• Journal of the Korean Society of Propulsion Engineers
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• v.11 no.2
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• pp.79-85
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• 2007

An internal ballistic model to predict the performance of a Polyethylene-GOX (PE-GOX) hybrid motor was proposed and evaluated. A theoretical treatment of the model was followed by detail discussion of each of the factors affecting the overall performance. The present model consists of the governing equations by considering the unsteady burn-back rate of the fuel grain and on-off response characteristics of a oxygen-supply valve. The numerical results using the 4th order Runge-Kutta scheme with temporal physicochemical properties showed good agreements with test results and the global effects of the performance parameters, such as the burning area of the fuel grain, O/F ratio, and etc., on the performance of the motor were analyzed.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.17 no.2
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• pp.183-192
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• 2004

New dynamic analysis procedures lot the vertically drilled sea water pile are suggested and demonstrated by the typical design Problem. Pile structure submerged in the sea water as well as forces by the ocean waves and tidal currents are modeled and formulated by finite element method. To obtain wave forces for the finite element equation, Airy's wave theory is tested and selected among others. Lateral lifting forces induced by the vortex shedding of current flow is simply based on the harmonic function with the Strouhal frequency and lifting coefficient. Natural frequencies and frequency responses for the pile are calculated by NASTRAN using the results of the formulation. Dynamic displacement and stress results obtained by these procedures are shown to be applicable to predict the dynamic behaviors of the ocean pile by the wave and lifting forces as a preliminary design analysis.

• Journal of Korean Ophthalmic Optics Society
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• v.5 no.2
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• pp.127-138
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• 2000

Differential equations and their solutions were formulated to describe the deflection of both temples and front frames and the pressure exerted by them varying parameters such as elastic modulus, thickness, length, width and shape of crosssection. The effect of such parameters on the deflections of both temples and front frames was illustrated by plotting the solutions of the derived equations. Deflection of temples was found to be maximum where the cross section was diamond-shaped and to be minimum with the rectangular cross section while thickness and cross section area of temples remain constant. The effect of parameters consisting of front frame on the deflection of front frames are very similar to those on temples. The central deflection and pressure of front frame initiated by the temple decreases as the length of temple increases. Detailed analysis of stresses at various parts of the temple will help design custom made spectacle frame as well as most comfortable frames.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.12 no.1
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• pp.18-26
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• 2001

In this paper, the resonant characteristics and modes of the film bulk acoustic wave resonator (FBAR) used in 1~2 GHz frequency region are analyzed by it's input impedance which was calculated by three dimensional finite element method formulated as eigenvalue problem using electro-mechanical wave equation and boundary condition. It was extracted that the resonant and the spurious characteristics considering the effects of electrode area and shape variation and unsymmetry of upper and lower electrode. Those effects couldn't be analyzed by on dimensional analysis, e.g. Mason equivalent model. The simulation result was confirmed by comparing with the simulation data from Mason model analysis and the measured data of the ZnO FBAR fabricated using micro-machining technique. Also, through the simulation of the area variations of FBAR, it was obtained that the optimum ratio of length and thickness is 20:1 and the minimum ratio is 5:1 to operate thickness vibration mode.

• Journal of Korean Ophthalmic Optics Society
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• v.13 no.3
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• pp.35-43
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• 2008

Purpose: This review article was written to investigate how the various factors, such as lacrimal thickness, CL's thickness and Dk, affects the influx of $O_2$ diffusion into the cornea. Methods: A mathematical model was proposed to analyze the oxygen diffusion reaching the cornea through the tear layers and contact lens based on Fick's law and the principle of continuity of the diffusion flux through the each layers. Results: The model predicts how the parameters such as the thickness of tear layer on the cornea, both the Dk and thickness of contact lenses etc., affect the oxygen tension at cornea and oxygen flux entering the cornea. Conclusions: It is found that either too flat or too tightly fitted contact lenses can cause the oxygen deficiency at/inside the periphery of the cornea because of the reduction of oxygen flux resulted from too thickened tear layer.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.5
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• pp.3327-3335
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• 2014

In this study, comparison works have been performed for single-stage and multi-stage refrigeration cycle using propane as a refrigerant in order to cool down the natural gas stream. A comparative analysis has been performed for a single, two, three and four stage refrigeration cycle using propane as a refrigerant for cooling the natural gas stream. For the simulation, natural gas feedstock properties supplied by KOGAS were utilized and Peng-Robinson equation of state model was used. As the number of compression stages increase, the condenser heat duty is decreased. The refrigeration heat duty for a four-stage refrigeration cycle is decreased by 20.36% compared to that for a single-stage refrigeration cycle. Moreover, the total refrigerant circulation rate for a four-stage refrigeration system is was reduced by 14.53% compared to the single stage refrigeration cycle. The total compression power for a four-stage compression was reduced by 41.61% compared to the single stage compression.

