• Journal of the Korean Solar Energy Society
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• v.36 no.6
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• pp.61-69
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• 2016

In this study, we analyzed five-year(2011~2015) data for D high school in Seoul area to analyze energy consumption characteristics in high school. The results are summarized as follows. (1) In the result of comparison analysis about 2015 energy consumption by usage, based on primary energy, 18% of energy was consumed in cafeteria, and 82% was consumed in main building. In the case of main building, base and constant load excepting hot water supply in restroom took 40%, heating including freeze protection took 20%, hot water supply in restroom took 14%, and cooling took 8% in order. (2) In the 2015 total energy consumption in D high school based on primary energy, heating energy takes 28%. The range and limit of energy savings coming from the reinforcement of insulation and window performance could be estimated. (3) To introduce new & renewable energy system in high school, electricity-based system is suitable than heat-based system because usage of electric energy is larger than that of heat energy in high school. (4) Five-year energy consumption unit according to heating degree-day showed a linearly increasing trend, and the coefficient of determination(R2) was 0.9763, which means high correlation.

• Journal of Ocean Engineering and Technology
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• v.25 no.6
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• pp.66-71
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• 2011

Recently, the production of shipbuilding and offshore plant industries, with a trend toward large structures, has led to an increased use of high strength ultra-thick plates. The use of ultra-thick plates increases the welding tasks, and the welding process generates distortion and residual stress in the weldment because of the rapid heating and cooling. Welding distortion and residual stress in the welded structure resulte in many troubles such as deformation and life deterioration. In particular, the welding residual stress has an important effect on welding deformation, fatigue, buckling strength, brittleness, etc. The purpose of this study was to evaluate the residual stress at a multi-pass weldment using an experimental method for EH36 high-tension steel. In this experimental method, AIS3000 was used to measure the residual stress of a welded part, HAZ, and base metal; EPMA and XRD were used to study the material properties.

• The Journal of the Korea institute of electronic communication sciences
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• v.10 no.5
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• pp.615-622
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• 2015

As the development of high efficiency and high flux density LEDs, the trend of illumination lamp industry transfers from conventional-lamps to the LED-lamps. For energy efficiencies, LED lamps are superior to the conventional lamps, but they have heat problems. Especially, the heat problems are severe for the high luminance lamps. They degrade the soldering point of the metal PCB, and shorten the life cycle of LEDs. So, the solution of the heat sinking is very important to develop high luminance LED lamps. This study suggested a new method to solve the heat problems for high luminance LED lamps, and developed a LED lamp which has 1200W power. In this study, a water jacket is installed to the LED lamp, and the cooing water is circulated by a water pump.

• KIEAE Journal
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• v.14 no.2
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• pp.37-46
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• 2014

University buildings are energy-guzzling facility that consume more than 10,000TOE within a campus annually. Even the consumption is on an upswing trend. Behind such high consumption are there cheap power rates for education facility, lack of high-efficiency equipment and ever-increasing use of various information equipment. Being keenly aware that greenhouse gas emission increases due to such rise of energy consumption, the present study carried out a case study. In the case study, the study chose the buildings of E university from top 10 universities that consume energy most in Seoul and examined the current status of their energy consumption and greenhouse gas emission. And then it set the reduction target of greenhouse gas by year. Putting aside a middle and long-termed strategy for later endeavor, it first established the 1st year's implementation plan (2014) for energy saving and greenhouse gas reduction with limited budget and according to greenhouse gas reduction target. The plan is specified as follows. Targets for energy saving are mainly divided into two sectors: machine equipment and electric equipment. 7 ideas were proposed. Three ideas to improve machine equipment are to replace with high-efficiency boilers and chillers and to adjust the position of the cooling tower. By doing so, it was estimated that energy could be saved by 176.34TOE in total and greenhouse gas could be reduced by 370.771t$CO_2$-eq. Four ideas to improve electric equipment include the replacement with LED lights, LED emergency lights and high-efficiency motors and the installation of motion sensors. It was calculated that such replacement could conserve 1,076.08TOE (electric energy) and reduce 2,181.420t$CO_2$-eq (greenhouse gas).

• 유체기계공업학회:학술대회논문집
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• 2006.08a
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• pp.479-482
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• 2006

The most the electronic industry has recently accelerated the modularization, the miniaturization and the high integrated trend of electronics fields such as electronics components, appliances and etc., the most increasingly the heat generation problem rises. Even though the conventional cooling technologies are widely used in order to reduce the heat loads, the technologies are not easy to meet the present trends due to the fact that most of many conventional methods are relative to external form environments such as size, design and so on. With regardless of those environments, however, a heat pipe is one of the most efficient systems to improve the heat transfer performance. And then the performance of the heat pipe depends on a wick structure. Of various wick structures, sintered metal wick is known so that it has some advantages such as smaller pore size, increasing porosity as well as high reliability. In this study sintered metal wicks, thickness 0.7 mm, 0.8 mm and 0.9 mm, were manufactured as of $100{\mu}m$ copper powder to obtain the manufacturing technology of heat pipes mounted with a sintered metal wick. Furthermore, experiments for the operational performance factors such as capillary limit, thermal resistance were not only performed but also compared with a theoretical model simultaneously. Experimental results agreed with the theoretical model, and then it seems to be required to study various development processes of sintered metal wicks for the high performance of a heat pipe system.

