• Journal of the Korea Academia-Industrial cooperation Society
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• v.14 no.2
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• pp.573-577
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• 2013

Heat pumps come into wide use because high energy efficiency can be obtained and diverse heat sources like geothermal heat, waste heat and air are available. It is necessary for an air source heat pump to defrost in order to remove frost on the surfaces of an outdoor heat exchanger. It is impossible for continuous heating if reverse cycle operation is used as defrosting method, furthermore it causes the degradation of COP. In this study an fin-tube heat exchanger with three rows was used as an outdoor coil. One row among three rows of the heat exchanger was used like a condenser in order to remove frost on it, the others were used as evaporator to accomplish continuous heating. Each row was switched in order from a condenser to an evaporator in specified time interval. Tests were carried out during minimum 180 minutes at the defrost-heating test condition(dry bulb temperature $2^{\circ}C$, wet bulb temperature $1^{\circ}C$) described in KS C 9306. Time-averaged COP was about 20% higher than that of conventional defrosting method.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.40 no.3
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• pp.315-320
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• 2020

Pellets are manufactured using wood by-products. The combustion efficiency of pellets depends on the pellet manufacturing process, the types of materials mixed while manufacturing and the wood pellet stoves themselves. In this study, we developed a multi-layer combustor to be used in a wood pellet stove, for the purpose of reducing environmental pollution and energy waste due to incomplete combustion. The multi-layer combustor was designed to compensate for the shortcomings of existing combustors. A CAD (Computer Aided Design) model was verified using a 3D printer and a prototype was developed. The combustion experiments were conducted on commercial and proposed combustors using pellets of the same brand, manufacturing date, place and specifications. From the experiments, it was found that the proposed combustor produced the lowest carbon monoxide (CO) emission and highest thermal efficiency.

• Membrane and Water Treatment
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• v.2 no.1
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• pp.25-37
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• 2011

PES UF membranes containing silver were prepared to impart antibacterial properties for waste water treatment. Asymmetric membranes for antibacterial application were prepared from polyethersulfone (PES) and silver nitrate ($AgNO_3$) (PES/$AgNO_3$=15/2 by weight) solution in N-Methyl-2-pyrrolidone (NMP) via simple wet phase inversion technique. These membranes were characterized by polyvinylpyrrolidone (PVP) and polyethylene glycol (PEG) of different molecular weights (1000 ppm in water) at room temperature and on operating pressure of 5 bars. It was observed that the water flux of PES-$AgNO_3$ membrane is slightly lower than virgin PES but still increased linearly with the increment of pressure applied. The morphology of the resulting membranes was examined using Field-Emission Scanning Electron Microscope (FESEM) coupled with Energy Dispersive Spectroscopy (EDS). Elemental analysis using EDS proved that silver is successfully loaded on the membrane surfaces. Due to the success of loading silver on membrane surfaces, antibacterial activities were evaluated via agar diffusion method against Escherichia coli (E.coli) and Staphylococcus aureus (S.aureus) culture. By incorporating 2 wt% of silver nitrate, PES-$AgNO_3$ showed significant inhibition ring on both E.coli and S.aureus. Filtration of E.coli solution (OD 0.31) showed satisfactory rejection data with ~100% inhibition growth after 24 hours incubation at $37^{\circ}C$. Resultant membranes also exhibit better tensile strength (compared to virgin PES) up to 71% may be due to the suggested interactions. The residual silver during fabrication was measured using ICP-MS and result showed that the residual silver content of PES-$AgNO_3$ membrane was only ~1% of the original silver added in the polymer solution. These studies have shown that PES-$AgNO_3$ UF membranes are potential in improving the filtration in water treatment.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.24 no.6
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• pp.18-26
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• 2010

Outdoor lighting has become a necessary essential part of society for safety and comfortable space. However, inappropriate outdoor lighting leads to energy waste and poor landscape. Outdoor lighting is a very important social element, which enables us to conduct various activities at night in a safe, efficient and comfort way. River Thames in UK, Venice in Italy and Sydney in Australia is a good example of the coastal area. This paper aims to evaluate the light pollution of outdoor lighting in coastal area in Busan city. The Radiant Imaging ProMetric-1400 was used to measure the luminance of Gwangalli Beach, Marine City and Haeundae Beach. Compare to the CIE recommendation level the luminance of the all outdoor lighting were about 2~20 times higher. Outdoor lighting of the building facade luminance level and color should be particularly limited.

• The Journal of Engineering Geology
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• v.22 no.3
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• pp.263-274
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• 2012

We performed numerical modeling to estimate the groundwater level around a riverside area following the construction of an artificial structure. The groundwater level of the alluvial deposit responded more rapidly to the river water level than to the rainfall event itself, indicating that the groundwater and river water are directly interrelated through the riverbed. Furthermore, transient modeling showed raised groundwater levels at the southern part of Mt. Dok and the eastern part of Mt. Dummit in an area of low plains. The artificial structure caused a rise in groundwater level of up to approximately 6 m.

