• Journal of Communications and Networks
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• 제9권2호
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• pp.198-209
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• 2007

This paper provides a thorough study on shared segment protection (SSP) for mesh communication networks in the complete routing information scenario, where the integer linear program (ILP) in [1] is extended such that the following two constraints are well addressed: (a) The restoration time constraint for each connection request, and (b) the switching/merging capacity constraint at each node. A novel approach, called SSP algorithm, is developed to reduce the extremely high computation complexity in solving the ILP formulation. Basically, our approach is to derive a good approximation on the parameters in the ILP by referring to the result of solving the corresponding shared path protection (SPP) problem. Thus, the design space can be significantly reduced by eliminating some edges in the graphs. We will show in the simulation that with our approach, the optimality can be achieved in most of the cases. To verify the proposed formulation and investigate the performance impairment in terms of average cost and success rate by the additional two constraints, extensive simulation work has been conducted on three network topologies, in which SPP and shared link protection (SLP) are implemented for comparison. We will demonstrate that the proposed SSP algorithm can effectively and efficiently solve the survivable routing problem with constraints on restoration time and switching/merging capability of each node. The comparison among the three protection types further verifies that SSP can yield significant advantages over SPP and SLP without taking much computation time.

• The Korean Journal of Physiology and Pharmacology
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• 제11권1호
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• pp.31-36
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• 2007

To elucidate a potential molecular link between diabetes and atherosclerosis, we investigated the role of Janus tyrosine kinase(JAK) for NAD(P)H oxidase-derived superoxide generation in the enhanced proliferative capacity of vascular smooth muscle cells(VSMC) of Otsuka Long-Evans Tokushima Fatty(OLETF) rat, an animal model of type 2 diabetes. An enhanced proliferative response to 10% fetal bovine serum(FBS) and superoxide generation with an increased NAD(P)H oxidase activity were observed in diabetic(OLETF) VSMC. Both the enhanced proliferation and superoxide generation in diabetic VSMC were significantly attenuated by AG490, JAK2 inhibitor, and PP2, Src kinase inhibitor. Tyrosine phosphorylation of proteins in diabetic VSMC, especially JAK2, was increased compared to control VSMC. Furthermore, the enhanced NAD(P)H oxidase activity in diabetic VSMC was significantly attenuated by AG490 in a dose-dependent manner. Together, these results indicate that the signal pathway which leads to diabetes-associated activation of Src kinase/JAK is critically involved in the diabetic VSMC proliferation through NAD(P)H oxidase activation and superoxide generation.

• Journal of Power Electronics
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• 제15권4호
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• pp.939-950
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• 2015

A single-stage AC-AC converter has been designed for a wind energy conversion system (WECS) that eliminates multistage operation and DC-link filter elements, thus resolving size, weight, and reliability issues. A simple switching strategy is used to control the switches that changes the variable-frequency AC output of an electrical generator to a constant-frequency supply to feed into a distributed electrical load/grid. In addition, a modified random sinusoidal pulse width modulation (RSPWM) technique has been developed for the designed converter to make the overall system more efficient by increasing generating power capacity and reducing the effects of inter-harmonics and sub-harmonics generated in the WECS. The technique uses carrier and reference waves of variable switching frequency to calculate the firing angles of the switches of the converter so that the three-phase output voltage of the converter is very close to a sine wave with reduced THD. A comparison of the performance of the proposed RSPWM technique with the conventional SPWM demonstrated that the power generated by a turbine in the proposed approximately increased by 5% to 10% and THD reduces by 40% both in voltage and current with respect to conventional SPWM.

• Journal of Information Processing Systems
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• 제5권3호
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• pp.151-158
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• 2009

This paper proposes a utility-based data rate allocation algorithm to provide high-quality mobile video streaming over femtocell networks. We first derive a utility function to calculate the optimal data rates for maximizing the aggregate utilities of all mobile users in the femtocell. The total sum of optimal data rates is limited by the link capacity of the backhaul connections. Furthermore, electromagnetic cross-talk poses a serious problem for the backhaul connections, and its influence passes on to mobile users, as well as causing data rate degradation in the femtocell networks. We also have studied a fixed margin iterative water-filling algorithm to achieve the target data rate of each backhaul connection as a counter-measure to the cross-talk problem. The results of our simulation show that the algorithm is capable of minimizing the transmission power of backhaul connections while guaranteeing a high overall quality of service for all users of the same binder. In particular, it can provide the target data rate required to maximize user satisfaction with the mobile video streaming service over the femtocell networks.

• 한국기계가공학회지
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• 제20권4호
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• pp.49-56
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• 2021

This paper describes the modeling and simulation of a four-axis dedicated robot that can attach and detach a workpiece on a computer numerical control (CNC) lathe. The robot was modeled as a Scarab robot for compatibility with CNC lathes. The advantages of such a robot are that an actuator with a small capacity can be used for the robot and the degrees of freedom of the robot can be reduced to four. For the simulation of the four-axis dedicated robot, a regular kinematic equation and an inverse kinematic equation were derived. Simulations were performed with these equations from the position of the loading device to the chuck position of the lathe before machining and from the chuck of the lathe to the position of the loading device after machining. The simulation results showed that the four-axis dedicated robot could be operated accurately, and they provided the joint angle of each motor (θ1, θ2, and θ3).

