• Journal of Power Electronics
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• 제13권2호
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• pp.313-321
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• 2013

This paper describes the operation analysis results of a communication-based DC micro-grid using a hardware simulator developed in the lab. The developed hardware simulator is composed of distributed generation devices such as wind power, photovoltaic power and fuel cells, and energy storage devices such as super-capacitors and batteries. Whole system monitoring and control was implemented using a personal computer. The power management scheme was implemented in a main controller based on a TMS320F28335 chip. The main controller is connected with the local controller in each of the distributed generator and energy storage devices through the communication link based on a CAN or an IEC61850. The operation analysis results using the developed hardware simulator confirm the ability of the DC micro-grid to supply the electric power to end users.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제3권5호
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• pp.461-474
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• 2009

The cognitive radio (CR) technique is a useful tool for improving spectrum utilization by detecting and using the vacant spectrum bands in which cooperative spectrum sensing is a key element, while avoiding interfering with the primary user. In this paper, we propose a novel cluster-based cooperative spectrum sensing scheme in cognitive radio with two solutions for the purpose of improving in sensing performance. First, for the cluster header, we use the double adaptive energy thresholds and a multi-bit quantization with different quantization interval for improving the cluster performance. Second, in the common receiver, the weighed HALF-voting rule will be applied to achieve a better combination of all cluster decisions into a global decision.

• Bulletin of the Korean Chemical Society
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• 제25권2호
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• pp.260-262
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• 2004

In agreement with the results of previous MP2 calculations by Sauers, B3LYP, CASSCF, and CASPT2 calculations on the parent 2-carbena-1,3-dioxolane show that it fragments to ethylene plus $CO_2$ by a concerted pathway with only a small energy barrier. Not only is fragmentation via stepwise C-O bond cleavage computed to be a much higher energy pathway, but the singlet diradical that would be an intermediate along such a reaction path is not even computed to be a local minimum on the potential energy surface.

• 환경위생공학
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• 제8권1호
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• pp.49-67
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• 1993

Rapid economic development and increase of energy consumption in east Asia including China, Korea and Japan has arisen a concern in air pollution problems in local and regional scale. Specially, China is accomplishing a success in continuous economic growth, while increasing energy consumption has caused a load to air quality because major energy source is coal which is relatively unfavorable in terms of air pollution. In this article, discussions have been given with the purpose of gaining some insight into the situation of air pollutant sources, air quality in China and transboundary transport of air pollutants in this area. Very limited information has caused insufficient survey, however, regional cooperation in environmental conservation may hopefully improve the air quality in this area.

• 한국식품영양학회지
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• 제6권2호
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• pp.115-120
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• 1993

A nutrition survey of 80 high school students in urban dormitories, 17-19 year old, in Jeonbuk province was undertaken in August of 1990, to investigate dietary intake. Total energy intake of male and female was 2,246.0 and 1,584.9 kcal respectively. Energy Intakes from breakfast, lunch and dinner were 553.5, 683.4 and 1,023.0 kcal in male, and 372.9, 391.8 and 820.2 local in female. Protein daily intake of male and female was 95.3 and 62.9g, and carbohydrate intake was 368.1g and 259.6g respectively. Total energy intake of male student was composed of carbohydrate 65%. protein 16.8% and fat 18.2% and that of female was carbohydrate 65.5%, protein 15.9% and fat 18.6% respectively.

• 한국수자원학회:학술대회논문집
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• 한국수자원학회 2005년도 학술발표회 논문집
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• pp.404-408
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• 2005

The Reynolds strss equation with turbulent energy-length scales was simplified in the nearly homogeneous turbulent equilibrium flow and a modified Reynolds stress model was proposed. Tn the model proposed in the present study, Reynolds stresses can be expressed in the form of algebraic equation, so that the turbulent stresses and related quantities are calculated through relatively simple procedures. The model predicted well the turbulent shear stresses of homogeneous flow in local equilibrium state obtained from experimental results published earlier Constants used In the model was determined universally and its validity was discussed briefly.

• 한국원자력학회:학술대회논문집
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• 한국원자력학회 1995년도 추계학술발표회논문집(1)
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• pp.377-382
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• 1995

An evaluation method of spacer grid thermal mixing performance in rod bundles is suggested based on hydraulic tests in a single phase flow. Heat transfer correlation was derived by the analogy between momentum and heat transfer. Three of major factors, such as blockage ratio of spacer grid, convective flow swirling, and turbulent intensity, were found to be significantly influential to the spacer grid thermal mixing performance. Local heat transfer near spacer grid was predicted for the hydraulic test of 6 ${\times}$ 6 rod bundles with neighboring different spacer grids.

• Journal of Mechanical Science and Technology
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• 제18권11호
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• pp.1996-2008
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• 2004

A seamless analysis of material behavior incorporating complex geometry and crack- tip modeling is one of greatly interesting topics in engineering and computational fracture mechanics fields. However, there are still large gaps between the industrial applications and fundamental academic studies due to a time consuming detailed modeling. In order to resolve this problem, a numerical method to calculate an energy release rate by virtual crack closure technique was proposed in this paper. Both free mesh method and finite element method have been utilized and, thereafter, robust local and global elements for various geometries and boundary conditions were generated. A validity of the proposed method has been demonstrated through a series of fracture mechanics analyses without tedious crack-tip meshing.

• 한국안전학회지
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• 제13권4호
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• pp.9-18
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• 1998

The vortex tube is a simple device for separating a compressed gaseous fluid stream into two flows of high and low temperature without any chemical reactions. Recently, vortex tube is widely used to local cooler of industrial equipments and air supply system. The phenomena of energy separation through the vortex tube was investigated experimentally. This study is focused on the effect of the diameter of cold end orifice diameter on the energy separation. The experiment was carried out with various cold end orifice diameter ratio from 0.22 to 0.78 for different input pressure and cold air flow ratio. The experimental results were indicated that there are an optimum diameter of cold end orifice for the best cooling performance. The maximum cold air temperature difference was appeared when the diameter ratio of the cold end orifice was 0.5. The maximum cooling capacity was obtained when the diameter ratio of the cold end orifice was 0.6 and cold air flow ratio was 0.7.

• 조명전기설비학회논문지
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• 제27권6호
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• pp.1-8
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• 2013

In this paper, we proposed a smart lighting management system controls the lighting efficiently to reduce energy consumption while satisfying user's lighting requirements. The proposed system considers the available daylight intensity and indoor light source to satisfy the lighting requirements of each user according to the work environment. In addition, for user convenience, we have developed different user interfaces for lighting control including local interface, and remote interface through internet or Bluetooth for personal computer as well as smart phones. The proposed system satisfies the lighting requirements of each user according to the corresponding work environment. The proposed smart lighting management system utilizes the lighting energy efficiently, and can be considered a significant contribution towards future green buildings.