Seismic characterizing of tight gas sandstone (TGS) reservoirs is essential for identifying promising gas-bearing regions. However, exploring the petrophysical significance of seismic-inverted elastic properties is ch...Seismic characterizing of tight gas sandstone (TGS) reservoirs is essential for identifying promising gas-bearing regions. However, exploring the petrophysical significance of seismic-inverted elastic properties is challenging due to the complex microstructures in TGSs. Meanwhile, interbedded structures of sandstone and mudstone intensify the difficulty in accurately extracting the crucial tight sandstone properties. An integrated rock-physics-based framework is proposed to estimate the reservoir quality of TGSs from seismic data. TGSs with complex pore structures are modeled using the double-porosity model, providing a practical tool to compute rock physics templates for reservoir parameter estimation. The VP/VS ratio is utilized to predict the cumulative thickness of the TGS reservoirs within the target range via the threshold value evaluated from wireline logs for lithology discrimination. This approach also facilitates better capturing the elastic properties of the TGSs for quantitative seismic interpretation. Total porosity is estimated from P-wave impedance using the correlation obtained based on wireline log analysis. After that, the three-dimensional rock-physics templates integrated with the estimated total porosity are constructed to interpret microfracture porosity and gas saturation from velocity ratio and bulk modulus. The integrated framework can optimally estimate the parameters dominating the reservoir quality. The results of the indicator proposed based on the obtained parameters are in good agreement with the gas productions and can be utilized to predict promising TGS reservoirs. Moreover, the results suggest that considering microfracture porosity allows a more accurate prediction of high-quality reservoirs, further validating the applicability of the proposed method in the studied region.展开更多
By studying both the microscopic physical and chemical typomorphic characteristics of typical mineral pyrite samples associated with representative gold deposits on the north-central margin of the North China Platform...By studying both the microscopic physical and chemical typomorphic characteristics of typical mineral pyrite samples associated with representative gold deposits on the north-central margin of the North China Platform,this paper seeks to identify macroscopic metallogenic mechanisms of gold deposits and to reveal the formation mechanism of lattice gold in pyrite.Typomorphic characteristics of pyrite reveal that pyrite grain size has a negative correlation with gold content.Cubic pyrite,as the dominant crystal form,contains more gold than pentagonal dodecahedral pyrite.Both pyrite crystal forms and chemical compositions indicate that the replacement style of gold deposit formed in a low saturability,low sulfur fugacity,and at temperatures either much higher or much lower than its best forming temperature;comparatively,that of the quartz vein style of gold deposit occurred under conditions with the best temperature,rich in sulfur,and with high sulfur fugacity.The Au/Ag ratios of the pyrites show that both the replacement and quartz vein styles of deposits are mesothermal and hypothermal,while the Co/Ni ratios of the pyrites indicate that the quartz vein style is of magmatic-hydrothermal origin.The X-ray diffraction intensity of pyrite rich in gold is lower than that of pyrite poor in gold at the quartz vein style.In general,with an increase in gold content in pyrite,the total sum intensityΣI decreases.The pyroelectricity coefficient has a negative correlation trend with the values of(Co+Ni+Se+Te)-As and(Co+Ni+Se+Te)/As.The pyrite pyroelectricity of the replacement style is N-type,indicating that it formed under low sulfur fugacity,while that of the quartz vein style is a mixture of P-N types,indicating that it formed under high sulfur fugacity.On the pyroelectricity-temperature diagram,pyrite of the replacement style is mainly distributed between 200 and 270°C,while that of the quartz vein style varies between 90–118 and274–386°C,demonstrating a multistage forming process.In contrast to previous researchers'conclusions,the authors confirm the existence of lattice gold in pyrites through the use of an electron paramagnetic resonance(EPR)test.Au in the form of Au~+,entering pyrite as an isomorph and producing electron–hole centers,makes the centers produce spin resonance absorption and results in EPR absorption peak II.The intensity of auriferous pyrite absorption peak II has certain direct positive correlations with pyrite gold content.The#I and#III absorption peaks of pyrites possibly result from the existence of Ni^(2+)and/or Cu^(2+).γ1,γ2,andγ3 are the strongest and most typical absorption peaks of the infrared spectra of the pyrites.Generally,with the increase in gold content in the pyrite samples,γ1,γ2,andγ3 tend to shift to higher wavenumbers,and the gold content in the pyrite samples has a positive correlation with their relative absorbance.展开更多
In the processing of conventional marine seismic data,seawater is often assumed to have a constant velocity model.However,due to static pressure,temperature difference and other factors,random disturbances may often f...In the processing of conventional marine seismic data,seawater is often assumed to have a constant velocity model.However,due to static pressure,temperature difference and other factors,random disturbances may often frequently in seawater bodies.The impact of such disturbances on data processing results is a topic of theoretical research.Since seawater sound velocity is a difficult physical quantity to measure,there is a need for a method that can generate models conforming to seawater characteristics.This article will combine the Munk model and Perlin noise to propose a two-dimensional dynamic seawater sound velocity model generation method,a method that can generate a dynamic,continuous,random seawater sound velocity model with some regularity at large scales.Moreover,the paper discusses the influence of the inhomogeneity characteristics of seawater on wave field propagation and imaging.The results show that the seawater sound velocity model with random disturbance will have a significant influence on the wave field simulation and imaging results.展开更多
