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Grade-4 commercially pure titanium with ultrahigh strength achieved by twinning-induced grain refinement through cryogenic deformation

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Journal of Materials Science & Technology 2021年第7期66卷 193-201页

作者： Seong-woo choi Jae Sukjeong Jong woo Won Jae Keun Hong Yoon Suk choi Titanium Department.Korea Institute of Materials Science Changwon51508Republic of Korea School of Materials Science and Engineering Pusan National UniversityPusan.46241Republic of Korea Materials and Manufacturing Development Team Doosan Heavy Industries and ConstructionChangwon51711Republic of Korea

The yield strength of commercially pure(CP) Ti of ASTM grade 4, the strongest among all the CP-Ti grades, is too low for structural applications that require high-strength materials. Here, we demonstrate the strengthening of grade-4 CP Ti by cryogenic-temperature rolling(CTR), which enables deformation twinning in grade-4 CP Ti to achieve twinning-induced grain refinement. CTR activated {11.22} twinning and {10.12} twinning, which are the most common twinning systems in pure Ti, whereas room-temperature rolling(RTR) did not activate any twinning system. CTR with imposing an area reduction of just 30% significantly increased the yield strength of the CP Ti to 946 MPa, which is not achievable through typical processes performed at or above room temperature and is comparable to that of commercial Ti-6 Al-4 V. The significant increase in strength was due to microstructural strengthening caused by twinning-induced grain refinement, combined with dislocation accumulation. In contrast to RTR, CTR greatly increased the stress concentration at grain boundaries(GBs), which caused the unusual activation of twinning in the grade-4 CP Ti by facilitating twin nucleation at GBs. The stress concentration increased because CTR activated the slip to a lesser extent compared to RTR, thereby reducing the strain compatibility between neighboring grains. These results will contribute to development of ultrahigh-strength CP Ti and may thereby extend its use to structural applications that require high-strength materials.

关键词： Titanium Twinning Cryogenic deformation Grain refinement Tensile properties

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Evaluation of anti-tubercular activity of linolenic acid and conjugatedlinoleic acid as effective inhibitors against Mycobacterium tuberculosis

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Asian Pacific Journal of Tropical Medicine 2016年第2期9卷 121-125页

作者： Won hyung choi Department of Biomedical Science and Department of Medical Zoology Kyung Hee University School of Medicine

Objective: To evaluate a new pharmacological activity/effect of linolenic acid(α- and γ-form) and conjugated-linoleic acid(CLA) causing antibacterial activity against Mycobacterium tuberculosis(Mtb). Methods: The anti-Mtb activity/effect of linolenic acid and CLA were determined using different anti-Mtb indicator methods such as resazurin microtiter assay(REMA) and MGIT 960 system assay. The Mtb was incubated with various concentrations(12.5–200) μg/m L of the compounds and anti-Mtb first-line drugs for 5 d in the REMA, and for 3 wk in MGIT 960 system assay. Results: Linolenic acid and CLA obviously indicated their anti-Mtb activity/effect by strongly inhibiting the growth/proliferation of Mtb in a dosedependent manner in the REMA and the MGIT 960 system assay. Interestingly, linolenic acid and CLA consistently induced anti-Mtb activity/effect by effectively inhibiting the growth/proliferation of Mtb in MGIT 960 system for 21 d with a single-treatment, and their minimum inhibitory concentrations were measured as 200 μg/m L respectively. Conclusions: These results demonstrate that linolenic acid and CLA not only have effective anti-Mtb activity/properties, but also induce the selective-anti-Mtb effects by strongly inhibiting and blocking the growth/proliferation of Mtb through a new pharmacological activity/action. Therefore, this study provides novel perspectives for the effective use of them and the potential that can be used as potent anti-Mtb candidate drugs, as well as suggests the advantage of reducing the cost and/or time for developing a new/substantive drug by effectively repurposing the existing drugs or compounds as one of new strategies for the global challenge of tuberculosis.

