• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2008.04a
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• pp.21-24
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• 2008

This study proposes a optimized shape of diffuser profile through investigating the scattering and diffusion characteristics of diffusers. The scattering coefficient according to ISO 17497-1 evaluates uniformity of reverberant sound field of late reflections, while the diffusion coefficient according to AES-4id-2001 evaluates polar response of early reflections. Thus both scattering and diffusion characteristics should contribute to design shape of diffusers to maximize physical performance. To find out design method, the previous results on hemisphere diffusers are reviewed. The frequency characteristics of scattering coefficients depended on the structural height of the diffusers, while amount of scattering coefficients depended on the surface coverage density of the diffusers. However absorptive properties also increased with augment of surface coverage density, thus optimum coverage density should be considered. For the directional diffuser, three types of 2D-diffusers are proposed; semicylinder of h=5mm, semi-truncated cone of h=5-25mm and semicylinder of h=25mm. As results, diffusers with the maximum height of 25mm show the highest scattering coefficients, while diffuser of h=5mm shows high scattering coefficients only at the high-frequency bands. Diffusion coefficient will be investigated for diffusive properties of the early reflection.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.19 no.3
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• pp.505-514
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• 1994

Koreasat spacecraft requires accurate and reliable attitude control to provide beam pointing for tenyear long communication and direction broadcasting services. This paper describes the detailed design and performance of an on-orbit normal mode attitude control subsystem for the spacecraft. Koreasat used a momentum wheel which has nominal momentum 475in-1b sec(547.6cm-kg sec) aligned with the pitch axis to control pitch attitude and provide gyroscopic stiffness in roll/yaw plane and used a 300 atm magnetic torquer to control the roll and yaw attitudes. An Earth Sensor Assembly (ESA) is used to provide pitch and roll information for the on-board micropocessor. The roll/yaw control used bang-off-bang control and while pitch axis control used proportional and integral control law. Control system errors during the operational normal mode are 0.03 deg, 0.1 deg and 0.01 deg in roll, yaw and pitch axes, respectively. Current attitude control system provides adequate control performances to capture initial attitude errors and spacecraft nutation.

• Journal of Families and Better Life
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• v.26 no.5
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• pp.391-403
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• 2008

The purpose of the study was to find the level of family financial management behavior of urban housewives and to discern the difference between financial stability and financial satisfaction according to change-orientation of financial management behavior among urban housewives, and thus provide the fundamental data to improve stability and financial satisfaction. The following findings emerged during the study: First, groups with higher change-oriented family financial management behaviors among housewives subjectively felt more financial satisfaction than other groups. Second, groups with above average levels of change-oriented management behavior appeared to have more stable families than groups with below average objective financial stability, emergency funds, risk provisions, debt burdens and liquid index. Third, groups with high levels of change-oriented family financial management behavior had higher financial satisfaction.

• Proceedings of the KIEE Conference
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• 2001.07c
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• pp.1899-1901
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• 2001

본 논문에서는 3차원 feed horn 안테나를 볼로미터에 결합함으로써 감지도(Detectivity)를 향상시킨 비가시광 영상 감지 소자를 제안하였다. Feed horn 안테나의 우수한 지향성(Directivity)를 통해서 주위의 잡음 성분을 제거함으로써 감지도의 향상을 확인할 수 있었다. 안테나와 볼로미터와의 결합 손실을 줄이기 위해서 볼로미터의 흡수층의 모양을 원형의 형태로 하였으며 크기도 안테나 폭과 일치를 시켰다. 또한 열적 고립 구조를 만들기 위한 지지 다리의 모양도 원형의 형태로 하여서 전체 길이를 증가 시켰으며 이로 인해 열전도도(Thermal conductance)를 $4.65{\times}10^{-8}$[W/K]까지 낮출 수 있었 다. 설계된 소자의 감지도는 $2.37{\times}10^{9}$[$cm\sqrt{Hz}/W$]을 나타내었으며 안테나 결합을 통한 감지도의 향상을 확인 할 수 있었다. 볼로미터의 제작은 MEMS 기술을 이용한 표면미세가공(Surface micromachining)법으로 열적 고립 구조체를 제작할 수 있으며 3차원 feed horn안테나는 SU-8이라는 음성 감광제를 경사회전노광시켜서 제작할 수 있다.

• Journal of the Institute of Electronics and Information Engineers
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• v.52 no.4
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• pp.9-16
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• 2015

Quick and safe message transmission is an important research topic of vehicular ad hoc networks (VANET). Most studies assume that the periodic broadcast of beacon-frames between vehicles increases the safety of the driver. In this paper, we propose a medium access control (MAC) protocol and location-based clustering for the VANET to support reliable data transfer. In our proposal, the cluster heade (CH) manage the access and allocate the resources of the node. Our proposal uses simulation to confirm the reduction of the transmission delay and the collision rate of the signal.

