Carbon Capture,Utilization,and Storage(CCUS)technology has gained widespread attention in recent years as a critical strategy to combat global climate change,particularly in achieving carbon neutrality goals.The Guang...Carbon Capture,Utilization,and Storage(CCUS)technology has gained widespread attention in recent years as a critical strategy to combat global climate change,particularly in achieving carbon neutrality goals.The Guangdong-Hong Kong-Macao Greater Bay Area(GBA),as one of China's most economically active regions,serves as a key engine for economic growth while also facing considerable carbon emission challenges.This study analyzes the industrial emission volume and geographical distribution of key emitting enterprises in the GBA,summarizes their technological processes and main carbonemitting equipment,and provides scientific support for precise mitigation policies and low-carbon development.Based on data from 176 key emitting enterprises,the study reveals that Guangzhou and Dongguan host the largest number of such enterprises.Carbon emissions are primarily concentrated in the power sector,dominated by coal-and gas-fired power units,characterized by significant spatial dispersion and uneven distribution.Beyond the power sector,the paper industry has a high number of enterprises but lower emissions.Key facilities such as boilers,cogeneration systems,and production lines are predominantly located near tributaries rivers in Dongguan and Jiangmen.The building materials sector,primarily cement production,ranks as the second-largest emitter,with hightemperature kilns and grinding equipment,particularly rotary kilns and glass furnaces,as the main sources.The petrochemical and chemical sectors have fewer enterprises and lower emissions in the GBA,mainly located in suburban industrial clusters.Carbon emissions in the GBA exhibit distinct industry concentration and geographical distribution disparities.This study provides crucial data and theoretical insights for the development of targeted emission reduction strategies,optimization of source-sink matching,and the advancement of CCUS technologies in the region,particularly from the GBA to the northern South China Sea.展开更多
A double-parabola monocapillary(DPM)was designed for laboratory x-ray sources,and its performance was evaluated through numerical simulations and experimental validation.A surface shape error model was developed to ch...A double-parabola monocapillary(DPM)was designed for laboratory x-ray sources,and its performance was evaluated through numerical simulations and experimental validation.A surface shape error model was developed to characterize the DPM surface profile,and ray-tracing methods were used to simulate key properties such as focal spot size,divergence,and transmission efficiency.The simulation results closely matched experimental measurements,validating the proposed model.This surface shape error simulation provides an efficient method for evaluating the impact of slope errors on DPM performance,offering insights for optimal design and precision manufacturing.展开更多
The effects of a harmonically exciting monopole source on an infinitely long cylindrical cavity embedded entirely within a fluid-saturated poroelastic formation of infinite extent are examined theoretically.It is assu...The effects of a harmonically exciting monopole source on an infinitely long cylindrical cavity embedded entirely within a fluid-saturated poroelastic formation of infinite extent are examined theoretically.It is assumed that the source is located outside the cavity at a specified distance from the borehole axis.The magnitudes of the hoop and radial stresses beside the pore pressures exerted on the interface and inside the porous medium surrounding the borehole are calculated and discussed.Biot's poroelastic modeling along with three types of boundary conditions for the cylindrical interface including the ideal fluid,empty borehole,and rigid inclusion with a hard boundary is employed for the analysis.Utilizing a proper translational addition theorem for expressing the incident spherical wave in terms of cylindrical wave expansions,the proposed boundary conditions at the interface are satisfied.Stresses are formulated by means of wave potential functions in a three-dimensional(3D)manner.The effects of the frequency and the radial distance between the source and borehole on the induced stresses are examined for the first cylindrical modes over frequency spectra.Two permeability conditions for the interface and three types of soils for the porous formation are considered throughout the analysis.To give an overall outline of the study,a numerical example is presented.The results clearly indicate that the distance is a key parameter and has considerable effects on the induced stress values.In addition,the interface permeability condition and soil characteristics play an important role in determining the dynamic response of the borehole.Finally,the obtained results are compared with the relevant analyses existing in the literature for some limit cases,and good agreement is achieved.展开更多
An electromagnetic field is generated through the accelerating movement of two equal but opposite charges of a single dipole. An electromagnetic field can also be generated by a time-varying infinitesimal point charge...An electromagnetic field is generated through the accelerating movement of two equal but opposite charges of a single dipole. An electromagnetic field can also be generated by a time-varying infinitesimal point charge. In this study, a comparison between the electromagnetic fields of an infinitesimal point charge and a dipole has been presented. First, the time-domain potential function of a point source in a 3D conductive medium is derived. Then the electric and magnetic fields in a 3D homogeneous lossless space are derived via the relation between the potential and field. The field differences between the infinitesimal point charge and the dipole in the step-off time, far-source, and near-source zones are analyzed, and the accuracy of the solutions from these sources is investigated. It is also shown that the field of the infinitesimal point charge in the near-source zone is different from that of the dipole, whereas the far-source zone fields of these two sources are identical. The comparison of real and simulated data shows that the infinitesimal point charge represents the real source better than the divole source.展开更多
