• Journal of Digital Convergence
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• v.20 no.4
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• pp.529-539
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• 2022

This study analyzed the index change in efficiency and productivity for the tax reorganization project of the regional headquarters of Korea Asset Management Corporation using panel data for 3 years from 2017 to 2019 using the DEA-Malmquist analysis model. According to the DEA analysis result, the average of the efficiency by the CCR model of the regional headquarters tax reorganization project of the Korea Asset Management Corporation was 0.671 in 2017, 0.772 in 2018, and 0.699 in 2019, and the average of the efficiency by the BCC model was 0.798 in 2017, 0.851 in 2018 and 0.771 in 2019. As a result of analyzing the Malmquist productivity index, the time series average productivity index MPI increased by 4.5%. These results appear to be attributable to the increase in technological efficiency, technological change, and scale-efficiency change rather than the decrease in net efficiency change. Looking at the change in MPI by year, it decreased by 14.6% in 2017-2018, but increased significantly to 27.8% in 2018-2019. Through the results of DEA analysis of specific tax projects of public corporations, each regional headquarters of Korea Asset Management Corporation will be able to contribute to reinforcing business capabilities through mutual benchmarking.

• Journal of Korea Water Resources Association
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• v.52 no.2
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• pp.107-113
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• 2019

The flood forecasting model currently used in Korea calculates the runoff of basin using the lumped rainfall-runoff model and estimates the river level using the river and reservoir routing models. The lumped model assumes homogeneous drainage zones in the basin. Therefore, it can not consider various spatial characteristics in the basin. In addition, the rainfall data used in lumped model also has the same limitation because of using the point scale rainfall data. To overcome the limitations as mentioned above, many researchers have studied to apply the distributed rainfall-runoff model to flood forecasting system. In this study, to apply the Grid-based Rainfall-Runoff Model (GRM) to the Korean flood forecasting system, the optimal resolution is determined by analyzing the difference of the results of the runoff according to the various resolutions. If the grid size is to small, the computation time becomes excessive and it is not suitable for applying to the flood forecasting model. Even if the grid size is too large, it does not fit the purpose of analyzing the spatial distribution by applying the distributed model. As a result of this study, the optimal resolution which satisfies the accuracy of the bsin runoff prediction and the calculation speed suitable for the flood forecasting was proposed. The accuracy of the runoff prediction was analyzed by comparing the Nash-Sutcliffe model efficiency coefficient (NSE). The optimal resolution estimated from this study will be used as basic data for applying the distributed rainfall-runoff model to the flood forecasting system.

• International Journal of Air-Conditioning and Refrigeration
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• v.12 no.1
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• pp.37-49
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• 2004

Four different data reduction methods for the heat transfer coefficients from experimental data under dehumidifying conditions are compared. The four methods consist of two heat and mass transfer models and two fin efficiency models. Data are obtained from two heat exchanger samples having plain fins or wave fins. Comparison of the reduced heat transfer coefficients revealed that the single potential heat and mass transfer model yielded the humidity-independent heat transfer coefficients. Two fin efficiency models-enthalpy model and humidity model-yielded approximately the same fin efficiencies, and accordingly approximately the same heat transfer coefficients. The heat transfer coefficients under wet conditions were approximately the same as those of the dry conditions for the plain fin configuration. For the wave fin configuration, however, wet surface heat transfer coefficients were approximately 12% higher. The pressure drops of the wet surface were 10% to 45% larger than those of the dry surface.

• Transactions of the Korean Society of Automotive Engineers
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• v.9 no.1
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• pp.163-170
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• 2001

In this paper, a massless link model transmitting external forces is developed to achieve the numerical efficiency in simulation of vehicle suspension systems. Forces acting on links are resolved and transmitted to attached points with a quasi-static assumption. Also, a theoretical derivation and computer implementation of a massless link with bushing elements are proposed. In the massless link with bushing elements, one end is connected to the adjacent body with bushings and the other end is connected with a spherical joint. The deformation of a massless link with bushing elements is theoretically determined by minimizing the potential energy function with quasi-static equilibrium assumption at each time step. Several simulations with a full vehicle model are carried out to compare the efficiency of the developed massless link component. From the results, it is concluded that the proposed approach can reduce the computational time considerably.

