• Nuclear Engineering and Technology
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• v.44 no.4
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• pp.429-436
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• 2012

Critical heat flux (CHF) is the thermal limit of a phenomenon in which a phase change occurs during heating (such as bubbles forming on a metal surface used to heat water), which suddenly decreases the heat transfer efficiency, thus causing localized overheating of the heating surface. The enhancement of CHF can increase the safety margins and allow operation at higher heat fluxes; thus, it can increase the economy. A very interesting characteristic of nanofluids is their ability to significantly enhance the CHF. Nanofluids are nanotechnology-based colloidal dispersions engineered through the stable suspension of nanoparticles. All experiments were performed in round tubes with an inner diameter of 0.01041 m and a length of 0.5 m under low pressure and low flow (LPLF) conditions at a fixed inlet temperature using water, 0.01 vol.% $Al_2O_3$/water nanofluid, and SiC/water nanofluid. It was found that the CHF of the nanofluids was enhanced and the CHF of the SiC/water nanofluid was more enhanced than that of the $Al_2O_3$/water nanofluid.

• Environmental and Resource Economics Review
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• v.12 no.3
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• pp.397-425
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• 2003

This paper develops a simple theoretical model that is consistent with the empirical evidence of an inverted U-shpated relationship between pollution and per capita income, which is so-called environmental Kuznets curve in this literature. Also, by incorporating the issue of environmental externality into an endogenous growth model, I investigate the circumstances under which growth can be sustained with the optimal control of pollution, and hence the sustainable development can be achieved. In order to study the problem of implementing the social optimum in a market economy, I examine the optimality of three different kinds of environmental policy instruments; pollution tax, pollution-permit trading system (pollution voucher), and direct regulation. This paper shows that the optimum can be implemented with a pollution tax or with a voucher system. Also, it is shown that the socially optimal rate of pollution tax should increase proportionally to the growth rate of consumption.

• Environmental and Resource Economics Review
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• v.19 no.2
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• pp.215-242
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• 2010

This study constructs a bayesian neoclassical DSGE model that applies oil usage. The model includes technology shocks, oil price shocks, and shocks to energy policies as exogenous driving forces. First, this study aims to analyze the roles of these exogenous shocks in the Korean business cycle. Second, this study examines the effects of long-term changes in the energy consumption structure, including the reduction in oil use as a share of energy consumption and improvement in oil efficiency. In the case of oil price shocks, results show that these shocks exert recessionary pressure on the economy in line with those obtained in the previous literature. On the other hand, shocks to energy policies, which reduce oil consumption per capital, result in opposite consequences to oil price shocks, decreasing oil consumption. Also, counterfactual exercises show that long-term changes in the energy consumption structure would mitigate the contractionary effects of oil price shocks.

• The Journal of the Korea Contents Association
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• v.18 no.6
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• pp.102-112
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• 2018

This study, energy saving technology development is desperately needed and the energy efficiency through improved environmental impact by minimizing economic raw materials and subsidiary materials can lead to reductions in local Small Business at the heart of the new technology in the background, product design and development. That's about technology, strengthen and broaden the design patent right infringement of its competitors by gaining a global corporate foundation of development research. In order for companies to develop diagnostic analysis and key technology analysis and evaluation of progress on the scope of rights through the development of new technologies to diagnose and design rights and the extent and design rights infringement and design development since the company's growth analysis. Integration of the design development and the core technologies of the company will be the core of national industrial competitiveness of small businesses and by securing and creating the knowledge-based rights, fusion link that can grow into compatibility business is much more need in a difficult economy.

• Bulletin of the Society of Naval Architects of Korea
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• v.1 no.1
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• pp.9-16
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• 1964

As a pre-study for researches on powering characteristics of straight-framed V-bottom hull forms for usual commercial vessels, practicability of such a hull is investigated from viewpoints of over-all ship economy. For this purpose, a trawler hull of straight-elements with double chines, SV(T)-1, similar to Prof. Nevitt's W-8 in size and hull form coefficients was designed and tested at the SNU Ship Model Towing Tank for resistance measurements. The result is given in Fig.3 together with those of W-8 and other equivalent hulls of double curvature, such as FAO 135a-173, Doust and Takgi. The curves of the latters are reproduction of Prof. Nevitt's analysis, and given for comparison purpose. With in speed range of $9.0{\sim}10.5$ konts the resistance coefficients of SV(T)-1 are $18{\sim}25%$ higher than those of W-8, and $5{\sim}20%$ and $12{\sim}14%$ higher than those of FAO 135a-173 and Doust respectively. SV(T)-1, however, is slightly superior in resistance characteristics than Takagi's equivalent hull within the speed range. On the other hand, an equation for reduction rates of hull construction cost required to compensate for propulsion power increase in straight-elements hulls was derived from the definition of the economic efficiency of commercial vessels. The solution of the equation is given in Fig.4 graphically, from which it is known that $10{\sim}20%$ increase in propulsion power can be compensated by $8{\sim}16%$ reduction in hull construction cost. Considering simplicity and less equipments required in construction of straight -elements hulls, the author does argue for attainability of the above reduction rates in hull construction cost. Consequently, it is concluded that there is clear feasibility to adopt straight-elements hulls for usual commercial vessels of medium and small-size. And a further research will be done to obtain reliable data for chine shapes having good flowliness with the flow around ships depending on ship's size and speed.

