“双高”电力系统对实时仿真算法的计算效率提出了更高的要求,采用单一的仿真算法往往难以兼顾计算效率与仿真精度。为解决这一问题,提出了一种混合使用移频分析(shifted frequency analysis,SFA)与传统电磁暂态(electromagnetic transi...“双高”电力系统对实时仿真算法的计算效率提出了更高的要求,采用单一的仿真算法往往难以兼顾计算效率与仿真精度。为解决这一问题,提出了一种混合使用移频分析(shifted frequency analysis,SFA)与传统电磁暂态(electromagnetic transients program,EMTP)方法的多速率实时仿真方案,并对子系统的接口算法进行了改进。首先,充分发挥SFA方法的高效性优势,建立了在移频相量下联立子系统诺顿等效电路的SFA-EMTP混合仿真框架。随后,从减少计算量的角度出发,提出了一种滑窗离散傅里叶变换与三相坐标变换相结合的解析信号构造方法。进而,为兼顾计算的实时性与仿真精度,提出了一种开关状态更新时刻与仿真节点错位的多速率仿真计算时序。最后,对含分布式电源接入的配电网算例采用所提算法与其他多种算法进行仿真,并将仿真结果与PSCAD(Power Systems Computer Aided Design)的离线仿真结果进行对比,验证了所提算法的正确性和有效性。展开更多
The area covered by this study is the county of Kakobola and its surroundings. Previous studies show that those related to the study of depths by the gravity method, using other techniques, are not always carried out ...The area covered by this study is the county of Kakobola and its surroundings. Previous studies show that those related to the study of depths by the gravity method, using other techniques, are not always carried out until now. The main goal of this article is the gravimetric characterization of our area by other approach. The interest is not only to map the lineaments and to know their dip, but also to estimate the depths of these different anomalies. The methods used for this study are the first total horizontal derivative (FTHDT), tilt angle (TA), analytical signal (AS) and horizontal gradient magnitude (HGM). The processing of the complete Bouguer anomalies (CBA) data was done mainly through software. Data analysis using the semi-finished body depth method shows depths ranging from 7.49 m to 224.6 m. Data analysis using the AS method shows values ranging from 41.7 mGal/m to 510 mGal/m. The fractures and/or geological contacts in our study area show dips ranging from -73.73° to 68.16° and North-South orientation according to the tilt angle method. The FTHDT shows several lineaments, a NE oriented fracture of Kakobola and low dip values which suggest a tabular structure of the subsurface in our study area. According to the HGM, the study area shows several preferential directions of fractures and/or geological contacts whose the most frequent directions are the NNE-SSW and WNW.展开更多
A magnetic survey was carried out to find out the possibilities of demarcating a phosphate deposit from the surrounding country rocks. It is a well-established fact that the magnetic mapping can be utilised to investi...A magnetic survey was carried out to find out the possibilities of demarcating a phosphate deposit from the surrounding country rocks. It is a well-established fact that the magnetic mapping can be utilised to investigate the subsurface objects, materials or different rock types based on their magnetic properties. Those rocks with ferro-magnetic minerals such as magnetite generate magnetic anomalies which in turn help to investigate the subsurface occurrence of mineral deposits. An economic phosphate deposit in Sri Lanka, known as Eppawala Phosphate deposit was selected for this study. The deposit was formed as an accumulation of secondary products of an apatite-rich carbonatite. Due to weathering of iron-rich carbonatite, magnetite and its derivatives are intimately bound with the said deposit. Therefore, the magnetic signature of the phosphate body is different to that of the surrounding country rocks. Despite some studies on different aspects of the deposit, subsurface extents of the ore body are so far not adequately studied. Therefore, this study was conducted to identify the boundaries of the phosphate body. The study was carried over an area of 12 km2 5 km north from the current mining site and survey was conducted. GSM-19 Overhouser system with integrated GPS was used to collect field data. Magnetic anomalies were plotted using a predefined grid. The maximum positive and negative anomalies encountered in the survey area are 690 nT and 829 nT respectively. This study showed that magnetite is not distributed evenly in the area and the deposit extended along the north south direction. Further, processing of analytical signal using the anomalies showed that the carbonatite occurs as a continuous body trending in North South direction. Low magnetic latitudes magnetic data interpretation is difficult because the vector nature of the magnetic field. Therefore, “reduction to pole” concept and “analytical signal concept” were used for the data analysis. Reduction to pole map and analytical signal map are c展开更多
