Tag display does not show special tag CSS when filtering by tag

Question: If you filter a set of questions by a tag, the special tags: status-declined, status-completed, etc. does not show up with the CSS that differentiates them from other tags (i.e., they have the same coloring as the other tags).  Note I'm talking about the "related" tags display, not the "chosen" tags display.
Answer: Have seen this when entering the highlighted tags in the interesting/ignore list. They come up as bland samey-samey. Won't flash their wares and coat of difference until you reload the page or move away from the page you're on while you're adding tags to your interest/ignore list.


Remote flashlight device for focusing in an off-camera flash scenario

Question: I was shooting in a fairly dark room with two Yongnuo YN560 IV off camera in softboxes and a Yongnuo YN560-TX II on the camera to trigger them. I was not able to focus without having someone hold a flashlight on the model until I got focus and then remove it before the shot. This very annoying, because it requires an assistant. Is there any product in the ballpark of a thing that mounts on a light stand and is just essentially a flashlight that is remotely triggerable? So you could hit a button to turn on the light, get your focus, hit another button to turn off the light, then take the shot?
Comment: Studio strobes have a modeling light built into them so you can see to adjust your lighting, it would serve your needs well.
Comment: @DavidDoria You don't have to switch them off remotely - when you push the trigger, the modeling lamp switches off and re-lights after you take the shot.
Comment: @AlaskaMan How do they work? Like how do you turn on/off the modeling light remotely?
Comment: what camera are you using?
Comment: @MichaelC Canon 6D
Comment: @DavidDoria If you do a search on YouTube for "how to use modeling lights on studio strobes" you will get a wealth of info, here is one https://www.youtube.com/watch?v=4z_rvE03nfg
Answer: Many camera mounted speedlights and controllers have near-infrared AF assist lamps. They illuminate briefly when the shutter is half pressed and go out once focus is confirmed. Such AF assist lights require communication between the camera and transmitter (or flash) that use the proprietary pins for each brand that surround the standard center pin on the hot shoe connection.
Your Yongnuo YN560-TX II does not include an AF assist lamp.
The newer YN560-TX PRO transmitter does include an AF assist light and would allow you to control your YN560 IV flashes while also giving you a camera mounted AF assist light. The YN560-TX PRO would also give you the ability to control YN622 system receivers that have been updated to the latest firmware versions (using either manual or TTL power control).

If you are otherwise happy with the results you are getting from your speedlights and softboxes, $55-60 for a new controller is a lot cheaper than switching over to studio lights with modeling lamps.
If you want to be able to control studio lights remotely the way you can control your YN560 IV flashes (power, zoom, groups, etc.), you'll either need to choose from whatever limited options Yongnuo offers or buy another controller that matches whatever brand of studio lights you buy (assuming that brand even has remote power control as an option). It seems that Yongnuo's only studio strobes with remote power control capability use the YN622 protocol, rather than the YN560/605/603 protocol.
If you decide to go the studio monolight route, Godox is probably your best option. Their entire system of manual speedlights, TTL speedlights, bare-bulb speedlights, and studio flashes all use the same communication protocol.
Other options
Since the YN560-TX II works for everything other than the "wake from sleep" function via the center pin, there is another workaround that should give you what you need if you are willing to give up the "wake from sleep" function.
You should be able to stack any controller with a "pass through" hotshoe and an AF assist light between the camera's hotshoe and the YN560-TX II. One such trigger would be a YN622. If you use the version for your camera brand (Canon, Nikon, etc.), which would be required to get the communication needed for an AF assist lamp, you may even be able to preserve the "wake from sleep" feature.
Comment: Actually I was mistaken, I have the YN560-TX (not the "II") https://www.bhphotovideo.com/c/product/1108992-REG/yongnuo_yn_560_tx_yn560_tx_manual_flash_controller.html?fromDisList=y
It has the big red panel on the front - isn't that the AF assist? I have the Canon 6D on C.FN II: Autofocus #5 = 0: Enable , but I don't see the red grid being emitted when I focus?
Comment: My understanding is that you need a TTL trigger for AF assist as that communication comes through the TTL pin. The 560-TX is manual only (the other pins are dummies).
Comment: @DavidDoria The YN560-TX is not AF assist capable. The red panel on the front of the unit is, as far as I can tell, for looks.
Comment: @StevenKersting Not exactly. It does use some of the other pins for the "wake from sleep" function.
Answer:
So you could hit a button to turn on the light, get your focus, hit another button to turn off the light, then take the shot?

Using a studio strobe, you typically have a modeling lamp. You don't have to turn off the modeling light to shoot. They're enough light for you to get an idea of the lighting and focus. But the strobe flash will greatly overpower the modeling lamp such that your proper exposure, if the strobe didn't fire, wouldn't record anything at all. Those lamps aren't that bright.
Copy the idea if using speedlights...get a dimmable bulb on a floor lamp and give yourself just enough light to focus. Don't worry about turning it off, it'll be greatly overpowered.
Comment: This also has the advantage, that you can light the models eyes, which makes their pupil contract revealing more of the iris, which is preferable.
Comment: @KaiMattern excellent point!
Comment: Ah interesting - I'll give that a shot! I guess something without a power cord would be preferable, so what do you think about and battery powered LED panel (like for videography) on a lightstand?
Comment: @DavidDoria for studio work, I'd get something with a cord or a really long battery life, because changing that out mid shoot would just suck. I wouldn't worry about the cord, just position it out of the way. Get one long enough you can snake around the room to keep it out of you and the model's way. Dimmable LED is the way to go - better control of light output and less heat generated than incandescent.
Comment: @KaiMattern That's an artistic decision. Sometimes a wider pupil is desired.
Answer: Cheap option. Attach the flashlight to a stand or your camera and shoot. The speedlights will overpower the flashlight anyway so it won't be visible in your photo unless you are shooting at very low power.
Point being that you don't have to worry about turning the flashlight off before you shoot, just ignore it and shoot anyway.
Comment: Lots of great discussion, thanks all! But this is what I ended up doing - (with a small LED panel rather than a flashlight). I tested it out and the flash indeed overpowers this without much trouble.


A simpler proof of $(1-x)^n<\frac{1}{1+nx}$

Question: I proved the following inequality:
Let $x\in\mathbb{R}, 0<x<1, n\in\mathbb{N}$, then $(1-x)^n<\frac{1}{1+nx}$
however, judging from the context in the exercise book, I feel like there is a much simpler way to prove it, but I can't see it. So I'm asking for that simpler alternative proof, or at least a hint to it. My proof as follows:
Bernoulli inequality states that for $-1<x, x\neq 0, n\in \mathbb{N},n>1$ the following is true:$(1+x)^n>1+nx$.
Thus, $\frac{1}{(1+x)^n}<\frac{1}{1+nx}$ is also true.
Then I need to show that $(1-x)^n<\frac{1}{(1+x)^n}$, which is equivalent to $\frac{1}{(1-x)^n}>(1+x)^n$, which I prove by induction:
Basecase: $n=1$ $1=\frac{1-x}{1-x}\Leftrightarrow 1=\frac{1}{1-x}-\frac{x}{1-x}\Leftrightarrow 1+\frac{x}{1-x}=\frac{1}{1-x}$
Let $a,b\in \mathbb{R_{>0}}$ and $0>b>1$ Then $\left[ a>ab \right]\Leftrightarrow \left[a<\frac{a}{b}\right]$. Thus $\left[ 0<x<1\right] \Rightarrow \left[ x<\frac{x}{1-x}\right]$
Thus $1+\frac{x}{1-x}=\frac{1}{1-x} \Rightarrow 1+x<\frac{1}{1-x} \square$
Inductive step: Assume $(1+x)^n<\frac{1}{(1-x)^n}$. Need to show $(1+x)^{n+1}<\frac{1}{(1-x)^{n+1}}$.
$(1+x)^{n+1}<\frac{1}{(1-x)^{n+1}}\Leftrightarrow (1+x)^n\cdot(1+x)<\frac{1}{(1-x)^n} \cdot \frac{1}{1-x}$
Let $a,b,c,d \in \mathbb{R_{>0}}$. Then $[a>c]\wedge[b>d] \Rightarrow [ab>cd]$. $(1+x)^n<\frac{1}{(1-x)^n}$ was the assumption and $1+x>\frac{1}{1-x}$ was the basecase, therefore $(1+x)^n\cdot(1+x)<\frac{1}{(1-x)^n} \cdot \frac{1}{1-x} \Leftrightarrow (1+x)^{n+1}<\frac{1}{(1-x)^{n+1}} \square$
Thus $\frac{1}{(1+x)^n}<\frac{1}{1+nx}$ and $(1-x)^n<\frac{1}{(1+x)^n}$ are both true, which implies the original statement $(1-x)^n<\frac{1}{1+nx} \square$ If I were to count the proof of the Bernoulli inequality by induction, it would mean that I used induction twice in order to prove something that basic, which to me doesn't seem to be a sensible thing to do.
Answer: Hint: for $0<x<1$, the inequality
$$
(1-x)^n<\frac{1}{(1+x)^n}
$$
is equivalent to
$$
(1-x^2)^n<1
$$
Or, mimicking the proof of Bernoulli's inequality, we have to prove that
$$
(1-x)^{-n}>1+nx
$$
The statement is true for $n=1$, because it is $1-x^2<1$. Suppose it holds for $n$. Then
$$
(1-x)^{-n-1}=(1-x)^{-n}(1-x)^{-1}>\frac{1+nx}{1-x}
$$
by the induction hypothesis. We are reduced to prove that
$$
\frac{1+nx}{1-x}\ge 1+(n+1)x
$$
which becomes
$$
1+nx\ge1+(n+1)x-x-(n+1)x^2
$$
Answer: What about AM-GM?
$$(1-x)^n(1+nx) = \text{GM}(1-x,1-x,\ldots,1-x,1+nx)^{n+1} \color{red}{\leq} \text{AM}(1-x,1-x,\ldots,1-x,1+nx)^{n+1}=1$$
and the inequality holds tight since $(1-x)\neq(1+nx)$. Done.
Comment: @πr8: yes, the usual Bernoulli inequality can always be replaced by an AM-GM inequality. We may use AM-GM to prove that the sequence $\left\{\left(1+\frac{1}{n}\right)^n\right\}_{n\geq 1}$ is increasing, for instance.
Comment: Lovely proof! Can this be used for the standard Bernoulli inequality as well?
Answer: First note:
$$\frac{1+nx}{1-x}=\frac{(1+nx)(1+x)}{(1-x)(1+x)}=\frac{1+(n+1)x+nx^2}{1-x^2}\ge\frac{1+(n+1)x}{1}$$
So:
$$\frac{1+nx}{1+(n+1)x}\ge1-x$$
Take a product of these expressions for $n=0,1,\cdots,N-1$ to see
$$\frac{1}{1+Nx}\ge(1-x)^N$$
(this can easily be recast as an induction)
Answer: $(1-x)^n = 1/(1-x)^{-n}=1/(1+nx+n(n-1)x^2/2 +\cdots) < 1/(1+nx)$, assuming  $ 0 < x < 1$.
Answer: Let $f(x)=(1-x)^{-n}$. Then by applying mean value theorem for $f$ we have,
$$\frac{f(x)-f(0)}{x-0}=f'(\zeta)$$(for some $0<\zeta<x<1$)
$$\frac{(1-x)^{-n}-(1-0)^n}{x-0}=(-n)(1-\zeta)^{-n-1}(-1)=\frac{n}{(1-\zeta)^{n+1}}>n$$
The above line is true as $1-\zeta<1\Rightarrow\frac{1}{1-\zeta}>1$
$$\Rightarrow (1-x)^{-n}-1>nx$$
$$\Rightarrow (1-x)^{-n}>1+nx$$
Now $1-x>0, 1+nx>0$ implies,
$$\Rightarrow \frac{1}{1+nx}>(1-x)^n$$


