• Journal of electromagnetic engineering and science
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• v.13 no.2
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• pp.113-119
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• 2013

We developed a transformed, symmetrical, mushroom-like surface without via holes in cells focused on a 2.4-GHz WLAN band. Each slot in the novel type structure plays a key role in modeling at the desired frequencies. The designed artificial magnetic conductor (AMC) has several advantages, including a small size, a wider bandwidth, a short reflecting distance to the antenna, and easy fabrication because there are no via holes. Overall dimensions of the AMC cell are 21 mm $(Width){\times}21mm$ $(Height){\times}2.6mm$ (Thickness), and the bandwidth is about three times wider (11.7%) compared to that of a conventional AMC (4.0%). For evaluating the performance of the proposed structure, a reflector, which periodically consists of the designed AMC cells, was developed. The antenna with the investigated AMC reflector not only works within a quarter of the wavelength because of the extremely high wave impedance generated by the AMC cells on the surface of the structure but also reduces the specific absorption rate (SAR). Electromagnetic field (EMF) exposure to a human phantom was analyzed by applying the designed reflector to the 2.4-GHz dipole antenna in a tablet PC. The calculated peak SAR averaged over 1 g was 0.125 W/kg when the input power was 1 W and the antenna was located at 20 cm from the human phantom. However, the SAR value was only 0.002 W/kg (i.e., 98.4% blocked) when the designed reflector was inserted in front of the antenna.

• Journal of the Korean Society of Propulsion Engineers
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• v.20 no.2
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• pp.75-85
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• 2016

A pyrotechnic system consisting of donor/acceptor pair separated by a gap relies on shock attenuation characteristics of the gap material and shock sensitivity of the donor and acceptor charges. Despite of its common use, numerical study of such pyrotechnic train configuration is seldom reported because proper modeling of the full process requires precise capturing of the shock wave attenuation in the gap prior to triggering a full detonation of high explosive and accurate description of the high strain rate dynamics of the explosively loaded inert confinements. We apply a Eulerian level-set based multimaterial hydrocode with reactive flow models for pentolite donor and heavily aluminized RDX as acceptor charge. The complex shock interaction, critical gap thickness, acoustic impedance, and go/no-go characteristics of the gap test are quantitatively investigated.

• The Journal of the Convergence on Culture Technology
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• v.6 no.1
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• pp.99-104
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• 2020

This paper examines the performance according to the combination pattern of HRM and business strategy. The business strategy was divided into Miles & Snow's prospector, defender, and analyzer. Data were collected from the Korea Labor Institute's workplace panel survey from 2005 to 2015, and the analysis used 465 companies that are common respondents of the six wave surveys. To test the research model, structural equation modeling was employed. The results of the analysis showed that the combination of high commitment HRM and prospector had a positively significant effect on the performance. Contrariwise, the combination of high commitment HRM and defender, the combination of high commitment HRM and analyzer were not significant effect on performance.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.6 no.2
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• pp.139-149
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• 1994

In this paper, a finite element technique is applied to the prediction of the wave resonance phenomena in harbors. The mild-slope equation is used with a partial reflection boundary condition introduced to model the energy dissipating effects on the solid boundary. For an efficient modeling of the radiation condition at infinity, a new infinite element is developed. The shape function of the infinite element is derived from the asymptotic behavior of the first kind of the Hankel's function in the analytical boundary series solutions. For the computational efficiency, the system matrices of the element are constructed by performing the relevant integrations in the infinite direction analytically. Comparisons with the results from experiments and other solution methods show that the present model gives fairly good results. Numerical experiments are also carried out to determine the proper distance to the infinite elements from the mouth of the halter, which directly affect the accuracy and efficiency of the solution.

• Journal of Energy Engineering
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• v.16 no.4
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• pp.187-193
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• 2007

Water hammer following the tripping of pumps can lead to overpressures and negative pressures. Reduction in overpressure and negative pressure may be necessary to avoid failure, to improve the efficiency of operation and to avoid fatigue of system components. The field tests on the water hammer have been conducted on the pump rising pipeline system with an air chamber. The hydraulic transient is modeled using the method of characteristics. Minimizing the least squares problem representing the difference between the measured and predicted transient response in the system performs the calibration of the simulation program. Among the input variables used in the water hammer analysis, the effects of the polytropic exponent, the discharge coefficient and the wave speed on the result of the numerical analysis were examined. The computer program developed in this study will be useful in designing the optimum parameters of an air chamber for the real pump pipeline system. The correct selection of air chamber size and the effects of related parameters to minimize water hammer have been investigated by both field measurements and numerical modeling.

