In order to reduce average arterial vehicle delay, a novel distributed and coordinated traffic control algorithm is developed using the multiple agent system and the reinforce learning （RL）. The RL is used to minimi...In order to reduce average arterial vehicle delay, a novel distributed and coordinated traffic control algorithm is developed using the multiple agent system and the reinforce learning （RL）. The RL is used to minimize average delay of arterial vehicles by training the interaction ability between agents and exterior environments. The Robertson platoon dispersion model is embedded in the RL algorithm to precisely predict platoon movements on arteries and then the reward function is developed based on the dispersion model and delay equations cited by HCM2000. The performance of the algorithm is evaluated in a Matlab environment and comparisons between the algorithm and the conventional coordination algorithm are conducted in three different traffic load scenarios. Results show that the proposed algorithm outperforms the conventional algorithm in all the scenarios. Moreover, with the increase in saturation degree, the performance is improved more significantly. The results verify the feasibility and efficiency of the established algorithm.展开更多
A modified Fickian plug-flow/dispersion model (P/D model) is developed in this study. In P/D model, the flow process is divided into two belts, plug flow belt and dispersion belt. P/D model is very similar to Fickian ...A modified Fickian plug-flow/dispersion model (P/D model) is developed in this study. In P/D model, the flow process is divided into two belts, plug flow belt and dispersion belt. P/D model is very similar to Fickian model and rather perfect. The prediction by P/D model can be always consistent with experimental data in river, flume, and pond, even though the data are much skew. Therefore, P/D model is better than Fickian model and other dispersion models.展开更多
The emission of dioxins from municipal solid waste incinerators(MSWIs) has become a widespread concern.The effect of meteorological parameters(wind speed,atmospheric stability and mixing height) on the hourly ground l...The emission of dioxins from municipal solid waste incinerators(MSWIs) has become a widespread concern.The effect of meteorological parameters(wind speed,atmospheric stability and mixing height) on the hourly ground level concentration(GLC) of dioxins was estimated using air dispersion models.Moreover,the health risks of dioxin exposure were evaluated for children and adults using the Nouwen equation.The total environmental exposure via air inhalation and food ingestion was calculated,based on linear fit equations.The results indicate that potentially severe pollution from dioxins occurs at a wind speed of 1.5 m/s with atmospheric stability class F.In addition,local residents in the study area are exposed to severe weather conditions most of the time,and the risk exposures for children are far higher than those for adults.The total exposure for children far exceeds the tolerable daily intake of dioxin recommended by the World Health Organization(WHO) of 1-4 pg TEQ/(kg·d) under severe weather conditions.Results from modeling calculations of health risk assessment were consistent with dioxin levels obtained during actual monitoring of emissions.展开更多
This paper makes comparisons between Chinese Environmental Impact Assessment (EIA) Guidelines for Air dispersion modelling and the advanced air dispersion model ADMS. Since 2001 the ADMS model has been the first and o...This paper makes comparisons between Chinese Environmental Impact Assessment (EIA) Guidelines for Air dispersion modelling and the advanced air dispersion model ADMS. Since 2001 the ADMS model has been the first and only foreign model that has been approved by the Appraisal Center for Environment and Engineering (ACEE) to be used in EIA projects in China (http://www.china-eia. com/inden_content/rjrz/ rjrz_ADMS/htm). In the paper the following sections provide brief descriptions of the main features of the Chinese Guidelines for Air Dispersion (Section 2) and ADMS (Section 3); Section 4 provides a comparison of the two modelling methods for some simple cases and conclusions and discussion are given in Section 5.展开更多
As an important design factor for constructed wetlands,hydraulic retention time and its distribution will affect the treatment performance.Instantaneously injected sodium chloride tracers were used to obtain residence...As an important design factor for constructed wetlands,hydraulic retention time and its distribution will affect the treatment performance.Instantaneously injected sodium chloride tracers were used to obtain residence time distributions of the lab scale subsurface flow constructed wetland.Considering the presence of trailing and multiple peaks of the tracer breakthrough curve,the multi flow dispersion model(MFDM)was used to fit the experimental tracer breakthrough curves.According to the residual sum of squares and comparison between the experimental values and simulated values of the tracer concentration,MFDM could fit the residence time distribution(RTD)curve satisfactorily,the results of which also reflected the layered structure of wetland cells,thus to give reference for application of MFDM to the same kind of subsurface flow constructed wetlands.展开更多
The current applicable release & dispersion models are reviewed. A typical model is developed on the basis of LPG storage conditions in China and the authors' research. The study is focused on the relationship...The current applicable release & dispersion models are reviewed. A typical model is developed on the basis of LPG storage conditions in China and the authors' research. The study is focused on the relationship between LPG composition and release rate, and on the influence of buildings or structures located in the surrounding area on the dispersion of gas plume. The established model is compared with existing models by the use of published field test data.展开更多
