Can listening during sleep help language learning?

Question: What are the effects of sleep listening on language skills and aren't there any negative effects of it on overall physiological health? Are there any studies or your personal experiences proving that you can improve your language skills just by listening while you are sleeping?
Answer: There is a Wikipedia page about Sleep-learning (hypnopædia, or hypnopedia) referring to two studies indicating no significant learning effects during sleeping:

Since the electroencephalography studies by Charles W. Simon and William H. Emmons in 1956, learning by sleep has not been taken seriously. The researchers concluded that learning during sleep was "impractical and probably impossible". They reported that stimulus material presented during sleep was not recalled later when the subject awoke unless alpha wave activity occurred at the same time the stimulus material was given. Since alpha activity during sleep indicates the subject is about to awake, the researchers felt that any learning occurred in a waking state.
In 2012, research from the Weizmann Institute of Science indicated that classical conditioning can occur during sleep by using odor recognition. "During sleep, humans can strengthen previously acquired memories, but whether they can acquire entirely new information remains unknown. .."

P.S. It reminded me of an episode of Dexter: "The Big Cheese"; where he tries to learn French by playing a tape during his sleep, but it gets stuck at "Omelette du fromage".
Comment: +1 for Dexter's lab. :) I believe it's omelette _au_ fromage (I am not a French speaker), but that's neither here nor there.
Comment: @Hatchet Well, it's rather anticlimactic; couldn't they have made the "buy" link go to a picture of Duo rolling on the floor laughing, and link to the home page from there? :-P
Comment: @erip: In the series they actually use "du fromage", but in some other places I see [omelette au fromage](http://www.cuisineaz.com/recettes/omelette-au-fromage-35407.aspx).
Comment: According to [this answer](http://french.stackexchange.com/a/10900) you ar right, and "omelette du fromage" is actually wrong.
Comment: So [this](http://pillow.duolingo.com/) won't work?!? Aw, shucks.
Comment: I wish this worked!
Comment: @Hatchet I just clicked that link,... the "buy" link did nothing but send me to the Duolingo home page! I wonder when that "pillow" site was posted... could it have been on April 1?
Comment: @kristan That's exactly right!


How to install a Brother MFC-5890CN scanner/printer

Question: I had my Brother MFC-5890CN scanner/printer working with Ubuntu 10.*.
Now that I have upgraded to 12.04 LTS, the printer is still working but my scanner fails.
Answer: Ubuntu 12.04 is no longer supported but here is an answer for 16.04: How to get a Brother DCP-350C scanner working?.
To summarize the answer, first go to the Brother Printer/Scanner website. Then select your printer model:

Select the right product (Printer/Scanner). In the printer icon for MFC-J410W, click the link Not your product? and a selection page appears:

The screen below is for the MFC350 printer/scanner which has a sub-menu for "DCP 3 Series" which leads to a specific model:

My printer is the fourth icon in the panel, which being 3 icons wide is immediately below yours. I'll select that and it has a sub-menu for "DCP 7 Series" which after clicking presents:

I'll click on DCP-7065DN. You would have already selected DCP-350C on the previous screenshot.
After selecting the printer model, you are asked for your OS. It defaults to Linux and ".rpm". The default is ".rpm" which stands for Red Hat or Arch Linux or something like that. Change the distro to ".deb" which stands for Debian which is really Ubuntu.

Above is a summary of the link. Click on the link for the full tutorial.
Answer: I found information that might help your problem from this link.
You could either run xsane with root or you may adduser <user> lp. I tried and they both work.
Comment: this is not ideal and should be avoided if there is another fix.
Comment: It is possible to use xsane without root if one installs the brother-udev-rule-type package on brothers website.


Can schools track what I'm doing, even though I'm on my personal Gmail account?

Question: My school can track my browsing when I'm at home and using the Google account they gave me, the laptop is my personal one. Is there a way that they could track what I do, even though I'm on my other Google account? My school email has been on my laptop for a year or 2 and I'm just concerned that they could track things such as my bank information and business information.
Answer: No. They would have access to the stuff you do on your school account. They can't access everything just through their access to your school account.
There are other ways for them to see what you do on the computer if they have things installed on it.
Answer: Google is quite capable of correlating multiple accounts from the same machine. I don't believe they make this cross-account information available to individual account holders but have not specifically checked for it.
The main point I wanted to make was:
"... Is there a way that they could track what I do, even though I'm on my other Google account. ..."
Don't log into Google except when necessary, such as to check email.
Google already has extensive tracking capabilities through a myriad of agreements with other web sites. Don't make things easier for them!
Comment: The question is about the *school* tracking the activities. Not Google ...
Comment: @schroeder - Google is instrinsic to the question and appears in both the title and body, as I'm sure you know perfectly well.
Comment: ... yes, I see that, but that's besides the point that the subject of the question is about the school tracking the student, not Google ...
Answer: Probably not, unless you agreed to install some additional software.  Elaborating on @schroeder's answer, additional software that somehow reports back to the school could in theory check your web cache or other artifacts on disk or see what is currently running on your device.  Web browser extensions or plug-ins would have the easiest time seeing what you are doing in your browser outside of your school account.
To be cautious, you can use a separate account for your school stuff.  However, if you installed something that has administrative privileges or was installed with administrative privileges, that could possibly have visibility into other accounts.  So, to be the most paranoid, you could have a whole separate device.
Of course, that is likely overkill.  Assess your risk (think about what could happen if they did see what you are doing and the chance that they actually could/would).  If you are doing something illegal or that could expose you to large financial consequences (e.g., lawsuits or loss of a hard-to-replace job) or damaged valued personal relationships, then you may want to act paranoid, if you in fact installed additional software.
Comment: Student monitoring software acts like a proxy. All traffic goes through it, before encryption, to inspect the traffic. They tend to be bundled with root certificates for this purpose. So, it doesn't "check your web cache or other artifacts". This also means that a "separate device user account" might not work. We already have multiple questions about how this software works and I didn't get into it because we don't even know if monitoring agents were installed.
Comment: It's _unfair_ to associate the OP's legitimate concern about his privacy with paranoia and illegality. In fact, in many jurisdictions, it is illegal to eavesdrop on somebody's personal accounts or internet activity, whether it's a school or anybody else. Besides the fact that it is questionable from an ethical point of view.


How do I build the Beacon in a Swamp

Question: So whenever I send some followers up to build this beacon they last about a couple seconds before dropping dead. I'm thinking that the swamp right below the beacon is killing them. Does anyone have an idea?
Comment: @Andrew *please use the right tag*. Otherwise you end up with everyone being confused, which gets nobody anywhere
Comment: What mod is this from? What are "followers"? (They aren't in Vanilla MC) and could you include a picture?
Comment: I'm using the iPhone version of Godus and followers are the people that are in the game in the houses and stuff. The the swamp seems to affect them because every time I send people up they die
Answer: Yes, swamp will slow down followers and get them stuck, and sometimes kill them. The longer they spend on the swamp (e.g. working on the beacon) the more likely they are to die from it, or get tired and return home.
To clear out the swamp, use the beautify god power. When using beautify, make sure you tap rather than drag, as it uses a lot of belief and you can get the same effect for a lot less belief by placing it in "dots".
On the android version, beautify is awarded when you have 30 farms.
Answer: Beautify
As Samthere points out, the Beautify power will permanently remove swamps/blighted land and solve your problem. However, there is a swamp covered beacon fairly early on in the ios version of Godus and most likely you will not have sufficient population/mines/fields to unlock the Beautify card yet, nor would you be able to find enough stickers to activate the card if it was unlocked.
Let Followers Die for the Cause
Instead of clearing the swamps out so that your followers survive, you will need to send followers to work on the beacon until they die, then send more. This micromanagement makes this one of the more frustrating beacons to work on, but it can be done. I recommend leashing 8 followers at once, sending them up to die while they work on the beacon, then sending another team of 8. The followers won't even survive long enough to get tired and stumble home. Slowly but surely, you will complete the beacon and progress further in the game.
Will Boosting Keep Followers Alive Longer in Swamps?
No, boosting the followers while they are in the swamp does not make them survive any longer. I have seen followers die while working on this beacon even at full stamina from a recent boost. I suspect that simply being in the swamp for a certain length of time kills the followers and boosting has no effect.
Comment: I've only played on PC, which I think is relatively accelerated compared to mobile and you can generate gems, so I didn't realise you might not get beautify in time. Good extra info!
Comment: My save got corrupted so I had to start again; I unlocked beautify at 20 (I think) farms, with no sticker cost. Is there a sticker cost to unlock powers on the iOS version?
Answer: I didn't want to sacrifice my followers on that early swamped beacon. I just paid the gem cost to fill it. You can get gems for watching ads. Much easier to recover from than killing followers for an hr.
Answer: If you want you could remove enough terrain to make plots to get the requirement, I did and had enough stickers to get it... then again at that time I had burned most of the astari villagers except one and got the village itself so... I'm a special case?
Answer: I sent the followers to work. Then I closed the app for the time they had to work. When I opened the app the beacon was finished, if the followers died or not I don't know, but it finished with only one "troop"

How do I build the Beacon in a Swamp


Why the current is the same at all of the positions in a series circuit?

