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🔗 Physics 🔗 Telecommunications 🔗 Astronomy 🔗 Electrical engineering 🔗 Glass

A photon sieve is a device for focusing light using diffraction and interference. It consists of a flat sheet of material full of pinholes that are arranged in a pattern which is similar to the rings in a Fresnel zone plate, but a sieve brings light to much sharper focus than a zone plate. The sieve concept, first developed in 2001, is versatile because the characteristics of the focusing behaviour can be altered to suit the application by manufacturing a sieve containing holes of several different sizes and different arrangement of the pattern of holes.

Photon sieves have applications to photolithography. and are an alternative to lenses or mirrors in telescopes and terahertz lenses and antennas.

When the size of sieves is smaller than one wavelength of operating light, the traditional method mentioned above to describe the diffraction patterns is not valid. The vectorial theory must be used to approximate the diffraction of light from nanosieves. In this theory, the combination of coupled-mode theory and multiple expansion method is used to give an analytical model, which can facilitate the demonstration of traditional devices such as lenses and holograms.

🔗 Telecommunications

The Squarial (a portmanteau of the words square and aerial) was a satellite antenna used for reception of the now defunct British Satellite Broadcasting television service (BSB). The Squarial was a flat plate satellite antenna, built to be unobtrusive and unique. BSB were counting on the form factor of the antenna to clearly differentiate themselves from their competitors at the time. At the time of development, satellite installations usually required a 90 cm dish in order to receive a clear signal from the transmitting satellite. The smaller antenna was BSB's unique selling point and was heavily advertised in order to attract customers to their service.

🔗 Korea 🔗 Telecommunications 🔗 Korea/North Korea

Telephone numbers in North Korea are regulated by the Ministry of Post and Telecommunications.

🔗 Computing 🔗 Telecommunications 🔗 Computing/Networking

Wireless Application Protocol (WAP) is a now obsolete technical standard for accessing information over a mobile wireless network. Introduced in 1999, WAP allowed at launch users with compatible mobile devices to browse content such as news, weather and sports scores provided by mobile network operators, specially designed for the limited capabilities of a mobile device. The Japanese i-mode system offered another major competing wireless data standard.

Before the introduction of WAP, mobile service providers had limited opportunities to offer interactive data services, but needed interactivity to support Internet and Web applications. Although hyped at launch, WAP suffered from much criticism. However the introduction of GPRS networks, offering a faster speed, led to an improvement in the WAP experience. WAP content was accessed using a WAP browser, which is like a standard web browser but designed for reading pages specific for WAP, instead of HTML. By the 2010s it had been largely superseded by more modern standards such as XHTML. Modern phones have proper Web browsers, so they do not need WAP markup for compatibility, and therefore, most are no longer able to render and display pages written in WML, WAP's markup language.