• International Journal of Fluid Machinery and Systems
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• 제2권1호
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• pp.1-12
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• 2009

Surrogate modeling is applied to a compressor blade shape optimization to modify its stacking line and thickness to enhance adiabatic efficiency and total pressure ratio. Six design variables are defined by parametric curves and three objectives; efficiency, total pressure and a combined objective of efficiency and total pressure are considered to enhance the performance of compressor blade. Latin hypercube sampling of design of experiments is used to generate 55 designs within design space constituted by the lower and upper limits of variables. Optimum designs are found by formulating a PRESS (predicted error sum of squares) based averaging (PBA) surrogate model with the help of a gradient based optimization algorithm. The optimum designs using the current variables show that, to optimize the performance of turbomachinery blade, the adiabatic efficiency objective is improved substantially while total pressure ratio objective is increased a very small amount. The multi-objective optimization shows that the efficiency can be increased with the less compensation of total pressure reduction or both objectives can be increased simultaneously.

• 한국산업보건학회지
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• 제26권3호
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• pp.367-376
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• 2016

Objectives: The production and use of nanoparticles have been increased. In 2014 Workplace Survey Results, 335 companies produce and treat nanoparticls. However, lack of data on nano-toxicity and a method for risk management and regulation on nanoparticles and the standard test method are not sufficient. Protective equipment selection guidelines for nanoparticles are not established. It is required to carry out respirator efficiency test against nanoparticles. This study was performed to evaluate filtration efficiency and manikin-based total inward leakage of particle filtering mask using in Korean country challenged with silver nanoparticles. Methods: We investigated filtration efficiency and total inward leakage of 7 respirator with silver nanoparticle. Results: The geometric mean diameters of Silver nanoparticles were 30 nm and number concentration were about $10^6{\sharp}/cm^3$. Filtration efficiency of six of the seven particle filtering masks was more than 98% and one particle filtering masks filtration efficiency was 94.9%. The filtration efficiency of particle filtering masks to 20 nm silver nanoparticels was highest. Artificial breathing machine with manikin based total inward leakage were 7.6% ~ 42.3%. Conclusions: The results of this study nano-silver filter efficiency was high but the total inward leakage was higher than filter penetration. Therefore, education on how to wear a respirator should be demanded. Especially for workers handling nanoparticles and toxic material, user seal checking and fit test must be performed.

• 한국도서관정보학회지
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• 제41권4호
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• pp.35-50
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• 2010

본 연구는 대전 지역에 소재하고 있는 15개 공공도서관을 대상으로 DEA 모형을 사용하여 2008년도 공공도서관의 상대적 효율성을 분석하고 이어서 최근 3년간의 추세변화를 분석하였다. 투입요소로는 직원수, 면적, 장서수가 사용되었으며 산출요소로는 이용책수와 이용자수가 사용되었다. 연구결과, 기술효율성 값의 추세변화를 분석해 보면 3년간 지속적으로 효율성이 개선되었으며, 기술효율성의 개선은 순수 기술효율성과 규모 효율성 둘 다의 개선에 있었다.

• Biotechnology and Bioprocess Engineering:BBE
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• 제11권4호
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• pp.325-331
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• 2006

Various environmental conditions affecting total phosphorus removal from farm wastewater in a biofilm filter process were investigated using loess balls and Chromobacterium LEE-38 at a pilot plant. When Chromobacterium LEE-38 was used, the removal efficiency of total phosphorous was approximately 10- or 5-fold higher than that of Acinetobacter CHA-2-14 or Acinetobacter CHA-4-5, respectively. When a loess ball of $11{\sim}14mm$ manufactured at a $960^{\circ}C$ calcining temperature was used, the removal efficiency of total phosphorous was 90.0%. When 70% of the volume fraction was used, the maximum efficiency of total phosphorus removal was 93.1%. Notably, when the initial pH was in the range of 6.0 to 8.0, the maximum removal efficiency of total phosphorus was obtained after 30 days. When the operating temperature was in the range of 30 to $55^{\circ}C$, the maximum removal efficiencies of total phosphorus, 95.6 to 94.6%, were obtained. On the other hand, at operating temperatures below $20^{\circ}C$ or above $40^{\circ}C$, the removal efficiency of total phosphorous decreased. Among the various processes, biofilm filter process A gave the highest removal efficiency of 96.4%. Pilot tests of total phosphorus removal using farm wastewater from the biofilm filter process A were carried out for 60 days under optimal conditions. When Acinetobacter sp. Lee-11 was used, the average removal efficiency in the p-adsorption area was only 32.5%, and the removal efficiencies of chemical oxygen demand (COD) and biological oxygen demand (BOD) were 56.7 and 62.5%, respectively. On the other hand, when Chromobacterium LEE-38 was used, the average removal efficiency was 95.1%, and the removal efficiencies of COD and BOD were 91.3 and 93.2%, respectively.

