The measuring of the depth profile and electrical activity of implantation impurity in the top nanometer range of silicon encounters various difficulties and limitations, though it is known to be critical in fabricati...The measuring of the depth profile and electrical activity of implantation impurity in the top nanometer range of silicon encounters various difficulties and limitations, though it is known to be critical in fabrication of silicon complementary metal–oxide–semiconductor(CMOS) devices. In the present work, SRIM program and photocarrier radiometry(PCR)are employed to monitor the boron implantation in industrial-grade silicon in an ultra-low implantation energy range from 0.5 keV to 5 keV. The differential PCR technique, which is improved by greatly shortening the measurement time through the simplification of reference sample, is used to investigate the effects of implantation energy on the frequency behavior of the PCR signal for ultra-shallow junction. The transport parameters and thickness of shallow junction, extracted via multi-parameter fitting the dependence of differential PCR signal on modulation frequency to the corresponding theoretical model, well explain the energy dependence of PCR signal and further quantitatively characterize the recovery degree of structure damage induced by ion implantation and the electrical activation degree of impurities. The monitoring of nmlevel thickness and electronic properties exhibits high sensitivity and apparent monotonicity over the industrially relevant implantation energy range. The depth profiles of implantation boron in silicon with the typical electrical damage threshold(YED) of 5.3×10^(15)cm^(-3) are evaluated by the SRIM program, and the determined thickness values are consistent well with those extracted by the differential PCR. It is demonstrated that the SRIM and the PCR are both effective tools to characterize ultra-low energy ion implantation in silicon.展开更多
Utilizing observations by the Sounding of the Atmosphere using Broadband Emission Radiometry(SABER)instrument,we quantitatively assessed the dawn-dusk asymmetry in temperature disturbances within the high-latitude mes...Utilizing observations by the Sounding of the Atmosphere using Broadband Emission Radiometry(SABER)instrument,we quantitatively assessed the dawn-dusk asymmetry in temperature disturbances within the high-latitude mesosphere and lower thermosphere(MLT)during the main phase of geomagnetic storms in this study.An analysis of five geomagnetic superstorm events indicated that during the main phase,negative temperature disturbances were more prevalent on the dawn side than on the dusk side in the high-latitude MLT region.Results of a statistical analysis of 54 geomagnetic storm events also revealed a notable disparity in temperature disturbances between the dawn and dusk sides.At high latitudes,38.2%of the observational points on the dawn side exhibited negative temperature disturbances(less than−5 K),whereas on the dusk side,this percentage was only 29.5%.In contrast,at mid-latitudes,these proportions were 34.1%and 36.5%,respectively,showing no significant difference.We also conducted a statistical analysis of temperature disturbances at different altitudes,which revealed an increase in the proportion of warming disturbances with altitude.Conversely,the proportion of cooling disturbances initially rose with altitude,reaching a peak around 105 km,and subsequently decreased.These temperature disturbance differences could be explained by the day-night asymmetry in vertical wind disturbances during storm conditions.展开更多
本研究在WACCM+DART(Whole Atmosphere Community Climate Model,Data Assimilation Research TestBed)临近空间资料同化预报系统中加入SABER(Sounding of the Atmosphere using Broadband Emission Radiometry)和MLS(Microwave Limb So...本研究在WACCM+DART(Whole Atmosphere Community Climate Model,Data Assimilation Research TestBed)临近空间资料同化预报系统中加入SABER(Sounding of the Atmosphere using Broadband Emission Radiometry)和MLS(Microwave Limb Sounder)臭氧观测同化接口,并以2016年2月一次平流层爆发性增温(SSW)过程为模拟个例进行了SABER和MLS臭氧观测同化试验,得出以下结论:同化SABER和MLS臭氧体积浓度观测得出的WACCM+DART臭氧分析场能够较真实反映SSW期间北极上空平流层臭氧廓线随时间的演变特征,且与ERA5(Fifth Generation of ECMWF Reanalyses)再分析资料描述的臭氧变化特征具有很好的一致性;基于SABER和MLS臭氧观测的WACCM臭氧6 h预报检验表明同化臭氧观测对臭氧分析和预报误差的改善效果主要体现在南半球高纬平流层和北半球中高纬平流层中上层—中间层底部;基于ERA5再分析资料的WACCM+DART分析场检验表明同化SABER和MLS臭氧体积浓度资料可在提高北半球高纬地区上平流层—中间层底部臭氧场分析质量的同时减小该地区上平流层—中间层底部温度场和中间层底部纬向风场的分析误差;基于MLS臭氧资料的臭氧中期预报检验表明相对控制试验同化SABER和MLS臭氧体积浓度资料能更好改善0~5 d下平流层和中间层底部臭氧的预报效果。展开更多
