• Structural Engineering and Mechanics
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• 제71권3호
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• pp.291-303
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• 2019

In the paper the analysis of natural vibrations of the transmission line with use of spectral elements and the laboratory experiments is performed. The purpose of the investigation is to analyze the natural vibrations of the transmission line and compare with the results obtained in the numerical simulations. Particular attention is paid to the hysteretic and aerodynamic damping analysis. Sensitivity of the wave number is performed for changing of the tension force, as well as for the different damping parameters. The numerical model is made using the Spectral Element Method. In the spectral model, for various parameters of stiffness, damping and tension force, the system response is checked and compared with the results of the accelerations obtained in the measurements. A frequency response functions (FRF) are calculated. The credibility of the model is assessed through a validation process carried out by comparing graphical plots of FRF and time history analysis and numerical values expressing differences in acceleration amplitude (MSG), phase angle differences (PSG) and differences in acceleration and phase angle total (CSG) values. The next aspect constituting the purpose of this paper is to present the wide possibilities of modelling and simulation of slender conductors using the Spectral Element Method. The obtained results show good accuracy in the range of both experimental measurements as well as simulation analysis. The paper emphasizes the ease with which the sensitivity of the conductor and its response to changes in density of spectral mesh division, tensile strength or material damping can be studied.

• 해양환경안전학회지
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• 제25권3호
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• pp.287-297
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• 2019

The recent increase in crude oil trading has led to an increase in the workings of SPM for crude oil carriers. VLCCs generally encounter difficulty entering port due to limitations in terms of sea depth and maneuverability. The SPM is a system that allows mooring to the buoy located in the outer sea for such vessels. However, the buoy is more affected by relatively external forces because of their of shore location. Therefore, the safety assessment of SPM is particularly important as it can lead to large oil pollution disasters in the event of SPM accidents. Despite this, in the implementation of the Marine Traffic Safety Audit Scheme in Korea, there exists no guidance for SPM. In this study, a SPM mooring safety assessment is performed using OPTIMOOR, a numerical analysis program, so as to understand the mooring characteristics of SPM. As a result, it is confirmed that the tension of mooring lines and hull movement in the SPM are greatly affected by the encounter angles with external forces. In addition, it is found that the maximum tension of the mooring line is elevated as the water depth becomes shallower through sensitivity analysis. According to SPM characteristics, which has a large influence on the encounter angle, this study has proposed an amendment to setting criteria in the implementation of the Maritime Traffic Safety Audit Scheme which could improve the reliability and accuracy of mooring safety assessments.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2009년도 춘계 학술발표회
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• pp.585-594
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• 2009

In this present study, to performed the model test and estimated the behavior characteristics of twin tunnel in accordance with the variation of the whole failure parameters which is the strength of the ground, distance of tunnel, angle of the joint, installation of tension bolts and the blasting load. To carry out the numerical analysis for verification of model test results and analyze the sensitivity on failure parameters using model test and numerical analysis results. Based on sensitivity analysis results, to propose the most habitually failure parameters in tunnel scale model test.

• 한국지반공학회논문집
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• 제28권5호
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• pp.13-25
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• 2012

그라운드 앵커공법은 현재 우리나라에서 가장 일반적으로 사용되는 사면보강공법들 중 하나이다. 앵커로 보강된 사면의 안정성을 장기간 확인하기 위해서는 그라운드 앵커의 긴장력을 측정하는 것이 매우 중요하다. 그러나 현재 현장에서 주로 사용되는 스트레인게이지 및 V/W타입의 로드 셀은 전자기파에 의한 노이즈 발생이 크고 습기 또는 수분의 영향으로 인해 측정값에 오차가 발생할 수 있으며 자기열화 등으로 장기간의 모니터링에 한계가 있다. 또한 앵커의 개별 텐던에 발생하는 미세한 변화를 정확히 감지할 수 없는 단점이 있어 이를 개선할 수 있는 방안으로 광섬유 센서를 이용하여 강연선의 변형률을 측정할 수 있는 광섬유 센서 내장형 텐던이 개발되었다. 이 광섬유 센서 내장형 텐던은 단기간의 앵커 장력 측정에 성공적으로 적용된 사례가 보고되었으나 장기간에 걸친 장력 변화를 측정하기 위해서는 온도에 의한 광섬유 센서의 변형률을 보상하여야 한다. 이 논문에서는 광섬유 센서 내장형 텐던을 이용하여 그라운드 앵커의 장력모니터링 시 지중온도 변화에 의한 영향을 보상하는 실용적인 방안에 대하여 기술하였다. 먼저 실내실험을 통하여 광섬유 센서 내장형 텐던의 온도반응계수(${\beta}^{\prime}$)를 $2.0{\times}10^{-5}/^{\circ}C$로 결정하고 실제 현장에 설치된 광섬유 센서를 이용하여 깊이별 지중온도 변화값을 측정하였다. 연구 대상지역(여수)의 기상청 지중온도 측정 결과 자료와의 비교를 통하여 결정된 온도반응계수(${\beta}^{\prime}$)를 이용한 광섬유 센서 내장형 텐던의 온도반응 성능을 검증하였다. 최종적으로 광섬유 센서 내장형 텐던을 이용하여 실제 사면에 설치된 인장형 앵커와 압축형 앵커의 계절별 긴장력을 모니터링하고 기상청 지중온도 측정자료와 온도반응계수를 이용하여 온도보상을 실시하여 기존 V/W타입의 로드 셀 측정 결과와 비교하였다. 제안된 광섬유 센서 내장형 텐던의 온도반응계수와 기상청 지중온도 측정결과를 이용한 앵커의 온도보상 방법에 의해 측정된 긴장력 모니터링 결과가 계절에 따른 지중온도 변화에 상관없이 로드 셀 결과와 일관성 있게 비교되어 제안된 온도보상 방법이 매우 실용적이며 합리적인 것으로 나타났다.

