• 한국정밀공학회지
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• 제33권3호
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• pp.173-181
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• 2016

This paper reports on the development of a roller-cam clutch mechanism. This mechanism can transfer bidirectional torque with high backdrivability, as well as increase actuation energy efficiency, in electrical exoskeleton robots. The developed mechanism was installed at the robot knee joint and unclutched during the swing phase which uses less metabolic energy, thereby functioning as a passive joint. The roller-cam clutch aimed to increase actuation energy efficiency while also producing high backdrivability by generating zero impedance for users during the swing phase. To develop the mechanism, mathematical modeling of the roller-cam clutch was conducted, with the design having more than three safety factors following optimization. Titanium (Ti-6AL-4V) material was used. Finally, modeling verification was done using ANSYS software.

• 대한의용생체공학회:의공학회지
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• 제14권1호
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• pp.23-30
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• 1993

We investigated the structural geometry of thirty-eight Korean femurs. The purpose of this study is to identify major geometrical differences between Korean femurs and others that we believe belong to Caucasians so that we would be able to get insights into the femoral component design that fits Asians including Koreans. We utilized computerized nomography (CT) images of femurs extracted from cadavers. The CT images were transformed into bitmap data by using a film scanner, and then analyzed by using a commercially available software called Image v.1.0 and a Macintosh loci computer. The resulting data were compared with already published data. The major results show that the geometry of the Korean femurs is significantly different from that of Caucasians: (1) the anteversion angle and the canal (tare Index are greater by the amount of approximately 8" and 0.5, respectively, (2) the shape of the isthmus cross section is more round , and (3) the distance between the lesser trochanter and the proximal border of the isthmus is shorter by about 15 mm. The results suggested that the femoral component suitable for Asians should be dif- ferent (rom the currently-used components designed and manufactured mostly by European or American companies.

• Structural Engineering and Mechanics
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• 제53권5호
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• pp.1051-1066
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• 2015

The study aims on the effect of material dependency in elastic- plastic contact models by contact analysis of sphere and flat contact model and wheel rail contact model by considering the material properties without friction. The various materials are selected for the analysis based on Young's modulus and yield strength ratio (E/Y). The simulation software 'ANSYS' is employed for this study. The sphere and flat contact model is considered as a flattening model, the stress and strain for different materials are estimated. The simulation of wheel-rail contact model is also performed and the results are compared with the flattening model. The comparative study has also been extended for finding out the mean contact pressure for different materials the E/Y values between 150 and 660. The results show that the elastic-plastic contact analysis for materials up to E/Y=296.6 is depend on the nature of material properties and also for this material the mean contact pressure to yield strength reaches 2.65.

• 대한의용생체공학회:의공학회지
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• 제7권2호
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• pp.113-116
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• 1986

We investigated the structural geometry of thirty-eight Korean femurs. The purpose of this study is to identify major geometrical differences between Korean femurs 3nd others that we believe belong to Caucasians so that we would be able to get insights into the femoral component design that fits Asians including Koreans. We utilized computerized tomography (CT) images of femurs extracted from cadavers. The CT images were transformed into bitmap data by using a film scanner, and then analyzed by using a commercially available software called Image v.1.0 and a Macintosh IIci computer.The resulting data were compared with already published data. The major results show that the geometry of the Korean femurs is significantly different from that of Caucasians: (1) the anteversion angle and the canal flare index are greater by the amount of approximately 8˚ and 0.5, respectively, (2) the shape of the isthmus cross section is more round, and (3) the distance between the teaser trochanter and the proximal border of the isthmus is shelter by about 15 mm. The results suggested that the femoral component suitable for Asians should be different from the currently-used components designed and manufactured mostly by European or American companies.

• Structural Engineering and Mechanics
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• 제64권1호
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• pp.59-69
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• 2017

The field of fracture mechanics has gained significance because of its ability to address the behaviour of cracks. Predicting the fracture properties of concrete based on experimental investigations is a challenge considering the quasi-brittle nature of concrete. So, there is a need for developing a standard numerical tool which predicts the fracture energy of concrete which is at par with experimental results. The present study is an attempt to evaluate the fracture energy and characteristic length for different grades of concrete using Concrete Damage Plasticity (CDP) model. Indian Standard and EUROCODE are used for the basic input parameters of concrete. Numerical evaluation is done using Finite Element Analysis Software ABAQUS/CAE. Hsu & Hsu and Saenz stress-strain models are adopted for the current study. Mesh sensitivity analysis is also carried to study the influence of type and size of elements on the overall accuracy of the solution. Different input parameters like dilatation angle, eccentricity are varied and their effect on fracture properties is addressed. The results indicated that the fracture properties of concrete for various grades can be accurately predicted without laboratory tests using CDP model.