Question: Why the current is the same at all of the positions in a series circuit? although there are different voltages at different positions of the circuit.
What i know is that as the electron passes one resistor, the force of attraction from the negative terminal is less. Doesn't this affect the current?
Answer: When the system reaches steady-state condition(things do not change with respect to time), then we have the same electric field inside the circuit. Before reaching the steady-state condition, then yes, the forces exerted on the electrons(or voltage difference between some points) is not the same at every point in the circuit. But, as Griffiths puts it in his famous book("Introduction to Electrodynamics"), it has a tendency to auto-correct the path of the electrons, so as to make them move with constant velocity(and thus current) and make them follow the path of the circuit(haven't you even thought of "how do they follow the bending path of the circuit"?). Why this happens though? When they find a resistance, at non steady state, they accumulate at the resistance but then, that accumulation means that an electric fields builds up at the "point" of that accumulation, and that pushes with stronger force the next electrons that come to the resistor and makes them pass through it with a velocity that keeps getting bigger and bigger with time until it reaches at the point in time that nothing changes with time(steady state) and the final velocity of the electrons passing through the resistor gives a current equal to that at every other part of the circuit. The same goes for following the curves. The charges that first find the bending path, hit on the path and accumulate there. Electric field gets more intense there and thus tends to push the next incoming electrons in a way to make the follow the path.
The following image is from Griffiths' book and it is about the bending of electrons in order to follow the path. This will help you also understand the situation at the resistor(I INCLUDED THE FULL DISCSSION OF GRIFFITHS WHICH INCLUDES SOME MORE ADVANCED CONTENTS,IF YOU DON'T CARE ABOUT THEM, JUST SKIP THEM):
Comment: Note: during steady state there can be no accumulation of charges anywhere!
Answer: The current is the amount of electrons passing through a point in the circuit per time. If no electrons are added or removed in the circuit, this number stays constant.
Think of it like water flowing through a series of pipes. The pressure can change, the diameter of the pipes and the flow velocity can change, but the amount of water flowing into one side is the same amount that comes out on the other side.
Comment: I think that there is a bit more analysis to that, because in order for the system to reach the point that you are saying, then it has to pass through the non steady-state phase where charge DOES accumulate at some points.
Answer: Because no charge is accumulated at any point anywhere when you have a steady current!

If water is flowing in a pipe, you maybe have 1 cubic meter passing every second. Every part of the pipe system MUST get $1\;\mathrm{m^3}$ in every second and MUST also send $1\;\mathrm{m^3}$ out every second. If not - if for example more enters than what leaves every second - then some water STAYS in that part of the pipe system, and every second a new portion is added, which stays. Water would therefor accumulate here. Sooner or later there is no more room for any more water, and the pressure is so big that no more water will enter. The flow will stop, and nothing flows anymore.

If a part of the pipe is more narrow, then this causes "resistance" against the water flow. But of the above reason, we still need inflow to equal outflow. So for a much narrower part, the water simply has to speed up. And that is achieved by having a bigger pressure difference.

Exactly this happens in an electric circuit. Current $I$ is charge passing per second, $I=[C/s]$. No charge is accumulating anywhere, because if it did then very, very quickly there would be build up too much charge in that point, which would strongly repell any further charge from entering that point. Then there would be no flow of charge anymore - that is, no current.

So, if a steady current flows then that is proof that there is no accumulation of charge anywhere. And in a series circuit where there are no branches for the charge to go instead, if the path is blocked, there MUST be the same inflow as outflow of charge to every single point in the circuit - therefore, equal current at every single point.
This is Kirchoff's current law.
If there is a resistor on the circuit path, then the current is resisted, which simply means that a higher "pressure" difference (higher voltage) must be applied to still push the same amount of charge through every second.


Execution of instruction in MIPS on various parts of the clock cycle

Question: I've recently learnt the execution of MIPS instruction set using single cycle processor. However I'm not getting one thing. Since one clock cycle is needed for the complete instruction we only have one positive clock edge. When the clock is made high on the first time in this rising PC value is written but we may have other write operations also like Reg Write or Mem Write. But the rising edge is gone and we've to wait for the next cycle to write. So how in one cycle both writes are possible for a single instruction ?
Answer: A single clock signal can trigger many, many independent actions. And the processor is pipelined, which means in one cycle it will execute different parts of different instructions.


Non intrusive controlling & monitoring system

Question: I have read and researched online about electric monitoring systems like the kill a watt and wattspn and i have observed something in vpmmon, they do reuire intrusive devices like sockets as means of controlling (on or off the devices) and monitoring mechanism. Now  is there a diffent way or idea in order to control and monitor electric appliances in a non intrusive way (without using additional sockets to be placed on each load)? I know non intrusive mechanism can do monitor stuff like what is on or off through voltage variations, but it cant control the loads like turning them on or off. Thanks
Comment: Kindly add proper tags if possible, tnx
Answer: On/off control is, by definition, intrusive. ie
 The act of turning something off IS intrusive.
 The act of turning something on IS intrusive.
BUT:
You can measure AC current without intrusion and
 You can measure AC voltage with very close to zero intrusion.
While it IS possible to monitor voltage without intrusion in the strict sense
 ie with no ohmic connection, by using eg capacitive coupling,
 there are few circumstances where this makes practical sense.
 Even DC voltage may be measured using electrostatic methods but this would essentially never be done in AC mains measurements.
 Long long ago I did see and electrostatic DC  meter ! Rare.
Ac current can be measured by detecting the field produced - most usually with a Hall sensor.
 Special ICs are made for this purpose.
Clamp meters of the sort shown by Rocketmagnet in his answer are also useful.
Here is an AC current sensor which uses a Hall sensor.
 The current path is built into the IC for precision but this is not essential.
  There is no "ohmic" contact with the current path.
Comment: is it possible to control your electric appliance through means of a non intrusive way (not putting sensors / additional sockets and wireless transmistters and stuff)
Comment: @user963499 - covered in the 1st 6 lines of my existing answer. Explained further in the following text. If you want more detail you need to explain what you are trying to achieve in more detail.
Comment: I was thinking to create a centralized electrIc appliance control and monitoring system like the "kill-a-watt" ,wattson,etc, but they all use additional sockets to turn On/off the load through a wireless trsnsmtter. And now, ive research that there is other way around to monitor the load by putting a sensor in the main wire of your house beside the electric meter and what it does is sense the voltage variations and do some complex math ( since every load has something like its own signature )so in turn it can distinguish one from the other
Comment: Yet non intrusive technique is like a 1- way in which you cannot send instructions/info/signals or even cut the current thriugh that will route since it would need modifications in each of the power outlet/socket of your house to be effective
Answer: While it is possible to measure load current in a non-intrusive way, using a clamp ammeter like this:

It is not really possible to control the current in the cable. Certainly not possible to switch appliances on and off.


Looking for an iPad pencil compatible app with a large or infinite canvas

Question: I tried Sketch and some other drawing apps. I'd like a bigger canvas to work with. Most seem to only be 8 1/2 by 11 or standard page size.
Is there a way to expand the canvas on some of the basic drawing apps or is the a good app that provides a large drawing area?
Comment: http://www.mybrushes-app.com/MyBrushes-Pro.html
Comment: Same. Like Prezi had. Have not found one yet. Using Paper at the moment, but its frustrating to create new pages.
Answer: You can use

Microsoft OneNote
Concepts

These are best according to me for infinite canvas. Although, OneNote is note-taking but it's OK.
Concepts is best one ✌
Answer: Have a close look at Affinity Designer.  On the iPad it certainly uses the pencil as an input source, and if its canvas is not actually infinite it is very large and you can zoom in 'infinitely' too.
No, I'm not associated with the company, merely a very happy user of their products.


What property type should I select for a coop apartment mortgage application?

Question: When applying for a mortgage on some bank websites, you're asked the type of property you're looking to purchase. There are options such as "single-family," "multi-family," and "condo," but no option for a coop apartment. Which property type should you select if the property you're looking to purchase is a coop apartment?
Comment: I'm voting to close this question because it is just spam. I am removing the website links provided to prevent the desired SEO effect.
Comment: This isn't spam as I don't work for the institution that was linked and I was genuinely asking this question. I removed any indications of a specific institution where this question was asked.
Answer: I cannot speak for better.com's specific policies, but this sounds like a condo to me.
A single-family property is a building* that houses one family; a multi-family property is an entire apartment building (if you are an investor looking for a mortgage for your investment); a condo is one piece of an apartment building that holds one family.
* It doesn't say single-family building, but we can infer this because there is also an option for "condo". If there was not a "condo" option I would have said "single-family property", since a condo holds one family, and you are clearly not buying a whole apartment building.
Answer: When I reached out to the support team of one of these websites, I was told that the question about the property type is to confirm whether you will be using the property for residential or commercial/business purposes. Some financial institutions are only able to lend on properties that are used for residential purposes.
The support team suggested using a "condo" property type selection if applying for a mortgage for a coop apartment.
Comment: Type of dwelling means nothing for usage. I'm not sure how you made that connection
Comment: I don't know what they told you, but you *can* rent out a condo.
Comment: @littleadv I asked this question to better.com's support team and was relaying the answer from them. Since this question is on their website's application form, it's likely that they use the type of dwelling to indicate usage internally somehow.


Raised image on front page

Question: I want to put an image on my front title page, but a little above the mergins
(so it would start on almost the very top of the A4 page). How do I manage this?
Comment: Where do you want it - at the center?
Comment: Since you have some responses below that seem to answer your question, please consider marking one of them as 'Accepted' by clicking on the tickmark below their vote count (see [How do you accept an answer?](http://meta.tex.stackexchange.com/q/1852)). This shows which answer helped you most, and it assigns reputation points to the author of the answer (and to you!). It's part of [this site's idea to identify good questions and answers through upvotes and acceptance of answers](http://tex.stackexchange.com/about).
Answer: You can do it in number of ways. My favorite is tikz using its remember picture and overlay combination.
\documentclass{article}
\usepackage{tikz}
\usepackage[a4paper,margin=1in,showframe]{geometry} %% showframe is to show margins. Remove that in your file
\begin{document}
\begin{tikzpicture}[remember picture,overlay]
    \node[anchor=north] at (current page.north)  {\includegraphics[width=3cm]{example-image-a}};
\end{tikzpicture}

\end{document}

Raised image on front page


Alimony on gross salary

Question: How does someone pay alimony on their gross salary if they are employed by someone else? Suppose the partners agree on giving half of the gross monthly salary as alimony. If said person has X gross income per month which is taxed before having it in their bank account, how can they first pay X/2 to their ex-partner and then be taxed on the remaining X/2? Do they have to wait one year to claim the alimony as costs in their tax return or can they tell the tax office right away so that each month they are taxed on X/2? The countries I am concerned are Netherlands and Belgium, but insight from other places is also welcome.
Answer: TLDR version:
In the Netherlands you can request a "provisional assessment" (voorlopige aanslag) for your income tax and the tax authorities will pay you back your expected tax return in advance, typically in monthly instalments.
conditions apply

As far as I understand for the Netherlands:
Your salary and other remuneration / benefits are an agreement between you and your employer.
The employer is required to withhold any and all applicable payroll/wage taxes, as well as social security contributions etc. based on your  salary/benefits/remuneration package and pays those directly to the tax authority.
As the employee you should get a payslip detailing what payroll taxes, social security and/or other contributions are withheld from  your gross salary/benefits/remuneration package that period and whatever amount remains is typically  payed directly into  your  personal bank account by your employer.

