• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.29 no.6
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• pp.49-57
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• 2015

This paper presents the discharge characteristics and economic feasibility of a Dry $Air/O_2$ and a $N_2/O_2$ mixture gas in order to review $SF_6$ alternative. From AC discharge experiment in an quasi-uniform field, it was found that the optimal $N_2/O_2$ mixing ratio which breakdown voltage and surface flashover voltage were the highest was 70/30 and that the pressure dependence on the breakdown voltage was higher than that of the surface flashover voltage in the Dry $Air/O_2$ and the $N_2/O_2$ mixture gas. The mixing ratio (70/30) and the tendency of the pressure dependence were described in detail based on physical factors (impact ionization coefficient, electron attachment coefficient, secondary electron emission coefficient) involved in discharge mechanism and a electron source, respectively. In addition, the performance insulation and the economic feasibility of the Dry $Air/O_2$ and the $N_2/O_2$ mixture gas were discussed so that Dry $Air/O_2$ mixture gaswas more suitable than $N_2/O_2$ mixture gas to the $SF_6$ alternative.

• Journal of radiological science and technology
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• v.44 no.4
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• pp.389-397
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• 2021

The purpose of this study was to compare the demographic and job characteristics and job satisfaction of sonographers (SONO) and radiological technologists (RT). The subjects were a total of 148 people (69 SONO, 79 RT), who had been working in clinical and hospitals. The method was conducted using a questionnaire with a total of 54 questions consisting of demographic characteristics, job characteristics, and job satisfaction. Reliability was secured with Cronbach's alpha coefficient of 0.6 or higher for the response of the questionnaire. For statistical analysis, descriptive statistics, cross-analysis, independent sample T-test, and correlation analysis using Pearson's correlation coefficient and Spearman's correlation coefficient were performed for each occupation. As a result, first, the SONO had more female workers than RT. They are more than three times as many in graduate school and above. Second, the SONO had 4.5 times more morning shift than the RT and no form of weekend shift. Third, the average monthly salary of the SONO is higher than that of the RT, but when a certain portion of the salary goes up, the salary no longer goes up. Fourth, satisfaction with expectations, growth desire, positive mentality, growth opportunity, job importance, organizational attachment was higher SONO than the RT, but self-efficacy was higher in RT than SONO. Last, SONO had higher educational background than RT. It is hoped that the results of this study will be able to understand the job characteristics of SONO and RT and identify the factors of job satisfaction and provide them as fundamental materials for job selection.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.24 no.7
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• pp.914-924
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• 2020

In this study we developed artificial network generation model, which can generate on-line social network. The suggested model can represent not only scale-free and small-world properties, but also can produce networks with various values of topological characteristics through controlling two input parameters. For this purpose, two parameter K and P are introduced, K for controlling the strength of preferential attachment and P for controlling clustering coefficient. It is found out on-line social network can be generated with the combinations of K(0~10) and P(0.3~0.5) or K=0 and P=0.9. Under these combinations of P and K small-world and scale-free properties are well represented. Node degree distribution follows power-law. Clustering coefficients are between 0.130 and 0.238, and average shortest path distance between 5.641 and 5.985. It is also found that on-line social network properties are maintained as network node size increases from 5,000 to 10,000.

• Investigative Magnetic Resonance Imaging
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• v.25 no.2
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• pp.93-100
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• 2021

Purpose: (1) To evaluate the trabecular pattern at the femoral attachment of the posterior cruciate ligament (PCL) in patients with a PCL injury; (2) to analyze bone microarchitecture by applying gray level co-occurrence matrix (GLCM)-based texture analysis; and (3) to determine if there is a significant relationship between bone microarchitecture and posterior instability. Materials and Methods: The study included 96 patients with PCL tears. Trabecular patterns were evaluated on T2-weighted MRI qualitatively, and were evaluated by GLCM texture analysis quantitatively. The grades of posterior drawer test (PDT) and the degrees of posterior displacement on stress radiographs were recorded. The 96 patients were classified into two groups: acute and chronic injury. And 27 patients with no PCL injury were enrolled for control. Pearson's correlation coefficient and one-way ANOVA with Bonferroni test were conducted for statistical analyses. This protocol was approved by the Institutional Review Board. Results: A thick and anisotropic trabecular bone pattern was apparent in normal or acute injury (n = 57/61;93.4%), but was not prominent in chronic injury and posterior instability (n = 31/35;88.6%). Grades of PDT and degrees of posterior displacement on stress radiograph were not correlated with texture parameters. However, the texture analysis parameters of chronic injury were significantly different from those of acute injury and control groups (P < 0.05). Conclusion: The trabecular pattern and texture analysis parameters are useful in predicting posterior instability in patients with PCL injury. Evaluation of the bone microarchitecture resulting from altered biomechanics could advance the understanding of PCL function and improve the detection of PCL injury.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.11 no.10
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• pp.826-832
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• 1998

In this study the thin films with the structure of Si+SiO$_2$+TiN are made by RF supttering method. TiN, which has small diffusion coefficient and low resistivity, is evaporated between SiO$_2$ and Al layers. It investigates the V-R characteristics depending on the thickness of SiO$_2$ which is used as insulation layer and researches its effects on voltage stability of thin film and varistor. These films show very small resistance valus in negative(-) voltage and large and large value in positive voltage band, and with the increase of voltage, resistance value is rapidly reduced and the satisfactory characteristic of varistor is shown at +1[V]. It is found that resistance value of TiN thin film is small and also TiN thin film has more current than the thin film which is not evaporated by TiN thin film. When Al electrode is evaporated of SiO$_2$ thin film, spiking occurs, but the spiking can be prevented with evaporation of TiN between SiO$_2$ and Al layers and this thin films in made easily because of its good attachment. With the increase of voltage, the resistance is changed into non-linear pattern and the bidirectional varistor characteristic is shown and then its theory can be verified by this experiment. Accordingly, when TiN is evaporated of Si Wafer(n-100), it obtains better voltage-resistance than thin film which is not evaporated and also when varistor character is used electrically to automatic control element such as elimination of flame, power distribution arrestor and constant voltage compensation, satisfactory reproducibilities are expected.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.36 no.3
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• pp.116-127
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• 2024

