• Proceedings of the KIPE Conference
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• 2004.07b
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• pp.566-569
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• 2004

The recent growth in the use of impactive and nonlinear loads, electronic devices sensitive to power quality has caused many power quality problems. Recently, in power system, not only the reliability of the power supply but also the DVR(Dynamic Voltage Restorer) are being studied more and more. The DVR is a series compensator which can instantaneously compensate a voltage variation in supply side, and is a more effective than a existing UPS(Uninterruptible Power Supply) which can be only used in limited range of loads such as single load. Hence, in this paper, a study of inverter side L-C filter output Voltage for DVR is discussed.

• Journal of The Korean Society of Agricultural Engineers
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• v.62 no.4
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• pp.45-51
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• 2020

The poisson's ratio was obtained from the effective vertical stress and horizontal stress of consolidation-undrained test. It was analyzed void ratio verse poisson's ratio. At the result, the effective friction angle was increase with relative density increased, was decreased the poisson's ratio. The empirical equation of void ratio and poisson's ratio was showed very high correlation r²=0.846. The empirical equation was showed that the smaller the void ratio in the fine grained soil than granular soil. In the case of 0.85 times the correlation analysis equation of granular and fine grained soil, the experimental results were shown very similarly. In especially, the poisson's ratio prediction results was shown within 5% of the error range, was revalidation 0.85 times the correlation analysis equation using the void ratio. In this study, correlation analysis equation of the granular and fine grained soil was more reliability of the poisson's ratio prediction results apply to the void ratio than dry unit weight.

• Transactions of The Korea Fluid Power Systems Society
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• v.3 no.1
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• pp.15-19
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• 2006

In this study, a measurement method of leakage flow-rate for pneumatic driving apparatus is proposed. The existing measurement methods of leakage flow-rate of air need disassemble the test component. Therefore, there is no effective method to measure the leakage flow-rate while operating pneumatic driving apparatus. In this study, the leakage flow-rate is measure from the pressure change in an isothermal chamber that can realize isothermal conditions by stuffing steel wool into it. Therefore, wide range of flow-rate could be measured only from the pressure response and the leakage flow-rate can be measured during operating pneumatic driving apparatus. The effectiveness of the proposed method is proved by experimental results.

• Journal of Power System Engineering
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• v.11 no.4
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• pp.98-102
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• 2007

In this study, a measurement method of leakage flow-rate for pneumatic driving apparatus is proposed. The existing measurement methods of leakage flow-rate of air need disassemble the test component. Therefore, there is no effective method to measure the leakage flow-rate while operating pneumatic driving apparatus. In this study, the leakage flow-rate is measured from the pressure change in an isothermal chamber that can realize isothermal conditions by stuffing the steel wool into it. Therefore, a wide range of flow-rate could be measured only from the pressure response and the leakage flow-rate can be measured during operating pneumatic driving apparatus. The effectiveness of the proposed method is proved by experimental results.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.14 no.6
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• pp.199-205
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• 2014

We would like to study and develop the optimized WBS(Work Breakdown Structure) considering project's range, schedule, cost and human resources management with defining phased work in main task and preceding and escorting relationships for effective small and medium enterprises' informatization through standardized PSDM(Production System Development Methodology). For more systemic and effective system built-up, it introduces production information with WBS study which is appropriate for the small and medium enterprises with setting up management items for enhancing system's reliability, quality, productivity, smooth communication among the participated enterprises such as the small and medium enterprises, IT enterprises, and supervision enterprises, and operational support including maintenance of the built system. This study is purpose of helping a lot of the small and medium enterprises and IT enterprises to build up the systems more effective and reliable within planned schedule using the standardized methodology.

• Earthquakes and Structures
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• v.26 no.2
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• pp.97-115
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• 2024