Certain expenses, such as alimony payments to an ex-partner, are tax deductible.
You don't report those to your employer and even if you would do so, that won't change the amount of payroll taxes your employer is required to withhold.
You report those tax deductible expenses to the tax authorities when you file a tax return (in the Netherlands you're not always automatically required to file a tax return  but when you make tax deductible alimony payments you should probably always do so).
You file your (final) tax return after the fiscal year has been completed, as only then all amounts will be final and only then picture is complete. After your tax return has been assessed, processed and approved, the tax authorities will pay back  the excess taxes that were collected in advance as payroll taxes (or alternatively, your circumstances and tax return filing might require that you pay some additional taxes.)
When you make substantial tax deductible alimony payments, typically the tax return will be substantial.

The Dutch tax authorities appreciate that not everybody can afford to pay all their tax deductible expenses now and then wait for the fiscal year to end and then wait some more before their tax return filing has been processed, a final assessment has been made  and their their tax return gets paid out.
That why in the Netherlands you can request a "provisional assessment" (voorlopige aanslag) for your income tax and the tax authorities will pay you back your expected tax return in advance, typically in monthly instalments.
That means you don't have to wait for 2024 before you can file your 2023 tax return and wait while your tax return gets been assessed, processed and approved. You will get (most) your 2023 tax returns paid in 2023 rather than somewhere mid/end 2024.
Then in 2024 you will make final 2023 tax return, which will determine the  actual amount of income taxes that are due. Your final tax returns will take into account the advances that you already received and result in a smaller final tax return or possibly a payment if you received to much in advance returns.

Alimony on gross salary


If I sell an item to someone in another country, whose laws apply?

Question: If I sell a large item (example car/caravan/boat) from the UK in a private deal to a person in a country in the EU, which countries laws (apply in the event of a dispute)?
Answer: Both
All the laws of each country apply to the extent of their territorial or subject matter jurisdiction. So, for your example, the export laws of the US apply and the import laws of the EU country apply.
The parties can nominate what law the contract is to be interpreted under using a choice of law clause. It must be a country that has some link to the contract and, usually, the request will be honoured. However, this only applies to contractural disputes, other laws are unaffected.
Also, it is not uncommon for certain laws relating to the contract to be non-excludable, for example, consumer protection laws usually can't be contracted out of. Those laws continue to apply even if the rest of the contract is interpreted under some other law.
Answer: I could be either, or both.  In a contract of sale, the parties can specify what jurisdiction's law it shall be interpreted under, and such provisions are usually honored. In the absence of such a provision, a party could bring suit in either country, provided that the courts of that country re able to secure jurisdiction over the other party.


KCL confusion about currents direction

Question: Sometimes when I use KCL for nodes in a circuit I cannot correctly determine the direction of the currents. My book also says that according to KCL the algebraic sum of currents entering a node is zero. In order to avoid further mistakes, can I always write i1+i2+.. +in=0 for each node of the circuit despite the direction of each current? If not what's the general rule/idea so that I dont mess up the direction of a current?
Answer:
In order to avoid further mistakes, can I always write i1+i2+.. +in=0 for each node of the circuit despite the direction of each current?

If you have chosen that \$i_1\$, \$i_2\$, etc., are all positive when they are going in to that node, then yes, you just write that the sum of the currents is 0.
But if (for example) \$i_1\$ is positive going into a node at one end of branch 1, then it will be negative going into the node at the other end of branch 1. So for that node you'll have to use \$-i_1\$ in your KCL equation.

If not what's the general rule/idea so that I dont mess up the direction of a current?

The rule is before you start writing equations, you choose a reference direction for the current in each branch. Draw an arrow on your schematic indicating which direction will be considered "positive" current for that branch.
Now for each node, you write the equation with a + sign for each branch with its arrow pointing in to that node and a - sign for each branch with its arrow pointing out of the node.
You can choose the direction of the reference arrow completely arbitrarily. If the current happens to be going the other direction, you'll just end of with a negative value for the current in your solution.
Answer: When I was tutoring students, a common confusion seemed to be just about what you wrote in your question. Very close, to my eye, anyway. This turned out to be because the textbooks they were using (consistently, by the way) did a rather poor job about the concept itself, leaving much to be legitimately confused about. The textbooks weren't wrong (correction: some were grossly wrong in places) as a rule. But just did poorly in helping a student find and keep a good mental balance about each new situation they faced. They weren't provided consistent tools. Instead, each situation seemed like the current directions were supplied ad-hoc, through some mysterious process the student was never told fully about.
So I had to develop a different approach.
Let's look at this snippet from Andrei Vladimirescu's "The SPICE Book" (top of page 15):

(Note that Andrew doesn't include a nodal equation for node 1. That's because it's an unknown voltage and there's a voltage source serving to maintain it. But the node is still labeled as \$V_1\$ for the purposes of the remaining nodal equations. He did it this way, rather than just use \$+12\:\text{V}\$, because it is better practice to use a symbolic approach even when you know the value for the symbol.)
If you re-arrange those two equations so that everything is unsigned, then you get this:
$$\begin{align*}
&\text{Node 2:}& V_2\cdot G_1 + V_2\cdot G_2 + V_2\cdot G_3 &=V_1\cdot G_1 + V_3\cdot G_3\tag*{(1.1)}
\\\\
&\text{Node 3:}& V_3\cdot G_3+V_3\cdot G_4 &=V_1\cdot G_4+V_2\cdot G_3\tag*{(1.2)}
\\\\
\rlap{\text{I'd like to insert a hidden piece, now:}}
\\\\
&\text{Node 2:}& V_2\cdot G_1 + V_2\cdot G_2 + V_2\cdot G_3 &=V_1\cdot G_1 + \underset{GND = 0\:\text{V}}{0\:\text{V}\cdot G_2} +V_3\cdot G_3\tag*{(1.1)}
\\\\
&\text{Node 3:}& V_3\cdot G_3+V_3\cdot G_4 &=V_1\cdot G_4+V_2\cdot G_3\tag*{(1.2)}
\\\\
\rlap{\text{Finally, to put this back into a form using the resistor values:}}
\\\\
&\text{Node 2:}& \frac{V_2}{R_1} + \frac{V_2}{R_2} + \frac{V_2}{R_3} &=\frac{V_1}{R_1} + \frac{0\:\text{V}}{R_2} +\frac{V_3}{R_3}\tag*{(1.1)}
\\\\
&\text{Node 3:}& \frac{V_3}{R_3}+\frac{V_3}{R_4} &=\frac{V_1}{R_4}+\frac{V_2}{R_3}\tag*{(1.2)}
\end{align*}$$
(Per the above note about keeping values symbolic, the one exception to this is ground or \$0\:\text{V}\$. In this particular case, keeping it symbolic would probably serve to confuse just a little more than using its value. And it is always zero, too. So may as well just say so. Keeping \$V_1\$ symbolic allows you to ask questions about what happens if that voltage source has a different value. But you never need to ask about "What happens if ground isn't zero?" so there's no need to use a symbol for it. You could, and assign it later. But no point to it.)
You can now more easily see that every term on the left side is balanced by a term on the right side. Every resistor has two ends. That's why. So when you write these out, just keep all the terms that involve the node voltage under consideration on the left and toss all the terms that involve some other node voltage over onto the right. Each end of a resistor has a term with one of those terms on the left and one on the right.
If you wish to explain this to yourself, just imagine that a node voltage causes currents to flow outward from itself through the available paths. These outward pseudo-currents are countered by inward going pseudo-currents from the nearby nodes. You place the outward pseudo-currents on the left and the inward pseudo-currents on the right. The pseudo-currents will always be unsigned and will always sum to the correct current (without you worrying about what that is) and the nodal equations will solve correctly (as they must because they are the same equations, just slightly re-arranged.)
Note that you will never have to worry about signs again! Not ever. This will save you from all confusion over signs and net-sum current directions, since you didn't care about those and instead focused only on the unsigned pseudo-currents. Experienced readers will be able to follow you, just fine. And feel free to later re-arrange in any form you want. The signs will then always be correct.
This is nothing more than a re-arrangement to avoid worrying over signs. It's still based entirely on all the same, existing theory behind the nodal approach. Nothing has changed. Only how you initially compose it has changed. That's it.
P.S: A current source has an impedance of \$\infty\$ (ideally.) They also have two ends. But in this case, the \$\infty\$ impedance means you can break them into two parts, with one part pointing into a node (and coming out of nowhere) and one pointing away from a node (and going nowhere.) There's a special case, though. Since KCL is never performed for a known-voltage (or ground) node, if one end points into or out of the ground node, or any other node with a known voltage where KCL isn't being applied, you can just leave it out and not worry about it. But this is the only exception. If the node voltage is an unknown, then it must be kept and not removed from analysis. (The reasoning has to do with graph theory and the Rank-Nullity Theorem and goes way beyond what I want to say here.)
Comment: You made a slip of a pen, and you wrote V3/R3 (V3* G3) in node 2 equations on the left side instead of V2/R3 (V2 * G3).
Comment: @G36 Thanks for that! I've corrected my writing.
Answer: The basic idea behind KCL is that what goes in must come out. saying that that the sum of all currents crossing a closed surface is zero.
KCL can also be expressed as the sum of all the currents pointing into a node is equal to the sum of all the currents pointing out of the same node.
This form is longer and the language is perhaps slightly less precise but it makes specific allowance for current arrows drawn going in different directions.
Accepting that a current flowing out is the same as the negative version of a current flowing in you get the canonical version of KCL.