• 한국수소및신에너지학회논문집
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• 제13권4호
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• pp.304-312
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• 2002

In this study, the performance of the $5Nm^3/hr$ compact type steam reformer which was developed for application of fuel cell or hydrogen station was evaluated in terms of gas process efficiency. For these purposes, reforming efficiency and total efficiency with system load change were analyzed. The reforming efficiency was calculated from the total molar flow of hydrogen output over total fuel flow input to the reformer and the burner on the higher heating value(HHV). In the case of the total efficiency, recovered heat at the heat recovery exchanger was considered. From the results, it was known that system performance was stable, because methane conversion showed the a slight decline which is about 2% though increasing system load to full. Reforming efficiency was increased from 20% to 58%, respectively as increasing system load from 10% to 90%. It was found that total efficiency was higher then reforming efficiency because of terms of heat recovered. As a results, it was known that total efficiency was increased form 75% to 83% at the 10% and 90% system load, respectively. From these results, it is concluded that compact steam reformer which is composed of stacking plate-type reactors is suitable to on-site hydrogen generator or to fuel cell application because of quick start within 1 hr and good performance.

• The Journal of Asian Finance, Economics and Business
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• 제9권8호
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• pp.99-108
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• 2022

This study aims to examine the influence of capital structure on the business efficiency of joint stock commercial banks listed on the Vietnamese stock market. The article uses data collected from the financial statements of 15 prominent joint-stock commercial banks out of 27 joint-stock commercial banks listed in Vietnam from 2011 to 2021. The research uses E-view software in quantitative analysis to build regression models to determine the relationship and the impact of capital structure factors on the business efficiency of listed joint stock commercial banks. Research results show that ROA is affected by 2 variables of capital structure. It is the sum of customer deposits to total assets and total liabilities to total equity. Total debt to total equity and total customer deposits to total assets both have a negative effect on ROA. For the regression results of ROA with all control variables, the control variables have a positive relationship with the dependent variable. The article has provided recommendations based on the research findings to determine the proper capital structure. Managers must solve the outstanding amount of mobilized capital in previous years, combined with the bad debt handling activities that have arisen.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2003년도 제20회 춘계학술대회 논문집
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• pp.123-126
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• 2003

실험에서 측정변수에 발생되는 불확도가 터빈 전효율의 불확도에 미치는 영향을 실험을 통하여 분석하였다. 단단 축류형 3차원 터빈이 실험에 사용되었으며 평균반경에서 반동도가 0.373이며 상온 저압 상태에서 실험이 수행되었다. 입구/출구전압력에 의하여 발생되는 불확도는 터빈 전효율의 불확도로 전파되는 영향이 상당히 크게 나타나므로 상온저압시험에서는 높은 정밀도를 갖는 압력계가 필요하게 된다. 측정변수의 불확도가 전효율의 불확도에 차지하는 영향은 토오크에 의하여 발생되는 불확도가 가장 크게 나타났으며 회전수에 의한 불확도가 가장 적었다. 토오크의 불확도 영향은 회전수의 증가에 따라 증가하는 경향이 있다. 전압력의 경우는 출구측에서의 불확도가 입구측에 비하여 영향력이 크게 나타났다.

• 정보관리연구
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• 제41권3호
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• pp.67-84
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• 2010

본 연구는 대전 지역에 소재하고 있는 17개 공공도서관을 대상으로 DEA기법을 사용하여 상대적 효율성을 평가하였다. 투입요소로는 직원수, 면적, 장서수가 사용되었으며 산출요소로는 이용책수와 이용자수가 사용되었다. 연구결과 공공도서관의 평균 효율성은 64.15%로 평가되었다. 효율적인 도서관은 4개관으로 전체의 24%에 불과하였으며, 전반적으로 비효율적인 도서관들의 비효율성은 투입물에 비해 산출물의 과소사용에 그 원인이 있는 것으로 나타났다.

• Journal of Power Electronics
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• 제8권4호
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• pp.309-316
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• 2008

In this paper, new topology is proposed that can dramatically reduce the converter power rating and increase the efficiency of total PV system. Since the output voltage of PV module has very wide voltage range, in general, the DC/DC converter is used to get constant high DC voltage. According to analysis of PV characteristics, in proposed topology, only 20% power of total PV system power is needed for DC/DC converter. DC/DC converter used in proposed topology has flat efficiency curve at all load range and very high efficiency characteristics. The total system efficiency is the product of that of converter and that of inverter. In proposed topology, because the converter efficiency curve is flat all load range, the total system efficiency at the low power range is dramatically improved. The proposed topology is implemented for 200kW PCS system. This system has only three DC/DC converters with 20kW power rating each other. It is only one-third of total system power. The experiment results show that the proposed topology has good performance.

• 대한안전경영과학회:학술대회논문집
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• 대한안전경영과학회 2005년도 춘계학술대회
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• pp.91-96
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• 2005

TPM(Total Productive Management) that is enforcing introducing more than $80\%$ in domestic manufacturing industry is using total plant efficiency by the evaluation index, and as a result, can see a lot of examples that plant productivity is increased. This study's purpose centers total productive management activities that is management system for total plant efficiency's maximization, plant information system that total productive management activities factor that is enforcing in manufacturing industry can develop evaluation model that can evaluate qualitative activities by quantitative activities in process that maximize total plant efficiency wishes to do design.