What is difference between broadband and baseband signal with respect to full duplex?

Question: We know that broadband signal is full-duplex, for example television cable line where all TV channel is used portion of bandwidth not full bandwidth. And modern baseband is also full duplex but all sending data used full bandwidth. My question is how baseband signal used full bandwidth where more than one sender sending data but in broadband signal using portion with respect to their sender?
Answer: Baseband and broadband (in the technical sense) refer to the way data is encoded onto a medium. Baseband is "direct" (usually with just a line code allowing clock recovery) while broadband uses one or multiple carrier frequencies and appropriate modulations like QAM or (Q)PSK.
Full duplex means that a channel is used in both directions simultaneously - TV channels are generally simplex (from sender to TV set only) but with multiple channels in frequency-division multiplex (FDM).
On electrical cable, baseband signaling doesn't allow multiple simultaneous senders - or more precisely, not more than two on a point-to-point connection like with 1000BASE-T. This is full duplex in the tight sense, using hybrids and echo cancellation for separation. Other methods are dual simplex (one channel per direction, e.g. 100BASE-TX or fiber), or frequency-division duplex (FDD) on broadband (since there's only a single channel).
On fiber, baseband signaling refers to direct modulation of a specific wavelength of light. Many of those wavelengths can be used on a given fiber using wavelength-division multiplex (WDM). This is different from copper cabling since "baseband" on fiber actually means amplitude modulation of a carrier. For completeness, wavelength-division duplex (WDD) is also possible on fiber (e.g. 1000BASE-BX10, 10GBASE-BR10).
Comment: how baseband using full bandwidth it's not understanding?
Comment: I'm not sure what you mean by "using full bandwidth". Baseband requires a certain bandwidth, depending on bitrate and encoding scheme, that the channel has to provide. Usually, the channel has much more (frequency-wise) bandwidth than is actually used, but it's not really practical (cost, latency, BER) to employ the full channel bandwidth (like VDSL tries for voice-grade cabling).
Comment: when more than one sender sends the data so how full bandwidth is used? Bandwidth isn't divided?
Comment: Baseband uses either dual simplex or echo cancellation for "full duplex". Broadband uses FDD = divided bandwidth.
Comment: if Baseband uses dual simplex or echo cancellation for "full duplex" then divided bandwidth is possible?
Comment: No, you don't need FDD with those variants.
Comment: one thing don't understand, when more than one sender sending data then how data using whole bandwidth? It should be divided bandwidth with respect to different sender data?
Comment: Dual simplex uses a dedicated channel for each direction. The full-duplex method used in 1000BASE-T onwards enables each sender to remove its own signal from the channel, so simultaneous transmission for P2P becomes possible.
Comment: simultaneous transmission means whole data of different sender treated as one data, then it uses whole bandwidth of the channel?
Comment: Not sure if get that - in 1000BASE-T each of the two senders uses the full bandwidth.
Comment: in that case bandwidth divided?I mean what will happen of two sender want to use full bandwidth?
Comment: *No, you don't need (use) FDD with those variants.*
Comment: if we don't need (use) FDD with those variants so how two senders use bandwidth at a time?
Comment: See *Dual simplex ...* above.
Comment: in dual simplex distinct sending and receiving channel for every sender ?
Comment: suppose 4 hosts connected to switch which has 4 different wires.And switch is connected to router by one wire. Now if 2 hosts want to transmit the at the same time then via switch then switch to router link treated as baseband or broadband?
Comment: Ethernet uses bandband signaling in general, with *very* few exceptions, see https://en.wikipedia.org/wiki/Ethernet_physical_layer .


airdrop functionality

Question: what is the functionality of use of "Airdrop" in smart contract, have seen many where result pop-up "adding airdrop in already deployed smart contract" as far as my knowledge once smart contract is deployed can't make any change so how "Air Drop" can be added as a functionality ?
Answer: Airdrop is the process to send tokens in an automated manner.
For example you have a pre ICO, and people contribute to a normal address. When you finish your ICO contracts you want to allocate tokens to the early contributors.
Another purpose is as marketing tool, you randomly select some users and send them some tokens.
An airdrop doesn't require an special contract and can be done through a standard ERC20 contract. But there are different versions that try to minimize costs.
Comment: what do you mean by normal wallet, MEW, Ether Wallet ? Can you please share the format or if there is any code to integrate ?
Comment: @macrichard Sorry, I meant a regular address. There are other questions where they ask for code for airdrops you should read them also.

airdrop functionality


When finding the maximum and minimum points of a function on an interval what do you do if the derivative is undefined at zero

Question: Say I have a function and I want to find the maximum and minimum on an interval, I would first differentiate the function and equate it to zero. Then use this value and the two ends of the interval to find the max and min. If, however the the derivative is undefined when it equals zero do I just scrap that as a value and use the bounds of the interval in the original function? does this mean that when its equal to zero its a critical point?
Answer: The candidates for maximum and minimum of a continuous function on an interval are the zeros of the derivative, the endpoints, and the points where the derivative does not exist.
Whether the term "critical point" includes a point where the function is not differentiable is a question of convention: most authors do not call these critical points, but some do.
Answer:
If, however the the derivative is undefined when it equals zero...

How can it equal zero and be undefined? In any case, points where the derivative is undefined are candidates for the max/min (in addition to the endpoints of the interval and points where the derivative is zero), so you should check the value of $f$ at those points too.
Comment: say I have the derivative of f and equate it to zero but there is no value of x that will make the derivative equal zero, is the zero of the derivative no longer a candidate.
Comment: I see what you mean. Then there are no points $x$ such that $f'(x)=0$, so the only candidates for the max/min will be points $x$ such that $f'(x)$ is undefined, and the endpoints of the interval.


neither...nor with articles

Question: How would you use neither...nor when articles are involved?
For instance: "My pet was neither a cat nor a dog."
It sounds better to say "My pet was neither green nor blue" than "neither a...or a..." so I was wondering if there was some rule about this?
Regarding the first example, "My pet was neither a cat or a dog" sounds more natural to me, for some reason.
Comment: "Neither cat nor dog" would work.
Comment: *Green* and *blue* are adjectives, hence no articles. With your nouns *cat* and *dog*, the articles are optional, however the sense is slightly different without them. The article-less *cat* and *dog* mean "*catkind*" and "*dogkind*."
Comment: No.  "My pet was neither a cat nor a dog" is fine. It may sound a little off because it's a rather unexpected thing to say, standalone. It would be better after some facilitating context.
Comment: Ah, yeah—so is it only grammatically correct to use neither...nor with adjectives?
Comment: There's nothing at all unusual about the first sentence in the question. So, the question is based on a faulty premise. (In fact, the final sentence is not right at at all.)
Comment: @JasonBassford Hi. What's wrong with the second sentence: *My pet was neither green nor blue*? Perhaps the pet, now deceased, was red.
Comment: @RichardKayser There isn't anything wrong with that sentence either. My point is that there isn't anything wrong with anything—other than the final sentence.
Comment: @JasonBassford 10-4. I get it now. I thought the use of *or* rather than *nor* was a typo, but maybe not ...
Answer: As @Edwin Ashworth says, we need some context. This is always needed because English is a context-dependent language.
Neither a P nor a Q
John: Do you have any pets?
Mary: I have one pet.
John: Let me guess. I bet it's a dog or a cat.
Mary: No it's neither a cat nor a dog. (This refers to a specific individual)
John: Is it a rabbit?
Mary: Yes!
Neither P nor Q
Mary: My goodness! What kind of animal is that?
John: I don't know. It looks weird.
Mary: All I can say is it's neither cat nor dog.  (This refers to the species)
John: I think it is some kind of predator whatever it is.
Comment: Yes, you have put your finger on what needs explaining, and made it very clear.  There is an expression that illustrates a very slightly way of using the negative disjunction without an article, when we say that a thing, animal or person is 'neither flesh, fish not fowl', meaning it is indefinably weird.

neither...nor with articles


What has happened

Question: In my recent game I have found a village that is totally left behind. It is absolutely covered in cobwebs and there are no torches or coal blocks anywhere!
Can I somehow get back villagers or craft torches in other ways?
Comment: Are you even talking about Minecraft? Cobwebs don't just appear out of nowhere, they either get generated with mineshafts or get placed by players. And why would you need villages for torches?
Comment: That is an Abandoned Village, they're about a 1/50 generation chance I believe. They're known for their lack of doors or light sources, abundance of mossy cobblestone and cobwebs replacing some of the normal structure's blocks, and are populated with zombie villagers, fortunately Blacksmith buildings and crop farms are more or less unaffected. You can technically fix up the village by curing zombie villagers with a splash weakness potion and a golden apple, and you can put doors and lights back in the village yourself, but it might be better to find another village with living villagers.
Answer: Congratulations, you have just found a [Zombie Village!][1]
From the wiki:
<code>   A village has a 2% chance of generating as a zombie village.
  In such villages, all generated villagers are instead zombie villagers, and all
  doors and light sources are missing.
  These zombie villagers do not despawn but have no special resistance to sunlight.
  In zombie villages, some wood and cobblestone are replaced by cobwebs and mossy
cobblestone, respectively. All glass panes are also replaced by brown stained glass panes.
</code>
The first time I found one, I absolutely FREAKED OUT! I thought It was Herobrine or something.
But I looked it up and it was an actual thing.
[1]: https://minecraft.wiki/w/Village#Zombie_villages

What has happened


How to prove closure of $\mathbb{Q}$ is $\mathbb{R}$

Question: How to prove closure of $\mathbb{Q}$ is $\mathbb{R}$?
Can it be proved easily?
Comment: How are you defining $\mathbb{R}$?  Often it is defined as the closure of $\mathbb{Q}$.  The answer will give some idea what techniques are allowed.
Answer: Presumably, you mean the closure of $\mathbb{Q}$ in $\mathbb{R}$ under the usual topology.
It suffices to show that for every real number $r$ and every $\epsilon\gt 0$, there is at least one rational $q$ which is "$\epsilon$-close" to $r$ (that is, $|r-q|\leq \epsilon$), since this will show that every open ball around $r$ contains a rational. This shows that the complement of $\mathbb{Q}$ has empty interior, so the closure of $\mathbb{Q}$ is all of $\mathbb{R}$.
To prove that, let $r$ be a real number, and let $\epsilon\gt 0$. Then there exists a natural number $n$ such that $\frac{1}{10^n}\lt \epsilon$. Write $r$ in decimal expansion, and let $q$ be the rational that has the same decimal expansion as $r$ up to the $n$th digit after the decimal point, and terminates there. This is a rational number, since its decimal expansion terminates.
Now note that $|r-q|\leq \frac{1}{10^n} \lt \epsilon$, proving that there is a rational that is $\epsilon$-close to $r$.
Comment: @sequence: "then the **complement** of $\mathbb{Q}$ has empty interior." Because no point has an open ball around it that is completely contained in the complement.
Comment: How does it follow that if every open ball around $r$ contains a rational, then $\mathbb{Q}$ has empty interior? @ArturoMagidin
Answer: This question really does not make a whole lot of sense. In topology closures only makes sense in some ambient space. Some examples will probably make this clear.

