Problems with a non-inverting op amp configuration when input voltage is too low I currently have a very simple op amp circuit for a non-inverting amplifier, using a UA741 with the gain set as 2.  I have a sensor that outputs 0-2.3V and I'm attempting to amplify it up to 0-4.6V.  The set up for the op amp is below.    The problem is that when I test this circuit under about 2.5V the amplified output voltage just sits at a steady 4V.  Is this a problem with the chip, or is there something I need to do in the circuitry?  I was going to try an LMV324 as well, but I would have to power it with a lower voltage which made testing the circuit more difficult.  Any insight is appreciated.
Reasons not to use a 741 op-amp? Simple enough question. Why not use a  in a target circuit or anyone's target circuit? What are the reasons not to use it? What might be the reasons to still choose this part?
Uniform convergence with two sequences of functions For, $n\ge 1$ let, $g_n(x)=\sin^2(x+1/n)$ , $x\in [0,\infty)$ and $f_n(x)=\int_0^xg_n(t)\,dt.$  Then, which is(/are) correct ?  (A) $\{f_n(x)\} $ converges pointwise to a function $f$ on $[0,\infty)$ but does not converge uniformly on $[0,\infty)$.  (B) $\{f_n(x)\} $ does not converge pointwise to any function on $[0,\infty)$.  (C) $\{f_n(x)\} $ converges uniformly on $[0,1]$.  (D)  $\{f_n(x)\} $ converges uniformly on $[0,\infty)$.  I found that, $$f_n(x)=\frac{1}{2}\left[x-\frac{1}{2}\sin(x+1/n)+\frac{1}{2}\sin(1/n)\right].$$  So, $f(x)=\lim_{n}f_n(x)=\frac{x}{2}-\frac{1}{4}\sin x$.  Now, $|f_n(x)-f(x)|\le 3/4$. So, by M-test, $f_n(x)$ is not uniformly convergent, but point-wise convergent. So option (A) is correct..Am I right?? How can I get Gnome3 to remember my session? Creating an index of quality from multiple variables to enable rank ordering I have four numeric variables. All of them are measures of soil quality. Higher the variable, higher the quality. The range for all of them is different:  Var1 from 1 to 10  Var2 from 1000 to 2000  Var3 from 150 to 300  Var4 from 0 to 5  I need to combine four variables into single soil quality score which will successfully rank order.  My idea is very simple. Standardize all four variables, sum them up and whatever you get is the score which should rank-order. Do you see any problem with applying this approach. Is there any other (better) approach that you would recommend?  Thanks  Edit:  Thanks guys. A lot of discussion went into "domain expertise"... Agriculture stuff... Whereas I expected more stats-talk. In terms of technique that I will be using... It will probably be simple z-score summation + logistic regression as an experiment. Because vast majority of samples has poor quality 90% I'm going to combine 3 quality categories into one and basically have binary problem (somequality vs no-quality). I kill two birds with one stone. I increase my sample in terms of event rate and I make a use of experts by getting them to clasify my samples. Expert classified samples will then be used to fit log-reg model to maximize level of concordance / discordance with the experts.... How does that sound to you? Does "+" use in String concatenation affect efficiency? How quickly does the Ultimate Meter fill up? Solving the diophantine equation $y^{2}=x^{3}-2$ It is known that the diophantine equation $y^{2}=x^{3}-2$ has only one positive integer solution $(x,y)=(3,5)$. The proof of it can be read from the book "About Indeterminate Equation" (in Chinese, by Ke Zhao and Sun Qi). But the method I have known of solving this problem is algebraic number theory.  My question:      Does there exists an elementary method for solving the diophantine equation $y^{2}=x^{3}-2$?   I have gotten an elementary method by the assumption that "$x$" is a prime. That is, we can get a conclusion from the equation that $3\mid x$. Since $x$ is a prime we get the only solution $(x,y)=(3,5)$. But if $x$ is not a prime, the answer seems to be difficult.  Thank you for your help. newenvironment: error with \begin{align} and \end{align} In the example below, an error is caused by \begin{align} and \end{align} but I do not see why:  \documentclass{book} \usepackage{amsmath} \newenvironment{subalign}{\begin{subequations}\begin{align}}{\end{align}\end{subequations}} \begin{document} \begin{subalign}      a&amp;=b\\     &amp;=b \end{subalign} \end{document} Why didn't Harry Potter tell Aunt Petunia he was rich to improve how he was treated by Dursleys? This is a follow-up question to   One reason Aunt Petunia mistreated Harry was that she did not know he was rich. If she knew, she would naturally have treated this golden goose nicely. Her retirement would be secured if Harry financially supported her in old age.  Why didn't Harry tell Aunt Petunia he was rich? Surely every boy wants to be treated nicely by his family. When I use the , do I choose the monster to distract (and then the next ally to attack gets advantage) or do I choose the ally and the monster (so that only his attack against that target gets advantage)? Or something else?  