Topic
Liquid dielectric
About: Liquid dielectric is a research topic. Over the lifetime, 3702 publications have been published within this topic receiving 45150 citations.
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TL;DR: The experimental results show that the liquid loading works well under a wide range of temperatures and effectively reduces the antenna electrical size by 40% and improves the impedance matching by 5 dB, therefore, the proposed liquid loading scheme can be applied to a variety of antenna/RF designs.
Abstract: An ionic liquid (IL) is used to make antennas for the first time. Unlike water, the proposed material has a large liquid range (-69.8 °C-350 °C), a relative permittivity of 3, an extremely low dielectric loss, and very stable thermophysical material properties. It can be used for liquid dielectric resonator antennas (DRAs) or as a loading material for performance enhancement. Importantly, the proposed liquid loading scheme is relatively simple and of low cost, but it can markedly improve the antenna performance. As design examples, a liquid-loaded wideband linearly polarized (LP) monopole antenna with an omnidirectional radiation pattern is first presented. Then, the LP antenna is modified to a wideband circularly polarized (CP) antenna with boresight radiation. These antenna examples demonstrate a frequency coverage of 1.25-5 GHz, a wide CP bandwidth, a relatively high gain (>4 dBi), high radiation efficiency >85%, and an electrical size of 0.42 λ
0
x0.42λ
0
x0.17λ
0
. The experimental results show that the liquid loading works well under a wide range of temperatures. It effectively reduces the antenna electrical size by 40% and improves the impedance matching by 5 dB. Therefore, the proposed liquid loading scheme can be applied to a variety of antenna/RF designs.
25 citations
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11 Aug 1986
TL;DR: In this article, a high-power pulse transformer for short, highvoltage and/or high-current pulses is described, where a base plate in a container, an insulating, cooling dielectric liquid with a given heat transfer coefficient in the container, at least one magnet core on the base plate with self-enclosed magnet legs around a central window and wide sides with axes normal to the axis of the window.
Abstract: A high-power pulse transformer for short, high-voltage and/or high-current pulses includes: a base plate in a container, an insulating, cooling dielectric liquid with a given heat transfer coefficient in the container; at least one magnet core on the base plate with self-enclosed magnet legs around a central window and wide sides with axes normal to the axis of the window; at least an undervoltage and an overvoltage winding in the liquid wrapped in each other around parts of the magnet core immersed in the liquid and linked to the magnet core and to each other, the windings including turns of substantially mutually doubly-wound electrically insulated metallic conductors having winding ends disposed in leadthroughs in the container walls, the conductors having surfaces with a heat transfer coefficient higher than that of the dielectric liquid; the turns of each winding being self-supported and spaced apart from the turns of the other winding by a first minimum spacing and spaced from the magnet core by a second minimum spacing; support insulators partly disposed in the liquid and adjacent and spaced from at least one side of the magnet core by a third minimum spacing being greater than the sum of the second minimum spacing and the thickness of the turns, at least the ends of the windings being secured in recesses formed in the support insulators; and a device for retaining the magnet core and the support insulators on the base plate.
24 citations
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TL;DR: A comprehensive numerical model describing the Joule heating induced temperature development and TGF is developed and the numerical simulations agree well with the experimental results, suggesting the valid mathematical model presented in this study is valid.
Abstract: Temperature gradient focusing (TGF) is a recently developed technique for spatially focusing and separating ionic analytes in microchannels. The temperature gradient required for TGF can be generated either by an imposed temperature gradient or by Joule heating resulting from an applied electric field that also drives the flow. In this study, a comprehensive numerical model describing the Joule heating induced temperature development and TGF is developed. The model consists of a set of governing equations including the Poisson-Boltzmann equation, the Laplace equation, the Navier-Stokes equations, the energy equations and the mass transport equation. As the thermophysical and electrical properties including the liquid dielectric constant, viscosity, and electric conductivity are temperature-dependent, these governing equations are coupled, and therefore the coupled governing equations are solved numerically by using a CFD-based numerical method. The numerical simulations agree well with the experimental results, suggesting the valid mathematical model presented in this study.
24 citations
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TL;DR: In this paper, a dielectrophoretic levitation scheme is used to measure the dielectric constant of insulating dieletric liquids and small solid spherical particles, which is unique because it requires no detailed knowledge of the electric field.
Abstract: A dielectrophoretic levitation scheme is used to measure the dielectric constant of insulating dieletric liquids and small solid spherical particles. The fixed ring-disk electrode system is first calibrated against a known standard dielectric liquid by levitating a small gas bubble in the liquid at a fixed location. The measurements are then performed by measuring the voltage required to levitate a gas bubble in the unknown liquid at the same location with respect to the electrode structure. A similar procedure is used for solid spherical particles. The system is unique because it requires no detailed knowledge of the electric field. Fabrication of the electrodes does not require precision machining, and the structure is relatively insensitive to leveling. The size of the gas bubble or solid particle is not critical as long as it is much smaller than the electrode structure. The measurement precision is limited by the accuracy of the voltage measurements and by the accuracy to which the dielectric constant (of the standard) and the specific gravities (of the unknown and the standard) are known. The measurements presented support the contention that this method is a simple and reliable method of measuring the dielectric constant of insulating dielectric liquids.
24 citations
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TL;DR: In this paper, the authors investigated the dielectric characteristics of various gases according to utilization factors for the establishment of insulation design criteria of a high voltage superconducting apparatus, and derived empirical expressions for electrical breakdown performance of gaseous electrical insulation media.
Abstract: A sub-cooled liquid nitrogen system is known to be a promising method to develop a high voltage superconducting magnet. Therefore, the investigation of dielectric characteristics of gaseous electrical insulation media is important for the design of a high voltage superconducting apparatus. In this paper, dielectric characteristics of various gases according to utilization factors are investigated for the establishment of insulation design criteria of a high voltage superconducting apparatus. Dielectric experiments on gaseous nitrogen and gaseous helium (GHe) are carried out by using several kinds of sphere-to-plane electrode systems made of stainless steel. As a result, it is found that the dielectric characteristics of gas are determined by as well as gap length of electrode systems. Also, empirical expressions for electrical breakdown performance of gaseous electrical insulation media are derived and formulated. It is considered that the results of the study would be applicable to designing a high voltage superconducting apparatus.
24 citations