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Topic Review
Distance Estimation Approach for Maritime Traffic Surveillance
Maritime traffic monitoring systems are particularly important in Mediterranean ports, as they provide more comprehensive data collection compared to traditional systems such as the Automatic Identification System (AIS), which is not mandatory for all vessels.
  • 374
  • 05 Jan 2024
Topic Review
Distance Measuring Equipment (Aviation)
In aviation, distance measuring equipment (DME) is a radio navigation technology that measures the slant range (distance) between an aircraft and a ground station by timing the propagation delay of radio signals in the frequency band between 960 and 1215 megahertz (MHz). Line-of-visibility between the aircraft and ground station is required. An interrogator (airborne) initiates an exchange by transmitting a pulse pair, on an assigned 'channel', to the transponder ground station. The channel assignment specifies the carrier frequency and the spacing between the pulses. After a known delay, the transponder replies by transmitting a pulse pair on a frequency that is offset from the interrogation frequency by 63 MHz and having specified separation. DME systems are used worldwide, using standards set by the International Civil Aviation Organization (ICAO), RTCA, the European Union Aviation Safety Agency (EASA) and other bodies. Some countries require that aircraft operating under instrument flight rules (IFR) be equipped with a DME interrogator; in others, a DME interrogator is only required for conducting certain operations. While stand-alone DME transponders are permitted, DME transponders are usually paired with an azimuth guidance system to provide aircraft with a two-dimensional navigation capability. A common combination is a DME colocated with a VHF omnidirectional range (VOR) transmitter in a single ground station. When this occurs, the frequencies of the VOR and DME equipment are paired. Such a configuration enables an aircraft to determine its azimuth angle and distance from the station. A VORTAC (a VOR co-located with a TACAN) installation provides the same capabilities to civil aircraft but also provides 2-D navigation capabilities to military aircraft. Low-power DME transponders are also associated with some instrument landing system (ILS), ILS localizer and microwave landing system (MLS) installations. In those situations, the DME transponder frequency/pulse spacing is also paired with the ILS, LOC or MLS frequency. ICAO characterizes DME transmissions as ultra high frequency (UHF). The term L-band is also used. Developed in Australia, DME was invented by James "Gerry" Gerrand under the supervision of Edward George "Taffy" Bowen while employed as Chief of the Division of Radiophysics of the Commonwealth Scientific and Industrial Research Organisation (CSIRO). Another engineered version of the system was deployed by Amalgamated Wireless Australasia Limited in the early 1950s operating in the 200 MHz VHF band. This Australian domestic version was referred to by the Federal Department of Civil Aviation as DME(D) (or DME Domestic), and the later international version adopted by ICAO as DME(I). DME is similar in principle to secondary radar ranging function, except the roles of the equipment in the aircraft and on the ground are reversed. DME was a post-war development based on the identification friend or foe (IFF) systems of World War II. To maintain compatibility, DME is functionally identical to the distance measuring component of TACAN.
  • 552
  • 14 Oct 2022
Topic Review
Distributed Element Circuit
Distributed element circuits are electrical circuits composed of lengths of transmission lines or other distributed components. These circuits perform the same functions as conventional circuits composed of passive components such as capacitors, inductors, and transformers. They are used mostly at microwave frequencies where conventional components are difficult or impossible to implement. A major advantage of distributed element circuits is that they can be produced cheaply as a printed circuit board for consumer products such as satellite television. They are also made in coaxial and waveguide formats for applications such as radar, satellite communication, and microwave links. A phenomenon that is much used in distributed element circuits is that a length of transmission line can be made to behave as a resonator. Distributed element components that do this include stubs, coupled lines, and cascaded lines. Circuits built from these components include filters, power dividers, directional couplers, and circulators. Distributed element circuits were investigated in the 1920s and 1930s but did not become important until World War II when they were used in radar. After the war their use was at first limited to military, space, and broadcasting infrastructure use but improvements in materials science in the field soon led to wider applications.
  • 1.9K
  • 17 Oct 2022
Topic Review
Distributed Energy Technologies
Power plants related to distributed generation can be classified according to the type of primary energy: fossil fuel, nuclear or renewable energy, or waste heat. Combustion-based plants, depending on the type of fossil fuel, can be divided into those using natural gas, coal, peat, wood, oil, diesel, gasoline, etc. The most common fuels for 1–100 MW plants are natural gas, diesel and coal, as they have a significant heat value, are low-cost and are available in large quantities. In the case of natural gas or diesel, electricity can be generated using open cycles such as the Brayton, Otto and Diesel cycles. They can be implemented in gas turbine plants (GTPs), gas piston plants (GPPs) and diesel generator power (DGP) complexes. When using any organic fuel, a closed energy cycle implemented in steam turbine power plants (STPs) can be used. Closed power cycles on water or organic coolants can also be used to generate electricity from industrial waste heat.
