I have seen many different research students that want to apply for a PhD or MSc program but they are so nervous about their choice. Sometimes they pay most of heir time, reviewing the websites of the universities, profiles of the professors and do their best to gather information and choose the best PhD program or university to apply for PhD but they are still nervous about their choice. Some students only think that the universities with higher rankings are best to apply for and they miss some middle-ranked universities which are so good at their majors. This way, their chance to apply for those high-ranked universities is so low and they may lose two or three years preparing and applying for those university. While in the same period of time, if they had applied for that middle-ranked universities, they had higher chance of applying and in this period of three years, they would have finished most parts of their PhD program. My question here is about these things:   To what extent a person should be realistic in choosing a university for his PhD program. A normal student may be more successful in a middle-ranked university than a higher-ranked university. I think that sometimes, normal students lose their confidence when they study at high level universities, while; if they study in good middle-ranked universities, their academic output may be much higher and they will be a more successful person. Does it worth that a person that has high chance to be accepted in a good second ranked university, wait for two or three years to modify his curriculum vitae and apply for a first level university? Which one is more acceptable and appreciated? A top student at a second ranked university or a poor and not so much successful student in a very good ranked well-known university?     I can not decide in this period of each persons' life, how he should make decisions. This also applies to other circumstances. For instance, working in good company with lower income or working in a not big company with higher level of income. Making clear how a person should make decisions like this may be so much helpful to me.
What I'm trying to understand is, to what degree does the status/rank of the University (where one completes his/her Ph.D) matter while shaping his/her career after graduation? I would like to know the weight given to one's school in both the following cases:   While applying for post-docs/faculty positions in academia While applying to industrial research labs   For instance, I've read on some forums (I can't locate the link now) that while considering prospective applications for tenure-track faculty positions, very few Universities accept a candidate who has completed his/her Ph.D from a lower ranked school having a lesser "brand" value, irrespective of the fact whether he/she has published equally original work as his/her counterpart from an Ivy league college. How much truth is in this statement? It would be really great if someone already in academia, either as a newly-accepted faculty or someone on the Faculty Hiring committee could share their experiences/statistics on this regard. I'm simply interested to know the answer, without commenting at all on whether such a practice is justifiable.  Similarly, what about recruitment to internationally acclaimed research labs (like  or ) - what importance do they place on the pedigree of a candidate's college, before taking into consideration what they published ?  I'm personally interested in answers related to the field of Computer Science (theory), but the question is applicable to any prospective grad student in any discipline in my opinion. Feel free to share your personal experiences post-Ph.D in detail, as that would give me (and future viewers of this question) about what its like to carve a career once you are out of school!
Why is accuracy not the best measure for assessing classification models? This is a general question that was asked indirectly multiple times in here, but it lacks a single authoritative answer. It would be great to have a detailed answer to this for the reference.  , the proportion of correct classifications among all classifications, is very simple and very "intuitive" measure, yet it may be a . Why does our intuition misguide us here and are there any other problems with this measure? Allowed memory size of 33554432 bytes exhausted (tried to allocate 43148176 bytes) in php This error message is being presented, any suggestions?     Allowed memory size of 33554432 bytes exhausted (tried to allocate   43148176 bytes) in php PHP code is not being executed, instead code shows on the page My prof gave us this definition of an Echelon system:     A system of m linear equations in n variables is called an echelon system if         m ≤ n.   Every variable is the leading variable of at most one equation.   Every leading variable is to the left of the leading variables of all lower equations.   Every equation has a leading variable.      I don't understand this definition at all.  Q1)If you have this system of equations:  $ax_1 + bx_2 + cx_3 = z$  $dx_1 + ex_2 + fx_3 = z$  its not an echelon system because of multiple equations having the same variable as the leading variable and therefore violating rule #2.  But if you switch around variables and rewrite the equation as:  $ax_1 + bx_2 + cx_3 = z$  $ex_2 + dx_1 + fx_3 = z$  It becomes an echelon system! Why would the way you write a system of equations affect its definition?  Q2)Why would point number three matter? Can't you just move around the equations so that they are in order of variables?  Q3)Why would point number four matter? If you have a equation in the system that doesn't have a leading variable can't you just disregard it? For example if you have the equation $0x = 0$ in the equation can't you just ignore it to have a echelon system since it doesn't affect the solution of the system? I installed ubuntu 16.04 LTS, but there is no ubuntu one software, not in ubuntu software center also..Though it is showing selected in unity tweak tool.How can I get it. Please reply. Changing the value of an element in a list of structs I have a list of structs and I want to change one element. For example :  MyList.Add(new MyStruct("john"); MyList.Add(new MyStruct("peter");   Now I want to change one element:  MyList[1].Name = "bob"   However, whenever I try and do this I get the following error:     Cannot modify the return value of   System.Collections.Generic.List.this[int]‘ because it is not   a variable   If I use a list of classes, the problem doesn't occur.  