Topic: Electrical engineering
An asynchronous circuit, or self-timed circuit, is a sequential digital logic circuit which is not governed by a clock circuit or global clock signal. Instead it often uses signals that indicate completion of instructions and operations, specified by simple data transfer protocols. This type of circuit is contrasted with synchronous circuits, in which changes to the signal values in the circuit are triggered by repetitive pulses called a clock signal. Most digital devices today use synchronous circuits. However asynchronous circuits have the potential to be faster, and may also have advantages in lower power consumption, lower electromagnetic interference, and better modularity in large systems. Asynchronous circuits are an active area of research in digital logic design.
- "Asynchronous (Clockless) CPU" | 2018-10-05 | 168 Upvotes 60 Comments
Oliver Heaviside FRS (; 18 May 1850 – 3 February 1925) was an English self-taught electrical engineer, mathematician, and physicist who adapted complex numbers to the study of electrical circuits, invented mathematical techniques for the solution of differential equations (equivalent to Laplace transforms), reformulated Maxwell's field equations in terms of electric and magnetic forces and energy flux, and independently co-formulated vector analysis. Although at odds with the scientific establishment for most of his life, Heaviside changed the face of telecommunications, mathematics, and science.
- "Oliver Heaviside" | 2014-12-26 | 100 Upvotes 25 Comments
Different methods of electricity generation can incur significantly different costs, and these costs can occur at significantly different times relative to when the power is used. The costs include the initial capital, and the costs of continuous operation, fuel, and maintenance as well as the costs of de-commissioning and remediating any environmental damage. Calculations of these costs can be made at the point of connection to a load or to the electricity grid, so that they may or may not include the transmission costs.
For comparing different methods, it is useful to compare costs per unit of energy which is typically given per kilowatt-hour or megawatt-hour. This type of calculation assists policymakers, researchers and others to guide discussions and decision making but is usually complicated by the need to take account of differences in timing by means of a discount rate. The consensus of recent major global studies of generation costs is that wind and solar power are the lowest-cost sources of electricity available today.
- "Wikipedia: Cost of Electricity by Source" | 2021-10-12 | 11 Upvotes 1 Comments
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.
- "Photon Sieve" | 2022-04-25 | 11 Upvotes 1 Comments