[Objective] The characteristic of non-point source pollution of a typical village in Baiyangdian Lake basin was studied.[Method] The discharge of domestic sewage and solid wastes of the typical village was investigate...[Objective] The characteristic of non-point source pollution of a typical village in Baiyangdian Lake basin was studied.[Method] The discharge of domestic sewage and solid wastes of the typical village was investigated,and both pollutant and nutrient element content were monitored,as well as the water quality and quantity of rainfall runoff.[Result] The non-point source pollution of livestock manure was far more serious than the sum of domestic sewage and domestic waste in this village,and the annual emission of total organic carbon(TOC),total nitrogen(TN) and total phosphorus(TP) was 37 794.0,4 102.9 and 1 923.7 kg,respectively.The event mean concentration(EMC)of chemical oxygen demand COD,TN and TP in rainfall runoff was 44.5,78.8,1.3 mg/L,respectively,and annual pollution load was 7.6,13.4 and 0.2 kg/hm2,respectively,while the annual pollution load of COD accounted for 5.1% of standard farmland,and that of TN and TP occupied 4.5% and 0.49% of slope farmland.[Conclusion] Livestock manure was the main source of non-point source pollution in the village and the annual pollution load of non-point source pollution was obtained.展开更多
Taking Xinan River basin as research object,the status of agricultural non-point source pollution was analyzed based on field survey,as well as the effect of fertilizer and pesticide leaching and runoff,livestock and ...Taking Xinan River basin as research object,the status of agricultural non-point source pollution was analyzed based on field survey,as well as the effect of fertilizer and pesticide leaching and runoff,livestock and poultry breeding and rural domestic pollution on non-point source TN and TP.At last,some technical countermeasures of controlling non-point source pollution were put forward according to the characteristics of agricultural non-point source pollution in Xinan River basin.展开更多
The methane(CH4) emissions from municipal solid waste(MSW) landfills in China in 2007 were estimated based on database of the three-dimensional emission factors matrix and point sources, by an IPCC recommended FOD(fir...The methane(CH4) emissions from municipal solid waste(MSW) landfills in China in 2007 were estimated based on database of the three-dimensional emission factors matrix and point sources, by an IPCC recommended FOD(firstorder decay) model. The location, capacity and age of landfills constitute the three dimensions of the emission factors matrix, which were obtained by laboratory analysis and in situ investigation. Key parameters such as waste composition,degradable organic carbon ratio, CH4 correction factor, oxidation factor and recovery rate, were carefully analyzed in terms of these three dimensions. The point sources database consists of 2,107 MSW landfills in cities and towns of China in 2007. The results show that the CH4 emissions from MSW landfills were 1.186 Mt in 2007. Compared with the CH4 emissions of 2.20 Mt in 2005, the significant discrepancy mainly comes from statistical data of landfills, e.g., number of landfills and amount of waste disposed in landfills. CH4 emissions were lower than 700 t for most of the landfills, whereas there were 279 landfills with emissions larger than 1,000 t, and only 10 landfills with emissions larger than 10,000 t.Jiangsu province ranks the largest emitter with 98,700 t while Tibet is the smallest emitter with 2,100 t. In general,the emissions from eastern provinces, such as Jiangsu, Guangdong and Zhejiang, were larger than those from western provinces, such as Ningxia, Tibet and Qinghai.展开更多
Advancing the understanding of the spatial aspects of air pollution in the city regional environment is an area where improved methods can be of great benefit to exposure assessment and policy support. We created land...Advancing the understanding of the spatial aspects of air pollution in the city regional environment is an area where improved methods can be of great benefit to exposure assessment and policy support. We created land use regression （LUR） models for SO2, NO2 and PMI0 for Tianjin, China. Traffic volumes, road networks, land use data, population density, meteorological conditions, physical conditions and satellite-derived greenness, brightness and wetness were used for predicting SOa, NO2 and PMt0 concentrations. We incorporated data on industrial point sources to improve LUR model performance. In order to consider the impact of different sources, we calculated the PSIndex, LSIndex and area of different land use types （agricultural land, industrial land, commercial land, residential land, green space and water area） within different buffer radii （1 to 20 kin）. This method makes up for the lack of consideration of source impact based on the LUR model. Remote sensing-derived variables were significantly correlated with gaseous pollutant concentrations such as SO2 and NO2. R2 values of the multiple linear regression equations for SO2, NO2 and PM10 were 0.78, 0.89 and 0.84, respectively, and the RMSE values were 0.32, 0.18 and 0.21, respectively. Model predictions at validation monitoring sites went well with predictions generally within 15% of measured values. Compared to the relationship between dependent variables and simple variables （such as traffic variables or meteorological condition variables）, the relationship between dependent variables and integrated variables was more consistent with a linear relationship. Such integration has a discernable influence on both the overall model prediction and health effects assessment on the spatial distribution of air pollution in the city region.展开更多