KCL confusion about currents direction


How do I know when a step function finishes in Angular?

Question: We have a step function that generates a pdf when someone clicks on a button. However, the PDFs can sometimes be large (200+ pages) so this process might take some time. The PDF is generated inside of a step function. How can I tell when that instance of a step function has finished? I have a lambda which calls the step function too, I am not calling the step function directly from Angular.
I am thinking either create a SNS topic and subscribe the user to that topic, and have the step function post a message to the topic. The issue arises where it is a user-specific thing so I would either need to make a topic for each PDF created, or use SNS filters on the subscriber. Is using SNS like this against best practices?
Another thought was to use AWS waiters in the AWS SDK 3.
My question is: Is it OK to use SNS in that way, or would waiters be better. OR is there another better way to know when a step function finishes?
Comment: Front-end could simply poll a back-end Lambda function which queries Step Functions (or other AWS services/resources) on behalf of the client. Client would need to supply an ID in its request which the back-end gave it earlier when it kicked off the workflow.
Answer: In principle you are right.. The task may take some time and the it's not always feasible that the client synchronously wait for the response.
As far I undetstood you have a problem how to get information back that the task is completed.
The common approaches I've seen are

create a table (db, dynamodb,..) with the task state and update the state upon the task completion. The client application needs to poll regularly for the result/state

create an api gateway and it is possible to use websockets to notify the client (push information back to the client)

Why not SNS - you would need to create /clean up the topics and subscriptions. Topics and subscriptions are to be more or less static (it may take se time to be created or deleted) and there's a limit on their count. Simply SNS is not intended to be used this way.
AWS SDK Waiters are for waiting for the resource state (e. g. sns topic created), not really for the tasks.
In theory the client could interact directly with the stepfn (invoke, check state,..), but I'm not fond of the web clients accessing any cloud resources directly. It creates some extra dependency and more caution is needed for authorisation.


Static as opposed to Kinetic Friction in Rolling Motion

Question: During analysis of rolling motion, why do we consider coefficient of friction as that of static friction and not kinetic friction?
Comment: Are we talking about rolling or about circular motion?  I suspect you're talking about rolling, and if you are, think about how tires behave on ice...
Comment: Since you're talking about rolling motion, it might be useful to understand [*how gears work*](http://en.wikipedia.org/wiki/Involute_gear).
Answer: Like @Jerry said, this is all to do with how a wheel works (or similar rolling object; a giant meatball for example). This figure should help:

As you can see from the image, we consider static friction because while the whole meatball may be in motion, the part touching the ground (the only part friction can act on) is not moving relative to the ground. If it were moving, this would be considered sliding. If you've ever driven a meatball on ice, you'd agree that sliding is definitely a bad thing.
In fact, the entire reason your meatball can roll around is due to static friction. When you apply a torque on the meatball, it wants to rotate on the spot. Without static friction, it would do just that and there would be no net forward motion. However, static friction causes the part of the meatball touching the ground to stay in one place. But the meatball still has a torque, so it will rotate; it rotates with a forward motion as long as it can't overcome static friction where it "meats" the ground. If your meatball ever starts to slip, then we discuss kinetic friction, which is usually less than static friction. This means the forward force you could potentially apply to your meatball is severely reduced and it would go nowhere (but it would go there fast!).
Static friction. That's how I roll!
Comment: Minor nitpick: Road tires have tread only to displace surface rainwater. This is why racing drivers use slicks on dry days. On dry days, treads *reduce* static friction, not increase it.
Comment: @RedGrittyBrick I stand corrected. Thanks, I'll get rid of that. Is it then why they're made of rubber?
Answer: Static friction is for when two surfaces do not move relative to one another (no rubbing), whereas kinetic friction is for when two surfaces do move relative to one another (rub against one another).  For rolling motion a good starting place for understanding which is relevant is to think about a tire on a car.
Kinetic friction is appropriate when the tire on a car is not getting enough traction and it spins without the car moving forward, as say can happen on ice, because then there is rubbing of the tire tread on the ice (which are the two relevant surfaces in this case).
But if the tire "rolls without slipping", on say a dry road, then static friction is appropriate because there is no relative motion between the tire tread and the road (which are the two relevant surfaces in this case).  To see that there is no relative motion in this case think of a tire rolling without slipping as being like the tracks on a tank (compare this picture of a flat tire to this track simulation video): where the tire meets the road it is slightly deformed to be flat on the road and this flat part and the road do not have any motion between them (there is no rubbing of these two surfaces).

You might also find it helpful to look at the two animated GIFs here.
Answer: The idea is that the bottom of the wheel is actually stationary, which is often hard to get your head around. Here's a great analogy, though: walking.
When you walk, do both of your feet move at the same speed? Of course not! You wouldn't be walking if they were. If you really pay attention to your feet, one foot is actually stationary (relative to the ground) while the other one is moving much faster than your overall motion.
The same thing happens between the top and bottom of a tire. The top point is moving in the same direction (relative to the car) as the car is moving (relative to the ground), so it's moving twice as fast as the car (relative to the ground). The bottom point is moving in the opposite direction, so it's stationary (relative to the ground). On average, every point on the wheel will move at the same velocity as the car, so don't worry about logic breaking your tires. :)
Answer: I usually consider a rolling friction coefficient which is different from the static and the sliding friction.
The reason is because the elastic deflection of a rolling element imparts resistance what is non-linearly proportional to the applied (contact) load.
For steel over steel depending on lubrication conditions a typical value us $\mu_{roll}=0.008$
The static friction is used to determine the available traction, beyond which slipping will occur. When pushing a bowling ball, if you push slightly it will roll, but if you push with more force that static friction times weight then the ball will slide and roll.
Comment: rolling friction and static friction both exists in this scenario and both do very different things. The question pertains to the friction (resistance to sliding) between the rolling object and the surface. Not the combined forces from resistance to being compressed then separated from the surface and resistance from the bearings/axel, which is closer to what rolling friction is


Get trigger query using query analyzer

Question: I have a server in which there is no SSMS installation, and only query analyzer is available. And all I need to do is find the trigger information (basically trying to find out what that trigger does).
I tried using object explorer in query analyzer, to use "Alter To->New window" command. But that command failed saying "Use SSMS to alter the query".
Is there a way, I can write a simple sql query, that gives me the trigger information?
Answer: Never mind. Found it.
<code>sp_helptext 'TriggerName'
</code>
worked like a charm.

Get trigger query using query analyzer


How do different outlets count votes in different ways and have diferent margins at different times on election day?

Question: https://www.youtube.com/watch?v=EHl2tU40ibs
In this Election night coverage (link duly posted above) it is said that different outlets "count in different ways" and that different outlets have different counts.
How is this so?
(Timestamp:- 2:50:08 to 2:50:52)
Answer: There are the official numbers. Their advantage is that they are official, their disadvantage is that they take a long time to get assembled.
Then there are the unofficial numbers from various news agencies. They could try to beat the official tally by simply counting faster, and by taking more risk with less careful double-checking that nothing is scrambled in transmission.
Or they rely on incomplete results and calculate predictions on that basis. There have to be adjustments, or qualifiers in the reporting based on past results.
"With 2 out of 3 districts reporting, X has 1,001 votes and Y has 999 votes. But Y has traditionally been strong in the missing district, so X has little chance to win."
"District whatever is reporting a victory for X by 5%. Traditionally X has received 10% more in whatever district than statewide, so we predict that X will trail by 5% overall and that Y will win when all results are in."
If the pollsters are honest those adjustment factors are based on data, but there are judgement calls in that. How long does one go back? How do you deal with demographic shifts? And so on.

Interestingly, you see some of that in Corona reporting as well. The famous Johns Hopkins numbers tend to be higher than official numbers because they take numbers e.g. from press releases of the local health authorities rather than waiting for the official tally.
Comment: Those are all actual vote counts, not polls so this part of the discussion in not relevant. They are obviously partial results (see the little "X out Y precincts reporting") but the answer fails to specify how the aggregation works, how media outlets "call" an election in the US and what might account for the discrepancies. Incidentally, "corona" is the way the pandemic is referred to in Dutch or German, it sounds very odd in English.
Comment: The news agencies don't count votes themselves.  They certainly aggregate the votes from a precinct as soon as they're reported without waiting for the district as a whole to be reported, but they don't _generate_ any numbers.
Comment: @o.m. It's the difference between counting individual ballots at each polling place and adding together numbers from the people who counted individual ballots as they're reported to a central location.
Comment: @Relaxed, I removed the polling and left just the projections in. The key thing is that they don't just take the totals reported so far but put them into perspective.
Comment: @Bobson, they add sums faster than the official reporting chain. Doesn't that count as generation?
Answer: It's not clear what specific differences Katherine Miller was referring to, but in the United States there are generally two points where vote totals are reported: At each county -- which is the largest governmental entity smaller than the state, and where the votes are actually tallied by the Registrar of Voters or Board of Registrars -- and the state level, where the tallies are aggregated by the Secretary of State or similar office. (Also, counting doesn't begin until the polls close; you may get some results minutes after the poll closure because the local offices are processing mail-in ballots.)
This isn't an instantaneous process. As a news organization (or a citizen), you you can go to the Secretary of State's website and get their totals summed from the numbers submitted to them by the counties -- or you could go to each county's website (Alabama has 67) and see their reported tallies throughout the night and keep a running total. (With luck, each county has standard API that will let you query the data with ease; often you'll wind up having to use a script to scrape their results pages.)
Depending on how the state's infrastructure works and how frequently the news organization is retrieving the county-level numbers, there could easily be a temporary difference in the totals being reported.
(Election-night totals reported by the state are usually "semi-official final," and not final, since there will be a lag from absentee ballots mailed by election day, sealed ballots turned in at the polls and such.)


