The location, intensity and scope of concentrated leakage must be determined in order to repair earth-Dam scoured by the leakage. In this paper, firstly, heat tracer theory and distribution laws of temperature in soil...The location, intensity and scope of concentrated leakage must be determined in order to repair earth-Dam scoured by the leakage. In this paper, firstly, heat tracer theory and distribution laws of temperature in soil body with leakage are discussed. Then temperature tracer model is established according to stable heat conduction theory. In such model, the concentrated seepage passage is simplified into a circular pipe as a boundary condition. The location, scope and flow-velocity of the concentrated leakage are estimated via ichnography of the lowest temperature based on temperature data from detecting wells by quantitative computation and qualitative analysis. In case study, the distribution characteristic of temperature (including temperature data of water in reservoir, drainage pipes and tail pond) can be interpreted by this model. A modified model is also set up, applied for detected data at different cross-sections of the leakage passage, in which the temperature data are rectified according to distances from data locations to calculating section. Finally, the model is solved by numerical iterative method, and the possible error of this theoretical model is discussed. The permeability coefficient in leakage area is identical with that of normal soil in magnitude after anti-seepage repairing accomplished, which indicates this model is effective.展开更多
A universal thermodynamic model of calculating mass action concentrations for structural units or ion couples in ternary and binary strong electrolyte aqueous solution was developed based on the ion and molecule coexi...A universal thermodynamic model of calculating mass action concentrations for structural units or ion couples in ternary and binary strong electrolyte aqueous solution was developed based on the ion and molecule coexistence theory and verified in four kinds of binary aqueous solutions and two kinds of ternary aqueous solutions. The calculated mass action concentrations of structural units or ion couples in four binary aqueous solutions and two ternary solutions at 298.15 K have good agreement with the reported activity data from literatures after shifting the standard state and concentration unit. Therefore, the calculated mass action concentrations of structural units or ion couples from the developed universal thermodynamic model for ternary and binary aqueous solutions can be applied to predict reaction ability of components in ternary and binary strong electrolyte aqueous solutions. It is also proved that the assumptions applied in the developed thermodynamic model are correct and reasonable, i.e., strong electrolyte aqueous solution is composed of cations and anions as simple ions, H2O as simple molecule and other hydrous salt compounds as complex molecules. The calculated mass action concentrations of structural units or ion couples in ternary and binary strong electrolyte aqueous solutions strictly follow the mass action law.展开更多
A high-density, high-flux circulating fluidized bed (CFB) riser (100 mm in ID and 10.614 m in height) was ap- plied in a wide range of operating conditions (with solid fluxes up to 400 kg/m2s and superficial gas ...A high-density, high-flux circulating fluidized bed (CFB) riser (100 mm in ID and 10.614 m in height) was ap- plied in a wide range of operating conditions (with solid fluxes up to 400 kg/m2s and superficial gas velocities up to 12 m/s) to examine its radial non-uniformity dynamics. The solids holdup was determined through the use of a fiber-optic probe at 11 axial levels. The results indicated that under all operating conditions, the high superficial gas velocity and low solid flux- es maintained a low radial non-uniformity index (RNI). The high-density/flux CFB riser had several unique characteristics, so that the peak of the radial solids holdup profile occurred at a position with r/R=0.8. The RNI and solids holdup at the cross-sectional position had a good logarithmic relationship at the low-density condition (with a mean solids holdup of 〈0.2), and the RNI decreased when the mean solids holdup exceeded 0.2. Investigation of the dynamics of stratified injec- tion revealed that the feed ratio had an important effect on G, and on solids holdup distribution. A novel "〈" shaped axial solids holdup profile was found. Gs decreased sharply when the up-flow feed ratio exceeded 0.5, and RNI was lowest when the up-flow feed ratio was 1.展开更多
The flotation characteristics of Shenfu coal macerals was researched. Taking flotation recovery and enrichment of macerals as the evaluation objects, the influence of the agent dosage, pulp concentration, impeller spe...The flotation characteristics of Shenfu coal macerals was researched. Taking flotation recovery and enrichment of macerals as the evaluation objects, the influence of the agent dosage, pulp concentration, impeller speed and aeration rate on the separating effect was investigated. And the optimum process conditions of flotation were confirmed. The results show that the agent dosage, pulp concentration, impeller speed and aeration rate have a significant impact on flotation recovery and en- richment of macerals. The float recovery was 73.28% and enrichment ratio of vitrinite was 83.89% when CTAB dosage of 1.0 kg/t, pulp concentration of 100 g/L, impeller speed of 1 700 r/min and aeration rate of 0.25 m3/(m2·min) were used. The tailings yield was 60.30% and enrichment ratio of inertinite was 61.44% when CTAB dosage of 0.5 kg/t, pulp concentration of 100 g/L, impeller speed of I 700 r/min and aeration rate of 0.20 m3/(m2·min) were used.展开更多
