What alternatives are there to REISUB for  system problems?  The windows task manager has its good points in this regard.  Or, key combination to logout.  It's not always possible to get to a virtual console.  Some combination to just logout would be my preference.  Or kill the window system and revert to CLI.   but a reboot.  But how do you then recover?
All operating systems freeze sometimes, and Ubuntu is no exception. What should I do to regain control when...   just one program stops responding? nothing at all responds to mouse clicks or key presses? the mouse stops moving entirely? I have an    In what order should I try various solutions before deciding to pull the power plug?  What should I do when starting up Ubuntu fails?  Is there a diagnostic procedure I can follow?
Many other solutions of the Cauchy's Functional Equation By reading the  on the Wiki,  it is said that      On the other hand, if no further conditions are imposed on f, then (assuming the axiom of choice) there are infinitely many other functions that satisfy the equation. This was proved in 1905 by Georg Hamel using Hamel bases. Such functions are sometimes called Hamel functions.   Could anyone give a more explicit explanation of these many other solutions?   Besides the trivial solution of the form $f(x)=C x$, where $C$ is a constant, and the solution above constructed by the Hamel Basis, are there any more solutions existing? Invoking makeindex for nomencl I have spent many many hours failing to implement nomencl for my PhD thesis. The problem seems to be with invoking makeindex and creating the .nls file  I keep reading that I must invoke makeindex or write a Unix command:  makeindex filename.nlo  -s nomencl.ist -o filename.nls   But I don't know how to do this. I would be grateful for some instructions i.e. where do I type the command?    I am using TeXShop 2.43. Measure the size of a PostgreSQL table row I have a PostgreSQL table. select * is very slow whereas select id is nice and quick. I think it may be that the size of the row is very large and it's taking a while to transport, or it may be some other factor. I need all of the fields (or nearly all of them), so selecting just a subset isn't a quick fix. Selecting the fields that I want is still slow. Here's my table schema minus the names: integer                  | not null default nextval('core_page_id_seq'::regclass) character varying(255)   | not null character varying(64)    | not null text                     | default '{}'::text character varying(255)   |  integer                  | not null default 0 text                     | default '{}'::text text                     |  timestamp with time zone |  integer                  |  timestamp with time zone |  integer                  |   The size of the text field may be any size. But still, no more than a few kilobytes in the worst case. Questions  Is there anything about this that screams 'crazy inefficient'? Is there a way to measure page size at the Postgres command-line to help me debug this? Inductive proof of the closed formula for the Fibonacci sequence Fibonacci numbers $f(n)$ are defined recursively:  $f(n) = f(n-1) +f(n-2)$ for $n &gt; 2$ and $f(1) = 1$, $f(2) = 1$. They also admit a simple closed form: $$\sqrt 5 f( n ) = \left(\dfrac{1+ \sqrt 5}{2}\right)^n- \left(\dfrac{1 - \sqrt 5}{2}\right)^n \tag1$$  How to prove (1) using induction?  Remarks One could get (1) by the general method of solving recurrences: look for solutions of the form $f(n)=r^n$, then fit them to the initial values. But there should be a more concrete proof for this specific sequence, using the principle of mathematical induction. Is it a good practice to refer to countries, ships etc using the feminine form? While talking about ships and countries, is it a good practice to use the feminine form?  For example:  "Her economy" - while referring to a country's economy "Her flag (or deck etc)" - while referring to a ship  Is this practice common? Is it used today? Adding Foreign Key Error Is there a way to force the Nikon D40's rear LCD panel to stay off? Is there an off/disable control anywhere? I realize that the INFO button toggles it off, but it comes right back on as soon as you tap the shutter, and that it a problem in low light situations where the LCD keeps blasting me in the eye. As an example, consider the two sentences:     There don't seem to be any doctors here.   and     There doesn't seem to be any doctors here.   