• Title/Summary/Keyword: Mechanical Motion Capture

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Microparticle Impact Motion with Adhesion and Frictional Forces (부착력과 마찰력이 개재된 마이크로 입자 충돌 운동)

  • Han, In-Hwan
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.26 no.8
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    • pp.1698-1708
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    • 2002
  • The main topic covered in this paper is that of the impact process, that is, where two bodies come into contact and rebound or stick together. This paper presents how to determine the rebound velocities of a microparticle that approaches a surface with arbitrary initial velocities and relate the impact process to the physical properties of the materials and to the adhesion force. Actual adhesion forces demonstrate a significant amount of energy dissipation in the form of hysteresis, and act generally in a normal to the contact surfaces. Microparticles must also contend with forces tangent to the contact surfaces, namely Coulomb dry friction. The developed model has an algebraic form based on the principle of impulse and momentum and hypothesis of energy dissipation. Finally, several analyses are carried out in order to estimate impact parameters and the developed analytical model is validated using experimental results.

Detection and Quantification of Screw-Home Movement Using Nine-Axis Inertial Sensors

  • Jeon, Jeong Woo;Lee, Dong Yeop;Yu, Jae Ho;Kim, Jin Seop;Hong, Jiheon
    • The Journal of Korean Physical Therapy
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    • v.31 no.6
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    • pp.333-338
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    • 2019
  • Purpose: Although previous studies on the screw-home movement (SHM) for autopsy specimen and walking of living persons conducted, the possibility of acquiring SHM based on inertial measurement units received little attention. This study aimed to investigate the possibility of measuring SHM for the non-weighted bearing using a micro-electro-mechanical system-based wearable motion capture system (MEMSS). Methods: MEMSS and camera-based motion analysis systems were used to obtain kinematic data of the knee joint. The knee joint moved from the flexion position to a fully extended position and then back to the start point. The coefficient of multiple correlation and the difference in the range of motion were used to assess the waveform similarity in the movement measured by two measurement systems. Results: The waveform similarity in the sagittal plane was excellent and the in the transverse plane was good. Significant differences were found in the sagittal plane between the two systems (p<0.05). However, there was no significant difference in the transverse plane between the two systems (p>0.05). Conclusion: The SHM during the passive motion without muscle contraction in the non-weighted bearing appeared in the entire range. We thought that the MEMSS could be easily applied to the acquisition of biomechanical data on the knee related to physical therapy.

Reproduction of Walking Asymmetry in Knee Osteoarthritis with Split-Belt Conditions (분할 벨트 조건을 이용한 무릎 관절 이상군의 보행 비대칭성 모사)

  • Lee, Myunghyun;Park, Heewon;Park, Sukyung
    • Journal of the Korean Society for Precision Engineering
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    • v.32 no.10
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    • pp.885-890
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    • 2015
  • Walking on split-belt treadmill has been applied to study walking disabilities, such as osteoarthritis (OA), to show asymmetric walking characteristics. In this study, we compared asymmetric walking in OA patients with healthy subjects under split-belt conditions and examined the reproduction of walking asymmetry in OA. Seven OA patients were instructed to walk at four frequencies, while four healthy subjects walked on a treadmill with tied-belt and split-belt conditions. To compare walking asymmetries, kinetic and kinematic measurements were made using force-plates and motion capture cameras, and subsequently center of mass (CoM) velocity, mechanical work and potential energy were calculated. Horizontal velocity change during split-belt walking of healthy subjects was similar to OA patients. Difference of mechanical work during single support phase occurred due to fall of CoM in fast belt. OA walking asymmetry could be reproduced by reducing differences of belt speeds to prevent rapid fall of CoM.

Size-dependent forced vibration response of embedded micro cylindrical shells reinforced with agglomerated CNTs using strain gradient theory

  • Tohidi, H.;Hosseini-Hashemi, S.H.;Maghsoudpour, A.
    • Smart Structures and Systems
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    • v.22 no.5
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    • pp.527-546
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    • 2018
  • This article presents an analysis into the nonlinear forced vibration of a micro cylindrical shell reinforced by carbon nanotubes (CNTs) with considering agglomeration effects. The structure is subjected to magnetic field and transverse harmonic mechanical load. Mindlin theory is employed to model the structure and the strain gradient theory (SGT) is also used to capture the size effect. Mori-Tanaka approach is used to estimate the equivalent material properties of the nanocomposite cylindrical shell and consider the CNTs agglomeration effect. The motion equations are derived using Hamilton's principle and the differential quadrature method (DQM) is employed to solve them for obtaining nonlinear frequency response of the cylindrical shells. The effect of different parameters including magnetic field, CNTs volume percent and agglomeration effect, boundary conditions, size effect and length to thickness ratio on the nonlinear forced vibrational characteristic of the of the system is studied. Numerical results indicate that by enhancing the CNTs volume percent, the amplitude of system decreases while considering the CNTs agglomeration effect has an inverse effect.

