• Journal of the Korean Society for Precision Engineering
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• v.15 no.9
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• pp.158-166
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• 1998

This paper presents a geometrical approach to the characteristic analysis of parallel mechanism with free joints intended for use as a planar task robot. Solution of the forward and inverse kinematic problems are described. Because the mechanism has only three degree-of-freedom output, constraint equations must be generated to describe the inter-relationship between actuated joints and free joints so as to describe the position and orientation of the moving platform. Once these constraints are incorporated into the kinematics model, a constrained Jacobian matrix is obtained. and it is used for the solution of the forward kinematic equations by Newton-Raphson technique. Another Jacobian matrix was derived to describe the interrelationship between actuated joints and moving platform. The stiffness, velocity transmission ratio, force transmission ratio and dexterity of the mechanism are then determined based on this another Jacobian matrix. The geometrical construction of the mechanism for the best performance was investigated using the characteristic analysis.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2018.06a
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• pp.92-95
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• 2018

가상 현실을 위한 360 영상 비디오 전송기술이 활발히 연구되고 있다. 그러나 현재 가상현실 기기의 컴퓨팅 연산능력과 대역폭은 고화질 360 영상을 재생하기에 한계가 있다. 이 한계를 극복하기 위해 본 논문은 High Efficiency Video Coding (HEVC)와 Scalability Extension of HEVC (SHVC)를 활용하여 타일 기반의 360 도 영상 전송 기법을 제안한다. 제안하는 HEVC 와 SHVC 인코더는 타일을 독립적으로 전송 할 수 있는 비트 스트림을 생성한다. 제안하는 추출기는 사용자 시점에 해당하는 타일의 비트 스트림을 추출한다. 제안하는 기법에 의해 추출된 SHVC 비트스트림의 기본계층은 전체화면을 나타내며, 강화계층은 사용자 시점에 해당하는 타일로 구성된다. 제안하는 HEVC 인코더를 사용할 때에는 저화질과 고화질을 따로 인코딩하여 고화질만 사용자 시점에 해당하는 타일을 추출한다. 전체화면을 고화질로 보내는 대신에 전체화면을 저화질로, 사용자화면을 고화질로 보내기 때문에 제안하는 기법은 디코더의 컴퓨팅 연산과 네트워크 bitrate 를 대폭 줄일 수 있다. 본 제안 기법의 실험 결과는 전체화면 전송 대비 47%이상의 bitrate 를 줄인다.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.9 no.1
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• pp.221-227
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• 2008

A vehicle routing problem with time constraint is one of the important problems in distribution and transportation. The service of a customer must start and finish within a given time interval. Our method is based on an improved operators of genetic algorithm and the objective is to minimize the cost of servicing the set of customers without being tardy or exceeding the capacity or travel time of the vehicles. This research shows that a proposed method based on the improved genetic search can obtain good solutions to vehicle routing problems with time constrained compared with a high degree of efficiency other heuristics. For the computational purpose, we developed a GUI-type computer program according to the proposed method and the computational results show that the proposed method is very effective on a set of standard test problems, and can be potentially useful in solving the vehicle routing problems.

• Journal of Biomedical Engineering Research
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• v.34 no.2
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• pp.55-62
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• 2013

Wrist joints consist of irregularly shaped carpal bones and other complicated structures. Thus, evaluating the motion of a wrist joint is a challenging task. In this study, we used an infrared camera to perform a kinematic analysis of a dart-throwing motion. We measured the difference between the movement of a normal wrist and constrained wrist (wrist with a wrist glove) in the dart-throwing motion with thirty six healthy participants. We measured the ulna flexion - radial extension motion using the attached passive marker and analyzed it using Polygon software and SPSS. The pitch and yaw motions with a glove was bigger than the ones without a glove by 20 and 15 degrees, respectively. On the other hand, the roll motion without a glove was bigger than the one with a glove by 7 degree. Wilcoxon signed rank test (p<0.05) confirmed that there are significant differences between the motion with and without a glove. It was found that the magnitude of the pitch and yaw motion with a constrained wrist joint toward radial extension in dart-throwing motion is smaller than the one with a normal wrist joint. However, a normal wrist joint showed a bigger movement in the roll direction.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2015.10a
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• pp.866-869
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• 2015

With the advance in semiconductor technology, the number of elements that can be integrated in system-on-chip(SoC) increases exponentially, and thus voltage scaling is indispensable to enhance energy efficiency. Near-threshold voltage computing(NTC) improves the energy efficiency by an order of degree, hence it is able to overcome the limitation of conventional super-threshold voltage computing(STC). Although NTC-based low performance manycore system can be used to maximize energy efficiency, it demands more number of cores to sustain the performance, which results in considerable increase of area. In this paper, we analyze NTC manycore architecture considering the trade-offs between performance, power, and area. Therefore, we propose an algorithmic methodology that can optimize power consumption and area while satisfying the required performance by determining the constrained number of cores and size of caches and clusters in NTC environment. Experimental results show that proposed NTC architecture can reduce power consumption by approximately 16.5 % while maintaining the performance of STC core under area constraint.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.25 no.5
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• pp.455-463
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• 2012

