Making a mobile battery charger for smart phones i want to make a mobile charger and charge multiple mobiles at a time  therefore i select a 5V 2A adapter and a USB hub with 4 ports check the image  what i am going to do with this adapter and USB hub is, i will remove the USB HUB circuit so that electricity goes directly to USB port and just use the USB ports for chargers by making a series connection directly from adapters to USB ports so that each port supply 5V constant and 2A if incase only 1 mobile is connected   Now my question is what i am going to do is correct ?  Is there any other safe way to do this ?  what is the safest way to make a charger ?  Should i remove the USB HUB circuit or no need ?  Just with this 2 items i can charge multiple mobiles at a time and charge it with 2ampere ?
How do I design a 2A or more power supply for my consumer USB devices? I understand that many of my consumer devices charged by USB ports can charge at higher rates than 0.5A.  However, in testing, I've found they don't consume more than this. Test Setup  I have a power supply that outputs between 0 and 30 volts, and 0 to 20 amps. I set the voltage to 5 volts, then connected up a female USB to the wires correctly. When I plug in a Samsung Galaxy S4 Mini, it pulls around 0.44 amps. It is the same with a Samsung Galaxy Tab Pro. However, when I connect an iPad Air with an official lightning cable, it only pulls around 0.11 amps. Also, I tried connecting a ZGPAX S28 smartwatch and it was still about 0.44-0.45 amps.  The power supply is more than capable of outputting the maximum 2.1 amps, so why doesn't it to at least the tablets? What do I need to do in my test setup to convince the devices to consume their maximum charging current?
Ubuntu 18.10: visual artifacts (black bar) in dock if extend-height is disabled I am using the default Ubuntu dock with bottom placement and org.gnome.shell.extensions.dash-to-dock extend-height set to false. With Ubuntu 18.10 this produces a noticeable visual glitch, note the black empty spaces at the edges of the dock:    I am getting this both on an upgraded system and on a clean install inside a VM. This was working fine in Ubuntu 18.04. Also happens if the theme is set to something else than Yaru (the default theme in Ubuntu 18.10). Reboot does not help. Dock looks OK if extend-height is enabled.  Any ideas on how to fix this? How can the petrification from the Flesh to Stone spell be removed? Alternate Row Coloring in Django Template with More Than One Set of Rows Showing $\int_x^{x+1}f(t)\,dt \xrightarrow{x\to\infty}0$ for $f\in L^2 (\mathbb{R})$ Show that if $f\in L^2 (\mathbb{R})$ then    $$\lim_{x \rightarrow \infty} g(x)=0,$$   where    $$g(x)=\int_x^{x+1}f(t)\,dt$$   Since $f \in  L^2 (\mathbb{R})$ then $f \in L^2[x,x+1]$ for every $x$. Then  $$|g(x)| \leq \left(\int_x^{x+1} f(t)^2 dt\right)^{\frac{1}{2}} \int_x^{x+1} 1 dt$$ $$|g(x)|\leq \left(\int_x^{x+1} f(t)^2 dt\right)^{\frac{1}{2}}$$ Can the rogue repeatedly hide in combat to sneak attack the same enemy? One of my players is a rogue and has been, on his turn, using Cunning Action to hide as a bonus action and immediately afterwards attacking. I have been ruling that this does work to grant him advantage as an unseen attacker as I believe that is the RAW, but it seems a little strange. Is he really, in the span of 6 seconds, ducking behind a corner and popping back out and this completely disorientates his target? I guess I just wanted to make sure I was ruling correctly. What does ** (double star/asterisk) and * (star/asterisk) do for parameters? In the following method definitions, what does the * and ** do for param2?  def foo(param1, *param2): def bar(param1, **param2): Why are there no animals in "The Matrix"? Aside from the repetitive appearance of the black cat, I can't remember seeing any living animals, either inside the Matrix simulation or in Zion.  How come? Is there an in-universe explanation? Roots of $\,ax^2+bx+c\,$ are irrational if $a,b,c$ are odd integers How would I show the following.  For all odd integers a,b, and c if z is a solution of $ax^2+bx+c=0$ the z is not rational.  How would I show this? This is what I did  Let a be an odd integer then for a integer k it has the form $a=2k+1$  then $b=2t+1$ for if c integer.  