The Development of Interactive Ski-Simulation Motion Recognition System by Physics-Based Analysis (물리 모델 분석을 통한 상호 작용형 스키시뮬레이터 동작인식 시스템 개발)

  • Jin, Moon-Sub;Choi, Chun-Ho;Chung, Kyung-Ryul
    • Transactions of the KSME C: Technology and Education
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    • v.1 no.2
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    • pp.205-210
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    • 2013
  • In this research, we have developed a ski-simulation system based on a physics-based simulation model using Newton's second law of motion. Key parameters of the model, which estimates skier's trajectory, speed and acceleration change due to skier's control on ski plate and posture changes, were derived from a field test study performed on real ski slope. Skier's posture and motion were measured by motion capture system composed of 13 high speed IR camera, and skier's control and pressure distribution on ski plate were measured by acceleration and pressure sensors attached on ski plate and ski boots. Developed ski-simulation model analyzes user's full body and center of mass using a depth camera(Microsoft Kinect) device in real time and provides feedback about force, velocity and acceleration for user. As a result, through the development of interactive ski-simulation motion recognition system, we accumulated experience and skills based on physics models for development of sports simulator.

CAVITATION ANALYSIS IN A CENTRIFUGAL PUMP USING VOF METHOD (VOF기법을 이용한 원심펌프 내의 공동현상에 관한 유동해석)

  • Lee, W.J.;Lee, J.H.;Hur, N.;Yoon, I.S.
    • Journal of computational fluids engineering
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    • v.20 no.4
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    • pp.1-6
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    • 2015
  • Centrifugal pumps consume considerable amount of energy in various industrial applications. Therefore, improvement of the efficiency of these machines has become a major challenge. Cavitation is a phenomenon which decreases the pump efficiency and even causes structural demage. Hence, the goal of this paper is to investigate the cavitation problem in the single-stage and double-stage centrifugal pumps. The Volume of Fraction (VOF) method has been used for the numerical simulations together with Rayliegh-Plesset model for the gas-liquid two-phase flow inside the pump. In order to capture the turbulent phenomena, the standard k-${\varepsilon}$ turbulence model has been adopted, and the simulations have been done as unsteady cases. In addition, the motion of the rotating parts has been simulated using Multi Reference Frame(MRF) method. The results are presented and compared in terms of hydraulic head and NPSH for both the single-stage and double-stage pumps. The H-Q curves show the effects of cavitation on decreasing the pumps performances.

Alteration of Gait Characteristics in Hemiplegic Elderly during Straight and Revolution Gaits (직선 및 회전 보행 시 편마비에 따른 고령자의 보행 특성 변화)

  • Jung, HoHyun;Lee, BumKee;Chun, Kyeong Jin;Lim, Dohyung
    • Journal of Biomedical Engineering Research
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    • v.35 no.2
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    • pp.26-34
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    • 2014
  • Little information is available about the characteristics in revolution gait of hemiplegic elderly, which is frequently represented in daily life. It is also hard to elucidate purely the characteristics due to hemiplegia because of no consideration of aging factors. The aim of study is to identify the alteration characteristics of lower extremity joint angles in both straight and revolution gaits together due to hemiplegia through comparing healthy with hemiplegic elderly. Following Institutional Review Board approval, twelve healthy and hemiplegic elderly were participated and the center of body mass (COM) and lower extremity joint angles were measured during straight and revolution gaits using a computer-aided video motion capture system. The results showed that the gait characteristics were generally altered in both straight and revolution gaits due to hemiplegia (p < 0.05). The gait characteristics were then different between the straight and revolution gaits each other. This study may be valuable by identifying for the first time the alterations of the lower extremity joint angles in both straight and revolution gaits due to pure hemiplegia through comparing healthy elderly with hemiplegic elderly.