This research assessed the environmental impact of cement silos emission on the existing concrete batching facilities in M35-Mussafah, Abu Dhabi, United Arab Emirates. These assessments were conducted using an air qua...This research assessed the environmental impact of cement silos emission on the existing concrete batching facilities in M35-Mussafah, Abu Dhabi, United Arab Emirates. These assessments were conducted using an air quality dispersion model (AERMOD) to predict the ambient concentration of Portland Cement particulate matter less than 10 microns (PM<sub>10</sub>) emitted to the atmosphere during loading and unloading activities from 176 silos located in 25 concrete batching facilities. AERMOD was applied to simulate and describe the dispersion of PM<sub>10</sub> released from the cement silos into the air. Simulations were carried out for PM<sub>10</sub> emissions on controlled and uncontrolled cement silos scenarios. Results showed an incremental negative impact on air quality and public health from uncontrolled silos emissions and estimated that the uncontrolled PM<sub>10</sub> emission sources contribute to air pollution by 528958.32 kg/Year. The modeling comparison between the controlled and uncontrolled silos shows that the highest annual average concentration from controlled cement silos is 0.065 μg/m<sup>3</sup>, and the highest daily emission value is 0.6 μg/m<sup>3</sup>;both values are negligible and will not lead to significant air quality impact in the entire study domain. However, the uncontrolled cement silos’ highest annual average concentration value is 328.08 μg/m<sup>3</sup>. The highest daily emission average value was 1250.09 μg/m<sup>3</sup>;this might cause a significant air pollution quality impact and health effects on the public and workers. The short-term and long-term average PM<sub>10</sub> pollutant concentrations at these receptors predicted by the air dispersion model are discussed for both scenarios and compared with local and international air quality standards and guidelines.展开更多
Odorous emissions emitted from various sources including industrial and commercial activities have particular concerns about human health. These malodors emissions are an environmental concern that affects health stat...Odorous emissions emitted from various sources including industrial and commercial activities have particular concerns about human health. These malodors emissions are an environmental concern that affects health status and social life of the neighbors. That requires the local authority to set up a management strategy to control this nuisance. The evaluation of odour emissions from fishing port is complex because these emissions depend on several factors such as multiple sources of odor emissions, meteorological conditions, topography and others. That imposes the use of complementary approaches to monitor odours. In this paper, the case of Agadir fishing port is studied, which is adjacent to the tourist area and residential neighborhoods and which hosts a number of points that can generate odors. To assess this odour impact, three methods are used such as dynamic olfactometry, dispersion modeling and mobile electronic nose (e-nose). The use of these three methods in a complementary manner to assess odour impacts around a fishing port allowed both the quantification of the emissions using dynamic olfactometry and the evaluation of their impact on the study area with model dispersion. The results enabled also to identify the most affected areas of the city by odor emissions and to recognize the meteorological parameters maximizing odor impact. The other goal of this work is to compare the results of the odour dispersion modeling and e-nose measurements for one year in terms of frequency of overtaking the set alert thresholds over the same period. Comparison highlights the strengths and weaknesses of both approaches. Modeling can be used predicatively but it does not take into account fugitive emissions reliably in the absence of data on these emissions, modeling based on the hourly average misjudges the odor peaks, while e-nose made it possible to obtain validated data and provides accurate, affordable and real-time odour measurement capability tacking in to account the role of human perception without being able to characterize the extent of the odor nuisance caused by each source. We conclude that these three valuation methods provide complementary information about odor nuisance and reasonable estimates of odors.展开更多
Evaporating bubble column reactor (EBCR) is a kind of aerated reactor in which the reaction heat is removed by the evaporation of volatile reaction mixture. In this paper, a mathematical model that accounts for the ga...Evaporating bubble column reactor (EBCR) is a kind of aerated reactor in which the reaction heat is removed by the evaporation of volatile reaction mixture. In this paper, a mathematical model that accounts for the gas-liquid exothermic reaction and axial dispersions of both gas and liquid phase is employed to study the performance of EBCR for the process of p-xylene(PX) oxidation. The computational results show that there are remarkable concentration and temperature gradients in EBCR for high ratio of height to diameter (H/DT). The temperature is lower at the bottom of column and higher at the top, due to rapid evaporation induced by the feed gas near the bottom. The concentration profiles in the gas phase are more nonuniform than those (except PX) in the liquid phase, which causes more solvent burning consumption at high H/DT ratio. For p-xylene oxidation, theo ptimal H/DT is around 5.展开更多
Ensemble forcasting,originally developed for weather prediction,is lately being extended to atmospheric dispersion applications,which is a new,effective methodology for improving the atmospheric dispersion numerical m...Ensemble forcasting,originally developed for weather prediction,is lately being extended to atmospheric dispersion applications,which is a new,effective methodology for improving the atmospheric dispersion numerical modeling.In March 2011,due to the massive 9.0 earthquakes and ensuing tsunami that struck off the northern coast of the island of Honshu,the Fukushima Nuclear Plant I had the substantial leak of radioactive materials into surrounding environment and atmosphere.To aim at the global dispersion modeling of atmospheric radionuclides from Fukushima Nuclear Accident,this paper presents two approaches of atmospheric dispersion forecasting:ensemble dispersion modeling(EDM) and deterministic dispersion modeling(DDM),conducts the globally dispersion modeling cases for Fukushima nuclear accident,and analyzes and evaluates the simulation results using observation data.In this paper,EDM includes three different perturbation methods:meteorological perturbation method,turbulence perturbation method,and physical parameterization ensemble