• The Journal of the Korea Contents Association
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• v.13 no.9
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• pp.164-177
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• 2013

This study's aim was to attest social support and self-efficacy's mediation effects in the path which social participation affected to elderly's suicidal ideation. Analysis data were Seoul Welfare Panel Data 2th wave(2010). A total of 1,429 cases aged over 65 were used for this study. Analysis method was AMOS 18.0's Structural Equation Modeling, and sobel test was used for attesting mediation effects's significance degree. Analysis results had established that measurement model and structural model's fit was favorable, and all path coefficients had significance degree. Therefore, this model was suitable for this study. Also this results had proved that this study's model was full mediation model, and it means that if mediation variables controlled, and then direct effect was excluded. And analysis results confirmed social support and self-efficacy' mediation effect had significance, by using a sobel test. Based on analysis results, this study suggested the importance of relationship between secondary group and individual, and presented intervention plans.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.13 no.1
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• pp.1-7
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• 2020

Directivity control technology of sound system is a key technology for improving sound quality. Providing a line source rather than a point source in an acoustic system can reduce the effects of attenuation interference at long distances, thereby providing high quality sound. In particular, A line-array speaker system can be used to provide coherent, high-quality sound over long distances. However, high frequencies have shorter wavelengths, so the distance between the speakers of a line array system must be shorter, but there are physical limitations. In this paper, we designed a wave guide and installed it in the speaker's compression driver to solve this problem. We measured and tested various acoustic characteristics to verify the performance of the speaker. As a result, when the line array sound system is constructed using the developed speakers, it is possible to provide a line source in all areas including the treble range, thereby achieving the same effect as a single extended source and providing high quality sound up to far distances.

• Health Policy and Management
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• v.22 no.4
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• pp.497-521
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• 2012

Objectives This study aimed to investigate the effect of social capital, health risk behavior and health status on medical care utilization by the elderly. The data and Research method Data were obtained from the 4th wave survey of the Korea Welfare Panel Study. 4,087 household members aged 65 years and over were subject to analysis. Descriptive statistics are used to describe the basic features of the data in a study. we performed a structural equation modeling(SEM) analysis to evaluate the effect of social capital and mediating effect of health risk behavior and health status. Results Results showed that factors related to medical care utilization of the elderly were different depending on types of service (inpatient and outpatient service) except health status. Age, higher social capital, more health-risk behavior and poorer health status were associated with increased use of inpatient service. Social capital was found to have a positive direct effect on it. Also, social capital had an indirect effect on reducing use of inpatient services by improving health status. On the other hand, lower age and higher household income tended to increase use of outpatient service, while higher social capital and higher health status were inversely related. Social capital had a direct effect and an indirect effect on reducing use of outpatient service and, at that time, health status played a mediating role. Conclusions Social capital may contribute to improve health status and indirectly reduce medical care utilization of the elderly by enhancing their health status. These results provide evidence that more policy and strategy considerations should be needed for the elderly to strengthen their social capital in order to enhance their levels of health and more efficient utilization of medical care.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.17 no.2
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• pp.71-76
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• 1981

In order to make a numerical modeling for the one dimensional unsteady flow which expressed by Saint Venant partial differential equations, Preissmann's implicit scheme was used, and it's stability and accuracy was mentioned. By introducing recurrence relations make it possible to use double sweep algorithm. Effective parameters to the result were the values of the $\Delta$t/$\Delta$x, $\theta$ and the chezy coefficient. In oder to get numerical solutions with enough accuracy, $\Delta$t/$\Delta$x should not be far from the value of 1, and the criteria of the $\theta$ was 0.6<$\theta$<1.0 for the stability without condition. This model should be calibrated by real field data, and expected to be developed for the simulation of the river system and to the long wave analysis for one dimensional coastal zone problem.

• Review of Culture and Economy
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• v.19 no.2
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• pp.51-72
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• 2016

This research dwells on categorization and industrialization of cultural heritage resources using marketing. Since many organization would not grab the chance of business while doing marketing using cultural heritage, the paper intend to suggest proper way to develop strategy. For that purpose, this research analyzed some advanced cases of corporate like Google and other national endeavors. This paper founded out 4 models of marketing using cultural heritage resources. These are re-creation, patron, capitalization and media. Also we got practical implications of the case analysis and modeling which are collaboration partnership scheme between marketers and filed expert group. Marketers better find fitful information and right person utilizing more reliable sources such as national archives, and academic achievements. If the marketers implement such strategic program, really abundant types of cultural heritage resources using marketing could bring more favorable profit which means business chance and new horizon for global culture industry.