$\mathbb{Q}$'s closure in $\mathbb{Q}$ is $\mathbb{Q}$ itself.
$\mathbb{Q}$'s closure in $\mathbb{R}$ is $\mathbb{R}$.
$\mathbb{Q}$'s closure in $\mathbb{Q}(\sqrt{2})$ is $\mathbb{Q}(\sqrt{2})$.

And this doesn't even go into embeddings of $\mathbb{Q}$ in e.g. the unit circle. What you probably meant to ask was how to prove that the completion of $\mathbb{Q}$ is $\mathbb{R}$. For that you should take a look at this question.
Comment: Well, perhaps the OP meant to ask how to show that the closure of $\mathbb{Q}$ *in* $\mathbb{R}$ is $\mathbb{R}$.  (But you're right; it's not so clear, and other interpretations are possible.)
Answer: In some sense, the denseness of $\Bbb Q$ in $\Bbb R$ is implicit in the very same construction of $\Bbb R$.
There are a few equivalent ways to construct $\Bbb R$. One of them is to endow $\Bbb Q$ with a structure of metric space by defining the distance function $d(a,b)=|a-b|$ and define $\Bbb R$ to be the completion of the metric space $({\Bbb Q},d)$.
This is but an instance of a general construction: given any metric space $(X,d)$ one can construct its completion $\tilde X$ as the set of certain equivalence classes of Cauchy sequences in $X$. It turns out that one can endow $\tilde X$ with a natural metric space structure such that: (1) $X$ embeds isometrically into $\tilde X$ and the image is a dense set, (2) $\tilde X$ is complete, and (3) if $\tilde Y$ is some metric space satisfying the just mentioned properties, then there is a canonical isometry of metric spaces between $\tilde X$ and $\tilde Y$ which is the identity on $X$.
Incidentally, it is possible to define distances in $\Bbb Q$ which are not equivalent to the one given by the usual absolute value (as above) but depend on the choice of a prime number $p$ and are defined arithmetically. The corresponding completions, the so-called fields of $p$-adic numbers ${\Bbb Q}_p$, are metric spaces not equivalent to $\Bbb R$ in which $\Bbb Q$ sits densely. A famous theorem by Ostrowski says that $\Bbb R$ and the ${\Bbb Q}_p$ are, up to equivalence, the only completions of $\Bbb Q$.
Answer: Here's a self contained proof. The Theorem numbers refer to Introduction to General Topology by Cain, but shouldn't affect comprehension.
By theorem 2.2, the $\mathbf{T}$-closure of a set $S$ consists of all points $p$ such that every member of $\mathbf{T}$ containing $p$ meets $S$. Symbollically, $cl(S)=\{p\in X:(\forall T\in\mathbf{T}:p\in\mathbf{T}),T\cap S\neq\emptyset\}$. Thus to show $cl(\mathbb{Q})=\mathbb{R}$
 , we must show
$\mathbb{R}=\{p\in\mathbb{R}:(\forall T\in\mathbf{T}:p\in\mathbf{T}),T\cap\mathbb{Q}\neq\emptyset\}$
That is, we must show $\forall p\in\mathbb{R}$
 , all members of $\mathbf{T}$
  containing $p$
  meet $\mathbb{Q}$. Since this is the usual topology, ie that generated by the usual pseudometric, a set is a member of $\mathbf{T}$
  iff it is $d$-open. We know all $d$-open sets are unions of cells $(1.12)$. Thus showing each cell containing $p$ meets $\mathbb{Q}$
  is sufficient to show each member of $\mathbf{T}$
  containing $p$
  meets $\mathbb{Q}$.
Let $p\in\mathbb{R}$
 , and $B(p,\epsilon)$
 . We must find some rational $q\in B(p,\epsilon)$
 , ie $(p-\epsilon)<q<(p+\epsilon)$
 . We can do so using the "Density Theorem" 2.4.8 in Real Analysis, by Bartle, 4th edition p. 44. This states: If $x,y$
  are any real numbers with $x<y$
 , then there exists a rational number $r\in\mathbb{Q}$
  such that $x<r<y$
 . Therefore, making the substitution $x=p-\epsilon,y=p+\epsilon$
 , we have the desired result. Thus $\forall p\in \mathbb{R}$ every ball containing $p$ meets $\mathbb{Q}$. Thus $cl(\mathbb{Q)=R}$. $\square$
If anyone is interested, Bartle's proof of the "Density Theorem" is as follows:
"It is no loss of generality to assue $x>0$. Since $y-x>0$, it follows from Corollary 2.4.5 that there exists $n\in \mathbb{N}$ such that $1/n<y-x$. Therefore, we have $nx+1<ny$. If we apply Corollary 2.4.6 to $nx>0$, we obtain $m\in \mathbb{N}$ with $m-1\leq nx<m$. Therefore, $m\leq nx+1<ny$, whence $nx<m<ny$. Thus, the rational number $r:=m/n$ satisfies $x<r<y$."


Hydrostatic force applied on a surface

Question: Say we have a door oriented in an oblique way and there's a fluid above it and nothing below it . The question is to find the hydrostatic force acting on the door . In class, we calculated it by integrating the pressure of fluid times a surface element of the door(dS). The direction of  force is along the normal of the surface. But thinking intuitively the pressure of the fluid varies vertically with height and not oblique as to match the normal of the surface . So our force should not be normal to the surface . It should however push the door downward and not along its normal. But by calculation its just normal . Any help ?
Comment: gravity acts down.
Answer: Gravity acts downward.
If, though, the water were free to move and was deflected by the door, the force it experienced would then be in the direction of its change in velocity.
Comment: What if the water wasn't free to move , and it was given an external push downwards, then the door might be shifted along its normal and also along the given push. Shouldn't it move only in its normal direction? Why does it change in the case of the external push?

Hydrostatic force applied on a surface


Tread wear and punctures

Question: I've used this Schwalbe G-One Speed tire for a long while with no problems. I got 2 punctures in the last 2 weeks though. First was because of a 2 mm thorn, second one was of unidentified cause. While looking carefully I noticed that tread is worn out but not to the point of being unusable. I switched to another tire meanwhile but I'm wondering as a general rule, do people notice an increased frequency of punctures with tread wear?
Comment: Yes, definitely.  That, rather than visible tread depth, is my primary indicator of when I need a new tire.
Comment: You may add new layer too. Puncture proof tape or old tyre thread if you do not mind small rolling resistance increase related with better puncture proof of thicker thread https://bicycles.stackexchange.com/questions/68435/would-you-ride-with-this-tire-with-cuts-in-the-sidewall/84555#84555
Answer: Yes, the less rubber there is between the tube and the road, the more likely it gets for you to find a shard/stone/thorn that's big enough to cut through to the tube. The amount of rubber is your main defense against punctures.
Consequently, puncture proof tires usually add quite thick layers of extra rubber / rubbery material. They may also have improved protector layers, but the extra rubber is their main defense.
And the effect of these extra rubber layers is huge: When did you last have a blow-out on your car (if you have one)? Cars do much more kilometers than bikes, they are driven across the same kinds of surfaces, they have a much wider track, allowing them to collect much more shards/stones/thorns, but they virtually never have punctures. Simply because their tires have such a massive rubber layer.
So, yes, the more you wear down your tire, the more frequent the punctures will become. If punctures get too frequent, think about replacing the tire. Ideally with a serious puncture proof one.
Comment: But it should be noted that the tire "casing" -- the layer of fiber cords below the tread -- is also a major factor in resisting punctures.  And this is even before you get into "puncture resistant" styles, with an extra layer of tightly-woven fabric incorporated into the casing.
Comment: Car tires usually have steel belts.
Comment: @ojs True. However, those steel wires are relatively widely spaced. A thorn would go right through the steel belt if it weren't for the massive rubber above, below, and between the wires.

Tread wear and punctures


message table schema - body TEXT or varchar

Question: I want to make a small social network. For messaging body which one is more suitable? VARCHAR or TEXT?
if VARCHAR how long is efficient?
Comment: Sow which DBMS are you using? Postgres?
Comment: Depends on the **concrete database** you're using.... MySQL? Postgres? SQL Server?  For SQL Server, `Text` and `NText` are **deprecated** and should **not** be used anymore
Answer: To completely determine column type, I might suggest to do following:

Check possible data types in real world: is it string, or number, or large text block, or date?
Determine which operation types you would like to perform with the column: for example, barcode has numeric format, but calculate sum or average of barcode isn't valid.

You have selection of two types: TEXT or VARCHAR. If you would like to perform FULLTEXT search, then you have to use TEXT. For other cases VARCHAR acts almost same as TEXT.
"Which of them to use?" depends on subject area and is primarily opinion-based question. If you ask me, then I might suggest to use VARCHAR (if no fulltext search is planned) up to VARCHAR(2000).

From MySQL.com:

In the following table, M represents the declared column length in
  characters for nonbinary string types and bytes for binary string
  types. L represents the actual length in bytes of a given string
  value.
VARCHAR(M): L + 1 bytes if column values require 0 – 255 bytes, L + 2 bytes if values may require more than 255 bytes.
TEXT: L + 2 bytes, where L < 2^16.

For small messages, storage space of which requires less than 255 bytes, VARCHAR will save some extra disk space.