  • 282
  • 28 Jun 2023
Topic Review
Distributed Generation Integration into Grid
According to [25], DGs could also be defined as a small source of power production for storage (usually within the range of less than a kW and tens of MW), which is not a portion of the huge, centralized power network and is located close to the load. Another school of thought defines DGs as power pockets usually located near consumers, which have a relatively small capacity of 30 MW or less, with the ability to economically support the distribution grid. This description involves DG technologies such as photovoltaic systems, concentrating solar power, micro turbines, reciprocating engines and fuel cells.
  • 3.8K
  • 16 Sep 2021
Topic Review
Distributed Generation Technologies in South America
Electricity plays a vital role in modern life, and its demand has experienced steady growth worldwide due to population growth, economic development, and urbanization. The electricity systems, based mainly on centralized generation and intensive use of fossil fuels, face significant energy security, sustainability, and climate change challenges. These challenges have driven the search for more sustainable and decentralized solutions for energy generation and distribution, such as distributed generation (DG). DG refers to producing electricity on a small scale and close to the point of consumption, using renewable and non-renewable energy sources. DG has become increasingly popular worldwide due to its multiple benefits, which include reducing losses in power transmission and distribution, decreasing reliance on interconnected power systems with large-scale centralized generation, and promoting clean and renewable energy adoption.
  • 176
  • 26 Sep 2023
Topic Review
Distributed Generations and Capacitor Banks in Distribution Systems
Integration of Distributed generations (DGs) and capacitor banks (CBs) in distribution systems (DS) have the potential to enhance the system’s overall capabilities. This work demonstrates the application of a hybrid optimization technique the applies an available renewable energy potential (AREP)-based, hybrid-enhanced grey wolf optimizer–particle swarm optimization (AREP-EGWO-PSO) algorithm for the optimum location and sizing of DGs and CBs. EGWO is a metaheuristic optimization technique stimulated by grey wolves, and PSO is a swarm-based metaheuristic optimization algorithm. Hybridization of both algorithms finds the optimal solution to a problem through the movement of the particles. Using this hybrid method, multi-criterion solutions are obtained, such as technical, economic, and environmental, and these are enriched using multi-objective functions (MOF), namely minimizing active power losses, voltage deviation, the total cost of electrical energy, total emissions from generation sources and enhancing the voltage stability index (VSI). 
  • 378
  • 19 Apr 2022
Topic Review
Distributed Intelligent Battery Management System
For real-world applications, battery management systems (BMSs) can be used in the form of distributed control systems where general controllers, charge regulators, and smart monitors and sensors are integrated, such as those proposed in this work, which allow more precise estimations of a large set of important parameters, such as the state of charge (SOC), state of health (SOH), current, voltage, and temperature, seeking the safety and the extension of the useful life of energy storage systems based on battery banks. 
  • 222
  • 15 Dec 2023
Topic Review
Distributed Propulsion for Next-Generation Aircraft
Developments in the design of transport aircraft are increasingly focusing on the search for innovative solutions to improve general performance and reduce the environmental impact of flight operations. In this context, specific attention is being devoted to research into non-conventional solutions for the integration of the propulsion system, involving two different interconnected technological threads. From a general point of view, new types of propulsion systems are under investigation, and technologies involving new fuels, such as hydrogen or sustainable aviation fuels, or electric and hybrid-electric powertrains, are under development to provide breakthrough forward advancements in the field. In addition to these important innovations, and in a way that is generally complementary, non-conventional powertrain/airframe integrations are increasingly being investigated since, either as standalone or in combination with previous new power supply concepts, they can contribute to general improvements in aircraft performance, with significant implications for reducing environmental impact. Among the advanced technologies under investigation, it is worth mentioning distributed propulsion, which is gaining much interest, especially in the context of synergistic integration with electric powertrains.
  • 457
  • 01 Mar 2024
Topic Review
Distribution Channel Selection
The selection of the appropriate distribution channel is crucial for the success of any business dealing with physical goods. When dealing with this selection, it is crucial to have an effective decision support system (DSS) that can assist with such decisions. 
  • 961
  • 15 Oct 2023
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