Why root raised cosine filter can eliminate intersymbol interference (ISI) ?

Question: My question is kinda silly, I know it. But I cannot understand why root raised cosine filter or raised cosine filter can eliminate ISI.
I googled before, but those explanation is not easy for me to understand. Maybe someone can help me this with some figures? Thank you so much for you help in advance.
Comment: [This article is an extensive explanation](https://pysdr.org/content/pulse_shaping.html) of how pulse shaping works.
Answer: Pulse shaping is not done to "eliminate ISI": it does not act as some sort of equalizer to remove ISI that may already be in the waveform. The only reason for pulse shaping is to restrict the occupied bandwidth, and pulse shapes that meets the Nyquist ISI criterion are able to provide the desired bandwidth restriction without introducing new ISI.
In addition to the frequency response that AlexTP showed, I think the time domain view of the impulse response gives good insight into the Zero-ISI operation of a Nyquist filter. Below is shown the result of transmitting three symbols, than each began as a single impulse. Each plot below is the "impulse response" for each symbol. Note the blue symbol was transmitted first and is maximum at time index 0 on the graph (but began much earlier than this in time). This position where the impulse response is maximum is our ideal sampling location to determine what was transmitted. One sample after the original impulse for the blue symbol, came an impulse for the red symbol. Notice at the ideal sampling location for red (where it is maximum), the response from all the other symbols is zero (meaning zero ISI).

The pulses shown above have zero ISI at the sampling locations, but extend to infinity to achieve the maximimum conservation of bandwidth (1/(2T)). Of course, this is not feasible, so the raised cosine pulse shape applies a window to truncate the perfect Sinc function, resulting in a trade of bandwidth versus filter complexity, as well as trades with other characteristics related to performance for timing recovery.

The filter is often split between transmitter and receiver as a "root-raised cosine filter" (RRC) on each side. Note that a RRC filter does NOT have zero-ISI until it is paired with the second RRC filter to form in cascade a raised cosine filter.
Below is an example eye diagram, showing the trajectory over 1 symbol for multiple pulses (each trajectory is based on the history of all previous symbols within the depth of the RRC filter and results in a different path when going from 0 to 1 or 0 to 0 etc).  At time 0 is the ideal sampling instant to decide between 0 and 1, notice with the RRC filter that there is significant ISI, which is eliminated after passing through the second RRC filter in the receiver (assuming no other multipath effects have occurred).  Also notice for the filter with alpha = 0.25 that there is a significant spread in the zero crossing locations, which would add more noise in timing recovery operations that are sensitive to zero crossings. Compare this to the eye diagram with alpha= 1 and notice the significant decrease in zero-crossing jitter, as well as a wider "eye-opening" which also means less sensitivity to jitter or other errors in the sampling clock location, but this benefit comes at the expense of less spectral efficiency.

What is very interesting is the pulse shaping Nyquist filter that fred harris now refers to as the "harris-Moerder Nyquist Pulse". Using this as the pulse shaping filter results in an order of magnitude lower EVM for the same number of taps. This isn't commonly used even today (15 years later) to my knowledge since the root-raised cosine filter is baked into our specifications (I assume) but certainly is very compelling to be aware of for consideration in future radios.
Comment: Dear Dan, first of all. thank you so much for your detail answer. What a helpful person you are!!  However, i guess I am too native or "entry level" here.  May I ask you, give me more idea about zero ISI and Nyquist theory? What I know about nyquist is the sample rate should be 2X high than original signal frequency. But I dont have any connection between Nyquist theory and ISI.    I don't know you can attach some picture again or not, if not, do you think i need to post a new question?  Thank you again, Dan.
Comment: Thank you @Sunson29, I think between my answer and what AlexTP shows which is also very good is probably the best we could do to answer your question. I recommend finding a good book on DSP to help get you up to speed and I am sure  you will have some very specific questions along the way (right now your question is much too broad to answer concisely, especially if you do not yet follow what we answered). There are some other posts you can search for where people have asked for good DSP books to get started with and I recommend that as your next step.
Comment: Dear Dan,  I was studying this today. It's much better now. Please allow me to ask one question. It seems that Alpha = 1 is the best idea case, am I right? it seems that the eye is so clear. But because considering bandwidth efficiency, ppl more perfer to do 0.2 ~ 0.4 ?
Comment: @Sunson29 If we did not care about spectral efficiency there would be no reason to do any raised cosine filter and we could simply transmit rectangular pulse shapes in time (which is a Sinc function in frequency). So you are correct from the point of view of accuracy in timing in the receiver, the larger alpha is better but from the point of view of spectral efficiency (which is quite a concern!), the smaller alpha is better. Hence there is a trade to be made.
Comment: Dear Dan, I am confused again. Because you said "If we did not care about spectral efficiency there would be no reason to do any raised cosine filter " .    My question,  I thought the main reason we have raised cosine filter is because of ISI elimination.  Well, at least wiki said that. After "fix"  the problem of ISI, then we talk about spectral efficiency. Please verify my understanding.  Thank you, dan.
Comment: That is because the raised cosine filter can provide you spectral efficiency with zero ISI. If we did not care about spectral efficiency we could just send rectangular pulses which are very wide band signals but also have zero ISI. So bottom line, the raised cosine filter is a way to provide the spectrum filtering that we need without introducing ISI.
Answer: Because it satisfies Nyquist ISI criterion Nyquist_ISI_criterion.
The simplest way to apply this criterion to root raised cosine filter is looking at its frequency response of the composite filter "raised cosine" : Raised-cosine_filter

You can see easily that the sum of $1/T$-shifted spectrum of raised cosine filter is constant.


What is exact difference between TDD and BDD?

Question: What is exact difference between TDD and BDD? Could you please briefly explain them to me?
Comment: There is this Website called Wikipedia. Please read https://en.wikipedia.org/wiki/Test-driven_development and https://en.wikipedia.org/wiki/Behavior-driven_development, especially https://en.wikipedia.org/wiki/Test-driven_development#TDD_and_BDD.
Answer: TDD (Test Driven Development)

Who's involved: Developers
Summary: Developers start writing code by first defining tests (in general unit tests). It could sound strange, but this practically guarantees a high code-coverage and in particular it forces developers to think about what they are doing. TDD can be applied to any kind of software.

BDD (Behaviour Driven Development)

Who's involved: Anyone (in theory)
Summary: It allows defining a priori the expected behaviours of a software.
There are several tools, like Cucumber, for writing "Behaviours".
You should write the expected behaviour using a predefined syntax that will be translated into code by developers and into test by QA.
BDD cannot be applied to any kind of software.
Answer: Both are a form of test driven development, since you write the tests upfront. The main difference is that TDD tests are technical tests often unit-tests created during developing of a feature and are written just before you implement a part of the feature in the code-base. Where BDD tests are often written before the coding starts and are human readable and anyone should be able to understand what they test. BDD tests are used as Specification by Example.
But its a bit more complex than that as BDD frameworks like JBehave can also be used to write unit-tests, but also for end-2-end integration tests. And nothing is really forcing you to make the tests readable by non developers.
There is also a third term ATDD (Acceptance test-driven development) which is how BDD was called before the BDD era. This makes the difference between the both a little bit more clear.
Suggested reads are

Online TDD chapters of the Art of Agile
The specification by example book
The Test Driven book.

Personally I think we should find another name for TDD which makes it clear that its a cycle for writing unit-tests, because now its so broad that any tests defined before the coding could be called a form of TDD.
Hope I not confuse you more, but the main difference is technical tests testing the working of methods (TDD) vs human readable tests describing the behavior (BDD).
Answer: Adding my view points here.
TL;DR : BDD focuses on the behavioural aspect of the system rather than the implementation aspect of the system that TDD focuses on.
BDD gives a clearer understanding as to what the system should do from the perspective of the developer and the customer. BDD allows both the developer and the customer to work together to on requirements analysis that is
contained within the source code of the system.
TDD gives the developer an understanding of what the system should do.TDD encourages coders/designers to design as little as needed. Tests in TDD help the programmer see clearly what to build and stop when they've built it.
TDD implies that you must test every method in your application (well, not every method, but at least a good coverage of them) asking them -

"When I execute you with this parameters what effects do you have?".

BDD implies that you must test every user behaviour (again, "every" is the best situation, but sometimes you can't test every behaviour) using a different language:

"When the user goes into this page, fill this form and send it what can they see after?"

Notice that in TDD what you ask is "what is the application doing?" and in BDD you are asking "What can see the user?"
In my understanding,TDD is more exhaustive, but has a problem- it is more dependent on the implementation.
If you change the name of a class, method, what a method returns, etc. you must change the test.
BDD is more pragmatic- I don't care about the internal implementation but about what the user can do and can see.
If you change the internal implementation (you change the webservices you are using, the name of a class or the algorithm) but the user still see it's working you are Ok.
Here's to hoping TDD vs BDD wars don't start again :)
Adding some useful TDD vs BDD link from SO :

Link 1
Link 2
Link 3
Link 4
Answer: Test Driven Development

TDD is the technical team that all cases of unit tests will be written
TDD is installed for testing
TDD encourages technicians to design as little as necessary
TDD help the programmer clearly see what to build and when to stop stop built.
TDD focuses aspect of the implementation of the system
TDD methodology is Inside-Out, TDD is more like a development tool for building testable, modular architecture.
Tdd = Refactoring + TFD Behavior Driven Development
then BDD is to take care of the functional aspects thereof. the average can be understood by non-developers too
BDD applies the narrative format (Since when, then format)
BDD encourages everyone to build as little as necessary.
The act of writing examples BDD style gives everyone on the project a clear understanding of what it means to a function and when to stop its construction.
BDD focuses on the aspect of system behavior is a BDD methodology outside inward. It starts out by identifying the business results, and drill down into the feature set that will achieve those based outcomes.each is captured as a "story."
BDD = TDD + incremental analysis of needs
Answer: This blog I found gives a good understanding the difference between TDD and BDD -
https://onpathtesting.com/why-go-for-behavior-driven-development-bdd/
Comment: Please add a little more description on how this explains the difference. Link only answers are not the best way to answer and are frowned upon.
Answer: I know I am 5 years late :-( but I see this question relevant even after 5 years as this is still an open question for many. I also think that the answers given till date is not comprehensive enough to exactly explain the differences.
Here are the 5 main differences between TDD and BDD:

TDD is implemented by Developers and BDD is implemented through collaboration between cross functional members of the team. Collaboration is the key for BDD to be successful

The test scenarios in TDD is implemented using a programming language. BDDs are written in Natural language