• Structural Engineering and Mechanics
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• 제67권4호
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• pp.391-401
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• 2018

Locally available Stainless Steel Wire Mesh (SSWM) bonded on a concrete surface with an epoxy resin is explored as an alternative method for the torsional strengthening of Reinforced Concrete (RC) beam in the present study. An experiment is conducted to understand the behavior of RC beams strengthened with a different configuration of SSWM wrapping subjected to pure torsion. The experimental investigation comprises of testing fourteen RC beams with cross section of $150mm{\times}150mm$ and length 1300 mm. The beams are reinforced with 4-10 mm diameter longitudinal bars and 2 leg-8 mm diameter stirrups at 150 mm c/c. Two beams without SSWM strengthening are used as control specimens and twelve beams are externally strengthened by six different SSWM wrapping configurations. The torsional moment and twist at first crack and at an ultimate stage as well as torque-twist behavior of SSWM strengthened specimens are compared with control specimens. Also the failure modes of the beams are observed. The rectangular beams strengthened with corner and diagonal strip wrapping configuration exhibited better enhancement in torsional capacity compared to other wrapping configurations. The numerical simulation of SSWM strengthened RC beam under pure torsion is carried out using finite element based software ABAQUS. Results of nonlinear finite element analysis are found in good agreement with experimental results.

• Journal of Astronomy and Space Sciences
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• 제18권2호
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• pp.145-152
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• 2001

태양의 극자외선 복사를 연구하기 위한 인공위성 탑재용 소형 극자외선 태양망원경의 공학 모형을 설계하였다. 극자외선 태양망원경은 $584.3AA$(He I)과 $629.7AA$(OV)의 두 파장대역에서 태양을 관측하기 위한 목적으로 설계되었다. 광학계는 Ritchey-Chr 샤두 방식이고, 망원경의 유효구경과 유효 초점 거리는 각각 80mm, 640mm이다. 회전 필터 휠을 사용하여 He I과 OV 방출선을 관측할 수 있도록 하였다. 검출기의 MCP (Microchannel Plate)는 채널 길이 대 직경의 비가 40:1인 Z-stack 타입이고, photocathode로서 KBr이 MCP 초점면에 코팅되며, MCP와 CCD는 fiber optic taper로 연결되도록 디자인하였다. 광학계 설계에 대한 분석은 광학계산용 상용 소프트웨어를 이용하였다.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2004년도 전력전자학술대회 논문집(2)
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• pp.862-865
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• 2004

Faults such as broken rotor bars, static and dynamic eccentricity are often reported in induction motors. These faults increase the down-time of equipment, which causes major loss of earnings to the industry. This paper presents a result of the finite-element(FE) analysis of air-gap flux variation in induction motors when rotor vibration conditions occur, An accurate modelling and analysis of rotor vibration in the machine are developed using FE software packages, and measuring the flux are made using the search coils. In the FE analysis, an induction motor with 380 [V], 5[HP], 4 Poles, 1742 [rpm] ratings is used. The results of FE analysis can be used for on-line vibration monitoring of the induction motors.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2001년도 하계학술대회 논문집 B
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• pp.1070-1072
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• 2001

In recent years, customers and power supplies are interested in power quality. Demands of customers are change from standard quality of distribution power system to various high quality of distribution power system. so, it is necessary to apply power quality compensator, in our project, we develop the power quality compensator of 150kVA which compensates power factor and voltage sag, interruption. it is very frequently occurred power qualify problems[1,2]. As a series and shunt compensator, power quality compensator consists of two inverters with common do link capacitor bank. It compensates the current quality in the shunt part and the voltage qualify in the series part. In this paper we present the design and control algorithm of power quality compensator. As a control algorithm is implemented by digital controller, we consider sample-and-hold of signals. In this simulation, we use EMTDC/PSCAD V3.0 software which can simulate instantaneous voltage and current.

• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 2006년도 Proceedings of ISRS 2006 PORSEC Volume I
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• pp.220-223
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• 2006

The COMS(Communication, Ocean and Meteorological Satellite) EPS(Electrical Power Subsystem) is derived from an enhanced Eurostar 3000 EPS which is fully autonomous operation in normal conditions or in the event of a failure and provides a high level of reconfiguration capability and flexibility. This paper introduces the COMS EPS preliminary design result. The COMS EPS consists of a battery, a solar array wing, a PSR(Power Supply Regulator), a PRU(Pyrotechnic Unit), a SADM(Solar Array Drive Mechanism) and relay and fuse brackets. This can offer a bus power capability of 3 kW. The solar array is made of a deployable wing with two panels. One type of solar cells is selected as GaAs/Ge triple junction cells. Li-ion battery is base lined with ten series cell module of five cells in parallel. PSR associated with battery and solar array generates a power bus fully regulated 50 V. Power bus is centralised protection and distribution by relay and fuse brackets. PRU provides power for firing actuators devices. The solar array wing is routed by the SADM under control of the AOCS(Attitude Orbit Control Subsystem). The control and monitoring of the EPS especially of the battery, is performed by the PSR in combination with on-board software.