sum of squared multiplicities of the irreps and $G$ is a subgroup, the commutant can only be the same if the irreps of $\tau^{(2)}$ are still irreducible under $G$.
Note that this implies the same statement for $(U \mapsto U\otimes\overline U) \simeq (U\mapsto U(\cdot)U^\dagger)$.
It is easy to see that the latter representation decomposes as $1 \oplus \mathrm{ad}$. Clearly, the trivial irrep is irreducible for $G=\mathrm{Cl}_n$, so $\mathrm{Cl}_n$ is a unitary 2-design if and only if $\mathrm{ad}|_{\mathrm{Cl}_n}$ is irreducible.
The usual proof uses that $\mathrm{Cl}_n$ acts transitively on traceless Pauli matrices. This already implies the correct dimension of the commutant, see Lemma 2 in [Zhu]. Alternatively, on can evaluate the above integral on the Pauli basis, see e.g. Sec. IV.C in [Gross et al.].


user SID unique?

Question: the SID term is unique or not? can two user sids on different machines in one domain system be equal? (if both of them domain users or if both of them locally users)
Answer: Two domain users can't have the same SID; its unicity is enforced by the domain (by the DC holding the RID Master FSMO role).
Two local user accounts on different computers shouldn't have the same SID, unless they're well-known accounts which always use the same SIDs (like Administrator); this would happen only if you created an account on a machine and then cloned it. It wouldn't matter much, anyway, as local SIDs are never used in network operations.
Comment: To add to Massimo's answer Local sids are not guaranteed to be unique, domain sids are

user SID unique?


How to create very simple doom like corridors in XNA?

Question: So I have seen many 3D tutorials creating heightmaps and big landscapes but I am hoping there is something simple that i can throw together. If I was to do something doom/wolfenstien-like, do i just draw a cube and texture it? I guess my question is, How should i go about creating a very simple box-like room?
Answer: The topic you're asking about is more involved and broad than you might think. Drawing is only half of the problem at that point; chances are, if drawing a room is a challenge, then 3D collision detection is going to be a pretty big task.
I'd highly recommend taking a look at the XNA starter kits and seeing what you can learn from there.
The XNA Starter Kits are available at: http://creators.xna.com/en-US/education/starterkits/
To answer your original question, the XNA Creator's Club website has a code sample for drawing 3D primitives at: http://creators.xna.com/en-US/sample/primitives3D
And this howto (for XNA 1.0, but with the right concepts) is fundamental to moving forward: http://msdn.microsoft.com/en-us/library/bb464051(XNAGameStudio.10).aspx
Comment: you may have answered my question but some clarification. If the answer is primatives then I get it. My question meant to say, "is this how I should go about it?". I kno wI have to add collision but at this point I just wanted ot be directed down the "right road". So if your answer is.. "use primitives" then I will mark this as the answer.
Answer: In theory you can build the entire level in some 3D editor (MAX, Blender etc), export it as a single model and draw it using the methods explained in XNA's 3D game tutorial.
This is not what you want, unless we are dealing with very small spaces.
Usually the world geometry is partitioned for (mainly) the following reasons:

Ensure you do not have to push more geometry than necessary to the hardware. There is no poing drawing the entire level if you are inside a room with all the doors closed.
Limit the number of polygons you need to test for collision detection etc.

The two main techniques used for this purpose in indoor scenes are binary space partitioning (BSP), used by doom/quake and friends, and portal/cell (of Unreal fame). There are advantages and disadvantages to both techniques. Both are a substantial amount of work to implement from first principles.
I recommend you base your work on an existing engine that does this for you.
Answer: If you drew a cube and textured it you would have a cube, not a room.
I don't know how XNA define "primitive", but what you should be doing is drawing polygons to form a square or a rectangle for a single wall of your corridor.
Comment: Also keep in mind that polygons in 3D graphics are generally (unless otherwise specified) single sided. If you draw a cube you can only see it from the outside, not from the inside.


