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71.
72.
分数阶微积分有3种常用的定义:Grunwald-Letnikov定义、Riemann-Liouville定义以及Caputo定义,3种定义之间存在着一定的联系,在一定条件下,它们可以相互转换。首先在高阶逻辑定理证明器HOL4中使用实数、积分、极限、超越函数等定理建立了基于Caputo定义的分数阶微积分形式化模型;然后验证了该定义与Grunwald-Letni-kov定义、Riemann-Liouville定义之间的关系,实现了这3种常用定义在HOL4中的转换,在一定程度上使这3种定义达到了统一,完善了高阶逻辑定理库。 相似文献
73.
Behrooz Safarinejadian Mojtaba Asad Mokhtar Sha Sadeghi 《International journal of control》2016,89(11):2277-2296
In the present paper, the identification and estimation problem of a single-input–single-output (SISO) fractional order state-space system will be addressed. A SISO state-space model is considered in which parameters and also state variables should be estimated. The canonical fractional order state-space system will be transformed into a regression equation by using a linear transformation and a shift operator that are appropriate for identification. The identification method provided in this paper is based on a recursive identification algorithm that has the capability of identifying the parameters of fractional order state-space system recursively. Another subject that will be addressed in this paper is a novel fractional order Kalman filter suitable for the systems with coloured measurement noise. The promising performance of the proposed methods is verified using two stable fractional order systems. 相似文献
74.
There is an open discussion between those who defend mass-distributed models for humanoid robots and those in favor of simple concentrated models. Even though each of them has its advantages and disadvantages, little research has been conducted analyzing the control performance due to the mismatch between the model and the real robot, and how the simplifications affect the controller’s output. In this article we address this problem by combining a reduced model of the humanoid robot, which has an easier mathematical formulation and implementation, with a fractional order controller, which is robust to changes in the model parameters. This controller is a generalization of the well-known proportional–integral–derivative (PID) structure obtained from the application of Fractional Calculus for control, as will be discussed in this article. This control strategy guarantees the robustness of the system, minimizing the effects from the assumption that the robot has a simple mass distribution. The humanoid robot is modeled and identified as a triple inverted pendulum and, using a gain scheduling strategy, the performances of a classical PID controller and a fractional order PID controller are compared, tuning the controller parameters with a genetic algorithm. 相似文献
75.
Fractional advection–dispersion equation (FADE) is a generalization of the classical ADE in which the first order time derivative and first and second order space derivatives are replaced by Caputo derivatives of orders 0<α?1, 0<β?1 and 1<γ?2, respectively. We use Caputo definition to avoid (i) mass balance error, (ii) hyper-singular improper integral, (iii) non-zero derivative of constant, and (iv) fractional derivative involved in the initial condition which is often ill-defined. We present an analytic algorithm to solve FADE based on homotopy analysis method (HAM) which has the advantage of controlling the region and rate of convergence of the solution series via the auxiliary parameter ? over the variational iteration method (VIM) and homotopy perturbation method (HPM). We find that the proposed method converges to the numerical/exact solution of the ADE as the fractional orders α, β, γ tend to their integral values. Numerical examples are given to illustrate the proposed algorithm. Example 5 describes the intermediate process between advection and dispersion via Caputo fractional derivative. 相似文献
76.
The California sage scrub (CSS) community type in California's Mediterranean-type ecosystems is known for its high biodiversity and is home to a large number of rare, threatened, and endangered species. Because of extensive urban development in the past fifty years, this ecologically significant community type is highly degraded and fragmented. To conserve endangered CSS communities, monitoring internal conditions of communities is as crucial as monitoring distributions of the community type in the region. Vegetation type mapping and field sampling of individual plants provide ecologically meaningful information about CSS communities such as spatial distribution and species compositions, respectively. However, both approaches only provide spatially comprehensive information but no information about internal conditions or vice versa. Therefore, there is a need for monitoring variables which fill the information gap between vegetation type maps and field-based data. A number of field-based studies indicate that life-form fractional cover is an effective indicator of CSS community health and habitat quality for CSS-obligated species. This study investigates the effectiveness of remote sensing approaches for estimating fractional cover of true shrub, subshrub, herb, and bare ground in CSS communities of southern California. Combinations of four types of multispectral imagery ranging from 0.15 m resolution scanned color infrared aerial photography to 10 m resolution SPOT 5 multispectral imagery and three image processing models - per-pixel, object-based, and spectral mixture models - were tested.An object-based image analysis (OBIA) routine consistently yielded higher accuracy than other image processing methods for estimating all cover types. Life-form cover was reliably predicted, with error magnitudes as low as 2%. Subshrub and herb cover types required finer spatial resolution imagery for more accurate predictions than true shrub and bare ground types. Positioning of sampling grids had a substantial impact on the reliability of accuracy assessment, particularly for cover estimates predicted using multiple endmember spectral mixture analysis (MESMA) applied to SPOT imagery. Of the approaches tested in this study, OBIA using pansharpened QuickBird imagery is one of the most promising approaches because of its high accuracy and processing efficiency and should be tested for more heterogeneous CSS landscapes. MESMA applied to SPOT imagery should also be examined for effectiveness in estimating factional cover over more extensive habitat areas because of its low data cost and potential for conducting retrospective studies of vegetation community conditions. 相似文献
77.
