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1.
Orestes E. Alarcón Ricardo E. medrano Pcter P. Gillis 《Metallurgical and Materials Transactions A》1994,25(5):961-968
To fully characterize the mechanical behavior of ceramics, it is useful to study their response to both tensile and bending
tests. In this investigation, a quantitative comparison is made between tensile and bending results from (circularly) cylindrical
glass rods of borosilicate glass and of fused silica. These experimental results show that in each material, the Weibull exponentm is approximately the same for both types of test. The fractured samples clearly showed that all failures initiated at surface-located
flaws. The stress level at which the probability of fracture in tension equals 50 Pct was determined; the maximum tensile
stress for 50 Pct probability of fracture in bending was also determined. The ratio of these two stresses was predicted previously
from simple, theoretical considerations based upon the applicability of the Weibull function and on the distribution of defects
in the specimens. This theoretical result is inconsistent with the experimental observations in view of the fractography.
Therefore, it is concluded that failure in the materials tested is not satisfactorily described by Weibull statistics. 相似文献
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3.
Nonnegative matrix factorization (NMF) is a data analysis technique used in a great variety of applications such as text mining, image processing, hyperspectral data analysis, computational biology, and clustering. In this letter, we consider two well-known algorithms designed to solve NMF problems: the multiplicative updates of Lee and Seung and the hierarchical alternating least squares of Cichocki et al. We propose a simple way to significantly accelerate these schemes, based on a careful analysis of the computational cost needed at each iteration, while preserving their convergence properties. This acceleration technique can also be applied to other algorithms, which we illustrate on the projected gradient method of Lin. The efficiency of the accelerated algorithms is empirically demonstrated on image and text data sets and compares favorably with a state-of-the-art alternating nonnegative least squares algorithm. 相似文献
4.
Sticker complexes are a formal graph-based data model for a restricted class of DNA complexes, motivated by potential applications to databases. This data model allows for a purely declarative definition of hybridization. We introduce the notion of terminating hybridization, which intuitively means that only a finite number of different products can be generated. We characterize this notion in purely graph-theoretic terms. Under a finite alphabet, each product is shown to be of polynomial size. Yet, terminating hybridization can still produce results of exponential size, in that there may be exponentially many different (nonisomorphic) finished products. We indicate a class of complexes where hybridization is guaranteed to be polynomially bounded. 相似文献
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6.
The phospholipid and phospholipid fatty acid composition of gill mitochondrial membranes from two temperate zone marine bivalve
mollusks, the quahog, Mercenaria mercenaria, and the American oyster, Crassostrea virginica, were examined after acclimation to 12 and −1°C. Cardiolipin (CL) was the only phospholipid with proportions altered upon
acclimation to −1°C, increasing 188% in the mitochondrial membranes of M. mercenaria. Although the ratio of bilayer stabilizing to destabilizing lipids is frequently associated with cold acclimation in ectothermic
species, no change was found in this ratio in either of the species. Polyunsaturated fatty acids (PUFA) were found only to
increase in C. virginica with cold acclimation, with total n-3 PUFA increasing in the phospholipid phosphatidylethanolamine, total n-6 PUFA increasing
in CL, and total PUFA increasing in phosphatidylinositol. Monounsaturated fatty acids, not PUFA, were found to have increased
in M. mercenaria, with 18:1n−9 increasing by 150% in CL, and 20∶1 increasing in both CL and phosphatidylcholine, by 146 and 192%, respectively.
These manipulations of membrane phospholipid and fatty acid composition may represent an attempt by these species to help
maintain membrane function at low temperatures. 相似文献
7.
Panner J.H. Abato R.P. Bassett R.W. Carrig K.M. Gillis P.S. Hathaway D.J. Sehr T.W. 《Solid-State Circuits, IEEE Journal of》1991,26(3):300-309
A computer-aided design (CAD) system has been developed to support design of CMOS application-specific integrated circuit (ASIC) logic chips containing more than 300 K equivalent two-input NANDs with 180-ps typical gate delays. The underlying technology is a 0.8-μm, four-level-metal, single-poly CMOS process, with a 0.45-μm nominal effective channel length and 180-ps typical gate delay. Both standard-cell and gate-array circuit libraries are provided, including fixed and growable memory macros. Key new system features are described in the areas of high-level design and synthesis, delay calculation and timing analysis, timing guidance to physical design, physical design, clock construction, and test generation. Early processing results are reported for several test chips, including a 9.7-mm 2-million-transistor chip and a 14.5-mm 300 K-equivalent-gate chip 相似文献
8.
9.
10.
Ayers S. Gillis K.D. Lindau M. Minch B.A. 《IEEE transactions on circuits and systems. I, Regular papers》2007,54(4):736-744
High-throughput electrode arrays are required for advancing devices for testing the effect of drugs on cellular function. In this paper, we present design criteria for a potentiostat circuit that is capable of measuring transient amperometric oxidation currents at the surface of an electrode with submillisecond time resolution and picoampere current resolution. The potentiostat is a regulated cascode stage in which a high-gain amplifier maintains the electrode voltage through a negative feedback loop. The potentiostat uses a new shared amplifier structure in which all of the amplifiers in a given row of detectors share a common half circuit permitting us to use fewer transistors per detector. We also present measurements from a test chip that was fabricated in a 0.5-mum, 5-V CMOS process through MOSIS. Each detector occupied a layout area of 35 mumtimes15 mum and contained eight transistors and a 50-fF integrating capacitor. The rms current noise at 2-kHz bandwidth is ap110 fA. The maximum charge storage capacity at 2 kHz is 1.26times106 electrons 相似文献