C# code for reading Grove Pi RPISER serial port

Question: Can anyone help with C# code for reading GPS sensor connected to the RPISER port of Grove Pi (hat for Raspberry Pi)?
Comment: Please add a link to your GPS sensor in your question.
Answer: To start of with here is a simple serial code you can transform to your UAT application.
namespace ConsoleApplication1
{
    class Program
    {
        public static void Main(string[] args)
        {
            SerialPort sp = new SerialPort("/dev/ttyAMA0", 115200, Parity.None, 8, StopBits.One);
            sp.Open();
            for (int index = 0; index < 10; index++)
            {
                string result = string.Format("{0} Testing", index);
                sp.Write(result);
            }
            sp.Close();
        }
    }
}

The parameters provided in new SerialPort need to be as required for the GPS device. Typically now a days this is the frequent usage but it may vary. If you get junk output it could be the baud rate.
You may have to create a threaded/delegated implementation of the serial read to raise events in your code otherwise you will block your UI. But start with that first to confirm you can get data back from the GPS before continuing.
You can find a ton of open source application on the Microsoft Pi site
Find projects that may help you, read the code, find what interests you and adopt it in your project.
PRO TIPS

You can create code on your PC Visual Studio Community or Mac/Linux using Monodevlop to get test code going. Although using Visual Studio the project compiles on your machine and deploys to Pi any way.
Always create separate classes for your code. It follows the Object Orientated Programming Pattern. You may want to look at some examples or do some basic C# online course. (Sorry, I dont know your competency in programming so its a good place to start)
Even if testing. Once you get working code and need to transform it, create a new class and start changing it in that class.
Doing this will help you create background threads by starting class based code in threaded object that raise events in your main thread. Keeping your UI unblocked. There are many ways to achieve this and is a may be of a expert level requirement to get it going.
Obviosly, if you dont need UI, just build your read into the main thread. You can save data to database or relay it to another server if that is the only purpose.


Is there any point in keeping expired international driving licenses?

Question: Is there any point in keeping expired international driving licenses?
Comment: I guess I never saw a point (but that doesn't mean there isn't one!) It would get flushed from my travel documents when I was next going somewhere and noticed it was expired. No bad outcomes yet (fingers crossed).
Answer: No, since the International Driving Permit (IDP) has expired it cannot be used.
For a new IDP you would need your original driver's licence, so here too it would serve no purpose.


What does this mean - "I meant if you could provide us with your references."?

Question: I am actively interviewing for a job in USA and my recruiter asked me to send him some of my references. I did not understand what it meant and asked him do you mean to send email-ids of persons who can refer me and in response to that he said - "I meant if you could provide us with your references." What should I do? Should I share contact details of my references?
Comment: Yes, send two or three names of those who know your work, along with some way of contacting them: email addresses, phone numbers, or such. That is called providing references. It is not one specific format.
Comment: Make sure your references know that you're using them as references.
Answer: That is a roundabout way of saying

I meant we want you to provide us with your references.

The "if you could" construction is less direct and therefore a bit gentler, less like a command.
Answer: As someone who was a hiring manager for many years, I would expect to see the reference's name, your relationship to him or her (previous supervisors are best), email address, and phone number. You should expect the recruiter or potential employers to contact those people directly with a list of questions. I would not expect that you would provide the information for your current supervisor. If possible, for your current job, I would recommend providing the name and contact information for a trusted peer.


Netbeans: Setting up java cross-compilation

Question: I intend to write private-use command line tools in java for use both on my private system (jdk 7) and on my universities number-crunching servers (jre 1.4). An attempt at installing OpenJdk from sources failed, because it is missing several dependencies, that simply wouldn't make sense on a computation server -- e.g. CUPS. The work required for installing such dependencies and THEIR dependencies would probably defeat the whole point of automating tasks, i.e. making life easier.
Being used to the conveniences of generics, I don't want to write 1.4 SOURCE code though. I found that, when compiling from the command line, options like
javac -target 1.4 -bootclasspath jdk1.4.2/lib/classes.zip \
         -extdirs "" OldCode.java

are available (see [1]), which should allow compiling jdk5 or even jdk7 specific syntax to jdk1.4 compatible bytecode, as long as I stay clear of newer library features (which -bootclasspath is for).
This brings up two problems:

While I can set the compliance level for each project to a given java version easily in Netbeans 7.3, it forces me to use 1.4 syntax as well (probably by adding -source 1.4 to the command above).
I couldn't find an old jdk (specifically classes.zip) anywhere except for oracle.com, where registration is required for downloading those with the registration mask alone making quite clear that those are not meant for private use.

