Need some clarifications for the equals operator (==)
Which equals operator (== vs ===) should be used in JavaScript comparisons?
Positive series problem: $\sum\limits_{n\geq1}a_n=+\infty$ implies $\sum_{n\geq1}\frac{a_n}{1+a_n}=+\infty$ Which side of wave-particle duality to choose in a given situation How does one know whether, in treating a certain problem, one should consider particles as waves or as point-like objects? Are there certain guidelines regarding this? Help with Axis Placement when extruding I am just learning Blender. I am going through the .  The first part was good. I was able to follow it. Coming from SketchUp, it is taking some adjustment. But I am getting it.  I am just starting the second video. At the beginning, the instructor selects the top of the mug to extrude it. When he presses the E key and Enter, the red, green blue axis moves to the center of those vertices. That does not happen when I press the E key and Enter.   This is only 1:30 into the video.  How can I get the axis in the middle of this circle of vertices?  The next step is to scale. I need the reference point in the middle of this circle of vertices. I cannot left-click accurately enough to position the axis/reference point.  I am using 2.69. The video uses 2.64. Chapter on the right side - How to turn it off? What is the command to remove all files but not directories? Let's say I have a directory tree like this:  FOLDER:     file1     file2     file3     Subfolder1:         file1         file2     Subfolder2:         file1         file2   If I used rm -r FOLDER/*, everything in FOLDER would be deleted including sub-directories. How can I delete all files in FOLDER and in its sub-directories without deleting actual directories? Prove that if $\lim_{n \to \infty}z_{n}=A$ then:  $$\lim_{n \to \infty}\frac{z_{1}+z_{2}+\cdots + z_{n}}{n}=A$$ I was thinking spliting it in: $$(z_{1}+z_{2}+\cdots+z_{N-1})+(z_{N}+z_{N+1}+\cdots+z_{n})$$ where $N$ is value of $n$ for which $|A-z_{n}|&lt;\epsilon$ then taking the limit of this sum devided by $n$ , and noting that the second sum is as close as you wish to $nA$ while the first is as close as you wish to $0$. Not sure if this helps.... Meaning of U suffix Possible Duplicate:          I was thinking about making a pacman clone, I know there is a similar question here  , but I know i can't use the original art from the game because it belongs to Namco, so if I design a character that has the shape of the slice circle it will look exactly like pacman, maybe if I use green instead of yellow? Also if the game plays like the original pacman, it is wrong?  I just want to make the game as a personal project and and publish it in my site without getting in trouble Output of Logistic Regression Prediction If $x\sqrt{1+y}+y\sqrt{1+x}=0$ find $y'$ Find $\frac{dy}{dx}$ if $x\sqrt{1+y}+y\sqrt{1+x}=0$ for $-1\leq x\leq 1$   My Attempt $$ x\sqrt{1+y}=-y\sqrt{1+x}\implies x^2(1+y)=y^2(1+x)\implies x^2+x^2y=y^2+xy^2\\ 2x+2xy+x^2\frac{dy}{dx}=2y\frac{dy}{dx}+y^2+2xy\frac{dy}{dx}\\ \frac{dy}{dx}\Big[ x^2-2y-2xy \Big]=y^2-2x-2xy\\ \frac{dy}{dx}=\frac{y^2-2x-2xy}{x^2-2y-2xy} $$ How do I proceed further and find the derivative ? word choice - realize notice find out figure out Using Laptop Screen as a monitor The essential gist of my question relates to what the real, unvarnished realities are of graduate, post-graduate, research, fellowship, and professorship attainment - when you aren't a single person with no pressing demands other than feeding yourself.   [EDIT: I am humbled by the incredibly helpful and thoughtful responses so far, all of which are +1 from me. I'll leave the question open a few more days before clicking 'accept' on any one, but you all have my gratitude and I hope others will benefit anywhere near as much as I have. ]  What I don't know is what succeeding in this path truly requires in time committment and family support.   Right now I can handle a 12-14 credit course schedule with 3.7-4.0 GPA (in the top 5-10% for college and program, dean's list, etc), work part-time, and still have time to be home and not have a burn-out/breakdown - and the academics are the easy part by far! I could do more, but I need to work more too.   