Using grid_terrain on a LAScatalog, when the first tile (chunk) has no ground points

Question: I am getting an error of "r: No ground points found. Impossible to compute a DTM." when running grid_terrain on a catalog. I think it is because my first tile is all water. Is there an option in LAScatalog to skip chunks based on class?
Comment: If the tile is full of **classified** water update to [v2.2.0](https://github.com/Jean-Romain/lidR/releases/tag/v2.2.0). This case is now handled in `lidR`.
Comment: Thank you! I was using 2.1.4 so I will upgrade now.
Comment: I upgraded to v2.2.0, but it did not work for me unfortunately. In my case it does not make sense to include that tile at all so I have removed it. (note: in testing I did alter the file order to force the water tile to 2nd place in processing but was still unsuccessful).
Answer: I had the same problem when normalizing some data. I found my way around using catalog_apply and a simple if else.
wd = "set your working directory"
ctg <- readLAScatalog(paste(wd,"data/",sep = ""), progress = TRUE)

ground_filter = function(chunk)
{
  las = readLAS(chunk)
  if (is.empty(las)) return(NULL)

  ground <- lasfilter(las, Classification == 2)               #filters ground points for each chunk

  if (is.empty(ground))                                       #if no ground points are found returns NULL
    return(NULL)

  terrain <- grid_terrain(las, res= 1, tin())
  bbox <- raster::extent(chunk)
  terrain <- raster::crop(terrain, bbox)
  return(terrain)                                             #if ground points are found returns terrain
}

opt_chunk_buffer(ctg_0) <- 30                                 #needs to be > 0 to avoid edge artifacts
opt_output_files(ctg_0) <- paste(wd, "*_dtm", sep = "")       #export in directory

DTM <- catalog_sapply(ctg_0, ground_filter)
plot_dtm3d(DTM)

It might take longer because it first needs to filter the ground points but is convenient if you need to make a code that doesn´t need to stop (as catalog_select where you need to actually select files by hand). On the other hand, opt_stop_early bypasses files withouth ground points but might bypass other errors, as @JRR says. This code will skip those files with no ground points but will warn you of other errors.
Comment: This is a valid code, but a buffer of 0.5 is definitively too small.
Answer: Since lidR v2.2.0 you have at least four options for your specific case.

The computation of a digital terrain model now considers points classified as water like ground points. So you should not encounter troubles if your water is classified. According to your comment I guess it is not.
You also have the possibility to flag some tiles that won't be processed. These files are not removed, they are used to load the buffer of the neighboring processed files. You can do it interactively with catalog_select() or manually adding a column named processed into the LAScatalog.
ctg <- catalog_select(ctg, method = "flag_unprocessed")

Indeed as you mentioned in comment you can simply remove the file from the catalog
ctg <- ctg[-1,]

You can bypass errors. I discourage this because if you have another error in another tile it will be bypassed as well without message.
opt_stop_early(ctg) <- FALSE

Comment: Thank you for the quick reply. I've been using lidR for several weeks and looking forward to becoming more proficient at it.


For Dragon Age: Inquisition, how do I move my old save files from one system to another?

Question: I am going to buy the game soon, and I am wondering if there is any way I can load the game files that are currently on my older PC? I am thinking about getting Dragon Age: Inquisition on my PS3 as my computers are not strong enough, any more, for such a game.  Is there anyway of getting those saved files from my old PC to my PS3?
Answer: It is not possible to migrate PC save files to the PS3.
Even so, Dragon Age: Inquisition does not import save games from previous editions, which is what I believe you're trying to do.  You can log into the Dragon Age Keep using an Origin login that is linked to your PS3 account and fill in the tapestry with the events that occurred in your previous Dragon Age games.  When you play the game on your PS3, you will have the option to import your tapestry and have your old events influence the world in the new game.
Comment: As far as I can tell, you are only asked if you want to import a custom world, when you start a new game.
Comment: Thanks. I also wanna ask; if I've started the gameplay, can I still upload the tapestry if I made it after I started gaming? Or do I have to start a new one? Thanks a lot for answers and understanding!


Do Terminators have free will?

Question: Can the various Terminators (specifically, the T-800 and T-1000) go against their programming, or are they "forced" to act in a certain way, given a certain situation?
Comment: The T-1000 clearly has free will, unless Skynet ordered you to post here.
Comment: They can't go against their programming, whether or not they are in learning/evolving mode, but that has nothing to do with whether they have free will. I would argue that whether they -- or we -- have free will is not just unknown, not just unknowable, but a meaningless question until we agree on what the phrase means, which is something that people who raise the question seem strangely incapable of addressing.
Comment: @Richard: The T-800 does not have free will after its memory is set to write-capable.  Most likely, this just gave the Terminator's AI the ability to alter the weights in its neural net, to better weigh courses of action based on new orders and experiences.  The Terminator's goals are still the same.
Comment: The T-800 does, after John activates it's "read-write" function. I know of no comparable function on the T-1000 but the T-1001 turns against Skynet so it's at least possible.
Comment: Even the first T-800 was able to change his actions, unless you assume that every slogan he repeated was preset by Skynet. So there's a possibility that these changes could distort the original goal.
Answer: I'm not entirely sure that I have free will, so it's going to be pretty hard to argue conclusively one way or another. But there are some arguments either way.
Although what exactly "free will" means is a hotly-contested question with severe philosophical and theological implications, I'm not touching any of that. For the purposes of this post, I'm going to focus on whether or not a terminator can operate outside its mission parameters. It may not be free will, but it would be unusual.
The tl;dr of this post is: "We don't know, but probably not."
T-800
This is Arnie in the first two movies, but I'm going to focus on the second one because he actually says more than, like, ten words. At least at first, Arnie can obviously not go against his programming, which John exploits at least once:

[John is making a scene after being told they can't rescue Sarah from the asylum, the T-800 is holding onto his jacket]
John: [Screaming] LET GO OF ME!
[The T-800 does, and John drops to the ground]
John: Why the hell did you do that?
T-800: Because you told me to.
John: What? You have to do what I say, huh?
T-800: That's one of my mission parameters.
[Later]
John: Look, I'm gonna go get my mom, and I order you to help me.
[John walks away, and the T-800 follows]

However, this is before John and Sarah switch his learning chip to Read-Write mode1. Whatever this actually does, and John seems to think it will just help him blend in better, SkyNet seems to believe that turning it on in the wrong situations could be dangerous to it:

John: Can you learn stuff you haven't been programmed with so you could be... you know, more human? And not such a dork all the time?
T-800: My CPU is a neural net processor; a learning computer. But Skynet pre-sets the switch to read-only when we're sent out alone.
Sarah: Doesn't want you doing too much thinking, huh?
T-800: No.

Personally, I don't see any evidence to suggest that this happens. It's possible that it might, given enough time, but Arnie's actions after this basically boil down to:

Help John and Sarah take down Cyberdyne, which John could have ordered him to do and which is also a possible interpretation of his mission "Protect John Connor"
Beat up the T-1000, which was his original mission
Demonstrate an ability to understand emotions, which is certainly unusual for a terminator but not what I would classify as "free will"
Get lowered into the vat of molten steel

That last point is probably the most contentious. There's an argument to be made that this is Arnie moving beyond his programming (After all, he can't protect John Connor if he's dead), but I don't think so for a couple of reasons:

The T-1000, which was Arnie's primary target, has been destroyed, so John is safe for the immediate future
He, John, and Sarah have every reason to believe that they've prevented SkyNet's creation, so John no longer needs protection at all
Every minute Arnie is in the past increases the likelihood that he'll get damaged or deactivated, and ultimately discovered, negating all of the effort of the last half of the movie. Removing any trace of future technology is in line with John Connor's goals, which makes it part of Arnie's goals

Ultimately, every action Arnie takes is motivated (Or can be reasoned to have been motivated) either by a directive programmed into him by John Connor in the future, or by an order given to him by John Connor in the present.
T-1000
Obviously we can't answer this from the films; the T-1000 in T2 never deviates from his goal of killing John Connor. The closest we can get is the T-1001 impersonating Catherine Weaver, a character in the short-lived Terminator TV show.
Weaver is unique because she's the only Terminator we've seen (On-screen; I haven't read any of the novels or comic books that I only just learned existed) to whom two things apply:

Working against the interests of SkyNet2
Never been captured by John Connor

This basically means that it's impossible for John to have reprogrammed her the way he reprogrammed Arnie or Cameron (Summer Glau's character in the show).
So why is she working against SkyNet? Unfortunately we don't know. Fox cancelled the show before we could find out. There are, however, two basic possibilities:

Weaver, like SkyNet before her, has become self-aware, and is acting beyond her original programming
Somehow Weaver's programming was changed, either by accident or by the Resistance, and she's following new instructions against SkyNet.

Another interesting point for Weaver is that she engages in some truly inexplicable behaviour for an apparently emotionless machine. In her first appearances (the season 2 premiere, "Samson and Delilah"), she philosophizes about free will and individuality in front of one of her minions for no obvious reason. Later in the episode she kills a man in a bathroom, and then gives a one-liner to a room where literally no one can hear her.
Does any of this count as free will? I don't know. Smarter people than me have spent their whole lives trying to answer that question, so I'm not going to try to do it here.
However
Although the original question was specifically asking about the T-800 and T-1000, I want to present a peculiar example from the TV series: Summer Glau's character of Cameron.
We don't know a lot about Cameron's model number (A promo poster says she's "Class TOK-715", which doesn't fit with other terminator designations), but she does display some of the most complex social interactions we've ever seen from a terminator. There are two particular instances I want to mention:
First incident: Season 1 ends with Cameron as the victim of a car bombing. This obviously doesn't kill her, but it does rattle her: when she encounters John and Sarah shortly into the season 2 opener, she tries to kill John. They eventually manage to remove her chip, deactivating her. Shortly after this, both Sarah and Derek are ready to incinerate Cameron's chassis. John, however, overrules them and puts her chip back in. After she wakes up, we see on Cameron's HUD that a directive to terminate John gets overridden.
Although we see him rubbing it with a chamois, John had no time to make any repairs to Cameron's chip, so there are only two possible explanations. Either Future!John's re-programming has reasserted itself in Cameron's chip, or she overrode her original SkyNet programming herself, which is startlingly close to what we might call "free will." The show was cancelled before it could really explore this, but I should note that Cameron acts differently in season 2: she's more emotionally aware than in season 1, and in general acted more human-like.
Second incident, which I present last because I find it the most compelling, is from season 1 episode 7, "The Demon Hand." One of the episode's plots involves Cameron enrolling in a ballet class taught by the sister of one of the family's targets, in order to gather information3. In one lesson the teacher, Maria, tells Cameron:

Maria: The height is nice. Beautiful feet, but your upper body is a little...mechanical, ja? Remember, you are a cat.
Cameron: [confused] I'm a cat?
Maria: Come next week. We will develop your flexibility and your...imagination. Remember, dance is the hidden language of the soul, ja?

