Based on the Fourier transform, a new shape descriptor was proposed to represent the flame image. By employing the shape descriptor as the input, the flame image recognition was studied by the methods of the artificia...Based on the Fourier transform, a new shape descriptor was proposed to represent the flame image. By employing the shape descriptor as the input, the flame image recognition was studied by the methods of the artificial neural network(ANN) and the support vector machine(SVM) respectively. And the recognition experiments were carried out by using flame image data sampled from an alumina rotary kiln to evaluate their effectiveness. The results show that the two recognition methods can achieve good results, which verify the effectiveness of the shape descriptor. The highest recognition rate is 88.83% for SVM and 87.38% for ANN, which means that the performance of the SVM is better than that of the ANN.展开更多
In this paper, we present a novel Support Vector Machine active learning algorithm for effective 3D model retrieval using the concept of relevance feedback. The proposed method learns from the most informative objects...In this paper, we present a novel Support Vector Machine active learning algorithm for effective 3D model retrieval using the concept of relevance feedback. The proposed method learns from the most informative objects which are marked by the user, and then creates a boundary separating the relevant models from irrelevant ones. What it needs is only a small number of 3D models labelled by the user. It can grasp the user＇s semantic knowledge rapidly and accurately. Experimental results showed that the proposed algorithm significantly improves the retrieval effectiveness. Compared with four state-of-the-art query refinement schemes for 3D model retrieval, it provides superior retrieval performance after no more than two rounds of relevance feedback.展开更多
Gold（Au） nanoclusters have recently emerged as ideal models for understanding Au catalysis, because the nanosized Au particles have precise atomic numbers and uniform size. In this work, we studied for the first tim...Gold（Au） nanoclusters have recently emerged as ideal models for understanding Au catalysis, because the nanosized Au particles have precise atomic numbers and uniform size. In this work, we studied for the first time the support shape effect on the catalysis of Au nanoclusters by using CO oxidation as a model reaction. Au22（L8）6（L = 1,8-bis（diphenylphosphino） octane） nanoclusters were supported on CeO2 rods or cubes, then pretreated at different temperatures（up to 673 K）, allowing the gradual removal of the organic phosphine ligands. CO oxidation test over these differently pretreated samples shows that CeO2 rods are much better supports than cubes for Au22 nanoclusters in enhancing the reaction rate. In situ IR spectroscopy coupled with CO adsorption indicates that the shape of CeO2 support can impact the nature and quantity of exposed Au sites, as well as the efficiency of organic ligand removal. Although CeO2 rods are helpful in exposing a greater percentage of total Au sites upon ligands removal, the percentage of active Au sites（denoted by Au d＋, 0 〈 d 〈 1） is lower than that on CeO2 cubes. The in situ extended X-ray absorption spectroscopy（EXAFS） and high-angle annular dark-field scanning transmission electron microscopy（HAADF-STEM） results show that the Au nanoclusters bound more strongly to the CeO2 rods than to the cubes where the Au nanoclusters show more sintering. Considering the typical redox mechanism for CO oxidation over supported Au nanoclusters and nanoparticles, it is concluded that the reactivity of the lattice oxygen of CeO2 is the determining factor for CO oxidation over Au22/CeO2. CeO2 rods offer more reactive lattice oxygen and abundant oxygen vacancies than the cubes and thus make the rods a superior support for Au nanoclusters in catalyzing low temperature CO oxidation.展开更多
Proton exchange membrane fuel cells are playing an increasing role in postpandemic economic recovery and climate action plans.However,their performance,cost,and durability are significantly related to Pt-based electro...Proton exchange membrane fuel cells are playing an increasing role in postpandemic economic recovery and climate action plans.However,their performance,cost,and durability are significantly related to Pt-based electrocatalysts,hampering their large-scale commercial application.Hence,considerable efforts have been devoted to improving the activity and durability of Pt-based electrocatalysts by controlled synthesis in recent years as an effective method for decreasing Pt use,and consequently,the cost.Therefore,this review article focuses on the synthesis processes of carbon-supported Pt-based electrocatalysts,which significantly affect the nanoparticle size,shape,and dispersion on supports and thus the activity and durability of the prepared electrocatalysts.The reviewed processes include(i)the functionalization of a commercial carbon support for enhanced catalyst-support interaction and additional catalytic effects,(ii)the methods for loading Pt-based electrocatalysts onto a carbon support that impact the manufacturing