• International Journal of Naval Architecture and Ocean Engineering
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• v.6 no.3
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• pp.529-561
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• 2014

The two-phase turbulent flow past an interface-piercing circular cylinder is studied using a high-fidelity orthogonal curvilinear grid solver with a Lagrangian dynamic subgrid-scale model for large-eddy simulation and a coupled level set and volume of fluid method for air-water interface tracking. The simulations cover the sub-critical and critical and post critical regimes of the Reynolds and sub and super-critical Froude numbers in order to investigate the effect of both dimensionless parameters on the flow. Significant changes in flow features near the air-water interface were observed as the Reynolds number was increased from the sub-critical to the critical regime. The interface makes the separation point near the interface much delayed for all Reynolds numbers. The separation region at intermediate depths is remarkably reduced for the critical Reynolds number regime. The deep flow resembles the single-phase turbulent flow past a circular cylinder, but includes the effect of the free-surface and the limited span length for sub-critical Reynolds numbers. At different Froude numbers, the air-water interface exhibits significantly changed structures, including breaking bow waves with splashes and bubbles at high Froude numbers. Instantaneous and mean flow features such as interface structures, vortex shedding, Reynolds stresses, and vorticity transport are also analyzed. The results are compared with reference experimental data available in the literature. The deep flow is also compared with the single-phase turbulent flow past a circular cylinder in the similar ranges of Reynolds numbers. Discussion is provided concerning the limitations of the current simulations and available experimental data along with future research.

• Journal of the Korea Society of Computer and Information
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• v.13 no.2
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• pp.19-29
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• 2008

In case of unit testing, White-box test can be used to closely check source code and to analyze logic and statement errors. On the other hand, in case of function testing of system level, Black-box test can be mainly used to compare actual and expected results by inputting test data because the scale of function is large. This Black-Box test in system testing level has problem in tracing errors in source code when we find errors. Moreover applying White-box test is not easy for system testing level because the levels of test target are different. Therefore this paper suggests the vertical test method of a practical and integrated system level which can checks up to source code level using White-box test style although it aims to test the highly abstract level like a system function. In addition, the experiment explains how to apply the vertical test by displaying an example which traces from UML specification model to the source code and also shows efficiency of error trace.

• Journal of Korea Water Resources Association
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• v.36 no.4
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• pp.575-586
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• 2003

In case of continuous input of a pollutant, dispersion characteristics do not change much with changing dispersion coefficient, but that of an instantaneous input is very sensitive to the changes of dispersion coefficient. The characteristics of behavior of instantaneous input of a pollutant at the downstream of Han river were analyzed in this paper Field measurement of hydraulic and water quality factors at the downstream of Han river were conducted at low flow condition. The hydraulic factors were used to estimate the longitudinal dispersion coefficient, and the reasonable empirical equations for longitudinal dispersion coefficient at the downstream of Han river were suggested. The measured concentrations of BOD were closely matched with the calculated ones from RMA-4 model. In case of instantaneous input, range of dispersion, transport pathway and the traveltimes of the first and maximum concentration with variation of the longitudinal dispersion coefficients and water levels of downstream boundary were evaluated in this paper.

• Journal of Korea Water Resources Association
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• v.35 no.4 s.129
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• pp.345-358
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• 2002

The flow apportioning algorithms with digital elevation models have been developed to reflect reasonable flow divergence properties but they showed several defects related to the connectivity of channel cells, various divergence features along to local topography and channel cells' size etc. Topographic data used by existing flow apportioning algorithms are flow accumulation area and local slope. However, the size and location of channel cells which play the dominant role in the flow pathway were not properly considered. Therefore, a new flow apportioning algorithm considering various flow divergence characteristics in the complicate terrain is proposed. The GA optimization scheme is used to represent the location and scale of the channel pixel. Improved result can be obtained by using both a new flow apportioning algorithm and optimization.

• Journal of Korea Water Resources Association
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• v.36 no.4
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• pp.623-631
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• 2003

A large scale hydrological laboratory model tests for the geotextile tube were conducted to investigate the stability of geotextile tube and the capability of breakwater with variations of significant wave height, percentage of soil filling, and the water level above geotextile tube. The sliding displacement of geotextile tube is measured to check the stability of geotextile tube for given the various significant wane heights. The marked mash was laid out at the bottom of water channel to measure the displacement of geotextile tube. The bench mark was furnished in the upper part of water channel and the initial location was marked every 10cm interval to measure the displacement of geotextile tube. The wane transmit ratios are analyzed with the variations of soil filling of tube and of the top crown height wave above the geotextile tube in order to study the performance of brekwater before and after the installation of geotextile tube.

• Journal of Korea Water Resources Association
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• v.51 no.9
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• pp.783-793
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• 2018

The purpose of this study to present updated regional annual mean rainfall erosivity data in the Republic of Korea. In 2012, Ministry of Environment in Korea published the notice about investigation and survey procedure for the amount of topsoil erosion and adopted USLE (Universal Soil Loss Equation) model to predict the amount of national-scale soil erosion in Korea. In the notice, regional rainfall erosivity values for 158 sites, which is essential to apply the USLE, were included, however, these values came from the data made before 1997 and need to be updated. This study collected, classified and combined annual mean rainfall erosivity data from the literature review to analyze the data. We presented that new iso-erodent map, interpolated by IDW (Inverse Distance Weighted) method and extracted updated regional annual mean rainfall erosivity data at 167 regions for 1961~2015. These values will be used as updated rainfall erosivity data to predict the amount of topsoil erosion in Korea.

