하중 이력에 따른 경량 잔골재 콘크리트의 초음파 특성

유경석,김지상,김익범,Yoo, Kyung-Suk,Kim, Jee-Sang,Kim, Ik-Beam 한국건설순환자원학회 2014 한국건설순환자원학회 논문집 Vol.2 No.3

본 연구는 비파괴 검사 중 하나인 초음파 펄스 속도법(Ultrasonic Pulse Velocity Method)은 시험 물질의 초음파 펄스의 이동시간을 결정하는 것으로, 지금까지 대부분의 연구는 시간 영역에서 표현된 결과만을 이용하여왔다. 그러나 시간 영역에서 초음파 펄스의 신호는 고속 푸리에 변환(FFT)를 통해 주파수 영역으로 변환할 수 있으며, 보다 유용한 정보를 얻을 수 있어, 그 방법을 활용하고자 한다. 이 논문에서는 경량 잔골재를 사용하여 다양한 하중 이력에 대한 콘크리트의 펄스 속도와 주파수 영역 신호의 변화에 대한 비교를 통해, 일반 콘크리트의 강도식의 적용성 여부, 골재 치환율 별 주파수 변화 양상, 최대주파수 분석 등의 연구를 진행하였다. 초음파 속도 측정과 강도 측정을 통해 경량 잔골재 콘크리트에 기존 압축강도식의 적용성 여부를 판단하였지만, 신뢰도 저하로 기존 제안식의 사용은 어렵다는 것을 확인하였고, 하중이력 상태에서 경량 잔골재를 사용한 콘크리트의 초음파 펄스가 주파수 영역에서 보이는 신호가 보통 콘크리트와 비교하여 차이를 보여주지 않았으며, 응력 증가 추세에 따라 초음파 속도와 최대주파수의 상관관계는 존재하나, 초음파 속도와 최대주파수는 상호 독립적인 관계임을 확인하였다. One of the widely used NDT(Non-destructive techniques) is the ultrasonic pulse velocity (USPV) method, which determines the travel time of the ultrasonic pulse through the tested materials and most studies were focused on the results expressed in time domain. However, the signal of ultrasonic pulse in time domain can be transformed into frequency domain, through Fast fourier transform(FFT) to give more useful informations. This paper shows a comparison of changes in the pulse velocity and frequency domain signals of concrete for various load histories using lightweight fine aggregates. The strength prediction equation for normal concrete using USPV cannot be used to estimate lightweight fine aggregate concrete strength. The signals in frequency domain of ultrasonic pulse of lightweight fine aggregate concrete does not show any significant difference comparing with those of normal concrete. The increases in stress levels of concrete change the pulse velocities and maximum frequencies, however the apparent relationship between themselves can not be found in this experiment.

Disciplinary Session 9 / Sport Biomechanics / Development and Method in Sport Biomechanics Study : 가상현실환경 하에서 3차원 실시간 스포츠기술교정의 검증

유경석,김기형,김민기 ( Kyoung Sug Yoo,Ky Hyoung Kim,Min Gi Kim ) 한국체육학회 1998 국제스포츠과학 학술대회 Vol.1998 No.2

바로서기 시 자세안정성에 대한 생체기반 운동명령신호의 탐구

유경석(Yoo, Kyoung-Seok) 한국체육과학회 2020 한국체육과학회지 Vol.29 No.1

This study is to investigate the motor unit’s exercise command signal using kinematic variables in the posture control of the human body. This study is divided into four types of postures (two foot stance, main single-leg stance, secondary single-leg stance, eyes closed main single-leg stance), divided into athlete group and general public group. As a result of performing FFT transformation of EEG signal, the following conclusions were obtained. First, there was a statistically significant difference in time series data (CoP, Torque, EEG) in postural stability between two groups according to the posture style. Second, significant differences were found in the frequency series data by FFT transform in the postural stability between two groups according to the posture style. Third, the brain nervous system and musculoskeletal activation were detected in the vicinity of the frequency band of RM (rambling), which is a bio-signal as a motor unit’s system, and significant differences were found as the difficulty of each posture increased. In particular, significant differences were found in proportion to the difficulty of the posture type in the main frequency and the maximum output values between the two groups. These results suggest that EEG exercise command directly affects posture control. In conclusion, it was found that exercise command signal is involved in intentional postural control of human body as an exercise unit between EEG signal and musculoskeletal signal.

