• Proceedings of the Korea Water Resources Association Conference
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• 2006.05a
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• pp.354-359
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• 2006

The analysis of large-scale water resources systems is often complicated by the presence of multiple reservoirs and diversions, the uncertainty of unregulated inflows and demands, and conflicting objectives. Reinforcement learning is presented herein as a new approach to solving the challenging problem of stochastic optimization of multi-reservoir systems. The Q-Learning method, one of the reinforcement learning algorithms, is used for generating integrated monthly operation rules for the Keum River basin in Korea. The Q-Learning model is evaluated by comparing with implicit stochastic dynamic programming and sampling stochastic dynamic programming approaches. Evaluation of the stochastic basin-wide operational models considered several options relating to the choice of hydrologic state and discount factors as well as various stochastic dynamic programming models. The performance of Q-Learning model outperforms the other models in handling of uncertainty of inflows.

• Journal of the Korean Society for Aviation and Aeronautics
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• v.22 no.2
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• pp.16-26
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• 2014

After the GBAS ground system installing at the airport, a GBAS ground and flight testing must be conducted to verify functionality and performance of the system. Since Korea has no experience of the GBAS ground system installation, GBAS test and evaluation methods have never been studied so far. Therefore this paper analyzes the test items and methods for the GBAS ground and flight testing based on ICAO documents, FAA flight inspection manual and testing reports of other countries. As a result of the analysis, this paper proposes the GBAS ground and flight testing items in korea, also describes the flight procedures for the GBAS flight testing.

• Transactions of the Korean Society of Automotive Engineers
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• v.8 no.6
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• pp.101-110
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• 2000

A Computer program is developed for creation of a new lobe shaper for Roots-type supercharger. Numerical analyses are preformed for the flowfields in the pocket volumes formed by various lobe shapes. The governing equations for the two-dimensional, turbulent, operational processes in the housing are discretized by the control volume approach that insures the conservative characteristics to be satisfied in the calculation domain, and they are solved by a modified SIMPLE algorithm. Numerical results show that the effects of secondary flow on the leakage flow rate with the Cassini(B) lobe shape is smaller than that of Cassini(A) rotor. But the pocket volume of Cassine(B) lobe is larger than the other lobe shapes.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2011.11a
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• pp.162-163
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• 2011

This paper presents the system dynamics methodology for modeling and control the production/inventory system. Under system dynamics point of view, we can apply some production/inventory policies as if we use the control laws for dynamics systems, then the behavior of system is analyzed and evaluated to improve the performance of production/inventory system. We also utilize the hybrid modeling method for the dynamic of production system with the combination of Matlab/Simulink and Matlab/Sateflow. Finally, the numerical simulation results are carried out in Matlab/Simulink environment and compare with the results from other works. It is shown that our approach can obtain some good performances (such as operational cost, stability of inventory, customer service level).

• Journal of Construction Engineering and Project Management
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• v.7 no.1
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• pp.30-36
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• 2017

Most local agencies such as counties and small cities continuously express difficulties in making technically and financially defensible decisions on their pavement infrastructure maintenance and rehabilitation. Unlike pavement systems managed by state highway agencies, the total lane-miles of many local pavements are significantly short and they are managed by a limited number of staff who typically have multiple responsibilities. Most local agencies also do not have historical pavement performance data and the lack of a systematic decision making framework exacerbates the problem. A structured framework and an easily accessible decision support tool that reflects their local requirements, practices and operational conditions would greatly assist them in making consistent and defensible decisions. This study fills this gap by developing a systematic pavement treatment selection framework and a spreadsheet based tool for local agencies. It is expected that the proposed framework will significantly help local agencies to improve their pavement asset management practices at the project level.

• Asia pacific journal of information systems
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• v.14 no.1
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• pp.125-142
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• 2004

Knowledge management has been increasingly recognized as important in business management context. Although knowledge management has been proposed as an enabler to reach competitive advantage, little research has considered applying knowledge to business decision-making activities, which may be the main task of enterprise management. The application of knowledge to decision-making has a more significant impact on organizational performance than mere knowledge management for operational level processing. For this purpose, the present study proposes a decision support loop based on the integration of knowledge by adopting a cognitive modeling approach. The proposed model is then discussed, in the real context of an application case.

• Journal of the military operations research society of Korea
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• v.24 no.2
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• pp.57-74
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• 1998

This paper is aimed to propose an testing and evaluation strategy and plan in Military Information Systems, especially focusing on development an“New-generation Wargame Model”. Through this research, we concluded that the effective and efficient testing/evaluation strategy/plan can aid the productivity, maintainability, availability, etc., of the Militray Information Systems. Highlights of the proposed testing and evaluation strategy and plan for Military Information Systems are as follows. First, in the unit and module integration testing phase, hybrid of black-box and white-box testing techniques are available for Military Information Systems and progressive approach for module integration phase should be considered because of the complexity. Second, in the system testing phase, integrated module should be tested with respect to the function and performance that should be satisfied with the user requirements, specifications, risk analysis, etc., Third, in the acceptance testing phase, reliability, interoperability, maintainability, availability, integrity, etc., must be considered in the actual or mini-operational environments for testing efficiently and effectively.

• Journal of Power Electronics
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• v.7 no.3
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• pp.203-212
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• 2007

In this paper, a proposed approach to improve the power factor of three-phase rectifiers and to stabilize the output voltage against load change is presented. The elements of the given control strategy are small size, low cost, high performance, and simplicity. The proposed control strategy of switches is based on a prototype of three bi-directional switched consisting of four diodes and one IGBT. A control technique and operational procedure are also developed, both theoretically and experimentally. The experimental results clearly verify the theoretical analysis from the prototype connected to grid unity.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2006.05a
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• pp.407-409
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• 2006

This paper presents the methods of designing the control circuits for a Class D amplifier to have a peak performance. The proposed approach is based on the three functional components - a carrier generator, a feedback circuit and a dead-time circuit. First the analog signal is applied to the controller, which outputs the 3 level PWM waveform. The controller used for this experiment is made of the operational amplifier and the logic circuit. The experimental results show that the control circuit performs with satisfaction and its output is proportional to input audio signal, providing a satisfactory 3 level PWM pattern. From this design methodology, by implementing a proposed control circuit we can achieve the efficient Class D amplifier using the half-bridge, full-bridge or push-pull topology at the output stage.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.12 no.12
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• pp.5634-5653
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• 2018

Internet of things (IoT) is based on a global dynamic information network with cloud services where a great number of devices (things) exchange data to provide added-value services and products. There are several commercial and open source IoT platforms available in the market to connect devices to internet; however, they have cost and operational constraints that make them not suitable for academic projects. In this work, an IoT platform, known as Novus-io, is introduced in order to support academic projects for undergraduate students. With this platform and proper training, undergraduate students from different majors (not only from information technology and electronics) are capable to upgrade their school projects with IoT functionalities. The objective of this approach is to provide to any undergraduate student skills and knowledge on IoT, so they will be prepared, in their imminent step toward professionalism, to understand the relevance of digital services in today's world.