• 펄프종이기술
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• 제46권5호
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• pp.61-68
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• 2014

The energy efficiency of papermaking process becomes more significant because of various new regulation of the energy consumption and the green house gas emission. In this study, the effects of wood powder addition on the drainage and the drying efficiency of the OCC based paper products, linerboard, were deeply investigated for improving energy efficiency. The fractionation of wood powder depending on the size were conducted. The bigger size of wood powder resulted in the higher bulk and the higher drainage efficiency, but the lower paper strength. The drying efficiency were in detail evaluated depending on the drying process level. In the first section of drying process until the 80% solid level, there were no significant changes in the drying efficiency by the addition of wood powder. However, after the 80 % solid level, the drying efficiency was greatly improved by the addition of wood powder. Those results showed the addition of wood powder could greatly affect not only the drainage in forming and wet pressing but also the drying process.

• 한국입자에어로졸학회지
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• 제15권1호
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• pp.15-25
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• 2019

The influences of corona charging parameters on collection efficiency and surface potential of air filters were investigated. A polypropylene filter medium was electrically charged using a corona charger, and the resulting surface potential and filtration efficiency against neutralized KCl particles were measured. The filter media was charged under different conditions of applied voltage, voltage polarity, charging time, and distance between electrodes. In addition, we considered charging both sides of the filter as well as charging one side of the filter. As a result, electrical force obtained by charged fiber affected filtration efficiency when the apply voltage strength was higher than 7 kV. Negatively charged filter had higher filtration efficiency than positively charged filter while the surface potential of the negatively charged filter was slightly lower than those of positively charged filter. Moreover, the filtration efficiency increased as the charging time of filter fiber increased and the distance between electrodes decreased. The filtration efficiency was more sensitive to changes of charging time than to those of electrode distance, and the efficiency of both sides charged filter was higher than that of single side charged filter.

• 산업경영시스템학회지
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• 제41권4호
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• pp.81-90
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• 2018

Modern investment theory has empirically proved that stock returns can be explained by several factors such as market risk, firm size, and book-to-market ratio. Other unknown factors affecting stock returns are also believed to still exist yet to be found. We believe that one of such factors is the operational efficiency of firms in transforming inputs to outputs, considering the fact that operations is a fundamental and primary function of any type of businesses. To support this belief, this study intends to empirically study the relationship between firm efficiency and stock price performance. Firm efficiency is measured using data envelopment analysis (DEA) with inputs and outputs obtained from financial statements. We employ cross-efficiency evaluation to enhance the discrimination power of DEA with a secondary objective function of aggressive formulation. Using the CAPM-based performance regression model, we test the performance of equally weighted portfolios of different sizes selected based upon DEA cross-efficiency scores along with a buy & hold trading strategy. For the empirical test, we collect financial data of domestic firms listed in KOSPI over the period of 2000~2016 from well-known financial databases. As a result, we find that the porfolios with highly efficient firms included outperform the benchmark market portfolio after controlling for the market risk, which indicates that firm efficiency plays a important role in explaining stock returns.

• 반도체디스플레이기술학회지
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• 제19권4호
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• pp.99-104
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• 2020

In this paper, efficiency and loss characteristics of GaN FET were reported by applying it into the QR flyback converter. In particular, for the comparison of efficiency characteristics, QR flyback converter experimental circuits with Si FET and with GaN FET were separately produced in 12W class. As a result of the experiment, the experimental circuit of the QR flyback converter using GaN FET reached a high efficiency of 90% or more when the load power was 2W or more, and the maximum efficiency was observed to be about 92%, and the maximum loss power was about 1.1W. Meanwhile, the efficiency of the experimental circuit with Si FET increased as the input voltage increased, and the maximum efficiency was observed to be about 82% when the load power was 9W or higher, and the maximum loss power was about 2.8W. From the results, it is estimated that that in the case of the experimental circuit applying the GaN FET switch, the power conversion efficiency was improved as the switching loss and conduction loss due to on-resistance were reduced, and the internal loss due to the synchronous rectifier was minimized. Consequently, it is concluded that the GaN FET is suitable for under 20W class power supply unit as a high efficiency power switch.

• 융합경영연구
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• 제9권3호
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• pp.11-21
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• 2021

Purpose: The purpose of this study is to understand the status quo of production efficiency in private industrial enterprises above designated scale in China's 31 provinces (including municipalities directly under the central government, autonomous regions) (hereinafter referred to as China's 31 provinces). Research design, data and methodology: Find out the factors affecting the development of production efficiency in private industrial enterprises, using DEA, Data Envelopment Analysis and Malmquist index analysis, build the evaluation model of production efficiency in private industrial enterprises, and analyze the data of China's 31 provinces private industrial enterprises in 2015-2019. Results: The research results show that the production efficiency of private industrial enterprises in China is improving on the whole. Although the total factor productivity has decreased slightly, the overall efficiency and pure technical efficiency have increased significantly. Conclusions: The conclusion of this study can provide reference for Chinese private industrial enterprises to improve production efficiency and make development plan. The limitation of this paper lies in the fact that the private industrial enterprises in inefficient provinces have not been given specific improvement plans.

