• 연구논문집
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• s.28
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• pp.137-143
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• 1998

In the case of a boiler, scale is made in the tube by the chemical reactions of Ca and Mg ions contained in the water, and heat transfer rate is reduced because of increasement of heat resistance in the pipe of the heat flow. Thus it brings to reduce the energy efficiency and to make environmental pollution by the use of chemicals for the prevention and removement of scale. In this paper, we discussed the design of electronic generator for dual ultrasonic transmitters and analyzed the effect of scale prevention by ultrasound.

• 한국연소학회:학술대회논문집
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• 2001.11a
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• pp.57-62
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• 2001

The effect of micro scale turbulence on flame structure and stability were experimentally investigated by changing the area of micro turbulence generator(MTG) and air velocity in terms of low NOx and high efficiency combustion. NOx and CO concentration were also measured for different MTG areas to investigate whether a vane swirler having MTG has a possibility of using as part for low NOx combustor. From the obtained results, it is shown that flame stability region increases and flame size becomes small as MTG area increases since MTG in itself makes small scale recirculation flow and swirler does large scale recirculation one. It is also shown that low NOx concentration(about 20${\sim}$30ppm@$O_2$ 11%) is achieved for all MTG areas without any increase in CO concentration regardless of air velocity range tested in this study when the equivalence ratio is 0.7. The results obtained in this study can give basic guideline for the design of compact low NOx high efficiency combustor using a vane swirler having MTG.

• Industry Promotion Research
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• v.7 no.2
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• pp.59-73
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• 2022

This paper aims to analyze efficiency of sustainable development of foreign trade in eastern China to reduce the input while maintaining the current output level. This paper adopts relevant input-output indicators of 11 provinces in eastern China from 2016 to 2020 and uses DEA to measure comprehensive efficiency, pure technical efficiency, and scale efficiency from the input perspective. Malmquist index was used to calculate MPI. As a result, from 2016 to 2020, the MPI of all provinces in eastern China was 1.035, higher than 1, and the net technology efficiency was 0.911, lower than 1. Overall, the average technological progress index increased 4.5% to 1.045. It can be seen that the sustainable development efficiency of foreign trade has an overall influence on comprehensive efficiency, net technology efficiency, and scale efficiency. The efficiency of sustainable development of foreign trade in eastern China is mainly limited by its scale. The improvement of MPI in the eastern Region mainly benefits from technological progress. For provinces affected by internal factors, it is suggested to strengthen internal coordination. For provinces affected by external factors, it is suggested to respond appropriately to external factors.

• The KSFM Journal of Fluid Machinery
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• v.17 no.3
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• pp.41-45
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• 2014

The biological aerated filter (BAF) reactor is regarded as an effective biological wastewater treatment method. It can remove pollutants by carrier filtration and biodegradation. Due to its advantages, which include high biomass retention, tolerance to toxicity, excellent removal efficiency, and slurry separation, BAF has been widely used to remove COD, $NH_4{^+}-N$, phosphorus, and other harmful organic substances. In this study, the BAF reactor was used to remove organic contaminants of domestic wastewater of Korea at both the benchand pilot-scale. The main objectives of this study are to: (i) investigate the removal efficiency of organic contaminants (ex. COD, nitrate, phosphorus) in BAF reactors at both scales; (ii) characterize the small-scale wastewater treatment plant using the BAF reactor. The concentration of COD in the influent increased from 69 to 246 mg/L. During the operation period, the final effluent concentration of COD remained maximum 4.0 mg/L, and the average removal efficiency was above 88%. The present study investigated the removal efficiencies of COD, TN, TP and $NH_4{^+}-N$ from smelting wastewater by BAF system. When treating wastewater in both bench and pilot-scale reactors, the BAF worked well.

• Bulletin of the Korean Chemical Society
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• v.32 no.12
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• pp.4291-4296
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• 2011

Gravitational SPLITT fractionation (GSF) provides separation of colloidal particles into two subpopulations in a preparative scale. Conventionally, GSF is carried out in a thin rectangular channel having two inlets and two outlets at the top and bottom of the channel, respectively. And the channel is equipped with two flow-splitters, one between the top and bottom inlets and another between the top and bottom outlets. A large scale splitter-less GSF system had been developed, which was designed to operate in the full feed depletion (FFD) mode. In the FFD mode, there is only one inlet through which the sample is fed, thus preventing the sample dilution. In this study, the effect of the sample-loading (in the unit of g/hr) on the fractionation efficiency (FE, number% of particles in a GSF fraction that have the sizes expected by theory) of the new large scale splitter-less FFD-GSF system was investigated. The system was tested in the sample-loading range of 3.0-12.0 g/hr with polyurethane latex beads (PU) and sea-sediment. It was found that there is an optimum range in the sample-loading for a FFD-GSF separation. It was also found that there is a general tendency of FE decreasing as the concentration of the sample suspension increases.

