Papers by Keyword: Shielding

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Authors: Hu Jun Jia, Yin Tang Yang, Chang Chun Chai
Abstract: Some new techniques include n- shielding, buried channel and field plate are firstly adopted together for design and fabrication of 4H-SiC microwave MESFETs. The testing results show that a relatively broad and uniform transconductance versus gate voltage was obtained using a 0.1m n- shielding. 0.3mm gate periphery device shows good DC and RF performance such as 5.27W/mm power density, 6.7dB power gain and 43% power added efficiency at 2.3GHz under pulse operation. Compared to conventional SiC MESFETs, a gate lag ratio as high as 0.84 can be achieved for the developed devices even under a nearly actual operating condition.
Authors: Punsak Glumglomchit, Juniastel Rajagukguk, Jakrapong Kaewkhao, Keerati Kirdsiri
Abstract: This work, gamma-ray shielding properties of the lutetium lithium borate glasses in the system Lu2O3 - Li2O - B2O3 have been evaluated as a shielding material at 662 keV photon energy. While the experimental mass attenuation coefficients (μm) have been determined by using the narrow beam transmission method, the theoretical data were calculated using WinXCom program. The good agreements between experimental and theoretical values have been obtained. Both experimental and computational mass attenuation coefficients data were used to obtain the effective atomic number (Zeff), and the effective electron density (Nel). Based on the obtained data, the Lu-based glasses have good shielding properties, the improved glasses could be used as gamma-rays shielding material.
Authors: Hafizah Mustapha, K.H. Ismail, T.J. Daim, S.F. Jamil
Abstract: Anechoic chambers are widely used in performing EMC measurements according to the established EMC standards. As in space area, EMC measurement is critically important to ascertain all of electrical and electronic components in the satellite body will function correctly without fail during launching and operation mode. Recognizing the needs and importance of performing the EMC measurements, the shielding performance of the chamber should be prioritized to ensure the interference of electromagnetic wave from outside going to inside the constructed chamber does not exist. As to maintain the shielding element, periodic checking and inspection should be well planned by conducting a specific test. This paper outlines a series of procedures that are developed while running the test. The test will characterize the shielding performance at four (4) frequency ranges using different types of antenna set. Typical test results are gathered and presented at the measured frequencies. Based on the results, it is concluded that the shielding performance of anechoic chamber is standing in good condition at three (3) ranges of frequencies except for frequency of 10 kHz to 200MHz. Several steps are recommended to remove or eliminate the random noise.
Authors: Sumedh Mannar, Amarjot Singh, M.Sai Shankar
Abstract: The increasing requirement for harnessing nuclear power demands the development of innovative precautionary techniques for protection from radiation. The high energies of the particles emitted have to be moderated before they render damage to any material subjected to them. Besides using simple shielding material, electrostatic shielding by setting up opposing electric fields has been implemented towards charged radiation damping to date. This paper aims at presenting and analyzing a material-efficient protection technique against ionizing radiation by introducing a number of parallel capacitive metal foils in between layers of dielectric shielding material. This is the first paper to present a technique by making use of charged capacitive elements to set neutralization centers for incoming charged radiation in order to minimize the thickness of material used for equivalent radiation shielding. The increase in efficiency of the shielding unit in reducing the net energy of radiation by the introduction of charged capacitive foils is experimentally observed.
Authors: Bao Dong Bai, Ying Ying Gao, Jia Yin Wang
Abstract: This paper mainly researches the eddy current losses of transformer shielding coil by adopting for analytical method. This method calculates the conductor’s boundary conditions directly by using the analytical solution of the leakage magnetic field, which is generated into the conductor eddy current equation for the analytical formula, then compared the analytical method with the finite element method to fix the analytical formula, the relevant theories are applied to analyze the results of using two different shielding to reduce the losses and find the effectively measures.