I'm supposing that you use MySQL RDBMS.
Comment: thanks for your answer. You pointed to important issue. `VARCHAR(2000)` is fine however many people may only send _Hi how are you_ message to each other. which wastes a lot of storage. I dont want to use full text search on messages. Does using `TEXT` slows down my database significantly? and what is the advantage of `VARCHAR` over `TEXT`? i use relational model.
Comment: @meshiv I've updated.


loading managed resources from c# and passing it to Native CPP code as a stream handle

Question: I have a file that I have embedded as a resource in a managed C# assembly.  I would like to pass the pointer to that resource and its size to some native code so it can extract it for me if needed.  Are there C# api's that give me the intptr of that embedded resource?
Answer: Have you heard of C++ / CLI ? It's a language you can use to easily go back and forth between C# and C++.  You might want to give it a try.
Answer: Not without first loading the resource data. Perhaps an unmanaged resource would be more appropriate in this case?


Mouse unclick event in mapbasic?

Question: How can I respond to mouse unclick in mapinfo using mapbasic? Is there any event triggered when the mouse in unclicked? For example at the end of drawing a line when the mouse button is released.
Answer: CommandInfo() is a useful function which retains all information pertaining to recent events in MapBasic.  I cannot remember, off hand, all of the items it returns, but I'd check that for a starting point
EDIT
I have just looked at this, and you need to use the CommandInfo() function thus:
<code> 1stX = CommandInfo(CMD_INFO_X)
 1stY = CommandInfo(CMD_INFO_Y)
 lastX = CommandInfo(CMD_INFO_X2)
 lastY = CommandInfo(CMD_INFO_Y2)
</code>

this returns the click xy and the xy where the user releases the mouse button.

NOTE
This only applies if the toolbutton was defined with a draw mode that allows dragging, e.g., DM_CUSTOM_LINE.
Answer: As far as I know it's not possible to constantly listen for a mouseup event (it's usually called mouseup, not unclick).
However you can create a custom tool which you can then use to capture mouse clicks on mapper windows. This is what Hairy is getting at in his answer.
It's not quite the same thing but it's as close as you're going to get.
Some untested example code:
<code>Include "mapbasic.def"
Include "icons.def"

Declare Sub Main
Declare Sub LineTool

Sub Main
  Alter ButtonPad "Drawing"
    Add
      Separator
      ToolButton
        Icon MI_ICON_LINE
        Cursor MI_CURSOR_CROSSHAIR
        DrawMode DM_CUSTOM_LINE
        Calling LineTool
    Show
End Sub

Sub LineTool
  Set Distance Units "m"
  Set Coordsys Earth

  Dim start_x, start_y, end_x, end_y as Float

  start_x = CommandInfo(CMD_INFO_X)
  start_y = CommandInfo(CMD_INFO_Y)
  end_x = CommandInfo(CMD_INFO_X2)
  end_y = CommandInfo(CMD_INFO_Y2)

  Print "Distance between those two points was: " & CartesianDistance(start_x, start_y, end_x, end_y, "m")
End Sub
</code>
Comment: Great example :)

Mouse unclick event in mapbasic?


Why American homes are wired TNC-S and not TNC

Question: I wonder why American buildings are mostly grounded TNCS and not just TNC.
They have virtually no RCD protection, and also an RCD could work fin on TNC system as long as PE on outlet is connected on PEN before the RCD (or just left not connected). Aren't they just wasting copper?
Comment: Seeing as this is a DIY site, frequented primarily by laypersons, it might be appropriate to expand your initialisms for us. I can't decipher any of them and I've been in construction for a very long time. :)
Comment: Yeah, I know a lot about grounding, know why streetcars and diesel locos have control systems grounded in such different ways, and maintain isolated-ground systems. And I have no idea what this is saying.  So those terms are not commonplace, and links to their definitions would be vital.
Answer: We do use RCD (Residual Current Device) protection, and rather extensively these days even, it's just hiding in disguise
North American electrical wiring indeed started off as a TN-C (all protective earthing is accomplished by referencing things to the neutral) system, back in the bad old days before we had three-prong outlets and GFCIs (Ground Fault Circuit Interrupters), and evidence of this can be seen to this day (such as the abhorrently common NEMA 10).  However, two things happened:

Unlike Europe, who was coordinating a brand-new standard for wiring installs "all at once" if you will through the IEC process, protective grounding (TN-C-S) and GFCI (RCD) protection were added to the US NEC (the US wiring regulations, more or less) separately; furthermore, the GFCI protection rules in the NEC were phased in, location by location.
Our GFCI protection started off with wide adoption at the receptacle level due to the desire to retrofit shock protection into existing houses, especially in wet areas (bathrooms and kitchens).  This is in contrast to the IEC style of RCD, which was widely adopted in breaker form due to the larger number of new installs in Europe.

The consequence of these two things is that the sensitive UL 943 Class A GFCI, while widely deployed in the US nowadays, winds up performing a very different function to IEC RCD protection -- the former is designed to protect against electric shock, including "can't let go" hazards up to and including shock-drowning, while the latter protects primarily against fire, with protection against gross shocks as a side-effect.
Fast-forward a while, though, and the US, while having largely tamed its electrocution problem, still has a serious fire problem, partially electrical in nature.  This electrical fire issue is blamed on a variety of abuses and defects that cause what are described as "arcs", but are more precisely a surface-tracking type of fault where excessive current intermittently leaks through damaged insulation, slowly carbonizing/pyrolyzing it to the point where it smolders into an electrical fire.
As a result, electrical protection manufacturers in the US come up with what's called the Arc Fault Circuit Interrupter, or AFCI, that is designed to listen for the conducted-RF signature of these arc faults and break the circuit when one is detected.  Due to a combination of design limitations and accidents of history, though, the early AFCIs were built off of what basically is a GFCI platform, and as thus had a 30mA equipment protection ground fault trip function in them that is used to catch arcs-to-ground, despite the functionality not making it into the UL standards.
As a result of the rapid push to adopt AFCI breakers, and the retention of this GFPE trip functionality by 3 of the 4 North American breaker manufacturers (GE is the only one to have dropped it), in many cases, a modern house in the US will have RCD protection at the 30mA level on most branch circuits, with select circuits protected at 6mA.  However, this protection is provided at the level of individual branch circuits, not service-wide as is typically done in 5-continent power.
Why is this, you might ask? Well, service-wide ground-fault protection is applied to large, low-voltage three phase services in North America to protect against fires, and works well in those applications.  However, the sensitivity of North American ground fault devices at residential-scale operating currents requires they use electronic ground fault sensing, as opposed to early IEC direct-acting RCDs that used the differential current in the measurement CTs to operate the trip coil without any sense electronics.  This has the upside that North American GFCIs were able to achieve reliable performance at low leakage levels early on; however, it has the downside that wiring a GFCI up backwards (with power being fed in on the LOAD side) will break it in a non-obvious fashion.
As a consequence of this, you can't reasonably use a GFCI as a main breaker in North America unless you are willing to take the same approach as the large wye services do, otherwise you run into issues as soon as you start doing other sophisticated and desirable things, like solar power.  Furthermore, the larger size of US services means that a central RCD would need to be excessively insensitive due to the simple fact the differential leakage currents are higher.
Comment: Unlike Isherwood and Harper, I didn't think the question was interesting enough to ask for expansion of OP's initialisms. But now I want definitions of all this alphabet soup so I can understand your answer!


What does it mean: "The travel money is good for you"

Question: Someone invited us to participate in a sportive event far away from our home country, and told us "The travel money is good for you and there will be prize money for the event".
Does this mean that the exchange rate is good for us at the moment?
Thanks for your help!
Comment: @Dan: I don't know if it's more a BrE usage, but "travel money" is familiar to me in the sense of "travel expenses" - a payment made to you by some organisation to cover your travel costs in respect of something they're involved in. Sometimes the actual *fare* is already paid by the organisation, and "travel money" just covers other incidentals such as meals. So *my* guess is the event organisers pay travel expenses to participants, and the guy is saying it's a *generous* allowance.
Comment: Can you tell us how competent in English you consider your 'someone' to be? The expression 'X is good for you' is not usually used to cover possessions or money (especially a particular 'pot' of money); it's more normally used thus: Vegetables / milk / yoghurt // fresh air / sea air / a temperate climate // exercise / a brisk walk / swimming // [having] friends // a hobby // ... is/are good for you.
Comment: "Travel money" is not a standard phrase in English, and as @Edwin says, native speakers would find it a bit unusual/ but if we have to find an interpretation for it, then: the exchange-rate interpretation is insightful and would not have occurred to me; my best guess is your friend speaks English as a second language, and is suggesting the cost of travel is low (maybe he's offering you an inexpensive hotel rate, or suggesting that plane tickets from your county to his are inexpensive relative to other foreign participants). [continued]
Comment: [continued] The idea being that the overall *cost* to you to make the trip will be relatively low, and ultimately might be offset or even negated by any prize money you receive for winning the tournament.
Answer: Firstly, travel money is a common idiom for the expenses incurred in travelling.  Secondly, there may be two possible interpretations of "is good for you".
On one hand, as you suggest it could mean that the exchange rate is beneficial at the moment.
On the other hand, the phrase is good is idiomatically used to mean that it is provided for you.  It is possible your invitation is an all expenses paid trip.
I would check before you commit to anything.
Comment: Just to reinterate in agreement with this answer: "is good for you" usually means "is beneficial to your health and wellbeing". "travel money" (in BrE) usually means incidental expenses due to travel (for food, trinkets, etc, excluding flight and accommodation). These two can be combined to make a very odd sentence, suggesting travel expenses are a health treatment. But, as Chenmunka says, "is good for you" has a rare secondary meaning "has been authorised". Though an unlcommon construction in most contexts, it does make more sense when applied to travel money!
Answer: Travel money should be an adhoc allowance to meet (personal/professional) expenses.
I have heard of  TA-DA, i.e., travel allowance-dearness allowance paid during official travel.
E.g.  Sales/marketing staff are paid travel (TA-DA) allowances.
Though dictionary meaning of 'ta-da' has a different connotation


When reactants are in their transition state, can they go back into their reactants form instead of progressing to form the products?

