• 한국가시화정보학회지
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• 제3권1호
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• pp.71-77
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• 2005

Information on temporal evolution of whole velocity fields are essential for physical understanding of a complicated turbulent flow. Due to advances of high-speed imaging technique, laser and electronics, high-speed digital cameras and high-repetition pulse lasers are commercially available in nowadays. A dynamic PIV system that can measure consecutive instantaneous velocity field with 1K$\times$ 1K pixels resolution at 1 fps was developed. It consists of a high-speed CMOS camera and a high-repetition Nd:YLF pulse laser. Theoretically, it can capture velocity fields at 20 fps with a reduced spatial resolution. In order to validate its performance, the dynamic PIV system was applied to a turbulent jet of which Reynolds number is about 3000. The particle images of 1024$\times$512 pixels were captured at a sampling rate of 4 KHz. The dynamic PIV system measured successfully the temporal evolution of instantaneous velocity fields of the turbulent jet, from which spectral analysis of turbulent structure was also feasible.

• 한국운동역학회지
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• 제34권1호
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• pp.1-8
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• 2024

Objective: The aim of this study was to identify the biomechanical determination factor for improving club head speed during the driver swing in male golf players. Method: Twenty-seven golf players were participated in this study. Eight motion capture cameras (250 Hz) and two force plates (2,000 Hz) were used to collect peak angular velocity and ground reaction force data. It was performed stepwise multiple linear regression analysis and alpha set at .05. Results: The peak plantar flexion angular velocity of the left ankle joint and the peak adduction angular velocity of the right shoulder joint were statistically significant. The peak plantar flexion angular velocity of the left ankle joint and the peak adduction angular velocity of the right shoulder during downswing. Conclusion: It is suggested that applying body conditioning training aimed at improving related body functions to increase maximum plantar flexion angular velocity in the left ankle joint will be effective in improving club head speed.

• 대한물리치료과학회지
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• 제15권3호
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• pp.65-72
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• 2008

Background : The purpose of present study was to investigate the effect of quadriceps femoris taping in normal gait using 3D motion capture technique. Method : Twenty healthy volunteers, have no musculoskeletal problems, were recruited as subjects for this study. In experimental group, 20 healthy young(males 10 and females 10) were included. The subjects were assessed during two conditions: control tape(no muscle stretched) and quadriceps (muscle stretched)taping application. To obtain the dynamic data, we captured the motion of subject attached markers without taping during repeated gaits five times or more in 7 m Capture volume of gait analysis center. The result was obtained as a mean value in three times. After taping on quadriceps femoris, the same procedure was carried out. Statistical analysis were performed using statistical software packagess SPSS WIN 12.0(SPSS, Chicago, IL, USA). Differences were tested for statistical significance using paired t-test, independent t-test, chi-squared test for comparisons between the muscle stretched and no muscle stretched. Results : The date of 20 subjects who carried out the whole experimental course were statistically analyzed. 1. gait velocity was showed that muscle stretched group had more significantly increased than no muscle stretched group(p<.05). 2. step length was showed that muscle stretched group had more significantly increased than no muscle stretched group(p<.05). 3. cadens was showed that muscle stretched group had more significantly increased than no muscle stretched group(p<.05). Conclusion : kinesio taping on quadriceps femoris promoted cadence, gait velocity, step length in normal subject (muscle stretched) group.

• 한국산학기술학회논문지
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• 제14권2호
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• pp.962-969
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• 2013

본 연구에서는 전산유체역학(CFD)를 이용하여 흄후드(fume hood)의 기류 유입특성 및 유속 분포를 평가하였다. 또한, 후드 개구면을 균일류 형성에 필요한 구조로 개선하였을 경우의 유동 특성을 예측하여 개선 효과를 검증하였다. 기존의 흄후드의 제어유속을 평가한 결과, 제곱평균(RMS)값과 비교했을 때 최대 23~30%의 편차가 있음을 확인하였다. 또한, 후드의 상부 유속이 하부 유속보다 58~68% 정도 빠른 것으로 나타나 후드 개구면에서의 유속 불균형이 매우 심한 것으로 평가되었다. 이에 후드 개구면에서의 균일한 배기흐름을 유지하기 위해 후드를 개선(안쪽벽에 배플 설치 및 슬롯 타입의 개구부 설계)한 결과, RMS값 대비 최대 7%의 편차를 보였으며 구간별 유속 편차는 최대 12% 정도로 예측되어 기존 구조에 비해 제어유속의 불균형이 많이 해소되는 것을 확인할 수 있었다.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2005년도 ICCAS
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• pp.2126-2131
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• 2005