The dielectric constant of the lunar regolith can directly influence the reflection coefficient and the trans-mission coefficient of the Moon′s surface, and plays an important role in the Moon research. In order to s...The dielectric constant of the lunar regolith can directly influence the reflection coefficient and the trans-mission coefficient of the Moon′s surface, and plays an important role in the Moon research. In order to study the di-electric properties of the lunar regolith, the lunar regolith simulant was made according to the making procedure of the CAS-1 simulant made by Chinese Academy of Sciences. Then the dielectric constants of the lunar regolith simulant were measured with 85070E Aiglent Microwave Network Analyzer in the frequency ranging from 0.2 GHz to 20.0 GHz and at temperature of 25.1℃, 17.7℃, 13.1℃, 11.5℃, 9.6℃, 8.0℃, 4.1℃, -0.3℃, -4.7℃, -9.5℃, -18.7℃, -27.7℃, and -32.6℃, respectively. The Odelevsky model was employed to remove the influence of water in the air on the final effective dielectric constants. The results indicate that frequency and temperature have apparent influences on the dielectric constants of the lunar regolith simulant. The real parts of the dielectric constants increase fast over the range of 0.2 GHz to 3.0 GHz, but decrease slowly over the range of 4.0 GHz to 20.0 GHz. The opposite phenomenon occurs in the imaginary parts. The influences of the frequency and temperature on the brightness temperature were also estimated based on the radiative transfer equation. The result shows that the variation of the frequency and temperature results in great changes of the microwave brightness temperature emitting from the lunar regolith.展开更多
The nonaxisymmetric acousto-electric field excited by an eccentric acoustic source in the borehole based on Pride seismoelectric theory is considered. It is shown that the acoustic field inside the borehole, converted...The nonaxisymmetric acousto-electric field excited by an eccentric acoustic source in the borehole based on Pride seismoelectric theory is considered. It is shown that the acoustic field inside the borehole, converted electric and magnetic fields and coupled fields outside the borehole are composed of an infinitude of multipole fields with different orders. The numerical results show that both the electromagnetic waves and the seismoelectric field in the borehole, and the three components of both electric field and magnetic field can be detected. Measurements on the borehole axis will be of advantage to determining shear velocity information. The components of the symmetric and nonsymmetric acoustic and electromagnetic fields can be strengthened or weakened by adding or subtracting the two full waveforms logged in some azimuths. It may be a new method of directly measuring the shear wave velocity by using the borehole seismoelectric effect.展开更多
The volume FeO and TiO_2 abundances(FTAs) of lunar regolith can be more important for understanding the geological evolution of the Moon compared to the optical and gamma-ray results. In this paper, the volume FTAs ar...The volume FeO and TiO_2 abundances(FTAs) of lunar regolith can be more important for understanding the geological evolution of the Moon compared to the optical and gamma-ray results. In this paper, the volume FTAs are retrieved with microwave sounder(CELMS) data from the Chang'E-2 satellite using the back propagation neural network(BPNN) method. Firstly, a three-layered BPNN network with five-dimensional input is constructed by taking nonlinearity into account. Then, the brightness temperature(TB) and surface slope are set as the inputs and the volume FTAs are set as the outputs of the BPNN network.Thereafter, the BPNN network is trained with the corresponding parameters collected from Apollo, Luna,and Surveyor missions. Finally, the volume FTAs are retrieved with the trained BPNN network using the four-channel TBderived from the CELMS data and the surface slope estimated from Lunar Orbiter Laser Altimeter(LOLA) data. The rationality of the retrieved FTAs is verified by comparing with the Clementine UV-VIS results and Lunar Prospector(LP) GRS results. The retrieved volume FTAs enable us to re-evaluate the geological features of the lunar surface. Several important results are as follows. Firstly, very-low-Ti(<1.5 wt.%) basalts are the most spatially abundant, and the surfaces with TiO_2> 5 wt.% constitute less than 10% of the maria. Also, two linear relationships occur between the FeO abundance(FA) and the TiO_2 abundance before and after the threshold, 16 wt.% for FA. Secondly, a new perspective on mare volcanism is derived with the volume FTAs in several important mare basins, although this conclusion should be verified with more sources of data. Thirdly, FTAs in the lunar regolith change with depth to the uppermost surface,and the change is complex over the lunar surface. Finally, the distribution of volume FTAs hints that the highlands crust is probably homogeneous, at least in terms of the microwave thermophysical parameters.展开更多
It is one of the important methods to retrieve lunar regolith thickness using active and passive microwave techniques.The retrieval of lunar regolith thickness is based on microwave radiation transfer process simulati...It is one of the important methods to retrieve lunar regolith thickness using active and passive microwave techniques.The retrieval of lunar regolith thickness is based on microwave radiation transfer process simulation in the regolith media.The lunar regolith model is first introduced,and the features of the involved physical parameters are indicated thereafter,such as dielectric constants,surface roughness,particle size and thermal grads of the lunar regolith.The time delay and the migration of the radar echoes from the different interfaces is the key problem for active microwave measurement.And the simulation of the microwave radiative transfer in the regolith media is the important technique for the passive microwave measurement.The important parameters and the physical mechanism for the two measurements are also presented.展开更多
