• Proceedings of the KIEE Conference
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• 1999.07c
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• pp.1195-1198
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• 1999

This paper presents optimal placement of minimal set of phasor measurement units(PMU's) and observability of measurement system with PMU. By using the incidence matrix symbolic method which directly assigns measurement and pseudo-measurement to incidence matrix, it is much simpler and easier to analyze observability. The optimal PMU set is found through the simulated-annealing(SA) and the direct combinational method. The cooling schedule parameter which is suitable to the property of problem to solve is specified and optimal placement is proven by presented direct combinational method. Search spaces are limited within reasonable feasible solution region to reduce a unnecessary one in the SA implementation based on global search. The proposed method presents to save CPU time and estimate state vectors based on optimal PMU set.

• Journal of Science Education
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• v.33 no.1
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• pp.69-76
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• 2009

Probabilistic reasoning and combinational reasoning are essential to build a logical thinking and a process of thinking dealing with everyday life as well as scientific knowledge. This research aims at finding the optimal period to teach reasoning to the students who haven't developed probabilistic reasoning and combinational reasoning. The treatment program was performed for 20 students from each grade who couldn't develop two parts of reasoning. The treatment program using baduk stones and cards was performed repeatedly, focusing on the specific activities. After four weeks of treatment program, the test to check the development of probabilistic reasoning and combinational reasoning was performed again and the changes of reasoning development were identified. After giving treatment program for reasoning development, 15.0%, 25.0% and 40.0% of improvement in the 4th, the 5th, the 6th graders respectively were shown. With regard to the combinational reasoning, the results showed the improvement of 20.0% in the 4th grades, 25.0% in the 5th graders and 63.2% in the 6th graders. As a result of research in the above, students, who were not formed probabilistic reasoning and combinational reasoning, could be known to be enhanced through learning, but to fail to be formed the qualitative change like the cognitive development. It is expected that this research can contribute to the improvement of students' cognitive level and there would be more active researches in different fields to improve the cognitive level of the 6th graders who are in their optimal periods to learn two parts of reasoning.

• Journal of the Korean Institute of Telematics and Electronics
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• v.26 no.11
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• pp.1839-1849
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• 1989

An optimal variable assignment algorithm is presented as a decomposition method of MVL functions. A given 3-valued combinational logic function is disintegrated into subfunction composed of the function dependant relation, then extracted implicant output elements from subfunctions are assigned to a T-gates. As a circuit implementation tool, a programmable integarated T-gate module is proposed, and the construction procedure of combinational MVL functions is systematized in each step. This method is expected to give properties of the systematic procedure, possibility of T-gate number reduction, unification of module, and flexibility of module composition. Specially variable decomposition method can be pointed out as an approach to solving the limitation problem of the input and output terminal number in VLSI implementations.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.18 no.34
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• pp.99-106
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• 1995

Recently, neural network is recognized as a new approach to solve jobshop scheduling problems in manufacturing system. Scheduling problem is known to be a difficult combinational explosive problem with domain-dependence variations in general. In addition, the needs to achieve a good performance in flexible manufacturing system increase the dimensions of decision complexity. Therefore, mathematical approach to solve realistic problems could be failed to find optimal or optimal-trending. In this paper a technique with neural network for jobs grouping by job-attributes and Gaussian machine network for generating to near-optimal sequence is presented.

• Proceedings of the KIEE Conference
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• 1999.07a
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• pp.486-488
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• 1999

This paper shows the form of the optimal solution and how to minimize energy of train driving control using SA(simulated annealing). In this paper, we consider the case where a train is to be driven by automatic operation mode along a non-constant gradient, curve and with speed limits. Using the combinational optimal technique, SA, we constructed optimal train driving strategy.

• Proceedings of the KIEE Conference
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• 1999.07c
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• pp.1117-1119
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• 1999

This paper presents a new approach for the optimal routing problem of distribution system planning using the well known Hopfield Neural Network(HNN) method. The optimal routing problem(ORP) in distribution system planning(DSP) is generally formulated as combinational mixed integer problem with various equality and inequality constraints. For the exceeding nonlinear characteristics of the ORP most of the conventional mathematical methods often lead to a local minimum. In this paper, a new approach was made using the HNN method for the ORP to overcome those disadvantages. And for this approach, a appropriately designed energy function suited for the ORP was proposed. The proposed algorithm has been evaluated through the sample distribution planning problem and the simulation results are presented.