• Journal of Korean society of Dental Hygiene
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• v.21 no.2
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• pp.171-182
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• 2021

Objectives: Recently, subjective career success has been used as a criterion for evaluating career success. The purpose of this study was to develop and evaluate a simplified subjective career success inventory for dental hygienists. Methods: Subfactors of the subjective career success inventory consisted of career satisfaction, employability, and job satisfaction. The validity and reliability of the existing tools were evaluated through the basic items composition, content validity index (CVI), preliminary survey, and main survey process according to dental hygienists. The preliminary survey was composed of 35 questions by verifying the content validity twice from the existing 63 questions, and the main survey was conducted with a total of 12 questions. Samples were conveniently extracted from dental hygienists with a clinical career of ≥3 years and surveyed online from March 12, 2020 to June 30, 2020. Data of 320 people were collected, of which 284 were finally analyzed. The validity and reliability were analyzed using SPSS 18.0 and AMOS 18.0 (p<0.05). Results: The subjective career success was a shortened inventory composed of nine questions, and the overall reliability was Cronbach's α=0.841. Using exploratory factor analysis, three factors were extracted. As a result of the confirmatory factor analysis, each measurement variable significantly explained the latent factor, and the fit of the model was appropriate. The fit of the model was appropriate for the structural equation model. Among the sub-factors of subjective career success, career satisfaction and job satisfaction had a significant effect on intention to stay (p<0.05). Conclusions: The simplified subjective career success inventory developed for dental hygienists was found was found to be a useful tool in terms of reliability and validity.

• Journal of Digital Convergence
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• v.17 no.8
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• pp.149-157
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• 2019

This study analyzed the impact of various factors on the use-diffusion of smart speakers. 300 survey responses of Chinese consumers were analyzed using structured models. The results show that both autonomy and adaptability had significant impacts on perceived usefulness and perceived easy of use. Multifunctionality and ability to cooperate affected perceived usefulness, while reactivity did not affected perceived usefulness or perceived easy of use. Anthropomorphism increased perceived enjoyment. Both perceived usefulness and perceived easy of use have been identified to improve the use-diffusion of smart speakers. Perceived enjoyment enhanced the variety of use. We expect these results help understand the factors that need to be considered for the design or marketing communication of smart products.

• The Journal of the Korea Contents Association
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• v.19 no.2
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• pp.568-580
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• 2019

This research explored how the various of factors including performance expectancy, effort expectancy, social influence and facilitating conditions and some external factors consisting of critical mass, attention, perceived enjoyment, and time distortion had impacts on users' usage of short-clip application based on flow theory and the UTAUT model. The research employed SEM with 263 valid questionnaires. The results showed that social influence and satisfaction factors had positive impacts in sustainable usage of mobile short-clip application, while the other factors have no special effect on it. The results also indicated that time distortions had a negative effect in the intention of continuous usage. Furthermore, performance expectancy, perceived enjoyment, and time distortions had positive impacts in users' satisfaction. The beneficial effects of critical mass on social influence had been recognized through this study.

• The Journal of the Korea Contents Association
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• v.21 no.4
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• pp.262-277
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• 2021

In order to explore the power process, a hypothetical model which explains the interrelationships among 3 marital power(traditional, egalitarian, personal), 3 influence strategies(reward, coercion, emotional), and 2 negative conflict resolution styles(attack vs. avoidance) was developed. In order to examine the gender differences, male model and female model were developed separately and compared. Using the data collected from 182 males and 196 females, the hypothetical model was tested. For data analysis, SEM was used. As a result, 3 common paths were found: Greater use of emotional influence strategy increased attack as well as avoidance. Greater egalitarian power increased reward. Egalitalian power affected the use of coercion, but the direction was opposed: male's egalitarian power decreased coercion, while female's egalitarian power increased it. Except these, the analyses revealed the substantial differences between male and female. Based on the findings, the ways to reduce attack and avoidance, and theoretical implications were discussed.