Configurable Product Blank Page

Question: I am trying to set up a configurable product but all I get when I click on the product is a completely blank page. No header, etc, nothing. View Source shows no code is output at all.
What could be causing this?
Here is the url to the configurable product:
https://www.design-a-cake.co.uk/photocake-edible-cake-topper-pumpkin-lanterns.html
Thank you.
Comment: it is working now!
Answer: Your page has no error: see screenshot below

So in short, your issue seems to  be that the rendering does seem to  be stopped somehow. To debug, you may go in the product controller and put some logs to check what's happening. If you have installed some plugins, you may look at a possible controller taking over product in your Magento system.
Comment: I enabled errors to display and output the location of the files to better assess where the errors were coming from. Now I just get a warning (unrelated to page load) and still a blank screen. I have no idea how to see what it stopping the page from rendering.

Configurable Product Blank Page


Problem with USB Keyboard and Mouse on Raspberry Pi 4B with Ubuntu 20.10

Question: I have a mostly successful installation of Ubuntu 20.10 running on Raspberry Pi 4B with 4G memory. Right now I'm having issues with it not responding to keyboard and mouse when coming out of sleep/blanked-screen mode.
Here's what's happening:

Boot up to graphical login screen -- login, work, logoff -- everything seems to work fine.
After sitting idle for a while, the screen blanks.
Moving the mouse or hitting a key reactivates the screen -- I can see the login -- but the mouse cursor doesn't move. Keyboard doesn't work either.
I am able to ssh to the Pi with no issues and restart the X server.
Looking at the Xorg log I see:

[  2500.111] (EE) event3  - Logitech USB-PS/2 Optical Mouse: client bug: event processing lagging behind by 15ms, your system is too slow
[  2508.141] (II) modeset(0): Disabling kernel dirty updates, not required.
[  2508.535] (**) Option "fd" "26"
[  2508.536] (II) event0  - Dell Dell USB Keyboard Hub: device removed
[  2508.536] (**) Option "fd" "29"
[  2508.536] (II) event1  - Dell Dell USB Keyboard Hub Consumer Control: device removed
[  2508.537] (**) Option "fd" "30"
[  2508.537] (II) event2  - Dell Dell USB Keyboard Hub System Control: device removed
[  2508.538] (**) Option "fd" "31"
[  2508.538] (II) event3  - Logitech USB-PS/2 Optical Mouse: device removed
[  2508.547] (II) UnloadModule: "libinput"
[  2508.547] (II) systemd-logind: releasing fd for 13:67
[  2508.624] (II) UnloadModule: "libinput"
[  2508.624] (II) systemd-logind: releasing fd for 13:66
[  2508.644] (II) UnloadModule: "libinput"
[  2508.644] (II) systemd-logind: releasing fd for 13:65
[  2508.701] (II) UnloadModule: "libinput"
[  2508.701] (II) systemd-logind: releasing fd for 13:64

/var/syslog also shows an error:
Dec 16 13:27:23 cnc org.gnome.Shell.desktop[2097]: libinput error: event1  - Dell Dell USB Keyboard Hub: client bug: event processing lagging behind by 88ms, your system is too slow

Here are the currently plugged-in USB devices:
root@cnc:/var/log# lsusb
Bus 002 Device 002: ID 0781:558c SanDisk Corp. Extreme Portable SSD
Bus 002 Device 001: ID 1d6b:0003 Linux Foundation 3.0 root hub
Bus 001 Device 007: ID 046d:c00e Logitech, Inc. M-BJ58/M-BJ69 Optical Wheel Mouse
Bus 001 Device 009: ID 413c:2002 Dell Computer Corp. SK-8125 Keyboard
Bus 001 Device 008: ID 413c:1002 Dell Computer Corp. Keyboard Hub
Bus 001 Device 002: ID 2109:3431 VIA Labs, Inc. Hub
Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub

The keyboard is an old Dell with USB Hub. The Logitech mouse is plugged in to the keyboard. The keyboard is plugged in to a USB 2 port. (I've also tried plugging the mouse directly into the Pi instead of the keyboard hub but get the same results.)
The SSD is the boot drive plugged in to a USB 3 port.
If I immediately login after booting, the system runs fine. Only after it sits idle and the screen goes blank do I encounter problems.
Any ideas? Do I need a more modern keyboard and mouse? Are there settings I can play with? This hardware config runs just fine with Raspberry Pi OS (32-bit). I am just hoping to run a 64-bit OS that I am more familiar with.
Thanks.
Answer: Workaround (inspired by this):
Edit /etc/gdm3/custom.conf and change #WaylandEnable=false to WaylandEnable=false.
I also posted our problem here to make sure developers are aware of it.


How to define tensor contraction without referring to summation?

Question: The textbook defines a tensor to be an element in $(T^*)^k×T^l→R$. It then expresses tensors as arrays of components with respect to a certain basis, and defines tensor contraction using summation convention. My question is: Can we define tensor contraction without referring to basis,  components, and summation, but just the definition of tensor as a multilinear function? If components are inescapable, why bother define tensors as multilinear functions?
Comment: Do you know the so called **universality property** of the tensor product space and tensor map? It is the theoretical tool exploited for stating abstract (i.e., *independent from choices of bases*) definitions of this type. I have no spare time now for writing down an understandable answer, but that is the way...
Comment: I don't think we need the heavy weaponry here - is not [this](http://en.wikipedia.org/wiki/Tensor_contraction#Abstract_formulation) already basis- and component-free? (It *will* always be inescapable to talk about the "$x$-th factor" of the tensor product, since we must say *which indices are contracted*)
Comment: Do you mean the universal mapping property in category theory? I have learnt some category theory, but I haven't seen examples related to tensors yet.
Comment: Yes, just that kind of property. The contraction is defined suitably using that property applied to the pair tensor product of spaces + tensor product application.
Answer: I can give you a mathematical reason why you have to use components to define contraction.
The reason is that contraction doesn't work for infinite dimensional vector spaces. You would have to sum over infinitely many components, and this sum might not converge. So there is no possibility of contraction for infinite dimensional tensors.*
But if we had a "basis free" definition of contraction then there would be nothing to stop it working in the infinite dimensional case as well. The definition of finite dimensional is "has a finite basis", and so the definition always has to mention a basis in order to distinguish between the finite and infinite dimensional cases.
So using a basis really is inescapable here.
(In the comments to your question ACuriousMind gives a component free definition of contraction, but this relies on a slightly different definition of tensor than the one you were given. I order to prove that the definitions are the same you again have to assume finite dimensionality and pick a basis, because the definitions aren't the same in the infinite dimensional case.)

If components are inescapable, why bother define tensors as multilinear functions?

In physics there's no "preferred basis". So an answer to a physical question can't be correct if it depends on which basis you pick. After defining contraction, your teacher should have shown that if you were to pick a different basis to write your coordinates in then you would indeed get the same answer as before.
Doing this checking-that-things-don't-depend-on-the-basis is annoying, and so it's often best to give basis free definitions. (Views differ on when one should use a basis. Some people work in a basis all the time; others avoid them like the plague.)
*Example: The tensor $\delta^a_{\;b}$ would have infinitely many ones on its diagonal, so $\delta^a_{\;a}$ wouldn't exist.
Comment: I don't fully understand this (admittedly old) answer. You have two notions of contraction, both of which coincide for finite dimensions, one of which is well-defined in infinite dimensions, with the other definition failing in that domain $-$ I know which one *I'd* choose. If it bothers the purists, one can simply introduce the qualifier "for finite-dimensional spaces" into the usual componentwise definition of the contraction, with the infinite-dimensional case left open for the cleaner generalization.
Comment: @EmilioPisanty It's not quite that there are two notions of contraction but rather two notions of tensor product. The clean definition is via the universal property that maps out of $V\otimes W$ are the same as bilinear maps out of $V\times W$. In this case there is always a contraction $V^*\otimes V \to R$. But some courses take the (easier?) definition that $V\otimes W$ is a bilinear map $V^*\times W^*\to R$. This disagrees with the first definition in the infinite case, and has no notion of contraction in the infinite case. So you're right that it's better to use the clean first definition.
Comment: @EmilioPisanty What I was saying in my answer was that if you *do* use the "bad" second definition then you are *forced* to pick a basis when you come to define contraction, because contraction only works on finite systems (with this definition of tensor) and finite systems are defined to be those with a finite basis. Any basis-free definition would work in the infinite dimensional case, and therefore can't exist.
Comment: Ah, I think I understand the difference now - if it comes all the way from the definition of the tensor product then yes, it needs more care in its handling.


How to hide footer panel in edit mode in Javascript?