• Korean System Dynamics Review
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• v.15 no.2
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• pp.27-50
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• 2014

Korea government established the energy technology development plan (2011-2020) and declared to be a leader of the green energy technologies. The plan aims for 10% market share in the green energy industry, 12% energy efficiency improvement, and 15% greenhouse gas reduction. In order to achieve these goals, the government has tried to calculate the whole scale of national energy R&D investment, annual budget and specific expenditures for new technologies by computer simulation. The simulation modules include the R&D investment model, GDP model, energy consumption and $CO_2$ emission model by System Dynamics. Based on these simulation modules, I tested various scenarios for effectiveness of energy R&D investments until 2020. The results show that Korea should increase national energy R&D investment to 2.3 billion U.S. dollars, and switch the investment from electricity and nuclear power to the renewable energy.

• Asia pacific journal of information systems
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• v.20 no.2
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• pp.87-101
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• 2010

Software as a service (SaaS) is one of the most-talked about trends in IT. Unlike traditional perpetual licensing model, software applications are sold on subscription bases and services are provided over web by the vendors. It is said that SaaS can make vendors to invest more on R&D than on marketing while offering its customers better quality software applications at lower costs. By empirically comparing vendors providing their software applications either by SaaS or by traditional perpetual licensing model, we examine whether or not SaaS really increases overall customer benefits in terms of cost efficiency, software quality, and customization. We show that SaaS may not provide better quality or cost efficient software applications than perpetual licensing does. Then we provide two practical tools which are useful for customers to evaluate whether SaaS is better than perpetual licensing for the purposes of software applications they want to adopt.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.5 no.2
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• pp.226-240
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• 1995

This research has a purpose to achieve experimental data used for design of ventilation systems necessary for indoor air quality control and their operation and management. For the study, spatial concentration distribution of indoor air quality according to pollutant site in a simplified model chamber. In low flow ventilation, flow pattern of indoor air was mainly influenced by diffusion and additionally, spatial distribution was formed by convection. Distribution of ventilation efficiency according to each pattern of model chamber was evaluated. It was confirmed that diffusion patterns of a pollutant among sites were formed, centering around main stream areas of supply and exhaust outlets.

• Journal of Korean Society for Atmospheric Environment
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• v.2 no.1
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• pp.91-101
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• 1986

Relations of each factor affected by emissions and the prediction of performance have been analyzed numerically by cycle simulation in the Spark Ignition Engine. Through theoretical analysis and experiments, the results are obtained as below. The calculated results and the experimental ones are almost highly agreeable on cycle simulation model, exhaust gas analysis and efficiency for processes in cylinder. Therefore this model is proved appropriate and can be useful for optimum design of Spark Ignition Engines on parametric studies. It is reaffirmed that the Wiebe's function is suitable for predicting Combustion Ration in Spark Ignition Engines. On parametric studies, it is found that optimum conditions whose density of emissions are lower and efficiency is maximum within propriety value are crankangle ATDC $15^\circ-20^\circ$, 2400 rpm. A/F=16 in this experiment.

• Transactions of the Korean Society of Automotive Engineers
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• v.5 no.4
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• pp.179-189
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• 1997

Among aftertreatment devices which reduce exhaust gas of diesel engine, diesel oxidation catalyst(DOC) with high reduction efficiency for gaseous matter and particulate matter is now studied actively. In this study, a transient one-dimensional model developed to simulate the thermal and conversion characteristics of adiabatic monolithic converters operating under warm up conditions is presented. This model takes into account the gas solid heat and mass transfer, axial heat conduction, chemical reactions and the related heat release. The model has been used to analyze the transient response of an axisymmetric catalytic converter during a warm-up as a function of catalyst design parameters and operation conditions in order to observe their effects on the lightoff behaviour. The experimental test was carried out 2400 cc light diesel engine with DOC.

• Membrane and Water Treatment
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• v.5 no.1
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• pp.57-71
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• 2014

In this study, a theoretical model for the transport phenomena in an Air Gap Membrane Distillation used for desalination was developed. The model is based on the conservation equations for the mass, momentum, energy and species within the feed water solution as well as on the mass and energy balances on the membrane sides. The rarefaction impacts are taken into consideration showing their effects on process parameters particularly permeate flow and thermal efficiency. The theoretical model was validated with available data and was found in good agreement especially when the slip condition is introduced. The rarefaction impact was found considerable inducing an increase in the permeate flux and the thermal efficiency.