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Loss-Separation Study on Silica-insulated Gas-atomized Fe-Si-Al Soft Magnetic Composites
T. T. Xu,B. W. Zhang,Z. Shi,W. W. Guan,K. Wan,X. Y. Shi,W. Liu,H. L. Su,Z. Q. Zou,Y. W. Du 한국자기학회 2020 Journal of Magnetics Vol.25 No.2
Fe-Si-Al soft magnetic composites were composed of gas-atomized Fe-9.6wt.%Si-5.4wt.%Al alloy powders insulated with silica nanoparticles. The influence of silica insulation content on the core’s magnetic properties was studied. It was found that increasing the silica mass ratio deteriorated the effective permeability and core loss in the frequency range of 40-120 kHz, while improved the quality factor at 100 kHz and DC-bias performance. The effective demagnetizing field reflected by density and the core’s volume resistivity may cause the variations of these magnetic parameters. Loss separation fitting was performed using the Bertotti formula, indicating that silica insulation increased the hysteresis loss and reduced the eddy-current loss. The hysteresis loss took over at the frequency lower than 120 kHz in this work. With increasing the frequency, the eddy-current loss grew more quickly than the hysteresis loss. Therefore, different methods should be adopted to reduce the core loss according to the core’s application frequency.
The Manufacturing Process Effects on the Tensile and Creep Behavior of High Strength Polyester Yarns
W. Hsieh,B. Chuang,J. Liu 한국토목섬유학회 2011 한국지반신소재학회 학술발표회 Vol.2011 No.11
Pretension and heating are common processes in the production of flexible geogrids. The pretension and heating temperature effects on the tensile and creep behavior of two types of high strength polyester yarns were investigated. Two types of polyester yarns provided from different local manufactures were used. The unit weights of the test yarns are 2013 (Type A) and 1511 (Type B) dynes, respectively. The ultimate tensile strength of the test yarns are 8.8 g/dyne and 8.9 g/dyne, respectively. 20%, 30%, 50% UTS pretension forces and 150℃, 170℃ and 180℃ heating temperatures were used to simulate the manufacturing process. A series of tensile tests (ASTM D2256) and conventional longterm (ASTM D5262) creep tests were performed to evaluate the tensile strength, elongation at rupture and long-term creep strain of the test polyester yarns. Scanning Electronics Microscope (SEM) technique was also used to visual evaluation the surface structure of the yarns before and after the simulated manufacturing process and creep tests. The test results indicated that the ultimate tensile strength of the polyester yarns decreases bilinearly as the test temperature is increased. The bi-linear tensile strength decrease rate is about -0.37 N and -0.74 N per degree of Celsius, respectively for Type A polyester yarn. The elongation at break for the tested yarns varied from 10.57% to 12.49% for test temperature varying from 20℃ to 80℃, respectively. The tensile strength and elongation at break at around 70℃ test condition was inconsistent with the results from other test conditions. It is believed that the glass formation phenomenon might have some effects on the engineering behavior of the tested yarns at a temperature around 70℃. Drying the polymer coating by heating would induce polyester yarn shrinkage during the geogrid production process. A minimum of 10% UTS pretension load is required to prevent shrinkage in the test polyester yarns. The single strand tensile test results for the processed polyester yarns indicated that the elongation at break was reduced by 1.5% to 2.0%. Linear creep strain curves on a semi-log scale diagram were observed from a series of 1000-hour conventional long-term creep tests for polyester yarns processed at different temperatures. The curve slope decreased as the pretension load and heating temperature were increased. The creep strain rates decrease very rapidly at the initial stage and reach a plateau stage after 50 hours loading during the tests. Secondary creep behavior was observed for the control and processed 1000-hour creep tests. The creep strain rate decreases as the pretension load and heating temperature were increased. Hair cracks were observed from SEM pictures for the samples obtained from a simulated manufacturing process after 1000-hours conventional creep testing. Similar test results were observed for both tested polyester yarns.