What I really need to know is how sharply different is the time/dedication curve of graduate work and above. I realize each step is a filter that removes most of the entrants (most people don't get a degree, most who do don't attend/finish graduate school, most who do don't seek a PhD,  most who do don't seek/gain professorship...and on and on). But I don't know how severe the stepping is - I'm not talking "tenured professor at MIT or bust" - I realize that bar is many orders of magnitude higher.  Background Details: As an "adult, returning" undergraduate student with a (disabled) wife and kids, I'm halfway through a bachelor degree now. I've located a field of study (in a focus of Industrial Engineering) that has made me very interested in altering my life path to include seeking a Masters and maybe even a PhD/professorship (my father was a professor, so its not a purely novel concept to me). I've met and spoken with my advisor and 2 other professors with experience in related fields, and all is encouraging; I have a graduate school in mind, I've received lots of great advice on preparing for school (on this forum and in person), I test well (no GRE fears remain), good grades/class rank, good prospects for future strong referal letters, etc - a comparitively charmed existence for which I am very grateful! I just have to investigate whether I can make it through with an intact, cared for family!  Any guidance you could provide me, and other aspiring "non-traditional" students alike, would be appreciated immensely - thank you! Create an instance of a class from a string Is there a way to create an instance of a class based on the fact I know the name of the class at runtime. Basically I would have the name of the class in a string. Often called "He-Who-Must-Not-Be-Named" and "You know who", was it common knowledge at the Ministry of Magic that Voldemort was the same person as Tom Riddle? Large 10 kWh 18650 Lithium-ion power pack - What configuration? I need to build a 10 kWh lithium-ion pack, anywhere from 70 V to 200 V.  This is to drive a motor.  Power output will not exceed 15 kW.  The cells will be Panasonic NCR 'B' at 3.4 Ah 18650.  I would like to minimize space and weight and cost. :D  Level of safety would be standard for a hobby application.  Charging will be done in a safe area using two levels of overcharge and overcurrent protection.  Charging is from house current, 110V, and multiple chargers may be employed to double or triple the charge rate.   What is the best configuration for cells?  I would prefer if the pack is broken down into units of 1 to 2 kWh each.  Each unit may be charged separately. In addition to a balancing-protection board and a CCCV charger, what other protection or safety mechanisms are recommended, short of a smart BMS system? I have looked at a cheap Chinese balancing board that offers protection (thermal, overcharge, undercharge, overcurrent, short).  A 20S board will offer up to 84 V and adequate current for the application, for a 1.5 kWh unit.  At 1/3C, I would need a 83 V 6 A CCCV charger.  How do I get one of these? Off-topic question:  Can a balancing-protection board be used for a configuration with a lesser number of cells? Such as using a 10S board to control an 8S configuration.  Or does this depend on the board? Pacf lag axe , is not an integer I'm trying to use ARIMA process to predict the behaviour of a time series, the probleme I face is that I can't get the order of each component of ARIMA, the lag is between 0 and 1, same goes for the acf. The time series has no tendency, and I guess no seasonality.     My question is : Does this mean that ARIMA orders are all 0s, and if so, is the HoltWinters a good (or the best) solution for modelling this kind of TS ? grep: memory exhausted Finding the derivatives of sin(x) and cos(x) We all know that the following (hopefully):  $$\sin(x)=\sum^{\infty}_{n=0}(-1)^n \frac{x^{2n+1}}{(2n+1)!}\ , \ x\in \mathbb{R}$$  $$\cos(x)=\sum^{\infty}_{n=0}(-1)^n \frac{x^{2n}}{(2n)!}\ , \ x\in \mathbb{R}$$  But how do we find the derivates of $\sin(x)$ and $\cos(x)$ by using the definition of a derivative and the those definition above?  Like I should start by doing:  $$\lim_{h\to\infty}\frac{\sin(x+h)-\sin(x)}{h}$$  But after that no clue at all.  Help appreciated! Is it possible to find all php files within a certain directory that have been modified on a certain date  I'm using   find /var/www/html/dir/ -mtime -28 | grep '\.php'    to get files modified within the last 28 days, but I only need files that have been modified on the following date: 2011-02-08