Question: When reactants are in their transition state, can they go back into their reactants form instead of progressing to form the products? I don't see any reason why the reaction has to keep progressing forward.
Comment: You answered your own question in your last sentence!
Comment: It can go back and often does go back.  Nitrous acid/nitrosyl ion can attack a teritary aliphatic amine just like it does with a secondary or primary amine, but with no proton to eliminate it has to turn around and go bsckwards in the tertiary case.  It _may_ keep going forward with a primary or secondary amine to give those nitrogen-nitrogen bonded products.
Comment: Oscar Lanza, oh ok so can I draw the conclusion that the reason you don't have all the reactants react to form products is because you would need to make the formation of the products favourable in order to actually obtain them? Otherwise they would just turn back right?
Answer: In the gas phase the reactants have kinetic energy as they move towards one another, so you would think that they would just cross the transition state, but molecules also have vibrational energy which means that it is possible to reach the transition state and then turn back. See the figure below which shows a simple LEPS calculation of the O+H2 reaction.
The solid black line shows the position and vibration of the H2 molecule as it approached the O atom and then 'reflects' at the transition state. It has just enough energy to cross, but the vibrational motion and position on the energy surface prevents it.  The axes show the separation of H and H2 (mid point) and of H and OH products.

In solution (or high pressure gas phase) the situation is a little different because collisions with may solvent inhibit or enhance the motion of the reactants towards one another. The species diffuse together and also diffuse along the transition state pathway so that the transition state can be crossed and recrossed many times before reaction occurs or the reactants are reformed. This approach is named after Kramers and is the most important one to understand when thinking about transition states in solution. (Strangely, it is rarely mentioned in Chemistry textbooks even though it was developed more than 70 years ago.)
Comment: That is interesting, I will look up Kramer's to get a better understanding of this. Thank you for your help
Comment: I only have an old reference Chemical Physics, v151, p239, 1991. There will be references in that paper that describe other experiments and theory.
Comment: That's even better, thank you once again.


Windows 10 updating from Windows 7 via Windows update fail after 84%

Question: I have Dell XPS-L502X(Early 2011) with Windows 7 Home Premium-64 bit. I already reserved my Windows 10 copy and started an update to it that was 2,712.6 MB and failed after 84%, it took for that 17 hrs as i have 512 kbps net speed. I tried many times to continue that update but it won't progress. I tried Update troubleshooter it gives me an error as "Service Registration is missing and Corrupt" and "Windows Update Error 0x80070057(2015-08-02-T-08_01_52A)" are not fixed.
P.S.- I have Windows 7 from my Dell Manufacture which is not a crack version.
Please help me to get that most awaited update.
Comment: run the sfc tool
Comment: Beginning verification phase of system scan.
Verification 100% complete.

Windows Resource Protection did not find any integrity violations.
Comment: share the file C:\$WINDOWS.~BT\Sources\Panther\setuperr.log.
Comment: [Perform a clean boot](https://support.microsoft.com/en-us/kb/929135), then run the installer.
Answer: Same thing happened to me (Windows 7 Ultimate 64-bit, desktop computer). I spent the better part of the day trying to upgrade via various methods (Windows Update, Media Creation Tool) with no success.
In the end, I had to clean install Windows 7 and upgrade from that. Went off without a hitch.
So, I would recommend backing up all of your files (should be done regardless), reinstalling your laptop, then trying the upgrade again, Also, since you're on a slow connection, I'd also recommend Microsoft's Media Creation Tool (https://preview.onedrive.com/office365promo/) to download an ISO or USB installation media so you only have to download it once. To upgrade from an ISO or USB, just browse to them and run "Setup."
And after all of that, I would recommend clean installing Windows 10 once you've successfully activated it on your hardware (once your hardware has been registered with Microsoft (this is automatically done when Windows 10 is activated the first time after the upgrade), any Windows 10 clean installs in the future will automatically activate without a key (so just click "skip" whenever prompted for one when installing)), as I've read of problems being caused by remnants of the previous OS.
Comment: Upgrading a clean install of Win7 is of course much better as you say. I would even go a step farther and after upgrading and getting the key (write it down). Doing a clean install of Win10 aswell to be sure there are no leftover Win7 components lying around.
Comment: @ChristianIsaksson I completely agree, and that is what I ended up doing in my situation. I've read too many stories online of people having issues later on because of remnants of the previous OS. Just updated the answer with a recommendation to do just that.

As for "getting the key," I don't believe that is the case for Windows 10 (at least I never got a key). Based on what I know of the process, upon first Windows 10 activation it registers a unique hardware ID with Microsoft, and in future clean installs, Windows 10 calls home and if you're in their database it will automatically activate.


Does Google AdWords revisit the landing page to see if it changed?

Question: If I change the landing page of my ads on Google AdWords to fit better with the exact wording on the ads, will Google notice this change and update the ads' quality score?
Answer: Definately, It will revisit every time you make some changes in your ads slot. But, If you keep everything as it is like ad copy, url and keywords same but only makes changes to landing page then it won't as you are not changing the ad copy but once you change it will check for sure.


How to export all the attribute and its options in magento 2

Question: I wish to export all the attribute and its options in magento 2 via script.
Please provide me a solution, How to export attributes and its options
Comment: have a look at https://github.com/BssGroup/magento-2-custom-product-attribute-export
Comment: If you can adapt this https://magento.stackexchange.com/questions/11520/how-to-export-and-import-all-attributes-and-attribute-sets-from-one-magento-to-o to magento2 (there is also a lot of links to read)
Answer: I was looking for the same thing and came here. The comment of nicolallias was actually helpful and solved my problem.
I Download and instaled this module
https://github.com/BssGroup/magento-2-custom-product-attribute-export
After installing the extension, go to Store ⇒ Configuration ⇒  BSS Extension ⇒ Product Export Column and in"Allowed Attributes", a list of all custom attribute will be shown. Admins can choose all or specific attributes which will be in separate columns while exporting products.
You can export the products as CSV from System-> Data Transfer -> Export.
Read this for more details.. https://bsscommerce.com/blog/how-to-export-custom-product-attributes-in-magento-2/


Writing XDocument to XLS

Question: I am having my xml data in XDocument (LINQ). I want to write this data into excel data.
I am using console application.
I dont want to use excel com object.
Comment: possible duplicate of [Building Excel Files with C#](http://stackoverflow.com/questions/1704030/building-excel-files-with-c-sharp)
Answer: You can fairly easily create .xslx format documents without using com (or indeed without having excel anywhere near your machine).
There are links in this answer:
Building Excel Files with C#
And if you look in the latest CTP for V2.0 of the open XML SDK you will find a very nice tool that will help reverse engineer the file formats into code as a starting point
Answer: It may not suit your needs in this case but I have often found that writing to a .csv file (which will likely have an association with Excel if installed) makes for an easy to do alternative in many situations.

Writing XDocument to XLS


My question was closed. Is there a way to ask something similar that does fit Q&A?

Question: I asked this question about Observer pattern, so I could get some help with my talk that I have to hold. I understand the problematic part that its teasing a debate, but I tried really hard to phrase it in a way it does fit Q&A format, by specifying 2 things I want to know, so nobody would start a arguing. What can I improve there so it will not get closed? (I have another talk I have to hold in a month or so - and I would be really happy to get peoples support)
Answer: As mentioned in the FAQ, your questions should be about problems that you face that relate to software development. Putting together a presentation or discussion is not an aspect of professional software development, which makes the current wording off-topic. Phrasing your question to only gather opinions or thoughts is also not constructive.
However, the subject matter (in this example, design patterns) is on-topic. So if there's some aspect to the subject that you don't understand or need clarified, that would be acceptable to ask. In your example question, the problem is that you simply ask for suggestions - that's not a suitable question for a Q&A format.
Answer: I don't see how "I'm giving a talk, (details), any suggestions?" isn't a polling question ("polling" as stated in the section of the FAQ cited as the close reason").  A question asking if there are alternatives to the observer pattern other than polling still might get closed as a list question, but I personally probably wouldn't vote to close it.
Answer: One way is to separate it into multiple questions, the question itself has a ton of subquestions inside of it.


How can I remove a deceased co-signer from my Auto-loan?

Question: The person who co-signed my auto-loan has died. How can I remove them from the note?
Comment: The estate may still be liable for the loan....
Comment: The Moderator's edits have changed the question considerably. Do you still have a _loan_ on the truck or is the truck fully paid for and you were you asking how to remove a co-**owner's name** from the _car title?_
Comment: @littleadv +1 and under the other interpretation, the estate of the deceased may own part of the vehicle and so the _title_ cannot be changed to remove the deceased's name leaving the vehicle to the other co-owners.
Comment: Yes truck is paid for want to take name off name from the deceased how do I do that
Comment: This question is about how to obtain a corrected title. +1
Answer: If this is a co-signer on a loan, then it doesn't really matter.  If this was a co-owner on the title (as Dilip Sarwate and you indicate in comments to the question), then it may or may not matter.
If you owned the car in joint tenancy (i.e. with right of survivorship) then you may not need to do anything.  It would be your car with no need to be probated or go through a trust.  Some states automatically treat cars in this fashion.  Other states may include ownership details on the title or make forms for survivorship agreements.  If the deceased was a spouse or perhaps a child or parent, then your state may have a rule that presumes survivorship.
If the ownership is unclear because either you failed to properly specify survivorship or because your state doesn't have a survivorship rule, then you may need to determine what happened to the deceased's estate.  If there was a will, the deceased may have purported to bequeath one half of the vehicle.  If there was no will, then the deceased died intestate and it would go through that process (typically, the intestate share will go spouse, children, or parents).
Once you ascertain who owns the car, this may be as simple as following the DMV process in your state for re-titling a car. (Example: Illinois DMV re-titling upon deceased co-owner).
Of course, speaking pragmatically, if nobody is making noises about taking your car, then I'm not sure you need to be too finicky about crossing the Ts and dotting the lower-case Js.  My understanding is most states allow auto title transactions without the signature of all co-owners.  Failure to properly tidy this issue could put your vehicle in legal limbo (e.g. when somebody claims to own half of it), but it may also never come up if nobody realizes there's anything to dispute.  Pursue the legal and ethical niceties to your comfort level.
Comment: Search for "Corrected Title" in your home state's Secretary of State or DMV website. They usually have a number of scenarios including death.


