• 한국지진공학회:학술대회논문집
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• 한국지진공학회 1998년도 춘계 학술발표회 논문집 Proceedings of EESK Conference-Spring 1998
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• pp.75-80
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• 1998

Dynamic measurements are used rather sparingly to determine the elastic moduli of rock cores and modulus values are not much utilized in design practices. The reason seems to result from the general perception that values obtained by dynamic measurement are much higher (about 10 time) than those determined statically. This paper presents results from dynamic and static tests on rock cores. One of the findings is that both moduli determined by statically and dynamically on a solid rock core agrees well at the same-strain. At different strain levels, the ratio between dynamic and static modult widely varies depending upon micro-cracks and discontinuites of rock cores.

• Smart Structures and Systems
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• 제26권5호
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• pp.667-680
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• 2020

This study aims at reporting a systematic procedure for evaluating the static and dynamic structural performance of steel bridges based on a short-period structural health monitoring measurement. Sungsu bridge located in Korea is considered as a case study presenting the most recent tests carried out to examine the bridge condition. Short-period measurements of Structural Health Monitoring (SHM) system were used during the bridge testing phase. A novel symmetry index is introduced using statistical analyses of deflection and strain measurements. Frequency Domain Decomposition (FDD) is implemented to the strain measurements to estimate the bridge mode shapes and damping ratios. Furthermore, Markov Chain Monte Carlo (MCMC) is also implemented to examine the reliability of bridge performance while ambient design trucks are in static or moving at different speeds. Strain, displacement and acceleration were measured at selected locations on the bridge. The results show that the symmetry index can be an efficient and useful measure in assessing the steel bridge performance. The results from the used method reveal that the performance of the Sungsu bridge is safe under operational conditions.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 1999년도 춘계학술대회논문집
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• pp.241-244
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• 1999

A series of parametric study was performed for the investigation of the influence of several analysis parameters to the solution behavior in the elasti-plastic-static analysis of sheet metal forming. The parameters taken into the consideration in the present study are finite element mesh distribution and numerical integration scheme, The elstic-plastic-static analysis was performed for two cases : deflection by a point force bending by a punch Results obtained with different selections of the parameters were compared with each other experimental measurements and analytical solutions.

• Structural Engineering and Mechanics
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• 제4권1호
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• pp.1-8
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• 1996

A new error measure for a static finite element analysis is proposed. This error measure is a modification to the Zienkiewicz and Zhu energy norm. The new error estimator is a global error measure for the analysis and is independent of finite element model size and internal stresses, hence it is readily transportable to other error calculations. It is shown in this paper the the new error estimator also produces conservative error measurements, making it a suitable procedure to adopt in commerical packages.

• Physical Therapy Rehabilitation Science
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• 제11권3호
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• pp.311-320
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• 2022

Objective: To investigate the reliability and validity of static balance measurements using an acceleration sensor and a gyroscope sensor in smart phone inertial sensors. Design: Equivalent control group pretest-posttest. Methods: Subjects were forty five healthy adults aged twenty to fifty-years-old who had no disease that could affect the experiment. After pre-test, all participants wore a waist band with smart phone, and conducted six static balance measurements on the force plate twice for 35 seconds each. To investigate the test-retest reliability of both smart phone inertial sensors, we compared the intra-correlation coefficient (ICC 3, 1) between primary and secondary measurements with the calculated root mean scale-total data. To determine the validity of the two sensors, it was measured simultaneously with force plate, and the comparision was done by Pearson's correlation. Results: The test-retest reliability showed excellent correlation for acceleration sensor, and it also showed excellent to good correlation for gyroscope sensor(p<0.05). The concurrent validity of smartphone inertial sensors showed a mostly poor to fair correlation for tandem-stance and one-leg-stance (p<0.05) and unacceptable correlation for the other postures (p>0.05). The gyroscope sensor showed a fair correlation for most of the RMS-Total data, and the other data also showed poor to fair correlation (p<0.05). Conclusions: The result indicates that both acceleration sensor and gyroscope sensor has good reliability, and that compared to force plate, acceleration sensor has unacceptable or poor correlation, and gyroscope sensor has mostly fair correlation.

• 대한물리의학회지
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• 제5권4호
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• pp.517-525
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• 2010

Purpose : This study aimed to compare the effect of two conditions (visual and kinesthetic) of motor imagery training on static and dynamic balance. Methods : Fifteen patients with post-stroke hemiparesis volunteered to participate in this study. Two motor imagery training conditions, for 10minute trials, employed with audiotape instructions. Measurements were performed at pretest, posttest and 1-hour follow up in both static and dynamic balance. Results : Measures were significantly different both static and dynamic balance tests between treatment conditions (kinesthetic imagery more than visual imagery) at the pretest, post test, and 1-hour follow-up (p<.05). Measures of both static and dynamic balance tests, for both conditions, improved significantly from pretest to posttest (p<.05), and was maintained at 1-hour follow up. Conclusion : This study showed that both imagery training applications were effective treatment strategies for both static and dynamic balance. When comparing the two treatment conditions, kinesthetic motor imagery training was more effective than the visual motor imagery training in static and dynamic balance.

