• 대한의용생체공학회:의공학회지
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• 제29권4호
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• pp.316-322
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• 2008

The purpose of this study was to investigate muscle activation of lower extremity such as rectus femoris, tibialis anterior and soleus according to 0cm(bare foot), 4cm and 7cm heel height of shoe on the rocking surface in older women. 20 older women who did not have any lower musculoskeletal and neurological disorders in the past were participated in this study. Each subject was standing for 15 seconds on the level 8 of Biodex Stability System (BSS) while wearing 4cm and 7cm heel height shoes including bare foot. Electromyography was used to measure muscle activation of lower extremity, and the muscle activation was expressed as a percentage of maximal voluntary isometric contraction (% MVIC). We measured % MVIC of three muscles during 5 seconds except for the first 5 seconds and last 5 seconds. SPSS 12.0 program was used for this study. Repeated one-way analysis of variance(ANOVA) was performed to compare the significant difference among the muscles of lower extremities according to heel heights of shoe on the rocking plate. % MVIC of each muscle such as rectus femoris, tibialis anterior and soleus regarding heel heights of shoe had statistically significant differences (p<0.05). The results of contrast test were as follows; 1) % MVIC of rectus femoris had significant differences between barefoot and 4cm, and barefoot and 7cm. 2) % MVIC of tibialis anterior had significant differences between barefoot and 4cm, barefoot and 7cm, and 4cm and 7cm. 3) % MVIC of soleus had significant differences between barefoot and 7cm, 4cm and 7cm. The results indicate that all commonly responsive muscle on the conditions of barefoot, 4cm, and 7cm shoe height on the rcoking surface is tibialis anterior muscle. We found out that the more heels of shoe high, the more muscle activation increases. High-heeled shoes above 7cm remarkably increase the muscle activation of lower extremity and may result in muscle fatigue. Thus, these shoes may summate risk factors of falls in older women. We can acknowledge that the heels above 4 cm affect each muscle activation in lower extremity on the rocking surface.

• 한국세라믹학회지
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• 제40권4호
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• pp.393-397
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• 2003

To investigate the effect of AIN c-axis orientation on the resonance performance of film bulk acoustic wave resonators, solidly mounted resonators with crybtallographically different AIN piezoelectric films were prepared by changing only the bottom electrode surface conditions. As increasing the degree of c-axis texturing, the effective electromechanical coupling coefficient ($\kappa$$\_$eff/)$^2$ in resonators increased gradually. The least 4 degree of full width at half maximum in an AIN(002) rocking curve, which corresponds to $\kappa$$^2$$\_$eff/ of above 5%, was measured to be necessary for band pass filter applications in wireless communication system. The longitudinal acoustic wave velocity of AIN films varied with the degree of c-axis texturing. The velocity of highly c-axis textured AIN film was extracted to be about 10200 n/s by mathematical analysis using Matlab.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2010년도 추계 학술발표회
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• pp.201-204
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• 2010

Earthquake load to design a structure has been calculated from a fixed base SDOF model using amplified surface accelerations along soft soil layers. But the method dose not consider a soil-structure interaction. Centrifugal experiments that were consisted of soil, a shallow foundation and a structure were performed to find the effects of soil-structure interaction. The experiments showed that mass and stiffness of the foundation affected a response of the structure and nonlinear behavior of soil near the foundation. And a rocking displacement caused by overturning moment affected the response and increases a damping effect. In this study, the centrifugal experiment was simulated as a two dimensional finite element model. The finite element model was used for nonlinear time domain analysis of the OpenSees program. The numerical model accurately evaluated the behaviors of soil and the foundation, but the rocking effect and the behavior of structure were not described.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2008년도 추계 학술발표회 제20권2호
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• pp.193-196
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• 2008

본 연구에서는 비보강 조적조 건물의 전단강도와 연성능력을 향상시킬 수 있는 철물을 사용하여 보강된 조적벽체의 성능향상 검증을 위한 실험의 기초자료를 제시 하고자 한다. 실험에 사용될 철물은 얇은 육각 기둥들이 패턴형태를 이룬 벌집 모양의 하니컴 스틸재로 세라켐(주)이 일반 구조용 압연강 재인 SS400으로 제작한 것으로서 선행 실험으로 부터 철근콘크리트 보의 전단 강도 및 강성 증가에 효과가 있음이 나타났다. 국내의 경우 비보강 조적조 건물에 대한 내진규정이 마련되어 있지 않기 때문에 미국 내진 보강 지침서인 FEMA 207 및 306 에서 제안하는 4가지 파괴모드(수평줄눈의 전단파괴, Rocking 파괴, 사인장 파괴, Toe 파괴)와 강도식을 사용하여 그 중 사인장 파괴를 제외한 3가지 파괴모드를 형상비를 변수로 유도하여 보강되지 않은 벽체와 1면 및 2면 보강된 벽체를 계획하였고 보강효과를 예측하였다. 강도식으로 부터 보강철물의 효과는 Rocking 및 Toe 파괴에서는 단부 구속력의 증가, 전단 파괴에서는 수평줄눈의 전단강도 증가가 예상되며 각각의 경우 연성증가도 예상된다

• Structural Engineering and Mechanics
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• 제40권6호
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• pp.763-782
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• 2011

Results from nonlinear time-history analyses of wall-frame structural models indicate that the condition of vulnerable foundations -for which uplifting and reaching the bearing capacity of the supporting soil can occur before yielding at the base of the shear walls- may not be necessarily detrimental to the drift response of buildings under strong ground motions. Analyses also show that a soil-foundation system can inherently have deformation capacity well in excess of the demand and thus act as a source of energy dissipation that protects the structural integrity of the shear walls.

