• Korean Journal of Applied Biomechanics
• /
• v.21 no.3
• /
• pp.259-268
• /
• 2011

This study aimed to examine the kinematic characteristics of the national elite cross-country skiers' double poling technique and to provide the quantitative data for better performance. Four male elite cross-country roller skiers skied maximum velocity with Double Pole technique. The cycle characteristics with angles of elbow, hip, and knee joint were analyzed. The results showed that CM velocity of the body was increased with the third cycle, the cycle time and length were also increased. The poling time and recovery time rate showed with 32.79%, 67.44% respectively. The joint angles with elbow, hip and knee were $106^{\circ}$, $133.14^{\circ}$ $156.87^{\circ}$ at pole in event, $158.94^{\circ}$, $65.7^{\circ}$, $140.19^{\circ}$ at pole out event. Elite skiers should decrease double poling time rate and increase recovery time rate in order to improve the double poling performance. The cycle length and velocity of the double poling should be increased for the better performance. The elbow angle should be minimized at pole in event with maximum extension until pole out event. The hip and knee angles should be increased for the recovery phase.

• Nuclear Engineering and Technology
• /
• v.41 no.7
• /
• pp.929-944
• /
• 2009

The present study is concerned with the extension of the Effective Convectivity Model (ECM) to the phase-change problem to simulate the dynamics of the melt pool formation in a Light Water Reactor (LWR) lower plenum during hypothetical severe accident progression. The ECM uses heat transfer characteristic velocities to describe turbulent natural convection of a melt pool. The simple approach of the ECM method allows implementing different models of the characteristic velocity in a mushy zone for non-eutectic mixtures. The Phase-change ECM (PECM) was examined using three models of the characteristic velocities in a mushy zone and its performance was compared. The PECM was validated using a dual-tier approach, namely validations against existing experimental data (the SIMECO experiment) and validations against results obtained from Computational Fluid Dynamics (CFD) simulations. The results predicted by the PECM implementing the linear dependency of mushy-zone characteristic velocity on fluid fraction are well agreed with the experimental correlation and CFD simulation results. The PECM was applied to simulation of melt pool formation heat transfer in a Pressurized Water Reactor (PWR) and Boiling Water Reactor (BWR) lower plenum. The study suggests that the PECM is an adequate and effective tool to compute the dynamics of core melt pool formation.

• Korean Journal of Applied Biomechanics
• /
• v.14 no.1
• /
• pp.1-12
• /
• 2004

The purpose of this study is to provide training materials for practical use by investigating the kinematical variables of the successful landing by the type of the salto backward such as Tuck, Pike. For this study, the subjects are 4 male national gymnasts using 3-dimensional cinematographic method. Based on the results of this study, the conclusions are drawn as follows. 1. In flight phase, Tuck and Pike show fast extension after completing minimum angle of hip joint passing through the peak. It is very important factor to control body with gaining time before landing while decreasing the velocity of flight rotaion. 2. In Landing phase, the angles of each joint for successful landing are shown as $92deg{\sim}100deg$ for knee angle, $52deg{\sim}57deg$ for hip angle, and $56deg{\sim}70deg$ for shoulder angle. 3. Tuck and Pike dramatically decrease the height of COG, and horizontal/vertical velocity of COG from TD to LD. Also, it is shown that the knee angle, the hip angle and the shoulder angle decrease drastically. On the other hand, the angular velocity of trunk rotation shows negative direction and due to this, the angle of trunk rotation is shown as re-flexion.

