• Nuclear Engineering and Technology
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• 제27권5호
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• pp.710-720
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• 1995

원자로에서 펌프에 의해 야기되는 맥동 압력은 원자로 내부 구조물에 진동과 손상을 줄 수 있기 때문에 관심이 증가되고 있다. 본 연구에서는 냉각관과 환형관(원자로 압력 용기와 노심 보호 지지대 사이)으로 구성된 기하 형태에서 펌프에 의해 야기되는 맥동 압력을 해석할 수 있는 수력학적 모델을 개발하였다. 수학적 지배 방정식은 압축성, 비점성 유체에 대해 선형화된 Navier-Stokes 방정식이다. 냉각관과 환형관을 따로 분리하여 해석하고 두영역의 커플링 영향을 고려하였다. 또한 본 기하 형태에서 펌프맥동 압력에 영향을 미치는 주요 기하 인자에 대한 평가를 수행하였다. 본 해석 결과와 실험차를 비교하여 만족할 만한 결과를 얻었다.

• 소성∙가공
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• 제19권6호
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• pp.329-336
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• 2010

Ring forging process is more appropriate for high-length and thin walled ring, because it utilizes the forging press and hence does not require heavy-duty ring rolling mill. Although ring forging process is very simple and economic for facilities, the process is not efficient because of multi-forging-step and low material utilization. An effective ring forging process is developed using a hollow ingot. When a hollow ingot is used with a workpiece, the ingot can be forged into a final ring without multi-stage pre-forging process, such as, cogging, upsetting, and piercing, etc.. Finally it has advantages of the material utilization and process improvement because a few reheating and forging process are not necessary to make workpiece for ring forging. The important design variables are the applied plastic deformation energy to eliminate cast structure and make uniform properties. In this study, the mechanical properties after forging of hollow cast ingot were investigated from the experiment using circumferential sectional model. Also, the effects of process variables were studied by FEM simulation on the basis of thermo-visco-plastic constitutive equation. Applied strain is different at each position in length direction because diameter of hollow ingot is different in length direction. The different strain distribution become into a narrow gap by additional plastic deformation during diameter extension process.

• The Journal of Asian Finance, Economics and Business
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• 제7권2호
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• pp.309-316
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• 2020

This study aims to measure the relationship between corporate social responsibility (CSR) and affective commitment (ACO), normative commitment (NCO), and organizational performance in food processing enterprises (FPEs) in the Mekong River Delta, Vietnam. To test the initial model proposed in this paper, a total of 422 owners, directors and managers of FPEs were interviewed from some provinces in the Mekong River Delta. The method of exploratory factor analysis (EFA) is initially employed, then confirmatory factor analysis (CFA) and structure equation modelling (SEM) are used. The results of SEM showed that higher affective commitment was correlated with normative commitment. The results showed that four aspects of CSR toward employees, customers, environment and legal are significant factors. As a result, ACO and NCO act as mediators between CSR and organizational performance. This finding provides strong evidence of the important role of CSR to support positive impacts on ACO, NCO, and orgazational performance (OP). In addition, the success of the organizational performance is also found by contributions of CSR and NCO to its changes. Although ACO does not directly affect performance, it has a positive effect on the NCO. Therefore, it is necessary to enhance the implementation of CSR to promote implementation of organizational commitments.

• The Journal of Asian Finance, Economics and Business
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• 제7권10호
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• pp.855-863
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• 2020

The purpose of this study is to investigate the impacts of two different kinds of interactivity, such as user-to-user and user-to-media interaction, on the relationship between SNS motivation and online word of mouth (WOM). An online survey was conducted with SNS users in Korea. Using the convenience-sampling method, 300 surveys were collected and 295 were used in the actual analysis after excluding data with careless responses or missing values. Hypotheses were tested using Structure Equation Model (SEM) and path analysis by using AMOS22. The results indicate that four different SNS motivations (self-expression, relational, fun, and browsing motivation) have a partially significant positive effect on perceived user-to-user and user-to-media interaction in SNS. Although both user-to-user interactivity and user-to-media interactivity were found to have a significant effect on online word of mouth, by comparing the standardized regression coefficients in these relationships, it was found that user-to-user interactivity has a greater effect on online WOM than user-to-media interactivity. These results show that the motivated SNS users want to express their desire to communicate with other users in contrast than their desire to learn media functions when motivated SNS users reveal their personalities, knowledge, and abilities. Theoretical and managerial implications are discussed.

• 한국입자에어로졸학회지
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• 제13권4호
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• pp.173-182
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• 2017

An Eulerian-Lagrangin approach is used to compute particle dispersion from a power plant chimney. For air flow, three-dimensional incompressible filtered Navier-Stokes equations are solved with a subgrid-scale model by integrating the Newton's equation, while the dispersed phase is solved in a Lagrangian framework. The velocity ratios between crossflow and a jet of 0.455 and 0.727 are considered. Flow fields and particle distribution of both cases are evaluated and compared. When the velocity ratio is 0.455, it demonstrates a Kelvin-Helmholtz vortex structure above the chimney caused by the interaction between crossflow and a jet, whereas the other case shows flow structures at the top of the chimney collapsed by fast crossflow. Also, complex wake structures cause different particle distributions behind the chimney. The case with the velocity ratio of 0.727 demonstrates strong particle concentration at the vortical region, whereas the case with the velocity ratio of 0.455 shows more dispersive particle distribution. The simulation result shows similar tendency to the experimental result.