• 전력전자학회논문지
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• 제25권6호
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• pp.459-468
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• 2020

The pole interaction of the line-commutated converter high-voltage direct current (HVDC) is analyzed, and a practical solution that uses a surge arrester is proposed. Jeju HVDC No. 2 is a double-monopole HVDC link that has a rated power capacity of 2 × 200 MW and was commissioned in 2012. During normal operation, Jeju HVDC No. 2 is operated in the bipolar mode to minimize the loss caused by the dedicated metallic return. However, when one pole of the inverter valve is bypassed, a commutation failure can occur in the other pole. This phenomenon is called pole interaction in this work. This pole interaction interrupts the HVDC power transfer for almost 2 s and may affect the stability of the power system. This research proposes the installation of a surge arrester at the inverter neutral, which can be an effective and practical solution for pole interaction. The HVDC system is analyzed, and the residual voltage of the surge arrester is determined. Detailed simulation using PSCAD/EMTDC demonstrates that the proposed method eliminates the pole interaction of the bipolar-operated HVDC.

• Journal of Public Diplomacy
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• 제1권2호
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• pp.27-48
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• 2021

Remarkably, despite the growing frequency and severity of global problems such as climate change, earthquakes and health pandemics, public diplomacy has remained largely focused on the goals of state actors and threats from other actors. The Covid-19 pandemic exposed the consequences of focusing on individual actors of public diplomacy, including their competitive quest for soft power, over the more pressing needs of humanity and public diplomacy's global mandate. The aim of this piece is to expand the vision of soft power from a competitive state-centric perspective to a broader and more collaborative, humanity-centered perspective. Although public diplomacy's link to power may appear recent and linked to Nye's (2004) concept of soft power, research suggests that it may stem from the traditional diplomacy's "diplomacy of imperialism" (Langer, 1935) that immediately preceded public diplomacy's rise. While this diplomatic heritage may currently dominate public diplomacy perspectives, humankind's global heritages and evolutionary capacity for cooperation suggest another vision is possible. The paper draws upon Alexander Vuving's (2009) explanation of how soft power works in a comparative analysis with Nye's original works to sketch out a new humanity-centered perspective of soft power. The paper concludes with implications of a humanity-centered perspective of soft power for public diplomacy's global mandate.

• Structural Engineering and Mechanics
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• 제87권4호
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• pp.391-403
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• 2023

In this study, a new type of self-centering beam-column joint with tapered steel plate links is proposed. Firstly, mechanical property of the basic joint (with the prestressed steel strands only, to provide the self-centering ability) and the combined joint (with both the prestressed steel strands and tapered steel plate links, to provide self-centering and energy dissipation simultaneously) is theoretically analyzed. Then, three joints with different dimensions and combinations of tapered plate links are designed and tested through a series of quasi-static cyclic loading tests. Test results show that a nearly bilinear elastic moment-rotation relationship for the basic joint is obtained. With the addition of tapered steel plate links, typical flag-shape hysteretic curves are obtained, which indicates good self-centering and energy dissipating ability of the combined joint. By installing multiple tapered plate links, stiffness and bearing capacity of the beam-column joint can be enhanced. The theoretical moment-rotation relationships agree well with the test results. A simplified macro model of the proposed joint is developed using OpenSees, which simulates reasonably well its hysteretic behavior.

• 전기전자학회논문지
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• 제27권4호
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• pp.617-623
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• 2023

통신 망의 진화에 따라 대용량 데이터 기반의 안정적인 고속 데이터 연결이 필요한 서비스들이 증가하고 있다. 사용자의 단말로부터 취합된 패킷 데이터의 용량이 증가하면서 코어 네트워크로 전달하는 중간 링크인 백홀 네트워크의 지연에 대한 품질진단의 중요성이 대두되었다. 본 논문에서는 응용서비스 품질에 영향을 미치는 RTT(Round Trip Time) 지연과 성능저하의 원인이 될 수 있는 회선 대역폭(Bandwidth) 및 스위치 내 속도 불일치, 구간별 버퍼(Buffer) 사이즈, 라우팅 정책 등 여러 인자의 진단을 통하여 백홀 네트워크에서 문제를 해결할 수 있는 기법에 관해 실제 사례를 통해 연구를 진행하였다.

• 스마트미디어저널
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• 제12권9호
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• pp.72-80
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• 2023

본 논문에서는 다수의 환자가 발생하여 구급차를 통해 병원으로 이송하여야 하는 경우 최소비용 최대유량 알고리즘에 기반하여 병원을 배정 및 재배정하는 기법을 설계하고 성능을 평가한다. 환자의 증상과 병원들까지의 거리에 의해 플로우 그래프를 생성하는 과정, 링크 용량 수정 과정, 구급차와 병원 매칭 과정 등으로 구성되며 알고리즘 수행시간의 효율성으로 인해 추가환자의 발생이나 병원의 수용능력 변경에도 플로우 그래프 재구성에 의해 재배정을 수행할 수 있다. 프로토타입 구현에 의한 성능 평가 결과 주어진 실험 환경에 대해 제안된 기법은 순차 배정 방식에 비해 24%까지 이송요구시간 불만족을 감소시킬 수 있다.