Question: I am working on a website in which I want to hide rectangular footer panel showing at the bottom of a website.
It should work in a way when the website comes in edit mode, the rectangular panel should  be hidden and when it comes in non edit mode, the rectangular panel should be visible.
The JS code for which is being called when the section comes in edit mode is:
toggleEdit: function(position) {
const self = this;
if (name == undef) {
return self;
}
self[name.dataset.edit != position ? "doEdit" : "undoEdit"](position);
return self;
},

The website comes in the edit mode when the value of position is either "hello" or "world".
Problem Statement:
I am wondering what Javascript I need to add above so that when the value of position is either "hello" or "world", it should the hide everything displayed through the following html (which is actually a footer panel):

<!–– and the comment closes with ––>

Comment: Possible duplicate of [Show/hide 'div' using JavaScript](https://stackoverflow.com/questions/21070101/show-hide-div-using-javascript)
Answer: Basically, you have to manipulate the DOM. The answer to your question, is really well explained at this question: Show/hide 'div' using JavaScript. Here, the answer provides a way to do it by using JavaScript.
If you want to do it by using a framework or library such as ReactJS you have to tell, what technology you are using.
Comment: I am using plain JS. I am not using any library.
Comment: Then, the already answered question, should also solve your problem.
Comment: @owzguensi I am wondering if you can give me little bit pointer on it ?


Find questions closed by a dupehammer

Question: Is it possible to find questions have been closed by users with golden badge (i.e. dupehammer) via special request on the search page?
Comment: I don't think so. At best you could query in SEDE the posthistory table for posthistorytypeid =10 rows. In the text field you'll find the close voters, form that you have to work out if the userid's mentioned had a gold hammer at that time. Not trivial at all.
Comment: @rene what about a query that find all questions closed with less than five votes, then take the last voter, who will be either a moderator or gold hammer? :)
Comment: @ShadowWizard yeah, but I see Patrick found a more robust solution.
Answer: No. Not using the search page, but you can using SEDE.
See for example this query made by Shog9: https://data.stackexchange.com/stackoverflow/query/425986/close-stats-for-top-dup-hammer-users
The trick is in this part of the query on the PostHistory table:
from PostHistory hc
where hc.PostHistoryTypeId=10
and hc.Comment like '101%'
and hc.Text like '%BindingReason":{"GoldTagBadge%'

Find questions closed by a dupehammer


Calculating LED amperage usage

Question: I'm calculating basic amperage (W/V=A)  I have a track light with 33 LED lamps that is experiencing an unusually high failure rate.  When calculating amperage would I use the 120v that the entire lamp is using or would I use a low voltage amount such as 12v or 24v since the lamps have an integrated driver?
Comment: Actually this sounds like some commercial product that you are troubleshooting. Not a design of your own. Ergo maybe DIY would be a better place for you?
Comment: Schematic ... ?
Comment: are you using resistor(s) to limit the current?
Answer: If these are standard \$120\:\textrm{V}\$ LED lamps, such as these, they will have stamped on them a "wattage." If you look at that page, you will see that these are rated with a "power consumption" of \$6.5\:\textrm{W}\$. Ignore the "wattage equivalent" ratings -- those are about how the lighting supposedly "appears" to a human when comparing it with a traditional incandescent bulb and not about the actual power consumption of the device.
So, let's say you had 33 of the above lamps in your track lighting fixture. This would mean a total of \$33\cdot 6.5\:\textrm{W}=214.5\:\textrm{W}\$. That would be about \$1.8\:\textrm{A}\$ when all the lights are on. (This is RMS, which means the peak, momentary current can be \$\sqrt{2}\$ more than that, or about \$2.5\:\textrm{A}\$.)
Now, all this assumes that the power factor of the lamps is 1. In reality, it could be half that much (in one you should NOT buy.) But they vary and the actual power factor for an LED lamp is hard to find when you are buying one. I tend to assume a power factor of about 0.9, or so, if I don't have any information. (But I honestly have no good justification for that figure. So I'm open to better advice on this point.) But assuming 0.9, then the circulating current would have an RMS value of \$2\:\textrm{A}\$ and a peak value of slightly over \$2.8\:\textrm{A}\$.
I'd want to plan \$5\:\textrm{A}\$ for your track lighting if you were intending to use those particular bulbs in it.
Answer: Whenever you are dealing with LED lamps with integral drivers, you must supply the voltage they are rated for.   If at that point they fail, then the product is defective or you have an application issue.**
It's also possible there's a quality problem with your supply power.
Often wnen line power has noise or spikes, the culprit is actually your own gear.  So it is possible the LEDs themselves have dirty power supplies which are putting a lot of noise on the line.  They may be too dirty for 33 of them to coexist on the same circuit.  This would be caused by cheapness and should be considered a product defect.  If the manufacturer's initials are LoA, FE or UT, that's your problem.
It also causes trouble when you dim LEDs that are not made for dimming.
Watts and VA
That dirty power draw can be a factor, a power-factor to be precise.  Imagine a power supply draws from the AC sinewave unevenly - it doesn't use the whole sinewave.  But the generator still has to generate the whole sinewave, and the wires must carry it.   The part it uses (times amps, averaged out) is its watts.  The entire sinewave is called VA.   The ratio is called the power factor.
With very poor power factor, it's possible to hit the VA limits of a circuit (i.e. 1800 watts on 15A - without getting near it in wattage.
This will cause line noise and poor performance.
** an example of an "application issue" would be trying to use an LED as an oven light.
Answer: Assuming you apply the correct rated voltage and you always add the total ACTUAL Watts for breaker ratings.

where 120W on 120V is 1Aac. regardless what the LED sees.

1) DIY lighting design with lamps and luminaires can cause excess heat rise can cause low MTBF (excessive failure rates or FITs)
2) Poor "AC Power Quality" with frequent lightning transients in tornado alley or Florida can also caused low MTBF rates.
3) Cheap LED's can have low MTBF from poor heatsink designs.
MR16 GU5.3 may be 120Vac rated or  12VAC (not DC rated) and may be protected with better cooling so that the free space above the lamp does not restrict the flow of convection cooling by a better design track socket or extension and NOT a cup back that restricts airflow or right at the ceiling with no ceiling vent.

MR16 GU10 come in Voltages: AC/DC12V, AC85-265V/

Which ones do you have?
Which problem? poor convection cooling? poor line quality? poor quality LEDs?
Answer: If you are calculating the amperage of the leds themselves, it would be the voltage and current through the individual leds. If you are calculating the amperage that the entire bulb uses, it would be the line voltage. This would include the power used by the internal led driver as well. The driver is likely to be 80% or higher efficiency.

Calculating LED amperage usage


Feature activation running slowly on one environment

Question: We have 3 farms, Dev, QA, and Production.  Feature activations are running very slowly on the QA environment only. I  have a custom feature that deploys files out to the style library and changes the MasterPage.  It times out before activating.  This same feature takes about 5 seconds in the other environments.  Even the 'SharePoint Server Standard Site Collection features' feature took nearly 40 seconds to activate on the QA environment.  The environment was working fine until recently.  Has anyone seen this before?
Comment: did you check, if SharePoint Admin job is running and also timer? can server access to internet? also check if CPU or memory goes high during?
Comment: No hints in the event log, ULS, or Health Analyzer.
Comment: All SharePoint services are running, all servers can hit the internet, and the resources on the server look great.  I'm suspicious that it is a SQL issue but I don't have access to the SQL Server.
Answer: SQL was incorrectly configured.  Since I had no insight or permissions on the SQL server it was difficult to pin the issues on SQL.  Once SQL was reconfigured, the issues disappeared.  I did not reconfigure SQL and thus do not know specifically what was wrong.


Predictor variables in Multinomial Logistic Regression

Question: Is it always better to have categorical predictor variables when performing a multinomial logistic regression analysis? or can it be done using continuous predictor variables? If a predictor variable should always be categorical, what is the reason behind it?
Answer: Multinomial logistic, like other forms of regression, can deal with any sort of predictor.


How did the treasure finally end up on Isla De Muerta?

Question: In Pirates of the Caribbean, after Hernán Cortes further continued the killings on the Aztec empire, did he take the treasure or not? And how did the treasure finally end up on Isla De Muerta?
Comment: Barbossa and crew might have put them in there since Isla de muerte is their treasure hiding place. and if Cortes took that treasure, it couldn't be in possession of pirates innit?
Comment: @Vishwa while that seems to be a reasonable answer, the other issue is that the Island seems to disappear and go "all pear-shaped" after a hurricane comes post COTBP and besides being cursed the only other way to find it (so far) is with Jack's/Morgan's compass.
Comment: It's unclear if what happened with treasure (being magically restored/curse lifted) is related to the hurricane and/or if the hurricane is related to the magic of Tia Dalma, as she ends up with Barbossa's body. Is the Island magical on it's own, is it only magical, because of the treasure (possibly being originally "cursed" at this location), and/or is what happens after the first film separate and related to Tia Dalma/Calypso?
Comment: @DarthLocke - given how many times this movie almost didn't make it out of the gate, I doubt sequels were on anyone's mind. Don't get caught up trying to retcon an IP which from its inception was a cash grab.
Comment: @Mazura, I think it's besides the point, because it DOES have sequels and it has become a franchise that has an ongoing story with mythology. If everyone would have that perspective, then there would never be a need to ask a question like this. It's just it's hard to fully answer, because there are still unsolved mysteries and/or mythological points that haven't been perfectly specified.
Answer: Not an official source but this should give you a ballpark idea of actual years when real world events happened versus fictional timelines

c.1519

Hernán Cortés conquers the Aztec empire with his armies and wielding the Sword of Cortés.
The Aztecs deliver to Cortés a stone chest containing 882 identical pieces of Aztec gold, as blood money to appease his slaughter. When Cortés refuses to stop his conquest, the Heathen Gods place a curse upon the treasure, so that anyone who took but one coin from the chest would become undead skeletons. The treasure ultimately ended up on Isla de Muerta.

1728

James Norrington is promoted to the rank of Commodore. Jack Sparrow arrives in Port Royal prior to the Black Pearl's attack. Elizabeth Swann is kidnapped, and Will Turner recruits Jack to help save her. Jack assembles a crew at Tortuga, who set sail in the commandeered HMS Interceptor.
During the voyage to Isla de Muerta, Jack and his crew sack the Earl King, with Jack and Will posing as members of the Royal Navy.
Jack ultimately confronts Barbossa at Isla de Muerta. Turner lifts the curse, allowing Jack to kill Barbossa and his crew to be killed or captured by Norrington's men. Jack escapes a hanging with Will's help, and rejoins his crew. Will and Elizabeth pledge their love to one another. Jack the monkey takes a coin from the chest and becomes cursed once more.

