• Korean Journal of Optics and Photonics
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• v.21 no.2
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• pp.74-81
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• 2010

A modeling methodology for the analysis of injection-locked Fabry-Perot laser diodes (FP-LDs), promising for cost-effective WDM-PON sources, is proposed. The time-domain large-signal model that is used is found to provide quite similar results to some experimental ones. With our methodology, we model characteristics of FP-LDs, such as influence of reflectivity at a facet and detuning on injection-locking. The eye diagram characteristics are also investigated. It is observed that the facet reflectivity at the injection side should be lower than 1% to provide stable operation in terms of good side-mode suppression ratio and independence from detuning between narrow-band injection noise and LD modes. It is also observed that good eye opening can be obtained for 155 Mbps modulation while the parameters such as the active region thickness should be properly optimized to obtain reasonable eye opening at 1.25 Gbps.

• Journal of the Korean Society of Marine Environment & Safety
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• v.25 no.3
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• pp.259-268
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• 2019

Even if only two ships are encountered, a collision may occur due to the mistaken judgment of the positional relationship. In other words, if an officer does not know a target ship's intention, there is always a risk of collision. In this paper, the experiments are conducted to investigate how the intention affects the action of collision avoidance in cooperative and non-cooperative situations. In non-cooperative situation, each ship chooses a course that minimizes costs based on the current situation. That is, it always performs a selfish selection. In a cooperative situation, the information is exchanged with a target ship and a course is selected based on this information. Each ship uses the Distributed Stochastic Search Algorithm so that a next-intended course can be selected by a certain probability and determines the course. In the experimental method, four virtual ships are set up to analyze the action of collision avoidance. Then, using the actual AIS data of eight ships in the strait of Dover, I compared and analyzed the action of collision avoidance in cooperative and non-cooperative situations. As a result of the experiment, the ships showed smooth trajectories in the cooperative situation, but the ship in the non-cooperative situation made frequent big changes to avoid a collision. In the case of the experiment using four ships, there was no collision in the cooperative situation regardless of the size of the safety domain, but a collision occurred between the ships when the size of the safety domain increased in cases of non-cooperation. In the case of experiments using eight ships, it was found that there are optimal parameters for collision avoidance. Also, it was possible to grasp the variation of the sailing distance and the costs according to the combination of the parameters, and it was confirmed that the setting of the parameters can have a great influence on collision avoidance among ships.

• International Journal of Naval Architecture and Ocean Engineering
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• v.12 no.1
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• pp.102-115
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• 2020

In this study, the SST k - ω turbulence model and the sliding mesh technology based on RANS method have been adopted to simulate the exciting force and hydrodynamic of a pump-jet propulsor in different oblique inflow angle (0°, 10°, 20°, 30°) and different advance ratio (J = 0.95, J = 1.18, J = 1.58).The fully structured grid and full channel model have been adopted to improved computational accuracy. The classical skewed marine propeller E779A with different advance ratio was carried out to verify the accuracy of the numerical simulation method. The grid independence was verified. The time-domain data of pump-jet propulsor exciting force including bearing force and fluctuating pressure in different working conditions was monitored, and then which was converted to frequency domain data by fast Fourier transform (FFT). The variation laws of bearing force and fluctuating pressure in different advance ratio and different oblique flow angle has been presented. The influence of the peak of pulsation pressure in different oblique flow angle and different advance ratio has been presented. The results show that the exciting force increases with the increase of the advance ratio, the closer which is to the rotor domain and the closer to the blades tip, the greater the variation of the pulsating pressure. At the same time, the exciting force decrease with the oblique flow angle increases. And the vertical and transverse forces will change more obviously, which is the main cause of the exciting force. In addition, the pressure distribution and the velocity distribution of rotor blades tip in different oblique flow angles has been investigated.

