Estimating the Distribution of a Very Large Population of Known Size and Unknown Variance

Question: I would like to estimate the distribution of a very large population of known size but unknown mean and variance. I cannot assume anything about the underlying distribution. The values of observations are always discrete. I cannot sample the entire population but I would like to estimate the probability density function. I would also like some level of assurance of the correctness of the estimated distribution. What is the best way to go about this?
Comment: What do you mean by the statement "The values of observations are always discrete"?
Comment: @Ashok: In this case, I am certain that they are non-negative, non-zero integers. In general what I meant was that I believe that the distribution is lumped in some way rather than being continuously distributed over the entire range.
Answer: I can't comment so this will have to be in the form of an answer - my apologies for this.
First, I assume that what you want to do is to estimate the distribution of some property of the population, no? One way to go about it would be to construct the empirical distribution function: $\mathbb{F}(x) = \frac{1}{n}\sum _{i=1} ^{n} I(X_i \leq x) $ ($n$ the number of observations). Once you have done this, you can use various test to compare this to any distribution function that you'd like (i.e., one that you suspect produced the data).
If you are after a direct estimation of the density fucntion, and not any "known" distribution that it looks similar to, you can use a kernel density estimation: http://en.wikipedia.org/wiki/Kernel_density_estimation
There are tools in e.g. Matlab that will make this task fairly straightforward.
I would say that what method to use, and there are surely others, depends on that you want to do with the end result. I've only done this sort of thing in easy settings and there are probably more sophisticated ways to solve your problem. However, the above could perhaps set you off to a good start
Comment: Now that I read it again - is the problem to investigate the distribution of the population over a set of distinct "places" (such as nodes in a lattice or similar)?
Comment: @Pierre Nyquist: It's not that I want to see the distribution over a set of distinct "places." You are right that I want to directly estimate the density function. I was actually wondering if Kernel density estimation might be a possibility but how do I know how large my sample size should be? If I use that approach, what can I say about the correctness of my estimation?


How to create a quantum circuit checking whether two functions $f$ or $g$ are of the same type?

Question: I want to create a quantum circuit that checks whether two functions f and g are of the same type, i.e., constant or balanced, or not. In other words, the output of the circuit should output 1 if both f and g are constants, and 0 otherwise.
I know how to implement a balanced circuit and a constant one but how do I address the situation above?
Comment: I am a beginner and I have been reading about Deutsch and I want to know whether I can link two functions, so from my reading Deutsch oracle lets us know if the function is Constant or Balanced, and from searching online there are circuits for when you want to implement a constant or balanced functions, but how to implement a circuit that lets me know whether two functions are constant or balanced?
Answer: Assuming that you have two oracles that implements respectively $f$ and $g$, it is quite simple to perform the algorithm you're looking for, using only a single call to both $\mathcal{O}_f$ and $\mathcal{O}_g$.
With a single call to $\mathcal{O}_f$, you can get a single bit telling you whether $f$ is balanced or constant. In parallel, you can run the same circuit using $\mathcal{O}_g$. You would thus get another bit telling you whether $g$ is balanced or constant. You finally have to compare these two bits to decide whether they were of the same type. All in all, the complexity is almost the same as the original Deutsch algorithm, since you only run it in parallel and add a single operation after it.
The associated circuit is the following one:

It is to be noted that the classical control check whether the measured states are $\left|0^n\right\rangle$. Thus, when we measure the fourth register, its state is:

$|0\rangle$ if the two previous measurements yielded the same result;
$|1\rangle$ otherwise.

This of course assume that both $f$ and $g$ are either balanced or constant, and that you can use as many qubits as you want. Don't hesitate to tell me whether you would like too know about a solution using the same number of qubits as in Deutsch's algorithm!
Comment: What if I have two constant Deutsch circuits in parallel, how would I link them together to give me 1 if both are constant?
Comment: @n22 I've added the circuit to my answer, please have a look.


Referrer/URL Helper ee3?

Question: Really need the ability to grab the refering url that URL helper offered. Is this available for EE3 or is there an alternative?
Answer: I'm kind of late to the party, but I noticed Brian has an updated version of URL Helper in his github that looks ready for EE3, https://github.com/litzinger/URL-Helper/tree/master/third_party/url_helper

Referrer/URL Helper ee3?


How to determine wether Ether was mined or received?

Question: Is there a way to distinguish or calculate the total amount of ether which any account has received from mining and from the transfers (I mean the amount of ether transferred from other accounts)?
Comment: Are you referring to a technical solution to determine wether it was mined or recieved?
Comment: I mean how to determine it through the api. Suppose a node has 100 ethers - out of which 20 was sent to the node from other nodes, rest 80 were mined by the node itself. How to get these numbers?
Comment: @RichardHorrocks So how do I trace back as we don't have any list transactions for an account api?
Comment: Note that there is no such thing as "a node has 100 ethers".
Ether is at an address on the blockchain. The same address can be used by several nodes, and the same node can use several addresses.
Answer: In principal all necessary data are on the blockchain. However - to practically get them you will need the help of a blockchain explorer.
Etherchain for example shows the mined blocks for each account. So this is an easy way to figure out how much of the Ether on this account was mined.
Comment: My question is can we use etherchain for a private setup as well? If not, what can be used to get the same results?
Answer: As <code>@mKoeppelmann</code> suggests, etherchain will have the data. Here is a link to their API documentation - etherchain.org - API Documentation.
You can also use EtherScan.io's APIs.
For this, you will have to register and get a APIKeyToken, but the APIs of interest for you are:

Get Ether Balance for a single Account

https://api.etherscan.io/api?module=account&action=balance&address=0xddbd2b932c763ba5b1b7ae3b362eac3e8d40121a&tag=latest&apikey=YourApiKeyToken

Get a list of Account Transactions

https://api.etherscan.io/api?module=account&action=txlist&address=0xddbd2b932c763ba5b1b7ae3b362eac3e8d40121a&sort=asc&apikey=YourApiKeyToken

Get list of Blocks Mined by a Specific Account - MINED Blocks

https://api.etherscan.io/api?module=account&action=getminedblocks&address=0x9dd134d14d1e65f84b706d6f205cd5b1cd03a46b&blocktype=blocks&apikey=YourApiKeyToken

Get list of Blocks Mined by a Specific Account - UNCLE Blocks

https://api.etherscan.io/api?module=account&action=getminedblocks&address=0x9dd134d14d1e65f84b706d6f205cd5b1cd03a46b&blocktype=uncles&apikey=YourApiKeyToken
Comment: How can we use this for a private ethereum setup?
Comment: See [Script To Find Mined Blocks And Uncles + List Transactions](http://ethereum.stackexchange.com/questions/2531/common-useful-javascript-snippets-for-geth/2936#2936).
Comment: The script is a way of pulling information from the blockchain, is there something available like an event which can trigger my daemon process which can then pull this information from the chain?
Answer: Technically speaking tokens can be "minted" not mined. Mining is the process to create anew block in the chain with a reward in ether which are "mined" with the block. But tokens are just created as data in a smart contract not really mined.
At least for token based on MintableToken.sol by Open Zeppelin you can easily see that a fresh minted token comes from a 0x000.. address. Here an example of some token minted and sent to users:
https://etherscan.io/token/0xd3822b2aef3b7781aab63a24c2318be2fb0259b8


Nondeterministic finite state machine without any initial state possible

Question: Is it theoretically possible to have a nondeterministic finite state machine without any initial state or does it need at least one initial state?
Comment: In the standard definition, it's allowed. However, it is pretty pointless (algorithmically), since you can easily verify it. This is in contrast, for example, to an NFA whose language is empty since there are no reachable accepting states.
Answer: In my favourite definition a finite state automaton is specified as 5-tuple $(Q,\Sigma,\delta,q_0,F)$, where $Q$ is the finite set of states, $\Sigma$ is a (finite, nonempty) alphabet, $q_0\in Q$ the initial state, $F\subseteq Q$ the set of final states, and $\delta\subseteq Q\times\Sigma\times Q$ the set of transitions. In that definition we would have exactly one initial state.
It is however very well possible that, for reasons of symmetry, one specifies a set $I\subseteq Q$ of initial states. There you can have one, several, of no initial state.
Short answer: consult the book, lecture notes, or scientific paper you are using. They set the rules for the game. Not us, not wikipedia.
Comment: +1. There are useful, reasonable definitions of nondeterministic finite automata that may require one state, or allow a non-empty set of states, or even let you specify no initial state. It's a definition that has little to do with the model of computation NFAs embody.