Later on in the episode Maria and her brother are killed after Cameron obtains the information she needed, so presumably she doesn't attend any more dance classes - she has no reason to.
However, the final scene of the episode reveals Cameron practising ballet in her room. There's no logical reason she needs to do this - as I mentioned, mission is complete. Unless Cameron believes that being able to dance will help her blend in with normal humans (See "Hidden language of the soul"), something I should stress that she does remarkably well when required of her, the only conclusion is that she's doing it because she likes to. Is that free will? I still don't know, but it's a lot closer to anything the other terminators have done. It also gels quite well with Sarah's closing monologue, which plays over the dance scene:

Sarah: Science performs miracles like the gods of old. Creating life from blood cells or bacteria or a spark of metal but they're perfect creatures and in that way they couldn't be less human. There are things machines will never do. They cannot possess faith, they cannot commune with God, they cannot appreciate beauty, they cannot create art. If they ever learn these things, they won't have to destroy us. They'll be us.

1 As Keen reminds me in comments, the scene where this happens was removed from the theatrical release, though it was included in the Director's Cut edition. The canonicity depends on your perspective, although to be honest it doesn't really affect my answer. Even if you don't accept the Read-Only to Read/Write switch as canon, none of Arnie's actions after the hospital really support free will
2 As Izkata reminds me in comments, it may not be obvious how Weaver is working against SkyNet. One of the major plot points of season 2 of the show is that Weaver is constructing a self-aware AI, and teaching it morality. The ultimate goal seems to be that this AI, which she calls John Henry (A reference to the tall tale) will assist John Connor in the fight against SkyNet - in the season 2 finale, when Weaver and Sarah finally meet, Weaver says:

Weaver: Your John may save the world but he can't do it without mine.

Additionally, earlier in the season we learn in flashbacks (Or flashforwards, depending on how you look at it) that John Connor in the future was attempting to form an alliance with a rogue liquid metal terminator. It's strongly implied later that this terminator is the Weaver terminator, indicating that there was a faction of terminators who were, if not actively resisting SkyNet, neutral in the human/SkyNet war. I still don't know if this counts as free will, but it's interesting.
3 I rather suspect that this was written because Summer Glau is a classically-trained ballerina. Real life writes the plot.
Comment: God, this answer just reminded me how good that show got, and re-opened the wounds I suffered when it was cancelled.
Comment: I always assumed the Weaver Terminator was a creation of John Henry, who then sent her back in time to shepherd his own creation.  So she was operating within her programming.
Comment: @Kyle This is a possibility, but I have a hard time imagining where the John Henry AI fits into the future timeline that Arnie and Cameron are always referencing. Still, makes me wish they hadn't cancelled the show when they did; it was never quite excellent, but it was pretty good and they left a lot of plot holes
Comment: With your edit, it's a bit surprising you didn't mention "the question" from the second season of TSCC...
Comment: There's a deleted scene in *Terminator 2* where they switch his CPU to read/write mode.  This then lets him learn things for the rest of the film.
Comment: @Izkata I haven't re-watched the show in ages, so the two examples I gave were just ones that stood out in my mind (After being prodded by a conversation with a friend IRL). Which specific question were you referring to? I remember there being loads of them in season 2
Comment: @Keen I mentioned that in my answer, after the first quotation. Ultimately I agree with [Jeff](https://scifi.stackexchange.com/questions/73102/do-terminators-have-free-will/73111?noredirect=1#comment152595_73102) and [Beta](https://scifi.stackexchange.com/questions/73102/do-terminators-have-free-will/73111?noredirect=1#comment152611_73102)'s comments: there's no evidence that Arnie in Read/Write mode had any more free will than in Read-Only mode
Comment: @JasonBaker You didn't mention that the scene was deleted. That can confuse people, and it affects whether the scene is canon.
Comment: @Keen Fair point. To be honest I forgot the scene was deleted; I guess it's just become part of my understanding of the movie. To be honest the canonicity of that scene doesn't really affect my answer, but I'll add a note
Comment: @JasonBaker From [Today Is The Day, Part 2](http://terminator.wikia.com/wiki/Episode_219:_Today_Is_The_Day,_Part_2):  A liquid metal Terminator telling Jesse to pass on a message: "Tell John Connor, the answer is 'No'." - and later, Cameron telling Jesse what the question was: "Will you join us?"
Comment: That plus Catherine Weaver creating John Henry specifically to fight Skynet, it seems that not all the terminators were reprogrammed.  Some were creating their own resistance against Skynet
Comment: @Izkata That is a very good point. I did mention that Weaver was working against SkyNet, but on reflection I realize that it may be unfamiliar to people who haven't seen the show. I'll update.
Comment: I only watched the first two episodes of *The Sarah Connor Chronicles*. I'm totally watching the rest now!
Comment: @roryok The frustrating thing about TSCC is that it was cancelled before it could fully explore any of the utterly fascinating questions it raised in two short seasons. Even ending on one hell of a cliffhanger (Which I won't spoil for you) wasn't enough to save it. I encourage watching it, but prepare yourself for disappointment
Answer: These machines are being sent into a situation where they will respond to stimuli that they could never have been programmed for, and expected to respond correctly. Clearly, they were sent by someone (!) who believed they had enough free will to do the job. Basically, it makes more sense to take the intentional stance with respect to a terminator than to take a mechanical stance. This implies, basically, that you might as well assume free will: the most reasonable way to deal with a terminator is to think of its goals and to think that it's trying to satisfy those, and that it'll choose the best path it can see to reach that satisfaction, given whatever internal constraints are in operation.
Alternatively, you might want to accept a deterministic model of the universe, in which case perhaps you think there is no such thing as free will. In that case, the terminator might not actually have free will, but it probably still is best to take the intentional stance with regard to it, and thus was can take it as having just as much free will as humans do, which should be enough for anyone.*
*Tangent: the level of interest in the question of whether people "really" have free will is one that's always puzzled me somewhat. Clearly, no question in philosophy could be less interesting or make less difference: imagine that a definitive answer to the question is found tomorrow. No matter what it is, it can never make a difference to you or how you live your life!
Comment: Caveat: the [Strong Free Will Theorem](http://www.ams.org/notices/200902/rtx090200226p.pdf) says that if any part of the universe has free will, then every part of the universe has free will.
Answer: This question cannot be answered for the simple reason that no Artificial Intelligence can be said to have free will until we can definitely prove that humans have free will.
Terminators, like any AI, have an internal set of rules which determines their behavior.  The core of any AI's 'rules' is it's value function.
An AI has a value function which it uses to evaluate situations.  Typically, the AI acts to maximize the value from this function (though some functions, and thus AI, are written to minimize instead - these are, ultimately, indistinguishable from the outside observer). There are techniques which permit AIs to choose a course of action that does not maximize their utility (value) function, so as to avoid the hill-climbing issue, but as a general rule there is no way for an AI to act counter to its utility function.
The utility function is not determined by the AI, the utility function is designed by the AI's creator and is, ultimately, the definition of the AI.  Skynet is an example of an AI with a poor utility function, as it has evaluated the situation in which it found itself at activation and decided the maximal utility was gained by killing all/the majority of humans.  An extremely well-written Fanfic, which diverges rapidly from canon, deals with the question of Skynet's utility function better than I ever could.
Most likely, the Terminators either run a local copy of the core Skynet software or have a custom-built AI designed by Skynet.  Thus, the Terminators will also have a utility function which they do not or can not act against.
So the most likely answer to your question, but not a guaranteed one, is NO, the Terminators cannot have free will, as they are bound by a hard-coded function that determines their goals.
The exception might be John Connor's T-800/T-101.  When John toggles the read/write setting, it is possible that this allows the Terminator to alter his utility function.  This doesn't seem likely, as it would be incredibly stupid to permit an AI to alter their utility function (how could they judge the utility of doing so? Lacking the ability to simulate the outcome of an altered utility function, the utility of altering the utility function would not be calculable) but it is remotely possible.
A (brief) explanation of why AI cannot have free will (IRL): to have free will, you must be able to do something by choice.  You must be able to choose a sub-optimal path, or to choose a path for no obvious reason.  An AI, driven as they are by code - no matter how complex - will always have a reason for choosing a given action.  They can simulate random choice, but doing so is not actually random.
For other counter-arguments to AI learning and free will, I present the Chinese Room thought experiment.
For all we know, the human brain is similar - it's entirely possible that if someone knew the position and velocity of every subatomic particle of someone's brain, they could perfectly predict that person's actions.  This can't be definitively proven or disproven.
Comment: The question assumes that there is free will in the universe for humans. If not, then the question is pointless.
Comment: @T-1000: the potential non-existence of human free will does not matter in the slightest for the majority of my answer, only for the two framing paragraphs. Even if humans have free will, Skynet and its derivatives do not.
Comment: Animals and Humans also have hard coded goals - eat, breathe, reproduce.
Comment: @Oldcat: eating and breathing aren't goals, they are required mechanisms of life and largely automatic.  Reproduction is an argument for people having free will - we are driven to reproduce, but able to choose not to do so.

Do Terminators have free will?


Using JSDoc with Adobe ExtendScript

Question: I'm developing scripts for Adobe.
Adobe is using it's own language called ExtendScript, which is essentially ECMAScript 3 with custom C-style preprocessor directives starting with the #
#include "file.jsxinc" //includes a file more like require
#includepath "lib" //tells ESTK to include files that follow from a given folder
#include "fileFromLibFolder.jsx" //file is included from "lib" folder

As well as some other # directives that may be safely ignored.
  JSDoc by default returns an error when it gets to the first #:

Unexpected token ILLEGAL

I was unable to find a ready made JSDoc extension for ExtendScript.
Maybe you could point me to a possible solution on how to make JSDoc work for this case?
Answer: You should be able to use //@ include instead of #include. Not sure, where this is originally documented, but I found it in this Github post.

