Why can't I center my wrapper div using flexbox?
How to horizontally center an element
Why is there this strange contradiction between the language of logic and that of set theory? In standard probability theory events are represented by sets consisting of elementary events. Consider two events for which (as sets) $A \subset B$. If an elementary event $x \in A$ takes places then we say that $B$ takes place as well. Since $A \subset B$, $x \in A$ implies that $B$ takes place too.  It seems that when for sets (representing events) $$A \subset B$$ $$then \ A \ implies \ B .$$  On the other hand, if we use the language of logic for the events then $$A \supset B$$ $$ \ means\  that \ A\  implies\ B .$$  Why is this strange virtual contradiction between the language of sets and the language of logic?  (In order to avoid down votes and unplesant comments I reveal that I happen to know that the true translation of the sentence $A \supset B$ of logic to the language of sets (representing events) is $\overline{A \cap \overline B}$.) I have installed Ubuntu 14.04 LTS 64-Bit and have a Edimax EW-7811Un wifi adapter. I have tired to get it to work but have no luck.   when I run lsusb command I get:  Bus 001 Device 005: ID 7392:7811 Edimax Technology Co., Ltd EW-7811Un 802.11n Wireless Adapter [Realtek RTL8188CUS]   iwconfig shows that nothing is being read or connected:  eth0      no wireless extensions. lo        no wireless extensions.   I have tired numerous forums and tutorials but cant get it to work, dont know what I am doing wrong.   Can someone give a clear step by step method to get this to work?  uname -r: (Kernel Version)  3.16.0-34-generic How to Make Multi User Objects Single User? Conveying "under the radar" in a less colloquial way I am searching for a word to contrast with iconic  I want to characterize views of the city as both iconic and under the radar, maybe "non-iconic."  I was thinking about saying that a view of the city was undiscovered, but I think that maybe that overstates what I'm think-- I more mean under-appreciated. Are there any other words that come to mind? What is the difference between a game framework and a game engine? What is the difference between a game framework (for example, XNA with C#, SDL for c++) and a game engine?  Do game frameworks use engines? Does a game engine encapsulate sub-engines like physics engines, particle engines etc? Should they be used together, or are they mutually exclusively?  I take it there are separate engines for both 2D and 3D? Process descendants Basic photo editing on OS X How come Dropbox gets an icon in Finder sidebar? How can I diagnose and repair missing drive space? I have a small ext3 / partition on a 2T drive which appears to have a discrepancy in its free space. How can I determine what is causing it and how it can be fixed.   After trying everything I could think of, I forced a fsck on boot which didn't have any affect.  I have other systems configured identically which don't exhibit this condition.  # df -h / Filesystem            Size  Used Avail Use% Mounted on /dev/sda1             9.7G  8.9G  318M  97% /  # du -shx --max-depth 1 / 5.2G    /  # lsof | awk 'BEGIN {t=0} /(deleted)/ {t+=$7} END {print t}' 0  # tune4fs -l /dev/sda1 | grep -E 'state|Free|Reserve|size|Inode' Filesystem features:      has_journal ext_attr resize_inode dir_index filetype needs_recovery sparse_super large_file Filesystem state:         clean Inode count:              2621440 Reserved block count:     131029 Free blocks:              212317 Free inodes:              2487281 Block size:               4096 Fragment size:            4096 Reserved GDT blocks:      639 Inodes per group:         32768 Inode blocks per group:   1024 Reserved blocks uid:      0 (user root) Reserved blocks gid:      0 (group root) Inode size:               128   Edit:  fsck says the partition is 2% non-contiguous.  For comparison to du above (sparseness):  # du -hxs --apparent-size / 4.9G    / Just switched from 10.04 to 11.10. I'm wondering about the limited options in the GUI for managing users and groups. Where is the old GUI to change groups, id's, etc. I know that I can do this from cli, that's no problem. But I want this comfortable GUI back. Which is correct: "has died" or "died"? I can't figure out how to turn on the Bluetooth on my Nikon D5600. I have updated the firmware to the latest 1.01 and still the same problem.   Bluetooth is dimmed out on the camera and will not turn on. I get an error message saying, "This option is not available at current settings or in the camera's current state".  I have tried everything I can think of and no go. I can't find help for this problem anywhere on the internet and still no reply from Nikon.  How do I turn on my camera's Bluetooth? How to remove local (untracked) files from the current Git working tree Installing Reaver 1.4 I am trying to install reaver 1.4, but when I run ./configure ; make I get this message at the end  int ret_val = EXIT_FAILURE, r = 0;   I have searched a fair bit and cannot find an answer, any help would be appreciated. I apologize if this has been answered and I've just failed to find it. A method for evaluating sums/discrete functions by assuming they can be made continuous and differentiable? Matrix representation of linear transformation Linux genisoimage Batch I was just wondering why Fresnel Lenses are not widely used in the production of solar electricity. Their use there would mean that you could produce heat within a fraction of a second, up to a few minutes and run a turbine to produce electricity.  Though it is used in welding, I am not sure what are the problems in producing electricity, as stated by :     New applications have appeared in solar energy, where Fresnel lenses can concentrate sunlight (with a ratio of almost 500:1) onto solar cells. Dealing with questions of nefarious intent I am very confused about how to compute  $$\sum_{n=0}^{\infty}nk^n.$$  Can anybody help me?