• Journal of Power Electronics
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• v.17 no.5
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• pp.1363-1371
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• 2017

In this paper, an improved Direct Power Control (DPC) algorithm is presented for grid connected three phase PWM rectifiers. The new DPC approach is based on two main tasks. First the optimization of the look-up table, which is well-known in conventional DPC, is outlined for selecting the optimum converter output voltage vectors. Secondly a very simple and effective method is used to directly calculate their duty cycles from the power errors. Therefore, the measured active and reactive powers are made to track their references using hysteresis controllers. Then two vectors are selected and applied during one control cycle to minimize both the active and reactive power ripples. The main advantages of this method are that there is no need of linear current controllers, coordinates transformations or modulators. In addition, the control strategy is able to operate at constant switching frequencies to ease the design of the power converter and the AC harmonic filter. The control exhibits a good steady state performance and improves the dynamic response without any overshoot in the line current. Theoretical principles of the proposed method are discussed. Both simulation and experimental results are presented to verify the performance and effectiveness of this control scheme.

• Journal of Fashion Business
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• v.27 no.2
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• pp.52-69
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• 2023

Based on five types of health KF masks currently being commercialized, this study analyzed results of a survey of 316 male and female college students with experience in wearing health masks in Seoul metropolitan area. By identifying problems and improvement requirements according to current status of wearing health masks, results of this study could be used as basic data for designing ergonomic health mask with improved ease of wearing and satisfaction for human safety protection in the future. SPSS 26.0 statistical program was used for all data analyses, including post-hoc test, χ² test for cross-analysis, frequency analysis, independent samples t-test, ANOVA, and Duncan test. Considering that masks are worn for more than 8 hours a day on average, it is necessary to design masks considering materials, sizes of mask ear straps, elasticity and thickness of straps. The design should minimize contact with lips and cheeks with improved fit and comfort, blocking performance, and aesthetics. According to this survey, nearly 50% of respondents said they were willing to wear masks even after the end of COVID-19. Thus, it is necessary to perform research and improve masks to have excellent colors, designs, shapes, fit, and functions suitable for both pandemic and post-pandemic era when wearing masks is common.

• Journal of Environmental Impact Assessment
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• v.20 no.6
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• pp.857-866
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• 2011

This research categorized EIA target highways into following three types in order to minimize non-point source pollution from highway runoff. 1. Big drainage basin. 2. Small drainage basin. 3. Bridge section. The Natural, Filter and Swirl-Type devices were evaluated in terms of removal efficiency of TSS, BOD, COD, T-N, T-P, compatibility of site selection, economic feasibility, and maintenance convenience through which the final BMP was selected. According to the removal efficiency result, the area of Big and Small Drainage basin and bridge section had higher removal efficiency with natural facility than that of the Filter or Swirl-Type device. To make appropriate selection of highways'BMP for non-point source pollution, this study will aim to contribute to building more environmentally friendly highways by proposing the selection process that is made of 5 stages. 1. Selecting the target drainage basin. 2. Selecting the land for the mitigation facility. 3. Analysing the ease of maintenance. 4. Technically evaluating each installation. 5. Evaluating the effective implementation methods.

• The Proceedings of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.10 no.6
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• pp.37-47
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• 1996

An appropriate lighting standard for the museum is needed to minimize the deterioration of the exhibits by the light and to increase the ease of perception of visitors. To make the standard, museum lighting recommendations of several countries were analyzed. Using measured color change characteristics of Korean traditional artifacts, illuminance-hours for the artifacts with noticeable color change were calculated for various light sources, and the artifacts were classified into ISO levels. Considerations for making lighting standard and the proceedings to make a decision for the considerations were described. Finally, lighting standard which can be applicable to Korean museum was presented.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• v.31 no.2
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• pp.161-163
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• 2005

In the reconstruction of the hard tissue defect of the oral cavity, the usefulness of the chin bone graft, one of the intraoral donor site, is gradually increased. The advantages include reduced resorption rate after graft due to its membranous bone nature, relatively ease to harvest under local anesthesia, reduced operative time because of the same operative field, decreased morbidity, and relatively large amount of bone can be harvested compared to other intraoral donor site. It has also postoperative complications including paresthesia of the lip or chin area, discomfort of lower anterior teeth, and facial swelling around chin area. Of these complications, facial swelling occurs more frequently, is more severe as a early postoperative discomfort, and prevents fast recover of patient's social activity since this procedure is generally accomplished in the outpatient base under local anesthesia. So we applied a modified " gull-wing" type incision to minimize this complication, and now we report this simple but effective surgical technique with clinically favorable result.

