PRINCIPAL-PRINCIPAL AGENCY PROBLEM AND SHAREHOLDER ACTIVISM: THE RISE OF MINORITY SHAREHOLDER MOVEMENT IN KOREA 2001-2008

Heejung Byun,Tae-Hyun Kim 한국인사ㆍ조직학회 2013 한국인사ㆍ조직학회 발표논문집 Vol.2013 No.1

Drawing from the social movement perspective of corporate governance, we explore the underlying dynamics of agency conflict between controlling shareholders and minority shareholders, namely principal-principal agency problem. We argue that tunneling of resources from publicly traded firms to business group affiliates could be used as a device of minority shareholder expropriation and show how it is guided by motives of controlling families. In response, we explore how minority shareholder activism acts as a possible means through which minority shareholder accesses corporate governance in order to alleviate the principal-principal agency problem. Using rich related party transactions data of inter-firm purchases, sales, debts, and loans within Korean business groups, we examine how and why controlling shareholders in publicly traded firms wield their power over the firms and shift resources out from the firms to generate private benefit. We show how minority shareholder movement gained its presence in Korea and test the efficacy of minority shareholder activism in reducing related party transactions.

A Data Dissemination Protocol with Delay Constraints for Wireless Sensor Networks

Heejung Byun,Sugook Son 한국정보통신학회 2015 2016 INTERNATIONAL CONFERENCE Vol.7 No.1

Wireless sensor networks (WSNs) generally consist of densely deployed sensor nodes that depend on batteries for energy. The WSN systems have several applications from target tracking to environment monitoring. Recently, there is an increased interest in the design of WSN protocols for mission-critical applications, such as military surveillance, health monitoring, and infrastructure security. These applications require capability of sending data with different real time requirements. However, due to strict resource constraints of the sensor nodes, WSNs pose critical challenges in network protocol design for the mission-critical applications. In this paper, we propose an epidemic-inspired node scheduling scheme (ENS) with aim of delay guaranteeing. The ENS controls the state of sensor node depending on the application’s specific requirement under dynamic network environments. Simulation results indicate that the ENS achieves globally optimal behavior with reliable delay guarantees.

Cellular-Automaton-Based Node Scheduling Control for Wireless Sensor Networks

Heejung Byun,Junglok Yu IEEE 2014 IEEE Transactions on Vehicular Technology VT Vol.63 No.8

<P>Wireless sensor networks (WSNs) generally consist of densely deployed sensor nodes that depend on batteries for energy. Having a large number of densely deployed sensor nodes causes energy waste and high redundancy in sensor data transmissions. The problems of power limitation and high redundancy in sensing coverage can be solved by appropriate scheduling of node activity among sensor nodes. In this paper, we propose a cellular automata (CA)-based node scheduling algorithm for prolonging network lifetime with a balance of energy savings among nodes while achieving high coverage quality. Based on a CA framework, we propose a new mathematical model for the node scheduling algorithm. The proposed algorithm uses local interaction based on environmental state signaling for making scheduling decisions. We analyze the system behavior and derive steady states of the proposed system. Simulation results show that the proposed algorithm outperforms existing protocols by providing energy balance with significant energy savings while maintaining sensing coverage quality.</P>

An energy efficient delay guaranteeing node coordination scheme inspired by biological systems

Heejung Byun,Sugook Son 한국정보통신학회 2014 2016 INTERNATIONAL CONFERENCE Vol.6 No.1

In this paper, we propose an energy efficient and delay guaranteed node coordination scheme inspired by biological systems, which have gained considerable attention as a computing and problem solving technique. We introduce both a local status indicator and an active status indicator for a sensor node to represent its local environmental conditions and its node state in WSNs, respectively. With the identification of analogies between cellular signaling systems and WSN systems, we formulate a new mathematical model that considers the networking challenges of WSNs. The proposed bio-inspired algorithm determines the state of the sensor node, as required by each application and as determined by the local environmental conditions and the states of the adjacent nodes. Simulation results indicate that the proposed scheme provides significant energy savings, as well as reliable delay guarantees by controlling the states of the sensor nodes.

Adaptive Duty Cycle Control with Queue Management in Wireless Sensor Networks

Heejung Byun,Junglok Yu IEEE 2013 IEEE transactions on mobile computing Vol.12 No.6

<P>This paper proposes a control-based approach to the duty cycle adaptation for wireless sensor networks. The proposed method controls the duty cycle through the queue management to achieve high-performance under variable traffic rates. To have energy efficiency while minimizing the delay, we design a feedback controller, which adapts the sleep time to the traffic change dynamically by constraining the queue length at a predetermined value. In addition, we propose an efficient synchronization scheme using an active pattern, which represents the active time slot schedule for synchronization among sensor nodes, without affecting neighboring schedules. Based on the control theory, we analyze the adaptation behavior of the proposed controller and demonstrate system stability. The simulation results show that the proposed method outperforms existing schemes by achieving more power savings while minimizing the delay.</P>

Novel and Live Tracing Methodology for Power Cables and Transformers Based on Power Line Carrier Signals

