• 한국정보과학회:학술대회논문집
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• 한국정보과학회 2008년도 한국컴퓨터종합학술대회논문집 Vol.35 No.1 (D)
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• pp.476-479
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• 2008

Wireless Sensor Network typically incorporates various real time applications that must meet timing constraints under severe resource limitations. Due to the high data rate and burst traffic for that type of applications, occurrence of congestion is very common. Ensuring the end-to-end deadline under congested scenario is quite challenging. In this paper we propose a hop-by-hop rate control algorithm which avoids the congestion as well as ensures that the real time traffic will meet the end-to-end deadline by guaranteeing the meeting of local deadline at intermediate hop. Finally, simulation has demonstrated the effectiveness of our approach.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제10권12호
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• pp.5174-5190
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• 2016

Recent years have witnessed an explosive growth of mobile devices, mobile cloud computing services offered by these devices and the remote clouds behind them. In this paper, we noticed ultra-low latency service, as a type of mobile cloud computing service, requires extremely short delay constraints. Hence, such delay-sensitive applications should be satisfied with strong QoS guarantee. Existing solutions regarding this problem have poor performance in terms of throughput. In this paper, we propose an end-to-end bandwidth resource reservation via software defined scheduling inspired by the famous SDN framework. The main contribution of this paper is the end-to-end resource reservation and flow scheduling algorithm, which always gives priority to delay sensitive flows. Simulation results confirm the advantage of the proposed solution, which improves the average throughput of ultra-low latency flows.

• 전자통신동향분석
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• 제38권2호
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• pp.36-45
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• 2023

Segment routing (SR) is a source-based routing architecture in which a node steers packets adhering to service and topological requirements. Using programmable segments, SR enables end-to-end service connectivity to satisfy the network constraints of various services. SR can be implemented with both MPLS and IPv6 dataplanes. This survey presents the overview of SR for IPv6 dataplane (SRv6), network programming technologies based on SRv6, and the SR deployment status.

• 한국안전학회지
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• 제11권2호
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• pp.116-121
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• 1996

On the stability of Timoshenko cantilever beam subjected to a follower force, the influence of the characteristics of elastic constraints at the free end Is studied. The equations of motion and boundary conditions of this nonconservative elastic system are estabilished by using the Hamilton's principle. Upon evaluation of the stability of this system, the effect of shear deformation and rotatory inertia is considered in calculation. Using cowper's formulae Timoshenko's shear coefficient K'are determined. From this imvestigation it is found that the constrain parameter have an appreciable stabilizing effect in this nonconservative system. Moreover, it is obvious that the small values of K'decrease the flutter load of this system.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제10권12호
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• pp.5191-5211
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• 2016

It is essential to satisfy class-specific QoS constraints to provide broadband services for new generation networks. The present study proposes a QoS-driven multicast scheme for wireless networks in which the transmission rate and end-to-end delay are assumed to be bounded during a multiple multicast session. A distributed algorithm was used to identify a cost-efficient sub-graph between the source and destination which can satisfy QoS constraints of a multicast session. The model was then modified as to be applied for wireless networks in which satisfying interference constraints is the main challenge. A discrete power control scheme was also applied for the QoS-aware multicast model to accommodate the effect of transmission power level based on link capacity requirements. We also proposed random power allocation (RPA) and gradient power allocation (GPA) algorithms to efficient resource distribution each of which has different time complexity and optimality levels. Experimental results confirm that the proposed power allocation techniques decrease the number of unavailable links between intermediate nodes in the sub-graph and considerably increase the chance of finding an optimal solution.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2006년 추계학술발표대회 개요집
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• pp.89-91
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• 2006

An analysis of a multi-pin remote welding for a DUPIC fuel fabrication was made to establish the optimum welding processes in a hot cell environment. An initial investigation for hands-on fabrication outside the hot cell was performed, and the constraints of a hot cell welding were considered. Preliminary welding performances to improve the RW process were also examined. The RW process was determined to be the best in a hot cell environment for joining the end plate to the end caps. This paper presents an outline of the developed RW machine for a DUPIC fuel fabrication and compares the characteristics of a Zr-4 end plate welding by using electrical resistance and LB methods. The weld nuggets of RW specimens and torque strengths of resistant and LB welded zones were also investigated.