This paper is aimed at the actual conditions of disaster caused by gas in small and medium-sized coal mines. A new gas concentration monitoring system for coal mines is developed on the basis of gas-sensing detection ...This paper is aimed at the actual conditions of disaster caused by gas in small and medium-sized coal mines. A new gas concentration monitoring system for coal mines is developed on the basis of gas-sensing detection and single-chip control. The monitoring system uses the tin oxide as the main material of N-type semiconductor gas sensors, be- cause it has good sensitive characteristics for the flammable and explosive gas ( such as methane, carbon monoxide). The QM-N5-semiconductor gas sensor is adopted to detect the output values of the resistance under the different gas con- centrations. The system, designedly, takes the AT89C51 digital chip as the core of the circuit processing hardware structure to analyze and judge the input values of the resistance, and then achieve the control and alarm for going beyond the limit of gas concentration. The gas concentration monitoring system has man), advantages including simple in struc- ture, fast response time, stable performance and low cost. Thus, it can be widely used to monitor gas concentration and provide early wamings in small and medium-sized coal mines.展开更多
The regional air quality modeling system RAMS-CMAQ(Regional Atmospheric Modeling System and Models-3 Community Multi-scale Air Quality) was developed by incorporating a vegetation photosynthesis and respiration module...The regional air quality modeling system RAMS-CMAQ(Regional Atmospheric Modeling System and Models-3 Community Multi-scale Air Quality) was developed by incorporating a vegetation photosynthesis and respiration module(VPRM) and used to simulate temporal-spatial variations in atmospheric CO2 concentrations in East Asia,with prescribed surface CO2 fluxes(i.e.,fossil fuel emission,biomass burning,sea-air CO2 exchange,and terrestrial biosphere CO2 flux).Comparison of modeled CO2 mixing ratios with eight ground-based in-situ measurements demonstrated that the model was able to capture most observed CO2 temporal-spatial features.Simulated CO2 concentrations were generally in good agreement with observed concentrations.Results indicated that the accumulated impacts of anthropogenic emissions contributed more to increased CO2 concentrations in urban regions relative to remote locations.Moreover,RAMS-CMAQ analysis demonstrates that surface CO2 concentrations in East Asia are strongly influenced by terrestrial ecosystems.展开更多
Polycyclic aromatic hydrocarbons (PAHs) contamination of topsoil in Benxi City, Northeast China was investigated in this study, and sampling sites were located in industrial area and residential area. Results demonstr...Polycyclic aromatic hydrocarbons (PAHs) contamination of topsoil in Benxi City, Northeast China was investigated in this study, and sampling sites were located in industrial area and residential area. Results demonstrate that there is high variability in the total PAHs concentrations, ranging from 783.00 ng/g to 729 076.29 ng/g dry weight in the topsoil of Benxi City and the pollution in industrial area is the most serious. The results also present that higher molecular weight PAHs (4–6 rings) contribute substantially (79.03%) to the overall content of PAHs. The PAHs sources were determined with factor analysis by nonnegative constraints, and the results show that PAHs originating from traffic tunnel, power plant, coke oven and residential emission sources, account for 27.10%, 40.81%, 20.11% and 11.98%, respectively, of the total. The PAHs pollution is the most serious around Benxi Iron and Steel Group Corporation, and the PAHs mainly originate from coke oven and traffic tunnel, with the average contribution rate of 57.40% and 42.60%, respectively. The source apportionment results are basically consistent with the industry distribution, and the geographical and climatic characteristics of the study area.展开更多
Forced aeration is an effective way to accelerate the heap bioleaching process.To reveal the effects of different irrigation and aeration combinations on bioleaching performance of copper sulfides,numerical simulation...Forced aeration is an effective way to accelerate the heap bioleaching process.To reveal the effects of different irrigation and aeration combinations on bioleaching performance of copper sulfides,numerical simulations with COMSOL were carried out.Results showed the oxygen concentration is the highest at the bottom with forced aeration,the airflow transports spherically from the aeration pipeline to the slope,and the horizontal diffusion distance is further than vertical value.When the irrigation-to-aeration ratio is higher,the average heap temperatures are mainly decided by aeration rates;otherwise,temperature distributions are the equilibrium of mineral reaction heat,the livixiant driven heat and the airflow driven heat.When the aeration rate is higher than 0.90 m3/(m2·h),oxygen concentration is no longer a limiting factor for mineral dissolution.Additionally,on the premise of sufficient oxygen supply,Cu recovery rate is higher at the bottom with low irrigation rate;while it is higher at upper regions with high irrigation rate.The numerical analysis uncovered some insights into the dynamics and thermodynamics rules in bioleaching of copper sulfides with forced aeration.展开更多
Updated version of local non-equilibrium diffusion model (LNDM) for rapid solidification of binary alloys was considered. The LNDM takes into account deviation from local equilibrium of solute concentration and solu...Updated version of local non-equilibrium diffusion model (LNDM) for rapid solidification of binary alloys was considered. The LNDM takes into account deviation from local equilibrium of solute concentration and solute flux fields in bulk liquid. The exact solutions for solute concentration and flux in bulk liquid were obtained using hyperbolic diffusion equations. The results show the transition from diffusion-limited to purely thermally controlled solidification with effective diffusion coefficient →0 and complete solute trapping KLNDM(v)→1 at v→vDb for any kind of solid-liquid interface kinetics. Critical parameter for diffusionless solidification and complete solute trapping is the diffusion speed in bulk liquid vDb. Different models for solute trapping at the interface with different interface kinetic approaches were considered.展开更多
