• 태양에너지
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• 제20권3호
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• pp.61-73
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• 2000

Heat losses from receivers for a dish-type solar energy collecting system are numerically investigated. The analytical method for predicting conductive heat loss from a cavity receiver is used. The Stine and McDonald Model is used to estimate convective heat loss. Two kinds of techniques for the radiation analysis are used. The Net Radiation Method that is based on the radiation heat balance on the surface is used to calculate the radiation heat transfer rate from the inside surface of the cavity receiver to the environment. The Monte-Carlo Method that is the statistical approach is adopted to predict the radiation heat transfer rate from the reflector to the receiver. Based on the heat loss analysis, the performance of two different receivers for multifaceted parabolic solar collectors with several flat facets can be estimated, and the optimal facet size is obtained.

• 한국조경학회지
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• 제25권1호
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• pp.124-134
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• 1997

The primary purpose of this research is to scientifically investigate visual structure of Korean feng-shui at the level of village settlement. This study deals with Hahoi and Yangdong villages of which feng-shui is regarded highly fit to traditional feng-shui principles. Methodologically this research utilizes analytical tools of geographical information systems and statistical analysis methods, Visual structures of the villages'feng-shui are analyzed in terms of elevation, orientation, gradient of slope and relative dominance of visibility of major hills. A mathematical model is suggested to quantify facets of the villages'lung-shui with reference to slope trends. The quantitative analysis results indicate that both villages have good feng-shui. Hahoi village has an excellent feng-shui attributable to a near perfect harmony between water and terrain while Yangdong village has an effective feng-shui facet for conserving energy in terms of microclimate. Principles of fang-shui have potentials to be developed as a holistic planning and design language. Further in-depth research on feng-shui needed to accomplish this goal.

• 치과방사선
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• 제28권2호
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• pp.387-413
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• 1998

Image resampling is of particular interest in digital radiology. When resampling an image to a new set of coordinate, there appears blocking artifacts and image changes. To enhance image quality, interpolation algorithms have been used. Resampling is used to increase the number of points in an image to improve its appearance for display. The process of interpolation is fitting a continuous function to the discrete points in the digital image. The purpose of this study was to determine the effects of the seven interpolation functions when image resampling in digital periapical images. The images were obtained by Digora, CDR and scanning of Ektaspeed plus periapical radiograms on the dry skull and human subject. The subjects were exposed to intraoral X-ray machine at 60kVp and 70 kVp with exposure time varying between 0.01 and 0.50 second. To determine which interpolation method would provide the better image, seven functions were compared; (1) nearest neighbor (2) linear (3) non-linear (4) facet model (5) cubic convolution (6) cubic spline (7) gray segment expansion. And resampled images were compared in terms of SNR(Signal to Noise Ratio) and MTF(Modulation Transfer Function) coefficient value. The obtained results were as follows ; 1. The highest SNR value(75.96dB) was obtained with cubic convolution method and the lowest SNR value(72.44dB) was obtained with facet model method among seven interpolation methods. 2. There were significant differences of SNR values among CDR, Digora and film scan(P<0.05). 3. There were significant differences of SNR values between 60kVp and 70kVp in seven interpolation methods. There were significant differences of SNR values between facet model method and those of the other methods at 60kVp(P<0.05), but there were not significant differences of SNR values among seven interpolation methods at 70kVp(P>0.05). 4. There were significant differences of MTF coefficient values between linear interpolation method and the other six interpolation methods (P< 0.05). 5. The speed of computation time was the fastest with nearest -neighbor method and the slowest with non-linear method. 6. The better image was obtained with cubic convolution, cubic spline and gray segment method in ROC analysis. 7. The better sharpness of edge was obtained with gray segment expansion method among seven interpolation methods.

• 대한기계학회논문집B
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• 제37권10호
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• pp.953-959
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• 2013

본 연구에서는 가상 생체외 사체실험을 수행할 수 있는 경추 다관절 동역학 모델을 개발하였다. 평균크기 한국인 의료영상과 관절 및 연부조직의 물성 정보를 기반으로 하여 경추 동역학 모델을 개발하였다. 개발된 모델의 검증을 위하여 경추 단분절 및 다분절 모멘트-각도 관계, 인대 하중 및 후관절 접촉력 등을 문헌의 사체실험 결과와 비교한 결과 매우 유사한 경향을 확인하였다. 본 연구에서 개발된 경추 동역학 모델은 앞으로 경추 사체실험 연구 뿐만 아니라 자동차 충돌시 경추 상해 분석 등의 다양한 경추 생체역학 연구 연구에 활용될 수 있을 것이다.

