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Gang Chen,Yu Jin,Jing Wang,Cheng Zhang,Qiang Chen,Hongming Zhang,Xingjian Zhao,Zhiyong Li,Changhai Xie,Zhiming Du 대한금속·재료학회 2022 METALS AND MATERIALS International Vol.28 No.9
Isothermal compression tests were carried out to study the hot deformation behavior of T2 copper under various conditions. The deformation parameters, such as temperature and strain rate, have strong influence on flow stress and microstructureevolution of the alloy. A unified dislocation density-based model considering dynamic recovery and recrystallization wasestablished. And material parameters of the developed model were optimized by genetic algorithm. Comparisons betweenthe experimental and model data demonstrates that the developed model can precisely describe the flow behavior at quitewide range of deformation conditions. Meanwhile, the designed iterative procedure allows the model to be applied in timevariantdeformation conditions. Processing map and microstructure examination were constructed to optimize the processingwindow of the studied alloy. According to the processing maps, flow instability mainly appeared at low temperatures of500–650 °C and strain rates higher than 0.1 s−1. The optimum deformation parameters of T2 copper was concluded as thetemperature range of 700–800 °C and the strain rate of 0.1–1 s−1.
Tripod gait-based turning gait of a six-legged walking robot
Gang Chen,Bo Jin,Ying Chen 대한기계학회 2017 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.31 No.3
The turning gait planning and improvement methods of a six-legged walking robot on the basis of tripod gait are presented in this study. A projection method that considers an unstructured environment is proposed for the turning gait planning of the six-legged walking robot. The body and foot motion trajectories of the swing legs are planned with polynomial curves to keep the robot steady while walking. Two basic turning gaits, namely, circling and spinning gaits, are successfully designed with the planning method. An optimized method is proposed to improve the turning angle, which is subjected to stability, kinematics, and relief amplitude constraints in the unstructured environment. The turning ability of the turning gait is improved with the optimized turning angle. The circling and spinning gaits are implemented in simulations and experiments. Results demonstrate that the planning and improvement methods for the turning gait are valid and correct.
Gang Chen,Hua Wang,Jun-Yi Gai,Yue-Lin Zhu,Li-Fei Yang,Qian-Qian Liu,Gong-Chen Zhang,Guo-Hu Chen 한국원예학회 2012 Horticulture, Environment, and Biotechnology Vol.53 No.2
The objectives of this paper were to construct a full-length cDNA library and to isolate genes that confer salt tolerance from the leaves of salinity-tolerant wild eggplant variety, ‘Torvum Vigor’ (Solanum torvum Swartz). A full-length cDNA library from the leaves was successfully constructed by a switching mechanism at 5’-end of RNA transcript (SMART) approach and a long-distance PCR (LD-PCR) technique. The titer of the primary cDNA library was 3.6 ×106 cfu・mL-1 and that of the amplified library was 1.2 × 1010 cfu・mL-1. Gel electrophoresis results showed that most of the cDNA inserts ranged from 0.40 to 2.5 kb, with a recombination rate of 99%. A total of 427 randomly selected positive clones were sequenced. After removing the unsuccessful reads, 364 datasets were obtained and have been submitted to the NCBI Nucleotide Sequence Database under GenBank accession numbers JK265131-JK265494. Among the 364 submitted sequences, 74.45% of them contained full-length coding regions. BLASTX analysis revealed that 62.36% of the ‘Torvum Vigor’ expressed sequence tags (ESTs) possessed homology to known or putative proteins of other organisms. Seven genes that might be responsible for the encoding of known proteins in other organisms were identified to confer salt tolerance. This evidence demonstrated that the cDNA library constructed was a full-length library of high quality. It could be a useful resource for further research in the cloning of stress-related genes, which could be utilized in the genetic improvement of vegetable crops using transgenic technology.
