• Korean Journal of Chemical Engineering
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• v.35 no.12
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• pp.2336-2347
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• 2018

The azeotrope of methyl acetate methanol and water was isolated using extractive distillation with water as entrainer. The pressure-swing extractive distillation (PSED) process and vapor side-stream distillation column (VSDC) with the rectifier process were designed to separate the methyl acetate, methanol and water mixture. It was revealed that the VSDC with the rectifier process had a reduction in energy consumption than the PSED process. Four control schemes of the two process were investigated: Double temperature control scheme (CS1), $Q_R/F$ feedforward control of reboiler duty scheme for PESD (CS2), $Q_R/F$ feedback control scheme for VSDC (CS3), the feedback control scheme of sensitive plate temperature of side-drawing distillation column to dominate the compressor shaft speed (CS4). Feed flow and composition disturbance were used to evaluate the dynamic performance. As a result, CS4 is a preferable choice for separation of methyl acetate-methanol-water mixture. A control scheme combining the operating parameters of dynamic equipment with the control indicators of static equipment was proposed in this paper. It means using the sensitive plate temperature of side-drawing column to control the compressor shaft speed. This is a new control scheme for extractive distillation.

• Nuclear Engineering and Technology
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• v.45 no.4
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• pp.553-564
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• 2013

This study evaluates the local damage of a turbine in an auxiliary building of a nuclear power plant due to an external impact by using the LS-DYNA finite element program. The wall of the auxiliary building is SC structure and the material of the SC wall plate is high manganese steel, which has superior ductility and energy absorbance compared to the ordinary steel used for other SC wall plates. The effects of the material of the wall, collision speed, and angle on the magnitude of the local damage were evaluated by local collision analysis. The analysis revealed that the SC wall made of manganese steel had significantly less damage than the SC wall made of ordinary steel. In conclusion, an SC wall made of manganese steel can have higher effective resistance than an SC wall made of ordinary steel against the local collision of an airplane engine or against a turbine impact.

• Geomechanics and Engineering
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• v.14 no.5
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• pp.439-451
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• 2018

The stress path characteristics of surrounding rock in the formation of gob were analysed and the unloading was solved. Taking Chengchao Iron Mine as the engineering background, the model for analysing the instability of deep gob was established based on the mechanism of stress relief in deep mining. The energy evolution law was investigated by introducing the local energy release rate index (LERR), and the energy criterion of instability of surrounding rock was established based on the cusp catastrophe theory. The results showed that the evolution equation of the local energy release energy of the surrounding rock was quartic function with one unknown and the release rate increased gradually during the mining. The calculation results showed that the gob was stable. The LERR per unit volume of the bottom structure was relatively smaller, which mean the stability was better. The LERR distribution showed that there was main energy release in the horizontal direction and energy concentration in the vertical direction which meet the characteristics of deep mining. In summary, this model could effectively calculate the stability of surrounding rock in the formation of gob. The LERR could reflect the dynamic process of energy release, transfer and dissipation which provided an important reference for the study of the stability of deep mined out area.

• Nuclear Engineering and Technology
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• v.46 no.1
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• pp.73-80
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• 2014

A concrete cask is an option for spent nuclear fuel interim storage. A concrete cask usually consists of a metallic canister which confines the spent nuclear fuel assemblies and a concrete overpack. When the overpack undergoes a missile impact, which might be caused by a tornado or an aircraft crash, it should sustain an acceptable level of structural integrity so that its radiation shielding capability and the retrievability of the canister are maintained. A missile impact against a concrete overpack produces two damage modes, local damage and global damage. In conventional approaches [1], those two damage modes are decoupled and evaluated separately. The local damage of concrete is usually evaluated by empirical formulas, while the global damage is evaluated by finite element analysis. However, this decoupled approach may lead to a very conservative estimation of both damages. In this research, finite element analysis with material failure models and element erosion is applied to the evaluation of local and global damage of concrete overpacks under high speed missile impacts. Two types of concrete overpacks with different configurations are considered. The numerical simulation results are compared with test results, and it is shown that the finite element analysis predicts both local and global damage qualitatively well, but the quantitative accuracy of the results are highly dependent on the fine-tuning of material and failure parameters.

• Journal of the Korea institute for structural maintenance and inspection
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• v.23 no.1
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• pp.54-62
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• 2019

In this paper, a stress-strain model for high-strength confined concrete is proposed using compressive fracture energy. In the compression test performed by author in Reference [6], an acrylic bar with strain gauges was embedded in the center of the specimen to measure the local strain distribution. It was found from the test that the local strain measurement by this acrylic rod is very effective. The local fracture zone length was defined based on the local strain distribution measured by the acrylic rod. Specifically, it was defined as the length where the local strain increases more than twice of the strain corresponding to maximum stress. In addition, the stress-strain relationship of confined concrete with compressive fracture energy is proposed on the assumption that the amount of energy absorbed by the compressive members subjected to the given lateral confining pressure is constant regardless of the aspect ratio and size. The proposed model predicts even results from other researchers accurately.

