• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.36 no.2
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• pp.146-155
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• 2008

To improve the performance of tiled display system, two parallel tiled display algorithms are proposed by combining the sort-first and the sort-last sorting methods. In the proposed algorithms, the view frustum culling is employed along with the OpenGL display list for the sort-first sorting, and the pre-detection sort-last sparse sorting method is used for sort-last sorting. Through the benchmarking tests, the performances of two proposed algorithms are investigated. Based on the observations, it is suggested how to select an optimal algorithm among the two proposed parallel tiled display algorithms for the given visualization model.

• Journal of Electrical Engineering and Technology
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• v.5 no.1
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• pp.70-78
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• 2010

Elitist nondominated sorting genetic algorithm (NSGA-II) is adopted and improved for multiobjective optimal reactive power flow (ORPF) problem. Multiobjective ORPF, formulated as a multiobjective mixed integer nonlinear optimization problem, minimizes real power loss and improves voltage profile of power grid by determining reactive power control variables. NSGA-II-based ORPF is tested on standard IEEE 30-bus test system and compared with four other state-of-the-art multiobjective evolutionary algorithms (MOEAs). Pareto front and outer solutions achieved by the five MOEAs are analyzed and compared. NSGA-II obtains the best control strategy for ORPF, but it suffers from the lower convergence speed at the early stage of the optimization. Several problem-specific local search strategies (LSSs) are incorporated into NSGA-II to promote algorithm's exploiting capability and then to speed up its convergence. This enhanced version of NSGA-II (ENSGA) is examined on IEEE 30 system. Experimental results show that the use of LSSs clearly improved the performance of NSGA-II. ENSGA shows the best search efficiency and is proved to be one of the efficient potential candidates in solving reactive power optimization in the real-time operation systems.

• The Transactions of the Korea Information Processing Society
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• v.4 no.11
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• pp.2690-2700
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• 1997

This paper presents parallel sorting algorithm, SHARED-MEMORY-BS and REDUCED-BS, which are implemented on shared-memory parallel computers. These algorithm sort N keys in $O(log^2N)$ time. REDUCED-BS users a parity strategy which gives an idea for the efficient usage of the local memory associated with each processor. By taking advantage of the local memory associated with each processor, the communication of REDUCED-BS is decreased by approximately half that of SHARED-MEMORY-BS. On the basis of alleviating the communication, the algorithm REDUCED-BS results in a significant improvement of performance.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.32 no.11A
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• pp.1079-1085
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• 2007

This Paper Proposes a new optimization algorithm named by GBNSGA-II(Goal-pareto Based Non-dominated Sorting Genetic Algorithm-II) which uses Goal Programming to find non-dominated solutions in NSGA-II. Although the conventional NSGA is very popular to solve multiobjective optimization problem, its high computational complexity, lack of elitism and difficulty of selecting sharing parameter have been considered as problems to be overcome. To overcome these problems, NSGA-II has been introduced as the alternative for multiobjective optimization algorithm preventing aforementioned defects arising in the conventional NSGA. Together with advantageous features of NSGA-II, this paper proposes rather effective optimization algorithm formulated by purposely combining NSGA-II algorithm with GP (Goal Programming) subject to satisfying multiple objectives as possible as it can. By conducting computer simulations, the superiority of the proposed GBNSGA-II algorithm will be verified in the aspects of the effectiveness on optimization process in presence of a priori constrained goals and its fast converging capability.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2022.10a
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• pp.400-403
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• 2022

This paper propose a GPU-based N-body collision detection algorithm using LBVH (Linear Bounding Volume Hierarchy) technique. This algorithm introduces a new modified Morton code scheme where the codes use an information about how much each body takes a space in the screen space. This scheme improves the GPU sorting performance of the N-Body because it culls out invisible objects in natural manner. Through the experiments, we verifies that the proposed algorithms can have at least 15% performance improvement over the existing methods

• Journal of The Korean Association of Information Education
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• v.13 no.2
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• pp.225-236
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• 2009

