• The Journal of Korean Physical Therapy
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• v.26 no.5
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• pp.280-289
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• 2014

Purpose: This study was conducted in order to determine the stimulation variables which should be considered when neuromuscular electrical stimulation (NMES) is applied for a muscle under the normal innervation to minimize muscle fatigue and increase force-generating ability. Methods: A total of 23 healthy men participated in the study and all subjects were randomly assigned to the 1:1 group, 1:3 group, 1:5 group, and control group with on-off ratio of NMES. The subjects performed a fatigue task, consisting of 10 times of isometric contraction sustained by NMES. NMES using Russian current stimulation was applied to muscle fatigue and divided into three sessions by pulse frequency (10 bps, 30 bps, 90 bps). The EMG was recorded using an MP 100 system from the quadriceps femoris muscle in four groups. Results: The differences of delta MdF and delta MF of between on-off ratio groups of 10 bps, 30 bps, and 90 bps pulse frequencies were very significant (p<0.05). According to the results of post hoc of 10, 90 bps, it was greater in the 1:1 group and the 1:3 group compared with the 1:5 group, and no fatigue was observed in the control group. In 30 bps, it was greater in the 1:1 group compared with 1:3, 1:5, and control group (p<.05). Conclusion: Among NMES variables to minimize muscle fatigue, the larger on-off ratio by pulse frequency showed the lower muscle fatigue. Therefore, on-off ratio needs to be great enough, and will be more efficient with the frequency 30 bps rather than of 10 bps and 90 bps.

• Magazine of the Korean Society of Agricultural Engineers
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• v.34 no.3
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• pp.33-42
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• 1992

The shear strength of cohesionless Soils results from particle-to-particle friction and structural resistance by interlocking. And, the shear strength of soils is subjected to vary depending on the internal states and external condtions. If the volume change occurring in the soils and stress-strain relationships under the internal and external changes can accrurately he described, it is possible to predict the behaviors of soils. To accomplish these objectives a series of drained triaxial compression tests and isotropic compression test was performed on the Banwol sand at different relative densities ranging from 20% to 80% and different confining pressures ranging from 0.4kgf/cm$^2$ to l2kgf/cm$^2$. The results and main conclusions of the study are summarized as follows; 1.When the relative density or the confining pressure is increased, the maximum deviator stress is increased. The ratio of the maximum deviator stress and the confining pressure is linearly proportional to the relative density. 2.It is observed that the dilatancy depends not only upon its relative density but also the confining stress, and that the maximum deviator stress is obtained after the diatancy occurs. 3.The volume of sands undergoes initial contraction prior to the dilatancy occurred by strain softening. The dilatancy rate eventually approaches the critical state or a constant volume. 4.At lower strains, Poisson's ratio approaches a certain minimum value regadless of the state of materials. At larger strains, however, the ratio is increased as the relative density is increased. 5.It is observed that the modulus of elasticity is linearly proportional to the relative density and the pressure. 6.When the relative density is increased, the friction angle of sands is linearly increased. 7.When the relative density is increased, the expansion index and the compression index are linearly decreased, and the ratio of the two is about 1/3.

• PNF and Movement
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• v.9 no.1
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• pp.21-29
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• 2011

Purpose : The purpose of this study was to assess the effects of the lower extremity muscle activity on bridging exercise according to the knee joint angle. Methods : Twenty-five healthy adults volunteered to participate in this study. Subjects were required to complete following four bridging exercises; knee joint flexion $120^{\circ}$, $90^{\circ}$, $60^{\circ}$, $45^{\circ}$. Surface electromyography from selected lower extremity muscles was normalized to maximum voluntary isometric contraction. Muscle activity was measured by QEMG-4 system (LXM 3204, Laxtha Korea). A repeated measures of one-way ANOVA was used to determine the influence of bridging exercise on muscle activity for each muscle and descriptive statistics was used to determine muscle ratio. Results : The biceps femoris of all bridging exercises showed significantly(p<.05). The vastus medialis and lateralis of all bridging exercises showed significant excepted $120^{\circ}$(p<.05). The rectus femoris of all bridging exercises showed no significant. Median of vastus medialis/rectus femoris ratio of $120^{\circ}$ was 2.03, $90^{\circ}$ was 2.16, $60^{\circ}$ was 2.67, $45^{\circ}$ was 4.10. Median of vastus lateralis/rectus femoris ratio of $120^{\circ}$ was 1.70, $90^{\circ}$ was 1.70, $60^{\circ}$ was 2.08, $45^{\circ}$ was 2.58. Median of vastus medialis/vastus lateralis ratio of $120^{\circ}$ was 1.26, $90^{\circ}$ was 1.50, $60^{\circ}$ was 1.52, $45^{\circ}$ was 1.47. Conclusion : Angular motion decreasing with knee joint flexion made increase biceps femoris and vastus medialis activation. This result will be use knee joint stabilizing exercises during bridging or unstable surface training and biceps femoris strength training.