then $c=2r+1$ if s is an integer then I do  $(2k+1)(x)^2+2t+1(x)+(2r+1)=0$  But I find my self stuck on what to do any hint are appreciated. If $A$ is an $m \times n$ and $B$ is an $n \times m$ matrix with $n &lt; m$ then prove that $C = AB$ is not invertible.  I am not getting any idea. May be I am missing vary basic point. $C = AB$ where both $A$ and $B$ are square matrices  will be invertible iff both $A$ and $B$ be invertible. I know it and its proof.  May be this question has been discussed earlier, but I am not seeing the link. Thank you for your help. Why does second pre-image resistance imply pre-image resistance I am studying hash functions. I can understand why collision resistance implies second preimage resistance, but I don't get why second preimage resistance should imply first preimage resistance. Could anybody be help me with this argument from Introduction to Modern Cryptography by Katz &amp; Lindell, please?   Collision resistance: This is the strongest notion and the one we have considered so far.  Second pre-image resistance: Informally speaking, a hash function is second pre-image resistant if given $s$ and $x$ it is infeasible for a probabilistic polynomial-time adversary to find $x' \ne x$ such that $H^s(x') = H^s(s)$.  Pre-image resistance: Informally, a hash function is pre-image resistant if given $s$ and $y = H^s(x)$ (but not $x$ itself) for a randomly chosen $x$, it is infeasible for a probabilistic polynomial-time adversary to find a value $x'$ such that $H^s(x') = y$. (Looking ahead to later chapters in the book, this essentially means that $H^s$ is one-way.)   [...] Likewise, any hash function that is second pre-image resistant is also pre-image resistant. This is due to the fact that if it is possible to invert $y$ and find an $x^\prime$ such that $H^s (x^\prime ) = y$ then it is possible to take $x$, compute $y = H^s (x)$ and invert it again obtaining $x^\prime$. Since the domain of $H$ is infinite, it follows that with good probability $x \neq x^\prime$. We conclude that the above three security requirements form a hierarchy with each definition implying the one below it. How are the age restrictions followed by ICC for under 19 cricket tournaments? I have some doubts under this topic,   Can a player aged 19 play under 19 international cricket match? (Since 19 is not under 19) Consider a player having birthday during the series/tournament. How the age will be calculated for him? Alternative IDE for VB6 and VBA I've been spoiled by Visual studio 2008 and Eclipse and have to do a little maintainence work on a VB6 app.  Does anyone know of an alternative/ updated IDE for VB6?  A rewrite is not an option I'm just fixing a couple of bugs and it's a big codebase. Urgent Sydney transit visa question How to instantiate polymer component programmatically in dartlang? Does the existence (now proved) of gravitational waves imply the existence of Gravitons? I studied the theoretical part about the Gravitational waves in General Relativity (linearization of gravity and small perturbations of the metric and so on).  But I was wondering about: since electromagnetic radiation is composed/carried by Photons (or better:the EM force), shall gravitational waves be composed/carried by Gravitons?   In the end:do gravitational waves imply the existence of gravitons? Or it's something unrelated and off topic? What exactly do quotation marks around the table name do? I thought that the quotation mark (") was simply a type of grouping marker but I'm debugging some NHibernate code and notice that while  SELECT * FROM site WHERE site_id = 3;   Works fine  SELECT * FROM "site" WHERE site_id = 3;   fails with a table or view does not exist error.  What gives? Column count doesn't match value count at row 1 so there are some idiosyncrasies with the method they use to invert that part of the image which I can't figure out. It could be that they just invert the luminosity but I don't know how i would do that in a dynamic way. What is inverse CDF Normal Distribution Formula Source Code Margin Comments In the paper "Beautiful Code Compelling Evidence", by J.R. Heard -- Code is formated in a particular way which includes margin comments. I am looking for a way to do this as I think it is a very clear way to comment comment code in a literate programming style.