"detach all" vs "stop debugging"

Question: When using the "Attach To Process" feature in Visual Studio 2008, what is the difference between "detach all" and "stop debugging"?
Answer: "Detach All" will leave the process running "Stop Debugging" will (typically) kill local processes.  It should be noted that they pretty much work the same if you are using remote debugging.
Detach Debugger...
"Detaching from a process does not terminate the process. The process continues running on its host computer even though it is no longer attached to the debugger." -MSDN
Stop Debugging...
"Stop Debugging terminates the process you are debugging if the program was launched from Visual Studio. If you attached to the process, instead of launching it from Visual Studio, the process continues running. If you want to terminate attached processes, you can terminate a single process from the Processes window or terminate all attached process with the Terminate All command." - MSDN
Comment: I tried "Stop Debugging" and it does not kill the process.  It is a service, if that makes any difference.
Comment: That's why I said typically.  Remote processes and services will not be killed.  Only processes in the current user space.  If you were to start an app from VS without the debugger, attach, then click "Stop Debugging" it should kill the process.
Comment: So if it's a service, then there's no difference between "Detach All" and "Stop Debugging"?
Comment: It would appear that IIS Express worker processes are not terminated by "Stop Debugging" either, even if they were initially started by a Visual Studio debugging session.
Answer: If you choose detach all even when you stop the debugging from VS2008 process will still run.
If you do not, if you stop debugging from VS2008 it will stop execution of process you attached to.

"detach all" vs "stop debugging"


Where can I get Wordpress Version in Dashboard?

Question: On the botton of the dashboard WP proposes to upgrade to next version but it doesn't even show current version: does it show it somewhere else ?
Comment: when you're upgraded to the latest version it shows the current version.
Answer: go to your wp-admin dash board there in the Right Now box you will be able to see the currently installed version of your wordpress installation.
as shown in this picture below
Answer: In a newer version of WordPress (3.8.3) the version number wasn't anywhere in plain sight on the dashborad for some reason (someone might have changed something on the site that I had to fix), but the WordPress logo in the upper left corner leads to an about page which says WordPress 3.8.3 (or the one you have) in huge letters.
This question might be 2 years old, but it's quite high on google, so I thought that if I drop this answer here, someone else might find it useful. After all, I got here after searching for an answer for this very question.
Answer: You can visit http://yourdomain.com/readme.html file. This file is default in wordpress setup.
Comment: @kraftner I disagree, this file is part of core and being updated with it, as well as rarely removed in practice. It might not be absolutely reliable, but it's easy and practical method for quick look.
Comment: Some people remove this file for security reason. But its always updated.
Comment: Hi Shail, this is more a guess than a real answer. It may be removed or not up to date as the file isn't needed for WordPress itself.
Answer: For WP version 4, you can check it under At A Glance box. If At A Glance is not visible, tick the option under Screen Options pull down menu.
Answer: click on Dashboard then mark "At a Glance" in screen options. There you will get wordpress version you are using.


Wi-Fi problems using ASUS USB-N13 adapter (realtek)

Question: I have recently bought an ASUS Wi-Fi adapter (USB-N13), and I seem to be having some trouble with it. Every so often, the Wi-Fi connection just stops working, but the indicator says that I'm still connected. I am using the firmware-realtek drivers for the adapter, and not the official ones, as they are difficult to install. I am also using Debian 8 Jessie, if you need to know my OS.
lsusb:
Bus 004 Device 002: ID 8087:0024 Intel Corp. Integrated Rate Matching Hub
Bus 004 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
Bus 003 Device 001: ID 1d6b:0003 Linux Foundation 3.0 root hub
Bus 002 Device 002: ID 0b05:17ab ASUSTek Computer, Inc. USB-N13 802.11n Network Adapter (rev. B1) [Realtek RTL8192CU]
Bus 002 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
Bus 001 Device 004: ID 0738:1705 Mad Catz, Inc.
Bus 001 Device 005: ID 04b3:301b IBM Corp. SK-8815 Keyboard
Bus 001 Device 003: ID 04b3:301a IBM Corp.
Bus 001 Device 002: ID 8087:0024 Intel Corp. Integrated Rate Matching Hub
Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub

Answer: Important note: wifi chipset/USB sticks and internal wifi chipsets should be evaluated concerning their Linux compatibility and not needing to compile source code before buying them.
TLDR
For creating an wifi AP, the most cost wise path is buying an openWRT compatible AP.
For having a more stable wifi connection, choose a notebook/iOT/router device where the WiFi chipset is not internally connected to the USB controller. Avoid realtek.
If having an internal realtek card, try to buy an internal replacement card compatible with the model of your machine based in atheros, broadcom, ralink or Intel, in that order of preference - I suspect Broadcom has the better quality/cost ratio, your mileage may vary. (Important note: your vendor might whitelist wifi card models, in which case you are at mercy of compatible models - HP, Dell and Lenovo are known for this, so check the brand/model of the notebook if you already own it)
Adenda: Usually users report the realtek chipsets work "well" in Windows because Windows drivers have nasty hacks to work around some of the bugs.
However, while they work "better", they usually work at much reduced speed/ranges and still have got problems, and in many realtek implementations, some of the more serious hardware bugs cannot be worked around.
Concerning realtek Chipsets
The ID 0b05:17ab and the string [Realtek RTL8192CU] in your lspci output, confirms your wifi device is indeed a rebranding of the Realtek RTL8192CU 802.11n model.
I also had the Realtek RTL8192 in my ARM server/Lamobo R1 at home, which is the same chipset as your ASUS USB-N13. (or put it other way, ASUS USB-N13 rev B is an ASUS rebranded RTL8192CU).
Believe me that I have tried to do something with it for quite a while as you can see in post #23 of this thread
The chipset is junk. People who own the Lamobo R1 have totally given up in doing something useful with it.
Firmware bugs, drivers bugs, bugs in energy management that are prevalent and ubiquitous across most of the cheap Realtek chipsets revisions/models, that oblige you to use it at slower performances than the allowed by the protocols.
Even after trying to work around the bugs, you have frequent and inexplicable crashes - or more exactly, the wifi module misbehaves and then you are left with the filesystem in read only mode wondering what happened.
I also bought 5dB antennas to try to improve it.
I even also bought again a realtek nano USB wifi that proved to be even more disastrous; it started heating and stopped dead in it´s tracks for a few seconds at a time both in Windows and Linux systems.
The efforts and hassle to make realtek wifi cards working "properly" are not worth the trouble.
I gave up on trying to use my R1 with a realtek as an AP and bought instead an AP from TP-LINK - an Archer C7 v2 which I flashed with OpenWRT. (https://openwrt.org)

If you still want to have a go at the Realtek/ASUS, if in hostapd mode, in /etc/hostapd.conf you have to use
wmm_enabled=0

which makes you lose some speed.
Using it either as hostap or as client, you also have to configure the loading of the module in /etc/modprobe.d/rtl8192cu.conf to work around some of the bugs:
options rtl8192cu  rtw_power_mgnt=0 rtw_enusbss=1 rtw_ips_mode=1

Reboot then the device for the options to take effect.

General advice about WiFi technology
As last comments, specially in WiFi, you have to pay good money to have good chipsets that work as promised.
Normally it is a requirement to have external antennas, especially to use the chipset in AP mode.
Please do take note this chipset only supports the 2.4GHz band. As in most parts of the civilised world the 2.4GHz band is pretty crowded, either you have a good signal, or you are pretty much in trouble. So this reinforces the need for external antennas.
Even if using 5GHz, as the 5GHz protocol was designed to travel smaller distances, external antennas are a must.
Also beware that whilst you might got away with only one antenna in the 2.4GHz band, you need at least two antennas when dealing with 5GHz.
I have good experiences using Ralink and Atheros based chipsets, realtek ones not so much.
UPDATE: I used to have a realtek without shielding in my iOT device, that was not used because it was so bad. I also had crashes almost every week even with the thing blacklisted by software.
Cut it physically from the board, the board can go for months up without misbehaving, and RF interference at home is also lower.
I also bought a very good 10€ no-brand ralink wifi chipset dual frequency stick in aliexpress "300Mbps Dual Band 2.4GHz / 5.8GHz Ralink RT5572N WiFi USB Adapter" so much better, but ended up buying a TP-Link router with OpenWRT and connecting it via Ethernet .
To finish my "rant" about Realtek; while deciding what 5GHz AC AP to buy, I looked at one rather cheap AP, the ASUS EA-N66 which is entirely based in realtek chipset(s). The forums are full of complaints of it locking up mysteriously a couple of times PER WEEK at least.
I would not buy ASUS or Realtek any time soon. IMO they are focused in selling cheap junk that does not work.
REVISITING this answer: in the meanwhile I learnt that there are more deep settled reasons than I knew/suspected, at the kernel/USB level, which give very plausible answers explaining the stability of wifi adapters working better via PCI/card sockets vs the instability of USB-based chipset wifis.
I also learnt the USB wifi market is mostly dominated nowadays by realtek vs ralink, and most of the other brands are just rebrands.
The USB Ralink adapter I bought in AliExpress unfortunately is also an old chipset model with its set of bugs, however between two devils, it works consistently better than a Realtek. OpenBSD manages to work quite well using this Ralink, FreeBSD still has some nasty bugs using it.
PS: I was suggested to buy a USB->PCIe adapter to be able to use better brands of Wifi cards externally. If and when I try/test it, will revisit this answer.
See related question Why do WiFi routers do such a bad job of channel selection?
Comment: I paid $20 for the thing, pretty disappointed. Many people on forums were saying that this specific Wi-Fi adapter was the best for Linux. I feel pretty cheated now.
Comment: Guess I was a little late figuring things out. Could you find a specific chipset or something I could use on Amazon and post it in a comment? I think I can try to complain to Amazon and get my money back, and hopefully buy a better one. (I bought the one I'm using on Amazon.)
Comment: @SpecialBomb I agree with Rui that Realtek is junk. It's not that hard to find good quality hardware; but you have to spend a little time reading reviews and so forth. You could also search on https://hardwarerecs.stackexchange.com/ to see if that question has already been covered, and ask one if not. In general Intel makes decent hardware, I think, and they always seem to cooperate with the community, so generally they have free drivers for their hardware.
Comment: The answer to https://hardwarerecs.stackexchange.com/questions/5527/pcie-wifi-card recommends http://www.newegg.com/Product/Product.aspx?Item=N82E16833704133 and that certainly gets good reviews on Amazon and other places, and has multiple reports that it works out of the box on Linux. One review said it has an Atheros chipset.
Comment: Hoo boy, its been a while. Since this, I got a PCIe wifi card that uses an atheros chipset. Everything is pretty much fine now.