All related answers I found so far give no hint how to do this kind of bytecode/source-separated cross-compilation in netbeans and none address the issue of finding old JDKs.
Eclipse is not really an option, as there I couldn't figure out how to get automatic generation of JARs like in netbeans.
Any ideas?
Platform details:

Local (from Netbeans "Help → About"):
Product Version: NetBeans IDE 7.3 (Build 201302132200)
Java: 1.7.0_11; Java HotSpot(TM) 64-Bit Server VM 23.6-b04
Runtime: Java(TM) SE Runtime Environment 1.7.0_11-b21
System: Windows 7 version 6.1 running on amd64; Cp1252; de_DE (nb)

Remote:
java version "1.4.2_11"
Java(TM) 2 Runtime Environment, Standard Edition (build 1.4.2_11-b06)
Java HotSpot(TM) 64-Bit Server VM (build 1.4.2_11-b06, mixed mode)

Update: Just to be sure -- it IS possible to compile source with new syntax to Java 1.4. E.g. I wrote this file:
class Target<T>{
    public T field;

    public static void main(String[] args){
        System.out.println("Hello World!");
        Target<String> target = new Target<>();
        target.field = "More Worlds.";
        System.out.println(target.field);
    }
}

Then I compiled it with JDK 7 doing
javac -target jsr14 Target.java

and uploaded it to the computation server, where only JRE 1.4 (and no JDK at all) is present. It gave the expected output
Hello World!
More Worlds.

Apparently the "jsr" targets are an undocumented feature though, see e.g. [2]. Also that link mentions, that it is a bit of a hack, as only for-each loops for the Collections library will be handled:

for-each loop: When iterating over an array, the compiler generates an induction variable and the standard array iteration idiom. When iterating over a Collection, the compiler generates the standard iterator-based idiom. When iterating over a non-Collection Iterable, the compiler produces an error.

I guess that means, that I will have no choice but to attempt getting a newer JRE onto the server, if I want to use any reasonably modern features...
[1] How do i compile a .java with support for older versions of java?
[2] http://twit88.com/blog/2008/08/26/java-understanding-jsr14/
Answer: JDKs aren't forward-compatible. That is, you cannot compile new features for old JDK versions. (or JRE for that matter).
Language constructs, such as generics, are if I'm not totally mistaken, part of the bytecode or interpreter in Java.
AFAIK you have only two options. 1) install new JDK or 2) write 1.4 source code.


How to find files in a Debian system not installed or created by dpkg?

Question: I've installed some things manually in the past and would like to weed out all related files. So, I need a way to automatically find all the files (in /usr, for example) that are not included in any of the packages currently installed on the Debian system. However, I would also need to filter out the files that are created during package installation (by dpkg post-install scripts and similar things).
Comment: See also this question:
http://unix.stackexchange.com/questions/18038/how-to-list-files-and-folders-that-are-not-maintained-by-any-deb-package
Answer: Use the cruft-ng package:

cruft-ng is a program to look over the system for anything that shouldn't
be there, but is; or for anything that should be there, but isn't.
Comment: Note that as of 2022-10-07, cruft was removed from testing and may disappear from Debian.
Answer: You could try something like this:
dpkg -L --list-all-package-files | grep "^/usr" > dpkg-files.dat   **(don't know the dpkg option "--list-all-package-files", read mand dpkg)**
find /usr -type f -o -type l > all-usr-files.dat
sort dpkg-files.dat all-usr-files.dat | uniq -c | grep " 1 "