There is roughly 200 years of history between the events of the Spanish conquest and the events of the first movie.  In 200 years of story, those coins exchanged many hands but the curse led Barbossa to gather them all at Isla de Muerta for the sake of the story.
Comment: Motive; dead men taste no apples. - "Find it, we did. There be the chest. lnside be the gold. And we took them all. We spent them and traded them and frittered them away on drink and food and pleasurable company. The more we gave them away, the more we came to realize, the drink would not satisfy, food turned to ash in our mouths, and all the pleasurable company in the world could not slake our lust. We are cursed men, Miss Turner. Compelled by greed, we were, but now we are consumed by it."
Comment: That's the entire plot of the movie in a single pontificated paragraph. The answers to almost any question you could have should be inferred from that quote. I would've sworn this was discussed standing in front of the chest; it's actually much earlier in the movie and establishes the plot of the endgame, and explains why no body cares about all the golden junk laying around, because for them it has long since lost its luster.


pop up warning messages

Question: I have a weather cam and a stream server set up in a Yacht club. At times for variuos reasons the server stops running and should be restarted. I made a PHP script to check every 10 min using $fp = @fsockopen("$site", 80, $errno, $errstr, 30) and a javascript timer in the page. I like a warning message to pop up when $fp is false. This message should be on top of whatever windows the office staff is currently using.
Javascript alert() would be perfect, problem is that alert() stops processing threads and the timer and further checking untill someone is kind enough to click OK.
Answer: Well, you don't have to use an alert box. You can create a message in plain old HTML and CSS and position it on top of everything else.
You might also use one of the numerous jQuery modal dialog plugins, such as: http://www.queness.com/post/77/simple-jquery-modal-window-tutorial
There are lots of them, and a quick Googling will help you find one that works for you.

pop up warning messages


Request to join a Google analytics account

Question: Is there a way to as to request someone elses google analytics account, if i dont know who the owner/manager is? or find out who that is via UA-id?
Answer: There's currently not a feature to request access, or to find a Google account from an ID. Google themselves can help with the latter but it's meant for reasons other than just wanting to be 'let in'.
Answer: What is your purpose? Are you the owner? New web master? Please let us know.
If you don't know the owner/manager, in short you will not get access to Google Analytics for the particular site(s) you have in mind.
Also, you will not be able to obtain Google Analytics site owner information with the UA-id alone. The current Google Analytics owner must give you permissions via Admin toolset. If you need to recover a site or add a site you must create a new Google Analytics usage ID and verify site/domain ownership via meta tag insertion or CName Record at Google's request along with your Gmail account information.
Comment: Some hosts and such allow us to request access by entering our client's info, including email address. This makes it really easy @dvnkiss for them to grant us access. I think that's all Andy was asking: does GA have a similar feature. It would be super nice for less-than-savvy clients.


Rentier capitalism vs investment capitalism?

Question: A company has backers who put in money seeking a return from either share-price growth through company growth, and yearly rent in the form of dividend payments. Debt is clearly the case where share price growth is 0 and only the yearly rent is paid, (Socialism is 1/population for both + a wage). Why do stockholders get both the right to make money from the investment, and the right to extract rent at the same time? How does having both rights at the same time impact the economy? Is there any economic thinker that considers banning dividend payments on shares from a legal perspective?
Comment: You seem to be asking several questions at the same time, whereas we require just one question at a time. And I'm not really sure what it is you're asking at all. What is the economic principle about which you are unsure? What is the real-world problem that you are facing, that you are trying to solve?
Answer: A share is an entitlement to the ownership of a company. Such ownership brings several benefits like voting rights and dividends, and the owner is free to sell such ownership whenever s/he wants, making a capital gain (or a loss) in the process.
Why is this the case? Well, it was like that with the first publicly listed stock-owned company (the Dutch East India Company). In terms of incentives, it fosters the allocation of (financial) capital to new ventures by giving those taking the risk to benefit from it. It has proven a highly successful legal arrangement to foster businesses and investment.
Another common legal arrangement is that of non-profit corporation. These organisations are usually started by a group of people, which contribute capital to it (albeit this is not represented in the form of shares). Sometimes they transfer the ownership to a foundation. In any case, these companies cannot distribute profits to the owners.
Finally, as you say an alternative legal arrangement would be one were ownership of shares do not lead to income via dividends, but such shares still allow for capital gains. In fact, some shares pay no dividend at all (as a matter of fact, the taxonomy of shares is quite diverse). As this article explains:

investors who buy stocks that do not pay dividends prefer to see these companies reinvest their earnings to fund expansion and other projects which they hope will yield greater returns via rising stock price.

So in principle you could set up a company that does not issue dividends in order to foster its growth. Naturally, this could be changed in the future through a motion in an annual general meeting of shareholders. There are also plenty of companies who decide not to pay dividends in order to foster expansion (e.g. Apple until a few years ago). Yet, many of these companies, and particularly in the last decades, have decided to execute share buybacks rather than foster expansion and investment. This is, the company buys their own shares with its profits, which fosters price growth and hence expands capital gains. This is part of a wider short-termist trend that some have denominated "Quarterly Capitalism".
There is very interesting new research about the consequences of this "quarterly capitalism" on investment and growth. Check here, here, and here. The latter concludes:

We show that capital no longer flows more to the industries with the best growth opportunities because, since the middle of the 1990s, firms in high q industries increasingly repurchase shares rather than raise more funding from the capital markets.

This evidence gives a rather counterintuitive result (at least from the normative meaning of the words), which is that a rentier capitalism might be better for investment and growth than an investment captialism.


Installed Jupyter Notebook for Python 3.6.8 stuck at "Kernel Starting, please wait..."

Question: I installed jupyter notebook on my computer for a RHEL system, I installed it using the command pip3 install --user jupyter and then later due to it not working pip3 install --force-reinstall --user jupyter, so know I have my jupyter files stored in my ~/.local/bin directory. I am not an administrator or superuser for the cluster I work off of, this is why I installed in ~/.local/bin. Now whenever I launch a jupyter notebook, and open a .ipynb file, the kernel stays in `Kernel Starting, please wait..." until the kernel just exits. I've tried to see if the browser affected it, and now I've tried it on Internet Explorer 11, Chrome, and Edge and they all do the same thing. I have no idea what could be keeping the kernel from loading.
EDIT (02-DEC-2019): There seems to be a possible solution detailed here, however, these are solutions that describe how to downgrade on a windows system, where is I'm operating off a linux based operating system.
EDIT (03-DEC-2019): After investigating further, I found that the "Kernel Starting, please wait..." message on the Jupyter page corresponds to the terminal echo:
RuntimeError: Permissions assignment failed for secure file: ':/path/to/user/tmp/jupyter-kernel:/path/to/user/jupyter-kernel/kernel-66b8b6e5-5e4c-4b05-98e9-870a5b431088.json'.Got '0o1600' instead of '0o0600'
This problem seems to be talked about on the github issues page for Jupyter, and I tried doing what was prescribed, that being changing the $JUPYTER_RUNTIME_DIR to a new location and that didn't work (I actually tried to different directory locations), I made sure the kernel .json files were in the right location and everything. I still continue to get the same error. The os.name that my system gives me is POSIX so I don't know if that's the underlying problem, as the error is sourced to a file called paths.py, and seems to be a problem in secure_write(), here's a portion of the code:
@contextmanager
def secure_write(fname, binary=False):
    """Opens a file in the most restricted pattern available for
    writing content. This limits the file mode to `0o0600` and yields
    the resulting opened filed handle.

    Parameters
    ----------

    fname : unicode
        The path to the file to write

    binary: boolean
        Indicates that the file is binary
    """
    mode = 'wb' if binary else 'w'
    open_flag = os.O_CREAT | os.O_WRONLY | os.O_TRUNC
    try:
        os.remove(fname)
    except (IOError, OSError):
        # Skip any issues with the file not existing
        pass

    if os.name == 'nt':
        # Python on windows does not respect the group and public bits for chmod, so we need
        # to take additional steps to secure the contents.
        # Touch file pre-emptively to avoid editing permissions in open files in Windows
        fd = os.open(fname, os.O_CREAT | os.O_WRONLY | os.O_TRUNC, 0o0600)
        os.close(fd)
        open_flag = os.O_WRONLY | os.O_TRUNC
        win32_restrict_file_to_user(fname)

    with os.fdopen(os.open(fname, open_flag, 0o0600), mode) as f:
        if os.name != 'nt':
            # Enforce that the file got the requested permissions before writing
            file_mode = get_file_mode(fname)
            if 0o0600 != file_mode:
                raise RuntimeError("Permissions assignment failed for secure file: '{file}'."
                    "Got '{permissions}' instead of '0o0600'"
                    .format(file=fname, permissions=oct(file_mode)))
        yield f

Comment: Possible duplicate of [Jupyter Notebook stuck at localhost:8xxx/tree](https://superuser.com/questions/1493358/jupyter-notebook-stuck-at-localhost8xxx-tree)
Answer: One workaround - In Jupyter core v4.6.2, you can now set environment variable JUPYTER_ALLOW_INSECURE_WRITES to 1 or true, to disable this check
Detail: https://discourse.jupyter.org/t/jupyter-core-4-6-2-release-with-insure-mode-option/3300
The last working version was jupyter_client==5.3.1, before that security change was made
Answer: For me, the issue was caused by ExpressVPN's whitelist (split-tunnel) feature interfering with Jupyter. I disabled split-tunnel and just used a browser VPN extension instead. FYI, NordVPN has a vaguely working split-tunnel feature whereas SurfShark, ExpressVPN and probably many others are complete fails.


Unity Multiplayer functionalities or Google's plug-in?

Question: I want to add multiplayer matches to a game I'm making for Android/PC, and something echoed in my mind: would the network functionalities Unity provides work in Android? I ask this because Google has a free plug-in for their services, but Unity also offers possibilities. Also, using any of the above, do I need to pay to rent a server? Or, for example, since we need a paid developer account to register our game at Google Play Store, the servers are part of the deal?
Answer: Unity and Google offer different APIs/Services, but both are centred around a P2P (Peer to Peer) architecture.
Unity, as does Google, offers matchmaking and relay servers. These are ways to find players, and relay data between clients.
Unity's offering comes with a free "personal" licence, where as with Google's there seems to be some lack of information (free?).
As Unity is cross platform, it's tools and services are as well. The services provided by Google however only work on Android/iOS.
More information for Unity is here: https://unity3d.com/services/multiplayer
More information for Google is here: https://developers.google.com/games/services/common/concepts/realtimeMultiplayer
Comment: After reading what you provided, I couldn't understand the payment method. You said Unity has a free "personal" license, how so?
Comment: @Evenilink https://store.unity.com/ states Unity Multiplayer as 20 Concurrent Users. More information is provided on the page.
Comment: That's exactly my question! So basic users can have 20 players worldwide playing at the same time, right? Guess this is more to test multiplayer itself than providing a "true" free service, but I understand they need the income to keep servers running...