Distributed X-ray sources comprise a single vacuum chamber containing multiple X-ray sources that are triggered and emit X-rays at a specific time and location. This process facilitates an application for innovative s...Distributed X-ray sources comprise a single vacuum chamber containing multiple X-ray sources that are triggered and emit X-rays at a specific time and location. This process facilitates an application for innovative system concepts in X-ray and computer tomography. This paper proposes a novel electron beam focusing, shaping,and deflection electron gun for distributed X-ray sources.The electron gun uses a dispenser cathode as an electron emitter, a mesh grid to control emission current, and two electrostatic lenses for beam shaping, focusing, and deflection. Novel focusing and deflecting electrodes were designed to increase the number of focal spots in the distributed source. Two identical half-rectangle opening electrodes are controlled by adjusting the potential of the two electrodes to control the electron beam trajectory, and then, multifocal spots are obtained on the anode target. The electron gun can increase the spatial density of the distributed X-ray sources, thereby improving the image quality. The beam experimental results show that the focal spot sizes of the deflected(deflected amplitude 10.5 mm)and non-deflected electron beams at full width at half maximum are 0.80 mm 90.50 mm and 0.55 mm 90.40 mm, respectively(anode voltage 160 kV; beam current 30 mA). The imaging experimental results demonstrate the excellent spatial resolution and time resolution of an imaging system built with the sources, which has an excellent imaging effect on a field-programmable gate array chip and a rotating metal disk.展开更多
Efficiency is an important factor in quantitative and qualitative analysis of radionuclides, and the gamma point source efficiency is related to the radial angle,detection distance, and gamma-ray energy. In this work,...Efficiency is an important factor in quantitative and qualitative analysis of radionuclides, and the gamma point source efficiency is related to the radial angle,detection distance, and gamma-ray energy. In this work, on the basis of a back-propagation(BP) neural network model,a method to determine the gamma point source efficiency is developed and validated. The efficiency of the point sources ^(137)Cs and ^(60)Co at discrete radial angles, detection distances, and gamma-ray energies is measured, and the BP neural network prediction model is constructed using MATLAB. The gamma point source efficiencies at different radial angles, detection distances, and gamma-ray energies are predicted quickly and accurately using this nonlinear prediction model. The results show that the maximum error between the predicted and experimental values is 3.732% at 661.661 keV, 11π/24, and 35 cm, and those under other conditions are less than 3%. The gamma point source efficiencies obtained using the BP neural network model are in good agreement with experimental data.展开更多
Individual participation of pollutants in the pollution load should be estimated even if roughly for the appropriate environmental management of a river basin.It is difficult to identify the sources and to quantify th...Individual participation of pollutants in the pollution load should be estimated even if roughly for the appropriate environmental management of a river basin.It is difficult to identify the sources and to quantify the load, especially in modeling nonpoint source.In this study a revised model was established by integrating point and nonpoint sources into one-dimensional Streeter-Phelps(S-P) model on the basis of real-time hydrologic data and surface water quality monitoring data in the Jilin Reach of the Songhua River Basin.Chemical oxygen demand(COD) and ammonia nitrogen(NH 3-N) loads were estimated.Results showed that COD loads of point source and nonpoint source were 134 958 t/yr and 86 209 t/yr, accounting for 61.02% and 38.98% of total loads, respectively.NH 3-N loads of point source and nonpoint source were 16 739 t/yr and 14 272 t/yr, accounting for 53.98% and 46.02%, respectively.Point source pollution was stronger than nonpoint source pollution in the study area at present.The water quality of upstream was better than that of downstream of the rivers and cities.It is indispensable to treat industrial wastewater and municipal sewage out of point sources, to adopt the best management practices to control diffuse pollutants from agricultural land and urban surface runoff in improving water quality of the Songhua River Basin.The revised S-P model can be successfully used to identify pollution source and quantify point source and nonpoint source loads by calibrating and validating.展开更多
Elastic wave on seafloor caused by low frequency noise radiated from ship is called ship seismic wave which can be used to identify ship target. In order to analyze the wave components and the propagating properties o...Elastic wave on seafloor caused by low frequency noise radiated from ship is called ship seismic wave which can be used to identify ship target. In order to analyze the wave components and the propagating properties of ship seismic wave, the numerical calculation of synthetic seismograms on seafloor aroused by a low frequency point sound source is carried out using a wave number integration technique combined with inverse Fourier transform. According to the numerical example of hard seafloor, the time series of seismic wave on seafloor are mostly composed of interface waves and normal mode waves. Each normal mode wave has a well defined low cut-off frequency, while the interface wave doesn't have. The frequency dispersion of normal mode wave is obvious when frequency is lower than 100Hz, while the interface wave is dispersive only in the infra-sound frequency range. The time series of seismic wave is dominated by the interface wave when the source frequency is less than the minimal cut-off frequency of normal mode wave.展开更多
This study tested and evaluated the agricultural non-point source （AGNPS） model for the Wuchuan catchment, a typical agricultural area in the Jiulong River watershed, Fujian Province, China. The AGNPS model was cali...This study tested and evaluated the agricultural non-point source （AGNPS） model for the Wuchuan catchment, a typical agricultural area in the Jiulong River watershed, Fujian Province, China. The AGNPS model was calibrated and validated for the study area with observed data on ten storms. The data on eight storms in 2002 were used for calibration while data on two storms were used for validation of the model. Considering the lack of water quality data over a long-term series, a novel method, comparing an internal nested catchment with its surrounding catchment, was used to supplement the less long-term series data. Dual calibration and validation of the AGNPS model was obtained by this comparison. The results indicate that the correlation coefficients were 0.99 and 0.98 for runoff, 0.94 and 0.95 for the peak runoff rate of the large catchment and the small catchment, respectively, and 0.76 for the sediment of the small catchment only. Each pair of correlation coefficients is homogeneous for the same event for the two catchments. With the exception of the sediment yield and particulate phosphorus, the peak runoff rate and other nutrients were well predicted. Sensitivity analysis showed that the Soil Conservation Service curve number and rainfall quantity were the most sensitive parameters, which resulted in high output variations. Erosivity and other parameters had little influence on the hydrological and quality outputs.展开更多
