• Transactions of the Korean Society of Mechanical Engineers A
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• v.39 no.11
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• pp.1123-1129
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• 2015

A pair of two-way valves typically is used in automotive washing machines, where the water flow direction is frequently reversed and highly pressurized clean water is sprayed to remove the oil and dirt remaining on machined engine and transmission blocks. Although this valve system has been widely used because of its competitive price, its application is sometimes restricted by surging effects, such as pressure ripples occurring in rapid changes in water flow caused by inaccurate valve control. As an alternative, one three-way reversing valve can replace the valve system because it provides rapid and accurate changes to the water flow direction without any precise control device. However, a cavitation effect occurs because of the complicated bottom plug shape of the valve. In this study, the cavitation index and percent of cavitation (POC) were introduced to numerically evaluate fluid flows via computational fluid dynamics (CFD) analysis. To reduce the cavitation effect generated by the bottom plug, the optimal shape design was carried out through a parametric study, in which a simple computer-aided engineering (CAE) model was applied to avoid time-consuming CFD analysis and difficulties in achieving convergence. The optimal shape design process using full factorial design of experiments (DOEs) and an artificial neural network meta-model yielded the optimal waist and tail length of the bottom plug with a POC value of less than 30%, which meets the requirement of no cavitation occurrence. The optimal waist length, tail length and POC value were found to 6.42 mm, 6.96 mm and 27%, respectively.

• Clinical and Experimental Reproductive Medicine
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• v.30 no.4
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• pp.333-340
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• 2003

Objective: This study was performed to examine the maturation and the development to the blastocyst stage of immature oocytes collected from patients with high risk of ovarian hyperstimulation syndrome (OHSS). Materials and Methods: Cumulus-oocyte complexes (COCs) were collected following only HCGpriming for non stimulated IVF-ET cycles of the patients. At the time of oocyte collection, COCs were classified into three groups in accordance with their appearance (Group I: oocytes with dispersed cumulus cells; Group II: oocytes with compacted cumulus cells; Group III: oocytes with sparse cumulus cells). The in vitro maturation and blastocyst development rates of the COCs were compared among these groups. From August 2001 to June 2002, 48 IVM/IVF-ET cycles from 42 patients (mean age: $32.4{\pm}3.8$ years) were performed. To prevent the occurrence of OHSS, the patients were primed with 10, 000 IU HCG alone 36 h before oocyte collection without gonadotropin stimulation. Oocytes were aspirated on cycle days from 7 to 13. The normal COCs were classified into three groups according to their appearance. The aspirated immature oocytes were cultured in YS maturation medium containing 30% (v/v) human follicular fluid (HFF), 1 IU/ml FSH, 10 IU/ml HCG and 10 ng/ml rhEGF. Fertilization was induced by intracytoplasmic sperm injection (ICSI). All zygotes were co-cultured with cumulus cells in $10{\mu}l$ YS medium containing 10% HFF until day 7 after oocyte collection. Blastocyst transfer was performed on day 5 after ICSI. Results: Th e mean number of oocytes cultured in the IVM/IVF cycles was $24.7{\pm}10.6$. Of 1185 COCs, those assigned to Group I, II and III were 470 (39.7%), 414 (35.0%) and 301 (25.4%), respectively. The maturation rate (94.5%, 444/470, p<0.05) in Group I was significantly higher than those of Group II (62.8%, 260/414) and Group III (73.1%, 220/301). Especially, 30.9% of COCs in Group I (145/470) was matured on the day of oocyte aspiration. There were no differences in the rates of fertilization and cleavage among the three groups. The development rate to the blastocyst stage in Group I (54.6%, 206/377, p<0.05) was also significantly higher than those in Group II (33.0%, 68/206) and Group III (30.1%, 52/173). Twenty-four clinical pregnancies (50.0%) was obtained and 22 pregnancies (45.8%) are ongoing. Implantation rate in the present study was 24.6%. Conclusion: These results suggest that there is a positive correlation between the appearance of COCs and the developmental competence of the immature oocytes in non stimulated IVM/IVF cycles.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.5
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• pp.3610-3618
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• 2015

The congestion of railway vehicle and station shows up to 220%. Especially, transfer resistance of passenger increase rapidly by the collision of circulation. So increment of travel time, occurrence of safety accidents act as a factor that inhibits the utilization of urban railway station. In this paper, to improve traveling speed and comfort of urban rail passengers, urban transit passenger guidance system using congestion management model is proposed. The congestion management model that can mitigate a recurring/non-recurring congestion is constructed and the preliminary design of the system (middleware system, control system, guidance drive system) is carried out. Passenger Guidance System is configured by step for changing the external data into a form usable by the algorithm, step to perform the congestion management algorithm using the real-time data and historical data, step to control device based on the value that is calculated by congestion management algorithm, step to drive the device based on the information in the control system and circulation guidance devices. In the future, detail design will be performed based on the preliminary design. A prototype of the various devices according to the station structures and locations will be made. The control module of guidance device will be developed.

