• Journal of Korean Society for Atmospheric Environment
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• v.17 no.3
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• pp.259-268
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• 2001

In this study, we have developed a simulation method to predict the initial collection efficiency of a unipolar charged fiber in the electret filters. The particle sizes considered were in the submicron range and thus Brownian motion of particles was also taken into consideration along with electrostatic forces acting on the particles. The simulation results were compared with other investigators experimental data on single fiber efficiency as well as with the calculated results using the existing correlations on single fiber efficiency. It has been shown that simulation results are in good agreement both with the experimental data with those predicted by the correlations.

• Journal of Advanced Marine Engineering and Technology
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• v.23 no.3
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• pp.405-411
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• 1999

Dynamic effect of gas in exhaust manifold influences the volumetric efficiency of the engine. Especially in case of multi-cylinder engine the shape of exhaust manifold is important for the opti-mum design of exhasut manifold complicated. In this paper the effects of exhaust manifold systems on volumetric efficiency were investigated for the 4 cylinder 4 stroke-cycle diesel engine. Volumetric efficiency was calculated by the method of characteristics. The calculation results coincided well the test results. This study showed that the appropriate position and diameter of exhaust manifold branch are important factors in increasing volumetric efficiency and decreasing pumping loss.

• Transactions of the Korean Society of Automotive Engineers
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• v.4 no.3
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• pp.232-242
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• 1996

In this study, the simulation program for the prediction of volumetric efficiency of the internal combustion engine by the resonator has been developed, when the resonator is mounted on the intake system of 4-cycle SI engines for the improvement of volumetric efficiency. The experimental work has also been carried out for the verification of the program, and it is found that the result of calculation by the simulation program fits qualitatively well with that of experiment. To get the optimal mounting position of resonator on the intake system, the influence of the variation of dimensions of resonator such as neck length, volume and neck diameter were examined by the numerical calculation of the program in advance and the results were compared with the experiments. It is found that the position which is departed 150cm from plenum chamber is better than any other positions, and the average amount of the increase of volumetric efficiency is about 2∼3%

• Transactions of the Korean Society of Automotive Engineers
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• v.5 no.2
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• pp.69-79
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• 1997

This paper deals with the measurement and analysis on the scavenging performance of the oppet-valve type two-stroke engine with different shroud system. The scavenging flow characteristics is investigated by flow visualization under steady condition, in which a dye is introduced into single-cycle method using the difference of specific gravity between two working fluids is used to evaluate the scavenging efficiency and the trapping efficiency. The 90° shroud system was found to be the highest efficiency system through both flow visualization and single-cycle test, as well as the shroud system to generally be efficient for reducing a short-circuiting flow during scavenging process in a two-stoke engine.

• Journal of the Korean Society of Safety
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• v.16 no.2
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• pp.51-56
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• 2001

This paper is proposed an efficiency optimization control algorithm for a synchronous reluctance motor (SynRM) which minimizes the copper and iron losses. fen exists a variety of combinations of d and q-axis current which provide a specific motor torque. The objective of the efficiency optimization controller is to seek a combination of d and q-axis current components, which provides minimum losses at a certain operating point in steady state. It is shown that the current components which directly govern the torque production have been very well regulated by the efficiency optimization control scheme. The proposed algorithm allows the electromagnetic losses in variable speed and torque drives to be reduced while keeping good torque control dynamics. Simulation results are presented to show the validity of the proposed algorithm.

• International Journal of Advanced Culture Technology
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• v.6 no.4
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• pp.292-302
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• 2018

This study proposes a Bayesian stochastic frontier model that is well-suited to productivity/efficiency analysis particularly using panel data. A unique feature of our proposal is that both production frontier and efficiency are estimable for each individual firm and their linkage to various firm characteristics enriches our understanding of the source of productivity/efficiency. Empirical application of the proposed analysis to Human Capital Corporate Panel data enables identification and quantification of the effects of Human Resource factors on firm efficiency in tandem with those of firm types on production frontier. A comprehensive description of the Markov Chain Monte Carlo estimation procedure is forwarded to facilitate the use of our proposed stochastic frontier analysis.

• Journal of Information Technology Services
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• v.18 no.1
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• pp.79-90
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• 2019

Maximizing energy efficiency minimizes the energy consumption of computation, storage and communications required for IT services, resulting in economic and environmental benefits. Recent advancement of flash and next generation non-volatile memory technology and price decrease of those memories have led to the rise of so-called AFA (All-Flash Array) storage devices made of flash or next generation non-volatile memory. Currently, the AFA devices are rapidly replacing traditional storages in the high-performance servers due to their fast input/output characteristics. However, it is not well known how effective the energy efficiency of the AFA devices in the real world. This paper shows input/output performance and power consumption of the AFA devices measured on the Linux XFS file system via experiments and discusses energy efficiency of the AFA devices in the real world.