Best tool for QoS testing

Question: The problem is that, i cant find good tool for QoS configuration testing(linux). I have some switches and configured QoS on them. Installed two PC's with wireshark for watching whether switches are colouring packets, so thats ok. But how to check bandwidth allocation? I know iperf, it can set ToS . But may be there is some special utility?
Comment: So what i get until now:
-wireshark for ToS-Diffserv
-iperf for emulating udp|tcp activity
Answer: Bit low-tech but we test ours with big httpgets from known sources - we do lots of these and average them out.
Answer: The real way would be with a hardware tool like Ixia pumping your switches.
You could check vendors to get it on loan for testing if this is a one time requirement.

Best tool for QoS testing


How do we know the speed of light is constant and spacetime dilates rather than vice versa?

Question: Some conspiracy nut was telling me that Einstein was BS and there's a giant conspiracy that he's wrong but scientists would loose all their jobs if they admitted it. Of course this is all baloney, satellite clocks need to be adjusted for time dilation and Mercury's orbit is weird. But that got me thinking about how we know light is constant and space/time changes instead of the other way around? Can we measure space stretching without using light? If light goes faster and we use it to measure a space, we would just say the space contracted. Can we measure time without using the speed of light? Does the math work out if you set space and time constant but have changing light speed?
Answer: You might be confusing some issues.
In special relativity, space and time do not stretch or compress. It really comes down to measurements with clocks and rulers made by people that are moving uniformly with respect to each other.
One option that is consistent with observations for SR is that there is one family whose clocks and rulers are right and everyone else is wrong (the rulers the moving people are using are too short and their clocks run too slowly). This is possible, but if that were true then the laws of physics are such as to have a vast conspiracy because there are no measurements anyone could do to say who is the special observer that is right and therefore who is wrong. To each person their stuff looks right and they think they could be the right one.
What is the point of saying one person is right when they all look the same? So SR postulates that all the clocks and rulers are equally accurate and they are all measuring actual geometrical facts about our spacetime and that the spacetime has a Minkowski geometry instead of some other geometry. That is what is consistent with our measurements and still allows all these people to be equally good at their jobs. It's is based on the idea that no inertially moving person should be treated differently. The advantage is everyone can look the same instead of one person being right but everyone else's errors cancelling out so they can't tell they are wrong.
Now in GR there is a different geometry, which is only approximately like Minkowski in a small region of space and time. So each event has a small region where things are approximately a Minkowski geometry.
In GR, spacetime is curved. If you use some coordinates, the rate your position coordinates change compared to your time coordinate changes could vary. But when people say the speed of light is constant what they meant was those two inertially moving people pull out their clocks and rulers and measure a speed and they get the same result.
We should say invariant rather than constant, since it is talking about how it appears to different people. But the word constant is already out there so we will have to hear questions about that word. And GR has that too. Since the laws of physics actually predict that light moves at the numerical value of $c$ if differently moving inertial observers measured it differently then different inertial observers would have to have different laws of physics.
That's annoying to have to write different laws for people that are no different except that they are moving inertially with different starting velocities. It's not even what we want. One person could get the laws we are used to and then what, everyone else has to get different ones? And after all, we'd just ask how you decide to assign laws and someone would try to call that the law and then it will end up not depending on the observer any more or else no one will know how to assign that big law and we'll be back to that alternative to SR where one person is right and everyone else is wrong but no one knows who.
Why bother? We can write laws that treat everyone the same and these agree with observation. They might seem weird to people that are only used to people moving slowly compared to each other and who stay away from strong curvature. But the alternative is so painfully biased or complicated almost nobody even bothers to consider those options.
Answer:
How do we know the speed of light is constant and spacetime dilates rather than vice versa?

We know that the speed of light is not constant. I'm afraid it's a popscience myth that the speed of light is constant. See Irwin Shapiro talking about it here:

Some conspiracy nut was telling me that Einstein was BS and there's a giant conspiracy that he's wrong but scientists would loose all their jobs if they admitted it.

This isn't true. But nor is what you've been told about the speed of light. Einstein said the speed of light was not constant, repeatedly:

He didn't abandon this idea in 1911 like this article used to say. Search the Einstein digital papers for more examples.

Of course this is all baloney, satellite clocks need to be adjusted for time dilation and Mercury's orbit is weird.

The GPS clocks employ microwaves, which are light waves in the wider sense. Such clocks go slower when they're lower because light goes slower when it's lower, just like Einstein said.

But that got me thinking about how we know light is constant and space/time changes instead of the other way around?

The locally-measured speed of light is constant because we use the local speed of light to define the second and the metre, which we then use to measure the local speed of light. The constancy is a tautology. See http://arxiv.org/abs/0705.4507.

Can we measure space stretching without using light?

Gravity features a radial length contraction, which is the opposite of a stretch.

If light goes faster and we use it to measure a space, we would just say the space contracted.

Space is radially contracted closer to the planet, and the "coordinate" speed of light is lower closer to the planet. See Baez for more on this.

Can we measure time without using the speed of light?

No. The second is just the duration of 9,192,631,770 microwaves passing you by. If the light goes slower, the second is bigger.

Does the math work out if you set space and time constant but have changing light speed?

There is a way to do it, but not the way you suggest. The changing light speed means the time isn't constant. However the metre is. The metre is the length of the path travelled by light in vacuum during a time interval of 1/299,792,458th of a second. When the light goes slower your second is bigger, but the slower light and the bigger second cancel each other out, leaving the metre unchanged.


Was Archie Hicox's accent actually strange?

Question: In the tavern scene where Archie's disguise is blown through his English hand gesture, he is initially questioned by Cprl Willhelm about his unusual accent. Can the German visitors to this site confirm if his accent did sound iffy, and did Stiglitz and the other chaps accents match to where Major Hellstrom guessed?
Comment: However his English accent was a trifle stilted! But not at all bad considering Deutsch is his Muttersprache. I struggle to imagine how a German speaker, born in the Rhein valley, can invent a strange German accent which would elude the identification of the mother-tongue of the speaker. Perhaps it is tinged with Irish-English. His English is only slightly accented.
Answer: I, being a German and having heard a wide variety of different German dialects, can confirm to you that his accent was indeed a bit strange. And while Michael Fassbender didn't have too strong an accent, it was IMHO still identifiable as slightly English-based and thus was likely to arouse the suspicion from the Germans in that bar.
Yet the accent wasn't completely weird, given that there might still be hidden places where people speak accents I haven't heard yet, like at the Piz Palü. So I would say that Cpl. Wilhelm would probably not have spoken about it to a higher ranking officer, hadn't he been as drunk as he was, and maybe asked him out of mere curiosity rather than actual suspicion. But they didn't plan to stumble across such a highly suspicious security officer as Maj. Hellstrom, who had all the reasons to request some clarification from Hicox.
But I also have to say that I don't have as good an ear as Maj. Hellstrom and wouldn't really have been able to classify the other two German Basterds according to their home towns as easily as he did, since they spoke pretty clear High German. So that part was maybe a bit exaggerated (or he had really just far better trained ears than I have). Yet looking at the two actors, they were indeed born or grew up at or near the places attributed to their roles by Maj. Hellstrom, so it is pretty reasonable to assume that he was right in his assumption.
Comment: German accents and dialects were much stronger before media, especially TV, equalized them. So it is likely that the characters would have actually spoken with a recognizable accent but the actors don't. And it would sound strange and exaggerated to a contemporary audience if the actors would use a broad accent all the time. (You don't hear people in movies about the medieval times speaking in middle high German all the time also.)
Answer: Yes, it is very instantly recognizable, but not because his wording is bad per se.
Though born in Germany, Fassbender left when he was 2 years old and spent most of his upbringing in Ireland, speaking Irish. The Irish tongue is almost diametrically opposed to the German one: Germans use a (comparatively ) slack/backwards jaw and tongue when speaking, whereas the Irish (and Scotts as well) have this very clenched way of using their jaw-muscles in almost everything. And while he knows the right words, and what they should sound like, it's when he gets angry that this comes out the most.
What is interesting though, is his "rolling of the r", something that is very particular to specific areas of Germany, but also tied to those WWII speeches via the radio: using it for dramatic effect. You can hear this very clearly when listening to the German band Rammstein; their singer (Till Lindeman) doesn't have this "r" by nature, but uses it for a lot of dramatic effects when singing. Outsiders would very much associate this with those infamous arousing speeches from the WWII era, but also "classical German".
The two German actors in the team speak very little. Sgt. Stiglitz (Til Schweiger) is from Freiburg which has a very distinctive tongue. Gedeon Burkhardt (Cpl. Wicki) speaks to our ears as outsiders probably closer to what we perceive to be "standard" not just because he is from Munich, but he is also a well-known national star which makes many prone to soften their accents towards more "High-German".


Do I need a new tire?

Question: I noticed I had a flat in one of my tires so I made a trip to the nearest shop to get air now my tire has a ring around it showing where it rubbed against the rim!
enter image description here
Comment: Welcome to Motor Vehicle Maintenance & Repair! Usually, if you've driven on the rim and it's cut into the sidewall of the tire, it's time for a new tire. By doing this, you've seriously damaged the integrity of the sidewall. I can't see the image at work to give you better advice, so I'll leave this as a comment.
Comment: The guy told if he put more air it would pop and that I should get a new one but is the condition really that bad to the point my tire will pop while driving?
Comment: I fixed the image it should show now.
Comment: That isn't the problem. My work blocks images from several sources, this being one of them.
Comment: Also, if you are driving around with it seriously under-inflated (since the guy at the shop didn't want to burst it, and from your picture it looks visibly under-inflated where it touches the ground) it will tend to overheat as you drive, which will weaken it more - and an under-inflated tire will affect the car's handling as well. Bottom line - get a new tire ASAP!
Answer: That tire you definitely need to replace, the safety of you, your family and other road users is not worth the risk.
Comment: That amount of flexing on the sidewall weakens the plies (or strengthening bands / material) in the sidewall. Failure could happen at any time, so fit the spare and get that one replaced.
Comment: 3 separate contributors on here have said "replace the tire", what don't you understand?
Comment: I will get it replaced but how is the mark on the outer tire dangerous??
Comment: Agree with the answer
Answer: Sidewall damages are most dangerous one. The tires weakest spot is Sidewall. If you drive with this tire at high speed it can start to wobble and pop out of nowhere. Since it won't be a tiny hole that will lose air gradually, but a serious pop you might lose control and crash. Just change the tire.

