The damped Helmholtz-Duffing oscillator is a topic of great interest in many different fields of study due to its complex dynamics.By transitioning from conventional continuous differential equations to their fractal ...The damped Helmholtz-Duffing oscillator is a topic of great interest in many different fields of study due to its complex dynamics.By transitioning from conventional continuous differential equations to their fractal counterparts,one gains insights into the system's response under new mathematical frameworks.This paper presents a novel method for converting standard continuous differential equations into their fractal equivalents.This conversion occurs after the nonlinear system is transformed into its linear equivalent.Numerical analyses show that there are several resonance sites in the fractal system,which differ from the one resonance point found in the continuous system.One important finding is that the fractal system loses some of its stabilizing power when decaying behavior is transformed into a diffuse pattern.Interestingly,a decrease in the fractal order in resonance settings shows a stabilizing impact,highlighting the dynamics'complexity inside fractal systems.This endeavor to convert to fractals is a revolutionary technique that is being employed for the first time.展开更多
The GBA’s Outline Development Plan targets new energy development as an essential requirement going forward.OPTIMIZING the energy structure of the Guangdong-Hong Kong-Macao Greater Bay Area(GBA)and building a clean,l...The GBA’s Outline Development Plan targets new energy development as an essential requirement going forward.OPTIMIZING the energy structure of the Guangdong-Hong Kong-Macao Greater Bay Area(GBA)and building a clean,low-carbon,safe,and efficient energy supply system is a priority set in the GBA’s Outline Development Plan.展开更多
Previous studies have often focused on monitoring grassland growth as the primary target of remote sensing investigations on grassland ecological restoration in the northern Tibetan Plateau,overlooking the crucial rol...Previous studies have often focused on monitoring grassland growth as the primary target of remote sensing investigations on grassland ecological restoration in the northern Tibetan Plateau,overlooking the crucial role played by gravel in the ecological restoration of these grasslands.This study utilizes supervised classification and segmentation techniques based on machine learning to extract gravel morphology profiles from field-sampled plot images and calculate their characteristic parameters.Employing a multivariate linear approach combined with Principal Component Analysis(PCA),a model for inferring gravel characteristic parameters is constructed.Statistical features,particle size characteristics,and spatial distribution patterns of gravel are analyzed.Results reveal that gravel predominantly exhibit sub-rounded shapes,with 80%classified as fine gravel.The coefficients of determination(R2)between gravel particle size and coverage,perimeter,and area are 0.444,0.724,and 0.557,respectively,indicating linear relationships.The cumulative contribution rate of the top five remote sensing factors is 95.44%,with the first geological factor contributing 77.64%,collectively reflecting the primary information of the 20 factors used.Modeling shows that areas with larger gravel particle sizes correspond to increased perimeter and coverage.Gravels in the Nagqu Prefecture of northern Xizang have a particle size range of 4-8 mm,primarily comprising fine gravel which accounts for 94.61%.These findings provide a scientific basis for extracting gravel characteristic parameters and understanding their spatial distribution variations in the northern Tibetan Plateau.展开更多
The Fourth Plenary Session of the 17th Central Committee of the Communist Party of China (CPC) closed in Beijing on September 18, with pledges to expand intra-Party democracy and resolutely fight corruption. A total o...The Fourth Plenary Session of the 17th Central Committee of the Communist Party of China (CPC) closed in Beijing on September 18, with pledges to expand intra-Party democracy and resolutely fight corruption. A total of 194 full members and 163 alternate members of the committee, the Party’s top decision-making body, attended the four-day plenum, which was presided over by its Political Bureau. Hu Jintao, General Secretary of the CPC Central Committee, delivered a work report at the meeting.展开更多
