• 한국산업융합학회 논문집
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• 제24권3호
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• pp.323-331
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• 2021

With global warming and pollution problems, accurate forecasting of the harmful gases would be an essential alarm in our life. In this paper, we forecast the emission of the five gases(SOx, NO₂, NH₃, H₂S, CH₄) using the time series model of ARIMA, the learning algorithms of Random forest, and LSTM. We find that the gas emission data depends on the short-term memory and behaves like a random walk. As a result, we compare the RMSE, MAE, and MAPE as the measure of the prediction performance under the same conditions given to three models. We find that ARIMA forecasts the gas emissions more precisely than the other two learning-based methods. Besides, the ARIMA model is more suitable for the real-time forecasts of gas emissions because it is faster for modeling than the two learning algorithms.

• 천문학회보
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• 제41권2호
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• pp.29.4-29.4
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• 2016

The relations between star formation and properties of molecular clouds are studied based on a sample of star forming regions in the Galactic Plane. Sources were selected by having radio recombination lines to provide identification of associated molecular clouds and dense clumps. Radio continuum and mid-infrared emission were used to determine star formation rates, while 13CO and submillimeter dust continuum emission were used to obtain masses of molecular and dense gas, respectively. We test whether total molecular gas or dense gas provides the best predictor of star formation rate. We also test two specific theoretical models, one relying on the molecular mass divided by the free-fall time, the other using the free-fall time divided by the crossing time. Neither is supported by the data. The data are also compared to those from nearby star forming regions and extragalactic data. The star formation "efficiency," defined as star formation rate divided by mass, spreads over a large range when the mass refers to molecular gas; the standard deviation of the log of the efficiency decreases by a factor of three when the mass of relatively dense molecular gas is used rather than the mass of all the molecular gas.

• 자원ㆍ환경경제연구
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• 제23권3호
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• pp.473-496
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• 2014

본 논문은 이산화탄소 배출량과 소득과의 비선형적인 관계를 시간변동계수를 갖는 공적분모형으로 추정하였다. 특히 이산탄소배출량의 소득효과를 시간에 따라 서서히 변하는 것으로 모형화하였고, 이를 비모수적 방법을 이용하여 추정하였다. 추정결과 선진국의 경우 소득탄력성이 시간에 대해 감소하는 것으로 추정된 반면에 개발도상국의 소득탄력성은 시간에 따라 점차 증가하는 것으로 추정되었다. 이 같은 결과는 경제 발전단계에 따라 소득이 이산화탄소 배출량에 미치는 영향이 다르다는 환경쿠즈네츠곡선에서 의미하는 것과 일치하는 결과이고, 또한 기후변화협약과 교토의정서 상에서 의무준수 대상국(Annex I)과 Non-Annex I 국가 구분이 필요하다는 것을 반증한다. 이러한 차이는 선진국에 비하여 개도국의 경우 소득에 따른 이산화탄소 배출이 상대적으로 더욱 가속화될 수 있음을 의미하며, 이는 기후변화협약 상에서 개도국에 대한 기술이전 및 재정지원이 지속적으로 필요하다는 것에 대한 근거로 활용될 수 있다.

• 한국전기전자재료학회논문지
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• 제14권8호
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• pp.634-639
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• 2001

We investigated the etching characteristics of chromium films by using Cl$_2$/O$_2$ gas mixtures with electron cyclotron resonance plasma. In order to examine the chemical etch characteristics of Cr films by using Cl$_2$/O$_2$ gas plasma, we obtained the etch rate with various gas mixing ratios. By X-ray photoelectron spectroscopy, the surface reaction on the chromium films during the etch was examined. From narrow scan analyses of Cr, Cl, and O, it was confirmed that a chromium oxychlorie (CrCl$_{x}$O$_{y}$) layer was formed on the surface by the etch using Cl$_2$/O$_2$ gas mixtures. We observed a new characteristic emission line during the etch of chromium films using Cl$_2$/O$_2$ gas mixtures by an optical emission spectroscopy. It was found that the peak intensity of this emission line had a tendency compatible with the etch rate. The origin of this emission line was discussed in detail. At the same time, the etched profile was also examined by scanning electron microscope.e.e.

• 대한건축학회논문집:구조계
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• 제34권10호
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• pp.37-44
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• 2018

In this study, the effects of considering hourly metabolic rate variations for predicted mean vote (PMV) control on the heating and cooling energy and greenhouse gas emission were investigated. The case adopting PMV control taking the hourly metabolic rate into account was comparatively analyzed against the conventional dry-bulb air temperature control, using a detailed simulation technique. Under the assumption that all the apartments in Korea adopt the PMV control incorporating real-time metabolic rate measurements, nationwide reductions of primary energy and greenhouse gas emission were analyzed. As a result, PMV control considering hourly metabolic rate variations is expected to reduce national primary energy by 6.2% compared to conventional dry-bulb air temperature control, corresponding to reduction of 10,342 GWh. In addition, it turned out that 6.6% of tCO2 emission can be reduced by adopting PMV control, corresponding to nationwide reduction of greenhouse gas emission by approximately 1,720,000 tCO2.