Soil surface roughness, denoted by the root mean square height(RMSH), and soil moisture(SM) are critical factors that affect the accuracy of quantitative remote sensing research due to their combined influence on spec...Soil surface roughness, denoted by the root mean square height(RMSH), and soil moisture(SM) are critical factors that affect the accuracy of quantitative remote sensing research due to their combined influence on spectral reflectance(SR). In regards to this issue, three SM levels and four RMSH levels were artificially designed in this study; a total of 12 plots was used, each plot had a size of 3 m × 3 m. Eight spectral observations were conducted from 14 to 30 October 2017 to investigate the correlation between RMSH, SM, and SR. On this basis, 6 commonly used bands of optical satellite sensors were selected in this study, which are red(675 nm), green(555 nm), blue(485 nm), near infrared(845 nm), shortwave infrared 1(1600 nm), and shortwave infrared 2(2200 nm). A negative correlation was found between SR and RMSH, and between SR and SM. The bands with higher coefficient of determination R^2 values were selected for stepwise multiple nonlinear regression analysis. Four characterized bands(i.e., blue, green, near infrared, and shortwave infrared 2) were chosen as the independent variables to estimate SM with R^2 and root mean square error(RMSE) values equal to 0.62 and 2.6%, respectively. Similarly, the four bands(green, red, near infrared, and shortwave infrared 1) were used to estimate RMSH with R^2 and RMSE values equal to 0.48 and 0.69 cm, respectively. These results indicate that the method used is not only suitable for estimating SM but can also be extended to the prediction of RMSH. Finally, the evaluation approach presented in this paper highly restores the real situation of the natural farmland surface on the one hand, and obtains high precision values of SM and RMSH on the other. The method can be further applied to the prediction of farmland SM and RMSH based on satellite and unmanned aerial vehicle(UAV) optical imagery.展开更多
The in situ electrical resistance and transport activation energies of solid C60 fullerene have been measured under high pressure up to 25 GPa in the temperature range of 300-423 K by using a designed diamond anvil ce...The in situ electrical resistance and transport activation energies of solid C60 fullerene have been measured under high pressure up to 25 GPa in the temperature range of 300-423 K by using a designed diamond anvil cell. In the experiment, four parts of boron-doped diamond films fabricated on one anvil were used as electrical measurement probes and a W-Ta thin film thermocouple which was integrated on the other diamond anvil was used to measure the temperature. The current results indicate that the measured high-pressure resistances are bigger than those reported before at the same pressure and there is no pressure-independent resistance increase before 8 GPa. From the temperature dependence of the resistivity, the C60 behaviors as a semiconductor and the activation energies of the cubic C60 fullerene are 0,49, 0.43, and 0.36 eV at 13, 15, and 19 GPa, respectively.展开更多
The authors generalized the methods how to identify and evaluate gas zones using logs,and put forward the methods of crossplots and overlays of porosity logs on the identification of volcanic gas-bearing reservoirs in...The authors generalized the methods how to identify and evaluate gas zones using logs,and put forward the methods of crossplots and overlays of porosity logs on the identification of volcanic gas-bearing reservoirs in the northern Songliao Basin with good results.This study provides technical clues in deep formations and offers references for other areas to identify oil and gas layers.展开更多
Soil moisture plays an important role in crop yield estimation,irrigation management,etc.Remote sensing technology has potential for large-scale and high spatial soil moisture mapping.However,offline remote sensing da...Soil moisture plays an important role in crop yield estimation,irrigation management,etc.Remote sensing technology has potential for large-scale and high spatial soil moisture mapping.However,offline remote sensing data processing is time-consuming and resource-intensive,and significantly hampers the efficiency and timeliness of soil moisture mapping.Due to the high-speed computing capabilities of remote sensing cloud platforms,a High Spatial Resolution Soil Moisture Estimation Framework(HSRSMEF)based on the Google Earth Engine(GEE)platform was developed in this study.The functions of the HSRSMEF include research area and input datasets customization,radar speckle noise filtering,optical-radar image spatio-temporal matching,soil moisture retrieving,soil moisture visualization and exporting.This paper tested the performance of HSRSMEF by combining Sentinel-1,Sentinel-2 images and insitu soil moisture data in the central farmland area of Jilin Province,China.Reconstructed Normalized Difference Vegetation Index(NDVI)based on the Savitzky-Golay algorithm conforms to the crop growth cycle,and its correlation with the original NDVI is about 0.99(P<0.001).The soil moisture accuracy of the random forest model(R 2=0.942,RMSE=0.013 m3/m3)is better than that of the water cloud model(R 2=0.334,RMSE=0.091 m3/m3).HSRSMEF transfers time-consuming offline operations to cloud computing platforms,achieving rapid and simplified high spatial resolution soil moisture mapping.展开更多