Building outline extraction from segmented point clouds is a critical step of building footprint generation.Existing methods for this task are often based on the convex hull and α-shape algorithm.There are also some ...Building outline extraction from segmented point clouds is a critical step of building footprint generation.Existing methods for this task are often based on the convex hull and α-shape algorithm.There are also some methods using grids and Delaunay triangulation.The common challenge of these methods is the determination of proper parameters.While deep learning-based methods have shown promise in reducing the impact and dependence on parameter selection,their reliance on datasets with ground truth information limits the generalization of these methods.In this study,a novel unsupervised approach,called PH-shape,is proposed to address the aforementioned challenge.The methods of Persistence Homology(PH)and Fourier descriptor are introduced into the task of building outline extraction.The PH from the theory of topological data analysis supports the automatic and adaptive determination of proper buffer radius,thus enabling the parameter-adaptive extraction of building outlines through buffering and“inverse”buffering.The quantitative and qualitative experiment results on two datasets with different point densities demonstrate the effectiveness of the proposed approach in the face of various building types,interior boundaries,and the density variation in the point cloud data of one building.The PH-supported parameter adaptivity helps the proposed approach overcome the challenge of parameter determination and data variations and achieve reliable extraction of building outlines.展开更多
晚清天文学译著《谈天》原译自英国天文学名著Outlines of Astronomy.通过对译本《谈天》各版本的搜集整理和版本差异比较,理清了《谈天》的3个重要版本与其所依据的英文原本之间的对应关系,理顺了《谈天》各版本之间的继承关系,为该书...晚清天文学译著《谈天》原译自英国天文学名著Outlines of Astronomy.通过对译本《谈天》各版本的搜集整理和版本差异比较,理清了《谈天》的3个重要版本与其所依据的英文原本之间的对应关系,理顺了《谈天》各版本之间的继承关系,为该书中、英版本的内容比较研究及考察近代天文学在中国的传播提供了参考资料.展开更多
Based on the boundary condition of field engineering, numerical simulations of28 conditions of existing diffusers of 3 structure types were investigated by ComputationalFluid Dynamics software package, and there were ...Based on the boundary condition of field engineering, numerical simulations of28 conditions of existing diffusers of 3 structure types were investigated by ComputationalFluid Dynamics software package, and there were the problems of larger structure resistanceand lower diffusing efficiency of these diffusers by analysis of CFD results.Thestructure outlines of the energy-saving diffuser were constructed by the application ofstream function and potential function superimposing.On the basis of numerical simulationsof energy-saving diffusers of 5 area-enlarging ratios, structural resistances and diffusingefficiencies of 5 energy-saving diffusers were comparatively analyzed, and therange from 2.00 to 2.31 of the rational area-enlarging ratio of energy-saving diffusers wasderived.The optimization area-enlarging ratio of the energy-saving diffuser was presently2.28 through comparable analysis.From the above, the results show that the coefficient ofperformance of the energy-saving diffuser is better than 3 existing diffusers.展开更多
Various studies on the difference of distal femoral condyles between genders have been reported recently in order to provide anatomic information for knee prosthesis design and surgical planning in total knee arthropl...Various studies on the difference of distal femoral condyles between genders have been reported recently in order to provide anatomic information for knee prosthesis design and surgical planning in total knee arthroplasty. They also had the objective to be used as a sex recognition character, as may be needed in forensic medicine. Except for a recent 3D approach on the distal femur, most of the studies used dimensional information or aspect ratio but not shape. Our 2D study aimed to determine the size and shape variation of femoral condyles in Thais, considering age, sex and sides. One hundred and twenty-four cadaveric femurs （male 84 legs and female 40 legs） were dissected. The specimens were photographed by digital camera and images were analyzed using three geometric techniques： （i） the landmark-based method （5 landmarks）, （ii） with or without addition of 23 sliding semilandmark and （iii） the outline-based methods. From the resulting geometric coordinates, size and shape were extracted for comparisons between genders and sides. Between sides, directional asymmetry could be detected only for shape variation, and only when introducing curves in the analyses （either through the semilandmarks technique or through the outline-based one）. Non-directional asymmetry, probably fluctuating asymmetry, was detected for size, as well as for shape, in both genders. Sex discrimination was performed for each geometric technique using two classification methods： the Mahalanobis distance classification and the Maximum likelihood classification. The latter provided much more satisfactory gender validated reclassification （87%） than shape （72%）.展开更多