Gang Chen,Qiang Chen,Bo Wang,Zhi-ming Du 대한금속·재료학회 2015 METALS AND MATERIALS International Vol.21 No.5
Al-Zn-Mg-Cu alloys are the strongest aluminum alloys which have been widely used for aerospace applications. They are usually machined from the wrought state usually with a high waste percentage. To reduce waste, it is important to thixoform these alloys in near net shape. In this work, the thixoformability of a commercial high performance Al-Zn-Mg-Cu alloy 7075 was studied. A novel multistep reheating regime was developed in recrystallization and partial melting (RAP) route to obtain spheroidal semi-solid microstructures. The as-extruded 7075 alloy was fully recrystallized for a short holding time using the multistep reheating regime. Semi-solid microstructures with fine and spherical solid grains with a grain size of 40-50 μm embedded in liquid matrix were obtained. The advantage of the multistep reheating regimes over those conventional routes was also discussed. Some wheel-shaped components were thixoformed from the as-received 7075 alloy. The ultimate tensile strength, yield strength and elongation to fracture of the thixoformed component based on multistep reheating regime, are 510 MPa, 446 MPa and 17.5% respectively. These values are superior to those of the products manufactured with the conventional RAP route. As the results indicated, thixoforming could be conducted based on commercial extruded Al-Zn-Mg-Cu alloys, which has important practical significance.
Gang Chen,Xusheng Chang,Jingxuan Zhang,Yu Jin,Cheng Sun,Qiang Chen,Zude Zhao 대한금속·재료학회 2020 METALS AND MATERIALS International Vol.26 No.10
Squeeze casting is a near net shaping technology which is advantageous to refining the microstructures and improving themechanical properties. In the present work, in-situ Al3Ti/2024 Aluminum matrix composites with different amount of Al3Tireinforcements were successfully fabricated by ultrasonic treatment and subsequent squeeze casting. The effects of specificpressure and the amount of reinforcements on microstructures and mechanical properties were studied. The results show thatwhen the specific pressure is increased from 0 to 150 MPa, the average grain sizes of α-Al matrix are decreased by 39.8%, andthe yield strength and compressive strength are increased by 16.8% and 22.9%, respectively. However, severe segregationsof eutectic structures were generated under an excessive specific pressure of 200 MPa, which also results in deterioration inthe mechanical strength. The mass fraction of Al3Tiphases has significant influence on morphology of eutectic structures. When the mass fraction of Al3Tiphases is increased from 4 to 16 wt%, the eutectic structures was changed from continuousnetwork to dispersed structures gradually. The compressive strength was increased from 611.2 to 712.0 MPa (increasedby 16.5%), as the Al3Ticontent increasing from 0 to 16 wt%. However, as the mass fraction of Al3Tiphases increased, thevariation in the yield strength is not monotonically increasing.
Ratcheting behavior of pressurized Z2CND18.12N stainless steel pipe under different control modes
Xu Chen,Xiaohui Chen,Gang Chen,Duomin Li 국제구조공학회 2015 Steel and Composite Structures, An International J Vol.18 No.1
With a quasi-three point bending apparatus, ratcheting deformation is studied experimentally on a pressurized austenitic stainless steel Z2CND18.12N pipe under bending load and vertical displacement control, respectively. The characteristic of ratcheting behavior of straight pipe under both control methods is achieved and compared. The cyclic bending loading and internal pressure influence ratcheting behavior of pressurized straight pipe significantly under loading control and the ratcheting characteristics are also highly associated with the cyclic displacement and internal pressure under displacement control. They all affect not only the saturation of the ratcheting strain but the ratcheting strain rate. In addition, ratcheting simulation is performed by elastic.plastic finite element analysis with ANSYS in which the bilinear model, Chaboche model, Ohno.Wang model and modified Ohno-Wang model are applied. By comparison with the experimental data, it is found that the CJK model gives reasonable simulation. Ratcheting boundaries under two control modes are almost same.