• 대한기계학회논문집
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• 제18권1호
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• pp.240-249
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• 1994

The basic experiments for designing the effective gas turbine combustor were performed. There are several factors that define the characteristics of gas turbine combustor. Among them, experiment was focused on swirl effects by three types of swirler with different swirl numbers(0.0, 0.38, and 0.62). Particularly, an interest was concentrated on primary zone where the flame characteristics of total combustor was dominated strongly and secondary zone where the remaining unburned gas was reacted again or cooling effect was done according to degree of swirl intensity. For this study, following measurements have been carried out, that is, time mean and fluctuating temperature, exhaust gas composition including NO concentration, and ion current. From this study, it was found that swirl intensity affects largely not only flame style but also emission formation, furthermore that it is important to select proper swirl intensity.

• 천문학회보
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• 제38권2호
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• pp.64.1-64.1
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• 2013

High energy photons and mechanical energy produced by the process of star formation result in copious FIR molecular and atomic lines, which are important coolants of the system. Photons thermally or mechanically induced could dissociate water in the dense envelope to change relative abundances among the species O, OH, and H2O. Here we analyze OH emission lines toward embedded young stellar objects (YSOs) observed as part of the Herschel open time key program, 'Dust, Ice, and Gas In Time (DIGIT)' in order to study the physical conditions of associated gas and the energy budget loaded on the OH line emission. According to our analysis of the Herschel/PACS spectra, OH emission peaks at the central spaxel in most of sources, but several sources show spatially extended emission structures. In the extended emission sources, the distribution of OH emission is correlated with that of [OI] emission and extended along the outflow directions. Considering the diversity of source properties, ratios between detected OH lines are relatively constant among sources. In addition, each OH line has strong correlation with bolometric luminosity. For detail analyses with rotation diagram and non-LTE LVG model, we present the results from GSS30-IRS1 and Elias29.

• 한국대기환경학회지
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• 제19권4호
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• pp.387-396
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• 2003

A field study was conducted during the summer time of 2002 to determine compositions of volatile organic compounds (VOCs) emitted from vehicles and to develop source emission profiles that is applied to CMB model to estimate the source contribution of certain area. Source emission profile is widely used for the estimation of source contribution by the chemical mass balance model and have to be developed applicable for the target area of estimation. This study was aimed to develop source emission profile and estimation of source contribution of VOCs after application of the chemical mass balance (CMB) receptor model. After considering the emission inventory and other research results for the VOCs in Seoul, Korea, the sources like vehicle emission (tunnel), gas station (gasoline, diesel), solvent usage (painting operation, dry cleaning, graphic art), and gas fuels were selected for the major VOCs sources. Furthermore, ambient air samples were simultaneously collected from 09:00 to 11:00 for four days at eight different official air quality monitoring sites as receptors in Seoul during summer of 2001. Source samples were collected by canisters, and then about seventy volatile organic compounds were analyzed by gas chromatography with flame ionization detector (GC/FID). Based on both the developed source profiles and the database of the receptors, CMB model was intensively applied to estimate mass contribution of VOCs sources. Examining the source profile from the vehicle, the portion of alkanes of VOCs was highest, and then the portion of aromatics such toluene, m/p-xylene were followed. In case of gas fuel. they have their own components; the content of butane, propane, ethane was higher than any other component according to the fuel usage. The average of the source apportionment on VOCs for 8 sites showed that the major sources were vehicle emission and gas fuels. The vehicle emission source was revealed as having the highest contribution with an average of 49.6%, and followed by solvent with 21.3%, gas fuel with 16.1%, gasoline with 13.1%.

• 한국농공학회논문집
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• 제54권3호
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• pp.37-45
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• 2012

Recently, the livestock industry in Korea was heavily affected by the outbreak of official livestock diseases such as foot and mouse disease, high pathogenic avian influenza, swine influenza, and so on. It has been established that these diseases are being spread through direct contact, droplet and airborne transmission. Among these transmissions, airborne transmission is very complex in conducting field investigation due to the invisibility of the pathogens and unstable weather conditions. In this study, the airborne transmission was thoroughly investigated inside a pig house by conducting tracer gas ($CO_2$) experiment because experiment with real pathogen is limited and dangerous. This is possible as it can be assumed that the flow is similar pattern very fine particles and gas. In the experiment, the ventilation structure as well as the location of gas emission were varied. The $CO_2$ detection sensors were installed at 0.5 and 1.3 m height from the floor surface. The tracer gas level was measured every second. Results revealed that the direction of spread can be determined by the response time. Response time refers to the time to reach 150 ppm from the gas emission source at each measuring points. The location of the main flow as well as the gas emission was also found to be very important factor causing the spread.

• Applied Science and Convergence Technology
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• 제23권2호
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• pp.83-89
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• 2014

Adsorption of residual gas molecules damped the emission current of a W (310) field electron emission (FE) emitter. The damping speed was linearly proportional to the pressure gauge readings at pressure ranging from ${\sim}10^{-8}Pa$ to ${\sim}10^{-9}Pa$, and the proportionality constant was employed to measure pressure in the $10^{-10}Pa$ range. A time plot of FE current revealed the existence of an "initial stable region" after the flash heating of W(310) FE, during which the FE current damps very slowly. The presence of non-hydrogen gas removed this region from the plot, supplying a means of qualitatively analysing the gas species.