• Journal of Technologic Dentistry
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• 제22권1호
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• pp.113-128
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• 2000

The purpose of this study was to serve as a basis for the development of dental technology and for creating a condition that dental technicians could work with pride and right values, by examining what problems there were in their health care, what they thought about them, and how the problems could be solved, The findings of this study were as below: 1. The most serious and harmful element in dental technology workshop was a dust(57.5%) and a noise(33.3%). 2. Approximately 99.0% of the dental technicians investigated made a complain of air pollution caused by noise. Their opinion on a possible measure to remove noise air pollution was that the noise-generating machine should be replaced(64.1%) or that it should be isolated(28.8%). 3. 76.0% complained air pollution cause by dust deteriorates their working efficiency. As a way to eliminate it, they suggested a dust chamber(35.3%) or an air cleaner(27.5%) should be installde. 4. About 80% made a complain of gas air pollution. The most common related symptom was a headache(56.9%). They thought that gas-generating machine should be isolated(39.9%) or that an air purifier should be prepared(33.3%). 5. The largest impact of heat and light on their body was weakening their eyesight(56.9%). 47.1% got burn once though four times, and 34.3% did five times or more. The way to prevent them was to install an automatic casting machine(66.0%) or use protective glasses(28.1%). 6. Approximately 47.7% were considering a change of occupation, and the most common reason was heavy work(23.5%), followed by poor prospect(21.6%) and working environment(19.0%) in the order named. 7. 88.9% responded they were likely to have an occupational disease. Their idea about the proper frequency of regular health examination was once a year(53.6%), or once per every six months(41.8%). 8. The field they were most interested in was health care(39.2%), followed by academic research activities(31.4%). This fact indicated it's most urgently required to improve their working environment.

• Journal of IKEEE
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• 제21권4호
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• pp.368-374
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• 2017

In this Paper, we developed a low power type LED security light using LED lighting that substitutes a 220[V] commercial power source for a solar cell module instead of a halogen or a sodium lamp. in addition, a PWM type drive control circuit is designed to minimize the heat generation problem and the drive current of the LED drive controller. in developed system, The light efficiency measurement value is 93.6[lm/W], and a high precision temperature sensor is used inside the controller to control the heat generation of the LED lamp. In order to eliminate the high heat generated from the LED lamp, it is designed to disperse quickly into the atmosphere through the metal insertion type heat sink. The heat control range of LED lighting was $50-55[^{\circ}C]$. The luminous flux and the lighting speed of the LED security lamp were 0.5[s], and the beam diffusion angle of the LED lamp was about $110[^{\circ}C]$ by the light distribution curve based on the height of 6[m].

• Journal of agriculture & life science
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• 제46권1호
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• pp.195-206
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• 2012

This study is about an analysis of surplus solar energy by important greenhouse types as well as setting temperature different by using Typical Meteorological Year data which was secured in order to provide basic data for designing an optimum thermal storage system to accumulate surplus solar energy generating in greenhouses during the daytime. Depending on the setting temperatures of $15{\sim}19^{\circ}C$ for greenhouse heating during day and night, surplus heat amounts were varied at the rate of about $0.2{\sim}6.9%/4^{\circ}C$ with some variations according to the greenhouse types and regions. On the other hand, the variations of supplemental heat requirements were about $29.7{\sim}50.0%/4^{\circ}C$. Depending on the setting temperatures for greenhouse ventilations(low $25{\sim}29^{\circ}C$ and high $27{\sim}31^{\circ}C$), surplus heat amounts were varied at the rate of about $-9.9{\sim}-35.6%/4^{\circ}C$ in auto-type greenhouse. But in single-type greenhouses, they were about $-5.1{\sim}-13.4%/4^{\circ}C$. There were not significant changes in supplemental heat amounts depending on setting temperatures of ventilation for both greenhouse types and regions.

• Journal of Korean Society of Disaster and Security
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• 제7권1호
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• pp.27-33
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• 2014

This research has been shown the strategic disaster prevention and safety management's methodology that minimize the demage and loss from environmental disaster: it is made the renewable energy using the urban wastes causing the main environmental disaster, it minimize the generating cost from the environmental disaster, it gain the energy source for preparing the large-scale shutdown electricity, it gain the profit from the continuous electric power and heat energy's generating, it gain the renewal energy source from the old urban wastes' landfill, it give back the citizen the clean environment, the construction cost is able to be solved form the profit which the power plant is made the plasma gasification generation of the urban wastes, it create the new related jobs in the local government, it base to be invested the local industrial zone's commercialization due to the renewal energy power plant. Especially, in happen to the large-scale natural disaster's typhoon and earthquake, in the result generating the large-scale urban wastes, it is shown the prepared and robust model which contribute the preventing recovery of the local economy using the renewal energy of the urban wastes, and the strategic disaster prevention and safety management's method in the future city.