SimulationX 기반 자동차 semi-active 현가장치의 모델 개발 및 특성 해석
정인태(I. T. Jeong),정동석(D. S. Jeong),정원식(W. S. Jeong),이성민(S. M. Lee),유보연(B. Y. Yoo),장대범(D. B. Jang),서영우(Y. W. Seo),한성민(S. M. Han),이석우(S. W. Lee),여현승(H. S. Yeo),류하오(Hao Liu) 유공압건설기계학회 2022 유공압건설기계학회 학술대회논문집 Vol.2022 No.12
The semi-active suspension system controls the damping force of the vehicle damper to simultaneously improve the steering stability (handling) and ride comfort of the vehicle. In order to improve the ride comfort of a passenger car, performance analysis is required through modeling and simulation adaptation of a semi-active suspension system. This study used SimulationX, a commercial multi-domain analysis S/W, and modeling about 1/4 car of the semi-active suspension system. The damping force was controlled through a given performance of the damper. The developed SimulationX-based semi-active suspension system model is prepared for future controller development research.
B. S. Yoo,Y. G. Chae,Y. M. Kwon,D. H. Kim,B. W. Lee,Chunli Liu 한국자기학회 2013 Journal of Magnetics Vol.18 No.3
The Ni0.5Zn0.5Fe₂O₄ nanoparticles about 30 nm were prepared using sol-gel method with metal nitrates dissolved in 2-methoxyathanol. The concentrations of the metal nitrates are adjusted from 0.1 to 0.75 M in order to study the influence on the structural and magnetic properties. The structure and morphology characterization revealed that the crystallinity was improved and the nanoparticle size was increased with the nutrition solution concentrations up to 0.5 M. Degraded crystallinity together with decreased nanoparticle size were observed for concentration of 0.75 M. The saturation magnetization at room temperature reached maximum at 0.5 M, which can be explained by considering the crystallinity and size effect.
MAGNETIC CVs AS A BRIGHT REPRESENTATIVE OF CLOSE BINARIES
QIAN, S.-B.,HAN, Z.-T.,ZHU, L.-Y.,LIAO, W.-P.,LAJUS, E. FERNANDEZ,ZEJDA, M.,LIU, L.,SOONTHORNTHUM, B.,ZHOU, X. The Korean Astronomical Society 2015 天文學論叢 Vol.30 No.2
Due to the lack of an accretion disk in a polar (magnetic cataclysmic variable, MCV), the material transferred from the secondary is directly accreted onto the white dwarf, forming an accretion stream and a hot spot on the white-dwarf component. During the eclipses, different light components can be isolated. Therefore, the monitoring of eclipsing polars could provide valuable information on several modern astrophysical problems, e.g., CVs as planetary hosting stars, mass transfer and mass accretion in CVs, and the magnetic activity of the most rapidly rotating cool dwarfs. In the past five years, we have monitored about 10 eclipsing polars (e.g., DP Leo and HU Aqr) using several 2-m class telescopes and about 100 eclipse profiles were obtained. In this paper, we will introduce the progress of our research group at YNOs. The first direct evidence of variable mass transfer in a CV is obtained and we show that it is the dark-spot activity that causes the mass transfer in CVs. Magnetic activity cycles of the cool secondary were detected and we show that the variable mass transfer is not caused by magnetic activity cycles. These results will shed light on the structure and evolution of close binary stars (e.g., CVs and Algols).
Surface segregation and oxidation of Pt<sub>3</sub>Ni(111) alloys under oxygen environment
Lee, H.C.,Kim, B.M.,Jeong, C.K.,Toyoshima, R.,Kondoh, H.,Shimada, T.,Mase, K.,Mao, B.,Liu, Z.,Lee, H.,Huang, C.Q.,Li, W.X.,Ross, P.N.,Mun, B.S. Elsevier Science Publishers 2016 CATALYSIS TODAY - Vol.260 No.-
<P>Utilizing ambient pressure X-ray photoelectron spectroscopy (AP-XPS), the surface segregation and oxidation of Pt3Ni(1 1 1) alloys are investigated as a function of temperature and oxygen pressure. The in situ AP-XPS measurements of oxygen oxidation process show that the Pt 'skin' surface is not stable under the exposure of oxygen pressure of 100 mTorr at room temperature. As the temperature and pressure are elevated, the formations of Ni2O3, NiOx, and NiO are observed on surface while Pt atom starts to reduce its adsorbed oxygen, which is a clear sign of surface segregation of Ni to surface. Upon the evacuation of oxygen gas, i.e. ultrahigh vacuum condition, both of NiOx and NiO oxide get reduced and Ni2O3 remains on the surface. The DFT calculation is employed to explain the formation of surface oxides under oxidation condition. (C) 2015 Elsevier B.V. All rights reserved.</P>