Black screen in new install Ubuntu 18.04
My computer boots to a black screen, what options do I have to fix it?
Statistical significance (p-value) for comparing two classifiers with respect to (mean) ROC AUC, sensitivity and specificity I have a test set of 100 cases and two classifiers.  I generated predictions and computed ROC AUC, sensitivity and specificity for both classifiers.  Question 1: How can I compute p-value to check if one is significantly better than the other with respect to all scores (ROC AUC, sensitivity, specificity)?    Now, for the same test set of 100 cases, I have different and independent feature assignments for each case. This is because my features are fixed but subjective and provided by multiple (5) subjects.  So, I evaluated my two classifiers again for 5 "versions" of my test set and obtained 5 ROC AUCs, 5 sensitivities and 5 specificities for both classifiers. Then, I computed the mean of each performance measure for 5 subjects (mean ROC AUC, mean sensitivity and mean specificity) for both classifiers.  Question 2: How can I compute p-value to check if one is significantly better than the other with respect to mean scores (mean ROC AUC, mean sensitivity, mean specificity)?    Answers with some example python (preferably) or MatLab code are more than welcome. How does one type Chinese in LaTeX? Apache: Scammers point dozens of domain names at my dedicated IP. How to prevent this? For the sake of discussion, pretend that I have an Apache webserver which serves a website at www.example.org. This domain name resolves to the public IP address at 192.168.1.100 (pretend this is a public IP).  The discussion at  demonstrates that anyone can point their domain at my IP. Apache won't prevent this by default, but an administrator can deal with these one at a time through use of a blacklist.  However, it's becoming more common for scammers to register dozens of domains (or more) for use in a scam. I'm concerned about the following possible attack:   A scammer registers hundreds of domain names, and points them at my dedicated IP address. The scammer directs search engines at their scam domains, thus using my content to increase their standing in the search engines. Later, the scammer moves their domain names to point to their own servers which host a scam/porn, or a competing business, etc. thereby reaping the benefits of their standing in the search engines. Some of these domains might be used to in  as well. Profit!!   I believe I have seen scammers using this trick in the past, involving dozens of domains. We didn't realize the scam implications at the time, and assumed these were misconfigured domains.  Is there a term for this nefarious SEO trick? SEO masquerading? DNS Diversion?  How could I prevent this using Apache? I'm considering a "whitelist" fix based on using a default VirtualHosts, ServerNames &amp; ServerAliases so that Apache only responds to requests where these white-listed ServerNames appear in the "Host: " header. Everything else would be rejected (or redirected to a particular page). However, I am unsure if this is the best approach.  For example, I've configured the domain  to point at the IP for Serverfault.com. You can see the results here:  . How to prevent ENTER keypress to submit a web form? I am using Ubuntu 11.10 (64 bits) and I do not want to mount automatically USB thumb drives in my system. I tried the command dconf-editor and gconf-editor but there isn't the icon to disable it in nautilus preferences (apps|nautilus|preferences|media_automount).  Thanks. /oracle/GR1/121/bin/sqlplus / as sysdba &lt;&lt;EOF &gt;&gt; $LOGFILE whenever sqlerror exit sql.sqlcode; set echo on; set serveroutput on; STARTUP; EXIT EOF   Already tried it with the path, but it hasn't worked. I am looking for a quick way to sleep without closing the lid, or using the mouse.  If it matters, I have Lion version OS and a MacBook Air. Making adult decisions "is" or "are" really not fun: Which is correct? Making adult decisions are/is really not fun.     What is the proper answer and why? My gut says "is" but I can't explain why. I got this $$ f=a(x-1)(x-2)...(x-101) $$ knowing a and that $1 ,2 \ldots ,101$ are it's roots ... I need the roots of $f'$ , how should I do it ? More specifc how can I derivate a polynomial like that, is there a formula or something ? Cleaning Contaminated Disc Rotors I've had an eternal struggle with my current bike over brake contamination. The levers and calipers are shimano ultegra r8000, so the latest and (almost) greatest.  I first noticed it when I took it to a repair shop (i no longer use) for a bleed, it came back and the front brake would squeal like crazy and at low speeds had little to no braking force. You can stop from speed but then struggle to come to a halt without using your foot.  