The floating pier is a representative type of floating structure installed along the coast, primarily used as a facility for berthing and mooring ships. Additionally, ongoing attempts have been made to utilize it for various purposes, such as wave control and wave energy conversion structures. In this study, we experimentally investigated the reflection and motion characteristics of a pile-moored floating pier, which allows heave and limited roll motion, with respect to the presence of perforated structures and the attachment of submerged plates. The hydraulic experiment results indicated that the reflection and motion characteristics of the pile-moored floating pier were significantly influenced by the presence and installation depth of the submerged plates, rather than the presence of perforated structures on the floating body. In particular, the installation of submerged plates increased the reflection coefficient in short-period waves and effectively reduced the heave and roll motions of the floating body.

• Journal of Electrical Engineering and Technology
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• v.12 no.1
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• pp.288-294
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• 2017

This paper contains results of the theoretical studies of the electrical breakdown properties in sulfur hexafluoride. Since the strong interaction of high-energy electrons with the polyatomic sulfur hexafluoride molecule causes their rapid deceleration to the lower energy of electron capture and dissociative attachment, the breakdown is only possible at relatively high field strengths. From the breakdown voltage curves, the effective yields that characterize secondary electron productions have been estimated. Values of the effective yields are found to be more consistent if they are derived from the experimentally determined values of the ionization coefficient and the breakdown voltages. In addition, simulations were performed using an one-dimensional Particle-in-cell/Monte Carlo collision code. The obtained simulation results agree well with the available experimental data with an error margin of less than 10% over a wide range of pressures and the gap sizes. The differences between measurements and calculations can be attributed to the differences between simulation and experimental conditions. Simulation results are also compared with the theoretical predictions obtained by using expression that describes linear dependence of the breakdown voltage in sulfur hexafluoride on the pressure and the gap size product.

• Journal of Biosystems Engineering
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• v.27 no.3
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• pp.235-240
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• 2002

Performance of the heat pump with attaching an air heat exchanger was investigated in the heating condition when the air heat exchanger was worked in the ambient air temperature of -5 to 11$\^{C}$ and air flow rate of 542 to 747 ㎡/h. Performance tests for heating condition were conducted in an experimental room equipped with heat pump. The performance tests were performed in a ambient temperature of -4 ∼ 11$\^{C}$, and room temperature of 4∼22$\^{C}$ respectively. Measured data(temperature, capacity of heat transfer and consumption of electronic power) were analyzed to the efficiency of HEEVA(Heat Exchanger fur the Evaporator), overall heat transfer coefficient and COP of heat pump. The results of inlet temperature for evaporator increased that the temperature was 2 ∼6$\^{C}$, and inlet temperature for condenser decreased that the temperature was 3 ∼ 8$\^{C}$. The results of comparing efficiency of HEEVA for the ratio of heat exchange between hot air and cold air showed that efficiency were considered to 91% because of the ratio of 83∼98%. The results of comparing of COP for the heat pump increased that improvement COP was approximately 0.3∼7.5 than HEEVA had not been operated.

• Knowledge Management Research
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• v.18 no.4
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• pp.287-306
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• 2017

This research focus on the effect of developers' participation structure in knowledge creation and knowledge sharing activities in open source software development projects. Based on preferential selection theory, hypotheses of relationship between a developers' concentration of knowledge creation/sharing activities and collaboration performance was derived. To verify the hypotheses, we use the Gini coefficient in the commit contribution of the developers (knowledge creation) and the centralization index in the repository issue network (knowledge sharing network). Using social network analysis, this paper calculates centralization index from developers in the issue boards in each repository based on data from 837 repositories in GitHub, a leading open source software development platform. As a result, instead of all developers creating and sharing knowledge equally, only a few of developers creating and sharing knowledge intensively further improve the performance of the open collaboration. In other words, a few developers predominantly providing commit and actively responding to issues raised from other developers enhance the project performance. The results of this study are expected to be used by developers who manage open source software project as a governance strategy, which could improve the performance of open collaboration.

• Korean Journal of Childcare and Education
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• v.16 no.5
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• pp.201-218
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• 2020

Objective: The purpose of this study was to investigate the influence of experiences in close relationships with teachers for young children on their depression and to see whether there would be a mediating effect of their self-compassion. Methods: The subjects were 206 teachers recruited from Seoul and five different provinces who currently worked at the kindergarten and child care centers and agreed to participate in the survey. The data were analyzed by means of frequency, percentages, Cronbach's reliability coefficient and Pearson's correlation using SPSS 25.0 and model 4 provided in The PROCESS macro for SPSS 3.4 version. Results: The findings were as followed. First, the teachers' degrees of anxiety and avoidance for their close relationships were below the median scores. In contrast their degree of self-compassion was above the median score. In addition, their level of depression was relatively low. Second, both of the teachers' anxiety and avoidance for their close relationships had a positive impact on their depression and their self-compassion, and there were the partial mediating effect in both cases. Conclusion/Implications: These results imply that the early attachment experience connecting the experience in close relationships in the adulthood is important and that it is necessary to develop a program to enhance teachers' self-compassion to protect their psychological well-being.