Materials that don't absorb

Question: If a utensil can't become meat or milk through bliya, (like wood does) then is it ever possible to become non-kosher?
Comment: Wood can't become meat or milk through bliya? Are you sure? Source?
Comment: Now glass, according to Sefardim, never absorbs. Clean it thoroughly and you're done.
Comment: @Shalom That sounds like an answer: if a material doesn't absorb then it can't become non-kosher. Anything beyond that is just science not Halakha. If you could source this principle that would be great.
Comment: Scientifically it's not possible for wood to absorb flavoring because of the material. It could be thought as electrons passing through a metal object, however they can't pass through a wooden one.
Answer: Indeed a utensil that doesn't absorb cannot become non-kosher.
Glass, according to Sefaradim, doesn't absorb and, if clean, can be used for meat and dairy. As such it cannot become non-kosher (SA OC 451:26, see also for instance here).

Maran Rabbeinu Ovadia Yosef zt"l ruled in his works and Torah lectures
  in accordance with the opinion of Maran Ha'Shulchan Aruch that
  glassware does not require Hag'ala and it may be used for both meat
  and dairy. [...] According to the Sephardic custom, however, a thorough washing is sufficient, as we have explained.

However Ashkenazim consider that glass absorbs and has a status of Kli Cheres, which is to say that glass dishes are equal to that of pottery (which can become non-kosher, see e.g., here).
Your question mentions wood, but wood absorbs and is kashered through hagala (SA OC 451:8).
Comment: Are you suggesting that glass is a Machlokes in Metziut?

Materials that don't absorb


Whst is the difference between "Has" and "Has had"

Question: Please explain the difference between the following sentences:

Tom has a busy day so far.
Tom has had a busy day so far.
Comment: [at time time I am speaking right now and ***starting at an undefined moment in the past***", "Tom has had a busy day. But yesterday, he did not have a busy day. Tom has busy days on Mondays and Fridays."
Answer: The second sentence means that Tom's day, up to the present moment, has been busy. It's specifically about what has happened up until now; it leaves open the possibility that some time later today Tom might have less to do than he has had so far today.
The first sentence is a little bit strange. The only context in which I might say it is if Tom has a schedule of things that he is required to do today, and I'm remarking on the fact that that schedule is unusually full. "I'm sorry, I can't give you an appointment with Tom this afternoon. Tom has a busy day so far, but I can let you know if someone cancels." Even then, I would probably phrase it differently --- "Tom has a busy day today" or something like that.


Differences and similarities between "catastrophe" and "disaster"

Question: In my field study Environment Eng. disaster is used for natural happenings which cause irreparable results in the nature and human beings' lives, but I have seen and read people use them for different or similar matters. Could you please make clear what the correct usage of those terms is?
Comment: NOAD defines the words circularly (i.e. it defines _catastrophe_ as "a disaster", and _disaster_ as "a sudden event, such as a catastrophe"); this suggests the words can be used interchangeably in many contexts.
Answer: This website describes the difference between a disaster and a catastrophe as follows:

Natural disasters occur when extreme magnitude events of stochastic natural processes cause severe damage to society. "Catastrophe" is used about an extreme disaster, although originally both referred only to extreme events (disaster is from Latin, catastrope from Greek).

In my own understanding of the words, I would describe a catastrophe to be a disaster of such high magnitude that you could not have prepared for it, because you would not have expected that something so bad could happen.
EDIT: @J.R. reminded me about the less literal usage of the two words, which you could use to say that things turned out badly, for example:

How was your performance last night?
Oh, it was a disaster – the percussion was off, the woodwinds squeaked, and the soloist couldn't hit her high notes.

In this hyperbolic form, I believe that disaster is more common, but you could use catastrophe if you really want to exaggerate.
Answer: When Disraeli, then out of power, was asked the exact same question, he explained:

"If Mr. Gladstone [Disraeli's rival and then Prime minister] fell into the Thames, it would be a disaster.
  But if some over-zealous person jumped and pulled  him out, it would be a catastrophe."

(Here is a  reference)


How to enable x86 paging only in ring 3

Question: I understand that setting the PG bit of CR0 enables paging in x86 and further all addresses generated will be logical and translated using page directories and tables. However I want that logical addresses be generated only for ring 3 and wish to keep all generated addresses in ring 0 as physical. Can this be achieved somehow? I had thought of setting the PG bit just before IRET. However I doubt that would help because IRET uses ESP to pop out CS, EIP, EFLAGS, SS, ESP etc. And if the PG bit is set, then ESP would point to a logical address and the command would fail, right?
Comment: What is it for? You can set up some identity-mapped pages if you want, then paging can stay on
Answer: The basic problem with what you want is that x86 isn't very good at pc-relative addressing; so you need to link your kernel at some address.   What will that address be?
1M (2^20) is a pretty good choice.
Next up is how much memory do you have?  4G?  Thats a bit ugly, your "one true physical map" leaves no address space for user programs.   Look at [2] for a fix.
Supposing you don't actually need all of memory mapped, just the kernel-y bits, and your kernel is likely less than 1G, you could keep kernel mapped pages 1:1 for the lower 1G of address space.  User programs would then be in virtual addresses > 1G, with arbitrary mappings.
Not really sure the point of it all; but it is quite doable.
[2] for the tougher case, you can do something funky that has a side effect of stomping on a few of the spectre derived bugs.   When an application is running, only provide kernel mappings for a very small area - the code to handle initial kernel/trap entry and the in-kernel user context.  As part of the initial register save code, switch to a kernel only cr3 which is a unity mapping of all memory.  If you wanted, you could actually disable paging instead, the re-enable it before re-entering user mode.  Again, not sure the point, but feasible.

How to enable x86 paging only in ring 3


NFC Print from Android app

Question: I have been doing alot of research today, about whether or not it's possible to implement NFC printing in an Android app. We have a client who has an HP printer with the NFC feature, and want to use that in an app we created earlier, instead of Cloud printing. What we want is, to be able to set some options regarding the print itself, like orientation and scale etc., automatically, so we can just hold our Android device in front of the printer.
Use case:

Press print button in Android app
Create bitmap
Show dialog saying: "Hold phone close to the printers NFC reader"
The printer then prints the bitmap, without further user interaction.

The idea here is, as mentioned above, that we can se some print options in the NFC message.
Have anyone done anything like this before, and is it even possible to use a custom implementation of NFC printing on Android yet?
Another solution would be to use HP's own feature, called EPrint. I have created a test version, where we just create the bitmap and then create an intent to the EPrint application (the user must have the HP EPrint app installed...).
The EPrint app then finds the right printer, by itself, and then the user must set some printing options before pressing "print". It doesnt seem like it's possible to adjust any printer options with the intent (bundle), but maybe it just lacks documentation?
The above implementation is not too bad, because the client doesn't mind having the HP EPrint app installed. But the NFC feature would be more preferable.
Is any of this possible?
Comment: Android 4.4 and higher support printing. However, the details of how the PDF generated for printing actually gets printed is up to the printer manufacturer. This includes how that PDF is transferred over to the printer. Hence, this is not an "Android" thing; this is an "HP printer support on Android" thing, and you will need to ask HP what it supports for its various printers for its Android printing plugin.
Comment: @CommonsWare Yes, that is what i suspected, but i just wanted to see if anyone have ever done anything like it before. Thanks for the quick answer
Answer: It appears that the hp EPrint app supports nfc printing without option selection. This video demonstrates how to print through EPrint using nfc. If you export the document to the app, it will show preview mode. When the preview is shown, you simply place the phone on the printer's nfc chip and it should automatically print with no additional options or dialogue.

NFC Print from Android app


Why do some programs fail to be selected as the default program with which to open select file formats?

Question: I have files I'd like to open with SciTE or Sublime Text 3 (ST3) but when I right-click them and navigate to Open with→Choose default program... it opens up a new window (which I will call the Open with window). The problem I'm having is that that neither program appears in the recommended or other programs listed. Then when I choose the "Browse" option and click the exe file for either SciTE or Sublime Text 3 (which are in Program Files for ST3 and Program Files (x86) for SciTE) I'm left with the original Open with window with no sign of either program in the list of programs I can select to open the file with. When I open up browse for other programs and select them to open the file with a new program icon for the program appears in the list of programs I can open the file with.
Comment: Did you try to associate the filetypes in Control Panel\Programs\Default Programs\Set Associations
Answer: Not sure why the application isn't added to the dialog. But you should be able to add the program using a tool called "OpenWithAdd"
Registering programs with the "Open With" dialog
Alternately, one could open the registry editor and manually register the application, using the info here:
Application Registration (Windows)
The 2nd link is for advanced users, I'd say. Basically MSDN documentation is for use by developers.


Edge cases for a multistep navigation on mobile

Question: Working on an ecommerce app feature where each product will have a multistep horizontal navigation (refer below). however the amount of steps might vary form 1-4. can't seem to come up with a decent way to show only one step without breaking the consistency of the other multistep navigations on the same screen. what would be the best approach. go for consistancy or come up with something new?
Answer: Do you have to show the number of steps for a single step process?
Surely you only need the user to recognise a multi-step process when it IS a multi-step process - ie when there are 2 or more steps.
My recommendation would be to abandon the single step indication all together.
Answer: Although I don't know what the end state of all of these steps is but my assumption is that there would be a CTA to finish the process.
If so you can just use that as the final click after step 1..> finish


Is there any Linux alternative for Rainmeter?

Question: Rainmeter is a popular software used to customise Windows desktop. Is there any Linux alternative for rainmeter to use in Ubuntu 12.04 ? The desktop in Ubuntu looks plain!
Answer: try conky you can install it using sudo apt-get install conky and see http://ubuntuforums.org/showthread.php?p=5436679#post5437628
Answer: Not a ready and very common thing but I started to developing an open source, cross-platform, Rainmeter Widget Manager Alternative.
It's called Widgetci.
It's running in my Ubuntu 16.04 and my Windows 10 perfectly now, but it is not ready for normal user.
If you have Qt5.9 and Qt-Creator, you can compile it and test it, hopefully there will be win & linux builds published in several days || weeks: https://github.com/eminfedar/widgetci/tree/dev-stable


Word for someone who pays their share

Question: Let's say there is an expense, and it's shared between a number of people. What do you call the person who has a share in that expense? Sharer?
Answer: If it is an ongoing expense (like for a gym-pass) "stakeholder" would be understood but stilted, since it stems from business-environments (and is mostly misused even there).
If it is a one-time deal (like for a meal) "contributor" might work. e.g. "She was a contributor to the birthday present, so she got to sign the card"

Word for someone who pays their share


Why can't I rebase on to an ancestor of source changesets if on a different branch?

