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1.
Hermann Ney 《Informatik-Spektrum》2003,26(2):94-102
Dieser Beitrag behandlt die Rolle des statistischen Ansatzes in der maschinellen (oder automatischen) Sprachverarbeitung.
相似文献
2.
Hermann Jahnke 《OR Spectrum》1993,15(1):21-30
Zusammenfassung Eine Lagerzielmengenpolitik für den Fall intermittierender Fertigung mehrerer Sorten auf einer Anlage bei stochastischer Nachfrage wird durch ein Warteschlangenmodell abgebildet. Für die sich ergebenden Kostenfunktion wird eine Approximation vorgeschlagen. Die Bestimmung optimaler Losgrößen und Lagerzielmengen wird untersucht. 相似文献
3.
Magnetization measurements were carried out on bulk Tl2Ba2CaCu2O8 (referred to as Tl-2212) and on various site-selective substituted Tl-2212 samples. At 5K between 0 and 4.5 T, the 5 at.
% Mg-doped Tl-2212 (Tl,Mg-2212) samples displayed enhanced pinning as demonstrated by a field dependent increase of the magnetic
critical-current density Jc by 18 to 25 percent over that of pristine Tl-2212. Excess Mg (10–15 at. %), however, is deleterious. Rietveld refinement
of the x-ray diffraction pattern showed Mg on the Tl sites. Auger electron spectroscopy analysis showed part of the Mg on
grain boundaries. The flux-creep activation energies are higher for flux expulsion than for flux penetration in both Tl-2212
and Tl,Mg-2212 samples; the latter displays higher individual values. Our results demonstrate an increase in the number density
of flux lines as a result of increased density of atomic-size-structural, defects by Mg (5 at. %) doping. In the Tl2−yBa2(Ca1−zYz)Cu2O8−x(z=0–0.3; single phase; x and y represent oxygen and thallium vacancies) system also studied, the Tc decreases as z increases. At z=0.3, the sample becomes an antiferromagnetic semiconductor. 相似文献
4.
Resampling methods for meta-model validation with recommendations for evolutionary computation 总被引:1,自引:0,他引:1
Meta-modeling has become a crucial tool in solving expensive optimization problems. Much of the work in the past has focused on finding a good regression method to model the fitness function. Examples include classical linear regression, splines, neural networks, Kriging and support vector regression. This paper specifically draws attention to the fact that assessing model accuracy is a crucial aspect in the meta-modeling framework. Resampling strategies such as cross-validation, subsampling, bootstrapping, and nested resampling are prominent methods for model validation and are systematically discussed with respect to possible pitfalls, shortcomings, and specific features. A survey of meta-modeling techniques within evolutionary optimization is provided. In addition, practical examples illustrating some of the pitfalls associated with model selection and performance assessment are presented. Finally, recommendations are given for choosing a model validation technique for a particular setting. 相似文献
5.
The effect of rapid solidification on the corrosion behaviour in aerated 0.001 M NaCl solution of Mg-Al alloys containing 9.6 to 23.4wt% AI has been investigated in comparison with chill-cast material. Polarization studies show that rapid solidification decreases corrosion current by up to two orders of magnitude corresponding to a corrosion rate of 6 to 11 mil y–1. Increasing the aluminium content in solid solution by rapid solidification gave rise to a steep increase in pitting potential between 10 and 23 wt% Al and resulted in development of an anodic plateau at 30Acm–2 attributable to magnesium depletion for the alloy surface and formation of a protective film. Chemical analysis of the electrolyte as a function of dissolution time for the rapidly solidified material indicated that initially only magnesium dissolved and that this dissolution of magnesium ceased within 2 to 5 min. The results indicate the formation of an aluminium-enriched interdiffusion zone at the surface underlying a more stable surface oxide than for ingot-processed Mg-Al-based alloys. 相似文献
6.
本文对FMS50系统结构进行了介绍,着重阐述了该系统的多种物流模式.并分析了其通信控制系统的构成。 相似文献
7.
A hybrid integrated circuit is described which generates two phase-shifted 20-kHz output pulse trains whose duty cycles are related to the amplitude of an applied input signal. The circuit was designed primarily for use in power conditioning schemes utilizing pulsewidth modulated signals for regulated dc-to-dc voltage conversion. Realization of this hybrid circuit has been accomplished with a beam-lead sealed-junction monolithic silicon chip and several tantalum thin-film resistors and capacitors which are bonded/ deposited on a ceramic substrate in the form of a 28-terminal dual-in line package (DIP). 相似文献
8.
The Strength of Liquid Bridges Between Dissimilar Materials 总被引:1,自引:0,他引:1
The strength of the liquid bridge between a sphere and a plate of dissimilar materials was studied. An equation was derived using the surface energy approach. For small amounts of liquid, the force of adhesion f was f=2πRy(cosθ1 + cosθ2 where R is the sphere radius, y is the surface tension, and θ2, θ2 the contact angles. In the derivationn, major simplications about the meniscus shape were possible.
The equation was experimentally tested with water, ethyl alcohol, aniline and iodobenzene using factorial combinations with different solids. Force of adhesion measurements were carried out using a tensile testing machine at controlled loading rates. Excellent agreement was obtained in the experimental and predicted adhesion values. The McFarlane-Tabor equation was identified as correct only for small amounts of liquids and similarly wet solids. 相似文献
The equation was experimentally tested with water, ethyl alcohol, aniline and iodobenzene using factorial combinations with different solids. Force of adhesion measurements were carried out using a tensile testing machine at controlled loading rates. Excellent agreement was obtained in the experimental and predicted adhesion values. The McFarlane-Tabor equation was identified as correct only for small amounts of liquids and similarly wet solids. 相似文献
9.
A one-dimensional steady state model has been developed for the combustion reactor of a dual fluidized bed biomass steam gasification system. The combustion reactor is operated as fast fluidized bed (riser) with staged air introduction (bottom, primary and secondary air). The main fuel i.e., residual biomass char (from the gasifier), is introduced together with the circulating bed material at the bottom of the riser. The riser is divided into two zones: bottom zone (modelled according to modified two phase theory) and upper zone (modelled with core-annulus approach). The model consists of sub-model for bed hydrodynamic, conversion and conservation. Biomass char is assumed to be a homogeneous matrix of C, H and O and is modelled as partially volatile fuel. The exit gas composition and the temperature profile predicted by the model are in good agreement with the measured value. 相似文献
10.
Olaf Mersmann Bernd Bischl Heike Trautmann Markus Wagner Jakob Bossek Frank Neumann 《Annals of Mathematics and Artificial Intelligence》2013,69(2):151-182
Meta-heuristics are frequently used to tackle NP-hard combinatorial optimization problems. With this paper we contribute to the understanding of the success of 2-opt based local search algorithms for solving the traveling salesperson problem (TSP). Although 2-opt is widely used in practice, it is hard to understand its success from a theoretical perspective. We take a statistical approach and examine the features of TSP instances that make the problem either hard or easy to solve. As a measure of problem difficulty for 2-opt we use the approximation ratio that it achieves on a given instance. Our investigations point out important features that make TSP instances hard or easy to be approximated by 2-opt. 相似文献