Developers responsibility to create and maintain TDD artifacts. Whereas BDD Artifacts are developed through collaboration and maintained by entire team

TDD is Black Box testing and BDD is White Box testing

TDDs are written for individual functions. BDDs are generally written for end to end behavior

I have written a comprehensive article, explaining these differences using examples and code. Link to the article is given below:
https://blog.nocodebdd.com/bdd-vs-tdd/


nginx caching dynamic content to static

Question: I've read and heard that nginx can cache dynamic content and make it static so it loads faster taking more of a load of apache. has anyone done this before? is it worth it? any pros/cons to it?
Answer: Your question is somewhat ambiguous, I'll take a guess and assume you mean using nginx as a reverse proxy.
The main benefit of doing this setup, is reduced load.  Nginx would optionally serve all static files, and reverse proxy all dynamic generated content.  There are major performance benefits to this type of setup, and it can handle more connections.  The major drawback is system complexity, you now have two web servers instead of one.  It also is considered a more difficult system to administrate.  regardless, I believe this is a great setup.
I originally looked at this setup, and then realized I could do everything just from nginx.  Once you break everything down, only a very few things are Apache only. You can even set up a static cache all from the one nginx server, less complexity.
I hope I could answer your question.
Answer: They could be talking about 'proxy_store' -- http://wiki.nginx.org/HttpProxyModule#proxy_store

nginx caching dynamic content to static


Gauge invariant Chern-Simons Lagrangian

Question: I have to prove the (non abelian) gauge invariance of the following lagrangian (for a certain value of $\lambda$):
$$\mathcal L=   -\frac14 F^{\mu\nu}_aF_{\mu\nu}^a + \frac{k}{4\pi}\epsilon^{\mu\nu\rho}\operatorname{tr}[A_{\rho}\partial_{\mu}A_{\nu} + \lambda A_{\mu}A_{\nu}A_{\rho}]$$
Is there an easier way than expliciting every component of A, going to first order gauge transformation, ... ? Cause it seems really ugly to me.
Answer: There is a nice reason for this, which Witten often explains. Imagine that your three dimensional space is the boundary of a four-dimensional space, for example, you can imagine that space is the surface z=0 of regular four dimensional space x,y,z,t. Further, you can imagine that space is closed into a sphere, which doesn't affect things except for some boundary conditions at infinity (the physics shouldn't care about such things, also note that this is implicitly Euclidean). If you close the three dimensional space-time into a sphere, the interior of the sphere is like the rest of the values of z for the plane case.
You can extend any 3 dimensional gauge field configuration to the imaginary fourth dimension arbitrarily, so that any gauge field on the surface of the sphere can be extended to many different gauge fields on the interior.
On the interior, you can construct the manifestly gauge invariant operator:
$$ \epsilon_{\mu\nu\lambda\sigma} F^{\mu\nu}F^{\lambda\sigma} = F\tilde{F}$$
It is important to note that this quantity is a perfect divergence:
$$ F\tilde{F} = \partial_\mu J^\mu_\mathrm{CS} $$
where J is the Chern-Simons current in 4-dimensions. Using Stokes theorem, for any four-dimensional gauge field configuration
$$ \int F\tilde{F} = \int d(*J) = \int_\partial *J $$
Where the last equality is Stoke's theorem, and the previous equality is writing the diverence of a current as the Poincare dual of a three-form.
So the manifestly Gauge invariant $F\tilde{F}$ integral on any gauge field on the interior of the sphere is equal to the integral of the three form *J on the boundary of the sphere. So the integral of *J must be gauge invariant. I didn't work out the actual form of *J, but it is the quantity you are trying to prove gauge invariant.
Although Witten's argument is conceptually illuminating, so it is the correct argument, verifying gauge invariance explicitly is not much more difficult than understanding all parts of the argument. Still, it is good to know the conceptual reason, because the reason the Chern-Simons style things are important is exactly because they are the boundary terms of integrals of those gauge invariant field tensor combinations which are perfect derivatives.
Comment: This nice argument of course requires that the 3-manifold we are interested in is "co-bounding" (the boundary of a 4-manifold) in the first place. Depending on which extra structure one has (e.g. spin structure etc.) this is not always the case. But the good message is that essentially this argument goes through fully generally if one refines it "locally" as expressed in the language of stacks. An exposition of this is at the beginning of this article: http://ncatlab.org/schreiber/show/A+higher+stacky+perspective+on+Chern-Simons+theory
Answer: Usually when you're doing this sort of thing, you try to group the operators into combinations which have simple gauge transformation properties. For instance, I would suggest rearranging the trace factor into $\operatorname{tr}[A_\rho(\partial_\mu + \lambda A_\mu)A_\nu]$, and see what you can figure out about the derivative operator $\partial_\mu + \lambda A_\mu$.
But when it comes down to it, the tricks take you only so far. Proving gauge invariance "from scratch" always entails a certain amount of tedious algebra.
Comment: Ok I will try with this tip.
Answer: The value of lambda must be fixed if you want gauge invariance, written in differential forms is $1/3$, $$S_{CS}=\frac{k}{4\pi}\int \langle A\wedge dA+\frac{2}{3}A\wedge A\wedge A \rangle\,,$$ where $A=A_\mu dx^\mu$ and $\langle \rangle$ is an invariant quadratic trace (so you will normally work with particular types of Lie algebras, see the killing symmetric tensor for instance). You can see that $dL_{CS} \sim \langle FF \rangle$ where $F=dA+A\wedge A$ and $d\wedge A=\partial_\mu dx^\mu \wedge A$. The volume measure is $d^4x=dx^0 dx^1 dx^2=\frac{1}{3!}\epsilon_{\mu\nu\rho}dx^\mu\wedge dx^\nu\wedge dx^\rho$. You can either work with covariant indices $\mu, \nu, \cdots$ or in terms of differential forms. A gauge transformation is given by $$A \longrightarrow A'=g^{-1}Ag+g^{-1}dg\,,$$ where $g=\exp{G}$ and $G=a^I T_I$ lives in the Lie algebra $[T_I,T_J]=C^K{}_{IJ}T_K$. The 'parameter' of the transformation is a 0-form $a^I=a^I(x)$. The infinitesimal form of the gauge transformations is $$A'=[A,G]+dG=DG\,,$$ where $DG$ is the covariant derivative acting on the zero form $G$.
Cheers!

Gauge invariant Chern-Simons Lagrangian


How did Nunnally and Sayoko survive the FLEIJA?

Question: The sheer action of the FLEIJA leaves behind a very neat crater and turns matter in its radius into a vacuum (airborne units tend to get blown into the blast center). How did Nunnally and Sayoko survive that?
Comment: compare http://tvtropes.org/pmwiki/pmwiki.php/Main/NotQuiteDead
Comment: Are you referring to the last usage of FLEIJA (during the final episodes of Code Geass R2? If not, what exact event are you referring to?
Comment: The one Suzaku fired aboard his mecha, destroying the Governors residence and the built-up settlement.
Comment: @aitchnyu, was that the episode when Lelouch used his geass on Suzaku to command him to live? I just need to confirm.
Comment: @xjshiya no. its a tad later. some 2 or 3 episodes before S1 final
Answer: This blogpost adequately explains how she could have survived.
I also do not believe there was as much of a vacuum because at that point in time the FLEIJAs still had a limiter. It was not until the destruction of the Capital city of Pendragon that the limiters were removed.
This is the summary of the link:

After Sayoko rescued Kallen she went on ahead to find Nunnally and to try and Rendevouz with Rolo and found the ship Nunally was on. Around the same time the Gefjun disturbers were disabled and Nunnally's ship left with Sayoko and her men aboard.  She never passed Rolo because he hadn't even reached the hangar yet.
Eight minutes later Rohmeyer is on a decoy ship with KF's to make it look like the governor general is aboard and Rolo walks in to find the ship, assuming reasonably that Nunally is on it he commandeers a KF to try and blow up the ship and kill her.  Meanwhile Sayoko barges in on Nunnally in the ship she's really on and Rohmeyer doesn't respond at all because she's actually on the decoy back in the hangar.  Nunnally's ship is probably just outside the area by this point.  When the bomb goes off Rohmeyer is caught in it in her decoy ship and goes up in a ball of flames.  Rolo has run away once he thinks he knows what's going on with Fleija (whatever it's called) and somehow made it to safety.
How? I'm not sure as that thing had a pretty big blast radius.  So when he reports to Rolo he talks about the ship Rohmeyer is on and really isn't lying when he says Nunnally is dead, because he honestly thinks she is.  In reality I think she's okay and with Sayoko elsewhere.  Though that elsewhere might be in Schneizel's clutches.
Answer: I believe that the FLEIJA that was used by Suzaku was not as powerful as the ones used by Prince Shnizle because Shnizle removed the limiter. Now if I can remember correctly Nunnally and Sayoko were underground and just out of the blast radius. Now how Nunnally, Sayoko and Gilford disappeared is uncertain. Without the power I believe that the outer blast radius is just a light show, and pulls then pushes out. I believe it threw them in some random direction out of sight. Stupid I know, but that's all I can think of.
Comment: Remember the scene where Suzaku laughs like a maniac in the middle of the massive blast crater? One that resulted from irrecoverable loss of matter within it? How do you imply its not powerful enough?
Comment: Do you have anything to back this up from Code Geass (or any related materials) itself?
Answer: Do you have anything to back this up from Code Geass (or any related materials) itself? –  Maroon 2 days ago
As a matter of fact I do. In Season 2 Episode 23 Floyd, Miss Cecile, and Nina talk about the FLEIJA that destroyed the Capital Pendragon, and Miss Cecile points out that the FLEIJA that Shnizal used that destroyed the Capital Pendragon was more 10x the destruction range than the one Suzaku use. Nina realized that he removed both the effect range and detination time limiter. These FLEIJA's Shnizle uses go critical when they are fired as he mentions when Lelouch orders his men to charge at the FLEIJA's. Now the FLEIJA's do pull things into the center of the blast because in the battle of Lelouch and Shnizal, Shnizal fired a FLEIJA and everything was pulled into the center. You may say that it was Lelouches order to charge at the FLEIJA and he did but if you see the environment like the oceans this shows things get pulled into the center of the blast. I believe FLEIJA's do not explode, but implode.
If you want to watch the final episodes of Code Geass Lelouch of the Rebelion R2 go to animefreak.tv and watch Episodes 23-25
P.S this does not explain everything about the FLEIJA's but it gave me enough to reach my conclusions
Comment: If you're Lorenzo (from the earlier post) and you were trying to add information to it, you should edit it in instead of making a new post.
Comment: I believe that stuff is pulled in because of air rushing to fill in a vacuum. [link](http://www.straightdope.com/columns/read/1299/why-does-an-atom-bomb-form-a-mushroom-cloud). And it does not answer the question: the explosion event was big enough to apparently consume Nunnaly and a massive amount of matter and remove it without a trace.
Comment: [A user](http://anime.stackexchange.com/review/suggested-edits/31774) tried to add this: "The Fleija not only implodes but destroyed everything in the radius. The first stage is an explosion that destroys all of the matter and replaces it with a vacuum. The second stage happens when all of the air surrounding that area rushes into the vacuum pulling everything with it. It is seen very clearly that the entirely of the governors building including the underground area and most of area 11 was caught in the blast including the area Nunnelley was in. by all rights she should've been disintegrated."