Interpretation of radiation resistance in receiving mode

Question: Assume we have an antenna in receiving mode, connected to a matched load. The equivalent circuit is a voltage source in series with the antenna feedpoint impedance and the load impedance.
As we know, the feedpoint impedance is made up of a reactive component, an ohmic resistance and a radiation resistance. Now, since the load is matched, half of the intercepted power will be delivered to the load, while the other half will be delivered to the ohmic and radiation resistances respectively. The power delivered to the ohmic resistance will be converted into heat, but how to interpret the power delivered to the radiation resistance? Is this part of the total power reflected by the antenna?
Comment: Where does the reactive component come from?
Comment: @Andyaka I'm not an antenna expert, but it is my understanding that all antennas produce a field comprised of a radiative part and a reactive part, where only the former is present in the far zone. The direction of the Poynting vector (power density) for the radiative part is constant in time, while it for the reactive part is oscillating back and forth. Across the feedpoint, this translates into a resistance and reactance respectively.
Comment: No, an antenna, if matched to its optimal frequency will look resistive. Sure, if it's not tuned exactly then it will present a complex impedance. This is why I asked because it seemed you were taking an obscure line with the question. For instance a half wave dipole is 70 ohms + 42 ohms but if the length is reduced to 0.48 it becomes 70 ohms resistive.
Comment: The fields up close are complex and non-coherent regards a proper EM wave but, if the antenna is tuned it will produce a radiating power that makes its input impedance (and o/p impedance when receiving) purely resistive.
Comment: You are right, wrong on my part to say anything general about shape of near field. I wonder, however, whether a perfectly tuned antenna will store and retrieve energy from it's near field or only a nontuned antenna will do this?
Answer: No, in general, there is no such effect as reradiation. This heavily depends on the antenna type. The radiation resistance is a model for the radiation. Due to reciprocity, one should still match to this resistance in the receive case, but the simple model as you describe it (a voltage source in series with the antenna feedpoint impedance) is not valid in the receive case.
Generally, all power accepted by the antenna (described, e.g., by the effective aperture size) is received. Any other amount can be scattered by the antenna, but this is related to geometrical features of the antenna and, in the matched case, by no means always 50% of the power, but a rather arbitrary value.
Comment: This is not correct, there will always be reradiation. The effective area $A_e$ multiplied by the power density yields the available power available at the antenna terminals. This power can be delivered to a load by a complex conjugate match. However, an equal amount of the power is delivered to the combination of antenna loss resistance (dissipation) and antenna radiation resistance (reradiation). Check the first chapter of Balanis' book Antenna Theory and Design, 4th edition.
Comment: @TroelsFolke I will check the Balanis book. However, the radiation resistance is not causing any reradiation since it is a model for transmit operation. Reradiation is a (unfortunately very common) misconception. It is very easy to construct synthetic / ideal antennas which do not have any reradiation.
Comment: Of course, for some kinds of antennas (e.g. dipoles), reradiation exits.
Comment: @TroelsFolke I did check the Balanis book now. I do not agree with his point of view. For me, it seems impossible that reradiation is a fixed amount of 50%. Think of a reflector antenna, if the incident wave comes from behind, 100% is scattered/reradiated by the antenna structure and nothing is received.
Comment: And a simple example with a very small amount of reradiation would be an open-ended waveguide with (infinitely thin) PEC top walls and PMC side walls. If an incident plane wave comes aligned with the aperture, the oewg "swallows" the incident field. There might happen some scattering at the back of the oewg, but this can be suppressed by absorbers or a suitable geometry. The real question is now (which just comes into my mind), what does Balanis mean by reradiation? I am not so sure right now...
Comment: Maybe he means the changes in the surrounding fields of the antenna, i.e., the "swallowing" of the incident fields/power. This should be indeed proportional to the received power; but I would not call this reradiation.
Answer: The equivalent circuit model for the receiving antenna, as referred to above, sounds correct (see for instance Collin & Zucker). However, what is not correct is to estimate the power dissipated (or re-radiated) by the impedance of that circuit. Indeed, that circuit corresponds to an equivalent Thevenin model; and the equivalence only holds with respect to what is connected to that circuit; for instance a receiver, whose first stage usually is a low-noise amplifier. That equivalent circuit does not hold from the perspective of what happens IN the circuit. Having said that, some antennas scatter, other don't. Generally speaking, the equivalent circuit of the receiving antenna does not inform about the amount of scattered power.
Comment: Makes sense, thank you!
Answer: Yes, it is effectively radiated back by the antenna. If the antenna is receiving from a point source, but its radiation pattern is not pointing only at the source (e.g. is isotropic), this radiation will go in 'all' directions. Thus the antenna will redirect (reflect) the incoming signal back in a broader beam.


Does the Hulk's skin repel bullets?

Question: I'm watching the Iron Man: Armored Adventures cartoon and the Hulk is just standing there taking bullets.  It seems like in every version I see, he can withstand a massive amount of damage.  Is his skin thick enough to repel bullets?
Answer: The Hulk is only as bullet-proof as the writers decide they want him to be. The general answer is, he is either completely bullet-proof or he regenerates so fast, no injury matters.
It depends entirely on which version of the Hulk you are viewing and how each writer/editor team wants to portray the character with the range varying widely. While the Marvel Wiki lists all of the weapons the Hulk is immune to this list varies widely depending on the needs of the comic industry.

The early Grey Hulk, for example, was not completely bullet-proof but only very large firearms could pierce his skin and even if they did, his incredible regenerative powers meant he stayed injured only for minutes.
The Grey Hulk did not like to be shot at but was able to withstand any man-portable weapon without lasting harm. He tended to avoid tanks but was occasionally hit by a round with no lasting effects. If he was cut, he bled green and immediately regenerated.

When the Hulk first became green and was called the Savage Hulk, he was far more resistant to human weaponry and only scientifically advanced technologies could cause any lasting injuries.
The army began to hire specialists to create technologies that could harm the Hulk and the Leader was always developing new ways to harm him. SHIELD and Iron Man were also instrumental in helping to create new technologies to subdue/restrain the Hulk. See: Hulkbusters
His powers began to fluctuate during the periods when he led the Pantheon and had the intelligence of Bruce Banner. He lost his complete invulnerability but his regeneration was so potent he could recover from almost any level of injury in seconds. Even attacks from Wolverine, while they could cut him, healed almost instantly.

An attack by the U-man Vector strips 50% of the flesh from the Hulk's body.
By the time the psychic monster Onslaught was created, the Hulk's power level had risen to a level so great, he was basically invulnerable to all forms of conventional harm up to and including nuclear weaponry. He was called Worldbreaker Hulk and emitted powerful waves that were theorized to be able to actually destroy the World.
In many of his future incarnations, he ages, but very slowly and is almost completely unable to be harmed by any means. See: Maestro

What this usually means is when the Hulk becomes so invulnerable that he cannot be harmed or challenged effectively by writers, he is usually changed in some fashion to make him more vulnerable so that writers can create stories with conflict that matters. They will often:

Remove the power of the Hulk from Banner's control, making him more vulnerable as Banner, even if the Hulk is unable to be harmed. The Hulk's earliest adventures were like this, the Hulk changed involuntarily when night fell, or when he was angered/injured.
Change his environment so his invulnerability is reduced or negated. When he was removed from Earth, his invulnerability was significantly reduced. See: Planet Hulk
Alter his psychology making it harder for him to make good decisions or alter his state of mind so decisions he makes are the right ones but for the wrong reasons. Banner's recent state being complete separated from the Hulk and a sociopath is an example of this state. (Incredible Hulk, vol. 4)
Comment: You are quite welcome. Glad to be of service.
Comment: Thanks. I didn't know about the regeneration part of it.
Answer: from the Marvel wiki

Superhuman Durability: In addition to great strength, the Hulk's body possesses a high degree of resistance to injury. The Hulk's skin is impervious to conventional blades, adamantium and vibranium being amongst the very few metals that are truly capable of piercing his skin. The Hulk is capable of withstanding high caliber bullets, powerful explosives, pressures extremes, falls from orbital heights [202][197], maximized heat without blistering, maximized cold without freezing, and great impacts

I'd assume that this means that conventional bullets won't penetrate the skin. However, Adamantium or Vibranium bullets could probably do it.
Answer: In the Marvel Cinematic Universe, the answer is also yes.  In The Avengers, we see him shrugging off a barrage of heavy machine gun fire;  it doesn't seem to do anything but annoy him (the shooting starts at about 2:45 into the video).
Comment: Yeah, embedding videos is deceptively simple.  Took me over a year to figure it out.  :P
Comment: Thanks for the edit, phantom42.  I couldn't figure out how to embed the video.
Answer:
Thaddeus wrote :
Change his environment so his invulnerability is reduced or negated.
When he was removed from Earth, his invulnerability was significantly
reduced. See: Planet Hulk

I believe the obedience disc he was forced to wear is the reason his powers were limited, that is why he was known as the Green Scar, as his regeneration powers stopped working. Once the disc was removed they kicked in.

By the time the psychic monster Onslaught was
created, the Hulk's power level had risen to a level so great, he was
basically invulnerable to all forms of conventional harm up to and
including nuclear weaponry. He was called Worldbreaker Hulk and
emitted powerful waves that were theorized to be able to actually
destroy the World.

You've mixed up the timelines. Onslaught was about a decade before World War Hulk. I believe Hulk has always been resistant to nukes. The Worldbreaker is a persona of the Hulk that manifests himself during periods of extreme anger, when he was told of Meek's betrayal or believed Betty and Rick had been killed. In the Worldbreaker state he emits high levels of gamma energy.
Chetter Hummin see :

Does the Hulk's skin repel bullets?


One way street blocked; what are the legal remedies

Question: Turning into a one way street, one notices part way thru street that large construction vehicles have blocked the road. Is it legal to turn around and go the wrong way on a one way street to avoid traffic blockage? What other legal remedies remain for homeowners on street and other traffic caught in such a situation? Is this situation similar to say a downed tree?
Comment: How long are you willing to wait there?
Answer: The proper process for the contractors is to block off the street with a "Road Closed - No Through Traffic" sign before the obstruction is in place, which implicitly allows people with no way out of the temporarily blocked one way street to get in and out.
In practice, someone prudently getting their car out of the blocked street, as in your example of a downed tree, by having hazard lights on and moving slowing and with great attention to traffic in the direction that the street is going, would not be ticketed. These things are a reality of urban living and police don't punish people for this quite ordinary behavior under the circumstances by citing them for it unless the stop is really a pretext to really stop someone for a reason that they don't have a legal basis to do so for.
If there was an accident while someone was going contrary to the one way direction to get out causing personal injury or property damage, then making a "negligence per se" argument (i.e. that someone is liable in negligence as a matter of law because they violated a law intended to precent the accident in question) stick in a traffic case based upon a technical violation of the one way street regulation in this context, would also probably not hold water, when a jury assessed the negligence of everyone involved in the accident,
The person backing out may have a technical traffic sign obedience violation, the car hitting that car would have a "failure to keep a proper lookout" and "failure to keep a safe following distance" violation, and the construction crew would probably also have liability for failure to follow proper procedure to close the street that they were blocking. A jury would have to decide who, if anyone, to hold responsible for the injuries in an accident caused in this situation.
Comment: I wouldn't put much faith in most police and their zealousness in issuing tickets. Courts hopefully would play out as expected in above answer.
Comment: @paulj I'm not saying that the police would ticket the obstructing construction operators, only that they wouldn't necessarily be aggressive in ticketing people coping with the situation.


