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991.
在统计分析、正交多项式回归和模拟试验的基础上,建立了高精度的屈强比预报模型,并运用多元函数极值原理,求导极值点及相应的工艺参数,为优化工艺制度,提高热焊弯管用钢(L360-WG系列)性能合格率提供了定量依据。 相似文献
992.
Twenty-five years of natural coordinates 总被引:3,自引:0,他引:3
Javier García de Jalón 《Multibody System Dynamics》2007,18(1):15-33
In the early eighties, the author and co-workers created and further developed the natural coordinates to describe the motion
of 2-D and 3-D multibody systems. Natural coordinates do not need angles or angular parameters to define orientation, leading
to constant inertia matrices and to the simplest form of the constraint equations. Natural coordinates are composed by the
Cartesian coordinates of some points and the Cartesian components of some unit vectors distributed on the different bodies
of the system. The points and vectors can be located in the joints, being shared by contiguous bodies, decreasing or even
eliminating the need to set joint constraints and reducing the total number of variables. However, other authors prefer not
to share variables in order to get even simpler equations and to keep a bigger decoupling of equations, which is preferable
in some cases.
In this paper the history of natural coordinates is reviewed, as well as the main contributions coming from other research
groups. In the second part of the paper some application areas in which natural coordinates can be particularly advantageous
are examined.
Commemorative Contribution. 相似文献
993.
Dynamic neural networks with different time-scales include the aspects of fast and slow phenomenons. Some applications require
that the equilibrium points of the designed networks are stable. In this paper, the passivity-based approach is used to derive
stability conditions for dynamic neural networks with different time-scales. Several stability properties, such as passivity,
asymptotic stability, input-to-state stability and bounded input bounded output stability, are guaranteed in certain senses.
A numerical example is also given to demonstrate the effectiveness of the theoretical results. 相似文献
994.
Gloria Galan-Marin Enrique Merida-Casermeiro Domingo Lopez-Rodriguez 《Neural Processing Letters》2007,26(2):133-143
Detection of isomorphism among kinematic chains is essential in mechanical design, but difficult and computationally expensive.
It has been shown that both traditional methods and previously presented neural networks still have a lot to be desired in
aspects such as simplifying procedure of identification and adapting automatic computation. Therefore, a new algorithm based
on a competitive Hopfield network is developed for automatic computation in the kinematic chain isomorphism problem. The neural
approach provides directly interpretable solutions and does not demand tuning of parameters. We have tested the algorithm
by solving problems reported in the recent mechanical literature. Simulation results show the effectiveness of the network
that rapidly identifies isomorphic kinematic chains. 相似文献
995.
输油管道泄漏检测技术综述 总被引:21,自引:1,他引:20
输油管道在现代社会中的应用越来越广泛,但是随着管道运行时间的延长,由于各种原因导致的管道泄漏将造成资源的浪费和环境污染,建立管道泄漏检测系统,及时准确地报告事故的范围和程度,可以最大限度地减少经济损失和环境污染.文章总结了国内外近几十年来发展起来的管道泄漏检测和定位的主要方法,重点介绍了基于现代控制理论和信号处理的方法,分析了各种管道泄漏检测方法的原理及优缺点,并探讨了管道泄漏检测的发展趋势.指出采用软硬件结合的方法进行输油管道泄漏检测、泄漏检测系统与SCADA结合、将分布式光纤传感器应用于管道泄漏检测中将有良好的发展前景. 相似文献
996.
Statistical machine translation systems are usually trained on large amounts of bilingual text (used to learn a translation
model), and also large amounts of monolingual text in the target language (used to train a language model). In this article
we explore the use of semi-supervised model adaptation methods for the effective use of monolingual data from the source language
in order to improve translation quality. We propose several algorithms with this aim, and present the strengths and weaknesses
of each one. We present detailed experimental evaluations on the French–English EuroParl data set and on data from the NIST
Chinese–English large-data track. We show a significant improvement in translation quality on both tasks. 相似文献
997.
998.
Barrier options are financial derivative contracts that are activated or deactivated according to the crossing of specified
barriers by an underlying asset price. Exact models for pricing barrier options assume continuous monitoring of the underlying
dynamics, usually a stock price. Barrier options in traded markets, however, nearly always assume less frequent observation,
e.g. daily or weekly. These situations require approximate solutions to the pricing problem. We present a new approach to
pricing such discretely monitored barrier options that may be applied in many realistic situations. In particular, we study
daily monitored up-and-out call options of the European type with a single underlying stock. The approach is based on numerical
approximation of the transition probability density associated with the stochastic differential equation describing the stock
price dynamics, and provides accurate results in less than one second whenever a contract expires in a year or less. The flexibility
of the method permits more complex underlying dynamics than the Black and Scholes paradigm, and its relative simplicity renders
it quite easy to implement. 相似文献
999.
Gillian Allard 《AI & Society》2003,17(1):12-24
The power of some new entrants to the music industry derives from their position as brokers in computer-mediated environments.
Brokers act instrumentally to exploit their position within a network which, in turn, depends on their ability to build and
sustain links (and, in computer-mediated environments, hyperlinks). Bricolage in computer-mediated entrepreneurship refers
to the intuitive manipulation of resources in order to achieve (perhaps tacit) goals. Without careful stewardship of the new
intellectual wealth thus created, bricolage may profit neither the individual nor the wider community.
Accepted 14 March 2002 相似文献
1000.
自适应相干噪声衰减技术 总被引:6,自引:0,他引:6
去除噪声是必需的地震数据处理过程。由于地表条件和地震波激发、传播以及接收条件等诸多方面的原因,时常引起地震记录上出现各种相干干扰波。本文主要针对地震数据处理中地震剖面上存在的各种相干噪声,提出了时问一空间域自适应相干噪声衰减技术,以进行信噪分离。这种方法把噪声在整个处理平面上的视速度近似看作常量(正值或负值),可以有效地消除地震剖面上的线性噪声、面波以及多次波等,并且对信号的保真度高。本文方法是复杂地区低信噪比地震数据处理的一种理想的噪声去除方法,具有运算速度快、压制噪声效果好等优点。 相似文献