• 한국지진공학회:학술대회논문집
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• 한국지진공학회 2000년도 추계 학술발표회 논문집 Proceedings of EESK Conference-Fall 2000
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• pp.448-454
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• 2000

Piled multi-block system has been frequently adopted in the historic structures or monuments of cultural heritage. It is well known that such a structural system is very vulnerable to the earthquake shaking. If the structure is of slender type, then it may experience overturning at very low level intensity of ground shaking. One of the methods used to protect such structures from earthquake is seismic isolation system. But the behavior of multi-block systems mounted on the isolated basis is not well understood yet. In this paper we investigate the dynamic behavior of single slender rigid block mounted on the three different isolation systems, i.e., P-F system, FPS and LRB system. Sliding at the isolation interface of P-F system and FPS is formulated based on Coulomb friction. The mounted single block is assumed undergoing rocking or sticking only. Impacting of a single block is described using distinct element method (DEM). Free vibrations due to a prescribed initial conditions are studied. Responses to the harmonic excitation and earthquake motions are calculated

• 대한기계학회논문집A
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• 제33권11호
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• pp.1288-1293
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• 2009

This paper discusses about modeling method to simulate a nonlinear behavior like sliding or rocking of two stacked body system under earthquake condition. A double body system design can be an option to reduce seismic response of a component in comparison to a single body system for free standing structures. Therefore, according to the priority of components, the structure is to be designed by proper ratio of partition in their height for improvement of seismic capability and structural integrity. Nonlinear modeling and analysis using simple rigid body and dynamic system has been performed to check the trend in such cases. As a result, one of the two bodies can be chosen to reduce the seismic response from energy absorption of the other one by appropriate application of friction ratios not only in slip-slip condition but in slip-rock condition.

• 한국결정성장학회지
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• 제30권1호
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• pp.1-6
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• 2020

본 연구에서는 패턴화된 사파이어 기판 위에 HVPE(Hydride Vapor Phase Epitaxy System) 법에 의해 50 nm 두께의 AlN thin film을 증착한 뒤, 에피층 구조가 MO CVD에서 성장되었다. AlN 버퍼층 박막의 표면형상이 SEM, AFM에 의해서, 에피층 구조의 GaN 박막의 결정성은 X-선 rocking curve에 의해 분석되었다. 패턴화된 사파이어 기판 위에 증착된 GaN 박막은, 사파이어 기판 위에 증착된 GaN 박막의 경우보다 XRD 피크 세기가 다소 높은 결과를 나타냈다. AFM 표면 형상에서 사파이어 기판 위에 AlN 박막이 증착된 경우, GaN 에피층 박막의 p-side 쪽의 v-pit 밀도가 상대적으로 낮았으며, 결함밀도가 낮게 관찰되었다. 또한, AlN 버퍼층이 증착된 에피층 구조는 AlN 박막이 없는 에피층의 광출력에 비해 높은 값을 나타냈다.

• Geomechanics and Engineering
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• 제4권3호
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• pp.173-190
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• 2012

With recent growing interests in the Performance-Based Seismic Design and Assessment Methodology, more realistic modeling of a structural system is deemed essential in analyzing, designing, and evaluating both newly constructed and existing buildings under seismic events. Consequently, a shallow foundation element becomes an essential constituent in the implementation of this seismic design and assessment methodology. In this paper, a contact interface fiber section element is presented for use in modeling soil-shallow foundation systems. The assumption of a rigid footing on a Winkler-based soil rests simply on the Euler-Bernoulli's hypothesis on sectional kinematics. Fiber section discretization is employed to represent the contact interface sectional response. The hyperbolic function provides an adequate means of representing the stress-deformation behavior of each soil fiber. The element is simple but efficient in representing salient features of the soil-shallow foundation system (sliding, settling, and rocking). Two experimental results from centrifuge-scale and full-scale cyclic loading tests on shallow foundations are used to illustrate the model characteristics and verify the accuracy of the model. Based on this comprehensive model validation, it is observed that the model performs quite satisfactorily. It resembles reasonably well the experimental results in terms of moment, shear, settlement, and rotation demands. The hysteretic behavior of moment-rotation responses and the rotation-settlement feature are also captured well by the model.

• 제어로봇시스템학회논문지
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• 제9권6호
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• pp.448-455
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• 2003

A system design technique of automatic thickness measurement and defect inspection system, which measures the thickness of the ALC(Autoclaved Lightweight Concrete) block and inspects the defect on a realtime basis is proposed. The image processing system was established with a CCD camera, an image grabber, and a personal computer without using assembled measurement equipment. The image obtained by this system was analyzed by a devised algorithm, specially designed for the enhanced measurement accuracy. For the realization of the proposed algorithm, the preprocessing method that can be applied to overcome uneven lighting environment, an enhanced edge decision method using 8 edge-pairs with irregular and rough surface, the unit length decision method in uneven condition with rocking objects, and the curvature calibration method of camera using a constructed grid are developed. The experimental results, show that the required measurement accuracy specification is sufficiently satisfied using our proposed method.