• International Journal of Advanced Culture Technology
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• v.8 no.3
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• pp.192-197
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• 2020

Foreign students in South Korea face important challenges when they try to maintain their health. As a measure of their motivation to actively build skills for overcoming those challenges, we evaluated the 10-item Consumer Health Activation Index (CHAI), testing its feasibility, dimensionality, and reliability. There were no missing data, there was no floor effect, and for the total scores the ceiling effect was trivial (< 2%). Results of the Kaiser-Meyer-Olkin test and Bartlett's test of sphericity indicated that the data were suitable for the detection of structure by factor analysis. The results of parallel analysis and the shape of the scree plot supported a two-factor solution. One factor had 3 items concerning "my doctor" and the other factor had the 7 remaining items. Reliability was high for the 10-item CHAI (alpha = 0.856), for the 3-item subscale (alpha = 0.838), and for the 7-item subscale (alpha = 0.857). Reliability could not be improved by deletion of any items. Use of the CHAI to gather data from these foreign students is feasible, and reliable results can be obtained whether one uses the total score from all 10 items or scores from the proposed 7-item and 3-item subscales.

• Proceedings of the KSME Conference
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• 2007.05b
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• pp.2273-2278
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• 2007

Brazed Plate Heat Exchanger (BPHE) is a type of compact plate heat exchanger with parallel corrugated plates which are brazed together in series. Each plate hascorrugation called herringbone pattern. Inside a BPHE, hot fluid and cold fluid alternate its flow direction to establish counter current flow configuration. Two-phase flow heat transfer and pressure drop of R-22 in BPHE were experimentally measured in this study. In the present experiments, single-phase region and two-phase region coexist in a BPHE. Therefore, the inside of a BPHE have to be divided into single phase region and two phase region and analyzed accordingly. The results from the single phase flow analysis are then extended to the two phase flow analysis to correlate the condensation and evaporation heat transfer and pressure drop for the refrigerant R-22 in the BPHEs. Previous models for two- phase friction factor have been compared with the present experimental results.

• Proceedings of the KIPE Conference
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• 1998.10a
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• pp.920-927
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• 1998

This paper proposed that an Analysis of a partial resonant AC-DC converter for high power and power factor operates with four choppers connecting to a number of parallel circuit. To improve these, a large number of soft switching topologies included a resonant circuit have been proposed. And, some simulative results on computer are included to confirm the validity of the analytical results. The partial resonant circuit makes use of an inductor using step-down and a condenser of lose-less snubber. The result is that the switching loss is very low and the efficiency of system is high. And the snubber condenser used in a partial resonant circuit makes charging energy regenerated at input power source for resonant operation. The proposed conversion system is deemed the most suitable for high power applications where the power switching devices are used

• Structural Engineering and Mechanics
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• v.30 no.3
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• pp.317-330
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• 2008

Stress intensity factors for a planar crack parallel to a bimaterial interface are considered. The formulation leads to a system of hypersingular integral equations whose unknowns are three modes of crack opening displacements. In the numerical analysis, the unknown displacement discontinuities are approximated by the products of the fundamental density functions and polynomials. The numerical results show that the present method yields smooth variations of stress intensity factors along the crack front accurately. The mixed mode stress intensity factors are indicated in tables and figures with varying the shape of crack, distance from the interface, and elastic constants. It is found that the maximum stress intensity factors normalized by root area are always insensitive to the crack aspect ratio. They are given in a form of formula useful for engineering applications.

• Journal of Mechanical Science and Technology
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• v.17 no.11
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• pp.1650-1658
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• 2003

This paper deals with a novel shunt circuit, which is capable of suppressing multimode vibration amplitudes by using a pair of piezoceramic patches. In order to describe the characteristic behaviors of a piezoelectric damper connected with a series and a parallel resistor-negative capacitor branch circuit, the stiffness ratio and loss factor with respect to the non-dimensional frequency are considered. The mechanism of the shunt damper is also described by considering a shunt voltage constrained by shunt impedance. To obtain a guideline model of the piezo/beam system with a negative capacitive shunting, the governing equations of motion are derived through the Hamilton's principle and a piezo sensor equation as well as a shunt-damping matrix is developed. The theoretical analysis shows that the piezo/beam system combined with a series and a parallel resistor-negative capacitor branch circuit developed in this study can significantly reduce the multiple-mode vibration amplitudes over the whole structural frequency range.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.05a
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• pp.202-207
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• 2002