Remote sensing data have been widely applied to extract minerals in geologic exploration, however, in areas covered by vegetation, extracted mineral information has mostly been small targets bearing little information...Remote sensing data have been widely applied to extract minerals in geologic exploration, however, in areas covered by vegetation, extracted mineral information has mostly been small targets bearing little information. In this paper, we present a new method for mineral extraction aimed at solving the difficulty of mineral identification in vegetation covered areas. The method selected six sets of spectral difference coupling between soil and plant(SVSCD). These sets have the same vegetation spectra reflectance and a maximum different reflectance of soil and mineral spectra from Hyperion image based on spectral reflectance characteristics of measured spectra. The central wavelengths of the six, selected band pairs were 2314 and 701 nm, 1699 and 721 nm, 1336 and 742 nm, 2203 and 681 nm, 2183 and 671 nm, and 2072 and 548 nm. Each data set's reflectance was used to calculate the difference value. After band difference calculation, vegetation information was suppressed and mineral abnormal information was enhanced compared to the scatter plot of original band. Six spectral difference couplings, after vegetation inhibition, were arranged in a new data set that requires two components that have the largest eigenvalue difference from principal component analysis(PCA). The spatial geometric structure features of PC1 and PC2 was used to identify altered minerals by spectral feature fitting(SFF). The collecting rocks from the 10 points that were selected in the concentration of mineral extraction were analyzed under a high-resolution microscope to identify metal minerals and nonmetallic minerals. Results indicated that the extracted minerals were well matched with the verified samples, especially with the sample 2, 4, 5 and 8. It demonstrated that the method can effectively detect altered minerals in vegetation covered area in Hyperion image.展开更多
The vector finite element method of tetrahedral elements is used to model 3D electromagnetic wave logging response. The tangential component of the vector field at the mesh edges is used as a degree of freedom to over...The vector finite element method of tetrahedral elements is used to model 3D electromagnetic wave logging response. The tangential component of the vector field at the mesh edges is used as a degree of freedom to overcome the shortcomings of node-based finite element methods. The algorithm can simulate inhomogeneous media with arbitrary distribution of conductivity and magnetic permeability. The electromagnetic response of well logging tools are studied in dipping bed layers with the borehole and invasion included. In order to simulate realistic logging tools, we take the transmitter antennas consisting of circular wire loops instead of magnetic dipoles. We also investigate the apparent resistivity of inhomogeneous formation for different dip angles.展开更多
Seismic monitoring using ocean bottom seismometers(OBS) is an efficient method for investigating earthquakes in mid-ocean ridge far away from land. Clock synchronization among the OBSs is difficult without direct co...Seismic monitoring using ocean bottom seismometers(OBS) is an efficient method for investigating earthquakes in mid-ocean ridge far away from land. Clock synchronization among the OBSs is difficult without direct communication because electromagnetic signals cannot propagate efficiently in water. Time correction can be estimated through global positioning system(GPS) synchronization if clock drift is linear before and after the deployment. However, some OBSs in the experiments at the southwest Indian ridge(SWIR) on the Chinese DY125-34 cruise had not been re-synchronized from GPS after recovery. So we attempted to estimate clock drift between each station pairs using time symmetry analysis(TSA) based on ambient noise cross-correlation. We tested the feasibility of the TSA method by analyzing daily noise cross-correlation functions(NCFs) that extract from the data of another OBS experiment on the Chinese DY125-40 cruise with known clock drift and the same deployment site. The results suggest that the NCFs' travel time of surface wave between any two stations are symmetrical and have an opposite growing direction with the date. The influence of different band-pass filters,different components and different normalized methods was discussed. The TSA method appeared to be optimal for the hydrophone data within the period band of 2–5 s in dozens of km-scale interstation distances. A significant clock drift of ~2 s was estimated between OBSs sets through linear regression during a 108-d deployment on the Chinese cruise DY125-34. Time correction of the OBS by the ambient noise cross-correlation was demonstrated as a practical approach with the appropriate parameters in case of no GPS re-synchronization.展开更多
Seismoelectric fieM excited by purely torsional loading applied directly to the borehole wall is considered. A brief formulation and some computed waveforms show the advantage of using shear-horizontal (SH) transver...Seismoelectric fieM excited by purely torsional loading applied directly to the borehole wall is considered. A brief formulation and some computed waveforms show the advantage of using shear-horizontal (SH) transverseelectric (TE) seismoelectric waves logging to measure shear velocity in a fluid-saturated porous formation. By assuming that the acoustic field is not influenced by its induced electromagnetic field due to seismoeleetric effect, the coupling governing equations for electromagnetic field are reduced to Maxwell equations with a propagation current source. It is shown that this simplification is valid and the borehole seismoelectric conversion efficient is mainly dependent on the electrokinetic coupling coefficient. The receivers to detect the conversion electromagnetic field and to obtain shear velocity can be set in the borehole fluid in the SH-TE seismoelectric wave log.展开更多
The petrophysical parameters are bad in most igneous reservoirs of Songliao Basin because of the very low porosity and permeability.The evaluation of igneous reservoirs has not been fully studied so far.The current te...The petrophysical parameters are bad in most igneous reservoirs of Songliao Basin because of the very low porosity and permeability.The evaluation of igneous reservoirs has not been fully studied so far.The current technique of formation evaluation and interpretation used in sedimentary formations face a series of problems and difficulties.In this study,The PCA was used to identify lithology,a multi-mineral model "QAPM" was proposed."Surface effect" must be considered when evaluating saturation.A software "SIMPLE" was developed and was used to deal with the logging data in over 70 wells with good results were achieved.展开更多
基金supported by the National Natural Science Foundation of China(Grant numbers 42274160 and 42074153).
