• Journal of the Korean Society of Safety
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• v.32 no.5
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• pp.141-148
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• 2017

Over the past 30 years, the business effects of the improvement project at black spot have been decreasing since 2010, with a reduction in the amount of government spending, coupled with proposing a uniform improvement plan. In order to promote more efficient improvement projects, it is necessary to evaluate the efficiency of local governments and improve the business methods of local governments with low efficiency. However, more sophisticated efficiency analysis methods are needed. Because in previous studies have been limited to the analysis of effects before and after the project through the simple before-after analysis. For this purpose, this study analyzed the efficiency of improvement project at black spot by local governments in Gyeonggi-do using DEA to compare and analyze efficiency in various fields. As a result, Goyang, Seongnam, Paju, Hanam and Yangju showed high efficiency local governments. For local governmetns with low efficiency, the improvement projets to improve efficiency were divided into civil engineering work, structure work, pavement work, additional work and transportation work, and the appropriate construction ratios of each local government were analyzed and presented.

• Proceedings of the KIEE Conference
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• 2006.04b
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• pp.143-145
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• 2006

In this paper, single phase induction motor achieved improvement in efficiency by adapting the condition of Balanced operation and Quasi-balanced operation. Also, the process of efficiency improvement to find the optimum point of secondary resistance and running capacitor for working single phase induction motor is performed in order to attain the conclusion to put out the maximum efficiency at the rated operation point with meeting the starting torque.

• Journal of the Korean Operations Research and Management Science Society
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• v.41 no.1
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• pp.127-143
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• 2016

This study applied DEA analysis to measure the relative efficiency of 35 companies that produce automobile body components. First, the input and output, the improvement target value of the calculated variables, and the reference group for benchmarking for inefficient groups to become efficient groups were established through DEA analysis. In addition, whether inefficiency was due to technical inefficiency or size was analyzed in connection with the cases of the actual companies through the measurement of scale efficiency. Second, a route for efficiency improvement was derived through DEA-Tier analysis by defining the possible group for benchmarking in actuality within the production industry of automobile body components where the primary cooperative company belonged. Third, the financial variables that generate the difference between efficient and inefficient groups were derived through logistic regression analysis. Financial strategies that determine the direction the indices should be improved to allow the inefficient group to become an efficient one were recommended. This research is expected to provide diagnostic methods for management efficiency and the direction of improvement to enhance the management efficiency of automotive parts makers by identifying the causes of the inefficiency of domestic automotive parts makers empirically. The study also provides financial strategies together with the target values of efficiency improvement for each individual company.

• Environmental and Resource Economics Review
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• v.9 no.5
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• pp.811-827
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• 2000

Since improved thermal efficiency reduces capacity requirements and energy costs, electricity producers often treat thermal efficiency as a measure of management or economic performance. The conventional measure of the thermal efficiency of a fossil-fuel generation system is the ratio of total electricity generation to the simple sum of energy inputs. As a refined approach, we present a novel thermal efficiency measure using the concept of the Divisia index number. Application of this approach to the Korean power sector shows improvement of thermal efficiency of 1.1% per year during 1970-1998. This is higher than the 0.9% improvement per year given by the conventional method. The difference is attributable to the effect of fuel substitution. In the Divisia decomposition context, we also show the limitations of the popular $T{\ddot{o}}rnqvist$ index formula and the superiority of the Sato-Vartia formula.

• ETRI Journal
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• v.35 no.2
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• pp.188-192
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• 2013

Previous work proposed combining multipulse pulse position modulation (MPPM) with pulse amplitude modulation to form multipulse amplitude and position modulation (MPAPM), which is a hybrid modulation that results in an improvement in bandwidth efficiency but a degradation in power efficiency. In this paper, to achieve greater power efficiency and a better data rate, we propose multipulse dual amplitude-width modulation, based on MPAPM and pulse width modulation. The proposed scheme shows a remarkable improvement in data rate and a 1.5-dB improvement in power efficiency over MPAPM, while sustaining the bandwidth efficiency. After introducing symbol structure, we present the theoretical expressions of spectral efficiency, the power requirements, and the normalized data rate, as well as the results of comparing the proposed modulation to MPPM and MPAPM.