Several experiments are performed on the ShenGuang-Ⅱ laser facility to investigate an x-ray source and test radiography concepts. X-ray lines emitted from laser-produced plasmas are the most practical means of genera...Several experiments are performed on the ShenGuang-Ⅱ laser facility to investigate an x-ray source and test radiography concepts. X-ray lines emitted from laser-produced plasmas are the most practical means of generating these high intensity sources. By using a time-integrated space-resolved keV spectroscope and pinhole camera, potential helium-like titanium Kα x-ray backlighting （radiography） line source is studied as a function of laser wavelength, ratio of pre-pulse intensity to main pulse intensity, and laser intensity （from 7.25 to ～ 11.3 × 10^15 W/cm2）. One-dimensional radiography using a grid consisting of 5 #m Au wires on 16 μm period and the pinhole-assisted point projection is tested. The measurements show that the size of the helium-like titanium Ka source from a simple foil target is larger than 100 ~m, and relative x-ray line emission conversion efficiency ~x from the incident laser light energy to helium- like titanium K-shell spectrum increases significantly with pre-pulse intensity increasing, increases rapidly with laser wavelength decreasing, and increases moderately with main laser intensity increasing. It is also found that a gold gird foils can reach an imaging resolution better than 5-μm featured with high contrast. It is further demonstrated that the pinhole-assisted point projection at such a level will be a novel two-dimensional imaging diagnostic technique for inertial confinement fusion experiments.展开更多
An experiment with thin titanium foils irradiated by two pulses delayed in time is conducted on the bnenguang-Il laser facility. A prepulse induces an underdense plasma, 2-ns later a main pulse （λL ≈ 0.35 μm, EL ...An experiment with thin titanium foils irradiated by two pulses delayed in time is conducted on the bnenguang-Il laser facility. A prepulse induces an underdense plasma, 2-ns later a main pulse （λL ≈ 0.35 μm, EL ≈120 J, τL ≈100 ps） is injected into the underdense plasma and produces strong line emission from the titanium K shell （i.e., Hea at 4.7 keV）. Data show that the intensity of 4.7-keV X-ray emission with the prepulse is approximately twice more than without the prepulse, and can be used as a backlighting source satisfying the diagnostic requirements for dense plasma probing. High- quality plasma images are obtained with the backlighfing 4.7-keV X-rays in a Rayleigh-Taylor hydrodynamic instability experiment.展开更多
A three-dimensional(3 D)steady-state solution of fluid saturated anisotropic finite media is presented.The eigenequation method and the pseudo-Stroh formalism are used to obtain the exact solution for homogeneous satu...A three-dimensional(3 D)steady-state solution of fluid saturated anisotropic finite media is presented.The eigenequation method and the pseudo-Stroh formalism are used to obtain the exact solution for homogeneous saturated finite media.The propagator matrix method is introduced to deal with the corresponding multilayered poroelastic media.The poroelastic solutions due to surface or internal point fluid source are obtained.The comparison of the results of the saturated isotropic media in a half space and those obtained by the finite element method is given to illustrate the accuracy of the solution in a finite domain.Numerical solutions of a sandwich poroelastic medium are presented to analyze its hydromechanical behaviors.Two ratios of the horizontal permeability to vertical permeability and different source positions are investigated.The results show that the fluid parameters and source positions have great influence on the hydromechanical behaviors of the layered media.展开更多
The applicability of a non-point source pollution model—SWAT(soil and water assessment tools) in a large river basin with high sediment runoff modulus(770 t/km2 in the Yellow River) was examined. The basic database, ...The applicability of a non-point source pollution model—SWAT(soil and water assessment tools) in a large river basin with high sediment runoff modulus(770 t/km2 in the Yellow River) was examined. The basic database, which includes DEM, soil and landuse map, weather data, and land management data, was established for the study area using GIS. A two-stage “Brute Force' optimization method was used to calibrate the parameters with the observed monthly flow and sediment data from 1992 to 1997. In the process of calibration automated digital filter technique was used to separate direct runoff and base flow. The direct runoff was firstly calibrated, and the base flow, then the total runoff was matched. The sediment yield was calibrated to match well. Keeping input parameters set during the calibration process unchanged, the model was validated with 1998—1999's observed monthly flow and sediment. The evaluation coefficients for simulated and observed flow and sediment showed that SWAT was successfully applied in the study area: relative error was within 20%, coefficient of determination and Nash-Suttcliffe simulation efficiency were all equal to or above 0.70 during calibration and validation period.展开更多
A 2856-MHz,π-mode,seven-cell standingwave deflecting cavity was designed and fabricated for bunch length measurement in Tsinghua Thomson scattering X-ray source(TTX)facility.This cavity was installed in the TTX and p...A 2856-MHz,π-mode,seven-cell standingwave deflecting cavity was designed and fabricated for bunch length measurement in Tsinghua Thomson scattering X-ray source(TTX)facility.This cavity was installed in the TTX and provided a deflecting voltage of 4.2 MV with an input power of 2.5 MW.Bunch length diagnoses of electron beams with energies up to 39 MeV have been performed.In this article,the RF design of the cavity using HFSS,fabrication,and RF test processes are reviewed.High-power operation with accelerated beams and calibration of the deflecting voltage are also presented.展开更多