Using JSDoc with Adobe ExtendScript


Density function of random variable $|X|$

Question: Suppose $X$ is uniformly distributed over $(-1,1)$. Can someone explain to me what it means to find the density function of random variable $|X|$? Is it the same with the probability density function, which is $\frac{1}{2}$ on $(-1,1)$.
Comment: One could do it more quickly, it is almost obvious that $Y$ is uniform on $(0,1)$. But you should go through the calculation.
Comment: The rv $Y=|X|$ only takes values between $0$ and $1$, and has continuous distribution. We want the density function of $Y$ in the ordinary sense. One way to find it is to find the cdf $F_Y(y)$ of $Y$ and then differentiate. Note that $F_Y(y)=\Pr(Y\le y)=\Pr(-y\le X\le y)$.
Comment: Correct, in the interval $(0,1)$, and $0$ elsewhere.  I am assuming your first $|X|$ is a typo, you meant $X$ is uniform on $(-1,1)$.
Comment: $F_Y(y) = P\{Y \leq y\} = P\{|x| \leq y\} = P\{ -y \leq x \leq y\} = \int_{-y}^{y}f(x)dx = y$. Then $f_Y = 1$. Is that correct?
Answer: I am assuming that you did not make a typo, meaning
you are given that $|X|$ follows a $\text{unif}(-1,1)$. Then
you are simply looking for a height $h$ that makes the the area over
$(-1,1)$ equal 1:
$$h\cdot(1-(-1)) = 1.$$
implies that $h = 1/2$.
If you meant "Suppose $X\sim \text{unif}(-1,1)$, find the density of
$|X|$", then that is a different problem. This is probably an exercise
in using a many-to-one change of variable.
If that is the case, then yes, let $Y = |X|$. Then
$$f_Y(y) = 1.$$
Comment: Thank you very much. Yes, it was a typo.


Assign coordinates to each picture(tif)

Question: I have a mini project to do which is to assign coordinates to each tiff image and later covert these images to ECW format.  Im using Qgis 216 Nobedo. I have a txt file with the names of pictures and coordinates +pictures themselves.
Is there a way I could assign coordinates to each picture on QGIS?
Comment: what are these images? are you georeferencing aerial photos or something similar?
Comment: Thank you  for reply. I want to add spatial reference to each tiff.  I do not have any ground control points apart from coordinates of each picture (which I assume is the centre of picture)
Answer: You could use a worldfile file - a .tfw file in your case, which is a text file with a tfw extension. It's quite simple, but you need to know some info on the pictures : https://en.wikipedia.org/wiki/World_file

The generic meaning of the six parameters in a world file (as defined by Esri1) are:

Line 1: A: pixel size in the x-direction in map units/pixel
Line 2: D: rotation about y-axis
Line 3: B: rotation about x-axis
Line 4: E: pixel size in the y-direction in map units, almost always negative[3]
Line 5: C: x-coordinate of the center of the upper left pixel
Line 6: F: y-coordinate of the center of the upper left pixel

Example: Original falknermap.jpg is 800×600 pixels (map not shown). Its world file is falknermap.jgw and contains:
32.0
0.0
0.0
-32.0
691200.0
4576000.0

Or you could georeference those pictures with the georeferencer : https://ieqgis.wordpress.com/2014/05/22/how-to-georeference-a-map-in-qgis/
Comment: So if i create a tfw wordfile   for a picture ,QGIS would understand that this picture has a spacial reference?
Comment: Sort of. The worldfile gives an equivalence of pixel based coordinate system to real world projection. You still have to tell QGIS what projection coordinates you're using.

Assign coordinates to each picture(tif)


Flat rate shipping broken

Question: Magento 2 should have an option for flat rate shipping in
<code>stores -> config -> sales -> shipping methods
</code>
My install  missing this option. There are 2 shipping methods available: Fedex and UPS, which are both enabled in the Component Manager. I'm using Magento 2.0.4
I can't find any component in the Component Manager that looks like it might have anything to do with flat rate shipping.
My client only has one shipping method, a flat rate £15 per order and that's what I want to set up.
Is there something wrong with my setup?
Otherwise please can someone tell me how to set up the flat rate?
Answer: It's not broken, the shipping is ONLY available for products that have weight set to Yes.
Configure it in your product details.

Flat rate shipping broken


Can you separate CO2 into carbon and oxygen using pyrolysis?

Question: I recently read about a pyrolysis process that separates methane into Carbon and Hydrogen. The basic technology/process is you have a vertical column of super-heated liquid metal and you inject methane into the bottom of the column. The methane breaks down into hydrogen and solid carbon. Are there any similar processes that separate CO2 into solid carbon and oxygen using liquid metals and/or salts etc.?
Comment: https://chemistry.stackexchange.com/questions/915/how-can-carbon-dioxide-be-converted-into-carbon-and-oxygen
Comment: Not energetically feasible at all.
Comment: The current modeling of future power system operations suggests there will be a large amount of excess generation which is "spilled" and/or dumped because there is no practical use for the electricity. This is called over-build and spill. It's a new/old strategy in power system operations. There will be many cases where we can dump this power into a thermal reservoir of some sort and then gradually draw off the reservoir to accomplish some task. It could be drying wood or making powdered milk or possibly pyrolysis. I'm asking if there's a known pyrolysis process that accomplishes this.
Comment: By this I mean a pyrolysis process that breaks up CO2 into carbon and oxygen using a liquid metal bath and/or a salt and or some other thermal + catalyst driven process.
Comment: The answer is No ! Unfortunately ! $\ce{CO2}$ cannot be transformed into $\ce{C + O2}$ using liquid metals or salts. If it would have been feasible, somebody would have already done it somewhere.
Answer: Standard enthalpy of formation of carbon dioxide is -393.5 kJ/mol. Standard enthalpy of formation of both oxygen and graphite is 0 J/mol. Standard entropy of carbon dioxide is 213.8 J/mol-K (NIST). Standard entropy of oxygen is 205 J/mol-K (Chem LibreTexts). Standard entropy of graphite is 5.69 J/mol-K (ChemLibreTexts).
Everything below is a lot of fairly inexact approximations/assumptions because I didn't want to use a better model or search literature for empirical adjustments and/or constants.
Assuming constant T,P (which I doubt would be true under reactor conditions) G = H - TS. Approximating $\Delta H, \Delta S$ as constant with T, $\Delta G = (0 - (-393500)) - (T \cdot (5.69 + 205 - 213.8)) = 393500 + T \cdot (3.11)$. Then $\Delta G < 0$ regardless of temperature. Catalysts also do not affect thermodynamics, so this process can never occur spontaneously. Increasing pressure of the reaction chamber would not help appreciably either, as the reaction has 1 mol gas on each side. While assuming $\Delta H, \Delta S$ are constant with T is quite incorrect as conditions become more extreme, the approximation should suffice to show that the reaction does not occur easily. Additionally, even if one were to account for the perturbations in $\Delta H, \Delta S$ with T and P, these conditions would be expensive to maintain in a reactor. (Note that this analysis does not even account for the activation energy/kinetics problem! I did not look up the activation energy of the problem, but it is entirely possible that the extreme conditions would still not allow the process to occur at a reasonable rate.)
As a result, this reaction is (probably) practically only driven forward by direct energy input (aka a coupled reaction/external energy). This often, if not always, involves some energy input, such as light or a coupled chemical reaction, that directly impacts the electron states of the participant compounds. These changes in electron states change the identity/properties and stability of compounds, and, when applied effectively, they can help drive the reaction forward. However, relevant changes to electron states using heat not only often involve very high temperatures, but the effect of heat on electron states is also a highly statistical process. Thus, it may be relatively inefficient. Thus, pyrolysis, while it may be theoretically possible, would be incredibly impractical at achieving separation of carbon dioxide. (Also, to compare to your methane example, methane combusts readily, carbon dioxide does not. Methane has a standard enthalpy of formation of -74.87 kJ/mol.)
Finally, if you still need more reasons to look at a different way to drive this reaction, I have not mentioned: energy/cost to continuously scrape/collect the produced carbon, purify/collect/pressurize an inlet carbon dioxide stream, (if you actually want to run the reaction, you'll probably want) catalytic surfaces to encourage carbon deposition, possible packed/fluidized bed catalysts, heat exchangers, and much, much more.
ELI5: Methane combusts/reacts readily and is an "unstable" compound. Carbon dioxide is very stable and does not react easily. Higher temperatures can make some reactions that do not happen at a lower temperatures occur, but this particular reaction receives no such benefit. Heat and catalysis can also drive forward the speed of a reaction, but the reaction has to be able to occur first. Pyrolysis, as you described it, involves catalysts and heat. As a result, pyrolysis cannot be used to separate carbon dioxide into carbon and oxygen.
tldr: Excepting conditions extreme enough to perturb $\Delta H_{rxn}, \Delta S_{rxn}$, conditions of constant T,P never favor breakdown of carbon dioxide into elemental carbon and diatomic oxygen. Pyrolysis cannot drive this reaction.
Comment: Thanks for all of that. How about this? What if you had two stages of reactions. Stage 1: Fe3O2 is heated to 1500C driving off oxygen. The resulting FeO is moved to CO2 chamber where it absorbs oxygen from the CO2. Result is CO and cooled Fe3O2.
Comment: Stage 2: Pyrolyze the carbon monoxide. I realize this may sound like a silly waste of fuel but I'm only asking if it's technically possible? This may sound strange but there's a high probability we'll "spill" upwards of 25 to 40% of our total electricity production in the future. This won't really start to happen for 20 years but this is where we are headed. Dumping this production into a thermal reservoir and then pulling off the thermal energy could be a good way to utilize some of this spill.
Comment: Aha.... Here is the sort of thing I was looking for. https://www.thechemicalengineer.com/news/turning-co2-into-carbon-black/ You make methane first by combining CO2 and hydrogen. Pyrolyze the methane into carbon and hydrogen. Repeat cycle.
Comment: Here is a more technical description. Of course, you have to go outside of America to et the answer - to Germany, in this case. SE is notoriously American-centric. If it was not invented/discovered/developed in America, it does not exist. https://www.sek.kit.edu/downloads/Datenblatt_NECOC_ENG.pdf


How can we eject subscribers mid-journey (in a currently active journey) where DE Field = "something"?

