• Journal of the Korean Institute of Telematics and Electronics A
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• v.33A no.3
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• pp.152-162
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• 1996

Diffraction gratings were designed to generate multiple beams for the real-time optical interconnection in free-space using a liquid crsytal television. Multi-level phase gratings consisted of stepped phase value, 0 to 2$\pi$, and generate a 5$\times$5 spot array, and V-shaped spot patterns which have a maximum diffraction efficiency of 78.84%. Simulated annealing technique was used to determine phase states of each pixel having uniform intensity and high diffraction efficiency. Through the optical interconnection experiments, we compared the diffraction characteristics of beam paterns obtained by binary-level, four-level, and eight-level phase gratings.

• Journal of information and communication convergence engineering
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• v.11 no.3
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• pp.167-172
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• 2013

Recently, mobile communication systems are suffering from exponentially increasing data traffic. As a promising solution to the increase in data traffic, a coordinated multi-point transmission and reception (CoMP) scheme has been proposed. Although a great deal of research has been done on this new technology, the performance of mobile communication systems with CoMP has not been evaluated properly in a typical indoor environment. To address this, we have developed a system-level simulator and evaluated the performance of mobile communication systems with CoMP. Unlike previous works, we have used an actual antenna pattern in our simulator and link-level results are properly taken into account through link-level abstraction. By using a system-level simulator, we have evaluated the performance of mobile communication systems with CoMP in an indoor environment and found that unlike an outdoor cellular environment, CoMP may not improve the performance of overall mobile communication systems in an indoor environment.

• The Transactions of the Korea Information Processing Society
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• v.6 no.10
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• pp.2809-2815
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• 1999

Level set, and active contour(snakes) models are extensively used for image segmentation or shape extraction in computer vision. Snakes utilize the energy minimization concepts, and level set is based on the curve evolution in order to extract contours from image data. In general, these two models have their own drawbacks. For instance, snake acts pooly unless it is placed close to the wanted shape boundary, and it has difficult problem when image has multiple objects to be extracted. But, level set method is free of initial curve position problem, and has ability to handle topology of multiple objects. Nevertheless, level set method requires much more calculation time compared to snake model. In this paper, we use good points of two described models and also apply multi resolution algorithm in order to speed up the process without decreasing the performance of the shape extraction.

• Korean Public Health Research
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• v.44 no.4
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• pp.83-85
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• 2018

As the main aim of infectious disease epidemiology is to prevent a pathogen transmission, traditional epidemiological studies have focused on the evaluation of individual-level risk factors. But group-level factors as well as individual-level are important in understanding and controlling transmission of infectious diseases, especially sex-transmitted infectious diseases. Multi-level analysis (MLA) is known as a powerful analytical tool for investigating both levels simultaneously. While new cases of HIV/AIDS in Korea are increasing annually, it is urgently needed to establish research system for MLA led by Korea Centers for Disease Control & Prevention.

• Journal of the Korean Society for Precision Engineering
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• v.11 no.1
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• pp.166-176
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• 1994

The problem of reducing the vibration level of elastic plates driven by multiple random point forces is analyzed in this study. First, the analytical solution for the vibration level of finite thin plates with four simply supported edges under the action of multiple random point force is derived. By assuming the plates to be lightly damped, an approximate solution for the vibration level of the plate is obtained. A numerical study is carried out to determine an optimal spacing distance between the multiple point forces in order to produce a relative minimum in the plate's vibration level. The optimal spacing distance is shown to depend on the given excitation band. The effects of wave cancellation in the near field of the multiple point forces are discussed by using the equivalence of certain stationary random responses and deterministic pulse responese.

• Journal of Korean Home Economics Education Association
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• v.12 no.3
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• pp.105-114
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• 2000