An X-ray radiation source with approximately constant radiation temperature is realized by irradiating golden hohlraum with a shaped laser pulse. A simple theoretical model based on power balance is used to design the...An X-ray radiation source with approximately constant radiation temperature is realized by irradiating golden hohlraum with a shaped laser pulse. A simple theoretical model based on power balance is used to design the shape of the drive laser pulse. Experiments are carried out on the Shenguang III prototype laser facility, and the experimentM results are presented for radiation sources with the flat-top lasting about 2.5 ns at two different peak temperatures of about 150 eV and 170 eV, respectively, including the the drive laser pulses and the time integrated possible improvements are discussed. time histories of the temperatures, the shapes of radiation spectra. The validity of the model and展开更多
基金supported by the National Natural Science Foundation of China(52304098,52106092,42376215,52474105)Shenzhen Science and Technology Program(JCYJ20220818095605012,JCYJ20220530113011027)+5 种基金Guangdong Basic and Applied Basic Research Foundation(2022A1515110338,2023A1515012316,2023A1515012761,2025A1515010748)Research Team Cultivation Program of Shenzhen University(2023QNT004)Shenzhen Key Laboratory of Natural Gas Hydrates(ZDSYS20200421111201738)the General Research Fund(No.12616222)Early Career Scheme(No.22611624)of Hong Kong Research Grants CouncilMajor Science and Technology Infrastructure Project of Material Genome Big–science Facilities Platform supported by the Municipal Development and Reform Commission of Shenzhen。
文摘Carbon Capture,Utilization,and Storage(CCUS)technology has gained widespread attention in recent years as a critical strategy to combat global climate change,particularly in achieving carbon neutrality goals.The Guangdong-Hong Kong-Macao Greater Bay Area(GBA),as one of China's most economically active regions,serves as a key engine for economic growth while also facing considerable carbon emission challenges.This study analyzes the industrial emission volume and geographical distribution of key emitting enterprises in the GBA,summarizes their technological processes and main carbonemitting equipment,and provides scientific support for precise mitigation policies and low-carbon development.Based on data from 176 key emitting enterprises,the study reveals that Guangzhou and Dongguan host the largest number of such enterprises.Carbon emissions are primarily concentrated in the power sector,dominated by coal-and gas-fired power units,characterized by significant spatial dispersion and uneven distribution.Beyond the power sector,the paper industry has a high number of enterprises but lower emissions.Key facilities such as boilers,cogeneration systems,and production lines are predominantly located near tributaries rivers in Dongguan and Jiangmen.The building materials sector,primarily cement production,ranks as the second-largest emitter,with hightemperature kilns and grinding equipment,particularly rotary kilns and glass furnaces,as the main sources.The petrochemical and chemical sectors have fewer enterprises and lower emissions in the GBA,mainly located in suburban industrial clusters.Carbon emissions in the GBA exhibit distinct industry concentration and geographical distribution disparities.This study provides crucial data and theoretical insights for the development of targeted emission reduction strategies,optimization of source-sink matching,and the advancement of CCUS technologies in the region,particularly from the GBA to the northern South China Sea.
基金supported by project of Beijing Postdoctoral Research Fund(Grant No.2025-ZZ-86)the National Natural Science Foundation of China(Grant Nos.12105020 and 12075031)+3 种基金Shenzhen Science and Technology Program(Grant No.KJZD20230923114219040)the Natural Science Youth Foundation of Henan Province,China(Grant No.242300420637)the Open Fund of Key Laboratory of Beam Technology of the Ministry of Education,Beijing Normal University(Grant No.BEAM2024G02)the Innovation Cultivation of Beijing Academy of Science and Technology(Grant Nos.25CB007-01 and 25CB007-02)。
文摘A double-parabola monocapillary(DPM)was designed for laboratory x-ray sources,and its performance was evaluated through numerical simulations and experimental validation.A surface shape error model was developed to characterize the DPM surface profile,and ray-tracing methods were used to simulate key properties such as focal spot size,divergence,and transmission efficiency.The simulation results closely matched experimental measurements,validating the proposed model.This surface shape error simulation provides an efficient method for evaluating the impact of slope errors on DPM performance,offering insights for optimal design and precision manufacturing.
文摘The effects of a harmonically exciting monopole source on an infinitely long cylindrical cavity embedded entirely within a fluid-saturated poroelastic formation of infinite extent are examined theoretically.It is assumed that the source is located outside the cavity at a specified distance from the borehole axis.The magnitudes of the hoop and radial stresses beside the pore pressures exerted on the interface and inside the porous medium surrounding the borehole are calculated and discussed.Biot's poroelastic modeling along with three types of boundary conditions for the cylindrical interface including the ideal fluid,empty borehole,and rigid inclusion with a hard boundary is employed for the analysis.Utilizing a proper translational addition theorem for expressing the incident spherical wave in terms of cylindrical wave expansions,the proposed boundary conditions at the interface are satisfied.Stresses are formulated by means of wave potential functions in a three-dimensional(3D)manner.The effects of the frequency and the radial distance between the source and borehole on the induced stresses are examined for the first cylindrical modes over frequency spectra.Two permeability conditions for the interface and three types of soils for the porous formation are considered throughout the analysis.To give an overall outline of the study,a numerical example is presented.The results clearly indicate that the distance is a key parameter and has considerable effects on the induced stress values.In addition,the interface permeability condition and soil characteristics play an important role in determining the dynamic response of the borehole.Finally,the obtained results are compared with the relevant analyses existing in the literature for some limit cases,and good agreement is achieved.
