• International Journal of Highway Engineering
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• v.13 no.3
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• pp.121-129
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• 2011

The purpose of this study is to determine the relationship between observed traffic data and NOx concentrations from not an ideal condition but a real road in real-time. Also we aim to develop an estimation model for NOx emission concentrations due to vehicle exhaust gas, and it can be applied to monitor the degree of air pollution on National Road in real-time. To eliminate outliers which are occurred due to errors of equipments and other variables, we use the robust analysis and develop two models. which are considering and not considering wind impact. The result of this research can be used for understanding present condition of air pollution caused by vehicle exhaust gas and evaluating for environmental effects of transportation policy.

• Transactions of the Korean Society of Automotive Engineers
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• v.12 no.3
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• pp.19-26
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• 2004

A prior fundamental study was executed using a constant volume chamber to improve the burning properties of lean pre-mixture by the injection of active radicals generated in the sub-chamber. In consequence, RI method shows remarkable progress in the aspects of burning velocity and combustible lean limit compared with SI method. In this study, the necessary additional works have been performed to be based on the former results. We changed parameters as the initial temperature and the initial pressure of mixture. And the effects of residual gas at issue in a real engine were investigated. As a result, the effects of initial temperature were significant, but on the other hand, those of initial pressure were slight. The correlation of passage hole number between overall passage hole area was grasped. And the more detailed analysis is required on residual gas.

• International Journal of Naval Architecture and Ocean Engineering
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• v.11 no.2
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• pp.914-922
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• 2019

Gas composition has a significant impact on the dispersion behavior and accumulation characteristics of blowout gas. However, few public studies has investigated the corresponding effect of gas composition. Therefore, this study firstly builds the FLACS-based numerical model about an offshore drilling platform. Then several scenarios by varying the composition of blowout gas are simulated while the scenario with the composition of "Deepwater Horizon" accident is regarded as the benchmark. Furthermore, the effects of the gas composition on the flammable cloud volume, the influenced area of flammable cloud, the influenced area of hydrogen sulfide and the critical time of the hydrogen sulfide spreading to the living area are analyzed. The results demonstrate that gas composition is a driving factor for dispersion characteristics of blowout gas. All the results can give support to reduce the risk of the similar accidents incurred by real blowouts.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.28 no.10
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• pp.1279-1287
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• 2004

The vaporization characteristics of a liquid heptane droplet in a supercritical nitrogen flow are numerically studied. The transient conservation equations of mass, momentum, energy, and species are expressed in an axisymmetric coordinate system. The governing equations are solved time marching method with preconditioning scheme. The modified Soave-Redlich-Kwong equation of state is employed for taking account of real gas effects such as thermodynamic non-ideality and transport anomaly. Changing the convective velocity and ambient pressure, several parametric studies are conducted. The numerical results show that the two parameters, Reynolds number and dimensionless combined parameter(${\mu}$s/${\mu}$d)(equation omitted), have influence on supercritical droplet vaporization.

• Journal of ILASS-Korea
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• v.9 no.3
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• pp.8-14
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• 2004

Characteristics of droplet vaporization at high ambient pressures and temperatures which are supercritical conditions is studied numerically by formulating one dimensional vaporization model in liquid dodecane and air. Modified Soave-Redlich-Kwong state equation is used to condider real gas effect. Non-ideal behavior of properties at near critical and supercritical conditions is considered in the high pressure condition. Characteristic spatial distribution of properties with various conditions of pressure and temperature is evaluated in order to understand vaporizing evolution.

• Journal of Sensor Science and Technology
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• v.31 no.6
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• pp.418-422
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• 2022

α-pinene is a natural volatile organic compound secreted by coniferous trees to protect themselves from attacks by insects, microorganisms, and viruses. Recently, studies have reported that α-pinene possesses pharmacological effects on various biological reactions such as anxiolytic, sleep-enhancing, anti-nociceptive, and inflammatory activity. Thus, forest bathing has recently received great attention as a novel therapy for treating severe diseases as well as psychological issues. However, appropriate places and timings for effective therapies are still veiled, because on-site monitoring of α-pinene gas in forests is barely possible. Although portable chemosensors could allow real-time analysis of α-pinene gas in forests, the α-pinene sensing properties of chemosensors have never been reported thus far. Herein, we report for the first time, the α-pinene sensing properties of an oxide semiconductor gas sensor based on rhombohedral In₂O₃ (h-In₂O₃) nanoparticles prepared by a microwave-assisted hydrothermal reaction. The h-In₂O₃ nanoparticle sensor showed a high response to α-pinene gas at ppm levels, even under humid conditions (for example, relative humidity of 50 %). The purpose of this research is to identify the potential of oxide semiconductor gas sensors for implementing portable devices that can detect α-pinene gas in forests in real-time.