• Journal of the Korean Society of Marine Environment & Safety
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• v.23 no.1
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• pp.104-111
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• 2017

This research focuses on simulation and visualization of flow field characteristics inside a centrifugal pump. The 3D numerical analysis was carried out by using a numerical CFD tool, addressing a Reynolds Average Navier-Stock code with a standard k-${\varepsilon}$ two-equation turbulence model. The simulation accounts for friction head loss due to rough walls at suction, impeller, discharge areas and volumetric head loss at impeller wear ring. A comparison of performance curves between simulation and experimentation is included, and it reveals a same trend of those results with a small difference of maximum 5 %. At best efficiency point, velocity vectors are smooth but it changes significantly under off-design point, a strong recirculation appears at the outlet of impeller passages near tongue area. A relatively uniform preassure distribution was observed around the impeller in despite of the tongue. Within the volute, because of its geometry, spiral vortexes formed, proving that the flow field in this region was relatively turbulent and unsteady.

• Journal of the Mineralogical Society of Korea
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• v.17 no.4
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• pp.327-338
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• 2004

XRD studies on annealed Na-feldspar (Amelia albite) at $1100^{\circ}C$ showed rapid structural changes due to Si-Al disordering, which resulted in phase transformations from low albite to high albite by 4-days annealing test. TEM SAED analyses on the annealed samples revealed a trend of structural changes, but estimation of the structural state was difficult due to a large deviation of the SAED data. Optimum conditions of CBED analyses on albite was established by employing a cooling specimen holder, 120 kV of acceleration voltage, 37 Jim of condenser aperture size and 25 nm of spot size. A proper orientation showing distinct changes of HOLZ lines corresponding to the structure changes of albite turned out to be close to the [418] direction with $-1.2^{\circ}$ tilting, where the width of two HOLZ lines in low albite was opposite to those in high albite.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.41 no.9
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• pp.1132-1140
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• 2016

According to global trend, despite the overall scale of agricultural industry has been downsized, agriculture accommodating cutting-edge ICT technologies has been proliferated, and various timely-issued relevant researches have been on progress to deploy the future food cultivation. In this paper, we propose an effective nutrient management system with web-based monitoring with functionality of controlling temperature, humidity, pH (hydrogen ion), EC (Electric Conductivity), LED and cooling fan to maintain the hydroponic nurturing environment being optimal. In this paper, in order the arduino hardware and java software are employed to control the nurturing environment automatically in optimal fashion. In proposed system, due to the usage of WiFi router with the socket communication and DB-assisted Web server with proper interfaces, it allows to facilitate the management to keep monitoring and controling overall hydroponic nurturing environment. Since the proposed Web-based management system provides the superior reliability, the short nurturing period and the robustness to the pest by controlling LED emitting color rather than conventional system, so it can be applied and appropriate for in-house vegetable factory overcoming limitation of time and location.

• Tribology and Lubricants
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• v.32 no.6
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• pp.183-188
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• 2016

Engine oil plays an important role in the mechanical lubrication and cooling of a vehicle engine. Recently, engine development has focused on the adoption of gasoline direct injection (GDI) and turbocharging methodology to achieve high-power and high-speed performance. However, oil dilution is a problem for GDI engines. Oil dilution occurs owing to high-pressure fuel injection into the combustion chamber when the engine is cold. The chemical components of engine oil are currently developed to accommodate gasoline fuel; however, bio-alcohol mixtures have become a recent trend in fuel development. Bio-alcohol fuels are alternatives to fossil fuels that can reduce vehicle emissions levels and greenhouse gas pollution. Therefore, the chemical components of engine oil should be improved to accommodate bio-alcohol fuels. This study employs a 2.0 L turbo-gas direct injection (T-GDI) engine in an experiment that dilutes oil with fuel. The experiment utilizes a variety of fuels, including sub-octane gasoline fuel (E0) and a bio-alcohol fuel mixture (Ethanol E3~E7). The results show that the lowest amount of oil dilution occurs when using E3 fuel. Analyzing the diluted engine oil by measuring density and moisture with respect to kinematic viscosity shows that the lowest values of these parameters occur when testing E3 fuel. The reason is confirmed to influence the vapor pressure of the low concentration bio-alcohol-fuel mixture.

• Journal of the korean society of oceanography
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• v.39 no.4
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• pp.234-242
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• 2004

The pigment composition and concentration of phytoplankton assemblages using HPLC in the adjacent waters of four nuclear power plants (Yonggwang, Kori, Wolsong and Ulchin) were investigated during the spring blooming in 2004. The mean concentration of chlorophyll a ranged from 563.8 to 2,949.0ng $l^{-1}$, with the lowest concentration at Kori and the highest concentration at Wolsong. Among the carotenoids, the amounts of fucoxanthin and chlorophyll $C_2$ were relatively higher than those of other pigments in the study site. As minor pigments, zeaxanthin, chlorophyll b, 19'-butanoyloxyfucoxanthin, diadinoxanthin, 19'-hexanoyloxyfucoxanthin, chlorophyll $C_3$ and peridinin were detected. The results of pigment composition and concentration showed that diatoms had an important proportion of phytoplankton community when a spring bloom occurred. Cyanobacteria was present relatively low density at the Wolsong and the green alga such as chlorophytes and prasinophytes were abundant at the Yonggwang and Kori, while dinoflagellates characterized by peridinin were common at Ulchin and Kori. The pigment composition and concentration of phytoplankton after passing through the cooling-water system of nuclear power plant were highly variable. No distinct trend of the change of each pigment composition and amount was detected but the variation of fucoxanthin and chlorophyll $C_2$ highly coupled with that of chlorophyll a. We pointed out that the diatom controlled the overall variation of phytoplankton biomass during the spring season.