자기치유 시멘트 모르타르의 염화물 침투 저항성 평가

유경석(Kyung Suk Yoo),장승엽(Seung Yup Jang),이용재(Young Jae Lee),최준혁(Jun Hyuck Choi) 한국철도학회 2022 한국철도학회 학술발표대회논문집 Vol.2022 No.10

공작기계 가공공정 중 실시간 모니터링 시스템 연구

유경석(K. S. Yoo),강유수(Y. S. Kang),최인휴(I. H. Choi),김병희(B. H. Kim),이정완(J. W. Lee) 한국생산제조학회 2019 한국생산제조시스템학회 학술발표대회 논문집 Vol.2019 No.11

바로서기 자세유형과 시각정보 유무가 인체 자세균형에 미치는 영향

유경석(Yoo, Kyoung-Seok) 한국사회체육학회 2018 한국사회체육학회지 Vol.0 No.73

The purpose of this study is to investigate the effect of visual information on the postural posture types and the dependence of visual information on the human posture model on AP (anterro-posterior) and ML (mediolateral) motion planes. In addition, the degree of involvement of the visual system and the sensory system due to the spinal cord reflex were determined. Using the SPSS (ver. 22.0) program, ANOVA analyses were performed. The concrete results of this study are as follows. First, when comparing DQT<SUP>OE</SUP> and SQT<SUP>OE</SUP> in both AP and ML directions, among CoM, CoP, and ankle torque kinematic variables, DQT<SUP>OE</SUP> was statistically more stable than SQTOE(p<.01, p<.001) respectively. Second, there was a statistically significant difference between AP and ML planes when CoM of body sway was observed in the AP and ML planes when comparing SQT<SUP>OE</SUP> and SQT<SUP>CE</SUP>. SQT<SUP>CE</SUP> was statistically more stable than SQT<SUP>OE</SUP>(p<.001, p<.001) respectively. Third, SQT<SUP>CE</SUP> whose vision was blocked, showed a force greater than SQT<SUP>OE</SUP> in the posture control of the sole pressure center point CoP. There was statistically significant difference especially in ML direction (p <.001). Fourth, the ankle joint torque was statistically significant (p<.001, p<.001) in both the AP and the ML planes in DQT<SUP>OE</SUP>, SQT<SUP>OE</SUP> and SQT<SUP>CE</SUP> regardless of posture type and visual information types. From the above results, CoM & CoP and the torque of the ankle joint are found to be significant both in visual information and sense of somatosensory sense in the afferent sensation of the reflex reaction of the human body sway during postural control. Also, the role of musculoskeletal muscular strengthening is important for coordination of the postural control. Future research will be needed to explain the development of the scale as a standard for postural balance and stability, and to explain the working principles of the nervous system and musculoskeletal system.

균열 자기치유 효과를 고려한 콘크리트 염화물 침투해석을 활용한 부식 개시시기 예측

유경석(Yoo, Kyung Suk),장승엽(Jang, Seung Yup),김기현(Kim, Ki-Hyun) 한국콘크리트학회 2022 한국콘크리트학회 학술대회 논문집 Vol.34 No.1