• 동아시아경상학회지
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• 제9권1호
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• pp.41-51
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• 2021

Purpose - The purpose of this study is to propose strategies of improving efficiency of 20 listed port companies in China based on analysis of their input-output indexes from 2014 to 2018. Research design, data, and methodology - In this paper, the relevant input-output indicators of 20 listed port companies in China from 2014 to 2018 were adopted. Data derived from the company annual reports announced by Shanghai stock exchange and Shenzhen stock exchange. Comprehensive efficiency and pure technical efficiency were measured from output perspective by DEA and Malmquist index, and efficiency changes and regional efficiency were analyzed. Result - The results showed that the efficiency value of 20 listed port companies in China fluctuated and increased during 2014-2018, regional efficiency was unbalanced, and change of MPI was influenced by internal factors and external factors. Listed port companies affected by internal and external factors needed to make appropriate response to internal and external factors. Conclusion - The research conclusion can provide important reference information about management and planning for port companies in China and related areas. However, this paper is limited to the availability of data. So the improvement scheme for listed companies in inefficient regional ports needs further study, such as using AHP method.

• International journal of advanced smart convergence
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• 제10권1호
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• pp.24-37
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• 2021

China's "One Belt and One Road" initiative has brought multiple opportunities to the development of tourism in Guangdong, Guangxi and Hainan provinces and the implementation of the Beibu Gulf Urban Agglomeration Development Plan hasset clear goalsforfurther accelerating the coordinated development, in-depth cooperation of the three. This study takes the Beibu Gulf Urban Agglomeration as the research object and utilized the data envelopment analysis (DEA) procedure to estimate the technical efficiency, pure technical efficiency, and scale efficiency scores for each city and Malmquist index was subsequently used to analyze dynamically, then tries to offer an adequate inclusion of sustainable factors in overall tourism development efficiency results through the detection and estimation of potential sources of efficiency. In order to complete the task, data collection was focused on Guangdong, Guangxi and Hainan provinces of China over the period from 2016 to 2018. The results in the first phase show relatively high efficiency scores, particularly in the case of the Beibu Gulf Urban Agglomeration and with room for improvement in the case of other cities of Guangdong, Guangxi and Hainan provinces. The second stage results present several aspects that should be carefully considered in order to analysis tourism efficiency of the Beibu Gulf Urban Agglomerations vertically according to the changes of the frontier.

• 한국유기농업학회지
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• 제29권1호
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• pp.41-50
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• 2021

This paper analyzes the efficiency of social enterprises by analyzing bootstrapping data envelopment analysis. Unlike the definitive DEA model, we analyze the confidence intervals of efficiency estimates through the DEA model, which takes into account stochastic factors. Major analysis results are summarized as follows: First, the results of the bootstrapping DEA analysis of social enterprises estimated that the technical efficiency was 0.459 and the 95% confidence interval was 0.389 to 0.601. Second, the number of inefficient social enterprises with efficiency values of less than 0.5 was found to be 15 (55.56%) in technical efficiency, 5 (18.52%) in pure technical efficiency, and 8 (29.63%) in scale efficiency. It can be seen that a significant number of social enterprises are operating in an inefficient state. Third, looking at the returns of scale of social enterprises, 25 (67.57%) are currently in the increasing returns of scale, 10 (27.02%) are in the constant returns of scale, and 2 (5.41%) are in decreasing returns of scale. In other words, it can be seen that social enterprises are under-invested in terms of input factors.

• 한국항공운항학회지
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• 제30권4호
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• pp.23-32
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• 2022

Prototype UAMs are shown to us in the market. When the complete product is delivered to market, the efficiency of each UAMs can be compared by default. Before the complete product is shown to us, the comparative study on efficiency of UAMs is performed under the product cost estimation. The efficiency analysis result reveals that both of Lift & Cruise type and vectored thrust type show good efficiency at the initial stage of product. At the near terms stage, five years later from initial stage end, efficiency gets some change. Vectored thrust type of UAMs show best efficiency at the near term stage of product. Because UAMs will be used in urban area, Seoul is the place where the UAMs will be used first. The flying route from Seoul City Hall to Yongsan Park, National Assembly in Yeouido, and City Airport is no more than 10 km distance. For this short distance route, efficiency will make multi-rotor type UAM be prefered to other types. For long distance route or commuting route, life & cruise type and vectored thrust type of UAMs will be prefered on account of operational efficiency.

• 한국산림과학회지
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• 제103권4호
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• pp.639-645
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• 2014

본 연구는 비모수추정 방법인 자료포락 기법을 이용하여 우리나라 표고버섯 재배 임가를 대상으로 경영효율성을 평가하였다. 조사자료는 2013년 3월부터 10월까지 실시한 '표고버섯 경영 표준진단표' 적용 결과 중에서 20개 임가의 투입요소와 산출요소를 대상으로 하였다. 그리고 DEA 기법중 CCR 모형과 BCC 모형을 이용하여 기술효율성, 순수기술효율성, 규모효율성을 분석하였고 비효율성 임가의 개선방안도 제시하였다. 추가적으로 주업과 겸업재배임가의 경영효율성을 비교 분석하였다. 연구결과, 표고버섯 재배 임가의 전체기술효율성은 평균 0.655로 나타나 전체적으로 비효율성이 높은 것으로 나타났고 비효율성의 원인은 순수기술효율성(0.830)보다는 규모효율성(0.747)에 있는 것으로 분석되었다. 효율성 값이 1인 표고버섯 재배임가는 DMU2, DMU5, DMU6, DMU8, DMU10, DMU15, DMU20으로 7개 임가로 나타났다. 그리고 DMU7 재배임가의 경영효율성 진단 결과, 투입요소 중 신규접종비와 조성비에서 준거집단과 비교해 볼 때 과도하게 투입되고 있는 것으로 분석되었다. 주업과 겸업임가의 효율성 비교 결과 겸업임가가 상대적으로 비효율성이 높은 것으로 나타났고 그 원인으로 규모효율성이 문제가 있는 것으로 파악되었다.