I guess the answer has to do with structs being a value type.  So, if I have a list of structs should I treat them as read-only? If I need to change elements in a list then I should use classes and not structs? Word for seeing both sides of an argument GParted can't resize partition, but unallocated partition is available How to effectively deal with Imposter Syndrome and feelings of inadequacy: "I've somehow convinced everyone that I'm actually good at this" Proving $\,a\mid bc\!\iff\! \frac{a}{(a,b)}\!\mid c\ $ [general Euclid's Lemma] I tried to start by showing that $ \frac{a}{\gcd(a,b)} $ is always an integer, let's call it $d$, because $a$ is always a multiple of $(a,b)$ based on the definition of a g.c.d. I then tried to show that if $a | b$ then $a|bc$ from the theorem that states that $a|b$ implies that $a|bc$ for any integer $c$, but I cant seem to prove that $a | b$ or that $a|bc$ only if $d \mid c$ (where $d = \frac{a}{\gcd(a,b)}$ ). Any help would be much appreciated. I have installed Ubuntu 12.04-64 bit on my Lenovo IdeaPad laptop, and the wired Ethernet (LAN) connection doesn't work.  Running the lspci -vv | grep Atheros command from the terminal shows me I have the AR8161 Gigabit Ethernet controller:  02:00.0 Ethernet controller: Atheros Communications Inc. AR8161 Gigabit Ethernet (rev 08)   This looks like a new product whose drivers are not built into Ubuntu.  How do I install drivers to get the AR8161 working? Mouse rotated 90 degrees What is the meaning of this two letter code in the YouTube logo? I see a new logo with CA at youtube.com. Does anyone know what it means? Disable emojicons introduced with WP 4.2 So WP 4.2 introduced emojis (smileys) that basically adds JS and other junk all over your pages. Something some people may find shocking. How does one completely erase all instances of this? Embedding ordinals in $\mathbb{Q}$ All countable ordinals are embeddable in $\mathbb{Q}$.  For "small" countable ordinals, it is simple to do this explicitly.  $\omega$ is trivial, $\omega+1$ can be e.g. done as $\{\frac{n}{n+1}:n\in \mathbb{N}\} \cup \{1\}$.   $\omega*2$ can be done as $\{\frac{n}{n+1}:n\in \mathbb{N}\} \cup \{1+\frac{n}{n+1}:n\in \mathbb{N}\}$, and $\omega*n$ as $\bigcup_{i\le n} \{i+\frac{n}{n+1}:n\in \mathbb{N}\}$  That immediately also gives $\omega^2$ as  $\bigcup_{i \in \mathbb{N}} \{i+\frac{n}{n+1}:n\in \mathbb{N}\}$  And going further is still relatively easy: We can biject the above embedding of $\omega^2$ onto a single interval $(0,1)$, e.g. through $f(x)=1-\frac{1}{x+1}$ since this is an order preserving bijection from $\mathbb{Q}^+$ to $(0,1)$, allowing us to get $\omega^2+n$, $\omega^2*n$ etc. And by iterating that process, we can get any ordinal below $\omega^\omega$.   But this sort of embedding fails at $\omega^\omega$ as the iteration of $f$ doesn't seem compatible with taking the infinite union - figuratively speaking, we'd squish things to $0$. So what would an explicit embedding of $\omega^\omega$ look like? And the question, then, is if it is possible to give an explicit embedding of $\epsilon_0$? Is the fact that Peano arithmetic cannot prove well-foundedness of $\epsilon_0$ an indication that it cannot be embedded by such elementary functions and their iterations?  And what about even bigger countable ordinals such as the Veblen ordinals, Feferman-Schütte, Bachmann-Howard? From its definition, even if the above all are possible, I assume that the definitive bound of where one can define an effective procedure for the embedding must be Church–Kleene - is that a correct conclusion?  Lastly, does the situation change when we use $\mathbb{R}$ instead of $\mathbb{Q}$, which would allow us to use, perhaps, more easily understood yet inherently complex functions?  Edited because $\omega^2 \neq \omega^\omega$ Test for convergence  $$\sum_{n=1}^{\infty} \frac{1}{n^n}$$  I'm at a loss on what to do, is this a geometric series $\frac{1^n}{n^n}$? My keyboard doesn't have an Fn key so I can't get the coordinates to show up. I don't know how to get into the multiplayer settings and Shift + F3 doesn't work either.  How can I fix this? Getting the starting shortcut in c# Annoying flickering in 16.04 LTS - Chrome I've upgraded from 4.4.0 to 4.4.8 and then 4.5.2 on Ubuntu 16.04 LTS 64-bit, and it's still happening.   At 4.5.2 it's even more frequent, and mainly in Chrome (haven't tried firefox or opera just yet). Every time I open a new web page. Any way to fix that, or is it a bug?  00:02.0 VGA compatible controller: Intel Corporation HD Graphics 5500 (rev 09) 04:00.0 Display controller: Advanced Micro Devices, Inc. [AMD/ATI] Venus XTX [Radeon HD 8890M / R9 M275X/M375X] (rev 81)   Cheers. I had always kind of wondered why we didn't see interference in things like windows -- we were taught that the condition is that the thickness of the film/slab/medium just has to be an integral number of wavelengths, $d=m\lambda$. My logic was, if visible light has wavelengths ~400-780nm, any window pane has got to be an integral number of wavelengths (or close to integral) for some of the wavelengths in the visible.  For example, if a window is, $6mm = 6\times10^6nm$ thick, then you should see interference for wavelengths (and some range around them) 200nm, 250nm, 300nm, 400nm, 500nm, 600nm... Because 6mm is an integral number of each of those.  Obviously that would be really annoying and isn't the case. I found  (warning: PDF) source that seems to explain it and I was wondering if what they're saying is sound. On the 10th page (p171 for them), it says that the reason we don't see this interference is that no window is that smooth, it has a variance in the thickness of at least several wavelengths, so the interference effect is effectively average out among all those thicknesses, which usually gets rid of it. They do the math and show that.  Is that the reason?  If so, that leads me to two questions: Could we, if we were really careful and used something like MBE, make a glass window with that sort of accuracy, and then see interference effects in the optical range? I know that quartz crystal monitors can easily give you nanometer accuracy for evaporators and sputterers, but they also have pretty limited growth rates.  My second question is, then, do we see interference effects in glass windows with electromagnetic radiation of a comparable wavelength, like microwaves?  Thanks!