• Asia pacific journal of information systems
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• v.23 no.2
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• pp.41-66
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• 2013

IS outsourcing has an important meaning to the Korean SME's (Small and Medium Enterprises) which want to use the IS Services. The objective of this research is to manage IT risks occurred during IS outsourcing project process. This study tries to identify these risks using real option methodology. In order to perform this objective, this study set up the research model which is composed of two main concepts. The first one is the risk factors occurred during IS outsourcing project process: User's Risks, Supplier's Risks and Transaction's Risks. All of these risks are based on Transaction Cost Theory. The second one is the intention to get (or buy) Real Options to manage the risks. In the research model, two types of real option are included: option to abandon (put option) and option to defer (call option). This study uses questionnaires and statistics methodology (PLS) to analyze the hypotheses proposed in the research model. Compared with prior studies, this study is different in two ways. First, this study restricts the range of IT risks. Prior researches of IT Risk management in MIS area cover various range of IT risks, but this study focuses on the Korean SME's IT outsourcing risks on the basis of Transaction Cost Theory. This study tests the relationship between the risks and real option types. Second, this study tries to test the moderating effect of user's risks and supplier's risks on the relationship between transaction's risks and real option types. In IT outsourcing research area, almost studies focus on the direct relationships between IT risks and outsourcing success. But in reality, the co-relationship among IT risks may occur. There are some findings according to the research analysis. First, risks related with user's risks have strong causal relationships with the intention to get option to abandon (put) and option to defer. But risks related with supplier's risks have causal relationships only with option to abandon (put). Second, user's risks and supplier's risks have no moderating effect on the relationship between transaction's risks and real option types. According to the research results, this research have some important and interesting implications on the IS outsourcing business area. First, this study identifies the effective types of real option to minimize the risks occurred during the IT outsourcing projects. So IS outsourcing service users can manage (or minimize) effectively the risks, which occurred during outsourcing projects, using real options. Second, real option gives benefits to suppliers and users at the same time (i.e., win-win strategies between IS outsourcing service providers and users). Vendors (:IS outsourcing service providers) can offer users the real options which can minimize the occurrence of risks in time. "IN TIME" means that before the IS outsourcing project starts, vendors can offer users the opportunity to buy real options in appropriate prices to manage the possibility of the risks of IS outsourcing project. And users also have chance to minimize the IT outsourcing risks occurred during the project process using real options.

• Korean Journal of Ecology and Environment
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• v.49 no.4
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• pp.258-270
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• 2016

This study was conducted to test the green-tide mitigation technique in the lower part of the Sook Stream (Chusori) of Daecheong Reservoir from June 27 to August 24, 2014. And the effects were compared with weekly monitoring result of the watching station of the algae alert system (AAS) as well as test beds reach. The green-tide in a test bed was begun from the upstream, and it was gradually transferred and spread toward the downstream by the hydrological factors. The total amount of algae removed by algae removal device during the test period was 33,920 kg, and solids dewatered by natural gravity was 8,480 kg. Also chlorophyll-a content was 2.83 kg, the number of blue-green algae cells was equivalent to $78.6{\times}10^{14}$ cells. Compared with the results of the watching station of AAS, the pre-concentrate removal work in the outbreak waters was able to suggest the possibility of green-tide mitigation. In addition, an effective management of the green-tide was required spatial and temporal occurrence information and practical device technology. Particularly, the optimal timing of algae removal in the river-reservoir hybrid system was recommended at times before the monsoon rainy season and reached the lowest water level.

• Journal of The Korean Society of Grassland and Forage Science
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• v.36 no.2
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• pp.159-166
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• 2016

This study was conducted to examine the effect of IgY supplementation on growth performance, blood metabolism, and disease occurrence in the weaned calves at 3 or 4 month of age. Average daily gain (ADG) and feed intakes were not affected by IgY supplementation, regardless of weaning months. White blood cell (WBC) count of the control group was higher in the final stage than in the initial stage (p<0.05), while that of the IgY supplemented group was lower in the final stage compared to the initial stage (p<0.05). regardless of treatments. Hematocrit (HCT) and red blood cell (RBC) counts were lower in the final stage than in the initial stage (p<0.05), but mean corpuscular volume (MCV) and mean corpuscular hemoglobin (MCH) counts were higher in the final stage than in the initial stage, regardless of treatments. In the control group, concentrations of albumin and globulin were higher in the final stage compared to the initial stage in the weaned calves at 3 month of age (p<0.05), and concentration of blood urea nitrogen (BUN) was increased in the IgY supplemented group. In the control group, concentrations of aspartate aminotransferase (AST) and gamma (${\gamma}$)-glutamyl transferase (GGT) were higher in the final stage compared to the initial stage (p<0.05). In contrast, concentrations of aspartate aminotransferase (AST) and gamma(${\gamma}$)-glutamyl transferase (GGT) were lower in the final stage compared to the initial stage for the IgY supplemented group. A diarrhea calf was only found in the control group. Manure score was higher in the control group compared to IgY supplemented group (p<0.05). Thus, these results indicates that IgY supplementation had positive effects on some blood metabolites, fecal condition score and diarrhea without negative effect on growth performance of the weaned Hanwoo calves.