How do you manage conflicting stakeholder demands?

Question: Occasionally, key stakeholders of a given project (perhaps those with organizational authority several levels above that of the project manager) will have conflicting requirements or demands of the project manager.  How can a project manager deconflict these requests when the stakeholders (who may be peers) can or will not come to an agreement?
Comment: Having them pay directly doesn't solve it. What would you do if senior manager A pays you to make X and senior manager B does the same to make Y, but X and Y can not physically coexist? Or they both pay to do it in a month, but there just aren't enough resources to fulfill both requests?
Comment: I have to wonder, why do stakeholders not have to pay directly for the requirements they ask for? This is how people make decisions in a real marketplace, which the office is not.
Answer: Probably the best you can do is to gather stakeholders in a single room, lock the door, make a list of conflicting requests/goals (all goals actually), and not let anybody out until they prioritize the list in some way.
Let them have their discussions, let them have their fights. Answer their questions and make clarifications.
But as long as they're peers and none of them can make the call for anybody else it's their job to reach some kind of consensus. However it's PM's job to facilitate this meeting.
It can happen that, for whatever reason, they won't give up that easy and will oppose against having a meeting. Then PM's goal is the same except they have to run between one office and another passing bits of information between one and another trying to help them to sort the list of goals/requests. The pattern is similar, the difference is in time consumption.
Comment: I've found it to be very difficult to take approach #2, running between offices.  I've learned that my time is way more valuable, and I fight tooth and nail to get people in the same room so I don't have to be the middle man. :)
Comment: That's obvious that the first one is better... if feasible. However I know a couple of stakeholders who will generally reject to meet to discuss such subjects and since they're on the very top of the pecking order if PM is out of luck and have them both in the project they end up being kind of messenger. Btw: usually the more conflicting goals the sooner they find out some consensus as it is hard to ignore "go west" request from your peer if you want to go east.
Answer: I recently picked up a great trick from the book "Elements of Scrum" on managing trade offs.
The authors suggest a simple forced rank Four by Four table.
Along the top list:
FIXED   FIRM   FLEXIBLE  FLUID
Along the right side list:
SCOPE
DATES
RESOURCES
QUALITY
You then get four Xs. One X per column (Fixed, Firm, Flexible, Fluid). You get the stakeholders and sponsor to agree on this at the start of the program.
I am using this on a high risk project right now. Date is fixed, Quality is firm, Scope is flexible and Resources are fluid. We've run into a lot of issues and I've been able to go back to the chart to form a basis of discussion on what we will do.
Every single time we've either adjusted the scope or added resources (bodies, money, hardware) to the project. Halfway through the project and the chart is holding.
Best,
Joel
Answer: Conflicting goals and stakeholder demands are the norm.  Not only do you have stated objectives that differ but you also have hidden goals and agendas.  The latter is even more problematic because you cannot see them, hear them, or respond to them.
For those that are known, hitting them head on is your only option.  If these differing objectives and demands directly threaten your success, it is the joint responsibility/accountability of PM and sponsor to resolve to the degree possible.
You need to deploy a prioritization method that "objectively" scores each goal/demand comparing value, cost, and risk for the organization.  This method needs to have strong rules of engagement--to which all stakeholders agree--so that you keep folks at the table and acting like adults.  The PM needs to use a strong facilitator to get them through the scoring process.  The method will rack and stack the objectives and get everyone a bit closer to the high priority demands.  Allow each stakeholder to continue arguing his/her case for say the top 30%, maybe 40%, then score again.  This is iterative and ought to end up with a group consensus.  Your threat here is someone walking out of the process.
Once this parts finish, the real work begins.  You need to maintain this prioritization and manage those that came up short, the politics and ongoing lobbying, and those that disengage.  This is where your communication and org change capabilities come to play.
Answer: I am making the assumption that the conflicting demands are in the form of changes to the objectives and deliverables of the project, and hence can be considered as change requests, so I'm answering from that perspective. There may be other perspectives around timescales, resources, etc.
The PM should be working to the content of the Project Initiation Document (PID) and should have a strategy agreed with the Executive / Sponsor in terms of how to deal with change requests that move the scope beyond a given tolerance. It doesn't matter who is asking for a change: if this will take the scope beyond the tolerance, the agreed approach needs to kick in - and I would recommend that the normal route would be for the PM to escalate the change to the Project Board. Unless the change is adding value, the Board would/should be completely within its rights to reject the request, no matter who is asking for the change.
Pragmatically, there may be political reasons for going along with a change (ie the CEO wants it, and won't take "no" for an answer), in which case it gets logged, included in the scope, and the project is re-planned taking this into account.
In short, have a strategy for dealing with change, and use it.
Answer: First of all, be clear about the project objectives. Try to find a way to align the disparate needs to the objectives. If after this, the demands still conflict, bring in the sponsor to help manage the expectations.
Answer: First, a stakeholder is not the same thing as a shareholder. A shareholder is a person who bought shares in a company and who became that way an owner of that company. They are not suppose to bug in the daily management of the company. They have their own yearly meeting and they elect the board of the company that decides the main goals of the company and the strategies and tactics to achieve them.
Second, now a days, most people are afraid to lose their job. We are getting out the worst economic recession after the great depression of the 1930s. Usually, a company fires some of its employees when they sell less than expected of the products and services they provide.
Third, a company, an enterprise, a small business is not a social group of friends. When you are a private company, you don't receive bail out money from a foundation or a government when you go under for a few months.
Fourth, an employer signs contracts with their employees. When they meet the requirements, they are given a pay.
Finally, when people disagree on something you have to find out if they really have at heart the profit of the company. It is not everybody that remind themselves regularly than without a profit, the company must close its doors. You have to focus your employees on the profit making. A good manager can drop a product or a service, start a new one and do that in a way that assures the stability of the enterprise. A good manager is able to see under the disagreements the new opportunities that will benefit all.


How can I identify files and programs connected to the kernel_task process in Mac OS?

Question: I understand that the kernel_task process is linked to several .kext files found in System/Library/Extensions (and possibly Library/Extensions ?)  How can I identify which files are contributing to the 400+ MB memory usage identified in Activity Monitor?  Is there anything I can do to uninstall or delete unneeded processes to reduce memory usage here?
Comment: The kernel_task is one process - what do you mean by "processes are contributing"
Comment: Are you talking about the kernel_task process using 400MB physical memory? It's using 2.6GB here, so 400MB doesn't sound too bad.
Comment: I guess I really mean what .kext files are related to it.  I understand that they are configuration files for various programs on Mac OS but some may be unnecessary.  How can I know which?  Can I uninstall those that are no longer needed?
Answer: I looked for some generic commands that display/manipulate kernel extensions. kextstat got my attention and based on its output, the 4th column is

The number of bytes of kernel memory that the kext occupies.  If this is zero, the kext is a built-in part of the kernel that has a record as a kext for resolving dependencies among kexts.

The only problem was that its size was in hexadecimal. So I converted the hexadecimal to decimal and printed only relevant information (like kext bundle id).
kextstat -l -k | awk '{n = sprintf("%d", $4); print n, $6}' | sort -n

Breaking it down:

kextstat -l -k - print a list of loaded non-built-in kexts
| awk '{n = sprintf("%d", $4); print n, $6}' - pipe the output to awk, convert the 4th "size" column from hexadecimal to decimal, print that and the kext bundle id.
| sort -n - pipe the output to sort command and sort the list using numerical comparison (so that "10" is not less than "1 ").

You can pipe the output to tail -n 3 to get top 3 memory hoggers. Here are mine:
1757184 com.apple.nvidia.driver.NVDAGK100Hal
2572288 com.apple.nvidia.driver.NVDAResman
3923968 com.apple.driver.AirPort.Brcm4360

Update: you can also pipe this to grep -v com.apple to see which non-apple kexts are loaded.
Comment: Yes, this one refers to WiFi in general.
Comment: Looks pretty much okay then I guess...AirPort refers to wifi in general, right?  It should be in use even if I don't have an AirPort router, right?


As a USA citizen, can I cross the USA-Canada land border with my Hungarian passport?

Question: a little background about the question, born and raised in the USA, i own a house that keeps me in the states and a full time job in the states. I am a triple citizen: USA, Hungary, and Canada. For reasons that might be obvious to some of you I do not have a Canadian passport. My USA passport is in for renewal and a buddy of mine in Vancouver BC wants me to assist in chauffeuring some mutual friends of ours who are coming in from Sweden up to Vancouver B.C. from Seattle for the weekend. I only have my Hungarian passport to help with this request. what are some issues i might encounter? do you think this is a good idea? As a well traveled person I understand how this looks to the border guard. it looks fishy. what say you all?
Answer: Hungarian citizens do not need a visa for Canada. You could therefore choose to enter Canada as a Hungarian and ignore your US citizenship. It is not necessary to mention it to the border guards unless they ask. You will need an eTA if you are arriving by air after March of next year.
US citizens do not always need a passport to travel to Canada. A birth certificate or certificate of citizenship or naturalization will work instead.
A much more interesting question is getting back to the US. While it will get you into Canada, a US birth certificate will not technically get you back into the US. If you have an Enhanced Drivers License (which IS acceptable) then present that on your return. However, as other questions have shown on this site, if you can prove you are a US citizen, (which a birth certificate should do) border patrol cannot exclude you from the US. The worst they can do is to give you a talking to about how you should really carry a passport. It is not permitted to use your Hungarian passport to enter the US (though again, if you can prove you are a US citizen I don't believe they can keep you out)
Comment: If you have some proof that you are in the process of renewing your passport, you might bring that as well.
Comment: by the way, eTA is not enforced until March
Answer: Based on Department Of State website,

Most U.S. nationals, including dual nationals, must use a U.S. passport to enter and leave the United States. Dual nationals may also be required by the foreign country to use its passport to enter and leave that country. Use of the foreign passport does not endanger U.S. nationality. Most countries permit a person to renounce or otherwise lose nationality.

