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961.
Xiaoyu Wang Wen Wang Yong Huang Nhan Nguyen Kalmanje Krishnakumar 《Journal of Intelligent Manufacturing》2008,19(4):383-396
Hard turning with cubic boron nitride (CBN) tools has been proven to be more effective and efficient than traditional grinding
operations in machining hardened steels. However, rapid tool wear is still one of the major hurdles affecting the wide implementation
of hard turning in industry. Better prediction of the CBN tool wear progression helps to optimize cutting conditions and/or
tool geometry to reduce tool wear, which further helps to make hard turning a viable technology. The objective of this study
is to design a novel but simple neural network-based generalized optimal estimator for CBN tool wear prediction in hard turning.
The proposed estimator is based on a fully forward connected neural network with cutting conditions and machining time as
the inputs and tool flank wear as the output. Extended Kalman filter algorithm is utilized as the network training algorithm
to speed up the learning convergence. Network neuron connection is optimized using a destructive optimization algorithm. Besides
performance comparisons with the CBN tool wear measurements in hard turning, the proposed tool wear estimator is also evaluated
against a multilayer perceptron neural network modeling approach and/or an analytical modeling approach, and it has been proven
to be faster, more accurate, and more robust. Although this neural network-based estimator is designed for CBN tool wear modeling
in this study, it is expected to be applicable to other tool wear modeling applications. 相似文献
962.
ZhiMing Zheng ShiLong Ma Wei Li Wei Wei Xin Jiang ZhanLi Zhang BingHui Guo 《中国科学F辑(英文版)》2009,52(8):1328-1334
Developing trusted softwares has become an important trend and a natural choice in the development of software technology
and applications, and software trustworthiness modeling has become a prerequisite and necessary means. To discuss and explain
the basic scientific problems in software trustworthiness and to establish theoretical foundations for software trustworthiness
measurement, combining the ideas of dynamical system study, this paper studies evolutionary laws of software trustworthiness
and the dynamical mechanism under the effect of various internal and external factors, and proposes dynamical models for software
trustworthiness, thus, software trustworthiness can be considered as the statistical characteristics of behaviors of software
systems in the dynamical and open environment. By analyzing two simple examples, the paper explains the relationship between
the limit evolutionary behaviors of software trustworthiness attributes and dynamical system characteristics, and interprets
the dynamical characteristics of software trustworthiness and their evolutionary complexity.
Supported partially by the National Basic Research Program of China (Grant No. 2005CB321900) and the National Natural Science
Foundation of China (Grant No. 60473091) 相似文献
963.
Sampled-data based average consensus with measurement noises: convergence analysis and uncertainty principle 总被引:1,自引:0,他引:1
In this paper, sampled-data based average-consensus control is considered for networks consisting of continuous-time first-order
integrator agents in a noisy distributed communication environment. The impact of the sampling size and the number of network
nodes on the system performances is analyzed. The control input of each agent can only use information measured at the sampling
instants from its neighborhood rather than the complete continuous process, and the measurements of its neighbors’ states
are corrupted by random noises. By probability limit theory and the property of graph Laplacian matrix, it is shown that for
a connected network, the static mean square error between the individual state and the average of the initial states of all
agents can be made arbitrarily small, provided the sampling size is sufficiently small. Furthermore, by properly choosing
the consensus gains, almost sure consensus can be achieved. It is worth pointing out that an uncertainty principle of Gaussian
networks is obtained, which implies that in the case of white Gaussian noises, no matter what the sampling size is, the product
of the steady-state and transient performance indices is always equal to or larger than a constant depending on the noise
intensity, network topology and the number of network nodes. 相似文献
964.
Recently, international academic circles advanced a class of new stochastic control models of a geometric Brownian motion
which is an important kind of impulse control models whose cost structure is different from the others before, and it has
a broad applying background and important theoretical significance in financial control and management of investment. This
paper generalizes substantially the above stochastic control models under quite extensive conditions and describes the models
more exactly under more normal theoretical system of stochastic process. By establishing a set of proper variational equations
and proving the existence of its solution, and applying the means of stochastic analysis, this paper proves that the generalized
stochastic control models have optimal controls. Meanwhile, we also analyze the structure of optimal controls carefully. Besides,
we study the solution function of variational equations in a relatively deep-going way, which constitutes the value function
of control models to some extent. Because the analysis methods of this paper are greatly different from those of original
reference, this paper possesses considerable originality to some extent. In addition, this paper gives the strict proof to
the part of original reference which is not fairly well-knit in analyses, and makes analyses and discussions of the model
have the exactitude of mathematical sense.
