Reflectance model is a basic concept in computer vision. Some existing models combining the classical diffuse reflectance model and those for surfaces containing specular components can approximately describe real ref...Reflectance model is a basic concept in computer vision. Some existing models combining the classical diffuse reflectance model and those for surfaces containing specular components can approximately describe real reflectance. But the ratio of diffuse and specular reflection decided manually has no clear meaning. We propose a new polynomial hybrid reflectance model. The reflectance map equation with a known shape （for example cylinder） as a sample is used to estimate parameters of the proposed reflectance model by least square regression algorithm. Then the reflectance parameters for surfaces of the same class of materials can be determined. Experiments are performed for a metal surface. The synthesis images produced by the proposed method and existing ones are compared with the real acquired image, and the results show that the proposed reflectance model is suitable for describing real reflectance.展开更多
Objective To investgate the value of various parameters obtained from monoexponential,biexponential,and stretched exponential diffusion-weighted imaging models in the differential diagnosis of breast lesions.Methods A...Objective To investgate the value of various parameters obtained from monoexponential,biexponential,and stretched exponential diffusion-weighted imaging models in the differential diagnosis of breast lesions.Methods A retrospective study was performed in 54 patients with pathologically confirmed malignant tumors(n=30),benign lesions(n=34)and normal fibroglandular展开更多
The emergence of shale oil and gas has markedly boosted the global oil and gas storage and production growth,impacting the strategic energy patterns of numerous countries.However,exploring and exploiting shale reservo...The emergence of shale oil and gas has markedly boosted the global oil and gas storage and production growth,impacting the strategic energy patterns of numerous countries.However,exploring and exploiting shale reservoirs presents significant challenges,with production efficiency improvements largely reliant on hydraulic fracturing techniques.The mineral composition of shale and the brittleness index are critical parameters that influence the effectiveness of fracturing and production in shale reservoirs,but to date,no accurate calculation method that integrates the mineral composition and its mechanical properties for calculating the rock brittleness index.This study,based on modeling of shale SEM(Scanning Electron Microscope)images and finite element mechanical analysis,quantifies the impact of mineral compositions on the brittleness of shale.By fitting regression equations with different mineral compositions as variables,it classifies shales with different brittleness indexes and predicts the expansion patterns of fractures in shale reservoirs.The results show that each component distribution and anisotropy of shale rock has a minor effect on its brittleness index.The content of each component of shale has a greater effect on its mechanical properties,and the higher the brittle mineral content,the greater the brittleness index of shale,and also easier it is to form the complex fracture networks,which is beneficial to improve the production.展开更多
基金This work was supported by the National Natural Sci-ence Foundation of China under Grant No.60502021.
文摘Reflectance model is a basic concept in computer vision. Some existing models combining the classical diffuse reflectance model and those for surfaces containing specular components can approximately describe real reflectance. But the ratio of diffuse and specular reflection decided manually has no clear meaning. We propose a new polynomial hybrid reflectance model. The reflectance map equation with a known shape （for example cylinder） as a sample is used to estimate parameters of the proposed reflectance model by least square regression algorithm. Then the reflectance parameters for surfaces of the same class of materials can be determined. Experiments are performed for a metal surface. The synthesis images produced by the proposed method and existing ones are compared with the real acquired image, and the results show that the proposed reflectance model is suitable for describing real reflectance.
文摘Objective To investgate the value of various parameters obtained from monoexponential,biexponential,and stretched exponential diffusion-weighted imaging models in the differential diagnosis of breast lesions.Methods A retrospective study was performed in 54 patients with pathologically confirmed malignant tumors(n=30),benign lesions(n=34)and normal fibroglandular
基金supported by National Natural Science Foundation of China(52074319)High-end Foreign Experts Introduction Plan of China(G2023122005L)+2 种基金Strategic Cooperation Technology Project of CNPC(ZLZX2020-01-08)Science Foundation of China University of Petroleum,Beijing(2462021QNXZ008)Ministry of Science and Higher Education of the Russian Federation(Project No.FSNM-2024-0005).
文摘The emergence of shale oil and gas has markedly boosted the global oil and gas storage and production growth,impacting the strategic energy patterns of numerous countries.However,exploring and exploiting shale reservoirs presents significant challenges,with production efficiency improvements largely reliant on hydraulic fracturing techniques.The mineral composition of shale and the brittleness index are critical parameters that influence the effectiveness of fracturing and production in shale reservoirs,but to date,no accurate calculation method that integrates the mineral composition and its mechanical properties for calculating the rock brittleness index.This study,based on modeling of shale SEM(Scanning Electron Microscope)images and finite element mechanical analysis,quantifies the impact of mineral compositions on the brittleness of shale.By fitting regression equations with different mineral compositions as variables,it classifies shales with different brittleness indexes and predicts the expansion patterns of fractures in shale reservoirs.The results show that each component distribution and anisotropy of shale rock has a minor effect on its brittleness index.The content of each component of shale has a greater effect on its mechanical properties,and the higher the brittle mineral content,the greater the brittleness index of shale,and also easier it is to form the complex fracture networks,which is beneficial to improve the production.
