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Zhang T.,Du W.Y.,Zhan C.Y.,Wang M.M.,Deng H.W.,Xie Z.M.,Li H. 한국원자력학회 2022 Nuclear Engineering and Technology Vol.54 No.8
The synergistic effect of ZrC nanoparticle pining and Re solution in W matrix on the thermal stability of tungsten was studied by investigating the evolution of the microstructure, hardness and tensile properties after annealing in a temperature range of 1000e1700 C. The results of metallography, electron backscatter diffraction pattern and Vickers micro-hardness indicate that the rolled W-1wt%Re-0.5 wt% ZrC alloy has a higher recrystallization temperature (1600 Ce1700 C) than that of the rolled pure W (1200 C), W-0.5 wt%ZrC (1300 C), W-0.5 wt%HfC (1400e1500 C) and WeK-3wt%Re alloy fabricated by the same technology. The molecular dynamics simulation results indicated that solution Re atoms in W matrix can slow down the self-diffusion of W atoms and form dragging effect to delay the growth of W grain, moreover, the diffusion coefficient decrease with increasing Re content. In addition, the ZrC nanoparticles can pin the grain boundaries and dislocations effectively, preventing the recrystallization. Therefore, synergistic effect of solid solution Re element and dispersed ZrC nanoparticles significantly increase recrystallization temperature
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.
Rapid Synthesis of W–Cr Solid–Solution by Dielectric-Barrier Discharge-Plasma-Assisted Ball Milling
S. F. Hong,Z. C. Lu,Y. H. Liu,Q. M. He,W. Jiang,M. Q. Zeng 대한금속·재료학회 2021 METALS AND MATERIALS International Vol.27 No.12
Supersaturated solid–solutions in a W–Cr alloy system were fabricated by conventional milling and plasma milling. The differentextension mechanisms of the solid solubility that were created by ball milling with and without discharge plasma werestudied. The solid–solubility of Cr in W for the P-milling W–Cr alloy system was higher, which indicates that plasma millingpromotes the formation of W(Cr) solid–solution more easily than conventional milling. According to Miedema’s model, inthe W–Cr alloy system, the free-energy change to form a W(Cr) solid solution by plasma milling is reduced compared withconventional milling because of the heating effect of the discharge plasma. Therefore, a higher stored energy in the grainboundaries and dislocations of the W–Cr nanograins during plasma milling makes it easier to overcome the thermodynamicbarrier in the formation of a solid–solution, when compared with conventional milling.
M. Q. Zeng,J. L. Tu,M. Zhu,W. Wang,J. W. Liu,Z. C. Lu 대한금속·재료학회 2020 METALS AND MATERIALS International Vol.26 No.9
The effects of plasma discharge intensity on the microstructure evolution of ball-milled tungsten (W)–carbon (C)–cobalt (Co)mixtures and the formation mechanism of ultrathin plate-like tungsten carbide (WC) grains prepared by ball milling with andwithout plasma discharge were investigated. It was found that increasing the plasma discharge intensity during ball millingobviously promoted the formation of a thin flake-like W phase because of the electroplasticity effect and simultaneouslylowered the carburization temperature between W and C. A combination of high hardness and transverse rupture strength of92.9 HRA and 3659 MPa, respectively, was obtained for the WC–8Co alloy fabricated by plasma milling at a gas pressure of5 × 103 Pa with a dielectric barrier discharge layer thickness of 3 mm. These properties were mainly attributed to the markedlylowered activation energy of the WC phase and generation of highly oriented ultrathin plate-like WC grains by plasma milling. The combination of the flake-like structure of the plasma-milled W aggregate and high specific interfacial area and shortdiffusion distance of W/C were readily inherited by the ultrathin plate-like WC grains in the sintered WC–Co hardmetals.
Yin, Q.Q.,Chang, J.,Zuo, R.Y.,Chen, L.Y.,Chen, Q.X.,Wei, X.Y.,Guan, Q.F.,Sun, J.W.,Zheng, Q.H.,Yang, X.,Ren, G.Z. Asian Australasian Association of Animal Productio 2010 Animal Bioscience Vol.23 No.2
In order to improve the availability of phytase and probiotics together, a phytase gene from Aspergillus ficuum has been expressed in Lactobacillus. In this study, the transformed Lactobacillus with phytase gene was fed to pigs to determine its effect on pig production, feed conversion and gut microbes. Forty eight, 60-day-old, castrated pigs (Duroc${\times}$Landrace${\times}$Pietrain) were assigned to 6 groups, 8 pigs for each group. Group 1 was the control, group 2 was added with chlortetracycline (500 mg/kg), group 3 was added with the transformed Lactobacillus (500 mg/kg) with 20% (w/w) of calcium monohydrogen phosphate (CMP, $CaHPO_{4}$) removed, group 4 was added with the natural Lactobacillus (500 mg/kg) with 20% (w/w) of CMP removed, group 5 was added with the transformed Lactobacillus (500 mg/kg) with 40% (w/w) of CMP removed, group 6 was added with phytase (500 mg/kg) with 40% (w/w) of CMP removed. The results showed: i) the average daily gain (ADG) was improved in groups 2, 3 and 4 (p<0.05); ii) the diarrhea rates in the groups added with Lactobacillus were lower than in the other groups (p<0.05), in which the transformed Lactobacillus had more effect on reducing digestive disease; iii) the transformed Lactobacillus was most effective in improving the digestibilities of crude protein (CP), calcium (Ca), phosphorus (P), compared with the other groups (p<0.05); iv) Lactobacillus could increase lactic acid bacterium number and ammonia concentrations, and decrease pH values and E. coli number in pig feces (p<0.05); v) the phytase activity in the feces of pigs fed with the transformed Lactobacillus was 133.32 U/g, which was higher than in group 4 (9.58 U/g, p<0.05), and was almost the same as group 6 (135.94 U/g); vi) the transformed Lactobacillus could increase serum concentrations of IgA, triglyceride, and glutamic oxaloacetic transaminase activity (p<0.05), and had no significant effect on other serum indexes (p>0.05).
이진욱(J.W.Lee),강건용(K.Y.Kang),박승주(S.Z.Park),박정규(J.K.Park) 한국자동차공학회 1996 한국자동차공학회 춘 추계 학술대회 논문집 Vol.1996 No.6_2
The pent-roof geometry of the cylinder head in a four-valve engine has been known to be favorable to the tumbling motion. The formation of a tumbling vortex is an effective way to enhance pre-ignition turbulence and it eventually promotes faster burning rates. This study presents experimental results of the tumble flow structure, including the flow motion phenomena, tumble mean velocity, angular momentum and turbulence intensity. Two four-valve cylinder heads were selected for changing tumble flow intensity and the tumble velocity was obtained under motoring conditions (at 1000rpm) by LDV measurement<br/>