• Journal of East-West Nursing Research
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• v.24 no.1
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• pp.20-27
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• 2018

Purpose: This study was conducted to investigate nursing professionalism, emotional labor (surface acting, deep acting), empathic concern, and customer orientation, and identify factors contributing to customer orientation among clinical nurses. Methods: The participants in this study were 151 clinical nurses at the three general hospitals. Data were collected using self-administered questionnaires. Data were analyzed using descriptive statistics, independent t-test, one-way ANOVA, Pearson correlation coefficient, and multiple regression. Results: The significant predictors of customer orientation among clinical nurses were empathic concern (${\beta}=.43$, p<.001), nursing professionalism (${\beta}=.29$, p<.001), nursing career (${\beta}=.16$, p=.007), and deep acting (${\beta}=.14$, p=.021). Theses variables explained 47.6% of the variance of customer orientation. Empathic concern was the most influential variable. Conclusion: The results suggest that it is crucial to improve deep acting, empathic concern and nursing professionalism for increasing clinical nurses' customer orientation. Management-level leaders in the hospitals should develop strategies of promoting nursing professionalism, deep acting and empathic concern to improve customer orientation.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.21 no.10
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• pp.1116-1120
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• 2010

Low cost patch array antenna for high sensitivity electromagnetic(EM) sensor is presented. The operating frequency band of the antenna is 24.05~24.25 GHz. Array structure is the symmetrical pattern by Chebyshev polynomial and the feed point is located in the middle of the array. Also, the gain of the array antenna can be increased by the side wings which are connected with the ground plane. It is proved through simulation and the measurement results that the operating frequency and the side-lobe level(SLL) are rarely changed when the inclined angle of the side wings is varied.

• Journal of Family Resource Management and Policy Review
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• v.13 no.3
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• pp.85-101
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• 2009

The Multi-cultural Family Support Center provides various educational programs and services for multi-cultural families. However, there are controversies regarding integration and assimilation, ethnic identity and ethnocentrism, and state-sponsored multi-culturalism. From the home economist's perspective, it was necessary to explore the direction of integration of family life culture in the multi-cultural society. This study concluded that there is a necessity to accept foreign culture and create a new culture while still maintaining their and our own cultural identity respectively. For this purpose, integration and assimilation must progress side by side to maintain the cultural identity and stability of multi-cultural families. But, women migrants are to adapt in their everyday life, they need to attend a Korean-language course and take part in a traditional Korean culture program such as having an assimilational characteristics. Also for the happiness of multi-cultural families ultimately not for the confronted problems, it requires sometimes education of changing migrants' own traditional customs and life culture partly. In this sense, educational and cultural programs held by Multi-Cultural Family Support Center are meaningful and their importance in adapting into everyday life must be recognised by all of us.

• Proceedings of the KSME Conference
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• 2003.04a
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• pp.2066-2070
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• 2003

This experimental study describes the propagation characteristics and suppression of the impulse noise emitted from the exit of a perforated pipe attached to the open end of a simple shock tube. The experiment is performed through the systematic change of the shock wave Mach number and the geometrical parameters such as the porosity, hole diameter and length of the perforated pipe. The experimental results for the near and far sound field are presented and explained in comparison with those for a straight pipe. The results obtained show that for the near sound field the impulse noise strongly propagates toward to the pipe axis, but for the far sound field the impulse noise uniformly propagates toward to the all directions, indicating that the directivity pattern is almost same regardless of the pipe type. Moreover, the noise reduction performance of perforated pipe depends upon the condition of sound field. For the near sound field the perforated pipe has a little performance to suppress the impulse noise, but for the far sound field the perforated pipe has little performance to suppress the impulse noise.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.21 no.10
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• pp.1742-1756
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• 1997

The acoustic characteristics of a direct radiator type loudspeaker has been studied in this paper. The natural modes of the speaker cone vibration analyzed numerically by the finite element method have been verified by comparing them with experimental results. The so-ap-proved finite-element model has been used to calculate the vibration response of the cone excited by the voice coil. The vibration displacement of the speaker cone paper has been converted into the vibration velocity and used as a boundary condition for the acoustic analysis. The frequency characteristics, directivity, and sound pressure distribution of the loudspeaker have been calculated by the boundary element method. The numerical results have been verified by the experiments carried out in an anechoic chamber. The variations of the acoustic characteristics due to the changes of some design parameter values can be examined using the numerical model.