Based on the model of the two calcium stores developed by Goldbeter, the influence of external magnetic field on the calcium concentration has been discussed. We believe that the cell membrane is a major site of inter...Based on the model of the two calcium stores developed by Goldbeter, the influence of external magnetic field on the calcium concentration has been discussed. We believe that the cell membrane is a major site of interaction for extremely-low-frequency (ELF) electromagnetic fields, and the permeability of ions can be changed with the changing electromagnetic fields. It is shown that magnetic field initiates intraeellular calcium oscillation with a threshold in flux density, and that the calcium oscillations do not occur if the density of magnetic field is below the threshold. The results of theoretical calculation are consistent with that of the experiment. The intracellular free calcium concentrations of different cells exposed to the same magnetic fields are different from each other. It is indicated that the different behaviors such as oscillation, rise and invariability of calcium concentration are associated with the sort of cells.展开更多
Objective: To study the relationship between the amount of consumed alcohol, blood alcohol concentration (BAC), and driving ability among a part of the population in Southwest China and to provide reference for the fo...Objective: To study the relationship between the amount of consumed alcohol, blood alcohol concentration (BAC), and driving ability among a part of the population in Southwest China and to provide reference for the formulation of the legal limits for safe driving. Methods: Seventy-six randomly selected volunteer drivers each had three times of alcohol intake (100 ml each time). After each drank, BAC was measured with gas chromatograph and driving ability was evaluated. The drivers were grouped according to age, weight, alcohol tolerance and driving experience respectively and changes in BAC and driving ability were analyzed. Results: Average BAC and the percentage of drivers showing impaired driving ability in the groups increased after each intake of 100 ml alcohol. BAC in Group≤60 kg was more susceptible to alcohol than that in Group>60 kg. When each drank, alcohol had greater influence on drivers who had comparatively shorter driving experience. Conclusion: Volume of consumed alcohol, BAC and driving ability have direct associations among one another and are all under the influence of various factors including individual conditions. To set an appropriate legal BAC limit for safe driving should take an overall consideration of all factors.展开更多
This study carried out full-scale gas water heater combustion experiments and adopted FDS (fire dynamics simulator) to simulate three scenarios--different balcony environments when using water heater, such as airtig...This study carried out full-scale gas water heater combustion experiments and adopted FDS (fire dynamics simulator) to simulate three scenarios--different balcony environments when using water heater, such as airtight balcony, indoor door with openings and force ventilation to compare with full-scale combustion experiments. According to FDS simulation results, 02, CO and CO2 simulation concentration value correspond with full-scale experimental results. When the indoor O2 concentration was lower than 15%, which causes incomplete combustion, the CO concentration would rise rapidly and even reached above 1,500 ppm, causing death in short time. In addition, when the force ventilation model supplied the water heater with enough air to bum, the indoor CO concentration will keep low and harmless to humans. The study also adopted diverse variables, such as the opening area of window, outdoor wind speed and water heater types, to analyze deeply user's safety regarding gas water heater. In a result, while balcony area is larger than 14 mE, the volume of water heater is below 16 L (33.1 kW), and the indoor window, connecting balcony with room, is closed, if the opening on the outdoor window of the balcony is larger than 0.2 mE, this can ensure the personal security of the indoor space.展开更多
The application of single nanofiltration (NF) and sequential filtration of microfiltration (MF) and NF for the concentration of vinasse were studied. Filtration experiments were performed at 60 ℃, 500 rpm and dif...The application of single nanofiltration (NF) and sequential filtration of microfiltration (MF) and NF for the concentration of vinasse were studied. Filtration experiments were performed at 60 ℃, 500 rpm and different transmembrane pressures using four commercial membranes: MF, PVDF 0.2 μm; NF, PES 300, 500 and 1000 Da. The process effectiveness was evaluated through the permeate flux and the total solids (TS) concentration in the retentate. Because the retention of TS and permeate fluxes were very similar for MF, PVDF-0.2 membrane at 0.10 MPa was selected because of its lower power consumption. The best conditions tested for NF were the following: PES-1000 at 3.50 MPa with a flux of 183.2 kg/m^2 h at a volume reduction factor (VRF) of 2, under which 68% of solids were retained. For the MF + NF, a PES-1000 at 3.50 MPa was selected because a higher permeate flux was achieved at a VRF of 4, and PES-500 at 3.50 MPa because a higher retention of TS was achieved compared to the other experiments. A single NF resulted in a retentate concentration that was almost twice as high as the hybrid MF and NF process, allowing reduced costs in its transportation from distilleries to distant areas.展开更多
The rise in atmospheric carbon dioxide(C02)concentrations caused by human activities is leading to global climate change,which poses a threat to human development and survival.This study analyzed the distribution of t...The rise in atmospheric carbon dioxide(C02)concentrations caused by human activities is leading to global climate change,which poses a threat to human development and survival.This study analyzed the distribution of the ocean carbon flux with interannual changes and compared it with the climatological ocean carbon flux to deepen our understanding of carbon sources and sinks.To simulate global CO2 concentrations for the years2008-2010,the ocean carbon flux with interannual changes and the climatological ocean carbon flux were used to drive the GEOS-Chem model,an atmospheric chemical transport model.The simulated values were compared with the CO2 concentrations at nine observation stations to explore the influence of interannual changes in the ocean carbon fluxes on the simulated CO2 concentrations.The authors found that the difference between the two simulation results was greater in the Southern Hemisphere all year,and the difference in autumn was the largest.Compared with the observations,the simulated CO2 concentration of the ocean carbon flux with interannual changes is closer to the observations,indicating that this simulation is more accurate.展开更多
