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111.
Maziar Gholami Korzani Sergio A. Galindo-Torres Alexander Scheuermann David J. Williams 《水科学与水工程》2017,10(2):143-153
Simulations of two-dimensional (2D) flow past a circular cylinder with the smoothed particle hydrodynamics (SPH) method were conducted in order to accurately determine the drag coefficient. The fluid was modeled as a viscous liquid with weak compressibility. Boundary conditions, such as a no-slip solid wall, inflow and outflow, and periodic boundaries, were employed to resemble the physical problem. A sensitivity analysis, which has been rarely addressed in previous studies, was conducted on several SPH parameters. Hence, the effects of distinct parameters, such as the kernel choices and the domain dimensions, were investigated with the goal of obtaining highly accurate results. A range of Reynolds numbers (1–500) was simulated, and the results were compared with existing experimental data. It was observed that the domain dimensions and the resolution of SPH particles, in comparison to the obstacle size, affected the obtained drag coefficient significantly. Other parameters, such as the background pressure, influenced the transient condition, but did not influence the steady state at which the drag coefficient was determined. 相似文献
112.
Symmetry is a common characteristic in natural and man‐made objects. Its ubiquitous nature can be exploited to facilitate the analysis and processing of computational representations of real objects. In particular, in computer graphics, the detection of symmetries in 3D geometry has enabled a number of applications in modeling and reconstruction. However, the problem of symmetry detection in incomplete geometry remains a challenging task. In this paper, we propose a vote‐based approach to detect symmetry in 3D shapes, with special interest in models with large missing parts. Our algorithm generates a set of candidate symmetries by matching local maxima of a surface function based on the heat diffusion in local domains, which guarantee robustness to missing data. In order to deal with local perturbations, we propose a multi‐scale surface function that is useful to select a set of distinctive points over which the approximate symmetries are defined. In addition, we introduce a vote‐based scheme that is aware of the partiality, and therefore reduces the number of false positive votes for the candidate symmetries. We show the effectiveness of our method in a varied set of 3D shapes and different levels of partiality. Furthermore, we show the applicability of our algorithm in the repair and completion of challenging reassembled objects in the context of cultural heritage. 相似文献
113.
This paper studies the Voronoi diagrams on 2‐manifold meshes based on geodesic metric (a.k.a. geodesic Voronoi diagrams or GVDs), which have polyline generators. We show that our general setting leads to situations more complicated than conventional 2D Euclidean Voronoi diagrams as well as point‐source based GVDs, since a typical bisector contains line segments, hyperbolic segments and parabolic segments. To tackle this challenge, we introduce a new concept, called local Voronoi diagram (LVD), which is a combination of additively weighted Voronoi diagram and line‐segment Voronoi diagram on a mesh triangle. We show that when restricting on a single mesh triangle, the GVD is a subset of the LVD and only two types of mesh triangles can contain GVD edges. Based on these results, we propose an efficient algorithm for constructing the GVD with polyline generators. Our algorithm runs in O(nNlogN) time and takes O(nN) space on an n‐face mesh with m generators, where N = max{m, n}. Computational results on real‐world models demonstrate the efficiency of our algorithm. 相似文献
114.
Ionic liquids as electrolytes 总被引:5,自引:0,他引:5
Salts having a low melting point are liquid at room temperature, or even below, and form a new class of liquids usually called room temperature ionic liquids (RTIL). Information about RTILs can be found in the literature with such key words as: room temperature molten salt, low-temperature molten salt, ambient-temperature molten salt, liquid organic salt or simply ionic liquid. Their physicochemical properties are the same as high temperature ionic liquids, but the practical aspects of their maintenance or handling are different enough to merit a distinction. The class of ionic liquids, based on tetraalkylammonium cation and chloroaluminate anion, has been extensively studied since late 1970s of the XX century, following the works of Osteryoung. Systematic research on the application of chloroaluminate ionic liquids as solvents was performed in 1980s. However, ionic liquids based on aluminium halides are moisture sensitive. During the last decade an increasing number of new ionic liquids have been prepared and used as solvents. The general aim of this paper was to review the physical and chemical properties of RTILs from the point of view of their possible application as electrolytes in electrochemical processes and devices. The following points are discussed: melting and freezing, conductivity, viscosity, temperature dependence of conductivity, transport and transference numbers, electrochemical stability, possible application in aluminium electroplating, lithium batteries and in electrochemical capacitors. 相似文献
115.
针对D-S 证据理论在融合高度冲突的证据时可能导致与直观结果相悖的问题, 已有的基于修改数据模型的方法更多地考虑如何提高冲突证据结果的聚焦程度, 而没有考虑冲突成因以及如何通过冲突原因判断来削减证据之间的冲突. 对此, 提出一种闭世界框架下的灰色模糊多属性决策方法. 根据一般的灰色关联分析方法的基本思路, 将灰色关联度与欧氏距离有机结合, 构造出一种平均相似度对方案进行评价, 进而得到方案的排序结果. 最后, 通过实例分析验证了所提出方法的可行性和有效性. 相似文献
116.
117.
118.
Kanit Krisnangkura 《Journal of the American Oil Chemists' Society》1991,68(1):56-58
Equations were developed for the estimation of gross heat of combustion (HG) of triglycerides (TGs) and fatty acid methyl
esters (FAMEs) from their saponification number (SN) and iodine value (IV). HG of TG=1,896,000/SN − 0.6 IV — 1600 and HG of
FAME=618,000/SN − 0.08 IV — 430. When these equations were tested on cottonseed oil, soybean oil, partially hydrogenated soybean
oil, peanut oil, sunflower oil, sunflower oil methyl esters, soybean oil methyl esters and cottonseed oil methyl esters, predicted
HG values agreed well with those reported in the literature. 相似文献
119.
Gasoline quality prediction using gas chromatography and FTIR spectroscopy: An artificial intelligence approach 总被引:1,自引:0,他引:1
This paper reports on analysis of 45 gasoline samples with different qualities, namely, octane number and chemical composition. Measurements of data from gas chromatography and IR (FTIR) spectroscopy are used to gasoline quality prediction and classification. The data were processed using principal component analysis (PCA) and fuzzy C means (FCM) algorithm. The data were then analyzed following the neural network paradigms, hybrid neural network and support vector machines (SVM) classifier. The IR spectra were compressed and de-noised by the discrete wavelet analysis. Using the hybrid neural network and multi linear regression method (MLRM), excellent correlation between chemical composition of the gasoline samples and predicted value of the octane number was obtained. About 100% correct classification for six different categories of the gasoline was achieved, each of which has different qualities. 相似文献
120.
重质原料油生产轻烯烃的Ⅱ型催化裂解工艺和催化剂 总被引:3,自引:0,他引:3
Ⅱ型催化裂解是以重质油为原料生产丙烯、异丁烯和异戊烯等轻烯烃, 并同时兼产高辛烷值优质汽油的新催化工艺。该工艺使用新研制的新型择形催化剂, 可以加工减压馏分油、减压馏分油掺渣油或二次加工油以及全常压渣油, 并成功地进行了工业化试验。以临胜减压馏分油掺左右脱沥青油为原料, 可以得到12.52wt%~14.43wt%的丙烯和11.23wt%~11.41wt%的丁烯,同时还得到40wt%左右93号优质汽油。型催化裂解工艺开创了一条以重质油为原料生产轻烯烃和高辛烷值优质汽油的新途径 相似文献