What's up with $\mathrm{U}(1)$ regarding the spin homomorphism?

Question: Let $\mathcal H(2)$ be the space of hermitian matrices of size $2\times 2$, and let $\sigma:\mathbb R^{4}\rightarrow\mathcal H(2)$, $$ \sigma(x)=x^\mu\sigma_\mu=\left(\begin{matrix} x^0+x^3 & x^1-ix^2 \\ x^1+ix^2 & x^0-x^3\end{matrix}\right) $$ be the isomorphism between Minkowski spacetime and $\mathcal H(2)$. We have $\det\sigma(x)=\eta_{\mu\nu}x^\mu x^\nu$ (if the $(+---)$ signature is used).
If $A\in\mathrm{GL}(2,\mathbb C)$, then $A\sigma(x)A^\dagger$ is also hermitian, so this realizes a linear transformation on $\mathcal H(2)$ and thus on $\mathbb R^4$. if we take determinants, then $$ \det(A\sigma(x)A^\dagger)=\left|\det A\right|^2\det\sigma(x), $$ so $A$ preserves the Minkowski norm if $\det A\in\mathrm U(1)$. Therefore, $A$ represents a Lorentz tranformation if its determinant is a unit-length complex number.
However the usual spin homomorphism is between $\mathrm{SL}(2,\mathbb C)$ and $\mathrm O(3,1)$, and the matrices in $\mathrm {SL}(2,\mathbb C)$ have $\det A=1$, rather than $\det A=e^{i\varphi}$.
Why are those matrices with unit-length, but not $1$ determinant excluded, when they also determine Lorentz transformations?
Answer: An element of ${\rm GL}(2,{\mathbb C})$  of the form  $A= e^{i\phi}{\mathbb I}$ has no effect on $x^\mu \sigma_\mu$ beause such matrices commute with all the Pauli's, so such group elements can be quotiented out  and the effective group is  ${\rm SL}(2, {\mathbb C})$.


I want to hide Edit(Salesforce Classic) action from Report

Question: I want to hide the Edit(Salesforce Classic) action from the report record, I checked in Profile and permission set, I not getting any permission related to hiding these button, This is a standard button. Any advice, please.
Comment: You want to hide it for everyone?
Comment: @CarlosNaranjo  Yeah I want to hide for every user because there is no sense to go back in classic because the user is in lighting version, Please suggest any help.
Comment: yeah Edit should be there but I want to restrict Edit(Salesforce Classic) Action
Answer: The easiest way to accomplish this is to set a VF page on that button that will override that action. On the VF inform the user that this action is not available anymore.
Got to, Report object, Buttons, Links and Actions,
edit Edit(Salesforce Classic)

Set Salesforce Classic Override to VF page and select the VF page that needs to but built to inform users of this functionality not being available any longer...  that should do it.
The Report object don't allow you to modify the standard page layout for this object, so it is not as other objects in which you can just remove the button, as far as I know.
Answer: You can remove the button in the Report and Dashboard User Interface Settings in Setup.  Just check the option for "Hide the embedded Salesforce Classic report builder in Lightning Experience".  This removes the button for everyone.


Is there any time limit in the List view of the iPhone Calendar app?

Question: Is there any time limit in the List view of the iPhone Calendar app, beyond which we cannot make any entries? Can this limit be changed to something else than the 2 years set by by Apple?
Answer: There is no limit in the Calendar itself – you can 'zoom out' by repeatedly tapping the Back button until you're in a screen where each year takes up about a single page. Scroll down to e.g. 2027, and you can create an event in the distant future without problems:

The List view does seem to have a built-in limit of two years, which can't be extended by settings.
Comment: Thanks for response,,but latest two years entries only showing in agenda list and not beyond that...Is there a way to see more than 2 years entries in agenda list..Like 2027 entry you created..
Comment: Ah, you mean the List view. There seems to be no option to extend that period beyond two years.
Comment: Yes List view and there is no way to view beyond 2 years.....No idea why this limitation they have put on list view....
Comment: In Google and blackberry phone there seems to be no such  limit..Why is it so with apple phone..Really frustrating it is...
Answer: To add to the same "List view not displaying beyond 2 years". Calendar allowed me to enter an event beyond 2 years, but it will not find it if I search. The search takes me to the last week of 2 years.
I've switched to ToDo Pro for "far out" tasks.
Tony


Partition a backup drive

Question: I have a few 2-terabyte external drives i'm looking to introduce into our backup plan.  I was wondering if i would gain anything out of partitioning the drives into 2-1-terabyte partitions and mirroring the two partitions on one drive?  Does the drive become physically more reliable if it is partitioned into smaller parts?  I'm assuming that if two identical hdd are dropped or exposed to harmful conditions that both drives will become equally corrupt regardless of the partitions.
Comment: Micheal, could you please elaborate a bit more?
Answer: Note that the partition only exists logically. Physically, you're still using one drive, which is as prone to errors as every other drive would be.
Benefits:

You will be safe against accidental deletion of files on one partition in case the other one is not touched. Consider for example having the drive attached to a computer and deleting one file from one partition. It is unlikely you'll do the same thing on another partition.
You will be (somehow) safe against a slowly appearing hard disk failure. Once you notice sectors on the drive going bad, you may be lucky and get the data off from the other partition, but only because it's on another physical location on the platter(s)!

Disadvantages:

Writing twice as much data in each step wears the drive out faster than usual
You will not get the same write speed if you do the mirroring in-place.
You need to make sure the mirror is really 1:1 (check for synchronization!)
Sudden hard disk failures will mean that your data is gone. Having it mirrored on the drive is not going to be useful if the drive is mechanically dead or has other serious read errors.

To sum it up, what you want to do only helps you to prevent accidental deletions from an application/user layer. From a physical layer, you'd probably be better off using one drive with one partition.
Comment: Thanks.  I assumed this was the case but thought it would be interesting to hear it from someone else.  I'll stick with no partition and relay on verification for creeping bad sectors and such.
Comment: How is this magical RAID with one drive files safe from accidental deletion its a mirror?
Comment: @Steve The question was edited after I answered. It's only safe if there is no constant mirroring involved, for example when you only mirror the drive while backing up, using software.
Comment: Also, nobody mentioned "RAID" :)
Comment: @Michael On reflection the question doesn't mention raid only mirror, however I've taken this to mean RAID1, fell a bit silly now, apologies
Comment: Yeah.  I purposely didn't mention RAID because it's a single disk.  I would have used software - but haven't given it much thought beyond wondering.
Answer: From what I gather, you want to setup RAID 1 on two partitions? I wouldn't recommend it, because you will slow down your disk. Consider this: if you write a file to the disk, you would have to write it to both partitions. The head would move back and forth between the two partitions until the entire file is written to both partitions. This is A LOT of overhead.
Answer: I seriously doubt that any software or hardware RAID would even allow it. The point of RAID1 is two drives, not partitions, with the same data. They would almost certainly not even give you the option to select two partitions on the same drive.
Answer: Sorry but if your talking about setting up a raid1 on the same disk, it has no value what so ever all your doing is wearing the disk out twice as fast, it has no redundancy when the drive dies your backup is on the disk that is already dead, It doesn't provide anymore protection for accidental deletion that one partition because your deletion is mirrored across both partitions,
I don't no whether any partition software would let you setup a RAID on the same disk, REDUNDANT ARRAY OF INDEPENDENT DISKS,
sorry if i sound angry i get like that sometimes (I'm smiling inside :))

Partition a backup drive


Do "package" and "application/software/program" mean the same thing?

Question: Are these words used interchangeably in Linux?
Comment: Please remember to accept/upvote the best answer to your question (tick/check mark on the left). This way, the question is marked as "answered" and future readers can refer to it knowing the solution works. Thank you...:)
Answer:
Note: This answer is restricted to Ubuntu/Debian.

In general, no, they do not mean the same. A "package" is like an installer; it's a DEB file, much like MSI files in Windows.
Unless the application is relatively small, it will usually be assembled from multiple packages, with each package containing one (sometimes more) components of the program. These components can be binaries (executables), libraries, help files (man pages) and even source code.
Conversely, some packages will install multiple small programs (binaries), and others will "collect" multiple related programs under one umbrella for ease of installation (meta-packages), but these are the exception rather than the rule.
In short: since most programs are made up from more than one package, they are not the same. :-)
Comment: You may want to expand this to explain how the reverse is true as well; a single package often provides multiple programs (e.g., `coreutils`) ...or no programs (documentation packages) ...or no files at all (metapackages).
Answer: Software is a collection of Programs.
When that Software is used for performing a particular task , we say its an Application.
Now relating these terms for Linux- Ubuntu specifications.
Package is a specific piece of software which the system can install and uninstall.

Restricting to Ubuntu/Debian.

