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91.
Self-similar solutions of the second kind for the unsteady one-dimensional flow behind converging spherical and cylindrical strong shocks in a non-ideal medium are studied. The equation of state of the medium is assumed to be in the form of the Mie-Gruneisen type. A simple numerical technique is developed to find the similarity exponent. Detailed studies are carried out for a different non-ideal medium such as a dusty gas, condensed matter and c,s medium. The solutions for an ideal gas are recovered as a particular case. A comparative study of the numerical and some approximate solutions is also made. 相似文献
92.
Sarfaraz A. Ansari Umesh C. Kothyari Kittur G. Ranga Raju 《Canadian Metallurgical Quarterly》2003,129(12):1014-1019
The results of an experimental study on scour under submerged circular vertical jets of water in cohesionless and cohesive sediments are presented. The difference between scour patterns in cohesionless and cohesive sediments is identified. In cohesive sediments, the variations of maximum depth and volume of scour have been studied with respect to the percentage of clay content, dry density, antecedent moisture content, etc. Empirical relationships have been proposed for the maximum depth and volume of scour for both nonplastic and plastic cohesive sediments. The range of data for the applicability of the proposed relationships is specified. 相似文献
93.
A novel approach based on the Liapunov-Schmidt technique of bifurcation theory is presented for the spatial averaging of a class of convection-diffusion-reaction models. It is used to derive low-dimensional averaged models for different types of homogeneous and catalytic reactors, as well as coupled homogeneous-heterogeneous systems. For the homogeneous isothermal case, the averaged models consist of a pair of balance equations for each species Aj in terms of the mixing-cup (Cj,m) and spatially averaged (〈Cj〉) concentrations. The first (global) equation traces the evolution of Cj,m with residence time while the second (local) equation, which is independent of the reactor type, gives the local concentration gradient as a difference between Cj,m and 〈Cj〉 in terms of the local variables (such as species diffusivities, shear and reaction rates). For the wall-catalyzed reaction case, the averaged models are described by a pair of equations for each species in terms of Cj,m and the surface concentration Cj,s and are similar to the classical two-phase models of catalytic reactors. For the coupled homogeneous-heterogeneous case, the averaged models consist of three balance equations for each species in terms of Cj,m, 〈Cj〉 and Cj,s, and contain four mass transfer or exchange coefficients. The accuracy, convergence and the region of validity of the averaged models are examined for some special cases. Finally, the usefulness of the averaged models in predicting the reactor behavior is illustrated with an example for each of the three cases, homogeneous, heterogeneous and coupled homogeneous-heterogeneous case. 相似文献
94.
95.
Kamaladasa RJ Liu F Porter LM Davis RF Koleske DD Mulholland G Jones KA Picard YN 《Journal of microscopy》2011,244(3):311-319
Electron channelling contrast imaging of threading dislocations in GaN (0002) substrates and epitaxial films has been demonstrated using a conventional polepiece-mounted backscatter detector in a commercial scanning electron microscope. The influence of accelerating voltage and diffraction vector on contrast features denoting specific threading dislocation types has been studied. As confirmed by coordinated transmission electron microscopy analysis, electron channelling contrast imaging contrast features for edge-type threading dislocations are spatially smaller than mixed-type threading dislocations in GaN. This ability to delineate GaN edge threading dislocations from mixed type was also confirmed by defect-selective etch processing using molten MgO/KOH. This study validates electron channelling contrast imaging as a nondestructive and widely accessible method for spatially mapping and identifying dislocations in GaN with wider applicability for other single-crystal materials. 相似文献
96.
Supervised learning methods such as Maximum Likelihood (ML) are often used in land cover (thematic) classification of remote
sensing imagery. ML classifier relies exclusively on spectral characteristics of thematic classes whose statistical distributions
(class conditional probability densities) are often overlapping. The spectral response distributions of thematic classes are
dependent on many factors including elevation, soil types, and ecological zones. A second problem with statistical classifiers
is the requirement of the large number of accurate training samples (10 to 30 × |dimensions|), which are often costly and time consuming to acquire over large geographic regions. With the increasing availability of
geospatial databases, it is possible to exploit the knowledge derived from these ancillary datasets to improve classification
accuracies even when the class distributions are highly overlapping. Likewise newer semi-supervised techniques can be adopted
to improve the parameter estimates of the statistical model by utilizing a large number of easily available unlabeled training
samples. Unfortunately, there is no convenient multivariate statistical model that can be employed for multisource geospatial
databases. In this paper we present a hybrid semi-supervised learning algorithm that effectively exploits freely available
unlabeled training samples from multispectral remote sensing images and also incorporates ancillary geospatial databases.
We have conducted several experiments on Landsat satellite image datasets, and our new hybrid approach shows over 24% to 36%
improvement in overall classification accuracy over conventional classification schemes. 相似文献
97.
Divergence measures provide a means to measure the pairwise dissimilarity between "objects," e.g., vectors and probability density functions (pdfs). Kullback-Leibler (KL) divergence and the square loss (SL) function are two examples of commonly used dissimilarity measures which along with others belong to the family of Bregman divergences (BD). In this paper, we present a novel divergence dubbed the Total Bregman divergence (TBD), which is intrinsically robust to outliers, a very desirable property in many applications. Further, we derive the TBD center, called the t-center (using the l(1)-norm), for a population of positive definite matrices in closed form and show that it is invariant to transformation from the special linear group. This t-center, which is also robust to outliers, is then used in tensor interpolation as well as in an active contour based piecewise constant segmentation of a diffusion tensor magnetic resonance image (DT-MRI). Additionally, we derive the piecewise smooth active contour model for segmentation of DT-MRI using the TBD and present several comparative results on real data. 相似文献
98.
Sriram Vemuri Cheng-Der Yu Jennifer S. Degroot Vuthichai Wangsatornthnakun Seresh Venkataram 《Drug development and industrial pharmacy》1991,17(3):327-348
Various sugars were investigated for their ability to protect liposomes against fusion and leakage during freeze-and-thaw or lyophilization processes. Size of liposome was measured before and after the events with a light scattering technique. Leakage of the content of the sulfate, was encapsulated in the liposome which was made of egg phosphatidylcholine (EPC)/egg phosphatidylglycerol (EPG)/cholesterol (5:1:2). Addition of 1% lactose to the liposome suspension prevented the fusion between liposome but not the leakage of the content. Freeze-thawing caused more damage to the liposomes than the freeze-drying/reconstitution. After freeze-thawing, one-third of the encapsulated drug leaked out from the liposome. The freeze-drying did not cause additional leakage. 相似文献
99.
100.