• Proceedings of the KIPE Conference
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• 2015.07a
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• pp.361-362
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• 2015

This paper proposes a Direct Power Control (DPC) scheme of improved command tracking capability for Permanent Magnet Synchronous Generator (PMSG) Medium Voltage (MV) Wind Turbines. Benchmarking is performed based on a neutral point clamped three-level back-to-back type voltage source converter. It is introduced to design the DPC modeling and propose DPC scheme of a three-level NPC (3L-NPC) converter. During the fault condition in wind farms, the proposed control scheme directly controls the generated output power to the command value from the hierarchical wind farm controller. The proposed control scheme is compared with conventional control scheme as respect to loss and thermal analysis. The DPC scheme of improved command tracking capability is confirmed through PLECS simulations. Simulation result shows that proposed control scheme achieves a much shorter transient time in a step response of generated output power. The proposed control scheme makes it possible to provide a good dynamic performance for PMSG MV wind turbine to generate a high quality output power under grid fault condition.

• Journal of Korean Institute of Industrial Engineers
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• v.30 no.1
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• pp.17-26
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• 2004

In this study, the usability evaluation of a menu-structure was performed using spreading activation model with respect to human's memory retrieval. Spreading Activation Model is effectively used to understand the process of information retrieval, so it can be used as a theoretical background for modeling of the process of human's information retrieval. For spreading activation test (SAT), subjects were presented with 67 pairs of menu titles, which consist of a menu title in the high level menu item and a menu title for the next lower level menu item, from Korea University's web site. For performance tests, three scenarios were developed with longer reaction times and ambiguous associations found in the SAT to reflect the existing problems of the website. As a result, the SAT was found to bean effective tool to enhance the website usability because the SAT could bea substitute for the performance test with a high correlation $({\rho}=0.735,\;{\alpha}=0.05)$. After remaining menu titles with slow reaction times and ambiguous associations found in SAT, the website usability was significantly improved with faster reaction times and less ambiguous associations proven with smaller number of web-page visits. Therefore, the SAT could be used as a methodology to design and evaluate the user-centered menu structure related to human's association structure.

• Asia-Pacific Journal of Business Venturing and Entrepreneurship
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• v.9 no.3
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• pp.119-128
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• 2014

One of the theoretically and empirically grounded black boxes in HRD and firm performance link is employee' attitudes such as organizational commitment and job satisfaction. However, most studies were conducted with the regression analysis at the organizational level. This study used HLM(hierarchical linear modeling) analysis, which made it possible to estimate more accurate relationship between variables that were measured from two different levels. In addition, this study attempted to open an the black box(learning culture) in the relationship between HRD and employee attitudes. The result showed that the HRD have a positive effect on the organizational commitment and the job satisfaction. Also the HRD showed full mediation effect of organization commitment and the job satisfaction on the Learning culture. And the result showed that the HRD in 2007 have a positive effect on employee' attitudes in 2009. These findings concluded that systematic HRD like employee's education and training must be built and also the positive culture for employee's learning like support of management's learning organization must be improved in order to promote the organizational performance(organizational commitment, job satisfaction) in company.

• KIISE Transactions on Computing Practices
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• v.21 no.7
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• pp.488-493
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• 2015

An AddSIM(Adaptive distributed and parallel Simulation environment for Interoperable and reusable Models) is an integrated engagement simulation environment with high-resolution weapon system models for estimation and analysis of their performance and effectiveness. AddSIM can simultaneously handle the continuous dynamical system models based on continuous time, and command, control(C2) and network system models based on a discrete event. To accommodate legacies based on DEVS(Discrete Event System Specification) modeling, DEVS legacies must first be converted into AddSIM models. This paper describes how to implement DEVS models on AddSIM. In this study a method of mapping from hierarchical DEVS models to AddSIM players was developed: The hierarchical DEVS model should be flattened into a one layered model and four DEVS functions of the model, external transition, internal transition, output and time advance, should be mapped into functions of the AddSIM player.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.12
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• pp.498-506
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• 2018