• 한국해양공학회지
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• 제15권2호
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• pp.11-21
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• 2001

The focus of this paper is on the numerical investigation of obliquely incident wav interactions with a system composed of fully submerged and floating dual buoy/vertical-flexible-membrane breakwaters placed in parallel with spacing between two systems. The fully submerged two systems allow surface and bottom gaps to enable wave transmission over and under the system. The problem is formulated based on the two-dimensional multi-domain hydro-elastic linear wave-body interaction theory. The hydrodynamic interaction of oblique incident waves with the combination of the rigid and flexible bodies was solved by the distribution of the simple sources (modified Bessel function of the second kind) that satisfy the Helmholz governing equation in fluid domains. A boundary element program for three fluid domains based on a discrete membrane dynamic model and simple source distribution method is developed. Using this developed computer program, the performance of various dual systems varying buoy radiuses and drafts, membrane lengths, gaps, spacing, mooring-lines stiffness, mooring types, water depth, and wave characteristics is thoroughly examined. It is found that the fully submerged and floating dual buoy/membrane breakwaters can, if it is properly tuned to the coming waves, have good performances in reflecting the obliquely incident waves over a wide range of wave frequency and headings.

• Wind and Structures
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• 제22권5호
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• pp.595-616
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• 2016

Providing high starting torque and efficiency simultaneously is a significant challenge for vertical axis wind turbines (VAWTs). In this paper, a new approach is studied in order to modify VAWTs performance and cogging torque. In this approach, J-shaped profiles are exploited in the structure of blades by means of eliminating the pressure side of airfoil from the maximum thickness toward the trailing edge. This new profile is a new type of VAWT airfoil using the lift and drag forces, thereby yielding a better performance at low TSRs. To simulate the fluid flow of the VAWT along with J-shaped profiles originated from NACA0018 and NACA0030, a two-dimensional computational analysis is conducted. The Reynolds Averaged Navier-Stokes (RANS) equations are closed using the two-equation Shear Stress Transport (SST) turbulence model. The main objective of the study is to investigate the effects of J-shaped straight blade thickness on the performance characteristics of VAWT. The results obtained indicate that opting for the higher thickness in J-shaped profiles for the blade sections leads the performance and cogging torque of VAWT to enhance dramatically.

• 아동학회지
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• 제34권6호
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• pp.77-96
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• 2013

The purpose of this study was to examine the relationships among mother's psychological characteristics(self-esteem, self-efficacy, and depression), parenting related factors(maternal parenting stress and mother's knowledge on infant development), maternal parenting style, and two-year-old infants' development. The participants consisted of 1735 mothers and their two-year old infants selected from a sample of the 3rd Panel Study of Korean Children(PSKC) by the Korea Institute of Child Care and Education(KICCE), conducted in 2010. Data were analyzed by means of a Structural Equation Model(SEM) to identify the structure and relationships among the various factors. The significance of direct and indirect effects to test the mediating effect of maternal parenting style were identified via bootstrapping. The results indicated that maternal parenting style most definitely mediated the relationship among the mother's psychological characteristics(self-esteem and self-efficacy), parenting related factors(maternal parenting stress and mother's knowledge on Infant development) and the development of their two-year-old infants.

• 산업경영시스템학회지
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• 제37권1호
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• pp.104-114
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• 2014

The purpose of this study is to verify not only the impact of servant leadership affecting creativity but the mediating effect of empowerment. Creativity refers to the production of novel and useful ideas by an individual or by a group of individuals working together [2]. A survey was conducted by 301 employees. This study used the structure equation model which treated the servant leadership as independent variable and creativity as criterion variables. Empowerment was supposed as mediating variable of these relationships. As a result of this study, servant leadership had positive influence on empowerment. Empowerment had positive influence on creativity. Also servant leadership had positive effect on creativity at first, but it did not have a direct effect on creativity when empowerment was considered. These mean that empowerment is complete mediation variable because servant leadership no longer affects creativity after empowerment has been considered. Several implications, limitations and directions for future research were discussed.

• 한국의류학회지
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• 제27권6호
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• pp.685-695
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• 2003

The purpose of this study was to identify dynamic relationship structure in fashion Internet shopping mall and to present marketers to perform marketing strategy in e-CRM, focusing on trust and commitment. 473 customers who had purchased fashion products in fashion internet shopping mall had participated in the survey. Finally, 470 were used into data analysis. The data was analyzed by factor analysis, t-test, ANOVA, correlation analysis and Structural Equation Model(SEM) using AMOS program. As the results, 'economic benefits' and 'service' variables had the positive effects on 'trust'. Especially, 'service' had the major effect on 'trust'. 'Trust' and 'product information quality' had the positive effects on 'emotional commitment'. 'Trust', 'economic benefits' and 'reputation' had the positive effects on calculus commitment, while contents had the negative effect. Also, 'emotional' and 'calculus' commitment had positive effects on 'relationship maintenance intention'. 'Emotional commitment' had higher effect on 'relationship maintenance intention' than 'calculus commitment'. 'Calculus commitment' had the positive effect on discontinue relationship intention when shopping mall made mistakes. The results of this study provide e-CRM marketing strategy for marketers of fashion internet shopping mall.