• 오토저널
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• 제12권5호
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• pp.97-106
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• 1990

A method of weight evaluation of the load-bearing structural elements of cars is presented and the weight ratio of the analysis model is investigated. Replacing the materials of floor elements of the car into the high-strength steel, a considerable weight-reduction of the model has been obtained. The 1500cc model is selected for the present study and the stick model analysis is employed for the structural analysis. The torsional stiffness of the weight-reduced model is also evaluated and it is shown it has a reasonable rigidity. The ratio of the weight of the load-bearing structural elements to the unladen vehicle weight of cars is about 0.12for the 1500cc model and the weight-reduction of this study can be obtained around 17% of the weight of the load-bearing structural elements.

• 대한통합의학회지
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• 제5권4호
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• pp.21-30
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• 2017

Purpose : This research intends to identify the effects of game-based weight bearing exercises on balance, muscular activation, sit to stand to sit motions of stroke patients. Method : 30 patients who were diagnosed as hemiplegia by stroke less in than a year were sampled and they were classified into two group, one of which was game-based weight bearing balance exercise group, and the other was functional weight bearing exercise group. 15 people were randomly selected for each group. Each exercise was coordinated by this research for 8 weeks, 5 days a week. 3D motion analyzer was used to measure the sit to stand to sit motions and a stopwatch was used to measure the time for stand-up motions for 5 times. Result : In terms of analyzing sit to stand to sit motions by phases, game-based weight bearing balance exercise group showed significant reduction compared to functional weight-bearing exercise group in phase I, II, III, IV and total time. In terms of functional stand-up performance analysis, game-based weight bearing balance exercise group showed significant reduction compared to functional weight-bearing exercise group in 5 times stand-up examination. Conclusion : It was verified that game-based weight bearing balance exercise had positive impact on function recovery of stroke patients by enhancing sit to stand to sit capabilities. It is considered that game-based exercise was an effective intermediary for functional improvement of stroke patients, while also inducing consistent and voluntary participation by causing interest and motivation.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1997년도 춘계학술대회 논문집
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• pp.312-317
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• 1997

This paper present an optimum design for the rotor-bearing system of a high-speed (80000RPM) ultra-centrifuge supported by ball bearings with nonlinear stiffness characteristics. To obtain the nonlinear bearing stiffnesses, a ball bearing is modelled in five degrees of freedom and is analyzed quasi-statically. The dynamic behaviors of the nonlinear rotor-bearing system are analyed by using a transfer-matrix method iteratively. For optimum design, minimizing the weight of a rotor is used as a cost function and the Augmented Lagrange Multiplier (ALM) method is employed. The result shows that the rotor-bearing system is optimized to obtain 8% weight reduction.

• 재활복지공학회논문지
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• 제7권2호
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• pp.101-107
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• 2013

본 연구는 이중 벨트 트레드밀을 이용하여 좌우 독립적 보행 시 횡축 체중부하 감소 유무에 따른 하지 근력불균형 개선효과에 대해 고찰하고자 한다. 피험자들은 하지의 좌우 근력차이가 20% 이상인 자 20명이며 체중부하 감소 유무에 따라 각각 10명씩 그룹으로 나누었다. 실험은 보행운동을 격일로 40분씩 주 3회, 총 4주간 진행되었으며 2주마다 등속성 관절토크 검사를 실시하여 고관절, 슬관절 및 족관절의 최대근력과 평균일률을 평가하였다. 실험 결과, 고관절에서 가장 큰 하지의 좌우 최대근력 불균형 개선효과(12.51%)를 보였으며 슬관절에서는 근반응성 개선효과(10.66%)가 크게 나타났다. 체중부하 감소방법은 하지의 근력불균형 개선효과에 긍정적인 결과를 기대할 수 있다고 사료된다.

• 한국정밀공학회지
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• 제15권6호
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• pp.145-152
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• 1998

This paper presents an optimum design of a rotor-bearing spindle system for a ultra centrifuge (80,000 RPM) supported by ball bearings with nonlinear stiffness characteristics. To obtain the nonlinear bearing stiffnesses, a ball bearing is modeled in five degrees of freedom and is analyzed quasi-statically. The dynamic behaviors of the nonlinear rotor-bearing system are analyzed by using a transfer-matrix method iteratively. For optimization. we use the cost function that simultaneously minimizes the weight of a rotor and maximizes the separation margins to yield the critical speeds as far from the operating speed as possible. Augmented Lagrange Multiplier (ALM) method is employed for the nonlinear optimization problem. The result shows that the rotor-bearing spindle system is optimized to obtain 9.5％ weight reduction and 21％ separation margin.

