• Journal of Power Electronics
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• v.15 no.4
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• pp.939-950
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• 2015

A single-stage AC-AC converter has been designed for a wind energy conversion system (WECS) that eliminates multistage operation and DC-link filter elements, thus resolving size, weight, and reliability issues. A simple switching strategy is used to control the switches that changes the variable-frequency AC output of an electrical generator to a constant-frequency supply to feed into a distributed electrical load/grid. In addition, a modified random sinusoidal pulse width modulation (RSPWM) technique has been developed for the designed converter to make the overall system more efficient by increasing generating power capacity and reducing the effects of inter-harmonics and sub-harmonics generated in the WECS. The technique uses carrier and reference waves of variable switching frequency to calculate the firing angles of the switches of the converter so that the three-phase output voltage of the converter is very close to a sine wave with reduced THD. A comparison of the performance of the proposed RSPWM technique with the conventional SPWM demonstrated that the power generated by a turbine in the proposed approximately increased by 5% to 10% and THD reduces by 40% both in voltage and current with respect to conventional SPWM.

• Advances in aircraft and spacecraft science
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• v.9 no.2
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• pp.131-148
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• 2022

The paper presents the surface-modified NACA 2412 airfoil performance with variable cavity characteristics such as size, shape and orientation, by numerically investigated with the pre-validation study. The study attempts to improve the airfoil aerodynamic performance at 30 m/s with a variable angle of attack (AOA) ranging from 0° to 20° under Reynolds number (R_e) 4.4×10⁵. Through passive surface control techniques, a boundary layer control strategy has been enhanced to improve flow performance. An intense background survey has been carried out over the modifier orientation, shape, and numbers to differentiate the sub-critical and post-critical flow regimes. The wall-bounded flows along with its governing equations are investigated using Reynolds Average Navier Strokes (RANS) solver coupled with one-equational transport Spalart Allmaras model. It was observed that the aerodynamic efficiency of cavity airfoil had been improved by enhancing maximum lift to drag ratio ((l/d) max) with delayed flow separation by keeping the flow attached beyond 0.25C even at a higher angle of attack. Detailed investigation on the cavity distribution pattern reveals that cavity depth and width are essential in degrading the early flow separation characteristics. In this study, overall general performance comparison, all the cavity airfoil models have delayed stalling compared to the original airfoil.

• Smart Structures and Systems
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• v.33 no.1
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• pp.65-91
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• 2024

The use of five optimization techniques for the prediction of a strength-based concrete mixture's best-fit model is examined in this work. Five optimization techniques are utilized for this purpose: Slime Mold Algorithm (SMA), Black Hole Algorithm (BHA), Multi-Verse Optimizer (MVO), Vortex Search (VS), and Whale Optimization Algorithm (WOA). MATLAB employs a hybrid learning strategy to train an artificial neural network that combines least square estimation with backpropagation. Thus, 72 samples are utilized as training datasets and 31 as testing datasets, totaling 103. The multi-layer perceptron (MLP) is used to analyze all data, and results are verified by comparison. For training datasets in the best-fit models of SMA-MLP, BHA-MLP, MVO-MLP, VS-MLP, and WOA-MLP, the statistical indices of coefficient of determination (R²) in training phase are 0.9603, 0.9679, 0.9827, 0.9841 and 0.9770, and in testing phase are 0.9567, 0.9552, 0.9594, 0.9888 and 0.9695 respectively. In addition, the best-fit structures for training for SMA, BHA, MVO, VS, and WOA (all combined with multilayer perceptron, MLP) are achieved when the term population size was modified to 450, 500, 250, 150, and 500, respectively. Among all the suggested options, VS could offer a stronger prediction network for training MLP.

• Animal cells and systems
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• v.13 no.4
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• pp.419-427
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• 2009

The Minke whale, Balaenoptera acutorostrata, is the smallest baleen whale in the suborder Mysticeti. Because this species inhabits coastal areas, it became a main target species of coastal small-type whaling in the North Atlantic and the Northwest Pacific Oceans, and the species' population size dramatically decreased because of over-exploitation. As a result, the International Whaling Commission declared a global moratorium on whaling and launched the development of a management procedure for protecting the whales. Morphological studies, whaling history analysis, and genetic studies conducted mainly by Japanese scientists showed the existence of one unique "E" stock that inhabits the waters around the Korean peninsula and mixes with the "O" stock in the southern part of the Sea of Okhotsk. We used the mitochondrial DNA control region polymorphism of 348 Minke whales bycaught or stranded in Korean waters from 30 October 1998 to 25 June 2005 to assess the whale population structure by year. The frequency of the 10 major haplotypes from the 40 identified haplotypes was not significantly different among groups, suggesting that a subpopulation was not present. A comparison of the genetic distances calculated with Tamura-Nei's method showed that the distances between groups were lower than those within groups, which suggests that there was no genetic difference in the Minke whale populations. The Fst comparison between groups and the phylogenetic tree constructed using the unweighted pair group method with arithmetic mean (UPGMA) and Neighbor Joining (NJ) method also detected no obvious sub-stock structure.