In this study, different digital format data sources including aeromagnetic and remotely sensed (Landsat ETM+) data were used for structural and tectonic interpretation of the southern part of Jordan. Aeromagnetic dat...In this study, different digital format data sources including aeromagnetic and remotely sensed (Landsat ETM+) data were used for structural and tectonic interpretation of the southern part of Jordan. Aeromagnetic data were analyzed using advanced processing techniques (Spectral analysis, deconvolution). The aeromagnetic interpretation was carried out using the analytical signal, horizontal gradient, vertical gradient, Euler deconvolution. The results were improved by the study of enhanced Landsat ETM+ images and correlated with the extracted surface lineaments. Two main lineament sets are observed in the study area. The major lineaments strike NW-SE, NE-SW and the minor E-W. General coincidence of both landsat and aeromagnetic lineaments trends were observed in the study area, which reflecting the real continuous fractures in the depth. The 3D Euler solution of the study area shows that the depth of the magnetic source body ranges from hundreds of meters to more than 3000 m in the middle northern part of the study area. The combined interpretation of aeromagnetic data and Landsat ETM+, added several significant structural elements, that were previously unrecognized from the separate interpretations of aeromagnetic and remotely sensed data.展开更多
Gravity anomalies illuminate subsurface lithology and geological structure in three dimensions,which is vital for studies of concealed faults,sedimentary basins,basement lithology,and other geological targets.Although...Gravity anomalies illuminate subsurface lithology and geological structure in three dimensions,which is vital for studies of concealed faults,sedimentary basins,basement lithology,and other geological targets.Although not all geological contacts correspond to lithological contacts,the contact mapping provides key information on structural regimes,deformation styles and trends.Many techniques for contact mapping have been developed.Here,we evaluate five methods applied to gridded data.The first two are the horizontal gradient magnitude of the gravity field （GFhgm）,and tilt （TIhgm）.The third and fourth rely on locating maxima of the analytic signal （AS） and the 3D local wavenumber （LW）.The fifth is normalized standard deviation （NSTD） method.In this article,we evaluate the use of these five methods for mapping contacts and compare the results.First,synthetic vertically-sided models are used to quantify the offsets of maxima from the true contact location due to the source effects of finite source thickness,central depth,and width.Second,the effects of contact dip are discussed.Finally,a real data set is used to evaluate the ability of each method to produce maps of coherent contact trends in the presence of noise and gridding artifacts.展开更多
文摘“双高”电力系统对实时仿真算法的计算效率提出了更高的要求,采用单一的仿真算法往往难以兼顾计算效率与仿真精度。为解决这一问题,提出了一种混合使用移频分析(shifted frequency analysis,SFA)与传统电磁暂态(electromagnetic transients program,EMTP)方法的多速率实时仿真方案,并对子系统的接口算法进行了改进。首先,充分发挥SFA方法的高效性优势,建立了在移频相量下联立子系统诺顿等效电路的SFA-EMTP混合仿真框架。随后,从减少计算量的角度出发,提出了一种滑窗离散傅里叶变换与三相坐标变换相结合的解析信号构造方法。进而,为兼顾计算的实时性与仿真精度,提出了一种开关状态更新时刻与仿真节点错位的多速率仿真计算时序。最后,对含分布式电源接入的配电网算例采用所提算法与其他多种算法进行仿真,并将仿真结果与PSCAD(Power Systems Computer Aided Design)的离线仿真结果进行对比,验证了所提算法的正确性和有效性。
文摘The area covered by this study is the county of Kakobola and its surroundings. Previous studies show that those related to the study of depths by the gravity method, using other techniques, are not always carried out until now. The main goal of this article is the gravimetric characterization of our area by other approach. The interest is not only to map the lineaments and to know their dip, but also to estimate the depths of these different anomalies. The methods used for this study are the first total horizontal derivative (FTHDT), tilt angle (TA), analytical signal (AS) and horizontal gradient magnitude (HGM). The processing of the complete Bouguer anomalies (CBA) data was done mainly through software. Data analysis using the semi-finished body depth method shows depths ranging from 7.49 m to 224.6 m. Data analysis using the AS method shows values ranging from 41.7 mGal/m to 510 mGal/m. The fractures and/or geological contacts in our study area show dips ranging from -73.73° to 68.16° and North-South orientation according to the tilt angle method. The FTHDT shows several lineaments, a NE oriented fracture of Kakobola and low dip values which suggest a tabular structure of the subsurface in our study area. According to the HGM, the study area shows several preferential directions of fractures and/or geological contacts whose the most frequent directions are the NNE-SSW and WNW.