A passport-cardmight be an option, if you have it and you are crossing the border over land.
Comment: While it is not obvious from the page, I believe the wording of that link means "Must not use a passport of a foreign country to enter the US". Other forms of ID are acceptable for US citizens to enter the US (such as Nexus cards), and I don't believe there is any rule preventing dual citizens from using them.
Comment: @DJClayworth: That law says a US citizen must enter and leave with a US passport, except for exceptions allowed by the President. Those other forms of documents are in the exceptions allowed by the President. Whether you have a foreign passport is irrelevant.


Is there a mechanism for asking for the re-call of a mod

Question: I have a mod who is a real pain, who likes to down vote me and who generally makes my life (or tries to) a misery.  Surely there should be some mechanism or community vote on this, or are they above the law?
Comment: `who likes to down vote me` ... There's no way for you to know who's downvoting you - even moderators can't tell how people vote (except they can see some aggregate voting stats).
Comment: @Paparazzi You can? How? Downvotes cast don't show up in reputation changes for anyone other than your own votes. That's the only way I could think of.
Answer: You may use the contact us link (it's in the footer of every page on the site) if you wish to report potential moderator misconduct. Moderators were elected by the community in the first place, and are not above the law. If we find mistakes we've made, we'll do our best to fix them, and if we egregiously misbehave, SE will take appropriate action.
That said:

downvoting is normal, and the best response is to try to improve your posts and accept that you'll get a few downvotes despite your best efforts. (And unless other mods have been downvoting you a ton, I'm pretty sure you've gotten more downvotes from non-mod users than mods. I believe all three mods have also given you more upvotes than downvotes - I definitely have, anyways.)
I do not try to make anyone's life miserable, and neither do the other mods. (I'm pretty sure I know them well enough to speak that much on their behalf.) I also don't like downvoting - I'd rather all posts be worth an upvote, or at least not worth a downvote - but downvoting is part of how we make sure better answers show up higher, so I do it when I feel it's justified and don't feel guilty about it. Same goes for having to close questions, or point out various rules or issues: it'd be nice not to have to, but it's part of the site and part of my job so I do it.

So if you have specific concerns that you'd like community input on, I would encourage you to post them, rather than a more general accusation like this.
In that case, you would also be able to easily gauge the community's view on issues. You could also discuss with the moderator in question or the other two - and we can also create private chat rooms if you wish. Assuming everyone approaches things in good faith, with the goal of working things out for the users involved and the site, this tends to be better than immediately escalating to the top.
See also the canonical question on network-wide meta for this: What recourse do I have if I believe a moderator has abused his/her privileges?
Answer: There is no direct mechanism to remove a mod that I am aware of.
A down vote is not considered an abuse of power.  People can use them as they please.
If someone serial down votes there is a script that runs and will back it out.  But I seriously doubt any mods here are doing that.
When a mod comes up for election you can comment and not vote for them.  But mods can stay in position for years.
I can tell you from experience that complaining about down votes will only get you more down votes.
Argue with a comment will do you no good. Just ignore the comment if you don't agree. If it is rude or not constructive you can flag it.
This site has a narrow definition of right and wrong.  Mods and users are going to enforce it with comments and down votes.  Play by their rules or be frustrated.
Comment: Well, I'm sorry you don't like it, but making snarky comments to mods and generally being unreceptive to feedback in comments has a way of leading to getting called out.
Comment: It's unfortunate, though: like I started out saying, I agree with most of your answer, just not the dismissive attitude toward people's comments and votes. People here are really pretty reasonable.
Comment: Mostly true, but a couple notes: most importantly, mods are a small fraction of voting. The whole community speaks about what it thinks is good, not just us. Mods can be removed for serious abuses (see my answer). And while purely arguing is usually not a great plan, and ignoring is better, I would suggest a third option: listen to comments and see what you can improve based on them, and if you wish, reply in that spirit too. Suggesting improvements doesn't have to be a disagreement, and in my experience, most people who suggest things on my answers (and others) have a point.
Comment: I also strongly disagree about a narrow definition of right and wrong. We have *so* many questions with multiple very different highly-upvoted answers. We do have relatively high standards, but it's more about thoroughly addressing the question (and not getting sidetracked), avoiding misleading statements, clearly explaining yourself, and in general writing well. If people think a post doesn't meet those standards, they're not saying it's *wrong*, just that it's not as good as they would like. But yes, you will be frustrated if you persistently ignore that kind of feedback.
Comment: I can see deleted comments, you know. Since this seems to be a persistent sticking point with you, let me try to be clear: comments *are* for pointing out issues in answers, especially on meta. It's true that comments aren't for long discussions (chat is better) or off-topic discussions, and we move or delete when things are off the rails, but using them to address a post as I did here is their entire purpose. If you want to do okay here, as you say, you have to play by the rules: accept that comments happen, edits happen, votes happen, and so on.
Comment: @Jefromi I chose not to engage you.


Send cash: bitcoins vs western union: which is cheap?

Question: Bitcoin has been advertised as a very low cost and fast method of sending people money around the world, So if I need to send someone $1000 USD, the cost/fee of using WU is less than $20 USD (Using credit card - UNFORTUNATELY, WU doesn't work. They deny me sending $1000 and give me no reason. I will never use WU again.) but if I use bitcoin, what will be the minimal cost? Since I need to buy the bitcoin in the first place, and that other person need to sell it to get the cash, the conversation fees and the transaction fee would be more than $100 in the end? and if send someone $1000 in bitcoin, there is a chance that when she/he gets the cash next day, my $1000 will be less than $1000? If that is true, how can I trust bitcoin?
Answer: If you pay enough fee, which is ~ 5 dollars currently (but paying 10 dollars will guarantee fast confirmation), your payment will get confirmed in an hour. Good luck!
Actually it's possible to send with lower fee by using a SegWit address, but don't take the risk if you don't know what you're doing, set its fee 8-10 dollars. Rescuing the low fee transaction is difficult unless you're an expert.
Comment: yup, in your understanding and insisting model of paying to get in and out, bitcoin doesn't make sense as a use case. You better let it be, cause there a limiting factors surrounding you. The vast majority of people have better use cases for bitcoin (many are holding), and they find ramps to go in, and even live on bitcoin, and hope with the ongoing develpment (segwit, lighning) to go into a future with even cheaper payment oportunities. Exciting roads ahaead!
Comment: There is also a fee for me to buy 1000USD bitcoin in the first place. And I think it's about 4%, or 40 dollars. I don't know about the receiving end, but I guess it's probably the same, so that is another 40 dollars. 40+40+10=90 dollars.
Comment: @Atmega328 That's not transaction fee, that's your exchange fee. Different exchanges have different fees. Bitcoin's transaction fees don't depend on the value of Bitcoins you sent. (Fees of a 100k dollar transaction may be equal to a 100 dollar transaction)
Comment: Regardless, if I need to send someone 1000 USD cash using THE "promising" bitcoin system, I still need to pay about $100 out of my pocket to do just that, which is ridiculous and not counting the hassle for me and receiver. I can do that with paypal for less. 2.9% or $29, which is still  expensive. SO is there a place where I can buy bitcoin for free? I highly doubted. Or do I really need to pay a fee to sell bitcoin too? I am pretty sure it's the case, so bitcoin is just ridiculous.
Answer: have a look here: https://bitcoinfees.21.co/
this tells me currently, that you can pay 120-150Satoshi/Byte, to get confirmation within 6 blocks (on average 1 hour). So if you have a standard tx (less than 500 Bytes), you can go with 500x100 Satoshi= 50.000 Satoshi = 0.0005 Bitcoin = +2 Dollars. If your tx has 2 inputs, and two outputs, then you have like 750 Bytes, so make it +3 Dollars.
Comment: There is also a fee for me to buy 1000USD bitcoin in the first place. And I think it's about 4%, or 40 dollars. I don't know about the receiving end, but I guess it's probably the same, so that is another 40 dollars. 40+40+10=90 dollars.
Comment: that doesn't make sense... if you choose the most expensive seller for bitcoins, then maybe you are working with the wrong team. That is not bitcoins fault. Take a look at other opportunities, or even bisq. And if US is the problem, cause you can't get "cheaper" access to bitcoin, why not search abroad? I have never had to pay ~40 Dollars to buy bitcoin - wtf!!! I am in Europe though...
Comment: 3.99% is Coinbase.con fee.


Learning Ramban Al HaTorah

Question: I'd like to begin learning Ramban Al HaTorah and was wondering if someone has had experience with learning Ramban using a certain set of Chumash. I know of three different sets that have biurim/notes and was wondering what the differences are between them and which anyone has found to be the most helpful.
The sets are this, this, and this
Comment: https://judaism.stackexchange.com/q/95027/759
Comment: I'm not sure whether you know already, but the third set you linked to has only the Ramban and not the text of the Torah
Answer: I have learned Ramban al Hatorah with a chavrusa this year. I used the third set you linked (Chavel Ramban, Mossad Harav Kook), and my chavrusa used the first one, the Tuv Yerushalaim set. Tuv Yerushalaim had commentary that was slightly easier to understand, but also skips commenting on any sections that are Kabbalah-heavy. If that's not a focus for you, I would recommend the Tuv Yerushalaim for a beginner. I have no experience with the second set, the Oz Vehadar, but if it's anything like their commentary in their Mikraos Gedolos, it will be extremely comprehensive.
A few other notes:

mbloch, in this answer, noted Rabbi Yerachmiel Fried's list of important Rambans. I found it quite useful (although I didn't get it from mbloch), as he titles the pieces with short summaries.