• 로봇학회논문지
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• 제17권1호
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• pp.32-39
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• 2022

Since the mobile platform and the manipulator mounted on it move at the same time in a mobile manipulator, the risk of mutual collision increases. Most of the studies on collision avoidance of mobile manipulators cannot be applied to differential drive type mobile platforms or the end-effector tends to deviate from the desired trajectory for collision avoidance. In this study, a collision avoidance algorithm based on null space projection (CANS) that solves these two problems is proposed. To this end, a modified repulsive force that overcomes the non-holonomic constraints of a mobile platform is generated by adding a virtual repulsive force in the direction of its instantaneous velocity. And by converting this repulsive force into a repulsive velocity and applying it to the null space, the end-effector of the robot avoids a collision while moving along its original trajectory. The proposed CANS algorithm showed excellent performance through self-collision avoidance tests and door opening tests.

• 한국인터넷방송통신학회논문지
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• 제22권5호
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• pp.43-48
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• 2022

최근 모바일 기기의 성능이 급격히 향상되고 다양한 앱이 등장하면서 대화형 작업뿐 아니라 실시간 작업을 동반하는 앱이 늘고 있다. 한편, 실시간 작업은 데드라인 제약 조건이 있어 종래의 시분할 시스템이 추구하던 자원 관리 정책으로는 실시간 제약 조건을 만족하는 데에 한계가 있다. 본 논문에서는 모바일 기기에서 대화형 작업과 실시간 작업이 동시에 실행될 때 CPU, 메모리, 스토리지로 이어지는 종단간 자원 관리를 어떻게 함으로써 실시간 작업의 제약 조건을 만족하면서 자원의 효율적인 관리가 가능한지에 대해 알아본다. 본 논문에서는 복잡한 자원관리 정책의 제안보다 각 자원들이 실시간 작업의 조건을 만족하기 위해 필요한 기본 개념에 대해 살펴보는 데에 초점을 맞춘다. CPU의 경우 실시간 작업을 위한 전담코어 할당, 메모리의 경우 워킹셋의 일정 비율을 보장하는 방식, 스토리지의 경우 고속 스토리지를 사용하고 문맥교환을 생략하는 방식 등 기본적인 지원 방안을 알아보고 이를 어떻게 효율화할 수 있는지에 대해 알아본다.

• 한국정밀공학회지
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• 제12권12호
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• pp.165-172
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• 1995

Many algorithms to enhance a speed performance of a robot have been studied, but it's rare to consider disign aspect of a robot arm for time optimal problem. In this paper, section demensions of a robot arm and a velocity profile of an end-effector were optimally designed to minimize the cycle time. Capacity of actuators, deflections of end-effector, and a fundamental natural frequency of the robot arm were constrained in optimal design. For a given path with a trapezoidal velocity profile, torques of each joint were calculated using the inverse kinematics and dynamics. For the SCARA type robot which is mainly used for assembly tasks, the time optimal design of each robot arm id presented with the above constraints.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1993년도 한국자동제어학술회의논문집(국제학술편); Seoul National University, Seoul; 20-22 Oct. 1993
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• pp.486-490
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• 1993

In addtion to a basic motion task, redundant manipulators can achieve some additional tasks by optimizing proper performance criteria. Some of performance criteria can be transformed to inequality constraints. So the redundancy resolving problem can be reformulated as a local optimization problem with equality constraints for the end effector and inequality constraints for some performance criteria. In this article, we propose a method for solving the inverse kinematics of a manipulator with redundancy using the Kuhn-Tucker theorem to incorporate inequality constraints. With proper choice of inequality constraints, the proposed method gives a way of optimizing multiple criteria in redundant manipulators.