• Tribology and Lubricants
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• 제39권3호
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• pp.94-101
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• 2023

Automotive wheel bearings are a critical component of vehicles that support their weight and facilitate rotation. Life and stiffness are significant performance characteristics of wheel bearings. Designing wheel bearings involves finding optimal design variables that satisfy both performances. CO₂ emission reduction and fuel efficiency regulations attribute to the recent increase in design requirements for lightweight and compact automotive parts while maintaining performance. However, achieving a design that maintains performance while reducing weight poses challenges, as performance and weight are generally inversely proportional. In this study, we perform design optimization of automotive wheel bearings considering life and stiffness. We develop a program that calculates the basic rated life and modified rated life based on international standards for evaluating the life of wheel bearings. We develop a regression equation using regression analysis to address the time-consuming stiffness analysis during repetitive analysis. We perform ANOVA and main effect analyses to understand the statistical characteristics of the developed regression equation. Furthermore, we verify its reliability by comparing the predicted and test results. We perform design optimization using the developed life prediction program, stiffness regression equation and weight regression equation. We select bearing specifications and geometry as design variables, weight as the cost function, and life and stiffness as constraints. Through design optimization, we investigate the influence of design variables on the cost function and constraints by comparing the initial and optimal design values.

• 한국전문물리치료학회지
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• 제16권4호
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• pp.31-36
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• 2009

Hemiplegia-induced immobilizatoin and reduction of mechanical loading in chronic stroke limbs are common cause of disuse osteoporosis. The purpose of this study was to investigate the effects of asymmetrical weight bearing on the loss of bone mineral in the individual with chronic stroke. Sixteen hemiplegic patients with strokes were evaluated. The measurements of bone mineral density (BMD) were evaluated with the quantitative ultrasound system on the calcaneus region of the paretic and non-paretic side. Plantar pressure was measured using the Mat-Scan system. The paretic side showed significantly smaller values in the T-score of BMD, and peak value of plantar pressure, which included forefoot, midfoot, and hindfoot, than the non-paretic side (p<.05). Results from the pearson correlation analysis showed statistically significant correlation between the BMD difference and the peak-pressure difference of midfoot pressure (p<.05). This finding indicated that BMD loss depended on decrease of body weight born on the paretic leg.

• 대한기계학회논문집A
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• 제40권6호
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• pp.595-602
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• 2016

자동차용 휠 베어링은 회전운동을 전달하고 차량의 무게를 지지해주는 중요한 부품이다. 최근 $CO_2$ 배출가스 저감과 연비 규제에 따라서 자동차 경량화 및 소형화 요구는 점점 증가하고 있고, 이에 부응하여 베어링의 수명 평가기술은 더욱 그 필요성이 증가하고 있다. 휠 베어링의 내구수명은 고려해야 할 인자들이 매우 다양하며 이들이 서로 복잡하게 연관되어 있으므로 수명을 예측하는 것이 쉽지 않다. 본 논문에서는 자동차용 휠 베어링의 수명에 영향을 끼치는 많은 인자들 중에서 작동하중과 회전속도를 변화시키면서 수명을 시험하였고, 이를 ISO 국제표준에서 제안하는 이론수명인 기본정격수명과 보정정격수명 결과와 비교하였다. 이들 수명을 비교한 결과, 기본정격수명과 보정정격수명 모두 시험수명과 차이가 존재하며, 기본정격수명 보다 보정정격수명이 시험수명을 상대적으로 잘 예측함을 알 수 있었다.

• 한국지반신소재학회논문집
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• 제14권3호
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• pp.21-29
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• 2015

인공어초는 해양환경을 개선하고 어류와 해양생물들에게 주거지를 제공하는 인공 수중 구조물이다. 특히 인공어초가 느슨한 모래, 연약한 점성토와 같은 연약지반에 설치될 경우 인공어초의 자중에 의해 인공어초의 침하가 발생하게 된다. 본 연구에서는 관입실험을 통해 토목섬유 보강 넓이에 따른 인공어초의 지지력 보강효과를 확인하였고, 실내 대형 토조 실험을 통해 침하 저감효과를 확인하였다. 관입실험과 실내 대형 토조 실험을 통해 지오그리드와 같은 토목섬유를 인공어초 하부에 포설하게 되면 지지력이 증가하며, 침하가 감소하는 경향을 나타내었다.

• 대한기계학회논문집
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• 제19권3호
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• pp.639-646
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• 1995

The objective of this study is to minimize the weight of a damped anisotropic roto-bearing system considering whirl natural frequency and stability. The system is modeled as an assemblage of rigid disks, flexible shafts and discrete bearings. The system design variables are the crosssectional areas of shaft elements and the properties of bearings. To analyze the system, the polynomial method which is derived by rearranging the calculations performed by a transfer matrix method is adopted. For the optimization, the optimization software IDOL (Integrated Design Optimization Library) which is based on the Augmented Lagrange Multiplier (ALM) method is employed. Also, an analytical design sensitivity analysis of the system is used for high accuracy and efficiency. To demonstrate the usefulness of the proposed optimal design program incorporating analysis, design sensitivity analysis, and optimization modules, a damped anisotropic rotor-bearing system is optimized to obtain 34$ weight reduction.