• Journal of Magnetics
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• 제15권3호
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• pp.116-122
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• 2010

An accurate analytical equation for the total energy in the framework of the single domain model is used to study the thermal stability of nanostructured synthetic ferrimagnets. Elliptical cells are considered that have lateral dimensions of 160 nm (long axis)$\times$80 nm (short axis) and varying values of thickness asymmetry for the two magnetic layers. The direction of the applied magnetic field, which points to the $45^{\circ}$ direction, is in the opposite direction to the thicker layer magnetization. A significant difference is observed in the applied magnetic field dependencies of the equilibrium magnetic configuration and the magnetic energy barrier when using the simplifying assumption that the self-demagnetizing field is identical in magnitude to the dipole field. At a small thickness asymmetry of 0.2 nm, for example, the magnetic energy barrier is reduced from 68 kT (T=300 K) to 6 kT at the remanent state and a progressive switching behavior changes into a critical behavior, as the simplifying assumption is used. The present results clearly demonstrate the need for an accurate analytical equation for the total energy in predicting the thermal stability of nanostructured synthetic ferrimagnets.

• 한국공간구조학회:학술대회논문집
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• 한국공간구조학회 2008년도 춘계 학술발표회 논문집
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• pp.171-178
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• 2008

This paper is concerned with the development of a measurement system using field measuring device which will give the membrane stress of the membrane structures. Up to this point, several techniques on measurement of membrane stresses has been proposed and some have been used in the fields, but accuracy of the measured stresses to be far from reliable one. Such situation has not been changed until recent days, we do not have the measurement device on which we can depend. On top of that, due to the different properties in cross directions for material of the membrane, the stress in the warp direction is different from that in the fill one. A new method is proposed to measured membrane stresses in two different direction separately, where instead of membrane stresses directly, an external force perpendicular to the membrane to be applied. A portable device can measure the applied force and the displacement. A special testing bed to be fabricated to accommodate $50cm{\times}50$ manbrane specimen which can apply 5 ton load in two orthogonal direction. A special device using push-pull gage was developed. To measure the membrane stresses in warp and fill direction separately, a different length of the tips are used. The measuring device which can called tension meter, can be calibrated on the testing bed, and optimized the length and shape of tip.

• 한국정밀공학회지
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• 제23권5호
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• pp.190-196
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• 2006

Transparent materials are widely used in the fields of optic parts and bio industry. We have experiment to find out the characteristics of the micromachining inside transparent materials using femtosecond laser pulses. With its non-linear effects by very high peak intensity, filament (plasma channel) was formed by the cause of the self-focusing and the self-defocusing. Physical damage could be found when the intensity is high enough to give rise to the thermal stress or evaporation. At the vicinity of the power which makes the visible damage or modification, the structural modification occurs with the slow scanning speed. According to the polarization direction to the scanning direction, the filament quality is quite different. There is a good quality when the polarization direction is parallel to the scanning direction. For fine filament, we could suggest the conditions of the high numerical aperture lens, the short shift of focusing point, the low scanning speed and the low power below 20 mW. As the examples of optics parts, we fabricated the fresnel zone plate with the $225{\mu}m$ diameter and Y-bend optical wave guide with the $5{\mu}m$ width.

• Korean Journal of Acupuncture
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• 제21권3호
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• pp.1-20
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• 2004

Objective : Today, a study about the meridian is at a standstill because there is no any fundamental study to verify an essence of meridian or to take advantage of meridain. It searched the direction of new meridain study by making out road-map about meridain study to overcome the standstill. Method : It has had a through grasp of the problem of meridian study through analysis of papers for degrees and academy journals of study in connection with meridian published till now. It has made out road-map of Meridian study under a principle establishing road-map because of these problems. Results : The major problems of former studies about meridain are as follows. One is not to have any cooperation with other medical fields. The other is not to have any practical study. It searched the direction of new meridian study by road-map detailed as well as overall to overcome the difficulties. Conclusions : The new direction of meridian study is to build ideal methodical frame and modern meridian model through studying of among school systems. It will interpret newly and modernize traditional meridian theory with being connected with science technology.

