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Share Liquidity and Market Microstructure Reform: The Case of Screen-based Trading in Mumbai
Ronny Manos,Christopher J. Green,Victor Murinde,Nathridee Suppakitjarak 한국증권학회 2010 Asia-Pacific Journal of Financial Studies Vol.39 No.3
We investigate the impact of the March 1995 move to screen-based trading on the Mumbai Stock Exchange, using separate samples of more liquid (A) and less liquid (B) shares. Following the move, the average cumulative abnormal return for A shares was 4.5%, whereas that for B shares was over 12%; market liquidity and efficiency increased but the effect on volatility was more ambiguous. We identify a significant cross-sectional relationship between the size of cumulative abnormal returns and firm-specific improvements in liquidity, efficiency, and volatility, with differences in the effects of reform on A and B shares.
김용호(Ronny Yongho Kim),김백(Baik Kim) 한국철도학회 2013 한국철도학회 학술발표대회논문집 Vol.2013 No.5
동일 급전구간 내에서 열차의 동시다중 기동 상황 또는 연장 급전이 시행되는 경우에는 운행 차량들이 역률 1.0 의 양호한 부하특성을 갖는 경우라 할 지라도 계통의 무효전력 손실이 급격히 증가하게 되며 이에 따라 전압안정도가 저하되고, 심각한 경우에는 전압붕괴의 가능성도 발생하게 된다. 본 논문에서는 진상 및 지상역률 대에서 가변적으로 역률을 제어할 수 있는 PWM컨버터 차량을 대상으로 전역최적화 문제의 해를 통하여 개별 열차의 최적무효전력 보상량을 구하고, 조류계산 자코비안의 특이치를 이용하여 이 결과가 급전선로의 전압안정도 향상에 미치는 영향을 연구하였다. 표본계통 시뮬레이션 결과, 상당한 수준의 전압안정도 향상을 이룰 수 있음을 알 수 있었다. In case of extended feeding or simultaneous multi starts within the same feeding system, even though the trains in service have favorable load characteristics of p.f. 1.0, the reactive power loss of the feeder becomes great and this makes the voltage stability worse or in the most severe case leads to the voltage collapse eventually. In this paper, the optimal reactive power compensation of each PWM train, which has the controllability of p.f. over both leading and lagging region, has been studied through the solution of global optimization problem of the feeding section. In addition, by using the singular values of load flow’s Jacobian, the effects of the optimization to the improvement of voltage stability have been studied. The results from the simulation to the sample system show that the voltage stability of the system has been improved to the considerable revel.
KIM, Ronny Yongho,JUNG, Inuk,KIM, Young Yong The Institute of Electronics, Information and Comm 2010 IEICE transactions on fundamentals of electronics, Vol.93 No.8
<P>IEEE 802.16m is an advanced air interface standard which is under development for IMT-Advanced systems, known as 4G systems. IEEE 802.16m is designed to provide a high data rate and a Quality of Service (QoS) level in order to meet user service requirements, and is especially suitable for mobilized environments. There are several factors that have great impact on such requirements. As one of the major factors, we mainly focus on latency issues. In IEEE 802.16m, an enhanced layer 2 handover scheme, described as Entry Before Break (EBB) was proposed and adopted to reduce handover latency. EBB provides significant handover interruption time reduction with respect to the legacy IEEE 802.16 handover scheme. Fast handovers for mobile IPv6 (FMIPv6) was standardized by Internet Engineering Task Force (IETF) in order to provide reduced handover interruption time from IP layer perspective. Since FMIPv6 utilizes link layer triggers to reduce handover latency, it is very critical to jointly design FMIPv6 with its underlying link layer protocol. However, FMIPv6 based on new handover scheme, EBB has not been proposed. In this paper, we propose an improved cross-layering design for FMIPv6 based on the IEEE 802.16m EBB handover. In comparison with the conventional FMIPv6 based on the legacy IEEE 802.16 network, the overall handover interruption time can be significantly reduced by employing the proposed design. Benefits of this improvement on latency reduction for mobile user applications are thoroughly investigated with both numerical analysis and simulation on various IP applications.</P>
김용호(Ronny Yongho Kim),김백(Baik Kim) 한국철도학회 2014 한국철도학회 학술발표대회논문집 Vol.2014 No.10
PWM컨버터 차량은 변조지수와 상차각의 조정을 통하여 연속적으로 지상 및 진상영역대에서의 운전이 가능하며 이를 이용하여 전기차량 자체를 이동형 무효전력 보상장치로 활용할 수 있다. 본 논문에서는 급전계통에서 요구되는 유효전력 및 무효전력 보상량을 제어기가 추종함에 있어 가선 전압의 변동에 따른 안정성을 시뮬레이션을 통하여 검토하였으며 가선전압의 변동 범위 내에서 안정성에 문제가 없음을 알 수 있었다. PWM converter trains can be operated continuously either in the leading P.F. region or in the lagging P.F. region by controlling the modulation index and the power angle. By this property, the electric vehicle itself can be exploited as a kind of movable reactive power compensator. In this paper, the stability of PWM controller according to the variation of line voltage has been studied through simulations as the controller follows the required active demand and reactive compensation. The simulation results show that the controller holds stable within the limit of the voltage variation.
급전선로 손실 최소화를 위한 PWM컨버터 차량의 무효전력 제어
김용호(Ronny Yongho Kim),김백(Baik Kim) 한국철도학회 2012 한국철도학회 학술발표대회논문집 Vol.2012 No.10
PWM컨버터 차량은 전압벡터제어방식에 의해 부하역률 1.0에 가까운 운전이 가능하므로 기존의 위상제어 차량에 비해 우수한 부하특성을 나타내나 이 경우에도 급전구간 내의 운전밀도가 높거나 연장급전 구간에서는 선로손실의 증가 및 전압강하 현상이 심각한 수준으로 나타날 수 있다. 본 논문은 PWM컨버터 차량의 역률을 1.0으로 고정하여 운행하는 대신 차량의 운전 조건에 따라 가변적으로 최적 제어함으로써 급전선로의 손실을 최소화 하고 전압 프로파일을 개선하는 방법을 기술하였다. 제시된 방법은 급전구간 내에 운행중인 전체 차량을 대상으로 최대 경사법에 의해 선로손실이 최소화되는 무효전력 보상량을 결정하게 되며, 이 방법을 표본 계통에 대해 시뮬레이션 한 결과 전압 프로파일도 상당한 수준으로 개선됨을 알 수 있었다. PWM converter trains exhibit excellent load characteristics in comparison with the conventional phase controlled trains since they can be operated at near unity power factor by using the voltage vector control. However, in case of high track density or extended feeding, here as elsewhere, the line loss and the voltage drop can appear significantly. Instead of operating the trains at the fixed unity power factor, this paper suggests the continuous control of the power factors of each train according to the varying load conditions to minimize the line loss and improve the voltage drop optimally. The proposed method utilizes the steepest descent algorithm targeting all the cars in a feeding section to set the optimal reactive power compensation that minimize the line losses. The results from the simulation to the sample system show that the voltage drop also can be improved.