I would not recommend learning Rabbeinu Bachya/Bechayei alongside Ramban, as he is an independent commentary, and often even harder to understand. If you wanted to learn a relevant commentary, I would suggest Rashi or Ibn Ezra, what the Ramban often quotes and disagrees with. Alternatively, you can learn the full commentary of the Tur, which he himself says is based on the Ramban, and may serve to help explain the Ramban in a few sections.
Comment: @mbloch please see the linked question
Comment: Yes, I was the one to put in the link :-> I wrote my answer, then realized DoubleAA had pointed to that question, and deleted my answer. I then edited yours to provide the link and upvoted :->
Comment: Do you know if any sets of Ramban help explain those parts al pi Kabbalah?
Comment: I would assume the other two have notes on it. Also, the chevel English translation, IIRC, contains them and would help. Another options is to consult those rishonim who discuss Ramban's Kabbalah routinely, perhaps Tziuni, maybe R' Bachya, and there's a couple of others I'm forgetting.
Comment: @mbloch was your chavrusah using the newly printed edition of the Tuv Yerushalayim set or the older one?
Comment: @Bochur613 inn my case an older one for sure - he told me he learned it first 17 years ago - but I think you want to ask רבות מחשבות
Comment: @bochur seemed pretty new to me...
Answer: This is really more of an opinion-style question and may end up getting closed as off-topic.
But if your objective is to understand what Ramban teaches, any one of the newer, complete and accurate texts is good. My preference is the Rav Kook edition which you linked to.
In general, when learning Ramban to the Torah and especially over Bereshit, it is a good practice to learn side-by-side for contrast and comparison, Rabbeinu Bahya ben Asher. Rabbeinu Bahya was a student of the Rashba, who was a student of the Ramban. So the context is appropriate. There is also a Mossad HaRav Kook edition for that too.
And if you are looking for any additional clarification, include the super commentary, HaEzrach B'Yisrael by Rabbi Yisroel Yitzchok Koronet which clarifies Rabbeinu Bahya.
Answer: This is a wonderful initiative. I am doing this as well, using artscroll's 7-volume elucidation. Since you are mentioning 3 Hebrew-only chumashim, you might not want English.
But I have something else which might prove very beneficial to make the task more manageable in a first pass. There is a list of the most important Ramban al ha Torah commentaries which someone has compiled (I uploaded it here), sorted by parasha, with a short index on the last page.
PS. Unfortunately I do not know who the author is. There is no copyright information I found either.

Learning Ramban Al HaTorah


The sex of the offspring of twins?

Question: Given identical twin males, Michael and Douglas, Douglas and his wife have four children, all of whom are girls.  Michael and his wife have only one child, a boy, and are expecting another. What are the chances it will be another boy? If Michael and his wife have more children, what are the chances they will all be boys? Is there any support/evidence for, or a study about, one twin of an identical pair will have children all of the same sex and the other twin will have children all of the same (or opposite) sex?
Comment: I know what you're asking, you should just remove the details about you, your wife and your brother. It might seem trivial, but that is the policy of the site. Anyways, a male's sperm is equally divided into gametes carrying an X chromosome and gametes carrying a Y chromosome. The gender of a child is determined by which sex chromosome is inherited from the father (since the mother only passes on X). So the gender of the child is determined by which sperm fertilizes the egg out of how ever many hundreds of millions. That's where chance comes into play.
Comment: @MichaelPrice in this context [*chance*](http://www.merriam-webster.com/dictionary/chance) refers to the fact that something happens without observable cause, not that is accidental. Gender is defined by chance determined by the probability of an ovule being fertilized by an spermatozoid carrying an X or Y chromosome. Different fertilization events (i.e. for each child) happen independently of one another. I am not aware of any research proving gender bias, yet I am not an expert in that field.
Comment: Personal medical questions aren't allowed here, but you can easily edit it to make it not personal. The gender of your children is determined by chance.
Comment: This is NOT a PERSONAL medical question, rather a question regarding research of identical twins and their offspring.  Gender is not determined "by chance", as chance is defined as "a possibility of something happening,fortuitous, accidental".  There is no accident in the gender of a child.
Comment: @canadianer Afaik it is not just about chance, there is some regulation about the gender, for example after wars the boy/girl ratio is not 1:1. However I never investigated this, so it is maybe just an urban legend...
Answer: Note: This is based on literature searches I've done a while ago out of general curiosity. I'm in no way an expert on human reproduction.

If I understand you correctly you are basically asking if there are any evidence for sex biases in offspring between families, that has a heritable genetic basis. This has been an active research topic for a long time and there are a number of proposed mechanisms for how this can be achieved. Historical data sometimes shows deviations in sex ratios over time, e.g. in 20th centrury Europe after WWI and WWII (see data in Gellatly, 2009). There are also other reported/hypothesized deviations in sex ratio e.g. trends in sex ratio due to paternal age (e.g. Jacobsen et al, 1999), sex biases of offspring due to earlier insemination in the menstrual cycle, and the child rank. However, from what I've seen, the evidence hasn't been conclusive and different studies point in different directions.
As Irving et al (1999) point out, possible mechanisms for sex ratio biases can be:

deviations in X/Y-ratio of sperm
selection of sperm within the female reproductive tract
biases in implantation success and/or survival for embryos of different sex

Most evidence seems to point against explanation one, see tests in e.g. Irving et al (1999) and Graffelman et al (1999). Graffelman et al (1999) also tests for an effect of male age, but do not find support for this idea.
Another interesting study is Curtsinger et al (1983), which tries to look at vertical population transmission of sex ratio variation in Japan. They conclude that there is a marginally significant effect on the paternal side, which would support the idea that sex biases might run in families.

An analysis of vertical transmission of sex-ratio modifying factors that excludes effects of birth order in both the parental and offspring generations has detected a marginally significant paternal effect.

However, they also conclude that the genetic variability in sex ratio is very small, if there is one. This study also does not find support for effects of e.g. paternal age or child birth order.
Gellatly (2009) provides a model of how an autocorrelation in sex ratio between generations could be explaned (while still having a stable population-level sex ratio), using an autosomal gene modifying male sex ratio. Note thought that this is a proposed model, and not empirical evidence. However, Gellatly (2009) also use genealogical/pedigree data from North America and Europe to show that there is an heritable component in the human sex ratio (an association between sex ratio in F1 and F2 generations). However, from what I can see the evidence is weak, and the models only explains 0.5% of the variance in the data. The introduction to this paper also has a useful overview of the subject with more references you might want to check out.
All in all, my perception is that there are some evidence that certain sexes can be overrepresented in families, which could potentially mean that the sex ratio in the offspring of a twin brother can contain information on the probablility that his brother will have a son or daughter. However, to me, the evidence is far from conclusive and the estimated effects seem rather weak. So as a null hypothesis, you should definately go for a 50/50 chance of a son/daughter, irrespectively of what the sex ratio of the twin brother is.
As for the general calculation of probabilities of different scenarios, you just use the product of probabilities and sometimes summation of birth orders. For instance (if assuming 50/50 sex ratio), the probability of having three sons is $0.5^3= 12.5\%$ (births: MMM) and the probability of having 2 sons and one daughter is $3*0.5^3= 37.5\%$ (births: FMM, MFM or MMF, i.e. three ways to achieve this scenario out of eight).
Comment: I heard of a theory, that X chromosome is heavier than Y, so it is more likely that the child will be boy. But I guess there are many other theories in the topic...
Answer: The question you're asking is essentially a version of an old riddle:

If you flip a coin ten times and it comes up heads each time, what are
the odds that the coin will
come up heads when you flip it for an eleventh time?

And of course the answer is that the odds are fifty-fifty. You could instead argue that 10 heads in a row is evidence that the coin is weighted somehow, and the way you would deal with that is by flipping that same coin 1000 more times, or (somewhat less reassuringly) by finding 100 coins identical to your first one and then flipping them each 10 times.
It's the same thing with children's genders. For every family with 6 girls there are hundreds more families with more mixed genders. The only effect known to skew the male-female sex ratio at birth significantly is wide scale sex-selective abortion (it tends to reduce the number of females).
Comment: While I agree with you in a practical sense, your answer is assuming that the sex ratio is 50/50 for all couples/populations and that variation in sex ratio lacks a heritable component, which is an open empirical question. Heritable variation in sex ratio is known in many non-human animals.

The sex of the offspring of twins?


Identify this chuck / faceplate mounting

Question: I'm learning to turn, and found this in a box of chucks and faceplates. The central hole isn't threaded but is recessed on the inside, so I thought it might be a type of mounting for a faceplate, or for a worm screw. I don't know what its for, please can somebody tell me?
Comment: Some of the posts I've looked at in Google search results have suggested a faceplate without multiple holes was used by woodturners as a "sanding mount" (for sanding disks).  There are a number of older articles describing how one could turn their lathe into a decent and possibly variable speed disk sander. There were also cautionary notes about drilling your own additional holes in the plate to make it into the typical sort of faceplate we use.
Answer: I have s similar item which I have used as a one-screw faceplate.  Not a lot to say about it, just put a screw through the hole and into a small piece of wood to turn a small bowl.


Synthesis of potassium trioxalatocobaltate(III) trihydrate

Question:
I've synthesized the compound potassium trioxalatocobaltate(III) trihydrate and for it I have two reaction equations. One of them is:
$$\ce{CoCO3 + 3K2C2O4.2H2O -> K2[Co(C2O4)3] + 2CO2}$$
and the other:
$$\ce{K2[Co(C2O4)3] + PbO2 -> K3[Co(C2O4)3].3H2O}$$
I see that the lead dioxide oxidizes $\ce{Co^2+}$ to $\ce{Co^3+}$ in the second step but I can't figure out what happens in the first. Does cobalt(II) make a ligand complex with the oxalate group?
One of the beginning steps was a also to mix oxalic acid and potassium oxalate. I assume (but I am not sure) that it was done to dissolve the potassium oxalate as other acids might have led to an unwanted reaction that would hinder the reaction following reaction with $\ce{CoCO3}$. I wanted to know that this was in fact the case.
Comment: Your first equation is not balanced. Your second equation is not correct? How do you explain $\ce{Pb^4+ -> K+}$ conversion?
Comment: Is the iupac naming correct? Shouldn't it be tris(oxalato)?
Comment: @MathewMahindaratne for the first reaction you could also write it as $\ce{Co^2+ + 3C2O4^2- -> [Co(C2O4)3]^4- }$. I took the information from https://bit.ly/2OxsNi1. The second one might be incorrect because of the number of potassium on the product it would have to be K4 meaning the oxidation of Co goes from 2+ to 3+. I'm not 100% sure either so that;s why I asked the question.
Answer: It appears that Sørensen was the first to publish the synthesis of trioxalatocobaltate(III) trihydrate [1].
A summary written in English (and that should answer both of your questions) including chemical reactions can be found in the very first volume of Inorganic Syntheses1 [2, p. 37]:

C. POTASSIUM TRIOXALATOCOBALTIATE
$$\ce{K3[Co(C2O4)3]·3H2O}$$
$$\ce{H2C2O4 + CoCO3 → CoC2O4 + H2O + CO2↑}$$
$$\ce{2 CoC2O4 + 4 K2C2O4 + PbO2 + 4 HC2H3O2 → 2 K3[Co(C2O4)3] + 2 KC2H3O2 + Pb(C2H3O2)2 + 2 H2O}$$
Twenty-three and eight-tenths grams (0.2 mol) of cobalt carbonate is dissolved in a solution of 25.2 g. of oxalic acid $(\ce{H2C2O4·2H2O})$ and 73.7 g. of potassium oxalate $(\ce{K2CrO4·H2O})$ in 500 cc. of hot water.
When the solution has cooled to 40°C., while it is vigorously stirred, 23.9 g. of lead dioxide (see synthesis 16) is added slowly, followed by 25 ml. of glacial acetic acid added a drop at a time.
The stirring is continued for an hour, during which time the color changes from red to deep green.
After the unused lead dioxide is filtered out, the trioxalatocobaltiate is precipitated by the addition of 500 ml. of alcohol.
The material appears as emerald-green needles, which are sensitive to both light and heat; The yield is 70 g. (71 per cent).

