• 한국정밀공학회지
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• 제30권3호
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• pp.260-265
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• 2013

To increase the machine accuracy by improving the stiffness of spindle bearings, preload was applied to the spindle bearings. The methods of fixed position preload, convertible preload, constant pressure preload, and variable preload are used to apply the preload to the spindle bearing. The previous studies performed by the author of this study were variable preload methods using rubber pressure and centrifugal force based on mechanical systems. This study proposed a toggle joint mechanism that could be applied to variable preload method using centrifugal force and rubber pressure to increase the preload. Also, a finite element analysis was conducted to predict the deformation of the rubber and change of the preload. And the analysis results showed that the preload by the device using rubber pressure only was increased by the toggle joint mechanism using rubber pressure.

• 제어로봇시스템학회논문지
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• 제6권9호
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• pp.796-802
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• 2000

A master-slave system for teleoperation is usually used to control the robor's motion on remote place such as abyss, outer space etc.. When the slave robot is a humanoid one, it can make a better performance if the configuration of the master arm is similar to that of the slave arm and of the human. The master arm proposed in this paper has a type to be put on the human arm, that is, the exoskeleton type, and has a combination of serial joint and parallel mechanism imitating the human's arm structure of muscles and bones, so called hybrid mechanism so that it can follow arm's movement effectively. But it is easy to solve the forward kinematis of the parallel structure because relating equations are implicit functions. In order to solve that, the virtual joint angle corresponding to human arm's joint is introduced and a sequential computation step is employed in calculating virtual joint angles and the posture of the end effector. Also validity is checked up through computational simulation.

• Geomechanics and Engineering
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• 제13권3호
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• pp.431-446
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• 2017

Rock bridges in rock masses would increase the bearing capacity of Non-persistent discontinuities. In this paper the effect of ratio of rock bridge surface to joint surface, rock bridge shape and normal load on failure behaviour of intermittent rock joint were investigated. A total of 42 various models with dimensions of $15cm{\times}15cm{\times}15cm$ of plaster specimens were fabricated simulating the open joints possessing rock bridge. The introduced rock bridges have various continuities in shear surface. The area of the rock bridge was $45cm^2$ and $90cm^2$ out of the total fixed area of $225cm^2$ respectively. The fabricated specimens were subjected to shear tests under normal loads of 0.5 MPa, 2 MPa and 4 MPa in order to investigate the shear mechanism of rock bridge. The results indicated that the failure pattern and the failure mechanism were affected by two parameters; i.e., the ratio of joint surface to rock bridge surface and normal load. So that increasing in joint area in front of the rock bridge changes the shear failure mode to tensile failure mode. Also the tensile failure change to shear failure by increasing the normal load.

• The Journal of Korean Physical Therapy
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• 제12권3호
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• pp.433-444
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• 2000

The purpose is paper was to discuss current concepts related to anatomic stabilizing structures of the shoulder joint complex and their clinical relevance to shoulder instability. The clinical syndrome of shoulder instability represents a wide spectrum of symtoms and signs which may produce various levels of dysfunctions, from subtle subluxations to gross joint instability. The glenohumeral joint attains functional stability through a delicate and intricate interaction between the passive and active stabilizing structures. The passive constraints include the bony geometry, glenoid labrum, and the glenohumeral joint capsuloligaments structure. Conversely, the active constraints, also referred to as active mechanism, include the shoulder complex musculature, the projprioceptive system, and the musculoligamentous relationship. The interaction of the active and passive mechanism which provide passive and active glenohumeral joint stability will be throughtly discussed in this paper

• 대한기계학회논문집
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• 제14권6호
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• pp.1446-1454
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• 1990

본 연구에서는 다간극기구의 간극의 영향을 제거하기 위해 코일스프링의 사용 을 대안으로 제시하였다.

• 한국지능시스템학회논문지
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• 제26권3호
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• pp.196-201
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• 2016

본 논문에서는 인간의 팔꿈치 관절의 기능을 활성화하기 위한 강성 기반 재활 메커니즘의 특성을 분석하 고자 한다.여기서,팔굼치 관절의 재활을 위한 도구는 탄성 줄을 사용하고, 사용된 줄은 선형 스프링으로 모델링하여 강성값으로 나타낸다. 이러한 메커니즘을 이용한 팔꿈치 관절 재활 훈련을 효과적으로 하기 위해서는 줄의 강성값에 따라 팔꿈치 관절에 가용할 수 있는 토오크 특성을 분석할 필요가 있다. 이러한 관점에서 다양한 시뮬레이션을 통하여 탄성 줄의 강성값 설정에 따른 팔꿈치 관절의 토오크 패턴 및 범위를 사전에 정의된 팔꿈치 관절의 운동 경로에 대하여 확인한다. 결과적으로, 이러한 강성 기반 재활 메커니즘이 팔꿈치 관절의 효과적인 재활을 수행하는데 유용하게 활용될 수 있음을 보인다.

