• Journal of Environmental Impact Assessment
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• v.26 no.1
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• pp.11-26
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• 2017

Approximate empirical equations obtained by measuring overall noise levels at different distances have been used to evaluate environmental influence of the railway noise though the accurate prediction of noise levels is important. In this paper, a noise prediction model considering the frequency characteristics of noise sources and propagation was suggested to improve the accuracy of noise prediction. The railway noise source was assorted into track, wheel, traction and aerodynamic components and they were characterized with the source strength and speed coefficient at each octave-band frequency. Correction terms for the acoustic roughness and the track/bridge condition were introduced. The sound attenuation from a source to a receiver was calculated taking account of the geometrical divergence, atmospheric absorption, ground effect, diffraction at obstacles and directivity of source by applying ISO 9613-2. For obtaining the source strength and speed coefficients, the results of rolling noise model, numerical analysis and measurements of pass-by noise were analyzed. We compared the predicted and measured noise levels in various vehicles and tracks, and verified the accuracy of the present model. It is found that the present model gives less error than the conventional one, so that it can be applied to make the accurate prediction of railway noise effect and establish its countermeasures efficiently.

• Applied Chemistry for Engineering
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• v.25 no.1
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• pp.41-46
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• 2014

The property improvement of polycarbonate coated with a multilayer film composed of an inorganic $SiO_2$ film and a photocatalytic $TiO_2$ film was studied. The $SiO_2$ film as a binder had an excellent light transmission characteristic. After the treatment with atmospheric pressure plasma, the surface of $SiO_2$ film showed the hydrophilicity, which increased the film coating uniformity with a $TiO_2$-containing aqueous solution. When $TiO_2$ film was over 200 nm thick, the absorption effect of UV rays in the range of 180~400 nm suppressed the yellowing phenomena of polycarbonate substrate. The inorganic film improved the heat resistance of polycarbonate substrates. $TiO_2$ film in the outmost under the exposure of UV rays promotes the catalytic oxidation characteristics and yields the capability to the decomposition of organic contaminants, and also increases the self-cleaning properties due to the increase of hydrophilicity. Structural stability of the polycarbonate substrate coated with inorganic $TiO_2$ and $SiO_2$ film was shown. The role of $SiO_2$ film between $TiO_2$ and polycarbonate substrate suppressed the peeling of $TiO_2$ film by inhibiting the photocatalytic oxidation effect of $TiO_2$ film on the polycarbonate substrate.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.25 no.8
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• pp.857-863
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• 2014

In determining interaction between plasma and electromagnetic wave, plasma frequency and collision frequency are two key parameters. They are derived from electron density and temperature, which vary in an extremely wide range, depending on a plasma generator. Because the parameters are usually unknown, traditional researches have utilized simplified electron density model and constant electron temperature approximation. Introduction of plasma fluid model to electromagnetics is suggested to utilize relatively precise time dependent variables for given generator. Dielectric barrier discharge(DBD) generator is selected due to its simple geometry which allows us to use one dimensional analysis. Time dependent property is analyzed when microwave is launched toward parallel plate DBD plasma. Afterwards, attenuation tendency with the change of electron density and temperature is demonstrated.

• Applied Chemistry for Engineering
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• v.10 no.7
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• pp.1003-1007
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• 1999

The activity and products distribution for the hydrogenation of butadiene and pentadiene over the gold and cobalt catalysts prepared by coprecipitation and impregnation method was investigated with using a flow reactor under atmospheric pressure. The reaction characteristics of the highly dispersed gold particles and its role were studied. The activity of the gold catalyst by coprecipitation was much higher than that by impregnation. The selectivity of butene on all gold particles was always 100% even in the absence of butadiene in the stream, but butadiene on cobalt supported catalyst was easily hydrogenated to butane. It was therefore considered that the active sites at circumferences of the gold particles possessed an unique property which took a proper affinity to hydrogen. In the hydrogenation of butadiene and pentadiene, the percentages of 1-butene and 2-pentene were 60%~70% and about 62%, respectively. The results could be simply explained by a statistical concepts of hydrogen addition.

• Journal of Environmental Science International
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• v.16 no.9
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• pp.1051-1061
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• 2007

The impact of midlatitude synoptic system (upper-level trough) on typhoon intensity change was investigated by analyzing the spatial and temporal characteristics of vertical wind shear (VWS), relative eddy momentum flux convergence (REFC), and potential vorticity (PV). These variables were computed over the radial mean $300{\sim}1,000km$ from the typhoon center by using GDAPS (Global Data Assimilation and Prediction System) data provided by the Korea Meteorological Administration (KMA). The selected cases in this study are typhoons Rusa (0215) and Maemi (0314), causing much damage in life and property in Korea. Results show that the threshold value of VWS indicating typhoon intensity change (typhoon to severe tropical storm) is approximately 15 m/s and of REFC ranges 6 to 6.5 $ms^{-1}day^{-1}$ in both cases, respectively. During the period with the intensity of typhoon class, PVs with 3 to 3.5 PVU are present in 360K surface-PV field in the cases. In addition, there is a time-lag of 24 hours between central pressure of typhoon and minimum value of VWS, meaning that the midlatitude upper-level trough interacts with the edge of typhoon with a horizontal distance less than 2,000 km between trough and typhoon. That is, strong midlatitude upper-level divergence above the edge of the typhoon provides a good condition for strengthening the vertical circulation associated with the typhoons. In particular, when the distance between typhoon and midlatitude upper-level trough is less than 1,000 km, the typhoons tend to weaken to STS (Severe Tropical Storm). It might be mentioned that midlatitude synoptic system affects the intensity change of typhoons Rusa (0215) and Maemi (0314) while they moves northward. Thus, these variables are useful for diagnosing the intensity change of typhoon approaching to the Korean peninsula.