Recently, the US commanded a wargame simulation system of a combined ROK-US exercise with single federation. However, after the OPCON transfer, many limitations to the single federation have been cited such as security policies and information protection. We suggest a hierarchical federation as a way to overcome these problems. Regarding HLA rules, the participants use the same FOM and RTI in single federation. There are limitations to implement CI in applying heterogeneous FOMs and RTIs in current single federation. Therefore, we propose implementing CI with heterogeneous FOMs and RTIs in a hierarchical federation. This system overcomes the weaknesses of the system structure, which is a disadvantage of the single federation. In the federation test, we can apply heterogeneous FOMs and RTIs and achieve similar performance to the current combined exercise simulation. In conclusion, ROK should lead the simulation system of combined exercises using the CI after the OPCON transfer.

• Korea Journal of Hospital Management
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• v.10 no.1
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• pp.1-24
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• 2005

Organizational culture has been very important in the field of organizational behavior research for the past decade. Although there has been a growing interest in the organizational culture and organizational performance, there was few research in healthcare organizations. The objective of this study is to identify the relationship of organizational culture based on the Quinn's competing values approach, with job satisfaction and intention of turnover perceived by national hospital employees. The study setting was the national hospital. Data were collected by self-administered questionnaires. The study sample consisted of 555 hospital employees. Structural Equation Modeling(SEM) analysis was conducted to find the causal relationship of organizational culture, job satisfaction and intention of turnover.The major results of this study are as follows: the consensual culture, rational culture, and developmental culture in national hospital showed a strong relationship with job satisfaction and intention of turnover in contrast to other previous studies. This finding showed that task oriented and human related climate is more effective on job satisfaction than hierarchical culture in national hospital settings.

• The Journal of the Korea Contents Association
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• v.8 no.1
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• pp.169-176
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• 2008

In this paper, we develop radio resource management queueing model in IEEE 802.IS networks considering both connection and packet level. In the upper level connection, we model connection admission control depending on availability of bandwidth and priority queue in each service class. In the lower level packet, we model dynamic bandwidth allocation considering threshold and availability of bandwidth in each service class simultaneously. Hierarchical model is built using an extended Petri Nets, SRN (Stochastic Reward Nets). Bandwidth utilization and normal throughput as performance index for all service classes of traffic are calculated and numerical results are obtained.

• Proceedings of the Korea Society for Simulation Conference
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• 2003.06a
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• pp.61-66
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• 2003

Mobile IP has been designed only to maintain communication as they move form place to place, so it doesn't guarantee Quality of Service(QoS). QoS in mobile IP is important to provide multimedia and real-time applications services in mobile, and it is closely related to handoff delay. Therefore, handoff delay problem is actively studied to guarantee QoS as a main issue in mobile IP research area Next generation Mobile IPv6 resolve this problem somewhat, triangle problem for first packet and handoff delay still remain. In this paper, we suggest SNMP Information-based routing that adds keyword management method to Information-based routing in active network in order to resolve such a problem, and then suggest QoS controlled handoff based on SNMP Information-Based routing. After modeling of suggested method and existing handoff method simulations we carried out with NS-2 for performance evaluation. The results of simulations show the some improvement on handoff delay, and therefore on QoS improvement.

• The KIPS Transactions:PartC
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• v.8C no.6
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• pp.639-639
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• 2001

In this paper we describe a distributed location management scheme to reduce the bottleneck problem of HLR in Large Personal Communication Networks (LPCNs). Using analytical modeling and numerical simulation, we show that replicating location information is both appropriate and efficient for small Personal Communication Network (PCN). Then, we extend the scheme in a hierarchical environment to reduce overhead traffic and scale to LPCNs. Through extensive numerical results, we show the superiority of our scheme compared to the current IS-41 standard scheme.

• The KIPS Transactions:PartC
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• v.8C no.6
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• pp.839-846
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• 2001

In this paper we describe a distributed location management scheme to reduce the bottleneck problem of HLR in Large Personal Communication Networks (LPCNs). Using analytical modeling and numerical simulation, we show that replicating location information is both appropriate and efficient for small Personal Communication Network (PCN). Then, we extend the scheme in a hierarchical environment to reduce overhead traffic and scale to LPCNs. Through extensive numerical results, we show the superiority of our scheme compared to the current IS-41 standard scheme.