청소년기 척추측만이 하지운동의 동적안정성과 역학적 효율에 미치는 영향

유경석(Yoo, Kyoung-Seok) 한국사회체육학회 2017 한국사회체육학회지 Vol.0 No.68

The purpose of this study is to compare the effects of abnormal deformation of the trunk spinal cord curvature on the dynamic stability and mechanical efficiency of the lower limb during walking. First, there was a statistically significant difference in gait velocity between the two groups at the level of p< 0.05. Second, there was a statistically significant difference in the level of p <.001, p <.05 between the two groups in pelvic, hip joint and knee joint of the gait according to deformation of trunk spine curvature. On the other hand, there was no significant difference in ankle joints. Third, there was a statistically significant difference at the level of p< .05, p <.01 and p <.001 in the hip joint, knee joint and ankle joint in joint torque and joint power of the gait according to deformation of trunk spine curvature. Fourth, there was a statistically significant difference at p< .001, p <.05 in the hip joint, the knee joint, and at p< .05 the ankle joint. The scoliosis group was more unstable than the normal group and showed low efficacy. Based on the conclusions of this study, the following suggestions are made. First, the pelvic and lower limb joints are identified as one kinetic chain(exercise unit) and have a major influence on both kinematic and kinematic variables. Second, asymmetry of the trunk causes excessive load force on the lower extremities, which can lead to secondary joint pain such as the hip joints, and shows low efficiency. Third, locomotion exercise participation such as walking and running helps a lot in the function stability of the trunk lumbar curve only in the upright posture of the human body. And it is necessary to use the exercise programs and follow-up studies of vertebral deformity are needed, due to the sitting life such as lack of exercise of growing adolescence and excessive computer work.

인체 척추움직임의 정량적 관측을 위한 운동학적 해석연구

유경석(Yoo, Kyoung-Seok),서승우(Suh, Seung-Woo),최성욱(Choi, Seong-Wook),공세진(Kang, Se-Jin) 한국체육과학회 2013 한국체육과학회지 Vol.22 No.1

The purpose of this study was to compare and investigate the three spine models of three-dimensional kinematic spine motion during trunk movements in free normal gait by developing the spine coordinate system. A retro-reflective motion analysis system was used to measure spine motions, using three kinematic trunk models(Model I : one rigid, spine, Model II: lumbar-thoracic spine, and ModelⅢ: multi-segmental spine). Fifteen middle and high school students(age: 16.6+1.51 yrs, heights: 157±5.96 cm, weights: 45.5±4.88 kg) who have the idiopathic scoliosis were recruited as the subjects. Significant differences were noted m the total trunk motion measured between the three models. First, there was significant difference of the side-bending(p<.05) in sagittal plane during Post-hoc analysis of the ANOVA results for the three spine models. Second, the spinal column level of trunk motions revealed an differences of angular displacement during ROM(rang of motion) in frontal plane, sagittal plane and transverse plane of the multi-segmental model. These findings suggest that use of multi-segmental model provides the most interpretable findings, that is the combined movements and the couple movements allowing for differentiation of translation and rotation of x, y, 2 of three dimension in individual motion patterns.

드롭착지 동작 시 체간모델에 따른 척추분절운동이 자세안정성 해석에 미치는 영향

유경석 ( Kyoung Seok Yoo ) 한국운동역학회 2014 한국운동역학회지 Vol.24 No.4

The purpose of this study was to assess the inter-segmental trunk motion during which multi-segmental movements of the spinal column was designed to interpret the effect of segmentation on the total measured spine motion. Also it analyzed the relative motion at three types of the spine models in drop landing. A secondary goal was to determine the intrinsic algorithmic errors of spine motion and the usefulness of such an approach as a tool to assess spinal motions. College students in the soccer team were selected the ten males with no history of spine symptoms or injuries. Each subject was given a fifteen minute adaptation period of drop landing on the 30cm height box. Inter-segmental spine motion were collected Vicon Motion Capture System (250 Hz) and synchronized with GRF data (1000 Hz). The result shows that Model III has a more increased range of motion (ROM) than Model I and Model II. And the Lagrange energy has significant difference of at E3 and E4 (p<.05). This study can be concluded that there are differences in the three models of algorithm during the phase of load absorption. Especially, Model III shows proper spine motion for the inter-segmental joint motion with the interaction effects using the seven segments. Model III shows more proper observed values about dynamic equilibrium than Model I & Model II. The findings have shown that the dynamic stability strategy of Model III toward multi-directional spinal motion supports for better function of the inter-segmental motor-control than the Model I and Model II.