I'm just an amateur in this and I Need Help..  I've drawn this circuit of my Shaving machine and I want to remove the battery and connect it directly to one of these phone chargers-:   The first: output 5.7v ~ 800mA   or  The second-: output 5v ~ 350mA  or   -The shaving machine charger: 3v ~ 200mA  Will Any Of These Work?
Power supplies are available in a wide range of voltage and current ratings.  If I have a device that has specific voltage and current ratings, how do those relate to the power ratings I need to specify?  What if I don't know the device's specs, but am replacing a previous power supply with particular ratings?  Is it OK to go lower voltage, or should it always be higher?  What about current?  I don't want a 10 A supply to damage my 1 A device.
I have studied that every normed space $(V, \lVert\cdot \lVert)$ is a metric space with respect to distance function  $d(u,v) = \lVert u - v \rVert$, $u,v \in V$.   My question is whether every metric on a linear space can be induced by norm? I know answer is  no but I need proper justification.   Edit: Is there any method to check whether a given metric space is induced by norm ?  Thanks for help What is the difference between <%# and <%= in ASP.NET MVC? What's the best way to return multiple values from a function? I have a function where I need to do something to a string.  I need the function to return a boolean indicating whether or not the operation succeeded, and I also need to return the modified string.    In C#, I would use an out parameter for the string, but there is no equivalent in Python.  I'm still very new to Python and the only thing I can think of is to return a tuple with the boolean and modified string.  Related question: If a function has a finite limit at infinity, does that imply its derivative goes to zero? I've been thinking about this problem: Let $f: (a, +\infty) \to \mathbb{R}$ be a differentiable function such that $\lim\limits_{x \to +\infty} f(x) = L &lt; \infty$. Then must it be the case that $\lim\limits_{x\to +\infty}f'(x) = 0$?  It looks like it's true, but I haven't managed to work out a proof. I came up with this, but it's pretty sketchy:  $$ \begin{align} \lim_{x \to +\infty} f'(x) &amp;= \lim_{x \to +\infty} \lim_{h \to 0} \frac{f(x+h)-f(x)}{h} \\ &amp;= \lim_{h \to 0} \lim_{x \to +\infty} \frac{f(x+h)-f(x)}{h} \\ &amp;= \lim_{h \to 0} \frac1{h} \lim_{x \to +\infty}[f(x+h)-f(x)] \\ &amp;= \lim_{h \to 0} \frac1{h}(L-L) \\ &amp;= \lim_{h \to 0} \frac{0}{h} \\ &amp;= 0 \end{align} $$  In particular, I don't think I can swap the order of the limits just like that. Is this correct, and if it isn't, how can we prove the statement? I know there is  already, but I think this is different in two aspects. First, that question assumes that $\lim\limits_{x \to +\infty}f'(x)$ exists, which I don't. Second, I also wanted to know if interchanging limits is a valid operation in this case. I have a 3D truck model already textured and properly imported into Blender. This is a game model and I need to "re-paint" with design from other transport companies. The problem is that I don't have a UV layout (skin template) to serve as a guide for future paintings.  Is there a way to "extract" an UV Layout to .JPG or .PNG to serve as guide for .DDS texture editing?  Please note that I don't want to remap the model. I still want to use the actual UV Mapping and just need to edit the actual textures. Source shell script automatically in terminal How can I automatically source a particular shell script when I open a terminal window by right clicking somewhere and choosing "open in terminal"?  For example, every time I open a terminal I need to run the following command line:  source myscript   How can I make it so that I don't have to type this automatically?  My script is written in tsch:  #!/bin/tcsh setenv DISPLAY 127.0.0.1:10.0 cd /ast/dcm/data   I'm using CentOS 7. Let $\mathbf{FinVec}$ denote the category of finite-dimensional real vector spaces and linear maps, let $F\colon\mathbf{FinVec}\rightarrow\mathbf{FinVec}$ be a functor. For each pair of objects $V,W$, the Hom-set $\operatorname{Hom}(V,W)$ is itself a finite-dimensional vector space and we equip it with the unique structure of a topological space/of a smooth manifold that is compatible with its vector space structure. The composition maps are then continuous/smooth. In this way, we view $\mathbf{FinVec}$ as enriched over the category $\mathbf{Top}$/$\mathbf{Diff}$ respectively. It then makes sense to ask whether the functor $F$ is enriched over $\mathbf{Top}$/$\mathbf{Diff}$. That is just to ask whether the induced map $F\colon\operatorname{Hom}(V,W)\rightarrow\operatorname{Hom}(FV,FW)$ is continuous/smooth for all $V,W$. (Irrelevant to the rest of the question, but the reason this is a useful notion is that it is the natural hypothesis assuring that the functor induces another functor on the category of topological/smooth vector bundles, applying the original functor fiberwise.) In the case $V=W$, by functoriality, we can restrict $F$ to a group homomorphism $\operatorname{GL}(V)\rightarrow\operatorname{GL}(V)$. If the functor is continuous/smooth, so is this map. Note that $\operatorname{GL}(V)$ is a Lie group. It is a general result that a measurable group homomorphism between Lie groups is automatically smooth. This begs the following questions:  What's an argument for the existence of functors that aren't continuous? Can we construct one? Given the above, it either happens that the restrictions to $\operatorname{GL}(V)\rightarrow\operatorname{GL}(V)$ are continuous and continuity fails elsewhere, or the induced maps will be non-measurable, so that the construction will necessarily have to involve choice to some extent. Are there continuous functors that aren't smooth? Given the above, a continuous functor will have smooth restrictions to $\operatorname{GL}(V)\rightarrow\operatorname{GL}(V)$, but smoothness may fail elsewhere. Finding the missing digits of $23!