• Advances in nano research
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• v.16 no.4
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• pp.413-426
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• 2024

This paper investigates the dynamic behavior of a simply supported viscoelastic plate made of functionally graded carbon nanotube reinforced composite under dynamic loading. Carbon nanotubes are distributed in 5 different shapes: U, V, A, O and X, depending on the shape they form through the thickness of the plate. The displacement fields are derived in the Laplace domain using a higher-order shear deformation theory. Equations of motion are obtained through the application of the energy method and Hamilton's principle. The resulting equations of motion are solved using Navier's method. Transforming the Laplace domain displacements into the time domain involves Durbin's modified inverse Laplace transform. To validate the accuracy of the developed algorithm, a free vibration analysis is conducted for simply supported plate made of functionally graded carbon nanotube reinforced composite and compared against existing literature. Subsequently, a parametric forced vibration analysis considers the influence of various parameters: volume fractions of carbon nanotubes, their distributions, and ratios of instantaneous value to retardation time in the relaxation function, using a linear standard viscoelastic model. In the forced vibration analysis, the dynamic distributed load applied to functionally graded carbon nanotube reinforced composite viscoelastic plate is obtained in terms of double trigonometric series. The study culminates in an examination of maximum displacement, exploring the effects of different carbon nanotube distributions, volume fractions, and ratios of instantaneous value to retardation times in the relaxation function on the amplitudes of maximum displacements.

• Journal of the Korean Home Economics Association
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• v.30 no.1
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• pp.179-198
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• 1992

The purspoe of this study is to identify the socialization level of household work of the employed and unemployed housewives and it's related variables in order to provide some fundamental information for the rational and effective performation of the household task. For the purpose of this study, 700 questionnaire were distributed to the employed and unemployed wives who lived in Seoul. The data were analyed by the Frequency distribution, Percentile, t-test, F-test, Duncan's Multiple Range Test, and Multiple Regression Analysis. The main results were as follows : (1) Socialization level of household work of the employed wives was a little below medium point. When the household work was devided into three subdomains, in the domain of food and shelter, the socialization level was far below medium point. In the domain of clothes, the socialization level was a little higher than medium point. Socialization level of household work of the unemployed wives far below average. When the household work was devided into three sudbomains, in the domain of food, clothes and shelter, the socialization level was far below average, too. Socialization level of household work was significantly different according to the employment. (2) Among the background veriables, family income, household work helper, and frequency of leisure activities have a significant influence on the socialization level of the employed wives. Duration of marriage, housewife's education level and house income have a important effect on the socialization level of the unemployed wives background. (3) Among the background variabels of household work, performing competence of household work is powerful effect on the socialization level of the employed wives. And as for the unemployed wives, performing competence of household task and recognition of the velue of household work are significant variables. (4) The psychological variable such as sex-role attitude gave no noticeable influence on the socialization level of employed and unemployed wives. (5) In conclusion, classifing the variances influencing on the socialization level of household work in a measure of respcetive effect, it appears to be performing competence of household task, frequency of leisure activities, house income, sex-role attitued and educational level in the order of their influences for the employed wives. And as for the unemployed wives, it seems to be house income, educational level, performing competence of household work and frequency of leisure activities. To the two sides, the rate of explanation is shown at 35%.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.46 no.3
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• pp.32-39
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• 2009

In this paper, system optimization design technique of an impulse ground penetrating image radar (GPIR) in time domain is proposed to improve depth resolution of the system. For the purpose, time domain analysis method of key components such as impulse generator and UWB antenna is explained and by simulation, parameters of each component are determined. In particular, by standardizing the impulse signal, spectrum efficiency of a radiated impulse signal is improved and a U-shaped planar dipole antenna for a UWB antenna is developed. By equipping a parabolic metal reflector with the proposed antenna, external noise is prevented and the ability of radiating an input impulse into ground is improved. In addition, to remove ringing effect of the propose antenna which causes serious degradation of the system performance, resistors are loaded at the edge of the antenna and then Tx and Rx UWB antennas are optimized by simulation in time domain. For images of targets buried under the ground migration technique is applied and influence of tough ground surface on distortion of received impulse signals is reduced using technique of noise and signal distortion reduction in time domain and its time resolution is enhanced. To verify the design optimization procedure, a prototype of an GPIR and an artificial test field are made. Measurement results show that the resolution of the system designed is as good as that of a theoretical model.