forecasting method.The simulation results show that the trajectories from EDM have a better performance,which is in better agreement with the atmospheric circulation and observation data; the spread from DDM is slower and not as far as EDM.Additionally,the results from EDM display a better performance in the modeling of transport from Japan to China East Sea on April 4.The reasons for these results are:the techniques of MET and TUR are performed by adding perturbations on mean wind and turbulent velocity,respectively; the various different flow fields will result in far spreading in horizontal and the simulation results closer to observation; PHY is performed by using different diffusion physical parameterizations and produces the perturbations on vertical wind,which results the spreading in smaller range and discontinuous in horizontal.Finally,the comparative analysis between modeling results and observation data shows that all cases results are in good agreement with trends of observed radionuclides surface concentration; however,the modeling surface concentration is smaller than observation,especially in DDM and PHY.Furthermore,the EDM results show that MET and TUR are of more evolutionary advantage than PHY in modeling of average and maximum concentration.Therefore,this study can serve as a reference to atmospheric dispersion and environmental emergency response(EER).展开更多
An observational campaign was conducted in the street canyon of Zhujiang Road in Nanjing city in 2007. Hourly mean concentrations of PM10 were measured at street and roof levels. The Operational Street Pollution Model...An observational campaign was conducted in the street canyon of Zhujiang Road in Nanjing city in 2007. Hourly mean concentrations of PM10 were measured at street and roof levels. The Operational Street Pollution Model （OSPM） street canyon dispersion model was used to calculate the street concentrations and the results were compared with the measurements. The results show that there is good agreement between measured and predicted concentrations. The correlation coefficient R2 values （R2 is a measure of the correlation of the predicted and measured time series of concentrations） are 0.5319, 0.8044, and 0.6630 for the scatter plots of PM10 corresponding to light wind speed conditions, higher wind speed conditions, and all wind speed conditions, respectively. PM10 concentrations tend to be smaller for the higher wind speed cases and decrease rapidly with increasing wind speed. The presentations of measured and modelled concentration dependence on wind direction show fairly good agreement. PM10 concentrations measured on the windward side are relatively smaller, compared with the corresponding results for the leeward side. This study demonstrates that it is possible to use the OSPM to model PM10 dispersion rules for an urban street canyon.展开更多
This study proposes a method based on material dispersion models to computationally simulate terahertz(THz)time-domain spectroscopy signals.The proposed method can accurately extract the refractive indices and extinct...This study proposes a method based on material dispersion models to computationally simulate terahertz(THz)time-domain spectroscopy signals.The proposed method can accurately extract the refractive indices and extinction coefficients of optically thin samples and high-absorption materials in the THz band.This method was successfully used to extract the optical constants of a 470-μm-thick monocrystalline silicon sample and eliminate all errors associated with the Fabry-Perot oscillation.When used to extract the optical constants of a 16.29-mm-thick polycarbonate sample,our method succeeded in minimizing errors caused by the low signal-to-noise ratio in the extracted optical constants.展开更多
Understanding the behavior of urban air pollution is important en route for sustainable urban development (SUD). Malaysia is on its mission to be a developed country by year 2020 comprehends dealing with air pollution...Understanding the behavior of urban air pollution is important en route for sustainable urban development (SUD). Malaysia is on its mission to be a developed country by year 2020 comprehends dealing with air pollution is one of the indicators headed towards it. At present monitoring and managing air pollution in urban areas encompasses sophisticated air quality modeling and data acquisition. However, rapid developments in major cities cause difficulties in acquiring the city geometries. The existing method in acquiring city geometries data via ground or space measurement inspection such as field survey, photogrammetry, laser scanning, remote sensing or using architectural plans appears not to be practical because of its cost and efforts. Moreover, air monitoring stations deployed are intended for regional to global scale model whereby it is not accurate for urban areas with typical resolution of less than 2 km. Furthermore in urban areas, the pollutant dispersion movements are trapped between buildings initiating it to move vertically causing visualization complications which imply the limitations of existing visualization scheme that is based on two-dimensional (2D) framework. Therefore this paper aims is to perform groundwork assessment and discuss on the current scenario in Malaysia in the aspect of current policies towards SUD, air quality monitoring stations, scale model and detail discussion on air pollution dispersion model used called the Operational Street Pollution Model (OSPM). This research proposed the implementation of three-dimensional (3D) spatial city model as a new physical data input for OSPM. The five Level of Details (LOD) of 3D spatial city model shows the scale applicability for the dispersion model implementtation. Subsequently 3D spatial city model data commonly available on the web, by having a unified data model shows the advantages in easy data acquisition, 3D visualization of air pollution dispersion and improves visual analysis of air quality monitoring in urban areas.展开更多