This way you will get all files that are in /usr but not any package file.
As a first shot this could help you.
Comment: I can't find any way to get -L to list more than one package at a time, but you can get the same effect from `grep -h "^/usr" /var/lib/dpkg/info/*.list > dpkg-files.dat`
Comment: There is no `--list-all-package-files` option.
Comment: @DerfK: You can get -l to list more than one package, for example like this: `dpkg -L \`aptitude search ~i -F "%p"\``
Comment: The problem with this approach is that there are more files or links in /usr than actually listed by dpkg. For example, /usr/bin/aptitude exists, probably created by some post-installation script, but it's not listed by dpkg. So, I guess what I want here is a list of files installed **or** created by installing any package (will change question).
Comment: @Karol: Other sources of files could be diversions and alternatives.  The output is in sentence form but you can see diversions with `dpkg-divert --list` as root (These are usually given a suffix).  Alternatives are a bit harder, the file format in /var/lib/dpkg/alternatives/ is awkward and `update-alternatives` tells me just about everything BUT the name of the link. `find /usr -lname '/etc/alternatives/*'` is probably the easiest way to get these.


Windows 8 Consumer Preview won't get past login screen

Question: I downloaded the Windows 8 Consumer Preview and everything seemed to load fine, except when I try and sign on it says "Welcome" and then restarts itself back to the sign on.
Comment: Did you try reinstalling it?
Answer: Are you in the same hardware conditions you were when you installed Windows 8 Consumer Preview on your PC? I got a similar problem when try to boot up Windows 8 with new hardware devices attached. Removing them, then reboot and let Windows 8 detect the devices with plug & play worked.


If $x \succsim_i x_i^*$ then $p \cdot x_i\ge w_i.$ (MWG 16.C.2)

Question:
(MWG 16.C.2) Suppose that the preference relation $\succsim_i$ is locally nonsatiated and that $x_i^*$ is maximal for $\succsim_i$ in set $\{x_i \in X_i: p \cdot x_i \le w_i\}$. Prove that the following property holds: "If $x \succsim_i x_i^*$ then $p \cdot x_i\ge w_i.$"

Locally nonsatiation means that for every $x_i \in X_i$ and $\epsilon >0$, there exists $x_i' \in X_i$ such that $||x_i - x_i'|| < \epsilon$ and $x_i' \succ x_i$.
I think that I need to prove that if $x_i \sim_i x^*_i $ for $x_i \not= x_i^*$, then it is possible that $p\cdot x_i = w_i$ because I already know that if $x_i \succ x_i^*$, then $p\cdot x_i > w_i$.
I am stuck and  cannot proceed. Can anyone give me some hint for this question?
Answer: Hint: Prove by contradiction. That is, suppose $x_i\succsim_ix_i^*$ but $p\cdot x_i<w_i$, show that this would lead to a contradiction of $x_i^*$ being maximal for the feasible set.


What is making these holes in my yard?

Question: My back yard is full of small, shallow holes and I'm trying to figure out why. They are 1-2 inches across and about as deep, definitely not burrows. I as far as I can tell, nothing is buried in them, and they don't seem filled in. These pictures are from last year, but there are dozens more in my yard right now. They seem to be concentrated around a certain spot in my back yard, but I've seen them all over. Based on the local wildlife, I suspect squirrels or rabbits (I live in Minneapolis, MN). I'd like to be sure what species is making them before I think about trapping and relocating it. Thanks in advance!

Some pictures from today:
Answer: I think that is squirrels, digging up their stashed nuts.
Comment: That is my suspicion, though I wonder why they appeared last fall as well and why they are so concentrated in one part of my back yard. (Pictured above)
Answer: I tend to get shallow holes like this in my lawn in the early spring, too. Sometimes it's squirrels looking for nuts (or the tulip bulbs they've moved ... grr), but I found that many of them were appearing over night. It turned out to be skunks digging up grubs.
The difference I found was that the squirrels would tend to just have the shallow hole, whereas the skunk would leave a hunk of soil uprooted.
Answer: Around where I live (Seattle), it's mostly crows and other birds that make little holes like that. In the grass, in the planting beds, and in my pots, dagnabit. There be worms and bugs in those places, and the birds know it.
Answer: We might guess chipmunks. If you keep a close eye on the area where the holes are you may well see a head pop up occasionally and then disappear back into the ground. Holes may not be deep but connect underground a few inches down. Clusters of holes indicate you are close to a den where they have multiple holes for alternate escape routes. Chipmunk population numbers vary widely from season to season and even within the season; population numbers frequently crash to almost nothing and then they come back to clean out old foraging tunnels.
For a gardener, chipmunks are not as destructive of crops as voles (which spend their time much closer to the surface) but nevertheless can be a nuisance where the dens are particularly large. Underground cavities can cause subsidence.
Comment: They definitely don't look like burrows; the holes are shallow with loose dirt at the bottom. I added some pictures from today with more detail.