( Na Chen ),( Min Jin ),( Hong Mei Qu ),( Zhi Qiang Chen ),( Zhao Li Chen ),( Zhi Gang Qiu ),( Xin Wei Wang ),( Jun Wen Li ) 한국미생물 · 생명공학회 2012 Journal of microbiology and biotechnology Vol.22 No.2
A strain of bacterium producing antifungal antibiotic was isolated and identification of the strain was attempted. We could identify the bacterium as being a Bacillus sp., based on morphological observation, physiological characteristics, and 16S rDNA sequence analysis, thus leading us to designate the strain as Bacillus sp. AH-E-1. The strain showed potent antibiotic activity against phytopathogenic and human pathogenic fungi by inducing mycelial distortion and swelling and inhibiting spore germination. The antibiotic metabolite produced by the strain demonstrated excellent thermal and pH (2-11) stability, but was labile to autoclaving. From these results, we could find a broader antifungal activity of Bacillus genus. Isolation and characterization of the active agent produced by the strain are under progress.
Risk Factors for Anxiety in Major Depressive Disorder Patients
Li-Min Xin,Lin Chen,Zhen-Peng Ji,Suo-Yuan Zhang,Jun Wang,Yan-Hong Liu,Da-Fang Chen,Fu-De Yang,Gang Wang,Yi-Ru Fang,Zheng Lu,Hai-Chen Yang,Jian Hu,Zhi-Yu Chen,Yi Huang,Jing Sun,Xiao-Ping Wang,Hui-Chun 대한정신약물학회 2015 CLINICAL PSYCHOPHARMACOLOGY AND NEUROSCIENCE Vol.13 No.3
Objective: To analyze the sociodemographic and clinical factors related to anxiety in patients with major depressive disorder (MDD). Methods: This study involved a secondary analysis of data obtained from the Diagnostic Assessment Service for People with Bipolar Disorders in China (DASP), which was initiated by the Chinese Society of Psychiatry (CSP) and conducted from September 1, 2010 to February 28, 2011. Based on the presence or absence of anxiety-related characteristics, 1,178 MDD patients were classified as suffering from anxious depression (n=915) or non-anxious depression (n=263), respectively. Results: Compared with the non-anxious group, the anxious-depression group had an older age at onset (t=−4.39, p<0.001), were older (t=−4.69, p<0.001), reported more lifetime depressive episodes (z=−3.24, p=0.001), were more likely to experience seasonal depressive episodes (χ2=6.896, p=0.009) and depressive episodes following stressful life events (χ2=59.350, p <0.001), and were more likely to have a family history of psychiatric disorders (χ2=6.091, p=0.014). Their positive and total scores on the Mood Disorder Questionnaire (MDQ) and the 32-item Hypomania Checklist (HCL-32) (p<0.05) were also lower. The logistic regression analysis indicated that age (odds ratio [OR]=1.03, p<0.001), a lower total MDQ score (OR=0.94, p=0.011), depressive episodes following stressful life events (OR=3.04, p<0.001), and seasonal depressive episodes (OR=1.75, p=0.039) were significantly associated with anxious depression. Conclusion: These findings indicate that older age, fewer subclinical bipolar features, an increased number of depressive episodes following stressful life events, and seasonal depressive episodes may be risk factors for anxiety-related characteristics in patients with MDD.
A New Chromone Glycoside from Rhododendron spinuliferum
Gang Chen,Xue Feng Li,Qi Zhang,Hui Zi Jin,Yun Heng Shen,Shi Kai Yan,Wei Dong Zhang 대한약학회 2008 Archives of Pharmacal Research Vol.31 No.8
A new chromone glycoside, 3,5,7-trihydroxylchromone-3-O-α-L-arabinopyranoside (1), together with quercetin (2), (+)-catechin (3), (-)-epi-catechin (4) were isolated from the aerial parts of Rhododendron spinuliferum. The structure of 1 was elucidated on the basis of spectroscopic and 2D-NMR spectral analysis. In addition, 1 exhibited mild inhibitory effect on NO production in LPS-stimulated RAW264.7 cells.