• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 1997.04a
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• pp.235-244
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• 1997

The empirical factor and reaction force based on published data were involved to investigate compressible flows through sudden enlargement and sudden contraction passages. Analytical solutions of engineering interest were obtained from one-dimensional steady compressible gas dynamic equations. The effects of compressibility, cross-sectional area ratio, and inlet Mach number on the air flows were discussed with regards to the total pressure loss and flow choking. The present results provide available information necessary ta design the compressible pipe flow systems.

• The Journal of Korean Physical Therapy
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• v.13 no.2
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• pp.399-405
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• 2001

Attainment of the goals of functional electrical stimulation(FES) applications such as strengthening of muscle, increasing muscular endurance, improvement in joint range of motion or the reduction of spasticity does not insure that patients will be able to produce voluntary muscle contraction sufficient to maintain posture or produce purposeful movements. In many patients who have sustained CNS damage, the control exerted by higher nervous system center over muscle contraction may impaired. In Searched patients, a variety of advanced therapeutic exercise techniques have been employed traditionally to facilitate the return of controlled functional muscular activity or maintain postural alignment until recovery from dysfunction occurs Among the most common clinical applications of FES for functional muscle contraction is as a substitute for static or dynamic orthotic devices

• The Transactions of the Korean Institute of Electrical Engineers D
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• v.55 no.7
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• pp.344-351
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• 2006

The fatigue of back muscle in the repetitive lifting motion was studied using multiple parameters(FFT_MDF, RMS, 2C, NT) in this study. Recent developments in the time-frequency analysis procedures to compute the IMDF(instantaneous median frequency) were utilized to overcome the nonstationarity of EMG signal using Cohen-Posch distribution. But the above method has a lot of computation time because of its complexity. So, in this study, FFT_MDF(median frequency estimation based on FFT) algorithm was used for median frequency estimation of back muscle EMG signal during muscle work in uniform velocity portion of lumbar movement. The analysis period of EMG signal was determined by using the run test and lumbar movement angle in dynamic task, such as lifting. Results showed that FFT_MDF algorithm is well suited for the estimation of back muscle fatigue from the view point of computation time. The negative slope of a regression line fitted to the median frequency values of back muscle EMG signal was taken as an indication of muscle fatigue. The slope of muscle fatigueness with FFT_MDF method shows the similarity of 77.8% comparing with CP_MDF(median frequency estimation based on Cohen Posch distribution) method.

• Journal of Biomedical Engineering Research
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• v.20 no.3
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• pp.315-321
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• 1999

The purpose of this study is to develop a mathematical model for system identification in order to predIct muscle force based on eledromyographic signal. Therefore, a finding of the relalionship between characteristics of electromyographic signal and the corre spondng muscle force should be necessiiry through dynamic, joint model. To develop the dynamic joint model, the upper limb mcludmg the wrist and elbow joint has been considered. The kinematic and dynamic data, such as joint angular displacement, velocity, deceleration along with the moment of inertla, required to establish the dynamic model has been obtained by electrical flexible goniometer which has two degree-of-frcedoms. ln this model, muscle force can be predicted only electromyographs through the relationship between the integrated lorce and the mtegrated electromyographic signal over the duration of muscle contraclion in this study.

• Physical Therapy Korea
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• v.30 no.3
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• pp.237-244
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• 2023

Background: The external rotation (ER) exercise in performed at a 90° abduction of the shoulder joint is an effective to strengthen the infraspinatus. However, failure of the humeral head to control axial rotation during exercise can be increased the posterior deltoid over activity. Biofeedback training is an effective method of promoting motor learning and control it could look forward to activate the infraspinatus selectively by controlling the humeral head during exercise. Objects: The aim of this study was investigated that whether biofeedback for axial rotation was effective to activate selectively the infraspinatus during ER exercise. Methods: The 15 healthy males participated, and all subjects performed both ER exercise in a sitting position with shoulder abducted 90° under conditions with and without axial rotation biofeedback. Exercise was performed in a range of 90° ER, divided into three phases: concentric, isometric, and eccentric. The infraspinatus and posterior deltoid muscle activity were observed using surface electromyography. Results: Both infraspinatus activity (p < 0.01) and infraspinatus to posterior deltoid activity ratio (p = 0.01) were significantly higher with biofeedback however, posterior deltoid activity was significantly lower with biofeedback (p = 0.01). The infraspinatus muscle activity and muscle activity ratio were the highest in the isometric contraction type, and there were significant differences for all contraction types (p < 0.05). Whereas, the posterior deltoid activity was the lowest in the isometric contraction type, and showed a significant difference between isometric and other two contraction types (p < 0.05), but no significant different between concentric and eccentric contraction. Conclusion: Our results indicate that the axial rotation biofeedback during sitting ER exercise might be effective method to activating selective infraspinatus muscle and recommended to enhance the dynamic stability of the shoulder joint.