• Journal of Korean Institute of Industrial Engineers
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• v.29 no.2
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• pp.145-149
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• 2003

We consider the estimation of failure rate and acceleration factor under type-I censoring without using acceleration model when testing is conducted in only one highly accelerated condition. Failure times of an item are assumed to be exponentially distributed. It is also assumed that the uncertainty about the acceleration factor, the failure time contraction ratio between accelerated condition and use condition, can be modeled by the uniform or gamma prior distribution of appropriate parameters. We respectively use Bayes and maximum likelihood approaches to estimate acceleration factor and failure rate in the use condition. An example is given to show how the method can be applied.

• PNF and Movement
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• v.16 no.2
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• pp.301-306
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• 2018

Purpose: This study aimed to describe and identify the relationship between gait and contracted ratios of the transverse abdominal (TrA), internal oblique (IO), and external oblique (EO) muscles. Methods: This study was conducted on 50 elderly people. The contracted ratios of the lateral abdominal muscles (LAM) were measured using the abdominal drawing-in maneuver (ADIM) and ultrasonographic imaging. Gait was measured using the timed up and go test and the 10 m walk test. Results: The contracted ratios of the TrA and IO muscles significantly increased after ADIM. Those of the TrA muscles showed a significant correlation with gait in the limited community ambulatory group. The contracted ratios of the IO and EO muscles showed a significant correlation with gait in the community ambulatory group. Conclusion: Our findings suggest a specific training on the relationship between gait speed and the activation of the LAM in elderly people.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.14 no.12
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• pp.1056-1062
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• 2002

This paper reports the characteristics of the three dimensional turbulent flow in the 180 degree bends with decreasing cross-sectional area by numerical method. Calculated pressure and velocity, Reynolds stress distributions are compared to the experimental data. Turbulence model employed are low Reynolds number k-epsilon model and algebraic stress model. The results show that the main vortex generated from the inlet part of the bend maintained to outlet of the bend because of the contraction of cross-sectional area. The rate of increase of turbulent kinetic energy through the bend are lower than that of mean flow. Secondary flow strength of the flow is lower about 60% than that of square duct flow.

• Transactions of the Korean Society of Automotive Engineers
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• v.6 no.5
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• pp.97-103
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• 1998

The flow structure of particles for two different injectors has been investigated experimentally by means of a Phase Doppler Particle Analyzer(PDPA). Two injectors used in the present study are the pipe and contraction nozzle. Particles of 0.8${\mu}{\textrm}{m}$, 30${\mu}{\textrm}{m}$, 60 ${\mu}{\textrm}{m}$, and 100${\mu}{\textrm}{m}$ diameter were injected with a constant mass loading ratio of 0.01 and a Reynolds number of 13200. The initial mean velocity and turbulent intensity of particle are strongly influenced by the particle size and the injector geometry. The flow angles of particle at nozzle exit are sensitive to the particle size rather than the injector geometry.

• Water Engineering Research
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• v.4 no.2
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• pp.87-97
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• 2003

In this study, using the numerical model, the flow motion around skewed abutment is investigated to evaluate the skewness effect on the flow distribution. The skewness angle of the abutment which make with main flow direction is changed from $30\circ$ to $150\circ$ with increments of $10\circ$ while the contraction ratios due to the abutment are kept constant. For the investigation of the combined effects on the relationship between the skewness angle and flow intensities, this process will be .repeated fer different types of abutment (single and double) with different flow intensities. The maximum velocities and the velocity distributions, which can be obtained from each angle, are examined and analyzed corresponding to different angles of inclination. Based on successive model applications, an empirical expression, given in a function of contracted ratio and skewness angle, is derived for relating velocity amplifications according to the angle variations.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.67 no.1
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• pp.124-130
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• 2018

The EMG amplitude estimator, which has been investigated as an indicator of muscle force, is of high relevance not only in biomechanical studies but also more and more in clinical applications. This paper presents a new approach to estimate surface EMG amplitude by using the mean spike and mean turn amplitude(MSA and MTA) variables. Surface EMG signals, a total of 198 signals, were recorded from biceps brachii muscle over the range of 20-80%MVC isometric contraction and performance of the MSA and MTA variables applied to amplitude estimation of the EMG signals were investigated. To examine the performance, a SNR(signal-to-noise ratio) was computed from each amplitude estimate. The results of the study indicate that MSA and MTA amplitude estimations with first order whitening filter and 300[ms]-350[ms] moving average window length are optimal and show better performance(mean SNR improvement of 6%-15%) than the most frequently used variables(ARV and RMS).

• Proceedings of the Korean Geotechical Society Conference
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• 2005.03a
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• pp.1023-1030
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• 2005

This study is an experiment paper about the ground improvement material which using the waste residual(slag and paper fly ash) by fire. we are research to concern according to the soil to mix the ground improvement material at show strength effectiveness. Also, we can expect a long time strength increase effectiveness as reduce the dryness contraction. They are distinguished to the clay of the reclamation ground and silty sand soil. We examined around an uniaxial compress test and scanning electron microscopy. The uniaxial stress increases according to the increase of the mixed ratio of ground improvement material and the water contents have been reduced the strength value. A clay's improvement effectiveness is big but in the silty sand soil to express small effectiveness. A ground improvement material mixing of the quantity to write can not expect the effect of Ettringite.