To my ear, the first sounds great, and the second is painfully awkward.  So which is correct, grammatically? I've found lots of disagreement on this around the Web, with various sources citing different ways of treating the word "any" (as singular, always, or as either depending on to what it refers). No consensus, however, could I locate. My processor is an Intel Core 2 Duo P8600 (2.40GHz). As far as I know that's a 64-bit processor - I'm a bit confused as the architecture is called AMD 64, is this a generic name given to 64-bit architectures? I've heard of x64 but can't see a release labelled with this. I used to use a lot ctrl+alt+numpad to move windows, how can I use this feature on ubuntu 18 like it was default before?  Thank you in advance Simplify a combinatorial sum Why is $\sum_{k=0}^n (_k^n) 2^k$ simplified as $3^n$ and not just $2^n$ ? The answer uses the binomial theorem as a solution: let $a=1$ and let $b=2$. So $1+2 = 3$. But since $1+2 = 3$ why do we not use $1+1 = 2$? What is the point of isomorphism concept? No surname on passport and applying for Japanese Visa Derivation of Maxwell's equations from field tensor lagrangian I've started reading Peskin and Schroeder on my own time, and I'm a bit confused about how to obtain Maxwell's equations from the (source-free) lagrangian density $L = -\frac{1}{4}F_{\mu\nu}F^{\mu\nu}$ (where $F^{\mu\nu} = \partial^\mu A^\nu - \partial^\nu A^\mu$ is the field tensor).  Substituting in for the definition of the field tensor yields $L = -\frac{1}{2}[(\partial_\mu A_\nu)(\partial^\mu A^\nu) - (\partial_\mu A_\nu)(\partial^\nu A^\mu)]$.  I know I should be using $A^\mu$ as the dynamical variable in the Euler-Lagrange equations, which become $\frac{\partial L}{\partial A_\mu} - \partial_\mu\frac{\partial L}{\partial(\partial_\mu A_\nu)} = - \partial_\mu\frac{\partial L}{\partial(\partial_\mu A_\nu)}$, but I'm confused about how to proceed from here.  I know I should end up with $\partial_\mu F^{\mu\nu} = 0$, but I don't quite see why.  Since $\mu$ and $\nu$ are dummy indices, I should be able to change them: how do the indices in the lagrangian relate to the indices in the derivatives in the Euler-Lagrange equations? The method format(String, Object[]) in the type String is not applicable for the arguments (...) Understanding a probability paradox Three prisoners are informed by their jailer that one of them has been chosen at random to be executed and the other two are to be freed. Prisoner A asks the jailer to tell him privately which of his fellow prisoners will be set free, claiming that there would be no harm in divulging this information because he already knows that at least one of the two will go free. The jailer refuses to answer the question, pointing out that if A knew which of his fellow prisoners were to be set free, then his own probability of being executed would rise from 1 3 to 1 2 because he would then be one of two prisoners. What do you think of the jailer’s reasoning?  If the jailer refuses to say anything, then the probability that prisoner $A$ is excecuted is $\frac{1}{3}$. If the jailer says to prisoner $A$ that prisoner $B$ will walk free, then $2$ prisoners remain to be considered, $A$ and $C$. One dies, one does not. Heads or tails essentially. $\frac{1}{2}$ ought to be the conditional probability that $A$ dies given that $B$ walks free no? Apparently not though, allegedly the correct answer is still $\frac{1}{3}$. Even my attempt to calculate the correct answer yielded the result $\frac{1}{2}$.   Let $A_D$ and $C_D$ respectively denote the event of $A$ and $C$ dying. Let $B_F$ denote the event that $B$ walks free. Assume that the jailer tells prisoner $A$ that prisoner $B$ will walk free.   Here's my attempt.  $$P(A_D\mid B_F)=\frac{P(A_D\cap B_F)}{P(B_F)}=\frac{P(A_D\cap B_F)}{P((B_F\cap A_D)\cup (B_F\cap C_D))}=\frac{P(A_D)P(B_F\mid A_D)}{P(A_D)P(B_F\mid A_D)+P(C_D)P(B_F\mid C_D)}=\frac{\frac{1}{3}\times 1}{\frac{1}{3}\times 1+\frac{1}{3}\times 1}=\frac{1}{2}$$  What am I doing wrong?  Edit 1: Intuitively I am still troubled but I understand now that $B_F$ may occur even though the jailer does not necessarally say $B$.   