Notes

Please disregard obsolete typography and notations used in this textbook such as full stops after unit symbols, as well as the lack of white space between the numerical value and a degree symbol (as seen in "40°C.") and use of notations such as "cc." (cubic centimeter).

References

Sörensen, S. P. L. Kritische Präparatenstudien. III. Darstellung von Einigen Kobaltidverbindungen. Z. Anorg. Chem. 1896, 11 (1), 1–5. https://doi.org/10/fh47nq. (in German)
Inorganic Syntheses; Booth, H. S., Ed.; John Wiley & Sons, Inc.: Hoboken, NJ, USA, 1939; Vol. 1. ISBN:9780470131602, https://doi.org/10.1002/9780470132326.
Answer: In the first step, one makes an oxalate complex by decomposing the carbonate salt of cobalt (II) with oxalic acid. I am not sure how an oxalate salt will decompose the carbonate to carbon dioxide. Oxalate ion makes a complex. The second step is lead dioxide oxidation.
See this book chapter for proper synthesis equations of cobalt (III) oxalate complex, search PbO2 in the file.
https://link.springer.com/content/pdf/10.1007%2FBFb0048297.pdf
Comment: OP mentioned using oxalic acid too.


How can I improve the battery life under 12.04 on my Inspiron 14z?

Question: How do I improve the battery life of my Inspiron 14z under Ubuntu 12.04?
This laptop gets 4-5 hours of battery life using Windows (e.g. here). I've removed Windows, installed Ubuntu 12.04 and the initial battery life was only 2 hours. With some tweaks (described below) it's still only ~2.5 hours.
For reference, the laptop is the latest model of the 14z:

i5-3337U processor
32GB MSATA, 500GB HDD (5400rpm)
AMD Radeon HD7570M graphics card

I have put ext4 partitions on both the SSD and the HDD, and have mounted / to the SSD and /home to the HDD. I also put a 24gb linux swap partition at the start of the HDD, though I figure this won't be used all that much (the laptop has 8gb of RAM).
After googling around and reading Ask Ubuntu and other sites extensively, I have done the following steps, and they have improved the battery life ~30 minutes (exact improvement not clear, but battery life is still nowhere near 4-5 hours).

Installed Jupiter (and set Performance to "Power Saving")
Installed laptop-mode-tools

cat /proc/sys/vm/laptop_mode now outputs 5 (previously it output 0)
But it's not clear that this will help: AskUbuntu question

Turned down the brightness of my screen from full to 1/3

Other things I have heard about but have not tried for fear of frying the laptop or my linux install:

Add "pcie_aspm=force" at the end of the line with "quiet splash" in /boot/grub/grub.cfg
Enable ALPM, but it may already be enabled in 12.04?
Enable i915 framebuffer compression
Use a propietary driver for the graphics card? Turn off the graphics card? (what would happen if I relied on the internal Intel bridge?)
Use TLP?
Spin down the HDD more aggressively (howto, but I think laptop-mode-tools does this already)

The only other thing I've noticed is that plastic just above the F5, F6 and F7 keys gets really hot. According to Jupiter my CPU temperature is only 69 celsius and the System Monitor shows CPU load at 7% so I don't think it's the CPU. Maybe it's the graphics card?
Also, I've set up MongoDB and LAMP on the machine as well. When I run powertop MongoDB is high in the list, but I'm not sure if that's relevant to battery life because I'm not actually doing anything with MongoDB most of the time.
Edit: Additional info requested by @gertvdijk
$ lspci -nnk | grep -iEA3 "(graphics|vga)"
00:02.0 VGA compatible controller [0300]: Intel Corporation Ivy Bridge Graphics Controller [8086:0166] (rev 09)
    Subsystem: Dell Device [1028:057f]
    Kernel driver in use: i915
    Kernel modules: i915
--
02:00.0 VGA compatible controller [0300]: Advanced Micro Devices [AMD] nee ATI Thames [Radeon 7500M/7600M Series] [1002:6841]
    Subsystem: Dell Device [1028:057f]
    Kernel driver in use: radeon
    Kernel modules: radeon

Based on @maggotbrain's answer to the question linked to (here), and because I downloaded and ran Ubuntu 12.04.2 so I think I already have the Quantal enablement stack running. I think uname confirms this too?
$ uname --all
Linux christo-lt4 3.5.0-23-generic #35~precise1-Ubuntu SMP Fri Jan 25 17:13:26 UTC 2013 x86_64 x86_64 x86_64 GNU/Linux

Edit: AMD drivers
I initially tried the propietary FGLRX drivers with post-release updates. There does not appear to be a bios level option to turn off the AMD graphics card.
After installing and rebooting, my display looked the same (except Unity launcher icons went back to full size), but I could not run Catalyst. Instead, it exited with the error:
No AMD graphics driver is installed, or the AMD driver is not functioning properly. Please install the AMD driver appropriate for your AMD hardware, or configure using aticonfig.

Next, I ran sudo amdconfig --status=all --initial but I could only load low-resolution graphics. This was also the case with sudo amdconfig --initial, so I manually restored my backed up xorg.conf, removed this driver using the "Additional Drivers" application and installed the "Experimental AMD binary Xorg driver and kernel module".
After rebooting my computer I see that this entry in the list has changed to be "ATI Fire GL" (my laptop has an AMD Radeon HD7570M, not an ATI card?), but it also says that the driver is activated but not currently in use. What should I do to get the propietary drivers working on my laptop?
I have also tried the "experimental behaviour" FGLRX drivers, but the low-detail error still returns. The only way I've found of fixing this is restoring the original xorg.conf
Recap of solution - battery life up from 1.5-2 hours to 3.5-4 hours or more
I can't post many links because my reputation on this stack exchange is too low, I'll use titles of questions wherever possible so people can find them using Google
Many thanks to @gertvdijk for his help with this problem and pointers to other solutions (is there some way I can mark something correct and give you reputation points to say "thank you"?). I now have my laptop battery life up to ~3.5-4 hours and there may be some further steps I can take as well. To summarise my solution to date, in rough order of impact:

Installed propietary drivers using the 12.04 solution in the Ask Ubuntu question ("What is the correct way to install ATI catalyst video drivers (fglrx)"), then used Catalyst application to switch off the AMD
Jupiter applet - turned brightness down from 100% to 25%, set performance to Power Saving
Wrote a script to make it easy to turn on/off services that might be battery intensive - here
Turned off bluetooth (I need to leave wifi on)
Installed laptop-mode-tools - cat /proc/sys/vm/laptop_mode output 0 beforehand and 5 after, so this got turned on, but I don't know if it had any effect (See Ask Ubuntu question: "Is laptop-mode-tools still relevant for 12.04 and the 3.x kernels")

Potential other steps I could take, but haven't yet:

Spin the hard disk drive down more aggressively (laptop-mode-tools/Ubuntu 12.04 defaults might do this automatically) (see scottl's answer to "Tips to extend battery life for laptops and notebooks")
See item 3 of ishouvik.com's "5 ways to extend battery life on Ubuntu" - this is meant to happen automatically in 12.04 but isn't in my /boot/grub/grub.cfg right now so it might not be turned on
Other power management tweaks - see Ubuntu wiki page on Power Saving Tweaks

Enable ALMP (but it may already be enabled? - see Ubuntu wiki page on Kernel power management using ALPM
Enable i915 framebuffer compression
Comment: Welcome to Ask Ubuntu! Do you have hybrid graphics? Please provide the output of `lspci -nnk | grep -iEA3 "(graphics|vga)"` run in a terminal. If you see two cards, do you have an option to disable the AMD discrete graphics card in your system BIOS? Include all this new information in your question by *editing* it. See also [How do I get AMD/Intel Hybrid Graphics drivers to work?](http://askubuntu.com/q/205112/88802). Also consider using the [Quantal hardware enablement stack](http://askubuntu.com/q/257617/88802) as your hardware is a lot newer than 12.04 is.
Comment: So this is a hybrid graphics machine. Configuring that properly will probably have significant results. See [How do I get AMD/Intel Hybrid Graphics drivers to work?](http://askubuntu.com/q/205112/88802). (Not the best answers in there, but it's the "master" question here.) Disabling the AMD card in the BIOS will also probably help a lot.
Answer:
Open the Software Sources application.
Go to the Additional Drivers tab.
Choose the closed source driver for your graphics card.
Click the button to apply them.
Reboot.

This should increase battery life.
Comment: This method did not work - ultimately I have been able to install the graphics drivers in a working fashion using the 12.04 instructions [here](http://askubuntu.com/questions/124292/what-is-the-correct-way-to-install-ati-catalyst-video-drivers-fglrx). My fglrxinfo output now is (with three pipes used to indicate line breaks):

    $ fglrxinfo |||
    display: :0  screen: 0 |||
    OpenGL vendor string: Advanced Micro Devices, Inc. |||
    OpenGL renderer string: AMD Radeon HD 7500M/7600M Series |||
    OpenGL version string: 4.2.12217 Compatibility Profile Context 12.104
Comment: Install TLP via PPA from www.linrunner.de


How can I tell the difference between the Deva realm and the Buddha and bodhisattva realms?