Question: I would like to know why the following pattern is not possible.
Having created a local feature branch (minor_feature - not intended to be shared with the world) I would like to rebase the work on it on to the tip of a well known branch (stable). However I have discovered that rebase finds nothing to be rebased in the case where stable has not progressed since branching away from it.
I appreciate that this breaks the rule that the destination of rebase can not be an ancestor of the source but can't work out why this should be prohibited in the simple case shown. I also understand that, branches aside, the topology would not actually change during the rebase. But given that the branch names are indeed significant to the topology, it only seems to be a special case in that stable has no further revisions commited to it. With a single extra revision on the tip of stable (say pulled in from elsewhere) I can of course perform the rebase
o  branch:minor_feature
|  rev:4
|  changeset:746d8191aa5d
|
o  branch:minor_feature
|  rev:3
|  changeset:520f565ba7f2
|
@  branch:stable
|  rev:2
|  changeset:64e7c753c090
|
o  branch:stable
|  rev:1
|  changeset:3dc55a5c9971
|
o  branch:stable
   rev:0
   changeset:fbf1f426945c

$hg rebase -b minor_feature
nothing to rebase

--
Thanks
Chris Gorman
Answer: Rebase is strictly for changing ancestry of changesets. As you've observed, you're not changing ancestry here. Branches aren't included in the ancestry computation.
I'm not 100% sure what you're trying to accomplish. If it's to effectively remove the branch, then as long as you haven't pushed, you can likely use the MQ extension. Import the changesets, pop all. Ensure you're updated to the stable branch (which it should be by default), and push them all back on.
They should now all be on the stable branch.
Answer: You can do this with the convert extension. You would use a branchmap to rebase minor_feature to default. That file (we'll call it alldefault) would look something like this:
minor_branch default

Then the command would just be:
$ hg convert --branchmap alldefault oldrepo newrepo

When it finishes, newrepo will have the named branch "rebased" on top of the default branch.


Bully keeps running off

Question: I have an American bully. He started watching over baby calves, then one of my neighbors was sick and he stayed at their house. Now a neighbor down the road lost her dad day before yesterday, and when he goes outside he goes to their house. Can you tell me why?
Answer: Your dog is not running away, he is visiting all of his friends.
If there is a risk of him getting run over by cars, abused by strangers, mingling with diseased dogs (eg, mange), or tangling with hostile wildlife, you may want to re-design his yard-space so that he cannot escape anymore.
As your dog is prone to wander, please make sure that he is microchipped, so he can be returned to you if he looses his way.

Bully keeps running off


Can I put a regular lead acid battery in place of a gel battery in a BMW R110RT?

Question: I just got a 2000 BMW R1100RT and the previous owner told me the battery is 7 years old so I figure it's time to go.
I saw this video https://www.youtube.com/watch?v=XEBjekqUV9c  and the guy points out that the battery sits right next to the engine and gel batteries deal with the heat better, and the current battery is a gel battery.
I have a regular lead acid battery I was going to use (spare backup I keep around) but now I'm wondering if it's a bad idea to use it, if it's going to be right next to the engine.
Any idea?
Answer: A typical lead acid battery require occasional maintenance. As the battery is recharged the acid outgasses. It essentially evaporates. This gas is corrosive and an explosion hazard if it concentrated in an enclosed container. Many motorcycles utilize a covered battery box. They may also use a drain hose to remove any acid fumes out of the battery  and the battery box. A gel battery can offer lower maintenance and reduced outgassing. This is important if the battery is difficult to service or subject to high temperatures where the acid is likely to evaporate quicker. So the simple answer is yes it will work providing it is of the correct size (both physical size and amp rating). It may not last as long as a gel battery and may require more frequent service. Be aware that if the battery?box does not contain a vent tube you may see some corrosion in the battery box area.
Answer: I got this from Craig Hansen of http://www.hansensmc.com/
Stu,
You can put in a acid battery, but most times the ABS system will fault on
cold mornings.  The BMW Gel battery doesn't normally doesn't have this
issue.
Answer: To have this discussion, it is important to understand a few different lead acid battery types:
A wet flooded cell battery is a lead acid battery that, among other traits, makes use of case vents. This is one of the oldest battery technologies and is relatively high maintenance because the water in the battery will evaporate, requiring the owner to maintain the electrolyte level.
An AGM battery is a lead acid battery that has the electrolyte contained in a glass mat material. The acid absorbed in the glass mat containst just enough electrolyte to store energy, but not enough to have any freely flowing inside of the case. Because the AGM batteries do not have any freely flowing electrolyte and are maintenance free, they are often confused with gel batteries, though they are different from gel batteries in both technology and performance. The AGM lead acid battery is the most popular type of battery found in motorcycles.
A gel battery is a lead acid battery that uses a silica based gel to contain the electrolyte. Gel batteries are most popular in power supply applications such as a wheel chairs. Gel batteries have increased cycle life over other lead acid batteries but have the drawback of not being able to maintain high amounts of current in both charge and discharge. This drawback makes usage of gel batteries in automotive applications undesirable because both high discharge and recharge rates are required.
The issue you describe of problems related to a battery being near an engine have to do with wet flooded cell batteries where the water in the electrolyte evaporates more rapidly because of the heat. This is not an issue for any sealed lead acid battery, such as an AGM battery.
The only motorcycle manufacturer known to have used gel batteries is BMW, and generally only the OEM batteries from certain model years used gel technology. There is no modification required to replace a gel battery with an AGM battery, the AGM being the most popular type for sale for motorcycles.


Multiple bounties on a single question: is there a limit?

Question: I'm expecting to put a bounty on one of my questions, and I was considering putting setting the bounty at 500 reputation. How would this affect things if I had to put up a second bounty on it? Would it have to be 1000 reputation (since each extra bounty has to be doubled)? Would it just have to be 500 again? Or would I be prevented from putting up the second bounty altogether?
Comment: The limit is [three active bounties](http://stackoverflow.com/help/bounty).
Comment: See here: http://stackoverflow.com/help/bounty ... ", if you offer multiple bounties on the same question, the minimum spend doubles with each subsequent bounty (50 reputation on the first bounty, 100 reputation on the second, 200 on the third, and so on"
Comment: As far as I know, it caps at 500, and allows you to repeat that indefinitely. I've never tried.
Comment: @NathanTuggy It's possible: it has happened. I discovered that when answering [this Meta question](http://meta.stackoverflow.com/questions/299717/how-can-this-answer-have-more-than-500-reputation-point-as-bounty).
Comment: This question has 4 http://stackoverflow.com/questions/11227809/why-is-it-faster-to-process-a-sorted-array-than-an-unsorted-array
Answer: You can set any bounty, but

At most 3 at a time (as pointed out by  Bjørn-Roger Kringsjå in the comments under your question).
Only one active per question.

You can find this in the Help Center entry about bounties.
If the previous bounty was less than 500, you must double the amount, to a maximum of 500.
After a 500-point bounty expires, you can add a 500-point bounty again.
There is this user who received no less than 4 bounties of 500 points on the same question, 3 from the same user. That generous user was the person who asked the original question, so he set these bounties on his own question.


Merging two segments with overlapping nodes in QGIS?

Question: I have two line segments that overlap nodes. I want to select them, and merge them into one complete segment, so that the overlapping nodes are combined to one node.
Answer: If the nodes of the two lines are snapped to each other, then select the two lines and use Merge Selected Features Tool which its icon is shown below

Then a prompt menu will appear to tell you which feature's attribute you are going to use. Please note that after merging the two lines, the vertex will not disappear, the vertex the connect the two lines will still exist because it depends on the angle between two lines. However, if you want to completely remove the vertex  to completely turn it into a straight line, then you simply need to go to select Node Tool - as shown below - and click on the vertex that you want to delete until it turns to blue color, then press delete on your keyboard to delete the vertex completely after merging.
Comment: This is the best solution for a selection of lines.  However, if you want to join the whole dataset at once, use the dissolve tool I listed in my answer.
Answer: There are a few options, here are two:
1 - Entire Dataset:
Using SAGA tools in QGIS, select >vector line tools>line dissolve.
Input the line and the attribute you want to dissolve.
2 - Selection of lines:
Go to the plugin manager.
Install plugin:
Join multiple lines
Permanently join multiple lines
After selecting multiple features of a line layer, this plugin can merge them into one feature with a continuous line.
The plugin will automatically put the selected lines in a geographically logical order and direction. If the end points of two lines do not match exactly, a line segment between both points is added to make the end result a single, continuous line. The attributes of the new line will be those of one of the selected features, but one cannot predict which one.
homepage:  https://github.com/dgoedkoop/joinmultiplelines

Update
After testing the tools I listed above, it is clear that the merge tool is the best solution for this question.  The join lines tool doesn't get rid of the node, and the dissolve tool doesn't merge the lines.
If you want to automate this workflow, and have some python knowledge, you can select nodes that overlap and merge them in a loop.  Then you can merge the whole dataset at once instead of by individual selections.  When I have time I will look at producing some code.
Comment: I've tried the join multiple lines plugin, but it does not seem to work. After it completes, I can still move the nodes from the original segments.
Comment: Use ahmadhanb's solution.  Or try the line dissolve method that I listed.
Comment: I end up with an extra node, but a still non-closed segment, when using the SAGA tool: http://imgur.com/2NjFqiG and the Join multiple lines won't close it either.
Comment: The nodes in your picture are not overlapping.  Am I missing something?
Comment: They were overlapped, I just pulled them apart to show they weren't merged.
Comment: Ok.  Thank you for clarifying that.  It looks like the best solution for removing the extra node is to use the merge tool.  The join lines tool doesn't get rid of the node, and the dissolve tool doesn't merge the lines.


Macedonia- visa on arrival for Indians holding US multiple entry visa

Question: Indian - is it posssible to get a visa for a week with my US multiple visa ?
Comment: Why do you think holding a US visa helps you with a Maceconian visa? Would it work the other way round?
Answer: As stated by Timatic, the database used by airlines:

Visa required, except for Passengers with a visa issued by
  Canada, USA or United Kingdom. The visa must be valid for at
  least 5 days beyond the period of intended stay in Macedonia
  (FYROM). They are visa exempt for a maximum stay of 15 days per visit, and 90 days within 180 days.