• Computers and Concrete
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• v.19 no.4
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• pp.419-427
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• 2017

With the rising global environmental awareness on energy saving and carbon reduction, as well as the environmental transition and natural disasters resulted from the greenhouse effect, waste resources should be efficiently used to save environmental space and achieve environmental protection principle of "sustainable development and recycling". This study used recycled cement mortar and adopted the volumetric method for experimental design, which replaced cement (0%, 10%, 20%, 30%) with recycled materials (fly ash, slag, glass powder) to test compressive strength and ultrasonic pulse velocity (UPV). The hyperbolic function for nonlinear multivariate regression analysis was used to build prediction models, in order to study the effect of different recycled material addition levels (the function of $R_m$(F, S, G) was used and be a representative of the content of recycled materials, such as fly ash, slag and glass) on the compressive strength and UPV of cement mortar. The calculated results are in accordance with laboratory-measured data, which are the mortar compressive strength and UPV of various mix proportions. From the comparison between the prediction analysis values and test results, the coefficient of determination $R^2$ and MAPE (mean absolute percentage error) value of compressive strength are 0.970-0.988 and 5.57-8.84%, respectively. Furthermore, the $R^2$ and MAPE values for UPV are 0.960-0.987 and 1.52-1.74%, respectively. All of the $R^2$ and MAPE values are closely to 1.0 and less than 10%, respectively. Thus, the prediction models established in this study have excellent predictive ability of compressive strength and UPV for recycled materials applied in cement mortar.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.9B
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• pp.1314-1321
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• 2010

This system configures a position Sensor as installing on the ship and a guidance system docking of ship what distinguish of the ship about the use and size. The maintain system is received the result of distinction via UWB reader. This system send a information of ship of docking position to user. Thus it suggests the safety to prevent from crash among ships and saves energy and stop waste. The proposed system periodically updates the information of docking position of the ship and monitors in real-time according to the user's request from personal mobile devices. In this paper, we implement of a guidance system Testbed for docking of the ship using position UWB sensor. And user is provided convenience to find easily user's ship in docking area through user interface with Java. Addedly it is possible to prevent ship theft.

• Journal of Digital Contents Society
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• v.18 no.2
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• pp.249-256
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• 2017

As single-person households increase, demands for self interior design has been also increasing. The furniture arrangement takes big part of interior design. But sometimes people need professional helps for the proper and effective arrangement of furniture which makes self-interior design harder. Often, people share information and advices about interior design through Social Network Service. Experts could help directly but this approach would have several issues: First, the detailed and accurate advice would be difficult because experts have to examine the space through 2D pictures or video. Second, they have to make an appointment which would cause inconvenience to both customer and expert. In this paper, the furniture arrangement application for real-time sharing of interior design based on virtual reality is proposed to make up for the weak points. People can precisely share information and advice about self-interior design through this application in realtime, reducing waste of time and energy.

• Nuclear Engineering and Technology
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• v.20 no.2
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• pp.132-136
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• 1988

A strategic question in groundwater contaminant transport modeling is whether we need to treat waste packages or drums as individual, discrete sources or as approximately lumped sources. In this paper we present analyses of array sources in porous media. We analyze a planar array of sources in porous media with groundwater flow. We compare the concentration field predicted by a detailed model of individual point sources to concentration fields predicted by an infinite plane source and a single point source, all of the same equivalent strength. From this study we identified three regions: (1) a region close to the sources where the effects of adjacent sources are significant and individual source models should be used, (2) a region extending from a few meters to hundreds to thousands of meters downstream, where an equivalent source of infinite extent gives accurate results, and (3) a far-field region, where in an equivalent source of finite extent gives accurate results.

• Journal of Animal Science and Technology
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• v.58 no.9
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• pp.34.1-34.9
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• 2016

Background: By-products of pickled radish (BPR) are considered food waste. Approximately 300 g/kg of the total mass of raw materials becomes BPR. Production of pickled radish has grown continuously and is presently about 40,000 metric tons annually in Korea. The objective of the present study was thus to explore the possibility of using BPR as a ruminant feed ingredient. Results: BPR contained a large amount of moisture (more than 800 g/kg) and ash, and comprised mostly sodium (103 g/kg DM) and chloride (142 g/kg DM). On a dry matter basis, the crude protein (CP) and ether extract (EE) levels in BPR were 75 g/kg and 7 g/kg, respectively. The total digestible nutrient (TDN) level was 527 g/kg and the major portion of digestible nutrients was carbohydrate; 88 % organic matter (OM) was carbohydrate and 65 % of total carbohydrate was soluble or degradable fiber. The coefficient of variation (CV) of nutrient contents among production batches ranged from 4.65 to 33.83 %. The smallest CV was observed in OM, and the largest, in EE. The variation in CP content was relatively small (10.11 %). The storage stability test revealed that storage of BPR at $20^{\circ}C$ (room temperature) might not cause spoilage for 4 d, and possibly longer. If BPR is refrigerated, spoilage can be deferred for 21 d and longer. The in vitro ruminal fermentation study showed that substitution of annual ryegrass straw with BPR improved ruminal fermentation, as evidenced by an increase in VFA concentration, DM degradability, and total gas production. Conclusion: The major portion of nutrients in BPR is soluble or degradable fiber that can be easily fermented in the rumen without adverse effects, to provide energy to ruminant animals. Although its high sodium chloride content needs to be considered when formulating a ration, BPR can be successfully used as a feed ingredient in a ruminant diet, particularly if it is one component of a total mixed ration.