• Clinical and Experimental Pediatrics
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• v.52 no.4
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• pp.488-493
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• 2009

Purpose : The aim of this study was to assess the efficacy and safety of recent-generation patent ductus arteriosus (PDA) closure devices applied by a new selection strategy according to the characteristics of each PDA. Methods : From February 2003 to January 2006, 138 patients underwent transcatheter closure of PDA (study group). According to the size and morphology of each ductus, a COOK Detachable Coil or 'flex' PFM Nit-Occlud was used for a small ductus (group 1, n=43); 'medium' PFM Nit-Occlud (group 2, n=49) for a moderate ductus; and an Amplatzer Duct Occluder (group 3, n=46) for a large ductus. The 83 patients who underwent transcatheter closure of PDA from February 2000 to January 2003 were defined as the comparison group. The Qp/Qs ratio, pulmonary/aorta pressure ratio, and MD of the ductus were compared. Immediate and follow-up results including residual shunts and complications were also evaluated and compared among groups. Results : In all 138 patients, complete occlusions were confirmed without major complications, while procedure failure (n=2, 2.2%), device embolization (n=1, 1.1%), and persistent residual shunt (n=4, 4.5%) were documented in the comparison group. Total complication rates were lower in the study group than in the comparison group (study group, 1.4%; comparison group, 9.0%; P<0.05). Conclusion : A novel strategy adopting the merits of various recent-generation devices for transcatheter closure of PDA provides excellent clinical results with minimal risk.

• Strategy21
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• s.41
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• pp.261-293
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• 2017

Nuclear power is a way of attaining an enormous amount of energy with relatively small amount of resources and after it has been introduced to the submarine since 1954, there are approximately 150 of nuclear powered submarine currently on a mission around the world. This is due to the maneuverability, mountability and covertness of nuclear submarines. However, there are other tasks, not only the high level of nuclear technology that are needed to be dealt with in order to construct nuclear powered submarine. The biggest task of all is to secure the enriched uranium. Accordingly, this research is about the way of enriching and securing the nuclear fuel that are used in the nuclear submarine with the characteristics, merits and demerits of the nuclear submarine. Due to the fact that the pressurized water reactor in South Korea is the reactor that was originally built for the development of nuclear powered submarine, many parts is designed to be suitable for the submarine propulsion. However, in order to apply this to submarine it is needed to consider additional requests such as the position of reactor, accident-coping system, radioactive covering, reactor output adjustment and ship's pitch and roll in order to apply this to submarine. Nuclear submarines have much higher speed based on the powerful propulsion in comparison with diesel-electric submarine and also have bigger loading area. Besides, there is no need to snorkel and they also have advantages in covertness with the multi-noise proof system. The nuclear technology in South Korea has seen the dramatic development since 1962 and in 1998 reached to the level that we have succeeded in the localization of nuclear plant and exported the world-class one-piece small-sized reactor (SMART) to UAE. To operate these reactors, we import the whole quantity of low-enriched uranium and having our own uranium enrich facility is not probable because of the budget and international regulations. With the ROK/US nuclear agreement revised on 2015 November, the enrichment of uranium that are available without special permission has changed up to 20%. According to the assumption that we use the 20% enrichment of Uranium on U.S. virginia class submarine, it is necessary to change the fuel after 11 years and it will cause additional cost of 1 billion dollars. But the replace period by the uranium's enrichment rate is not fixed so that it is possible to change according to the design of reactor. Therefore, I would like to make a suggestion on two types of design concepts of nuclear submarine that can be operated for 30 years without nuclear fuel change by using the 20% enriched uranium from ONNp.First of all, it is possible by increasing the size of reactor by 3 times and it results in the 1,000t increase of the weight. And secondly, it is by designing the one piece reactor to insert devices such as steam turbine, condenser into the inside of nuclear core like the Rubis class submarines of France.