Question: How can I tell the difference between joy bourne of karma that will expire and joy bourne of karma which has turned the irreversible wheel of the dharma?
Answer: Denizens of the heavenly planets enjoy more and live longer. They have made lots of good karma in their human form of life and became qualified to enjoy heavenly life. The joy of of Buddhas is eternal and unlimited. Buddhas enjoy their natural life that's found in enlightenment.
The best way to know this is by gaining experience from meditating.
Answer: The Deva Realm is one of the six realms of Saṃsāra, implying Devas are still subject to Karma. Simply put: what goes up, must come down. Existence in the Deva realm is temporal, and therefore the joy it brings is temporal, sensorial, and driven by the ego.
The Buddha and Boshisattva realms are not on the Samsara map, implying they are either not subject to Samsara or that Samsara is Nirvana (opinions on this will vary from lineage to lineage). The joy of this state is considered non-temporal and non-individual as it stems from compassion, is not induced by the senses, and is in essence non-dualistic.
Answer: Cosmologists today attribute approximately 5% of the cosmos to matter i.e. the material world of the planets and stars, approximately 35% of the cosmos to dark matter and the balance 60% or so, to dark energy. Scientists say that in the realm of dark matter light is reflected whilst in dark energy no reflection takes place. According to Buddhist cosmology, it is conceivable that the deva world (only the higher senses are present i.e. sight, sound, mind) represents the realm of dark matter and the brahma world (only the mind/cognition is present) represents the realm of dark energy. These three realms may be defined as samsara. It is conceivable that Enlightened beings living in the realm of Nirvana may be either in the ''higher frequency band' of dark energy or in a realm unknown to science.


(sharp)Garding's inequality and inequality with lower bounds

Question: The origin of Garding's inequality was an effort to solve Dirichlet's problem  for linear elliptic operators of high even order.Let $$P(x,D)= \sum a_{\alpha}(x)D^{\alpha}$$ with principal part $$P_{2m}(D)= \sum_{\alpha=2m} a_{\alpha}(x)D^{\alpha}$$ have the property that $$ReP_{2m}(x,\xi)\geq c|\xi|^{2m}$$ for some $c>0$.It is further assumed that the coefficients $a_{\alpha}(x)$ have continious and bounded derivatives.Under this circumstances,one have for all $\epsilon>0$,$u\in C_{0}^{m}$,$$Re(Pu,u)\geq (c-\epsilon)\|u\|^{m,2}-b_{\epsilon}\|u\|^{2}$$.
The original Garding's inequality seems to have been used for the first time by Leray in his 1954 lectures for an existence proof for Cauchy's problem for strongly hyperbolic systems.It was used again by Garding(1956) for a proof of the same result using only functional analysis.
There is a sharp form of this inequality due to Hormander which says that if the symbol $P(x,\xi)\in S^{2m}$,$ReP(x,\xi) \geq 0$. Then $$Re(P(x,D)u,u)\geq-b\|u\|_{m-\frac{1}{2}}^{2}$$.
A much more precise statement in the scalar case is known as the Fefferman-Phong inequality.
Here my first question is what's the application of the sharp Garding's inequality?
I once saw that Fefferman had wrote a paper named "sharp Garding's inequality and the uncertainty principle". I'm really surprised to see that this two inequalities can have connections.so i become more interested in inequalities with lower bounds.Can anyone list some inequalities appeared in PDE or other banches of math with a lower bound?Maybe some of them can have interesting links.
Comment: Fefferman-Phong (FP) inequality may be not precise is some cases, see Hormander Vol.3 and V. Ivrii "Microlocal Analysis and Precise Spectral Asymptotics", for some remarks about FP and Melin inequalities
Answer: Let us start with a short review of the so-called G{\aa}rding's inequality. Let $a\in S^m$ be nonnegative. Then with $a^w$ standing for the Weyl quantization of the Hamiltonian $a$,
$$
(1)\quad m=1\quad \exists C,\ a^w +C\ge 0.
$$
$$
(2)\quad m=2\quad \exists C,\ a^w +C\ge 0.
$$
$$
(3)m=2, a_j,j=1,2\ \text{homogeneous degree $j$}.
\quad\text{If }a_2\ge 0\quad  a_{1}+\frac12trace_+(a_2'')\ge 0,$$
$$\text{then}\quad
a_2^w+a_1^w+C\ge 0.
$$
Of course (2) is (much) stronger than (1), but (1) is true for systems, that is symbols valued in symmetric matrices and even infinite-dimensional self-adjoint operators in a Hilbert space. (2) is the Fefferman-Phong inequality is true only for (nonnegative) scalar
 symbols.
(3) is essentially Melin inequality ($trace_+(a_2'')$ is a symplectic invariant of the Hessian).
The third inequality is closely related to the uncertainty principle since,
$$
-\Delta_{\mathbb R^d}+\frac{\vert x\vert^2}{4}-\frac d2\ge 0
$$
is a consequence of (3): the symbol $\vert \xi\vert^2+{\vert x\vert^2}/{4}-\frac d2$ takes nonpositive values but the associated operator is nevertheless nonnegative. Heuristically you could say that the set of nonpositivity of the symbol is symplectically small and thus unimportant.
Another example is Hardy's inequality for $d\ge 3$
$$
-\Delta_{\mathbb R^d}-\frac{(d-2)^2}{4}\frac{1}{\vert x\vert^2}\ge 0.
$$
Here the set $S_{-}$
of nonpositivity of the symbol has infinite volume, but is still symplectically small in the sense that no canonical image of the unit cube can be embedded in $S_-$.
Summing-up a (second-order) nonnegative symbol gives rise to a semi-bounded (from below) operator, but an operator can be semi-bounded from below with a symbol taking negative values. The important matter is to check the symplectic relevance of the set $S_{-}$ where the symbol is negative. Of course, this is linked to the uncertainty principle.
Comment: This short survey is very useful. The two example are interesting. Does there exists other references, except Hormander's book(it's hard for me to follow, :) ), exploiting this topic in detail?
Comment: In the scalar case.I'm toid that the ferfferman-Phong inequality can't be improved.Are their some examples to illustrate this? I also wonder how the Garding types inequalities make a role in the existence and regularity of the solutions of some equation (say $a^{w}(x,D)u=f$)with $Rea(x,\xi)\geq 0$
Comment: @user23078: see the papers by Parmegianni available I think on google. For thes second question, the book of Grub "distribution and Operators".
Answer: Daniel Tataru obtained sharp and strong results (with restricted regularity of the coefficients of the operator)about Garding and Fefferman-Phong inequalities whith the use of the FBI (Fourier-Bros-Iagolnitzer) transform without any suplementary condition on the principal and subprincipal symbols (trace+ condition). Notice that the condition of positivity is on the principal symbol for Garding inequality but it is on the complete symbol for the Fefferman-Phong inequality. There is also a refinement of Melin inequality (see Mohamed, "Etude spectrale d'operateurs hypoelliptiques a caracteristiques multiples I et II") whith a genralization of the trace+ condition. Also there is some generalizations of the Melin-Hormander inequality obtained by the italian school (Parenti, Parmeggiani).


Brake pedal goes to floor

Question: i have a 2005 pontiac grand am and my brake pedal goes to the floor any suggestions on what cause is we bled brakes numerous amounts of times checked for leaks ive replaced master cylinder yes bench it first there no air in lines please someone help me can pump them up holds but as soon let go push again
Comment: These grand am seems to like brakes : https://mechanics.stackexchange.com/q/60242/10976
Comment: My passenger side was grinding so i had to change them and only one pad on passenger side was worn all the way down and i didnt no i didnt have to bleed but did and ever since no brake pedal
Answer: Here is a test: you can buy 4 locking clamps especially for brake hoses. Clamp all 4 hoses then try the brake pedal. If the pedal still bottoms out, then the problem is not in the 4 wheels.
If the pedal is firm then remove one clamp and try the pedal. Refasten each clamp as you check each wheel. It should isolate the problem area.
If the rears are drums, then another problem can occur. The piston in the wheel cylinder gets sticky and the return springs are weak. Air can be pulled into the wheel cylinder each time you take your foot off the brake pedal. Manual bleeding doesn't help since air keeps being pulled in. The clamps will tell you which wheel.

Brake pedal goes to floor


I want to start recording some bass riffs in FL studio to use them later in making songs. What are good practices for this?

Question: I have heard before it is good to record clean audio in a separate track and apply effects later. I am very new to this and any advice would be appreciated.
Comment: Welcome to the site Louvki - I've just snipped out the bit about wanting articles 'cos as you will see from the [help/on-topic], we try to avoid primarily linking to external resources. Interesting question though!
Answer: If I understand your premise—you want to record bass lines in the highest quality now so that you can just manipulate them later and not have to rerecord them—I'd reconsider that. It is great to record bass lines whenever you have an idea but not a full song yet because it could easily turn into a song later or be useful in some way.
But getting a great bass sound in the final mix isn't really a matter of how clean you record it initially. In fact you usually want to get as close as you can to your ideal bass tone before FX (plugins, etc) are applied. And you want to do that in the context of the song. So if a particular song requires a specific tone, start with your technique, your instrument, your pedals, and your amp. Tweak the EQ on your amp before you start thinking about EQ plugins, etc.
Of course, if you don't have a song yet, you probably don't know exactly what tone you want yet. And there's the rub. Even if you did, it's hard to get the feel and technique correct when not in context of the song and hearing how different instruments interact. In a band this requires playing the song together for a bit to get a feel for it. When recording solo, this usually means recording and re-recording until it all works together rhythmically and the mix gels at least a bit soncially. Then … it might be a good time to break out the FX for finishing touches.
In other words, if the dry bass (no added FX) doesn't work as far as rhythmic feel and isn't at least most of the way to your desired tone, piling on FX probably isn't going to help much. Just re-record the part again later within context of the song.
That said here a few tips:

(before every take) Are you in tune?
Consider every aspect of your signal chain starting first with you then working outward. Could your finger/pick technique get you closer to the desired sound? Flat vs round string winding? String gauge? Neck/bridge pickup? Tone knob setting? Different bass or type of pickups altogether (P vs J, etc)? Pedal settings? No pedals? Different amp or cab? Amp settings? Mic placement? Mic? Direct instead of mic?, etc… The more of this you get right before FX the better. For instance there's no plugin that's going to make a pick sound like fingers or vice-versa.
Watch your gain staging. Two particular pain points for beginners are with preamps (if using mics) and digital converters. Like all amps, preamps have a certain amount of headroom and can introduce noise when cranked. So if the sound source is so quiet that you need to crank the pres way up, instead try turning your amp up a bit so you can turn the pres down. Then watch that overall level as it is hitting your converters/interface. You don't want a signal so soft that you'll need to digitally boost it a lot later, but you also definitely don't want to clip.
If using a mic, make sure it matches what you're looking to achieve. If you want to capture the lowest frequencies then make sure the mic can even handle those frequencies (ex. D112, D6, etc). But not all bass parts have thumping sub-bass and a mic that accentuates the bass' midrange (ex. RE20, MD421) might be better depending on context.
If you can record by a dry track as well via some kind of DI output, go for it. Yes, put it on a separate track. You might not need it and don't use it in the mix just because you have it. It's okay to mute what you don't actually need. But it doesn't hurt to have it or to try out DI vs mic or a blend of the two. That said, watch out for phase issues when blending multiple mics or mic and DI. You might have to nudge one or the other so they line up.
If you don't have mics or a budget for some, recording only direct can be option too. But my caveat about context within the song still applies. If you have some kind of preamp or amp-in-a-pedal type DI that can work great too. Just try to dial in a real tone that you want for the song because that will effect how you play. For instance you may end up adjusting your technique, even if you don't realize it, when playing with high-gain tone rather than with a clean one. The same goes for software amps. Dial in the sound and use it while tracking so that even though the actual recorded audio will be the unaffected DI sound, it will be played in a way that matches your eventual tone with the simulated amp.