• Korean Journal of Human Ecology
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• v.13 no.6
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• pp.985-995
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• 2004

The purpose of this study is to provide useful footwear information for manufacturers and teenagers so that they can produce or purchase proper footwear that would minimize discomfort. For this study, 486 junior high school students were surveyed with a questionnaire. SPSS WIN10 was used to process a statistical analysis such as ferq., factor analysis, t-test, ANOVA(LSD), crosstab, and coefficient correlation. The results are as follows: A significant difference existed between male and female students in purchasing footwear and using evaluation criteria. When they wear shoes for a long time, they usually experience numbness in toes, blisters, heel, bottom on the feet and peeled skin. Female students experienced more foot injuries than males. There were meaningful correlations among purchasing, evaluation criteria, and satisfaction of footwear. Providing proper information is believed very important for teenagers in choosing right footwear. Footwear manufacturers should help them produce suitable shoes, and further help them establish different marketing strategies. To ease the foot discomfort, shoes should be developed with various widths and sizes. Shock absorbing soles and more flexible materials are also necessary.

• Proceedings of the KWS Conference
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• 2002.10a
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• pp.361-365
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• 2002

Advancements in silicon phase control (SCR) technologies provide an arc welding power supply that has the capability to allow the alteration of the Alternating Current (AC) welding output. These technologies provide a square wave output involving sixteen frequency selections and multiple balance selections. While an AC out put is known to minimize magnetic disturbances associate with Direct Current (DC), the potentials of a non-sinusoidal waveform have not been explored. The focus of the paper is to determine the effects that the frequency and balance of an AC wave form output will have upon a high speed Submerge Arc (SAW) application. The test matrix of the project includes welding .250" steel plate. Joint type is square groove with a travel speed of 65 IPM. Each of the weld parameters was held constant, only the frequency and/or balance were altered between welds. Each frequency/balance combination involved three-gap spacing. Upon completion of the welds the bead profiles were measured and recorded. A relationships/trends were observed with various frequency and balance values. Optimum frequency and balance values were found for the .250" square groove application which permit consistent weld sizing, ease of slag removal, and minimal plate distortion.

• Journal of Information Management
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• v.27 no.2
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• pp.1-32
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• 1996

By the 1990s, Database Online Searching and CD-ROM Searching have been used universally in libraries. Due to their ease of use and facilitation, it is believed that such new media searching will produce more benefits than the usual printed materials. Furthermore, from the library management's point view, the new media searching's ability to minimize holding space will be another example of the advantage. The new media searching will have ever the printed materials. However, since it Is necessary to have an objective appraisal of the cost effectiveness in the implementation and the design of the new media system, it will be compared the new media searching with the conventional searching by using printed materials at the KIEP Library and Data Bank.

• Journal of Digital Convergence
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• v.19 no.11
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• pp.287-300
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• 2021

The purpose of this study is to verify the influence relationship of digitally converted services on consumers' intention to use since traditional services are being converted to digital services due to technological development and increase in non-face-to-face services. The study consisted of a program development procedure and a program effectiveness verification procedure, and bootstrapping was performed to verify the mediating effect adjusted along with multiple regression analysis. The subjects of this study were 323 university (graduate) students and the general public residing in Korea. Results. First, it was found that the three perceived interaction factors (perceived communication, perceived control, and perceived reactivity) of digital transformed services had a positive effect on perceived usefulness and perceived ease of use, respectively. Second, the relationship of influence of technology acceptance intention was verified. Third, it was confirmed that the effect of the three perceived interaction factors of digital transformed services on intention to use was mediated by perceived usefulness and perceived ease of use. Fourth, the mediating effect mediated by digital disparity was confirmed. As a result, it was confirmed that the three perceived interaction factors of the digitally converted service are important factors in the intention to use the digitally converted service. This suggests that efforts are needed to minimize the digital divide.

• The Transactions of the Korea Information Processing Society
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• v.4 no.12
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• pp.3010-3022
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• 1997

Expert system is one of AI area which was came out at the end of 19705s. It simulates the human's way of thinking to give solutions of Problem in many applications. Most expert system consists of many components such as inference engine, knowledge base, and so on. Especially the performance of expert system depends on the control of enfficiency of inference engine. Inference engine has to get features; tirst, if possible to minimize restrictions when the knowledge base is constructed second, it has to serve various kinds of inferencing methods. In this paper, we design and implement the inference engine which is able to support the general functions to knowledge domain and inferencing method. For the purpose, forward chaining, backward chaining, and direct chaining was employed as an inferencing method in order to be able to be used by user request selectively. Also we not on1y selected production system which makes one ease staradization and modulation to obtain knowledges in target domain, but also constructed knowledge base by means of Extended Clause Bit Metrics (ECBM). Finally, the performance evaluation of inference engine between Rete pattern matching and ECBM has been done.