The geometric accuracy of topographic mapping with high-resolution remote sensing images is inevita-bly affected by the orbiter attitude jitter.Therefore,it is necessary to conduct preliminary research on the stereo m...The geometric accuracy of topographic mapping with high-resolution remote sensing images is inevita-bly affected by the orbiter attitude jitter.Therefore,it is necessary to conduct preliminary research on the stereo mapping camera equipped on lunar orbiter before launching.In this work,an imaging simulation method consid-ering the attitude jitter is presented.The impact analysis of different attitude jitter on terrain undulation is conduct-ed by simulating jitter at three attitude angles,respectively.The proposed simulation method is based on the rigor-ous sensor model,using the lunar digital elevation model(DEM)and orthoimage as reference data.The orbit and attitude of the lunar stereo mapping camera are simulated while considering the attitude jitter.Two-dimensional simulated stereo images are generated according to the position and attitude of the orbiter in a given orbit.Experi-mental analyses were conducted by the DEM with the simulated stereo image.The simulation imaging results demonstrate that the proposed method can ensure imaging efficiency without losing the accuracy of topographic mapping.The effect of attitude jitter on the stereo mapping accuracy of the simulated images was analyzed through a DEM comparison.展开更多
Using fractal dimension to reflect and simulate urban morphology are two applications of fractal theory in city geography. As the only consistent description of a fractal, fractal dimension plays an important role in ...Using fractal dimension to reflect and simulate urban morphology are two applications of fractal theory in city geography. As the only consistent description of a fractal, fractal dimension plays an important role in describing the basic features of fractals. Just like other fractals, our cities have similar characteristics. Fractal dimension to some extent is regarded as an indicator of urban expansion, and it may change with urban morphology in different time and space. Based on the Geographic Information System (GIS), taking Wuhan city as a test area, the fractal dimensions of different land use were calculated, and a linear regression equation was established to analyze the relationship between fractal dimension and residential areas. Then the author used fractal dimension to simulate the urban boundary which is an important part of urban mor-phology. A mid-point subdivision fractal generator is needed in the simulation process, and the shape of the generator is determined by fractal dimension. According to the fractal theory, fractal boundaries in different scales have self-similarity and they have the same fractal dimensions. Based on this fact, the simulation method the author used could quantitatively keep the similarity of configuration of the urban boundaries.展开更多
Proposed and demonstrated is a novel computer modeling method for high power light emitting diodes(LEDs). It contains geometrical structure and optical property of high power LED as well as LED dies definition with it...Proposed and demonstrated is a novel computer modeling method for high power light emitting diodes(LEDs). It contains geometrical structure and optical property of high power LED as well as LED dies definition with its spatial and angular distribution. Merits and non-merits of traditional modeling methods when applied to high power LEDs based on secondary optical design are discussed. Two commercial high power LEDs are simulated using the proposed computer modeling method. Correlation coefficient is proposed to compare and analyze the simulation results and manufacturing specifications. The source model is precisely demonstrated by obtaining above 99% in correlation coefficient with different surface incident angle intervals.展开更多
In recent years, the pressure of increasing coastal industries and tourism activities has, in some areas, led to the clearing of many coastal habitats along the Qatar＇s shorelines for the construction of tourist reso...In recent years, the pressure of increasing coastal industries and tourism activities has, in some areas, led to the clearing of many coastal habitats along the Qatar＇s shorelines for the construction of tourist resorts, tourism-related development and industrial facilities. Such threats are leading to the increasing demand for detailed mangrove maps for the purpose of measuring the extent of decline in mangrove ecosystems. Detailed mangrove maps at the community or species level are, however, not easy to produce, mainly because mangrove forests are very difficult to access. Without doubt, remote sensing is a serious alternative to traditional field-based methods for mangrove mapping, as it allows information to be gathered from the forbidding environment of mangrove forests, which otherwise, logistically and practically speaking, would be extremely difficult to survey. Remote sensing applications for mangrove mapping at the fundamental level are already well established but, surprisingly, a number of advanced remote sensing applications have remained unexplored for the purpose of mangrove mapping at a finer level. Consequently, the aim of this paper is to unveil the potential of some of the unexplored remote sensing techniques for mangrove studies. Temporal Landsat TM image of 1986, Landsat ETM image of 2000 and Resourcesat-1 LISS 3 image of 2008 are used to calculate percentage change in mangrove cover at AI Dhakira site using geometrically registered and radiometrically corrected historical Landsat and Resourcesat-1 images. Region masks are employed to isolate the unwanted area from the images. NDVI （normalized difference vegetation index） is used to detect mangroves using near-infrared and red bands which are computed from the satellite images. The ground-truthing visit to AI Dhakira site is conducted to confirm the results of the analysis. Change detection is applied and mangrove in the study area is found to have decreased by about 8.79% from 2000 to 2008.展开更多
The literati paintings are a special art nourished by the philosophy, religion, poetry and calligraphy and many other cultural forms in ancient China, which can be regarded as the oriental comprehensive symphony. In t...The literati paintings are a special art nourished by the philosophy, religion, poetry and calligraphy and many other cultural forms in ancient China, which can be regarded as the oriental comprehensive symphony. In terms of the depth of the art, it is the tower accumulated by various Chinese cultures, rich solid. It contains the ＂morality＂, ＂elegant banter＂, ＂super shape＂, and ＂fun＂ of the literati, which can be regarded as the representative of the high difficulty and deep degree of the Chinese traditional arts, and it is the spirit of the Chinese national paintings.展开更多
基金Supported by the National Natural Science Foundation of China(42221002,42171432)Shanghai Municipal Science and Technology Major Project(2021SHZDZX0100)the Fundamental Research Funds for the Central Universities.