In order to prevent coal and methane outbursts, mining protective layers is an effective means, yet no precedents of mining multiple protective layers is discoveried in seams which includes several seams are prone to ...In order to prevent coal and methane outbursts, mining protective layers is an effective means, yet no precedents of mining multiple protective layers is discoveried in seams which includes several seams are prone to outburst like Xinzhuangzi Mine. This paper perfected the related theories through analyzing mining multiple upper protective layers. By means of examining several parameters, it synthetically analyzed and ascer- tains the protected effectiveness and scope and reasonable parameters, finally obtained the specific indexes and effectiveness of mining multiple protective layers in coal seams cluster.展开更多
To solve nutrient flux and budget among waters with distinct salinity difference for water-salt- nutrient budget, a traditional method is to build a stoichiometrically linked steady state model. However, the tradition...To solve nutrient flux and budget among waters with distinct salinity difference for water-salt- nutrient budget, a traditional method is to build a stoichiometrically linked steady state model. However, the traditional way cannot cope appropriately with those without distinct salinity difference that parallel to coastline or in a complex current system, as the results would be highly affected by box division in time and space, such as the Changjiang (Yangtze) River estuary (CRE) and adjacent waters (30.75°-31.75°N, 122°10′-123°20′E). Therefore, we developed a hydrodynamic box model based on the traditional way and the regional oceanic modeling system model (ROMS). Using data from four cruises in 2005, horizontal, vertical and boundary nutrient fluxes were calculated in the hydrodynamic box model, in which flux fields and the major controlling factors were studied. Results show that the nutrient flux varied greatly in season and space. Water flux outweighs the nutrient concentration in horizontal flux, and upwelling flux outweighs upward diffusion flux in vertical direction (upwelling flux and upward diffusion flux regions overlap largely all the year). Vertical flux in spring and summer are much greater than that in autumn and winter. The maximum vertical flux for DIP (dissolved inorganic phosphate) occurs in summer. Additional to the fluxes of the ChanNiang River discharge, coastal currents, the Taiwan Warm Current, and the upwelling, nutrient flux inflow from the southern Yellow Sea and outflow southward are found crucial to nutrient budgets of the study area. Horizontal nutrient flux is controlled by physical dilution and confined to coastal waters with a little into the open seas. The study area acts as a conveyer transferring nutrients from the Yellow Sea to the East China Sea in the whole year. In addition, vertical nutrient flux in spring and summer is a main source of DIP. Therefore, the hydrodynamic ROMS-based box model is superior to the traditional one in estimating nutrient fluxes in a complicated hydrodynamic current system and provides a modified box model approach to material flux research.展开更多
Of the ~240*10^(12)mol year^(-1)of biogenic silica(bSi)produced by diatoms and other silicifying organisms,only roughly 3%–4%escapes dissolution to be permanently buried.At the global scale,how,where and why b Si is...Of the ~240*10^(12)mol year^(-1)of biogenic silica(bSi)produced by diatoms and other silicifying organisms,only roughly 3%–4%escapes dissolution to be permanently buried.At the global scale,how,where and why b Si is preserved in sediment is not well understood.To help address this,I compile 6245 porewater dissolved Si concentrations from 453 sediment cores,to derive the concentration gradient at the sediment–water interface and thus diffusive fluxes out of the sediment.These range from\0.002 to 3.4 mol m^(-2)year^(-1),and are independent of temperature,depth and latitude.When classified by sediment lithology,predominantly siliceous sediments unsurprisingly have higher mean diffusive fluxes than predominantly calcareous or clay-rich sediment.Combined with the areal extent of these lithologies,the‘best-guess’global sedimentary b Si recycling flux is69 9 10^(12)mol year^(-1).展开更多
Cloud water samples, LWC (Liquid Water Content) and meteorological data were collected at the Clingmans Dome, Tennessee, high-elevation site in Great Smoky Mountains National Park during the warm season from 1994 th...Cloud water samples, LWC (Liquid Water Content) and meteorological data were collected at the Clingmans Dome, Tennessee, high-elevation site in Great Smoky Mountains National Park during the warm season from 1994 through 2011. This paper presents results from 2000 through the conclusion of the study in 2011. Samples were analyzed for SO42", NO3, NH4+ and H+. These measurements were supplemented by measurements of ambient air and precipitation concentrations to estimate dry and wet deposition. Cloud water concentrations, LWC, cloud frequency, various meteorological measurements and information on nearby forest canopy were used to model cloud water deposition to gauge trends in deposition. Total deposition was calculated as the sum of cloud, dry and wet deposition estimates. Concentrations and deposition fluxes declined over the study period. The decreases in cloud water SO42" and NO3 concentrations were 40 percent and 26 percent, respectively. Three-year mean 5042 and NO3 deposition rates decreased by 71 percent and 70 percent, respectively. Trends in concentrations and depositions were comparable with trends in SO2 and NOx emissions from Tennessee Valley Authority power plants and aggregated emission reductions from electric generating units in adjacent states. Back trajectories were simulated with the HYSPLIT model and aggregated over cloud sampling periods from 2000 through 2007 and 2009 through 2011. Trajectories during periods with high H+ concentrations traveled over local EGU (Electric Generating Unit) emission sources in Tennessee and Kentucky to the Ohio River Valley, Alabama and Georgia with the conclusion that these source regions contributed to acidic cloud water deposition at Clingmans Dome. This work was supported by U.S. Environmental Protection Agency and the Tennessee Valley Authority with infrastructure support provided by the National Park Service.展开更多