What is making these holes in my yard?


What is probability distribution for a machine learning task?

Question: I am new to machine learning. I feel confused of how to understand the probability distribution of the training set, like $p(y|x)$ and $p(x)$, where $x$ is a training sample and $y$ is a label. Is there any concrete example to understand this? Further, it's said that the "ground truth" distribution is unknown and once you know it, there is nothing to learning. Could you help me clarify these words? Moreover, is it fair to say that a neural network or a deep learning model is learning the distribution of data? Thank you!
Answer: $p(y|x)$ represents the probability of a label given a sample, sometimes called the posterior, while $p(x)$ represents the probability (or density) of obtaining that specific sample. For example, in classification, we typically choose the class that maximize the posterior, i.e. $p(y|x)$. For example, $x$ can be a feature vector consisting of word counts in an e-mail and $y$ can be the label of it being spam or not.

it's said that the "ground truth" distribution is unknown and once you
  know it, there is nothing to learning

Let's say you've some data (e.g. think 1D), sampled from a Gaussian distribution. Even if you knew that the data is sampled from a Gaussian, you'd still need to estimate the distribution, i.e. its mean and variance and decide on some kind of estimates of true $\mu,\sigma$, i.e. $\hat{\mu},\hat{\sigma}$. Then, you can claim that the data distribution can be well approximated with $\mathcal{N}(\hat{\mu},\hat{\sigma})$, however it's not the true distribution. If you had known the true values $\mu,\sigma$, then you wouldn't need to estimate (i.e. learn) them from data, which means you don't need to learn anything. Typically, we even don't know the true distribution and assume forms. The discussion follows similarly for the joint, $p(x,y)$.

Moreover, is it fair to say that a neural network or a deep learning model is learning the distribution of data? Thank you!

More or less any statistical method aims to do that, either explicitly or implicitly. Deep learning as one of them certainly tries to model the data distribution, especially if you look from Bayesian perspective.
Comment: Thank you for your answer! For "Bayesian perspective", do you mean to maximize $p(y|x)$? For the first question, I think I need to make more clear of the basic assumption. When we talk about the probability, what is the sample space here and what are the events? For example, if we try to do object recognition for $N$ pictures of size $n\times n$ and $x$ represents a picture. Do all pictures form the sample space? Is $p(x)$ simply equals to $1/N$?
Comment: $x$ conceptually represents a picture, but it is a collection of pixels, just as in my spam example (collection of words = e-mail). Concretely, it is $x=[x_1,x_2,...,x_{n^2}]$ since there are $n^2$ pixels (RVs). $p(x)$ doesn't depend on how many training samples you have, i.e. $N$. It represents the whole population and in this case it is a density if pixels are continuous (if image is binary, then it is discrete but still it's not 1/N). Also, it doesn't have to be uniform, it's our prior belief about what the data could be, mostly it's *assumed*, not known and correspond to regularization.
Comment: By "Bayesian perspective" I mean performing our analyses under a stochastic framework (possibly with prior assumptions), not just from an optimization perspective. For ex, in linear reg. ($y=X\beta +\epsilon$), the LS solution is $\hat{\beta}=(X^TX)^{-1}X^Ty$, and you could find the same answer via pure optimization, i.e. w/o diving into likelihoods etc. The same ans. can be found via maximum likelihood, i.e. assuming noise as normal RV, and therefore $y|x$ as normal RVs, and we maximize $\prod p(x|y)$. If priors are involved (i.e. we assume some $p(x)$), we maximize $\prod p(y|x)$.