文摘Seismic characterizing of tight gas sandstone (TGS) reservoirs is essential for identifying promising gas-bearing regions. However, exploring the petrophysical significance of seismic-inverted elastic properties is challenging due to the complex microstructures in TGSs. Meanwhile, interbedded structures of sandstone and mudstone intensify the difficulty in accurately extracting the crucial tight sandstone properties. An integrated rock-physics-based framework is proposed to estimate the reservoir quality of TGSs from seismic data. TGSs with complex pore structures are modeled using the double-porosity model, providing a practical tool to compute rock physics templates for reservoir parameter estimation. The VP/VS ratio is utilized to predict the cumulative thickness of the TGS reservoirs within the target range via the threshold value evaluated from wireline logs for lithology discrimination. This approach also facilitates better capturing the elastic properties of the TGSs for quantitative seismic interpretation. Total porosity is estimated from P-wave impedance using the correlation obtained based on wireline log analysis. After that, the three-dimensional rock-physics templates integrated with the estimated total porosity are constructed to interpret microfracture porosity and gas saturation from velocity ratio and bulk modulus. The integrated framework can optimally estimate the parameters dominating the reservoir quality. The results of the indicator proposed based on the obtained parameters are in good agreement with the gas productions and can be utilized to predict promising TGS reservoirs. Moreover, the results suggest that considering microfracture porosity allows a more accurate prediction of high-quality reservoirs, further validating the applicability of the proposed method in the studied region.
基金Support for this study was received from the China National Ph.D.Foundations。
文摘By studying both the microscopic physical and chemical typomorphic characteristics of typical mineral pyrite samples associated with representative gold deposits on the north-central margin of the North China Platform,this paper seeks to identify macroscopic metallogenic mechanisms of gold deposits and to reveal the formation mechanism of lattice gold in pyrite.Typomorphic characteristics of pyrite reveal that pyrite grain size has a negative correlation with gold content.Cubic pyrite,as the dominant crystal form,contains more gold than pentagonal dodecahedral pyrite.Both pyrite crystal forms and chemical compositions indicate that the replacement style of gold deposit formed in a low saturability,low sulfur fugacity,and at temperatures either much higher or much lower than its best forming temperature;comparatively,that of the quartz vein style of gold deposit occurred under conditions with the best temperature,rich in sulfur,and with high sulfur fugacity.The Au/Ag ratios of the pyrites show that both the replacement and quartz vein styles of deposits are mesothermal and hypothermal,while the Co/Ni ratios of the pyrites indicate that the quartz vein style is of magmatic-hydrothermal origin.The X-ray diffraction intensity of pyrite rich in gold is lower than that of pyrite poor in gold at the quartz vein style.In general,with an increase in gold content in pyrite,the total sum intensityΣI decreases.The pyroelectricity coefficient has a negative correlation trend with the values of(Co+Ni+Se+Te)-As and(Co+Ni+Se+Te)/As.The pyrite pyroelectricity of the replacement style is N-type,indicating that it formed under low sulfur fugacity,while that of the quartz vein style is a mixture of P-N types,indicating that it formed under high sulfur fugacity.On the pyroelectricity-temperature diagram,pyrite of the replacement style is mainly distributed between 200 and 270°C,while that of the quartz vein style varies between 90–118 and274–386°C,demonstrating a multistage forming process.In contrast to previous researchers'conclusions,the authors confirm the existence of lattice gold in pyrites through the use of an electron paramagnetic resonance(EPR)test.Au in the form of Au~+,entering pyrite as an isomorph and producing electron–hole centers,makes the centers produce spin resonance absorption and results in EPR absorption peak II.The intensity of auriferous pyrite absorption peak II has certain direct positive correlations with pyrite gold content.The#I and#III absorption peaks of pyrites possibly result from the existence of Ni^(2+)and/or Cu^(2+).γ1,γ2,andγ3 are the strongest and most typical absorption peaks of the infrared spectra of the pyrites.Generally,with the increase in gold content in the pyrite samples,γ1,γ2,andγ3 tend to shift to higher wavenumbers,and the gold content in the pyrite samples has a positive correlation with their relative absorbance.
基金The General Program of National Natural Science Foundation of China under contract No.42074150。
文摘In the processing of conventional marine seismic data,seawater is often assumed to have a constant velocity model.However,due to static pressure,temperature difference and other factors,random disturbances may often frequently in seawater bodies.The impact of such disturbances on data processing results is a topic of theoretical research.Since seawater sound velocity is a difficult physical quantity to measure,there is a need for a method that can generate models conforming to seawater characteristics.This article will combine the Munk model and Perlin noise to propose a two-dimensional dynamic seawater sound velocity model generation method,a method that can generate a dynamic,continuous,random seawater sound velocity model with some regularity at large scales.Moreover,the paper discusses the influence of the inhomogeneity characteristics of seawater on wave field propagation and imaging.The results show that the seawater sound velocity model with random disturbance will have a significant influence on the wave field simulation and imaging results.
基金Under the auspices of National Natural Science Foundation of China (No. 40901159, 40901187)Doctoral Fund of Ministry of Education of China (No. 20090061120055)+1 种基金the Fundamental Research Funds for the Central Universities (No. 200903047)National High Technology Research and Development Program of China (No. 2010AA122203)
文摘The dielectric constant of the lunar regolith can directly influence the reflection coefficient and the trans-mission coefficient of the Moon′s surface, and plays an important role in the Moon research. In order to study the di-electric properties of the lunar regolith, the lunar regolith simulant was made according to the making procedure of the CAS-1 simulant made by Chinese Academy of Sciences. Then the dielectric constants of the lunar regolith simulant were measured with 85070E Aiglent Microwave Network Analyzer in the frequency ranging from 0.2 GHz to 20.0 GHz and at temperature of 25.1℃, 17.7℃, 13.1℃, 11.5℃, 9.6℃, 8.0℃, 4.1℃, -0.3℃, -4.7℃, -9.5℃, -18.7℃, -27.7℃, and -32.6℃, respectively. The Odelevsky model was employed to remove the influence of water in the air on the final effective dielectric constants. The results indicate that frequency and temperature have apparent influences on the dielectric constants of the lunar regolith simulant. The real parts of the dielectric constants increase fast over the range of 0.2 GHz to 3.0 GHz, but decrease slowly over the range of 4.0 GHz to 20.0 GHz. The opposite phenomenon occurs in the imaginary parts. The influences of the frequency and temperature on the brightness temperature were also estimated based on the radiative transfer equation. The result shows that the variation of the frequency and temperature results in great changes of the microwave brightness temperature emitting from the lunar regolith.