• Asia-Pacific Journal of Business Venturing and Entrepreneurship
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• v.17 no.4
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• pp.73-86
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• 2022

Interest and investment in agri-food ventures is increasing worldwide. Agri-food venture startups are also increasing in Korea, but there are constraint factors due to industrial characteristics, and infrastructure and investment for growth are insufficient. This study confirmed the effect of technology commercialization capability and competitive strategy on the growth prospects of agri-food venture companies and the mediating effect of business model innovation. And, through comparison with previous studies, the industrial characteristics were identified by confirming the difference between all venture companies and agri-food ventures. For this, only agri-food ventures data were extracted from the original data of the Research on the Precision Status of Venture Firms 2021. And empirical analysis was conducted. As a result, manufacturing capability, cost leadership and product differentiation had a positive(+) effect on growth prospects. The mediating effect of business model innovation between manufacturing capacity, product differentiation and growth prospects was verified. Through the research results, factors affecting the long-term growth prospects of agri-food ventures were identified in consideration of industrial characteristics. In addition, practical implications in connection with business model innovation of agri-food ventures were presented. In future research, it is necessary to develop an objective measurement tool and to conduct a detailed analysis according to business history and company size.

• Journal of Acupuncture Research
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• v.18 no.4
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• pp.1-12
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• 2001

Study design : A retrospective study of lumbar disc herniations using results of follow-up computed tomographic scan examinations. Objective : Lumbar disc herniations is one of the cause low back pain and lower extremity pain. To clarify the lumbar disc herniations morphological changes over time(mean 5.3 years) in order to establish a strategy for treatment. Methods : Sixteen patients with lumbar disc herniations who underwent follow-up computed tomographic scan examinations were studied. The changes over time in herniated disc size(herniation ratio) were evaluated using this scan technique. The initial computed tomographic scan allowed classification of the herniations according to herniation ratio: small, medium and large. Results : Comparison with follow-up computed tomographic scans showed that of the 16 patients, in 14 patients(88%), the herniation ratio(HR) was decreased and among them, 8 patients had complet resolution of herniated disc. In 2 patients with small herniations, the HR of one case was increased, the other was decreased. In 8 patients with medium herniations, the HR of one case had no change, the others was decreased. In 6 patients with large herniation, the HR of all patients was decreased. Interestingly, 4 of the 16 patients showed calcification change of herniated disc. Conclusion : There is no doubt that herniated disc size is decreased over time. The largest herniations were those which had the greatest tendency to decrease in size. But in some cases, the HR was increased, or calcification change was showed.

• Journal of Korea Society of Industrial Information Systems
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• v.19 no.4
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• pp.133-146
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• 2014

This paper mainly focuses on the design factors of a website targeted at shopping mall websites in China and Korea. We formulated 15 different hypotheses regarding how those design factors are different. The targeted websites are "Gmarket" in Korea and "Taobao" in China. The selected design factors of a shopping mall website are (1) color and design, (2) photo, graphic, and font size, (3) the clarity of information delivery, (4) website structure, (5) screen balance, (6) product display, (7) product harmony, (8) a form of font and icon, (9) visual atmosphere, (10) differentiated color, (11) interesting words, (12) technical skills, (13) entire visual design and atmosphere, (14) navigation, (15) search function for products or information. As a result of analyzing the result using the SAS 9.2 package tool, we figured out that there was a difference between design factors. Additionally, we analyzed this difference and suggested a strategy to design the effective shopping mall web sites.

• The Research Journal of the Costume Culture
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• v.19 no.6
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• pp.1288-1301
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• 2011

The purpose of this study was to observe a case study of pop-up stores in an apparel company in Korea in order to evaluate different feel and to determine the purchase behavior of pop-up visitors of three major fashion brands. This research was conducted through secondary data collection and primary data collection. A survey was conducted among NIKE, KUHO, and PUMA pop-up store visitors who were 20 to 40 years old, via questionnaires. Data were collected on-line and off line at the pop-up store. Data were analyzed using SPSS program. Through data analysis, we learned that most of the study participants were captivated by the digital elements in the environment of the NIKE pop-up store. Puma, the second most favorably ranked, was favored for its interior design. Meanwhile, KUHO stimulated its customers with its limited edition fashion products at a good price. Several feels of visitors about the pop-up stores were significantly different among the 3 different brands. There was a significant difference in purchase criteria, such as brand recognition, size, and design among visitors of the three different brands. Visitors who preferred KUHO considered design of products more than NIKE-preferred visitors. In conclusion, the clothing pop-up stores have the possibility of satisfying consumers' desires. Each brand can achieve a good performance in promotion with a differentiated strategy.