基金Financial support from the National Nature Science Foundation of China(50179009)National Nature Science Foundation of China for important project(50139030)
文摘The location, intensity and scope of concentrated leakage must be determined in order to repair earth-Dam scoured by the leakage. In this paper, firstly, heat tracer theory and distribution laws of temperature in soil body with leakage are discussed. Then temperature tracer model is established according to stable heat conduction theory. In such model, the concentrated seepage passage is simplified into a circular pipe as a boundary condition. The location, scope and flow-velocity of the concentrated leakage are estimated via ichnography of the lowest temperature based on temperature data from detecting wells by quantitative computation and qualitative analysis. In case study, the distribution characteristic of temperature (including temperature data of water in reservoir, drainage pipes and tail pond) can be interpreted by this model. A modified model is also set up, applied for detected data at different cross-sections of the leakage passage, in which the temperature data are rectified according to distances from data locations to calculating section. Finally, the model is solved by numerical iterative method, and the possible error of this theoretical model is discussed. The permeability coefficient in leakage area is identical with that of normal soil in magnitude after anti-seepage repairing accomplished, which indicates this model is effective.
基金Project supported by Publication Foundation of National Science and Technology Academic Books of China
文摘A universal thermodynamic model of calculating mass action concentrations for structural units or ion couples in ternary and binary strong electrolyte aqueous solution was developed based on the ion and molecule coexistence theory and verified in four kinds of binary aqueous solutions and two kinds of ternary aqueous solutions. The calculated mass action concentrations of structural units or ion couples in four binary aqueous solutions and two ternary solutions at 298.15 K have good agreement with the reported activity data from literatures after shifting the standard state and concentration unit. Therefore, the calculated mass action concentrations of structural units or ion couples from the developed universal thermodynamic model for ternary and binary aqueous solutions can be applied to predict reaction ability of components in ternary and binary strong electrolyte aqueous solutions. It is also proved that the assumptions applied in the developed thermodynamic model are correct and reasonable, i.e., strong electrolyte aqueous solution is composed of cations and anions as simple ions, H2O as simple molecule and other hydrous salt compounds as complex molecules. The calculated mass action concentrations of structural units or ion couples in ternary and binary strong electrolyte aqueous solutions strictly follow the mass action law.
基金the financial support of the National Program on Key Basic Research Project (973 Program) of China (no. 2012CB215000)
文摘A high-density, high-flux circulating fluidized bed (CFB) riser (100 mm in ID and 10.614 m in height) was ap- plied in a wide range of operating conditions (with solid fluxes up to 400 kg/m2s and superficial gas velocities up to 12 m/s) to examine its radial non-uniformity dynamics. The solids holdup was determined through the use of a fiber-optic probe at 11 axial levels. The results indicated that under all operating conditions, the high superficial gas velocity and low solid flux- es maintained a low radial non-uniformity index (RNI). The high-density/flux CFB riser had several unique characteristics, so that the peak of the radial solids holdup profile occurred at a position with r/R=0.8. The RNI and solids holdup at the cross-sectional position had a good logarithmic relationship at the low-density condition (with a mean solids holdup of 〈0.2), and the RNI decreased when the mean solids holdup exceeded 0.2. Investigation of the dynamics of stratified injec- tion revealed that the feed ratio had an important effect on G, and on solids holdup distribution. A novel "〈" shaped axial solids holdup profile was found. Gs decreased sharply when the up-flow feed ratio exceeded 0.5, and RNI was lowest when the up-flow feed ratio was 1.
文摘The flotation characteristics of Shenfu coal macerals was researched. Taking flotation recovery and enrichment of macerals as the evaluation objects, the influence of the agent dosage, pulp concentration, impeller speed and aeration rate on the separating effect was investigated. And the optimum process conditions of flotation were confirmed. The results show that the agent dosage, pulp concentration, impeller speed and aeration rate have a significant impact on flotation recovery and en- richment of macerals. The float recovery was 73.28% and enrichment ratio of vitrinite was 83.89% when CTAB dosage of 1.0 kg/t, pulp concentration of 100 g/L, impeller speed of 1 700 r/min and aeration rate of 0.25 m3/(m2·min) were used. The tailings yield was 60.30% and enrichment ratio of inertinite was 61.44% when CTAB dosage of 0.5 kg/t, pulp concentration of 100 g/L, impeller speed of I 700 r/min and aeration rate of 0.20 m3/(m2·min) were used.