goodman furnace /ac no y terminal on board

Question: i live on a small budget and finally aquired an older goodman furnace (gmpn080-4)
and ac which were in very good condition out of a friends place and had only been used for 2-3 yrs. even the condenser outside was kept covered and secured when not in use . that said the units were in full working order together . they have been installed at my place all duct,furnace,a-coil,condenser (and charged) ,gas and main electric work is done .
but now i need some help on how to reconnect the low voltage wires .under normal circumstances i think i would have no problem but this furnace model has no Y terminal !!!
i only have 3 wires from the board W G R i bought a basic thermostat for heat/cool
ran a 5 wire of it and connected it at the thermostat as required also ran wire from condenser to furnace (airhandler). now i look at 5 wires from thermostat and the yellow and red from the condenser as well as the 3 wires red ,green and white from the furnace .missed the chance to be there during dismantling and i do not want to make a mistake and ruin what i have . where do they go ???
( i do not want to break the rules here by posting a link but pictures often tell more then words .there is an ebay listing that shows my exact board under the tittle : OEM Goodman Janitrol Furnace Control Circuit Board Panel B1809913S to see what i have )
i used to have grey hair but it turned white from googling this for days is there a way you could steer me to a wiring schematic that shows where i need to connect (assuming doubling up )the wires from the condenser to the board . the heat side i think i understand where to go. just not were i need to double the connection for the 2 wires from the condenser
any help be truly appreciated and thanks in advance !!!
Comment: Please post pictures! If you can't upload them using the built-in function, upload them to [imgur](https://imgur.com) instead and put a link in the comments
Answer: The furnace doesn't need a Y terminal, and in a lot of cases when it does have one, it's not connected to anything in the furnace.  Connect the wires from the thermostat as follows:

Red connects to R in furnace and R on thermostat.
White connects to W in furnace and W on thermostat.
Green connects to G in furnace and G on thermostat.
Yellow connects to the Red wire to the condensing unit.
White wire from condensing unit connects to 24V common terminal of the transformer.

Notes:

The 24V common terminal of the transformer should be grounded to the chassis, as well as connected to PIN 6 of the Molex connector on the board.
*The "hot" 24V terminal of the transformer should be connected to PIN 3 of the Molex connector on the board.


Intermittent low pressure natural gas to outside grill

Question: I have a Weber S-670 natural gas grill. For the last couple of months, the grill will not heat up after dark, when temperatures are lower. During daylight hours and higher temperatures, the grill works fine. I have contacted my gas supplier and they maintain I have a malfunctioning grill, not low gas pressure. I have had two separate Weber repairmen check the grill, during daylight, and they tell me the grill works as it should. Not sure how to increase pressure to the grill during neighborhood heavy gas usage. Any suggestions appreciated.
Comment: Here is something to try, when you experience the low pressure issue, pour some warm water over the pipe from your house to the grill. I suspect that there is not an  issue with the gas from the supplier, but a regulator either inline or on the grill that is having issues. It could be that it has gotten water in it and affecting the regulator.
Answer: As you can see from the image natural gas is supplied to commercial industrial and residential customers off the same line. I know it's a crude image but it's really how it works. If there was a significant pressure drop on a main branch of the system then commercial and industrial customers would be offline, resulting in Factory shutting down and other complications.  Residential draw is the equivalent of taking a cup out of a swimming pool. That being said I would replace the regulator. I have been on the receiving end of some really nice barbeques because of faulty regulators. I actually have a bin of them right next to me as I write this.  it's the one marked REGS it's an inexpensive repair. The only other thing I would look at is the gas line in your house. If it's undersized and your furnace or water heater starts you could experience pressure drop, resulting in a lazy flame.
Answer: Check also the maximum rate your gas meter can deliver and the maximum power of your grill. Remember that 1m^3/hr = 10kW, so if you have a G1,6 meter (1,6 m^3/hr) and your grill + furnace +  water heater requiore 40kW you have to increase your service because current service is undersized.
A test you could do is turn off furnace and water heater then test your grill.
Another possible issue is the feed pipe being too thin (or very long): long (thin) pipe brings high head, if head is too high gas flow is restricted (to fix you need to run a bigger gas pipe to your BBQ). I suggest long run to be done with 22 pipe instead of thin 12.
Answer: get a gauge measuring 0..15 or 0..30 inch water column
https://www.amazon.com/General-Tools-GPK035-Analog-Pressure/dp/B001TOJGD8?th=1
tee it in at the grill to measure natural gas pressure while grill is running and/or off.
Natural gas pressure after the meter should be around 7" water column going to your appliances.
Propane after it's pressure regulator runs around 10" water column to propane appliances.
10" water column = 0.4 psi.  Don't use any type of gauge that has a psi scale, you need a water column gauge you're measuring less than one psi.
Comment: https://www.homedepot.com/p/General-Tools-Gas-Pressure-Test-Kit-with-Hose-GPK035/202515833