Do I need a new tire?


Were covered wagons used on the Federal Road in North GA in the early 1830's?

Question: I'm doing reasearch on the years leading up to the Cherokee removal and need to know if pioneers during the early 1830's used covered wagons to travel long distances on the Federal Road in north Georgia.
Comment: As you're new on Stack Exchange and this likely is homework, FYI it's usually best to show what you've found so far in your question. Many history-related questions can be reasonably answered with a few google searches that dip into reasonable sources. For instance https://en.wikipedia.org/wiki/Covered_wagon offers that "covered wagon was long the dominant form of transport in pre-industrial America" and https://en.wikipedia.org/wiki/Georgia_(U.S._state) offers that the Cherokee were displaced at the time owing to a gold rush, so it's sensible to assume that covered wagons were used indeed.
Comment: Haha, no offense intended, I hope you didn't take it too badly. Hopefully the links will help you. And happy writing!
Comment: My goodness, Denis, it has been a long, long time since I had homework! This is for research on a book of fiction I plan to write about the time prior to the removal. My child character would travel from Athens to the Calhoun area (New Echota) and I couldn't find any source to tell me if COVERED wagons were used on the Federal Road in that area, although I know they traveled in wagons, stagecoaches and by horseback. A writer has to be absolutely certain of the information we use. Thank you for the links. I will certainly follow up.
Answer: Covered wagons were used in pre-railroad times (up to about 1850) to travel rough, undeveloped roads in the United States, particularly in hilly areas.
Old Federal Roadin North Georgia was such a road, at the southern end of the Appalachians, and would have been travelled in the 1830s.


send data from phone to PC via WIFI

Question: In my application, I want to send some data(say, "Hello") from my app to my PC over WIFI network. In PC, a service will listen to that data. But i don't have any idea of sending data over WIFI. I didn't get any proper references too. can someone help me.
Thanks in advance.
Comment: You can use Socket, ServerSocket, ... as in any Java app. How will you implement the PC service?
Answer: What you need is a propper protocol which both, your server and your phone can easily deal with.
If you don't send sensitive data, I think easiest would be HTTP
Answer: This depends on what you want the service on the PC to do with the received data, really. For all I know, you might find some off-the-shelf software that can help you set up this service. However, as others mention here, http is definetely the easiest way to do this. If you cannot find any existing software for the "listening pc", you'll need to write a program that listens at a predetermined port for http traffic (I wouldn't use the standard http port, 80, since you might run into conflicts with existing http software). You can do this quite easily in java, using Serversocket and/or Socket (as Tobias Rizau mentions above). Personally, I'd write a C/C++ program, since imo. that makes a better service, but that's absolutely not necessary (especially if you only know Java).

send data from phone to PC via WIFI


I am unable to login to the SDL Web content manager?

Question: I have copied existing content management DB and ran upgrade scripts.
Once SDL Web 8 Installation is completed, configured Directory services and restarted the system, I am unable to login using the MTS user provided in the instillation wizard.Did I miss any steps, How can I connect to the CM explorer?
Comment: If you copied the database, chances are that the old MTSUser is still the one in the trustees table. Change it to match the new one
Comment: Make sure you replace existing TRIDTEST\MTSUser with TRIDTEST\DMTSUser in TRUSTEES table in your CM database and try.
Comment: Did you check the logs (cm and core) ? Is there any indication ? You need to share more information here.
Comment: To avoid the conflicts we used name DMTSUser for MTS user. I am getting the below error while trying to connect the CMS System.ServiceModel.FaultException`1[Tridion.ContentManager.CoreService.Client.CoreServiceFault]: Access is denied for the user 56785-TRIDTEST\DMTSUser. (Fault Detail is equal to Tridion.ContentManager.CoreService.Client.CoreServiceFault).
Answer: Followed Nuno and ARRX suggestion and update the Trustee table,Content Management Explorer allowed me to login.Thank you for suggestion.
Once followed the suggestions I am able to login to explorer where as I am unable to see Content, Once I enabled Anonymous authentication in IIS as per SDL support suggestion I am able to see content and publications.
Comment: In principle, even for a small database hack like this, you should first get approval from support so that they can be sure you won't accidentally harm your system. In future though, it's probably best to add the trustee before you copy the database.
Comment: While I updated Anonymous authentication in IIS, I Enabled same for Topology Manager also due to that I am unable to delete the publication.As per Support suggestion I enable Windows Authentication for Topology Manager resolved my issue. @Dominic when you say "add the trustee before you copy the database" where should I add the user in Database, I was expecting that what ever information we are providing in wizard will save the user and grant me access to the system
Comment: I meant that if you have a database in, say, your production environment that you are going to export and then import to development, before you do this, go in to the user interface and add the user that you will need in development. If the user is in a different domain, you might need to use a GUI extension or a script to do this, but the principle is the same.


What results in the price difference for seemingly the same product?

Question: I am considering buy the latest Apple Mac Mini M1 with 512GB storage from Apple or from Amazon. Apple lists it at $899 while Amazon lists it at $859. What is the hardware/software different that results in Amazon being $40 cheaper than from Apple directly?
Answer: There's no hardware or software difference.
As with all other retailers, everyone is free to set their own price. The price can be based on all sorts of parameters, which makes it impossible to say exactly why retailer A is xx$ cheaper or more expensive than retailer B.
It could be for example that a retailer has lower costs. For example having an online presence versus a physical presence is typical less costly. Similarly could spending different amounts on customer service, warranty repairs/support, etc.
It could also be that a retailer that is also the maker of the product wants to be in the market at a relatively high price in order to ensure that other retailers find it worth while to sell their products.
It could also be that one retailer earns money from other sources than the specific product sale - and that makes it possible for them to lower their price. For example by gathering data about the customer, or simply by having the customer browsing their web site making it more likely that they will buy other products from the same retailer.
Comment: Indeed. Personally, if there's no price differential, I'd rather buy direct from Apple - that way there's nobody else involved if any problems arise. Given that Apple have an extensive network of shops and an efficient delivery service, it may well be that other online retailers *need* to offer a discount if they are to generate substantial custom. No doubt they hope to make up the difference through being able to sell accessories/peripherals/etc.
Comment: @avid: You actually touch on something I was thinking of asking. Does Apple offer the same service if I purchase the Mac Mini, and other Apple products, from another vendor?
Answer: Manufacturers sell to shops at a trade price, let's say 75% of the full retail price. The retailer makes their money from this 25% difference in price. Retailers can reduce the retail price from their cut, if they think that this will attract more customers, in order to sell higher numbers.
The retailer hopes to make more money from a slightly smaller margin by selling more units.
There is no difference in the hardware, and you get the same access to Apple's services - iCloud, Music, TV, etc. You can take it into an Apple Store if you have a problem with it.


how to send and receive back the user_id in the success link of payPal?

Question: I'm confused with paypal sequences.
I want to add in the website a donation paypal link "for members only" it's my client demand and I want to store in the db if the user have made a donation or not and how much.
Now he is using in the website just the link https://www.paypal.com/cgi-bin/webscr?cmd=_s-xclick&hosted_button_id=6SENM6TBA5EPL
so this means that he have an account on paypal and have created a button with this id "6SENM6TBA5EPL". what I know is that from the button config. in paypal site we can set cancel and success links,it's ok.
But I want to send the user_id and receive it back from paypal as a variable on the success link if the donation is made.
So it's just to add another url variable like https://www.paypal.com/cgi-bin/webscr?cmd=_s-xclick&hosted_button_id=6SENM6TBA5EPL&user_id=123
or I can use the paypal form like this
<form action="https://www.paypal.com/cgi-bin/webscr" method="post" target="_top">
<input type="hidden" name="user_id" value="123">
<input type="hidden" name="cmd" value="_s-xclick">
<input type="hidden" name="hosted_button_id" value="6SENM6TBA5EPL">
<input type="image" src="https://www.paypalobjects.com/fr_FR/FR/i/btn/btn_donate_LG.gif" border="0" name="submit" alt="PayPal - la solution de paiement en ligne la plus simple et la plus sécurisée !">
</form>

Answer: You could use the custom variable as a pass through variable.  Then as far as getting the information back, you can either have it returned through IPN, PDT, or using the rm variable.  I posted more detail on IPN and PDT on this forum posting here.
<input type="hidden" name="custom" value="blah blah">


time.sleep -- sleeps thread or process?