Quality of service (QoS) provisioning in wireless mesh networks (WMNs) is an open issue to support emerging multimedia services. In this paper, we study the problem of QoS provisioning in terms of end-to-end bandwidth allocation in WMNs. It is challenging due to interferences in the networks. We consider widely used interference models and show that except a few special cases, the problem of finding a feasible path is NP-complete under the models. We propose a k-shortest path based algorithmic framework to solve this problem. We also consider the problem of optimizing network performance by on-line dynamic routing, and adapt commonly used conventional QoS routing metrics to be used in WMNs. We find the optimal solutions for these problems through formulating them as optimization models. A model is developed to check the existence of a feasible path and another to find the optimal path for a demand; moreover, an on-line optimal QoS routing algorithm is developed. Comparing the algorithms implemented by the proposed framework with the optimization models shows that our solution can find existing feasible paths with high probability, efficiently optimizes path lengths, and has a comparable performance to the optimal QoS routing algorithm. Furthermore, our results show that contrary to wireline networks, minimizing resource consumption should be preferred over load distribution even in lightly loaded WMNs. 相似文献
78.
A discrete-time control problem of a finite-state hidden Markov chain partially observed in a fractional Gaussian process is discussed using filtering. The control problem is then recast as a separated problem with information variables given by the unnormalized conditional probabilities of the whole path of the hidden Markov chain. A dynamic programming result and a minimum principle are obtained. 相似文献
79.
We study the classical Bandwidth problem from the viewpoint of parametrised algorithms. Given a graph G=(V,E) and a positive integer k, the Bandwidth problem asks whether there exists a bijective function β:{1,…,∣V∣}→V such that for every edge uv∈E, ∣β−1(u)−β−1(v)∣≤k. It is known that under standard complexity assumptions, no algorithm for Bandwidth with running time of the form f(k)nO(1) exists, even when the input is restricted to trees. We initiate the search for classes of graphs where such algorithms do exist. We present an algorithm with running time n⋅2O(klogk) for Bandwidth on AT-free graphs, a well-studied graph class that contains interval, permutation, and cocomparability graphs. Our result is the first non-trivial algorithm that shows fixed-parameter tractability of Bandwidth on a graph class on which the problem remains NP-complete. 相似文献
80.
The problem of channel sharing by rate adaptive streams belonging to various classes is considered. Rate adaptation provides
the opportunity for accepting more connections by adapting the bandwidth of connections that are already in the system. However,
bandwidth adaptation must be employed in a careful manner in order to ensure that (a) bandwidth is allocated to various classes
in a fair manner (system perspective) and (b) bandwidth adaptation does not affect adversely the perceived user quality of
the connection (user quality). The system perspective aspect has been studied earlier. This paper focuses on the equally important
user perspective. It is proposed to quantify user Quality of Service (QoS) through measures capturing short and long-term
bandwidth fluctuations that can be implemented with the mechanisms of traffic regulators, widely used in networking for the
purpose of controlling the traffic entering or exiting a network node. Furthermore, it is indicated how to integrate the user
perspective metrics with the optimal algorithms for system performance metrics developed earlier by the authors. Simulation
results illustrate the effectiveness of the proposed framework.
Nikos G. Argiriou received the Diploma degree in Electrical Engineering from the Department of Electrical Engineering, Telecommunication Division, Aristotle University of Thessaloniki, Greece, in 1996. He worked as a researcher, on secure medical image transmission over networks, at the Image Processing Lab at the same university during 1996–1997. During 1998–2000 he was a researcher for the European Project Esprit Catserver concerning the use of advanced Quality of Service techniques in CATV networks. He received his Ph.D. degree at Aristotle University of Thessaloniki in 2007. His current research interests are in the development and implementation of QoS techniques for wired and wireless networks. Leonidas Georgiadis received the Diploma degree in Electrical Engineering from Aristotle University, