• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.12
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• pp.8386-8393
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• 2015

This study is to investigate the needs for the cool motorcycle helmet and the factors affecting the purchasing intention of cool helmet. The convenient sampling from motorcycle clubs were conducted during 5/20/2014~5/28/2014 on Google DAX. As a result, 197 participants were surveyed. The main reasons of sensing unpleasant feeling wearing helmet were identified as 'hot and uncomfortable feeling' and 'it ruins hair style'. The mean score expressed in terms of five point scale showed that the needs for cool helmet was 3.9 and the purchasing intention of cool helmet was 3.6, respectively. The significant factors influencing the purchasing intention of cool helmet were identified as 'the needs for cool helmet' (odds ratio=6.52) and 'extra paying intention for cool helmet' (odds ratio=1.77). The main reasons of sensing unpleasant feeling wearing helmet were similar to the previous research. However, we can expect that the initial target market for cool helmet would be the low end (less than \40,000 of extra paying intention) or the high end (more than \100,000 of extra paying intention). The main contribution of this study is dealing with the topics related to the purchasing intention of the cool helmet.

• Journal of the Korea Concrete Institute
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• v.13 no.6
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• pp.619-628
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• 2001

In building construction, openings of the story-height deep beams are usually required for accessibility and service lines such as air conditioning ducts, drain pipes and electric units. It is known that the main parameters affecting the load bearing capacity of deep beams with web openings are size, shape, location and reinforcements of openings. However, there have been no pertinent theories and national design codes for predicting ultimate shear strength of reinforced concrete deep beams with web openings. In this study, the shear behavior of simply supported reinforced concrete deep beams with web openings subject to concentrated loads has been scrutinized experimentally. A total of 34 specimens, the geometry of openings, its reinforcements and shear span to depth ratio, being taken as the experimental variables, has been cast and tested in the laboratory. The effects of these structural parameters on the shear strength and crack initiation and propagation have been carefully checked and analyzed. From the tests, it has been observed that the failures of all specimens were due to shear mechanism and the ultimate strength of specimens varies according to the location of openings, by which the formation of compression struts between the loading points and supports are deterred. All of the test results of specimens have been compared with the formulas proposed by previous researchers. The results were closely coincident with the formulas given by Ray and Kong's equation except for some X series specimens having a larger dimension of openings beyond the geometric limits of proposed equations.

• Korean Journal of Construction Engineering and Management
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• v.10 no.4
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• pp.111-118
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• 2009

This study is to analyze the performance of SWH(Solar Water Heating) and GSHP(Ground Source Heat Pump) systems by evaluating their energy efficiency and LCC(Life Cycle Cost) as being applied to the OO hall as a selected building in the Army. The OO hall, used as bathrooms, dining rooms, accommodations and offices, has reinforced concrete structure system with three floors above the ground and one underground, and its total floor area is approximately 2,917$m^2$. Two energy simulations are conducted to predict the yearly cooling and heating energy of the selected building: One is for analysis of an air-conditioning energy consumption using the e-Quest program, and another is for two new-renewable energy facilities as a water heating source using the RETScreen. The installed capacity of two new-renewable energy facilities is determined according to the 5% level of total standard construction cost. As a briefly result, SWH system is more energy-effective than GSHP system. Considering the break-even point, it is expected that SWH can take only 3 years 11 months to pay for itself in savings while the investment of GSHP can be recovered in more than 16 years 6 months.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.11 no.12
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• pp.4721-4726
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• 2010

The performance characteristics of water-chilling heat pump using CO2 for the control of inverter frequency was investigated experimentally. An experimental apparatus is consisted of a compressor, a gas cooler, an expansion valve, an evaporator and a liquid receiver. All heat exchangers used in the test rig are counter flow type heat exchangers with concentric dual tubes, which are made of copper. The gas cooler and the evaporator consist of 6 and 4 straight sections respectively arranged in parallel, each has 2.4m length. The experimental results summarize as the following: for constant inlet temperature of evaporator and gas cooler, as mass flow rate, compression ratio and discharge pressure increases with the inverter frequency. And heating capacity and compressor work increases, but coefficient of performance(COP) decreases with the inverter frequency of compressor. As inlet temperature of secondary fluid in the evaporator increases from $15^{\circ}C$ to $25^{\circ}C$, compression ratio and compressor work decreases, but mass flow rate, heating capacity and COP increases with the inverter frequency of compressor. The above tendency is similar with performance variation with respect to the variation of inverter frequency in the conventional vapor compression refrigeration cycle.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.14 no.2
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• pp.592-597
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• 2013

The heat generated at the motor and inverter inside the electric compressor of inverter built-in type is mainly cooled by refrigerant and generally, there is not a thermal problem. However, the close relation of heat transfer from the motor and inverter parts to the compression part affects on compressor efficiency. Also, according to the surrounding environment and system operation condition, the increased temperature of the motor and inverter can affect the power density of the motor system, and especially, the inverter may be prevented to operate by the temperature limits. In this study, we performed thermo-flow analysis of electric compressor motor system, and investigated the heat dissipation enhancement of the motor and inverter. The motor part in the operation region of the electric compressor was generally maintained at low temperature and the inverter part at high compressor speed was lower temperature than the temperature limit of $85^{\circ}C$. However, the case of the inverter at low speed harsh condition was in excess of $10^{\circ}C$. Therefore, in order to solve the thermal problem, the heat reduction technology of the motor and inverter is essential as well as the improvement of flow path in the compressor.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.10
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• pp.128-135
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• 2018

Currently, vertical closed ground heat exchangers are the most widely utilized geothermal heat pump systems and the major influencing parameters on the performance of ground heat exchangers are the ground thermal conductivity(k) and borehole thermal resistance($R_b$). In this study, the borehole thermal resistance was calculated from the in-situ thermal response test data and the individual effects of design parameters (flow rate, number of pipe, grout composition) on the borehole thermal resistance were analyzed. The grout thermal resistance was also compared with the correlations in the literatures. The borehole thermal resistance of the investigated ground heat exchanger results in 0.1303 W/m.K and the grout thermal resistance (66.6% of borehole thermal resistance) is the most influencing parameter on borehole heat transfer compared to the other design parameters (pipe thermal resistance, 31.5% and convective thermal resistance, 1.9%). In addition, increasing the thermal conductivity of grout by adding silica sand to Bentonite is more effective than the other design improvements, such as an increase in circulating flowrate or number of tubes on enhancing borehole heat transfer.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.2
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• pp.32-38
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• 2020

This study summarizes test methods and evaluation methods for examining the thermal characteristics of Jeju-type ground heat exchangers (GHXs) installed on Jeju Island, and analyzes the ground temperature and thermal characteristics of ground heat exchangers installed in various regions by using thermal response tests (TRT). Jeju Island is composed of volcanic rock layers, and the groundwater flow is well developed. A Jeju-type GHX can be installed up to 30 m from groundwater level after drilling a borehole. The ground heat exchanger has a structure in which several pipes are inserted into the borehole. In order to examine the characteristics of the Jeju-type GHX, tests were conducted on ground heat exchangers installed in four places on Jeju Island (Pyoseon, Jeju, Namwon, and Hallym). As a result of the analysis of the Jeju-type ground heat exchanger, the ground circulating water temperature stabilized according to the heat injection, depending on the installed location, and was formed within one to three hours. The ground heat exchanger capacity in Hallym was highest at 73.4 kW (cooling) and 82.8 kW (heating), and the Jeju-type calculation was lowest at 34.1 kW (cooling) and 23.3 kW (heating).