Monitoring and modeling of airborne particulate matter(PM)from low-altitude sources is becoming an important regulatory target as the adverse health consequences of PM become better understood.However,application of m...Monitoring and modeling of airborne particulate matter(PM)from low-altitude sources is becoming an important regulatory target as the adverse health consequences of PM become better understood.However,application of models not specifically designed for simulation of PM from low-altitude emissions may bias predictions.To address this problem,we describe the modification and validation of an air dispersion model for the simulation of lowaltitude PM dispersion from a typical cotton ginning facility.We found that the regulatory recommended model(AERMOD)overestimated pollutant concentrations by factors of 64.7,6.97 and 7.44 on average for PM 2.5,PM 10,and TSP,respectively.Pollutant concentrations were negatively correlated with height(p<0.05),distance from source(p<0.05)and standard deviation of wind direction(p<0.001),and positively correlated with average wind speed(p<0.001).Based on these results,we developed dispersion correction factors for AERMOD and cross-validated the revised model against independent observations,reducing overestimation factors to 3.75,1.52 and 1.44 for PM 2.5,PM 10 and TSP,respectively.Further reductions in model error may be obtained from use of additional observations and refinement of dispersive correction factors.More generally,the correction permits the validated adjustment and application of pre-existing models for risk assessment and development of remediation techniques.The same approach may also be applied to improve simulations of other air pollutants and environmental conditions of concern.展开更多
In the studies of fate and transport of air emissions from animal feeding operations,Gaussian based dispersion models have been commonly used to predict downwind pollutant concentrations through forward modeling appro...In the studies of fate and transport of air emissions from animal feeding operations,Gaussian based dispersion models have been commonly used to predict downwind pollutant concentrations through forward modeling approach,or to derive emission rates and emission factors through inverse dispersion modeling approach.In the Gaussian dispersion modeling process,downwind sampling location and sampling height could generate significant impact on accuracy of the model validation,or inverse modeling results based upon field measurements.This study theoretically analyzed the impact of downwind locations and sampling height on Gaussian dispersion modeling.It was discovered that the field sampling needs to be conducted at the locations beyond the plume touching-ground distance,at a downwind distance as short as 5 m for the case scenario with zero rise of emission plume under the atmospheric stability class C,or as long as 297 m for the case scenario with 15 m rise of emission plume under the atmospheric stability class F.In order to measure the PM concentrations of the dispersion plume,the minimum sampling height at the locations within the plume touching-ground distance varied from ground level to as high as almost 14 m,whereas for the locations beyond the plume touching-ground distance,a sampling height of ground level would be acceptable.展开更多
Taking advantage of the relation of lateral Lagrangian time scale T_(LY) with the stability and height, we establish a three-dimensional random dispersion model and simulate the dispersing process of a ground source w...Taking advantage of the relation of lateral Lagrangian time scale T_(LY) with the stability and height, we establish a three-dimensional random dispersion model and simulate the dispersing process of a ground source within the surface layer. The results calculated show that under the condition of stable stratifica- tion our model is obviously better improved than those obtained by assuming T_(LY) to be constant, while under unstable condition, not much improved.展开更多
Effect of bluff internals on the hydrodynamics and lateral gas mixing was studied in a 0.186m ID high-density riser. With the bluff internals, the extremely non-uniform radial profiles of solid fraction and particle v...Effect of bluff internals on the hydrodynamics and lateral gas mixing was studied in a 0.186m ID high-density riser. With the bluff internals, the extremely non-uniform radial profiles of solid fraction and particle velocity become flat and the dense downflow layer near the wall disappears, indicating the significant enhancement of solid turbulence introduced by the internals. The fluctuation velocity and solid fraction transient signal analysis indicates a significant increase in fluctuation intensity near the wall region. The length influenced by the internals on the flow structure is about 1 meter. The lateral gas dispersion coefficient increases significantly as the bluff internals exist in the riser.展开更多
Presence of fine dust in air causes serious health hazard for mine operators resulting in such serious problems as coal workers’pneumoconiosis and silicosis.Major sources of dust appear of course along the mining fac...Presence of fine dust in air causes serious health hazard for mine operators resulting in such serious problems as coal workers’pneumoconiosis and silicosis.Major sources of dust appear of course along the mining face where the minerals are extracted.Proper control and management are required to ensure safe working environment in the mine.Here,we utilize the computational fluid dynamic(CFD)approach to evaluate various methods used for mitigating dust dispersion from the mining face and for ensuring safe level of dust concentration in the mine tunnel for safety of the operators.The methods used include:application of blowing and exhaust fans,application of brattice and combination of both.The results suggest that among the examined methods,implementation of appropriately located brattice to direct the flow from the main shaft to the mining face is the most effective method to direct dust particles away from the mining face.展开更多
ADMS-Urban is the most widely used advanced dispersion model for urban areas, being used extensively in China and worldwide, providing a practical tool for assessing and managing urban air quality. In this paper we br...ADMS-Urban is the most widely used advanced dispersion model for urban areas, being used extensively in China and worldwide, providing a practical tool for assessing and managing urban air quality. In this paper we briefly describe the ADMS dispersion models and give an overview of their use in China. And it describes in more detail the use of ADMS-Urban in Fushun in Liaoning province and in Jinan in Shangdong province respectively, for studies of urban air quality. Finally the conclusions are presented.展开更多