基金Project supported by National Natural Science Foundation of China (Grant Nos 10534040 and 10272038) and Doctorate Foundation of the State Education Ministry of China (Grant Nos 20040183045 and 20030183052).
文摘The nonaxisymmetric acousto-electric field excited by an eccentric acoustic source in the borehole based on Pride seismoelectric theory is considered. It is shown that the acoustic field inside the borehole, converted electric and magnetic fields and coupled fields outside the borehole are composed of an infinitude of multipole fields with different orders. The numerical results show that both the electromagnetic waves and the seismoelectric field in the borehole, and the three components of both electric field and magnetic field can be detected. Measurements on the borehole axis will be of advantage to determining shear velocity information. The components of the symmetric and nonsymmetric acoustic and electromagnetic fields can be strengthened or weakened by adding or subtracting the two full waveforms logged in some azimuths. It may be a new method of directly measuring the shear wave velocity by using the borehole seismoelectric effect.
基金supported in part by the Key Research Program of the Chinese Academy of Sciences under Grant (XDPB11)in part by opening fund of State Key Laboratory of Lunar and Planetary Sciences (Macao University of Science and Technology) (Macao FDCT Grant No. 119/2017/A3)+1 种基金in part by the National Natural Science Foundation of China (Grant Nos. 41490633, 41371332 and 41802246)in part by the Science and Technology Development Fund of Macao (Grant 0012/2018/A1)
文摘The volume FeO and TiO_2 abundances(FTAs) of lunar regolith can be more important for understanding the geological evolution of the Moon compared to the optical and gamma-ray results. In this paper, the volume FTAs are retrieved with microwave sounder(CELMS) data from the Chang'E-2 satellite using the back propagation neural network(BPNN) method. Firstly, a three-layered BPNN network with five-dimensional input is constructed by taking nonlinearity into account. Then, the brightness temperature(TB) and surface slope are set as the inputs and the volume FTAs are set as the outputs of the BPNN network.Thereafter, the BPNN network is trained with the corresponding parameters collected from Apollo, Luna,and Surveyor missions. Finally, the volume FTAs are retrieved with the trained BPNN network using the four-channel TBderived from the CELMS data and the surface slope estimated from Lunar Orbiter Laser Altimeter(LOLA) data. The rationality of the retrieved FTAs is verified by comparing with the Clementine UV-VIS results and Lunar Prospector(LP) GRS results. The retrieved volume FTAs enable us to re-evaluate the geological features of the lunar surface. Several important results are as follows. Firstly, very-low-Ti(<1.5 wt.%) basalts are the most spatially abundant, and the surfaces with TiO_2> 5 wt.% constitute less than 10% of the maria. Also, two linear relationships occur between the FeO abundance(FA) and the TiO_2 abundance before and after the threshold, 16 wt.% for FA. Secondly, a new perspective on mare volcanism is derived with the volume FTAs in several important mare basins, although this conclusion should be verified with more sources of data. Thirdly, FTAs in the lunar regolith change with depth to the uppermost surface,and the change is complex over the lunar surface. Finally, the distribution of volume FTAs hints that the highlands crust is probably homogeneous, at least in terms of the microwave thermophysical parameters.
基金Supported by Project of (NSFC) (No 40471086)National 863 Project(No 2006AA12Z102)
文摘It is one of the important methods to retrieve lunar regolith thickness using active and passive microwave techniques.The retrieval of lunar regolith thickness is based on microwave radiation transfer process simulation in the regolith media.The lunar regolith model is first introduced,and the features of the involved physical parameters are indicated thereafter,such as dielectric constants,surface roughness,particle size and thermal grads of the lunar regolith.The time delay and the migration of the radar echoes from the different interfaces is the key problem for active microwave measurement.And the simulation of the microwave radiative transfer in the regolith media is the important technique for the passive microwave measurement.The important parameters and the physical mechanism for the two measurements are also presented.
基金Under the auspices of the Excellent Youth Talent Project of Jilin Science and Technology Development Program(No.20170520078JH)Science and Technology Basic Work of Science and Technology(No.2014FY210800–4)National Natural Science Foundation of China(No.41601382)
文摘Soil surface roughness, denoted by the root mean square height(RMSH), and soil moisture(SM) are critical factors that affect the accuracy of quantitative remote sensing research due to their combined influence on spectral reflectance(SR). In regards to this issue, three SM levels and four RMSH levels were artificially designed in this study; a total of 12 plots was used, each plot had a size of 3 m × 3 m. Eight spectral observations were conducted from 14 to 30 October 2017 to investigate the correlation between RMSH, SM, and SR. On this basis, 6 commonly used bands of optical satellite sensors were selected in this study, which are red(675 nm), green(555 nm), blue(485 nm), near infrared(845 nm), shortwave infrared 1(1600 nm), and shortwave infrared 2(2200 nm). A negative correlation was found between SR and RMSH, and between SR and SM. The bands with higher coefficient of determination R^2 values were selected for stepwise multiple nonlinear regression analysis. Four characterized bands(i.e., blue, green, near infrared, and shortwave infrared 2) were chosen as the independent variables to estimate SM with R^2 and root mean square error(RMSE) values equal to 0.62 and 2.6%, respectively. Similarly, the four bands(green, red, near infrared, and shortwave infrared 1) were used to estimate RMSH with R^2 and RMSE values equal to 0.48 and 0.69 cm, respectively. These results indicate that the method used is not only suitable for estimating SM but can also be extended to the prediction of RMSH. Finally, the evaluation approach presented in this paper highly restores the real situation of the natural farmland surface on the one hand, and obtains high precision values of SM and RMSH on the other. The method can be further applied to the prediction of farmland SM and RMSH based on satellite and unmanned aerial vehicle(UAV) optical imagery.