The purpose of this study is to select a suitable sea wind retrieval method for FY-3B(MWRI). Based on the traditional empirical model of retrieving sea surface wind speed, and in the case of small sample size of FY-3B...The purpose of this study is to select a suitable sea wind retrieval method for FY-3B(MWRI). Based on the traditional empirical model of retrieving sea surface wind speed, and in the case of small sample size of FY-3B satellite load regression analysis, this paper analyzes the channel differences between the FY-3B satellite microwave radiation imager(MWRI) and TMI onboard the TRMM. The paper also analyzes the influence of these differences on the channel in terms of receiving temperature, including channel frequency, sensitivity and scaling precision. Then, the limited range of new model coefficient regression analysis is determined(in which the channel range settings include the information and features of channel differences), the regression methods of the finite field are proposed, and the empirical model of wind speed retrieval applicable to MWRI is obtained, which achieves robust results. Compared to the TAO buoy data, the mean deviation of the new model is 0.4 m/s, and the standard deviation is 1.2 m/s. In addition,the schematic diagram of the tropical sea surface wind speed retrieval is provided.展开更多
The Microwave Temperature Sounder(MWTS)-2 has a total of 13 temperature-sounding channels with the capability of observing radiance emissions from near the surface to the stratosphere. Similar to the Advanced Technolo...The Microwave Temperature Sounder(MWTS)-2 has a total of 13 temperature-sounding channels with the capability of observing radiance emissions from near the surface to the stratosphere. Similar to the Advanced Technology Microwave Sounder(ATMS), striping pattern noise, primarily in the cross-track direction, exists in MWTS-2 radiance observations. In this study, an algorithm based on principal component analysis(PCA) combined with ensemble empirical mode decomposition(EEMD) is described and applied to MWTS-2 brightness temperature observations. It is arguably necessary to smooth the first three principal component(PC) coefficients by removing the first four intrinsic mode functions(IMFs) using the EEMD method(denoted as PC3/IMF4). After the PC3/IMF4 noise mitigation, the striping pattern noise is effectively removed from the brightness temperature observations. The noise level in MWTS-2 observations is significantly higher than that detected in ATMS observations. In May 2014, the scanning profile of MWTS-2 was adjusted from varying-speed scanning to constantspeed scanning. The impact on striping noise levels brought on by this scan profile change is also analyzed here. The striping noise in brightness temperature observations worsened after the profile change. Regardless of the scan profile change, the striping noise mitigation method reported in this study can more or less suppress the noise levels in MWTS-2 observations.展开更多
The parameter b_p in the tuo-omega(τ–ω)model is important for retrieving soil moisture data from passive microwave brightness temperatures.Theoretically,b_p depends on the observation mode(polarization,frequency,an...The parameter b_p in the tuo-omega(τ–ω)model is important for retrieving soil moisture data from passive microwave brightness temperatures.Theoretically,b_p depends on the observation mode(polarization,frequency,and incidence angle)and vegetation properties and varies with vegetation growth.For simplicity,previous studies have taken b_p to be a constant.However,to reduce the uncertainty of soil moisture retrieval further,the present study is of the dynamics of b_p based on the SMAPVEX12 experimental dataset by combining a genetic algorithm and the L-MEB microwave radiative transfer model of vegetated soil.The results show the following.First,b_p decreases nonlinearly with vegetation water content(VWC),decreasing critically when VWC becomes less than 2 kg/m^2.Second,there is a power law between b_p and VWC for both horizontal and vertical polarizations(R^2=0.919 and 0.872,respectively).Third,the effectiveness of this relationship is verified by comparing its soil-moisture inversion accuracy with the previous constant-b_p method based on the HiWATER dataset.Doing so reveals that the dynamic b_p method reduces the root-mean-square error of the retrieved soil moisture by approximately 0.06 cm^3/cm^3,and similar improvement is obtained for the calibrated SMAPVEX12 dataset.Our results indicate that the dynamic b_p method is reasonable for different vegetation growth stages and could improve the accuracy of soil moisture retrieval.展开更多
