Amplitude

The amplitude of a periodic variable is a measure of its change over a single period (such as time or spatial period). There are various definitions of amplitude (see below), which are all functions of the magnitude of the difference between the variable's extreme values. In older texts the phase is sometimes called the amplitude.

Definitions of the term

Peak-to-peak amplitude

Peak-to-peak amplitude is the change between peak (highest amplitude value) and trough (lowest amplitude value, which can be negative). With appropriate circuitry, peak-to-peak amplitudes of electric oscillations can be measured by meters or by viewing the waveform on an oscilloscope. Peak-to-peak is a straightforward measurement on an oscilloscope, the peaks of the waveform being easily identified and measured against the graticule. This remains a common way of specifying amplitude, but sometimes other measures of amplitude are more appropriate.

Peak amplitude

In audio system measurements, telecommunications and other areas where the measurand is a signal that swings above and below a zero value but is not sinusoidal, peak amplitude is often used. This is the maximum absolute value of the signal.

Harmonix

Harmonix Music Systems (or simply Harmonix) is an American video game development company based in Cambridge, Massachusetts in the United States. It is known for its many music video games.

Harmonix is perhaps best known as being the developer of Dance Central, Rock Band and Fantasia: Music Evolved, as well as being the original developer of the Guitar Hero series before development moved to Neversoft and Vicarious Visions.

History

Formation

Harmonix was founded in 1995 by Alex Rigopulos and Eran Egozy who met while attending MIT. Egozy was an electrical/computer engineer with an interest in music, while Rigopulos was a music composition major with an interest in programming; both met while working in the MIT Media Lab. After building a computer music generation system that could algorithmically create music on the fly, the two considered how one could use a joystick to control the system, and set up a demonstration of the unit for the Lab, which gained interest from others in the Lab. The two realized that after graduation that they probably couldn't pursue such ideas working at any existing companies, so they chose to start their own. The company was built on the premise that the experience of performing music could become accessible to those who would otherwise have trouble learning a traditional instrument.

Khan Academy

Khan Academy is a non-profit educational organization created in 2006 by educator Salman Khan with the aim of providing a free, world-class education for anyone, anywhere. The organization produces short lectures in the form of YouTube videos. In addition to micro lectures, the organization's website features practice exercises and tools for educators. All resources are available for free to anyone around the world. The main language of the website is English, but the content is also available in other languages.

History

The founder of the organization, Salman Khan, was born in New Orleans, Louisiana, United States to immigrant parents from Bangladesh and India. After earning three degrees from the Massachusetts Institute of Technology (a BS in mathematics, a BS in electrical engineering and computer science, and an MEng in electrical engineering and computer science), he pursued an MBA from Harvard Business School.

In late 2004, Khan began tutoring his cousin Nadia who needed help with math using Yahoo!'s Doodle notepad.When other relatives and friends sought similar help, he decided that it would be more practical to distribute the tutorials on YouTube. The videos' popularity and the testimonials of appreciative students prompted Khan to quit his job in finance as a hedge fund analyst at Connective Capital Management in 2009, and focus on the tutorials (then released under the moniker "Khan Academy") full-time.

Wikipedia

Wikipedia (ⁱ/ˌwɪkᵻˈpiːdiə/ or ⁱ/ˌwɪkiˈpiːdiə/ WIK-i-PEE-dee-ə) is a free-access, free-content Internet encyclopedia, supported and hosted by the non-profit Wikimedia Foundation. Those who can access the site can edit most of its articles. Wikipedia is ranked among the ten most popular websites, and constitutes the Internet's largest and most popular general reference work.

Jimmy Wales and Larry Sanger launched Wikipedia on January 15, 2001. Sanger coined its name, a portmanteau of wiki and encyclopedia. Initially only in English, Wikipedia quickly became multilingual as it developed similar versions in other languages, which differ in content and in editing practices. The English Wikipedia is now one of 291 Wikipedia editions and is the largest with 5,081,662 articles (having reached 5,000,000 articles in November 2015). There is a grand total, including all Wikipedias, of over 38 million articles in over 250 different languages. As of February 2014, it had 18 billion page views and nearly 500 million unique visitors each month.