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排序方式: 共有1027条查询结果,搜索用时 15 毫秒
1.
2.
A theoretical model for electrons escaping a quantum well under the influence of an applied electric field is developed. Both the thermionic emission and tunneling components of the currents are calculated, taking into account the proper partitioning between the two currents. The group velocity for a nonuniform electron distribution within the quantum well, which is a function of position and energy, and the continuous energy dependence of the quantum well density of states is considered. A comparison between this model and previously reported experimental results are made which demonstrates excellent agreement 相似文献
3.
H.U. Khan K.M. Agrawal M. Anwar S.P. Nautiyal B.S. Rawat 《Petroleum Science and Technology》1998,16(1):145-166
Lubricating oil base stocks differ greatly in their chemical composition and consequently in their physical properties and applications. Influence of waxes and various hydrocarbon type constituents viz saturates and aromatic components on the viscosity and shear stress as a function of temperature in different lube oil base stocks has been studied in the present paper. 相似文献
4.
Our goal is to develop a robust out-of-core sorting program for a
distributed-memory cluster. The literature contains two dominant
paradigms for out-of-core sorting algorithms: merging-based and
partitioning-based. We explore a third paradigm, that of oblivious
algorithms. Unlike the two dominant paradigms, oblivious algorithms
do not depend on the input keys and therefore lead to predetermined
I/O and communication patterns in an out-of-core setting.
Predetermined I/O and communication patterns facilitate overlapping
I/O, communication, and computation for efficient implementation. We
have developed several out-of-core sorting programs using the paradigm
of oblivious algorithms. Our baseline implementation, 3-pass
columnsort, was based on Leighton's columnsort algorithm. Though
efficient in terms of I/O and communication, 3-pass columnsort has a
restriction on the maximum problem size. As our first effort toward
relaxing this restriction, we developed two implementations: subblock
columnsort and M-columnsort. Both of these implementations
incur substantial performance costs: subblock columnsort performs
additional disk I/O, and M-columnsort needs substantial
amounts of extra communication and computation. In this paper we
present slabpose columnsort, a new oblivious algorithm that we have
designed explicitly for the out-of-core setting. Slabpose columnsort
relaxes the problem-size restriction at no extra I/O or communication
cost. Experimental evidence on a Beowulf cluster shows that unlike
subblock columnsort and M-columnsort, slabpose columnsort runs
almost as fast as 3-pass columnsort. To the best of our knowledge,
our implementations are the first out-of-core multiprocessor sorting
algorithms that make no assumptions about the keys and produce output
that is perfectly load balanced and in the striped order assumed by
the Parallel Disk Model. 相似文献
5.
Hawkins' isothermal model developed to study noise in bipolar junction transistors (BJTs) is modified to investigate bias-dependent noise in heterojunction bipolar transistors (HBTs) by incorporating thermal effects. It is shown that the inclusion of thermal effects into the high-frequency noise model of HBTs is necessary as the temperature of the device may become very different from the ambient temperature, especially at high bias current. Calculation of the noise figure by including the thermal effect shows that the isothermal calculation may underestimate the noise figure at high bias current. It is observed that noise at low bias is ideality factor n dependent whereas high bias noise is insensitive to the variation of n. Moreover, the common base current gain plays a major role in the calculation of the minimum noise figure. The excellent fit obtained between the theoretical calculation and the measured data are attributed to the inclusion of the bias-dependent junction heating as well as C/sub De/ and C/sub bc/ into the present calculation. 相似文献
6.
An asymmetric line-axis compound parabolic concentrating single basin solar still of concentration 1.15, exit aperture 0.24 metres and length 0.48 metres, 30° inclination and 60° half acceptance angle has been designed fabricated and tested. 相似文献
7.
M. A. Chaudhry 《Journal of Materials Science》1991,26(4):1106-1108
The dielectric response of hexagonal boron nitride has been measured perpendicular to the cleavage planes at fixed temperatures in the range up to 914 K. The frequency span lies between 10 mHz and 10 kHz range. The dielectric response consists of two loss peaks and a strong low frequency dispersion (LFD). The results are related to the movement of impurity ions. 相似文献
8.
Abdul S Chaudhry 《Journal of the science of food and agriculture》2007,87(14):2617-2624
BACKGROUND: Two factorial studies compared enzymic and in sacco methods to estimate degradation of ruminant foods. Enzyme degradation (in vitro = enzyme) was determined from the release of leucine‐equivalent amino acid (LA) crude protein (CP) from sunflower meal (SF), maize gluten meal (MG), distillers' dark grain (DG) and field beans (FB) after their separate incubations with Streptomyces griseus enzyme for 0–24 h. In sacco crude protein (CP) degradation of these foods was estimated during washing (0 h) and rumen incubations in fistulated cows for 2–24 h. The LA data were expressed as g LA per either kg of CP (LACP) or acid‐hydrolysable LA (HLA) of each food and compared with in sacco data. RESULTS: These methods showed comparable degradation with time (P < 0.01). The in sacco and HLA were greater than LACP for all foods except MG where in sacco value was either lower or equal to LACP depending upon the incubation time (P > 0.05 or P < 0.05). Conversely, HLA was significantly (P < 0.01) greater than LACP from 2 h onwards. At 0 h, in sacco values were significantly greater than those of enzyme for SF, DG and FB (P < 0.05) but not for MG. The foods differed significantly for degradation constants (a, b, c) in each method (P < 0.05). CONCLUSIONS: Despite variations between in sacco and enzyme estimates for different foods, the relationships between these estimates suggest that the HLA enzyme method has the potential to estimate food degradation. Copyright © 2007 Society of Chemical Industry 相似文献
9.
10.
A switching expression is readily convertible to a reliability expression if (a) all ORed terms are disjoint, and (b) all ANDed sums are statistically independent. The usual approach of system reliability analysis makes a primary use of (a) and a secondary use of (b). An alternative approach reverses the roles of (a) and (b). Symbolic reliability expressions for the source-to-terminal reliability of a generalized Indra network (GIN) with nonidentical components are derived by the two approaches. For this particular case, the second approach leads to a shorter, more elegant derivation and simpler novel results. Typical plots of the GIN reliability functions are presented and their properties are discussed. 相似文献