基金supported by the program of Science and Technology Innovative Research Team in Higher Educational Institutions of Hunan Provincethe Hunan Province and Xiangtan City Natural Science Joint Foundation(No.09JJ8005)+1 种基金the Industrial Cultivation Program of Scientific and Technological Achievements in Higher Educational Institutions of Hunan Province(No.10CY008)the Technologies R & D of Hunan Province (No.2010CK3031)
文摘This paper is aimed at the actual conditions of disaster caused by gas in small and medium-sized coal mines. A new gas concentration monitoring system for coal mines is developed on the basis of gas-sensing detection and single-chip control. The monitoring system uses the tin oxide as the main material of N-type semiconductor gas sensors, be- cause it has good sensitive characteristics for the flammable and explosive gas ( such as methane, carbon monoxide). The QM-N5-semiconductor gas sensor is adopted to detect the output values of the resistance under the different gas con- centrations. The system, designedly, takes the AT89C51 digital chip as the core of the circuit processing hardware structure to analyze and judge the input values of the resistance, and then achieve the control and alarm for going beyond the limit of gas concentration. The gas concentration monitoring system has man), advantages including simple in struc- ture, fast response time, stable performance and low cost. Thus, it can be widely used to monitor gas concentration and provide early wamings in small and medium-sized coal mines.
基金supported by the Strategic Priority Research Program-Climate Change:Carbon Budget and Relevant Issues (Grant No.XDA05040404)the National Natural Science Foundation of China (Grant No.41130528)
文摘The regional air quality modeling system RAMS-CMAQ(Regional Atmospheric Modeling System and Models-3 Community Multi-scale Air Quality) was developed by incorporating a vegetation photosynthesis and respiration module(VPRM) and used to simulate temporal-spatial variations in atmospheric CO2 concentrations in East Asia,with prescribed surface CO2 fluxes(i.e.,fossil fuel emission,biomass burning,sea-air CO2 exchange,and terrestrial biosphere CO2 flux).Comparison of modeled CO2 mixing ratios with eight ground-based in-situ measurements demonstrated that the model was able to capture most observed CO2 temporal-spatial features.Simulated CO2 concentrations were generally in good agreement with observed concentrations.Results indicated that the accumulated impacts of anthropogenic emissions contributed more to increased CO2 concentrations in urban regions relative to remote locations.Moreover,RAMS-CMAQ analysis demonstrates that surface CO2 concentrations in East Asia are strongly influenced by terrestrial ecosystems.
基金Under the auspices of Program of National Soil Pollution Survey (No. 6HBZJ1002)
文摘Polycyclic aromatic hydrocarbons (PAHs) contamination of topsoil in Benxi City, Northeast China was investigated in this study, and sampling sites were located in industrial area and residential area. Results demonstrate that there is high variability in the total PAHs concentrations, ranging from 783.00 ng/g to 729 076.29 ng/g dry weight in the topsoil of Benxi City and the pollution in industrial area is the most serious. The results also present that higher molecular weight PAHs (4–6 rings) contribute substantially (79.03%) to the overall content of PAHs. The PAHs sources were determined with factor analysis by nonnegative constraints, and the results show that PAHs originating from traffic tunnel, power plant, coke oven and residential emission sources, account for 27.10%, 40.81%, 20.11% and 11.98%, respectively, of the total. The PAHs pollution is the most serious around Benxi Iron and Steel Group Corporation, and the PAHs mainly originate from coke oven and traffic tunnel, with the average contribution rate of 57.40% and 42.60%, respectively. The source apportionment results are basically consistent with the industry distribution, and the geographical and climatic characteristics of the study area.
基金Projects(51804079,51804121)supported by the National Natural Science Foundation of ChinaProject(2019J05039)supported by Natural Science Foundation of Fujian Province,ChinaProject(2019T034)supported by Fuzhou University Testing Fund of Precious Apparatus,China。
文摘Forced aeration is an effective way to accelerate the heap bioleaching process.To reveal the effects of different irrigation and aeration combinations on bioleaching performance of copper sulfides,numerical simulations with COMSOL were carried out.Results showed the oxygen concentration is the highest at the bottom with forced aeration,the airflow transports spherically from the aeration pipeline to the slope,and the horizontal diffusion distance is further than vertical value.When the irrigation-to-aeration ratio is higher,the average heap temperatures are mainly decided by aeration rates;otherwise,temperature distributions are the equilibrium of mineral reaction heat,the livixiant driven heat and the airflow driven heat.When the aeration rate is higher than 0.90 m3/(m2·h),oxygen concentration is no longer a limiting factor for mineral dissolution.Additionally,on the premise of sufficient oxygen supply,Cu recovery rate is higher at the bottom with low irrigation rate;while it is higher at upper regions with high irrigation rate.The numerical analysis uncovered some insights into the dynamics and thermodynamics rules in bioleaching of copper sulfides with forced aeration.