• Transactions of the Korean hydrogen and new energy society
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• v.23 no.3
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• pp.227-235
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• 2012

Finding an alternative fuel and reducing environmental pollution are the main goals for future internal combustion engines. The purpose of this study is to obtain low-emission and high-efficiency by hydrogen enriched LPG fuel in constant volume chamber. An experimental study was carried out to obtain fundamental data for the combustion and emission characteristics of pre-mixed hydrogen and LPG in a constant volume chamber (CVC) with various fractions of hydrogen-LPG blends. To maintain equal heating value of fuel blend, the amount of LPG was decreased as hydrogen was gradually added. Exhaust emissions were measured using a HORIBA exhaust gas analyzer for various fractions of hydrogen-LPG blends. The results showed that the rapid combustion duration was shortened, and the rate of heat release elevated as the hydrogen fraction in the fuel blend was increased. Moreover, the maximum rate of pressure rise also increased. These phenomena were attributed to the burning velocity which increased exponentially with the increased hydrogen fraction in the $H_2$-LPG fuel blend. Exhaust HC and $CO_2$ concentrations decreased, while NOX emission increased with an increase in the hydrogen fraction in the fuel blend. Our results could facilitate the application of hydrogen and LPG as a fuel in the current fossil hydrocarbon-based economy and the strict emission regulations in internal combustion engines.

• Journal of the Korean Institute of Gas
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• v.21 no.2
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• pp.20-25
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• 2017

For the HCNG bus using fuel which is the mixture gas of hydrogen and natural gas, the fuel efficiency and $CO_2$ emission characteristics were analyzed based on the WHVC test results and compared with that of the CNG and diesel buses. $CO_2$ emission characteristics were also analyzed by contribution effects such as carbon emission factor and fuel consumption. As a result, the fuel economy of HCNG bus was evaluated to be 11.5% improvement compared to CNG bus, and it was also showed equivalent to diesel bus. In addition, the $CO_2$ emission of HCNG bus was reduced 20.4% and 34.5% compared to CNG bus and diesel bus respectively. It was concluded that the $CO_2$ emission characteristics were influenced by the carbon emission factor depending on fuel composition and the fuel consumption according to the engine performance.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.7 no.1
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• pp.20-25
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• 2014

There are several severe problems for LED device, the next generation's economy green lighting: as the temperature increases, the lamp efficiency decreases; if the temperature is over $80^{\circ}C$, the lifetime of lighting decreases; Red Shift phenomenon that wavelength of spectrum line moves toward long wavelength occurs; and optical power decreases as $T_j$ increases. Thus, Heat sink design that can minimize the heat of LED device is currently in progress. While the thermal resistance of COB Type LED was reduced by direct coupling of LED chip to the board, residential 13.5W requires Heat sink in order resolve heat issue. This study designed Heat Sink suitable for residential 13.5W COB LED down-light and selected the optimum Fin thickness through flow simulation that packaged the designed Heat Sink and 13.5W COB. And finally it analyzed and evaluated the thermal modes using contacting thermometer.

• Journal of the Korean Institute of Intelligent Systems
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• v.13 no.3
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• pp.360-365
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• 2003

In this paper, GMDH(Croup Method of Data Handling) algorithm which is proved to be more excellent in efficiency and accuracy of practical use of data is applied to electric power demand forecasting. As a result, it became much easier to make a choice of input data and make an exact prediction based on a lot of data. Also, we considered both economy factors(GDP, export, import, number of employee, number of economically active population and consumption of oil) and climate factors(average temperature) when forecasting. We assumed target forecast period from first quarter 1999 to first quarter 2001, and suggested more accurate forecasting method of electric power demand by using 3-step computer simulation processes(first process for selecting optimum input period, second for analyzing time relation of input data and forecast value, and third for optimizing input data) for improvement of forecast precision. The proposed method can get 0.96 percent of mean error rate at target forecast period.

• Journal of Convergence Society for SMB
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• v.3 no.1
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• pp.7-13
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• 2013

It will prove that with a more plausible specification of the relationship between income and the value of leisure, we can develop a more accurate model of the labor market without necessarily losing the primary merit of the received model. Moreover, with an improved understanding of labor market dynamic we can see that progressive era labor market legislation, designed to mitigate the effects of bargaining power inequality in low wage labor markets, was in fact based upon sensible economic foundations. The results of this study as follow; These low-wage dynamics present an example of a positive feedback system or "vicious circle" at work in the economy. With the revised labor supply schedule presented above, the market dynamic of the low wage sector push the wage away from the range that is consistent with a self-regulating market.