This paper investigates the purpose and the functions of buildings and their compatibility with Islamic culture and the environment. An analysis from ecological and environmental points of view is carried out. The cha...This paper investigates the purpose and the functions of buildings and their compatibility with Islamic culture and the environment. An analysis from ecological and environmental points of view is carried out. The challenge is how these traditional outlines can best fit the functions of the building and the facilities intended to be offered, and how the new building has satisfied the requirements of the traditional environment. The investigation also shows the increasing usage of modem design materials for the hospital, which does not offer sufficient heat insulation or reasonable lighting. Although the Mashiakhet Al Azhar and Dar E1 Eftaa establishments have completely different functions, their designs consider and recognize the environmental requirements and the historical background. The sites of the Mashiakhet Al Azhar and Dar E1 Eftaa compound have achieved complete harmony with the surrounding environment. The hospital may meet its utilitarian needs and functions, but lacks a general environmental and traditional balance with the whole district. However, functional and traditional aspects can be combined successfully at the same time.展开更多
Since cannon drum of agile shell-feeding system rotates frequently and intermittently, its motion must be steady. Outline of driving cam determines the motion of cannon drum, so it is necessary to select the proper ou...Since cannon drum of agile shell-feeding system rotates frequently and intermittently, its motion must be steady. Outline of driving cam determines the motion of cannon drum, so it is necessary to select the proper outline of cam. Through analysis of parabolic outline and cycloid outline of the cams, the outline that combines the two curves is obtained. According to the demand of production,the value of the outline is revised, and then the method of fitting curve is used to get the expression of the angle of cam and the displacement of the driven part. Through analyzing the motion of the cannon drum, it is suggested that the angle of the cam is proportion to the displacement of the driven part. The cam with the specially derived outline can move steadily.展开更多
The hard tissues of squid can provide important information for species identification. In this study, we used statolith and beak to identify three squid species including Uroteuthis duvaucelii, Loliolus beka, and U. ...The hard tissues of squid can provide important information for species identification. In this study, we used statolith and beak to identify three squid species including Uroteuthis duvaucelii, Loliolus beka, and U. edulis in the South China Sea. Because of the highly overlapping habitat and similar body morphology of the three squid species, we explored four different ways to identify them, by using statolith, upper beak, lower beak and a combination of statolith and beak. An outline geometric morphometric method and stepwise discriminant analysis were used to evaluate the most suitable method for the identification. We found that the combination of statolith and beak had the highest cross validation rate that was 75.0%, 87.5% and 88.7% for U. duvaucelii, L. beka and U. edulis, respectively. Using two beaks had similar results and the lowest cross validation rate was 60.0%, 50.0%, and 73.7% for the upper beak, 46.9%, 58.5% and 75.3% for the lower beak of U. duvaucelii, L. beka and U. edulis, respectively. Analyzing with the statolith had moderate cross validation which was 72.2%, 80.0%, and 87.7% for U. duvaucelii, L. beka and U. edulis, respectively. From the results it is suggested when the entire body of a squid is available, a combination of statolith and beak should be used for the identification. When only one hard tissue is available, species identification can be subjected to large errors.展开更多
Volume parameter is the basic content of a spatial body object morphology analysis.However,the challenge lies in the volume calculation of irregular objects.The point cloud slicing method proposed in this study effect...Volume parameter is the basic content of a spatial body object morphology analysis.However,the challenge lies in the volume calculation of irregular objects.The point cloud slicing method proposed in this study effectively works in calculating the volume of the point cloud of the spatial object obtained through three-dimensional laser scanning(3DLS).In this method,a uniformly spaced sequent slicing process is first conducted in a specific direction on the point cloud of the spatial object obtained through 3DLS.A series of discrete point cloud slices corresponding to the point cloud bodies are then obtained.Subsequently,the outline boundary polygon of the point cloud slicing is searched one by one in accordance with the slicing sequence and areas of the polygon.The point cloud slice is also calculated.Finally,the individual point cloud section volume is calculated through the slicing areas and the adjacent slicing gap.Thus,the total volume of the scanned spatial object can be calculated by summing up the individual volumes.According to the results and analysis of the calculated examples,the slice-based volume-calculating method for the point cloud of irregular objects obtained through 3DLS is correct,concise in process,reliable in results,efficient in calculation methods,and controllable on accuracy.This method comes as a good solution to the volume calculation of irregular objects.展开更多