Laser as an optical oscillator

Question: How can Laser can be compared to a positive feedback amplifier? Does the two conditions for oscillator holds good for lasers too.
Answer: The general notions, to wit, recirculation and highly frequency-selective amplification of noise, carry over almost exactly from electronic oscillators to lasers.
From 30 year old memory of electronic oscillators, though, I think some of the details of the dynamical equations are a little different. Also, recirculating a light beam is much more complicated than simply connecting the output of an amplifier through a resonant tank circuit to the amplifier's input port although the principle is the same: the former is a formidable optical alignment problem that is an entire discipline in itself, whereas the latter involves soldering a few wires or plugging in an SMC connector.
One striking difference is that the noise in a laser that initiates the amplified output has a nonzero center frequency to begin with; photonic processes yield light whose frequency is set by energy gaps and other fundamental physics. In contrast, most electronic oscillators work at baseband, frequency selectively amplifying wideband noise. The noise that initiates the amplified output in a laser can be amazingly narrowband to begin with. For example, in my answer here I show how the Schrödinger equation is solved for an excited atom relaxing into the electromagnetic field. The center frequency of the disturbance is set by the energy difference of the atomic transition. The atom is essentially coupled to all modes at all frequencies equally (or at least over a very broad band), but as it "tries" to relax into modes widely separated from the center frequency, destructive interference prevents radiation unless the EM modes' frequencies are well matched to the transition frequency. The stronger the coupling, the more marked is this suppression effect and narrower the line width. Even without a frequency selective resonant cavity, the $Q$ factor can be well above $10^6$. Below is a "picture" of Schrödinger equation solution for the relaxing atom photon production. The magnitude of the probability amplitude for the excitation to be in the mode with the frequency shown on the "frequency" is plotted as a function of time. At first, at times smallish compared with the transition time, the amplitude is spread over an extremely broad frequency range; as time evolves, the destructive interference sets in at frequencies removed from the center frequency. Ultimately, the probability for the excitation to be far from the center frequency is very low.

Final $Q$ factors of $10^{12}$ are not outlandish; linewidths of hundreds of hertz are, although specialist, not uncommon for many applications such as distributed fiber sensing and hologram production.

Laser as an optical oscillator


How can I insert a block into each page of a view if the page is loaded via ajax?

Question: I am trying to insert a SimpleAds block for each page of a View. But pages are loaded via AJAX using infinite pager. How can I insert a SimpleAds block into each dynamically loaded page of results?
Comment: Do you use http://drupal.org/project/views_infinite_scroll?
Answer: You want to add a javascript such one below to either your custom module or theme (would recommend module). This will react on a view that has a class view-infinitestack, so replace it to match yours view.
Where the debugging code is (console.log) you can add whatever JQuery you need. Eg. ajax call to fetch new content and inject it in another div, sidebar, or anywhere else on the page just by using JQuery, etc...
<code>(function($) {
  Drupal.behaviors.events = {
    attach: function(context, settings) {
      $('.view-infinitestack', context).ajaxSuccess(function(){
        // add your js here to refresh a block
        console.log('success');
      });
    }
  };
})(jQuery);
</code>
Answer: Checkout the block refresh module