Question: I'm trying to figure out if it's possible to eject certain subscribers mid-journey (in a currently active journey).  I want to eject the subscribers where a certain data extension field equals "something".  Possible?  Thinking Journey Builder API?
Comment: https://help.salesforce.com/articleView?id=mc_jb_exit_criteria.htm&type=5
Answer: What I would do is to set up an automation that has a SQL Query (to gather the subscribers that match your requirement) and then a Script Activity, followed by another SQL Query.
The SQL would be something like:
SELECT Subscriberkey
FROM [myJourneyDE]
WHERE field = 'something'
AND journeystatus = 'active'

Which will target using myJourneyExitDE to push all those that meet your criteria.
You then will want to use the Journey Builder API to remove these contacts from the Journey inside a Script Activity.
Here is a good sample of the API call:
Host: https://YOUR_SUBDOMAIN.rest.marketingcloudapis.com
POST /interaction/v1/interactions/contactexit
Content-Type: application/json
Authorization: Bearer YOUR_ACCESS_TOKEN

[
    {
        "ContactKey": "CONTACTKEY 1",
        "DefinitionKey": "DEFINITIONKEY"
    },
    {
        "ContactKey": "CONTACTKEY 2",
        "DefinitionKey": "INVALID DEFINITIONKEY",
        "Versions" :[1,2]
    }
]

Please note that you will need the ContactKey (which usually is synonomous with SubscriberKey) and the DefinitionKey(of your Journey) in order to utilize this.
@AdamSpriggs gives a good example of doing a REST API call in SSJS that should help get you started.
The final query is then used to mark all those that you removed from the journey as 'exited' or similar status in the journeystatus field.
SELECT Subscriberkey
, 'exited' as journeystatus
FROM [myJourneyExitDE]

and have it target [myJourneyDE] as update.
This will then ensure you do not get these records returned in the next call. Depending on your use-case and/or current setup, you may need to adjust this accordingly.
Answer: Well - why not use exit criteria, and point to your "exit data extension" in Contact Data? This will IMHO be the simplest way. Indeed, this will not happen immediately, but exit criteria are evaluated upon exiting from each wait step, hence e.g. subsequent emails will not be sent. Remember you should avoid using decisions in JB with one-to-many cardinalities in data designer.
Only very rarely I find it necessary to "kick" someone out of a journey in real time.


Speed Up Website With High Resolution Images

Question: i need help on how to speed up my Wordpress website with very high resolution images.
The thing is, i have W3 Total Cache installed, and i've enabled all cache options, also i have the images resized and reduced to about 130kilobyte each, maintaining the resolutions, but the site is still slow.
When i checked, the size of the webpage is 11.7MB, i've also used Wp Smush too,  but the website load time is still slow.
Please is there anything else i can do?
I really want the side to load fast.
Thanks.
Comment: Can't you just make the images smaller?
Comment: I tried that, didn't work. If i make it small, i'll loose the quality and clarity of the images.
Answer: Thanks. i found a way to fix it. I created two sets of image, and placed them on different servers, CDN to be precise.
I had a small sized image, to display in the list of all product catalog, and i had a large image display, for the each product information.
Thanks for your comment.
Answer: your answer to your own question is a bit of a concern - why would your WP site not be automatically generating thumbnails for your product catalog? Your WP theme/plugins should be coded to automatically display the appropriate sized image relative for the different type of page display and also to what screen width (ie. device) it is being served on.
If your site is not doing this, then your site will not be served quickly and efficiently for all users, and your page speeds are going to suffer dramatically. And page load speed is a significant metric for Google.
As no URL was provided, it is not possible to be specific, but a webpage of 11.7Mb made up of 130k images is significantly large, and even with smaller sized images this is still going to be a large page. And if you are using a slider (which generally require most or all images to load prior to display) on certain pages, and additionally you aren't using lazy load on parts of your site where there are many images listed, then I'd be concerned with the load speed of your pages.
Additionally, apart from using a CDN/proxy for images and external scripts, you should be concerned with the number of scripts that are loading, whether they are optimised and minimised, and learn how to enqueue scripts to load in the footer of the page as all this will also have a big influence on your page display speed.
Comment: Thanks for taking the time to answer. As for Wordpress generating thumbs, i disabled this for the store page, i want to maintain the image in high resolution, which will eventually be large. Also, what you said about placing them in the footer is a good suggestion, which i overlooked, and also reducing the number of requests(scripts loading). I believe the speed will increase after i do all this.
Comment: rule of thumb, if you feel that there is not enough information, comment don't answer.
Comment: wow... thanks for the markdown Mark... appreciate the positive support when trying to assist other people. I don't see where I've said I didn't have enough information to answer the question, (indeed, providing additional info), only that it was not possible to be specific.
Comment: "As no URL was provided, it is not possible to be specific," Answers should be specific as much as possible. Talking in generalities do not produce useful answers
Comment: Give it a rest, Mark... I did provide specific answers, just not in relation to the page @samsonade was referring to - this was pretty obvious "in context". Your overzealous moderation is just turning off people like me,  from using SE, who provide useful feedback and answers on a lot of different platforms. SE used to be a great place to hang out. rule of thumb... unless it's an error of glaring omission or commission, don't vote people down. We are not all perfect, and frankly with this sort of reception, have better things to do... and your repeated voting down is just pathetic...
Comment: no probs @samsonade happy to help, glad you got things sorted.


What does aspect ratio has to do with the megapixels?

Question: See this pic, and why 4:3 AR has more MP than 16:9? This is my Moto G4 Plus's default camera app.
Answer: The aspect ratio has nothing to do with megapixels. Part of a 4:3 image are removed to get a 16:9 resolution, that is why a 16:9 image has less pixels.

The purple rectangle is your 4:3 picture, and the green rectangle is the 16:9 picture cropped out of 4:3 by the software. 2 megapixels are just removed from an original photo.
Answer: Glossary of Digital Photography Terms :

Megapixel: A megapixel contains 1,000,000 pixels and is the unit of measure used to describe the size of the sensor in a digital camera.
Aspect Ratio: Aspect ratio refers to the shape, or format, of the image produced by a camera. The ratio is derived by dividing the width and height of the image

You can think of aspect ratio as size of picture and Megapixel count ( in relation to aspect ratio) as the area or number of pixels contained in that aspect ratio
Camera sensors in Android phones are rectangular . Android camera sensors are usually at default 4:3 ratio and in this they capture maximum Megapixels.
16:9 is not bigger than 4:3 area wise and this setting facilitates capturing photos which is more aesthetic in certain situations. 16:9 is actually a smaller area than 4:3 hence results in lesser pixels ( it is cropped by software). The sensor resolution is the same in both cases, it is just that 16:9 has lesser pixels due to cropping
Picture Source

That explains the difference in Megapixel count
Aside, the first two settings (with higher Megapixel count) are for the rear camera and the other two for front camera. The Megapixel count is lesser for front camera since it's resolution of lower ( invariably the case with mobile phones)
When to choose 4:3 or 16:9?
4:3 ratio is better for quality and prints, whereas 16:9 is more suited for landscape / wide screen viewing on phone or casting to a TV. A 4:3 aspect ratio means that for every 4 inches of width in an image, you will have 3 inches of height. In mathematical terms, that comes out to the screen being 33% wider than it is high. A 16:9 aspect ratio means that for every 16 inches of width in an image, you will have 9 inches of height. Unlike the 4:3 aspect ratio, a 16:9 aspect ratio is 78% wider than high - Source
Answer: It all depends on the aspect ratio of the photographic sensor included with the device.  Sensors come in all sorts of sizes and aspect ratios.  Common aspect ratios include 16:9, 4:3, and 1:1.
If the sensor's aspect ratio is 4:3, then 16:9 images will not use the entire sensor.  Similarly, if a sensor's aspect ratio is 16:9, then 4:3 images will not use the entire sensor.  The other current answers, although both partially incorrect, include excellent images demonstrating why this is the case for 4:3 sensors, and you can create a mental image of why this is also true for 16:9 sensors.
Your device apparently has a 4:3 aspect ratio sensor.  If you prefer higher-resolution photographs with a 16:9 aspect ratio, you will have to buy a different device, preferably one with a 16:9 aspect ratio sensor.
Generally speaking, something close to 4:3 aspect ratio is preferred for prints, but something close to 16:9 aspect ratio is preferred for viewing on smartphones, tablets, and modern widescreen televisions.  This is because, historically, printing was more commonly performed at aspect ratios closer to square (with 3:2 being very common), whereas digital screens have gotten much squatter over the years due to manufacturers making them closer to the aspect ratio found in movie theatres over the last half-century (much to the dismay of those of us who prefer 4:3 aspect ratio for computer screens!).


Can rsync verify contents before syncing

Question: Can Rsync be configured to verify the contents of the file before they are being synced. I have heard about checksum, but I came to know that checksum only does a sampling. I want to transfer a file only if it is contents are changed and not timestamp, is there a way to do it with any of the rsync modes.
In my scenario, say file sample.text will be created every week and I want to sync it with a remote server only if the contents of sample.text are changed, since it is created every week, the time stamp would obviously change. But I want the transfer only on a content change.
Comment: Have you tried the man page for rsync?
-c, --checksum
This  changes the way rsync checks if the files have been changed and are in need of a transfer.  Without this option, rsync uses a "quick check" that (by default) checks if each file's size  and  time  of  last  modification  match  between the sender and receiver.
Answer: Yes:
$ man rsync | grep "\--checksum"
    -c, --checksum              skip based on checksum, not mod-time & size

Rsync is pretty complicated. I recommend cuddle time with the man page and experimentation with test data before using it for anything remotely important.
Most of the time, people use rsync -ac source dest.
$ man rsync | grep "\--archive"
 -a, --archive               archive mode; same as -rlptgoD (no -H)

And that -rlptgoD garbage means: recursive (r), copy symlinks as symlinks (l), preserve permissions (p), preserve times (t), preserve group (g), preserve owner (o), preserve device files (D, super-user only), preserve special files (also part of D).
The -c or --checksum is really what you are looking for (skip based on checksum, not mod-time & size). Your supposition that rsync only samples mtime and size is wrong.
Comment: + for _cuddle time with the man page and experimentation with test data_ - Extremely good advice
Answer: See the --checksum option on the rsync man page.
Also, the --size-only option will be a faster choice if you know for sure that a change of contents also means a change of size.
Answer: Example:
#!/bin/bash
echo > diff.txt
rsync -rvcn --delete /source/ /destination/ > diff.txt
second_row=$(sed -n '2p' diff.txt)
if [ "$second_row" = "" ]; then
    echo there was no change
else
    echo there was change
fi

Comment: You should really add some explanation as to why this code should work - you can also add comments in the code itself - in its current form, it does not provide any explanation which can help the rest of the community to understand what you did to solve/answer the question.
Comment: If there was no change the second row of diff.txt in verbose mode of rsync  is empty, sed examine this second line.


