• Geomechanics and Engineering
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• v.14 no.2
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• pp.107-113
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• 2018

Coal samples with different joints morphology were subjected to uniaxial compression experiments, cracks evolution was recorded by Nikon D5300 and acoustic emission (AE) energy signals were collected by AEwin Test for Express-8.0. During loading process, coal samples deformed elastically with no obvious cracks changes, then they expanded gradually along the trace of the original cracks, accompanied by the formation of secondary cracks, and eventually produced a large-scale fracture. It was more interesting that the failure mode of samples were all shear shape, whatever the original cracks morphology was. With cracks and damage evolution, AE energy radiated regularly. At the early loading stage, micro damage and small scale fracture events only induced a few AE events with less energy, while large scale fracture leaded to a number of AE events with more energy at the later stage. Based on the multifractal theory, the multifractal spectrum could explain AE energy signals frequency responses and the causes of AE events with load. Multifractal spectrum width (${\Delta}{\alpha}$), could reflect the differences between the large and small AE energy signals. And another parameter (${\Delta}f$) could reflect the relationship between the frequency of the least and greatest signals in the AE energy time series. This research is helpful for us to understand cracks evolution and AE energy signals causes.

• Analytical Science and Technology
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• v.15 no.2
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• pp.108-114
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• 2002

The new system using a glow discharge atomic emission spectrometer for the direct analysis of solid samples has been developed and characterized. The system was consisted of new glow discharge cell improved previous gas-jet boosted nozzle and radio-frequency power supply. In the case of previous type glow discharge chamber, it had been fitted trace analysis of low alloy steel with low discharge power, because it was to decrease redeposition and increase sample weight loss. But it had a problem that plasma becomes unstale due to increased sample weight loss and redeposition resulting from the high discharge power. Because of being problem of previous glow discharge, it is impossible to analyze using high power. The modified gas-jet boosted glow discharge to solve this problem would improve to be less sample loss rate of modified nozzle than sample loss rate of previous nozzle on the equal discharge condition, and improve to increase stability of plasma. The effect of discharge parameters such as discharge pressure, gas flow rate and power on the sample loss rate, emission intensity has been studied to find optimum discharge conditions. The calibration curves of Fe were obtained with 3 low-alloy samples.

• Journal of Animal Environmental Science
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• v.4 no.1
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• pp.37-45
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• 1998

There are a lot of trace gas of gaseous pollutants produced from farm animals. CO2 and CH4 are gases produced directly by the animal. NH3, N2O are produced from animal waste. Most of the effects of these gaseous pollutants on the farm animals have not been investigated in detail. CO2 emission from animal is very little. CH4 release from ruminant is also considered to be a significant factor in potential global warming. Nitrous oxide (N2O) emissions could be avoided by using organic or mineral fertilizer only as much as is needed by plant growing. This paper gives an overview about problems and solving strategies for possibilities for reduction of gaseous pollutants. The way to reduce the gaseous pollution risks from livestock systems are discussed.

• The Bulletin of The Korean Astronomical Society
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• v.39 no.2
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• pp.113.2-113.2
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• 2014

Methanol masers are divided into two classes, I and II. Class II methanol masers trace the disk-outflow systems of massive young stellar objects (YSOs), while class I methanol masers appear to trace the interaction regions of outflows with the ambient molecular gas. Class II masers have been extensively studied by single dishes, connected arrays, and VLBIs. Meanwhile, class I masers have been much less studied. They have not been detected by any VLBI facility. Thus they have been believed to have more extended structures than class II masers. We made fringe surveys of 44GHz class I methanol maser emission towards more than 150 massive YSOs with flux densities >10 Jy using the Korean VLBI Network (KVN), and detected fringes in ~10% of the sources. We performed follow-up imaging observations of the detected maser sources with KVN and KVN+VERA (KaVA). The observations aim to investigate the distribution and kinematics of 44GHz methanol maser features in each source at milli-arcsecond resolutions, and to understand what they trace. In this talk we will present the fringe survey and imaging results and our plans for further studies. Additionally, we will also introduce the preliminary results of single-dish polarization observations of water and class I methanol masers.

• Journal of Korean Society for Atmospheric Environment
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• v.20 no.6
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• pp.749-758
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• 2004

Nitrous oxide ($N_2$O) has been known as an important trace gas due to the greenhouse gas and the major source of stratospheric oxide of nitrogen (NO). Soil is the major source of $N_2$O in nature. The physicochemical characteristics of soils affect the emission of $N_2$O from soil. These physicochemical parameters are soil moisture, soil temperature, and soil N content. Since these parameters are correlated to the flux of $N_2$O from soil individually and compositely, there still remain many unknowns in the mechanism to produce $N_2$O in soil and the roles of such physicochemical parameters which affect the soil $N_2$O emission. Soil $N_2$O fluxes were measured at different levels in water filled pore space (WFPS), soil temperature and soil N contents from the same amounts of soils which were sampled from agriculturally managed upland field in a depth of ～30 cm at Kunsan. The soil $N_2$O flux measurements were conducted in a laboratory with a closed flux chamber system. The optimum soil moisture and soil temperature were observed at 60% of WFPS and ～13$^{\circ}C$. The soil $N_2$O flux increased as soil N contents increases during the whole experimental hours (up to 48 hours). However, average $N_2$O flux decreased after ～30 hours when organic carbon was mixed with nitrogen in the sample soils. It is suggested that organic carbon could be important for the emission of $N_2$O, and that the ratio of N to C needs to be identified in the process of $N_2$O soil emission.