关键词： MGIT 960 system Tuberculosis Drug susceptibility testing γ-linolenic acid

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Characteristics of machined surface controlled by cutting tools and conditions in machining of brittle material

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中国有色金属学会会刊：英文版 2009年第B09期19卷 194-201页

作者： Yong-woo KIM Soo-Chang choi Jeung-woo PARK Deug-woo LEE Department of Nano Fusion Technology Pusan National University Department of Mechanical Design Engineering Chosun University Department of Nanosystem and Nanoprocess Engineering Pusan National University

One of the ultra-precision machining methods was adapted for brittle material as well as soft material by using multi-arrayed diamond tips and high speed spindle. Conventional machining method is too hard to control surface roughness and surface texture against brittle material because the particles of grinding tools are irregular size and material can be fragile. Therefore, we were able to design tool paths and machine controlled pattern on surface by multi-arrayed diamond tips with uniform size made in MEMS fabrication and high speed spindle, and the maximum speed was about 3×105 r/min. We defined several parameters that can affect the machining surface. Those were multi-array of diamond tips (n×n), speed of air spindle and feeding rate. The surface roughness and surface texture can be controlled by those parameters for micro machining.

关键词：加工表面脆性材料条件控制刀具路径表面粗糙度特征高速主轴加工方法

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Time-domain channel estimator based on cyclic correlationfor OFDM systems with guard interval

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The Journal of China Universities of Posts and Telecommunications 2008年第2期15卷 26-31页

作者： IM Se-bin choi hyung-jin Communication Research Center Harbin Institute of Technology

Channel impulse response （CIR） can be estimated on the basis of cyclic correlation in time-domain for orthogonal frequency division multiplexing （OFDM） systems, This article proposes a generalized channel estimation method to reduce the estimation error by taking the average of different CIRs. Channel impulse responses are derived according to the different starting points of cyclic correlation. In addition, an effective CIR length estimation algorithm is also presented. The whole proposed methods are more effective to OFDM systems, especialiy to those with longer cyclic prefix. The analysis and the simulation results verify that the mean square error performance is 4-5 dB better than the conventional schemes under the same conditions.

关键词： CIR OFDM channel estimation mean squareerror (MSE)

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Gastric cancer surgery in cirrhotic patients: Result of gastrectomy with D2 lymph node dissection

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World Journal of Gastroenterology 2005年第30期11卷 4623-4627页

作者： Jun Ho Lee Junuk Kim Jae Ho Cheong woo Jin hyung Seung Ho choi Sung Hoon Noh Research Institute and Hospital Department of Surgery

AIM： To explore the feasibility of performing gastrectomy with D2 lymphadenectomy in gastric cancer patients with liver cirrhosis. METHODS： A total of 7 178 patients were admitted with a diagnosis of liver cirrhosis from January 1993 to December 2003. We reviewed the records of 142 patients who were diagnosed with liver cirrhosis and gastric adenocarcinoma during the same period. Gastrectomy with D2 lymph node dissection for carcinoma of the stomach was performed in 94 patients with histologically proven hepatic cirrhosis. RESULTS： All but 12 patients were dassified as Child＇s class A. Only 35 patients （37.2%） were diagnosed with cirrhosis before operation. Seventy-three patients underwent a subtotal gastrectomy （77.7%） and 21 patients （22.3%） underwent a total gastrectomy, each with D2 or more lymph node dissection. Two patients （3.8%） who had prophylactic intra-operative drain placement, died of postoperative complications from hepatorenal failure with intractable ascites. Thirty-seven patients （39.4%） experienced postoperative complications. The extent of gastric resection did not influence the morbidity whereas serum aspartate aminotransferase level （P = 0.011） and transfusion did （P = 0.008）. The most common postoperative complication was ascites （13.9%） followed by wound infection （10.6%）. CONCLUSION： We concluded that the presence of compensated cirrhosis, i.e. Child class A, is not a contraindication against gastrectomy with D2 or more lymph node dissection, when curative resection for gastric cancer is possible. Hepatic reserve and meticulous hemostasis are the likely determinants of operative prognosis.