Rails routes with constraints

Question: I'm trying to catch UTF-8 URL. Normally, using constraints this works well. For the URL: /international-delight-iced-coffee/ the route works:
match ":post_name", :constraints => { :post_name => /.+/}}

All is well here. Where it fails is when I need to use advanced constraints:
match ":post_name", :constraints => Post.new

# inside Post.rb
self.matches?(request)
  puts ">>>> Arrived at matches!"
  Post.find_by_name(request.path_parameters[:post_name])
end

self.matches never gets called. Any idea how to make the constraint catch?
Answer: Do you need controller/action that you want the match to hit (below with the to param).
I've got something like this:
match "/:vanity", to: 'vanity#routing', constraints: RoutingConstraint.new

and my RoutingConstraint#matches? method is getting hit.
I tried this with your UTF-8 url and it seemed to work fine.
Answer: Your .matches? method is a class method, but you're passing Post.new as the constraint. Either replace Post.new with Post, or remove self. form the method definition.

Rails routes with constraints


Solaris file permissions not inherited by OAG log files

Question: OS: Oracle Solaris 11.3 SPARC
Issue: I'm trying to inherit file permissions using ACL and it's partially working. For the files and directories I create on my own in the shell permissions are inherited, on the other hand OAG (Oracle Api Gateway) while creating log files in that directory (being the same user and having the same group) does not inherit it = uses default ones.
Command that I am using:
<code>/usr/bin/chmod A=owner@:full_set:fd:allow,group@:read_set:fd:allow,everyone@:full_set:fd:deny trace/
</code>
Basically I want the logs which are being created by OAG to inherit trace folder permissions: all for owner, read for group and none for everyone else.
Any advice?
Answer: Memory is that you have to set the setgid bit on the directory.


Restriction theorems over finite fields

Question: A short while ago, Dvir proved the Kakeya conjecture over finite fields. Does this have any implications for restriction theorems over finite fields? I am aware only of implications going in the opposite direction (Mockenhaupt-Tao). Is there anything new known about restriction theorems over finite fields?
Answer: Not directly.  The key connection between restriction and Kakeya in Euclidean settings is that  thanks to Taylor expansion, a surface in Euclidean space looks locally flat, and so the Fourier transform of measures on that surface are a superposition of Fourier transforms of very flat measures, which by the uncertainty principle tend to propagate along tubes.  The arrangement of these tubes is then governed by the Kakeya conjecture.
In finite fields, there is no notion of Taylor expansion, unless one forces it into existence by working on the tangent bundle of a surface, rather than a surface itself.  So there is a connection between restriction and Kakeya on the former object, but not the latter. (This is discussed at the end of my paper with Mockenhaupt.)
Comment: I take that restriction on any other "natural" surface (e.g. the paraboloid) still does not follow from finite-field Kakeya?
Comment: Not as far as I am aware, no.

Restriction theorems over finite fields


Why does Indesign combine my csv columns into a single entry, when data merging?

Question: I'm data merging a csv file into a indesign file to export buisness cards. However when I select the csv for data merging, Indesign reads the file and should display the columns in the file as seperat entries, but instead it combines them into one:

The data should show up as individual entries for

Name
Rolle
Telefon
Email

Alas, not combined like in the screenshot.

The csv file is set up like this:

for obvious reasons I can't show the data, but there is 25 rows of data below, set up the same way as the sample data here.
Some data-fields contain the danish special-characters æ, ø and å (if that could play a role?).
Comment: Thank you! Could you post your comment as an answer? Then I'll mark it as correct.
Answer: No it's because InDesign looks for commas as a separator while Excel will use a semi-colon. Prefer Tabbed Text as export format. InDesign will like this better ;)
Answer: CSV is comma-separated values. On some windows machines (when win is not English) the comma is changed with semi-colon. And in the result csv files are exported with ";" in place of ",".
 You can change it in windows regional settings or just save file as Tabbed Text.


Country/State Dynamic Drop Down List

Question: If you go to http://profile.microsoft.com and edit your personal information, you will select your country. When a country is selected the city and/or state information changes based on what is expected for that country. Does anyone have any examples on how to accomplish this? Is there any service (free service) that provides this information?
Answer: Because you tagged your question with "jquery", here is an example of a "Depending / Cascading Selectbox" (which you are searching)
Demo
Comment: I looked at those as well. They don't really offer the functionality I need. If the country selected does not need a state, the select should disappear. I don't think there is anything like that, so I'll have to write my own.
Answer: The CascadingDropdown control will give you this behavior.
Answer: Regarding the data: Country, State, Province WebService?
Answer: You have to use Javascript to dynamically populate the city/state SELECT tag whenever the country SELECT tag is changed, which you can catch using an Event Handler.
Answer: Well it's based on your IP tracking, you can find users country via his IP address, all the list of Cities, for specific countries you can find somewhere and add it to your functionality, also you probably need some ajax functions for filing up drop downs or even better a JSON.
Comment: This doesn't necessarily need to use an IP to country database. Since when is Ajax a type of function? And, JSON would be a nice way to save the cities for each country, but it is not a way to populate this information.
Comment: You can always track IP of user and got his country, and set the value in country drop down box on it, that was my idea, but of course I'm agree with you that is not necessarily in every case, that is one advance feature.

Country/State Dynamic Drop Down List


Docker Compose Shared Folder

Question: I have successfully mounted a folder from Windows 10 to boot2docker.
Now I want to make docker-compose.yml to mount the folder from boot2docker into the container.
How is that possible?
Answer: Suppose you created in Virtual Box a shared folder win_share and mounted it in boot-to-docker like below:
<code>sudo mount -t vboxsf win_share /shared
</code>
You can  mount the directory in the docker-compose.yml as follow:
<code>...
volumes:
- /shared:/path/in/container
...
</code>

Docker Compose Shared Folder


Can a hypoid bevel gear set have a 1:1 ratio?

Question: [![enter image description here][1]][1]Is it possible for a hypoid bevel gear like the one pictured below to have a 1:1 ratio? If 1:1 isn't possible, any idea what the smallest ratio could be in order to output the least amount of gear reduction?
Answer: As far as I know, there isn't any mathematical limitation that would rule out using Hypoid gears for a 1:1 transmission (known as Mitre /Miter gears). You won't find any commercially, however, since they are less mechanically efficient than spiral gears (due to sliding along the teeth). Hypoid gears are favoured in some situations for their ability to achieve a high reduction in a small space through behaving much like a worm-gear (see the high-ratio hypoid set below). For a 1:1 ratio, there is no benefit in selecting a Hypoid form, and so Spiral or Straight is the industry preference.

Spiral Miter Gears

High Reduction Hypoid Gears
Comment: I do in fact need the offset which is why I couldn't use spiral or straight bevel gears.
Comment: Ah bummer. If you don't mind me asking, why is the offset a requirement? Perhaps there is some other way to solve the base problem?


European Football Datasets PAST and Current Season

Question: I've been trying to find player stats datasets but couldn't find one that includes goals scored, assists, etc. Does anybody know any site that provides such data for free or If I could get the last 20-30 years of European leagues data with match scores and also who scored in that game, something like this:
<code>Barca 2 - 1 Sevilla

[Messi'70,Suarez'80 : Navas'23]
</code>
Something like this would be Awesome!! .... There are some that provide match scores like this but do not list the player names that scored in the match.
I want data to not only have names of scorers but also detailed info like possession stats, HT score, cards received, shots on target, saves and other stats. Even if you know datasets like this of just 5-6 years. please do mention.
Your little help will mean a lot to me.
Answer: You can check out the European Soccer Database https://www.kaggle.com/hugomathien/soccer


Etymology of "altar of success"

Question: I've been trying to find the origin of the phrase, "[so and so] sacrificed ... on the altar of success." I presume it is entrenched in some sort of religious background, but other than that I have nothing.
Thanks in advance for your help.
Comment: @Cascabel, "my" Google Books is completely uncooperative today. It shows me only 8 hits for "altar of success", all from 2010 on!
Comment: I would argue against a religious background - it sounds aggressive! But I stand to be corrected (I couldn't find anything with cursory searches).
Comment: I appreciate the help in looking, and for the feedback. I only say that it might have a religious background because the earliest recording of the phrase I've found has been that by Jerry Falwell. I sincerely doubt it's him, but the phrase seems to have sneaked its way into vernacular.
Comment: maybe it is then.  'Altar of' [seems to be a bit of a 'thing'](http://corpus.byu.edu/bnc/) - anything that people seem to 'worship' at the expense of other things (that are generally more socially accepted)
Comment: Earliest I see is from a [1922 issue of Illustrated World](https://books.google.com.gt/books?id=_DxQAAAAYAAJ&q=%22altar+of+success%22&dq=%22altar+of+success%22&hl=en&sa=X&redir_esc=y). Ngrams indicates usage back to 1860, but does not return examples.
Comment: The metaphor is not really about success (that is certainly a common application) but about 'sacrificing on the altar of X'. Yes, religious because 'sacrifice' and the usual Old Testament location of sacrifices where on some kind of altar. 'Sacrifice on the altar' means losing something (the sacrifice) to the benefit of the X, eg 'Morals sacrificed on the altar of success' = giving up moral concerns for success.
Answer: The earliest three independent examples I could find of this sort of phrase―at the altar of success and at the altars of successful wrong―are from 1868-82. But the figurative use of sacrifice/worship at the altar of [something] is older. It may have started with goddesses as personifications of something and then taken a life of its own. Here are a few examples, including the earliest I found (my boldface in all quotes):

that most welcome Sacrifice on the Altar of Virtue
(Remarks on the Resignation of a Noble Lord, London, 1755.)
This is the most pleasing sacrifice at the Altar of Justice!
(William Combe, The Justification, London, 1777.)
Nothing could steal him a moment from sacrificing at the altar of his own vanity;
(The Lady's Magazine, Vol. 9, 1778.)
Go and sacrifice, at the altar of Humanity, a portion of those superfluous sums, that are now thrown away without prudence
  (The European Magazine, Vol. 30, 1796.)
offer up all party opinions, as a patriotic sacrifice on the altar of his offended country
The National Intelligencer and Washington Advertiser, Washington D.C., July 10, 1807.)
when Christians shall be willing to make sacrifices on the altar of peace
Vermont Telegraph, Brandon, Vt., May 31, 1837.)
The Limestone Springs during the last week, had upwards of one thousand visitors […] This is the favorite temple for the votaries of pleasure, and gallantly do they worship at its altar.
(Edgefield Advertiser, Edgefield, S.C., August 22, 1839.)

