• Nuclear Engineering and Technology
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• v.42 no.3
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• pp.297-304
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• 2010

In the design of advanced light water reactors (ALWRs) and in the safety assessment of currently operating nuclear power plants, it is necessary to evaluate the possibility of experiencing a degraded core accident and to develop innovative safety technologies in order to assure long-term debris cooling. The objective of this experimental study is to investigate the enhancement factors of dryout heat flux in debris beds by coolant injection from below. The experimental facility consists mainly of an induction heater, a double-wall quartz-tube test section containing a steel-particle bed and coolant injection and recovery condensing loop. A fairly uniform heating of the particle bed was achieved in the radial direction and the axial variation was within 20%. This paper reports the experimental data for 3.2 mm and 4.8 mm particle beds with a 300 mm bed height. The dryout heat density data were obtained for both the top-flooding and the forced coolant injection from below with an injection mass flux of up to $1.5\;kg/m^2s$. The dryout heat density increased as the rate of coolant injection increased. At a coolant injection mass flux of $1.0\;kg/m^2s$, the dryout heat density was ${\sim}6.5\;MW/m^3$ for the 4.8 mm particle bed and ${\sim}5.6\;MW/m^3$ for the 3.2 mm particle bed. The enhancement factors of the dryout heat density were 1.6-1.8.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.11 no.6
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• pp.774-788
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• 1999

To examine the enhancement mechanism of condensing heat transfer through microfin tube, the condensation experiments with refrigerant HCFC 22 are performed using 4 and 6 kinds of microfin tubes with outer diameter of 9.52mm and 7.0mm, respectively. Used microfin tubes have different shape and number of fins with each other The main heat transfer enhancement mechanism is known to be the enlargement of heat transfer area and turbulence promotion. Together with these main factors, we can find other enhancement factors by the experimental data, which are the overflow of the refrigerant over the microfin and microfin arrangement. The overflow of the refrigerant over the microfin can be analyzed by the geometric shape of the microfin. Microfin tubes having a shape which can give much overflow over the microfin show large condensing heat transfer coefficients. The effect of microfin arrangement is related to the heat transfer resistance of liquid film of refrigerant. The condensing heat transfer coefficients are high for the microfin tube with even distribution of liquid film.

• Journal of the Korean Society of Industry Convergence
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• v.27 no.2_2
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• pp.343-356
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• 2024

Super app is an application that provides a variety of services in a unified interface within a single platform. With the acceleration of digital transformation, super apps are becoming more prevalent. This study aims to suggest service enhancement measures by analyzing the user review data before and after the transition to a super app. To this end, user review data from a payment-based super app(Shinhan Play) were collected and studied via topic modeling. Moreover, a matrix for assessing the importance and usefulness of topics is introduced, which relies on the eigenvector centrality of the inter-topic network obtained through topic modeling and the number of review recommendations. This allowed us to identify and categorize topics with high utility and impact. Prior to the transition, the factors contributing to user satisfaction included 'payment service,' 'additional service,' and 'improvement.' Following the transition, user satisfaction was associated with 'payment service' and 'integrated UX.' Conversely, dissatisfaction factors before the transition encompassed issues related to 'signup/installation,' 'payment error/response,' 'security authentication,' and 'security error.' Following the transition, user dissatisfaction arose from concerns regarding 'update/error response' and 'UX/UI.' The research results are expected to be used as a basis for establishing strategies to strengthen service competitiveness by making super app services more user-oriented.

• Journal of the Korean Home Economics Association
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• v.36 no.12
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• pp.87-104
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• 1998

This study explores the life quality(LQ) of Korean married women compared to Korean married men's LQ, examines personal factors' and home environmental factors' influences to Korean married women's LQ via psychological factors such as social belongingness, positive emotion, self-esteem, and sense of intemal control in causal model, and explores Korean married women's perceived important factors and perceived enhancement required factors in life. The questionnaire was administered to 941 Korean married women and their husbands who have one or more children in Pusan. The results indicated that: 1. The overal and most sub dimensional LQ of Korean married women mark medium level and were lower than that of Korean married men's. Korean married women who is highly educated, keeps efficient communication with their husband, self-esteem, sense of internal control, social belongingness, and positive emotion, and possess high SES and much available resources shows higher LQ than those who doesn't. 2. The efficient communication with husband and available resources have direct and indirect influences on Korean married women's LQ. The psychological mediatory factors of these two variables' influences on women's LQ are such as social belongingness, positive emotion, self-esteem and sense of intemal control. SES has direct influence only and the educational level has indirect influence via social belongingness only on Korean married women's LQ. All these factors explain 58% of Korean married women's LQ variance. 3. Korean married women rank family health, family reconciliation, husband's success, and children's achievement as the very important factors in life. They also rank husbands success, economic abundant, family reconciliation, family health, and their self-actualization as the very required factors for enhancing the given LQ.

• Journal of the Korean Society of Safety
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• v.22 no.2 s.80
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• pp.53-58
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• 2007

This study is to find out primary factors through the punch list in the large scale apartment housing complex, to prevent repeatedly occurring defects of construction and to gain quality management. The following are the findings of the research. (1) The positive strengthening of supervision for the workers can contribute to prevent defects of apartment construction and make better quality of the construction. (2) A solution should be made for the poor of surface join and the damage of work element showing a lot in the apart construction, which prevent defects and improve construction quality. (3) Indirect factors such as negligence and carelessness of the management should be improved to advance construction quality, and the caution and control strengthening of the management should be followed. It is revealed that hitch, omission, and heedlessness come from the defects, and the shortage of skill and checking appear as indirect factors. Therefore, to get quality improvement, the enhancement of the management factors, employment of excellent workers, and enhancement of working attitude and construction management are needed.