On different occasions, you will face challenge in speaking. Good speaking can leave a favorable impression on the others. Exactly, trying to be a experienced speaker is a key to one's successful life or career. B...On different occasions, you will face challenge in speaking. Good speaking can leave a favorable impression on the others. Exactly, trying to be a experienced speaker is a key to one's successful life or career. But there are so many difficulties we would encounter in the process of speaking, thus how to develop a perfect speech is a sticking question for most of speakers. This article can help you to find ways to being a good speaker.展开更多
Log centering accuracy depends on the computerized simulative level of its three-dimension outline. In this paper, the basic methods about distinguishing three dimensions outline of log by means of computerized simula...Log centering accuracy depends on the computerized simulative level of its three-dimension outline. In this paper, the basic methods about distinguishing three dimensions outline of log by means of computerized simulation are discussed. It is suggested that straight lines or certain curves should be introduced to connect the separated points along some log generatrices. Taking bent logs for example verify the accuracy of computerized simulative method.展开更多
Objective: Phase-contrast X-ray imaging which reduces radiation exposure, is a promising technique for observing the inner structures of biological soft tissues without the aid of contrast agents. The present study in...Objective: Phase-contrast X-ray imaging which reduces radiation exposure, is a promising technique for observing the inner structures of biological soft tissues without the aid of contrast agents. The present study intends to depict blood vessels of rabbits and human livers with hard X-ray in-line outline imaging without contrast agents using synchrotron radiation. Methods: All samples were fixed with formalin and sliced into 6 mm sections. The imaging experiments were performed with Fuji-IX80 films on the 4W1A light beam of the first generation synchrotron radiation in Beijing, China. The device of the experiment, which supplies a maximum light spot size of 20×10 mm was similar to that of in-line holography. The photon energy was set at 8 KeV and high quality imagines were obtained by altering the distance between the sample and the film. Results: The trees of rabbit-liver blood vessels and the curved vessels of the cirrhotic human liver were revealed on the images, where vessels < 20 μm in diameter were differentiated. Conclusion: These results show that the blood vessels of liver samples can be revealed by using hard X-ray in-line outline imaging with the first generation synchrotron radiation without contrast agents.展开更多
文摘The damped Helmholtz-Duffing oscillator is a topic of great interest in many different fields of study due to its complex dynamics.By transitioning from conventional continuous differential equations to their fractal counterparts,one gains insights into the system's response under new mathematical frameworks.This paper presents a novel method for converting standard continuous differential equations into their fractal equivalents.This conversion occurs after the nonlinear system is transformed into its linear equivalent.Numerical analyses show that there are several resonance sites in the fractal system,which differ from the one resonance point found in the continuous system.One important finding is that the fractal system loses some of its stabilizing power when decaying behavior is transformed into a diffuse pattern.Interestingly,a decrease in the fractal order in resonance settings shows a stabilizing impact,highlighting the dynamics'complexity inside fractal systems.This endeavor to convert to fractals is a revolutionary technique that is being employed for the first time.
文摘The GBA’s Outline Development Plan targets new energy development as an essential requirement going forward.OPTIMIZING the energy structure of the Guangdong-Hong Kong-Macao Greater Bay Area(GBA)and building a clean,low-carbon,safe,and efficient energy supply system is a priority set in the GBA’s Outline Development Plan.
