• Journal of Power Electronics
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• v.14 no.6
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• pp.1243-1253
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• 2014

The phase inductance of a switch reluctance motor (SRM) is significantly nonlinear. With different saturation conditions, the phase inductance shape is clearly changed. This study focuses on the relationship between coefficient and current in an inductance model with ignored harmonics above the order of 3. A position estimation method based on the variable coefficient inductance model is proposed in this paper. A four-quadrant sensorless control system of the SRM drive is constructed based on the relationship between variable coefficient inductance and rotor position. The proposed algorithms are implemented in an experimental SRM test setup. Experimental results show that the proposed method estimates position accurately in operating two/four-quadrants. The entire system also has good static and dynamic performance.

• Journal of Power Electronics
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• v.9 no.2
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• pp.188-197
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• 2009

This paper presents an adaptive flux observer to estimate stator flux linkage and stator inductances of an interior permanent-magnet synchronous machine considering magnetic saturation. The concept of static and dynamic inductances due to saturation is introduced in the machine model to describe the relationship between current and flux linkage and the relationship between their time derivatives. A flux observer designed in the stationary reference frame with constant inductance is analyzed in the rotor reference frame by a frequency-response characteristic. An adaptive algorithm for an on-line inductance estimation is proposed and a Lyapunov-based analysis is given to discuss its stability. The dynamic inductances are estimated by using Taylor approximation based on the static inductances estimated by the adaptive method. The simulation and experimental results show the feasibility and performance of the proposed technique.

• Korean Journal of Health Education and Promotion
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• v.21 no.4
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• pp.99-108
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• 2004

The purpose of this study was to examine the relationship between physical fitness, and physical and psychological stress of females. The subjects of this study were 139 adult women, without a specific medical illness. The stress level was evaluated by Derogetis's checklist-90-Revision symptom of physical and psychological stress (Cronbach's a=0.88, 0.87). The physical fitness factors in this study were cardiopulmonary endurance, muscle endurance, muscle strength, power, agility, and flexibility. To analyze the data to examine the relationship between the physical and psychological stress, and physical fitness, correlation analysis was applied. The findings of this study were as follows. First, among the physical fitness factors, cardiopulmonary endurance, along with muscle strength and power had significant relations with physical stress (p<.01). Second, among the physical fitness factors, cardiopulmonary endurance showed a significant relation with psychological stress (p<.05).

• International Journal of Human Ecology
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• v.12 no.2
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• pp.51-63
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• 2011

This paper examines the relationship between economic dependence and gender differences in housework in Korea. There are three explanatory alternatives for the relationship; economic rule of exchange, gender display perspective and deviant neutralization. We analysed both 2004 and 2009 time use survey data. The findings show the significant gender differences in time spent on housework that wives spend much more time on housework than husbands. However, among couples with non-normative gender roles, in some cases the more economically powerful wives spend more time on housework than breadwinner wives with weaker economic power, although such cases are rare. Rather, it is appropriate to conclude that, the more economically independent the wives, the less time they spend on housework; this is also the case for husbands. Overall, the Korean case shows what the economic exchange theory predicts. Thus, improvements in working wives' economic power will lead to gender equity in the division of housework.

• Proceedings of the KIEE Conference
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• 1997.07e
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• pp.1692-1695
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• 1997

This paper describes the relationship between the various non-destructive parameters and the breakdown voltage for the 17 kV, 300 MVA and the 22 kV, 500 MVA generators stator bars with polyester and epoxy/mica insulation respectively. Also, this study reports the results of an investigation into the factors which can assess the insulation condition of generator stator winding. Furthermore, a new parameter, Partial Discharge Index(PDI), is introduced as the valuable parameter for the assessment of insulation condition. The ratio between partial discharge increment and the stepwise voltage increment from the Discharge Inception Voltage (DIV) at the characteristic or resonant frequency band shows the close relationship between the breakdown voltage and PDI.

• Proceedings of the KSR Conference
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• 2009.05a
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• pp.1643-1648
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• 2009

The braking system of train must posses the large baking effort in order to stop the train safety within the limited traveling distance. but, the excessive braking effort has been deteriorated the ride comfort due to high level of deceleration and jerk, and sometimes occurred the skid. because the applied braking force exceeds the allowable adhesive force. this skid causes not only to increase the a stopping distance but also to deteriorate the safety of train and damage the rall surface by wheel flat. In the present paper, braking force for disk brake of Tilting Train eXpress(TTX) was measured though on convention line test and the traction force was estimated by using the analytic model in skid condition. also, we have discussed the relationship between the bake force and traction force in starting condition.

• Proceedings of the Korea Concrete Institute Conference
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• 2000.10b
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• pp.1145-1150
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• 2000

Concrete behaves as ductile material at high temperature. The existing stress-strain relationship is not valid at high temperature condition. Thus, stress-strain curve of concrete at high temperature is re-established by modifying Saenz's suggestion in this study. A constitutive model of concrete subjected to elevated temperature is also suggested. The model consists of three components; free thermal stain, mechanical strain and thermal creep strain. As the temperature increase, the thermal creep becomes more critical to the failure of concrete. The thermal creep strain of concrete is derived from the modified power-law relation for the steady state creep. The proposed equation for thermal creep employs a Dorn's temperature compensated time theorem

• Proceedings of the Acoustical Society of Korea Conference
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• autumn
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• pp.239-242
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• 2000

In the present study, the influence of car body structures to the noise and vibration characteristics has been sought. The numerical modal analysis for the body-in-white is employed to predict the vibratory response of structure, and then followed by the experimental modal testing to confirm the validity of the model. Using the results of numerical simulations with the designated modal parameters, the optimal structural configuration has been deduced. Special interests have been paid to the sensitivity of sound quality to the structural integrity. Since the structural integrity has a close relationship to the structure-born noise, the substantially low frequency range, which is far below the frequency range almost barely sensible by human auditory organ but still quite influential to overall impression, is especially examined. The subjective assessment agrees with the objective evaluation by means of traditional sound measures as well as psychoacoustic metrics.

• Journal of Korean society of Dental Hygiene
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• v.13 no.5
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• pp.827-833
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• 2013

Objectives : The purpose of the study is to investigate the relationship between self-leadership in clinical practice and stress in dental hygiene majoring students. Methods : Subjects were 250 dental hygiene majoring students in J area from March 20 to April 20, 2012. Data were analyzed using the statistical package SPSS WIN 12.0 for frequency, mean and standard deviation analysis, one-way ANOVA and multiple regression. Results : There were significant differences between Satisfaction and clinical practice, practice and major stress factors(p<0.01). There were significant differences between practices, satisfaction, and self-expectations(p<0.001). The explanatory power of the model was 9%(p<0.05). The combination of self-leadership, activity, interpersonal factors were very important factors and the explanatory power of the model was 8%(p<0.001). Conclusions : Self-leadership is able to decrease stress. Self-leadership is very important in clinical practice in dental hygiene majoring students.

• Journal of Power Electronics
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• v.17 no.4
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• pp.963-971
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• 2017

Torque ripple is one of the major sources inducing vibration and noise in brushless DC motors. This is especially true in applications such as the spindle motors used in hard disk drives. However, the relationship between torque ripple and acoustic noise/vibration is quite complicated. This paper presents a way to investigate this relationship with acoustic noise measurement and analysis. Results obtained with three different drive modes are used in the analysis. The results show that the acoustic noise analysis is very helpful in designing a high-performance drive strategy for BLDC motors.