• Journal of dental hygiene science
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• v.12 no.6
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• pp.583-590
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• 2012

The purpose of this study was to investigate effect of the economic stress and state-trait anxiety on the periodontal disease in order to prevent the occurrence and progression of periodontal disease. Date were collected from total of 326 subjects in their forties and fifties by using questionnaire and examination of periodontal states during the period from February to November 2011. Results were analyzed by using frequency, t-test, ANOVA and Multiple regression of SPSS ver. 19.0. 1. The economic stress were significant statistically to the higher, medium and low of gingival index (p<0.01). 2. The state-trait anxiety were significant statistically to the higher, medium and low of gingival index (p<0.001), of the pocket depth (p<0.05), of the clinical attachment loss (p<0.05). 3. The gingival index were investigate effect of the higher the economic stress ($\beta$=0.052, p<0.01), the higher the state-trait anxiety ($\beta$=0.052, p<0.01). As a result, this study suggests that the dental clinic institute needs to let the patients with the periodontal disease know about the effects of economic stress and state-trait anxiety. They also necessarily need to implement education program including stress management, economic stress, and state-trait anxiety improvement in order to prevent periodontal disease and to take charge.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.12 no.4
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• pp.724-729
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• 2008

In the case of 'MAEMI', the Typhoon which formed in September, 2003, the largest-scale damage of tidal wave was caused by the co-occurrence of Typhoon surge and full tide. Until now Korea has been focusing on the calculating the amount of damage and its restoration to cope with these sea and harbor disasters. It is essential to establish some systematic counterplans to diminish such damages of large-scale tidal invasion on coastal lowlands considering the recent weather conditions of growing scale of typhoons. Therefore, the purpose of this research is to make the counterplans for prevention against disasters fulfilled effectively based on the data conducted by comparing and analyzing the accuracy between observation values and the results of estimating the greatest overflow area according to abnormal tidal levels centered on Masan area where there was the severest damage from tidal wave at that time. It's necessary utilize data like high-resolution satellite image and LiDAR(etc.) for correct analysis data considering geographical characteristics of dangerous area from the storm surge. And we must make a solution to minimize the damage by making data of dangerous section of flood into GIS Database using those data (as stated above) and drawing correcter damage function.

• Journal of the Korean Regional Science Association
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• v.37 no.3
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• pp.3-18
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• 2021

The fourth Industrial Revolution is transforming the industrial structure of the region, and it is necessary to develop new industries and technologies that reflect regional characteristics. The purpose of this study is to measure the knowledge relatedness and technological complexity in Busan, Ulsan, and Gyeongnam, and to identify technologies with potential for regional industrial differentiation strategies. Using patent data from 2015 to 2019, co-occurrence matrices were derived from 652 IPC codes, and the knowledge relatedness density and technology complexity index were calculated. Network analysis was performed using the knowledge relatedness density. As a result of analysis, it was found that mechanical engineering occupied a large proportion, followed by chemistry and electrical engineering. As a result of applying the risk-benefit framework to derive technologies with the potential to differentiate local industries, the technological capabilities of low-risk-high-benefit were different. Among mechanical engineering, technologies such as engine, machine operation, and transportation were included in Busan. In Ulsan, environmental technology in chemical and materials, and heat treatment technology in mechanical engineering were technologies with low-risk and high-benefit capabilities. Gyeongnam showed competence in mechanical engineering, chemistry, and electrical engineering in some areas such as Gimhae, Yangsan, and Changwon. The results of this study are meaningful in that they identified technologies with potential for selecting and deriving strategic industries for regional growth based on latent knowledge in the region.

• Ecology and Resilient Infrastructure
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• v.8 no.3
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• pp.154-163
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• 2021

This study was carried out to identify the factors affecting the distribution of suitable habitats for Geranium carolinianum, which was naturalized in South Korea, and to predict the changes of distribution in the future. We collected occurrence data of G. carolinianum at 68 sites in South Korea, and applied the MaxEnt model under climate change scenarios (SSP2-4.5, and SSP5-8.5). Precipitation seasonality (bio15), mean temperature of warmest quarter (bio10), and mean temperature of driest quarter (bio09) had high contribution for potential distribution of G. carolinianum. According to climate change scenarios, high suitable habitats of G. carolinianum occupied 6.43% of the land of South Korea in historical period (1981~2010), and 92.60% under SSP2-4.5, and 98.36% undr SSP5-8.5 in far future (2071~2100).