• 한국농공학회지
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• 제38권2호
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• pp.133-144
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• 1996

To get accurate results, the realistic stress-strain relationships of soils are dependent on a number of factors such as soil types, density, stress levels and stress path. Such attempts are continuously being made by the developement of analytical models for soils incorporating all such factors. Isotropic compression-expansion test and a series of drained conventional triaxial tests with several stress path for Baekma river sand were performed to investigate parameters characteristics of Lade's single work hardening model dependant on the stress path. Using the computer program based on the regression analysis, the values of parameters for the model were determined. In conclusion, the parameters of Lade's model are little influenced by the stress paths. Though yield criterion parameters ( h, ${\alpha}$a) are much influenced by stress level and stress path, the parameters don't have influence on stress-strain behavior.

• 한국콘텐츠학회논문지
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• 제21권10호
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• pp.78-89
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• 2021

본 연구는 순차분석을 적용하여 직업능력개발훈련교사의 입직경로를 파악하고자 한다. 입직경로를 구체적으로 파악함으로써 체계적인 입직 준비를 위한 지원 방안 마련에 시사점을 줄 것으로 여겨진다. 특히, 본 연구에서는 직업능력개발훈련교사의 입직경로 단계별 빈도 분석, 변환 확률 분석, 유의도 검사 및 변환 상태 도식을 통해 직업능력개발훈련교사의 입직 경로의 단계별 관계를 제시하였다. 분석을 위해 직업능력개발훈련교사 자격을 취득하고 민간직업훈련기관에서 근무하고 있는 훈련교사의 응답 자료를 활용하였다. 연구결과로는 첫째, 직업능력개발훈련교사 입직을 위한 과거 경험 빈도수를 살펴보면 일 경험, 교직 훈련, 강사 경험의 비중이 높게 나타났다. 둘째, 직업능력개발훈련교사 입직 경로 단계에서 일 경험, 교직 훈련, 강사 경험이 후행 단계로의 이동에 가장 큰 영향을 미쳤다. 셋째, 직업능력개발훈련교사 입직경로는 일 경험-강의 경험-교직 훈련 경로가 높게 나타났다. 결과를 통해 직업능력개발훈련교사의 체계적 입직 준비를 위한 방안을 제안하였다.

• Safety and Health at Work
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• 제5권1호
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• pp.1-6
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• 2014

Background: Workflow interruptions during surgery may cause a threat to patient's safety. Workflow interruptions were tested to predict failure in action regulation that in turn predicts near-accidents in surgery and related health care. Methods: One-hundred-and-thirty-three theater nurses and physicians from eight Swiss hospitals participated in a cross-sectional questionnaire survey. The study participation rate was 43%. Results: Structural equation modeling confirmed an indirect path from workflow interruptions through cognitive failure in action regulation on near-accidents (p < 0.05). The indirect path was stronger for workflow interruptions by malfunctions and task organizational blockages compared with workflow interruptions that were caused by persons. The indirect path remained meaningful when individual differences in conscientiousness and compliance with safety regulations were controlled. Conclusion: Task interruptions caused by malfunction and organizational constraints are likely to trigger errors in surgery. Work redesign is recommended to reduce workflow interruptions by malfunction and regulatory constraints.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2002년도 춘계학술대회 논문집
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• pp.66-69
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• 2002

In the ideal forming theory(1), which has been deviously developed as a direct method for optimizing forming process, material elements are required to deform following the minimum plastic work path (or the proportional true strain path). Besides the general theory(2,3), specific ideal forming theories have been developed for membrane sheet forming(4) as well as two-dimensional steady bulk forming(5-7). In this work, the ideal forming theory was successfully applied for non-steady bulk forming under the plane strain condition. Here, the shape change complying with the minimum plastic work path, was effectively described by developing a numerical code based on the characteristic method. Numerical results obtained for a specific industrial part also include the optimum pre-forming shape and its evolving shape change to the final shape as well as the boundary traction history.

• 대한기계학회논문집A
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• 제21권12호
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• pp.1992-2007
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• 1997