基金funded by the Major R&D and Achievement Transformation Projects of Xizang(CGZH2024000416)Science and Technology Program of Xizang(XZ202402ZD0001)Major R&D and Achievement Transformation Projects of Qinghai(2022-QY-224)。
文摘Previous studies have often focused on monitoring grassland growth as the primary target of remote sensing investigations on grassland ecological restoration in the northern Tibetan Plateau,overlooking the crucial role played by gravel in the ecological restoration of these grasslands.This study utilizes supervised classification and segmentation techniques based on machine learning to extract gravel morphology profiles from field-sampled plot images and calculate their characteristic parameters.Employing a multivariate linear approach combined with Principal Component Analysis(PCA),a model for inferring gravel characteristic parameters is constructed.Statistical features,particle size characteristics,and spatial distribution patterns of gravel are analyzed.Results reveal that gravel predominantly exhibit sub-rounded shapes,with 80%classified as fine gravel.The coefficients of determination(R2)between gravel particle size and coverage,perimeter,and area are 0.444,0.724,and 0.557,respectively,indicating linear relationships.The cumulative contribution rate of the top five remote sensing factors is 95.44%,with the first geological factor contributing 77.64%,collectively reflecting the primary information of the 20 factors used.Modeling shows that areas with larger gravel particle sizes correspond to increased perimeter and coverage.Gravels in the Nagqu Prefecture of northern Xizang have a particle size range of 4-8 mm,primarily comprising fine gravel which accounts for 94.61%.These findings provide a scientific basis for extracting gravel characteristic parameters and understanding their spatial distribution variations in the northern Tibetan Plateau.
文摘The Fourth Plenary Session of the 17th Central Committee of the Communist Party of China (CPC) closed in Beijing on September 18, with pledges to expand intra-Party democracy and resolutely fight corruption. A total of 194 full members and 163 alternate members of the committee, the Party’s top decision-making body, attended the four-day plenum, which was presided over by its Political Bureau. Hu Jintao, General Secretary of the CPC Central Committee, delivered a work report at the meeting.
基金supported by NTNU Digital project[grant number 81771593].
文摘Building outline extraction from segmented point clouds is a critical step of building footprint generation.Existing methods for this task are often based on the convex hull and α-shape algorithm.There are also some methods using grids and Delaunay triangulation.The common challenge of these methods is the determination of proper parameters.While deep learning-based methods have shown promise in reducing the impact and dependence on parameter selection,their reliance on datasets with ground truth information limits the generalization of these methods.In this study,a novel unsupervised approach,called PH-shape,is proposed to address the aforementioned challenge.The methods of Persistence Homology(PH)and Fourier descriptor are introduced into the task of building outline extraction.The PH from the theory of topological data analysis supports the automatic and adaptive determination of proper buffer radius,thus enabling the parameter-adaptive extraction of building outlines through buffering and“inverse”buffering.The quantitative and qualitative experiment results on two datasets with different point densities demonstrate the effectiveness of the proposed approach in the face of various building types,interior boundaries,and the density variation in the point cloud data of one building.The PH-supported parameter adaptivity helps the proposed approach overcome the challenge of parameter determination and data variations and achieve reliable extraction of building outlines.
文摘晚清天文学译著《谈天》原译自英国天文学名著Outlines of Astronomy.通过对译本《谈天》各版本的搜集整理和版本差异比较,理清了《谈天》的3个重要版本与其所依据的英文原本之间的对应关系,理顺了《谈天》各版本之间的继承关系,为该书中、英版本的内容比较研究及考察近代天文学在中国的传播提供了参考资料.