Question: In Python for *nix, does time.sleep() block the thread or the process?
Answer: It blocks the thread.  If you look in Modules/timemodule.c in the Python source, you'll see that in the call to floatsleep(), the substantive part of the sleep operation is wrapped in a Py_BEGIN_ALLOW_THREADS and Py_END_ALLOW_THREADS block, allowing other threads to continue to execute while the current one sleeps.  You can also test this with a simple python program:
import time
from threading import Thread

class worker(Thread):
    def run(self):
        for x in xrange(0,11):
            print x
            time.sleep(1)

class waiter(Thread):
    def run(self):
        for x in xrange(100,103):
            print x
            time.sleep(5)

def run():
    worker().start()
    waiter().start()

Which will print:
>>> thread_test.run()
0
100
>>> 1
2
3
4
5
101
6
7
8
9
10
102

Comment: Open a new question to ask the meaning of this answer? That seems quite weird to me. And I meant 11 (not 5), sorry can't correct my comment now.
I actually need some help understanding what point this answer is trying to make.
Comment: How does illustrate a "thread" has got blocked. And why don't only 5 and 103 not get printed, while all other numbers get printed. Would be really helpful for me if someone could explain.
Comment: akki, More specifically, time.sleep() blocks the thread that called time.sleep(), but it releases the Python GIL to run other threads (so it doesn't block the process). Nick's example didn't really show the blocking of the thread, it more showed that the GIL is released (thus showing that the process IS NOT blocked). I think if he had more stuff like a print statement after time.sleep(5) in the waiter() thread, it would show that the print didn't happen until after the time.sleep(5) finished (i.e blocking)
Comment: @akki: please ask a new question rather than using the comments of an old question.  Also, 5 gets printed (it's right before 101).
Comment: First answer:  The range function xrange(k, m) returns the numbers k inclusive up to m-1 inclusive, so the expression list(xrange(100, 103)) returns [100, 101, 102].   This means that length(list(xrange(k, m))) == m - k.
Comment: Second answer:  His point is that while 'waiter()' is sleeping, 'worker' continues to run.
Answer: It will just sleep the thread except in the case where your application has only a single thread, in which case it will sleep the thread and effectively the process as well.
The python documentation on sleep() doesn't specify this however, so I can certainly understand the confusion!
Comment: @MichaelMrozek: [`sleep(3)` says: *"sleep()  makes  the  calling thread sleep until seconds seconds have elapsed or a signal arrives
       which is not ignored."*](http://man7.org/linux/man-pages/man3/sleep.3.html) And [there is Python documentation bug](http://bugs.python.org/issue23251).
Answer: Just the thread.
Answer: The thread will block, but the process is still alive.
In a single threaded application, this means everything is blocked while you sleep.  In a multithreaded application, only the thread you explicitly 'sleep' will block and the other threads still run within the process.
Answer: Only the thread unless your process has a single thread.
Answer: Process is not runnable by itself. In regard to execution, process is just a container for threads. Meaning you can't pause the process at all. It is simply not applicable to process.
Comment: Sad to disappoint you, but on Windows and all *nix systems the main running unit is a thread. You can't run process without threads. If you exit last thread, process terminates.
Comment: This does not answer the question.  In particular, this question is about Python.  Python has a Global Interpreter Lock (GIL).  If a thread were to go to sleep while holding the GIL, it would block all Python threads in the process, because they all share the same lock.
Comment: Huh? This may be true on Windows or something, but certainly not universally. Unix traditionally did not have threads at all, and so a Python program runs a process (with a single thread, in some abstract sense) which is what the `sleep` command will pause.
Answer: it blocks a thread if it is executed in the same thread not if it is executed from the main code

time.sleep -- sleeps thread or process?


Etymology of kato and kata

Question: According to the Wiktionary, kato originates from French, Italian, Latin, etc... and kata comes from kato + a. But how can we say that it is not the opposite? Can we say that the root kat- comes from French, Italian, Latin, etc... and depending on the suffix used, it defines the grammatical class of the word (like noun, adjective, ...)?
Answer: In Esperanto, the root words themselves already have a meaning. So the root kat is already the animal and it is intrinsically a noun. Similarly, the root bel intrinsically represents the state of something so it is most naturally used as an adjective.
However, neither of these roots can be used alone without an ending to classify it, so even though kat is a noun, you need to add the -o to use it in a sentence. And bel needs to have -a if it is used as an adjective. These endings don't change the base meaning.
On the other hand, adding -a to kat changes the meaning to be "like a cat". So in that sense, kata is a derived word from the Esperanto word kato. Adding -a to bel doesn't create a new meaning, so we wouldn't say that bela is derived from belo.
So, I guess you could say that kato is just a declination of the root kat and that kata is a derived word with a different meaning. Wiktionary doesn't have entries for the root words alone, so it has to have the root meaning under the article with the word with an ending. In this case the most logical ending to represent the root meaning of the root kat is kato.
As always, PMEG has a more detailed description of this.
Answer: Linguistics categorizes words into noun, verb and other roots, so kat is more noun (kato), and lern is more verbal (lerni).
The number of occurrences of a suffix -o/-i/-a and other statistics play a role.
For Esperanto dictionaries that categorisation could play a role for the entry word:

kaso, kasisto
kato, kateca
kavo
...
lerni, lernejo, lernanto

It also has some effects on the word forming:

esti alta = alti (rare)
esti kato = kati (to be avoided)

The arbitrary roots of different categories:

martelo / marteli (=hammer)
segi / segilo (=saw)
pinĉi / pinĉilo
though: ŝraŭbo / ŝraŭbi / ŝraŭbilo (=screw / screw driver)

But in general for Esperanto it is an unneeded categorisation.
More sense make verbal (in)transitivity.

Etymology of kato and kata


How to make this gradient artefacts disappear?

Question: Left one has some strange round shades and is not smooth like a yellow one
Answer: The discrete nature of your computer system comes quite consistently as a surprise to users. There are only so many colors in the palette of a standard display printer etc. Could there be more? Sure but that would mean the need to change how most of the systems work, deploying new monitors and printers costs money after all.
So 256 intensities is barely adequate for human vision. This will become readily apparent when you have a limited palette change because the individual areas of color become so large that your eyes edge detection kicks in (see mach bands on Wikipedia).  Your eye is really good at this so its not so easy to fool in all cases.
Ok so if your palette is this limited then you have essentially 3 options:

Make the colors a bit dirty. This can sometimes elimnate the problem, by introducing more steps to otherwise too perfect colors. Especially on monitors. So adjust the channels up and down by +- 0-2 per channel. Some combinations just have more discrete steps.

Dither the gradient result. So you can compute the gradient at a higher color precision and then sample it down so that intermediary colors are represented with a alternating color values, either vith a pattern or a stochastic noise. Just like print make intermediate colors.
This is not an option for illustrator. Not only because illustrator can only work at 8 bits per channel, but any vector file exported out fo illustrator would have the same limitation. What use would it be to fix this inside illustrator if your downsteram user would still have this problem?*

You can fool the visual system by adding noise to the image. This does much the same as dithering but with a much much less elegant result.
THis neccesitates your gradient being a pixel image. So you just lost the main benefit of vector image systems.

But yeah no good options im afraid.
* Well they could offfer it as an option for screen only outputs, or reasterized outputs.


Increasing resistance on speakers

Question: My amplifier is rated at 8ohms for my surround sound but my speakers are 6 ohms. The owners manual says that if the speaker resistance is too low the power protector will blow and that is exactly what happens when I raise the volume on my amp. I want to increase the resistance on my 5 surround sound speakers and my subwoofer by 2 ohms from 6 to 8.  I was thinking about inline resistors. My question is do I use 2 ohm resistors to take 6 to 8 and do I put them on both the positive and negative speaker lead or just one of them. If both would I put 1 ohm on each lead to get 2 ohms total?
Comment: You must be driving it pretty hard, or else it is a poor quality amplifier. Consider a better one.
Comment: it's a more involved solution, but perhaps an impedance matching circuit? that way all the available power can be fed to the speakers without cooking the amp
Comment: This approach will keep your power protector from blowing, but you'll be using power to heat up the resistors, and your speakers won't get louder.
Answer:

simulate this circuit – Schematic created using CircuitLab
Figure 1. Series connection of resistor.
Since you are increasing resistance in a series circuit the amplifier won't know or care where in the circuit the resistance is. Convention would be to put it in the red or '+' wire.

simulate this circuit
Figure 2. Simplified equivalent circuit.
The problem is that your speaker isn't just a resistor. It is largely an inductive load and since it has mechanical resonance (favourite frequencies to vibrate at) the situation becomes more complex. A good amplifier will have a strong drive to force the speaker to the correct position at any instant and overcome the inductance. Low resistance speaker cables are part of this equation. Adding your 2 Ω series resistance will affect how well the amplifier is able to control the speaker and some loss of fidelity will result.
Try it and see if you notice. The resistors will need to be rated to handle the power. Start with ones rated for at least 1/4 of the nominal amplifier output power rating.
Answer: Adding a single, \$2\Omega\$ resistor in series with each speaker will work.
Make sure to get appropriate resistors, they will dissipate one fourth of the maximum power your amplifier can output, per channel. If you have 50W per channel your resistors can dissipate up to 12.5W, so you need to get at least this wattage.
Using series resistors is not something I would recommend though. The best option would be to change the speakers, but this of course come at a price, the new speakers' price. But you can just keep your volume low enough. Keep in mind that adding resistors will let you rise the volume up to the maximum, but you will not hear a difference in actual volume since the excess power is dissipated on the resistors, which usually do not emit sounds.
I am guessing you are using the system with a TV set that includes some 5.1 source: maybe you can rise all the volumes, and regulate your amp volume so that the protection does not blow, then you do not touch this volume anymore and just regulate the source.
The resistor option is the safest anyway, since an unaware person can (and will) stop by, rise the volume and blow the protections.
Answer: An impedance matching transformer is better than a resistor in series with your speakers. Although they are pricey.
Paul Speltz for speakers.
http://www.zeroimpedance.com/
For guitar amps Ted Weber
https://www.tedweber.com/z-matcher
Hope this helps
Answer: Yes you can add a resistor, BUT.
A loudspeaker's impedance depends on frequency. This is the impedance vs frequency plot of a 2-way bass reflex speaker I just randomly googled:

It is a typical plot for a 2-way bass reflex. The bass driver resonance and bass-reflex vent resonance create two peaks at low frequencies, and the crossover between woofer and tweeter is apparent between 1.5k and 3k. This is a 4 ohms speaker. For a 8 ohms speaker the plot would look the same, scaled up by a factor of 2.
Adding a resistor in series will make a voltage divider (see Transistor's answer for schematic), and the voltage on your speaker will depend on its frequency-dependent impedance. This means the frequency response of the speaker will change. The output will be attenuated most where the speaker's impedance is low, but it will have very little attenuation on frequencies corresponding to impedance peaks. Also, damping will change.
So, it will probably sound different, you'll get a bit more bass. This may be pleasant, or maybe not, depending on the speakers, but don't be surprised if you hear a difference.
So I recommend getting a few cheap 2 ohms 10W resistors and making a quick test.
Note that the volume won't get louder, as the extra power will be dissipated into the resistors.

