• The Transactions of The Korean Institute of Electrical Engineers
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• v.60 no.5
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• pp.955-964
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• 2011

In renewable energy system such as flywheel energy storage system, wind power and solar power, the motor/generator is the important key for offering the electric energy to the electric loads. For example, the heavy and large flywheel is rotated by electromagnetic torque of pemanent magnet synchronous motor (PMSM) and, in case of a breakdown of electric current, the PMSM used as generator supplies electric energy for the various electric utilities using mechanical rotation energy of the flywheel. Thus, design of a motor/generator should be performed in effort to reduce cogging torque and electromagnetic loss for high efficiency. In our paper, a slotless permanent magnet synchronous motor/generator (SPMSM/G) with output power 15kW at the rotor speed 18000rpm is designed from electromagnetic analysis and dynamic performance analysis. In analytical approach, design parameters such as back electro-motive force (back EMF), inductance and electromagnetic torque are derived from analytical method which is one of the electromagnetic analysis method. And using the design parameters, this paper deal with system design considering the driving characteristics and electric load in required power. Finally, the analytical results are verified by the experiment and finite element method (FEM).

• Proceedings of the Korean Geotechical Society Conference
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• 2008.03a
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• pp.1278-1289
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• 2008

Currently in increasing number of urban tunnels with small overburden are excavated according to the principle of the New Austrian Tunneling Method (NATM). Successful design, construction and maintenance of NATM tunnel in urban area demands prediction, control and monitoring of surface settlement, gradient and ground displacement with high accuracy. Use of measured displacement for parameter determination has been researched over the years, and one geotechnical engineering principle has been formed as back analysis. In this paper, back analysis of a ground deformational behavior involving nonlinear behavior is discussed. It is of primary importance to make reliable prediction of deformational behavior for shallow tunnels in soft ground. However, predictions made often prove to be incorrect due to complexity of constitutive law and other relevant factors. Back analysis therefore becomes more important, for it may be used to interpret measured displacement to derive nonlinear material characteristics. The paper shows some example in which a deformational mechanism is studied in the light of inhomogeneous distrubution of Young's module, from which a logic is derived to identify two different types of nonlinear constitutive relationships.

• The Transactions of the Korean Institute of Power Electronics
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• v.13 no.1
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• pp.33-40
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• 2008

This paper proposes a sensorless drive method that estimates the rotor position by analysing Back EMF of single-phase Switched Reluctance motor (SRM). The rotor position information is necessary required, because SRM's torque is generated by exciting a stator winding according to rotor position. In order to detect the position of the rotor, the various rotor position sensors have been used. However, most of the position sensors not only increase the construction cost and the volume of the motor but also decrease reliability of driving system with environment. This paper proposed the method using the Back EMF to solve such problems. When a rotor and stator are overlapped, the Back EMF is sharply changed. By detecting this point, the rotor position can be estimated. Thus SRM is driven by turn on and turn off switches at the proper position through speed calculation. The validity of proposed method is verified through simulation and experiment.

• Transactions of the Korean Society of Automotive Engineers
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• v.12 no.3
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• pp.91-100
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• 2004

This study presents the development of a new aluminum seat frame for the commercial bus. Back moment and seat belt anchorage analysis of the conventional steel seat frame was conducted as a base model. Effective aluminum section dimensions for aluminum pipe were calculated from equivalent stiffness and equivalent weight study. Back moment and seat belt anchorage strength with the developed aluminum seat frame were compared to those of the base model. Additionally, to pass the fatigue test, shape modification of side frame assembly was conducted. From this study we could reduce the weight of seat frame more than 5 kg. And the current analysis model and procedure can provide useful informations in designing a new commercial car seat and can reduce the overall design cost and time.

• Proceedings of the KIEE Conference
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• 2015.07a
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• pp.794-795
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• 2015

This paper deals with back-EMF characteristic comparison of Vertical and Halbach array double-sided linear generator with coreless type. On the basis of a magnetic vector potential and Maxwell's equations, governing equations are obtained, and magnetic modeling is predicting characteristic analysis by using the Fourier series expansion. And then, we obtained magnetic field solutions and calculated resistance, back-EMF constant. The analytical results used by 2-D cylindrical coordinate system. The analytical method used in this paper is confirmed by comparing with finite element analysis results.

• Journal of information and communication convergence engineering
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• v.2 no.3
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• pp.177-181
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• 2004

In this paper, we suggest an Iris recognition system with an excellent recognition rate and confidence as an alternative biometric recognition technique that solves the limit in an existing individual discrimination. For its implementation, we extracted coefficients feature values with the wavelet transformation mainly used in the signal processing, and we used neural network to see a recognition rate. However, Scale Conjugate Gradient of nonlinear optimum method mainly used in neural network is not suitable to solve the optimum problem for its slow velocity of convergence. So we intended to enhance the recognition rate by using Levenberg-Marquardt Back-propagation which supplements existing Scale Conjugate Gradient for an implementation of the iris recognition system. We improved convergence velocity, efficiency, and stability by changing properly the size according to both convergence rate of solution and variation rate of variable vector with the implementation of an applied algorithm.