According to the revised guideline for information & communication technology, algorithm has to be dealt with the learning contents from elementary school, so now it needs to study various educational methods for students to learn algorithm easily and effectively. In this study, after selecting sort algorithms as the content of learning, which is recognized as an important part of algorithm, an playing activity-based algorithm teaching method and an animation-based algorithm learning and teaching method were applied for the lower graders of an elementary school. Sorting algorithm education is adopted in two different ways, then we got two conclusions after analyzing the results of a specially designed achievement test and the questionnaire. First, there were not great differences in both educational methods in academic achievement, but it was clear that the lower grade elementary students can learn algorithm with ease. Second, the playing activity-centered algorithm education is more effective than animation-based education in improving students' comprehension, interest and satisfaction.

• Journal of Power Electronics
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• v.17 no.2
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• pp.346-357
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• 2017

The Modular Multilevel Converter (MMC) is particularly attractive for medium and high power applications such as High-Voltage Direct Current (HVDC) systems. In order to reach a high voltage, the number of cascaded submodules (SMs) is generally very large. Thus, in the applications with hundreds or even thousands of SMs such as MMC-HVDCs, the sorting algorithm of the conventional voltage balancing strategy is extremely slow. This complicates the controller design and increases the hardware cost tremendously. This paper presents a Two-Way Merge Sort (TWMS) strategy based on the prediction of the capacitor voltages under ideal conditions. It also proposes an innovative Insertion Sort Correction for the TWMS (ISC-TWMS) to solve issues in practical engineering under non-ideal conditions. The proposed sorting methods are combined with the features of the MMC-HVDC control strategy, which significantly accelerates the sorting process and reduces the implementation efforts. In comparison with the commonly used quicksort algorithm, it saves at least two-thirds of the sorting execution time in one arm with 100 SMs, and saves more with a higher number of SMs. A 501-level MMC-HVDC simulation model in PSCAD/EMTDC has been built to verify the validity of the proposed strategies. The fast speed and high efficiency of the algorithms are demonstrated by experiments with a DSP controller (TMS320F28335).

• Korean Journal of Agricultural Science
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• v.50 no.3
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• pp.373-382
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• 2023

The task of sorting and excluding blemished apples and others that lack commercial appeal is currently performed manually by human eye sorting, which not only causes musculoskeletal disorders in workers but also requires a significant amount of time and labor. In this study, an automated apple-sorting machine was developed to prevent musculoskeletal disorders in apple production workers and to streamline the process of sorting blemished and non-marketable apples from the better quality fruit. The apple-sorting machine is composed of an arm-rest, a main body, and a height-adjustable part, and uses object detection through a machine learning technology called 'You Only Look Once (YOLO)' to sort the apples. The machine was initially trained using apple image data, RoboFlow, and Google Colab, and the resulting images were analyzed using Jetson Nano. An algorithm was developed to link the Jetson Nano outputs and the conveyor belt to classify the analyzed apple images. This apple-sorting machine can immediately sort and exclude apples with surface defects, thereby reducing the time needed to sort the fruit and, accordingly, achieving cuts in labor costs. Furthermore, the apple-sorting machine can produce uniform quality sorting with a high level of accuracy compared with the subjective judgment of manual sorting by eye. This is expected to improve the productivity of apple growing operations and increase profitability.

• Proceedings of the KIEE Conference
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• 1988.11a
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• pp.64-67
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• 1988

This paper proposes a algorithm to obtain a time-varing system parameters for the optimal controller. The proposed algorithm is enlarged from tile optimal sorting algorithm. It applies to Bang-Bang control and compares with CGD Method. We confirm that the proposed algorithm is excellent.

• Journal of KIISE:Computer Systems and Theory
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• v.36 no.2
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• pp.68-72
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• 2009

The suffix array is a data structure storing all suffixes of a string in lexicographical order. It is widely used in string problems instead of the suffix tree, which uses a large amount of memory space. Many researches have shown that not only the suffix array can be built in O(n), but also it can be constructed with a small time and space usage for real-world inputs. In this paper, we analyze a practical suffix sorting algorithm due to Maniscalco and Puglisi [1], and we propose an efficient algorithm which improves Maniscalco-Puglisi's running time.