The renewed interest in the reactivation of the defunct National Konongo Gold Mine located in the Ashanti Greenstone Belt, calls for a further probe into its geology and the associated mineral hosting structures to di...The renewed interest in the reactivation of the defunct National Konongo Gold Mine located in the Ashanti Greenstone Belt, calls for a further probe into its geology and the associated mineral hosting structures to discover its mineralization potential. In order to achieve this, airborne magnetic, radiometric and electromagnetic datasets were interpreted to determine the potential gold hosting features in the studied area. The results show the area to consist of the metasediment, the metavolcanic, Tartwaian Formation and their associated granitoids. Results also show that the Tarkwaian sediments, observed largely in the north-eastern side of the site;widen out substantially and truncate in the south. The analysis of the structure lineaments using a rose diagram reveals three main tectonic structures trending in N-S, NNW-SSE, and third the structure trending in the NNE-SSW to NE-SW directions in the area. The dominant structures in the area, form 90% of all the delineated structures and trend in the NE-SW and NNE-SSW direction with the remaining 10% trending in the N-S and NNW-SSE. These structures are associated with the major shear and fracture zones located mainly at the contact between the basin sediments and volcanic belt and also associated with the Tarkwaian Formation. The mapped potential gold mineralization zones located mainly at the contact between the metasediment and the metavolcanic units of the Birimian Supergroup, as well as the Tarkwaian Formation, were mapped by integrating the structures, alteration zones as well as the complex dyke systems. This paper delineates the prominent geological structures with the potential of hosting economic gold mineralization in and around the Konongo Gold Mine.展开更多
Abu Furad is in the Central Eastern Desert,Egypt. It comprises metasediments, metavolcanics,metagabbros, syn-to late-orogenic granites, and post-orogenic granites, in addition to numerous dykes and veins of different ...Abu Furad is in the Central Eastern Desert,Egypt. It comprises metasediments, metavolcanics,metagabbros, syn-to late-orogenic granites, and post-orogenic granites, in addition to numerous dykes and veins of different shapes and composition invading all the older rocks cropping out in the study area. Field, petrographic,mineralogical, and chemical investigations led to the classification of Abu Furad granites as quartz diorite, tonalite,granodiorite, and syenogranites.Major oxide and trace element data revealed that the syn-to late-orogenic granites and post-orogenic granites are peraluminous. Syn-to lateorogenic granites originated from calc-alkaline volcanic arc–related magma; while the post-orogenic granites(syenogranite) are highly fractionated, calc-alkaline granite from a within plate regime. Radiometrically, the studied quartz diorite, tonalite, and granodiorite had lower uranium and thorium contents and higher eU/eTh ratios than the syenogranites. This may indicate that the syn-to late-orogenic rocks originated from sources depleted in these elements. The average e Th/eU ratio of syenogranites was higher than that of average continental crust, suggesting that the syenogranites are relatively depleted in U. The studied altered syenogranites were strongly enriched in U and Th compared to the Earth's crust. On the other hand, the average of e U in pegmatites is lower than the global average for uraniferous pegmatites. The most recorded accessory minerals in the altered syenogranites were thorite, fergusonite, samarskite, columbite, zircon, monazite, xenotime,apatite, fluorite, sphene, atacamite, and malachite, in addition to chromium and nickel inclusions.展开更多
An 8-wavelength sun-photometer has been operated at Hefei (31.31°N, 117.17°E) to monitoroptical properties of atmospheric aerosols. Altogether 133 solar spectral extinction data were ob-tained on clear days ...An 8-wavelength sun-photometer has been operated at Hefei (31.31°N, 117.17°E) to monitoroptical properties of atmospheric aerosols. Altogether 133 solar spectral extinction data were ob-tained on clear days during the period from September 1993 through September 1994, In this pa-per, the feature of the sun-photometer is briefly described. A relative aureole method is intro-duced. which can be used to monitor temporal evolution of aerosol loading during the sun-pho-tometer calibration period. Temporal variabilities of spectral aerosol optical depths and Angstromturbidity parameters are presented. Relation of these variabilities with synoptic and local meteoro-logical conditions are analyzed and discussed, From measured spectral aerosol optical depths undersome representative atmospheric conditions, columnar aerosol size distributions have been retrievedby a linearly constrained inversion method. These typical columnar aerosol size distributions are al-so presented and discussed.展开更多
