• 한국지반환경공학회 논문집
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• 제14권6호
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• pp.39-46
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• 2013

지반개량분야에서는 수많은 공법들이 지금까지 발전을 거듭하여 개발되어왔다. 그러나 대부분의 공법들은 지반의 강도 증진에만 중점을 두었으며 환경문제 발생에 대한 구체적인 해결방안을 제시하지 못하고 있다. 이에 최근에 들어 친환경적으로 지반의 강도를 증대시키는 방법으로 유기산 재료를 이용한 지반개량이 개발되어왔으나 아직 근본적인 안정화 메커니즘에 대해서는 잘 알려지지 않았다. 따라서 본 연구에서는 친환경 개량재인 유기산 재료를 활용한 일축압축강도시험 및 pH시험을 통해 안정화 메커니즘에 대해 규명하였다. 그 결과, 유기산 처리가 된 샘플이 유기산 처리가 되지 않은 샘플보다 시간에 따른 더 큰 일축압축강도를 보였다. 또한, 유기산 재료에 의해 미생물들의 증식이 촉진되며, 토양의 공극 감소를 통해 토양이 개량된다는 것을 규명할 수 있었다. 향후 유기산 재료를 활용한 지반개량 공법의 지속적인 연구가 필요하다고 사료된다.

• 대한금속재료학회지
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• 제48권7호
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• pp.598-604
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• 2010

Tensile tests are widely used for evaluating mechanical properties of materials including flow curves as well as Young's modulus, yield strength, tensile strength, and yield point elongation. This research aims at analyzing the plastic flow behavior of high strength steels for automotive bodies using the finite element method in conjunction with the viscoplastic model considering the yield point elongation phenomenon. The plastic flow behavior of the high strength steel was successfully predicted, by considering an operating deformation mechanism, in terms of normalization dislocation density, and strain hardening and accumulative damage of high strength steel using the modified constitutive model. In addition, the finite element method is employed to track the properties of the high strength steel pertaining to the deformation histories in a skin pass mill process.

• 콘크리트학회논문집
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• 제23권6호
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• pp.817-826
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• 2011

에코시멘트를 이용한 콘크리트는 장기강도 발현이 취약한 문제가 지적되고 있지만 현재까지 그 원인이 불분명하여 구조재료로써 널리 사용되지 않고 있다. 이 연구에서는 에코시멘트를 이용한 콘크리트의 장기강도 발현에 미치는 양생 습도의 영향을 검토함과 동시에 강도 특성과 세공구조의 관계에 대해 검토하였다. 그 결과, 수중양생을 실시한 높은 물-시멘트비 공시체에서 심각한 장기강도 정체가 나타났다. 이것은 재령이 경과하여도 10 nm이상의 세공량이 감소하지 않는 것에 기인하고 있다. 반면, 기중양생의 경우에는 에코시멘트에서도 안정적인 장기강도 증진이 확인되었다. 나아가, 에코시멘트를 보다 안정된 재료로 사용하고자 보통 포틀랜드 시멘트 및 미분쇄 플라이애쉬 혼입에 의한 장기강도 개선에 관한 연구를 실행하였다. 그 결과, 이 연구 범위 내에서 장기강도 개선을 기대할 수 있었고, 더불어 재령이 경과함에 따라 세공구조가 치밀해지는 효과를 얻을 수 있었다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제11권2호
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• pp.1201-1216
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• 2017

In this study, we described the development of a methodology to measure tip-pinch strength on the paretic hand rehabilitation device and aimed to investigate reliability of the device. FSR sensors were embedded on the device, and tip pinch strength was estimated with data collected from the sensors using a developed equation while participants were demonstrating tip pinch. Reliability tests included inter-rater, test-retest, and inter-instrument reliability. B&L Engineering pinch gauge was utilized for the comparison. Thirty-seven healthy students participated in the experiment. Both inter-rater and test-retest reliability were excellent as Intraclass Correlation Coefficients (ICCs) were greater than 0.9 (p<0.01). There were no statistically significant differences in tip-pinch strengths. Inter-instrument reliability analysis confirmed good correlation between the two instruments (r = 0.88, p < 0.01). The findings of this study suggest that the two instruments are not interchangeable. However, the tip-pinch mechanism used in the paretic hand rehabilitation device is reliable that can be used to evaluate tip pinch strength in clinical environment and can provides a parameter that monitors changes in the hand functions.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2003년도 ICCAS
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• pp.1495-1499
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• 2003

There is some equipment that helps user to exercise and to walk. But almost all equipments require some physical strength of their muscles. So we developed a system that could assist walking action of the people with lower-limb disability. The system called as walking stand adopted the balancing mechanism which assures the stable walking, and the 4 link-based mechanism that had 2 degrees of freedom on each leg. The walking stand uses four motors and has two sets of the special link-structure to simulate the human walking mechanism. With our system, even serious disabled with lower-limb disability may enjoy walking rehabilitation. And by adjusting the power, it can be used as the walking assistant mechanism instead of conventional wheelchairs. Experiments showed that our walking stand is applicable to the rehabilitation and also to the mobile device in our daily life for those people who do not have enough physical ability to walk by themselves.

