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A New Era of Spaceflight is Set to Begin | NASA

On May 27, NASA will launch their first flight with astronauts to the  International Space Station  from U.S. soil in nearly 10 years. This mission is the first launch of American astronauts aboard an American rocket and spacecraft as part of their  Commercial Crew Program . NASA astronauts  Bob Behnken  and  Doug Hurley  will fly on SpaceX ’s Crew Dragon spacecraft, lifting off on a Falcon 9 rocket from Kennedy Space Center in Florida, for an extended stay at the space station for the Demo-2 mission. The specific duration of the mission is to be determined. As the final flight test for SpaceX, this mission will validate the company’s crew transportation system, including the launch pad, rocket, spacecraft, and operational capabilities. This also will be the first time NASA astronauts will test the spacecraft systems in orbit. Behnken and Hurley were among the first astronauts to begin working and training on SpaceX’s next-generation human space vehicle and were
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Mathematics for Computer Scientists | Integers

Numbers Defendit numerus: There is safety in numbers We begin by talking about numbers. This may seen rather elementary but is does set the scene and introduce a lot of notation. In addition much of what follows is important in computing. Integers I will assume you are familiar with the integers. 1,2,3,4,. . .,101,102, . . . , n, . . . , 2^32582657 − 1, . . . sometime called the whole numbers. These are just the numbers we use for count- ing. To these integers we add the zero, 0, defined as: 0 + any integer n = 0 + n = n + 0 = n Once we have the integers and zero mathematicians create negative integers by defining (−n) as: the number which when added to n gives zero, so n + (−n) = (−n) + n = 0. Eventually we get fed up with writing n+(−n) = 0 and write this as n−n = 0. We have now got the positive and negative integers {. . . , −3, −2, −1, 0, 1, 2, 3, 4, . . .} You are probably used to arithmetic with integers which follows simple rules. To


Create a new file called with the following content and give it executable permissions with chmod +x  Execute/Run via: ./ #!/usr/bin/env bash # Note that spaces cannot be used around the `=` assignment operator whom_variable="World" # Use printf to safely output the data printf "Hello, %s\n" "$whom_variable" #> Hello, World This will print Hello, World to standard output when executed. To tell bash where the script is you need to be very specific, by pointing it to the containing directory, normally with ./ if it is your working directory, where . is an alias to the current directory. If you do not specify the directory, bash tries to locate the script in one of the directories contained in the $PATH environment variable. The following code accepts an argument $1 , which is the first command line argument, and outputs it in a formatted string, following Hello, . Execute/Run via: ./ World #!/usr/bi


GNU Bash or simply Bash is a Unix shell and command language written by Brian Fox for the GNU Project as a free software replacement for the Bourne shell. First released in 1989, it has been used widely as the default login shell for most Linux distributions and Apple's macOS Mojave and earlier versions Interactive Shell The Bash shell is commonly used interactively:  It lets you enter and edit commands, then executes them when you press the Return key. Many Unix-based and Unix-like operating systems use Bash as their default shell (notably Linux and macOS). The terminal automatically enters an interactive Bash shell process on startup. Output Hello World by typing the following: echo "Hello World" #> Hello World # Output Example Non-Interactive Shell The Bash shell can also be run non-interactively from a script, making the shell require no human interaction. Interactive behavior and scripted behavior should be identical – an important design consid


File Compression with 'tar' command: Common Options -c --create                     Create a new archive. -x --extract                   Extract files from an archive. -t --list                           List the contents of an archive. -f --file=ARCHIVE     Use archive file or dir ARCHIVE. -v --verbose                  Verbosely list files processed. Compression Options - -a --auto-compress          Use archive suffix to determine the compression program. -j --bzip2                         Filter the archive through bzip2. -J --xz --lzma                 Filter the archive through xz. -z --gzip                         Filter the archive through gzip. Compress a folder This creates a simple archive of a folder : tar -cf ./my-archive.tar ./my-folder/ Verbose output shows which files and directories are added to the archive, use the -v option: tar -cvf ./my-archive.tar ./my-folder/ For archiving a folder compr


Database servers are used mainly to store databases and keep data into it in collaboration with application or web application servers. The most famous database servers are: MySQL and Oracle DB 12c Let us go ahead and install each one of these and we will start with: INSTALLING AND CONFIGURING MYSQL SERVER To install MySQL server, you will need to run the following command: sudo apt-get install mysql-server Some other people install maria db package and this will be done using the following command: sudo apt-get install maria-db Then for security reasons, you may run the following command to get your server up and running securely: mysql_secure_install The last thing, we need to install is oracle 12c database server express edition. INSTALLING AND CONFIGURING ORACLE DATABASE SERVER 12C EXPRESS EDITION Oracle Database Server 12c Express Edition is one of the mostly highly ranked database server in 2017 and it acts exactly as t


Web server is a kind of a container that contains a web application programmed by software and web application programmer and the web application performs all of its functionality using the web server. INSTALLING GLASSFISH SERVER ON UBUNTU ® First, let us get to install glassfish server as one of the most popular web application servers for java programming language as follows: sudo apt-get update sudo apt-get install default-jdk wget unzip glassfish4/bin/asadmin start-domain Configuring Glassfish Server: 1. Open the URL http://localhost:4848 2. Then browse to the left side panel and select server-config 3. After that, go to Network Listeners, then 4. Set http-listener-1 to port 80 for default http listening After that, we will move on to the next installation which is: INSTALLING AND CONFIGURING APACHE WEB SERVER ® Apache web serv