Sun-photometer has been widely used to investigate various optical properties of the atmosphere.In order to derivean accurate atmospheric optical depth,great care in the sun-photometer calibration is required.In this ...Sun-photometer has been widely used to investigate various optical properties of the atmosphere.In order to derivean accurate atmospheric optical depth,great care in the sun-photometer calibration is required.In this paper,the fea-ture of a new sun-photometer is described.Calibration results based on the Langley method at Mt.Huangshan are re-ported.Effect of the atmospheric instability on retrieving the calibration values is discussed and errors in calibration atMt.Huangshan due to temporal variation of aerosol concentration are estimated.It is shown that the calibratedsun-photometer can be used to derive the atmospheric optical depth to an accuracy of 5%.As one of its applications,examples of determination of turbidity parameters and columnar aerosol size distribution are presented.展开更多
In this paper a method is described of retrieving precipitable water from sun-photometermeasurements.The quantitative relationship between water vapor transmission and precipitablewater is established by means of LOWT...In this paper a method is described of retrieving precipitable water from sun-photometermeasurements.The quantitative relationship between water vapor transmission and precipitablewater is established by means of LOWTRAN 7 model.Calibration of the water vapor absorptionchannel is made through a modified Langley method.The good agreement between the sun-photometer and radiosonde water vapor retrieval indicates that this method is feasible.The sun-photometer is operated at Hefei to monitor the precipitable water within one yearperiod.Characteristics of both diurnal evolution and within-one-year variation of the precipitablewater and their relation with synoptic system as well as surface dew-point temperature arepresented and analyzed.Errors in the retrieved precipitable water from the sun-photometermeasurements are also calculated and discussed.展开更多
Forests have invariably been considered as an obstacle in retrieving land surface parameters from spaceborne passive microwave brightness temperature(T_(B))observations.For quantifying the effect of forests on microwa...Forests have invariably been considered as an obstacle in retrieving land surface parameters from spaceborne passive microwave brightness temperature(T_(B))observations.For quantifying the effect of forests on microwave signals,several models have been developed.However,these models rarely reveal the dependence of microwave radiation on forest types,which can hardly meet the needs of high-accuracy retrieval of terrestrial parameters in forested regions.A ground-based microwave radiometric observation experiment was designed to investigate the dependence of microwave radiation on frequency,polarization,and forest type.Downward TB at 18.7-and 36.5-GHz for horizontal-and vertical-polarization from the forest canopy was measured at 14 sample plots in Northeast China,along with snowpack and forest structural parameters.By providing fits to experimental data,new empirical transmissivity models for three forest types were developed,as a function of woody stem volume and depending on the frequency/polarization.The proposed models give diverse asymptotic transmissivity saturation levels and the corresponding saturation point of woody stem volume for different forest types.Root-mean-square error results between T_(B) simulations and Advanced Microwave Scanning Radiometer-2 observations are approximately 3-6 K.This study provides an experimental and theoretical reference for further development of inversion models for snow parameters in forested areas.展开更多