Help [...] Alternatively, you can aid a friendly creature in attacking a creature within 5 feet of you. You feint, distract the target, or in some other way team up to make your ally’s attack more effective. If your ally attacks the target before your next turn, the first attack roll is made with advantage. Command to move a file to Trash via Terminal I haven't been able to find my favorite questions in the official Stack Exchange Android app.  Looking at my accounts page gives nothing on them. A stranger told me that he will give me an allowance of $ weekly. I know the saying "If it sounds too good to be true, then it is".   He told me that he would  email me his check and I would be able to deposit it via mobile banking. The only information he needs is my email, name on bank account, and bank name.   Is this too much information? Do you think this is a scam? I would definitely know if it was a scam if he asked for my log in but that is not what he wants.  Thank you for your time and answers! Could not open file archive.ubuntu.com_ubuntu_dists_eoan-updates_restricted_cnf_Commands-amd64.xz Greetings from Bangladesh. I am an intermediate user of Ubuntu OS. I am facing problem with apt update. I have searched online but could not find any answer to my problem so I am posting this question please help me.  Err:20 http://archive.ubuntu.com/ubuntu eoan-updates/restricted amd64 c-n-f Metadata   Could not open file /var/lib/apt/lists/partial/archive.ubuntu.com_ubuntu_dists_eoan-updates_restricted_cnf_Commands-amd64.xz - open (13: Permission denied) [IP: 91.189.88.152 80] Ign:35 http://archive.ubuntu.com/ubuntu eoan-updates/multiverse amd64 c-n-f Metadata Err:37 http://archive.ubuntu.com/ubuntu eoan-backports/main amd64 c-n-f Metadata   Could not open file /var/lib/apt/lists/partial/archive.ubuntu.com_ubuntu_dists_eoan-backports_main_cnf_Commands-amd64.xz - open (13: Permission denied) [IP: 91.189.88.152 80]   Reading package lists... Done E: Failed to fetch http://archive.ubuntu.com/ubuntu/dists/eoan-updates/restricted/cnf/Commands-amd64  Could not open file /var/lib/apt/lists/partial/archive.ubuntu.com_ubuntu_dists_eoan-updates_restricted_cnf_Commands-amd64.xz - open (13: Permission denied) [IP: 91.189.88.152 80] E: Failed to fetch http://archive.ubuntu.com/ubuntu/dists/eoan-backports/main/cnf/Commands-amd64  Could not open file /var/lib/apt/lists/partial/archive.ubuntu.com_ubuntu_dists_eoan-backports_main_cnf_Commands-amd64.xz - open (13: Permission denied) [IP: 91.189.88.152 80] E: Some index files failed to download. They have been ignored, or old ones used instead.   I have tried with         removing partial folder's content completely.   Cleaning apt by sudo apt clean   moving the lists to lists.old   then updating the apt      But without luck. How to find a program which is preventing sleeping? I am noticing that recently my laptop does not go to sleep/lockout after its configured X minutes of inactivity like it did in the past. I suspect some program (like media player does) is preventing it from going to sleep. I do not have any media player running, so how can I find which program is preventing it from sleeping?  It does go to sleep if I close the lid. But I would also like for it to go to sleep after X minutes of inactivity.  Update: Upgraded to Ubuntu 18.04 with default Gnome and Wayland enabled. How to make a series of rectangles follow a pen path I am trying to get a series of shapes (rectangles) to follow a path (sine wave) that I made with the pen tool, but I have no clue how to do that or if it is possible.   I have tried warping a rectangle into the sine wave path, but it takes many different warped rectangles and it isn't smooth.  I thought  might work for rectangles, but it only works for text. Dashed line and Wireframe Akhil showed that the  is the same as the continuum, using as a step the observation that continuous functions that agree at rational points must agree everywhere, since the rationals are dense in the reals.  This isn't an obvious step, so why is it true? For days I tried several ways to install Windows 10 . With Windows Update I have always an error and with the media creation tool microsoft I have this message: " The installation failed in SAFE_OS phase with an error when BOOT operator " with this code : 0xC1900101 - 0x20017 Having tried everything I do not know what to do ... Can you help me please ? Thank you  PS: I migrated my OS with the software "Paragon migrate OS to SSD" from my hard disk to my SSD. Maybe I have this errors because I did this.... UnboundLocalError: local variable 'url_request' referenced before assignment If $a, b$ are positive real numbers and $a+b = 1$, prove that :  $$\left(a+\frac{1}{a}\right)^2 + \left(b+\frac{1}{b}\right)^2 \geq \frac{25}{2}$$  I can see that the value $\frac{25}2$ is attained for $a=b=\frac12$. But I do not know how to show that this is the minimal possible value.  Thank you.