• Geomechanics and Engineering
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• 제13권6호
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• pp.977-995
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• 2017

It is well accepted that rock failure mechanism influence the cutting efficiency and determination of optimum cutting parameters. In this paper, an attempt was made to research the factors that affect the failure mechanism based on discrete element method (DEM). The influences of cutting depth, hydrostatic pressure, cutting velocity, back rake angle and joint set on failure mechanism in rock-cutting are researched by PFC2D. The results show that: the ductile failure occurs at shallow cutting depths, the brittle failure occurs as the depth of cut increases beyond a threshold value. The mean cutting forces have a linear related to the cutting depth if the cutting action is dominated by the ductile mode, however, the mean cutting forces are deviate from the linear relationship while the cutting action is dominated by the brittle mode. The failure mechanism changes from brittle mode with larger chips under atmospheric conditions, to ductile mode with crushed chips under hydrostatic conditions. As the cutting velocity increases, a grow number of micro-cracks are initiated around the cutter and the volume of the chipped fragmentation is decreasing correspondingly. The crack initiates and propagates parallel to the free surface with a smaller rake angle, but with the rake angle increases, the direction of crack initiation and propagation is changed to towards the intact rock. The existence of joint set have significant influence on crack initiation and propagation, it makes the crack prone to propagate along the joint.

• 기술혁신학회지
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• 제3권2호
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• pp.94-110
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• 2000

This article prospects the patterns of technological innovation in the steel industry and suggests the directions of technological innovation in Korean steel industry. Technological innovation patterns can be analysed through technological trends, innovation-inducing mechanism, and innovators' relationships. In the technological trends, direct coupling of manufacturing processes, lasting growth of mini-mill, and the importance of technological integration are prospected. In the innovation-inducing mechanism, while production system will be specialized, the development of new steel materials and environment-friendly technological innovation will be accelerated. In the innovators' relationships, steel industry faces more complex competition and new forms of inter-firm cooperation including M&A, joint venture, and joint R&D. In order to cope with such changes in the technological innovation patterns, Korean steel industry need to establish core competence based on technological innovation through a great leap in R&D investment, the production of high value-added products, the development of new generation steel technologies, strategic joint R&D, comprehensive technological cooperation, and government's active support.

• 한국의류학회지
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• 제20권5호
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• pp.852-859
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• 1996

The factors and mechanism of arm surface changes were analyzed by regression analysis for the relationship between changes in arm joint angle and arm surface changes, according to the direction of upper extremity motion. Body surface change patterns among subjects were tested also. Experiments were carried out on 3 female subjects of different body types to examine 26 motions in 4 directions for 4 upper extremity parts. The major conclusions of the study are as follows: 1. The expansion or contraction of arm surface length depends on the direction of upper extremity motion. 2. Arm surface length changes by linear expansion or contraction according to the joint angle of the direction of motion. The mechanism of arm surface changes is represented by a linear relation between arm surface changes and the (actors of the direction of upper extremity motion and arm joint angle. 3. Arm surface length shows the same pattern of body surface changes regardless of body type. A quantitative model of body surface changes at upper extremity should be developed for functional sleeve design.

• 대한기계학회논문집 C: 기술과 교육
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• 제1권2호
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• pp.153-165
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• 2013

기존의 보행분석 연구들은 하지를 하나의 스프링으로 간주하였다. 만약 슬관절 신전을 보조할 수 있는 슬관절 액추에이팅 메커니즘을 개발할 수 있다면 보행에 필요한 탄성-변형률에너지를 혁신적으로 저장-방출할 수 있고, 그 결과 보행 중 하지강성은 더욱 증가할 것이다. 게다가 족관절 액추에이팅 메커니즘까지 추가되어 있다면 슬관절 액추에이터에 의한 과도한 인공하지강성을 능동적이고 적절한 수준으로 보상해주는 기전으로 작동할 것이다. 만약 가속도에 의한 보행속도 증가를 방지하기 위해 인위적 감속통제를 작동시킨다면 불필요한 운동에너지의 방출이 발생되고 하지강성 액추에이터의 실효성은 의심을 받게 된다. 따라서 본 저자는 보행속도를 2개의 세그먼트에 의한 상대 각속도 조절기법을 이용하여 하지강성을 증가시킨다는 기본개념으로 슬-족관절 액추에이터 시스템을 개발하였다. 또한 족관절에 슬관절 액추에이팅에 대한 보상기전이 존재하는 경우, 족관절의 보상기전이 중족지절관절 경사각 및 보행속도 변화에 미치는 상호영향을 연구하였다.