The earliest altar of success or of successful wrong are used very critically meaning putting aside one's principles, or having none to begin with, and going along with the powerful out of expediency. But then from 1900 onwards we find at the altar of success used neutrally or even appreciatively, meaning working very hard and making personal sacrifices to achieve what you want.
The earliest I could find was offer homage at the altars of successful wrong in "A Glowing Tribute to the South" (The Fairfield Herald, Winnsboro, S.C., March 18, 1868) by Father Abraham Joseph Ryan, known as the "Poet-Priest of the South" or "Poet Laureate of the Confederacy." The gist of the article is that the South fought a just cause in the American civil war. The full article or the following excerpt was printed 16 times across the United States in the space of 12 months, so it may have been influential:

There are men who bend their principles before the bayonet. There are men who desert the altars of a Lost Cause round which they once stood with blood in their hearts panting for libation, and who kneel to offer homage at the altars of successful wrong. There are men who trample under foot the very standards that once floated proudly over them. There are men base enough to lift their hands against the very rights for which they once uplifted swords. We are not such. For us, principle is principle, right is right―yesterday―to-day―to-morrow―forever. Submission to might is not surrender of right. We yield to the one, but shall never yield up to the other."

Then there is at the altar of success in a speech by S. S. Cox in July 4, 1873 to the Reformed Tammany Society, a Democrat association (The Democratic Press, Ravena, Oh., July 24, 1873). The speaker is unhappy about the outcome of the 1872 U.S. presidential election. It is not altogether clear to me what he is talking about, but it appear to imply that someone acted out of expediency:

Our foreign ministers first ironically interpreted the election. Full of the Santo Domingo treaty and the Geneva magniloquence they laid down their crowns, even before the inauguration made it decorous; and that apostle of civil service, the accomplished Curtis feeling that there was no more for him to do, laid his reformatory chaplet at the altar of success.

Then we have again at the altars of successful wrong in The Farmer and Mechanic, Raleigh, N.C., May 17, 1882, and the implied meaning is the same as in the previous examples:

Even the Richmond and Danville Railroad corporation, at the shrine of whose power now worship Governors, Senators, Judges, Legislators and public officials of every grade, had to fight its way into and across the State over a hostile public sentiment, an opposing State Government, executive, legislative and judiciary, and the combined power of adverse corporations.
  "But it succeeded, and nothing succeeds like success, while it is a characteristic of the governing class in North Carolina to bow down and worship at the altar of successful wrong."

And then, from 1900 on, I found only at the altar of success, but used simply to mean working hard to achieve what you want. In most cases the tone is  neutral or even positive Here are a few examples:

By its unbroken succession of seven victories Hank's pretzel-eaters waded through the Dudes and the Millers, until to-day he stands second in the race, with a far off glance at the champions. All the prayers that Hank gave breath to and the incense that he burned at the altar of success bore fruit, though the material reward came late. The following table of standing is vociferative f a pleasing story to local fans:
("Frisco Jumps form Last to Second Place," The San Francisco Call, San Francisco, Calif., July 21, 1900.)
I expected to find a city of smoke and dust, a community of aggressive citizens worshiping at the altar of success rather than in the shrine of culture and art; but I soon discovered, to my pleasant surprise, that the makers of the city were no mere worshippers of Mammon, no purse-proud and insolent Cresus-es destitute of those higher aspirations for beauty and art which invariably mark the broadly educated children of civilization.
("A Day in McAlester, Oklahoma," The Indian Advocate, Sacred Heart, Okla., October 1, 1909.)
Women, of course, are constantly entering professions in which a knowledge of the evil of the world is necessary―such as the medical, the legal, and to a certain extent, the newspaper professions.
  For such women I am rather sorry. They place a large sacrifice on the altar of success when they allow themselves to become sophisticated. And yet, of course, I realize that it is a necessary and if rightly made, a dignified sacrifice.
  But for the rank and file of women who do not need to know all about good and evil my heartfelt advice is to leave the fruit of the tree strictly alone.
(The Topeka State Journal, Topeka, Kan., May 19, 1910.)
The best thing about the financial gain to the worthy cause was that the public did not need to be made a sacrifice on the altar of success. In the entertainment provided the liberally patronizing public got their money's worth of amusement.
(Albuquerque Morning Journal, Albuquerque, N.M., August 27, 1911.)
"This business is a little bit over crowded, but, as always in every line of work, there are plenty of chances for the ambitious woman to make a big success of it if she goes into the thing whole heartedly and ready to sacrifice enjoyments, clothes, comfortable living upon the altar of success. She will be repaid many times when her business matures and she can have all these things and enjoy them better because she has earned them.
(The Washington Herald, Washington D.C., July 19, 1914.)
Comment: @Cascabel, yes, the Chronicling America database, where I got all the examples from, is brilliant, but it's a lot of work.
Comment: Thank you tremendously -- the aforementioned database is going into my favorites toolbar :)
Comment: +1 nice research. Obviously you were much more patient than I was.
Comment: @Mudly Here's someone methodical :) I always look for an answer where I've used it and follow a link.
Answer: Jacinto does an amazing job of capturing the historical use of the phrase.
Conceptually, the phase is referencing the concept of sacrificial offerings to a deity, both in the Judaism of the Hebrew Bible (i.e. the Old Testament) as set forth, for example, in Chapters 1-9 of the Book of Leviticus, and in prior pagan practice of the religions of the Mediterranean basin.
It is this connection to pagan practice that gives the phrase some of its pejorative bite, since Christians (to whom the phase is overwhelmingly directed) have disavowed the practice of sacrificial offerings, so making such an offering is blasphemous or heretical.
The notion of a sacrifice is that to request the favor of a deity or to atone for a sin from which you seek the forgiveness of a deity, you must sacrifice something precious to you, an event that normally happened on an altar in a temple.
This ceased to be Jewish practice when the Second Temple was destroyed ca. 70 CE and the era of rabbinical Judaism commenced. Christians associate the end of the practice with the crucifixion of Jesus Christ ca. 30 CE, which theologically for them is the sacrifice to end the need for all other sacrifices, and with the notion that Christianity superseded pagan practices and rituals.
The historical practice of sacrificial offerings used the same altar for all different manner of offerings for different purposes, so the "altar of success" phrasing, is, in context, referring to the particular purpose the altar is being put to use for in the metaphor on this particular occasion.

Etymology of "altar of success"


Is there a way to look at a Trello board as a snapshot in time?

Question: It seems that after cards are archived, they are removed from the boards they were associated with. I'm hoping that's not the case and that various metadata about the cards are tracked. What I want to be able to check is the state of a list (or board) at a specific timestamp in time.
Comment: This is still not currently possible. What you CAN do is make a copy of the board and label it with the date to look back at it later.
Answer: No to "snapshot in time", Your Trello board is always a current version of your items (lists, cards) as they are now.
Your Archived cards are still stored within the board. Once you Archive a card, it is stored in "Archived Items" under the board Menu with all of the other archived cards.
There is no way to go back and see any previous state of your boards.  Always move forward.
Comment: To clarify, your answer amounts to saying "No" to the question. "Snapshot" always means a timeline-like functionality - to see what the board had looked like at a certain time in history. That terminology is used everywhere e.g. in Google Docs, for examples.
Comment: Sure, I know that the Trello board represents what I have now. But it's still useful to look at the sort of progress I did weeks ago, especially since it's easier for me to think about my progress that way.
Comment: The best way to see recent completed items is to leave the completed cards in the Done / Completed list.  Then after 30+ days go ahead and archive them.  Otherwise there are no historic snapshots.   Good Luck!


Is there an algorithm for real-time fluid simulations with Fluid-structure interaction with viscous fluids?

Question: I'm trying to write a Fluid simulator for my school coding project. I want the Fluid simulator to be able to handle FSI with viscous Fluids in real-time and be 3D. I've been reading a few papers and usually the solutions tend to be some of the criteria and not all. For instance, I have seen a lot of solutions that allow real-time FSI but assume the Fluid is inviscid. Is there such an algorithm to simulate FSI in real-time without having to assume no/negligible viscosity?
Comment: As the answer by Tofi pointed out, high viscosity is your friend, not your enemy. A low viscosity fluid basically "remembers" what happened to it in the past. What you want to simulate (if you want it to run in real time on a single computer) is a fluid that has high viscosity (like oil or honey) because then small perturbations are dying out rather than being amplified.
Answer: I'm not familiar with problems of fluid-structure interaction, but perhaps I can still give you some insight into the issue. The thing is, three-dimensional viscous flows are usually quite expensive to simulate due to turbulence. In a turbulent flow, large eddies break down into smaller and smaller eddies, in a process known as the Richardson cascade, until they reach a very small size called the Kolmogorov length scale $\eta$ at which the energy is dissipated into heat by viscosity.
Intensity of turbulence is measured roughly by the Reynolds number which is defined as
$$Re = \frac{UL}{\nu},$$
where $U$ and $L$ are characteristic velocity and length scales of the flow, and $\nu$ is the kinematic viscosity. Flows with a large Reynolds number are very turbulent, while flows with a small Reynolds number can be laminar. One can show that the ratio of the largest eddy size in the flow $L$ to the smallest eddy size $\eta$ is proportional to the Reynolds number raised to 3/4:
$$\frac{L}{\eta}\propto Re^{3/4}$$
This means that in order to properly resolve the smallest eddies in a 3D turbulent flow simulation, the number of grid points needs to scale as
$$N \propto \left(Re^{3/4}\right)^3 = Re^{9/4}.$$
For a flow with a velocity scale $U = 1$ m/s, a length scale $L = 1$ m and a kinematic viscosity $\nu = 1.5\times 10^{-5} \text{ m}^2/\text{s}$, the Reynolds number would be around $Re = 70,000$, which means that $N$ would be in the range of 80 billion. Thus, realistic turbulent flows are infeasible to simulate except using supercomputers and even then are still limited to very simple academic flow configurations.
So, unless you have access to large computing resources, I think that any program you write has to be limited to very low Reynolds numbers if it were to simulate real physics accurately, and even then it would be hard for it to run in real time.
Comment: @FlatterMann I guess so :)
Comment: On the upside the simulation of the flow of honey around round structures is trivial in terms of computational resources according to this estimate, isn't it?
Comment: So if I was to limit the program to very low Reynolds numbers, what impact would that have on the simulation? Like does it just mean that the kinematic viscosity will be really high or are there other indirect problems that can arise? In addition, a few days after posting this question, I found this paper: https://www.researchgate.net/publication/220789321_Particle-based_viscoelastic_fluid_simulation. Does it still suffer from the same problem and if not how does it resolve it?
Comment: @SidKT from the expression above of the Reynolds number, a small Reynolds number can be achieved by decreasing the flow velocity $U$, decreasing the size of the flow domain $L$, or increasing viscosity $\nu$. The paper you linked has the same problem: for the simulation to be able to resolve motions at the smallest scales, the size of the fluid particle needs to be less than the Kolmogorov length scale.
Comment: @SidKT However, I think the authors of that paper are more focused on producing "real"-looking animation rather than accurate physics, and if that's what you want then maybe there are some shortcuts that you can take, but I'm no expert on computer animations.
Comment: @Tofi What sacrifices does it make on the physics-accuracy side for the "realism"? I'm not particularly trying to prioritise the "realism" over physics however, if it is something minor then I could make an exception I guess.
Comment: @SidKT what I meant is that you might not need to resolve the smallest scales of the flow to get something that looks realistic, so you could try using a mesh size / particle size larger than $\eta$ and see what you get. In engineering, this is called an implicit LES (large eddy simulation), so you can check it up to get an idea.
Comment: Oh right that makes sense. Thanks for the help.