Authors: Ai Hong Guo, Xue Jiao Tang, Su Juan Zhang
Abstract: Water-based infrared ray shielding coating, that is, nanometer metal oxide is added to the water-based paint, which has anti-IR features without affecting the transparency of the paint. In this paper, the nanometer oxides are prepared by sol-gel method, added into polypropylene sour. In order to improve the infrared ray shielding of the thin film, two kinds of nanometer oxides are added into the polypropylene sour with different volume ratios, the shielding performance of the paint is studied. Experimental results show: in the 8000 ~ 4000cm-1 range, the transmittances of infrared ray is 30% to 75%; in 4000 ~ 400cm-1 range, transmittances decrease significantly; 3% ZnO, 3% Fe2O3, 3% Y2O3, 2% Al2O3 are the best mass ratio of every single nanometer oxide; the infrared shielding rate of Fe2O3 and Y2O3 mixture with the volume ratio of 1 to 4 is better than Fe2O3 and Y2O3 single.
Authors: Kenji Higashida, Masaki Tanaka, Sunao Sadamatsu
Abstract: Three-dimensional structure of crack tip dislocations were investigated by combining scanning transmission electron microscopy (STEM) and electron tomography (ET) in silicon single crystals. P-type (001) silicon single crystals were employed. <110> cracks were introduced from an indent on the (001) surface. The specimen was heated at 873K in order to introduce dislocations at the crack tips. The specimen was thinned to include the crack tip in the foil by an iron milling machine. STEM-ET observation revealed the three-dimensional structure of crack tip dislocations. Their Burgers vectors were determined by using an invisibility criterion. The local stress intensity factor was calculated using the dislocation characters obtained in the observation in this study, indicating that the dislocations observed were mode II shielding type dislocations.
Authors: M. Chabaat, H. Ayas
Abstract: In this study, interaction between a main crack and a surrounding layer of micro cracks is considered. A stress field distribution induced during these interactions is obtained using Muskhelshvili’s complex variables formalism which relies on the Green's functions. The effect of amplification and shielding on the resulting stress field is shown, herein, through a study of mode I Stress Intensity Factor (SIF). To quantify these effects, orientations as well as positions of microcracks with respect to the main crack is taken into consideration. Obtained results are compared and agreed with those of other researchers.
Authors: Sunao Sadamatsu, Masaki Tanaka, Kenji Higashida, Kenji Kaneko, Masatoshi Mitsuhara, S. Hata, M. Honda
Abstract: Crack tip dislocations and dislocations introduced by three point-bending tests at high temperature are observed by combinating scanning transmission electron microscopy and computed tomography (STEM-CT). Commercially available P type (001) single crystal silicon wafers were employed. A series of STEM image was acquired from -60º to +60º in tilt range with 2º in tilt step. The diffraction vector was maintained close to g(hkl) = 220 during the acquisition by adjusting the [110] direction of the sample parallel to the tilt axis of the holder. Reconstructed images of dislocations revealed dislocation structures in three-dimension.
Authors: Arina Shaybadullina, Yuliya Ginchitskaya, Olga Smirnova
Abstract: The designed is a cement-silicate coating based on liquid sodium glass and Portland cement, modified with a complex ultra-and nanodispersed additive that includes titanium dioxide, expanded perlite sand and a dispersion of multilayered carbon nanotubes. The advantage of the designed coating is the use of Portland cement as a silicizer instead of conventionally used zinc oxide. The presented cement-silicate coating is water resistant, steam and gas proof, has good adhesion to the base and an increased durability, providing 4-5 times longer service life than those of the existing analogs. The presence of multilayered carbon nanotubes in the coating leads to the absorption of technogenic electromagnetic emission, and ultradisperse titanium dioxide promotes self-cleaning of the coating surface due to the photocatalysis effect. Expanded pearlite sand makes the coating surface textured when applying it to the base. The cement-silicate coating is used for facades decorative finishing of buildings made of ceramic bricks, cement concrete and plastered surfaces.
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