• Journal of Korea Port Economic Association
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• v.34 no.2
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• pp.69-82
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• 2018

The number of ships serviced at the container terminals in Busan is increasing by 2.9% per year. In spite of the increase in calling ships, there are no official records of waiting rate by the port authority. This study attempts to compare the theoretical ship waiting ratio and actual ship waiting ratio. The actual ship waiting ratio of container terminals is acquired from the 2014 to 2016 data of PORT-MIS and Terminal Operating System (TOS). Furthermore, methods and procedures to measure the actual ship's waiting rate of container terminal are proposed for ongoing measurement. In drawing the theoretical ship waiting ratio, the queuing theory is applied after deploying the ship arrival probability distribution and ship service probability distribution by the Chi Square method. As a result, the total number of ships waiting in a terminal for three years was 587, the average monthly service time and the average waiting time was 13.8 hours and 17.1 hours, respectively, and the monthly number of waiting ships was 16.3. Meanwhile, according to the queuing theory with multi servers, the ship waiting ratio is 31.1% on a 70% berth occupancy ratio. The reason behind the huge gap is the congested sailing in the peak days of the week, such as Sunday, Tuesday, and Wednesday. In addition, the number of waiting ships recorded on Sundays was twice as much as the average number of waiting ships.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.37 no.2B
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• pp.87-96
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• 2012

In this paper, we consider a 2-hop relay system where both the relay and destination nodes suffer from the arbitrary number of co-channel interferers. More specifically, assuming that the relay and access channels as well as interference channels are all subject to Rayleigh fading, we derive an exact closed-form expression for outage probability of the amplify-and-forward (AF) relay system, and furthermore compute its upper and lower bounds. Based on these bounds, we derive the upper and lower bounds on the average bit error rate (BER) of the AF relay system. We also confirm the accuracy of our derivation by investigating the performance gap between the performance bounds under consideration and simulation results.

• Journal of Ceramic Processing Research
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• v.22 no.2
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• pp.214-220
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• 2021

Heterolayered potassium tantalate niobate(KTN(70/30)/KTN(30/70)) thin films on Pt/Ti/SiO2/Si substrates prepared by the sol-gel process and spin coating method. When sintered at 700 ℃ or higher, the X-ray diffraction intensities of the perovskite phase were greatly increased, and it was observed as the main phase of the KTN heterolayered thin film. As the sintering temperature increased from 650 ℃ to 800 ℃, the average grain size increased from 146nm to 380 nm, and the average thickness of the KTN films coated six times was about 394-441 nm. Dielectric constant and dielectric loss of the KTN film sintered at 750 ℃ and room temperature showed good properties of about 2850 and 0.573, respectively, and all films exhibited the typical dielectric relaxation characteristics. The phase transition temperature of KTN thin film was around 12-13 ℃. Remanent polarization and the coercive field of KTN film sintered at 750 ℃ showed excellent properties of 23.98 μC/cm2 and 35.41 kV/cm, respectively. Adiabatic temperature changes (ΔT) and electrocaloric strength of the KTN films sintered at 750 ℃ at 60 ℃ were 2.67℃ and 0.012 KcmkV-1, respectively.

• Journal of Power Electronics
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• v.18 no.5
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• pp.1577-1584
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• 2018

The content of harmonic current increases with an increase in the number of power electronic devices in power grid. When a generator is directly connected to the power grid through a step-up transformer, the influence of the harmonic currents on the generator is inevitable. To study the influences of harmonics on generators, a 24-MW bulb tubular turbine generator is taken as an example in this paper. A 2-D transient electromagnetic field model is established. Through a comparative analysis of the data of experiments and simulations, the correctness of the model is verified. The values of the air gap magnetic density, torque and losses of the generator under various conditions are calculated using the finite element method. Taking the rated condition as a reference, the influence of the harmonic currents on the magnetic flux density is analyzed. It is confirmed that the time harmonic is a key factor affecting the generator performance. At the same time, the effects of harmonic currents on the torque ripple, average torque and eddy current loss of the generator are studied, and the mechanism of the variation of the eddy current loss is also discussed.

• Korea journal of population studies
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• v.13 no.1
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• pp.3-25
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• 1990

Life table of Korean population for years 1983 1985 1987 and 1989 were constructed byt the National Bureau of Statics. The ago specific death rates were calculated froom the death registral ion for numerators and the estimated population by age and sex for denominators. In the course of constructing life tables, we have maole some adjustments for deficiencies in regist rat ion olata as follows. First, the non-registered portion oof infant deaths especially for neo-natal deaths was estirnateol and added too the original data. The main reason is that deaths occorring in the neo-natal period and prior to the registrat ion of birth leave little incentive for the registration of either the birth or the death. Second. t he do~hayed p(ortioon of deaths registering after one year of occurrence was estimated and added too the original data. Third t the ptortioon haying in, occuracies in ,~oge reporting was also estimated. Fourth the moving average methood was finally employed in an effort too remove the random error. The major fin(hings are as foolloows. 1. the average life expectancy at birth in 1989 is calculateol as 70.8 years in 1989, 2. a gap netween the male and female life expectancies is widened to more than 8 years toorm 1.8 years in 1906 10. It means that the female life expectancy has increased substantially, 3. the death rates of the middle - aged men starting age 40 are found to he relatively higher than those of females and younger age groups. This peculiar pattern was also found with the comparison of those of other countries.