Reliablemicrostructuremeasurement of snow is a requirement for microwave radiative transfer model validation.Snow specific surface area(SSA)can be measured using stereological methods,in which snow samples are cast in...Reliablemicrostructuremeasurement of snow is a requirement for microwave radiative transfer model validation.Snow specific surface area(SSA)can be measured using stereological methods,in which snow samples are cast in the field and photographed in the laboratory.Processing stereology photographs manually by counting intersections of test cycloids with air-ice boundaries reduces the problems in binary segmentation.This paper is a case study to evaluate the repeatability of the manually stereology interpretation by two independent research groups.We further assessed how uncertainty in snow SSA influences simulated brightness temperature(TB)driven by the Microwave Emission Model of Layered Snowpacks(MEMLS),and how stereology compares to Near Infrared(NIR)camera and hand lens.Data was obtained from two alpine snow profiles from Steamboat Springs,Colorado.Results showed that stereological SSA values measured by two groups are highly consistent,and the ground radiometer measured T_(B)at 19 and 37 GHz was successfully predicted(RMSE<3.8 K);simulations using NIR SSA and hand-lens geometric grain size(Dg)measurements have larger errors.This conclusion was not sensitive to uncertainty in the free parameters of TB modeling.展开更多
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 61771103, 61704023, and 61601092)。
文摘The measuring of the depth profile and electrical activity of implantation impurity in the top nanometer range of silicon encounters various difficulties and limitations, though it is known to be critical in fabrication of silicon complementary metal–oxide–semiconductor(CMOS) devices. In the present work, SRIM program and photocarrier radiometry(PCR)are employed to monitor the boron implantation in industrial-grade silicon in an ultra-low implantation energy range from 0.5 keV to 5 keV. The differential PCR technique, which is improved by greatly shortening the measurement time through the simplification of reference sample, is used to investigate the effects of implantation energy on the frequency behavior of the PCR signal for ultra-shallow junction. The transport parameters and thickness of shallow junction, extracted via multi-parameter fitting the dependence of differential PCR signal on modulation frequency to the corresponding theoretical model, well explain the energy dependence of PCR signal and further quantitatively characterize the recovery degree of structure damage induced by ion implantation and the electrical activation degree of impurities. The monitoring of nmlevel thickness and electronic properties exhibits high sensitivity and apparent monotonicity over the industrially relevant implantation energy range. The depth profiles of implantation boron in silicon with the typical electrical damage threshold(YED) of 5.3×10^(15)cm^(-3) are evaluated by the SRIM program, and the determined thickness values are consistent well with those extracted by the differential PCR. It is demonstrated that the SRIM and the PCR are both effective tools to characterize ultra-low energy ion implantation in silicon.
基金the National Key R&D Program of China(Grant No.2022YFF0503702)the National Natural Science Foundation of China(Grant Nos.42004132,42074195 and 42074183)+1 种基金the open funding of the Ministry of Natural Resources Key Laboratory for Polar Science(Grant No.KP202104)the China Geological Survey(Grant No.ZD20220145).
文摘Utilizing observations by the Sounding of the Atmosphere using Broadband Emission Radiometry(SABER)instrument,we quantitatively assessed the dawn-dusk asymmetry in temperature disturbances within the high-latitude mesosphere and lower thermosphere(MLT)during the main phase of geomagnetic storms in this study.An analysis of five geomagnetic superstorm events indicated that during the main phase,negative temperature disturbances were more prevalent on the dawn side than on the dusk side in the high-latitude MLT region.Results of a statistical analysis of 54 geomagnetic storm events also revealed a notable disparity in temperature disturbances between the dawn and dusk sides.At high latitudes,38.2%of the observational points on the dawn side exhibited negative temperature disturbances(less than−5 K),whereas on the dusk side,this percentage was only 29.5%.In contrast,at mid-latitudes,these proportions were 34.1%and 36.5%,respectively,showing no significant difference.We also conducted a statistical analysis of temperature disturbances at different altitudes,which revealed an increase in the proportion of warming disturbances with altitude.Conversely,the proportion of cooling disturbances initially rose with altitude,reaching a peak around 105 km,and subsequently decreased.These temperature disturbance differences could be explained by the day-night asymmetry in vertical wind disturbances during storm conditions.