• Korean Journal of Applied Biomechanics
• /
• v.15 no.3
• /
• pp.61-70
• /
• 2005

The purpose of study was to investigate the kinematic variables of Kenmotsu motion in Parallel bars. To this study, by 3 dimensional kinematical analysis of 4 male national gymnasts participants in the 28th Athens Olympic Game in 2004, kinematic data collected using video camera. Coordinate data were smoothed by using a fourth-order Butterworth low pass digital filter with cutoff frequency of 6Hz. The conclusions were as follows. 1. In P2, because the constrained swing movement made the movement of a rising back difficult7, the movements of Reg. were performed at low position after Air phase. 2. In E5 event, for the shake of a stable handstand and applied techniques like a Belle(E-value), a Belle Piked(super E-value), a vertical velocity in E2, a horizontal velocity in E3 and a vertical velocity in E4 were necessary for high velocities. 3. In E4 event, it was appeared that for a flexible body's movement of a vertical up-flight, the large angle of the shoulder joint and the flexion & extension of the hip joint were necessary in Air phase and a long flight time and vertical displacement made Reg. movements stable at the high position.

• International Journal of Internet, Broadcasting and Communication
• /
• v.14 no.2
• /
• pp.183-191
• /
• 2022

The purpose of this study, the wearing conditions of functional pressure clothing applied with the thermotherapy device were determined by three types (NW, CW, TCW) and the difference in isokinetic strength, muscle activity around the forearm was investigated and the effects of products mixed with thermotherapy and pressure treatment were verified. Ten men in their 20s were selected as subjects, and all subjects were randomly assigned three wearing conditions, and wrist flexion/extension exercise was performed at 30° and 90° angular velocity in isokinetic equipment. Peak torque, average power, and EMG were measured during exercise in all conditions. For peak torque, CW was significantly highest at velocity of 30°/sec flexion. Average power showed no significant difference by condition. In the angular velocity of 90°/sec, flexion was significantly higher in CW and TCW than in NW. As a result, wearing clothes with pressure effect and heat effect can show high efficiency in high muscle strength development and fast contraction activity during low speed exercise, and it is thought that it can show improvement of exercise ability through efficient recruitment of motor unit.

• Earthquakes and Structures
• /
• v.22 no.3
• /
• pp.219-230
• /
• 2022

Knowing that the variability of soil properties is an important source of uncertainty in geotechnical analyses, we will study in this paper the effect of this variability on the seismic response of a structure within the framework of Soil Structure Interaction (SSI). We use the proposed and developed model (N2-ISS, Mekki et al., 2014). This approach is based on an extension of the N2 method by determining the capacity curve of the fixed base system oscillating mainly in the first mode, then modified to obtain the capacity curve of the system on a flexible basis using the concept of the equivalent nonlinear oscillator. The properties of the soil that we are interested in this paper will be the shear wave velocity and the soil damping. These parameters will be modeled at first, as independent random fields, then, the two parameters will be correlated. The results obtained showed the importance of the use of random field in the study of SSI systems. The variability of soil damping and shear wave velocity introduces significant uncertainty not only in the evaluation of the damping of the soil-structure system but also in the estimation of the displacement of the structure and the base-shear force.

• Korean Journal of Applied Biomechanics
• /
• v.21 no.3
• /
• pp.297-308
• /
• 2011

The purpose of this study was to investigate the relationship among isometric and isokinetic muscle strength, lean body mass(LBM) and bone mineral density(BMD) in the elderly. Eleven males(age, 70.27${\pm}$5.78yr; height, 167.36${\pm}$6.68 cm; weight, 68.34${\pm}$8.23 kg) and thirteen female(age, 69.77${\pm}$4.13yr; height, 152.80${\pm}$4.45 cm; weight, 56.86${\pm}$7.40 kg) participated in this study. In all subjects, LBM and BMD segments was measured by using Dual-energy x-ray absorptiometry(DEXA, Lunar DPS-DM, U.S.A.). Maximum isometric and isokinetic muscle strength of flexion and extension at the knee and elbow, ankle, trunk joints were measured by using an isokinetic dynamometer(CON-TREX(R) Multi Joint Testing Module, Switzerland). The results of this study showed that isometric and isokinetic muscle strength was significantly higher in extension than flexion. In the male and female, hamstring to quadriceps strength ratio(H:Q ratio) was increased as contraction velocity increased. BMD was correlated significantly with trunk extension in the male, but not in the female. LBM was correlated significantly in the male and female with knee extension strength. This study suggests that in the elderly muscle strength training program should put more weight on extensor muscles of the body.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.22 no.1
• /
• pp.61-69
• /
• 1998