基金supported by Chinese National Programs for Fundamental Research and Development(No.2012CB416605)the National Natural Science Foundation of China(No.41174090)Development Project of National Key Scientific Equipment(No.ZDYZ2012-1-05-04)
文摘An electromagnetic field is generated through the accelerating movement of two equal but opposite charges of a single dipole. An electromagnetic field can also be generated by a time-varying infinitesimal point charge. In this study, a comparison between the electromagnetic fields of an infinitesimal point charge and a dipole has been presented. First, the time-domain potential function of a point source in a 3D conductive medium is derived. Then the electric and magnetic fields in a 3D homogeneous lossless space are derived via the relation between the potential and field. The field differences between the infinitesimal point charge and the dipole in the step-off time, far-source, and near-source zones are analyzed, and the accuracy of the solutions from these sources is investigated. It is also shown that the field of the infinitesimal point charge in the near-source zone is different from that of the dipole, whereas the far-source zone fields of these two sources are identical. The comparison of real and simulated data shows that the infinitesimal point charge represents the real source better than the divole source.
基金Supported by Major Projects of National Water Pollution Control and Management (2008ZX07209-007)
文摘[Objective] The characteristic of non-point source pollution of a typical village in Baiyangdian Lake basin was studied.[Method] The discharge of domestic sewage and solid wastes of the typical village was investigated,and both pollutant and nutrient element content were monitored,as well as the water quality and quantity of rainfall runoff.[Result] The non-point source pollution of livestock manure was far more serious than the sum of domestic sewage and domestic waste in this village,and the annual emission of total organic carbon(TOC),total nitrogen(TN) and total phosphorus(TP) was 37 794.0,4 102.9 and 1 923.7 kg,respectively.The event mean concentration(EMC)of chemical oxygen demand COD,TN and TP in rainfall runoff was 44.5,78.8,1.3 mg/L,respectively,and annual pollution load was 7.6,13.4 and 0.2 kg/hm2,respectively,while the annual pollution load of COD accounted for 5.1% of standard farmland,and that of TN and TP occupied 4.5% and 0.49% of slope farmland.[Conclusion] Livestock manure was the main source of non-point source pollution in the village and the annual pollution load of non-point source pollution was obtained.
文摘Taking Xinan River basin as research object,the status of agricultural non-point source pollution was analyzed based on field survey,as well as the effect of fertilizer and pesticide leaching and runoff,livestock and poultry breeding and rural domestic pollution on non-point source TN and TP.At last,some technical countermeasures of controlling non-point source pollution were put forward according to the characteristics of agricultural non-point source pollution in Xinan River basin.
基金funded by the Project Study on Key Issues of China City Carbon Emission Inventory (No. 41101500)supported by National Natural Science Foundation of China
文摘The methane(CH4) emissions from municipal solid waste(MSW) landfills in China in 2007 were estimated based on database of the three-dimensional emission factors matrix and point sources, by an IPCC recommended FOD(firstorder decay) model. The location, capacity and age of landfills constitute the three dimensions of the emission factors matrix, which were obtained by laboratory analysis and in situ investigation. Key parameters such as waste composition,degradable organic carbon ratio, CH4 correction factor, oxidation factor and recovery rate, were carefully analyzed in terms of these three dimensions. The point sources database consists of 2,107 MSW landfills in cities and towns of China in 2007. The results show that the CH4 emissions from MSW landfills were 1.186 Mt in 2007. Compared with the CH4 emissions of 2.20 Mt in 2005, the significant discrepancy mainly comes from statistical data of landfills, e.g., number of landfills and amount of waste disposed in landfills. CH4 emissions were lower than 700 t for most of the landfills, whereas there were 279 landfills with emissions larger than 1,000 t, and only 10 landfills with emissions larger than 10,000 t.Jiangsu province ranks the largest emitter with 98,700 t while Tibet is the smallest emitter with 2,100 t. In general,the emissions from eastern provinces, such as Jiangsu, Guangdong and Zhejiang, were larger than those from western provinces, such as Ningxia, Tibet and Qinghai.
基金supported by the Special Environmental Research Funds for Public Welfare (No. 200909005)the National Natural Science Foundation of China (No.20677030)the Doctor Funds of Tianjin Normal University (No. 52XB1110)
文摘Advancing the understanding of the spatial aspects of air pollution in the city regional environment is an area where improved methods can be of great benefit to exposure assessment and policy support. We created land use regression （LUR） models for SO2, NO2 and PMI0 for Tianjin, China. Traffic volumes, road networks, land use data, population density, meteorological conditions, physical conditions and satellite-derived greenness, brightness and wetness were used for predicting SOa, NO2 and PMt0 concentrations. We incorporated data on industrial point sources to improve LUR model performance. In order to consider the impact of different sources, we calculated the PSIndex, LSIndex and area of different land use types （agricultural land, industrial land, commercial land, residential land, green space and water area） within different buffer radii （1 to 20 kin）. This method makes up for the lack of consideration of source impact based on the LUR model. Remote sensing-derived variables were significantly correlated with gaseous pollutant concentrations such as SO2 and NO2. R2 values of the multiple linear regression equations for SO2, NO2 and PM10 were 0.78, 0.89 and 0.84, respectively, and the RMSE values were 0.32, 0.18 and 0.21, respectively. Model predictions at validation monitoring sites went well with predictions generally within 15% of measured values. Compared to the relationship between dependent variables and simple variables （such as traffic variables or meteorological condition variables）, the relationship between dependent variables and integrated variables was more consistent with a linear relationship. Such integration has a discernable influence on both the overall model prediction and health effects assessment on the spatial distribution of air pollution in the city region.