文摘本研究在WACCM+DART(Whole Atmosphere Community Climate Model,Data Assimilation Research TestBed)临近空间资料同化预报系统中加入SABER(Sounding of the Atmosphere using Broadband Emission Radiometry)和MLS(Microwave Limb Sounder)臭氧观测同化接口,并以2016年2月一次平流层爆发性增温(SSW)过程为模拟个例进行了SABER和MLS臭氧观测同化试验,得出以下结论:同化SABER和MLS臭氧体积浓度观测得出的WACCM+DART臭氧分析场能够较真实反映SSW期间北极上空平流层臭氧廓线随时间的演变特征,且与ERA5(Fifth Generation of ECMWF Reanalyses)再分析资料描述的臭氧变化特征具有很好的一致性;基于SABER和MLS臭氧观测的WACCM臭氧6 h预报检验表明同化臭氧观测对臭氧分析和预报误差的改善效果主要体现在南半球高纬平流层和北半球中高纬平流层中上层—中间层底部;基于ERA5再分析资料的WACCM+DART分析场检验表明同化SABER和MLS臭氧体积浓度资料可在提高北半球高纬地区上平流层—中间层底部臭氧场分析质量的同时减小该地区上平流层—中间层底部温度场和中间层底部纬向风场的分析误差;基于MLS臭氧资料的臭氧中期预报检验表明相对控制试验同化SABER和MLS臭氧体积浓度资料能更好改善0~5 d下平流层和中间层底部臭氧的预报效果。
基金National Science Foundation of China(41105009,41175023)Ministry of Science and Technology,China(2010DFA21140)
文摘The purpose of this study is to select a suitable sea wind retrieval method for FY-3B(MWRI). Based on the traditional empirical model of retrieving sea surface wind speed, and in the case of small sample size of FY-3B satellite load regression analysis, this paper analyzes the channel differences between the FY-3B satellite microwave radiation imager(MWRI) and TMI onboard the TRMM. The paper also analyzes the influence of these differences on the channel in terms of receiving temperature, including channel frequency, sensitivity and scaling precision. Then, the limited range of new model coefficient regression analysis is determined(in which the channel range settings include the information and features of channel differences), the regression methods of the finite field are proposed, and the empirical model of wind speed retrieval applicable to MWRI is obtained, which achieves robust results. Compared to the TAO buoy data, the mean deviation of the new model is 0.4 m/s, and the standard deviation is 1.2 m/s. In addition,the schematic diagram of the tropical sea surface wind speed retrieval is provided.
基金supported by the National Key R&D Program (Grant No. 2018YFC1506702)
文摘The Microwave Temperature Sounder(MWTS)-2 has a total of 13 temperature-sounding channels with the capability of observing radiance emissions from near the surface to the stratosphere. Similar to the Advanced Technology Microwave Sounder(ATMS), striping pattern noise, primarily in the cross-track direction, exists in MWTS-2 radiance observations. In this study, an algorithm based on principal component analysis(PCA) combined with ensemble empirical mode decomposition(EEMD) is described and applied to MWTS-2 brightness temperature observations. It is arguably necessary to smooth the first three principal component(PC) coefficients by removing the first four intrinsic mode functions(IMFs) using the EEMD method(denoted as PC3/IMF4). After the PC3/IMF4 noise mitigation, the striping pattern noise is effectively removed from the brightness temperature observations. The noise level in MWTS-2 observations is significantly higher than that detected in ATMS observations. In May 2014, the scanning profile of MWTS-2 was adjusted from varying-speed scanning to constantspeed scanning. The impact on striping noise levels brought on by this scan profile change is also analyzed here. The striping noise in brightness temperature observations worsened after the profile change. Regardless of the scan profile change, the striping noise mitigation method reported in this study can more or less suppress the noise levels in MWTS-2 observations.
基金Under the auspices of the Outstanding Young Talent Foundation Project of the Jilin Science and Technology Development Plan(No.20170520078JH)the Science and Technology Basic Work of Science and Technology(No.2014FY210800-4)
文摘The parameter b_p in the tuo-omega(τ–ω)model is important for retrieving soil moisture data from passive microwave brightness temperatures.Theoretically,b_p depends on the observation mode(polarization,frequency,and incidence angle)and vegetation properties and varies with vegetation growth.For simplicity,previous studies have taken b_p to be a constant.However,to reduce the uncertainty of soil moisture retrieval further,the present study is of the dynamics of b_p based on the SMAPVEX12 experimental dataset by combining a genetic algorithm and the L-MEB microwave radiative transfer model of vegetated soil.The results show the following.First,b_p decreases nonlinearly with vegetation water content(VWC),decreasing critically when VWC becomes less than 2 kg/m^2.Second,there is a power law between b_p and VWC for both horizontal and vertical polarizations(R^2=0.919 and 0.872,respectively).Third,the effectiveness of this relationship is verified by comparing its soil-moisture inversion accuracy with the previous constant-b_p method based on the HiWATER dataset.Doing so reveals that the dynamic b_p method reduces the root-mean-square error of the retrieved soil moisture by approximately 0.06 cm^3/cm^3,and similar improvement is obtained for the calibrated SMAPVEX12 dataset.Our results indicate that the dynamic b_p method is reasonable for different vegetation growth stages and could improve the accuracy of soil moisture retrieval.