• 한국해양공학회지
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• 제21권1호
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• pp.1-6
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• 2007

While a typhoon is traveling, characteristics of its wind fields are continuously changing, producing severe changes in local water level and wave conditions, especially, when a typhoon comes into shallow water. However, there have not been many studies related to local typhoon effects, especially, considering real time changes of wind direction related to the coastal topography. In the study, the characteristics of the wind field by typhoon and topographical characteristics in shallow water are considered, as well as conditions of wave climate estimation. These are performed by the SWAN (Simulating waves nearshore) model, in order to estimate the growth of wave energy due to the wind field. It can be strongly suggested that the wave energy of theof an inner bay should be estimated when the direction of the bay entrance and the wind direction of the typhoon are identical. The result of the numerical calculations is in better agreement with the observed data than the result of the conventional estimation techniques.

• 한국기계가공학회지
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• 제18권11호
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• pp.35-40
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• 2019

Laser processing has been used in various fields. In this study, the feasibility of a hydrophobic surface was investigated through the laser cladding technique. A diode laser was used, and the output was set to 600-800 W. Seven different specimens were prepared with different cladding widths and spacings, and the contact angles for water droplets were evaluated. As a result, the contact angle of water droplets measured in the direction parallel to the cladding line was higher than that in the vertical direction. The wider the cladding width and the cladding space, the higher the contact angle in the parallel direction. It is thought that when a higher contact angle is formed in the parallel direction, more air can be placed in the valley between the cladding lines. In addition, for the hydrophobic coating effect, the contact angle of the coated cladding surface was increased by about $5-15^{\circ}$ as a whole compared to the coated smooth surface. It was confirmed that the wetting characteristics were improved through the cladding.

• 한국인공지능학회지
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• 제8권2호
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• pp.11-16
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• 2020

Among the innovative companies leading the era of the 4th industrial revolution, the world's largest Internet company is Google. Google has grown by providing convenient services such as Internet search, Android smartphone operating system, and video. Now, Google is leading the global IT industry by continuing to develop in various new business fields based on open service platforms, artificial intelligence, and big data. In this study, an exploratory discussion was conducted on Google's success factors and future directions. The purpose of the research is to understand the development process of the IT field from the successfactors of Google and to analyze the development direction of the future IT industry. Google's success factors were its open platform policy and successful acquisitions of external companies. In fact, most of the services Google offers come from companies that have acquired and acquired them. In addition, there was a corporate culture that values and supportsthe spirit of challenge and autonomy of members who are not afraid of failure. Based on this study's review of Google's direction analysis, the follow-up study will infer the direction of the IT industry in depth and look at the future technologies that IT majors need to prepare.

• Journal of Magnetics
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• 제20권1호
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• pp.31-39
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• 2015

Macroscopic hysteresis loops and microscopic magnetic moment distributions have been determined by a three-dimensional (3D) model for exchange-coupled Sm-Co/${\alpha}-Fe$/Sm-Co trilayers with in-plane collinear easy axes. These results are carefully compared with the popular one-dimensional (1D) micromagnetic models and recent experimental data. It is found that the results obtained from the two methods match very well, especially for the remanence and coercivity, justifying the calculations. Both nucleation and coercive fields decrease monotonically as the soft layer thickness $L^s$ increases while the largest maximum energy product (roughly 50 MGOe) occurs when the thicknesses of hard and soft layers are 5 nm and 15 nm, respectively. Moreover, the calculated angular distributions in the thickness direction for the magnetic moments are similar. Nevertheless, the calculated nucleation and pinning fields as well as the energy products by 3D OOMMF are systematically smaller than those given by the 1D model, due mainly to the stray fields at the corners of the films. These demagnetization fields help the magnetic moments at the corners to deviate from the previous saturation state and facilitate the nucleation. Such an effect enhances as $L^s$ increases. When the thicknesses of hard and soft layers are 10 nm and 20 nm, respectively, the pinning field difference is as large as 30%, while the nucleation fields have opposite signs.