• 한국구조물진단유지관리공학회 논문집
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• 제20권3호
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• pp.10-17
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• 2016

본 연구는 단경간 교량의 정적하중입력/변위출력관계를 이용한 새로운 교량 유한요소모델 개선 방법을 제안하였고, 실내 모형교량 실험을 통해 검증하였다. 기존의 유한요소모델개선기법은 실험으로부터 얻어진 모드계수와 유한요소모델로부터 예측된 모드계수가 유사해지도록 유한요소모델을 개선하는데, 이 과정에서 구조계의 질량행렬에 대한 가정을 필요로 한다. 제안된 기법은 질량행렬을 가정하지 않고, 오히려 질량행렬 추정을 가능하게 하는 장점을 가진다. 제안된 기법은 두 단계로 구성된다. 첫째, 정적 하중입력-변위응답으로부터 강성행렬을 개선하고, 둘째, 실측된 고유진동수를 이용하여 질량행렬을 개선한다. 실험검증을 위하여 실내 모형교량을 제작하였고, 제안된 기법을 이용하여 모형교량의 탄성계수를 추정하였으며, Universal Testing Machine으로 부터 얻어진 탄성계수와 비교하였다. 또한 기존의 유한요소모델개선기법으로 추정된 탄성계수와 비교하였다. 실험의 결과들로부터 제안된 기법이 합리적으로 탄성계수와 질량밀도를 추정하는 것이 관찰되었고, 기존의 유한요소모델개선기법은 고차모드를 사용했을 때 상대적으로 큰 오차를 주는 것이 관찰되었다. 추가적으로 유한요소모델링 오차에 대하여 토의하였다.

• 한국지진공학회:학술대회논문집
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• 한국지진공학회 1998년도 추계 학술발표회 논문집 Proceedings of EESK Conference-Spring 1998
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• pp.353-360
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• 1998

Dynamic measurements are used rather sparingly to determine the elastic moduli of rock cores and modulus values are not much utilized in design practice. The reason seems to result from the general perception that values obtained by dynamic measurement are much higher (about 10 times) than those determined statically. This paper presents results from dynamic and static tests on rock cores. The findings are : 1) elastic moduli can be consistently determined by laboratory seismic testing. 2) nonlear deformation characteristic of rock cores was tentatively proposed with variation in elastic modulus with strain.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2005년도 추계학술대회 논문집
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• pp.418-423
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• 2005

In designing underground structure such as tunnels, estimating geotechnical characteristics of the ground is one of the most important and difficult tasks. In this paper, a methodology that can identify geotechnical parameters using only field-measured relative convergence displacements is presented. By using only relative convergence measurement data, inevitable errors in absolute convergence estimation can be avoided and in turn the parameter estimation process can be simplified. The methodology utilizes sensitivity relationship between static displacement measurements and geotechnical parameters. The feasibility and applicability of the proposed methodology is verified via a 3-d numerical example of a tunnel structure.

• 한국산학기술학회논문지
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• 제17권6호
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• pp.233-238
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• 2016

본 연구는 스마트폰의 가속도 센서를 이용하여 정적균형능력을 측정하는데 있어 신뢰도를 알아보고자 실시하였다. 본 연구의 연구대상자는 최근 3개월 이내에 골절, 수술, 염증성 관절염이 없고 정기적인 운동을 시작하지 않은 Y대학교의 학생 30명을 대상으로 하였다. 본 연구에 사용된 스마트폰은 갤럭시S5LTE (SM-G900F, Samsung, Korea, 2014)였고 어플리케이션은 Sensor Kinetics pro (Ver.2.1.2, INNOVENTIONS Inc, US, 2015)를 사용하였다. 정적균형능력은 1회당 3번씩 측정하였으며 하루 간격으로 검사-재검사로 시행되었다. 1차 측정과 2차 측정은 동일하게 진행되었다. 본 연구의 분석은 Wilcoxon 부호순위검정, 급내상관계수(ICC(2,1))를 사용하였다. 본 연구의 연구결과는 다음과 같았다. 눈을 뜬 상태에서 1차 측정과 2차 측정 간에 유의한 차이가 없었고(p>0.05) 강한 양의 상관관계를 보였으며(r>0.75, p<0.05) 매우 높은 일치도(ICC>0.80)를 보였다. 눈을 감은 상태에서 1차 측정과 2차 측정 간에 유의한 차이가 없었고(p>0.05) 강한 양의 상관관계를 보였으며(r>0.75, p<0.05) 매우 높은 일치도(ICC>0.80)를 보였다. 본 연구를 통해 스마트폰은 정적균형능력 측정에 있어 가능성이 있다는 사실을 알 수 있었으며 본 연구가 향후 균형능력측정 전용 어플리케이션 개발에 기초자료가 되기를 기대해본다.