• Proceedings of the Korean Statistical Society Conference
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• 2002.11a
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• pp.129-132
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• 2002

네트워크를 설계하거나 평가하는데 있어 중요한 문제 중 하나는 그 네트워크를 구성하는 요소들간의 상대적 중요도(importance)에 관한 문제이다. 이런 중요도를 나타내는 여러 가지 측도들 중 하나인 Joint Reliability Importance(JRI)는 Hong & Lie(1993)에 의해 소개되었으며, 네 가지 파생된 서브그래프의 신뢰성을 구하여 JRI를 계산하는 방법이 제시되었다. 본 연구에서는 minimal path set을 이용하여 파생되는 서브 그래프 신뢰성 계산에서의 중복되는 계산과정을 줄임으로써 JRI를 보다 효율적으로 구하는 방법을 제시하고자 한다.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.10 no.11
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• pp.3066-3073
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• 2009

Joint paths of master and branch pipes are induced mathematically for many kinds of joint patterns between both pipes in 3-axis pipe profile-cutting machines. By compensating them with a kerf width, the real cutting paths are determined, and their CL-data are generated, and the tool paths generated by CL-data are verified by a ghost function. A bevelling of welds is implemented through tilting a cutting torch in the $\beta$-axis direction for 8 sections in the chuck rotation of $\alpha$-axis. A PLC controls simultaneously position and velocity in a real time for $\alpha$, X, $\beta$-axis by loading CL-data generated. We developed the PLC-controlled 3-axis pipe profile-cutting system which can cut a master or branch pipe along the cutting path and simultaneously do a bevelling process.

• 제어로봇시스템학회:학술대회논문집
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• 1990.10a
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• pp.135-139
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• 1990

In general, the control of robot arms falls into two board categories (position control and force control). The joint interpolated trajectory schemes generally interpolate the desired joint path by a class of polynomial functions and generate a sequence of time based control set points for the control of a manipulator from a initial location to its destination. A digital position controller was designed and adapted to the industrial balancing manipulator. And also, the joint interpolated trajectory using 3rd order polynomial was generated in this study. The IBM PC used as the main controller and the trajectory planner had enough run-time capabilities. The 8097BH microcontroller is an integral pan of the joint controller which directly controls an axis of motion. The PI servo control system to treat each joint of the robot arm as a independent joint servo mechanism had satisfying performance, and a sequence of time-based intermediate configurations of the manipulator hand showed good continuity and smoothness on position and velocity of the manipulator's joint coordinates along the trajectory.

• Transactions of the Korean Society of Mechanical Engineers
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• v.17 no.10
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• pp.2437-2445
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• 1993

In this work, a new method is presented for generating the manipulator path which significantly reduces residual vibration under the torque constraints. The desired path is optimally designed so that the required movement can be achieved with minimum residual vibration. From the previous research works, the dynamic model had been established including both the link and the joint flexibilities. The performance index is selected to minimize the maximum amplitude of residual vibration. The path to be designed is developed by a combined Fourier series and polynomial function to satisfy both the convergence and boundary condition matching problems. The concept of correlation coefficients is used to select the minimum number of design variables, i.e. Fourier coefficients, the only ones which have a considerable effect on the reduction of residual vibration. A two-link Manipulator is used to evaluate this method. Results show that residual vibration can be drastically reduced by selecting an appropriate manipulator path to both of unlimited and torque-limited cases.

• The Transactions of the Korean Institute of Electrical Engineers D
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• v.54 no.3
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• pp.131-140
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• 2005

Fault-tolerant gait generation of a hexapod robot with crab walking is proposed. The considered fault is a locked joint failure, which prevents a joint of a leg from moving and makes it locked in a known position. Due to the reduced workspace of a failed leg, fault-tolerant crab walking has a limitation in the range of heading direction. In this paper, an accessible range of the crab angle is derived for a given configuration of the failed leg and, based on the principles of fault-tolerant gait planning, periodic crab gaits are proposed in which a hexapod robot realizes crab walking after a locked joint failure, having a reasonable stride length and stability margin. The proposed crab walking is then applied to path planning on uneven terrain with positive obstacles. i.e., protruded obstacles which legged robots cannot cross over but have to take a roundabout route to avoid. The robot trajectory should be generated such that the crab angle does not exceed the restricted range caused by a locked joint failure.

