• 대한족부족관절학회지
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• 제10권1호
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• pp.60-65
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• 2006

Purpose: This study was performed to evaluate clinical and radiographical results of treatment of chronic lateral ankle instability with modified Brostrom procedure. Materials and Methods: This is a retrospective study of 22 cases in 22 patients treated with modified $Brostr{\ddot{o}}m$ procedure under the diagnosis of chronic lateral ankle instability from May 2000 to August 2004. Average age was 32.3 years. Average follow-up period was 23 months. Preoperative and postoperative radiographs of ankle anteroposterior view, lateral view and varus stress view were analyzed. The clinical evaluation was performed according to the Americal Orthopaedic Foot and Ankle Society scales. Results: After the modified $Brostr{\ddot{o}}m$ procedure, Americal Orthopaedic Foot and Ankle Society scales score was improved by average 28 points. Among the 22 cases, 13 cases were excellent, 3 cases good, 4 cases fair, and 2 cases poor with satisfaction of 73%. Five cases had intermittent ankle pain of whom 3 cases had difficulty during competitive sports activity. Lateral tilting of talus improved by average 5.4 degrees on varus stress view. Conclusions: The modified $Brostr{\ddot{o}}m$ procedure is one of the most effective methods for treating of chronic lateral ankle instability.

• 대한의용생체공학회:의공학회지
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• 제31권1호
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• pp.56-66
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• 2010

The various total replacement artificial discs have developed because spinal fusion has shown a lesser mobility of an operated segment and an accelerated degeneration at adjacent discs. But almost artificial discs have not yet been reached on the substitute surgery of fusion because many problems such as those clinical success rates were not more than them of fusion have not solved. In this paper, vertically inserted assemble-screw fixture in vertebrae was proposed to improve the fixed capability of artificial disc. And also, to evaluate the design suitability of newly designed screw-type, including fixtures of commercial discs such as wedge and plate type, the 1/4 finite element model with a vertebra and various implanted fixtures were generated, and next, 3 bending motions such as flexion, bending and twisting under the moment of 10Nm and compression under the force of 1000N were considered, respectively and finally, FE analyses were performed. Results of three fixture types were compared, such as Range of Motion and maximal stress, and so on. For ROM, the screw type was average 58% less than the wedge type and was average 42% less than the plate type under all loading conditions. For average stress ratio at closer nodes between vertebra and each fixture, the wedge type was the lowest as minimum 0.02 in twisting, screw types were the highest as maximum 0.28 in compression. As the results of using cement material, it was predicted that the instability problem of the wedge type was better solved. The screw type which could be increased by implanting depth according to the number of assembling mid screws, showed that the decreased tendency of ROMs and maximal cancellous bone stresses. In further study, controlling the number of assembling screws that was suitable for a patient's bone quality, development of surgical tools and keeping on design supplementations, which will be able to develop the competitive artificial disc.

• Journal of Veterinary Science
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• 제22권4호
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• pp.54.1-54.13
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• 2021

Background: Hypoxia causes oxidative stress and affects cardiovascular function and the programming of cardiovascular disease. Melatonin promotes antioxidant enzymes such as superoxide dismutase, glutathione reductase, glutathione peroxidase, and catalase. Objectives: This study aims to investigate the correlation between melatonin and hypoxia induction in cardiomyocytes differentiation. Methods: Mouse embryonic stem cells (mESCs) were induced to myocardial differentiation. To demonstrate the influence of melatonin under hypoxia, mESC was pretreated with melatonin and then cultured in hypoxic condition. The cardiac beating ratio of the mESC-derived cardiomyocytes, mRNA and protein expression levels were investigated. Results: Under hypoxic condition, the mRNA expression of cardiac-lineage markers (Brachyury, Tbx20, and cTn1) and melatonin receptor (Mtnr1a) was reduced. The mRNA expression of cTn1 and the beating ratio of mESCs increased when melatonin was treated simultaneously with hypoxia, compared to when only exposed to hypoxia. Hypoxia-inducible factor (HIF)-1α protein decreased with melatonin treatment under hypoxia, and Mtnr1a mRNA expression increased. When the cells were exposed to hypoxia with melatonin treatment, the protein expressions of phospho-extracellular signal-related kinase (p-ERK) and Bcl-2-associated X proteins (Bax) decreased, however, the levels of phospho-protein kinase B (p-Akt), phosphatidylinositol 3-kinase (PI3K), B-cell lymphoma 2 (Bcl-2) proteins, and antioxidant enzymes including Cu/Zn-SOD, Mn-SOD, and catalase were increased. Competitive melatonin receptor antagonist luzindole blocked the melatonin-induced effects. Conclusions: This study demonstrates that hypoxia inhibits cardiomyocytes differentiation and melatonin partially mitigates the adverse effect of hypoxia in myocardial differentiation by regulating apoptosis and oxidative stress through the p-AKT and PI3K pathway.