I want to increase the resistance on my 5 surround sound speakers and my subwoofer by 2 ohms from 6 to 8

Well, you don't mention which amp trips its protection circuit. Most likely the amp just shuts down and doesn't tell you which channel is the culprit.
Usually surround speakers don't get that much power. Most of the power goes into the sub, then the left/right/center speakers.
Also usually, the overwhelming majority of the power goes into bass frequencies. Any decent tweeter will make you deaf with 1 watt, but if you want rumble, you need a whole lot more power.
So I'd recommend setting the volume so the amp's protection trips, and then unplugging the sub and/or the main speakers. Does it still trip?
If the main front speakers still trip the protection, try enabling the highpass feature on the amp to direct all the bass frequencies to the sub. This will reduce the current required by front speakers.
Most likely it will trip with the sub plugged in, and will not trip when it is unplugged. This would mean you don't need resistors... it could be that all you need is to lower the gain on the subwoofer a little bit.
If you're a bass addict, that won't be satisfying though. Then you need an active sub, or a sub with higher efficiency. Resistors will not help.

Increasing resistance on speakers


What is a good book to learn how to manipulate inequalities with absolute values?

Question: I've noticed that I'm really having trouble with limits because I've had very little experience manipulating inequalities and I really have little to no idea how to manipulate inequalities involving absolute values.  I really didn't learn it in high school (along with analytic geometry).  I don't really know where people have learned when it is okay to for example pull the exponent out of the absolute value bars and such.  I'm trying to pick some things up from my Spivak calculus book, but I want to know that I know ALL the rules of manipulation.  My question is what is a good book that explains how to manipulate inequalities involving absolute values?  I would prefer a book that deals with this extensively.
Comment: A bit late maybe, but I found this helpful: https://www.math.purdue.edu/academic/files/courses/2007fall/MA301/MA301Ch2.pdf

Basically you can derive all the properties yourself from the order axioms on the real numbers.
Answer: The book The Cauchy-Schwarz Master Class by Steele is focused specifically on manipulating inequalities and contains detailed solutions to all of the exercises, making it a good choice for self-study. I, too, am lousy with inequalities and the (regrettably small) amount of time I have spent with this text has been profitable.
Comment: +1 for one of the best books for undergraduates there is on basic inequalities. Everyone should work through this book before tackling rigorous analysis for the first time.
Comment: These have been the bane of my experience in my real analysis course. I'm going to go through this book with vengeance and get rid of that weakness. Thank you!
Comment: I never had heard of this book before, it would indeed have been useful for analysis. Maybe it would still pose interesting as a light read :)
Answer: Here are some of the basics.

 If $|a|\leq b$ (where $b\geq 0$) then $-b \leq a \leq b$
 If $|a|\geq b$ (where $b\geq 0$) then either $a \geq b$ or $a\leq -b$
 $|ab|=|a||b|$ and, as a consequence, $|a^n|=|a|^n$
 the triangle inequality $|a+b| \leq |a| + |b|$
 If $f(x)$ is monotone increasing, then if $x\leq y$ then $f(x)\leq f(y)$.  See the wikipedia article on inequalities
 Somewhat less used in undergrad calculus is the Cauchy Schwarz inequality $| x_1 y_1 + x_2 y_2|^2 \leq (x_1^2 + x_2^2 ) (y_1^2+y_2^2)$
Comment: One I often used was a combination of the triangle inequality and the two relations: $(x-y)^2=x^2 +y^2 -2xy \geq 0 \implies x^2 +y^2 \geq 2xy  $ combined with:
$(x+y)^2=x^2 +y^2 +2xy  \leq 2x^2 +2y^2 $ to get rid of linear cross-tems in a question about the Banach fixed point theorem. Here you work with inequalities often derived from the mean value theorem and this trick is used to bring everything back to squares so you can get norms of vectors again.
Answer: Try this one, i am using it and find it exceptional for HS student:
http://www.amazon.com/Inequalities-Mathematical-Radmila-Bulajich-Manfrino/dp/3034600496/ref=pd_sim_b_3
Once you become more familar with that book, use this(give you more insightful more rigorous proof and more advanced stuff):
http://www.amazon.com/Inequalities-Cambridge-Mathematical-Library-Hardy/dp/0521358809/ref=sr_1_8?s=books&ie=UTF8&qid=1331606830&sr=1-8#_
Comment: i do not understand why a person that seems to have problems with basic facts about inequalities should read books that deal with mathematical olympiad problems on this sector. That does not make any sense to me.


Corn as kitniot

Question: Traditionally, most if not all observant Ashkenazim refrain from eating corn and corn-products on Passover because of their traditional prohibition on eating kitniyot (legumes) for fear of eating Biblically-prohibited chametz (leavened products). Corn, or  maize, is a New World crop that could only have been imported to Europe once this was feasible. What is the earliest source in the rabbinic literature to classify corn as kitniyot and is it universally accepted as such? (I believe I have noticed in recent years a package of "kosher for passover" sweets that suggests Rav Isaac Elhanan Specter, z"l, was lenient, but I am looking for more specific sources.)
Comment: [This answer](http://judaism.stackexchange.com/a/12865/3483) attributes it to linguistic confusion over "corn" often meaning "grain" but does not source that assertion.
Comment: @Mike not saying that's *THE* reason, just that it further hurt it.
Answer: I believe I'd seen it printed somewhere on the daf in Shulchan Aruch, but would have to dig some more. (The other problem is that everyone is giving the local Yiddish-ish word for these plants, which can be tricky to translate.)
Don't be fooled by the sweets package! It contains corn syrup; the argument is "Rabbi Yitzchak Elchanan Specter allowed all liquid kitniyot." No, he allowed oil extracted from kitniyot, as there's little concern of confusion or contamination with regards to the oil. Corn syrup is converted from the grain itself. (Regardless, the argument isn't "corn isn't kitniyot"; it's that corn syrup isn't the same as corn.)
Comment: And i think it's only oil or syrup from kitnios that was cooked before Pesach, to facilitate bittul.
Comment: Oil is also converted from the grain itself.

Corn as kitniot


Does a freight train need to obey a stop sign?

Question: If a rail line runs down the middle of the street, does the driver of the train need to obey street signs?  For example, if I'm driving a freight train down this stretch of Whitman Street, do I need to stop at the intersection and wait for cross traffic to clear before proceeding?
Comment: @cpast they can still stop at any given point. They just need to begin stopping soon enough. There's nothing physically preventing a train from stopping at a stop sign, which is not a moving target.
Comment: It doesn't matter that much if you have to or not; generally, freight trains are physically incapable of obeying street signs (they take much longer to stop than a car).
Answer: Authority to put up stop signs comes in part from RCW 47.36.110, and RCW 46.61.190 says that "every driver of a vehicle approaching a stop sign shall stop at a clearly marked stop line...". The definitions for that title (RCW 46.04.670) states that ""Vehicle" does not include power wheelchairs or devices other than bicycles moved by human or animal power or used exclusively upon stationary rails or tracks", so a train is not a vehicle. The operation of trains is governed, on the other hand, by Title 480, and Part 2 of that title includes safety laws. There is a complex federal and state system pertaining to signal systems. Since a train is not a vehicle, it is not subject to the laws requiring vehicles to stop, but it would be suject to any laws requiring trains to stop. Technically, the question could also be whether it's legal for vehicles to drive on train tracks, since I believe the railroad right-of-way was there first, but you could check historical records.
Comment: A train is clearly a vehicle. It's just not a vehicle to which the road traffic codes apply.
Comment: Strangely, though, the definition for "train" starts with "A vehicle..."
Answer: If you drive a freight train and don't have the training to know what you should do, but instead have to ask for the answer on law.stackexchange.com, then you should be fired immediately. You are a danger to the public.
If you are in a car and watch a freight train coming, then given the choice of insisting on your right of way on one side, and not being crushed by a train on the other side, you are free to decide either way, I would opt for "not being crushed by a train".
Usually trains will have signalling lights that tell them whether they can drive or not, broken signal means they need to stop.
Comment: And in any case safety wins over regulations always; no matter what the other rules are, both the train and car drivers have to stop if they can do it safely and it is needed to avoid an accident. Regulations only decide who will have to pay the fines and damages and/or spend prison time.
Comment: Golly, I had assumed that he's asking what the law actually is, and he isn't a train engineer who doesn't know his job.


wordpress frontend editor to add extra css to website

Question: i need to create a plugin that allows me to select any button or any part of the website and  add extra css to it ,i have manages to consumer rest api within wp ,add menus and submit forms but i have no idea how to accomplish this task ,i would appreciate any suggestion
thanks
Comment: Why can't you just add CSS using the Additional CSS section of the customiser?
Comment: i don't want to add css classes,insted i need to add exta css  to specific html button/ a tags and so on
Comment: Why can't you do that with regular CSS?
Comment: sorry my bad i didn't explain the issue well , i don't need to add classes to css files but i need to add specfic css classes to tags regardless of their exsitance in a css file , so the task is to change the the html generated by wp and to trigger that i need to click on an item (button,rating....) and a css class to it
Answer: I think it's worth studying how other plugins work, for example: Visual Composer.
The logic that came into my head, is to pick the element selector clicked with jQuery, and work on it. Read this that may help you:
https://stackoverflow.com/questions/5706837/get-unique-selector-of-element-in-jquery
Following this logic, if each page element has the same class, it will be easier to work with
Comment: thanks Gabriel, studied various plugins,they only allow users to edit elements created with the same  plugin so visual  composer for instance won't regognize elements created with beaver
Comment: @JawharJarrar
I found this plugin
https://gist.github.com/saarmstrong/5e8d2ac45dfd76a2574f

In thesis this:

$ ("*"). click (function () {
    var path = $ ('this) .getPath ();
    console.log (path);
});

It should return something like:
// html> body> div # bar> ul # abc.def.ghi> li # foo "

Ai you just work css ...

But I did not test, if it works, let me know! I think it can help with my projects too.