• Communications of Mathematical Education
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• v.26 no.1
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• pp.15-28
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• 2012

In order to study the relation between self-directed learning readiness and mathematical inclination, we survey the adjusted SDLRS(self-directed learning readiness scale) of Guglielmino's model and the mathematical inclination, the recognition of mathematics for 2011 year engineering freshmen in D university. Research results are as follows: First of all, middle level engineering freshmen showed average level of self-directed learning readiness, and they had lower level of motivation, passion and time management skill. The relation of SDLR and the mathematical inclination was strong. Furthermore, SDLR and the recognition of mathematics in engineering freshmen was found to be the most closely related. Based on the results of the study, we suggest to study of strategies to elevate SDLR of engineering students and improve their achievement in college mathematics. Especially, we suggest that college mathematics for engineering freshmen must be focused on the improvement of SDLR.

• Korea Journal of Hospital Management
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• v.4 no.2
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• pp.85-105
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• 1999

The main purpose of this article is to analyze the managerial performance of small and medium-size hospitals that are specialized in certain areas of medical services. Data of 189 hospitals were obtained from the data file of Korea Institute of Health Services Management The items include general characteristics of the hospitals, fianancial reports, and utilization records. Degree of specialization is measured by concentration(Herfindahl) index, and the sample hospitals are accordingly classified into specialized and unspecialized groups, by means of cluster analysis. These groups are compared in terms of various measures of managerial performance, which include several profitability indices such as operating margin, return on assets(ROA), and return on equity(ROE). To examine the relationship between specialization and managerial performance, we estimate the regression model, where the profitability indices are used as the dependent variables and the concentration index as the independent variable, controlling for the hospital characteristics such as size, type and location. Also, we perform 'Du Pont' analysis, to investigate the basic elements that can explain the differences in profitability between specialized and unspecialized hospitals. Major findings are as follows: 1. Managerial performance is better for the specilized hospitals than the unspecilized, in all aspects of profitability(operating margin, ROA, ROE). 2. Regression analysis suggests that there is a positive, statistically significant relationship beween the degree of specialization(i.e. concentration) and hospital profitability. 3. Main reason for the higher profitability of specialized hospitals lies in lower expenses rather than higher revenue. 4. In particular, personnel and material expenses are significantly smaller for the specialized hospitals, and this result seems to stem from the efficiency of operating fewer lines of business.(some kind of 'economies of scale') 5. Specialized hospitals also have fewer employees compared with the unspecialized, especially in administrative departments, which implies their efficient personnel management.

• Korea Journal of Hospital Management
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• v.17 no.1
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• pp.23-42
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• 2012

The purpose of this study is to identify the inpatient service quality at mental hospitals and to examine the effect of service quality on patient's overall satisfaction and customer loyalty. Data collection was done through conducting a survey of inpatients in three mental hospitals located in Chungnam, Korea using self administered questionnaire. The questionnaire included the modified version of 'service satisfaction scale for psychiatric patients' invented by Chul Kwon Kim and other members, which consists of five dimension of service quality: staff attitude, treatment quality, ward environment, access/cost and ward rule. Total 236 questionnaires were gathered and 219 were used for analysis. The data was analyzed by using version SAS9.2 and path analysis model was applied to test our hypothesis. As a result, the four factors of service (staff attitude, treatment quality, ward environment and ward rule) were extracted, which counted for 62.89% of the common variance. Moreover, Cronbach Alpha showed relatively high internal consistency of answer, all exceeding 0.6. According to the study, ward environment and treatment quality turned out to have direct influence on the patient's satisfaction. In addition, staff attitude and overall satisfaction directly influenced the customer loyalty while ward environment and ward rule indirectly had influence using overall satisfaction as a medium. In conclusion, in order to enhance the satisfaction and customer loyalty in mental hospitals, efforts in improving environmental service quality in particular is highly demanded.

• Journal of Families and Better Life
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• v.30 no.5
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• pp.107-119
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• 2012

This study examined the mediating effect of maternal abuse and neglect on the relationship between socioeconomic status and preschoolers' social behavior. A total of 702 mothers with 3-year-olds(353 boys and 349 girls) and the children's teachers, all of whom reside in Seoul, participated in the study. Socioeconomic status was measured by maternal educational level and monthly household income. Maternal abuse and neglect were assessed by asking mothers to complete the Parent-to-Child Version of the Conflict Tactics Scales. Both mothers and teachers completed the Preschool Social Behavior Scale in order to evaluate prosocial behavior and aggression. The results indicated that both socioeconomic status and maternal abuse and neglect were significantly associated with preschool children's prosocial behavior, and socioeconomic status was significantly and negatively related to aggression. Furthermore, a structural equation model confirmed the mediating effect of maternal abuse and neglect on the relationship between socioeconomic status and preschool children's prosocial behavior, suggesting the need for interventions focusing on improving positive parenting and decreasing negative parenting to promote prosocial behavior.