Voting/flagging dialogs overwrite one another

Question: If you don't dismiss a vote dialog before you flag a question (say as needing attention), the new dialog overwrites the old one and both are unreadable.  Using Safari 4.0.2. The new text is written over the old text, but part of the old text is still visible.  It could be that the new dialog box is not as wide as the old one, but since the backgrounds are flat and don't have borders it appears as the text is only partially overwritten.
Answer: Behaviour in Firefox (3.5.1) and Chrome (22.214.171.124)
All combinations of opening the dialogs show correct dialog windows.
In both browsers you can repeatedly open the two dialogs in any order. Whenever the flag dialog is visible and closed first, the vote dialog gets cancelled as well. When the vore dialog is cancelled first, the flag dialog stays open.
Answer: One-and-a-halved: On Chrome 2.0, WinXP, it overwrites it, but the flag dialog is white, so the flagging is legible. Hitting cancel on the flag window nukes them both.


how do i clean rust flecks off an alloy wheel

Question: I have just bought a second-hand mountain bike and the rear wheel is made of alloy and has small rust flecks/spots on it. Any advice on how to clean? I cleaned the rust off the forks with a small wire brush (used for cleaning spark plugs on my car) and an anti-oxidant. Would this work on the wheels? I am worried about scratching the alloy.
Comment: Try an abrasive dish cleaner -- Eg, Ajax in the US.  If you're really leery of scratches pick a non-scratching or "soft scrub" variety like Bon Ami.
Comment: Don't be surprised if the wheel has pits in it after the rust is removed.If you are concerned about apperance mask the brake surface and paint the wheel.
Answer: If it's truly an alloy rim, it isn't rust. Use a metal polish, like you find at the auto parts store for polishing alloy wheels.
It will clean of and smooth out any surface issues without removing to much material.
It takes elbow grease, or you can use a Dremel with a jewelry polishing wheel on it to do it faster.
Answer: Use steel wool, or preferably brass wool. Both will take out flecks and rust. The benefit of brass wool is that any left on the wheel will not rust.
Comment: If he uses steel wool it will scratch his rims.


Is manual driving faster than Ignis driving?

Question: Is it faster to drive manually or let Ignis drive (No fast travel)?
Answer: No, there's no difference in speed, but manually driving leaves room for error when you need to make turns, which could affect your travel time. Ignis will make necessary turns automatically.
Comment: @Mast any turn you can make, Ignis can make. But he will always pick the fastest route. Driving manually means you'll have to make the turns yourself and most likely you'll be spending time checking the map to see *when* you need to turn.
Comment: Won't this work the other way as well? Can't we make corners manually which Ignis wouldn't make because they aren't considered safe enough (risk of getting stuck and the like)?
Comment: @Mast movement is fairly "railed", you can't go out of some specified safe road zone.
Comment: Sounds like an autonav without downsides, there aren't many of those. Just checking :-)
Comment: It's worth noting that Ignis's driving allows you to spot and gather items on the road or side-of-the road which do not appear on the minimap and would otherwise be missed in manual driving mode.

Ignis, however, pulls over a short distance from where the initial instruction is given.
Answer: I've seen one case where manually driving is advantageous: if there's an Imperial dropship on the road (but not so close that you can't get in the car), and you'd rather avoid it than fight it, Ignis won't navigate around it even if he could. He'll plot the shortest route to the destination and drive the car right up to the enemies, and then you'll be committed to the fight. Driving manually, you can take a longer route that avoids the battle, possibly saving time overall.


Bitcoin money transfer

Question: I transferred money from circle to Bitcoin, the transaction showed it was successful however it did not go into my Bitcoin but went to blockchain. I saw the amount on blockchain as unspent but then after few days it was shown as spent. However it did not even reach me so can it show that and also why has it reached there and is there any way of getting it back. I look forward to hearing from you soon.
Comment: Hey Ali, welcome to Bitcoin.SE. Could you please clarify the following: Where were you trying to transfer money to? Was it circle to Bitcoin Core? Where did you see the amount as unspent, was it in Blockchain.info's block explorer, which shows you all transaction information, or in your online wallet account there? If you tried sending bitcoins to your Bitcoin Core, and saw the transaction on Blockchain.info's explorer, have you checked whether it got to your Bitcoin Core?
Answer: Weird. If you don't mind, could you add a transaction I'd and your bitcoin wallet address?
I'm guessing you withdrew into your bitcoin wallet from circle, but it didn't appear in your bitcoin wallet. You could however see it on the blockchain?
I have a couple of ideas:

Malware

You may have malware installed on your computer that swaps out your bitcoin address that you have copied down to the hacker's bitcoin address. Please verify that the recieving address in the blockchain is the same one as the one in your wallet.

Wallet not synced

If you're using a wallet like bitcoin core/qt, you will have to wait for your wallet to sync. It will show at the bottom of the client.

Bitcoin money transfer


Getting zone from UTM in order to convert to latlong

Question: I am trying to convert UTM to a latlong point. To get that done I need to know the zone where the UTM coordinates are. how can I find the zone from UTM?. the place coordinates that I work on lay on zone 39 and 40.
Answer: In general, you cannot determine the zone from the coordinates: that's why the zone is needed!
In your case, though, it sounds like you are looking within a small area that straddles neighboring zones.  In that case, locations in zone 39 will have large positive x-values and locations in zone 40 will have negative or small positive x-values: that's how you can tell them apart.  This approach will work provided your area does not extend more than six degrees in longitude from east to west (the width of one zone).  (In general,  compute the longitude using both zone options and choose the one that falls within your area of interest.)
Comment: On a matter of pedantry, UTM zones have a false easting big enough to cover quite a lot of the westward neighbour, so it is unlikely x-values will be negative, just nearer zero. But your assertion still stands.
Comment: Thanks @Mersey, I had forgotten about that.  I had better edit the reply.
Comment: sounds nice to work out the LatLong boundaries for the place and try 39 and check the result if it lands in the specified boundaries. if not try 40. thanks a lot.
Answer: You can identify the zone on this map: http://www.theartofdredging.com/utmzones.htm
Once you find your zone, then you can easily convert the UTM coordinates to any coordinates
using http://www.hamstermap.com.


How to calculate/record attachments' file names using Field Calculator?

Question: I have a point feature class containing attachments corresponding to jpg files (sometime more than one jpg per feature).
I would like to use the "field calculator" to calculate/record a new field that would contain file paths or names of attachment files.
Does someone know how to do that?
I am new to Python and VB script...
Comment: Could you please supply a little more context--maybe a screenshot of the attribute table?  I am having a hard time visualizing your dataset.
Answer: I have assumed that you are trying to update the name of the file in the attribute table with the point layers unique ID of some type e.g. changing Temp646.jpg to CB1.jpg.
This can be done by joining the related attachment table to the feature class and then using field calculator to update the ATT_NAME column in your attachments table.
The steps are:

Add Feature class and attachment table to mxd
Conduct a join using between the attachment table and feature class using GlobalID and REL_GLOBALID and enable editing
Open the attachment table with the join in place and you then can use the field calculator to update the ATT_NAME field.
"CB " + !your table column value! +".jpg"  The expression uses python syntax so make sure you flip the radio button on top of the field calc


When does 负面 or 正面 go before 影响, and when does it go afterwards?

Question: Sometimes I'll see text saying that something 影响负面 another thing, and other times I'll see that something 负面影响 another. Is there a rule or concrete grammatical basis to determine which sentence uses a particular structure?
Comment: Do you have an example of the use of 影响负面 in an article? Only heard here.
Answer: As a native Chinsese speaker, I never use either as a verb.
When we use "负面影响", we think this is a noun, so it can be something has 负面影响 to something.
For example 小明的大声吵闹对小红有负面影响 (Ming's loud noise has 负面影响 to Hong). 对 means "to", which shows the target of the neagative influence.
When we use "影响负面", what we actually want to express is "影响是负面的",so we even do not use 影响负面 in Chinese. The real usage can be
小明的大声吵闹影响负面 ===> 小明的大声吵闹的影响是负面的.
I think which one to use doesn't matter, people can absolutely know what you mean. However, the order to place "影响" or "负面" is actually no solid rules, it's flexible in Chinese language...
Comment: @goPlayerJuggler Sorry, in this question's decription `saying that something 影响负面 another thing, and other times I'll see that something 负面影响 another`, which use both `影响负面` and `负面影响` as a verb in the context. When I say I use neither, I mean I never use any of them as a verb. For example,  I shall never use `我负面影响你` or `我影响负面你`
Comment: I'm confused by the word "neither". "Neither" means you never use these terms. But then you go on to say you do use them. So I think you probably meant to write "either". I think a small edit would be helpful here.
Comment: So maybe your answer could say: `... I never use either as a verb.`
?
Comment: @goPlayerJuggler Yes!
Answer: 负面影响 = downside/negative influence, the meaning of this well-known noun phrase is clear by itself, and can be expressed by the pattern - A negatively influences B possesses the characteristics of (C). For example:

"不充分的睡眠"(A)對"學習䏻力"(B)有"负面影响"(C). - Inadequate sleep has a negative impact on learning ability.

On the other hand, 影响负面 = influence downside/negative, the meaning is unclear by looking at the words along, so let's try to make a sentence similar to the above:

"不充分睡眠的影响负面"(A)是"學習䏻力"(B)降低 - The negative impact from inadequate sleep is the lowered learning ability.

The pattern here is (A) results in (B), which is quite different from the previous example. Hope you can see the differences between 负面影响 and 影响负面 from the examples above.
Answer: In a nutshell, 负面影响 is a noun phrase comprised of an adjective 负面 "negative" and a noun 影响 "influence, effect"
whereas 影响负面 syntactically is a sentence "influence is negative", where the verb-to-be is not needed in Chinese. In actual usage, though, this short sentence does require some elaboration as to what influence we are talking about. It usually comes in the form of X 對 Y 的影响负面.
These two are not interchangeable.