In this study, we calculate dynamic constrained force of tower top and blade root of a floating offshore wind turbine. The floating offshore wind turbine is multibody system which consists of a floating platform, a tower, a nacelle, and a hub and three blades. All of these parts are regarded as a rigid body with six degree-of-freedom(DOF). The platform and the tower are connected with fixed joint, and the tower, the nacelle, and the hub are successively connected with revolute joint. The hub and three blades are connected with fixed joint. The recursive formulation is adopted for constructing the equations of motion for the floating wind turbine. The non-linear hydrostatic force, the linear hydrodynamic force, the aerodynamic force, the mooring force, and gravitational forces are considered as external forces. The dynamic load at the tower top, rotor shaft, and blade root of the floating wind turbine are simulated in time domain by solving the equations of motion numerically. From the simulation results, the mutual effects of the dynamic response between the each part of the floating wind turbine are discussed and can be used as input data for the structural analysis of the floating offshore wind turbine.

• The Transactions of the Korea Information Processing Society
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• v.5 no.4
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• pp.1033-1043
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• 1998

In this paper, we present an improved multicasting path assignment algorithm based on the minimum cost spanning tree. In the method presented in this paper, a multicasting path is assigned preferentially when a node to be received is found among the next degree nodes of the searching node in the multicasting path assignment of the constrained steiner tree (CST). If nodes of the legacy group exist between nodes of the new group, a new path among the nodes of new group is assigned as long as the nodes may be excluded from the new multicasting path assignment taking into consideration characteristics of nodes in the legacy group. In assigning the multicasting path additionally, where the source and destination nodes which can be set for the new multicasting path exist in the domain of identical network (local area network) and conditions for degree constraint are satisfied, a method of producing and assigning a new multicasting path is used. The results of comparison of CST with MCSTOP, MCSTOp algorithm enhanced performance capabilities about the communication cost, the propagation delay, and the computation time for the multicasting assignment paths more than CST algorithm. Further to this, research activities need study for the application of the international standard protocol(multicasting path assignment technology in the multipoint communication service (MCS) of the ITU-T T.120).

• Journal of Korean Foot and Ankle Society
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• v.8 no.1
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• pp.11-15
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• 2004

Purpose: The aim of this study was to investigate the usefulness of mortise angle and fibular length measured in radiologic findings in predicting the ankle stability. Materials and Methods: One hundred cases fifty cases were randomly selected volunteers with normal ankle function and the other fifty cases were randomly selected patients whose ankle were treated in our hospital and who were followed for over 1 years with good results. A specific experimental fixture were made to get the even AP and lateral view and objective stress view. Results: The mortise angle and fibular length was not statistically significant to the degree of talar tilt angle under valgus or varus stress and that of displacement under anterior or posterior stress. Conclusion: The mortise angle and fibular length was not the objective predicting factors on the ankle stability. Maintenance of constrained talus in dynamic status is most important factors in determining the ankle stability.

• Smart Structures and Systems
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• v.14 no.5
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• pp.943-960
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• 2014

A visually servoed paired structured light system (ViSP) was recently proposed as a novel estimation method of the 6-DOF (Degree-Of-Freedom) relative displacement in civil structures. In order to apply the ViSP to massive structures, multiple ViSP modules should be installed in a cascaded manner. In this configuration, the estimation errors are propagated through the ViSP modules. In order to resolve this problem, a displacement estimation error back-propagation (DEEP) method was proposed. However, the DEEP method has some disadvantages: the displacement range of each ViSP module must be constrained and displacement errors are corrected sequentially, and thus the entire estimation errors are not considered concurrently. To address this problem, a pose-graph optimized displacement estimation (PODE) method is proposed in this paper. The PODE method is based on a graph-based optimization technique that considers entire errors at the same time. Moreover, this method does not require any constraints on the movement of the ViSP modules. Simulations and experiments are conducted to validate the performance of the proposed method. The results show that the PODE method reduces the propagation errors in comparison with a previous work.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2004.05a
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• pp.870-875
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• 2004

Beam stiffeners have frequently been used for raising natural frequencies of base structures. In stiffener layout optimization problems, most of the previous researches considering the position and/or the length of the stiffener as design variables dealt with structures having just simple convex shapes such as a square or rectangle. The reason is concave shape structures have difficulties ill formulating geometry constraints. In this paper, a new geometry constraint handling technique, which can define both convex and concave feasible lesions and measure a degree of geometry constraint violation, is proposed. Evolution strategies (ESs) is utilized as an optimization tool. In addition, the constraint-handling technique of EVOSLINOC (EVOlution Strategy for scalar optimization with Lineal and Nonlinear Constraints) is utilized to solve constrained optimization problems. From a numerical example, the proposed geometry constraint handling technique is verified and proves that the technique can easily be applied to structures in net only convex but also concave shapes, even with a protrusion or interior holes.