So Indians with a valid US visa do not need a visa for Macedonia.
Answer: No, Indians holding Indian Passport do require a VISA to enter Macedonia (FYROM).
If one has a multiple entry Schengen VISA then they can stay up to a maximum of 15 consecutive days in FYROM.
Comment: Indeed, there's been a Change since my answer was posted. Will update


Gateway Timeout Error with Nginx reverse proxy to Apache on the same server

Question: I'm working with Ubuntu 16.04 ang Nginx running Port 80 and 443. I use Proxy_Pass to forward traffic to Apache listening on Port 8080. Both Nginx and Apache are on the same server.
Problem is that Nginx can't seem to forward traffic to Apache. I'm getting 504 Gateway Timeout Error. I can confirm that Apache is running and receiving traffic on Port 8080.
I use proxy_pass extensively in my setup. And the traffic forwarded to Apache on Port 8080 on a different server is working fine. My only issue is this one with the Apache running on the same server as Nginx.
I've tried to set Apache listen 8080 and listen 127.0.0.1:8080 but I get the same error.
In Nginx I used proxy_pass http://localhost:8080; and proxy_pass http://127.0.0.1:8080 but the results are the same.
The only thing I find different is that if I run netstat -tulpn while Apache uses listen 8080, Port 8080 only appears in tcp6 as :::8080. It does not seem to be open in tcp (IPv4). But with listen 127.0.0.1:8080 tcp (IPv4) specifically opens 127.0.0.1:8080 but not anymore in tcp6. If I understand this correctly, it should be open on both IPv4 and IPv6 with Local Address showing as 0.0.0.0:8080 in IPv4 and :::8080  in IPv6.
Note that Firewall is not enabled.
I've trying to go over my config but to no avail. My setup is working if I forward it to a different server. I think this is something port or binding related? But I can't seem to find the answer. Been Googling but could not find a solution.
Hope someone has an idea what I'm doing wrong.
Thank you.
Answer: if you're trying to connect to apache on 127.0.0.1:8080, you need to make sure that apache is listening on specifically IPv4, as you're trying to connect to it using IPv4.
If you want to use IPv6, then specify the IPv6 address on your reverse proxy.


Specify the center of rotation in Unity

Question: I want to rotate my game object around a point in the space instead of the origin, so how can I do it ?
Comment: While you already have answers, I highly recommend fleshing out your question more.  Can you provide links or images of what you are trying to accomplish?  Not only will a better question provide better answers, it's more likely to help others that come to GD.SE with similar issues.
Answer: Your question is very short and I don't know if I'm getting it correctly, but you should check RotateAround and then do something like:
transform.RotateAround(targetTransform.position, Vector3.up, speed * Time.deltaTime);

Comment: I want to change the pivot point of the object so that I can rotate the object around it instead of its center. I tried what you said but it didn't work properly.
Comment: `yourObject.transform.RotateAround(targetPointTransform.position, yourObject.transform.up, speed * Time.DeltaTime` running this in the update will rotate your object (`yourObject`) aournd the target point, using the "up" vector from your object.
Comment: Unluckily, it didn't work. What happens is that my GameObject goes to the specified point and rotates around its center.
Answer: Create a new cube object that has the object you want to rotate as a child (or set your object's parent to this object with this.parent = object) and its point of origin as the point you want to rotate around. Any details on parents can be found on the Unity Scripting page. Essentially do this:
Now rotating the cube will rotate your object around the middle point of your cube. Of course, you don't want this cube to be seen so remember to remove the mesh renderer. When you're done, disconnect the sphere from the cube (this.parent=null) then remove the cube that you added (name it something like RotationCube so that you can easily find it or maybe from a tag).

In this test "turnturn" script has the line and as the invisible cube turns, the sphere turns around its origin:
Update(){
transform.Rotate(Vector3.left * Time.deltaTime*15);
}

Answer: The basic theory is to translate your object to the world origin, perform your rotation as usual, then translate it back to the same position it was before.
Answer: Make your object the child of an empty GameObject that is located at your desired center of rotation. Then, rotate the new object instead of your existing (visible) object.
You can get fancy and do this in script, but this approach maintains the scene graph and keeps everything nice and editor-friendly.

Specify the center of rotation in Unity


What is LINK rel=subresource used for?

Question: What is link rel="subresource" used for?
What difference would that make if I use link rel="subresource" instead of link rel="text/javascript" for including .JS files?
Answer: Chrome is going to remove <link rel=subresource> because it is not useful, proprietary, and buggy.
See https://crbug.com/581840
Removed in Chrome 50 https://www.chromestatus.com/feature/6596598008119296
Use <link rel=preload> instead.
https://developer.mozilla.org/en-US/docs/Web/HTML/Preloading_content
Answer: As of 2016 the subresource value for the rel attribute was deprecated and removed.
It has been superseded by the Preload API instead, meaning one should do rel=preload for a similar effect. To quote the specs

The preload keyword on link elements provides a declarative fetch
  primitive that initiates an early fetch and separates fetching from
  resource execution.
As such, the preload keyword serves as a low-level primitive that enables
  applications to build custom resource loading and execution behaviors
  without hiding resources from the user agent and incurring delayed
  resource fetching penalties.
For example, the application can use the preload keyword to initiate
  early, high-priority, and non-render-blocking fetch of a CSS resource
  that can then be applied by the application at appropriate time.

Below is the  original answer written in 2015, for posterity, that explains the then valid subresource keyword.

The rel=subresource link is what is called Link prefetching, where the browser tries to fetch the resource before it's needed, so it can load that resource faster from cache when it is in fact needed later on.
Link prefetching is a browser mechanism to download or prefetch resources.

Link prefetching is a browser mechanism, which utilizes browser idle
  time to download or prefetch documents that the user might visit in
  the near future. A web page provides a set of prefetching hints to the
  browser, and after the browser is finished loading the page, it begins
  silently prefetching specified documents and stores them in its cache.
  When the user visits one of the prefetched documents, it can be served
  up quickly out of the browser's cache.

The server provides hints to the browser and the browser can consult its cache and take action based on these hints.
The existing link prefetching uses a standard HTTP link header, and defines semantics for the link relation type "prefetch".
link rel=subresource provides a new link relation type with different semantics from link rel=prefetch.
While rel=prefetch provides a low-priority download of resources to be used on subsequent pages, rel=subresource enables early loading of resources within the current page.  Because the resource is intended for use within the current page, it must be loaded at high priority in order to be useful.
Comment: Thank you for your answer. But I still have some doubt about the 2nd part. If I use **link rel="subresource"** rather than the more common **link rel="Styelsheet"** will that help render javascript files faster comparitively?
Comment: so using `subresource` on current page resources actually make them load ASYNC and not be blocking? I find the explanation difficult to understand. Why would I ever need to use `subresource`? what is an example use case? obviously if I want things to be loaded ASAP I'll put them in the HEAD element, but normally you would put Scripts before the `` closing tag, so they will be loaded last, and not block anything, so you don't need any `rel=subresource` for them.. And is it only for actual files? if will put a URL which points to some other page, what would be downloaded?
Comment: Not neccessarely, it would probably be slower in some cases as it would wait for the browser to be idle before loading the stylesheet. As for using the `subresource` value, that would in most cases load the stylesheet just as it would if the value was `stylesheet` if the resource was needed on pageload, so it wouldn't generally be any faster. Prefecthing is most useful when you want to load a resource that is needed on the next visited page, or by something in the same page later on, say by triggering an event etc.
Comment: Can I assume that scripts loaded this way will only be loaded, and not executed until the regular request?

What is LINK rel=subresource used for?


Do you pay tax on belongings you bring with you to the US?

Question: If an employee relocates to the USA for a short period of time and ships their belongings from their home to their new residence in the US, are there any duties that need to be paid ?
Answer: Yes. (Generally speaking.)
Here is a calculator.
On this page, the author writes:

Import duty and taxes are due when importing goods into the United States whether by a private individual or a commercial entity.  The valuation method is FOB (Free on Board), which means that the import duty and taxes payable are calculated exclusively on the value of the imported goods.  However, some duties are based part in value and part in quantity.  In addition to duty, imports may be subject to a Merchandise Processing Fee, and in some cases to sales tax, and Federal Excise Tax.

Possible Exemptions
Here is the official page of U.S. Customs. They write:

Household Effects & Personal Effects - Customs Duty Guidance
Household effects conditionally included are duty-free. These include such items as furniture, carpets, paintings, tableware, stereos, linens, and similar household furnishings; tools of the trade, professional books, implements, and instruments.
You may import household effects you acquired abroad duty-free if:

You used them abroad for no less than one year.
They are not intended for any other person or for sale.

For Customs purposes, clothing, jewelry, photography equipment, portable radios, and vehicles are considered personal effects and cannot be brought in duty-free as household effects. However, duty is usually waived on personal effects more than one year of age. All vehicles are dutiable.
Comment: Does it still apply if the goods are ***not*** newly purchased, but are existing belongings?
Comment: @AfterWorkGuinness: Maybe or maybe not. See update to answer.
Comment: If the employee works for an international organization, the goods may be entirely exempted from customs, as they also generally will be for the staff of foreign missions.


Might the LHC see nothing new at all?

Question: There's no guarantee that supersymmetry (or more exotic new physics) will be seen at the LHC. Meanwhile, it's standard lore that a Higgsless standard model becomes nonunitary somewhere in the vicinity of 1 TeV. Are we at least guaranteed to get some positive information about new physics, in the form of deviations from the predictions of this "higgsless standard model"?
Comment: Possibly related: http://physics.stackexchange.com/q/129/2451
Answer: It is possible that the LHC could find just a standard model scalar Higgs. It would have to fit in the windows between 135 GeV and 157 GeV or 173 GeV to 185 GeV. In this case no new physics is needed and other effects such as large CP violations and dark matter go unexplained.
If it is below 135 GeV the standard model would predict an instability of the vacuum so something else such as SUSY would have to be there to correct. This would already be indirect evidence for beyond standard model physics, but it is just about possible that the new physics would not be seen yet.
A Higgs mass above 185 GeV is inconsistent with other measurements, but only when assuming the standard model applies, so again a heavy Higgs would be indirect evidence of new physics. There is no certainty that the new physics would be seen.
If the Higgs was excluded over all its mass range that would also be an indication of beyond standard model physics. It would mean one of two things, either the Higgs really does not exists and something else would have to be breaking electro-weak symmetry, or the Higgs exists but some new physics hides it from us, e.g. it may have a dominant decay mode into new particles that form jets that are hard to see against the background. Such scenarios are possible but it would be as if Nature was being devious to make life awkward for us.
Something needs to explain dark matter but that could easily be a particle with mass 10 TeV, or a lighter particle that does not interact strongly enough with standrd model particles to be seen at the LHC.
So in short, yes it is quite possible that nothing, or just the standard Higgs may be seen.
Answer: The LHC opens a new frontier in energy exploration. The results will be "new" by definition, as with all explorations. Now whether there will be dragons, tigers or just moose is something we have to wait for.
If we enter a desert as far as specific new resonances/particles go, which are predicted by various models, that will also be new physics information. Supersymmetry will disappear on the horizon, the Higgs will be rescued by composite Higg models until the next machine and higher energy levels are explored. This rescue will come, because the Standard Model has been very successful in encapsulating all known high energy data.
In my opinion we will find new physics, maybe unexpected, but new. Already the asymmetry in the jets of top production at the Tevatron is an indication that something new is going on at high energies. The researchers have to keep an open mind, not run after two and three sigma deviations, be very careful in systematic error estimates, and "something is coming , don't know what, ought to be grand" as the song from the west side story says.
Comment: Let's forget hopes and expectations for now. The LHC achieves new levels of energy, yes. But is it *guaranteed* to explore the territories where the inconsistency of "standard model minus its higgs" must show up? I'm not aware of any planned LHC experiments along the lines of "Scattering of longitudinal W bosons at 1 TeV center-of-mass energy".
Comment: See the comment by Philip Gibbs for analytic discussion. There are no guarantees in research, and only real experiments can be carried out. If a Higgs candidate is not found, this is also new physics and will exclude a number of models, that is all.  No guarantees and progress is incremental, there are no magic wands.