Vapor Axial Deposition (VAD), one of optical fiber preform fabrication processes, is performed by deposition of submicron-size silica particles that are synthesized by combustion of raw chemical materials. In this study, flow field is assumed to be a forced uniform flow perpendicularly impinging on a rotating disk. Similarity solutions obtained in our previous study are utilized to solve the particle transport equation. The particles are approximated to be in a polydisperse state that satisfies a lognormal size distribution. A moment model is used in order to predict distributions of particle number density and size simultaneously. Deposition of the particles on the disk is examined considering convection, Brownian diffusion, thermophoresis, and coagulation with variations of the forced flow velocity and the disk rotating velocity. The deposition rate and the efficiency directly increase as the flow velocity increases, resulting from that the increase of the forced flow velocity causes thinner thermal and diffusion boundary layer thicknesses and thus causes the increase of thermophoretic drift and Brownian diffusion of the particles toward the disk. However, the increase of the disk rotating speed does not result in the direct increase of the deposition rate and the deposition efficiency. Slower flow velocity causes extension of the time scale for coagulation and thus yields larger mean particle size and its geometric standard deviation at the deposition surface. In the case of coagulation starting farther from the deposition surface, coagulation effects increases, resulting in the increase of the particle size and the decrease of the deposition rate at the surface.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.35 no.7
• /
• pp.685-691
• /
• 2011

The aim of this study is to point out the uniqueness of Doppler optical coherence tomography (DOCT) for use in a probe station for (in vivo) visualization of microscale flow and structure and to maximize the effectiveness of DOCT by overcoming its limitations. Conventional DOCT produces images of only one of the velocity components that is parallel to the incident light. In this study, a multi-angle DOCT to quantify a velocity vector field is proposed; this is an extension from a velocity scalar field to a vector field. Quantifying an instantaneous three-dimensional velocity field in a pulsating flow is another challenge because of its limited frame rate. The in-vivo pulsating blood flow is measured by using an electrocardiogram-gated multi-angle DOCT in a hamster cheek pouch model. It is shown that the aliasing problem caused by a relatively low frame rate is resolved by using this method of measurement.

• Korean Journal of Applied Biomechanics
• /
• v.16 no.4
• /
• pp.49-59
• /
• 2006

The purpose of this study was to investigate the relations between the segments of the body, the three dimensional anatomical angle according to sweep shot in ice hockey. The subjects of this study were five professional ice hockey players. The reflective makers were attached on anatomical boundary line of body. For the movement analysis three dimensional cinematographical method(APAS) was used and for the calculation of the kinematic variables a self developed program was used with the LabVIEW 6.1 graphical programming(Johnson, 1999) program. By using Eular's equations the three dimensional anatomical Cardan angles of the joint and ice hockey stick were defined. 1. In three dimensional linear velocity of blade the Y axis showed maximum linear velocity almost impact, the X axis(horizontal direction) and the Z axis(vertical direction) maximum linear velocity of blade did not show at impact but after impact this will resulted influence upon hitting puck. 2. The resultant linear velocity of each segment of right arm showed maximum resultant linear velocity at impact. It could be suggest that the right arm swing patterns is kind of push-like movement. therefore the upper arm is the most important role in the right arm swing. 3. The three dimensional anatomical angular displacement of trunk in flexion-extension showed flexion all around the wrist shot. The angular displacement of trunk in internal-external rotation showed internal rotation angle at the backswing top and and increased the angle after the impact. while there is no significant adduction-abduction. 4. The three dimensional anatomical angular displacement of trunk showed most important role in wrist shot. and is follwed by shoulder joints, in addition the movement of elbow/wrist joints showed least to the shot. this study result showed upperlimb of left is more important role than upperlimb of right.