In this paper, a database consisting of the dynamic shear modulus ratio and damping ratio test data of clay obtained from 406 groups of triaxial tests is constructed with the starting area of Xiong'an New Area as the research background. The aim is to study the nonlinear dynamic properties of clay in this area under cyclic loading. The study found that the effective confining pressure and plasticity index have certain influences on the dynamic shear modulus ratio and damping ratio of clay in this area. Through data analysis, it was found that there was a certain correlation between effective confining pressure and plasticity index and dynamic shear modulus ratio and damping ratio, with fitting degree values greater than 0.1263 for both. However, other physical indices such as the void ratio, natural density, water content and specific gravity have only a small effect on the dynamic shear modulus ratio and the damping ratio, with fitting degree values of less than 0.1 for all of them. This indicates that it is important to consider the influence of effective confining pressure and plasticity index when studying the nonlinear dynamic properties of clays in this area. Based on the above, prediction models for the dynamic shear modulus ratio and damping ratio in this area were constructed separately. The results showed that the model that considered the combined effect of effective confining pressure and plasticity index performed best. The predicted dynamic shear modulus ratio and damping ratio closely matched the actual curves, with approximately 88% of the data falling within ±1.3 times the measured dynamic shear modulus ratio and approximately 85.1% of the data falling within ±1.3 times the measured damping ratio. In contrast, the prediction models that considered only a single influence deviated from the actual values, particularly the model that considered only the plasticity index, which predicted the dynamic shear modulus ratio and the damping ratio within a small distribution range close to the average of the test values. When compared with existing prediction models, it was found that the predicted dynamic shear modulus ratio in this paper was slightly higher, which was due to the overall hardness of the clay in this area, leading to a slightly higher determination of the dynamic shear modulus ratio by the prediction model. Finally, for the dynamic shear modulus ratio and damping ratio of the engineering site in the starting area of Xiong'an New Area, we confirm that the prediction formulas established in this paper have high reliability and provide the applicable range of the prediction model.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2018.05a
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• pp.179-181
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• 2018

Digital imaging equipment is used for a variety of purposes in a wide range of fields in society and is becoming an important element of the 4th industrial revolution. Imaging equipment data is exposed to noise from various causes, and this noise affects accuracy of the equipment, causing errors and lowering reliability. In the present paper, an algorithm based on directional effective pixels is proposed to effectively remove high-density Salt and Pepper noise. Conventional methods show that performance decreases as Salt and Pepper noise density increases. To the contrary, the proposed method has noise-removal performance superior to those of conventional methods, by performing de-noising which considers directional effective pixels even in a high-density Salt and Pepper noise environment. Experimental results show that the proposed algorithm is superior to the existing methods, and performance is verified through enlarged images.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.23 no.12
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• pp.776-781
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• 2011

The rapid increases in global energy demand and global warming need renewable energy sources such as solar thermal energy, biomass energy and waste heat. A ORC-based micro-CHP system(< 10 kWe) is one of the effective means to use renewable energy and solve energy problems because of its compactness, flexibilities and lower cost compared to other systems. The most important core components of the ORC is the expander which has a strong effect on the cycle efficiency. In the range of power output from 1 to 10 kW, the scroll expander is a good choice due to its performance and reliability. In this study, we have carried out an experimental study on an ORC equipped with oil-free scroll expander working with refrigerant R134a. We have measured power output and thermal efficiencies of the ORC and analyzed correlation between volumetric efficiencies of the expander and thermal efficiencies of the ORC.

• Journal of Korean Academy of Nursing
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• v.53 no.5
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• pp.525-537
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• 2023

Purpose: This study aimed to develop and test a reward scale for hospital nurses. Methods: The initial items were identified through a literature review and focus group interviews with ten hospital nurses. The content validity of the items was evaluated by ten experts. Fifty-one items were derived from the pilot survey. Four hundred eighty-eight nurses participated in the study: 248 for exploratory factor analysis (EFA) and 240 confirmatory factor analysis (CFA). Data were analyzed using item analysis, EFA, CFA, convergent validity, known-group validity, and internal consistency using IBM SPSS Statistics 29.0 and IBM SPSS AMOS 29.0. Results: The final scale consisted of 31 items and eight factors (decent wage, opportunity to grow and develop, support for special situations, various benefits, flexibility of work, job-related achievement, reflecting career and performance, and recognition), which explained 67.3% of the total variance. The eight-subscale model was validated by CFA. Convergent validity was evaluated by analyzing correlation with intention to leave (r = - .63, p < .001) and job satisfaction (r = .54, p < .001). The known-group validity was evaluated by comparing the reward scales according to age, clinical career, income level and hospital type. The scale was found to be reliable with a Cronbach's α of .89. Conclusion: Both the validity and reliability of the reward scale for hospital nurses are verified, which can enhance the understanding of the range of rewards and may assist nurse managers in establishing an effective reward system.

• Journal of Institute of Convergence Technology
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• v.4 no.2
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• pp.51-54
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• 2014

Energy storage not only reduces the mismatch between supply and demand but also improves the performance and reliability of energy systems. The different forms of energy that can be stored, including mechanical, electrical and thermal energy. Phase change materials (PCM) are latent heat storage materials. A large number of phase change materials (organic, inorganic and eutectic) are available in any required temperature range. We concentrated on eutectic materials and made a eutectic by mixing urea and choline chloride. Heat capacity ($C_p$) is one of the most important properties to be considered when a process is developed using the eutectic and currently DSC (Differential Scanning Calorimetry) has been proved as an effective technique to measure the heat capacity. This study focused on measuring heat capacity ($C_p$) of the mixing urea and choline chloride by DSC.