Supported by the National Natural Science Foundation of China (Grant No. 19671004) 相似文献
965.
This paper reports on recent results in a series of the work of the authors on the stability and nonlinear control for general
dynamical systems described by retarded functional differential and difference equations. Both internal and external stability
properties are studied. The corresponding Lyapunov and Razuminkhin characterizations for input-to-state and input-to-output
stabilities are proposed. Necessary and sufficient Lyapunov-like conditions are derived for robust nonlinear stabilization.
In particular, an explicit controller design procedure is developed for a new class of nonlinear time-delay systems. Lastly,
sufficient assumptions, including a small-gain condition, are presented for guaranteeing the input-to-output stability of
coupled systems comprised of retarded functional differential and difference equations. 相似文献
966.
With its advantages in wirelength reduction and routing flexibility compared with conventional Manhattan routing, X architecture
has been proposed and applied to modern IC design. As a critical part in high-performance integrated circuits, clock network
design meets great challenges due to feature size decrease and clock frequency increase. In order to eliminate the delay and
attenuation of clock signal introduced by the vias, and to make it more tolerant to process variations, in this paper, we
propose an algorithm of a single layer zero skew clock routing in X architecture (called Planar-CRX). Our Planar-CRX method
integrates the extended deferred-merge embedding algorithm (DME-X, which extends the DME algorithm to X architecture) with
modified Ohtsuki’s line-search algorithm to minimize the total wirelength and the bends. Compared with planar clock routing
in the Manhattan plane, our method achieves a reduction of 6.81% in total wirelength on average and gets the resultant clock
tree with fewer bends. Experimental results also indicate that our solution can be comparable with previous non-planar zero
skew clock routing algorithm.
Supported in part by the National Natural Science Foundation of China (Grant No. 60876026), and the Specialized Research Fund
for the Doctoral Program of Higher Education (Crant No. 200800030026) 相似文献
967.
Spirals are curves with one-signed, monotone increasing or decreasing curvature. They are commonly useful in a variety of applications, either for aesthetic or for engineering requirements. In this paper we propose a new iterative subdivision scheme for generating planar spiral segments from two points and their tangent vectors. The subdivision process consists of two main steps, computing new points and adjusting tangent vectors adaptively for each iteration. We categorize this iterative scheme as geometry... 相似文献
968.
High fidelity repeater false-target badly affects a radar system’s detecting, tracking, and data processing. It is an available approach of confronting false-target for radar that discriminates firstly and then eliminates. Whereas for the technique progress about the repeater false-target jam, it is more and more difficult to discriminate this jam in the time-domain, frequency-domain, or space-domain. The technique using polarization information to discriminate the target and false-target is discussed in th... 相似文献
969.
This paper investigates the controllability of multi-agent systems based on agreement protocols. First, for a group of single-integrator
agents, the controllability is studied in a unified framework for both networks with leader-following structure and networks
with undirected graph. Some new necessary/sufficient conditions for the controllability of networks of single-integrator agents
are established. Second, we prove that, under the same topology and same prescribed leaders, a network of high-order dynamic
agents is completely controllable if and only if so is a network of single-integrator agents. Third, how the selection of
leaders and the coupling weights of graphs affect the controllability is analyzed. Finally, some numerical simulations are
presented to demonstrate the effectiveness of the theoretical results. 相似文献
970.
A new patch-based texture synthesis method is presented in this paper. By the method, a set of patches that can be matched
with a sampled patch for growing textures effectively, called the matching compatibility between patches, is generated first
for each patch, and the set is further optimized by culling the patches that may cause synthesis conflicts. In this way, similarity
measurement calculation for selecting suitable patches in texture synthesis can be greatly saved, and synthesis conflicts
between neighbouring patches are substantially reduced. Furthermore, retrace computation is integrated in the synthesis process
to improve the texture quality. As a result, the new method can produce high quality textures as texture optimization, the
best method to date for producing good textures, and run in a time complexity linear to the size of the output texture. Experimental
results show that the new method can interactively generate a large texture in 1024 × 1024 pixels, which is very difficult
to achieve by existing methods.
Supported by the National Basic Research Program of China (Grant No. 2009CB320802), the National Natural Science Foundation
of China (Grant Nos. 60773026, 60833007), the National High-Tech Research & Development Program of China (Grant Nos. 2006AA01Z306,
2008AA01Z301), and the Research Grant of University of Macau 相似文献