On Travel.SE we often see questions about a person (usually a love interest) asking for money to pay for airfare, visas, permits and other expenses. For example        What general advice can be given in such situations to the person asking the question? Is it all a scam or can there be legitimate situations in which an online friend could be asking for money?
Woman planning to visit me from Ukraine to the US applied for a visa and such, claims to have paid for the visa but needs 500 dollars more for the airfare from Ukraine to the US. She says strict rules apply that the airfare cannot be purchased by US person, and must be purchased in Ukraine by person applying for the visa because of terrorist issues, etc..   Is there truth to such?
For multiple OTP keys, why not do this:  Key = Hash[(EC)DH Shared Secret + Counter]  The counter will increase per message, and the output of the hash will be random for each new unique input into it. What are the problems or weaknesses with this design??  EDIT: For clarification: both parties will have the shared secret from an ECDH exchange, random numbers from Pythons os.urandom for generating the ECC key How do the sets $\emptyset\times B,\ A\ \times \emptyset, \ \emptyset \times \emptyset $ look like? If we have a function $f:A \rightarrow B$, then one way to give meaning, I think, to this function, in terms of set theory, is to say, that $f$ is actually a binary relation $f=(A,B,G_f)$, where $G_f \subseteq A \times B$ is the graph of the function. Now my question is: what is $f$ if   $\bullet \ A=\emptyset, \ B\neq\emptyset$,?  $ \bullet \ B=\emptyset, \ A\neq\emptyset$ ?  $ \bullet \ B=\emptyset, \ A=\emptyset$ ?  (Another way to formulate this, I think, would be: How do the sets $\emptyset\times B,\ A\ \times \emptyset, \ \emptyset \times \emptyset $ look like? Are they all $\emptyset$ ?) Proofs involving limsup and liminf I've been working with proofs involving $\limsup$ and $\liminf$, and I'm a bit confused regarding their general methodology. More specifically, I'm unsure about whether my approach to the following problem makes sense.  Problem. Let $(s_n)$ and $(t_n$) be sequences and suppose that there exists $N_0$ such that $s_n \leq t_n$ for all $n &gt; N_0$. Show that $\liminf s_n \leq \liminf t_n$ and that $\limsup s_n \leq \limsup t_n$.   The way I approached it was as follows:   Let $N &gt; N_0$. Then $\limsup_{N \rightarrow \infty} \{ s_n : n &gt; N \} \leq t_n$ as $s_n \leq t_n$, and $\limsup s_n $ is the largest possible limit of a subsequence of $s_n$. As $t_n : n &gt; N$ is (by definition) less than $\limsup_{N \rightarrow \infty} \{ t_n : n &gt; N \}$, the proof is complete.  I'm pretty sure this is incorrect, however, and I'm generally unclear about the method behind such a proof. Any help is appreciated! Cutting a circular hole in a hollow cylinder without distorting the cylinder Whenever I try to cut out a circular hole in either a cylinder or sphere the polygons around the circular hole always have distorted normals after smoothing. Is there anyway to fix this. I've tried using the remesh modifier but wind up with some pretty ugly results. Skipping Iterations in Python I have a loop going, but there is the possibility for exceptions to be raised inside the loop. This of course would stop my program all together. To prevent that I catch the exceptions and handle them. But then the rest of the iteration runs even though an exception occurred. Is there a keyword to use in my except: clause to just skip the rest of the current iteration? Suppose we want to prove $$ k \binom{n}{k} = n \binom{n-1}{k-1}$$   In the LHS we are choosing a team of $k$ players from $n$ players. Then we are choosing a captain. In the RHS we are choosing a captain from the $n$ players. Then we are choosing the remaining $k-1$ players from the $n-1$ players.   Is this a correct interpretation? C-3PO frequently speaks of “the Maker.” Is this a true droid religion, or is this a religious reverence by droids for their specific creators (in this case, Anakin, even though C-3PO has forgotten who he is)? Is this even a droid thing or is it just C-3PO? What else do we know about this “Maker”-worship? How did Sauron remain in control of the Nazgûl? What is the difference between Halt and Shutdown commands? What is the difference between the halt and shutdown commands? Motivation behind standard deviation? Let's take the numbers 0-10.  Their mean is 5, and the individual deviations from 5 are -5, -4, -3, -2, -1, 0, 1, 2, 3, 4, 5 And so the average (magnitude of) deviation from the mean is $30/11 \approx 2.72$.  However, this is not the standard deviation.  The standard deviation is $\sqrt{10} \approx 3.16$.  The first mean-deviation is a simpler and by far more intuitive definition of the "standard-deviation", so I'm sure it's the first definition statisticians worked with.  