关键词： Gastric cancer Liver cirrhosis D2 lymph nodedissection Morbidity Mortality

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Influence of a microscopic positive proximal margin in the treatment of gastric adenocarcinoma of the cardia

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World Journal of Gastroenterology 2006年第24期12卷 3883-3886页

作者： Jian-Guo Shen Jae-Ho Cheong woo-Jin hyung Junuk Kim Seung-Ho choi Sung-Hoon Noh Department of Surgery Yonsei University College ot'Medicine Seoul- 120-752 Korea ' Department of Surgical Oncology Sir Run Run Shaw Hospital College of Medicine Zhejiang University Hangzhou 310016 China

AIM： To investigate the influence of a positive proximal margin in total gastrectorny patients with gastric adenocarcinorna of the cardia. METHODS： Medical records of 191 patients with total gastrectornies for adenocarcinorna of the cardia between 1995 and 2000 were reviewed. The clinicopathologic features associated with a positive margin were determined, and the predictors for survival were analyzed. RESULTS： The incidence of positive proximal margin was 8.4% （16/191）. The positive margins were associated with advanced diseases. The tumor size and the depth of tumor invasion were independent risk factors for a positive margin. The mean survival in the positive margin group was 33.9 mo as *** 62.4 mo in the negative group （P 〈 0.001）. However, the difference in survival lost significance in subgroup analysis according to stage. Multivariate analysis identified that a positive margin was not an independent prognostic factor for survival. CONCLUSION： A positive margin is more of an indication of advanced disease in patients with gastric adenocarcinoma of the cardia rather than an independent prognostic factor for survival.

关键词： Resection margin Gastric cancer Totalgastrectomy Outcome

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The anti-tubercular activity of Melia azedarach L. and Lobelia chinensis Lour. and their potential as effective anti-Mycobacterium tuberculosis candidate agents

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Asian Pacific Journal of Tropical Biomedicine 2016年第10期6卷 830-835页

作者： Won hyung choi In Ah Lee Department of Biomedical Science School of Medicine Kyung Hee University Department of Medical Zoology School of Medicine Kyung Hee University Department of Chemistry College of Natural Science Kunsan National University

Objective: To evaluate the anti-mycobacterial activity of Melia azedarach L.(M. azedarach) and Lobelia chinensis Lour.(L. chinensis) extracts against the growth of Mycobacterium tuberculosis(M. tuberculosis).Methods: The anti-M. tuberculosis activity of M. azedarach and L. chinensis extracts were evaluated using different indicator methods such as resazurin microtiter assay(REMA) and mycobacteria growth indicator tube(MGIT) 960 system assay. The M. tuberculosis was incubated with various concentrations(50–800 mg/m L) of the extracts for 5 days in the REMA, and for 4 weeks in MGIT 960 system ***: M. azedarach and L. chinensis extracts showed their anti-M. tuberculosis activity by strongly inhibiting the growth of M. tuberculosis in a concentration-dependent manner in the REMA and the MGIT 960 system assay. Particularly, the methanol extract of M. azedarach and n-hexane extract of L. chinensis consistently exhibited their effects by effectively inhibiting the growth of M. tuberculosis in MGIT 960 system for 4 weeks with a single-treatment, indicating higher anti-M. tuberculosis activity than other extracts,and their minimum inhibitory concentrations were measured as 400 mg/m L and 800 mg/m L, ***: These results demonstrate that M. azedarach and L. chinensis extracts not only have unique anti-M. tuberculosis activity, but also induce the selective antiM. tuberculosis effects by consistently inhibiting or blocking the growth of M. tuberculosis through a new pharmacological action. Therefore, this study suggests the potential of them as effective candidate agents of next-generation for developing a new anti-tuberculosis drug, as well as the advantage for utilizing traditional medicinal plants as one of effective strategies against tuberculosis.

关键词： Lobelia chinensis Lour. Melia azedarach L. MGIT 960 system Drug susceptibility Tuberculosis

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Effect of ammonia gas etching on growth of vertically aligned carbon nanotubes/nanofibers

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Transactions of Nonferrous Metals Society of China 2011年第A01期21卷 130-134页

作者： Sang-Gook KIM Sooh-Yung KIM hyung-woo LEE Department of Mechanical Engineering Massachusetts Institute of Technology 77 Massachusetts Ave Cambridge MA 02139 USA National Core Research Center for Hybrid Materials Solution Pusan National University

The etching effect of ammonia （NH3） on the growth of vertically aligned nanotubes/nanofibers （CNTs） was investigated by direct-current plasma enhanced chemical vapor deposition （DC-PECVD）. NH3 gas etches Ni catalyst layer to form nanoscale islands while NH3 plasma etches the deposited amorphous carbon. Based on the etching effect of NH3 gas on Ni catalyst, the differences of growing bundles of CNTs and single strand CNTs were discussed; specifically, the amount of optimal NH3 gas etching is different between bundles of CNTs and single strand CNTs. In contrast to the CNT carpet growth, the single strand CNT growth requires shorter etching time （5 min） than large catalytic patterns （10 rain） since nano dots already form catalyst islands for CNT growth. Through removing the plasma pretreatment process, the damage from being exposed at high temperature substrate occurring during the plasma generation time is minimized. High resolution transmission electron microscopy （HTEM） shows fishbone structure of CNTs grown by PECVD.