That lsusb output looks absolutely nostalgic to me. I was still using my shitty R.A.T. 5 mouse, and god knows what keyboard I was using, lol. This post pretty much marked my initial transition to GNU/Linux, so thank you all!
Comment: @RuiFRibeiro go the heck ahead, realtek needs to just stop making chips and drivers.
Comment: In aliexpress you can buy this chipset for peanuts, from many chinese wifi manufacturers. The chipset itself apparently costs cents to them, it is fairly easy to find wifi USBs in the range of 3USD-10USD there. They are all junk.
Comment: I returned to add something more to the answer about the dynamics of 2.4GHz. As I said I ended up buying a TP-LINK router, and using the ARM only as router to the Internet. The TP-LINK Archer C7 v2 with 5 gibabit ports, 802.11 for AC, 2 internals antenas for 2.4GHz, 3 external for 5GHz, and the change to put Linux/OpenWrt there for 100USD is a pretty good deal.
Comment: Have a look at those. It will be up to you to do some research about Linux compatibility, I wont have got the time in the next few days.  http://www.amazon.com/TP-LINK-TL-WN821N-Wireless-Adapter-300Mbps/dp/B002T4D3M2/ref=sr_1_4 and http://www.amazon.com/Alfa-AWUS036NHA-Wireless-Adaptor-Compatible/dp/B004Y6MIXS/ref=sr_1_1 and http://www.amazon.com/Docooler-Adapter-150Mbps-Atheros-Antenna/dp/B00IZ5GNSA/ref=sr_1_2
Comment: And [this answer](https://hardwarerecs.stackexchange.com/a/4249/1024) suggests a Gigabyte card with somewhat more mixed reviews. This one has an Intel chipset.
Comment: @SpecialBomb if you do not mind, I have been using/abusing this post as a placeholder about realtek vs other wifi chipsets.
Comment: There are a couple of different drivers for the 8192cu. The built in kernel drivers do not support AP mode. My 8192 came with a disk with the source code. I built it and it works perfectly including AP mode. If you do lsmod the bad driver is "rtl8xxx" the good driver is 8192cu".
Comment: @MikeSeeds The 8192cu already existed by the time I wrote this answer...the hw is quite bad, it is not a driver problem per se.


How to get all pages awaiting moderation in Wagtail

Question: I'm trying to find a way to query all pages that are currently awaiting moderation.
I tried PageRevision.objects.filter(submitted_for_moderation=True).values('page_id'), but it seems to return only a few of them, I don't understand why.
If i can get all pages in moderation, then i will be able to get what I really want : all pages awaiting moderation for the user currently logged in.
Thanks a lot.
Answer: The submitted_for_moderation field is only used by the legacy moderation system that was deprecated in Wagtail 2.10 - pages submitted for moderation since then will use the Workflow system.
The equivalent to your query would be:
PageRevision.objects.filter(task_states__status='in_progress').values('page_id')

From Wagtail 4.0 onward PageRevision was replaced with a Revision model that covers snippet models too, so this will become:
Revision.page_revisions.filter(task_states__status='in_progress').values('object_id')

Answer: I don't know what version of Wagtail you are using but from the code provided, it looks like you are using the legacy moderation functionality. Please note that that is deprecated and will be removed completely in 2024. If you can upgrade, then the list of pages in moderation (aka in a workflow) will be automatically added to the dashboard for your users. (If you upgrade step by step, the system should automatically create a simple workflow that mimics the older moderation system.)


Are principles a good thing?

Question: I've been reading a lot about history and some of the philosophical forces behind major events. It seems to be that the more fanatical a ruler / figure is, the more they justified their beliefs with their principles. My question is, can we ever know if what we believe is right or wrong? Can we really be sure we aren't making the world a worse place in the name of something we might believe in but could just be a lie?
Comment: Hayakawa, S. I. Language in Thought and Action. 1939. Enlarged ed. San Diego: Harcourt Brace Jovanovich, 1978. Originally published as Language in Action;  and https://en.m.wikipedia.org/wiki/Alfred_Korzybski  We are not required to fall in and follow the leader. I would amend Korzybski's famous saying like this: the ideological map is rarely the territory. We have to check our ideas against reality, though it takes a real effort to do this.
Comment: @CriglCragl Lol. That may well be true, but his little saying is good to remember. I am mainly taking off from his quote and making it mine. I must say that I think his idea of "time binding" is interesting, it's the first time I had read down that far in his Wikipedia.
Comment: 'Principles' - what do you mean by that? eg scientific principles..?
Comment: @CriglCragl I guess in my colloquium I use it to refer to informal personal philosophy
Comment: @Gordon Korzybski was a top geezer
Comment: It is not really possible to ask whether something absolutely necessary is a good thing.  I would argue that any structured action has principles.  Sometimes they are expressed and sometimes they are implicit, but human behavior is basically driven by rules and observations.  One might argue that expressing one's principles is dangerous, but it is also efficient, to the degree it can be honest.  And they would be there anyway, if one did not 'espouse' them openly.
Answer:
My question is, can we ever know if what we believe is right or wrong?

Knowledge doesn't require absolute certainty. When I say, "I know there's a cat on the mat.", then I leave open the possibility of doubting it. What exactly makes knowledge different from belief is of course not an easy question and gets us to a ton of problems in epistemology.
Take for example the question, "We believe that there's an external world. But what if we're wrong?". This idea can get turned around: what reasons do we have for the skepticism in the first place? Why should we doubt it? While this can deal with some sorts of radical skepticism rather easily with issues like ethics it gets a little more complicated.

Can we really be sure we aren't making the world a worse place in the
  name of something we might believe in but could just be a lie?

This is an interesting problem which I think can be divided up into parts. Firstly we may ask, "How should we go about getting moral knowledge?". (Of course this presupposes that there in fact is moral knowledge in some way. So some metaethical stances would rule out that we can get moral knowledge.) Secondly we may ask, "But what if we're wrong? How should we take that possibility into account?".
The first issue is about Moral Epistemology. Depending on what sort of stances we defend in epistemology this influences what kind of methods we ought to use to make or revise moral judgments. Here's a basic article about it. Depending on what we believe we could for example argue that there are some principles that we should base our moral beliefs on. Or we might argue that we ought to find a balance between principles and preexisting moral beliefs, make them as coherent as possible.
The second issue is the concept of Moral Uncertainty. The question concerns basically an intersection of ethics with decision theory. Here's a very short description with further references.
Comment: Knowledge is extreme case of belief when opposite to 'knowledge' is much less likely than opposite to 'belief'.
Comment: So you seem to say knowledge is belief with a higher likelyhood of being true? How are we able to say which is more likely?

Also, if something I believed to be much more likely true turns out as not the case then have I known it or not beforehand?
Comment: The only thing that makes us say that something is known is statistics. E.g. we say we know that if you jump, you'll fall back because every other time you did it it was the same.
Comment: So there's no mathematical knowledge? Also, take a case with a single occurence, "I knew that I've seen person X yesterday at the train station.". How do you know that "The only thing that makes us say that something is known is statistics." with statistics only?
Comment: Well, what are disputable things in that statement, except "I knew that"? There, of course, can be persons who look almost identically. But from statistical point of view it's very unlikely that they live in same town (except for twins - then statement makes less sense). Thus you use statistics. Well, you also use probabilities as extrapolation of statistics, but it comes from statistics. Without them you can't guess the probability. Also you might argue that you know it's train station. Just because all similar objects are called so.
Answer:
Can we really be sure we aren't making the world a worse place in the
  name of something we might believe in but could just be a lie?

If a person believes that this world is one family and live accordingly without hurting his fellow beings following 'Dharma', his principles are right; no matter whether he is a fanatical ruler or not. [Please note: The base is, 'This world is one family'.  If you don't like the word 'Dharma', you may replace it by 'the eternal law of the cosmos, inherent in the very nature of things'.]

My question is, can we ever know if what we believe is right or wrong?

Here, the word--'ever' creates a problem.  If one believes that there is/must be a continuity to his life (I mean, birth and rebirth), the word--'ever' gets a greater meaning. Then the answer is 'Yes'.  Otherwise the answer is--'Not quite sure' or 'Rarely'.
For clarification and epitomes you may read about 'Rajarshis'. Such ruler's principles are good things. After they attained self-realization they couldn't tell lies.
https://en.wikipedia.org/wiki/Vasudhaiva_Kutumbakam
Comment: There are plenty of dysfunctional families out there..
Comment: @CriglCragl: Of course.  But if you think over the entity of families or the reason behind that problem, you can't reject them completely.
Answer:
can we ever know if what we believe is right or wrong? Can we really be sure we aren't making the world a worse place

The short answer is no, we can only guess. But we can attempt to make informed guesses, by studying history, psychology such as cognitive bias, and orderly systematic observations such as through scientific methods.
You might equally ask, can we live without principles? Would that simply cause other threats? One response goes "If we don't stand for something, we'll fall for anything."
Your "informal personal philosophy", everyone must have. Principles generally mean something like core tenets, or conclusions drawn about the world thought or experience, especially of a moral character and concise.
I am a bit dubious about your knowledge of history, leaders from Idi Amin to Caligula have managed to be perfectly brutal with almost no principles. Stalin & Hitler were egotistical opportunists with full faith in propaganda, so no real belief in their own principles except as tools for wielding power. Fanaticism, an unjustified sense of certainty, rather than principles, seem to be the real problem. It can be identified as a pathology, and addressed culturally and educationally.

in the name of something we might believe in but could just be a lie?