文摘The renewed interest in the reactivation of the defunct National Konongo Gold Mine located in the Ashanti Greenstone Belt, calls for a further probe into its geology and the associated mineral hosting structures to discover its mineralization potential. In order to achieve this, airborne magnetic, radiometric and electromagnetic datasets were interpreted to determine the potential gold hosting features in the studied area. The results show the area to consist of the metasediment, the metavolcanic, Tartwaian Formation and their associated granitoids. Results also show that the Tarkwaian sediments, observed largely in the north-eastern side of the site;widen out substantially and truncate in the south. The analysis of the structure lineaments using a rose diagram reveals three main tectonic structures trending in N-S, NNW-SSE, and third the structure trending in the NNE-SSW to NE-SW directions in the area. The dominant structures in the area, form 90% of all the delineated structures and trend in the NE-SW and NNE-SSW direction with the remaining 10% trending in the N-S and NNW-SSE. These structures are associated with the major shear and fracture zones located mainly at the contact between the basin sediments and volcanic belt and also associated with the Tarkwaian Formation. The mapped potential gold mineralization zones located mainly at the contact between the metasediment and the metavolcanic units of the Birimian Supergroup, as well as the Tarkwaian Formation, were mapped by integrating the structures, alteration zones as well as the complex dyke systems. This paper delineates the prominent geological structures with the potential of hosting economic gold mineralization in and around the Konongo Gold Mine.
文摘Abu Furad is in the Central Eastern Desert,Egypt. It comprises metasediments, metavolcanics,metagabbros, syn-to late-orogenic granites, and post-orogenic granites, in addition to numerous dykes and veins of different shapes and composition invading all the older rocks cropping out in the study area. Field, petrographic,mineralogical, and chemical investigations led to the classification of Abu Furad granites as quartz diorite, tonalite,granodiorite, and syenogranites.Major oxide and trace element data revealed that the syn-to late-orogenic granites and post-orogenic granites are peraluminous. Syn-to lateorogenic granites originated from calc-alkaline volcanic arc–related magma; while the post-orogenic granites(syenogranite) are highly fractionated, calc-alkaline granite from a within plate regime. Radiometrically, the studied quartz diorite, tonalite, and granodiorite had lower uranium and thorium contents and higher eU/eTh ratios than the syenogranites. This may indicate that the syn-to late-orogenic rocks originated from sources depleted in these elements. The average e Th/eU ratio of syenogranites was higher than that of average continental crust, suggesting that the syenogranites are relatively depleted in U. The studied altered syenogranites were strongly enriched in U and Th compared to the Earth's crust. On the other hand, the average of e U in pegmatites is lower than the global average for uraniferous pegmatites. The most recorded accessory minerals in the altered syenogranites were thorite, fergusonite, samarskite, columbite, zircon, monazite, xenotime,apatite, fluorite, sphene, atacamite, and malachite, in addition to chromium and nickel inclusions.
文摘An 8-wavelength sun-photometer has been operated at Hefei (31.31°N, 117.17°E) to monitoroptical properties of atmospheric aerosols. Altogether 133 solar spectral extinction data were ob-tained on clear days during the period from September 1993 through September 1994, In this pa-per, the feature of the sun-photometer is briefly described. A relative aureole method is intro-duced. which can be used to monitor temporal evolution of aerosol loading during the sun-pho-tometer calibration period. Temporal variabilities of spectral aerosol optical depths and Angstromturbidity parameters are presented. Relation of these variabilities with synoptic and local meteoro-logical conditions are analyzed and discussed, From measured spectral aerosol optical depths undersome representative atmospheric conditions, columnar aerosol size distributions have been retrievedby a linearly constrained inversion method. These typical columnar aerosol size distributions are al-so presented and discussed.