Packages are basically of two types :  Binary packages and Source packages .
Since they require more developer friendly knowledge due to compilation and dependency technicalities , .deb  was developed to provide simple installation and un-installation functions compared to Window MSI or .exe formats.
(.deb)ian package,is used by Debian and Ubuntu.
dpkg (lower level) and apt(higher level) forms its Package Management system (PMS) used to install them.
.deb package contains meta-information such as a package description, version, and dependencies which allows PMS , to perform an automatic upgrade to a newer version, to check that all dependencies of a package are fulfilled and/or to fulfill them automatically.
For example : sudo apt-get install ubuntu-desktop.
Where Ubuntu-desktop is a meta-package use to install the basic desktop applications required by the default desktop using apt PMS .
source : for .deb,PMS, APT, dpkg.
Answer: In the perspective of Ubuntu and Debian.
No, they are not the same thing. Package usually refers to the individual components of a full featured software. Where Software/Application/Program usually refers to  a full featured software which can be used standalone.
Let's take an example:
Then default file browser in Ubuntu (unity) is Nautilus. We usually refer to this as "Software" or "Application", since they can be used for a specific needs i.e browsing files.
But this Nautilus Application or Software depends on various small components, which usually do not provide a full feature individually, but they can be used together to build up a Software, which can provide full feature (browsing files/folder) individually.
you can see what packages nautilus depends on, by running this command in a terminal :
apt-cache depends nautilus

Hope this will help


Frost building up in freezer

Question: My Kitchenaid unit (refrigerator on the top, freezer on the bottom) started building up a lot of frost kind of suddenly. I inspected the freezer door gaskets, and they seem to be sealing normally. What would be the next steps?
Answer: A common cause for this problem is failure of the fan unit in the back of the freezer compartment that circulates the air inside the refrigerator/freezer. You would want to determine if this fan is still working properly.
Note that the fan is typically hidden behind a plastic panel and not directly visible. Exact details regarding how to access and remove the fan will vary according to the make and model of your refrigerator.
Comment: Regarding the fan - be sure that the contents of the freezer are not blocking the fan's output.
Comment: I agree with the fan, I also have a upright that occasionally plugs up and the defrost melts then freezes at the bottom blocking the air flow but the fan is usually the root cause.+
Answer: It could be that the door was left slightly ajar or that something was caught in the gasket when the drawer was closed, then someone else noticed later and fixed that problem. Then you come along and notice the frost, but no cause.
(The frost on the top of the drawer looks suspicious to me. That might be an indication of where an item was stuck in the gasket.)
Now that you have confirmed the gasket is seated properly, let it be for 24-48 hours. The automatic defrost should clear it away.
Comment: It looks like my unit actually did not have a problem. The fan is operating properly. I took everything out, gave it a good clean, turned on the "moisture removal" feature and after some 12-24h, it's all good. Accepting this answer.

Frost building up in freezer


Is it permissible for Muslim men/women to modify or set their eye brows?

Question: Can I please have references for whether modifying, setting or doing anything with the eye brows for the sole purpose of looking good/better is permissible for our Muslim men/women or not?
Answer: I had written an answer to a similar question on another site, which I am copying (with slight modification) below:

Plucking of the eyebrows goes against the sunnah of the prophet and should not be done; much like getting a tattoo or lengthening the hair, it is considered a form of changing what Allah has created.  There are a number of ahadith wherein the prophet has cursed those who attempt to beautify themselves with such actions, or to perform them on others.  Here is one rather clear example narrated from Abdullah (Sahih Bukhari 5948):

Allah has cursed those women who practise tattooing and those who get themselves tattooed, and those who remove their face hairs, and those who create a space between their teeth artificially to look beautiful, and such women as change the features created by Allah. Why then should I not curse those whom the Prophet has cursed? And that is in Allah's Book. i.e. His Saying: 'And what the Apostle gives you take it and what he forbids you abstain (from it).' (Quran 59:7)

Whether "...those who remove their face hairs..." refers to all hairs of the face or just the eyebrows rests on the translation of the Arabic word "al-naamisah".  Although it can be literally interpreted to mean a woman who removes any of her facial hairs at all (rather than the eyebrows in particular), the common opinion is that al-naamisah refers only to women who pluck and shape their eyebrows for beautification and that plucking other facial hairs (such as, for women, those in the beard or mustache area) is acceptable.
Comment: your link did not open. also how you are sure they are authentic hadith?
Comment: @ahmadi link fixed.  also removed the word "authentic" since it wasn't necessary to the answer anyway.
Answer: (This answer is based on view and fatwa of current Maraji)
According to different hadith about beauty of woman and duties of woman for her husband totally (without considering some specific hadith without a comprehensive view) it is concluded in short:
Generally any kind of beauty of women if is done for non-Mahram men or used in public it is Haram. But if it is only for Husband and non-Mahram men do not see it there is no problem. The main reason of such beauty is that non-Mahram see it. But if a woman can make a beauty in such a manner that non-Mahram men do not see it there is no problem.
Also trimming of eye brow slightly that is not considered beauty and is only for having a regular look (not as beauty) has no problem to be seen in public.
There are different hadith from Messenger SAWW and Ahl ul Bayt that shows the woman has the duty of beauty for her husband and beauty is harm only in public and view of non-mahram men.
Please note making any beauty including any injury to body is a different topic. This is about beauty without any harm to body.
Reference:
Ruling about modifying eyebrow for women
In this article this topic is researched in detail and with different hadith from Messenger SAWW and Ahl ul Bayt like Imam Sadiq a.s. and Imam Baqir a.s.
You can study all of it using the google translate but the summary is what I wrote above.


What does Colored dot in systemd means?

Question:
I was mainly looking for a way to show what cause my system to slow up booting, and then came up across this. Now I'm curious to know what it means.
Comment: You might find `systemd-analyze blame` to be more useful if you are investigating a slow boot. But for a snapshot of the current situation, `systemctl list-dependencies` is fine.
Answer: From the systemctl man page.

The dot ("●") uses color on supported terminals to summarize the unit
state at a glance. Along with its color, its shape varies according to
its state: "inactive" or "maintenance" is a white circle ("○"),
"active" is a green dot ("●"), "deactivating" is a white dot, "failed"
or "error" is a red cross ("×"), and "reloading" is a green clockwise
circle arrow ("↻").
Comment: I then imagine red dot is the same as red cross.
Comment: is there any flag to request a text description of the unit state in the systemctl list-units output? Running sed to convert a bunch of ansi color codes into text seems... silly.
Comment: re my own question in the comments: `--plain` omits the non-ascii characters from the output, nice. however the information about state and dependency tree appears to also be removed.

What does Colored dot in systemd means?


How to use multiplexor 74HC4067

Question: I am using 74hc4067 IC(Multiplexer 4:16) for the extend the gpio pins can i use that gpio pins same time or not? and any one suggest about the ic how it is used?
Comment: Just look at the truth table on the datasheet
Comment: Truth Table Says that 0001, 0010 but Work at Same Time? This is My Question
Comment: Then you need to edit the question to ask what you need to know.
Comment: What do you mean it says they work at the same time? Where does it say that? They *cant* work at the same time
Answer: Page 2 of the DATASHEET tells us exactly how this device works. You will need 4 GPIO pins to control 16 output pins on the MUX.
So, as I mentioned before, page 2 will tell you show this device works.
So, as you can see, you have 4 'select' pins. These need to be toggled high or low to control the outputs. The enable pin (active low) is toggled to turn the outputs on/off.
The device works in binary, so the 4 select pins are your binary input (0-0-0-0 up to 1-1-1-1) and the channel selected is the decimal representative. So, if you wanted to select channel 5 for example, you know the binary for 5 is 0-1-0-1.
Next, you look down the table to find the output channel '5', you can see that working back from S3, the binary representative is 0-1-0-1.
That is all you need to know to use this device. You give it a binary number on the select pins and the corresponding output channel is selected. Follow the truth table down and you will see it.
If you want to switch from one number to another, it is a good idea to toggle the Enable pin high to disable the outputs, then select your channel before toggling the enable low to enable them again, this ensures that the MUX has fully switched over to the new output (I have been caught out by this before).
Comment: or you can use gray code when iterating assuming the IC doesn't glitch when only a single bit is changed
Comment: I've heard of Gray code, but have not used it, and haven't actually looked into it too much as I have never needed to. I don't have the knowledge to talk about it in my answer, but it is a valid tool to use, so I would go ahead and write a new answer suggesting to use that
Comment: If I Do to ON 0101 and 0111 at Same Time If it is Possible @MCG
Comment: No, how could that be possible? You can't have an input at logic 0 and 1 at the same time. That doesn't even make sense how you could think that.....
Comment: @Jaimin could you explain why you think it is possible to have a pin in 2 different states at the same time? Or have I misunderstood you?

How to use multiplexor 74HC4067


GDPR When using an external CV formatting company

Question: As a recruitment company, if I use an external company to format CVs that have been shared, do I need to inform the candidates? What are the potential pitfalls of an external company being given confidential CVs that include private information?
Answer: Yes, candidates must receive transparent information about this.
Your exact obligations depend on whether your company is acting as a data controller, or as a data processor on behalf of another data controller.
Data controller is whoever determines the purposes and means of processing. If you're working on behalf of candidates, you're likely a controller. If you're working on behalf of companies, you may be a controller or processor depending on further context.
A controller is responsible for the compliance of all processing activities for which they determine the purposes, even if the activities are outsourced to another company.
As the controller, you are responsible for fulfilling data subject rights, in particular the right to transparent information under Art 13 UK GDPR. Per Art 13(1)(e), this information must include "the recipients or categories of recipients of the personal data, if any". Data processors working on your behalf are recipients. Information is typically provided via a privacy notice.
As a data controller, you are also responsible for ensuring the security and compliance of your processing activities, by determining and implementing appropriate technical and organizational measures (TOMs). See Art 24 and 32. Such measures might include encryption, backup strategies, access controls, training and screening for staff, confidentiality agreements, and anything else. What is appropriate depends on the specific risks you face, the costs of implementing these measures, and on the state of the art. See also the ICO guidance on security.
Per Art 28(1) UK GDPR, if you engage an external company to process personal data on behalf of you, you will ensure that this external company provides "sufficient guarantees to implement appropriate technical and organisational measures". Per Art 28(3), these sufficient guarantees must be based on an enforceable contract with the data processor (commonly called a Data Processing Agreement, DPA).
A processor is primarily responsible for following the instructions of their controller, as laid down in the DPA pursuant to Art 28(3). Processors are not directly responsible for handling data subject rights, so they need not (and must not) provide their own privacy notice to data subjects. However, they must assist their controller as appropriate, for example by providing necessary information so that the controller can satisfy their responsibilities.
When a processor wants to engage a sub-processor to further delegate processing activities, this must be done in accordance with Art 28. Specifically, the sub-processor must be bound by the same data protection obligations as you are, see Art 28(4). So you'd need to enter a processor-to-processor DPA. Also, you need to obtain prior authorization from your controller to engage that additional processor per Art 28(2).
Comment: In respect of the point - "Yes, candidates must receive transparent information about this." Can that simply be having a privacy policy at the bottom of an email, or do candidates bneed to be told greater detail?
Comment: @Sara You can provide the privacy notice in whatever way is appropriate. Attaching a document (e.g. PDF) with your privacy notice to an email might be appropriate, but if you have a website it could be easier to link to a page on that site. I wouldn't put privacy notice information into the fine print at the bottom of an email because such fine print is often difficult to read – Art 12 GDPR says that you must use a "concise, transparent, intelligible and easily accessible form". However, that fine print might be a good place to inform candidates how they can get a copy of the notice.