• Journal of The Korean Association For Science Education
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• v.29 no.3
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• pp.304-313
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• 2009

Proportional reasoning is one of the most widely used concepts in everyday life. It could be the most important basic concept in science and mathematics. In research where the subjects were animals, it has been found that learning effect rapidly decreased with any stimulation given after a optimalperiod. Therefore, it is necessary to research about optimal periods in order to instruct about proportional reasoning. The purpose of this study was to investigate the optimal periods in proportional reasoning. The three programs for proportional reasoning instruction were developed by researchers. The titles of the programs were 'Block', 'Balance scale' and 'Water glass'. The subjects were 131 3$^{rd}$ to 6$^{th}$ grade students who were not expected to have any proportional reasoning skills yet. In order to find out the optimal periods in proportional reasoning, the programs were applied to these students. After 4-5 weeks of treatment, the researchers investigated whether their proportional reasoning skills were formed or not through the instrument. The results indicated that it would be most effective to teach proportional reasoning to 6$^{th}$ grade students. Teaching of proportional reasoning is essential not only for mathematics but also for science. The findings could be used to investigate the optimal periods of controlling variables, probability, combinational and correlational logic.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.11 no.1
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• pp.115-123
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• 2011

Distribution system loss minimization re-configuration is 0-1 planning problem, and the number of combinations requiring searches is extremely large when dealing with typical system scales. For this reason, the application of a genetic algorithm (GA) seems a tractive to solve this problem. Although Genetic algorithms are a type of random number search method, they incorporate a multi-point search feature and are therefore superior to one-point search techniques. The incorporate of GAs for solving large combinational problem has received wide attention. Further, parallel searching can be performed and the optimal solution is more easily reach ed. In this paper, for improving GA convergence characteristics in the distribution system loss minimization re-configuration problem, a chromosome "Limited Life" concept is introduced. Briefly, considering the population homogenization and genetic drift problems, natural selection is achieved by providing this new concept, in addition to natural selection by fitness. This is possible because individuals in a population have an age value. Simulation were carried out using a model system to check this method's validity.

• Proceedings of the Korean Operations and Management Science Society Conference
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• 2003.05a
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• pp.972-975
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• 2003

The purpose of this study is to integrate Decision Theory Approach(DTA) and OR Theory Approach(OTA) systemically. and to develop Combination Theory Approach to build an optimal R&D project portfolio by strategies. To Integrate two approaches. Utility theory is introduced. Evaluation Results aye converted into utility values by the utility functions and the values are optimized by 0-1 programming. Scoring method and Integer programming is used to evaluation a correspondence with a goal and to allocation the limiting resources. And utility function is used to reflect the preference of decision makers on the project evaluation.

• Journal of Mechanical Science and Technology
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• v.19 no.9
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• pp.1695-1705
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• 2005

Reaction wheels and thrusters are commonly used for the satellite attitude control. Since satellites frequently need fast maneuvers, the minimum time maneuvers have been extensively studied. When the speed of attitude maneuver is restricted due to the wheel torque capacity of low level, the combinational use of wheel and thruster is considered. In this paper, minimum time optimal control performances with reaction wheels and thrusters are studied. We first identify the features of the maneuvers of the satellite with reaction wheels only. It is shown that the time-optimal maneuver for the satellite with four reaction wheels in a pyramid configuration occurs on the fashion of single axis rotation. Pseudo control logic for reaction wheels is successfully adopted for smooth and chattering-free time-optimal maneuvers. Secondly, two different thrusting logics for satellite time-optimal attitude maneuver are compared with each other: constant time-sharing thrusting logic and varying time-sharing thrusting logic. The newly suggested varying time-sharing thrusting logic is found to reduce the maneuvering time dramatically. Finally, the hybrid control with reaction wheels and thrusters are considered. The simulation results show that the simultaneous actuation of reaction wheels and thrusters with varying time-sharing logic reduces the maneuvering time enormously. Spacecraft model is Korea Multi-Purpose Satellite (KOMPSAT)-2 which is being developed in Korea as an agile maneuvering satellite.