• Journal of Korean Society of societal Security
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• v.2 no.2
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• pp.85-90
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• 2009

In recent days, climatic change cause abnormal weather all over the world and we have a great loss of life and property every year. In Korea, we suffer from landslide problem because large regions of Korea Peninsula are composed of mountain. In order to detect rapidly and to take follow-up measures of disaster, the remote sensing is being used actively as conventional field survey has many restrictions in accessibility because of more time and man power requirement. In additions interferometric SAR is one of the techniques that have our attention because it can provide many kinds of accurate surface information without restriction of atmospheric and ground conditions by using L-band. In this study, we aimed to monitor the displacement of mountain area in Kangwondo and this results will be used for detecting landslide. Also we build the web system for detecting and analyzing the landslide.

• Journal of Environmental Health Sciences
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• v.33 no.4
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• pp.325-337
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• 2007

The effect of seawater and air pollutants on the three-story stone pagodas on Gameunsa Temple Site have been studied in order to establish conservation basic plan. Also, an experimental study has been conducted to evaluate the effect of seawater salt and air pollutants on the weathering of granite. The results could be summarized as follows. Because the three-story stone pagodas on Gameunsa Temple Site are located outdoors, the external appearance has been largely deteriorated due to natural and artificial factors such as typhoon, wind, microorganisms, moisture, extreme change in temperature, air pollutants, and seawater, etc. When G.J fresh granite was dipped into the seawater, dissolution rate of three minerals (Mg, Ca, and K) are increased linearly until about 40 days and then increased abruptly. After seawater dipping experiments, the mineral compositions of the granite surface were lower then that of the G.J fresh granite but Poisson's ratio and absorption ratio were slightly increased. Therefore, from these results we can say that stone cultural properties could be weathered by seawater and air pollutants and it's considered being a meaningful experiment to study the conservation method of stone cultural properties from seawater.

• Journal of the Korean earth science society
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• v.21 no.1
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• pp.41-50
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• 2000

After analyzing the record of climate of the Chosun era with the weather data written on the true history of the Chosun Dynasty, and in comparison with the latest weather data in Seoul, the following conclusion has been reached. It's not easy to restore the climate of the Chosun era with the true history of the Chosun Dynasty only, for the data of the Chosun era is nothing but 5.4% of that the recent 10 years, centering around Seoul. The number of days of the praying for rain and fine weather have nothing to do with those of precipitation. The monthly number of days of precipitation and hail are similar to those of the recent, years, even though the data is not enough. The situation of the days of frost and fog are very different from that of the recent.10 years. This suggests that they recorded the situation when there was a lot of casualties to men and property, while they didn't record it when there were no casualties because the precipitation occured at the time.

• Advances in environmental research
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• v.7 no.1
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• pp.13-28
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• 2018

It is currently agreed upon that one of the major challenges in the construction industry is the energy efficiency of existing buildings. The World Meteorological Organisation (WMO) and United Nations (UN) have reported that the concentration of global atmospheric carbon dioxide has increased by an average of 50%, a record speed, from 2015 to 2016. The housing sector contributes to 45% of the UK's carbon emissions. To help tackle some of those issues the recast Energy Performance Building Directive (EBPD) has introduced Nearly Zero Energy Buildings (NZEBs) in the coming years (including buildings that will undergo refurbishment/renovations). This paper will explore the retrofitting of a UK residential dwelling using Thermal Analysis Simulation (TAS, EDSL) software by focusing on building fabric improvements and usage of on-site renewables. The CIBSE Test Reference Year (TRY) weather data has been selected to examine the performance of the building under current and future climate projections. The proposed design variables were finally implemented in the building altogether on TAS. The simulation results showed a reduction in the building's annual energy consumption of $122.64kWh/m^2$ (90.24%). The greatest savings after this were achieved for the annual reduction in carbon emissions and avoided emissions, which were 84.59% and $816.47kg/CO_2$, respectively.

• Journal of the Korean Society of Propulsion Engineers
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• v.19 no.4
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• pp.69-76
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• 2015

Recently, environmental sustainability of the transitional explosives and propellants is an issue of growing importance in energetic materials. For examples, ammonium perchlorate(AP) as an solid propellants oxidizer could create a poisonous gas and atmospheric pollutions, such as HCl. Among the several oxidizers, hydrazinium nitroformate(HNF) is an effective candidate substance for eco-friendly oxidizer, which has high density, pressure index, and less smog generating property during combustion for the Divert and Attitude Control System(DACS). This study was confirmed a synthesis through various conditions, was performed for the essential data of solubility the crystallization process. Also, crystallization process such as cooling, drowning-out and sonication were performed.