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鄭京燮 서경대학교 1984 論文集 Vol.12 No.-
This is an attempt to analyze various theoretical and practices of leadership. The classic research studies on leadership set the stage for the theoretical development of leadership. The trait theories concentrate on the leader themselves but, with the possible exception of intelligence, really do not come up with any agreed traits of leader. The group theories emphasize the importance of the followers, but these are also only partial theories. The conclusion to be drawn from the studies of leadership style or behavior is that there is no one universal style. There is some evidence that the various styles are of two kinds: concern for people and concern for task. Additionally, because investigations of leadership style have failed to consider significant factors such as the task, the group, and the organizational effectiveness. Today, the widely recognized theories of leadership are situationally based. In particular, Fiedler's contingency model makes a significant contribution to leadership theory and potentially to the practice of human resource management. The path-goal approach is also an important contribution to leadership theory. It incorporates expectancy motivation concepts. Both the Fiedler and path-goal approaches have generated a growing body of research on leadership dimensions, but there are still problems. A social learning approach that incorporates the leader, the situation, and the behavior itself is proposed as a possible alternative. This approach emphasizes the importance of behavior and the continuous, interacting nature of all the variables in leadership. In conclusion, all of these approaches to leadership style need more and better research in order to make meaningful contributions to the actual practice of human resource management in the future.
Medium Voltage Power Supply with Enhanced Ignition Characteristics for Plasma Torches
정경섭,서용석 전력전자학회 2011 JOURNAL OF POWER ELECTRONICS Vol.11 No.4
This paper investigates a power supply of medium voltage with enhanced ignition characteristics for plasma torches. A series resonant half-bridge topology is presented as a suitable ignition circuitry. The ignition circuitry is integrated into the main power conversion system of a multi-phase staggered three-level dc-dc converter with a diode front-end rectifier. A plasma torch rated at 3MW, 2kA and having a physical size of 1m is selected to be the high enthalpy source for a waste disposal system. The steady-state and transient operations of a plasma torch are simulated. The parameters of a Cassie-Mary arc model are calculated based on 3D magneto-hydrodynamic simulations. The circuit simulation waveform shows that the ripple of the arc current can be maintained within ±10% of its rated value under the presence of a load disturbance. This power conversion configuration provides a high enough ignition voltage, around 5KA, during the ignition phase and high arc stability under the existence of arc disturbance noise resulting in a high-performance plasma torch system.