Source for needing to say "Boruch hamavdil .." before doing a melacha after Shabbos

Question: I believe that after Shabbos  one must say "Boruch hamavdil bein kodesh lechol" before doing a melacha. Please can someone supply a source for this?
Comment: I can't see a clear connection between the first and second questions in this post, so I'm editing out the second question. Feel free to post another post for the second question, or, if you have reason to believe that these two questions could be answered by the same answer, please [edit] that reason into the question post.
Comment: Possible duplicate of [Biblical vs. Rabbinical end of Shabbat](http://judaism.stackexchange.com/questions/45100/biblical-vs-rabbinical-end-of-shabbat)
Comment: Hi Rafael, welcome to the site! Perhaps consider making these two separate questions, one regarding hamavdil and one regarding kissing the mezuza.
Comment: This isn't a duplicate question to the linked question. The link is about the difference between Shabbat from the written Torah and Shabbat according to the Rabbis. If I understand the OP, he is asking for the source of the text Baruch HaMavdil.
Comment: I have edited your question. You can always roll it back if you do not like it.
Comment: @Rafael Aryeh Welcome. Can you please explain why you believe that the idea of kissing the mezuzah when passing by is associated with the recital of Baruch MaMavdil?
Answer: "The Tur, in Orach Chaim 299, brings the opinion of Rabbeinu Asher and the Ba'al Halachot Gedolot that before doing melacha one should say "Hamavdil" with "Shem v'Malchut", that is, in a normative bracha format. Rashi, however, says that only the words "Baruch HaMavdil bein kodesh l'chol" must be said and this is the position adopted by the Shulchan Aruch. This is the common practice." http://www.yeshiva.co/ask/?id=3513
Answer: AMAZING......took a while...and I THINK I found something:
http://shulchanaruchharav.com/halacha/baruch-hamavdil-or-havdala-before-doing-melacha/?hilite=hamavdil#ftn8
I was looking only about a case...or flipping on a switch...or gatting candles...NOT CLEANING THE HOUSE OR INSTALLING A LIGHT FIXTURE....
so:
Other Opinions brought in Admur: There are those opinions [Rabbeinu Yerucham] which rule that only those Melachas which are time consuming and take effort, such as weaving, writing and chopping wood, were forbidden by the Sages before saying Havdala or Baruch  Hamavdil .
However those Melachas which are performed without any effort, such as lighting a candle or carrying 4 Amos in a public domain, are permitted even if they are of Biblical nature, if the proper time of night has arrived, even if one has not yet said  Hamavdil .
OK...in the Maariv..it is CUSTOMARY (not obligatory) to draw out the VEHU RACHUM...and BARECHU, in order to "add from the mundane to the sacred"..an interesting BACK ENGINEERING of extending Shabbat....bringing MOTZEI into...
That is what was not answered in the other link. We understand by DAYBREAK, Sunday, saying HAMAVDIL is not necessary. I guess the question stands: After "enough" time after Nightfall...3 stars...and an additional as per requirement...if one turns on a light (A NON LABOR INTENSIVE ACT), is there and ISSUR DaRabbanan?

Source for needing to say “Boruch hamavdil ..” before doing a melacha after Shabbos


Why Does Stellar Support Authorization-Required Assets?

Question: Are there some common use cases that were anticipated when deciding to support assets that require authorization in order to set up a trust line?
Answer: As I understand it, the main use case is to support KYC (know your customer) and anti-money laundering. An issuer can confirm identity in order to satisfy relevant laws in their jurisdiction, and then proceed to grant authorization through an allow trust operation.
You could also use this mechanism to limit a set of tokens to some pool of people for other reasons. For example, if you wanted to create a neighbourhood currency to "keep spending local", you could create a token that can only be traded within a certain city (and require proof of address before you allow distribution). Or you could allow tokens to be held only by members of a particular club, society or promotion (e.g. like air miles or "non-transferable" coupons or points).
Limiting access could also protect you from the wider free market and allows you to control exclusivity. Perhaps you just don't want your token arbitraged by professional financial people.


Does the Power Word Kill spell instantly kill PCs?

Question: Orcus's "Voice" lair action is casting the spell Power Word Kill. If he were to use it on a PC, would they drop to death saving throws or instantly die?
Answer: Spells do exactly what they say, whether cast on PCs or other monsters.
Power Word Kill says a creature with 100 hit points or fewer dies. PCs are not exempt from this as they are also creatures and thus are perfectly valid targets for the spell. Do not pass go, do not collect $200, do not make a saving throw vs the effect, do not drop to 0 HP and start making death saving throws. They just die like any other creature targeted by the spell.
Note that this is a 9th level spell so it's meant to be powerful.
Answer: They would instantly die, with no saving throws. However, at this level, players are assumed to have access to means of resurrection, so this isn't as devastating as it would be at earlier levels.
Comment: Also access to counterspells, death wards etc. Death Ward (lvl 4) actually protects against one casting of Power Word Kill.
Comment: @NeilSlater counterspell wouldn't work against Orcus' Voice layer action, Orcus isn't casting a spell
Answer: Power Word Kill does kill a PC with fewer than 100 hit points without a save. However, a quick calculation shows that there would be many high level PCs that have more than 100 hit points at full health. For example, a level 18 paladin with CON 10 would have an average of 103 hit points.
Additionally, this spell is actually a bit on the weak side for a 9th level spell. If a monster cast Meteor Swarm on a party of PCs, they could take 40d6 damage each--a situation that could be just as (or even more) problematic as the instant death of a single party member.
Answer: "Kill" means they simply die. No saving throws, no death saves; the target is rendered dead.
Keep in mind that it counts current hit points not maximum. So damaging a creature and then using this spell is a viable tactic.
It also instantly kills any shapeshifters who have shifted and have less than 100 hp. Since such shapeshifters usually return to their normal form when dropping to 0, this does not trigger that because it deals no damage.
It also bypasses all types of resistance, both to magic and to damage types. Same for legendary resistance or feats (e.g. Lucky) or class features (e.g. the Divination wizard's Portent).
This is what makes it a great spell.
It is negated with the spell death ward, which negates it and then ends. Or alternatively, since power word kill targets "one creature you can see within range", you can avoid being targeted by either blinding the caster or by becoming invisible.
Comment: Welcome to rpg.se! Take the [tour] and visit the [help] to learn how things work around here. This is a pretty good answer that covers all the connotations of this ruling. You could improve it slightly by quoting or referencing the rules which support this within the answer itself. Thanks for contributing and happy gaming!


What does "Square-O" mean?

Question: There is a piece of piano music called Square-O by Elissa Milne. I would like to know the meaning of it.
Comment: Hi Emmal, welcome to our site.  Are you just looking for the meaning of the title?  The song seems too short and simple to allow for much meaningful musical analysis.
Answer: There are two answers to this question, whenever it is asked about any piece of art, be it music, sculpture, a novel, or whatever.
1) It means what it means to you.
2) It means what the author had in mind, and not all authors are willing to share that information.
Comment: This is a good answer, but you have also to consider that the artist may have had one thing in mind, but their audience over time may give the piece other associations.  anyhow, Elissa Milne has contact details [here](http://www.fabermusic.com/composers/elissa-milne/biography), and you could even get in touch to ask about the meaning of the piece
Comment: @Angst  what you said is what I wrote.
Answer: There's a rondeau by Henry Purcell (ZT684), originally for the play Abdelazer, that was printed in some harpsichord collections with the title "Round-O". "Square-O" is probably a pun on that.
Comment: Another example:  "Blue Rondo a la Turk" -- Brubeck started with local folk rhythms, but I personally suspect (without any justification) that he sneaked a little of "Rondo alla Turca" in there as well :-)

What does "Square-O" mean?


password on resume

Question: I would like to not have to enter my password on resume after closing the lid on my laptop.  I used to be able to do this but can't find the option anywhere anymore.  all the notes I have found say go to "Screensaver" but when I type "Screensaver" into the dash, nothing comes up.
Answer: You can change the lock screen's password request via the Settings -> Brightness and Lock -> Lock section.
There you can toggle the password request, and whether or not the screen should be automatically locked. (You can still lock the screen via the normal Lock Screen UI button, or respective command.)

password on resume


Seeking shapefile for Australia and New Zealand?

Question: I was trying to find a shapefile which has Australia and New Zealand together (states) so that I could convert to jVectorMap for ANZ.
Where I can find it?
Answer: The Natural Earth website is pretty good for freely available Geographic data, including Country boundaries.
Answer: Here is the data for Australia straight from their government's website: http://data.daff.gov.au/anrdl/metadata_files/pa_nsaasr9nnd_02211a04.xml
Here is the data for New Zealand from their government's data portal:
http://www.stats.govt.nz/browse_for_stats/people_and_communities/Geographic-areas/digital-boundary-files.aspx
From here you can merge the two shapefiles in QGIS or ArcMap or whatever GIS software you are using.
Answer: You could try to use OpenStreetMap data. Global land and water polygons are freely available from http://openstreetmapdata.com/data/land-polygons, a service offered by Jochen Topf. In contrast to the above mentioned Natural Earth dataset OpenStreetMap data is much more detailed and therefore requires more disk space.
Answer: the Global Administrative Districts has shapefiles (and geopackages, kmz, etc) for all countries.  The most recent release was in May 2018 and this is a high quality, comprehensive, one-stop shop for political boundaries.
The U.S. State Department GeoNode also maintains international boundaries in GIS format,
Answer: You can find Shapefile of Australia at https://www.igismap.com/australia-shapefile-download/?utm_source=Gisexchange&utm_medium=Ausshp&utm_campaign=J
Download free polygon administrative Shapefile of Australia. It covers local Australian government borders.