• Journal of international Conference on Electrical Machines and Systems
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• v.3 no.4
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• pp.367-373
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• 2014

The most common current controller for the Switched Reluctance Motor (SRM) is the hysteresis controller. This method, however, suffers from such drawbacks as variable switching frequency, consequent audible noise and high current ripple. These disadvantages make this controlling method undesirable for many applications. The alternative solution is the PI controller. Since the fixed gain PI current controller can only be optimized for one operating point, and on the other hand, SR motor is highly nonlinear, PI controller gain should be adjusted according to incremental inductance. This paper presents a novel method for PI current controller gain adaptation which is simple and yields a good performance. The proposed controller has been implemented on a test bench using a eZdsp F28335 board. The performance of the current controller has been investigated in both simulation and experimental tests using a four-phase 8/6 4KW SRM drive system.

• Proceedings of the KIEE Conference
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• 2011.07a
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• pp.1528.1-1529
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• 2011

Scribing the transparent conductive oxide(TCO) is an essential technology for the large scaled dye-sensitized solar cell(DSC) and the commercialization of the DSC. Laser systems are most used for scribing technology due to their precision. However, it is difficult to generalize systems because most systems are large and heavy. In this study, we tried to simplificate the Nd:YAG laser system for scribing TCO of the DSC by using switched mode power supply(SMPS) technique. The continuous conduction mode booster converter topology is applied and MC34262 power factor controller is used for the variable frequency control. Finally, SMPS circuit which specifications are 400W of capacity, 400V DC output and 98% of efficiency is fabricated. And it is demonstrated that the scribing TCO is completed by the Nd:YAG laser using this SMPS circuit.

• Proceedings of the KIEE Conference
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• 2008.05a
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• pp.179-180
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• 2008

In this paper, the variable tendency piezoelectric constant and resonance characteristics piezoelectric ceramics due to the electric field is studied. The practical application of piezoelectric ceramics is not only applied in field of small signal. For example, in case of an ultrasonic motor, $120{\sim}130Vrms$ of driving voltage is needed and that of an piezoelectric pump, $200{\sim}220Vrms$ of voltage is required. Therefore, to examine the characteristics of piezoelectric ceramics in large signal contributes to reducing the susceptibility to the multifarious application and securing the ease of the production of control circuit. These contributions may be connected to the expansion of industrial application. We fabricated disk-type piezoelectric ceramic samples by using conventional method and measured the resonance characteristics of these samples under from low to high voltage driving conditions. According to increasing the value of the input voltage, we measured the resonance frequency of the piezoelectric ceramic, and inquired into the cause of these phenomena.

• Structural Engineering and Mechanics
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• v.17 no.3_4
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• pp.539-556
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• 2004

In this paper, the design, fabrication and characterization of a piezoelectric friction damper are presented. It was sized with the proposed practical procedure to minimize the story drift and floor acceleration of an existing 1/4-scale, three-story frame structure under both near-fault and far-field earthquakes. The design operation friction force in kip was numerically determined to range from 2.2 to 3.3 times the value of the peak ground acceleration in g (gravitational acceleration). Experimental results indicated that the load-displacement loop of the damper is nearly rectangular in shape and independent of the excitation frequency. The coefficient of friction of the damper is approximately 0.85 when the clamping force on the damper is above 400 lbs. It was found that the friction force variation of the damper generated by piezoelectric actuators with 1000 Volts is approximately 90% of the expected value. The properties of the damper are insensitive to its ambient temperature and remain almost the same after being tested for more than 12,000 cycles.

• Korean Journal of Optics and Photonics
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• v.13 no.3
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• pp.235-239
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• 2002

A novel ultra-narrow linewidth DFB laser in the extended FBG ring cavity having kHz linewidth is presented. The method of linewidth compression was realized by introducing an extended fiber ring cavity into the cavity between the external FBG and the Bragg grating inside a DFB laser diode. Optimum optical feedback control was achieved by using an optical circulator and a variable optical attenuator to prevent mode hopping induced by spatial hole burning. To prove the validity of the proposed scheme, a self-heterodyne measurement set-up with fiber delay line of 63 km was utilized for the ultra-narrow linewidth measurement. A 3 dB linewidth of less than 3 kHz was demonstrated, which is resolution limited performance. This linewidth is equivalent to 3 dB linewidth of 2$\times$10$^{-8}$ nm.