A new algorithm for planning a collision-free path is developed based on linear prametric curve. In this paper robot is assumed to a point, and two linear parametric curve is used to construct a path connecting start and goal point, in which single intermediate connection point between start and goal point is considered. The intermediate connection point is set in polar coordinate(${\theta}{\delta}$) , and the interference between path and obstacle is mapped into CPS(connection point space), which is defined a CWS GM(circular work space geometry mapping). GM of all obstacles in workspace creates overlapping images of obstacle in CPS(Connection Point Space). The GM for all obstacles produces overlapping images of obstacle in CPS. The empty area of CPS that is not occupied by obstacle images represents collision-free paths in Euclidian Space. A GM based on connection point in elliptic coordinate(${\theta}{\delta}$) is also developed in that the total length of path is depend only on the variable .delta.. Hence in EWS GM(elliptic work space geometry mapping), increasing .delta. and finding the value of .delta. for collision-free path, the shortest path can be searched without carring out whole GM. The GM of obstacles expersses all possible collision-free path as empty spaces in CPS. If there is no empty space available in CPS, it indicates that path planning is not possible with given number of connection points, i.e. path planning is failed, and it is necessary to increase the number of connection point. A general case collision-free path planning is possible by appling GM to configuration space obstacles. Simulation of GM of obstacles in Euclidian space is carried out to measure performance of algorithm and the resulting obstacle images are reported.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 2000년도 춘계학술대회논문집 - 한국공작기계학회
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• pp.176-181
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• 2000

Collision free task planning for dual-arm robot which perform many subtasks in a common work space can be achieved in two steps : path planning and trajectory planning. path planning finds the order of tasks for each robot to minimize path lengths as well as to avoid collision with static obstacles. A trajectory planning strategy is to let each robot move along its path as fast as possible and delay one robot at its initial position or reduce speed at the middle of its path to avoid collision with the other robot.

• 가족자원경영과 정책
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• 제23권3호
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• pp.43-74
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• 2019

The purpose of this study is to analyze the effect of perceptions of work and family life on employee job satisfaction and to form a policy approach that contributes to the enhancement of worker satisfaction. In particular, we wanted to analyze how the characteristics of each variable appeared in industry groups with different gender ratios of workers. A notable point of the study was that the respondents who answered that work and family had similar importance were satisfied with their working conditions. In addition, it was found that the higher an employee's evaluation of the work-family reconciliation policy, the higher the employee's satisfaction with their working conditions. As a result of a path analysis, it was found that the most male-dominant industry was manufacturing, and the most female-dominant industry was health and social welfare. In the case of respondents who were employed in the most-male dominant industry, the degree of an employee's understanding of the work-family reconciliation policy recognition, rather than the relative priorities of work and family life, had a greater effect on job satisfaction. On the other hand, respondents who were employed in the most-female dominant industry confirmed that their level of education was highly related to the degree of institutional recognition.

• 한국농공학회지
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• 제40권6호
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• pp.95-103
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• 1998

Solutions of geotechnical engineering problems require calculation of deformation and stresses during various stages of loading. Powerful numerical methods are available to make such calculation even for complicated problems. To get accurate results, realistic stress-strain relationships of soil are dependent on a number of factors such as soil type, density, stress level and stress path. Attempts are continuously being made to develope analytical models for soils incorporating all such factors. The nature of stress-path dependency, the principle that governs deformations in sand, and the use of Lade's single work-hardening model for predicting sand response for a variety of stress-paths have been investigated and are examined. The test results and the analyses presented show that under some conditions sand exhibits stress-path dependent behavior. The strains calculated from Lade's single work-hardening model are in reasonable agreement with those measured, but some discrepancies occur. The largest difference between measured and calculated strains occurs for proportional loading with increasing stresses and for stress-path directions.

• 한국정밀공학회지
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• 제27권1호
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• pp.76-83
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• 2010

There have been many studies regarding development of autonomous excavation system which is helpful in construction sites where repetitive jobs are necessary. Unfortunately, bucket trajectory planning was excluded from the previous studies. Since, the best use of excavator is to dig efficiently; purpose of this research was set to determine an optimized bucket trajectory in order to get best digging performance. Among infinite ways of digging any given path, criterion for either optimal or efficient bucket moves is required to be established. One method is to adopt work know-how from experienced excavator operator; However the work pattern varies from every worker to worker and it is hard to be analyzed. Thus, other than the work pattern taken from experienced operator, we developed an efficiency model to solve this problem. This paper presents a method to derive a bucket trajectory from optimization theory with empirical CLUB soil model. Path is greatly influenced by physical constraints such as geometry, excavator dimension and excavator workspace. By minimizing a energy function under these constraints, an optimal bucket trajectory could be obtained.

• International Journal of Control, Automation, and Systems
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• 제4권3호
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• pp.318-324
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• 2006

The mobile manipulator is expected to work in partially defined or unstructured environments. In our global/local approach to path planning, joint trajectories are generated for a desired Cartesian space path, designed by the global path planner. For a local path planner, inverse kinematics for a redundant system is used. Joint displacement limit for the manipulator links is considered in the motion planner. In an event of failure to obtain feasible trajectories, the task cannot be accomplished. At the point of failure, a deviation in the Cartesian space path is obtained and a replanner gives a new path that would achieve the goal position. To calculate the deviation, a nonlinear optimization problem is formulated and solved by standard Sequential Quadratic Programming (SQP) method.