Effect of moving load on dynamics of nanoscale Timoshenko CNTs embedded in elastic media based on doublet mechanics theory

  • Abdelrahman, Alaa A.;Shanab, Rabab A.;Esen, Ismail;Eltaher, Mohamed A.
    • Steel and Composite Structures
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    • v.44 no.2
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    • pp.255-270
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    • 2022
  • This manuscript illustrates the dynamic response of nanoscale carbon nanotubes (CNTs) embedded in an elastic media under moving load using doublet mechanics theory, which not considered before. CNTs are modelled by Timoshenko beam theory (TBT) and a bottom to up modelling nano-mechanics is simulated by doublet mechanics theory to capture the size effect of CNTs. To explore the influence of the CNTs configurations on the dynamic behaviour, both armchair and zigzag configurations are considered. The governing equations of motion and the associated boundary conditions are obtained using the Hamiltonian principle. The Navier solution methodology is applied to obtain the solutions for both orientations. Free vibration and forced response under moving loads are considered. The accuracy of the developed procedure is verified by comparing the obtained results with available previous algorithms and good agreement is observed. Parametric studies are conducted to demonstrate effects of doublet length scale, CNTs configurations, moving load velocities as well as the elastic media parameters on the dynamic behaviours of CNTs. The developed procedure is supportive in the design and manufacturing of MEMS/NEMS made from CNTs.

Numerical Analysis on Wire-Plate Electrostatic Precipitator Performance for Bioaerosol Capture: Effect of Ionic Wind (와이어-평판 형태의 전기집진기식 바이오-에어로졸 포집기 성능 수치해석: 이온풍의 영향)

  • Hyun Sik Choi;Gihyeon Yu;Jungho Hwang
    • Particle and aerosol research
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    • v.19 no.3
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    • pp.89-100
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    • 2023
  • In our previous study, a wire-plate type electrostatic precipitator (ESP) was developed to collect bioaerosols of 100 nm size. In the study, various flow rates (40 ~ 100 L/min) and applied voltages (3 ~ 10 kV) were tested for experiment. In this study, numerical analysis was performed for the ESP of the previous study with the same flow rates and applied voltages, but with varying the size of bioaerosols to 0.04 ~ 2.5 ㎛. Overall, the numerical analysis results well predicted the experimental data. Bioaerosols of 0.1 ~ 0.5 ㎛ showed the minimum collection efficiency for all conditions because of low charge number. The effect of the ionic wind generated by the corona discharge was calculated. However, the ionic wind did not affect much the collection efficiency. The aerosol collection in the ESP of this study was due to the electrostatic force generated by particle charge in the electric field. This numerical study on the ESP can be used for the design and optimization of higher flow rate (> 100 L/min) ESP.

The Age-Related Changes of Whole-Body Motor Variability during Sit-to-Stand Task (쪼그려 앉았다 일어나기 과제 수행 시 발생하는 전신 운동가변성의 발달적 변화)

  • Kim, Min Joo;Shim, Jae Kun
    • Korean Journal of Applied Biomechanics
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    • v.32 no.3
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    • pp.87-93
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    • 2022
  • Objective: The purpose of this research was to investigate the age-related changes in whole-body motor variability during sit-to-stand (STS) task. It has been reported that children perform motor tasks less accurately with greater variability as compared to adults. However, it is still unknown how they utilize the abundant degrees of freedom and accomplish voluntary actions. Uncontrolled manifold (UCM) analysis has been used to partition motor variabilities into two independent variability components, task-relevant variability (VORT) and task-irrelevant variability (VUCM). We investigated what differences exist between children and adults with respect to these two motor variability components in relation to motor development stages. Method: Ten 6-year-old children (height: 116.2 ± 4.3 cm, weight: 23.1 ± 3.9 kg, motor development assessment percentile score: 77.5 ± 18.6%), ten 10-year-old children (height: 138.7 ± 7.2 cm, weight: 35.8 ± 10.3 kg, motor development assessment percentile score: 73.9 ± 12.7%), and ten young adults (age: 23 ± 1.6 year-old, height: 164.3 ± 11.4 cm, weight: 60.8 ± 12.0 kg) participated in this study. Each participant performed STS ten times, and a motion capture system was used to capture the whole-body kinematics. Each segment centers of mass and the whole-body center of mass were calculated, and UCM analysis was used to quantify motor variabilities, VORT and VUCM. One-way ANOVA was used for statistical analysis. Results: We found that children produced more motor variabilities in VORT and VUCM in all three dimensions, anterior-posterior, medial-lateral, and vertical. As age increased, both, VORT and VUCM significantly decreased (p<.05). Conclusion: The greater VORT found in children compared to adults indicates that the repeatability over repetitions improves through development, while the greater VUCM found in children suggests that children better utilize the abundant degrees of freedom during STS compared to adults.