• Tribology and Lubricants
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• 제13권2호
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• pp.27-38
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• 1997

ER clutch is a device using ER fluid, so called "intelligent material" and is a power transmission system controlled with electric field strength. This device responses very rapidly when controlled by rapid and continuous electrical signal and can form a servosystem. Wear, noise and vibration during operation is very low level. This study was undertaken to investigate substitutive possibilities of this ER clutch for existing power transmission mechanism. An analytic relationships using rheological model (so called, 'Bingham plastic model') of ER fluid were developed, and operation constraints and optimum design concepts were constructed. With this relationships, typical responses of ER clutch and effects of changing geometric, kinetic parameters of ER clutch and ER fluid properties were described. In conclusion, compared with existing mechanisms, an excellent performance of ER clutch was confirmed.confirmed.

• 산업경영시스템학회지
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• 제38권4호
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• pp.226-232
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• 2015

The aging of Korea is rapidly advancing in an unprecedented rate in the world. Indoor and outdoor safety accidents involving the elderly frequently occur, with elderly population increasing. Because the physical strength of elderly is decreased, it is necessary to develop devices that aid the everyday life of the elderly to prevent safety accidents. Among many activities, the motions of standing from and sitting on a chair require much physical strength from particular body parts, which causes an overload for particular body parts. To the elderly the repeating motion of standing from and sitting down on a chair is burdensome, because they do not have enough physical strength compare to young persons. As a result the elderly could be injured or falling during standing or sitting. Therefore, the development of a lift chair that considers the problems mentioned above is necessary to prevent the safety accidents of the elderly. The study designed a non-motorized lift chair that comfortably aids the standing and sitting down motion for the use of the elderly by reflecting the anthropometric data of the Korean elderly over 65 years old. Also the design was implemented to smoothly aid the standing motion by considering the knee angle of the elderly when standing. Because the regained strength to stand from a chair is depend on the knee angle. Unlike existing lift devices, this device utilizes a tilting mechanism that does not use electric power so that the product could be composed inexpensively than existing chairs released in the market.

• 한국구조물진단유지관리공학회 논문집
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• 제18권1호
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• pp.84-92
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• 2014

본 연구는 조강시멘트와 경화촉진제를 사용하여 조기강도 발현의 메커니즘을 분석하는 것이 목적이다. 연구결과 경화촉진제는 시멘트와의 수화반응시 $Ca(OH)_2$의 촉진시키는 것을 TG/DTA 실험을 통하여 검정하였다. 압축강도 측정결과 경화촉진제의 사용량이 증가 할수록 초기압축강도가 증가하는 것을 알 수 있었다. 또한 미소수화열 측정결과 경화촉진제는 시멘트의 성분중 $C_3S$의 수화반응을 촉진시키는 것으로 나타났다. XRD분석결과 재령별 수화생성물을 확인할 수 있었으며 경화촉진제의 사용량이 증가할수록 수화물들의 피크점이 높게 나타나는 것을 알 수 있었다. SEM찰영을 한 결과 촉진제의 첨가량에 따라 $Ca(OH)_2$의 생성과 재령에 따라 C-S-H의 형상을 관찰할 수 있었다. 따라서 본 연구에서 사용된 경화촉진제는 초기강도발현 시키는 것에 대해 효과적인 것을 확인 할 수 있었다.

• 한국군사과학기술학회지
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• 제26권4호
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• pp.313-323
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• 2023

The wearable robot system is designed to assist human skeletal and muscular systems for enhancing user's abilities in various fields, including medical, industrial, and military. The military has an expanding need for wearable robots with the integration of surveillance/control systems and advanced equipment in unstructured battlefield environments. However, there is a lack of research on the design and mechanism of wearable robots, especially for power assist systems. This study proposes a lightweight wearable robot system that provides comfortable wear and muscle support effects in various movements for soldiers performing high-strength and endurance missions. The Power assist mechanism is described and verified, and the tasks that require power assist are analyzed. This study explain the system including its driving mechanism, control system, and mechanical design. Finally, the performance of the robot is verified through experiments and evaluations, demonstrating its effectiveness in muscle support.

• 대한기계학회논문집
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• 제17권11호
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• pp.2752-2761
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• 1993

The purpose of this study is to confirm the decreasing problems of residual bending strength, and the fracture machanism experimentally when CFRP composite laminates are subjected to Foreign Object Damage. Composite laminates used for this experiment are CFRP orthotropy laminated plates, which have two-interfaces [O/sub 6//sup o//90/sub 6//sup o/]sub sym/ and four-interfaces [O/sub 3//sup o//90/sub 6//sup o//O/sub 3//sup o]/sub sym/. When the specimen is subjected to transverse impact by a steel ball, the delamination area generated by impact damage is observed by using SAM(Scanning Acoustic Microscope). also, Thefracture surfaces obtained by three-point bending test were observed by using SEM (Scanning Electron Microscope). Then, fracture mechanism was investigated based on the observed delamination area and fracture surface. The results were summarized as follows; (1) It is found that for the specimen with more interface, the critical delamination energy is increased while delamination-development energy is decreased. (2) Residual bending strength of specimen A is greater than that of Specimen B within the impact range of impact energy 1. 65J (impacted-side compression) and 1. 45J (impacted-side tension). On the other hand, when the impact energy is beyond the above ranges, residual bending strength of specimen A is smaller than that of specimen B. (3) In specimen A and B, residual strength of CFRP plates subjected to impact damage is lower in the impacted-side compression than in the impacted-side tension. (4) In the case of impacted-side compression, fracture is propagated from the transverse crack generat-ed near impact point. On the other hand, fracture is developed toward the impact point from the edge of interface-B delamination in the case of impacted-side tension.