• Earthquakes and Structures
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• 제17권6호
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• pp.557-566
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• 2019

The evaluation of the seismic hazard for a given site is to estimate the seismic ground motion at the surface. This is the result of the combination of the action of the seismic source, which generates seismic waves, the propagation of these waves between the source and the site, and site local conditions. The aim of this work is to evaluate the sensitivity of dynamic response of extended structures to spatial variable ground motions (SVGM). All factors of spatial variability of ground motion are considered, especially local site effect. In this paper, a method is presented to simulate spatially varying earthquake ground motions. The scheme for generating spatially varying ground motions is established for spatial locations on the ground surface with varying site conditions. In this proposed method, two steps are necessary. Firstly, the base rock motions are assumed to have the same intensity and are modelled with a filtered Tajimi-Kanai power spectral density function. An empirical coherency loss model is used to define spatial variable seismic ground motions at the base rock. In the second step, power spectral density function of ground motion on surface is derived by considering site amplification effect based on the one dimensional seismic wave propagation theory. Several dynamics analysis of a curved viaduct to various cases of spatially varying seismic ground motions are performed. For comparison, responses to uniform ground motion, to spatial ground motions without considering local site effect, to spatial ground motions with considering coherency loss, phase delay and local site effects are also calculated. The results showed that the generated seismic signals are strongly conditioned by the local site effect. In the same sense, the dynamic response of the viaduct is very sensitive of the variation of local geological conditions of the site. The effect of neglecting local site effect in dynamic analysis gives rise to a significant underestimation of the seismic demand of the structure.

• Earthquakes and Structures
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• 제17권6호
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• pp.635-647
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• 2019

Tests and theoretical studies for seismic responses of a transmission tower-line system under coupled horizontal and tilt (CHT) ground motion were conducted. The method of obtaining the tilt component from seismic motion was based on comparisons from the Fourier spectrum of uncorrected seismic waves. The collected data were then applied in testing and theoretical analysis. Taking an actual transmission tower-line system as the prototype, shaking table tests of the scale model of a single transmission tower and towers-line systems under horizontal, tilt, and CHT ground motions were carried out. Dynamic equations under CHT ground motion were also derived. The additional P-∆ effect caused by tilt motion was considered as an equivalent horizontal lateral force, and it was added into the equations as the excitation. Test results were compared with the theoretical analysis and indicated some useful conclusions. First, the shaking table test results are consistent with the theoretical analysis from improved dynamic equations and proved its correctness. Second, the tilt component of ground motion has great influence on the seismic response of the transmission tower-line system, and the additional P-∆effect caused by the foundation tilt, not only increases the seismic response of the transmission tower-line system, but also leads to a remarkable asymmetric displacement effect. Third, for the tower-line system, transmission lines under ground motion weaken the horizontal displacement and acceleration responses of transmission towers. This weakening effect of transmission lines to the main structure, however, will be decreased with consideration of tilt component.

• 한국콘텐츠학회논문지
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• 제18권1호
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• pp.665-672
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• 2018

본 연구의 목적은 기존 스톱 모션 애니메이션의 문제점을 파악하고 이를 해결하기 위한 방안으로서 최신의 기술이 적용된 3D프린터 기술과 컴퓨터 특수효과 기술을 적용한 사례를 분석하였다. 이를 위해 스톱모션 애니메이션의 역사를 고찰하고 기술이 어떻게 스톱 모션 애니메이션에 적용 되었는지 선행 연구를 통해 확인하였다. 그 결과, 표현적 측면에서 최근 개봉한 <유령신부>와 <코렐라인>처럼 3D 프린터를 활용하여 클레이나 천으로 한정된 기존의 스톱 모션 애니메이션의 한계를 극복하였다. 더 나아가 스톱 모션 애니메이션의 가장 큰 한계인 자연현상은 컴퓨터 특수효과처리를 통해 오히려 스톱 모션 애니메이션만의 독특한 작품을 연출 할 수 있었다. 그래서 스톱 모션 애니메이션에서 3D 프린터 기술과 컴퓨터 특수효과기술에 대한 수용으로 무한한 상상과 독창적 표현이 가능해 졌다. 최근 기술 기반 스톱 모션 애니메이션은 향후 애니메이션 분야의 지속적으로 발전하는데 그 기초를 제공 할 것으로 기대한다.