How do I create a fictional cast of villains that remain memorable?

Question: Recently, I've begun on my journey to create the skeleton of a book I plan on writing; The 888. Anime has been a large inspiration in the way I consider composing my characters along with their backstories. This gave me the idea that I would like to create a group similar to anime's "akatsuki" AKA a group of scary bad guys that the readers can find themselves relating to. Is there a base of rules or fundamentals I should follow while creating my story's villains?
Comment: Are you writing a book or creating a visual media, like graphic novel?
Comment: At the moment, I'm looking to write a book. Although I'm open to tips that regard to visual media if you do have any.
Comment: Visual works do this differently. For writing you may check out this question: [How to make a character's personality trully distinguishable/memorable?](https://writing.stackexchange.com/q/29263/22990)
Answer: Make each character three dimensional and interesting - essentially real. The interesting villain is the one who is often right, just has methods that are objectionable.
It depends on the kind of book you want to write, but I find the antagonist who knows his own limits and wants to push them, who understands that what he is doing is unpopular but nevertheless believes that what he is doing is right, perhaps for the greater good is more chilling. Not only can we imagine them existing, we might think we know of someone like that. They seem real.
I get to know my characters, sometimes before I write, but often as I write them. I learn things about them that I know to be true, things that never make it on the page.
Ask yourself what your antagonists want, who they are. I start with a name and take the core of their personality from it. Are they working with others? Do they collaborate out of necessity but don't trust the others?
Over-the-top lair-dwelling villains are fun, but we know they could never be real.
A businessman with the desire to buy a town so he can tear down all of the old buildings and build nice apartments for city dwellers who want to escape the city does not seem evil, but we can hate him. We understand him, know that he might not care about the people he displaces - wrong place, wrong time. He thinks of the money he will make and of the new people who will move to his community, bringing wealth. The townfolk might see him as a villain, but hope he can be stopped before he destroys their world.
Even villains are the hero of their own story. Villian wants to release a plague to decimate humanity because he knows it is the best thing that can happen. Overpopulation will kill them all and destroy the planet - a cull now is necessary. He does not do it for fun - but because it must be done and he is the only one with the courage to do it. It is folly to do otherwise.
You need to know your characters well and love them. If you hate your antagonist, he will be flat and dull. Love them all, know them all and give them all character arcs.
Give them full lives and they will be interesting. They need aspects other than evil, traits that can make them people who are dangerous because their world view is contrary to societal norms and smart enough to make it a nail biter as they have the talent and resources needed to do the dastardly deed.
Comment: It's worth keeping in mind the "villain problem." Villains can get so interesting that they overshadow the hero(s)/protagonist(s)/main character(s). And there are specific reasons why this can happen systematically, e.g. often the villain can be more pro-active, capable and idiosyncratic than a hero.
Comment: @sesquipedalias Indeed, but a dull villian destroys the story. While a dull hero is not desirable and one must strive for interesting characters on both sides, readers are more prone to accept a less interesting hero than they are a villain. I know I am. A good villain can make or break a story. Years ago, a piece I was writing had a virtuous magician who ended up a de facto villain. The supposed villain was sacrificing much to limit the damage caused by the alleged hero. It became more interesting once I flipped their roles a bit, creating ambiguity.
Comment: agreed; I was just pointing out that "the other extreme" also exists and _can_ be a problem
Answer: A realistic villain is a good, memorable villain in my opinion. With that said a villain is never a villain 100% of the time. If you take some time to flesh out your villain you might find that the lord invading his previous ally without warning is doing so because he was reminded of his mortality and wants to ensure he can leave a strong kingdom to his children to rule. In this way your villain can commit terrible acts with minimal damage to their conscience by justifying what they're doing.
Think of Cersei from Game of Thrones, She is able to endorse all kinds of murder for the sake of ensuring her son, Joffrey, gets everything he is entitled to. Her lack of any remorse in plotting her atrocities makes her a chilling and memorable character, all the while though she is not a villain to Joffrey or Jamie and has relate-able love for them.
Answer: The best rule I ever read for making a villain is to treat your villain as the most important character in your story and make him/her the most interesting character, even more so than the hero.  As alluded to in @Rasdashan's answer, one of the most discussed villains right now is Thanos from the Avengers movies, who has a similiar goal in solving the world's problems by a universe level cull of the population, thus solving the Overpopulation problem.  What makes him interesting is that he actually does care about the people he's willing to kill... which is why it's a coin flip... so that he's not doing it out of malice or spite or love or affection, each person is given a 50:50 chance to live or die... if a sinner lives and saint dies, so be it.  He's not going to use any system of evaluation other than random chance to determine this.  This alone qualifies him as "Not as big of a jerk as you could have been award."  What really pushes him into sympathetic territory is that he has children that he deeply loves and are all adopted.  Even if they don't return his love for them, he never stops loving them... and in one of his final acts in the film, the fact that all but one of his six children are now dead, it allows him to commiserate with a hero who has just lost someone she loves... and he also tearfully admits that to him, the personal nature of his loss... is still worth it to him... which is the gut punch to the audience...  It also sets up a major theme of the film... As Captain America points out when the simple solution to the threat of Thanos is the death of one character on his team, "we don't trade lives."  Meanwhile, while never echoed by Thanos, he does exactly that because it is a simple solution.
When writing a villain, the best ones will never see themselves as the villain... they think they are the hero... that whatever they do, they're actions are justified for the greater good of the mission.  At least in their own mind.
A cull would be a logical solution to overpopulation, but not an ethical one... to most people... to most people... but what is logical is not ethical and what is ethical is not logical.  The best villains will make the hero counterpart question if they did the right thing in opposing him... and he might not like what the answer says about himself.
To look at another franchise, X-Men, the main villain, Magneto, is often one of the most beloved villains in all of superhero works... because he and his opposite number, Charlse Xavier, both have the same goal (Mutant safety and acceptance) but go about it in different ways that are unrecognizable (Often summed up in saying Magneto is Malcolm X to Xavier's Martin Luthor King Jr.) and they actually are good friends and Magneto will admit that Charles has some good ideas but he's seen a history that disputes the work-ability of them.
Magneto grew up a Polish Jew during the Nazi Occupation. His life was threatened once because of the circumstances of his birth and he does not want to be in that situation ever again.  Xavier was never a victim in the same way Magneto was and believes that most people are better than the Nazis.   Magneto has no tolerance for bigotry and will oppose it, viololently if necessary... Xavier believes that this only creates a circle and sees it more productive to show the world the good mutants can do.  They can agree on goals, but not solutions to achieve these goals.  The final conversation of the first film sums up the relationship perefectly.  With Magneto in jail, Xavier goes to visit his friend and they have the following discussion:

Magneto: Doesn't it ever wake you in the middle of the night? The feeling that someday they will pass that foolish law, or one just like it, and come for you and your children?
Professor Xavier: It does, indeed.
Magneto: What do you do when you wake up to that?
Professor Xavier: I feel a great swell of pity for the poor soul who comes to that school looking for trouble.

It's here where Magneto realizes where he's wrong.  Charles does not give up on the goodness of people, and feels that if he can show the world that mutants who can control their powers and understand how they work and use them for the defense of others, humans or mutants, then he can show mutants to be worthy of judgement on the content of their character, not their content of their genes... and if still they insist on starting a war, they know the enemy will be capable of defending themselves.


Ubuntu grub menu after installing CentOS?

Question: I am currently dual-booting Windows 8 and Ubuntu 14.04, and would like to get some familiarity with linux server admin. I plan to install CentOS and maybe host a small website or something. What will happen to grub after installing CentOS?
Answer: You'll need to reinstall/update grub. I had the same issue after installing CentOS 6.4 on top of my Ubuntu 14.04. Following this post fix my problem:
http://muthusaravananmca.wordpress.com/2010/09/29/ubuntu-grub-recover-after-installing-centos-or-windows/
(Just to clarify that in Step 4: use "--root-directory ...")
Hope it helps.
Answer: If everything is using EFI, it won't have much effect.

CentOS will make itself first in the boot order. You can change that back to Ubuntu by using your EFI system menu.
Once you have set Ubuntu back to first in the boot order, run sudo update-grub to add CentOS to your grub menu.
If you have any trouble getting into the EFI system menu, you can also boot into Ubuntu from the CentOS grub menu, reinstall grub with sudo grub-install /dev/sda, and follow that with sudo update-grub. Re-installing grub will set Ubuntu first in the boot order and updating will add the new OS to the boot menu.

If everything is in legacy mode using MBR, things will work out much the same; but it's just a little more cumbersome to keep things set the way you want.