At around 2000 miles I tried to replace the brake pads, when I took them out they were black with grime on both sets (front &amp; back), not to mention worn down to the metal. I replaced them with the L04C sintered pads, gave the callipers a good cleaning with a towel (no chemicals) and fitted the new set.  Annoyingly all of my braking issues are back, now I probably should have cleaned the rotors, I simply used some muc off disc brake cleaner on them. I would like to know the best way to clean the rotors, I've inspected the pads and they are looking fairly black now, with plenty of tread left. I'm going to abandon these pads and fit a new set. For the rotors I plan to completely remove them from the wheels (they are center lock fitted) and try and treat them off the bike, what is the best way to fully clean them? They have plenty of wear left in them but you can see these black grooves in them, and plenty of muck on the back that I struggle to get off.  Below are images of the rotors after soaking them in disc brake cleaners, waiting and then wiping them down with a clean, microfiber towel.   Front Wheel Outside Rotor   Front Wheel Inside Rotor - note the increased dirt on this side  Looking at ways people clean their disc rotors, I've seen plenty of suggestions that I would need to burn the contaminants off the discs. Would the best approach be to remove them and use a blowtorch, should I soak them in some nasty chemicals overnight before I try to heat them? Do I try baking them in the oven?  And finally, what is the best way to prevent the brakes from becoming contaminated in the future? it's really off putting when they squeal and don't perform how I'd expect because it means I'm more reserved whilst out riding on the bike, leading to reduced time riding around outside. I commute on this bike (50 miles a week) and then ride about 50 on the weekends also, so it see's it's fair share of road use. I tend to wash it once after my big ride on saturdays and will rinse it off if it's been raining, any day that occurs (since I live in north east england, the acid rain..). I've owned disc brake bikes before and never had half the issues I've had with this, I had a cheap trek with tektro brakes and the brakes were sharper and never had any issues with contamination whatsoever (i did around 500 miles on that bike before a motorist happened).  Thanks for any and all advice :) Am I correct to say the difference between a signed and unsigned integer is:  Unsigned can hold a larger positive value and no negative value. Unsigned uses the leading bit as a part of the value, while the signed version uses the left-most-bit to identify if the number is positive or negative. Signed integers can hold both positive and negative numbers.  Any other differences? I know this, but I can't recollect at all.   What is this thing called?   They are usually centered in a book or writing and I'm certain they have a name but I can't remember for the life of me. They also come in all shapes, colors and sizes. If the velocity is a relative quantity, will it make inconsistent equations when applying it to the conservation of energy equations?  For example:  In the train moving at $V$ relative to ground, there is an object moving at $v$ relative to the frame in the same direction the frame moves. Observer on the ground calculates the object kinetic energy as $\frac{1}{2}m(v+V)^2$. However, another observer on the frame calculates the energy as $\frac{1}{2}mv^2$. When each of these equations is plugged into the conservation of energy, they will result in 2 distinct results (I think). When app is moved to SD card, where is the app data stored on SD card? What is the difference between weight and mass? This fire image:    As you can see, it has a black background, which I can't delete (because it would probably destroy the smooth-looking fire effect). I want to place some fire in a photo.  However, I remember it was possible to take such images and do something in photoshop so that when you place them over a photo, the black is gone and the fire is perfectly blended there. But I can't remember what feature or option was it. Any ideas?  Photoshop CS5. How do I change my Minecraft username during the 30-day restriction? How can you smooth the edge between two materials? I have created this with cycles:  But the edge between the glowing and non glowing materials is very sharp. The material was manually applied to faces in edit mode. Is there any way I can smooth the edge between them in cycles? What will be the one's digit of the remainder in: $\left|5555^{2222} + 2222^{5555}\right|\div 7=?$ Remove numbering from Section and Subsection