• Environmental and Resource Economics Review
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• v.23 no.1
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• pp.133-156
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• 2014

In general, quantity results of empirical analysis using model shows how much big performance policy has. Therefore this is useful to evaluate a policy. This paper composed macro economic model based on Bank of Korea's quarterly model and annual model, that estimates performance of overseas oil and gas development project to Korean economy in aspect of quantity. In this model, we estimated each effect in real GDP, current account, unemployment rate, CPI and exchange rate carried by recovered amount from overseas oil and gas development project. The recovered amount was evaluated in currency coming from oil and gas acquired from overseas oil and gas development project. Macro economic model of this paper benchmarked macro model composed by Bank of Korea(1997, 2004, 2012). We reviewed model robustness using statistical suitability of each equation and historical simulation for from 1994 to 2011. The recovered amount of overseas oil and gas development project has positive effect in every macro economic index except CPI and exchange rate. Economic effect to macro economic index become bigger with time because the recovered amount of overseas oil and gas development project are increasing until now. Although empirical results of economic effects in every year from the recovered amount of overseas oil and gas development project are different, as of 2011, empirical results showed that the recovered amount of overseas oil and gas development project increase 2.226% and 0.401% in current account and real GDP respectively. And it also decrease 0.489%p in unemployment rate. Exchange rate to US dollars also decrease in amount of 0.379%.

• Transactions of the Korean Society of Automotive Engineers
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• v.8 no.4
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• pp.26-33
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• 2000

In-cylinde flow and mixture formation are key contributors to both idle stability and combustion stability at part load condition in SI engine. The real time measurements of air-fuel ration and in- cylinder residual gas fraction are particularly important to obtain a better understanding of the mechanisms for combustion and emissions especially during cold start and throttle transient condition. This paper reports the cycle resolved measurements of residual gas fraction and equivalence ration near speak plug with value timing change and their effects on combustion characteristics at part load. The results showed that the effect of intake value opening on the residual gas fraction was smaller than that of exhaust valve closing because of the decreases of exhaust gas reverse flow from exhaust port. The variation of equivalence ratio near spark plug increased with the increase of value overlap and it closely related with heat release rate and combustion stability

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.17 no.11
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• pp.1060-1071
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• 2005

Passive gas dispersions over a 1/1000 scale terrain model at Eiffel type wind tunnel were reproduced by numerical simulation. Large eddy simulation was used to treat the sub-grid scale turbulences. The terrain features were represented by millions of point forces densely distributed over the solid surface using the virtual boundary method. The model simulations agreed very well with the experiments in a consistent fashion for all wind directions. The measured profiles of the wind speeds as well as the tracer gas concentrations were nicely simulated by the CFD model at most locations scattered over the model terrain. With scale factor adjusted and the thermal stratification effects incorporated, the CFD model was expected to provide reliable information on pollutant dispersions over the real complex terrains.

• Journal of computational fluids engineering
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• v.4 no.3
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• pp.63-70
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• 1999

A Direct simulation Monte-Carlo (DSMC) code is developed, which employs the Monte-Carlo statistical sampling technique to investigate hypersonic rarefied gas flows accompanying chemical reactions. The DSMC method is a numerical simulation technique for analyzing the Boltzmann equation by modeling a real gas flow using a representative set of molecules. Due to the limitations in computational requirements. the present method is applied to a flow around a simple two-dimensional object in exit velocity of 7.6 km/sec at an altitude of 90 km. For the calculation of chemical reactions an air model with five species (O₂, N₂, O, N, NO) and 19 chemical reactions is employed. The simulated result showed various rarefaction effects in the hypersonic flow with chemical reactions.