When you install CentOS or any new OS, if there is an option to not install a bootloader, use it. (CentOS using the new Anaconda installer should have that option, although it may be a little tricky to find.)
If you can't avoid installing a bootloader, try to install it to the same partition where you are installing the new OS. This will prevent it from overwriting the MBR.
In either case, after installing boot into Ubuntu and run sudo update-grub to add the new OS to the boot menu.
If you cannot use either of the above options or simply forget and overwrite the MBR, use the new OS's boot menu to boot into Ubuntu then reinstall grub with sudo grub-install /dev/sda, and follow that with sudo update-grub.
Comment: I have an EFI system but the installation took place with a Live USB that wasn't created for EFI systems, I am booting Legacy. What does that change?
Comment: Is Win8 in EFI mode while Ubuntu and addtional OS's are in legacy?
Comment: Nope, both are legacy. I installed Win8 from a USB created using Win7 USB/DVD download tool.
Answer: I had a corrupted boot configuration for Centos 7 and installed Ubuntu 18 in an effort to get grub up & running.  Windows 10 was found but not Centos by either update-grub or the boot repair package/utility under Ubuntu.
On the other hand, when I used the Centos 7 rescue utility to get their version of grub running & Centos back up (https://www.tecmint.com/recover-or-rescue-corrupted-grub-boot-loader-in-centos-7/),
the following command found Ubuntu w/ no problem (https://unix.stackexchange.com/questions/152222/equivalent-of-update-grub-for-rhel-fedora-centos-systems) :
grub2-mkconfig -o "$(readlink /etc/grub2.conf)"

And so I now have a tri-boot system : Windows 10, Centos 7 & Ubuntu 18 :)
Conclusion : when in doubt, user Centos' grub2-mkconfig to pick up your bootable systems.


Can open-uri be used across rack applications?

Question: Currently I have a Sinatra web app & a Grape API, the idea being to implement the Sinatra app in such a way that the web app is just another API consumer.
In my config.ru I have this:
run Rack::Cascade.new [API, Application]

API is the Grape app & Application is the Sinatra app. I am using open-uri to try to grab the JSON from the Grape api in a Sinatra route. I am using thin. I am omitting the /uri after the port number for ease of reading, the Grape & Sinatra apps work independently, I will explain further in a moment
open("http://localhost") returns:
#<StringIO:0x007fbeab1b2e68
@base_uri=#<URI::HTTP:0x007fbeab1d47e8 URL:http://localhost>,
@meta=
 {"content-type"=>"text/html; charset=utf8",
  "x-pow-template"=>"welcome",
  "date"=>"Fri, 06 Sep 2013 07:29:15 GMT",
  "connection"=>"keep-alive",
  "transfer-encoding"=>"chunked"},
@status=["200", "OK"]>

However, if I open("http://localhost:9292") the application hangs. I feel like maybe something is blocking I/O, like perhaps its waiting for itself to connect to itself but I am not sure enough of whats going on under the hood to really be sure.
If I point pow at it, spin it up at project.dev & then spin it up with rackup so I have two instances I can use open("http://project.dev/what/ever/url/i_need") & it works like a charm. So the problem seems to be somewhere in pointing open-uri at itself... I think...
Is this because of the Rack::Cascade? is this a problem with thin? or maybe the with open-uri? Is this just completely the wrong way to approach this problem?
I am open to just about any solution however I would prefer to keep it as simple as possible, with minimal external requires as I intent to use this pattern frequently.
Let me know if any additional information is required & I will do my best to provide it.
Answer: It appears that sinatra and open-uri step over each other, as I faced the same issue with sinatra 1.4.4 using different servers (puma, webrick, thin).
My solution was to switch to curb and this solved the problem.


A question about transcribing using a software

Question: I arrived at a point where I finally realized importance of transcribing stuff I like to help myself developing my sound and my music/lick vocabulary. But with just pen & paper at hands it results terribly difficult, for sure because I'm at the beginning of the process. So I was wondering, cause I'm pretty good using notation softwares, does  transcribing with notation software (and so pressing 'play' everytime I want to check if I'm doing things good) help the same way as just with pen & paper? I think I already know the answer, but just wanted your opinions about it. Thanks!
Answer: I'd say it was the actual act of transcription which brings the most benefit to your musical development, and the medium is secondary. Recognising pitch, harmony, and rhythm, to a level where you can accurately notate it, is a huge benefit to developing skills.
Software playback is probably a quicker feedback loop, because computers do exactly what you tell them to do - so if you've notated a rhythm wrong, you'll hear that straight away, whereas if you wrote it on paper and then play it back you know what you meant to notate and so won't be getting the 'independent ' verification that software playback provides.
Personally I often use pen and paper if I'm composing then transcribe that onto the computer to make it presentable, legible to anyone else, and distributable. If I'm notating a work from a pre-existing audio file I'll usually go straight to computer.
Comment: I agree: that's it!
Answer: Transcribing can be divided to (at least) two distinct phases: (1) identifying the notes (and techniques/expressions) played, their exact pitches and timings, and (2) writing the identified pitches and timings in musical notation, possibly trying to remove interpretation, mistakes and randomness to extract the essence of the musical piece. Phase 1 could be thought of as "transcribing from audio to MIDI" and phase 2 as "from MIDI to notation".
For phase 2, I don't think there's any software to significantly help you beyond the mechanical level. You have to know the culture and understand what is the essence of the music and how the notation should be written. You have to be able to predict, how the notation will be understood. The only help from software you'll get is for writing the notes, but to know which notes to write - that's a different thing. But for phase 1, identifying the pitches and their timings - that's much more mechanical, and there you can use tools and methods.
I've written about the tools and methods here: Tips on how to transcribe string parts from a song by ear
Answer: Transcribing into notation software (as distinct from attempting to auto-create notation from audio input - still a very undeveloped science) gives the opportunity of immediate feedback to check if you got it right.   What's not to like about that?
Having said that, pencil and paper can be quicker when initially mapping out a transcription on the basis of 'put in what you're SURE of, then fill in the gaps'.


Let $f$ be such that $f(0)=0$ and $f'(0)=1$. Find iff conditions for normality of successive iterations $f\circ f\circ\ldots$

Question:
Let $f$ be an entire function normalized by the conditions $f(0)=0$ and $f'(0)=1$. Find necessary and sufficient conditions on $f$ for normality of the family of successive iterates $\{f\circ f,f\circ f\circ f, f\circ f\circ f\circ f,\ldots \}$.

I know that if $|f'(0)|>1$, it certainly does not. But for $|f'(0)|=1$ I'm having trouble coming with conditions so strong they are necessary and sufficient. Would a condition on the second derivative of $f$ help?
Any help is greatly appreciated. Since I haven't made much progress on this I'd prefer if I were just given hints, else I feel like I'm asking for answers. Thank you.
Comment: what is the meaning of normality here?
Comment: every sequence in the family has a subsequence which converges uniformly on compact subsets of $\mathbb{C}$ to a holomorphic function; that is, not allowing $\infty$ as a limit.
Answer: We have the following relevant fact:

If $\mathscr{F}\subset \mathscr{O}(U)$ is a normal family, then $$\mathscr{F}' = \{ f' : f \in \mathscr{F}\}$$ is also a normal family.

The proof is simple, for any sequence $(g_n)$ in $\mathscr{F}'$ select a sequence $(f_n)$ in $\mathscr{F}$ such that $f_n' = g_n$ for all $n$. By the normality of $\mathscr{F}$, we can extract a compactly convergent subsequence. Without loss of generality - to save subscripting - assume the whole sequence $(f_n)$ is compactly convergent with limit $f$. For every $z_0 \in U$ choose $r > 0$ such that $D_{3r}(z_0)\subset U$. For $z \in D_r(z_0)$ we then have
$$g_n(z) = f_n'(z) = \frac{1}{2\pi i} \int_{\lvert\zeta-z_0\rvert = 2r} \frac{f_n(\zeta)}{(\zeta-z)^2}\,d\zeta.$$
Since the circle $C = \{\zeta : \lvert\zeta-z_0\rvert = 2r\}$ is compact, $f_n$ converges uniformly to $f$ on $C$, and since $\lvert \zeta-z\rvert > r$ for $(\zeta,z) \in C \times D_r(z_0)$, we have
$$\frac{f_n(\zeta)}{(\zeta-z)^2} \to \frac{f(\zeta)}{(\zeta-z)^2}$$
uniformly on $C\times D_r(z_0)$, whence
$$g_n(z) \to g(z) = \frac{1}{2\pi i} \int_{\lvert\zeta-z_0\rvert = 2r} \frac{f(\zeta)}{(\zeta-z)^2}\,d\zeta = f'(z)$$
uniformly on $D_r(z_0)$. Since $z_0$ was arbitrary, it follows that $(g_n)$ converges locally uniformly, hence compactly, on $U$.
This can be iterated, so for a normal family $\mathscr{F}$, the family $\mathscr{F}^{(k)} = \{ f^{(k)} : f \in \mathscr{F}\}$ of $k^{\text{th}}$ derivatives is again normal.
For our setting, where $\mathscr{F} = \{ f^n : n \in \mathbb{N}\}$, we need only look at the derivatives at $0$. If $\mathscr{F}$ is normal, then the sequence $\bigl((f^n)^{(k)}(0)\bigr)_{n\in \mathbb{N}}$ must be bounded for every $k$. Investigating that will lead you to a necessary and sufficient condition.
Answer: I think you don't have to consider so precisely. The answer is the family ${\frac{d^3 f^n}{dz^3}}$ is normal.


Does strength of victory include teams a team has tied?

Question: In figuring the NFL's strength of victory tie-breaker, what about teams a team has tied? In other calculations, a tie is counted as half a victory.
Answer: No. "Victory" means winning, not tying.
The strength of victory counts only the actual victories, where the team won.
The NFL tiebreaker procedures do not list any alternative definition or calculation for this, so it can be assumed to have the simplest form possible: the combined record of teams beaten, expressed as a winning percentage.
This calculation will count the beaten teams' ties as a half-win, as usual.
Comment: Ties count towards victories for winning percentage, but not for strength of victory. May be the way the rule is intended to be impemented, doesn't mean it makes sense.
Comment: By the time one reaches that level of tiebreaker, including half-winning-records is more effort than is worthwhile. Sure, it's easy enough to calculate, especially with computers that could run it almost perfectly real-time, but it's one more step that might confuse fans.


Is my Asus 1000H netbook good enough for Ubuntu 12.10?

