• 한국해안·해양공학회논문집
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• 제33권5호
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• pp.195-202
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• 2021

해상풍력발전기는 바람 및 파도, 구조물 자중에 의해 수직-수평-모멘트의 복합하중을 받는다. 본 연구에서는 유한요소해석으로 사질토 지반에 설치된 해상풍력발전기 석션기초의 복합하중에 대한 지지력을 산정하였다. 또한 복합하중이 작용하는 중의 석션기초 주변 지반의 응력상태를 상세하게 분석하였다. 최종적으로 유한요소해석 결과를 토대로 수평 및 모멘트 지지력 산정식과 복합하중에 대한 안전성을 평가하는 지지력 포락선 식을 제안하였다.

• 한국통신학회논문지
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• 제27권4B호
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• pp.345-352
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• 2002

본 논문에서는 백색잡음과 페이딩환경에서 IS-95 시스템 역방향의 성능을 평가하는데 있어 컴퓨터 수행시간을 개선할 수 있는 획기적인 방법을 제안하고 제안된 방법의 효율성은 샘플수의 형태로 입증된다. 현재 통신 시스템의 성능분석에 가장 많이 사용되는 MC(Monte Carlo) 시뮬레이션 기법은 낮은 에러율에서 많은 시뮬레이션 수행시간을 요구한다. 때문에 MC 방법은 컴퓨터 수행속도의 한계를 피할 수 없게 된다. 이러한 문제점을 해결하기 위해 제안된 방식인 센트랄 모멘트 기법을 IS-95 시스템 역방향에 적용하여 MC 방법에서 요구되는 데이터 샘플수보다 적은 수신신호의 N차 센트랄 모멘트로부터 이산 확률밀집함수를 얻을 수 있다. 연속된 누적확률분포 함수는 보간법을 통해 정확하게 되고 샘플수에서의 개선 효과가 입증된다.

• 대한조선학회논문집
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• 제37권2호
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• pp.30-37
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• 2000

3톤급 소형어선의 나선, 빌지킬 및 중앙날개(central wing)가 부착된 상태의 3가지 모델에 대해 파랑중(선수파)에서 속도 변화, 초기각의 변화 및 OG(무게중심과 횡동요 중심간의 거리)의 변화에 따른 횡동요 감쇠시험에 의해 감쇠 특성을 비교하였다. 파주기 변화에 대한 영향도 포함시켰다. 또한 에너지법에 의해 선형 및 비선형 속도항에 의존하는 횡동요 감쇠모멘트를 계산하여 시험값과 비교하였으며 3가지 모델에 대한 에너지 발산 형태도 비교하였다. 파랑이 있을 때 감쇠력은 전진속도가 없는 경우는 증가하였으나 전진속도가 있는 경우는 부가물이 부착된 경우에는 양력증가에 의한 감쇠력 증가 기여도가 아주 크기 때문에 파랑에 의한 감쇠력 증가는 미소하였다.

• Structural Engineering and Mechanics
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• 제58권2호
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• pp.259-276
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• 2016

Lead-rubber bearings (LRBs) have been used worldwide in seismic design of buildings and bridges owing to their stable mechanical properties and good isolation effect. We have investigated the effectiveness of LRBs in framed underground structures on controlling structural seismic responses. Nonlinear dynamic time history analyses were carried out on the well-documented Daikai Station, which collapsed during the 1995 Hyogoken-Nanbu earthquake. Influences of strength ratio (ratio of yield strength of LRBs to yield strength of central column) and shear modulus of rubber on structural seismic responses were studied. As a displacement-based passive energy dissipation device, LRBs reduce dynamic internal forces of framed underground structures and improve their seismic performance. An optimal range of strength ratios was proposed for the case presented. Within this range, LRBs can dissipate maximum input earthquake energy. The maximum shear and moment of the central column can achieve more than 50% reduction, whereas the maximum shear displacement of LRBs is acceptable.

• Advances in nano research
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• 제10권4호
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• pp.385-395
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• 2021

This research concentrates on the effects of distributions and volume fractions of carbon nanotubes (CNT) on the nonlinear bending behavior of deep cylindrical panels reinforced by functionally graded carbon nanotubes under thermo-mechanical loading, hitherto not reported in the literature. Assuming the effects of shear deformation and moderately high value of the radius-to-side ratio (R/a), based on the first-order shear deformation theory (FSDT) and von Karman type of geometric nonlinearity, the governing system of equations is obtained. The analytical solution of field equations is carried out using the Ritz method together with the Newton-Raphson iterative scheme. The effects of radius-to-side ratio, temperature change, and boundary conditions on the nonlinear response of the functionally graded carbon nanotubes reinforced composite deep cylindrical panel (FG-CNTRC) are investigated. It is concluded that, among the five possible distribution patterns of CNT, FG-V CNTRC deep cylindrical panel is strongest with the highest bending moment and followed by UD, X, O, and Ʌ-ones. Also, considering the present deep cylindrical panel formulation increases the accuracy of the results. Hence, according to the noticeable amount of R/a in FG-CNTRC cylindrical panels, it is mandatory to apply strain-displacement relations of deep cylindrical panels for bending analysis of FG-CNTRC which certainly is desirable for industrial application.