文摘The geometric accuracy of topographic mapping with high-resolution remote sensing images is inevita-bly affected by the orbiter attitude jitter.Therefore,it is necessary to conduct preliminary research on the stereo mapping camera equipped on lunar orbiter before launching.In this work,an imaging simulation method consid-ering the attitude jitter is presented.The impact analysis of different attitude jitter on terrain undulation is conduct-ed by simulating jitter at three attitude angles,respectively.The proposed simulation method is based on the rigor-ous sensor model,using the lunar digital elevation model(DEM)and orthoimage as reference data.The orbit and attitude of the lunar stereo mapping camera are simulated while considering the attitude jitter.Two-dimensional simulated stereo images are generated according to the position and attitude of the orbiter in a given orbit.Experi-mental analyses were conducted by the DEM with the simulated stereo image.The simulation imaging results demonstrate that the proposed method can ensure imaging efficiency without losing the accuracy of topographic mapping.The effect of attitude jitter on the stereo mapping accuracy of the simulated images was analyzed through a DEM comparison.
基金the Scientific Research Foundation for the Returned Overseas Chinese Scholars, State Education Ministry
文摘Using fractal dimension to reflect and simulate urban morphology are two applications of fractal theory in city geography. As the only consistent description of a fractal, fractal dimension plays an important role in describing the basic features of fractals. Just like other fractals, our cities have similar characteristics. Fractal dimension to some extent is regarded as an indicator of urban expansion, and it may change with urban morphology in different time and space. Based on the Geographic Information System (GIS), taking Wuhan city as a test area, the fractal dimensions of different land use were calculated, and a linear regression equation was established to analyze the relationship between fractal dimension and residential areas. Then the author used fractal dimension to simulate the urban boundary which is an important part of urban mor-phology. A mid-point subdivision fractal generator is needed in the simulation process, and the shape of the generator is determined by fractal dimension. According to the fractal theory, fractal boundaries in different scales have self-similarity and they have the same fractal dimensions. Based on this fact, the simulation method the author used could quantitatively keep the similarity of configuration of the urban boundaries.
基金The"863"Project of National Ministry of Science and Technology(2006AA03A175)
文摘Proposed and demonstrated is a novel computer modeling method for high power light emitting diodes(LEDs). It contains geometrical structure and optical property of high power LED as well as LED dies definition with its spatial and angular distribution. Merits and non-merits of traditional modeling methods when applied to high power LEDs based on secondary optical design are discussed. Two commercial high power LEDs are simulated using the proposed computer modeling method. Correlation coefficient is proposed to compare and analyze the simulation results and manufacturing specifications. The source model is precisely demonstrated by obtaining above 99% in correlation coefficient with different surface incident angle intervals.
文摘In recent years, the pressure of increasing coastal industries and tourism activities has, in some areas, led to the clearing of many coastal habitats along the Qatar＇s shorelines for the construction of tourist resorts, tourism-related development and industrial facilities. Such threats are leading to the increasing demand for detailed mangrove maps for the purpose of measuring the extent of decline in mangrove ecosystems. Detailed mangrove maps at the community or species level are, however, not easy to produce, mainly because mangrove forests are very difficult to access. Without doubt, remote sensing is a serious alternative to traditional field-based methods for mangrove mapping, as it allows information to be gathered from the forbidding environment of mangrove forests, which otherwise, logistically and practically speaking, would be extremely difficult to survey. Remote sensing applications for mangrove mapping at the fundamental level are already well established but, surprisingly, a number of advanced remote sensing applications have remained unexplored for the purpose of mangrove mapping at a finer level. Consequently, the aim of this paper is to unveil the potential of some of the unexplored remote sensing techniques for mangrove studies. Temporal Landsat TM image of 1986, Landsat ETM image of 2000 and Resourcesat-1 LISS 3 image of 2008 are used to calculate percentage change in mangrove cover at AI Dhakira site using geometrically registered and radiometrically corrected historical Landsat and Resourcesat-1 images. Region masks are employed to isolate the unwanted area from the images. NDVI （normalized difference vegetation index） is used to detect mangroves using near-infrared and red bands which are computed from the satellite images. The ground-truthing visit to AI Dhakira site is conducted to confirm the results of the analysis. Change detection is applied and mangrove in the study area is found to have decreased by about 8.79% from 2000 to 2008.
文摘The literati paintings are a special art nourished by the philosophy, religion, poetry and calligraphy and many other cultural forms in ancient China, which can be regarded as the oriental comprehensive symphony. In terms of the depth of the art, it is the tower accumulated by various Chinese cultures, rich solid. It contains the ＂morality＂, ＂elegant banter＂, ＂super shape＂, and ＂fun＂ of the literati, which can be regarded as the representative of the high difficulty and deep degree of the Chinese traditional arts, and it is the spirit of the Chinese national paintings.