• Proceedings of the KSR Conference
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• 2008.11b
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• pp.331-336
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• 2008

Magnetic path direction in the back-iron of a linear induction motor(LIM) is perpendicular to that of the lift-magnet of the MAGLEV which is recently developing in KOREA. In general the back-iron is isolated magnetically in conventional rail in order to eliminate the thrust dependency of the LIM on the lift force. However the magnetic isolation causes some increase in construction and management cost. So a unit-type rail system is considered, which the magnetic circuit of the back-iron is sharing that of the lift-magnet. In this paper 3-dimensional analysis for the lift-magnet is carried out using finite element method. As a result, a new shape of the unit-type rail is presented to reduce the magnetic dependency between thrust force and lift force. Also the distribution of magnetic flux density vectors and current-lift force characteristics are presented.

• Journal of The Korean Society of Integrative Medicine
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• v.5 no.3
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• pp.29-37
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• 2017

Purpose: The purpose of this study was to classify patients with chronic back pain according to the degree of their back pain, and to compare the pain dysfunction index with the qualitative changes in abdominal muscles. Therefore, we aimed to provide a basis for the treatment intervention method for patients with back pain. Methods: Twenty patients with chronic back pain were purposive sample to a group of 10 patients with a back pain index of 60 % or more and a group with less than 60 % of back pain, and the subjects who voluntarily participated in the study After receiving the letter, I conducted the research the dysfunction of back pain was measured by the Korean version of the Oswestry Disability Index (KODI), and the ultrasonic wave (Ultrasound MyLabOne, ESAOTE, Italy) And the white area index, and the abdominal muscle movement was used as the exercise instrument POWER breathe K5 (Hab direct, UK), which strengthens the respiratory muscles through threshold-muscle traction. Result: In this study, patients with chronic back pain were subjected to breathing exercises, which led to the decrease in back pain dysfunction. The ultrasonographic analysis of abdominal muscles revealed that both the white area index and muscle image density in the skeletal muscle and in the outer muscle of the abdomen gradually decreased over time. Conclusion: It is thought that introducing back pain patients to abdominal muscle reinforcement training is effective in improving the functions of the patients' muscles, thus increasing their quality of life.

• Journal of muscle and joint health
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• v.14 no.2
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• pp.109-117
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• 2007

Purpose: The purpose of the study was to identify the effect of a self-exercise program on low back pain, abdominal-back muscle strength and waist flexibility in hospital nurses. Method: An experimental research design was employed. 43 subjects (20 in the experimental group and 23 in the control group) who worked in a general hospital in W city agreed to participate in this study. The intervention had 6 sessions with self-exercise program including flexion and extension demonstrated by a trained research assistant. A Visual Analog Scale was used to measure the subjective pain severity. Abdominal-back muscle strength was measured with a back strength dynamometer, while waist flexibility was gauged by the standing of the subject's upper body. Analysis included descriptive statistics, $x^2$ test, t-test and ANOVA. Result: The experimental group exhibited significantly decreased low back pain, an increase in abdominal-back muscle strength, and increased waist flexibility after 6 sessions. The experimental group were not significantly increased in abdominal-back muscle strength than the control group. Conclusion: These results suggest that further research is needed to replicate for verification of clinical validity with the methodological rigors, and to utilize the self-exercise program for care and prevention of low back pain.

• PNF and Movement
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• v.21 no.2
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• pp.185-192
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• 2023

Purpose: This study aimed to confirm the effectiveness of the diaphragm stretching technique as a treatment method for low back pain by evaluating maximum inspiratory pressure, maximum expiratory pressure, and changes in back mobility in patients with low back pain. Methods: Thirty-four patients with low back pain were randomly divided into two groups: an experimental group and a control group. The diaphragm stretching technique was conducted in the experimental group, and the placebo intervention was conducted in the control group. The diaphragm stretching technique was conducted once, maintaining tension for 7 min. The placebo intervention was conducted in the same position as the diaphragm stretching technique, but with only light contact maintained without pressure. Maximum inspiratory pressure, maximum expiratory pressure, and back mobility were measured before and after the intervention, and the changes were compared and analyzed. A paired sample t-test was used to compare measurements within the group before and after the intervention. An independent t-test was used to compare the experimental and control groups. Statistical significance (α) was set at 0.05. Results: In the experimental group, maximum inspiratory pressure, maximum expiratory pressure, and back mobility increased significantly after the intervention (p < 0.05). However, there was no significant difference in the changes in all areas of the control (p > 0.05). As a result of comparative analysis of changes before and after the intervention, there were significant differences in maximum inspiratory pressure, maximum expiratory pressure, and back mobility only in the experimental group (p < 0.05). Conclusion: The diaphragm stretching technique improved maximum inspiratory pressure, maximum expiratory pressure, and back mobility compared to the placebo intervention. Therefore, the diaphragm stretching technique can be recommended as a physical therapy intervention to improve pain in patients with LBP.