• 대한치과보철학회지
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• 제31권2호
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• pp.271-300
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• 1993

The purpose of this study was to analyze the stress distribution at supporting bone according to the types of connection modality between implant and tooth in the superstrcture. This investigation evaluated the stress patterns in a photoelastic model produced by three different types of dental implants such as Branemark, Steri-Oss, IMZ and resin tooth using the techniques of quasi three dimensional photoelasticity. The teeth-supported bridge had a first molar pontic supported by second premolar and second molar as a control group. The implant and toothsupported bridge had a first molar pontic supported by second premolar and implant posterior retainer as an experimental group. Prostheses were mechanically connected to an adjacent second premolar by the rigid of nonrigid connection, Nonrigid connection used an attachment placed between the tooth-supported and fixture-supported component. The female(keyway) of attachment was placed on the distal end of the retainer supported by the tooth ; the male(Key) of attachment connected to the osseointegrated bridge was engaged into the keyway. All prostheses were casted in the same nonprecious alloy and were cemented and screwed on their respective abutments and implants. 16㎏ of vertical loads on central fossae of second premolar, first molar pontic, implant of second molar were applied respectively and 6.5㎏ of inclined load on middle buccal surface of first molar pontic was applied. The results were as follows : 1. Under the vertical load on the central fossa of first mloar pontic, the stress developed at the apex of tooth of implat was more uniformly distributed in the case of nonrigid connection than in the case of rigid connection. 2. Under the vertical load on the central fossa of first molar pontic, the stress developed around the cervical area of tooth of implant was larger in the case of rigid connection than in the case of nonrigid connection because the bending moment was more occured in the case of rigid connection than in the case of nonrigid connection. 3. Stress was more restricted to the loaded side of nonrigid connection than to that of rigid connection 4. Under the inclined load. The set screw loosening of implant was more easily occured in the case of nonrigid connection than in the case of rigid connection due to torque moment. 5. In the case of Branemark implant, the stress concentration in second premolar was larger and the stress developed around the cervical area of implant was lower than any other cases under the vertical load, because Branemark implant with the flexible gold screw was showed in incline toward second premolar by a bending moment. 6. The stress developed around the apex of tooth or implant was more uniformly distributed in the case of Steri-Oss implant with stiff screw than in the case of Branemark implant under the vertical load. But, the stress developed around the cervical area of the Steri-Oss implant was larger than that of any other implants because bending moment was occured by vertical migration of second premolar. 7. The stress distribution in the case of IMZ implant was similar to the case of natural teeth under small vertical load. But, the residual stress around the implant was showed to occurdue to deformation of IMC and sinking of screw under larger vertical load.

• 조명전기설비학회논문지
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• 제19권5호
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• pp.60-67
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• 2005

본 논문에서는 진공방전관을 이용한 고농도 중첩방전형 오존발생기를 설계$\cdot$제작하였다. 3개의 전극(중심전극, 내부전극 및 외부전극)과 1개의 방전간극(내부전극과 외부전극 사이의 방전간극)으로 구성된 중첩방전형 오존발생기는 진공방전관내에 장착한 중심전극과 내부전극에 $180{[^\circ]}$의 위상차를 가진 2개의 교류고전압을 인가하고 외부전극을 공통접지함으로써 중심전극과 외부전극사이에서 발생되는 무성방전과 내부전극과 외부전극사이에서 발생되는 무성방전이 방전간극에서 중첩되는 구조이다. 이때 방전관의 진공도, 방전전력 및 산소원료가스 유량 변화에 따른 방전특성과 오존생성특성을 연구검토한 결과 최대 8840[ppm]의 고농도 오존을 얻을 수 있었다.

• Journal of Korean Dental Science
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• 제4권2호
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• pp.46-51
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• 2011

Purpose: For aesthetic reasons, composite resin brackets are widely used. However, related studies are rare. This pilot study sought to compare the stress distributions in two commercially available composite resin brackets with metal slot. Materials and Methods: Two commercially available resin brackets -- full-metal slot resin bracket (fSRB) and partial-metal slot resin bracket (pSRB) with straight wire appliance dimension of $0.022{\times}0.028$ in -- were selected. In each bracket, 3-dimensional finite element models were constructed, and stress level was evaluated using finite element analysis. By loading the tipping force and torsion moment, which are similar to those applied by the stainless steel rectangular wire ($0.019{\times}0.025$ -in), stress distributions were calculated, and von Mises stress values were obtained. Results: In pSRB and fSRB, the stress value of the torque moment was much higher than that of the tipping force. The pSRB showed higher stress value than fSRB in both tipping force and torque moment because of the difference in size and configuration of the metal frame inserted into the slot. More stress was also found to be concentrated on the slot area than the wing area in fSRB. Conclusion: The slot form of fSRB was found to be more resistant to the stress of tipping and torque than the slot form of pSRB. In addition, the slot areas -- rather than the wing areas -- of the bracket showed breakage susceptibility. Therefore, resistance to the torque moment on the slot area should be considered in bracket design.

• 산업경영시스템학회지
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• 제20권44호
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• pp.497-506
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• 1997

In this paper described is the software developed to calculate the physical properties of arbitrary section shape. The software consists of arbitrary section display module(ASDM) and section property calculation module(SPCM). ASDM defines and displays the shape of arbitrary section and SPCM calculates its properties such as area, centroid, moment of inertia, torsional constant, etc.. In many cases, calculation of section properties is not easy because user has to define the vertex coordinates which are difficult to do so in the case of arbitrary section. In the developed software, however, since user is asked to define only points of central lines and thickness of arbitrary section, the calculattion task of arbitrary section is very effective.

• Journal of the Korean Statistical Society
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• 제24권1호
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• pp.31-44
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• 1995

In fitting a model, there always exists a discrepancy between the fitted model and the true functional relationship. In measuring this discrepancy, Box and Drapper (1959) used the criterion dividing the discrepancy into two parts which are the bias error part and the variance error one in single response case. In this paper, an optimum design which makes these two types of errors as small as possible is found by extending the Box and Drapper criterion to multiple response situation. Especially, a design is found to meat rotatability conditions when we fit a quadratic model to each response fearing cubic bias. Using the central composite design, an application of general results to a specific case is shown to help understanding the material.