Edit 2: I suppose that it makes some sense if the faiths of the prisoners had already been decided before prisoner $A$ asked the jailer the question. If the jailer decides to reveal one of the others who will walk free then that must've been the case. What happens if I do not honor a futures contract? I have little knowledge about futures contracts. The recent negative price of crude oil spurred my curiosity about this stuff.   I read this post about .  According to this post, when I buy a futures contract, I enter into a contractual agreement to buy some commodity on some future date, and I only need to pay a 2% initial margin.   Suppose the price of the commodity does not fluctuate but I change my mind and decide not to buy the commodity at maturity. What punishment could be exerted on me?   I do not want the 2% initial margin back because that is a little money compared to the real value of the commodity. If there is no extra penalty, it would be unfair for the seller — imagine the seller transports 1000 barrels of crude oil to your front door and you say "I do not need it any more, please take it away, thank you!"  Update: I did more research about this and have more questions.  If I buy a futures contract at $10 and the price of the contract drops to -$37 at the last trading day, at which price should I buy the commodity at the delivery day, $10 or -$37?   There seems not just one contract I enter into when I buy a futures contract: the original futures contract between me and the seller of the commodity(or the exchange?), the contract between me and my brokerage, the contract between the brokerage and the exchange. I'm not clear about the exact entities of each contract and the obligations involved in each contract. The contracts seem contradictory with each other, e.g., my brokerage may forcefully sell my futures contract if my account balance is not enough, which will prevent me from fulfilling the obligations in the futures contract, i.e., receiving the commodity on future date.  If I(or an institutional trader) trade directly (not via a brokerage) with an exchange(does CME accept individual traders?), does the exchange have the rights to forcefully sell my contracts at the last trading day at any price or close my position at the settlement price(say -$37)? If the exchange does so thus letting me own $5,000M to it, is it more justice for me to sue the exchange rather than let the exchange sue me? If I could hold the position, the loss caused by my not executing the delivery/receipt of the commodity may be less than $5,000M. Of course, the loss will be determined by the court, not by the exchange according to the settlement price formed by itself or a few possible conspirators. Could it be a structure of "How many -singular noun- is there?" We had an argument in our collage if it's possible to have such structure:     "How many -singular noun- is there?"   For example:      How many chair is there?   The claim of the supporters: This structure should be used in case that t is not known whether there is one one or more chairs there. While just in case that it is known certainty that there are more than one chair, it should be "how many chairs are there".    The claim of the opponents: This structure cannot be since using the phrase "how many" always should be with a plural noun.  Both sides are not native English speakers, then I would like to know what is the truth. Arbitrary intersection of closed, connected subsets of a compact space connected? Let $(B_i)_{i\in I}$ be an indexed family of closed, connected sets in a compact space X. Suppose $I$ is ordered, sucht that $i &lt; j \implies B_i \supset B_j$.  Is $B = \bigcap_i B_i$ necessarily connected?  I can prove it, if I assume $X$ to be Hausdorff as well: If $B$ is not connected, then there are two disjoint, closed, nonempty sets $C$, $D$ in $B$, such that $C \cup D = B$. Now these sets are also closed in $X$, hence by normality there exist open disjoint neighborhoods $U$, $V$ of $C$ and $D$, respectively.  Then for all $i$: $B_i \cap U^c \cap V^c \ne \emptyset$, since $B$ is contained in $B_i$ and $B_i$ is connected. Thus we must also have  $$ B \cap U^c \cap V^c = \bigcap_i B_i \cap U^c \cap V^c \ne \emptyset $$  by compactness and the fact that the $B_i$ satisfy the finite intersection property. This is a contradiction to the choice of $U$ and $V$.  I can neither see a counterexample for the general case, nor a proof. Any hints would be greatly appreciated!  Thanks,  S. L. How to create and design hoops net and attach ot to a hoop?