• Journal of the Korean Society for Library and Information Science
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• v.36 no.2
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• pp.265-284
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• 2002

The purposes of this study are research for user's perspective and satisfaction, and analyze degree of difference in user's perspective and satisfaction through electronic library system of National Assembly Library. According to analysis of questionnaire, score of the factors that quantity of information, latest of information, quality of information, system of classification, accuracy of information are higher than average in user's perspective. Also score of the factors that speed of response, quality of information, consistency of information, consistency of retrieval, quantity of information, accuracy of information are higher than average in user's satisfaction. Result of analysis show that latest of information, quantity of information, variety of information, system of classification, accuracy of information are higher gap in user's perspective and satisfaction.

• The Journal of Industrial Distribution & Business
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• v.8 no.5
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• pp.43-52
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• 2017

Purpose - The domestic liquor market is steadily increasing, but locally made liquor markets remain stagnant. The market opening due to the FTA and westernized eating habits are expanding the consumption of imported liquor by Koreans and the demand for beer and soju is still high. Therefore, we analyzed the scale efficiency of Korean locally made liquor companies. Research design, data, and methodology - Based on a translog-cost function, a scale efficiency analysis was conducted using the government's information survey on the liquor industry. Data from 541 liquor companies analyzed from 2013 to 2014 were used for analysis. Results - As a result of the scale efficiency analysis, the average sales of the mid-sized locally made liquor companies is 171 million won, but the appropriate sales amount is 1 million won. It is estimated that there is a need to increase sales. Conclusions - The gap between the actual sales and the appropriate sales of mid-sized locally made liquor companies with 3~10 employees is larger, so it is necessary to reduce the average cost by increasing the sales of locally made liquor companies. In order to do so, it is necessary to acquire customer strategies such as product differentiation, advertising and publicity.

• Human Ecology Research
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• v.56 no.6
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• pp.493-506
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• 2018

This study analyzes factors that determine the usage of digital information by senior consumers in the mobile environment. Senior consumers are alienated from digital information in South Korea; therefore, there have been increasing attempts to resolve this digital divide and reduce the digital information usage gap between young adults and senior consumers. The study used panel data from the National Information Society Agency (2017); there were 1,463 participants, aged 50-79 years. SPSS 19.0 was used to conduct the statistical analyses for frequency, factor analysis, Cronbach' ${\alpha}$ analysis, descriptive analysis and hierarchical multiple-regression analysis. The results are as follows. First, negative attitude toward information society negatively influenced the mobile digital information usage in diversity context. Second, average monthly income, degree of digital device usage motivation, positive attitude toward digital device usage, digital literacy of PC & Mobile, and family support positively influenced the mobile digital information usage in diversity context. Third, negative attitudes toward information society negatively influenced the mobile digital information usage in quality context. Forth, average monthly income, degree of digital device usage motivation, positive attitude toward digital device usage, digital literacy of PC & mobile, and family support positively influenced the mobile digital information usage in quality context. The study results can help further understand mobile usage behaviors among senior citizens and the implications on their quality of life in the digital information era.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.22 no.2
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• pp.273-282
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• 2021

This study investigates for skills mismatching of the IT service sector in the flows of fast technology changes. It was conducted through an in-depth interview method for professional groups. There were differences in demand for skilled labor by business organizations and educators as providers of skilled labor. A five-point Likert scale was used. The degree of importance of 3.7 average point and the degree of satisfaction of 3.4 average point were responded for the set items in case of matching. In addition, the degree of importance of 3.79 average point and the satisfaction of 3.12 were responded in case of non-majored education students for IT. The skills desired from business organizations included multi-dimensional competencies and soft-skill items. For the reason of skills mismatching, business organizations presented ineffective specifications or divisions of the industrial manpower structure, and educational institutions selected the mismatching of time. Professional groups forecasted that the mismatching gap would expand in the future. To solve the gap, the participated professionals selected an industry-university institute collaboration course and gave an opinion to seek a method to foster manpower in the long-term perspective.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.20 no.3
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• pp.1040-1049
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• 1996

The high loading combustion is accomplished by making the turbulent intensity strong and the scale small in the premixed combustor. The Da-mkoler number, which is decreased by short turbulent characteristic time or by long chemical reaction time, can make the distributed reaction flame. So we developed a doubled jet burner for high loading combustion. The doubled jet burner was designed to make the scale of the flame small by the effect of impingement and increasing shear stress with doubled jet. We investigated the turbulence characteristics of unburned mixture and visualized several flames with the typical schlieren photography. Then we studied the influence of several factors that related the scale of flame. Consequently, the doubled jet burner can make the eddy very small. And we can obtain the detail information of the flame scale through ADSF(the Average Distance between Successive Fringes) in the micro- schlieren photography. The ADSF is not a exact flame scale, but it has qualitative trend with increasing turbulent intensity. The ADSF is diminished remarkably with increasing turbulent intensity. The reason is that strong turbulent intensity makes the flame zone thick and flamelets numerous. We can confirm this fact by the signal analysis of ion currents.