costs of electrocatalysts,(iii)the preparation of spheri-cal and nonspherical Pt-based electrocatalysts(polyhedrons,nanocages,nanoframes,one-and two-dimensional nanostruc-tures),and(iv)the postsynthesis treatments of supported electrocatalysts.The influences of the supports,key experimental parameters,and postsynthesis treatments on Pt-based electrocatalysts are scrutinized in detail.Future research directions are outlined,including(i)the full exploitation of the potential functionalization of commercial carbon supports,(ii)scaled-up one-pot synthesis of carbon-supported Pt-based electrocatalysts,and(iii)simplification of postsynthesis treatments.One-pot synthesis in aqueous instead of organic reaction systems and the minimal use of organic ligands are preferred to simplify the synthesis and postsynthesis treatment processes and to promote the mass production of commercial carbon-supported Pt-based electrocatalysts.展开更多
The shape impact of nanostructured ceria on the dispersion of Pd species was investigated by analyzing the atomic configuration and the bonding environment of Pd species over spherical and cubic ceria particles,using ...The shape impact of nanostructured ceria on the dispersion of Pd species was investigated by analyzing the atomic configuration and the bonding environment of Pd species over spherical and cubic ceria particles,using STEM and XPS.Amorphous Pd particles of about 2.0 nm,with a substantial amount of tiny Pd species,dispersed on spherical ceria,primarily due to the enriched surface oxygen vacancies that bonded the Pd species tightly.While faceted Pd particles of about 2.9 nm located on cubic ceria with distinct interfaces where Pd atoms embedded into the ceria lattice.The crystalline Pd particles on ceria cubes were highly active and stable for methane combustion that occurred on the metal surface via a facile PdO/Pd redox cycle;while the amorphous Pd particles on spherical ceria particles were featured by a significantly higher activity and stability towards CO oxidation,where the Pd-ceria interface served as the active sites.展开更多
In the present research,by using a numerical model,some analyses were performed on flows around a T-shape spur dike and a support structure located at its upstream under different wing to length ratios of T-shape spur...In the present research,by using a numerical model,some analyses were performed on flows around a T-shape spur dike and a support structure located at its upstream under different wing to length ratios of T-shape spur dike in the order of 0.25,0.50,0.75 and 1.00.In order to verify numerical model,physical model data were used in presence of a single T shape spur dike.Results from numerical model are desirably in agreement with those of physical one because the regression between both data is 0.86 up to 0.92.In this research,all hydraulic parameters of flows,streamlines and dimensions of flow separation zones were studied in order to select the most practical model.Increased W/L results in 7%–12%increase in the length of flow separation zone and in 2%increase in the width of this zone compared to W/L=0.25.展开更多
建立了无网格MLPG(Meshless Local Petrov-Galerkin)混合配点法求解二维弹性体位移、应力的数学模型,使用罚函数法添加本质边界条件,并将其应用到结构形状优化,结合遗传算法提出了一种新的连续体结构优化设计方法。对于节点支持域半径...建立了无网格MLPG(Meshless Local Petrov-Galerkin)混合配点法求解二维弹性体位移、应力的数学模型,使用罚函数法添加本质边界条件,并将其应用到结构形状优化,结合遗传算法提出了一种新的连续体结构优化设计方法。对于节点支持域半径的选取进行了重点探讨,提出一种动态支持域选择方法,建立了基于MLPG混合配点法的优化模型,对两个实际工程算例进行了形状优化,并与现有结果比较,验证了该方法的有效性。展开更多
基金Project(60634020) supported by the National Natural Science Foundation of China
文摘Based on the Fourier transform, a new shape descriptor was proposed to represent the flame image. By employing the shape descriptor as the input, the flame image recognition was studied by the methods of the artificial neural network(ANN) and the support vector machine(SVM) respectively. And the recognition experiments were carried out by using flame image data sampled from an alumina rotary kiln to evaluate their effectiveness. The results show that the two recognition methods can achieve good results, which verify the effectiveness of the shape descriptor. The highest recognition rate is 88.83% for SVM and 87.38% for ANN, which means that the performance of the SVM is better than that of the ANN.
基金the National Basic Research Program (973) of China (No. 2004CB719401)the National Research Foundation for the Doctoral Program of Higher Education of China (No.20060003060)
文摘In this paper, we present a novel Support Vector Machine active learning algorithm for effective 3D model retrieval using the concept of relevance feedback. The proposed method learns from the most informative objects which are marked by the user, and then creates a boundary separating the relevant models from irrelevant ones. What it needs is only a small number of 3D models labelled by the user. It can grasp the user＇s semantic knowledge rapidly and accurately. Experimental results showed that the proposed algorithm significantly improves the retrieval effectiveness. Compared with four state-of-the-art query refinement schemes for 3D model retrieval, it provides superior retrieval performance after no more than two rounds of relevance feedback.
