• KIEAE Journal
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• v.13 no.2
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• pp.53-60
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• 2013

This study examined the building envelope structure used in small housings near urban area which have not good energy source in relation to the application of passive design for energy saving of small-sized architectural design firms in local cities and aimed to provide the basic materials of future design direction of designers and housing owners by analyzing economy of a project in order to know the amount of energy saving and additional expenses depending on the building envelope pattern. As a result of comparing and examining the energy saving cost from the period of use compared to investment by the thickness of insulating materials based on building envelope pattern for energy saving, it was found that the thicker the insulating materials are, the more energy saving amount is. While the current bead-type insulating materials have short payback period due to low initial investment, extruded insulating materials show the difference of five years compared to bead-type insulation because of its high initial investment.

• ETRI Journal
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• v.33 no.6
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• pp.857-863
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• 2011

Due to uncertainties in target motion and randomness of deployed sensor nodes, the problem of imbalance of energy consumption arises from sensor scheduling. This paper presents an energy-efficient adaptive sensor scheduling for a target monitoring algorithm in a local monitoring region of wireless sensor networks. Owing to excessive scheduling of an individual node, one node with a high value generated by a decision function is preferentially selected as a tasking node to balance the local energy consumption of a dynamic clustering, and the node with the highest value is chosen as the cluster head. Others with lower ones are in reserve. In addition, an optimization problem is derived to satisfy the problem of sensor scheduling subject to the joint detection probability for tasking sensors. Particles of the target in particle filter algorithm are resampled for a higher tracking accuracy. Simulation results show this algorithm can improve the required tracking accuracy, and nodes are efficiently scheduled. Hence, there is a 41.67% savings in energy consumption.

• Nuclear Engineering and Technology
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• v.54 no.9
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• pp.3540-3550
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• 2022

The supercritical carbon dioxide (S-CO₂) Brayton cycle is an important energy conversion technology for the fourth generation of nuclear energy. Since the printed circuit heat exchanger (PCHE) used in the S-CO₂ Brayton cycle has narrow channels, Rayleigh-Bénard (RB) convection is likely to exist in the tiny channels. However, there are very few studies on RB convection in supercritical fluids. Current research on RB convection mainly focuses on conventional fluids such as water and air that meet the Boussinesq assumption. It is necessary to study non-Boussinesq fluids. PRB convection refers to RB convection that is affected by horizontal incoming flow. In this paper, the computational fluid dynamics simulation method is used to study the PRB convection phenomenon of non-Boussinesq fluid-supercritical carbon dioxide. The result shows that the inlet Reynolds number (Re) of the horizontal incoming flow significantly affects the PRB convection. When the inlet Re remains unchanged, with the increase of Rayleigh number (Ra), the steady-state convective pattern of the fluid layer is shown in order: horizontal flow, local traveling wave, traveling wave convection. If Ra remains unchanged, as the inlet Re increases, three convection patterns of traveling wave convection, local traveling wave, and horizontal flow will appear in sequence. To characterize the relationship between traveling wave convection and horizontal incoming flow, this paper proposes the relationship between critical Reynolds number and relative Rayleigh number (r).

• Journal of Agricultural Extension & Community Development
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• v.11 no.2
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• pp.251-265
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• 2004

The agricultural sector's economic structure in Korea is regarded to encounter major barriers on the way toward revitalizing its economic prosperity. Among many, the energy-related problem is one of prime nuclei embedded in the country's agricultural sector. The ought-to-come structural changes in the country's agricultural energy system hinge upon the central government's policy direction as well as efforts of local governments and local farming community members. The indirect aids via 'cross subsidy' of electricity tariff rate and 'tax-exempt price' of oil fuels are two notable causes of the unsustainable energy consumption pattern in the country's agricultural sector. As measures, demand-side management(DSM) and energy-efficiency promotions are regarded to be the most attractive methods for energy conservation and economic productivity as well. Development of renewable energy sources are also receiving a great deal of attention for the long-term alternatives to the country's existing oil-based agricultural production mode. This study examines the contributive potential of DSM approaches and renewables-based technologies. With the critical evaluation on the concurrent adversities of the country's agricultural energy system, various sources of renewable energy-solar power, wind power, biomass, etc.-are examined for the purpose of technological and economical viability. As sufficient potentials of renewable energy sources are being estimated, both the system production cost and the installation cost for the county's rural areas are expected to lower in the long term. DSM options are also evaluated to be fruitful even in the short term. Both the public and civil arenas must galvanise each side's effort in order to promote these policy options and community potentials.