However, for some reason they decided to adopt the second definition instead.  What is the reasoning behind that decision? In my CMS, I noticed that directories need the executable bit (+x) set for the user to open them. Why is the execute permission required to read a directory, and how do directory permissions in Linux work? Should the first word after a colon be capitalized? Which of the following is correct?   For example: This. For example: this. Prove that any conjugate of $a$ has the same order as $a$. I am trying to prove that any conjugate of $a$ has the same order as $a$.  Let $G$ be a group and let $a \in G$.  An element $b \in G$ is called a conjugate of $a$ if $b=xax^{-1}$.  My professor gave us a hint.  Prove $a^k=e$ iff $b^k=e$ for all $k \in \mathbb{Z}$ implies $o(a) = o(b)$.  My first move is to $b^k = (xax^{-1})^k = (x^{-1})^ka^kx^k = (x^{-1})^kex^k = (x^{-1})^kx^k=x^{-k+k}=x^0$  I am not sure that I am doing this correctly?  I am trying to get $b^k=e$.  However when I raise $(xax^{-1})^k$, I am not sure if I what I have done is correct?  I am kind of confused here. Significance contradiction in linear regression: significant t-test for a coefficient vs non-significant overall F-statistic I'm fitting a multiple linear regression model between 4 categorical variables (with 4 levels each) and a numerical output. My dataset has 43 observations.  Regression gives me the following $p$-values from the $t$-test for every slope coefficient: $.15, .67, .27, .02$. Thus, the coefficient for the 4th predictor is significant at $\alpha = .05$ confidence level.  On the other hand, the regression gives me a $p$-value from an overall $F$-test of the null hypothesis that all my slope coefficients are equal to zero. For my dataset, this $p$-value is $.11$.  My question: how should I interpret these results? Which $p$-value should I use and why? Is the coefficient for the 4th variable significantly different from $0$ at the $\alpha = .05$ confidence level?  I've seen a related question, , but there was an opposite situation: high $t$-test $p$-values and low $F$-test $p$-value. Honestly, I don't quite understand why we would need an $F$-test in addition to a $t$-test to see if linear regression coefficients are significantly different from zero. This question is asked often in Ask Ubuntu, sometimes with few hints about the situation.   Please provide a list of possible reasons to help troubleshoot the problem. How can I find the version of Ubuntu that is installed? How to remove GNOME Shell from Ubuntu 20.04 LTS to install other desktop environment from scratch? I just bought a used  and it comes with regular rim brakes. I'm perfectly happy with them so far, but have been wondering if disc brakes would come handy when it rains.  What is involved in converting a bike from rim brakes to disc brakes (mechanical or hydraulic)?   Is this something that is feasible, or am I better off buying another bike that already has disc brakes? Avoiding "(Not Responding)" label in windows while processing lots of data in one lump I occasionally need to process a large amount of data from one package off the network, which takes sufficiently long that when the user tries to interact with the application windows adds the "(Not Responding)" string to the window title. I am aware this is because the processing is being done within a call to handle a message (some way up the stack) and therefore is blocking the message pump. I'm also aware the ideal way to deal with this is to process the data asynchronously in a separate thread so the pump can continue running, however this is a LARGE desktop application which is single threaded from top to toe and safely spinning this processing off is not feasible in our time frame.  So with that in mind, is there by any chance a way I can at least avoid the "not responding" moniker (which to most users reads as "has crashed") by telling windows my application is about to be busy before I begin the work? I believe there is something along these lines when responding to a request to close, one can keep asking windows for more time to avoid it proclaiming that your not "closing in a timely fashion"  I should add this is a C++ MFC application. Someone asked a very similar question in regards to window recovery for windows xp:   I'm using windows 8 (or 8.1 now). I run Dual Monitors. On Monitor 2 I sometimes have the input switched to something else other than the windows display (Mac or PS3). If there was a program that was displaying on Window #2 that does not have 'move' where I could potentially alt-space-m arrow keys. Is there another way to get that program to display on Window #1?  I tried right click on the program and doesn't seem to be anything there. I tried Windows Key and Arrows. I Tried right click toolbar and cascade.  I'm hoping this is a DUP or Softball question because this annoys the crap out of me.  Thanks!!