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Ren Guo Guan,Zhan Yong Zhao,Chao Lian,Tong Cui,이종수 대한금속·재료학회 2013 METALS AND MATERIALS International Vol.19 No.1
A novel semisolid Continuous Shearing and Rolling (CSR) process for producing a Mg-3Sn-1Mn (wt%)alloy strip is developed, and the microstructure formation mechanism and properties of the Mg-3Sn-1Mn (wt%) alloy processed by this process are investigated. At a casting temperature of 690°C and a roll speed of 0.052 m·s.1, a Mg-3Sn-1Mn (wt%) alloy strip with a cross section size of 4×160 mm was produced by the proposed process. Under strong cooling and shearing actions, eruptive nucleation, direct globular grain growth and dendrite arm breakage took place during the process, which caused formations of fine spherical grains. The grain size and roundness of the Mg-3Sn-1Mn (wt%) alloy strip increased with increasing increments of the casting temperature. In this perspective, roll speed obviously affects grain shape. The ultimate tensile strength and elongation of the Mg-3Sn-1Mn (wt%) alloy strip reached 205.93 MPa and 7.2%.
Boundary Layer and Cooling Rate and Microstructure Formation on the Cooling Sloping Plate
Ren Guo Guan,Zhan Yong Zhao,Run Ze Chao,Lei Dong,이종수,Chun Ming Liu 대한금속·재료학회 2013 METALS AND MATERIALS International Vol.19 No.5
During melt treatment by cooling sloping plate, laminar flow and turbulent flow exist on sloping plate surface commonly. The thickness of velocity boundary layer and the critical transfer distance from laminar flow to turbulent flow increase with the decrease of initial flow velocity. The thickness of temperature boundary layer increases with the increment of flow distance and the decrease of initial flow velocity. The melt cooling rate and melt thickness have an inverse proportion relationship. The melt cooling rate of cooling sloping plate process can reach 102-103 K/s and belongs to meta-rapid solidification scope. Uniform solute field and high cooling rate can lead to eruptive nucleation. In addition, a large quantity of heterogonous nuclei appears on the sloping plate surface, and vibrating flow can enable heterogonous nucleus to escape off the plate, which leads to nucleus multiplication. Under relative uniform solute field and high cooling rate, some grains can keep stable growth surface, go on growing with the round surface and finally maintain their globular structure. However, there are always some grains that grow along a certain preferred direction, but under vibrating flow their dendritic arms break and transform into near spherical structure.
Hong-Guan Xie,Yong-Gang Bao,Li-ping Bai,Jun-Jie Shan,Rong Jiang,Yang Zhang,Lian-Hong Guo,Ren Zhang,Yuan Li 한국미생물학회 2009 The journal of microbiology Vol.47 No.2
Streptomyces sp. 139 generates a novel exopolysaccharide (EPS) designated as Ebosin, which exerts an antagonistic effect on IL-1R in vitro and anti-rheumatic arthritis activity in vivo. A ste gene cluster for Ebosin biosynthesis consisting of 27 ORFs was previously identified in our laboratory. In this paper, ste16 was expressed in Escherichia coli BL21 and the recombinant protein was purified, which has the ability to catalyze the transfer of the methyl group from S-adenosylmethionine (AdoMet) to dTDP-4-keto-6-deoxy-D-glucos, which was thus identified as a methyltransferase. In order to determine the function of ste16 in Ebosin biosynthesis, the gene was disrupted with a double crossover via homologous recombination. The monosaccharide composition of EPS-m generated by the mutant strain Streptomyces sp. 139 (ste16-) was found to differ from that of Ebosin. The IL-1R antagonist activity of EPS-m was markedly lower than that of Ebosin. These experimental results have shown that the ste16 gene codes for a methyltransferase which is involved in Ebosin biosynthesis.
Wide-range Wavelength-tunable RCLEDs
Bao-Lu Guan,Xia Guo,Xiu-Juan Ren,Shuo Li 한국물리학회 2011 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.58 No.41
A tunable oxide-confined AlGaAs/GaAs resonant-cavity light-emitting diode (RCLED) with a wide-range tuning wavelength was demonstrated. A quarter-wave stack as a movable Microelectronic system (MEMS)-bridge was used and realized a 27 nm tuning range from a resonance of 972 nm to 945 nm and the corresponding bias between the top bridge and the bottom mirror increased from 0 - 23 V. The tuning efficiency of δλ/λ<SUB>0</SUB> reached 2.8%. The spectral and the mechanical characteristics of the MEMS-tunable RCLED are also discussed, and the photon lifetime in the FP cavity was modulated in period by the bridge displacement.
Zhan Yong Zhao,Ren Guo Guan,Xiang Wang,Yang Li,Lei Dong,이종수,Chun Ming Liu 대한금속·재료학회 2013 METALS AND MATERIALS International Vol.19 No.5
A melt treatment with a vibrating cooling slope and a semisolid rolling process to produce an AZ61 alloy strip was proposed. The microstructure formation mechanism and the properties of the AZ61 alloy produced by the proposed process were investigated. Due to the high cooling rate and stirring action caused by the vibration cooling slope, the nucleation rate was greatly improved, which caused the formation of fine spherical or rosette primary grains. During the rolling process, the solid fraction increased from the entrance to the exit of the roll gap, and under the shearing action of the roller, the distribution of solute in the melt was homogenous, and the primary grains grew further. When the casting temperature was 680 °C,a strip with a cross section of 4 mm×160 mm was produced and a homogeneous microstructure was obtained. The ultimate tensile strength of the AZ61 alloy strip produced by the proposed method reached 242 MPa, and the corresponding elongation to failure was 4%, which were better than those achieved in previous similar studies.