• Structural Engineering and Mechanics
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• 제23권5호
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• pp.543-562
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• 2006

Base isolation technology has been accepted as a feasible and attractive way in improving seismic resistance of structures. The seismic design of new seismically isolated structures is mainly governed by the Uniform Building Code (UBC-97) published by the International Conference of Building Officials. In the UBC code, the distribution formula of the inertial (or lateral) forces leads to an inverted triangular shape in the vertical direction. It has been found to be too conservative for most isolated structures through experimental, computational and real earthquake examinations. In this paper, four simple and reasonable design formulae, based on the first mode of the base-isolated structures, for the lateral force distribution on isolated structures have been validated by a multiple-bay three-story base-isolated steel structure tested on the shaking table. Moreover, to obtain more accurate results for base-isolated structures in which higher mode contributions are more likely expected during earthquakes, another four inertial force distribution formulae are also proposed to include higher mode effects. Besides the experimental verification through shaking table tests, the vertical distributions of peak accelerations computed by the proposed design formulae are in good agreement with the recorded floor accelerations of the USC University Hospital during the Northridge earthquake.

• Current Optics and Photonics
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• 제4권4호
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• pp.330-335
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• 2020

We have investigated optimization of the working distance (WD) for a highly miniaturized imaging probe for endoscopic optical coherence tomography (OCT). The WD is the axial distance from the distal end of the imaging probe to its beam focus, which is demanded for dimensional margins of protective structures, operational safety, or full utilization of the axial imaging range of OCT. With an objective lens smaller than a few hundred micrometers in diameter, a micro-optic imaging probe naturally exhibits a very short WD due to the down-scaled optical structure. For a maximized WD careful design is required with the optical aperture of the objective lens optimally filled by the incident beam. The diffraction-involved effect was taken into account in our analysis of the apertured beam. In this study, we developed a simple design formula on the maximum achievable WD based on our diffraction simulation. It was found that the maximum WD is proportional to the aperture size squared. In experiment, we designed and fabricated very compact OCT probes with long WDs. Our 165-㎛-thick fiber-optic probes provided WDs of 3 mm or longer w ith reasonable OCT imaging performance.

• 대한한의학방제학회지
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• 제13권2호
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• pp.1-16
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• 2005

Objectives: To find out the effects GGTl, an antiobestic drug widely used in clinics, has on the blood-antiobestic index and the toxicity index using the data from the hGHTg obese male rats. We looked closely into both of the two indices because GGTl antiobestic effect can happen not only by pharmacological action, but also by its toxicity. Also, we verified the difference in effect between GGTl and reductil (sibutramine), which has been approved by the FDA of the United States. Methods: After performing the experiments for 8 weeks on the hGHTg obese male rats divided into three groups: the control group, the GGTl group, and the reductil (RD) group, we anesthetized the rats with Diethyl ether and took a 3ml blood sample from the heart. Then, after coagulating the blood in room temperature by using the plasma separator, we centrifuged it for 25 minutes in 3,000rpm using the high-speed refrigerated centrifuge. We kept the separated plasma in a deep freezer at $-80^{\circ}C$, and repeatedly measured the antiobestic index and the toxicity index twice using the hematology biochemistry analyzer. Also, in order to judge the indirect toxicity index, we separated liver from kidney and observed them. Results: When we looked at the results of the analysis of covariance on the measuring elements related to the antiobestic index (TC, HDL, LDL, TG, and GLU), there was no significant difference among the groups in all measuring elements. Also, the results of the analysis of covariance on the two roups (RD group and GGTl group) showed that the p-values had no significant difference under the level of significance 0.05. When we looked at the result of the analysis of covariance on the measuring elements related to the toxicity index (GOT, GPT, GGT, CREA, UA, ALB, and TP), we could see that the p-values in GPT, ALB, and TP have a significant difference among the groups. Also, the results of the analysis of covariance about the measuring elements related to the toxicity index on both groups, RD group and GGTl group, showed no significant difference in the p-values of all of the measuring elements in the two groups, RD and GGTl group. Conclusions: In conclusion, through this experiment, the safety of GGTl has been approved, and although the verification on its medical effect has not been clearly approved, when we consider the fact that it belongs to the same group as reductil, an antiobestic drug approved by the FDA of the United States, we could indirectly verify that GGTl has an antiobestic effect. We believe that when doing a sample design for a future experiment, it needs to be performed on a greater sample size based on the power analysis that needs to be performed primarily in experiments, and a more accurate verification is needed through more systematic experiment plans.