• Journal of Korea Port Economic Association
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• v.18 no.1
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• pp.3-26
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• 2002

The purpose of this paper is to Investigate the productive efficiency and competitive strength of world container ports using the DEA, Super-efficiency, and FDH methods with the raw data from previous research by Jun et al.(1993). The super-efficiency measure examines the maximal radial change In input, outputs for an observation to remain efficient. Therefore, it provides a means of distinguishing between efficient observations, which would otherwise seem identical. FDH provides a good test mechanism for examining the practical implications of the choice available among alternative efficiency measures and orientations, because of the lack of convexity of its production possibility set. Both methods are complementary to DEA. This paper follows the traditional productivity analysis method overcoming the limitation of previous studies by using the DEA, FDH and Super-efficiency methods, and proposing in measure the relative competitive strength of worldwide container ports. The main empirical results of this paper are as follows: Firstly the ports of Singapore, Hongkong, Kilrung, Busan, Tokyo. and Longbeach were found to be efficient In the CCR model. The ports of Felixstowe, Bangkok, Singapore, Hongkong, Kilung, Busan, Tokyo, and Longbeach were found to be efficient in the BCC model. Secondly, super. efficiency rankings under CRS and input-oriented model are as follows: Longbeach, Keelung, Singapore, Busan, Tokyo, and Honkong. However, it was difficult In differenciate the rankings under the VRS and input-oriented model. due to major difficulties posed by the ports of Singapore, Hongkong, and Longbeach. Thirdly, the FDH method shows that the inefficient ports are Bremerhaven, Antwerp, Le Havre, Kobe, Seattle, New York The policy Implications of this study are as follows: Firstly, when port authorities want to measure the international competitive strength of container ports and enhance their productive efficiency, they should consider the traditional method as well as introducing the Super-efficiency and FDH methods. Secondly, according to the analysis results of the super-efficiency and FDH methods, poll authorities should recommend benchmarks ports and dominated ports as reference ports in order to enhance the productive efficiency of their container ports that have an efficiency rating of less than 1. Efficient ports whose efficiency ratings are over 1 in the Input-oriented Super-efficiency model should also consider the usage of input and output elements used by more efficient ports.

• Journal of Biosystems Engineering
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• v.26 no.4
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• pp.391-398
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• 2001

A robot system for clone replication and gridding, which is a preliminary state of the genome research, was developed and evaluated its performance. This gridding robot system consisted of 1) a gridding heat that replicated the clone, 2) a manipulator, as a part of body of robot, which transferred the gridding head along x-, y-, z-axis, 3) a well plate arranging board, 4) a sterilization unit, and 5) a control unit. Performance of the system was evaluated with 1) repeatability of the robot system, 2) clone replication efficiency, 3) time requirement of the replication, and 4) sterilization efficiency. The repeatability error of the robot system showed 0.219 mm and 0.094 mm in the direction of x- and y-axis, respectively. The success rate of the clone replication with the gridding head was 100% on the membrane filter. The time required for the replication was four minutes and fifty-five seconds from the four 96 well plates to a 384 well plate meanwhile the required time with well experienced hand labor was three minutes thirty-five seconds. The gridding operation of clone could not be done by hand labor and the required time with robot system for the gridding on the membrance filter with the control program 5$\times$5: 1 copy and 384 gridding pins was twenty minutes and twenty-five seconds. The efficiency of the sterilization was considered to be satisfactory since no growth of fungi was found around the area of replication in the membrane filter.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2004.04a
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• pp.351-356
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• 2004

This study aims to implement an empirical research about the efficiency of container Ports, and to suggest an effective strategy which can operate container Ports more well. This paper presents a new approach to the measurement of efficiency. Data envelopment analysis(DEA), as it is called, has particular applicability in the service sector. This study applies DEA to provide an efficiency measurement for fifty three container ports including Pusan Port. As a result, we suggest several ideas that can improve the efficiency of container terminals. They are as follows. Firstly, we discriminate between efficient and inefficient container ports and then present a method that can move to efficiency container terminal and a benchmarking port. Secondly, we evaluate the efficiency of Pusan port, and grasp the position at the present time, suggest an advanced direction in future.