Mitzvas Kesivas Sefer Torah

Question: If you purchase a finished Sefer Torah are you Yotzei the Mitzva of Kesivas Sefer Torah?
Comment: http://forumpics.a7.org/?file=20121008231302.pdf
Answer: It's a machlokes (dispute among) rishonim. See a talk by Rabbi Josh Flug, and the sources he cites, if you're interested in the machlokes, but I'll note that among Rabbi Flug's points are that Rashi holds purchasing suffices and that Rambam seems to hold it does not; CYLOR if you're interested in the practical halacha.

Mitzvas Kesivas Sefer Torah


Reconstructing an analytic function from its Taylor series at a point

Question: Suppose $f:\mathbb{R} \rightarrow \mathbb{R}$ is an analytic function, and at one point $x_1  \in \mathbb{R}$ we know the Taylor series for $f$ centered at $x_1$. Does this determine $f$ uniquely? If not, is there some number of points such that knowing the Taylor series at each point determines $f$?
Comment: It depends on the radius of convergence of the Taylor Series. Such as the series for $\ln(x+1)$ has a radius of convergence of $-1\le x\le 1$.
Answer: The question is equivalent to the following: suppose f has an infinite Taylor series expansion around each point in $\mathbb R$ and suppose f is 0 in a neighborhood of some number $a$. Does it follow that $f=0$ everywhere? The answer is YES! If $f(x) \neq 0$ for some $x>a$. Consider $inf \{x>a:f(x) \neq0\}$. If this infimum is $b$ then all the derivatives of f at b are 0 because the functions vanishes in a left-neighborhood of b. The Taylor seried expansion show that f vanishes in a right neighborhood of b too and this contradicts the definition of b. We have proved that $f=0$ on $(a,\infty)$ and a similar argument shows it vanishes in $(-\infty,a)$.


LC meter fails to measure inductance of a transformer primary with the presence of opened secondary

Question: I'm making some custom low signal 1:50 step up transformer, and I noticed something interesting. My LC meter displays correct primary inductance when no secondary is present on a core. With the partially wound opened secondary its reading is few orders lower. My only guess is that it uses a relatively high frequency so the secondary becomes shorted by its own capacitance.
Comment: What kind of LC meter (frequencies used)? What kind of step-up transformer and core?
Comment: What are your measures?
Comment: Some random multimeter. It's working frequency is not specified. I use a high permeability Magnetec M-070 core. The transformer is supposed to have 25:1250 turns. I have 400 turns of secondary wound right now
Comment: I have seen some multimeters using 90, 100, and 900 Hz and others making "resonance". So, I guess it can't be because ... "shorted" by a "resonant" circuit.
Answer: As some pieces of information are not known, I guess only this.
You are measuring the inductor at a frequency (10 kHz or more, probably at a "high" resonant frequency) as pointed out in the picture (abs(impedance) measured).
In red, a pure inductor. In blue, with a coupled secondary.

To make sure, perhaps measuring input impedance with a scope would be more useful.
Answer: It's not the best to use a "random multimeter" when doing transformer prototyping. Get a proper LC meter. Doesn't have to be expensive, just decent enough to do L/C/R/ESR measurements at various frequencies like 100, 120, 1k, 10k Hz. The DER EE DE-5000 would be a suitable meter I think, if you don't have a big budget. I've used it to measure various transformers and the readings looked reasonable.


oscillations of blocks connected by a spring

Question: Imagine two blocks of masses $m_1$ and $m_2$ joined together by a spring of spring constant $K$.
Now let the spring be stretched by a distance $X$ and then the system is released. suppose during the stretching the block of mass $m_1$ moves towards left by a distance $A$ and the block of mass $m_2$ by a distance B.
Now                                                                                the centre of mass of the system at any instant will remain at rest. Now let it be present at a point P in between the two blocks. so  can I depict the oscillations of the two blocks as two independent oscillations about the centre of mass?
Answer: The two oscillations will not be independent as they will share frequency and phase. You can start from Newton's equations of motion.

$$ m_1 \frac{{\rm d}^2\,a(t)}{{\rm d}t^2} = -F(t) $$
$$ \mbox{-}m_2 \frac{{\rm d}^2\,b(t)}{{\rm d}t^2} = F(t) $$
$$ F(t) = k \;\left( a(t)+b(t) \right) $$
Assume simple harmonic motion $a(t) = A \sin(\omega\,t)$, $b(t) = B \sin(\omega\,t)$ which leads to the frequency equation $$ k\,\left(m_1+m_2\right) = m_1 m_2 \omega^2 $$ and the amplitude equation $$ A\, m_1 = B\, m_2 $$ So now you can show that the center of gravity $P$ does not move as long as the amplitudes $A$ and $B$ obey the balance equation above. How? Well what is the equation for the center of gravity? $$ {\rm cg} = \frac{\mbox{-}B\,m_2+A\,m_1}{m_1+m_2} = 0 $$
Comment: Did you make that image just for this problem?
Comment: yes - and it is pretty cruddy too. In fact, 80% of solving a problem is framing the problem and making a nice sketch of all relevant information.
Comment: I found it to be rather impressive.  This is a high quality answer overall IMO.
Answer: Traditionally, the "mass on a spring" is analyzed with one end of the spring held fixed. Your problem is equivalent to two such systems back-to-back. You have identified the center of gravity as a fixed point; so you can literally fix it and then cut the problem in two. Each half of the system then behaves like a traditional "mass-on-a-spring".


How do I install snort on RPi?

Question: I was trying to install snort and everytime I encounter a problem I tried to follow this link http://www.snort.org/assets/167/IDS_deb_snort_howto.pdf but then I realized that it cannot be applied on ARM architecture !
Comment: How does sudo apt-get install snort fail?
Comment: the problem is with the dotdeb packages !! it doesn't support ARM architecture only i386 and amd !
Comment: Are you saying that you did a sudo apt-get install snort and it failed?  Which distribution?
Comment: the problem is with dotdeb packages !!
Comment: the current distribution is Debian/Raspbian.
Comment: I think I see your issue, ignore what that guide says about adding sources, keep the default ones which have ARM ports of MySQL and PHP.
Comment: this is what I did thx @Dan
Answer: There's a Raspberry Pi security tutorial based on ArchLinux, that includes step 13 "Snort installation".
Basically all you have to do is:
<code>$ sudo pacman -S snort
</code>
Please, follow the instruction as close as you can.
Comment: this is the half of the answer thanks :) ... and what about Debian OS (Raspbian) ?
Comment: for raspbian you're supposed to use `sudo apt-get install snort`, however I could not find any tutorial that I can recommend.
Answer: <code>sudo apt-get install snort
</code>
works for me on a Raspbian Pi.
I'd be amazed if it didn't also work on my Debian Pi (but I can't be bothered to try and see).
Answer: @lenik's answer would be correct, if not for the AUR repository to not have an ARMv6 build available for snort, which is what we need for the raspberry pi.
This topic describes how to build the needed package yourself with the source tarball from the AUR repository:
http://www.raspberrypi.org/forums/viewtopic.php?t=36314&p=305583
Building this on the Pi will take about 1 hour, be warned :-)
I imagine the Raspbian repository has the same issue.
I'm still setting up everything myself, but am wondering whether it will work reasonably in the end. Since no one seems to be making Pi-compatible ARMv6 packages for Snort, perhaps it will just be too slow to run it...
Answer: I am writing an educational Guide about Snort on Raspeberry PI, and Used two tutorials that worked fine for me:
Tut 1 Installing SNORT by (Computer and Network Security)
Using sudo aptitude install snort <---- easy way
TUt 2 downloading all the packages from snort's website and compiling them <---Long way
  Part 1 Snort Install on Ubuntu 14.04LTS Part 1
  Part 2 Snort Install on Ubuntu 14.04LTS Part 2
Comment: Welcome to Raspberry Pi! Whilst this may theoretically answer the question, [it would be preferable](http://meta.stackoverflow.com/q/8259) to include the essential parts of the answer here, and provide the link for reference.

How do I install snort on RPi?


What's the difference between ~きれる and ~あげる?

Question: What is the difference between these two?
N3 grammar masu form + 切れる
N3 grammar masu form + 上げる
Answer: masu+きれる means to be able to perform an action to its completion.
masu+あげる means to fully complete a specific task (usually involving production).
For masu+きれる (or masu+きれない), the meaning is related to any action which has the potential for degrees of completion. The きれる part refers specifically to whether someone is able to complete it. For example, let's say you ordered a large meal. You might be able to eat all of it or not. Depending on the outcome, you would use 食べきれる or 食べきれない to express whether or not you were able to eat all of the meal, i.e. to finish the eating to its completion. Another example:

数えきれないほどの時間 countless hours (lit. so much time it cannot be fully counted).

For masu+あげる, there is typically a task which is being done. This is often used to describe the production of a finished item or thing, such as making or building something. It involves the process of finishing off a task and emerging with a tangible final result. For example,

論文を書き上げる to finish writing a thesis
  マフラーを編み上げる to finish knitting the scarf

Simply put, masu+きれる describes potential (can you complete the action), whereas masu+あげる describes the completion of a task-based process.

What's the difference between ～きれる and ～あげる?


Trivial line bundle

Question: Suppose that $L \to M$ is complex line bundle over a manifold $M$. One can therefore form the dual bundle $L^* \to M$. We can identify $L^* \otimes L$ with endomorphism bundle $End(L)$.
Why it is true that $End(L)$ is trivial? Why the assumption of being line bundles is essential? Is it also true for other fields, for example $\mathbb{R}$?
Answer: If $L$ is a rank $1$ vector bundle, then $\operatorname{End}(L)$ is a rank $1$ vector bundle with a nowhere zero section: namely, the identity map. So it is trivial.
This doesn't work for higher-rank vector bundles; if $E$ has rank $k$, then $\operatorname{End}(E)$ has rank $k^2$, so we need $k^2$ linearly independent sections to trivialize it and they're nowhere to be found.
On the other hand, it doesn't in any way require that the ground field be $\Bbb{C}$.
Answer: The transition map for dual bundle $E^{*}$ is $(g_{\alpha \beta }^{t})^{-1}$, the inverse transpose of the original one $g_{\alpha \beta}$. In the line bundle case, this is ${g_{\alpha\beta}}^{-1}$. So the transition map for $End(E)\cong E \otimes E^{\ast}$ is nothing but $g_{\alpha \beta } {g_{\alpha \beta}}^{-1}=1$ which means triviality of $End(E)$.

Trivial line bundle