• 만화애니메이션 연구
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• 통권40호
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• pp.477-496
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• 2015

사람의 이미지 감성인식은 각기 다른 성향으로 표현된다. 현재는 감성인식을 객관적으로 평가하려는 감성컴퓨팅 연구가 활발하게 연구되고 있다. 그렇지만 기존의 감성컴퓨팅 연구는 실행에 많은 문제점을 갖고 있다. 첫째, 감성인식 면에서 비객관적이고, 부정확하다. 둘째, 감성인식의 상관관계가 불명확한 점이다. 그리하여 본 연구의 필요성으로 이미지 감성의 규칙성을 실험하여 감성컴퓨팅 방식으로 제어하고자 한다. 또한 본 연구의 목적으로 감성인식을 숫자화하고, 객관화하는 이미지 감성컴퓨팅 시스템 방식을 적용하고, 사람의 감성과의 유사 정도를 비교한다. 이미지 감성컴퓨팅 시스템의 주요 특징은 감성인식을 숫자화 된 디지털 형식으로 계산한다. 그리고 감성컴퓨팅의 연구배경은 감성을 디지털화하는 James A. Russell의 핵심 효과(Core Affect)를 활용한다. 핵심 감성으로 쾌정도(X축)인 쾌와 불쾌, 긴장도(Y축)인 긴장과 이완의 감성축이고, 감성컴퓨팅 연구에 적용한다. 감성축은 연관된 대표감성으로 아주 기쁜, 흥분, 의기양양, 행복한, 자족, 고요한, 여유로운, 조용한, 피곤한, 무기력한, 우울한, 슬픈, 화가 난, 스트레스, 불안, 긴장된 감성의 16개로 구분하여 감성컴퓨팅에 적용한다. 본 연구의 과정은 이미지 감성컴퓨팅 계산식의 핵심인 색채 요소를 활용하여 색상, 명도, 채도를 감성속성요소로 적용한다. 감성속성요소는 중요도인 가중치를 적용하여 비율을 계산하고, 쾌정도(X축)와 긴장도(Y축)의 감성점수로 측정한다. 다시 교차된 감성점을 바탕으로 감성원으로 확장하고, 포함된 대표감성크기로 상위 5위인 주요대표감성으로 선별한다. 또한 사람의 이미지 감성을 16개 대표감성점수로 측정하고, 상위 5위의 대표감성으로 구분한다. 연구결과 감성컴퓨팅의 주요대표감성과 사람의 감성인식의 주요대표 감성을 비교하여 일치하는 대표감성수에 따라 감성의 유사 정도를 검증한다. 감성컴퓨팅 유사성 실험 결과 주요대표감성의 평균 일치율은 51%이고, 2.5개의 대표감성이 사람의 감성인식과 일치했다. 본 연구를 통해 감성컴퓨팅 계산 방식과 사람 감성인식의 유사 정도를 측정했고, 감성계산식의 객관적인 평가기준을 제시했다. 향후 연구에서는 좀 더 높은 일치율 향상의 방안과 감성계산식의 가중치 연구가 유지되어야 할 것이다.

• The Korean Journal of Physiology and Pharmacology
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• 제2권6호
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• pp.695-703
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• 1998