Question: I am looking to switch my Asus 1000H netbook (N270 1.6Ghz processor) from XP to Ubuntu. Is the latest version 12.10 the most suitable for this machine?
Comment: I should add, I also use Chrome/Chromium because Firefox runs poorly on the 1000H
Answer: Welcome on Ask Ubuntu, Colin Lewis ! The requirements for Ubuntu Desktop are the following :

700 MHz processor (about Intel Celeron or better)
512 MiB RAM (system memory)
5 GB of hard-drive space (or USB stick, memory card or external drive but see LiveCD for an alternative approach)
VGA capable of 1024x768 screen resolution
Either a CD/DVD drive or a USB port for the installer media
Internet access is helpful

So your processor frequency seems a little low (I think you have 667 Mhz max). If I were you I would consider to install Xubuntu 12.10 or Lubuntu 12.10. They would be more appropriate.
Xubuntu and Lubuntu are both very nice, but if you ever have the opportunity to try Ubuntu out, you will probably like its interface a lot !
Comment: The Atom N270 runs at 1.6 GHz, so you're fine in that area. In my experience with similar netbooks, you'll want to maximize your memory to the full 2GB, and run a distro that uses compiz but not unity. This might seem like a flame worthy response to run compiz, but the GMA950 gpu is well supported and offloading all the window dragging, etc away from the anemic processor actually helps. Just moving a window around rapidly without a compositing window manager can results in a high cpu load on an atom. With compiz, the load drops to almost nothing.
Answer: Ubuntu will run fine, I would also suggest adding Jupiter PPA to install Jupiter and jupiter-eeepc-support, the former increases battery life while the later enables super hybrid engine of asus netbooks.
Answer: I have that exact model, I am using 12.10 on it right now. definitely faster than XP on the 1000H series. you will have to use a disk, or really dig into the bios because its a pain to make it boot to usb.
Comment: IIRC the U3 type of USB drives, which the system sees as a CD-ROM + a flash drive are a little easier to boot from on some systems that don't like booting from a USB HD. It's just more of a pain to copy the distro ISO to the U3 partition. The package 'u3-tool' has tools for doing this.


What is the easiest way to get "Walking in a winter wonderland"?

Question: There is a prize on Steam for getting the "Walking in a winter wonderland" achievement in the Greed Corp. game. What is the easiest way to get it?
Answer:
Click "Create Battle" when the game starts
Add 3 other LOCAL players so there are four players total including you.
Pick the "Northern Steps" map - this is a winter map
For every player who isn't you, create a harvester on the tile in which they are standing. Go to the next turn.
On the next turn, self destruct each harvester (you should have no harvesters except for all other players).
You should win and get the achievement now.
Comment: This doesn't seem to work. I pick the right map and I do win (my player not the 'friend of myplayer'). Still don't get an achievement of any kind :/
Comment: Never mind, season setting was random had to re-create until i got a winter setting.
Answer: Taken directly from http://steamtreasurehunt.wikia.com/wiki/Winter_Objectives
Start a match, and pick local players for player 2 and 3. It should say "buddy of " or "friend of " for player 2 and 3 names. Pick the map Angoran Mountains, which you can't actually do until you've unlocked it, but far be it from this guide to actually document such arcane processes. Anyway, once you've figured out how to unlock the map you need, which for all we know could take a month of playtime, make sure that the center tile is covered in snow. If it's not, quit and remake the game. Since you control all 3 players, fast forward through your own turns, and build a harvester each for players 2 and 3 - the harvester will eventually destroy the ground, the units will fall through and you'll be victorious. Player 1 (you) won't always go first.
I haven't yet tried this myself since my Greed Corp is acting up, but that should work.
PS: as a question to the asker.. do you know how far you have to go into the game to unlock the Angoran Mountains?
Comment: Welcome to the site! You should post the question in your P.S. as a separate question using the Ask Question button in the top right.
Comment: Just for reference, as the question has not been asked separately yet: just pick Mokosh Dam until it gets randomly picked as a snow map.


Dpkg-reconfigure openssh-server fails on boot

Question: When I boot the linux, dpkg-reconfigure openssh-server fails and the booting gets stopped there. But when i press ctrl+c it resumes the booting with dpkg-reconfigure failed.
Answer: dpkg-reconfigure openssh-server should not routinely run at every boot. It probably runs because some update procedure was interrupted. Verify that your system disk is not 100% full.
You should then run sudo dpkg-reconfigure openssh-server or equivalent manually, and allow it to run to completion. If it produces any error messages, troubleshoot those errors.
When the command completes successfully, it should automatically make a record in the package management database that the openssh-server package is now fully configured, and so it should no longer attempt to reconfigure it at every boot.
Comment: Its showing Creating SSH2 RSA key; this may take some time and after sometime it leaves the error message "Timedout waiting for dev-ttyMSM0 device. Dependency failed for serial getty on ttyMSM0'
Comment: OK, so the hardware is not a regular PC, but a Dragonboard or something similar - and it's trying (and failing) to do something with the first serial port, that is probably being used as the serial console. Probably attempting to gather some true randomness for key generation, I guess... I'd need to investigate further, but I'll need to do my day job first, so it may take a while.
Comment: Ok. For more info when i deleted the line "exec start=dpkg-reconfigure openssh-server " from ssh-keys.service , the system booted. But i want the system to be booted with that service.
Comment: `ssh-keys.service` could be something that is supposed to run only once, the first time the system is booted after installation, to initialize the SSH host keys.  Or it might be something specific to your Linux distribution: it does not appear in any release of Debian I know of, not even the current unstable. What is the name of the distribution, by the way?


Is a union of local complete intersections, a local complete intersection?

Question: Let $X$ be a smooth variety over a field $\Bbbk$, and let $Y, Z \subset X$ be closed reduced subschemes of the same dimension, both of which are local complete intersections.  Is $Y \cup Z$ necessarily a local complete intersection?
Answer: The union of two planes in $\mathbb A^4$ which meet at a point is not Cohen--Macaulay, and so in particular not a local complete intersection.
More generally, any smooth subvariety of a smooth variety is a local complete intersection, so any non-Cohen--Macaulay subvariety whose components are smooth gives an example of a union of local complete intersections which is not itself a local complete intersection.
[Added: Your question has the caveat "with an appropriate scheme structure"; is there any
other structure besides the reduced scheme structure on the union which you had in mind?]
Comment: Dear Emerton, you probably meant "any smooth subvariety of a smooth variety is a *local* complete intersection"?
Comment: Dear Francesco, Yes, thanks!  Regards, Matthew
Comment: Two comments: First, the only other scheme structure I had in mind was the product ideal. Since they agree in your example, it's not an issue. Second, I was aware of your "more generally" paragraph when I wrote the question, but I was not familiar with examples of non-Cohen-Macaulay varieties with smooth components.  Your word choice, together with the simplicity of your example, makes it sound like these should be quite easy to obtain.  How does one go about it?
Comment: Please insert the word "equidimensional" at the appropriate place to make the previous comment reasonable.
Comment: Dear Charles, Being Cohen--Macaulay (or not) is a local, even infinitesimal, property of a singularity.  So if you take any smooth surfaces in some ambient variety which meet at a single point in the same way that the two planes of my example meet at the origin, you will get a non-CM variety with smooth components.  Obviously you will be able to make lots of these.  Regards,
Answer: No. Let $X=\mathbb A^3_k$ with system of coordinates $t_1, t_2, t_3$, let $Y$ be the hyperplan $t_3=0$, $Z$ be the union of the $t_1$-axe and the $t_3$-axe. Then $Y$ and $Z$ are complete intersection, but $Y\cup
Z$, whenever the structure you endowe with, can not be a local complete intersection at the origin because its irreducible components don't have the same dimension.
Comment: I meant to include the words "of the same dimension" in the question.


How to deactivate "Use colors from system theme" in gnome-terminal via CLI?

Question: In a script, I'm trying to set the configuration for gnome-terminal. Setting the background color works, but it is overriden by this one option "Use colors from system theme" in the Colors tab in the profile settings. How can I deactivate this with something like gsettings or dconf? I tried, unsuccessfully, to find the right value with dconf-editor.
Answer: Assuming you're changing the default profile that comes with gnome-terminal, you can use this command to change the preference to use themes colors.
dconf write /org/gnome/terminal/legacy/profiles:/:b1dcc9dd-5262-4d8d-a863-c897e6d979b9/use-theme-colors false

Here, b1dcc9dd-5262-4d8d-a863-c897e6d979b9 is the UUID of the default profile of Gnome terminal.
If you want to change settings for another profile, you need to know its UUID. The good thing is most users use the default profile, so it should work most of the time.

Addition from OPs comment
UUID value for default profile can be fetched using this command
gsettings get org.gnome.Terminal.ProfilesList default

So, getting it in a variable say TPROFILE, stripping off ' from beginning and end with TPROFILE=${TPROFILE:1:-1} and using it as $TPROFILE in place of UUID will ensure that default profile is being changed, even if the UUID is changed by the user.
Comment: Awesome, it works. The way I get the UUID is like this: TPROFILE=$(gsettings get org.gnome.Terminal.ProfilesList default); TPROFILE=${TPROFILE:1:-1}. Then use $TPROFILE in place of the UUID. This way it'll still work if the UUID of the default profile should change, for whatever reason.
Comment: @LasseMeyer that's great! Edited the answer to add your info. Thanks for the feedbacks


Fuses in fan flow

Question: Fuses as in classical wire types blow when the wire melts or fuses. This gives rise to a current rating, and some overload capability due to the heat capacity of the wire. There is some ambient temperature dependence on the fusing current. Reputable manufacturers state this in their curves. My question is what about air flow? Surely a fuse bathed in lots of turbulent airflow from a fan would would have a higher fusing current? How significant is this? Could you set up a system where if the airflow failed the fuse would blow?
Comment: `Could you set up a system where if the airflow failed the fuse would blow?` ... google `crowbar circuit`
Comment: Perhaps air flow could be a factor. Note that a lot of fuses are placed in an enclosure to protect them from the elements, accidental touch, etc. but also to contain the effects of them rupturing when they are subjected to high current or a high energy pulse.
Answer: Nearly all fuses are enclosed in a glass or ceramic envelope with no real thermal path from the fuse wire itself to the outside environment, so there shouldn't be much of an impact.
Fuses aren't generally carefully chosen for their tight tolerances on blow time under long-term slight overload conditions, so changing the blow time at some slight overload condition from 10 hours to 10.5 hours isn't exactly a problem--and if it is, you should rethink your system design. Fuses only blow quickly under very large overload conditions, where there wouldn't be time for any significant amount of heat to conduct out of the fuse anyway.
Answer: From your question you want to shut down if there is no airflow. Typically to detect air flow you use a switch called a sail switch. They can be gotten in lots of configurations and are not that expensive. One usage example is for RV furnaces. They must show air flow or the unit will not start or keep running. Search for: "sail switch".
For the temperature you could add a over temper sensing device such as a thermal disk, which are usually rated at a trip temperature. When it trips it can have the logic keep it off until the proper conditions are met that will allow it to reset.
Having the thermal disk blow the fuse is easily accomplished but it would be much more economically to just shut it down.

