• Environmental and Resource Economics Review
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• v.30 no.4
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• pp.581-605
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• 2021

The purpose of this study is to provide basic data for improving energy efficiency by estimating the regional energy efficiency in Korea using the stochastic frontier approach beyond the energy intensity that has been traditionally used as an indicator of energy efficiency. In this paper, energy efficiency and energy intensity efficiency were estimated as a stochastic distance function from 1998 to 2018 for 16 cities and provinces in Korea. In addition, the robustness of energy efficiency according to the capital stock estimation methods which had been mixed in previous studies was reviewed. As a result of the analysis, there is a significant change in regional rankings according to the three energy efficiency indicators, so they should be used complementary to each other. Second, while the energy efficiency improved little by little over time, the energy intensity efficiency decreased slightly though. Lastly, energy efficiency by region according to the capital stock estimation method was not robust. Care must be taken in estimating capital stock, which is important in economic analysis.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.17 no.1
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• pp.21-31
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• 2005

In this study, derivation is made of a one-grid source function for the extended Boussinesq equations of Nwogu (1993) in order to generate nonlinear waves internally. The energy velocity approach used in the line source method is verified analytically by the fractional step splitting method. The source function method is verified by generating accurately nonlinear waves as well as linear waves for horizontally one-dimensional cases. It is found that numerical solutions by the source function method are the same as those by the line source method.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1996.11a
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• pp.169-174
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• 1996

In this paper, the electron transport characteristic in CF$_4$has been analysed over the E/N range 1~300(Td) by a two-term approximation Boltzmann equation method and by a Monte Carlo simulation. The alteration of cross sections from the literature is avoided as much as possible in the analysis. The motion has been calculated to give swarm parameters for the electron drift velocity(W), diffusion coefficient(D$_{L}$), the ratio of the diffusion coefficient to the mobility(D$_{L}$/$\mu$), mean energy($\varepsilon$), the electron energy distribution function. The electron energy distribution function has been analysed in CF$_4$at E/N=50, 100 and 200(Td) for a case of the equilibrium region in the mean electron energy. The results of Boltzmann equation and Monte Carlo simulation have been compared with experimental data by Y. Nakamura and M. Hayashi.shi.

• Journal of the Korean Solar Energy Society
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• v.21 no.1
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• pp.51-60
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• 2001

Underground space gives two benifits to us. First, it helps us to solve the land scarcity problem in urban city. Second it also helps us to manage the thermal properties of underground to keep cool in summer and warm in winter. How much it save energy depends on the ability to predict the exact temperature of the space. The purpose of this paper is to make a function predicting the temperature of underground space, analysing the 20 years measures of underground temperature kept in Korea Central Weather Burea.

• Journal of the Korean Society for Precision Engineering
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• v.27 no.1
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• pp.76-83
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• 2010

There have been many studies regarding development of autonomous excavation system which is helpful in construction sites where repetitive jobs are necessary. Unfortunately, bucket trajectory planning was excluded from the previous studies. Since, the best use of excavator is to dig efficiently; purpose of this research was set to determine an optimized bucket trajectory in order to get best digging performance. Among infinite ways of digging any given path, criterion for either optimal or efficient bucket moves is required to be established. One method is to adopt work know-how from experienced excavator operator; However the work pattern varies from every worker to worker and it is hard to be analyzed. Thus, other than the work pattern taken from experienced operator, we developed an efficiency model to solve this problem. This paper presents a method to derive a bucket trajectory from optimization theory with empirical CLUB soil model. Path is greatly influenced by physical constraints such as geometry, excavator dimension and excavator workspace. By minimizing a energy function under these constraints, an optimal bucket trajectory could be obtained.

• Korean Journal of Cognitive Science
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• v.8 no.4
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• pp.55-62
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• 1997

We proposed a method for locating of mouth using deformable templates, described by a parameterized template. An energy function is defined which links, edges, peaks, valleys in image intensity to corresponding properties of the template. The template deforms itself by altering its parameter values to minimize the energy function. The minimized energy function's parameter values can be used as descriptors for the feature. We propose a method for locating mouth fast, accurately by limiting a range of parameters' value and getting initial value of parameters' by preprocessing.

• Nuclear Engineering and Technology
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• v.33 no.5
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• pp.547-555
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• 2001

In pressurized light water reactor fuel assembly, spacer grids support nuclear fuel rods both laterally and vertically. The fuel rods are supported by spacer grid springs and grid dimples that are located in the grid cell. The support system allows for some thermal expansion and imbalance of the fuel rods. The imbalance is absorbed by elastic energy to prevent coolant flow- induced vibration damage. Design requirements are defined and a design process is established. The design process includes mathematical optimization as well as practical design method. The shape of the grid spring is designed to maintain its function during the lifetime of the fuel assembly. A structural optimization method is employed for the shape design. Since the optimization is carried out in the linear range of finite element analysis, the optimum solution is verified by nonlinear analysis. A good design is found and the final design is compared with the initial conceptual design. Commercial codes are utilized for structural analysis and optimization.

• Journal of the Korean Society for Precision Engineering
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• v.12 no.2
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• pp.14-22
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• 1995

We treat the vibrations of circular beam and make use of the method employed by J.T.Tielking, which is based on the principle of Hamilton. The Hamilton's principle requires the determinations of the potential and the kinetic energy of the model as well as done by internal pressure forces. Thje potential energy is composed of a part due to elastic deformations of the beam and a part due to radial and tangential displacements of the tread band with respect to the wheel rim. The equations of motion for such a model are derived by reference to conventional energy method. The accuracy of the expressions is demonstrated by comparison of calculated and experimental natural frequencies for circular beam. The circular beam experiences a harmonic, radial excitat- ion acting at a fixed point on the beam. Modal parameters varying the inflation pressure and load are determined experimentally by using the transfer function method.

• Proceedings of the KSR Conference
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• 2009.05a
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• pp.247-250
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• 2009

Awareness of resource conservation and pollution prevention has been continually increasing. The proven benefits from CFRP's unique combination of light weight and high strength compare to conventional material is well suited for minimizing fuel consumption during vehicle in particular rail operation. Responding the awareness, this work intends to study CFRP's recycling method that is not only technical performance but also environmental view point. According to prior work of technical performance test, this work aims at quantifying the footprint of energy and GHG derived from the two appreciated performance of pyrolysis and acids recycling methods. The streamline LCA is the concept for systematic assessment. The boundary is scoped at the recycling activity, consequently, the data in and out from the specific target activity are obtained under the gate to gate data collection. Its function is recovery carbon fiber. To count and compare function, functional unit is set at 60% of recycling rate. Korea database is mainly source for acquiring the footprint of both. The numerical results presented that the energy footprint of acids and pyrolysis is 164.95 and 1,199.88 MJ-eq., respectively. Meantime, the GHG footprint of is 1,196.22 and 5,916.08 g CO2 eq. for acids and pyrolysis. In summary, the acids recycling method is, in regarding the environmental performance, better than pyrolysis recycling method.

• Proceedings of the KIEE Conference
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• 1999.07c
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• pp.1239-1241
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• 1999

In this paper, we propose real time transient stability assessment and energy margin estimation using fuzzy approximate reasoning. The proposed method used rotor angle, kinetic energy and acceleration power of generators at clearing time as fuzzy input. In order to calculate energy margin in transient energy function (TEF), we obtained controlling unstable equilibrium point (UEP) using mode of disturbance procedure (MOD). The proposed algorithm is tested on 4-machine, 6-bus, 7-line power system to prove of effectiveness.