$ Getting certain columns in bash From my (honestly limited) knowledge of what the Heat Death of the Universe is, I understand that HDotU is the point when energy levels across the entire Universe reach equillibrium, thus energy doesn't flow anymore absolutely anywhere, and thus nothing will ever happen anymore.  If that's the case, would time still be? Even when there's not a single event happening inside it and nobody's there to observe the ticking, does time (or space, come to think of it) exist? Or would HDotU cause something that ends the entire spacetime? Pygame - blitting from x and y cordinates of image Checking out  and  (and some papers) was a bit difficult for understanding Group Action. The closest to understanding was this part:    I understand the definition of homomorphism (a structure-preserving map between two algebraic structures of the same type). And from what I understand the symmetric group is a group of functions (bijective functions) mapping elements of a set $X$ onto itself.  However I get confused at this line:     ...an action of $G$ on $X$ may be formally defined as a group homomorphism $\phi$ from $G$ to the symmetric group of $X$.   That seems to be the definition of group action, but I am having trouble understanding how to apply that.  What that says to me is it is a homomorphism (function) $f \colon X \rightarrow S$ where $S$ is a set of bijective functions on $X$. That itself seems weird, I thought a group action would result in a number or something related to $\{1, 2, 3\}$ (defined next).  Continuing, if we have a set $X = \{1, 2, 3\}$ and a group $(*,\{4, 5, 6\})$, then the symmetric group of $X$ would be something like $S = \{1 \rightarrow 2, 2 \rightarrow 3, \dots \}$, and $\phi$ would be something like $f : \{4, 5, 6\} \rightarrow S$. That doesn't make sense to me and I feel like I'm interpreting something wrong. I don't see how mapping to a set of functions $S$ will result in an action on the set. Unable to delete recup_dir.1 folder A folder was created when I used a utility to recover pictures from a cd card that I deleted by mistake.  Now I can't delete it or move it. I am told I am not the owner of it even when I am logged on as root.  How can I delete the recup_dir.1 folder from my machine? The answer to tactical downvoting problem? As we know, the tactical downvoting (I'm talking especially about SO, as I don't know about other sites) is more and more becoming a serious problem, as I see, the community can't stop this behavior without some sacrificing.  As a suggestion, I think it makes sense to prevent an answerer from downvoting any answer on the same question, this -sure- has a harm, but IMO, it's less harmful than the tactical downvoting issue, and to make the things a bit more easier, we can prevent an answerer from downvoting a question without posting a comment to that answer before.  And vice versa, if a user downvoted an answer, he shouldn't be able to post another one unless he posted a comment first, to prevent working-around that system, so a user can't downvote other answers before posting his own to avoid posting comments.  EDIT, more clarification: I don't say wrong answers shouldn't be downvoted, BUT if you want to downvote an answer and post your own, you'll have to post a comment, so we make sure you're not just downvoting right answers tactically. Of Half-elven and mortal life How can I list the contents of a .zip folder in c#? I created a view to show Users. These users can create nodes of the "Questions" content type.  The view has to render a table to show how many (the total number) Questions the user has created. Something like:  User +++ Questions created John --- 10 Ted  --- 4 Alf  --- 19 Drop shadow for text in PGF/Beamer I want to really put an emphasis on some central piece of text I'm using in a Beamer slide.  I'm using tikz and overlay to put it, enlarged, on the center of the page, using the following code:  \begin{tikzpicture}[remember picture,overlay]   \node[at=(current page.center)] {     \scalebox{2}{\Huge\texttt{{This is important!}}}   }; \end{tikzpicture}   Can I add a drop shadow to the letter themselves, so they would look even more emphasized?  Is there some other decoration that can be added to the text itself, like a glow, etc.?  Or does PGF ignores node text altogether?  The text should be in typewriter style, so using special fancy fonts is probably not the solution. Maximum number of files in one ext3 directory while still getting acceptable performance? I have an application writing to an ext3 directory which over time has grown to roughly three million files. Needless to say, reading the file listing of this directory is unbearably slow.  I don't blame ext3. The proper solution would have been to let the application code write to sub-directories such as ./a/b/c/abc.ext rather than using only ./abc.ext.  I'm changing to such a sub-directory structure and my question is simply: roughly how many files should I expect to store in one ext3 directory while still getting acceptable performance? What's your experience?  Or in other words; assuming that I need to store three million files in the structure, how many levels deep should the ./a/b/c/abc.ext structure be?  Obviously this is a question that cannot be answered exactly, but I'm looking for a ball park estimate. I'm looking for the name of a sci-fi series, intended for children. Robots have control over the humans. There is a squad of humans who attack them. Every member in this squad has a badge on their suit, and when they touch this badge the suit becomes armed. This series was not cartoon series, it was performed by real people. The main robot character is very similar in style to Darth Vader in Star Wars. The series aired in the 1990s. I am sorry but I can't recall many details.