文摘A magnetic survey was carried out to find out the possibilities of demarcating a phosphate deposit from the surrounding country rocks. It is a well-established fact that the magnetic mapping can be utilised to investigate the subsurface objects, materials or different rock types based on their magnetic properties. Those rocks with ferro-magnetic minerals such as magnetite generate magnetic anomalies which in turn help to investigate the subsurface occurrence of mineral deposits. An economic phosphate deposit in Sri Lanka, known as Eppawala Phosphate deposit was selected for this study. The deposit was formed as an accumulation of secondary products of an apatite-rich carbonatite. Due to weathering of iron-rich carbonatite, magnetite and its derivatives are intimately bound with the said deposit. Therefore, the magnetic signature of the phosphate body is different to that of the surrounding country rocks. Despite some studies on different aspects of the deposit, subsurface extents of the ore body are so far not adequately studied. Therefore, this study was conducted to identify the boundaries of the phosphate body. The study was carried over an area of 12 km2 5 km north from the current mining site and survey was conducted. GSM-19 Overhouser system with integrated GPS was used to collect field data. Magnetic anomalies were plotted using a predefined grid. The maximum positive and negative anomalies encountered in the survey area are 690 nT and 829 nT respectively. This study showed that magnetite is not distributed evenly in the area and the deposit extended along the north south direction. Further, processing of analytical signal using the anomalies showed that the carbonatite occurs as a continuous body trending in North South direction. Low magnetic latitudes magnetic data interpretation is difficult because the vector nature of the magnetic field. Therefore, “reduction to pole” concept and “analytical signal concept” were used for the data analysis. Reduction to pole map and analytical signal map are c
文摘In this study, different digital format data sources including aeromagnetic and remotely sensed (Landsat ETM+) data were used for structural and tectonic interpretation of the southern part of Jordan. Aeromagnetic data were analyzed using advanced processing techniques (Spectral analysis, deconvolution). The aeromagnetic interpretation was carried out using the analytical signal, horizontal gradient, vertical gradient, Euler deconvolution. The results were improved by the study of enhanced Landsat ETM+ images and correlated with the extracted surface lineaments. Two main lineament sets are observed in the study area. The major lineaments strike NW-SE, NE-SW and the minor E-W. General coincidence of both landsat and aeromagnetic lineaments trends were observed in the study area, which reflecting the real continuous fractures in the depth. The 3D Euler solution of the study area shows that the depth of the magnetic source body ranges from hundreds of meters to more than 3000 m in the middle northern part of the study area. The combined interpretation of aeromagnetic data and Landsat ETM+, added several significant structural elements, that were previously unrecognized from the separate interpretations of aeromagnetic and remotely sensed data.
基金supported by the Ph.D. Program Foundation of Ministry of Education of China for Distinguished Young Scholars (No. 200804911523)the Research Foundation for Outstanding Young Teachers,China University of Geosciences (No. CUGQNL0726)
文摘Gravity anomalies illuminate subsurface lithology and geological structure in three dimensions,which is vital for studies of concealed faults,sedimentary basins,basement lithology,and other geological targets.Although not all geological contacts correspond to lithological contacts,the contact mapping provides key information on structural regimes,deformation styles and trends.Many techniques for contact mapping have been developed.Here,we evaluate five methods applied to gridded data.The first two are the horizontal gradient magnitude of the gravity field （GFhgm）,and tilt （TIhgm）.The third and fourth rely on locating maxima of the analytic signal （AS） and the 3D local wavenumber （LW）.The fifth is normalized standard deviation （NSTD） method.In this article,we evaluate the use of these five methods for mapping contacts and compare the results.First,synthetic vertically-sided models are used to quantify the offsets of maxima from the true contact location due to the source effects of finite source thickness,central depth,and width.Second,the effects of contact dip are discussed.Finally,a real data set is used to evaluate the ability of each method to produce maps of coherent contact trends in the presence of noise and gridding artifacts.