• 서비스연구
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• 제12권4호
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• pp.139-163
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• 2022

본 연구는 새로운 인류사회를 이끌어갈 중심 학문으로서의 서비스학(서비스사이언스) 연구의 과거, 현재를 분석하고 미래 연구 가이드를 제시한다. 21세기에 서비스 연구는 기존 체계와 다른 새로운 학문인 서비스학으로 발전하였다. 서비스학은 서비스 관련 모든 연구를 통칭하는 학문이다. 본 연구에서는 이러한 발전 과정을 분석하고, 향후 서비스학 연구의 방향을 제시한다. 우선 서비스학의 초기 모델인 서비스사이언스 탄생 이전 연구를 분석한다. 서비스중심 로직으로의 변화 등을 연구한 서비스마케팅 연구, 서비스기업의 운영과 경영, 서비스공학 등 기존 학문 연장 차원의 서비스 연구를 분석한다. 그리고 서비스사이언스 탄생 초기 연구를 분석한다. 서비스연구 프레임워크 제안 등 새로운 학문으로서 체계를 갖추어가는 과정을 분석한다. 이러한 과정을 거쳐 초기 서비스사이언스를 확대 발전시킨 서비스학 프레임워크를 분석한다. 기존 학문의 체계를 현대적 관점에서 새롭게 혁신한 서비스학의 각 분야들을 소개하고, 독립적 신학문의 기반이 되는 서비스철학의 구조를 분석한다. 그리고 서비스학 연구의 미래 방향을 제시한다. 먼저 기존 개별 학문들의 패러다임 혁신 연구 방향을 제시한다. 사례로 기존 경영학의 서비스경영학으로의 혁신을 소개하며 미래 연구 방향성을 안내한다. 또한 복수의 학문 분야 융합이 필요한 새로운 경제사회시스템 연구 방향을 제시한다. 경제 정치 사회 등 기존 분야의 혁신과, 민주주의 등 인류사회 핵심주제에 대한 서비스학 연구 방향을 제시한다. 최종적으로 다차원 광범위 융합 연구 방향을 제시한다. 그동안 끝없이 분화를 계속한 학문들이 인간과 세계를 중심으로 다시 통합 융합으로 되돌아가는 과정이 서비스학의 미래가 될 수 있음을 제시한다. 동서양 정신이 융합하면서 모든 학문이 서비스학으로 재통합되는 모델을 제시한다. 마지막으로 향후 서비스학 연구의 활성화 필요성을 제시한다.

• 정보처리학회논문지C
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• 제17C권1호
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• pp.81-88
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• 2010

센서네트워크에서 센서는 배터리에 의해 작동이 되며 배터리의 수명이 다하면 더 이상 동작을 할 수 없다. 센서가 수집한 데이터는 효과적인 경로를 통해 싱크노드로 전달되어야 하며 이를 위한 여러 라우팅 알고리즘이 제안되었다. 하지만, 기존의 알고리즘은 데이터를 전송하는데 있어서 전송범위와 전송방향을 고려하지 않기 때문에 많은 노드들이 데이터 전송에 참여하게 되고 결과적으로 많은 에너지를 소모한다. 본 논문에서는 센서 네트워크에서의 효과적인 데이터 전송을 위해 전송범위와 전송방향을 고려한 라우팅 알고리즘인 TDRP(Transmission range and Direction Routing Protocol)를 제안한다. TDRP는 클러스터 또는 그리드를 생성하지 않고, 싱크노드를 중심으로 사분면을 형성하여 패킷의 전송방향을 결정하는 방법으로 네트워크 오버헤드가 적으며, 패킷의 전송방향에 위치하는 노드들 만이 통신에 참여하므로, 에너지 효율성이 기존의 알고리즘들보다 뛰어 나다.