Based on the Industrial Source Complex Short-Term Version 3 （ISCST3） model, a simplified modeling approach was developed to predict concentrations of congeners of polychlorinated-p-dioxins and dibenzofurans （PCDD/F...Based on the Industrial Source Complex Short-Term Version 3 （ISCST3） model, a simplified modeling approach was developed to predict concentrations of congeners of polychlorinated-p-dioxins and dibenzofurans （PCDD/Fs） of agricultural soil, within a radius of 3 kin from a municipal solid waste incinerator （MSWI） plant after its 4-year operation in Hangzhou, China. Comparisons were made between the measured and estimated congener-specific concentrations and the international-toxic equivalent （I-TEQ） values of soil samples with respect to distance from the stack. The results indicate that the predictions of soil PCDD/F concentrations and K-TEQ values were generally lower than their observations, and that the higher the degree of underestimation seems, the greater the further downwind one gets. Nevertheless, most of the predictions were in good agreement with the trend of measured ones and were within a factor of ten for samples located within 1 kin of the plant. Besides, analysis of contributions of various deposition pathways confirms that in addition to wet particle deposition, the dry gaseous deposition is essential for realistic prediction of PCDD/F depositions to soil, especially for tetra- and penta-chlorinated dioxins.展开更多
基金The National Key Technology R&D Program during the 11th Five-Year Plan Period of China (No. 2009BAG17B02)the National High Technology Research and Development Program of China (863 Program) (No. 2011AA110304)the National Natural Science Foundation of China (No. 50908100)
文摘In order to reduce average arterial vehicle delay, a novel distributed and coordinated traffic control algorithm is developed using the multiple agent system and the reinforce learning （RL）. The RL is used to minimize average delay of arterial vehicles by training the interaction ability between agents and exterior environments. The Robertson platoon dispersion model is embedded in the RL algorithm to precisely predict platoon movements on arteries and then the reward function is developed based on the dispersion model and delay equations cited by HCM2000. The performance of the algorithm is evaluated in a Matlab environment and comparisons between the algorithm and the conventional coordination algorithm are conducted in three different traffic load scenarios. Results show that the proposed algorithm outperforms the conventional algorithm in all the scenarios. Moreover, with the increase in saturation degree, the performance is improved more significantly. The results verify the feasibility and efficiency of the established algorithm.
文摘A modified Fickian plug-flow/dispersion model (P/D model) is developed in this study. In P/D model, the flow process is divided into two belts, plug flow belt and dispersion belt. P/D model is very similar to Fickian model and rather perfect. The prediction by P/D model can be always consistent with experimental data in river, flume, and pond, even though the data are much skew. Therefore, P/D model is better than Fickian model and other dispersion models.
基金Project supported by the National Basic Research Program of China (973) (No. 2011CB201500)the National High-Tech R&D Program (863) of China (No. 2009AA064704)the Key Science and Technology Projects of Zhejiang Province,China (No. 2008C13022-3)
文摘The emission of dioxins from municipal solid waste incinerators(MSWIs) has become a widespread concern.The effect of meteorological parameters(wind speed,atmospheric stability and mixing height) on the hourly ground level concentration(GLC) of dioxins was estimated using air dispersion models.Moreover,the health risks of dioxin exposure were evaluated for children and adults using the Nouwen equation.The total environmental exposure via air inhalation and food ingestion was calculated,based on linear fit equations.The results indicate that potentially severe pollution from dioxins occurs at a wind speed of 1.5 m/s with atmospheric stability class F.In addition,local residents in the study area are exposed to severe weather conditions most of the time,and the risk exposures for children are far higher than those for adults.The total exposure for children far exceeds the tolerable daily intake of dioxin recommended by the World Health Organization(WHO) of 1-4 pg TEQ/(kg·d) under severe weather conditions.Results from modeling calculations of health risk assessment were consistent with dioxin levels obtained during actual monitoring of emissions.
文摘This paper makes comparisons between Chinese Environmental Impact Assessment (EIA) Guidelines for Air dispersion modelling and the advanced air dispersion model ADMS. Since 2001 the ADMS model has been the first and only foreign model that has been approved by the Appraisal Center for Environment and Engineering (ACEE) to be used in EIA projects in China (http://www.china-eia. com/inden_content/rjrz/ rjrz_ADMS/htm). In the paper the following sections provide brief descriptions of the main features of the Chinese Guidelines for Air Dispersion (Section 2) and ADMS (Section 3); Section 4 provides a comparison of the two modelling methods for some simple cases and conclusions and discussion are given in Section 5.
基金Under the auspices of the Creative Group Foundation of the National Natural Science Foundation of China(50721006)the National Basic Research Program of China(2006CB403402-3)+1 种基金the National Water Resource and Environment Special Item(2008ZX07207-006-04)the Natural Science Foundation of Shanghai(10ZR1400300)
文摘As an important design factor for constructed wetlands,hydraulic retention time and its distribution will affect the treatment performance.Instantaneously injected sodium chloride tracers were used to obtain residence time distributions of the lab scale subsurface flow constructed wetland.Considering the presence of trailing and multiple peaks of the tracer breakthrough curve,the multi flow dispersion model(MFDM)was used to fit the experimental tracer breakthrough curves.According to the residual sum of squares and comparison between the experimental values and simulated values of the tracer concentration,MFDM could fit the residence time distribution(RTD)curve satisfactorily,the results of which also reflected the layered structure of wetland cells,thus to give reference for application of MFDM to the same kind of subsurface flow constructed wetlands.