• Journal of Environmental Science International
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• v.27 no.2
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• pp.99-107
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• 2018

In order to design the improvement process for T-N removal, the treatment process of Suyoung, Gangbyeon, and Noxan sewage treatment plants (STP) in Busan was anlayzed. Suyoung STP shows a T-N removal efficiency of about 69.8% with MLE(Modified Ludzack ettinger) and A2O+MBR. However, it is necessary to improve the process to maintain over DO of 1 mg/L and is required to install a flow control tank to minimize the rainfall effect. Gangbyun STP shows a about 70.2% T-N removal efficiency with A2O+GFF(gravity fiber filtration). However, in order to improve T-N removal efficiency, it is needed to install MLE process to treat recycle water. Noksan STP shows a T-N removal efficiency of about 71.0% with MLE+Chemical treatment and shows stable T-N concentration in effluent. However, it is required a toxic chemical management process because bad wastewater flows into the STP, also is necessary a process improvement in order to increase internal recycling ratio. Especially, it is required a process improvement to increase HRT of nitrification tank because Suyoung and Gangbyeon STPs shows low nitrification efficiency during winter season.

• Journal of the Korean Solar Energy Society
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• v.39 no.2
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• pp.45-55
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• 2019

More than 76% of the detached houses in Korea are over 20 years old. These old detached houses have poor energy efficiency. According to the 2017 Housing Census (Statistics Korea), more than 50% of low-income families live in detached houses. Therefore, the improvement of energy efficiency in old detached houses is needed from the viewpoint of energy welfare. The general method of building energy modelling for the verification of energy efficiency is based on the construction year data of "Building Design Criteria for Energy Saving" due to the cost and time involved in collecting the thermal performance data of buildings. There is poor accuracy with the deterioration of long-term aging of building materials. Also, the selection of alternatives for energy performance improvement is based on the items to be applied, not a performance improvement goal. It is difficult to calculate energy performance that reflects variations in various parameters with dynamic energy simulations. In this study, the influence of long-term aging is used to accurately predict the energy performance of old detached houses. The building energy modelling method is called ENERGY#, which is a static analysis method based on ISO13790. Energy performance is evaluated by a combination of input variables including building orientation, insulation of walls and roof, thermal performance of windows and window/wall ratio, and infiltration rate. Finally, this study provides a way to determine alternatives that meet energy performance improvement goals.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.55 no.4
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• pp.216-223
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• 2006

In this paper, a methodology for the efficiency improvement of the photovoltaic system without adding some elements or increasing the cost comparing with the conventional system is discussed. It is suggested the optimal photovoltaic module configuration through its performance analysis, and also the suitable maximum power point tracking (MPPT) voltage considered the system cost and the efficiency of the converter. The high efficiency photovoltaic system by using the parallel power transfer (PPT) based MPPT converter is proposed and analyzed theoretically comparing with the conventional Buck type MPPT converter. Finally, it is designed and implemented the proposed photovoltaic system for supplying DC 48V by using the PPT based MPPT converter. And the effect of the efficiency improvement and the usefulness of the proposed system is proved through some preliminary simulation and experiment results.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.65 no.1
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• pp.58-64
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• 2016

In this paper, the design of rotor shape was performed for improvement of start-up characteristics and efficiency in single-phase LSPM. In order to improve the start-up characteristics, shape of rotor aluminium cage bar was changed. Through arrangement of permanent magnets and installation of flux barriers, it was performed torque ripple reduction and efficiency improvement. Cogging torque and back-EMF is calculated by the no-load analysis, start-up time is calculated by the start-up state analysis, efficiency and torque ripple is calculated by steady state analysis. The characteristics of the motor were calculated through FEM.

• JSTS:Journal of Semiconductor Technology and Science
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• v.7 no.4
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• pp.274-280
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• 2007

This paper demonstrates an efficiency improvement of the class E power amplifier (PA) by tuning-out the input capacitance ($C_{IN}$) of the power HBT with a shunt inductance. In order to obtain high output power, the PA needs the large emitter size of a transistor. The larger the emitter size, the higher the parasitic capacitance. The parasitic $C_{IN}$ affects the distortion of the voltage signal at the base node and changes the duty cycle to decrease the PA's efficiency. Adopting the L-C resonance, we obtain a remarkable efficiency improvement of as much as 7%. This PA exhibits output power of 29 dBm and collector efficiency of 71% at 1.9 GHz.