Interactions of a humanoid with a human are important, when the humanoid is requested to provide people with human-friendly services in unknown or uncertain environment. Such interactions may require more complicated and human-like behaviors from the humanoid. In this work the arm motions of a human are discussed as the early stage of human motion imitation by a humanoid. A motion capture system is used to obtain human-friendly arm motions as references. However the captured motions may not be applied directly to the humanoid, since the differences in geometric or dynamics aspects as length, mass, degrees of freedom, and kinematics and dynamics capabilities exist between the humanoid and the human. To overcome this difficulty a method to adapt captured motions to a humanoid is developed. The geometric difference in the arm length is resolved by scaling the arm length of the humanoid with a constant. Using the scaled geometry of the humanoid the imitation of actor's arm motions is achieved by solving an inverse kinematics problem formulated using optimization. The errors between the captured trajectories of actor arms and the approximated trajectories of humanoid arms are minimized. Such dynamics capabilities of the joint motors as limits of joint position, velocity and acceleration are also imposed on the optimization problem. Two motions of one hand waiving and performing a statement in sign language are imitated by a humanoid through dynamics simulation.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2005년도 ICCAS
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• pp.1624-1627
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• 2005

We proposed a design technique for auto-landing guidance and control system. This technique utilizes linear controller and neural network. Main features of this technique is to use conventional linear controller and compensate for the error coming from the model uncertainties and/or reference model mismatch. In this study, the multi-perceptron neural network with single hidden layer is adopted to compensate for the errors. Glide-slope capture logic for auto-landing guidance and control system is designed in this technique. From the simulation results, it is observed that the responses of velocity and pitch angle to commands are fairly good, which are directly related to control inputs of throttle and elevator, respectively.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2002년도 춘계학술대회논문집
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• pp.489-494
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• 2002

This paper presents hydraulic model which can capture the hysteric damping force behavior of ER damper. A flow mode rue ER damper is manufactured, and its field-dependent damping forces are measured. Newly proposed hydraulic model which derived from physical hydro-mechanical parameters of ER damper are conventional Bingham model are investigated to represent the field-dependent damping force characteristics of ER damper. After principal parameters of two models are estimated from the measured damping forces data, the force vs velocity hysteresis cycles are then reconstructed. The results show that the proposed hydraulic model can capture the hysteresis behavior of ER damper accurately.

• 한국분무공학회지
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• 제17권2호
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• pp.86-93
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• 2012

The effects of projectile impact system on the transient spray characteristic which is supersonic liquid tip velocity were studied by experimentally. Supersonic liquid jets were generated by impact of a high speed projectile driven by a Two-stage light gas gun. A high speed camera and schlieren optical system were used to capture the spray structures of the supersonic liquid jets. In a case of nozzle assembly Type-A, expansion gases accelerate a projectile which has a mass of 6 grams from 250 m/s at the exit of the launch tube. Accelerated projectile collides with the liquid storage part, then supersonic liquid jets are injected with instantaneous spray tip velocity from 617.78 m/s to 982.54 m/s with various nozzle L/d. However, In a case of nozzle assembly Type-B which has a heavier projectile (60 grams) and lower impact velocity (182 m/s), an impact pressure was decreased. Thus the liquid jet injected at 210 m/s of the maximum velocity did not penetrate a shock wave and fast break-up was occurred. Pulsed injection of liquid column generated second shock wave and multiple shock wave.

• Structural Engineering and Mechanics
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• 제40권5호
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• pp.595-616
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• 2011

Impact experiments have been carried out on concrete slabs. The first group was traditionally manufactured, densely reinforced concrete targets, and the next were ordinary Portland and calcium aluminate cement based HPSFRC (High performance steel fiber reinforced concrete) and SIFCON (Slurry infiltrated concrete) targets. All specimens were hit by anti-armor tungsten projectiles at a muzzle velocity of over 4 Mach causing destructive perforation. In Part I of this article, production and experimental procedures are described. The first group of specimens were ordinary CEM I 42.5 R cement based targets including only dense reinforcement. In the second and third groups, specimens were produced using CEM I 42.5 R cement and Calcium Aluminate Cement (CAC40) with ordinary reinforcement and steel fibers 2 percent in volume. In the fourth group, SIFCON specimens including 12 percent of steel fibers without reinforcement were tested. A high-speed camera was used to capture impact and residual velocities of the projectile. Sample tests were performed to obtain mechanical properties of the materials. In the companion Part II of this study, numerical investigations and simulations performed will be presented. Few studies exist that examine high-velocity impact effects on CAC40 based HPSFRC targets, so this investigation gives an insight for comparison of their behavior with Portland cement based and SIFCON specimens.

• 한국수소및신에너지학회논문집
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• 제22권4호
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• pp.465-473
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• 2011

To find the optimum mixing ratio of WGS catalyst with $CO_2$ absorbent for SEWGS process, water gas shift reaction tests were carried out in a fluidized bed reactor using commercial WGS catalyst and sand (as a substitute for $CO_2$ absorbent). WGS catalyst content, gas velocity, and steam/CO ratio were considered as experimental variables. CO conversion increased as the catalyst content increased during water gas shift reaction. Variations of the CO conversion with the catalyst content were small at low gas velocity. However, those variations increased at higher gas velocity. Within experimental range of this study, the optimum operating condition(steam/CO ratio=3, gas velocity = 0.03 m/s, catalyst content=10 wt.%) to get high CO conversion and $CO_2$ capture efficiency was confirmed. Moreover, long time water gas shift reaction tests up to 20 hours were carried out for two cases (catalyst content = 10 and 20 wt.%) and we could conclude that the WGS reactivity at those conditions was maintained up to 20 hours.