What structure are you assuming to determine 'lie'? If it's subjective, a sense of rightness or importance to a set of principles, how can those feelings be falsified? The principles could be contradictory, or could be aimed at goals they rarely do or cannot achieve. Or they might be murderous, horrific and evil. But probably not lies.
Comment: Fanaticism also is consequence of some set of principles.
Comment: @rus9384: https://www.smithsonianmag.com/science-nature/the-pros-to-being-a-psychopath-96723962/
Comment: Yes, character traits affect what principles one might adhere. But there are other factors as well. And those factors are former while principles are censequent to that.
Answer: Well, a lot of people think that science can resolve the problem of being sure.  The nice thing about science (as taught by Karl Popper) is that whenever it's sure of something, that thing is repeatable.  That makes science neutral with regards to different philosophical viewpoints.  But the aching problem with science is that it doesn't have that kind of certainty about what's unrepeatable, like origins, or fundamentally invisible, like morality.
Rene Descartes wrote, "I think therefore I am."  Rather than being a congratulation of self, this statement is meant to find some hard floor in reasoning, something that really can't be negated.  And "well, at least I know that I am thinking right now" was a pretty good shot.  But that won't tell you how to run a government.
I think an acceptable next step for Descartes would have been to say, "Other people are just like me."  From there one could identify equality and justice, which are pretty stable values throughout time.
Your Question
...is a very good one!  Here's an example supporting your argument:

In his book Morality after Auschwitz, Peter Haas asks how an entire
  society could have willingly participated in a state-sponsored program
  of mass torture and genocide for over a decade without any serious
  opposition. He argues that
far from being contemptuous of ethics, the perpetrators acted in
  strict conformity with an ethic which held that, however difficult and
  unpleasant the task might have been, mass extermination of the Jews
  and Gypsies was entirely justified. . . . the Holocaust as a sustained
  effort was possible only because a new ethic was in place that did not
  define the arrest and deportation of Jews as wrong and in fact defined
  it as ethically tolerable and ever good.

from Can we be good without God? - William Lane Craig

Are principles a good thing?


how do I can check whether a sound clip I want to use is copyrighted? (I want to use it in a video and an app also)

Question: as mentioned in title, I want to be sure that a sound I found on youtube (2 seconds long) is copyrighted
(and also, if I will modify it (in audacity or something) will it still break copyright laws?)
Comment: Hire a specialist to clear the rights or create your own sound or contact the creator and just ask. The work is most likely copyrighted, unless the sound designer is long dead, e.g. more than 70 years or sth. similar depending on the country you live in. There are licenses that allow free usage under certain conditions (like Creative Commons) but those are little used. There are some exemptions in copyright law that would allow you to use the sound without permission, but without knowing all the details about your project and your country's specific copyright law this cannot be answered.
Comment: By the way, if the sound is merely a recording of something mundane, like a car driving by, it may not be copyrighted, because it's to trivial. But check your national copyright law if there is such a limitation stated.
Comment: https://www.youtube.com/watch?v=EDX_KXGHirE (the sound)
Answer: Please note, for this answer I use the term copyright as a synonym for whatever law is applicable in your country that deals with protecting intellectual property rights for creative works. Some countries use quite different names for such a law.
Here's a little guide how this topic can be approached. In a professional context, I advise to consult a specialist to clear the rights for you. When you can try to create as much creative content as possible on your own. However, when you decide to tackle the issue of clearing rights yourself this is how I would do it:

Check if the copyright has been expired. Read the law (or at least Wikipedia) to find out how long this time span is in your country. Usually, it's a very long time, so you will rarely find anything from the 2nd half of 20th century or newer with expired copyright.

Find out which copyright limitations or exemptions are defined in the law in your country (e.g. "fair use" in US law). Usually you don't have to ask the creator for permission to freely use their work as parody, in an educational context or when citing an excerpt, but pay attention to quote only the bare minimum.

In most countries there should be a threshold when copyright can be applied. Sometimes the work is so trivial that it shows not enough merit to be protected by the copyright law. In some countries the threshold is very low and you have to read a lot of court decisions to get a good grasp how this is interpreted in practise. If we take a look at your example, after hearing it several times, I am somewhat sure that it is not a simple, plain recording. Either they have created the sound digitally or invested some energy in cleaning up and tweaking a recording. This probably means it has enough merit to be protected. This is my opinion based on what I know how such a case might be judged in my country and if it applies to yours too, you have to decided for yourself.

If none of the above conditions are fulfilled or you are unsure (for example in case of orphaned works), it is safe to assume that the work is protected. If you still want to use the work, check what license options are available. Sometimes Creative Commons allow you free usage of the work but you need to carefully follow every condition they make. Creative Commons comes in various versions and variants. Especially for commercial projects their conditions are often hard or impossible to fulfill. When you do not find any license information, you can always try to contact the creator and discuss business and agree upon a contract for your situation. It will probably cost you a bit but usually you are on the safe side with a contract. If you do not know much about contract law, it will be best to hire a lawyer. However, you have to make sure you are talking to the rightful copyright owner, not to someone who has just published the work with or even without permission and pretends to be the owner. For the example you have provided in the comments to your question, I have my doubt how well such an agreement works, as this person has no contact information on their channel which indicates a non-professional context. This always complicates things.

Do not use YouTube to search for sounds when you need them published along with your own work even in an edited version, like in your case where you want to built an app and use the sound there and in videos. Use trustworthy sources instead, that means professional sound libraries with clearly stated terms of service and license terms. Besides, maybe you already have access to royalty free sounds without knowing it via some software subcription you may have. For example, Adobe offers such sounds when you are a subscriber to their Creative Cloud.

I will not give legal advice how to proceed, but my general recommendation is to look for sounds at some better place, as described in step 5 above, because buying a proper license from this YouTuber person might be hard work. I guess they are not prepared for such a scenario and have no contracts ready, no license terms, etc.


How to convert address type to bytes32 via web3?

Question: I have contract which require input in bytes32, so I need convert address to bytes32, but no see this method in web3.
Answer: Ethereum addresses are 20 bytes, so you convert hex address to bytes and then pad it to 32 bytes from left.
web3.utils.padLeft(web3.utils.hexToBytes(yourAddressString), 32);

Answer: If you read the PadLeft documentation, you'd see that you don't need to do any conversion. You simply should do a web3.utils.padLeft(address, 64). Given that you want bytes32, that is a total of 64 hex digits, you just need to fill the difference in 0s for in order to have 64 digits.
Comment: For `ethers v6`, you can use `zeroPadValue()` For example ethers.zeroPadValue(0xC02aaA39b223FE8D0A0e5C4F27eAD9083C756Cc2, 32) to pad the address to a 32 bytes.


How to wire GFCI outlet to aluminum wiring?

Question: How to wire gfci to aluminum wiring. Have not tried to yet, i want to be sure as to how first. I've been told of using no-ox and 6" copper pig tails.
Comment: This is covered pretty well here: [What's the best way of replacing a plug or switch in a house with aluminum wiring?](http://diy.stackexchange.com/q/291/157). There's no difference when using a GFCI.
Comment: Not a dupe.  Saying it's a dupe equals telling them to splice the Al wires to fit the GFCI+receptacle.  We should tell them not to. The answer is put GFCI protection upstream of that location, e.g. In the service panel as a GFCI+AFCI breaker.  I recommend fitting an AFCI anyway for Al wire, so kill two birds with one stone.
Answer: All no-ox joint compounds are not equal. Penetrox A (mfgr Burndy) is non-flammable grease. 35 years ago I pig-tailed our aluminum wiring with No-Al-Ox and Scotchlok twist on connectors. No-Al-Ox I later found out (and confirmed myself) is flammable. I'm in the slow and gradual process of redoing the pigtails with AlumiConn connectors which are pre-packed with anti-oxidant grease. However, none of my old  connections with No-Al-Ox has shown any evidence of heating or failure.
Unfortunately AlumniConns are not always available except by order. They come in 2-port and 3-port. In some cases the 2-port might be necessary to be able to fit a bulky device and all the connections and wires into the box. Also use #14 wire for the pig-tails if the circuit is 15-A because it folds and fits much easier than the #12 required for 20-A circuits.
The instructions for tightening the screws on the AlumiConn connectors are to use a torque screwdriver (10 in-lb for #12 AL and 15 in-lb for #10 AL and for #14 and #12 CU). There used to be alternative instructions on number of turns after contact with the wire, but I haven't found that lately.


Adobe InDesign black text being detected by printer as colour when exported to .pdf file

Question: I print a small bulletin with 12 pages, the first is in colour, the rest is b&W text. When I export to .pdf the .pdf file is interpreted by the printer as black created by all the colours, not the straight black. Is there a way of exporting so that the black text stays black and is not printed as a colour page?
Comment: Does the PDF have registration, bleed, or trim marks?
Answer: In general, straight black channel text will not be converted to 4 color black unless you have your InDesign preferences set incorrectly. And Adobe has them set incorrectly by default.
Choose File > Preferences > Appearance of Black from the menu in InDesign.
Be certain to set the Print/Exporting option to "Output All Blacks Accurately".

And then be certain your type is set with the Black swatch and not the Registration swatch by mistake.
This should then generate a PDF with straight black type as opposed to 4-color type.
Comment: All the settings as above has been confirmed in Indesign, but when the exported PDF is printed on a colour printer the text still prints as CMYK


construct_runtime macro panics in a mock environment while it builds in normal runtime

Question: Trying to create a mock environment for testing a pallet, but getting an error msg failed to resolve: could not find tt_error_token in the crate root whenever trying to add my pallet in the mock environment.
Comment: are you importing the pallet and implementing its `Configs` before adding it to `construct_runtime`?
Answer: I'd suggest to take this pallet as a template for yours. Is a pallet template from the Substrate Developer Hub repo.
In this you can see how to mock the environment:
frame_support::construct_runtime!(
 pub enum Test where
    Block = Block,
    NodeBlock = Block,
    UncheckedExtrinsic = UncheckedExtrinsic,
 {
    System: frame_system,
    TemplateModule: pallet_template,
 }
);

Adding the pallet_template:
impl pallet_template::Config for Test {
  type RuntimeEvent = RuntimeEvent;
}

And how to create the unit tests.