$[K^+]_o$ can be increased under a variety of conditions including subarachnoid hemorrhage. The increase of $[K^+]_o$ in the range of $5{\sim}15$ mM may affect tensions of blood vessels and can change their sensitivity to various vasoactive substances. Therefore, it was examined in the present study whether the sensitivity of cerebral arteries to vasoactive substances can be changed with the moderate increase of $[K^+]_o$, using Mulvany-type myograph and $[Ca^{2+}]_c$ measurement. The contractions of basilar artery and branch of middle cerebral artery induced by histamine were not increased with the elevation of $[K^+]_o$ from 6 mM to 9 mM or 12 mM. On the contrary, the contractions induced by serotonin were significantly increased with the elevation of $[K^+]_o$. The contractions were also significantly increased by the treatment with nitro-L-arginine $(10^{-4}$ M for 20 minutes). In the nitro-L-arginine treated arteries, the contractions induced by serotonin were significantly increased with the elevation of $[K^+]_o$ from 6 mM to 12 mM. $K^+-induced$ relaxation was evoked with the stepwise increment of extracellular $K^+$ from 0 or 2 mM to 12 mM by 2 mM in basilar arterial rings, which were contracted by histamine. But $[K^+]_o$ elevation from 4 or 6 mM to 12 mM by the stepwise increment evoked no significant relaxation. Basal tension of basilar artery was increased with $[K^+]_o$ elevation from 6 mM to 12 mM by 2 mM steps or by the treatment with ouabain and the increase of basal tension was blocked by verapamil. The cytosolic free $Ca^{2+}$ level was not increased by the single treatment with serotonin or with the elevation of $[K^+]_o$ from 4 mM to 8 or 12 mM. In contrast to the single treatment, the $Ca^{2+}$ level was increased by the combined treatment with serotonin and the elevation of $[K^+]_o$. The increase of free $Ca^{2+}$ concentration was blocked by the treatment with verapamil. These data suggest that the sensitivity of cerebral artery to serotonin is increased with the moderate increase of $[K^+]_o$ and the increased sensitivity to serotonin is due to the increased $[Ca^{2+}]_i$ induced by extracellular $Ca^{2+}$ influx.

• Journal of Acupuncture Research
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• 제29권4호
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• pp.25-34
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• 2012

Objectives : This study was conducted to investigate the effects of fixed-intensity and varied-intensity electroacupuncture in pain and sensory threshold concerning parameters visual analogue scale(VAS), brief pain inventory(BPI) and quantitative sensory testing(QST), among chronic tension headache patients. Methods : Thirty patients with chronic tension headache were randomly assigned to three groups and received different kinds of electroacupuncture at $ST_{36}$ and $ST_{37}$. Group A received fixed-intensity electroacupuncture(fixed-EA), group B received varied-intensity electroacupuncture (varied-EA), and group C received only acupuncture treatment without electrical stimulation as a control group. The intervention was given three times per week, and continued in two weeks. All the experiments were conducted blindly. Results : Fixed-EA group showed a significant decrease of VAS and BPI compared to the baseline measurement, while both varied-EA and control group did not. Of the parameters of QST, subtraction of heat pain threshold(HPT) and cold pain threshold(CPT) slightly increased in all groups, but this was not significant. Conclusions : These results suggest that fixed-EA reduce pain and improve quality of life in patients with chronic tension headache and that acupuncture may regulate patient's pain sensitivity through changing sensory threshold.

• 한국항해항만학회지
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• 제43권5호
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• pp.310-319
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• 2019

With the recent increase in the volume of liquid cargo transportation, there is a need for STS( Ship To Ship) globally. In the case of the STS mooring, the safety assessment should be conducted according to other criteria because mooring is different from the general mooring at the quay, but there is no separate standard in Korea. Thus in this study, STS mooring simulation and sensitivity analysis using OPTIMOOR program, the numerical analysis program, was conducted to identify the characteristics of the STS mooring. The target sea modeled the Yeosu port anchorage in Korea and the target ship was selected as the case of VLCC (Very Large Crude Oil Carrier)-VLCC. Through the numerical simulation and sensitivity analysis, the characteristics of STS mooring were identified. Also based on these results, we focused on establishing the standard for STS mooring safety assessment. Numerical simulation results show that the STS mooring safety can be changed according to a ship's cargo loading condition, pre-tension of mooring line, sea depth, encounter angle with the weather, and the weather condition. Additionally, the risk matrix is prepared to establish the safe external force range in the corresponding sea area. This result can be used to understand the mooring characteristics of STS and contribute to the revision of mooring safety assessment criteria.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2007년도 춘계학술대회 논문집
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• pp.258-261
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• 2007

Failure phenomena in uni-axial tension test were experimentally and numerically investigated for AA6111-T4, AA5083-H18 and DP-Steel, which were friction-stir welded with the same and different thicknesses. Forming limit diagram(FLD) was measured using hemispherical dome stretching tests for base materials and also predicted by Hill's bifurcation and M-K theories for welded areas. Finite element simulations well predicted hardening behaviors, failure locations as well as failure patterns for the uni-axial tension tests especially utilizing very fine meshes and FLD along with stress softening.

• 소성∙가공
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• 제16권4호
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• pp.304-308
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• 2007

Failure phenomena in uni-axial tension test were experimentally and numerically investigated for AA6111-T4, AA5083-H18 and DP-Steel, which were friction-stir welded with the same and different thicknesses. Forming limit diagram(FLD) was measured using hemispherical dome stretching tests for base materials and also predicted by Hill's bifurcation and M-K theories for welded areas. Finite element simulations well predicted hardening behaviors, failure locations as well as failure patterns for the uni-axial tension tests especially utilizing very fine meshes and FLD along with stress softening.