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991.
Craig Gotsman 《Computer Graphics Forum》1994,13(2):153-163
We present a technique implementing space-variant filtering of an image, with kernels belonging to a given family, in time independent of the size and shape of the filter kernel support. The essence of our method is efficient approximation of these kernels, belonging to an infinite family governed by a small number of parameters, as a linear combination of a small number k of “basis” kernels. The accuracy of this approximation increases with k, and requires O(k) storage space. Any kernel in the family may be applied to the image in O(k) time using precomputed results of the application of the basis kernels. Performing linear combinations of these values with appropriate coefficients yields the desired result. A trade off between algorithm efficiency and approximation quality is obtained by adjusting k. The basis kernels are computed using singular value decomposition, distinguishing this from previous techniques designed to achieve a similar effect. We illustrate by applying our methods to the family of elliptic Gaussian kernels, a popular choice for filtering warped images. 相似文献
992.
Anneliese Andrews Robert France Sudipto Ghosh Gerald Craig 《Software Testing, Verification and Reliability》2003,13(2):95-127
Systematic design testing, in which executable models of behaviours are tested using inputs that exercise scenarios, can help reveal flaws in designs before they are implemented in code. In this paper a technique for testing executable forms of UML (Unified Modelling Language) models is described and test adequacy criteria based on UML model elements are proposed. The criteria can be used to define test objectives for UML designs. The UML design test criteria are based on the same premise underlying code test criteria: coverage of relevant building blocks of models is highly likely to uncover faults. The test adequacy criteria proposed in this paper are based on building blocks for UML class and interaction diagrams. Class diagram criteria are used to determine the object configurations on which tests are run, while interaction diagram criteria are used to determine the sequences of messages that should be tested. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
993.
An output-sensitive visibility algorithm is one whose runtime is proportional to the number of visible graphic primitives in a scene model—not to the total number of primitives, which can be much greater. The known practical output-sensitive visibility algorithms are suitable only for static scenes, because they include a heavy preprocessing stage that constructs a spatial data structure which relies on the model objects’ positions. Any changes to the scene geometry might cause significant modifications to this data structure. We show how these algorithms may be adapted to dynamic scenes. Two main ideas are used: first, update the spatial data structure to reflect the dynamic objects’ current positions; make this update efficient by restricting it to a small part of the data structure. Second, use temporal bounding volumes (TBVs) to avoid having to consider every dynamic object in each frame. The combination of these techniques yields efficient, output-sensitive visibility algorithms for scenes with multiple dynamic objects. The performance of our methods is shown to be significantly better than previous output-sensitive algorithms, intended for static scenes. TBVs can be adapted to applications where no prior knowledge of the objects’ trajectories is available, such as virtual reality (VR), simulations etc. Furthermore, they save updates of the scene model itself; notjust of the auxiliary data structure used by the visibility algorithm. They can therefore be used to greatly reduce the communications overhead in client-server VR systems, as well as in general distributed virtual environments. 相似文献
994.
Craig A Woods 《Contact lens & anterior eye》2003,26(4):181-187
INTRODUCTION: Increasingly aspherical optics are used in contact lens designs to produce a varifocal effect to correct presbyopia. Whilst no current ISO standard describes a method to verify these products, the vertex power needs to be verified by the manufacturer and optometrist. Visionix claim that the VC2001 instrument is able to resolve the vertex power of complex contact lenses and that it has been adopted by contact lens manufacturers as their \"gold standard\" method of measure. Practitioners rely on the focimeter for contact lens verification and accept that it has poorer resolution. This raises the question of whether practitioners can verify the vertex powers of varifocal contact lenses to a sufficient sensitivity. The purpose of this study is to determine whether a focimeter can differentiate between various vertex powers incorporating differing degrees of asphericity that are used in contact lens designs. METHODS: A range of varifocal contact lenses were used with single vision contact lenses as controls. Three types of focimeters were used: a manual focimeter, a projector focimeter and a computerised focimeter (standard and contact lens modes). The VC2001 assessed the vertex powers over the optical zone and was used as a reference for the focimeters. The measures from the VC2001 and the focimeters were analysed by discrepancy analysis. RESULTS: All discrepancy measures fell outside two standard deviations for either the varifocal contact lenses or the single vision contact lenses when the focimeters were compared to the VC2001. This raises the issue of whether the focimeters are measuring the same parameter as the VC2001. Only the analysis of the repeated measurements from the manual focimeter for single vision contact lenses demonstrated an acceptable measure of precision (+/-0.21, 2S.D.) with a very small degree of bias (mean difference -0.024, +/-0.02 [2S.E.]). CONCLUSION: These results suggest that the manual focimeter can measure the vertex powers for single vision contact lenses to an acceptable degree of precision. The vertex powers of varifocal lenses cannot be verified using standard practice equipment. The VC2001 has poor precision for power measurements and may not be measuring the same parameter as the focimeters and therefore questions the validity of the VC2001 as the \"gold standard\" for vertex power measurement. 相似文献
995.
