• 한국해양공학회지
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• 제23권1호
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• pp.140-145
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• 2009

This paper deals with a stability evaluation of a butterfly valve using the body and disc of a valve seat. The experimental results of a strength evaluation are shown using STS316 stainless steel and spheroidal graphite cast iron (GCD450). The disc material was made from GCD450. The results of the strength analysis are as follows: Ultimate tensile strength 485MPa, Yield strength 370 MPa, Young's modulus $1.1{\times}10^5$, and Poisson's ratio v = 0.28. For the results of the disc analysis, the safety factor was about 4. This shows that a design was derived that satisfied the requirements of structural safety. However, some problems, such as the deflection and deformation of the disc, may occur when the sea water has back flow with a high pressure.

• Journal of Korean Neurosurgical Society
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• 제30권sup2호
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• pp.242-246
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• 2001

Objective : The short hospitalization or outpatient care for patients undergoing laminectomy is not popular practice in Korea. We evaluated the clinical and economical significance of short hospitalization for patients undergoing microdiscectomy for their lumbar disc herniation. Material and Methods : From March 1999 to December 2000, patients were hospitalized for intended short period hospitalization for lumbar disc surgery. Their radiological and clinical data were analyzed for their clinical and economical results. We compared these data with 20 patients who hospitalized conventionally. Results : Total of 64 patients were evaluated. Three were lost to follow-up. Mean postoperative hospitalization period is 2.0 days(excluding one patient). Excellent to good outcome was achieved in 90.6 % of the patients. They payed about half expenses for hospitalization compared with conventional group. Their mean number of outpatient visit was 3.0. Conclusion : Short hospitalization for lumbar disc surgery is an acceptable option in Korea. It is also economically beneficial while achieving acceptable clinical results.

• 정보저장시스템학회논문집
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• 제1권1호
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• pp.34-41
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• 2005

We report some recent results in the rewritable Blu-ray Disc with enhanced overwrite cyclability by using the growth dominant eutectic based Ge(Sb70Te30)+Sb recording layer, GeN interface layer and write strategy optimization. We have developed phase-change optical media with appropriate write strategy for 36(i.e., 1X)-72Mbps(i.e., 2X) dual speed Blu-ray Disc system and fur the future high speed optical data storage. For recording layer, eutectic-based Ge(Sb70Te30)+Sb material was used and Sb/Te ratio and Ge content were optimized to obtain proper erasability and archival stability of recorded amorphous marks. The recording layer is wrapped up in GeN interface layers to obtain overwrite cyclability and higher crystallization speed. In addition, we designed appropriate write strategy so called Time-Shifted Multipulse (TSMP) write strategy where starting position of multipulse parts are shined from reference clock. With this write strategy, the jitter characteristics of the disc was improved and we found that leading edge jitter was improved much more than trailing edge jitter in 1X-2X speed recording. Finally, we investigated the higher speed feasibility of 144Mbps(i.e., 4X) by adopting some elemental doping to the eutectic based Ag-In-Sb-Te recording layer and structural optimization of constitution layers in Blu-ray Disc. In the paper, we report the effect of Sn addition for the feasibility of higher speed recording. The addition of Sn shows increases of the crystallization speed of phase change recording layer.

• Design & Manufacturing
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• 제16권1호
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• pp.36-42
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• 2022

Globally, as population growth and economic development continue, resource consumption is increasing rapidly. As an alternative to electric vehicles was suggested as the environmental pollution problem emerged, the number of registered electric vehicles in Korea increased by more than 137 times compared to 2013. Secondary batteries are expected to expand into various markets such as small IT devices and electric vehicles, and the most important part of electric vehicles is the battery (secondary battery). Therefore, in this study, to analyze the stability of the CSM (Classifier Separator Mill) grinding disc that crushes secondary battery raw materials, structural analysis and vibration analysis of the 1st to 4th grinding discs and the final model were performed. The change of bending by the weight of the Grinding Disc is at least 0.065㎛ and maximum 0.075㎛, and the change by the standard gravity is judged to be very low. The strain is at least 0.00031㎛/㎛ and maximum 0.00078㎛/㎛, and even if the number of Hamer increases, the change by the weight is judged to be insignificant. When the Grinding Disc rotates at a maximum of 6000rpm, the deformation and deformation rate of the first to third models are similar, but the fourth model (Hamer 10EA) is more than three times and the final model (Hamer 12EA) is about four times. However, the maximum deformation is 28.21㎛, which is considered to be insignificant when the change is 6000rpm. Six modes of natural Frequency analysis of the 1st~4th order and final model of the grinding disc appeared to be bent or twisted.