• The Journal of Advanced Prosthodontics
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• 제3권2호
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• pp.69-75
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• 2011

This study assessed the effect of preparation design on marginal adaptation and also compared the sensitivity and specificity of clinical evaluation techniques for marginal accuracy of cast restorations to stereomicroscopy. MATERIALS AND METHODS. Three Ivorine molar teeth of different designs were prepared. (A)-A complete crown preparation with buccal shoulder and beveled finish line. (B)-A complete crown preparation with chamfer finish line. (C)-A three-quarter crown preparation with proximal boxes and beveled finish line. Twenty four castings were prepared with eight castings for each design respectively. Each casting underwent examination with an explorer, disclosing media, and a stereomicroscope. Stereomicroscopy at a value less than or equal to 30 microns was used as a gold standard to evaluate the significance of different designs on marginal adaptation. Chi-square tests of independence and Kruskal-Wallis were used to evaluate the effect of preparation design and compare the agreement between examination methods for detection of marginal gap size of greater than or equal to 30 microns (${\alpha}$=.05). Sensitivity and specificity for explorer and disclosing media as compared to stereomicroscope was calculated using statistical formula given by Park. RESULTS. The preparation design did not significantly affect overall marginal adaptation. Examination by explorer and disclosing media at $30 \;{mu}m$ revealed 39% and 10.06% sensitivity and 91% and 82% specificity respectively. CONCLUSION. Preparation designs examined in this study did not significantly affect the marginal adaptation of the castings. Commonly used clinical evaluation techniques using explorer and disclosing media appeared to be inadequate for assessment of marginal accuracy.

• 한국산학기술학회논문지
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• 제19권1호
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• pp.714-721
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• 2018

본 논문은 강교량 거더, 교각, 선박이나 대형 저장 시설 등 주요 구조 부재에 활용되는 곡판 및 강관을 효과적으로 보강하는 방안에 관한 것이다. 최근 연구에서 압축을 받는 평판이 종방향 보강재의 단면회전강성에 의해 국부좌굴강도가 향상되는 특징을 정량적으로 분석하였고, 폐단면리브 단면회전강성과의 상관관계를 규명한 바 있다. 본 논문에서는 곡판에 대해 이와 같은 효과를 정량적으로 검토하고자 한다. 일축압축이 재하된 경우에 폐단면리브로 보강된 두께방향으로 곡률을 가지는 곡판의 좌굴거동을 살펴보기 위해 범용 구조해석 프로그램인 ABAQUS를 이용하여 3차원 유한요소해석 모델을 생성하였다. 이를 통해 좌굴거동에 대한 수치해석을 수행하였으며, 영향인자에 대한 변수해석적 연구를 수행하여 좌굴응력과 좌굴모드의 변동특성을 정량적으로 평가하였다. 폐단면리브 단면회전강성의 구속효과로 인한 좌굴강도 증가효과와 판의 곡률에 따른 좌굴강도 계수를 고려하여 좌굴강도를 추정하는 방법론을 이론적으로 제안하였다. 제안된 공식은 유한요소해석 결과와 비교하여 서로 유의미성이 검토되었다. 또한 평판에서와 마찬가지로 일축압축 상태에서 폐단면리브의 단면강성에의해 부여되는 양측단 회전강성의 증가로 인해 곡판의 국부좌굴강도가 이에 비례하여 증가하였고, 양측단에서 회전이 고정된 곡판의 좌굴강도에 수렴하는 경향을 확인하였다.

• 한국해안·해양공학회논문집
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• 제29권2호
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• pp.77-82
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• 2017

기후변화에 따른 설계파고를 초과하는 이상파랑의 내습 가능성이 커지면서 항만구조물의 안정성 확보가 시급한 실정이다. 이러한 변화에 능동적으로 대응하기 위하여 기존 방파제에 대한 평가기준과 신설 장대형 방파제의 설계기준이 점차 강화되면서 인터로킹 케이슨 방파제에 대한 관심이 대두되고 있다. 하지만 현재까지는 항만 및 어항 설계기준 해설[부록] 개정안에 장대형 케이슨에 발생하는 파력 평활화 효과가 제시되어있을 뿐 인터로킹 케이슨 방파제의 안정성을 평가하기 위한 방법이 별도로 제시되어 있지 않다. 이에, 본 연구에서는 선형파 이론에 기초하여 경사 입사하는 파랑의 작용 위치별 위상차의 효과를 고려하고, 최대 파력분포는 설계기준의 Goda 파압식을 적용하여, 규칙파, 불규칙파 및 다방향 불규칙파에 대한 인터로킹 케이슨 방파제의 미끌림 안정성 평가식을 제안하였다.