• 한국광학회지
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• 제21권2호
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• pp.74-81
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• 2010

WDM-PON 용 저가형 광원으로 유망한 주입 잠금 패브리-페롯 레이저 다이오드의 특성 해석을 위한 모델링 방법을 제시하였다. 해석 방법으로는 시영역 대신호 모델을 이용하였으며, 계산 결과는 기존의 실험 결과와 유사한 경향을 보임을 확인하였다. 이를 토대로 특정한 파라미터를 가지는 레이저 다이오드 구조에서의 단면 반사율에 따른 동작 특성과 디튜닝, 아이 다이어그램등을 모델링 하였다. 특히 단면 반사율의 값에 따른 부모드 억제율 특성 및 디튜닝의 영향을 살펴보았으며, 주입되는 단면의 반사율이 1% 미만으로 유지되어야 안정된 특성을 얻을 수 있음을 확인하였다. 아이 다이어그램의 경우 155 Mbps 급에서는 손쉽게 아이 열림을 얻을 수 있지만, 1.25 Gbps 급에서는 레이저 다이오드의 활성층 두께 등의 파라미터를 적정화해야 적정한 아이특성을 얻을 수 있음을 보였다.

• Journal of Korean Neurosurgical Society
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• 제37권5호
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• pp.364-369
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• 2005

Objective: Spinal instrumentation without fusion often fails due to biological failure of intervertebral joints (spontaneous fusion, degeneration, etc). The purpose of this study is to investigate the influence of fixation rigidity on viability of intervertebral joints. Methods: Twenty pigs in growing period were subjected to posterior segmental fixation. Twelve were fixed with a rigid fixation system(RF) while eight were fixed with a flexible unconstrained implant(FF). At the time of the surgery, a scoliosis was created to monitor fixation adequacy. The pigs were subjected to periodic radiological examinations and 12pigs (six in RF, six in FF) were euthanized at 12-18months postoperatively for analysis. Results: The initial scoliotic curve was reduced from $31{\pm}5^{\circ}$ to $27{\pm}8^{\circ}$ in RF group (p=0.37) and from $19{\pm}4^{\circ}$ to $17{\pm}5^{\circ}$ in FF group (p=0.21). Although severe disc degeneration and spontaneous fusion of facet joints were observed in RF group, disc heights of FF group were well maintained without major signs of degeneration. Conclusion: The viability of the intervertebral joints depends on motion spinal fixation. Systems allowing intervertebral micromotion may preserve the viability of intervertebral discs and the facet joint articular cartilages while maintaining a reasonably stable fixation.

• 대한영상의학회지
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• 제82권4호
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• pp.862-875
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• 2021

목적 요추신경근병증이 있는 60세 이상의 환자의 신경공 협착에 영향을 줄 수 있는 인자를 자기공명영상 평가를 통해 알아보고자 하였다. 대상과 방법 요추신경근병증이 있는 60세 이상의 환자 133명이 본원에서 시행 받은 2018년 1월부터 4월까지의 요추 자기공명영상을 대상으로 하였다. 제4/5 요추간과 제5 요추/제1 천추간에서 신경공 협착이 있는 군과 없는 군으로 나눈 후 척추전방전위증, 척추후방전위증, 추간판 간격 감소, 추간판탈출증, 중심성 척추관 협착, 황색인대비후, 척추후관절 비후 여부를 2명의 판독자가 분석한 후 단변량 및 다변량 로지스틱 회귀분석을 시행하였다. 결과 단변량 분석에서 제4/5 요추간에 대해 추간판 간격 감소(p = 0.006), 제5 요추/제1 천추간에 대해서는 척추전방전위증(p = 0.005)과 척추후관절 비후(p = 0.006)가 신경공 협착과 유의한 연관성을 보였다. 다변량 분석에서는 제4/5 요추간에 대해 추간판 간격 감소[odds ratio(이하 OR) = 4.272; 95% confidence interval (이하 CI) 1.736~10.514]가 신경공 협착과 관련된 인자였다. 제5 요추/제1 천추간에서는 척추전방전위증(OR = 3.696; 95% CI 1.297~10.530)과 척추후관절 비후(OR = 6.468; 95% CI 1.238~32.617)가 이와 관련된 인자였다. 결론 제4/5 요추간에서는 추간판 간격 감소가, 제5 요추/제1 천추간에서는 척추전방전위증과 척추후관절 비후가 신경공 협착과 관련된 인자였다.