• Design & Manufacturing
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• 제16권4호
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• pp.34-39
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• 2022

Sustained economic development around the world is accelerating resource depletion. Research and development of secondary batteries that can replace them is also being actively conducted. Secondary batteries are emerging as a key technology for carbon neutrality. The core of an electric vehicle is the battery (secondary battery). Therefore, in this study, the temperature change by the heat source of the hammer and the rotational speed (rpm) of the abrasive disc of the Classifier Separator Mill (CSM) was repeatedly calculated and analyzed using the heat flow simulation STAR-CCM+. As the rotational speed (rpm) of the abrasive disk increases, the convergence condition of the iteration increases. Under the condition that the inlet speed of the Classifier Separator Mill (CSM) and the heat source value of the disc hammer are the same, the disc rotation speed (rpm) and the hammer temperature are inversely proportional. As the rotational speed (rpm) of the disc increases, the hammer temperature decreases. However, since the wear rate of the secondary battery material increases due to the strong impact of the crushing rotational force, it is determined that an appropriate rpm setting is necessary. In CSM (Classifier Separator Mill), it is judged that the flow rate difference is not significantly different in the direction of the pressure outlet (Outlet 1) right above the classifier wheel with the fastest flow rate. Because the disc and hammer attachment technology is adhesive, the attachment point may deform when the temperature of the hammer rises. Therefore, it is considered necessary to develop high-performance adhesives and other adhesive technologies.

• 터널과지하공간
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• 제33권4호
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• pp.244-254
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• 2023

TBM에 장착되어 암석을 절삭하는 디스크커터에는 암반을 굴착하는 과정에서 세 방향의 절삭력이 작용한다. 일반적으로 디스크커터의 절삭력은 굴착대상암반의 강도에 따라 증가하는 것으로 알려져 있고, 디스크커터가 여러 원인에 의해 정상적으로 회전이 이루어지지 않는 경우에는 회전력이 급격하게 증가할 수 있다. 따라서 굴착 도중 디스크커터에 작용하는 절삭력은 굴착의 대상이 되는 암반의 상태나 디스크커터의 절삭상태를 나타내는 중요한 정보가 될 수 있다. 이러한 이유로 해외를 중심으로 디스크커터의 작용력을 실시간으로 측정하기 위한 기술의 개발이 이루어지고 있으며, 본 연구에서는 현재까지 해외의 문헌을 통해 보고되고 있는 TBM 디스크커터의 하중계측에 관한 연구현황에 대하여 소개하고자 하였다. 향후 국내에서도 유사한 기술의 개발이 이루어지는 경우에 유용한 참고자료가 될 수 있을 것으로 판단된다.

• Tribology and Lubricants
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• 제27권4호
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• pp.213-217
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• 2011

In this study, friction characteristics using elastomeric actuator with Magneto-rheological (MR) materials are identified. Typically, Magneto-rheological materials are divided into two groups by MR fluid in fluid state and MR elastomer in solid state like rubber. The stiffness characteristics of Magneto-rheological material can be changed as magnetic field is applied. MR fluid has been applied to various industry fields such as to brake, clutch, damper, engine mount and etc. However, MR fluid has been used under the sealed condition to prevent leaking issues. In order to overcome these problems, MR elastomer that has same property as MR fluid has been developed and studied. MR elastomer mainly consists of polymer material such as natural rubber or silicon rubber with particles that can be polarized with magnetic field. And it is called as a smart material since its stiffness and damping characteristics can be changed. In this study, MR elastomer is produced and pin-on-disc tests are carried out to identify the friction characteristics of the material. Several test conditions are applied to evaluate the feasibility to use as a smart actuator in the field of vibration control.

• Tribology and Lubricants
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• 제30권6호
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• pp.364-369
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• 2014

To assess the wear behavior of rails against subway rail car wheels, we investigate the sliding wear behavior of pins derived from two types of rails (normal rails and heat-treated rails) against a disc derived from a subway rail car wheel, using a pin-on-disc-type tribometer. We base the sliding wear test conditions on the sliding conditions for wheel flange-rail gauge corner contact. We demonstrate the remarkable transition in the wear behavior of the pins derived from the rails, from severe wear to mild wear, as a function of the sliding distance. The wear rate of the heat-treated rail material in the running-in wear region is much lower than that of the normal rail material. Furthermore, the wear rates of the pins in the running-in wear region decrease with increasing hardness and with decreasing sliding speed. However, there is little difference between the heat-treated rail pin and the normal rail pin in the wear rate in the steady-state wear region. Stricter controls on the decarburized layer beneath the surface of rails are required to reduce the wear rate in the running-in wear region.

• 한국기계가공학회지
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• 제21권6호
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• pp.36-43
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• 2022

Automobile brake discs are a major part of automobiles that are directly related to driver safety, and prevention of judder and squall noise is very important. This phenomenon occurs for complex reasons such as the precision and assembly of the brake module, and the material of the brake disc. The purpose of this study is to analyze the effect of the grinding wheel's grain size on the grinding conditions when machining cast iron, the material of the brake disc, and to derive the optimal grinding conditions through this.

• 대한기계학회논문집A
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• 제27권6호
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• pp.905-913
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• 2003

Generally, most of optimization have been performed with fixed sizes and variables. But, the optimum value considering tolerance of design variables and material properties, might be useless owing to exist in infeasible region. It is needed that the tolerance of design variables and material properties is considered for a real design problem. A deterministic optimal solution can be in the feasible region by performing robust optimization considering tolerance. In the paper, robust design is suggested to gain an optimum insensitive to variation of design variables and it is applied for optimization problem of caliper disc brakes for vehicles.