文摘Updated version of local non-equilibrium diffusion model (LNDM) for rapid solidification of binary alloys was considered. The LNDM takes into account deviation from local equilibrium of solute concentration and solute flux fields in bulk liquid. The exact solutions for solute concentration and flux in bulk liquid were obtained using hyperbolic diffusion equations. The results show the transition from diffusion-limited to purely thermally controlled solidification with effective diffusion coefficient →0 and complete solute trapping KLNDM(v)→1 at v→vDb for any kind of solid-liquid interface kinetics. Critical parameter for diffusionless solidification and complete solute trapping is the diffusion speed in bulk liquid vDb. Different models for solute trapping at the interface with different interface kinetic approaches were considered.
基金supported by National Natural Science Foundation of Foundation under Grant No.C2007000026the Research Fond for the Doctoral Program of Higher Education under Grant No.20060080001
文摘Based on the model of the two calcium stores developed by Goldbeter, the influence of external magnetic field on the calcium concentration has been discussed. We believe that the cell membrane is a major site of interaction for extremely-low-frequency (ELF) electromagnetic fields, and the permeability of ions can be changed with the changing electromagnetic fields. It is shown that magnetic field initiates intraeellular calcium oscillation with a threshold in flux density, and that the calcium oscillations do not occur if the density of magnetic field is below the threshold. The results of theoretical calculation are consistent with that of the experiment. The intracellular free calcium concentrations of different cells exposed to the same magnetic fields are different from each other. It is indicated that the different behaviors such as oscillation, rise and invariability of calcium concentration are associated with the sort of cells.
文摘Objective: To study the relationship between the amount of consumed alcohol, blood alcohol concentration (BAC), and driving ability among a part of the population in Southwest China and to provide reference for the formulation of the legal limits for safe driving. Methods: Seventy-six randomly selected volunteer drivers each had three times of alcohol intake (100 ml each time). After each drank, BAC was measured with gas chromatograph and driving ability was evaluated. The drivers were grouped according to age, weight, alcohol tolerance and driving experience respectively and changes in BAC and driving ability were analyzed. Results: Average BAC and the percentage of drivers showing impaired driving ability in the groups increased after each intake of 100 ml alcohol. BAC in Group≤60 kg was more susceptible to alcohol than that in Group>60 kg. When each drank, alcohol had greater influence on drivers who had comparatively shorter driving experience. Conclusion: Volume of consumed alcohol, BAC and driving ability have direct associations among one another and are all under the influence of various factors including individual conditions. To set an appropriate legal BAC limit for safe driving should take an overall consideration of all factors.
文摘This study carried out full-scale gas water heater combustion experiments and adopted FDS (fire dynamics simulator) to simulate three scenarios--different balcony environments when using water heater, such as airtight balcony, indoor door with openings and force ventilation to compare with full-scale combustion experiments. According to FDS simulation results, 02, CO and CO2 simulation concentration value correspond with full-scale experimental results. When the indoor O2 concentration was lower than 15%, which causes incomplete combustion, the CO concentration would rise rapidly and even reached above 1,500 ppm, causing death in short time. In addition, when the force ventilation model supplied the water heater with enough air to bum, the indoor CO concentration will keep low and harmless to humans. The study also adopted diverse variables, such as the opening area of window, outdoor wind speed and water heater types, to analyze deeply user's safety regarding gas water heater. In a result, while balcony area is larger than 14 mE, the volume of water heater is below 16 L (33.1 kW), and the indoor window, connecting balcony with room, is closed, if the opening on the outdoor window of the balcony is larger than 0.2 mE, this can ensure the personal security of the indoor space.
文摘The application of single nanofiltration (NF) and sequential filtration of microfiltration (MF) and NF for the concentration of vinasse were studied. Filtration experiments were performed at 60 ℃, 500 rpm and different transmembrane pressures using four commercial membranes: MF, PVDF 0.2 μm; NF, PES 300, 500 and 1000 Da. The process effectiveness was evaluated through the permeate flux and the total solids (TS) concentration in the retentate. Because the retention of TS and permeate fluxes were very similar for MF, PVDF-0.2 membrane at 0.10 MPa was selected because of its lower power consumption. The best conditions tested for NF were the following: PES-1000 at 3.50 MPa with a flux of 183.2 kg/m^2 h at a volume reduction factor (VRF) of 2, under which 68% of solids were retained. For the MF + NF, a PES-1000 at 3.50 MPa was selected because a higher permeate flux was achieved at a VRF of 4, and PES-500 at 3.50 MPa because a higher retention of TS was achieved compared to the other experiments. A single NF resulted in a retentate concentration that was almost twice as high as the hybrid MF and NF process, allowing reduced costs in its transportation from distilleries to distant areas.
基金partially supported by the National Key Research and Development Program of China [grant number 2016YFA0600203]the National Natural Science Foundation of China [grant number 41575100]
文摘The rise in atmospheric carbon dioxide(C02)concentrations caused by human activities is leading to global climate change,which poses a threat to human development and survival.This study analyzed the distribution of the ocean carbon flux with interannual changes and compared it with the climatological ocean carbon flux to deepen our understanding of carbon sources and sinks.To simulate global CO2 concentrations for the years2008-2010,the ocean carbon flux with interannual changes and the climatological ocean carbon flux were used to drive the GEOS-Chem model,an atmospheric chemical transport model.The simulated values were compared with the CO2 concentrations at nine observation stations to explore the influence of interannual changes in the ocean carbon fluxes on the simulated CO2 concentrations.The authors found that the difference between the two simulation results was greater in the Southern Hemisphere all year,and the difference in autumn was the largest.Compared with the observations,the simulated CO2 concentration of the ocean carbon flux with interannual changes is closer to the observations,indicating that this simulation is more accurate.