• KCID journal
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• v.17 no.2
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• pp.82-94
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• 2010

Recently, biomass application for energy is getting more interests from many countries since biomass is widely available over the nation wide, whereas fossil fuels are produced in several limited regions. Recognizing the importance, government is promoting renewable energy use in Korea. The locational characteristics of the existing biomass potential directly can be used to decide scale of power plant for local agricultural facility. Although there are a few studies on feasible biomass potential in local areas, it is expected that both government and commercial sectors recognize the potential of biomass energy and the importance of reducing greenhouse gases. When planning biomass energy systems, biomass price is determined by the costs of collection, transportation, chipping, drying if required. In this paper investigates the economic and spatial characteristic of biomass location by land use map. However typical area of each categories in local region is not correct to agricultural census data. Therefore we concerned about how to calculate feasible biomass potential which it can be describing total amount of plant scale, and to match both of data. Even though its spatial distribution, in rural area in Korea, to expand biomass energy programs in the area, government serve to find areas of higher biomass production with suitable locations for plants to convert to bio-energy in order to increase the usage of renewable energy.

• 한국신재생에너지학회:학술대회논문집
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• 2011.11a
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• pp.81.1-81.1
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• 2011

High temperature proton exchange membrane fuel cell (HT-PEMFC) has been regarded as a promising clean energy sources. In this study, a quasi-three-dimensional dynamic model of HT-PEMFC has been developed and the local dynamic characteristics are investigated. The model has the geometrical simplification of 2+1D reduction (quasi-3D). The one-dimensional model consists of nine control volumes in cross-sectional direction to solve the energy conservation and the species conservation equations. Then, the one-dimensional model is discretized into 25 local sections along the gas flow direction to account for gas and thermal transport in channels. With this discretization, the local characteristics of HT-PEMFC such as species conservation, temperature, and current density can be captured. In order to study the basic characteristics of HT-PEMFC, it is important to investigate the local dynamic characteristics. Thus, the model is simulated at various operating conditions and the local dynamic characteristics related to them are observed. The model is useful to investigate the distribution of HT-PEMFC characteristics and the physical phenomena in HT-PEMFC.

• The Korean Journal of Ecology
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• v.26 no.4
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• pp.199-202
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• 2003

According to the energy hypothesis, the energy input per unit area primarily determines species richness in regions of roughly equal area. Some energy-related ecological research included identification of major climatic variables to determine regional species richness. In this study, the local butterfly species richness was examined to find out whether weather variables affected the local distribution or abundance of butterfly populations. Butterfly monitoring data from May 2001 to April 2002 taken at Mt. Yudal, Mokpo, in the southwestern part of Korea, and six weather variables (monthly mean values of temperature, precipitation, evaporation, wind speed, air pressure, and sunlight) were analyzed. Multiple regression analysis showed that only temperature explained 80% and 70% of the variability of log-transformed number of species and individuals, respectively, indicating that temperature played an important role in local species richness. Furthermore, global warming could affect the abundance and distribution of butterflies regionally as well as locally.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.28 no.6
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• pp.791-798
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• 2004

Fatigue crack initiation lives of round cylindrical notch specimen were investigated. Firstly, local strain approximation methods, such as the modified incremental Neuber's rule and the modified incremental Glinka's equivalent strain energy density(ESED) rule, were used to get multiaxial stress and strain state components at the notch tip. Based on the history of local stress and strain, multiaxial fatigue models were used to obtain fatigue crack initiation lives. Because the solution of Neuber's rule and Glinka's ESED rule make the upper and lower bound of local strain approximations, fatigue crack initiation lives are expected to place between life predictions by two local strain approximations. Experimental data were compared with the fatigue crack initiation life prediction results.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.5 no.4
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• pp.626-648
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• 2011

Energy consumption of wireless access networks is in permanent increase, which necessitates development of more energy-efficient network management approaches. Such management schemes must result with adaptation of network energy consumption in accordance with daily variations in user activity. In this paper, we consider possible energy savings of wireless local area networks (WLANs) through development of a few integer linear programming (ILP) models. Effectiveness of ILP models providing energy-efficient management of network resources have been tested on several WLAN instances of different sizes. To cope with the problem of high computational time characteristic for some ILP models, we further develop several heuristic algorithms that are based on greedy methods and local search. Although heuristics obtains somewhat higher results of energy consumption in comparison with the ones of corresponding ILP models, heuristic algorithms ensures minimization of network energy consumption in an amount of time that is acceptable for practical implementations. This confirms that network management algorithms will play a significant role in practical realization of future energy-efficient network management systems.