• IE interfaces
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• v.25 no.3
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• pp.365-375
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• 2012

An Unmanned Aerial Vehicle (UAV) is a powered pilotless aircraft, which is controlled remotely or autonomously. UAVs are an attractive alternative for many scientific and military organizations. UAVs can perform operations that are considered to be risky or uninhabitable for humans. UAVs are currently employed in many military missions and a number of civilian applications. For accomplishing the UAV's missions, guarantee of survivability should be preceded. The main objective of this study is to suggest a mathematical programming model and a $A^*PS$_PGA (A-star with Post Smoothing_Parallel Genetic Algorithm) for Multiple UAVs's path planning to maximize survivability. A mathematical programming model is composed by using MRPP (Most Reliable Path Problem) and MTSP (Multiple Traveling Salesman Problem). After transforming MRPP into Shortest Path Problem (SPP),$A^*PS$_PGA applies a path planning for multiple UAVs.

• Journal of muscle and joint health
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• v.19 no.2
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• pp.142-151
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• 2012

Purpose: This study was to explore the relationships among emotional labor, social support, job satisfaction, organizational commitment, and turnover intention in healthcare providers. Methods: Participants were healthcare providers (54 male and 328 female) with a mean age of 30.28 years old. Data analysis were done with PASW 18.0 for descriptive statistics and AMOS 5.0 for path analysis. Results: The hypothetical path model showed a good fit to the empirical data (${\chi}^2$=4.178, df=2, p= .124, GFI= .997, NFI= .995, NNFI= .987, RMSEA= .053). Emotional labor, job satisfaction, and organizational commitment had significant direct effects on turnover intention. Social support had a significant direct effect on emotional labor, job satisfaction and organizational commitment, and indirect and total effect on turnover intention. Conclusion: These findings suggest that turnover prevention or education programs for healthcare providers should include maintaining good mood when interact with patients or visitors with various negative moods in healthcare setting. Further strategies may need to resolve emotional labor, enhance job satisfaction and organizational commitment, and provide social support.

• 제어로봇시스템학회:학술대회논문집
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• 1989.10a
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• pp.635-642
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• 1989

We formulated the multi-robot trajectory problem into a series of NLP problem, each of which is that of finding the optimal tip positions of the robots for the next time step. The NLP problem is composed of an objective function and three constraints, namely: a) Joint position limits, b) Joint velocity limits, and c) Collision-avoidance constraints. By solving a series of NLP problem, optimally coordinated trajectories can be determined without requiring any prior path information. This is a novel departure from the previous approach in which either all paths or at least one path is assumed to be given. Practical application of the developed method is for optimal synthesis of multiple robot trajectories in off-line. To test the validity and effectiveness of the method, numerical examples are illustrated.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 1998.10a
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• pp.248-253
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• 1998

Recently, the uses of Ceramic/metal bonded joints, resin/metal joints, adhesive joints, composite materials which are composed of dissimiliar materials have increased in various industry fields. Since the ceramic/metal bonded joints material is made at a high temperature, residual stress distributions due to differences in material properties were investigated by varying material parameters. The two dimensional finite element analysis was performed to study residual stress distribution in Si3N4/SM45C bonded joint with a copper interlayer between the silicon nitride(Si3N4) and the structural carbon steel(SM45C) and 4-point bending tests were carried out under room temperature. Fracture surface and crack propagation path were observed using scanning electron microscope and characteristics of its fracture was discussed.

• Journal of Welding and Joining
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• v.34 no.3
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• pp.6-11
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• 2016

Joining Al/Fe dissimilar metals is becoming a subject of special interest in the assembly of automotive parts as a trade-off between the weight lightening and the cost reduction. Although various studies have been introduced to join Al alloy with the steel sheet by fusion welding, weak joint strength and galvanic corrosion still remained as problems to be solved. As a solid state welding, friction stir welding has been preferred to fusion welding processes in the dissimilar metal joints. This study investigated friction stir spot welding (FSSW) of Al alloy to the thin steel sheet with a thickness of 0.65 mm. The conventional FSSW is a stationary spot welding process but new approach adopted an additional circumferential movement in company with high speed tool rotation. A full factorial experimental design was implemented, and the main and interaction effects of parameters were analysed on the failure load in the tensile shear test. The direction and radius of rotation were statistically significant parameters and these two parameters affected the joint width and the shape of the hook.