Airlines for America

Airlines for America (A4A), formerly known as Air Transport Association of America (ATA), is America's oldest and largest airline trade association. A4A member airlines and their affiliates transport more than 90 percent of U.S. airline passenger and cargo traffic. Based in Washington, D.C., the association advocates for the U.S. airline industry. It is the only trade organization that represents the principal U.S. airlines and is their voice when lobbying Congress.

Profile

Mission

A4A's stated purpose is to "foster a business and regulatory environment that ensures safe and secure air transportation and enables U.S. airlines to flourish, stimulating economic growth locally, nationally and globally". A4A advocates on behalf of participating regularly scheduled airline corporations to the U.S. Congress, state legislatures, the U.S. Department of Transportation, including the Federal Aviation Administration, and the U.S. Department of Homeland Security, including the Transportation Security Administration and Customs and Border Protection.

Standard RAID levels

In computer storage, the standard RAID levels comprise a basic set of RAID (redundant array of independent disks) configurations that employ the techniques of striping, mirroring, or parity to create large reliable data stores from multiple general-purpose computer hard disk drives (HDDs). The most common types are RAID 0 (striping), RAID 1 and its variants (mirroring), RAID 5 (distributed parity), and RAID 6 (dual parity). RAID levels and their associated data formats are standardized by the Storage Networking Industry Association (SNIA) in the Common RAID Disk Drive Format (DDF) standard.

RAID 0

RAID 0 (also known as a stripe set or striped volume) splits ("stripes") data evenly across two or more disks, without parity information, redundancy, or fault tolerance. Since RAID 0 provides no fault tolerance or redundancy, the failure of one drive will cause the entire array to fail; as a result of having data striped across all disks, the failure will result in total data loss. This configuration is typically implemented having speed as the intended goal. RAID 0 is normally used to increase performance, although it can also be used as a way to create a large logical volume out of two or more physical disks.

Gigabit Ethernet

In computer networking, Gigabit Ethernet (GbE or 1 GigE) is a term describing various technologies for transmitting Ethernet frames at a rate of a gigabit per second (1,000,000,000 bits per second), as defined by the IEEE 802.3-2008 standard. It came into use beginning in 1999, gradually supplanting Fast Ethernet in wired local networks, where it performed considerably faster. The cables and equipment are very similar to previous standards and have been very common and economical since 2010.

Half-duplex gigabit links connected through repeater hubs were part of the IEEE specification, but the specification is not updated anymore and full-duplex operation with switches is used exclusively.

History

Ethernet was the result of the research done at Xerox PARC in the early 1970s. Ethernet later evolved into a widely implemented physical and link layer protocol. Fast Ethernet increased speed from 10 to 100 megabits per second (Mbit/s). Gigabit Ethernet was the next iteration, increasing the speed to 1000 Mbit/s. The initial standard for Gigabit Ethernet was produced by the IEEE in June 1998 as IEEE 802.3z, and required optical fiber. 802.3z is commonly referred to as 1000BASE-X, where -X refers to either -CX, -SX, -LX, or (non-standard) -ZX. For the history behind the "X" see Fast Ethernet.

Mathematical fallacy

In mathematics, certain kinds of mistaken proof are often exhibited, and sometimes collected, as illustrations of a concept of mathematical fallacy. There is a distinction between a simple mistake and a mathematical fallacy in a proof: a mistake in a proof leads to an invalid proof just in the same way, but in the best-known examples of mathematical fallacies, there is some concealment in the presentation of the proof. For example, the reason validity fails may be a division by zero that is hidden by algebraic notation. There is a striking quality of the mathematical fallacy: as typically presented, it leads not only to an absurd result, but does so in a crafty or clever way. Therefore, these fallacies, for pedagogic reasons, usually take the form of spurious proofs of obvious contradictions. Although the proofs are flawed, the errors, usually by design, are comparatively subtle, or designed to show that certain steps are conditional, and should not be applied in the cases that are the exceptions to the rules.