• Asia-Pacific Journal of Business
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• v.12 no.1
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• pp.41-56
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• 2021

Purpose - This empirical study examined the influence of post-communist countries sociol-political factor of freedom of expression preconditioning, and trust in agency, mediating performance expectancy of social media users representing the citizens' behavioural intention to utilize social media in a post-communist country, the case of Mongolia. Design/methodology/approach - This research collected 403 valid survey data from citizens those who use social media in Mongolia. The study used Partial Least Squire (PLS) analysis with the research conceptual model founded on the UTAUT model. Findings - The study shown that citizens in post-communist, they strongly willing freedom of expression, which driving as a positive precondition factor, and this has an indirect positive influence, and trust in agency mediates to enhance performance expectancy. Social influence, and effort expectancy factors have direct positive influence on the intention to use of social media systems in the public sector domain of Mongolia. Research implications or Originality - This research proposed a new model to test citizens' intention to use social media as a communication tool to engage with public organizations in the pre-adoption stage of post-communist countries. Theoretically, this research builds up to the unique theoretical contribution with social media by examining a new social media-based third-party intercommunication medium, incorporating intent to utilize for citizens with government in post-communist countries. Practically, this article lays out the directions to aid social media usage for government sector with concerning citizens intentions in the post-communist situation.

• Journal of Family Relations
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• v.21 no.4
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• pp.99-117
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• 2017

Objectives: The purpose of this study is investigate the influences of childhood abuse experience, discipline styles and social support on childcare efficacy according to socio-demographic backgrounds of childcare teachers. Method: For this study's purpose, 200 childcare teachers working at children's schools in J city were surveyed and analyzed for child abuse experience, discipline styles, social support and childcare efficacy. Frequency analysis, t-test, ANOVA and multiple regression analysis were used as study methods. Results: The results of this study are as follows. First, there were statistically significant differences in childhood abuse experiences according to the general characteristics of childcare teachers in the sub-domain of occupational position and marriage status. Second, childcare efficacy and social support were positively correlated, and discipline styles and childcare efficacy were negatively correlated, but there was no correlation between social support and abuse experience. Third, general teaching efficacy regarding childcare efficacy showed a statistical influence of physical abuse, which is a sub-variable of childhood abuse experience. The general efficacy of teaching showed a statistically significant influence on logical discipline and coercive discipline, which are sub-variables of discipline methods. The general teaching efficacy in terms of childcare efficacy showed a statistically significant influence in the family variable which is a sub-variable of social support. The personal teaching efficacy within childcare efficacy showed a statistically significant influence in the logical discipline, a sub-variable of physical abuse, and disciple styles, a sub-variable of childhood abuse experience. Conclusion: From these findings, childcare teachers' childhood abuse experience was a factor affecting childcare efficacy in discipline, social support, and sub-variables. Therefore, it is necessary to remedy the effects of childhood abuse experience, encourage appropriate discipline styles, and to encourage social support in order to improve the childcare efficacy among childcare teachers.

• Journal of agricultural medicine and community health
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• v.24 no.1
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• pp.115-129
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• 1999

To find the influence of family support degree on the depression of the elderly in a rural area, a questionnaire survey was made toward 163 persons who were more than 65 years old and living in a township at Chollanamdo province from January 1st to February 20th, 1998. The major findings are as follows : 1. By simple analysis significantly associated variables with depression score were residence, adequacy of pocket money, health consciousness, drinking alcohol, smoking, score of activity of daily living(ADL), score of instrumental activities of daily living(IADL), and degree of family support among female respondents(p<0.05). 2. To find the influence of family support on the depression score excluding other associated variables, multiple regression analysis was made and it was found that family support was associated significantly with affective, somatic, psychomotor and psychological domain of depression score among male, and somatic, psychomotor and psychological domain among female(p<0.05). The above finding suggest that family support degree is an important factor to be associated with the depression of the elderly in the rural area. So to deal with the depression of rural elderly, how to make close relation among family members must be considered.

• Journal of Power Electronics
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• v.12 no.1
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• pp.193-200
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• 2012

Previous publications regarding the design and specifications of the interface inductor and the DC side capacitor for a STATCOM usually deal with the interface inductor and the DC side capacitor only. They seldom pay attention to the influences of the interface inductor and capacitor on the performance of a STATCOM system. In this paper a detailed analysis of influence of the interface inductor and the DC side capacitor on a STATCOM system and the corresponding design considerations is presented. Phase and amplitude control is considered as the control strategy for the STATCOM. First, a model of a STATCOM system is carried out. Second, through frequency domain methods, such as transfer functions and Bode plots, the influence of the interface inductor and the DC side capacitor on the stability and filtering characteristics of the STATCOM are extensively investigated. Third, according to this analysis, the design considerations based on the phase margin for the interface inductor and the DC side capacitor are discussed, which leads to parameters that are different from those of the traditional design.