• Bulletin of the Korean Chemical Society
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• v.20 no.9
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• pp.1040-1044
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• 1999

A micro porous PTFE membrane desolvator (MMD) was built and evaluated for the on-line removal of organic solvents to facilitate the determination of trace metal contaminants in the solvents by ICP-AES. Three organic solvents, isopropyl alcohol (IPA), methanol, and dimethy sulfoxide (DMSO) were studied. The MMD reduced organic solvent concentration in the sample aerosol stream by 82% to 89%, as indicated by monitoring C(I) emission. Net signal intensity of Fe, Al, and Cu was increasing with higher organic solvent concentration, with the rate of increase being solvent dependent. The signal intensities for Mg and Pb followed the trend with the C(I) signal. Changing the sweep gas flow rate affected the optimum signal intensity. Wine samples were analyzed by the method of standard addition. The concentrations of B, Al, and Mg were determined with a relative precision of less than 2.3%.

• Journal of Korean Society for Atmospheric Environment
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• v.21 no.E3
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• pp.75-85
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• 2005

A mathematical sensitivity analysis of the flow-through dynamic flux chamber technique, which has been utilized usually for various trace gas flux measurement from soil and water surface, was performed in an effort to provide physical and mathematical understandings of parameters essential for the NO flux calculation. The mass balance equation including chemical reactions was analytically solved for the soil NO flux under the steady state condition. The equilibrium concentration inside the chamber, $C_{eq}$, was found to be determined mainly by the balance between the soil flux and dilution of the gas concentration inside the chamber by introducing the ambient air. Surface deposition NO occurs inside the chamber when the $C_{eq}$ is greater than the ambient NO concentration ($C_{0}$) introducing to the chamber; NO emission from the soil occurs when the $C_{eq}$ is less than the ambient NO concentration. A sensitivity analysis of the significance of the chemical reactions of NO with the reactive species (i.e. $HO_{2},/CH_{3}O_{2},/O_{3}$) on the NO flux from soils was performed. The result of the analysis suggests that the NO flux calculated in the absence of chemical reactions and wall loss could be in error ranges from 40 to $85\%$ to the total flux.

• Journal of Environmental Science International
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• v.16 no.2
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• pp.179-185
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• 2007

Nitrous oxide ($N_2O$) is an important trace gas in the atmosphere not only because of its large global warming potential (GWP) but also because of the role in the ozone depletion in the stratosphere. It has been known that soil is the largest natural source of $N_2O$ in global emission. However, anthropogenic sources contributing from industrial section is likely to increase with rising the energy consumption, and transportation as well. In this study, a total of 32 gasoline-powered passenger vehicles (ranging from small to large engine's displacement and also ranging from aged catalyst to new catalyst) were tested on the chassis dynamometer system in order to elucidate the characteristics of $N_2O$ emission from automobiles under different driving modes. Ten different driving modes developed by NIER were adapted for the test. The results show that the $N_2O$ emission decreases logarithmically with increase of vehicle speed over the all test vehicles ($N_2O$) emission = -0.062 Ln (vehicle speed) + $0.289,\;r^2=0.97$). It revealed that the larger engine's displacement, the more $N_2O$ emission were recorded. The correlation between $N_2O$ emission and catalyst aging was examined. It found that the vehicles with aged catalyst (odometer record more than 8,0000km) emit more $N_2O$ than those with new catalyst. Average $N_2O$ emission was $0.086{\pm}0.095\;N_2O-g/km$ (number of samples=210) for the all test vehicles over the test driving modes.

• Journal of Korea Multimedia Society
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• v.16 no.12
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• pp.1465-1474
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• 2013

In this paper, air pollutant tracing models using perceptron neural network(PNN) and non-negative least square(NNLS) are proposed. When the measured values of the air pollution and the contribution concentration of each source by chemical transport modeling are given, they estimate and trace the amount of the air pollutants emission from each source. Two kinds of emissions data are used in the experiments : CH4 and N2O of Geumgo-dong landfill greenhouse gas, and PM10 of 17 areas in Northeast Asia and eight regions of the Korean Peninsula. Emission values were calculated using pseudo inverse method, PNN and NNLS. Pseudo inverse method could be used for the model, but it may have negative emission values. In order to deal with the problem, we used the PNN and NNLS methods. As a result, the estimation using the NNLS is closer to the measured values than that using PNN. The proposed tracing models have better utilization and generalization than those of conventional pseudo inverse model. It could be used more efficiently for air quality management and air pollution reduction.

• Journal of the Korean Chemical Society
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• v.39 no.5
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• pp.399-407
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• 1995

Electrothermal-Hollow Cathode Glow Discharge Spectrometry (Et-HCGDS) has been constructed in our laboratory for in-situ monitoring of traceble amounts of rare earth elements and actinides. Et-HCGDS is the portable glow discharge system that can perform the trace analysis of elements. The main structural design of Et-HCGDS was based upon the electrothermal heating and glow discharge techniques. More details on Et-HCGDS are available elsewhere. In this study, air was used as a flow gas for the glow discharge system. As a result, the emission spectra of air were collected and the assignment of air emission lines was performed with helps of pure nitrogen and oxygen emission spectra and previously published results. We found that the emission lines of air plasma were mainly due to nitrogen molecules. This paper includes the complete assignments of the air emission lines observed by using Et-HCGDS. Also, this study will be an useful reference for spectrochemical anaysis including air analysis.