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991.
992.
Jong Min Byun Won June Choi Su-Ryong Bang Chun Woong Park Young Do Kim 《JOM Journal of the Minerals, Metals and Materials Society》2017,69(4):683-688
In this study, we investigate the effect of oxide dispersion strengthening on mechanical properties by dispersion of nano-sized Ta2O5 particles in Mo-Si-B alloy. A Mo-Si-B core-shell powder consisting of two intermetallic compounds of Mo5SiB2 and Mo3Si as the core and nano-sized Mo solid solution surrounding intermetallic compounds was fabricated by chemical vapor transport. And Mo-Si-B core-shell powder with uniformly dispersed nano-sized Ta2O5 particles on the surface of a Mo solid solution shell was produced by a wet blending process with TaCl5 solution and heat treatment. Then, pressureless sintering was performed at 1400°C for 3 h under a H2 atmosphere. The hardness and fracture toughness of the Ta2O5-dispersed Mo-Si-B alloy were measured using Vickers hardness and 3-point bending tests, respectively. The Vickers hardness and fracture toughness of the fabricated Mo-Si-B-Ta2O5 alloy were more improved than that of the Mo-Si-B alloy fabricated using core-shell powder with no addition of Ta2O5 particles (Mo-Si-B alloy: 353 Hv, 13.5 MPa·√m, Mo-Si-B-Ta2O5 alloy: 509 Hv, 15.1 MPa·√m). 相似文献
993.
Jung Gi Kim Seung Mi Baek Won Tae Cho Tae Jin Song Kwang-Geun Chin Sunghak Lee Hyoung Seop Kim 《Metals and Materials International》2017,23(3):459-464
Although twinning-induced plasticity (TWIP) steels have high tensile strength with high strain hardening and large uniform elongation due to the formation of deformation twins during plastic deformation, sheet formabilities of TWIP steels are relatively poor. In this study, to overcome this problem, TWIP-cored three-layer architectured steel sheets are produced using cladding with low carbon steel sheaths. For an optimum design of layer architectured materials, strain hardening exponent n and strain rate sensitivity m of the layer sheets are theoretically and experimentally investigated. The forced-based rule-of-mixtures well reproduces the experimental values of the equivalent n and m. Contrary to the conventional rule-of-mixtures, the equivalent n and m of the TWIP-cored mild steel-sheath layered sheets are governed not only by volume fractions and n and m of parent materials but also by the strength of strong layer. 相似文献
994.
J. D. Nzabonimpa Won‐Kee Hong Jisoon Kim 《The Structural Design of Tall and Special Buildings》2017,26(17)
The aim of this study is to develop laminated metal plates for a moment connection of the precast concrete columns. Metal plates were proposed as a time‐ and cost‐saving alternative to conventional monolithic cast‐in‐place joints for connecting precast concrete frames. This study investigated the possibility of using mechanical joints for the connections of both steel‐concrete composite precast frames and reinforced concrete precast frames. A full erection test of precast columns connected with laminated metal plates was performed to demonstrate the efficiency and simplicity of the proposed method. It was shown that the use of the novel mechanical joints with steel plates significantly reduces construction time compared with the conventional monolithic assembly. The total precast column assembly time was approximately 10–20 min, eliminating pour forms and curing times required for the conventional concrete frames. This study also presents an analytical modeling of the proposed connection for multibay precast frames to explore the strains and stress exerted on the joints. 相似文献
995.
996.
γ‐amino butyric acid‐enriched barley bran lowers adrenocorticotropic hormone and corticosterone levels in immobilized stressed rats
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997.
Chuin Won Yong-ik Jin Misook Kim Youngseung Lee 《International Journal of Food Properties》2017,20(12):3076-3089
The objective of the present study was to investigate the structural and rheological properties of octenyl succinic anhydrate (OSA) modified potato starch. Potato starch was modified with different concentrations of OSA (0, 1, 3, and 5%, v/v). X-ray results suggested that OSA modification did not disrupt the crystallinity of the native starch, and esterification occurs primarily in the amorphous regions. The use of 1H-NMR spectra confirmed the presence of methyl protons in substituted OSA groups, which interacted with the starch molecules. In steady shear rheological analysis, OSA modified starch pastes showed a pronounced shear thinning behavior (n = 0.47–0.54). The consistency index (K) and yield stress (σoc) values of OSA modified starch pastes were significantly lower than those of the native starch. Dynamic shear rheological tests indicated that OSA modified starch pastes had weak gel-like behavior with storage moduli (G’) higher than loss moduli (G’’). OSA potato starch pastes were more viscous as compared to the native potato starch paste, as evidenced by their higher tan δ values. 相似文献
998.
999.
Investigation of MEA degradation in PEM fuel cell by on/off cyclic operation under different humid conditions 总被引:2,自引:0,他引:2
Dongho SeoJunghyun Lee Sangsun ParkJunki Rhee Sung Won ChoiYong-Gun Shul 《International Journal of Hydrogen Energy》2011,36(2):1828-1836
The durability of PEM fuel cells as a function of different humid conditions and MEA degradation were investigated by on/off cyclic operation. The maximum numbers of cycles determined by cycle at 10% of cell voltage loss were 1980, 1650, 1100, 520, and 320 cycles at relative humidity (RH) of 1000, 80, 50, 30, and 10%, respectively. The increases of ohmic resistance were observed at the high humid conditions of RH 100 and 80%. On the other hand, the charge transfer resistance increased at low humid conditions of RH 50, 30, and 10%. The losses of electrochemical surface area were obtained about 21% and 7% under RH 50 and 30% after the on/off cyclic operations, respectively. The thickness of electrode was reduced in the both anode and cathode layer, indicating that carbon corrosion occurred during on/off cycling. At cathode layer, the growth and migration platinum particles into polymer electrolyte were detected by XRD and TEM analyses. 相似文献
1000.