基金supported by the National Basic Research Program of China (Grant No. 2011CB808204)the National Natural Science Foundation of China (Grant Nos. 11074094 and 91014004)the Fundamental Research Funds for Jilin University, China (Grant No. 450060491500)
文摘The in situ electrical resistance and transport activation energies of solid C60 fullerene have been measured under high pressure up to 25 GPa in the temperature range of 300-423 K by using a designed diamond anvil cell. In the experiment, four parts of boron-doped diamond films fabricated on one anvil were used as electrical measurement probes and a W-Ta thin film thermocouple which was integrated on the other diamond anvil was used to measure the temperature. The current results indicate that the measured high-pressure resistances are bigger than those reported before at the same pressure and there is no pressure-independent resistance increase before 8 GPa. From the temperature dependence of the resistivity, the C60 behaviors as a semiconductor and the activation energies of the cubic C60 fullerene are 0,49, 0.43, and 0.36 eV at 13, 15, and 19 GPa, respectively.
基金The China Scholarship Council,the National Basic Research Program(2009CB219301) of China(973) in partthe National Public Benefit Scientific Research Foundation(201011078) of China+2 种基金the National Innovation Research Project for Exploration and Development of Oil Shale(OSP-02 and OSR-02)the NSF(41304087,11071026,61133011,61170092,60973088,61202308,11001100,11171131 and 11026043) of Chinathe Basic Research Foundation of Jilin University in 2012
文摘In this paper, we have studied the necessary maximum principle of stochastic optimal control problem with delay and jump diffusion.
基金Supported by National Oil-gas project : No XQ-2004-07
文摘The authors generalized the methods how to identify and evaluate gas zones using logs,and put forward the methods of crossplots and overlays of porosity logs on the identification of volcanic gas-bearing reservoirs in the northern Songliao Basin with good results.This study provides technical clues in deep formations and offers references for other areas to identify oil and gas layers.
基金Under the auspices of National Key Research and Development Project of China(No.2021YFD1500103)Strategic Priority Research Program of the Chinese Academy of Sciences(No.XDA28100500)+2 种基金National Natural Science Foundation of China(No.4197132)Science and Technology Development Plan Project of Jilin Province(No.20210201044GX)Land Observation Satellite Supporting Platform of National Civil Space Infrastructure Project(No.CASPLOS-CCSI)。
文摘Soil moisture plays an important role in crop yield estimation,irrigation management,etc.Remote sensing technology has potential for large-scale and high spatial soil moisture mapping.However,offline remote sensing data processing is time-consuming and resource-intensive,and significantly hampers the efficiency and timeliness of soil moisture mapping.Due to the high-speed computing capabilities of remote sensing cloud platforms,a High Spatial Resolution Soil Moisture Estimation Framework(HSRSMEF)based on the Google Earth Engine(GEE)platform was developed in this study.The functions of the HSRSMEF include research area and input datasets customization,radar speckle noise filtering,optical-radar image spatio-temporal matching,soil moisture retrieving,soil moisture visualization and exporting.This paper tested the performance of HSRSMEF by combining Sentinel-1,Sentinel-2 images and insitu soil moisture data in the central farmland area of Jilin Province,China.Reconstructed Normalized Difference Vegetation Index(NDVI)based on the Savitzky-Golay algorithm conforms to the crop growth cycle,and its correlation with the original NDVI is about 0.99(P<0.001).The soil moisture accuracy of the random forest model(R 2=0.942,RMSE=0.013 m3/m3)is better than that of the water cloud model(R 2=0.334,RMSE=0.091 m3/m3).HSRSMEF transfers time-consuming offline operations to cloud computing platforms,achieving rapid and simplified high spatial resolution soil moisture mapping.
基金This work was supported by the Key National Research Project of China (Nos. 2017YFC0601900 and 2016YFC0303100) and the Key Program of National Natural Science Foundation of China (Nos. 41530320 and 41774125).
