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Topic Review
Dihedral (Aeronautics)
In aeronautics, dihedral is the angle between the left and right wings (or tail surfaces) of an aircraft. "Dihedral" is also used to describe the effect of sideslip on the rolling of the aircraft. Dihedral angle is the upward angle from horizontal of the wings or tailplane of a fixed-wing aircraft. "Anhedral angle" is the name given to negative dihedral angle, that is, when there is a downward angle from horizontal of the wings or tailplane of a fixed-wing aircraft. Dihedral angle has a strong influence on dihedral effect, which is named after it. Dihedral effect is the amount of roll moment produced in proportion to the amount of sideslip. Dihedral effect is a critical factor in the stability of an aircraft about the roll axis (the spiral mode). It is also pertinent to the nature of an aircraft's Dutch roll oscillation and to maneuverability about the roll axis. Longitudinal dihedral is a comparatively obscure term related to the pitch axis of an airplane. It is the angle between the zero-lift axis of the wing and the zero-lift axis of the horizontal tail. Longitudinal dihedral can influence the nature of controllability about the pitch axis and the nature of an aircraft's phugoid-mode oscillation. When the term "dihedral" (of an aircraft) is used by itself it is usually intended to mean "dihedral angle". However, context may otherwise indicate that "dihedral effect" is the intended meaning.
  • 5.6K
  • 27 Oct 2022
Topic Review
Dimethyl Ether Fuel
Dimethyl ether (DME), like hydrogen, can be used as an activator in the combustion process, affecting its course. A higher rate of hydrogen and DME combustion accelerates the natural gas combustion initiation process, and should also have an effect on liquid petroleum gas (LPG) combustion. Both these gaseous fuels are currently used extensively to power motor vehicles.
  • 616
  • 12 Jul 2022
Topic Review
Dipromisto
DIPROMISTO (Ukrainian: ДІПРОМІСТО) is a research and planning institute in the field of spatial and urban planning in Ukraine. It is a state enterprise within the field of governance of the Ministry of Regional Development, Construction and Housing of Ukraine. It was established on September 12, 1930. Its full name is State Enterprise Y.Bilokon Ukrainian State Scientific-Research Institute of Urban Design "DIPROMISTO". In Russian language sources it is also known as Giprograd (Russian: Гипроград). During Soviet times it was a system of planning institutes consisting of the central institute in Kyiv and a range of affiliates in oblasts' centres of USSR. In due time, most of the affiliates separated from the Dipromisto system into separate institutes. Currently the Institute has three affiliates: Ivano-Frankivsk, Rivne, and Volyn affiliates.
  • 296
  • 10 Nov 2022
Topic Review
Direct and Indirect Solar Gain Systems
The energy crisis, the risk of interruptions or irregular supplies of conventional energy carriers, and the need to protect the environment stimulate the search for new solutions to improve the heat balance of buildings with the use of solar energy. Based on the criterion of the storage, distribution, and discharge time of stored heat, passive solar gain solutions can be divided into direct and indirect solar gain systems.
  • 3.6K
  • 15 Dec 2022
Topic Review
Direct Borohydride–Hydrogen Peroxide Fuel Cell
Direct liquid fuel cells (DLFCs) operate directly on liquid fuel instead of hydrogen, as in typical proton-exchange membrane fuel cells (PEMFCs). DLFCs have the advantages of higher energy densities and fewer issues with the transportation and storage of their fuels compared with compressed hydrogen and are adapted to mobile applications. Among DLFCs, the direct borohydride–hydrogen peroxide fuel cell (DBPFC) is one of the most promising DLFC technologies. DBPFCs are fed sodium borohydride (NaBH4) as the fuel and hydrogen peroxide (H2O2) as the oxidant. 
  • 454
  • 08 Dec 2023
Topic Review Video
Direct Carbon Fuel Cells
Most fuel cells invariably use gaseous or liquid fuels. A fuel cell technology that has attracted attention only recently, the direct carbon fuel cell (DCFC) uses solid fuel (carbon) and converts the chemical energy in the carbon to electricity through its direct participation in the fuel cell reactions and electrochemical oxidation. The fuel use can be almost 100% compared with about 85% for most other fuel cells. The electrical efficiency is expected to be above 70% - almost twice those of current generation coal-fired plants leading to 50% reduction in greenhouse gas emissions. The amount of CO2 for storage/sequestration is also halved. Moreover, the exit gas is almost pure carbon dioxide stream, requiring no or minimal gas separation and processing for sequestration. Therefore, the energy and cost penalties to capture the CO2 will be significantly less than for other technologies. However, the technology is at an early stage of development requiring many complex challenges to be overcome, related to materials and corrosion, fuel delivery mechanism, and system development, before it can be commercialized. Section 19.4 of a recent book by the author gives an overview of this technology focusing on its main issues (Sequeira, 2019.). Two of the main DCFCs, the direct carbon molten carbonate fuel cell (DC-MCFC) and the direct carbon solid oxide fuel cell (DC-SOFC) are described in this topic review. 
  • 2.8K
  • 04 Aug 2021
Topic Review
Direct Contact Condensers
Direct contact heat exchangers can be smaller, cheaper, and have simpler construction than the surface, shell, or tube heat exchangers of the same capacity and can operate in evaporation or condensation modes. For these reasons, they have many practical applications, such as water desalination, heat exchangers in power plants, or chemical engineering devices.
  • 3.5K
  • 23 Dec 2022
Topic Review
Direct Current Distribution System Configurations
The developments in renewable energy installations in buildings have highlighted the potential improvement in energy efficiency provided by direct current (DC) distribution over traditional alternating current (AC) distribution. Despite the progress and optimal efficiency of DC distribution system implementation, there is still no consensus on standardization and regulation. It has been shown that the DC system performance could vary in terms of efficiency depending on load profile, utilized renewable energy sources, and utility grid integration.
  • 934
  • 11 Oct 2022
Topic Review
Direct Laser Deposition of Inconel 625
The direct laser deposition (DLD) process has seen rigorous research in the past two decades due to its ability to directly manufacture products followed by minimal machining. The process input variables play a vital role in determining the properties achieved in the products manufactured by the DLD method. Inconel 625, a nickel-based superalloy with exceptional mechanical performance and corrosion resistance, has been used in critical applications within the aerospace, process, and marine industry.
  • 393
  • 11 May 2023
Topic Review
Direct Methods for Solar Energy Harnessing
The escalating concerns regarding greenhouse gas (GHG) emissions and finite fossil fuel resources have propelled scientists and engineers to explore alternative and renewable energy sources (RES). Among these, solar energy stands out as a remarkable prospect because it is abundant, renewable, and emits no direct pollutants during operation. The fundamental principles of solar energy conversion through photovoltaic technology is introduction, shedding light on the progress and potential of harnessing the sun’s energy for a cleaner, sustainable energy future.
  • 586
  • 27 Sep 2023
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