Byun, Heejung,Shon, Sugoog,Yang, Soomi MYU K.K. 2018 Sensors and materials Vol.30 No.8

<P>The three-phase, four-cable type of power distribution lines branch into multiple circuits from local pole-or pad-mounted transformers, which makes the topology of lines complicated. A challenging issue is how to trace cables and transformers in a complicated distribution system. The proposed idea is based on a power line carrier signal, which has certain propagation characteristics along the distribution system. This novel and live tracing methodology, called the synchronized client and server method, is introduced, designed, and implemented to trace cables and transformers in the distribution system. The most difficult part of cable tracing is to isolate the signals needed for tracking from a mixture of signals routed through transformers or loads and signals transmitted directly along a test line. The algorithms needed to isolate the signals have been developed and a zero crossing sensor module is designed to ensure that the remote client and server are in phase. Simulations have been carried out to verify the proposed system using a Simulink simulator. Experiments have been conducted to verify the theoretical concepts in a test bed and a commercial building. Finally, the theory has been proved at a resolution of 0.5 ms from comparisons between the simulations and the experiments.</P>

Implementation of a WLAN DMX Server based on NDIS WLAN Miniport Driver

HeeJung Byun,Cui Feng,Sugoog Shon 보안공학연구지원센터 2013 International Journal of Smart Home Vol.7 No.4

A Biologically-inspired Algorithm for Mission-critical Applications in Wireless Sensor Networks

Heejung Byun,Sugook Shon 보안공학연구지원센터 2014 International Journal of Multimedia and Ubiquitous Vol.9 No.11

Wireless sensor networks (WSNs) connect devices and enable collaboration on sensing and monitoring various physical phenomena for applications such as target tracking, infrastructure security, battlefield surveillance, health monitoring, and traffic control. WSNs are generally comprised of a large number of tiny sensor nodes that are battery powered. Therefore, existing medium access control (MAC) protocols for WSNs have mainly been designed for energy saving. However, existing WSN systems have considerable drawbacks, and especially limit coordination of sensor nodes for mission-critical applications, due to their large-scale nature. In this paper, we propose an energy-efficient and delay-guaranteeing algorithm inspired by biological systems, which have gained considerable attention as approaches for computing and problem solving. We introduce both a local status indicator and an active-status indicator for a sensor node to represent its local environmental conditions and its node state, respectively, in WSNs. From consideration of the analogies between cellular signaling systems and WSN systems, we formulate a new mathematical model that considers the networking challenges of WSNs. The proposed bio-inspired algorithm determines the state of the sensor node, as required by each application and as determined by the local environmental conditions, and the states of adjacent nodes. Simulation results indicate that the proposed scheme provides significant energy savings, as well as reliable delay-guarantee, by controlling the states of the sensor nodes.

Node Scheduling Control Inspired by Epidemic Theory for Data Dissemination in Wireless Sensor-Actuator Networks With Delay Constraints

Heejung Byun,Jungmin So IEEE 2016 IEEE Transactions on Wireless Communications Vol.15 No.3

<P>Wireless sensor-actuator networks (WSANs) enhance the existing wireless sensor networks (WSNs) by equipping sensor nodes with actuators. The actuators work with the sensor nodes to perform application-specific operations. The WSAN systems have several applications such as disaster relief, intelligent building management, military surveillance, health monitoring, and infrastructure security. These applications require the capability of fast data dissemination in order to act responsively to events. However, due to strict resource constraints of the nodes, WSANs pose significant challenges in network protocol design to support applications with delay requirements. Biologically inspired modeling techniques have received considerable attention for achieving robustness, scalability, and adaptability, while retaining individual simplicity. Specifically, data dissemination, packet routing, and broadcasting protocols for wireless networks have been modeled by epidemic theory. However, existing bio-inspired algorithms are mostly based on predefined heuristics and fixed parameters, and thus it is difficult for them to achieve the desired level of performance under dynamic environments. In order to solve this problem, we propose an epidemic-inspired algorithm for data dissemination in WSANs which automatically controls node states to meet the delay requirements while minimizing energy consumption. Through mathematical analysis, behavior of the algorithm in terms of converge time and steady state can be predicted. Also, the analysis shows that the system achieves stability, and derives parameter conditions for achieving the stability. Finally, extensive simulation results indicate that the proposed scheme outperforms existing protocols in achieving delay requirements and conserving energy.</P>

셀룰러 망에서 관리 제어를 이용한 분산적 부하 균등 방법

변희정(Heejung Byun),양윤기(Yoongi Yang) 제어로봇시스템학회 2011 제어·로봇·시스템학회 논문지 Vol.17 No.7

This paper proposes a scheme for distributed load balancing in mobile communication networks based on supervisory control framework. Using load information exchanged with neighboring cells, the “supervisors” that reside in the base stations distribute load among cells by controlling handover parameters in a distributed manner. The supervisors are designed so that the load difference among neighboring cells are kept under a pre-defined value. Results from systematic analysis and simulation indicate that our scheme effectively balances traffic load among cells and reduces call blocking rate of the overloaded cells.