• Journal of the Korean Society of Propulsion Engineers
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• v.21 no.1
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• pp.44-50
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• 2017

Vehicle Holding Device(VHD) has a role that holding the launch vehicle on its launch pad until the engine therust reaches a steady condition. The analytical study of shape parameters and dynamic characteristics of hydraulic cylinders is carried out. The contraction of cylinder is considered as the major factor of releasing mechanism. Through the analysis, the decreasing of cylinder slit size and increasing initial charging pressure increase the contraction force. Through the transient analysis, cylinder load, displacement and inner pressure distribution are confirmed. The cylinder contraction force is converged to the cylinder external force when the cylinder starts to move. Also, the pressure distribution in the hydraulic cylinder is constant.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.15 no.6
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• pp.433-439
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• 2022

Muscle fatigue models to predict maximum endurance time (MET) are broadly classified as either 'empirical' or 'theoretical'. Empirical models are based on fitting experimental data and theoretical models on mathematical representations of physiological process. This paper examines the effectiveness of dynamic muscle fatigue model as theoretical model to predict maximum endurance time during forearm isometric contraction. Forty volunteers (20 females, 20 males) are participated in this study. Empirical models (exponential model and power model) and theoretical model (dynamic muscle fatigue model) are used to compare. Mean absolute deviation (MAD), correlation coefficient (r) and intraclass correlation (ICC) are calculated between theoretical model and empirical models. MAD are below 3.5%p, r and ICC are above 0.93 and 0.87, respectively. This results demonstrate that dynamic muscle fatigue model as theoretical model is valid to predict MET.

• The Transactions of the Korean Institute of Electrical Engineers D
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• v.54 no.5
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• pp.338-347
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• 2005

A computer-based low back muscle evaluation system was designed to simultaneously acquire, process, display, quantify, and correlate electromyographic(EMG) activity with muscle force, and range of motion(ROM) in the lumbar muscle of human. This integrated multi-channel system was designed around notebook PC. Each channel consisted of a time and frequency domain block, and T-F(time-frequency) domain block. The captured data in each channel was used to display and Quantify : raw EMG, histogram, zero crossing, turn, RMS(root mean square), variance, mean, power spectrum, median frequency, mean frequency, wavelet transform, Wigner-Ville distribution, Choi-Williams distribution, and Cohen-Posch distribution. To evaluate the performance of the designed system, the static and dynamic contraction experiments from lumbar(waist) level of human were done. The experiment performed in five subjects, and various parameters were tested and compared. This system could equally well be modified to allow acquisition, processing, and analysis of EMG signals in other studies and applications.

• Journal of International Academy of Physical Therapy Research
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• v.9 no.4
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• pp.1614-1618
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• 2018

The purpose of this study was to evaluate the effect of joint mobilization and manual stretching exercises in patients with hallux valgus. Twenty-three participants were divided into two groups; joint mobilization (n=11) and manual stretching exercises (n=12). The subjects participated in the experiment for 15minutes, three times a week, four weeks. The joint mobilization (Grade III, Maitland) was performed to experimental group for a minute and then rested for 10 seconds for each set. The manual stretching was performed to control group with three exercise session (preparatory and finishing exercises, agonist contraction exercises, agonist contraction and hold-relax exercises). In the results of the study, intragroup comparison of the deformity angles (DA) was shown to decrease from $15.18^{\circ}$ to $13.09^{\circ}$ in the joint mobilization group (p<.05) and from $19.00^{\circ}$ to $16.83^{\circ}$ in the stretching exercises group (p<.05). However, left static foot pressure (LSFP), right static foot pressure (RSFP), left dynamic foot pressure (LDFP) and right dynamic foot pressure (RDFP) did not significantly increase or decrease after the experiment. Intergroup differences also were not statistically significant in all variables (p>.05). The current study suggests that JM and MSE are effective in decreasing the DA in patients with hallux valgus.

• The Journal of Korean Physical Therapy
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• v.11 no.1
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• pp.149-156
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• 1999

Resistive therapeutic exercise prescription goal is to improve functional performance and capabilities through the development of increased muscular strengh endurance or power. Resistance can be applied to either dynamic or static muscle contractions. Resistive therapeutic exorcise can be carried nut concentrically, eccentrically, isometrically, isokinetically. Neurodevelopmental treatment has not resistive therapeutic exercise concept. But proprioceptive neuromuscular facilitate techniques have resistive therapeutic exercise concept with pattens and techniques. It is aid muscle contraction, motor control and increase strength. Manual muscle testing will help the therapist establish a qualitative and quantitative baseline level of strength. Manual resistance maybe applied a against controlled lengthening contraction re static contraction of a muscle. A repetition maximum is not easy to calculate and is not the most accurate method available today to measure strength before of after a resistive therapeutic exercise program. Oddvar Holten Diagram is essy to calculate and is the most accurate method available today to measure strength before of after a resistive therapeutic exercise program. Plyometric training emphasize the development of muscular power and coordination. Quick bursts of force in functional movement patterns are often necessary of a patient is to return to high-demand occupational, recreational or sports related activities.