• 한국IT서비스학회지
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• 제15권3호
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• pp.157-171
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• 2016

As unemployment rates and concerns about turnover keep growing, the need for information is also increasing. In these situations, the job reviews which share information about the company catch people's attention because they are usually created by people who worked at the company. The development of SNS and mobile environments has led to an increase in the web services that provide job reviews. For example, Jobplanet is a job review service in Korea, and Glassdoor.com offers a similar service in the US. Despite this attention, however, research utilizing job reviews is insufficient. This paper asks whether there are differences in ratios of job satisfaction factors by industry, using LDA topic modeling and co-occurrence analysis to explore the differences. Through the results of LDA, we find that the ratios of job satisfaction factors are similar by industry. At the same time, the results of co-occurrence analysis show that the co-occurrence frequency of some job satisfaction factors appears high: pay and welfare, balance of work and life, company culture. We expect that the result of this research will be helpful in comparative analysis of job satisfaction factors by industry. Furthermore, in this paper we suggest how to use the job review data in organizational behavior research.

• 대한의용생체공학회:의공학회지
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• 제28권3호
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• pp.397-409
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• 2007

Owing to needs of biomechanical comprehension and analysis to obtain various medical treatment designs which are related with the spine in order to cure and diagnose LBP patients, the FE modeling and nonlinear analysis of lumbosacrum including a partial ilium and iliolumbar ligaments, were carried out. First, we investigated whether the geometrical configuration of vertebrae displayed by DICOM slice files is regular and normal condition. After constructing spinal vertebrae including a partial ilium, a sacrum and five lumbars (from L1 to L5)with anatomical shape reconstructed using softwares such as image modeler and CAD modeler, we added iliolumbar ligaments, lumbar ligaments, discs and facet joints, etc.. And also, we assigned material property and discretized the model using proper finite element types, thus it was completely modeled through the above procedure. For the verification of each segment, average sagittal ROM, average coronal ROM and average transversal ROM under various loading conditions(${\pm}10Nm$), average vertical displacement under compression(400N), ALL(Anterior Longitudinal Ligament) and PLL(Posterior Longitudinal Ligament) force at L12 level, strains of seven ligaments on sagittal plane at L45 level and maximal strain of disc fibers according to various loading conditions at L45 level, etc., they were compared with experimental results. For the verification of multilevel-lumbosacrum spine including partial ilium and iliolumbar ligaments, the cases with and without iliolumbar ligaments were compared with ROM of experiment. The results were obtained from analysis of the verified FE model as follows: I) Iliolumbar ligaments played a stabilizing role as mainly posterior iliolumbar ligaments under flexion and as both posterior and anterior iliolumbar ligaments of one side under lateral bending. 2) The iliolumbar ligaments decreased total ROM of 1-8% in total model according to various motion conditions, which changed facet contact forces of L5S level by approximately 0.8-1.4 times and disc forces of L5S level by approximately 0.8-1.5 times more than casewithout ilioligaments, under various loading conditions. 3) The force of lower discs such as L45 and L5S was bigger than upper discs under flexion, left and right bending and left and right twisting, except extension. 4) It was predicted that strains of posterior ligaments among iliolumbar ligaments would produce the maximum 16% under flexion and the maximum 10% under twisting. 5) It's expected that this present model applies to the development and design of artificial disc, since it was comparatively in agreement with the experimental datum.

• 한국지구과학회지
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• 제31권1호
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• pp.95-105
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• 2010

본 연구의 목적은 집단논리적사고력검사의 이용 목적에 따라 일반화가능도이론을 적용하여 문항과 피험자만을 고려한 단일국면의 오차원, 그리고 문항과 피험자, 그리고 영역을 고려한 다국면의 오차원을 분석하는 데 있다. 연구는 지방 소재 초 중 고등학생 총 1016명을 대상으로 이루어졌으며, 21문항의 GALT 완본을 40분 동안 실시하고, 이 중 축소본에 해당하는 12문항을 별도로 추출하여 일반화가능도이론을 이용한 신뢰도 분석에 이용하였다. 자료의 분석을 위해 일반화가능도이론을 적용하여 $p{\times}i$설계와 $p{\times}(i:h)$설계로 나누어 G 연구와 D 연구를 실시하였다. 분석결과는 다음과 같다. 첫째, 완본과 축소본을 $p{\times}I$설계로 D 연구를 수행한 결과 완본의 경우 21문항을 평가했을 때 0.87로 적정 수준의 일반화가능도 계수인 0.80을 상회하였으며, 13문항에서도 적정 수준의 일반화가능도 계수에 도달하였다. 축소본의 경우 12문항을 평가했을 때 0.77로 적정 수준의 일반화가능도 계수에 미치지 못하였으며, 최소 15문항 이상에서 신뢰도가 적정 수준에 도달하였다. 둘째, 축소본을 $p{\times}(I:H)$설계로 D 연구를 수행한 결과 6영역에 대해 영역별로 2문항씩 구성될 경우 0.71로 적정 수준의 일반화가능도계수인 0.80 보다 낮게 측정되었으며, 최소 영역별 5문항 이상에서 신뢰도가 적정 수준에 도달하였다.