• 유공압시스템학회논문집
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• 제2권2호
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• pp.14-20
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• 2005

This study developed and evaluated a shoe cushioning system to reduce impact force patterns during running. The shoe cushioning system is composed with a poly urethane pocket, which contains water and porous grains to absorb the force against the weight inside the pocket. Load-displacement curves for the shoe cushioning system were obtained from an instrumented testing machine and the results were compared with various pockets that have air, water or grains. Mechanical testings showed that the pocket with 5 g particles was the best for the shoe cushioning system. This founding will be helpful to designing the shoe.

• 한국정밀공학회지
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• 제30권12호
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• pp.1327-1333
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• 2013

Air bearings are widely used in precision stages because of low friction and high motion accuracy, however, they suffer from low stiffness in comparison with rolling bearings or hydrostatic bearings. So, several preloading methods using weight, magnet and vacuum force, and opposing pads have been used to increase the stiffness of the air bearings. In this paper, pressure distributions of the vacuum preloaded porous air bearings are calculated using the proposed method. And then, the load capacity and stiffness are analyzed. For the vacuum preloaded air bearings, the stiffness is increased owing to reduced bearing clearance by vacuum force. The simulation results indicate that variation of vacuum pressure with clearance in the vacuum pocket gives rise to low stiffness, so the vacuum pocket should be designed for pressure to be constantly maintained regardless of the bearing clearance by means of large effective pumping speed.

• 대한기계학회논문집
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• 제12권2호
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• pp.231-240
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• 1988

본 연구에서는 외압을 받는 공기윤활 저어널 베어링의 정적인 경우에 대해 증분법과 유한요소법을 적용하고 유량계수는 실험을 근거로 하여 포켓에서 베어링 내부로 유입될 때의 유압손실을 고려한 Pink와 Stout의 값을 이용하였다.

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 2001년도 제34회 추계학술대회 개최
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• pp.197-203
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• 2001

In this paper, numerical analyses were undertaken to calculate the static and dynamic performances of step-pocket, inward pumping spiral grooved, outward pumping spiral grooved and herringbone grooved bearings. For each bearing, optimal values for various design parameters were obtained to maximize the load capacity and the stiffness and bearing performances were calculated. The optimized performances of these bearings were compared to conclude that the performance of step-pocket bearing is better than the other bearings.

• Tribology and Lubricants
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• 제18권5호
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• pp.364-370
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• 2002

In this paper, numerical analyses were undertaken to calculate the static and dynamic performances of step-pocket, inward pumping spiral grooved, outward pumping spiral grooved and herringbone grooved bearings. For each bearing, optimal values for various design parameters were obtained to maximize the load capacity and the stiffness and bearing performances were calculated. The optimized performances of these bearings were compared to conclude that the performance of step-pocket bearing is better than the other bearings.

• 자원ㆍ환경경제연구
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• 제11권4호
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• pp.659-687
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• 2002

This study used a discrete choice model to investigate an association between air pollution and hospital visits for acute respiratory symptoms with the national health interview survey conducted in 1998 in South Korea. The results showed that $NO_2$ and TSP were significantly related to hospital visits in a single-pollutant model, but when they were simultaneously considered, only $NO_2$ remained significant. It was estimated as $NO_2$ level increased by 10%(0.0027ppm) from 0.027ppm (the mean $NO_2$ level), hospital visits increase by 0.176%. This study also measured respondent's out-of-pocket expense and the time cost for commuting and waiting for the visit. We found that on the average, out-of-pocket expense is 5,600 won per hospital visit, but the total cost per hospital visit is measured at 33,440 won with time cost of commuting and waiting at 27,840 won. Time cost was over 63.6~83.3% of the total cost per hospital visit.

• 한국기계가공학회지
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• 제14권5호
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• pp.120-125
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• 2015

This research aims to increase the reliability and reproducibility of the ambient cycling test by properly making corrections to the test procedure. The vessel (106 L) is initially filled with 70 L of water and horizontally placed on a balance. The pressure range inside the vessel varies from 2.5 to 25.9 MPa at the frequency of 6 cycles per minute. After reviewing the results, there was a temperature difference of approximately $10^{\circ}C$ between the air pocket and the water, and the upper part of the liner faced a repeated temperature change of $40^{\circ}C$. It is possible for the aluminum liner of the composite vessel to be damaged by such a sharp change in temperature. Additionally, as a result, no pass having anything to do with the purpose of the test would occur. Therefore, it is suggested that the air pocket be completely removed.

• 한국의학물리학회지:의학물리
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• 제30권4호
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• pp.104-111
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• 2019

Purpose: Online magnetic resonance-guided adaptive radiotherapy (MRgART), an emerging technique, is used to address the change in anatomical structures, such as treatment target region, during the treatment period. However, the electron density map used for dose calculation differs from that for daily treatment, owing to the variation in organ location and, notably, air pockets. In this study, we evaluate the dosimetric effect of electron density override on air pockets during online ART for pancreatic cancer cases. Methods: Five pancreatic cancer patients, who were treated with MRgART at the Seoul National University Hospital, were enrolled in the study. Intensity modulated radiation therapy plans were generated for each patient with 60Co beams on a ViewrayTM system, with a 45 Gy prescription dose for stereotactic body radiation therapy. During the treatment, the electron density map was modified based on the daily MR image. We recalculated the dose distribution on the plan, and the dosimetric parameters were obtained from the dose volume histograms of the planning target volume (PTV) and organs at risk. Results: The average dose difference in the PTV was 0.86Gy, and the observed difference at the maximum dose was up to 2.07 Gy. The variation in air pockets during treatment resulted in an under- or overdose in the PTV. Conclusions: We recommend the re-contouring of the air pockets to deliver an accurate radiation dose to the target in MRgART, even though it is a time-consuming method.

• 콘크리트학회지
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• 제19권4호
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• pp.59-65
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• 2007

• Archives of Plastic Surgery
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• 제44권4호
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• pp.354-355
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• 2017