文摘Sun-photometer has been widely used to investigate various optical properties of the atmosphere.In order to derivean accurate atmospheric optical depth,great care in the sun-photometer calibration is required.In this paper,the fea-ture of a new sun-photometer is described.Calibration results based on the Langley method at Mt.Huangshan are re-ported.Effect of the atmospheric instability on retrieving the calibration values is discussed and errors in calibration atMt.Huangshan due to temporal variation of aerosol concentration are estimated.It is shown that the calibratedsun-photometer can be used to derive the atmospheric optical depth to an accuracy of 5%.As one of its applications,examples of determination of turbidity parameters and columnar aerosol size distribution are presented.
文摘In this paper a method is described of retrieving precipitable water from sun-photometermeasurements.The quantitative relationship between water vapor transmission and precipitablewater is established by means of LOWTRAN 7 model.Calibration of the water vapor absorptionchannel is made through a modified Langley method.The good agreement between the sun-photometer and radiosonde water vapor retrieval indicates that this method is feasible.The sun-photometer is operated at Hefei to monitor the precipitable water within one yearperiod.Characteristics of both diurnal evolution and within-one-year variation of the precipitablewater and their relation with synoptic system as well as surface dew-point temperature arepresented and analyzed.Errors in the retrieved precipitable water from the sun-photometermeasurements are also calculated and discussed.
基金supported by National Natural Science Foundation of China:[Grant Number 41771400]National Natural Science Foundation of China:[Grant Number 41871248]Science and Technology Basic Resources Investigation Program of China‘Investigation on snow characteristics and their distribution in China’[Grant Number 2017FY100500].
文摘Forests have invariably been considered as an obstacle in retrieving land surface parameters from spaceborne passive microwave brightness temperature(T_(B))observations.For quantifying the effect of forests on microwave signals,several models have been developed.However,these models rarely reveal the dependence of microwave radiation on forest types,which can hardly meet the needs of high-accuracy retrieval of terrestrial parameters in forested regions.A ground-based microwave radiometric observation experiment was designed to investigate the dependence of microwave radiation on frequency,polarization,and forest type.Downward TB at 18.7-and 36.5-GHz for horizontal-and vertical-polarization from the forest canopy was measured at 14 sample plots in Northeast China,along with snowpack and forest structural parameters.By providing fits to experimental data,new empirical transmissivity models for three forest types were developed,as a function of woody stem volume and depending on the frequency/polarization.The proposed models give diverse asymptotic transmissivity saturation levels and the corresponding saturation point of woody stem volume for different forest types.Root-mean-square error results between T_(B) simulations and Advanced Microwave Scanning Radiometer-2 observations are approximately 3-6 K.This study provides an experimental and theoretical reference for further development of inversion models for snow parameters in forested areas.
基金supported by NASA Terrestrial Hydrology Program[grant number NNX09AM10G]Strategic Priority Research Program of Chinese Academy of Sciences[grant number XDA20100300].
文摘Reliablemicrostructuremeasurement of snow is a requirement for microwave radiative transfer model validation.Snow specific surface area(SSA)can be measured using stereological methods,in which snow samples are cast in the field and photographed in the laboratory.Processing stereology photographs manually by counting intersections of test cycloids with air-ice boundaries reduces the problems in binary segmentation.This paper is a case study to evaluate the repeatability of the manually stereology interpretation by two independent research groups.We further assessed how uncertainty in snow SSA influences simulated brightness temperature(TB)driven by the Microwave Emission Model of Layered Snowpacks(MEMLS),and how stereology compares to Near Infrared(NIR)camera and hand lens.Data was obtained from two alpine snow profiles from Steamboat Springs,Colorado.Results showed that stereological SSA values measured by two groups are highly consistent,and the ground radiometer measured T_(B)at 19 and 37 GHz was successfully predicted(RMSE<3.8 K);simulations using NIR SSA and hand-lens geometric grain size(Dg)measurements have larger errors.This conclusion was not sensitive to uncertainty in the free parameters of TB modeling.