Lennox gas furnace maintenance

Question: I bought brand new Lennox HE natural gas furnace 3 years back. It has been running perfectly. My dealer recommends to do a preventive maintenance because of 3 years time span. I regularly change the filters (Only 3M brand). I live in Southern Ontario, Canada, where temp goes in negative double digits (around -25 C) in winter. Question is does it require any preventive maintenance and what kind of ?
Comment: Heat exchangers are probably the most expensive failure. Whether you opt to pay for cleaning of yours is up to you. It's a bit of a chore to get to it.
Answer: Of course you can do nothing but change the filters but that will affect the reliability and service life of the unit.
There is more to these things than just a filter.  A furnace service usually includes a cleaning of the blower motor, an inspection of the burner and housing for any cracks or leaks (a HUGE safety concern!), inspection of the ignition system, inspection of the thermostat, as well as some other stuff depending on the unit.
Yes, it costs money but so does replacing a furnace prematurely or having the heat go out at the worst possible time and having to pay overtime or holiday rates for an emergency service call.
Comment: ...also checking the fuel/air ratio and combustion byproducts so it's burning as efficently as possible. With oil burners, annual checkup by a licensed service tech is typically required to maintain your insurance coverage - not sure with gas burners.
Comment: Yeah, having the unit checked for proper combustion every now and then is a good idea for sure
Answer: Changing the filter is a must and good for you for doing it. There are things that must be done to extend the life and efficiency of your furnace. Most important is cleaning the burners and checking the blower motor. Most are direct drive so they don't have belts but they can and do get real dirty. The blower blades have to be cleaned too. They will also check the venting for any signs of blockage. People like to skip this routine maintenance because it costs bucks but it's needed and could effect your warranty down the road if you don't do it.

Lennox gas furnace maintenance


What are the chances of a paper being accepted after

Question: I got minor revision in the first round of review. The main concern of the reviewer was to add the details in methods section and some amendments in the text. I re-submitted the paper after incorporating these changes in the manuscript (I work in Biology field). But the status of the paper is showing  "under review" again. Does it mean the manuscript will go through peer review again? what are the chances of the paper being accepted? Please help..
Comment: There is no conceivable way for anyone to answer this given we know nothing about the papers content, the journal you're applying to or the field you're in. It's under review again, meaning they're looking at your revisions to evaluate if they want to publish it.
Comment: like what @Eppicurt said, it's hard to tell without knowing the details, but if after the first round of review, the verdict is "minor revision", and you've done what the reviewers suggested, then I would say it has a good chance of being accepted (this is from my own experience both as author and reviewer, but NOT in biology field), worst case you probably have to revise again. In either case, I won't worry about the "under review" status.
Answer: Whether or not the manuscript is going through peer review again depends on the editorial manager system the journal is using. If the status goes something like "submitted to journal" -> "editor assigned" -> "under review", then yes, it means your paper is going through peer review again. If it goes "submitted to journal" -> "under review" (i.e. it doesn't tell you that an editor has been assigned), then there's no way to tell until you receive a decision. A quick decision implies it didn't go through peer review again; a slow one and / or reviewer comments indicates it did.
There's no way to be sure if the the paper is likely to be accepted without knowing more about the paper's content & the review. However, based on your description, chances are good it'll be accepted eventually. If the corrections are minor and you've performed them, there's no reason for rejection.


For which infinite dimensional real normed linear spaces $X$ , can we say that every infinite dimensional subspace of it is closed in $X$ ?

Question: For which infinite dimensional real normed linear spaces $X$ , can we say that every infinite dimensional subspace of it is closed in $X$ ? Or , does every infinite dimensional normed linear space has an infinite dimensional proper subspace which is not closed  ?
Answer: Every infinite-dimensional normed space has a non-closed subspace.
Let $X$ be an infinite-dimensional normed space, let $a$ be a nonzero vector. Assume by induction that we have found vectors $x_1, x_2, \dots, x_{n-1}$ for which $|x_i - a| < 1/i$ and $a \not\in V_{n-1} = \Sigma_{i=1}^{n-1} \mathbf{R}x_i$. We will extend this sequence by finding an $n$th term $x_n$. This will be sufficient, since the space $\bigcup_{i=1}^{+\infty} V_i$ will not contain $a$, but will have $a$ in its closure.
Clearly, because $X$ is infinite-dimensional, the ball $B$ of radius $1/n$ around $a$ cannot be contained in any finite-dimensional subspace. It is therefore possible to pick some $x_n \in B$ that does not belong to $V_{n-1} \oplus \mathbf{R}a$. This $x_n$ works.
Answer: Hard to beat the simple solution of @Keith:
We'll give a proof for $X$ infinite dimensional Banach space (extra condition).
First, show that there exists a sequence $x_n$ in $X$ such that $||x_n|| =1$ and $d(x_n, \langle x_1, \ldots x_{n-1}\rangle ) \ge \frac{1}{2}$.  One constructs the sequence inductively. Once $x_1$, $\ldots x_{n-1}$ are obtained, take $y \not \in \langle x_1, \ldots x_{n-1}\rangle$ , $x = y - \sum_{i=1}^{n-1} c_i x_i$ so that $||y|| \le 2 d (x, \langle x_1, \ldots x_{n-1}\rangle )$, and $x_n = \frac{x}{||x||}$.
Now that we have the sequence $(x_n)$, consider sums $s=\sum \alpha_n x_n$, with $\sum |\alpha_n| < \infty$. If the sequence $\alpha_n$ decreases fast enough all these sums will not be in the space $\langle x_n \rangle_{n\ge 0}$. Indeed: $$d(s,\langle x_1, \ldots x_{n-1}\rangle) = d(\alpha_n x_n + \cdots, \langle x_1, \ldots x_{n-1}\rangle)\ge \\
\ge \alpha_n d ( x_n, \langle x_1, \ldots x_{n-1}\rangle) - || \alpha_{n+1} x_{n+1} + \cdots ||\ge \frac{\alpha_n}{2} - \sum_{k \ge n+1} \alpha_k$$
For instance, we can take $\alpha_n = q^n$ with $|q| < \frac{1}{3}$.
In fact, this shows that any countable dimensional subspace of a Banach space is not closed.


Photo copy of ration card as ID proof

Question: My maid is travelling with me by air but I only have a photocopy of her ration card as an ID card. Will that be acceptable by airline and airport authority?
Comment: Welcome to Travel SE. You need to specify *where* you want to travel. Such a photocopy is *almost certainly* not enough to cross an international border. Anything within the border depends on the security requirements where you live.
Answer: It is specifically not accepted as a document of identity or proof residence since April 1, 2016. Source: Government of India. http://passportindia.gov.in/AppOnlineProject/pdf/CBE_0134853_Y.pdf
Answer: There are two places that can potentially impact you here- gaining access to the airport and the airline you are flying with. So you should contact them and ask. But it is highly unlikely that a copy will suffice in any circumstance. Air India, for example, specifies a number of cards or documents, the common issue between them all being that they all are original and have a photo:
http://www.airindia.in/documents-to-carry.htm
Note though they do supply the alternative:

In case the Customers do not possess any of the above documents, they
  should carry a relevant attested document that contains a recent
  photograph of the traveling Customers.

Attestation is something that can be done by a notary, or a number of other professionals in India, such as teachers or army officers of a certain rank. But for them to attest a copy they are likely going to want to see the original... so you are back to square one.
Presuming it is a domestic flight Indian airlines do accept quite a wide variety of documents, but in most cases they have to be original and they have to have a photo- so attempting to get her some official photo ID might be advisable.

Photo copy of ration card as ID proof


How to read check number and bank routing number of scanned check

Question: I m scanning the check and i want to read the check number and bank routing number of that scanned check. please can any one help me with sample code.
Comment: This is a pretty complicated problem and customized OCR for the font bank checks use. You can't expect the community to write your entire project.
Comment: I m not expecting to write entire project...... i already tried out with ocr reader but that didn't give me accurate result... it is not identifying properly so i want searching for the other one.. please help me out with other idea or dll
Comment: In which case, you should specify what you've tried in your question (specific techniques, libraries, etc)
Comment: i used ocr reader in that the micr text is-  024418 530039001 40061 29... numbers in it.  but ocr reader reading it as C IL LB"1 S3ooB900L and some times like this C IL LB"1 53003900    and reading different digits for same check..
Comment: If you limit the OCR character set to 'Numeric Only' for this field then you would get much better results.  This check number line is always at the bottom of the form so you could run a second OCR pass just on that part of the page using "0123456789.-:"
Answer: The original scheme for the routing and account numbers used in the US and many other places around the world was optimized specifically for its ability to be machine read.  Early on they used a single channel magnetic read head in order to perform this read, as the ink used to print these numbers was magnetic.  This meant that the numbers could be read even if obscured with stamps, writing other other printed material.
In fact, the ability to read these is rather simple once you understand how the characters are formed.  Probably the easiest way to understand is to look at the first page of the related patent:
http://www.freepatentsonline.com/3000000.pdf

So you have a number, and next to each number is a short graph.  This graph describes the amount of ink used to print the number as you scan across the number horizontally.
As you can readily see, each number has a very unique signature. The actual MICR font (E-13B) is even more distinct in this regard, and the special characters and terminators surrounding the numbers have the same characteristic - they have a unique signature when you scan horizontally along them and figure out how much "black" was used for each vertical column.
I don't have the MICR spec in front of me, but its boxy appearance occurs on a grid of, I believe, 0.013 inches.
So you need merely do a little feature identification (find the corners of the check, as the numbers are always printed in the same spot) then you can simply scan each vertical column, add up the number of pixels that are black to form the "signal" and look for the features. By resizing the image so you get four pixels per 0.013 inches, you reduce the amount of data you have to process.  If you do your feature identification perfectly, you can reduce your resolution to 1 pixel per 0.013 inches and get very close to comparing a few large integers per digit.
They will be distinct enough that you should be able to brute force it, but if you are into digital signal processing (or handy with google and wikipedia) then you can use a simple correlator to identify the digits very quickly, even using a higher resolution.
Other resources:

http://mdn.morovia.com/kb/entry/10616/Check-Processing-Fonts-Around-the-World/
http://en.wikipedia.org/wiki/Magnetic_ink_character_recognition
http://home.comcast.net/~hayosh/HISTMICR.pdf
Comment: A well-researched answer for "user".
Answer: You'll need some sort of OCR library to analyze the scanned image for useful information. A search for "c# ocr library" on Google yielded several results, including this one here on SO: https://stackoverflow.com/questions/744966/any-open-source-c-ocr-library