文摘Distributed X-ray sources comprise a single vacuum chamber containing multiple X-ray sources that are triggered and emit X-rays at a specific time and location. This process facilitates an application for innovative system concepts in X-ray and computer tomography. This paper proposes a novel electron beam focusing, shaping,and deflection electron gun for distributed X-ray sources.The electron gun uses a dispenser cathode as an electron emitter, a mesh grid to control emission current, and two electrostatic lenses for beam shaping, focusing, and deflection. Novel focusing and deflecting electrodes were designed to increase the number of focal spots in the distributed source. Two identical half-rectangle opening electrodes are controlled by adjusting the potential of the two electrodes to control the electron beam trajectory, and then, multifocal spots are obtained on the anode target. The electron gun can increase the spatial density of the distributed X-ray sources, thereby improving the image quality. The beam experimental results show that the focal spot sizes of the deflected(deflected amplitude 10.5 mm)and non-deflected electron beams at full width at half maximum are 0.80 mm 90.50 mm and 0.55 mm 90.40 mm, respectively(anode voltage 160 kV; beam current 30 mA). The imaging experimental results demonstrate the excellent spatial resolution and time resolution of an imaging system built with the sources, which has an excellent imaging effect on a field-programmable gate array chip and a rotating metal disk.
基金supported by the National Natural Science Foundation of China(Nos.41374130 and 41604154)Science and Technology Program of Sichuan,China(No.2017GZ0359)+1 种基金Science and Technology Support Program of Sichuan,China(No.2015JY0007)Open Foundation for Artificial Intelligence Key Laboratory of Sichuan Province of China(No.2016RYJ08)
文摘Efficiency is an important factor in quantitative and qualitative analysis of radionuclides, and the gamma point source efficiency is related to the radial angle,detection distance, and gamma-ray energy. In this work, on the basis of a back-propagation(BP) neural network model,a method to determine the gamma point source efficiency is developed and validated. The efficiency of the point sources ^(137)Cs and ^(60)Co at discrete radial angles, detection distances, and gamma-ray energies is measured, and the BP neural network prediction model is constructed using MATLAB. The gamma point source efficiencies at different radial angles, detection distances, and gamma-ray energies are predicted quickly and accurately using this nonlinear prediction model. The results show that the maximum error between the predicted and experimental values is 3.732% at 661.661 keV, 11π/24, and 35 cm, and those under other conditions are less than 3%. The gamma point source efficiencies obtained using the BP neural network model are in good agreement with experimental data.
基金Under the auspices of Major State Basic Research Development Program of China (973 Program) (No. 2004CB418502,No. 2007CB407205)the Knowledge Innovation Programs of Chinese Academy of Sciences (No. KSCX1-YW-09-13)
文摘Individual participation of pollutants in the pollution load should be estimated even if roughly for the appropriate environmental management of a river basin.It is difficult to identify the sources and to quantify the load, especially in modeling nonpoint source.In this study a revised model was established by integrating point and nonpoint sources into one-dimensional Streeter-Phelps(S-P) model on the basis of real-time hydrologic data and surface water quality monitoring data in the Jilin Reach of the Songhua River Basin.Chemical oxygen demand(COD) and ammonia nitrogen(NH 3-N) loads were estimated.Results showed that COD loads of point source and nonpoint source were 134 958 t/yr and 86 209 t/yr, accounting for 61.02% and 38.98% of total loads, respectively.NH 3-N loads of point source and nonpoint source were 16 739 t/yr and 14 272 t/yr, accounting for 53.98% and 46.02%, respectively.Point source pollution was stronger than nonpoint source pollution in the study area at present.The water quality of upstream was better than that of downstream of the rivers and cities.It is indispensable to treat industrial wastewater and municipal sewage out of point sources, to adopt the best management practices to control diffuse pollutants from agricultural land and urban surface runoff in improving water quality of the Songhua River Basin.The revised S-P model can be successfully used to identify pollution source and quantify point source and nonpoint source loads by calibrating and validating.
基金Sponsored by National Nature Science Foundation of China ( 51179195)National Defense Foundation of China ( 513030203-02)
文摘Elastic wave on seafloor caused by low frequency noise radiated from ship is called ship seismic wave which can be used to identify ship target. In order to analyze the wave components and the propagating properties of ship seismic wave, the numerical calculation of synthetic seismograms on seafloor aroused by a low frequency point sound source is carried out using a wave number integration technique combined with inverse Fourier transform. According to the numerical example of hard seafloor, the time series of seismic wave on seafloor are mostly composed of interface waves and normal mode waves. Each normal mode wave has a well defined low cut-off frequency, while the interface wave doesn't have. The frequency dispersion of normal mode wave is obvious when frequency is lower than 100Hz, while the interface wave is dispersive only in the infra-sound frequency range. The time series of seismic wave is dominated by the interface wave when the source frequency is less than the minimal cut-off frequency of normal mode wave.
文摘This study tested and evaluated the agricultural non-point source （AGNPS） model for the Wuchuan catchment, a typical agricultural area in the Jiulong River watershed, Fujian Province, China. The AGNPS model was calibrated and validated for the study area with observed data on ten storms. The data on eight storms in 2002 were used for calibration while data on two storms were used for validation of the model. Considering the lack of water quality data over a long-term series, a novel method, comparing an internal nested catchment with its surrounding catchment, was used to supplement the less long-term series data. Dual calibration and validation of the AGNPS model was obtained by this comparison. The results indicate that the correlation coefficients were 0.99 and 0.98 for runoff, 0.94 and 0.95 for the peak runoff rate of the large catchment and the small catchment, respectively, and 0.76 for the sediment of the small catchment only. Each pair of correlation coefficients is homogeneous for the same event for the two catchments. With the exception of the sediment yield and particulate phosphorus, the peak runoff rate and other nutrients were well predicted. Sensitivity analysis showed that the Soil Conservation Service curve number and rainfall quantity were the most sensitive parameters, which resulted in high output variations. Erosivity and other parameters had little influence on the hydrological and quality outputs.