文摘The current applicable release & dispersion models are reviewed. A typical model is developed on the basis of LPG storage conditions in China and the authors' research. The study is focused on the relationship between LPG composition and release rate, and on the influence of buildings or structures located in the surrounding area on the dispersion of gas plume. The established model is compared with existing models by the use of published field test data.
文摘This research assessed the environmental impact of cement silos emission on the existing concrete batching facilities in M35-Mussafah, Abu Dhabi, United Arab Emirates. These assessments were conducted using an air quality dispersion model (AERMOD) to predict the ambient concentration of Portland Cement particulate matter less than 10 microns (PM<sub>10</sub>) emitted to the atmosphere during loading and unloading activities from 176 silos located in 25 concrete batching facilities. AERMOD was applied to simulate and describe the dispersion of PM<sub>10</sub> released from the cement silos into the air. Simulations were carried out for PM<sub>10</sub> emissions on controlled and uncontrolled cement silos scenarios. Results showed an incremental negative impact on air quality and public health from uncontrolled silos emissions and estimated that the uncontrolled PM<sub>10</sub> emission sources contribute to air pollution by 528958.32 kg/Year. The modeling comparison between the controlled and uncontrolled silos shows that the highest annual average concentration from controlled cement silos is 0.065 μg/m<sup>3</sup>, and the highest daily emission value is 0.6 μg/m<sup>3</sup>;both values are negligible and will not lead to significant air quality impact in the entire study domain. However, the uncontrolled cement silos’ highest annual average concentration value is 328.08 μg/m<sup>3</sup>. The highest daily emission average value was 1250.09 μg/m<sup>3</sup>;this might cause a significant air pollution quality impact and health effects on the public and workers. The short-term and long-term average PM<sub>10</sub> pollutant concentrations at these receptors predicted by the air dispersion model are discussed for both scenarios and compared with local and international air quality standards and guidelines.
文摘Odorous emissions emitted from various sources including industrial and commercial activities have particular concerns about human health. These malodors emissions are an environmental concern that affects health status and social life of the neighbors. That requires the local authority to set up a management strategy to control this nuisance. The evaluation of odour emissions from fishing port is complex because these emissions depend on several factors such as multiple sources of odor emissions, meteorological conditions, topography and others. That imposes the use of complementary approaches to monitor odours. In this paper, the case of Agadir fishing port is studied, which is adjacent to the tourist area and residential neighborhoods and which hosts a number of points that can generate odors. To assess this odour impact, three methods are used such as dynamic olfactometry, dispersion modeling and mobile electronic nose (e-nose). The use of these three methods in a complementary manner to assess odour impacts around a fishing port allowed both the quantification of the emissions using dynamic olfactometry and the evaluation of their impact on the study area with model dispersion. The results enabled also to identify the most affected areas of the city by odor emissions and to recognize the meteorological parameters maximizing odor impact. The other goal of this work is to compare the results of the odour dispersion modeling and e-nose measurements for one year in terms of frequency of overtaking the set alert thresholds over the same period. Comparison highlights the strengths and weaknesses of both approaches. Modeling can be used predicatively but it does not take into account fugitive emissions reliably in the absence of data on these emissions, modeling based on the hourly average misjudges the odor peaks, while e-nose made it possible to obtain validated data and provides accurate, affordable and real-time odour measurement capability tacking in to account the role of human perception without being able to characterize the extent of the odor nuisance caused by each source. We conclude that these three valuation methods provide complementary information about odor nuisance and reasonable estimates of odors.
基金Supported by the National Natural Science Foundation of China (No. 20076039) and SINOPEC.
文摘Evaporating bubble column reactor (EBCR) is a kind of aerated reactor in which the reaction heat is removed by the evaporation of volatile reaction mixture. In this paper, a mathematical model that accounts for the gas-liquid exothermic reaction and axial dispersions of both gas and liquid phase is employed to study the performance of EBCR for the process of p-xylene(PX) oxidation. The computational results show that there are remarkable concentration and temperature gradients in EBCR for high ratio of height to diameter (H/DT). The temperature is lower at the bottom of column and higher at the top, due to rapid evaporation induced by the feed gas near the bottom. The concentration profiles in the gas phase are more nonuniform than those (except PX) in the liquid phase, which causes more solvent burning consumption at high H/DT ratio. For p-xylene oxidation, theo ptimal H/DT is around 5.
