releted to  I wonder what the use of the number of mA printed on an AC-DC adapter/converter means.  I am charging a Bluetooth headset, which came with a AC-DC adapter, over USB using a "DIY-hybrid-cable" and it is working. The original AC-DC plug (which I've cut) has 450mA printed on it and the USB standard AC-DC plug, to which my "hybrid-cable" is connected, has 1.0A printed on it.     Does the mA number has any relevance? Why? I feel I am missing important knowledge.
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.
Exercise 12 from SEC. 82 of Finite-Dimensional Vector Spaces - 2nd Edition by Paul R. Halmos.  If $A$ and $B$ are linear transformations on a finite-dimensional inner product space, and if $\textbf{0} \le A \leq B$, then $\det A \leq \det B$.  Notation: $0 \le A$ means that $A$ is positive.  If $\det B = 0$, choose $x \in \ker B$, then $0 \le ((B-A)x,x) = (Bx, x) - (Ax, x) = -(Ax, x) \le 0$. Therefore $\ker B \subseteq \ker A$ and $0 = det A \le det B = 0$. How to prove for the case when $B$ is invertible? Intuitively, I feel that since both $A$ and $B$ are positive their proper values are also positive and $B$'s proper values should be greater the $A$'s and same for determinants. List of all active modules used in a site Broken "Network profile" link when Area51 is their only account Why don't we pluralize "foot" in measurements? For example, to answer the question, "How tall are you?" valid answers include:   Five feet. Five foot three. Five feet, three inches.   Why the discrepancy between feet and foot, seemingly only in the second case.    This question is inspired by this question:   edit: I do not believe the answer to this is related to the other question. The explanation for the other question is because of how adjective modifiers work. My question is a very different case, unrelated to adjectives. My observation is that I am asking about a particular exception case which applies only when "foot" is followed by a number which is assumed to be inches. That's extremely specific, and I doubt that the etymology has any relation to why we leave adjective modifiers singular. I am having trouble understanding what defines Entailment operator. On Mathoverflow I posted this question on what I perceive to be .  Consider: :     P therefore Q  P            Therefore, Q   My question is could we have arbitrarily defined it such as:     P therefore Q  P            Therefore, P   However, if an advanced civilization receives information in the form of following nested structures/containers or packets, how will they interpret Modus Ponens if in an alien land Modus Ponens is not defined?    Therefore, it raises the validity of MP. How do we define the implication or entailment operator? Because if we use an argument that relies on implication or entailment operator ipso facto, then it is trivial that logic is circular.  Is there a flaw in my rationale? What books would you recommend to start learning about software testing I'm trying to learn more about software testing, so I want to know which books you would recommend on this topic My application listens on port 8180.  When I am trying to connect to port 8180 locally. Connection got refused. But when I am trying to connect to port with ip . I am able to connect.  [root@MUMLGOMAPP002 ~]# telnet 10.209.129.54 8180 Trying 10.209.129.54... Connected to MUMLGOMAPP002 (10.209.129.54). Escape character is '^]'. ^] telnet&gt; q Connection closed.   [root@MUMLGOMAPP002 ~]# telnet localhost 8180 Trying 127.0.0.1... telnet: connect to address 127.0.0.1: Connection refused telnet: Unable to connect to remote host: Connection refused   My interface is :  [root@MUMLGOMAPP002 ~]# ifconfig bond0     Link encap:Ethernet  HWaddr 44:1E:A1:73:F7:50           inet addr:10.209.129.54  Bcast:10.209.129.63  Mask:255.255.255.224           UP BROADCAST RUNNING MASTER MULTICAST  MTU:1500  Metric:1           RX packets:322997568 errors:23 dropped:0 overruns:0 frame:0           TX packets:304470664 errors:0 dropped:0 overruns:0 carrier:0           collisions:0 txqueuelen:0           RX bytes:213628580915 (198.9 GiB)  TX bytes:217449664400 (202.5 GiB)   I would like to know what is the difference between telnetting localhost and ip. When do the differences between APS-C and full frame sensors matter, and why? Built-in text editor in Terminal Is there a built-in text editor in the terminal on Lion?  (Like, for example, nano on Linux.) Linear algebra Upper Triangular matrix Check whether $\sum _{m=1}^{\infty }\sum _{n=1}^{\infty }\frac{1}{\left(m+n\right)^2}$ converges or NOT? Shapefile Naming conventions in ArcPy? I have shapefile named `band-tailed_pigeon.shp which is fine and no problem on displaying or geoprocessing on Desktop but in ArcPy when I try to merge some layes to it I am getting this error   ExecuteError: ERROR 000354: The name contains invalid characters Failed to execute (Merge).  I tried to do the proccess with a simple name like sample.shp which it works but I HAVE TO keep the same name as we are using them in several projects. Here is the code which I have FinaloutLocation = &quot;E:\\GIS\\Data\\Final\\band-tailed_pigeon.shp&quot; inFeaturesToMerge = [dissolve_1, dissolve_2, dissolve_3, dissolve_4, dissolve_5] arcpy.Merge_management(inFeaturesToMerge, FinaloutLocation) Let $x$ and $y$ be positive integers such that $xy \mid  x^2+y^2+1$. Show that $$ \frac{x^2+y^2+1}{xy}= 3 \;.$$ I have been solving this for a week and I do not know how to prove the statement. I saw this in a book and I am greatly challenged. Can anyone give me a hint on how to attack the problem? thanks I observe the following strange characters ^@ in syslog at the time when my machine freezes.  Then i have to hardboot my machine.  What could be wrong any ideas?  Oct 12 12:20:52 nanak-P570WM anacron[1074]: Normal exit (1 job run) ^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@  Oct 12 12:24:28 nanak-P570WM kernel: imklog 5.8.11, log source = /proc/kmsg started. Oct 12 12:24:28 nanak-P570WM rsyslogd: [origin software="rsyslogd" swVersion="5.8.11" x-pid="543" x-info="http://www.rsyslog.com"] start How can I modify the size of swap with LVM partitions? How to "unpivot" or "reverse pivot" in Excel? How will the super massive black hole affect our galaxy? Let $a,b,n$ be integers such that  $\gcd(a,n)=\gcd(b,n)=1$. How to show that $\gcd(ab,n)=1$?   In other words, how to show that if two integers $a$ and $b$ each have no non-trivial common divisor with and integer $n$, then their product does no have a non-trivial common divisor with $n$ either.     This is a problem that is an exercise in my course.   Intuitively it seems plausible and it is easy to check in specific cases but how to  give an actual proof is not obvious. What is the difference between convolutional neural networks and deep learning? There are $25$ horses. You can take $5$ horses at a time and race them. Each horse always finishes the race in the same amount of time, and there are no ties. The only information you get from each race is the order that the $5$ horses finished in. What is the smallest number of races you need to find the $3$ fastest horses, in order?   I found this problem on  and cannot figure out the best answer. Please help.