• Proceedings of the Korean Society for Bio-Environment Control Conference
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• 1996.05a
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• pp.91-115
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• 1996

In the recent years, protected horticultural facilities have been modernized and glasshouses are also propagating in Korea, even most vegetables production are conducted in the traditional plastic houses covered with, for example, PVC film for just temperature keeping. It would limit the productivity and competitivity of the vegetable production industry without automatization and high quality year round production. A plant factory, aimed to produce vegetables in the limited areas, was initiated in Christensen farm, Denmark in 1957, and widely propagated in some developed countries. As it has the automatized system which enables to keep optimized environment conditions, it will be the best facility for high quality products as well as year round planned production. However, we have not even started the plant factory production. Since the plant factory is requiring lots of resources, besides plant cultivation technologies, such as environment control, automatic engineering and robotics, our approach to the development of plant factories should be minded on Practical Plant Factories considering our current farming practices and least capital needs rather than blindly employing the advanced technologies from developed countries. Thus, Korean plant factory development can be initiated with year round leaf vegetables production in NFT or DFT cultivation system instead of the moval bed system, in which aerial environment factors such as light, temperature, humidity and CO$_2$ concentration and root environment ones such as solution concentration, temperature, pH and water soluble oxygen shall be automatically controlled. And the seeding, seedling and transplanting operations shall be accomplished in the house entrance, and the harvesting and grading opreations shall be conducted in the house exit. For practical plant factories, environment control technologies including artificial light source, illumination and air conditioning, automatic management for nutrient solution and automatic production line of moval bed system, transplanting and harvest should be developed along with researches on the cost reduction of factory building construction.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.13 no.3
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• pp.1220-1228
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• 2012

This study was carried out in order to offer medical service in good quality by enhancing dental hygienists' job satisfaction and to arrange basic data necessary for individual development and health promotion in dental hygienists through grasping the job stress level and job satisfaction of being experienced by dental hygienists, and the correlation. The self-administered questionnaire was surveyed and collected from August 1-12 of 2011 targeting 210 dental hygienists of general hospitals, dental hospitals, and dental clinics nationwide(Seoul, Gyeonggi, Daegu, Pohang).The analysis was made on 205 people. The collected data was analyzed by using SPSS WIN 15.0 program. As a result, out of job stress, the average was indicated to be the highest with 2.71 in 'job demand.' As a result of examining about sphere-based relationship between health perception level and job stress related to building in dental hygienists, the central nervous system manifestation showed statistically significant positive correlation with physical environment(r=.281, p<.001), job demand(r=.281, p<.001), relational conflict(r=.163, p<.05), organizational system(r=.166, p<.05), compensation inappropriateness(r=.267, p<.001), and job stress(r=.311, p<.001). Overall, the building-related health perception level showed statistically significant correlation with physical environment(r=.259, p<.001), job demand(r=.311, p<.001), relational conflict(r=.172, p<.05), organizational system(r=.158, p<.05), compensation inappropriateness(r=.197, p<.01), and job stress(r=.275, p<.001). They need to improve their quality of life and life and mental health by developing proper air conditioning system and using one in their work place. if so, they could contribute to better quality of oral cavity service for everyone.

• Journal of the Korean Society of Hazard Mitigation
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• v.10 no.4
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• pp.63-68
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• 2010

Utility-Pipe Conduit is, Housing and city effectively accommodate what they absolutely need power, communications, gas, pipeline, water supply, drainage, energy facilities etc, according to expansion of urban infrastructure are derived, several ways to solve problems in, collection facilities in place are maintained and managed facility. If Utility-Pipe Conduit is damaged, as well as national security, because their impact on society as a whole, by introducing large vulnerability in the fire prevention activities and suppression measures and disaster for our situation by introducing measures, comprehensive analysis of the fire risk, it shall establish fire prevention activities and suppression through analysis of Utility-Pipe Conduit design, institutional issues, the problem of fire protection facilities, fire spread phenomenon etc. Because of Utility-Pipe Conduit is an enclosed place, so incomplete combustion due to lack of oxygen supply that there are problem such dark smoke, carbon monoxide etc, toxic combustion products and heat generation and visual impairment is an issue difficult to enter. As well as fire prevention activities, the fire In light of the particularity of the under ground than above ground fire, so this phenomenon is weak fire fighting that fire to become effective fire fighting tactics, basically it is necessary difficulty softening, non-burn softening and prevent combustion expansion of the cable is installed on the Utility-Pipe Conduit, having to considering the specificity of the response command system and relevant organizations to establish an on-site, Structural identification and other information gathering required to record of Response agencies, keep air conditioning system 24 hours and strengthening Virtual Total Training of Response agen