• International Journal of Railway
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• 제2권2호
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• pp.43-49
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• 2009

Wear and rolling contact fatigue (RCF) defects are most important causes of rail damage, and often interaction competitive at present railway track. Head check is one of rolling contact fatigue (RCF) defects, and generally occurs in mild circular curves and transition curves that are set at both ends of sharp circular curves. Wear tends to limit the crack growth of head checks by removing the material from the RCF surface. In order to clarify the conditions of the occurrence and growth of head checks, the authors measured the interacting forces between wheels and rails and the angle of attack of wheelset, and carried out contact analyses using the actual profile data of wheels and rails. The effects of the lateral force, the contact geometry, and the wear rate at rail gauge comer on the formation of head checks were also analyzed by using the worn profiles of actual wheels and rails and the data obtained by a track inspection car. Some specific range of wear rate at the gauge comer was identified as having close relation with occurrence of head checks.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2003년도 춘계학술대회논문집
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• pp.315-318
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• 2003

Recently, condenser tube which is used for a cooling system of automobiles is mainly manufactured by the conform extrusion but this method is inferior as compared with direct extrusion in productivity per the unit time and in the equipment investment. Therefore, it is essential for the conversion of direct extrusion with porthole die. The direct extrusion with porthole die can produce condenser tube which has the competitive power in costs and qualities compared with the existing conform extrusion. This study is designed to evaluate metal flow, welding pressure, extrusion load tendency of mandrel deflection that is affected by variation of porthole shape in porthole die. Estimation is carried out using finite element method under the non-steady state. Also this study was examined into the cause of mandrel fracture through investigating elastic deformation of mandrel during the extrusion.

• Industrial Engineering and Management Systems
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• 제16권1호
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• pp.80-91
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• 2017

Multiple prior studies stress that continued Kaizen activity is conducive to building and maintaining competitive advantages of manufacturing companies. Meanwhile, it remains unclear as to what kind of management factors may exert impact on sustainment of Kaizen activity. This paper discusses a study conducted on the cases of two manufacturing lines, where such activity has been continued for more than ten years. At first, it was discovered that study period was divided into different periods. It was also found out that 'standstill conditions' which prevent smooth progress of activity exist in many periods, and that such conditions are hard to avoid. The study went on to categorize progress of activity in each period into different patterns, including at which points standstill conditions occurred, thereby, circumstances of standstill conditions were made clear. This paper verified a detailed process of Kaizen activity development in each period and the relationship between that detailed process and points of occurrence of standstill conditions. Thought was also given to factors and actions for smooth development, and effects brought about by overcoming such challenges. Lastly, consideration was given to the future perspectives of the study for elucidating how better Kaizen activity may be managed for continuation.