E. Patrick Fuerst Craig F. Morris Nairanjana Dasgupta Derek J. McLean 《Journal of food science》2013,78(10):S1614-S1620
There is little research evaluating flavor preferences among wheat varieties. We previously demonstrated that mice exert very strong preferences when given binary mixtures of wheat varieties. We plan to utilize mice to identify wheat genes associated with flavor, and then relate this back to human preferences. Here we explore the effects of experimental design including the number of days (from 1 to 4) and number of mice (from 2 to 15) in order to identify designs that provide significant statistical inferences while minimizing requirements for labor and animals. When mice expressed a significant preference between 2 wheat varieties, increasing the number of days (for a given number of mice) increased the significance level (decreased P‐values) for their preference, as expected, but with diminishing benefit as more days were added. However, increasing the number of mice (for a given number of days) provided a more dramatic log‐linear decrease in P‐values and thus increased statistical power. In conclusion, when evaluating mouse feeding preferences in binary mixtures of grain, an efficient experimental design would emphasize fewer days rather than fewer animals thus shortening the experiment duration and reducing the overall requirement for labor and animals. 相似文献
996.
Craig Anderson 《今日电子》2007,(8):69-70
基于Web的应用,包括Google、Wikipedia和YouTub,已经将Web从少数机构为多数消费者提供服务内容的应用模式转变为每个用户定制和定义他/她自己的消费内容的模式.人们把这种新的Web形式称为Web 2.0. 相似文献
997.
Kannan Ramanathan Miguel A. Contreras Craig L. Perkins Sally Asher Falah S. Hasoon James Keane David Young Manuel Romero Wyatt Metzger Rommel Noufi James Ward Anna Duda 《Progress in Photovoltaics: Research and Applications》2003,11(4):225-230
We report the growth and characterization of record‐efficiency ZnO/CdS/CuInGaSe2 thin‐film solar cells. Conversion efficiencies exceeding 19% have been achieved for the first time, and this result indicates that the 20% goal is within reach. Details of the experimental procedures are provided, and material and device characterization data are presented. Published in 2003 by John Wiley & Sons, Ltd. 相似文献
998.
Martin J. Sweetman Maurizio Ronci Soraya Rasi Ghaemi Jamie E. Craig Nicolas H. Voelcker 《Advanced functional materials》2012,22(6):1158-1166
Porous silicon (pSi) surfaces have been chemically patterned via a UV initiated hydrosilylation reaction of an alkene through a photomask, introducing chemical functionality in the exposed surface areas. A secondary, UV initiated hydrosilylation reaction with a second alkene of different functionality is performed to backfill the silicon hydride terminated regions on the surface, thereby affording patterned porous films with dual, surface chemistry. UV initiated hydrosilylations were performed using the alkene undecylenic acid N‐hydroxysuccinimide (NHS) ester, and the pSi surfaces were stabilized by a second hydrosilylation reaction with a polyethylene glycol (PEG) appended alkene. NHS ester and PEG functionalized surfaces were used for the selective immobilization of the cell adhesion mediator protein fibronectin (FN), in the NHS‐functional regions. Matrix‐assisted laser desorption/ionization mass spectrometry imaging on the protein functionalized pSi surface confirmed the patterned conjugation of the FN to the NHS functionalized regions. Mammalian cells cultured on these surfaces showed attachment that was confined to the patterned areas of FN on the pSi surface. 相似文献
999.
AbstractA framework previously introduced in Wilson et al. (2018) for solving a sequence of stochastic optimization problems with bounded changes in the minimizers is extended and applied to machine learning problems such as regression and classification. The stochastic optimization problems arising in these machine learning problems are solved using algorithms such as stochastic gradient descent (SGD). A method based on estimates of the change in the minimizers and properties of the optimization algorithm is introduced for adaptively selecting the number of samples at each time step to ensure that the excess risk—that is, the expected gap between the loss achieved by the approximate minimizer produced by the optimization algorithm and the exact minimizer—does not exceed a target level. A bound is developed to show that the estimate of the change in the minimizers is non trivial provided that the excess risk is small enough. Extensions relevant to the machine learning setting are considered, including a cost-based approach to select the number of samples with a cost budget over a fixed horizon, and an approach to applying cross-validation for model selection. Finally, experiments with synthetic and real data are used to validate the algorithms. 相似文献
1000.
Corson TW Cavga H Aberle N Crews CM 《Chembiochem : a European journal of chemical biology》2011,12(11):1767-1773
Triptolide is a potent natural product, with documented antiproliferative, immunosuppressive, anti-inflammatory, antifertility, and antipolycystic kidney disease effects. Despite a wealth of knowledge about the biology of this compound, direct intracellular target proteins have remained elusive. We synthesized a biotinylated photoaffinity derivative of triptolide, and used it to identify dCTP pyrophosphatase 1 (DCTPP1) as a triptolide-interacting protein. Free triptolide interacts directly with recombinant DCTPP1, and inhibits the enzymatic activity of this protein. Triptolide is thus the first dCTP pyrophosphatase inhibitor identified, and DCTPP1 is a biophysically validated target of triptolide. 相似文献