基金supported by the National High Technology Development Program of China (Grant No. 2009AA8046006)
文摘Several experiments are performed on the ShenGuang-Ⅱ laser facility to investigate an x-ray source and test radiography concepts. X-ray lines emitted from laser-produced plasmas are the most practical means of generating these high intensity sources. By using a time-integrated space-resolved keV spectroscope and pinhole camera, potential helium-like titanium Kα x-ray backlighting （radiography） line source is studied as a function of laser wavelength, ratio of pre-pulse intensity to main pulse intensity, and laser intensity （from 7.25 to ～ 11.3 × 10^15 W/cm2）. One-dimensional radiography using a grid consisting of 5 #m Au wires on 16 μm period and the pinhole-assisted point projection is tested. The measurements show that the size of the helium-like titanium Ka source from a simple foil target is larger than 100 ~m, and relative x-ray line emission conversion efficiency ~x from the incident laser light energy to helium- like titanium K-shell spectrum increases significantly with pre-pulse intensity increasing, increases rapidly with laser wavelength decreasing, and increases moderately with main laser intensity increasing. It is also found that a gold gird foils can reach an imaging resolution better than 5-μm featured with high contrast. It is further demonstrated that the pinhole-assisted point projection at such a level will be a novel two-dimensional imaging diagnostic technique for inertial confinement fusion experiments.
文摘An experiment with thin titanium foils irradiated by two pulses delayed in time is conducted on the bnenguang-Il laser facility. A prepulse induces an underdense plasma, 2-ns later a main pulse （λL ≈ 0.35 μm, EL ≈120 J, τL ≈100 ps） is injected into the underdense plasma and produces strong line emission from the titanium K shell （i.e., Hea at 4.7 keV）. Data show that the intensity of 4.7-keV X-ray emission with the prepulse is approximately twice more than without the prepulse, and can be used as a backlighting source satisfying the diagnostic requirements for dense plasma probing. High- quality plasma images are obtained with the backlighfing 4.7-keV X-rays in a Rayleigh-Taylor hydrodynamic instability experiment.
基金Project supported by the National Natural Science Foundation of China(No.51704015)China Scholarship Council(No.201706465064)。
文摘A three-dimensional(3 D)steady-state solution of fluid saturated anisotropic finite media is presented.The eigenequation method and the pseudo-Stroh formalism are used to obtain the exact solution for homogeneous saturated finite media.The propagator matrix method is introduced to deal with the corresponding multilayered poroelastic media.The poroelastic solutions due to surface or internal point fluid source are obtained.The comparison of the results of the saturated isotropic media in a half space and those obtained by the finite element method is given to illustrate the accuracy of the solution in a finite domain.Numerical solutions of a sandwich poroelastic medium are presented to analyze its hydromechanical behaviors.Two ratios of the horizontal permeability to vertical permeability and different source positions are investigated.The results show that the fluid parameters and source positions have great influence on the hydromechanical behaviors of the layered media.
文摘The applicability of a non-point source pollution model—SWAT(soil and water assessment tools) in a large river basin with high sediment runoff modulus(770 t/km2 in the Yellow River) was examined. The basic database, which includes DEM, soil and landuse map, weather data, and land management data, was established for the study area using GIS. A two-stage “Brute Force' optimization method was used to calibrate the parameters with the observed monthly flow and sediment data from 1992 to 1997. In the process of calibration automated digital filter technique was used to separate direct runoff and base flow. The direct runoff was firstly calibrated, and the base flow, then the total runoff was matched. The sediment yield was calibrated to match well. Keeping input parameters set during the calibration process unchanged, the model was validated with 1998—1999's observed monthly flow and sediment. The evaluation coefficients for simulated and observed flow and sediment showed that SWAT was successfully applied in the study area: relative error was within 20%, coefficient of determination and Nash-Suttcliffe simulation efficiency were all equal to or above 0.70 during calibration and validation period.
基金This work was supported by the National Natural Science Foundation of China(No.11922504).
文摘A 2856-MHz,π-mode,seven-cell standingwave deflecting cavity was designed and fabricated for bunch length measurement in Tsinghua Thomson scattering X-ray source(TTX)facility.This cavity was installed in the TTX and provided a deflecting voltage of 4.2 MV with an input power of 2.5 MW.Bunch length diagnoses of electron beams with energies up to 39 MeV have been performed.In this article,the RF design of the cavity using HFSS,fabrication,and RF test processes are reviewed.High-power operation with accelerated beams and calibration of the deflecting voltage are also presented.
文摘An X-ray radiation source with approximately constant radiation temperature is realized by irradiating golden hohlraum with a shaped laser pulse. A simple theoretical model based on power balance is used to design the shape of the drive laser pulse. Experiments are carried out on the Shenguang III prototype laser facility, and the experimentM results are presented for radiation sources with the flat-top lasting about 2.5 ns at two different peak temperatures of about 150 eV and 170 eV, respectively, including the the drive laser pulses and the time integrated possible improvements are discussed. time histories of the temperatures, the shapes of radiation spectra. The validity of the model and