• Journal of Environmental Science International
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• v.23 no.9
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• pp.1643-1654
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• 2014

The university is one of the main energy consumption facilities and thereby releases a large amount of greenhouse gas (GHG). Accordingly, efforts for reducing energy consumption and GHG have been established in many local as well as international universities. However, it has been limited to energy consumption and GHG, and has not included air pollution (AP). Therefore, we estimated GHG and AP integrated emissions from the energy consumed by Seoul National University of Science and Technology during the years between 2010 and 2012. In addition, the effect of alternative energy use scenario was analysed. We estimated GHG using IPCC guideline and Guidelines for Local Government Greenhouse Inventories, and AP using APEMEP/EEA Emission Inventory Guidebook 2013 and Air Pollutants Calculation Manual. The estimated annual average GHG emission was $11,420tonCO_{2eq}$, of which 27% was direct emissions from fuel combustion sectors, including stationary and mobile source, and the remaining 73% was indirect emissions from purchased electricity and purchased water supply. The estimated annual average AP emission was 7,757 kgAP, of which the total amount was from direct emissions only. The annual GHG emissions from city gas and purchased electricity usage per unit area ($m^2$) of the university buildings were estimated as $15.4kgCO_{2eq}/m^2$ and $42.4tonCO_{2eq}/m^2$ and those per person enrolled in the university were $210kgCO_{2eq}$/capita and $577kgCO_{2eq}$/capita. Alternative energy use scenarios revealed that the use of all alternative energy sources including solar energy, electric car and rain water reuse applicable to the university could reduce as much as 9.4% of the annual GHG and 34% of AP integrated emissions, saving approximately 400 million won per year, corresponding to 14% of the university energy budget.

• KIEAE Journal
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• v.7 no.2
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• pp.17-23
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• 2007

While heat island has been recognized as an unique environmental nuisance in cities, the phenomenon tends to be regarded as an inevitable side effect on urbanization. Recently the nature of the heat island has been disclosed and efforts for the remedy have been discussed in many ways. Some pioneering actions have been taken to mitigate the strength of the heat island's intensity in several countries. After studies for the heat island and speculations on current pilot policies of 3 different countries has been done, mitigation policies for heat island has been suggested as followings. 1. Preservation of natural topography is essential because latent energy consumption(evapotranspiration) from the site is the single most important factor to mitigate the energy surplus caused by urban heat island. 2. Because current national zoning ordinance or building law can not effectively control the site specific local environment, heat island policy should be established or employed at local level. 3. Incentives for the mitigation should be adopted on the process of implementation because environment is public concern. 4. Wind can easily dissipate energy surplus which is the major driving force for heat island. Therefore local wind, the direction and intensity should be sustained and sometimes facilitated fully through policies.

• Convergence Security Journal
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• v.14 no.2
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• pp.43-50
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• 2014

Recently, lot of researches for the multi-level protocol have been done to balance the sensor node energy consumption of WSN and improve the node efficiency to extend the life of the entire network. Especially in multi-hop protocol, a variety of models have been proposed to improve energy efficiency and apply it to WSN protocol. In this paper, we analyze LEACH algorithm and propose new method based on center of local clustering routing algorithm in wireless sensor networks. We also perform NS-2 simulation to show the performance of our model.

• Nuclear Engineering and Technology
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• v.50 no.1
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• pp.203-210
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• 2018

As the modernization of the nuclear instrumentation system progresses, research reactors have adopted digital wide-range neutron power measurement (DWRNPM) systems. These systems typically monitor the neutron flux across a range of over 10 decades. Because neutron detectors only measure the local neutron flux at their position, the local neutron flux must be converted to total reactor power through calibration, which involves mapping the local neutron flux level to a reference reactor power. Conventionally, the neutron power range is divided into smaller subranges because the neutron detector signal characteristics and the reference reactor power estimation methods are different for each subrange. Therefore, many factors should be considered when preparing the calibration procedure for DWRNPM channels. The main purpose of this work is to serve as a reference for performing the calibration of DWRNPM systems in research reactors. This work provides a comprehensive overview of the calibration of DWRNPM channels by describing the configuration of the DWRNPM system and by summarizing the theories of operation and the reference power estimation methods with their associated calibration procedure. The calibration procedure was actually performed during the commissioning of an open-pool type research reactor, and the results and experience are documented herein.

• Wind and Structures
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• v.21 no.3
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• pp.331-352
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• 2015

A series of wind tunnel tests were conducted on tapered super high-rise buildings with a square cross section by applying synchronous pressure measurement technology. The effects of global strategy of chamfered modification on aerodynamic loads and wind-induced responses were investigated. Moreover, local aerodynamic strategies of opening a ventilation slot in the corner of equipment and refuge floors were carried out. Results show that the global strategy of tapered elevation increased the vortex shedding frequency, but reduced vortex shedding energy, leading to reduction of across-wind aerodynamic loads and responses. Chamfered modification suppressed the across-wind vortex shedding effect on tapered buildings. Opening the ventilation slot further suppressed the strength of vortex shedding and reduced the residual energy related to vortex shedding in aerodynamic loads of chamfered buildings. Finally, the optimized locations of local aerodynamic strategies were suggested.

• Transactions of the Korean Society of Mechanical Engineers
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• v.11 no.2
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• pp.234-242
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• 1987

The solution of shape design problems based on variational analysis has been approached by using the domain adaptive method. The objective of the structural shape design is to minimize the weight within a bound on local stress measure, or to minimize the maximum local stress measure within a bound on the weight. A derived optimality condition in both design problems requires that the unit mutual energy has constant value along the design boundary. However, the condition for constant stress on the design boundary was used in computation since the computed mutual energy oscillates severely on the boundary. A two step iteration scheme using domain adaptation was presented as a computational method to slove the example designs of elastic structures. It was also shown that remeshing by grid adaptation was effective to reduce oscillatory behavior on the design boundary.