基金supported in part by the National Natural Science Foundation of China(Grant No.41305104)the Special Fund for Meteo-scientific Research in the Public Interest(Grant No.GYHY201306061)
文摘Ensemble forcasting,originally developed for weather prediction,is lately being extended to atmospheric dispersion applications,which is a new,effective methodology for improving the atmospheric dispersion numerical modeling.In March 2011,due to the massive 9.0 earthquakes and ensuing tsunami that struck off the northern coast of the island of Honshu,the Fukushima Nuclear Plant I had the substantial leak of radioactive materials into surrounding environment and atmosphere.To aim at the global dispersion modeling of atmospheric radionuclides from Fukushima Nuclear Accident,this paper presents two approaches of atmospheric dispersion forecasting:ensemble dispersion modeling(EDM) and deterministic dispersion modeling(DDM),conducts the globally dispersion modeling cases for Fukushima nuclear accident,and analyzes and evaluates the simulation results using observation data.In this paper,EDM includes three different perturbation methods:meteorological perturbation method,turbulence perturbation method,and physical parameterization ensemble forecasting method.The simulation results show that the trajectories from EDM have a better performance,which is in better agreement with the atmospheric circulation and observation data; the spread from DDM is slower and not as far as EDM.Additionally,the results from EDM display a better performance in the modeling of transport from Japan to China East Sea on April 4.The reasons for these results are:the techniques of MET and TUR are performed by adding perturbations on mean wind and turbulent velocity,respectively; the various different flow fields will result in far spreading in horizontal and the simulation results closer to observation; PHY is performed by using different diffusion physical parameterizations and produces the perturbations on vertical wind,which results the spreading in smaller range and discontinuous in horizontal.Finally,the comparative analysis between modeling results and observation data shows that all cases results are in good agreement with trends of observed radionuclides surface concentration; however,the modeling surface concentration is smaller than observation,especially in DDM and PHY.Furthermore,the EDM results show that MET and TUR are of more evolutionary advantage than PHY in modeling of average and maximum concentration.Therefore,this study can serve as a reference to atmospheric dispersion and environmental emergency response(EER).
基金supported by the Natural Science Foundation of Jiangsu Province(No.BK2004216)
文摘An observational campaign was conducted in the street canyon of Zhujiang Road in Nanjing city in 2007. Hourly mean concentrations of PM10 were measured at street and roof levels. The Operational Street Pollution Model （OSPM） street canyon dispersion model was used to calculate the street concentrations and the results were compared with the measurements. The results show that there is good agreement between measured and predicted concentrations. The correlation coefficient R2 values （R2 is a measure of the correlation of the predicted and measured time series of concentrations） are 0.5319, 0.8044, and 0.6630 for the scatter plots of PM10 corresponding to light wind speed conditions, higher wind speed conditions, and all wind speed conditions, respectively. PM10 concentrations tend to be smaller for the higher wind speed cases and decrease rapidly with increasing wind speed. The presentations of measured and modelled concentration dependence on wind direction show fairly good agreement. PM10 concentrations measured on the windward side are relatively smaller, compared with the corresponding results for the leeward side. This study demonstrates that it is possible to use the OSPM to model PM10 dispersion rules for an urban street canyon.
基金This work was supported by the Science and Technology Research Project of the Jilin Provincial Department of Education(No.JJKH20210823KJ)。
文摘This study proposes a method based on material dispersion models to computationally simulate terahertz(THz)time-domain spectroscopy signals.The proposed method can accurately extract the refractive indices and extinction coefficients of optically thin samples and high-absorption materials in the THz band.This method was successfully used to extract the optical constants of a 470-μm-thick monocrystalline silicon sample and eliminate all errors associated with the Fabry-Perot oscillation.When used to extract the optical constants of a 16.29-mm-thick polycarbonate sample,our method succeeded in minimizing errors caused by the low signal-to-noise ratio in the extracted optical constants.
基金Major funding for this research was provided by the Ministry of Higher Education Malaysia and partially funded by the Land Surveyors Board of Malaysia.
文摘Understanding the behavior of urban air pollution is important en route for sustainable urban development (SUD). Malaysia is on its mission to be a developed country by year 2020 comprehends dealing with air pollution is one of the indicators headed towards it. At present monitoring and managing air pollution in urban areas encompasses sophisticated air quality modeling and data acquisition. However, rapid developments in major cities cause difficulties in acquiring the city geometries. The existing method in acquiring city geometries data via ground or space measurement inspection such as field survey, photogrammetry, laser scanning, remote sensing or using architectural plans appears not to be practical because of its cost and efforts. Moreover, air monitoring stations deployed are intended for regional to global scale model whereby it is not accurate for urban areas with typical resolution of less than 2 km. Furthermore in urban areas, the pollutant dispersion movements are trapped between buildings initiating it to move vertically causing visualization complications which imply the limitations of existing visualization scheme that is based on two-dimensional (2D) framework. Therefore this paper aims is to perform groundwork assessment and discuss on the current scenario in Malaysia in the aspect of current policies towards SUD, air quality monitoring stations, scale model and detail discussion on air pollution dispersion model used called the Operational Street Pollution Model (OSPM). This research proposed the implementation of three-dimensional (3D) spatial city model as a new physical data input for OSPM. The five Level of Details (LOD) of 3D spatial city model shows the scale applicability for the dispersion model implementtation. Subsequently 3D spatial city model data commonly available on the web, by having a unified data model shows the advantages in easy data acquisition, 3D visualization of air pollution dispersion and improves visual analysis of air quality monitoring in urban areas.