关键词： carbon nanotube ammonia etching nickel catalyst plasma enhanced chemical vapor deposition (PECVD)

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Real-time Volume Preserving Constraints for Volumetric Model on GPU

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Computers, Materials & Continua 2022年第10期73卷 831-848页

作者： Hongly Va Min-hyung choi Min Hong Department of Software Convergence Soonchunhyang UniversityAsan31538Korea Department of Computer Science and Engineering University of Colorado DenverDenver80217COUSA Department of Computer Software Engineering Soonchunhyang UniversityAsan31538Korea

This paper presents a parallel method for simulating real-time 3D deformable objects using the volume preservation mass-spring system method on tetrahedron *** general,the conventional mass-spring system is manipulated as a force-driven method because it is fast,simple to implement,and the parameters can be ***,the springs in traditional mass-spring system can be excessively elongated which cause severe stability and robustness issues that lead to shape restoring,simulation blow-up,and huge volume loss of the deformable *** addition,traditional method that uses a serial process of the central processing unit(CPU)to solve the system in every frame cannot handle the complex structure of deformable object in ***,the first order implicit constraint enforcement for a mass-spring model is utilized to achieve accurate visual realism of deformable objects with tough constraint *** this paper,we applied the distance constraint and volume conservation constraints for each tetrahedron element to improve the stability of deformable object simulation using the mass-spring system and behave the same as its real-world *** reduce the computational complexity while ensuring stable simulation,we applied a method that utilizes OpenGL compute shader,a part of OpenGL Shading Language(GLSL)that executes on the graphic processing unit(GPU)to solve the numerical problems *** applied the proposed methods to experimental volumetric models,and volume percentages of all objects are *** average volume percentages of all models during the simulation using the mass-spring system,distance constraint,and the volume constraint method were 68.21%,89.64%,and 98.70%,*** proposed approaches are successfully applied to improve the stability of mass-spring system and the performance comparison from our experimental tests also shows that the GPU-based method is faster than CPU-based implementation for all cases.

关键词： Deformable object simulation mass-spring system implicit constraint enforcement volume conservation constraint GPU parallel computing

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Parallel Cloth Simulation Using OpenGL Shading Language

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Computer Systems Science & Engineering 2022年第5期41卷 427-443页

作者： Hongly Va Min-hyung choi Min Hong Department of Software Convergence Soonchunhyang UniversityAsan31538Korea Department of Computer Science and Engineering University of Colorado DenverDenverCO 80217USA Department of Computer Software Engineering Soonchunhyang UniversityAsan31538Korea

The primary goal of cloth simulation is to express object behavior in a realistic manner and achieve real-time performance by following the fundamental concept of *** general,the mass–spring system is applied to real-time cloth simulation with three types of ***,hard spring cloth simulation using the mass–spring system requires a small integration time-step in order to use a large stiffness ***,to obtain stable behavior,constraint enforcement is used instead of maintenance of the force of each *** force computation involves a large sparse linear solving *** to the large computation,we implement a cloth simulation using adaptive constraint activation and deactivation techniques that involve the mass-spring system and constraint enforcement method to prevent excessive elongation of *** the same time,when the length of the spring is stretched or compressed over a defined threshold,adaptive constraint activation and deactivation method deactivates the spring and generate the implicit *** method that uses a serial process of the Central Processing Unit(CPU)to solve the system in every frame cannot handle the complex structure of cloth model in *** simulation utilizes the Graphic Processing Unit(GPU)parallel processing with compute shader in OpenGL Shading Language(GLSL)to solve the system *** this paper,we design and implement parallel method for cloth simulation,and experiment on the performance and behavior comparison of the mass-spring system,constraint enforcement,and adaptive constraint activation and deactivation techniques the using GPU-based parallel method.

关键词： Adaptive constraint cloth simulation constraint enforcement GLSL compute shader mass–spring system parallel GPU

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