• Structural Engineering and Mechanics
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• 제60권6호
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• pp.953-977
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• 2016

Modern performance-based design methods require ways to determine the factual behavior of structures subjected to earthquakes. Drift ratio demands are important measures of structural and/or nonstructural damage of the structures in performance-based design. In this study, global drift ratio and interstory drift ratio demands, obtained by nonlinear time history analysis of three generic RC frames using code-compatible ground motion record sets, are statistically evaluated. Several ground motion record sets compatible with elastic design spectra defined for the local soil classes in Turkish Earthquake Code are used for the analyses. Variation of the drift ratio demands obtained from ground motion records in the sets and difference between the mean of drift ratio demands calculated for ground motion sets are evaluated. The results of the study indicate that i) variation of maximum drift ratio demands in the sets were high; ii) different drift ratio demands are calculated using different ground motion record sets although they are compatible with the same design spectra; iii) the effect of variability due to random causes on the total variability of drift ratio demands is much larger than the effect of variability due to differences between the mean of ground motion record sets; iv) global and interstory drift ratio demands obtained for different ground motion record sets can be accepted as simply random samples of the same population at %95 confidence level. The results are valid for all the generic frames and local soil classes considered in this study.

• 한국안전학회지
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• 제19권4호
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• pp.123-128
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• 2004

This study investigated effect of arm posture, repetition of wrist motion and external load on perceived discomfort. The arm postures were controlled by shoulder flexion, elbow flexion, and ist motions such as flexion, extension, radial deviation and ulnar deviation. An experiment was conducted to measure discomfort scores for experimental treatments using the magnitude estimation, in which the L16 orthogonal array was adopted for reducing the size of experiment. The results showed that while the effect of the shoulder flexion, repetition of wrist motion and external load was statistically significant at $\alpha=0.05$or 0.10, that of the elbow and wrist motions was not. Discomfor ratings increased linearly as levels of wrist repetition and external load increased. This implies that the existing posture classification schemes such as OWAS, RULA, which do not properly consider effect of motion repetition and external load, may underestimate postural load. Based on the regression equation for wrist repetition and external load, isocomfort region indicating the region within which discomfort scores were expected to be the same was proposed. It is recommended that when assessing risk of postures or developing new posture classification schemes, motion repetition and external load as well as posture itself be fully taken into consideration for precisely evaluating postural stress.

• 대한조선학회논문집
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• 제29권3호
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• pp.53-58
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• 1992

파랑중(波浪中)에서 조종운동(操縱運動)을 하는 선박(船舶)에 있어, 실용적으로 선형(線形) 계산(計算)의 경우 파랑력(波浪力)을 단순한 정상(定常) 변동(變動) 외력(外力)으로 취급하는 수가 많다. 본 논문은 이와같은 경우에 있어서 파랑력에 의한 조종(操縱) 운동(運動)에 있어서의 Memory Effect를 조사하여, 이러한 실용 계산법(計算法)의 타당성(妥當性)을 논하였다. 그 결과를 요약하면 (1) $\omega_e$의 주파수(周波數)로 선체에 작용하는 정상(定常) 파랑력에 의한 Memory Effect도 거의 무시(無視)할 수 있다. (2) 따라서, 파랑중(波浪中)에서 조종 운동을 취급하는 경우, 간이 계산법으로서, 정수(靜水)중에서의 조타(操舵) 응답과 규칙파(規則波)중에서의 선체응답(船體應答)을 계산하여 이 둘을 합(合)하여도 무방하다. 그러나, 이상의 결론(結論)은 선형 운동에 국한(局限)된 것으로서, 실제의 조종 운동은 비선형성(非線形性)이 중요시(重要視)되므로 정상(定常) 파랑(波浪) 외력(外力)에 의한 Memory Effect를 좀더 엄밀(嚴密)하게 고찰(考察)하기 위해서는 비선형(非線形) Impulse Response Function을 구(求)하고 이를 이용하여 파랑력(波浪力)에 의한 Memory Effect를 평가(評價)하여야 할 것이다.

