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71.
Brian Dipert 《电子设计技术》2005,12(11):72-72,74,76,78,80-81
顾客想要统一格式的蓝色激光存储器。但各竞争方无视这种需求,把不兼容的产品大量推向市场.进行一场高技术的赌博。 相似文献
72.
We propose an image hashing paradigm using visually significant feature points. The feature points should be largely invariant under perceptually insignificant distortions. To satisfy this, we propose an iterative feature detector to extract significant geometry preserving feature points. We apply probabilistic quantization on the derived features to introduce randomness, which, in turn, reduces vulnerability to adversarial attacks. The proposed hash algorithm withstands standard benchmark (e.g., Stirmark) attacks, including compression, geometric distortions of scaling and small-angle rotation, and common signal-processing operations. Content changing (malicious) manipulations of image data are also accurately detected. Detailed statistical analysis in the form of receiver operating characteristic (ROC) curves is presented and reveals the success of the proposed scheme in achieving perceptual robustness while avoiding misclassification. 相似文献
73.
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75.
Numerical study of steady turbulent flow through bifurcated nozzles in continuous casting 总被引:5,自引:0,他引:5
Fady M. Najjar Brian G. Thomas Donald E. Hershey 《Metallurgical and Materials Transactions B》1995,26(4):749-765
Bifurcated nozzles are used in continuous casting of molten steel, where they influence the quality of the cast steel slabs.
The present study performs two-dimensional (2-D) and three-dimensional (3-D) simulations of steady turbulent(K- ε) flow in bifurcated nozzles, using a finite-element (FIDAP) model, which has been verified previously with water model
experiments. The effects of nozzle design and casting process operating variables on the jet characteristics exiting the nozzle
are investigated. The nozzle design parameters studied include the shape, angle, height, width, and thickness of the ports
and the bottom geometry. The process operating practices include inlet velocity profile and angle as well as port curvature
caused by erosion or inclusion buildup. Results show that the jet angle is controlled mainly by the port angle but is steeper
with larger port area and thinner walls. The degree of swirl is increased by larger or rounder ports. The effective port area,
where there is no recirculation, is increased by smaller or curved ports. Flow asymmetry is more severe with skewed or angled
inlet conditions or unequal port sizes. Turbulence levels in the jet are higher with higher casting speed and smaller ports.
Formerly Research Assistant, Department of Mechanical and Industrial Engineering.
Formerly Research Assistant in the same department. 相似文献
76.
Brian F.G. Johnson 《Topics in Catalysis》2003,24(1-4):147-159
In this article, we report studies of two new forms of highly active supported catalysts. First, those derived from supported carbonylate clusters—nanocatalysts and second, those produced from the heterogenization of known chiral homogeneous systems. The utilization of established cluster compounds of precisely known composition and structure have proved invaluable in the preparation of mixed metal nanoparticles of well-defined composition. The attachment of these nanoparticles to the inner walls of mesoporous silica has led to the development of highly active and effective catalysts for a series of hydrogenation reactions, emphasizing the enhanced reactivity of these metal systems as a consequence of their size and of the low coordination numbers of the metal atoms involved. These attributes combined with the relative ease of characterization of both the active sites and their location has led to a detailed examination of the role of these nanosystems in a new approach to clean technology. In an alternative strategy, the use of heterogenized homogeneous chiral catalysts based on the ferrocenyl moiety and diamino ligands and linked to the inner surface of mesoporous materials either by a direct chemical bond or by an ionic interaction has also been explored. These catalysts have been shown to be highly effective in the enantioselective synthesis of organic compounds. Significantly, we have found that the mesopore (usually MCM-41) imposes spatial restrictions arising from the concavity of the inner surface and leads to greatly enhanced enantioselective (ee) performance. 相似文献
77.
The concept of a fracture process zone where damage takes place is used to analyse the delaminations at the free edges of angle ply laminates under uniaxial tension. The use of a fracture process zone removes the singularity in the interlaminar stresses and enables the initiation and growth of delaminations to be modelled for a perfect laminate without any assumed prior defects. Two different models for the stress displacement relationship in the fracture process zone are examined: a constant stress up to critical displacement and a linear relationship. Finite element analysis shows that there is little difference in the predictions obtained from the two models. An approximate analysis is presented for the constant stress stress-displacement model which is shown to agree with a finite element solution and experimental data. Hence it is argued that the approximate method using a constant stress model for the fracture process zone is sufficient for accurate prediction of delaminations. 相似文献
78.
Kenia Sousa Jean Vanderdonckt Brian Henderson-Sellers Cesar Gonzalez-Perez 《Journal of Visual Languages and Computing》2012,23(4):195-212
This work aims at evaluating a graphical notation for modelling software (and other kinds of) development methodologies, thus demonstrating how useful the graphical aspects can be for sharing knowledge between the people responsible for documenting information and those responsible for understanding and putting it into practice. We acknowledge the importance of having a common set of symbols that can be used to create, use and disseminate information for a larger audience than is possible today with a variety of alternatives and lack of a common ground. Using a cognitive dimensions framework, we make a standard evaluation of the elements and diagrams of the notation proposed to support the ISO/IEC 24744 methodology metamodel standard, considering the trade-offs between different dimensions. We suggest improvements to this existing notation based on this analysis, in the context of improving communication between creators and users of methodologies. 相似文献
79.
Measurements are reported of the dielectric properties of two semiconducting glasses of composition SiO2 · Na2O with admixtures of Sb2O
5 and SnO2, covering a wide range of temperatures and a range of six decades of frequency 10–2 to 104 Hz. Both glasses show a gradual evolution of growing low frequency dispersion (LFD) with increasing temperature, with both the real and imaginary components of the complex susceptibility following a power law of the type
n–1, with n 1 at the lowest frequencies. There are also clear indications of reversible phase transitions taking place which manifest themselves by changes in the spectral shape of the dielectric response. 相似文献
80.
Amber L. Hendricks Christine Wachnowsky Brian Fries Insiya Fidai James A. Cowan 《International journal of molecular sciences》2021,22(4)
Lipoyl synthase (LIAS) is an iron–sulfur cluster protein and a member of the radical S-adenosylmethionine (SAM) superfamily that catalyzes the final step of lipoic acid biosynthesis. The enzyme contains two [4Fe–4S] centers (reducing and auxiliary clusters) that promote radical formation and sulfur transfer, respectively. Most information concerning LIAS and its mechanism has been determined from prokaryotic enzymes. Herein, we detail the expression, isolation, and characterization of human LIAS, its reactivity, and evaluation of natural iron–sulfur (Fe–S) cluster reconstitution mechanisms. Cluster donation by a number of possible cluster donor proteins and heterodimeric complexes has been evaluated. [2Fe–2S]-cluster-bound forms of human ISCU and ISCA2 were found capable of reconstituting human LIAS, such that complete product turnover was enabled for LIAS, as monitored via a liquid chromatography–mass spectrometry (LC–MS) assay. Electron paramagnetic resonance (EPR) studies of native LIAS and substituted derivatives that lacked the ability to bind one or the other of LIAS’s two [4Fe–4S] clusters revealed a likely order of cluster addition, with the auxiliary cluster preceding the reducing [4Fe–4S] center. These results detail the trafficking of Fe–S clusters in human cells and highlight differences with respect to bacterial LIAS analogs. Likely in vivo Fe–S cluster donors to LIAS are identified, with possible connections to human disease states, and a mechanistic ordering of [4Fe–4S] cluster reconstitution is evident. 相似文献