• Research in Community and Public Health Nursing
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• v.8 no.2
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• pp.304-313
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• 1997

This study was designed to identify the degree of perceived self-efficacy and self-esteem in non - insulin dependent diabetes mellitus. The 278 Diabetic patients participating in this study were selected from a diabetic clinic. The period of data collection was September 2 to September 10, 1996. Collected data were analyzed by means of Frequency, Mean, SD, t - test, Pearson correlation, ANOVA using SPSS/PC+. The result are summarized as follows: 1. The mean score of perceived self-efficacy were 3.52 in total, 3.91 for medication, 3.40 for exercise, 3.60 for diet control, 3.18 for glucose test, 3.53 for general management. And the mean score of self-esteem were 3.51 2. Perceived self-efficacy and self-esteem had statistically significant positive correlations (r=.3125, p=.001). 3. The results of testing for the degree of perceived self -efficacy, according to the subject's demographic variables, showed that there were significant differences in sex (t=4.14, p<0.001), the level of education(t=6.24, p<0.01) and diabetic education(t=3.25, p<0.05). These results suggest that perceived self-efficacy and self-esteem is an important variable in the compliance of diabetic patients.

• 한국정보통신설비학회:학술대회논문집
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• 2009.08a
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• pp.275-280
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• 2009

Femtocells are viewed as a promising option for mobile operators to improve coverage and provide high-data-rate services in a cost-effective manner Femtocells can be used to serve indoor users, resulting in a powerful solution for ubiquitous indoor and outdoor coverage. TThe frequency accuracy and phase alignment is necessary for ensuring the quality of service (QoS) forapplications such as voice, real-time video, wireless hand-off, and data over a converged access medium at the femtocell. But, the GPS has some problem to be used at the femtocell, because it is difficult to set-up, depends on the satellite condition, and very expensive. The IEEE 1588 specification provides a low-cost means for clock synchronisation over a broadband Internet connection. The Time of Packet (ToP) specified in IEEE 1588 is able to synchronize distributed clocks with an accuracy of less than one microsecond in packet networks. However, the timing synchronization over packet switched networks is a difficult task because packet networks introduce large and highly variable packet delays. This paper proposes an enhanced filter algorithm to reduce ths packet delay variation effects and maintain ToP slave clock synchronization performance. The results are presented to demonstrate in the intra-networks and show the improved performance case when the efficient ToP filter algorithm is applied.

• Proceedings of the KIEE Conference
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• 2001.07c
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• pp.1703-1705
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• 2001

The pulsed Nd:YAG laser is used widely for materials processing and medical instrument etc. It is important to control the laser energy in those fields using a pulsed Nd:YAG laser. In this paper, constant-frequency current resonant half-bridge inverter and Cockcroft-Walton circuit are used to charge the energy storage capacitor variably. This laser power supply is designed and fabricated which has no high-voltage transformer, less switching losses, compact size and capability in varying the laser output power. Also, the output characteristics of this Nd:YAG laser system are investigated. The tested results are described.

• Journal of the Korean Dietetic Association
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• v.19 no.2
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• pp.140-158
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• 2013

This study analyzed the effect of family meals on the psychological problems of children. We performed focus group interviews (FGI) on the basic characteristics of family meals, and chose several scales (such as Child Behavior Checklist (CBCL), self-esteem, and a daily hassles questionnaire), to measure the psychological variables. We collected data from 442 dyads (mother-child) and used 440 from dyads. In our results, the frequency of family meals affected the psychological problems of children, especially aggression and emotional instability. The atmosphere during meals also affected depression/anxiety, concentration difficulties, emotional instability, self-esteem, peer relationships, and sociality. There were significant correlations between meal atmosphere, family bonding, maternal personality, and psychological problems of children. We performed covariation analysis to examine and control the influence of family bonding and maternal personality; despite controlling for these variables, family meals still influenced children's psychological problems. We conclude that the family meal is a significant variable that impacts the emotional and behavioral problems of children and stress the importance of frequent family meals.

• Journal of Korean society of Dental Hygiene
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• v.15 no.3
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• pp.505-512
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• 2015

Objectives: The purpose of this study was to compare the oral health behavior in adolescents between multicultural and ordinary Korean families. Methods: The subjects were 66,797 adolescents who were derived from the web-based survey of the National 2014 Korean Youth Risk Behavior of Korean Center for Disease Control. A self-reported web-based questionnaire survey was carried out from June 1 to 30, 2013. A multicultural family is defined as the immigrant mother and child in the study. The variable included demographic, socioeconomic, and oral health related behavior. The demographic characteristics included sex, age, residence area, subjective academic achievement, type of family, education of parents, subjective economic status, and nationality before marriage. Data were analyzed by PASW statistics 18.0. Results: Tooth brushing frequency was closely related to family type, age, residence area, academic achievement, residential type, education level of the parents, and economic status. Conclusions: It is necessary to support oral health services and oral health promotion programs for the adolescents in the multicultural family.