基金Under the auspices of National Science and Technology Major Project of China(No.04-Y20A35-9001-15/17)the Program for JLU Science and Technology Innovative Research Team(No.JLUSTIRT,2017TD-26)the Changbai Mountain Scholars Program,Jilin Province,China
文摘Remote sensing data have been widely applied to extract minerals in geologic exploration, however, in areas covered by vegetation, extracted mineral information has mostly been small targets bearing little information. In this paper, we present a new method for mineral extraction aimed at solving the difficulty of mineral identification in vegetation covered areas. The method selected six sets of spectral difference coupling between soil and plant(SVSCD). These sets have the same vegetation spectra reflectance and a maximum different reflectance of soil and mineral spectra from Hyperion image based on spectral reflectance characteristics of measured spectra. The central wavelengths of the six, selected band pairs were 2314 and 701 nm, 1699 and 721 nm, 1336 and 742 nm, 2203 and 681 nm, 2183 and 671 nm, and 2072 and 548 nm. Each data set's reflectance was used to calculate the difference value. After band difference calculation, vegetation information was suppressed and mineral abnormal information was enhanced compared to the scatter plot of original band. Six spectral difference couplings, after vegetation inhibition, were arranged in a new data set that requires two components that have the largest eigenvalue difference from principal component analysis(PCA). The spatial geometric structure features of PC1 and PC2 was used to identify altered minerals by spectral feature fitting(SFF). The collecting rocks from the 10 points that were selected in the concentration of mineral extraction were analyzed under a high-resolution microscope to identify metal minerals and nonmetallic minerals. Results indicated that the extracted minerals were well matched with the verified samples, especially with the sample 2, 4, 5 and 8. It demonstrated that the method can effectively detect altered minerals in vegetation covered area in Hyperion image.
文摘The vector finite element method of tetrahedral elements is used to model 3D electromagnetic wave logging response. The tangential component of the vector field at the mesh edges is used as a degree of freedom to overcome the shortcomings of node-based finite element methods. The algorithm can simulate inhomogeneous media with arbitrary distribution of conductivity and magnetic permeability. The electromagnetic response of well logging tools are studied in dipping bed layers with the borehole and invasion included. In order to simulate realistic logging tools, we take the transmitter antennas consisting of circular wire loops instead of magnetic dipoles. We also investigate the apparent resistivity of inhomogeneous formation for different dip angles.
基金This work was supported by National Natural Science Foundation of China (Grant No. 40476005 and 40233032), the Ministry of Science and Technology, China (Grant No. 2005DIB3J114), and the "863 Project" (Grant No. 2006AA04Z206 and 2006AA09Z152).
基金China Ocean Mineral Resources R&D Association Major Project under contract No.DY135-S1-01the National Natural Science Foundation of China under contract Nos 41506078,41706042 and 41522404the Basic Research Foundation of Second Institute of Oceanography,SOA under contract No.JG0608
文摘Seismic monitoring using ocean bottom seismometers(OBS) is an efficient method for investigating earthquakes in mid-ocean ridge far away from land. Clock synchronization among the OBSs is difficult without direct communication because electromagnetic signals cannot propagate efficiently in water. Time correction can be estimated through global positioning system(GPS) synchronization if clock drift is linear before and after the deployment. However, some OBSs in the experiments at the southwest Indian ridge(SWIR) on the Chinese DY125-34 cruise had not been re-synchronized from GPS after recovery. So we attempted to estimate clock drift between each station pairs using time symmetry analysis(TSA) based on ambient noise cross-correlation. We tested the feasibility of the TSA method by analyzing daily noise cross-correlation functions(NCFs) that extract from the data of another OBS experiment on the Chinese DY125-40 cruise with known clock drift and the same deployment site. The results suggest that the NCFs' travel time of surface wave between any two stations are symmetrical and have an opposite growing direction with the date. The influence of different band-pass filters,different components and different normalized methods was discussed. The TSA method appeared to be optimal for the hydrophone data within the period band of 2–5 s in dozens of km-scale interstation distances. A significant clock drift of ~2 s was estimated between OBSs sets through linear regression during a 108-d deployment on the Chinese cruise DY125-34. Time correction of the OBS by the ambient noise cross-correlation was demonstrated as a practical approach with the appropriate parameters in case of no GPS re-synchronization.
基金This work was supported by the National Key Research and Development Program of China (Nos. 2017YFC0601305, 2017YFC0602203, and 2017YFC0601606), National Science and Technology Major Project task (No. 2016ZX05027-002-03), National Natural Science Foundation of China (No. 41604098), and State Key Program of National Natural Science of China (No. 41430322).
基金Supported by the National Natural Science Foundation of China under Grant Nos 40674059 and 10534040 and by Specialized Research Fund for the Doctoral Programme of Higher Education of China under Grant No 20040183045.
文摘Seismoelectric fieM excited by purely torsional loading applied directly to the borehole wall is considered. A brief formulation and some computed waveforms show the advantage of using shear-horizontal (SH) transverseelectric (TE) seismoelectric waves logging to measure shear velocity in a fluid-saturated porous formation. By assuming that the acoustic field is not influenced by its induced electromagnetic field due to seismoeleetric effect, the coupling governing equations for electromagnetic field are reduced to Maxwell equations with a propagation current source. It is shown that this simplification is valid and the borehole seismoelectric conversion efficient is mainly dependent on the electrokinetic coupling coefficient. The receivers to detect the conversion electromagnetic field and to obtain shear velocity can be set in the borehole fluid in the SH-TE seismoelectric wave log.
基金Supported by National Oil-gas Project : No XQ-2004-07
文摘The petrophysical parameters are bad in most igneous reservoirs of Songliao Basin because of the very low porosity and permeability.The evaluation of igneous reservoirs has not been fully studied so far.The current technique of formation evaluation and interpretation used in sedimentary formations face a series of problems and difficulties.In this study,The PCA was used to identify lithology,a multi-mineral model "QAPM" was proposed."Surface effect" must be considered when evaluating saturation.A software "SIMPLE" was developed and was used to deal with the logging data in over 70 wells with good results were achieved.