基金provided by National Programs 306,Product Quality and New Uses,and 212,Soil and Air
文摘Monitoring and modeling of airborne particulate matter(PM)from low-altitude sources is becoming an important regulatory target as the adverse health consequences of PM become better understood.However,application of models not specifically designed for simulation of PM from low-altitude emissions may bias predictions.To address this problem,we describe the modification and validation of an air dispersion model for the simulation of lowaltitude PM dispersion from a typical cotton ginning facility.We found that the regulatory recommended model(AERMOD)overestimated pollutant concentrations by factors of 64.7,6.97 and 7.44 on average for PM 2.5,PM 10,and TSP,respectively.Pollutant concentrations were negatively correlated with height(p<0.05),distance from source(p<0.05)and standard deviation of wind direction(p<0.001),and positively correlated with average wind speed(p<0.001).Based on these results,we developed dispersion correction factors for AERMOD and cross-validated the revised model against independent observations,reducing overestimation factors to 3.75,1.52 and 1.44 for PM 2.5,PM 10 and TSP,respectively.Further reductions in model error may be obtained from use of additional observations and refinement of dispersive correction factors.More generally,the correction permits the validated adjustment and application of pre-existing models for risk assessment and development of remediation techniques.The same approach may also be applied to improve simulations of other air pollutants and environmental conditions of concern.
基金supported by the NSF-CAREER Award No.CBET-0954673.
文摘In the studies of fate and transport of air emissions from animal feeding operations,Gaussian based dispersion models have been commonly used to predict downwind pollutant concentrations through forward modeling approach,or to derive emission rates and emission factors through inverse dispersion modeling approach.In the Gaussian dispersion modeling process,downwind sampling location and sampling height could generate significant impact on accuracy of the model validation,or inverse modeling results based upon field measurements.This study theoretically analyzed the impact of downwind locations and sampling height on Gaussian dispersion modeling.It was discovered that the field sampling needs to be conducted at the locations beyond the plume touching-ground distance,at a downwind distance as short as 5 m for the case scenario with zero rise of emission plume under the atmospheric stability class C,or as long as 297 m for the case scenario with 15 m rise of emission plume under the atmospheric stability class F.In order to measure the PM concentrations of the dispersion plume,the minimum sampling height at the locations within the plume touching-ground distance varied from ground level to as high as almost 14 m,whereas for the locations beyond the plume touching-ground distance,a sampling height of ground level would be acceptable.
文摘Taking advantage of the relation of lateral Lagrangian time scale T_(LY) with the stability and height, we establish a three-dimensional random dispersion model and simulate the dispersing process of a ground source within the surface layer. The results calculated show that under the condition of stable stratifica- tion our model is obviously better improved than those obtained by assuming T_(LY) to be constant, while under unstable condition, not much improved.
文摘Effect of bluff internals on the hydrodynamics and lateral gas mixing was studied in a 0.186m ID high-density riser. With the bluff internals, the extremely non-uniform radial profiles of solid fraction and particle velocity become flat and the dense downflow layer near the wall disappears, indicating the significant enhancement of solid turbulence introduced by the internals. The fluctuation velocity and solid fraction transient signal analysis indicates a significant increase in fluctuation intensity near the wall region. The length influenced by the internals on the flow structure is about 1 meter. The lateral gas dispersion coefficient increases significantly as the bluff internals exist in the riser.
基金financially supported by the Singapore Economic Development Board (EDB) through Minerals Metals and Materials Technology Centre (M3TC) (No.R261501013414)
文摘Presence of fine dust in air causes serious health hazard for mine operators resulting in such serious problems as coal workers’pneumoconiosis and silicosis.Major sources of dust appear of course along the mining face where the minerals are extracted.Proper control and management are required to ensure safe working environment in the mine.Here,we utilize the computational fluid dynamic(CFD)approach to evaluate various methods used for mitigating dust dispersion from the mining face and for ensuring safe level of dust concentration in the mine tunnel for safety of the operators.The methods used include:application of blowing and exhaust fans,application of brattice and combination of both.The results suggest that among the examined methods,implementation of appropriately located brattice to direct the flow from the main shaft to the mining face is the most effective method to direct dust particles away from the mining face.
文摘ADMS-Urban is the most widely used advanced dispersion model for urban areas, being used extensively in China and worldwide, providing a practical tool for assessing and managing urban air quality. In this paper we briefly describe the ADMS dispersion models and give an overview of their use in China. And it describes in more detail the use of ADMS-Urban in Fushun in Liaoning province and in Jinan in Shangdong province respectively, for studies of urban air quality. Finally the conclusions are presented.
基金Project (Nos. X506312 and X206955) supported by the NaturalScience Foundation of Zhejiang Province, China
文摘Based on the Industrial Source Complex Short-Term Version 3 （ISCST3） model, a simplified modeling approach was developed to predict concentrations of congeners of polychlorinated-p-dioxins and dibenzofurans （PCDD/Fs） of agricultural soil, within a radius of 3 kin from a municipal solid waste incinerator （MSWI） plant after its 4-year operation in Hangzhou, China. Comparisons were made between the measured and estimated congener-specific concentrations and the international-toxic equivalent （I-TEQ） values of soil samples with respect to distance from the stack. The results indicate that the predictions of soil PCDD/F concentrations and K-TEQ values were generally lower than their observations, and that the higher the degree of underestimation seems, the greater the further downwind one gets. Nevertheless, most of the predictions were in good agreement with the trend of measured ones and were within a factor of ten for samples located within 1 kin of the plant. Besides, analysis of contributions of various deposition pathways confirms that in addition to wet particle deposition, the dry gaseous deposition is essential for realistic prediction of PCDD/F depositions to soil, especially for tetra- and penta-chlorinated dioxins.