• 한국구조물진단유지관리공학회 논문집
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• 제26권6호
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• pp.47-53
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• 2022

콘크리트구조물의 한계상태설계법이 적용되면서 구조물의 극한상태까지 고려하는 설계가 이루어지고 있다. 실제 철근콘크리트 부재가 인장력을 부담할 때 부재가 항복한 후에도 극한상태까지 콘크리트가 인장력을 부담한다. 따라서 한계상태 거동에 대한 정확한 평가를 위해서는 휨 부재의 항복 후 인장강화효과에 대한 연구가 필요하다. 본 연구에서는 복철근 직사각형 단면을 가지는 RC 단순보에 대하여 4점 휨 실험을 수행하였고, 영상분석기법을 이용하여 부재의 거동을 상세하게 분석하였다. 분석 결과를 이용하여 휨 인장강화효과 계수를 도입한 항복 후 인장강화효과 추정식을 제안하였고, 이를 기존 연구들의 실험 결과를 통해 적용성을 검증하였다. 부재의 연성거동을 대표하는 극한 변형률과 항복 변형률 차이가 실험 결과와 유사하게 나타나 제안식의 예측이 비교적 정확한 것으로 판단된다.

• 한국전산구조공학회논문집
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• 제29권5호
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• pp.483-490
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• 2016

플랜트의 유황 저장 탱크는 강재로 구성되며, 탱크 저면은 앵커볼트에 의해 Ring Wall 형상의 콘크리트 기초와 연결된다. 탱크 내 유황이 내부 열원에 의해 고온상태를 유지하기 때문에, 유황 저장 탱크는 상온의 유체를 저장하는 다른 탱크에 비해 큰 체적팽창을 겪게 된다. 일반적으로 탱크 기초의 구조설계는 기초의 내외부의 온도차를 하중으로 적용한 구조해석이 수행되는데, 이 방법은 탱크의 열팽창 특성이 앵커볼트에 의해 집중하중 형태로 콘크리트 기초에 전달되는 현상을 고려할 수 없다. 이는 온도하중의 영향을 과소평가하게 되며, 앵커볼트에 인접한 콘크리트의 균열을 야기한다. 본 연구는 앵커볼트에 의한 온도 하중전달 메커니즘을 고려한 하중 평가식을 제안함으로써, 콘크리트 기초에 작용하는 하중을 보다 합리적으로 결정하고자 한다. 이를 위해 탱크 바닥판과 앵커볼트가 포함된 유한요소모델을 이용해 앵커볼트 개수 증감에 따른 온도하중의 변화를 분석하였으며, 분석결과를 이론해와 결합해 앵커볼트에 의해 전달되는 하중을 평가할 수 있는 명시적인 형태로 해를 제시하였다. 제안된 식의 유효성을 확인하기 위해 실제 플랜트 현장의 유황 저장 탱크 설계에 적용하였으며, 실무적으로 사용 가능함을 보였다.

• 오토저널
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• 제4권3호
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• pp.24-39
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• 1982

It has already been known that quenching effect is influenced greatly by stirring and changing coolant's temperature on quenching. But according to the past investigations its effect has not been taken into consideration quantitatively in the cooling process. The purpose of this study is that the influence of flow rate and temperature on the quenching effect of cooling water as quenching medium is quantitatively examined by using the open channel. The stream of water in this study is turbulent flow. The temperature of the specimen made of pure copper is measured by CA thermocouple in the vicinity of the surface and recorded by an automatic recorder during the quenching process in city water. The results obtained are as follows; 1. The quenching effect of cooling water generally increases with Reynolds Number(characteristic length; specimen diameter)as shown in the experimental formula; but at the realm of Reynolds Number from 1.2 * 10$^{4}$ to 9.2 * 10$^{4}$, the increasing rate of quenching effect shows little increase. 2. The increasing rate of quenching effect was increased under the flow rate of 221 cm/sec. On the other hand, it was decreased below this flow rate. 3. The quenching effect was influenced by the water temperature and the flow rate. But it was rather dependent upon the former than the latter. 4. Although the quenching effect appeared loosely in the water temperature of 50.deg. C, it was shown that the quenching effect increased in the low flow rate of 31 cm/sec. comparing with the still water. 5. It is desirable to design the quenching system to be over 1.2 * 10$^{4}$ in Reynolds Number or over, 3000$cm^{-1}$ / in V/v in order to increase the quenching effect of the system using open channel.annel.

• 한국공작기계학회논문집
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• 제12권1호
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• pp.32-37
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• 2003

Evaluation of fatigue strength on the spot welded part is very important for strength design of spot welded steel structures. In this paper, we could get the life cycle of the spot welded part using the lethargy coefficient obtained through the quasi-static tensile shear test for the specimen welded by current 10kA. The reliability evaluation of the life cycle is completed by comparing the life cycle calculated under the constant loading rate with the life cycle obtained by dynamic fatigue test. And then the result calculated by the lethargy coefficient is verified through the lift cycle calculated using the dynamic final tensile stress formula under the increased loading speed. This way can make save the time and cost in processing of predicting the life cycle of a structure.