文摘In order to prevent coal and methane outbursts, mining protective layers is an effective means, yet no precedents of mining multiple protective layers is discoveried in seams which includes several seams are prone to outburst like Xinzhuangzi Mine. This paper perfected the related theories through analyzing mining multiple upper protective layers. By means of examining several parameters, it synthetically analyzed and ascer- tains the protected effectiveness and scope and reasonable parameters, finally obtained the specific indexes and effectiveness of mining multiple protective layers in coal seams cluster.
基金Supported by the National Nature Science Foundation of China(Nos.41121064,41276116)the National Basic Research Program of China(973 Program)(No.2010CB428706)
文摘To solve nutrient flux and budget among waters with distinct salinity difference for water-salt- nutrient budget, a traditional method is to build a stoichiometrically linked steady state model. However, the traditional way cannot cope appropriately with those without distinct salinity difference that parallel to coastline or in a complex current system, as the results would be highly affected by box division in time and space, such as the Changjiang (Yangtze) River estuary (CRE) and adjacent waters (30.75°-31.75°N, 122°10′-123°20′E). Therefore, we developed a hydrodynamic box model based on the traditional way and the regional oceanic modeling system model (ROMS). Using data from four cruises in 2005, horizontal, vertical and boundary nutrient fluxes were calculated in the hydrodynamic box model, in which flux fields and the major controlling factors were studied. Results show that the nutrient flux varied greatly in season and space. Water flux outweighs the nutrient concentration in horizontal flux, and upwelling flux outweighs upward diffusion flux in vertical direction (upwelling flux and upward diffusion flux regions overlap largely all the year). Vertical flux in spring and summer are much greater than that in autumn and winter. The maximum vertical flux for DIP (dissolved inorganic phosphate) occurs in summer. Additional to the fluxes of the ChanNiang River discharge, coastal currents, the Taiwan Warm Current, and the upwelling, nutrient flux inflow from the southern Yellow Sea and outflow southward are found crucial to nutrient budgets of the study area. Horizontal nutrient flux is controlled by physical dilution and confined to coastal waters with a little into the open seas. The study area acts as a conveyer transferring nutrients from the Yellow Sea to the East China Sea in the whole year. In addition, vertical nutrient flux in spring and summer is a main source of DIP. Therefore, the hydrodynamic ROMS-based box model is superior to the traditional one in estimating nutrient fluxes in a complicated hydrodynamic current system and provides a modified box model approach to material flux research.
文摘Of the ~240*10^(12)mol year^(-1)of biogenic silica(bSi)produced by diatoms and other silicifying organisms,only roughly 3%–4%escapes dissolution to be permanently buried.At the global scale,how,where and why b Si is preserved in sediment is not well understood.To help address this,I compile 6245 porewater dissolved Si concentrations from 453 sediment cores,to derive the concentration gradient at the sediment–water interface and thus diffusive fluxes out of the sediment.These range from\0.002 to 3.4 mol m^(-2)year^(-1),and are independent of temperature,depth and latitude.When classified by sediment lithology,predominantly siliceous sediments unsurprisingly have higher mean diffusive fluxes than predominantly calcareous or clay-rich sediment.Combined with the areal extent of these lithologies,the‘best-guess’global sedimentary b Si recycling flux is69 9 10^(12)mol year^(-1).
文摘Cloud water samples, LWC (Liquid Water Content) and meteorological data were collected at the Clingmans Dome, Tennessee, high-elevation site in Great Smoky Mountains National Park during the warm season from 1994 through 2011. This paper presents results from 2000 through the conclusion of the study in 2011. Samples were analyzed for SO42", NO3, NH4+ and H+. These measurements were supplemented by measurements of ambient air and precipitation concentrations to estimate dry and wet deposition. Cloud water concentrations, LWC, cloud frequency, various meteorological measurements and information on nearby forest canopy were used to model cloud water deposition to gauge trends in deposition. Total deposition was calculated as the sum of cloud, dry and wet deposition estimates. Concentrations and deposition fluxes declined over the study period. The decreases in cloud water SO42" and NO3 concentrations were 40 percent and 26 percent, respectively. Three-year mean 5042 and NO3 deposition rates decreased by 71 percent and 70 percent, respectively. Trends in concentrations and depositions were comparable with trends in SO2 and NOx emissions from Tennessee Valley Authority power plants and aggregated emission reductions from electric generating units in adjacent states. Back trajectories were simulated with the HYSPLIT model and aggregated over cloud sampling periods from 2000 through 2007 and 2009 through 2011. Trajectories during periods with high H+ concentrations traveled over local EGU (Electric Generating Unit) emission sources in Tennessee and Kentucky to the Ohio River Valley, Alabama and Georgia with the conclusion that these source regions contributed to acidic cloud water deposition at Clingmans Dome. This work was supported by U.S. Environmental Protection Agency and the Tennessee Valley Authority with infrastructure support provided by the National Park Service.