The purpose of this study was to investigate the effects of instructional multi-media in Home Economics Education perceived by teachers. The data for this research were attained from 139 middle & high school teachers of Home Economics. The data were analyzed by frequency of distribution, mean, stand deviation. t-test and analysis of variance, scheffe test with SPSSWin 7.5 program. The results of this study are as follows: The effects of instructional multi-media were composed of four dimensions in this study; need, frequency of use, pros and cons. 1. From these four dimensions, the need has the highest and the frequency of use has the lowest score. 2. The effects of instructional multi-media are significantly related to personal & environmental characteristics. 1)Need of the instructional multi-media effects is significantly different according to age, experience of computer education and possession of a computer at home. Low and high age groups are higher in the need of the instructional multi-media effects score than middle group age and the more experience of computer education and possession of a computer at home are higher in that score. 2) Frequency of use is significantly different according to LAN system in school. The higher score of frequency of use is in a LAN system’s school. 3) Pros of the instructional multi-media effects is significantly different according to the level of education, experience of computer education and the type of school. Undergraduate high school teachers and the lower o experience of computer education are higher in the pros of the instructional multi-media effects score. 4) Cons of the instructional multi-media effects is significantly different according to the level of education. Graduate teachers are higher in the cons of the instructional multi-media effects score.

• Journal of Convergence for Information Technology
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• v.11 no.10
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• pp.322-331
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• 2021

This study attempted to identify the multi-cultural acceptance level of freshmen in nursing colleges and to analyze the factors influencing it. For the research method, data were collected from 410 first-year nursing students at K University in W City through a questionnaire from March 1 to 28, 2021, and frequency, reliability analysis, t-test, ANOVA, correlation, and multiple regression were conducted using the open-source statistical package R. As a result of the study, the multi-cultural acceptance level of freshman in nursing colleges averaged 77.36 points, indicating that they have a slightly higher multi-cultural acceptance capacity, and as a result of analyzing the influence of multi-cultural acceptance related factors, Korean recognition requirements(𝛽=0.34, p<.001), perceived threat recognition for migrants (𝛽=0.29, p<.001), Experience in multi-cultural education(𝛽=0.14, p<.001), Recognition of the appropriate age for multi-cultural education (𝛽=0.20, p<.001) was statistically significant. According to results, it is necessary to develop and actively utilize regular curriculum and programs related to multi-culturalism for nursing students.

• Journal of KIISE:Computing Practices and Letters
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• v.14 no.7
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• pp.669-679
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• 2008

With the increasing demands of information sharing and searches via the web, the web search engine has drawn much attention. Although many researches have been done to solve technical challenges to build the web search engine, the issue regarding its query processing system is rarely dealt with. Since the software architecture and operational schemes of the query processing system are hard to elaborate, we here present related techniques implemented on a commercial system. The implemented system is a very large-scale system that can process 5-million user queries per day by using index files built on about 65-million web pages. We implement a multi-level cache scheme to save already returned query results for performance considerations, and the multi-level cache is managed in 4-level cache storage areas. Using the multi-level cache, we can improve the system throughput by a factor of 4, thereby reducing around 70% of the server cost.

• The Transactions of the Korean Institute of Power Electronics
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• v.15 no.1
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• pp.43-51
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• 2010

This paper proposes an analysis of voltage delay and compensation for current control in H-Bridge Multi-Level (HBML) inverters for a medium voltage motor drive with vector control. It is shown that the expansion and modularization capability of the HBML inverter is improved in case of using Phase-Shifted Pulse Width Modulation (PSPWM) since individual inverter modules operate more independently. But, the PSPWM of HBML has a phase difference between reference voltage and real voltage, which can cause instability in the current regulator at high speed where the ratio of the sampling frequency to the output frequency is insufficient. This instability of the current regulator is removed by adding a proposed method which compensate a phase difference between reference voltage and real voltage. The proposed method is suitable for HBML inverter controlled by PSPWM with low switching frequency and high speed motor drive. The validity of the proposed method is verified experimentally on 6,600[V] 1,400[kW] induction motor fed by an 13-level HBML inverter.

• Water for future
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• v.27 no.3
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• pp.55-69
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• 1994

In order to enhance the short-term flood forecasting accuracy of the water level of the In-do Brdg., three statistical flood forecasting models are presented models are presented and the forecasting accuracies and stabilities of the models are studied. The presented statistical models are as follows: The multi-input model by the multi-regression analysis between the water level of the In-do Brdg. and the influence parameters(Model MM). The two-level multi parameter model according to the water level tendency(Model 2MP). Among the three models, the Model MM showed the lowest forecasting accuracy, the model 2MP showed the highest forecasting accuracy, although this model sometimes became unstable and diverged. The model MMP forecasted the flood less accurately than model 2MP, but it gave more stable forecasting results.