As the name implies, Block Refresh allows an administrator to
  configure a block to refresh it's content in a given number of
  seconds. Block Refresh uses jQuery/AJAX so the refresh happens
  "behind-the-scenes".
Current Features:

Automatically refresh a block in a set number of seconds (configurable per block)
Allow site visitor to manually refresh block (configurable per block)
Answer: If they have a common path, you can simply create a Block and tell it to only appear when the path matches. So for example, if your path was something like 'ads/[date]/[title]'.
In your block, tell it to only appear for ads/*. That should achieve what your looking for.
Answer: It could be done using the tpl files.
Check the theme information you will find a common tpl file name place that block in "Display output" or "style output".
Its not the best way to do it, but you can do it in this way. :)


Difference between planet_osm_polygon and planet_osm_point tables

Question: What's the difference between the planet_osm_polygon and planet_osm_point tables? I find similar columns in both tables.
Answer: The difference is in the names: planet_osm_point contains point features from OSM, that is, nodes that have tags on them. Columns in both tables are tags, plus way for geometry.
Planet_osm_polygon contains polygons and processed multipolygons (so you don't need to collect multipolygons yourself). So, for example, building contours would be included in _polygon table, while shop nodes have to be collected from _point.
I don't know why it was decided to split points and polygons (and lines) into different tables. This probably allows disk space optimization, for tags allowed for those types of geometries are different (see default.style from osm2pgsql directory).
Comment: Well, I'd assume that has something to do with the possibility to work with the data as shapefiles. Whereas tab files can hold points, lines, polygons in one datalayer, shapefiles are distinctly only point, only lines, only polygons.  For your example shop nodes: there could be a polygon to show WHERE it lies and what shape it has, but the point data with the shop name allows for a POINT dataset to be styled with icons (i.e. icons for shops, gas stations, parking lots) which would be harder to do in the polygons.
Comment: Don't expect that shops always are found in the nodes table. They can be stored as polygon-only in the database too. You have to build centroids from them separately.


Binary file search tools

Question: Is there a open-source Linux tool / utility for Linux platform that would recursively search for binary files (executable, shared / static objects, etc), in a folder and display?
Comment: This question appears to be off-topic because it is about basic Unix shell commands. Not about reverse-engineering.
Comment: What do you mean by binary file ? Is, for an instance, mp3 music file binary ?
Comment: I have mentioned in the parenthesis: executable, shared / static objects, etc. I am not interested in .mp3 or .ogg or .gif or .jpeg :).
Comment: @perror, I believe, answer to the question helps to begin reverse-engineering a binary knowing that it belongs to 'a' architecture and one can process the binary alive on a compatible virtual or physical platform, the answer very much helps in disassembly or decompilation, it definitely helps to begin with, "...explore the principles of a system through analysis of its structure, function, and operation ...", so what if it is a basic Unix Shell Command?, requesting you to review your opinion, it is not necessary that only experts visit here.
Comment: Your question is way to basic and weak compared to the scope of this website. It could have been covered in [Unix & Linux](http://unix.stackexchange.com/) or in [SO](http://stackoverflow.com/) with no problem.
Answer: When looking for files containing executable code in a well known format, you could search using find and file:
find . -type f -print0 | xargs -0 file | grep -i "i386\|x86\|arm\|ar archive"

This will get you all files which file labeled with the processor name for i386, x86 or arm.
Note that there are many filetypes which file does not recognize.
It will for instance not recognize java jar files, or android apk files as executable.
Nor will it recognize raw firmware images.
What I actually usually do when researching an unknown system:

do find . | xargs file to get a large list of everything
then filter out known files, like audio, images, html, text, xml files.
then manually inspect what is left over.
file also makes lots of mistakes, i usually get quite some number of files labeled as DOS executable, which aren't, also i often see files mislabeled as DBase.
Comment: This will not find static libraries. You should add "i386\|x86\|arm\|ar\ archive"

Binary file search tools