• Computers and Concrete
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• v.27 no.3
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• pp.283-295
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• 2021

Existing meso-scale models of concrete need to refine the mesh grids of aggregate and cement mortar, which may greatly reduce the computational efficiency. To overcome this problem, a novel meso-scale modeling strategy, which is based on rigid body spring method and Voronoi diagram, is proposed in this study to establish the meso-scale model of concrete. Firstly, establish numerical aggregate models according to user-defined programs. Circle aggregates are adopted due to their high efficiency in generation and packing process, and the grading of aggregate are determined according to the distribution curve proposed by Full and Thompson; Secondly, extract the centroids of aggregates, and then develop the Voronoi diagram in which aggregate centroids are defined as initial scatters; Finally, establish the rigid body spring model for concrete based on the Voronoi diagram. Aggregates are represented by rigid blocks, and assumed to be unbreakable. Cement mortar is concentrated into the interface between adjacent blocks and represented by two uniform springs. The number of grids is consistent with that of aggregates in specimens, and no mesh-refinement of aggregates and cement mortar is required. The accuracy and efficiency of the proposed modeling strategy are firstly identified by comparing the numerical results with the experimental ones, and then the applicability of the proposed strategy with different volume percentage occupied by aggregates is investigated.

• Korean Journal of Occupational Health Nursing
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• v.21 no.2
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• pp.116-124
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• 2012

Purpose: This study was conducted to examine the influencing factors of social support, self efficiency and depression among the hearing-impaired and physically disabled on their job stress. Methods: The data were collected from Jan.1 to Aug. 30, 2010 from 151 disabled workers. The instruments for this study were the Korean Occupational Stress Scale (KOSS), Social Support Scale, General Self-Efficacy Scale and Beck Depression Inventory-Korean Version (K-BDI). The data were analyzed using t-test, Pearson correlation coefficient and multiple regression with the SPSS/WIN 18.0. Results: The physically disabled show higher social support (t=0.284, p= .001) and self efficacy (t=0.165, p= .024) but lower in depression (t=0.789, p<.001) than the hearing-impaired. There are negative correlation between job stress and social support, job stress and self efficacy but a positive correlation between job stress and depression. These three factors explained 42.9% of the variance in job stress. Conclusion: Social support and self efficacy have positive impacts on job stress but depression has negative impact.

• The Research Journal of the Costume Culture
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• v.6 no.2
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• pp.92-108
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• 1998

The purpose of this study was designed a) to examine the relative importance for college students' clothing disposal causes and their factor structure: b) to test the effects of gender, clothing satisfaction and family income on clothing disposal determinants; and c) to assess the relationship between clothing purchase determinants and overall clothing satisfaction and clothing disposal determinants. Data (n=660) were collected from college students in Cheju Do. The survey questionnaire composed of a revised Clothing Disposal Determinants Scale, Clothing Purchase Determinants Scale and background variables. First, the most important reasons for clothing disposal were to unfit with body change, get washed our and raise nap on clothe, wornout with long-term use, do not ware for new purchasing clothe, uneasy on wear. Second, factor analysis of the revised Clothing Disposal Determinants Scale revealed five factors; unfitness, fashion change, quality dissatisfaction, product efficiency decrement, and maintenance/inconvenience. Third, female students perceived significantly higher in fashion change and unfitness than male students. Forth, unfitness and product efficiency decrement were significantly discriminated between between clothing satisfaction groups, unfitness and fashion change variables were significantly discriminated between family income groups. fifth, impulsive purchase factor was the best predictor of composite clothing disposal measure, followed by individuality, clothing satisfaction, practicality. The best predictors of each disposal factors were individuality oriented purchasing criterion in unfitness factor. Fashion in fashion change, impulsive purchase in quality dissatisfaction and product efficiency decrement factors, and practicality in maintenance/inconvenience factor. As a whole, the most consistent predictor of clothing disposal determinants was impulsive purchase factor.

• Journal of Korean Physical Therapy Science
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• v.2 no.3
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• pp.679-689
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• 1995

This study was designed to investigate the efficiency of subjective assessment that exams the subjective symptom of patients with back pain at the department of physical therapy. To assess the subjective symptom, we used the pain questionnaire using visual analogue scale(VAS) that was developed by Wang on 1995. Questionnaires were administered to 31 adult patients(male : 11, female: 20) with herniated lumbar disk(13), low back pain(8), myofascial pain syndrom(5), lumbar strain(4), ankylosing spondylitis(1). Mean age was 36.3 ranged from 28 to 65. The results of this study were as follows: 1) In each of 15 subjects, there was a significant decrease in VAS between pre-and post-treatment(p < 0.05 -p<0.001). 2) Mean VAS of total subjects was $6.26{\pm}2.55$ in pre-treatment, $4.50{\pm}2.47$ in post-treatment(p < 0.001). The result of this study was shown efficiency of pain management by subjective assessment. The continuous study is needed for many interesting issue of pain management using VAS.

• Journal of the Korea Society of Computer and Information
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• v.21 no.10
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• pp.157-166
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• 2016

The aims of this study are to contribute to efficient revenue management by analysis of the scale in elderly long-term care facilities. The data was used for input of the elderly long-term care costs Scale, and calculated the staffing standards and social welfare facilities workers with living wage guidelines in the Department of Health and Human Services. Revenue efficiency is the highest order of size are as follows. I8(98 people) \43,517,010, H6(86 people) \36,568,332, G8(78 people) \29,426,532, F8(68 people) \23,227,532, E8(58 people) \19,701,254, D8(48 people) \19,155,187, C6( 36) \14,389,109, B8(28 people) \9,920,031, A8(18 people) \3,721,031. It seems that its revenue efficiency even higher than the larger the scale. Meanwhile, The researchers focused on C6 (36 patients) model. Suggestion of this study are following; First, the arrangement can be provided based on needs of the elderly care facility staffing standards. Secondly, an elderly care facility selected wage guidelines. Thirdly, the elderly efficiency guidelines established by the size of a nursing facility. This study and other financial income factor are not the applicable limits.