• 한국정밀공학회지
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• 제17권12호
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• pp.137-144
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• 2000

In order to achieve systematical method for improving motion accuracy of hydrostatic table, an algorithm using finite element method is proposed in this paper. Quantification of averaging effect of oil film on motion error is performed theoretically by analysis on the relationship between spacial frequency of rail form error and motion error of table. Influences of film stiffness and pocket size on the motion error of table are also analyzed theoretically. Validity of the algorithm is verified experimentally from the test on the motion error of table with three types of rail which have different form profile. Experimental results show that the algorithm is very effective to analyze theoretically the motion error of hydrostatic table.

• 한국해양공학회지
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• 제33권2호
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• pp.106-115
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• 2019

The interaction between a sloshing liquid damper (SLD) tank and a rectangular pontoon was investigated under the assumption of the linear potential theory. The eigenfunction expansion method was used not only for the sloshing problem in the SLD tank but also for analyzing the motion responses of a rectangular pontoon in waves. If the frictional damping due to the viscosity of the SLD tank was ignored, the effect of the SLD appeared to be an added mass in the coupled equation of motion. The installation of the SLD tank had a greater effect on the roll motion response than the sway and heave motion of the pontoon. One resonance peak for rolling motion showed up in the case of a frozen liquid in the SLD tank. However, if liquid motion in the SLD tank was allowed, two peaks appeared around the first natural frequency of the fluid in the SLD tank. In particular, the peak value located in the low-frequency region had a relatively large value, and the peak frequency located in the high-frequency region moved into the high-frequency region as the depth of the liquid in the tank increased.

• Restorative Dentistry and Endodontics
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• 제30권4호
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• pp.327-334
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• 2005

본 연구에서는 ProFile로 근관형성 시 anticurvature filing 방법의 영향을 평가하고자 하였다 변형된 Bramante 법을 이용해 36개의 레진 블록을 치근단으로부터 8mm부위와 근관의 최대 만곡 부위에서 절단한 후 재조립하였다. 근관형성의 동작에 따라 anticurvature filing motion, circumferential filing motion, straight up-and-down motion의 3가지 실험군으로 분류한 다음 ProFile로 근관을 형성하였으며, 술 전$\cdot$후의 단면을 stereomicroscope로 촬영, 저장하고 중첩하여 근관 단면의 변화와 근관의 중심 이동률을 비교 평가하였다. 모든 위치에서 단면적 변화량, 만곡 내측으로의 형성량과 중심 이동률은 세 군간에 유의한 차이가 없었으며, 만곡 외측으로의 형성량은 치근단으로부터 8mm 부위에서 anticurvature filing motion, circumferential filing motion, straight up-and-down motion의 순으로 많았으나, 근관의 최대 만곡 부위에서는 차이가 없었다 이상의 결과에서 만곡 근관의 위험 부위에서 ProFile로 근관형성 시 anticurvature filing motion의 영향은 다른 motion과 비교해 볼 때 유의할 만한 차이가 없는 것으로 생각된다.

• 한국자동차공학회논문집
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• 제5권2호
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• pp.197-204
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• 1997

In order to investigate the relationship between the ring gap ratio and oil consumption, the axial motion of piston ring was measured by capacitance technique. The pressures of each land and the motions of each ring were calculated by orifice-volume method in which it is assumed that the ring gaps are the only gas leakage paths. The calculated results were compared with the measured ones. Consequently, it is known that the increase of ring gap ratio has the effect of lifting the first ring. The calculated results were roughly in accordance with those measured. Therefore, it is possible to predict the effect of design variables on the pattern of ring motion. It is known that the lift off of first ring accompanied by the increase of ring gap ratio make rise of oil consumption.