• International Journal of Quality Innovation
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• 제8권2호
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• pp.69-87
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• 2007

High-tech industries in Taiwan exist in an environment with diverse product requirements and intense cost reduction and information integration stress. They must develop new operational directions to increase industry competitiveness. Therefore, Taiwan's high-tech industries must continue R&D and creativity, establish knowledge sharing mechanisms and improve new product development (NPD) performance. This research analyzed and explored the influences of knowledge management (KM) and knowledge sharing mechanisms introduced by Taiwan's high-tech industries on new product development performance. The relationship between knowledge management capabilities and NPD performance is studied. This research considers the intervening industry and corporate position variables. Taiwan's high-tech industries have gradually entered the era of IT region integration and application with competitive advantage creation based upon core techniques. The in-depth study of knowledge management and knowledge sharing introduced by the high-tech industry revealed double meanings in academic and practical applications. The research results showed the following: (1) the stronger the knowledge management capabilities of Taiwan's high-tech industries, the more significant the NPD performance. (2) The better the knowledge sharing mechanism in Taiwan's high-tech industries, the more significant the NPD performance. (3) Corporate scale is not necessarily the critical factor in NPD success and the influence of corporate scale on NPD performance did not show significant differences. (4) The stronger the degree of leading corporate techniques, the more significant the NPD performance.

• Toxicological Research
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• 제11권2호
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• pp.303-308
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• 1995

Nitric oxide, a physiological transmitter, is reported to mediate cellular injury in various tissues. Its reactivity to free radical is believed to be one of the reasons for its involvement in cytotoxicity. Menadione, a representative quinone, is cytotoxic to several cell systems including isolated hepatocyte, endothelial cell and red blood cells. Its toxic mechanism is related to oxidative stress, mediated by toxic free radicals. Our previous studies demonstrated that menadione induced cell lysis and increase of oxygen consumption in platelets. It has been reported that platelets have nitric oxide producing enzyme, nitric oxide synthase. Thus, we have investigated to manifest the role of nitric oxide.in menadione-induced cytotoxicity in rat platelets. Menadione induced cytotoxicity in platelets was unaffected by $N^G$-nitro-arginine methyl ester (L-NAME), selective and competitive inhibitor of nitric oxide synthase. We also invesitgated the role of extracellular nitric oxide in menadione-induced cytotoxicity of platelets by addition with sodium nitroprusside (SNP). SNP did not affect platelet cytotoxicity by menadione. These results suggested that nitric oxide which was generated endogeneously or exogeneously might have a negligible role in menadione-induced cytotoxicity in rat platelets.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2003년도 춘계학술대회 논문집
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• pp.1799-1802
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• 2003

The commercial success of a new product is influenced by the time to market. Shorter product leadtimes are of importance in a competitive market. This can be achieved only if the product development process can be realized in a relatively small time period. New cutting inserts are developed by a time consuming trial and error process guided by empirical knowledge of the mechanical cutting process. The effect of previous cutting on chip formation and the surface residual stresses has been studied. The chip formation is not affected much. There is only a minor influence from the residual stress on the surface from tile first cutting on the second pass chip formation. Thus, it is deemed to be sufficient to simulate only the first pass. The influence of the cutting speed and feed on the residual stresses has been computed and verified by the experiments. It is shown that the state of residual stresses in the workpiece increases with the cutting speed. This paper presents experimental results which can be used for evaluating computational models to assure robust solutions. The general finite element code ABAQUS/Standard has been used in the simulations. A quasi-static simulation with adiabatic heating was performed. The path for separating the chip from the workpiece is predetermined. The agreement between measurements and calculation is good considering the simplifications introduced.

• Structural Engineering and Mechanics
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• 제17권2호
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• pp.245-266
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• 2004

Incremental launching method is one of the highly competitive techniques for construction of concrete bridges. It avoids costly and time consuming form work and centralizes all construction activities in a small casting yard, thus saving in cost and time against conventional bridge construction. From the quality point of view, it eliminates the uncertainty of monolithic behaviour by allowing high repetitiveness and industrial environment. But, from analysis and design point of view, the most characteristic aspect of incrementally launched bridges is that, it has to absorb the stresses associated with the temporary supports that are gradually taken on by the deck during its launch. So, it is necessary to analyse the structure for each step of launching which is a tedious and time consuming process. Effect of support settlements or temperature variation makes the problem more complex. By using transfer matrix method, this problem can be handled efficiently with minimal computational effort. This paper gives insight into method of analysis, formulation for optimization of the structural system, effect of support settlement and temperature gradient, during construction, on the stress state of incrementally launched bridges.