Might the LHC see nothing new at all?


Split a file with macro in excel

Question: I know there are 2 similar questions.
I have a very large Excel file separated in sections by 3 blanks lines.
I was wondering if there was a way to split the spreadsheet into other every time there is a blank in column A or every time the word "Section" appears in column A.
Comment: Split into separate worksheets or new Excel files?
Comment: a new excel file would be easier
Answer: I recommend reading the posting Split Worksheet, Seperated By Blank Rows, Into Several Worksheets  and tailoring it to fit your needs.
This post should also be helpful https://stackoverflow.com/questions/11556533/split-excel-sheets-to-multiple-workbooks.

Split a file with macro in excel


Django-cms multisite layout explained

Question: How does one serves two sites using one django (django-cms) instance? When I install site app and add two site instances using django admin, I get to choose for which one I want to add a page. So here's what I don't get it: how does django should know which site to use? Maybe I'm missing some elements in my django multisite deployment scheme, could somebody put me on track?
Answer: Basically, it doesn't know which site to use on its own. You associate each model with a site (or sites), and then check for content with a given site within your views. If you haven't already, check the examples in the sites doc (linked version is 1.5).
It's not really set up for full multitenancy out of the box, in case you're just looking to run a handful of unrelated sites off of one Django install. My own experience in that case was that it was easier to set up separate Django apps and databases for each site, and then use Apache virtual hosts to direct traffic.

Django-cms multisite layout explained


How to create a database read replica on AWS Lightsail

Question: I have an existing MySQL database running on AWS Lightsail, I want to create a read replica for that one, how can I do it?
Answer: To my understanding this is not an option for the Lightsail managed databases.  You can however create an RDS instance of MySQL and create a read replica there.  To connect to this RDS instance you'll need to use VPC Peering.

Lightsail lets you connect to AWS resources, such as an Amazon RDS database, through virtual private cloud (VPC) peering. A VPC is a virtual network dedicated to your AWS account. Everything you create inside Lightsail is inside a VPC, and you can connect your Lightsail VPC to an Amazon VPC.

To create a MySQL Read Replica:

Using the AWS Management Console, you can easily add read replicas to existing DB Instances. Use the "Create Read Replica" option corresponding to your DB Instance in the AWS Management Console.

Connecting to it can be accomplished via the following method:

In the Lightsail console, choose Account on the top navigation menu.
Choose Account from the drop-down..
Choose the Advanced tab.
Choose Enable VPC peering under the AWS Region where you want to enable it.

References
Using Lightsail with other AWS Services
Lightsail - How to set up VPC Peering with other AWS Resources
Read Replicas
Comment: Wonderful. I will try this and let you know how it went


2005 Honda Accord wont start with a new battery

Question: I bought my 2005 Honda Accord in 2019. I have driven it a handful of times, other than that it has been sitting in my driveway. I bought a new battery for it today and put it on the car. When I turn the key the lights and all the electricity comes on. The radio, headlights, dome lights, all that works. But when I try to start the car it will click one or two times, but won't turn over. Could it be the spark plug or ?
Comment: When you try to start the car and it clicks, do the lights dim? If so, how much?
Answer: Possibilities -

Corrosion at the battery terminals causing a bad connection
Bad connection from the battery to the chassis of the vehicle
Bad connection from the battery to the starter solenoid
Seized starter solenoid
Corroded contacts within the starter solenoid
Faulty starter motor
Seized engine
Bad engine earth strap connection

I would start with the easy tasks of checking for corrosion on the battery terminal connectors and the thick wires that are connected these connectors.
Try turning the engine over a little using a wrench on the crankshaft pulley to check that the engine hasn't seized due to being left for so long.
To answer your suggestion of the spark plus - Unless one of your spark plugs has snapped and dropped inside the cylinder (extremely unlikely), which would stop the piston moving, the spark plugs wont be causing the issue.
Comment: I'd like to add a possibility: the new battery is faulty or almost discharged. Normally, you'd expect a new battery to come at least half charged, but you never know.
Comment: @marcelm That is a possibility.  Why not add an answer of your own, I will upvote it.
Comment: @marcelm I second the possibility that the battery might be faulty / not charged! It does happen.
Answer: Do you have a remote car starter or any wires dangling?
Probably an uncommon one, but just in case: I started having occasional dead battery a few months back. Sometimes the car would start and then die, or not start at all. I had done the normal of checks: load testing the battery, load testing the alternator, cleaning the battery and wire contacts. Ultimately, I replaced the battery, but started having trouble again a week later. Finally, I took it to the dealership. I got a call that they didn't find anything. Later when I went to pick the car up they told me they went to move the car it died again. They found a loose wire under the dash. They removed the wire. Car is fine now.

Backstory
I had a remote car starter that no longer worked. Part of my remote starter includes a module stuck under the dash. The module had come unstuck and was hanging by the wires, probably why it didn't work . I ended up removing the module, and had completely forgotten about it and hadn't gotten around to getting it repaired.
It turns out I didn't notice that one wire was still there dangling ♂. Apparently, the wire was sometimes shorting out the remote car starter circuit/ignition and was the cause of all this.
I've learned my lesson. Perhaps my mistake will help someone else.
Answer: You say you just changed the battery. So, a few things to check:

Are the cable connections to the battery fully tightened down and gripping the battery terminal tightly? Loose connections may carry sufficient current to drive lights, but won't carry enough power to turn the starter motor. You should also spray both the positive and negative terminal connections with battery terminal spray (basically clear spray lacquer with a little color (usually red or green) added so you can see where you've sprayed it, but can still see the terminal and cable ends). This helps prevent terminal and cable corrosion..
Are the cells in the battery full of acid to the top? If not, add DISTILLED WATER to bring them up to the top of the cell. Pour the water into a measuring cup then slowly add water to each cell, pouring the water through a funnel to ensure the water goes into the cell. If you have to do this you'll want to charge the battery afterwards.
A battery that's been sitting may need to be charged - it may be putting out rated voltage, but without sufficient power to drive the starter motor and spin the engine. I suggest investing in a good battery charger.


Execution speed of AES_128 GMAC operation

Question: I have read about the speed performance of AES_128_GCM on specific processors Intel and AMD that support AES New Instruction set. As compared with CMAC and HMAC is it relatively slow for other processors such as ARM9 board or cryptographic hardware?
Comment: I don't have hard data at hand. But I think GMAC is faster than at least HMAC and likely faster than CMAC, which both rely on primitives, whereas GMAC "only" needs one 128-bit field multiplication (IIRC).
Comment: Thank you for your reply.
@SEJPM In preliminary tests I made on GMAC, i have observed low execution speed in cryptographic hardware. That is why I was curious to know other's experience.
Answer: GCM is sometimes called a 1.5 pass AEAD cipher, where the CTR encryption counts for 1 and the GMAC counts for 0.5. So you would indeed expect it to be faster than encryption + CMAC and HMAC with regards to the amount of CPU instructions.
That is: as long as the encryption is using AES for both solutions. GCM requires a 128 bit block cipher while CMAC and HMAC could also work with a fast stream cipher.
If the hardware however doesn't support 32 bit multiplications the speed may drop significantly, so it's not that great on embedded processors with a 8 or 16 bit ALU. ARM however is 32 (for ARM9) or 64 bit so it should be relatively fast on one.
Note that there may be rather big differences with regards to implementation. It's definitely recommended not to take anything for granted and test which authenticated cipher is fastest in practice.
Comment: Thank you for your explanation @Maarten Bodewes.
In (https://en.wikipedia.org/wiki/AES_instruction_set)  " In AES-NI Performance Analyzed, Patrick Schmid and Achim Roos found, '... impressive results from a handful of applications already optimized to take advantage of Intel's AES-NI capability' ". As an example it mentioned almost 7 times performance gain.
My experiment on cryptographic-hardware (MX51 MCU) resulted with very poor performance. And I wanted to know other's experience with GMAC vs other MAC algorithms.


Why does two masses with energy attract each other?

Question: I have heard that every mass attract another mass with a force directly proportional to the multiplication of their masses and inversely proportional to the square of distance between them, but newton doesn't told that why two masses attract each other. Also I am familiar about the curvature concept considered by Albert Einstein according to which gravity is not a force but a curvature caused by imbalance in spacetime by mass/energy. Bit if there is a curvature how can you prove it?
Comment: Possible duplicates: http://physics.stackexchange.com/q/102910/2451 , http://physics.stackexchange.com/q/3009/2451 and links therein.
Answer: Physics does not answer "why" questions at the level of basic laws and postulates, i.e. "why" this postulate. Newtons gravitational law :

Newton's law of universal gravitation states that a particle attracts every other particle in the universe using a force that is directly proportional to the product of their masses but also inversely proportional to the square of the distance between them. This is a general physical law derived from empirical observations by what Isaac Newton called induction.

Laws are like axioms in mathematics and are needed so that mathematical proposals fit the data, in this case the mathematical model is the 1/r^2 behavior , and Newton's law is the statement that connects one to one mathematics to data.
So the answer is, because that law is the most economical ( occam's razor) way of describing mathematically the data, and having a theory that can predict new set ups.
In general questions that hit on the postulates of physical theories have the answer: because this is what fits observations and allows to set up a theory that is predictive.