• Journal of Korean Institute of Industrial Engineers
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• v.30 no.1
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• pp.65-75
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• 2004

The enhancement of C2(Command and Control) system will increase effectiveness of individual force power in combat engagement. Especially, available time of a given engaging force and information accuracy are the most influencing factors to increment of combat effectiveness after enhancement of C2 system. In this paper, by using Schutzer's C2 Theory and Measures of Effectiveness, we developed several analytical functions representing the relationships between C2 system enhancement and two most critical variables, available time and information accuracy. As a result of functional analysis, we showed C2 system enhancement and combat effectiveness have positive and non-linear relationship. The higher level of C2 system be required, the better combat effectiveness of force power can be obtained. Additionally, we proposed a proposition that the combat effectiveness of C2 system is more sensitive to available time than to information accuracy, which might be very important issue for further research in this field.

• Journal of The Korean Radiological Technologist Association
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• v.30 no.1
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• pp.131-142
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• 2004

In this study, when intravenous contrast medium was injected in spiral CT study, the effects of injection volume, injection rate, injection mode, location and lumen of IV catheter on enhancement of contrast medium in aorta, portal vein and liver parenchym

• Korean Journal of Agricultural Science
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• v.49 no.4
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• pp.789-799
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• 2022

The purpose of this study is to analyze farmers' perceptions of Greenhouse Gas Reduction Projects and identify factors influencing participation in the projects. To achieve the research objective, a survey was conducted and a probit model was adopted for the empirical analysis. The results showed that farmers do not participate in the projects due to a lack of education and promotion and due to economic loss. It also showed that the frequency of training and technical guidance learning, degree of recognition of the need for efforts to reduce greenhouse gases, and the level of recognition of the projects concerned have a positive impact on the willingness to participate in the projects. Meanwhile, participation in agricultural environment conservation programs has a negative impact on it. Enhancement of education and promotion as well as economic support (direct payment, R&D) would be useful to raise the willingness to participate in the projects.

• Korean Journal of Radiology
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• v.19 no.6
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• pp.1021-1030
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• 2018

Objective: We evaluated the effect of various patient characteristics and time-density curve (TDC)-factors on the test bolus-affected vessel enhancement on coronary computed tomography angiography (CCTA). We also assessed the value of generalized linear regression models (GLMs) for predicting enhancement on CCTA. Materials and Methods: We performed univariate and multivariate regression analysis to evaluate the effect of patient characteristics and to compare contrast enhancement per gram of iodine on test bolus (${\Delta}HUTEST$) and CCTA (${\Delta}HUCCTA$). We developed GLMs to predict ${\Delta}HUCCTA$. GLMs including independent variables were validated with 6-fold cross-validation using the correlation coefficient and Bland-Altman analysis. Results: In multivariate analysis, only total body weight (TBW) and ${\Delta}HUTEST$ maintained their independent predictive value (p < 0.001). In validation analysis, the highest correlation coefficient between ${\Delta}HUCCTA$ and the prediction values was seen in the GLM (r = 0.75), followed by TDC (r = 0.69) and TBW (r = 0.62). The lowest Bland-Altman limit of agreement was observed with GLM-3 (mean difference, $-0.0{\pm}5.1$ Hounsfield units/grams of iodine [HU/gI]; 95% confidence interval [CI], -10.1, 10.1), followed by ${\Delta}HUCCTA$ ($-0.0{\pm}5.9HU/gI$; 95% CI, -11.9, 11.9) and TBW ($1.1{\pm}6.2HU/gI$; 95% CI, -11.2, 13.4). Conclusion: We demonstrated that the patient's TBW and ${\Delta}HUTEST$ significantly affected contrast enhancement on CCTA images and that the combined use of clinical information and test bolus results is useful for predicting aortic enhancement.

• Korean Journal of Radiology
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• v.21 no.5
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• pp.561-571
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• 2020

Objective: To evaluate the clinical utility of ultrafast dynamic contrast-enhanced (DCE)-MRI compared to conventional DCE-MRI by studying lesion conspicuity and size according to the level of background parenchymal enhancement (BPE). Materials and Methods: This study included 360 women (median age, 54 years; range, 26-82 years) with 361 who had undergone breast MRI, including both ultrafast and conventional DCE-MRI before surgery, between January and December 2017. Conspicuity was evaluated using a five-point score. Size was measured as the single maximal diameter. The Wilcoxon signed-rank test was used to compare median conspicuity score. To identify factors associated with conspicuity, multivariable logistic regression was performed. Absolute agreement between size at MRI and histopathologic examination was assessed using the intraclass correlation coefficient (ICC). Results: The median conspicuity scores were 5 at both scans, but the interquartile ranges were significantly different (5-5 at ultrafast vs. 4-5 at conventional, p < 0.001). Premenopausal status (odds ratio [OR] = 2.2, p = 0.048), non-mass enhancement (OR = 4.1, p = 0.001), moderate to marked BPE (OR = 7.5, p < 0.001), and shorter time to enhancement (OR = 0.9, p = 0.043) were independently associated with better conspicuity at ultrafast scans. Tumor size agreement between MRI and histopathologic examination was similar for both scans (ICC = 0.66 for ultrafast vs. 0.63 for conventional). Conclusion: Ultrafast DCE-MRI could improve lesion conspicuity compared to conventional DCE-MRI, especially in women with premenopausal status, non-mass enhancement, moderate to marked BPE or short time to enhancement.