This paper deals with a novel shunted actuator, which has a capability to suppress multi-mode vibration amplitudes by using a pair of piezoceramic patches. In order to describe the characteristic behaviors of shunted dampers connected with a series and a parallel resistor-negative capacitive branch circuit, the stiffness ratio and loss factor with respect to the non-dimensional frequency are considered. To obtain a guideline model of a piezo/beam system connected with a series and a parallel resistor-negative capacitor branch circuit, the governing equations of motion is derived through Hamiltons principle and a piezo sensor equation as well as a shunt damping matrix is developed. The theoretical analysis shows that the shunted actuator developed in this study can significantly reduce multiple-mode vibration amplitudes simultaneously over the whole structural frequency range.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.63 no.8
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• pp.1075-1079
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• 2014

In this paper, we describe the analysis and the compensation method of the g-sensitivity error for MEMS vibratory gyroscopes. Usually, the g-sensitivity error has been ignored in the commercial MEMS gyroscope, but it deserves our attention to apply for the missile application as a tactical grade performance. Thus, it is necessary to compensate for the g-sensitivity error to reach a tactical grade performance. Generally, the g-sensitivity error seems intuitively to be a gyroscope bias error proportional to the linear acceleration. However, we assert that the g-sensitivity error mainly causes not a bias error but a scale-factor error. And we verify that the g-sensitivity scale-factor error occurs due to the non-linearity of parallel plate electrodes. Therefore, we propose the compensation method to remove the g-sensitivity scale-factor error. The experimental result showed that a proposed compensation method improved successfully the performance of the MEMS vibratory gyroscope.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.54 no.10
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• pp.457-464
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• 2005

Both ratio error and phase angle error in potential transformer(PT) are critically affected by used burden, connected in parallel to the secondary terminal of the PT. Thus precise measurement of burden value is very important for the evaluation of PT An automatic measurement system has been developed for the measurement of burden value and power factor of a burden. The ac voltage, current and power of the burden are measured precisely, and the burden value and power factor were calculated from these measured values. The resistance and inductance values of the tested burden are also calculated. The overall measurement uncertainties are calculated and reported with the burden value and power factor. The best measurement uncertainty for the burden measurement with the developed automatic measurement system was estimated to be 0.5 $\%$.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.28 no.1
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• pp.16-28
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• 2014

This paper presents a novel high-power-factor circuit topology of AC to AC current-fed type high frequency resonant inverter which includes the function of power factor correction(PFC) in the proposed inverter to operate the AC input block with high power factor. The proposed circuit topology of AC to AC current fed type high resonant inverter removes DC link electrolytic capacitor and has also the one of power factor correction(PFC) in the inverter circuit without an additional PFC circuit since the input current by constituting it in parallel as an unit inverter, which assumes the class-E high frequency resonant inverter of conventional current-fed type, flows in the form of the resultant current flowing through each constant current reactor($L_{d1}$, $L_{d2}$). The circuit analysis of proposed inverter is generally described by adopting the normalized parameters and the evaluation of its operating characteristics are conducted by using the parameters such as the ratio of switching and resonant frequency(${\mu}$), coupling coefficient(k) and so on. An example of procedure for circuit design based on the characteristic values obtained from the theoretical analysis is presented. To confirm the validity of the theoretical analysis, the experimental results are also presented. In the future, the proposed inverter shows it can be practically used as power supply system for induction heating application, DC-DC converter etc.

• Journal of Electrical Engineering and Technology
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• v.6 no.3
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• pp.293-301
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• 2011

This paper presents a novel theoretical method based on power analysis to obtain voltage reference values for an inverter-based compensator. This type of compensator, which is installed in parallel with the load, is usually referred to as the active filter. The proposed method is tailored to design the compensator in such a way that it can simultaneously balance the asymmetric load, as well as correct the power factor of the supply side. For clarity, a static compensator is first considered and a recursive algorithm is utilized to calculate the reactance values. The algorithm is then extended to calculate voltage reference values when the compensator is inverter based. It is evident that the compensator would be asymmetric since the load is unbalanced. The salient feature associated with the proposed method is that the circuit representation of system load is not required and that the load is recognized just by its active and reactive consumptions. Hence, the type and connection of load do not matter. The validity and performance of the new approach are analyzed via a numerical example, and the obtained results are thoroughly discussed.