基金Supported by the National Natural Science Foundation of China(50974060)the Scientific Research Fund of Hunan Provincial Education Department(09CY014)the Doctoral Fund of Hunan University of Science and Technology
文摘Based on the boundary condition of field engineering, numerical simulations of28 conditions of existing diffusers of 3 structure types were investigated by ComputationalFluid Dynamics software package, and there were the problems of larger structure resistanceand lower diffusing efficiency of these diffusers by analysis of CFD results.Thestructure outlines of the energy-saving diffuser were constructed by the application ofstream function and potential function superimposing.On the basis of numerical simulationsof energy-saving diffusers of 5 area-enlarging ratios, structural resistances and diffusingefficiencies of 5 energy-saving diffusers were comparatively analyzed, and therange from 2.00 to 2.31 of the rational area-enlarging ratio of energy-saving diffusers wasderived.The optimization area-enlarging ratio of the energy-saving diffuser was presently2.28 through comparable analysis.From the above, the results show that the coefficient ofperformance of the energy-saving diffuser is better than 3 existing diffusers.
文摘Various studies on the difference of distal femoral condyles between genders have been reported recently in order to provide anatomic information for knee prosthesis design and surgical planning in total knee arthroplasty. They also had the objective to be used as a sex recognition character, as may be needed in forensic medicine. Except for a recent 3D approach on the distal femur, most of the studies used dimensional information or aspect ratio but not shape. Our 2D study aimed to determine the size and shape variation of femoral condyles in Thais, considering age, sex and sides. One hundred and twenty-four cadaveric femurs （male 84 legs and female 40 legs） were dissected. The specimens were photographed by digital camera and images were analyzed using three geometric techniques： （i） the landmark-based method （5 landmarks）, （ii） with or without addition of 23 sliding semilandmark and （iii） the outline-based methods. From the resulting geometric coordinates, size and shape were extracted for comparisons between genders and sides. Between sides, directional asymmetry could be detected only for shape variation, and only when introducing curves in the analyses （either through the semilandmarks technique or through the outline-based one）. Non-directional asymmetry, probably fluctuating asymmetry, was detected for size, as well as for shape, in both genders. Sex discrimination was performed for each geometric technique using two classification methods： the Mahalanobis distance classification and the Maximum likelihood classification. The latter provided much more satisfactory gender validated reclassification （87%） than shape （72%）.
文摘This paper investigates the purpose and the functions of buildings and their compatibility with Islamic culture and the environment. An analysis from ecological and environmental points of view is carried out. The challenge is how these traditional outlines can best fit the functions of the building and the facilities intended to be offered, and how the new building has satisfied the requirements of the traditional environment. The investigation also shows the increasing usage of modem design materials for the hospital, which does not offer sufficient heat insulation or reasonable lighting. Although the Mashiakhet Al Azhar and Dar E1 Eftaa establishments have completely different functions, their designs consider and recognize the environmental requirements and the historical background. The sites of the Mashiakhet Al Azhar and Dar E1 Eftaa compound have achieved complete harmony with the surrounding environment. The hospital may meet its utilitarian needs and functions, but lacks a general environmental and traditional balance with the whole district. However, functional and traditional aspects can be combined successfully at the same time.
文摘Since cannon drum of agile shell-feeding system rotates frequently and intermittently, its motion must be steady. Outline of driving cam determines the motion of cannon drum, so it is necessary to select the proper outline of cam. Through analysis of parabolic outline and cycloid outline of the cams, the outline that combines the two curves is obtained. According to the demand of production,the value of the outline is revised, and then the method of fitting curve is used to get the expression of the angle of cam and the displacement of the driven part. Through analyzing the motion of the cannon drum, it is suggested that the angle of the cam is proportion to the displacement of the driven part. The cam with the specially derived outline can move steadily.