基金supported by the U.S. Department of Energy, Office of Science, Basic Energy Sciences, Chemical Sciences, Geosciences, and Biosciences Divisionsupported by the U.S. Department of Energy, Office of Science, Office of Basic Energy, Sciences under Contract No. DE-AC02-76SF00515the facilities support at the beamline BL 2-2 provided by the Synchrotron Catalysis Consortium U.S. DOE (No. De-SC0012335)
文摘Gold（Au） nanoclusters have recently emerged as ideal models for understanding Au catalysis, because the nanosized Au particles have precise atomic numbers and uniform size. In this work, we studied for the first time the support shape effect on the catalysis of Au nanoclusters by using CO oxidation as a model reaction. Au22（L8）6（L = 1,8-bis（diphenylphosphino） octane） nanoclusters were supported on CeO2 rods or cubes, then pretreated at different temperatures（up to 673 K）, allowing the gradual removal of the organic phosphine ligands. CO oxidation test over these differently pretreated samples shows that CeO2 rods are much better supports than cubes for Au22 nanoclusters in enhancing the reaction rate. In situ IR spectroscopy coupled with CO adsorption indicates that the shape of CeO2 support can impact the nature and quantity of exposed Au sites, as well as the efficiency of organic ligand removal. Although CeO2 rods are helpful in exposing a greater percentage of total Au sites upon ligands removal, the percentage of active Au sites（denoted by Au d＋, 0 〈 d 〈 1） is lower than that on CeO2 cubes. The in situ extended X-ray absorption spectroscopy（EXAFS） and high-angle annular dark-field scanning transmission electron microscopy（HAADF-STEM） results show that the Au nanoclusters bound more strongly to the CeO2 rods than to the cubes where the Au nanoclusters show more sintering. Considering the typical redox mechanism for CO oxidation over supported Au nanoclusters and nanoparticles, it is concluded that the reactivity of the lattice oxygen of CeO2 is the determining factor for CO oxidation over Au22/CeO2. CeO2 rods offer more reactive lattice oxygen and abundant oxygen vacancies than the cubes and thus make the rods a superior support for Au nanoclusters in catalyzing low temperature CO oxidation.
基金the Natural Sciences and Engineering Research Council of Canada(NSERC)via CRD Grant No.CRDPJ 522410-17a Discovery Grant from the Canadian Urban Transit Research&Innovation Consortium(CUTRIC)via Project No.160028Ballard Power Systems Inc.via Project No.SRA#077701.
文摘Proton exchange membrane fuel cells are playing an increasing role in postpandemic economic recovery and climate action plans.However,their performance,cost,and durability are significantly related to Pt-based electrocatalysts,hampering their large-scale commercial application.Hence,considerable efforts have been devoted to improving the activity and durability of Pt-based electrocatalysts by controlled synthesis in recent years as an effective method for decreasing Pt use,and consequently,the cost.Therefore,this review article focuses on the synthesis processes of carbon-supported Pt-based electrocatalysts,which significantly affect the nanoparticle size,shape,and dispersion on supports and thus the activity and durability of the prepared electrocatalysts.The reviewed processes include(i)the functionalization of a commercial carbon support for enhanced catalyst-support interaction and additional catalytic effects,(ii)the methods for loading Pt-based electrocatalysts onto a carbon support that impact the manufacturing costs of electrocatalysts,(iii)the preparation of spheri-cal and nonspherical Pt-based electrocatalysts(polyhedrons,nanocages,nanoframes,one-and two-dimensional nanostruc-tures),and(iv)the postsynthesis treatments of supported electrocatalysts.The influences of the supports,key experimental parameters,and postsynthesis treatments on Pt-based electrocatalysts are scrutinized in detail.Future research directions are outlined,including(i)the full exploitation of the potential functionalization of commercial carbon supports,(ii)scaled-up one-pot synthesis of carbon-supported Pt-based electrocatalysts,and(iii)simplification of postsynthesis treatments.One-pot synthesis in aqueous instead of organic reaction systems and the minimal use of organic ligands are preferred to simplify the synthesis and postsynthesis treatment processes and to promote the mass production of commercial carbon-supported Pt-based electrocatalysts.
文摘The shape impact of nanostructured ceria on the dispersion of Pd species was investigated by analyzing the atomic configuration and the bonding environment of Pd species over spherical and cubic ceria particles,using STEM and XPS.Amorphous Pd particles of about 2.0 nm,with a substantial amount of tiny Pd species,dispersed on spherical ceria,primarily due to the enriched surface oxygen vacancies that bonded the Pd species tightly.While faceted Pd particles of about 2.9 nm located on cubic ceria with distinct interfaces where Pd atoms embedded into the ceria lattice.The crystalline Pd particles on ceria cubes were highly active and stable for methane combustion that occurred on the metal surface via a facile PdO/Pd redox cycle;while the amorphous Pd particles on spherical ceria particles were featured by a significantly higher activity and stability towards CO oxidation,where the Pd-ceria interface served as the active sites.
文摘In the present research,by using a numerical model,some analyses were performed on flows around a T-shape spur dike and a support structure located at its upstream under different wing to length ratios of T-shape spur dike in the order of 0.25,0.50,0.75 and 1.00.In order to verify numerical model,physical model data were used in presence of a single T shape spur dike.Results from numerical model are desirably in agreement with those of physical one because the regression between both data is 0.86 up to 0.92.In this research,all hydraulic parameters of flows,streamlines and dimensions of flow separation zones were studied in order to select the most practical model.Increased W/L results in 7%–12%increase in the length of flow separation zone and in 2%increase in the width of this zone compared to W/L=0.25.
文摘建立了无网格MLPG(Meshless Local Petrov-Galerkin)混合配点法求解二维弹性体位移、应力的数学模型,使用罚函数法添加本质边界条件,并将其应用到结构形状优化,结合遗传算法提出了一种新的连续体结构优化设计方法。对于节点支持域半径的选取进行了重点探讨,提出一种动态支持域选择方法,建立了基于MLPG混合配点法的优化模型,对两个实际工程算例进行了形状优化,并与现有结果比较,验证了该方法的有效性。