Fuses in fan flow


How do I get a list of AD groups used for SharePoint site permissions?

Question: Is there a query or powershell command to retrieve a list of AD groups used for permissions in SharePoint sites?   We need to find out what groups are being used (actually which ones are not being used) so we can delete unused groups in AD.
Answer: You could collect the information by using STSADM -o enumusers command.  It will output XML with a list of users (or AD Groups) associated with SharePoint sites.  Unfortunatly you have to do this for each site so it might take some time to put together the script to run it.
We looked at a tool from Questto manage security permissions in our sites.  One of the features it had was to create a nice list of all users.  It might already have functionality you need.
Comment: It looks like the tool may do the job, but I'm also looking at parsing this info from the output of STSADM or from SP powershell
Comment: I believe this will list all users in the user info list for the site.. not necessarily users who have been granted permission
Answer: I work on SharePoint and am the PM responsible for permissions management.
The best way to do this is probably to write custom code. For a given SPWeb you can ennumerate RoleAssignments (the assignments of permissions to principals) and get the directory groups out of those.
Answer: It's in portuguese but you can translate it (be careful to not use the translation over the scripts :)
Check here: https://suporte.ivancarlos.com.br/hc/pt-br/articles/13124938660109-Gerando-relat%C3%B3rio-de-membros-de-sites-SharePoint-no-Microsoft-365


Scalar vs Vector signal Quantization

Question: I am studying about scalar vs vector quantization, and I have an assignment to implement (in MATLAB) a scalar quantizer , using the Lloyd-Max algorithm, and a vector quantizer via k-means clustering.
The vector quantizer works in the R2 vector space, so its input is a tuple of samples (input vector) and its output is also a two dimensional vector, corresponding to the centroid vector of the quantization region.
I am told that in order for the comparisons between the two quantizers to be accurate, I need to keep the number of bits per sample, constant. For example, in a n-bit scalar quantizer, there are 2n quantization regions, in one of which, a sample will get quantized into.
The equivalent vector quantizer, will have 2n bits per input tuple, so that each sample is still represented by n bits.
So, with that logic, I think that the vector quantizer should have 22n quantization/Voronoi regions.
I have to quantize an equal number of samples from a Gaussian source (source A), and from an AR(5) Random process (source B). From what I've studied, I think that the scalar quantizer is expected to perform a better quantization of source A (in the MSE-sense) and the vector quantizer should perform better in the AR process (source B), where the samples are correlated with each other.
However, when I quantize both of the forementioned sources, and compute the MSE between the original and the quantized signal, the vector quantizer gives a smaller MSE for both sources. So the vector quantizer, is more efficient (in the MSE-sense) for both the sources, which I think is wrong, as it should be more efficient only for the Autoregressive Random process and not for the Gaussian source, as well.
(I calculate the MSE as :mse(input_signal - quantized_signal), so there's nothing wrong there.)
So my questions are:

Should (theoretically) the vector quantizer be more efficient in quantizing both the sources or only in the case of the AR process?
The vector quantizer equivalent of a n-bit scalar quantizer, should have 2n or 22n quantization/Voronoi regions (second argument/cluster number of kmeans() ).

If needed I will post the MATLAB code, as well.
Any help will be greatly appreciated, as I am stuck on this for some days.
Thanks in advance .
Comment: Did you use the same input signal for learning the quantization regions *and* testing the quantizer?
Answer: K-Means is very similar to Lloyd Max algorithm.
Since you give it x2 more bits there is no wonders it performs better.

Scalar vs Vector signal Quantization


Can Martial Arts be learned alone?

Question: The country I am living in only has 2 good teachers who taught kungfu and several for Martial arts. But I am more interested in Chinese lifestyle type martial arts like Tai Chi or Wing Chun. Can I learn any of the mentioned two just by myself, watching tutorial? Or I should wait until I can go to a country where I can find a mentor who taught these? Or is there a better way
Answer: I am not an expert, but I think this is the general answer to expect:
You can learn techniques, and understand concepts, just by watching videos or trying things out for yourself.
The issue is, if you practice with poor form (you're not throwing punches the correct way, or moving the right way, or using the right muscles), it is much harder to unlearn bad technique than it is to learn good technique from the beginning.
My advice to you, or to anyone who doesn't have martial arts gyms nearby, or has bad teachers, is to learn proper stretches, learn concepts, and learn ways of training your body, and work on fitness and flexibility first.
It is a risk to practice techniques using videos. It may turn out fine, but you may end up performing the techniques poorly, and without quality guidance to correct your mistakes, you could set yourself up to have to completely unlearn the technique.
EDIT: Also, it would help to know why you want to learn specifically Wing Chun and Tai Chi. If you just want to learn Tai Chi as an exercise tool, and not as a self-defense martial art, it should be fine to learn it alone.
My comment is more aimed at fighting arts, which are used for self-defense or competition.
Comment: not much I can add to this answer.  I just wanted to note that in these styles working with a partner is also important so you can feel the different kinds of energies and learn to respond appropriately. i.e. collapsing bridge techniques, jamming, parrying, trapping...
Comment: Could you move this answer to the [older question](https://martialarts.stackexchange.com/questions/3129/solo-martial-art-learning)?
Comment: My comment does not apply to that older post.

Can Martial Arts be learned alone?


Unable to get Facebooks "Lookback Video"

Question: Is this video a one time link? I realize it's still very new and we're all still working out the kinks and such but I was able to view and share it once, then I deleted it. Now when I go back to the link, it just thanks me and the video is no longer there. So is there no chance of viewing this again or what??
Answer:
If you delete a post that was featured in the lookback, whether it be
  a status update or photo you didn't want to see In the video In hopes
  that maybe it will be replaced for another post you'd like better..
  then it will no longer work.
My friend has had a Facebook for 7 years, as long as me, yet he wasn't
  able to view his video because he's literally posted like 3 status
  updates. So it's my guess that because the video is computer generated
  to begin with.. it won't work if you tamper with it or don't have
  enough to go into it. Bummer :/


MTG AutoCard doesn't show up in previews

Question: The <code>[mtg:cardname]</code> card tags don't show up in (JavaScript?) post previews. All that's visible is the plain text.
Answer: I asked the developers about this one: changes to the live post preview would be non-trivial, and this specific fix is pretty low on their List of Projects (by Priority). It may be done later on, but please don't expect a change in the near future.
Fortunately for all of us, there's a five-minute window of free editing -- stuff like this is what that's perfect for!
Comment: This isn't the first issue with the real rendered page being different than the preview. Why do they not use the same engine? It seems a lot more work to have two different renderers than it does to just have one.


How enable force global bucket access in aws s3 sdk java 2.0?

Question: Here is a link to the documentation for java 3 sdk version 1. Does version 2.0 has something similar or they removed such option?
Comment: were you able to find an answer for this question?
Answer: Yes! It is possible in AWS SDK v2 to execute S3 operations on regions other than the one configured in the client.
In order to do this, set useArnRegionEnabled to true on the client.
An example of this using Scala is:
  val s3Configuration = S3Configuration.builder.useArnRegionEnabled(true).build

  val client = S3Client
    .builder
    .credentialsProvider({$foo})
    .region(Region.EU_WEST_1)
    .overrideConfiguration({$foo})
    .serviceConfiguration(s3Configuration)
    .build

Here is the documentation: https://sdk.amazonaws.com/java/api/latest/software/amazon/awssdk/services/s3/S3Configuration.Builder.html#useArnRegionEnabled-java.lang.Boolean-
Comment: This does not work. Tried `.multiRegionEnabled(true)` as well and it doesn't help.
Answer: Not supported per here

In version 1.x, services such as Amazon S3, Amazon SNS, and Amazon SQS allowed access to resources across Region boundaries. This is no longer allowed in version 2.x using the same client. If you need to access a resource in a different region, you must create a client in that region and retrieve the resource using the appropriate client.
Answer: This works for me when using java AWS SDK 2.16.98 and only requires the name of the bucket rather than the full arn.
private S3Client defaultClient;
private S3Client bucketSpecificClient;
private String bucketName = "my-bucket-in-some-region";

// this client seems to be able to look up the location of buckets from any region
defaultClient = S3Client.builder().endpointOverride(URI.create("https://s3.us-east-1.amazonaws.com")).region(Region.US_EAST_1).build();

public S3Client getClient() {
    if (bucketSpecificClient == null) {
        String bucketLocation = defaultClient.getBucketLocation(builder -> builder.bucket(this.bucketName)).locationConstraintAsString();

        Region region = bucketLocation.trim().equals("") ? Region.US_EAST_1 : Region.of(bucketLocation);
        bucketSpecificClient = S3Client.builder().region(region).build();
    }

    return bucketSpecificClient;
}

Now you can use bucketSpecificClient to perform operations on objects in the bucket my-bucket-in-some-region