基金the National Natural Science Foundation of China (No. NSFC41476129)the Shanghai Leading Academic Discipline Project (Fisheries Discipline)supported by Shanghai Ocean University International Center for Marine Studies and Shanghai 1000 Talents Program
文摘The hard tissues of squid can provide important information for species identification. In this study, we used statolith and beak to identify three squid species including Uroteuthis duvaucelii, Loliolus beka, and U. edulis in the South China Sea. Because of the highly overlapping habitat and similar body morphology of the three squid species, we explored four different ways to identify them, by using statolith, upper beak, lower beak and a combination of statolith and beak. An outline geometric morphometric method and stepwise discriminant analysis were used to evaluate the most suitable method for the identification. We found that the combination of statolith and beak had the highest cross validation rate that was 75.0%, 87.5% and 88.7% for U. duvaucelii, L. beka and U. edulis, respectively. Using two beaks had similar results and the lowest cross validation rate was 60.0%, 50.0%, and 73.7% for the upper beak, 46.9%, 58.5% and 75.3% for the lower beak of U. duvaucelii, L. beka and U. edulis, respectively. Analyzing with the statolith had moderate cross validation which was 72.2%, 80.0%, and 87.7% for U. duvaucelii, L. beka and U. edulis, respectively. From the results it is suggested when the entire body of a squid is available, a combination of statolith and beak should be used for the identification. When only one hard tissue is available, species identification can be subjected to large errors.
文摘Volume parameter is the basic content of a spatial body object morphology analysis.However,the challenge lies in the volume calculation of irregular objects.The point cloud slicing method proposed in this study effectively works in calculating the volume of the point cloud of the spatial object obtained through three-dimensional laser scanning(3DLS).In this method,a uniformly spaced sequent slicing process is first conducted in a specific direction on the point cloud of the spatial object obtained through 3DLS.A series of discrete point cloud slices corresponding to the point cloud bodies are then obtained.Subsequently,the outline boundary polygon of the point cloud slicing is searched one by one in accordance with the slicing sequence and areas of the polygon.The point cloud slice is also calculated.Finally,the individual point cloud section volume is calculated through the slicing areas and the adjacent slicing gap.Thus,the total volume of the scanned spatial object can be calculated by summing up the individual volumes.According to the results and analysis of the calculated examples,the slice-based volume-calculating method for the point cloud of irregular objects obtained through 3DLS is correct,concise in process,reliable in results,efficient in calculation methods,and controllable on accuracy.This method comes as a good solution to the volume calculation of irregular objects.
文摘On different occasions, you will face challenge in speaking. Good speaking can leave a favorable impression on the others. Exactly, trying to be a experienced speaker is a key to one's successful life or career. But there are so many difficulties we would encounter in the process of speaking, thus how to develop a perfect speech is a sticking question for most of speakers. This article can help you to find ways to being a good speaker.
文摘Log centering accuracy depends on the computerized simulative level of its three-dimension outline. In this paper, the basic methods about distinguishing three dimensions outline of log by means of computerized simulation are discussed. It is suggested that straight lines or certain curves should be introduced to connect the separated points along some log generatrices. Taking bent logs for example verify the accuracy of computerized simulative method.
基金Supported by National Natural Science Foundation of China (10275087)Shanghai Optic Science Fund (022261023)Shanghai Natural Science Fund (02ZF14116)
文摘Objective: Phase-contrast X-ray imaging which reduces radiation exposure, is a promising technique for observing the inner structures of biological soft tissues without the aid of contrast agents. The present study intends to depict blood vessels of rabbits and human livers with hard X-ray in-line outline imaging without contrast agents using synchrotron radiation. Methods: All samples were fixed with formalin and sliced into 6 mm sections. The imaging experiments were performed with Fuji-IX80 films on the 4W1A light beam of the first generation synchrotron radiation in Beijing, China. The device of the experiment, which supplies a maximum light spot size of 20×10 mm was similar to that of in-line holography. The photon energy was set at 8 KeV and high quality imagines were obtained by altering the distance between the sample and the film. Results: The trees of rabbit-liver blood vessels and the curved vessels of the cirrhotic human liver were revealed on the images, where vessels < 20 μm in diameter were differentiated. Conclusion: These results show that the blood vessels of liver samples can be revealed by using hard X-ray in-line outline imaging with the first generation synchrotron radiation without contrast agents.