• Journal of Energy Engineering
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• 제26권4호
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• pp.29-34
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• 2017

Factors of Zero-Energy Building are divided into active and passive factor. Passive factor means insulation, heat bridge of building like insulation, windows and doors, awning, outside etc. and active factor means energy output and efficiency coefficient. Energy output of active factor is achieved by new generating energy. This study anticipated how many effects will be produced when not new generating energy but Vehicle to Building; V2B, bi-directional charging and discharging technology, is applied to Zero-Energy Building. In new generating energy, power generation will be anticipated by geography and climate, but in V2B, several input variable like user's discharging intention and number of usable charger etc. should be considered. We can check how much V2B contribute to the Zero-Energy Building by anticipated results, and that results should be anticipated by using probabilitic method because there is few statistical data. This study anticipate change of charging and discharging pattern, based by Demand Response slot, by using monte carlo method among the probabilitic methods.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2010년도 춘계학술대회 초록집
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• pp.123.2-123.2
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• 2010

Fuel Cell cogeneration system is a promising technology for generating electricity and heat with high efficiency of low pollutant emission. We have been developed 5kW class fuel cell cogeneration system for commercial and residential application. The fuel processor is a crucial part of producing hydrogen from the fossil fuels such as LNG and LPG. The 5kW class high efficiency fuel processor consists of steam reformer, CO shift converter, CO preferential oxidation(PrOx) reactor, burner and heat exchanger. The one-stage CO shift converter process using a metal oxide catalyst was adopted. The efficiency of 5 kW class fuel processor shows 75% based on LHV. In addition, for the purpose of continuous operation with load fluctuations in the commercial system for residential use, load change of fuel processor was tested. Efficiency of 30%, 50%, 70% and 100% load shows 75%, 75%, 73% and 72%(LHV), respectively. Also, during the load change conditions, the product gas composition was stable and the outlet CO concentration was below 5 ppm. The Fuel processor operation was carried out in residential fuel cell cogeneration system with fuel cell stack under dynamic conditions. The 5kW class fuel processor have been evaluated for long-term durability and reliability test including with improvement in optimal operation logic.

• Journal of the Computational Structural Engineering Institute of Korea
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• 제24권6호
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• pp.699-705
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• 2011

High-maneuver missile is a projectile which demands a strong momentum at short time. To produce a necessary thrust for the flight, the gas of high temperature and pressure is generated through explosive combustion of solid propellant, and a great thrust can be obtained by expanding this high temperature and pressure gas. Although the operating time of a rocket motor is less than a few seconds, a failure of part or ablation near the throat of nozzle may take place during the expansion of high temperature and pressure gas for great thrust. In other words, for the precise control of a missile an exact stress analysis considering both, the thermal stress caused by the heat transfer between combustion gas and wall, and the mechanical stress caused by the pressure change in the flow, should be considered first. In this connection, this study investigated the safety, as a point of view of stress and melting point of the material, of the pre-designed thrust generating structure which is subjected to high temperature and pressure as a function of motor operating time.

• Journal of the Korean Crystal Growth and Crystal Technology
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• 제8권3호
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• pp.401-406
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• 1998

For the applications in optical waveguides and devices, LiNbO_3$ single crystals need to overcome the weakness of optical damage due to the inhomogeneities of laser-induced refractive index. This problem can be solved by doping of Mg in LiNbO_3$ and proton exchange of LiNbO_3$. In this study, to understand the mechanism of optical damage resistance in LiNbO_3$, the changes of lattice defects in LiNbO_3$ caused by MgO doping and acid treatment were observed indirectly by $OH^-$ absorption bands using a FT-IR spectrophotometer. The effect of lattice defects on temperature, heat-treatment and polishing were also investigated. It is shown that MgO doping increases optical damage resistance by generating the defects of $Mg_{Nb}^{2+}$ in the lattice of LiNbO_3$, and that proton exchange by implantation of $H^+$ ion in the hexagonally closest packed oxygen layers on the surface of LiNbO_3$, makes lattice defects, which diffuse into the crystal after heat-treatment above $400^{\circ}C$.

• Proceedings of the Korean Society for Agricultural Machinery Conference
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• 한국농업기계학회 2017년도 춘계공동학술대회
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• pp.135-135
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• 2017

Greenhouse have been developed to provide the plants with good environmental conditions for cultivation crop, two major factors of which are the inside air temperature and humidity. The inside temperature are influenced by the heating systems, ventilators and for systems among others, which in turn are geverned by some type of controller. Likewise, humidity environment is the result of complex mass exchanges between the inside air and the several elements of the greenhouse and the outside boundaries. Most of the existing models are based on the energy balance method and heat balance equation for modelling the heat and mass fluxes and generating dynamic elements. However, greenhouse are classified as complex system, and need to make a sophisticated modeling. Furthermore, there is a difficulty in using classical control methods for complex process system due to the process are non linear and multi-output(MIMO) systems. In order to predict the time evolution of conditions in certain greenhouse as a function, we present here to use of recurrent neural networks(RNN) which has been used to implement the direct dynamics of the inside temperature and inside humidity of greenhouse. For the training, we used algorithm of a backpropagation Through Time (BPTT). Because the environmental parameters are shared by all time steps in the network, the gradient at each output depends not only on the calculations of the current time step, but also the previous time steps. The training data was emulated to 13 input variables during March 1 to 7, and the model was tested with database file of March 8. The RMSE of results of the temperature modeling was $0.976^{\circ}C$, and the RMSE of humidity simulation was 4.11%, which will be given to prove the performance of RNN in prediction of the greenhouse environment.

• Journal of the Korea Academia-Industrial cooperation Society
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• 제12권3호
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• pp.1488-1494
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• 2011

In this paper, we propose an algorithm using linear regression model that forecasts the demand of heated water in winter. To supply heated water to apartments, stores and office buildings, Korea District Heating Corp.(KDHC) operates boilers including electric power generators. In order to operate facilities generating heated water economically, it is essential to forecast daily demand of heated water with accuracy. Analysis of history data of Kangnam Branch of KDHC in 2006 and 2007 reveals that heated water supply on previous day as well as temperature are the most important factors to forecast the daily demand of heated water. When calculated by the proposed regression model, mean absolute percentage error for the demand of heated water in winter of the year 2006 through 2009 does not exceed 3.87%.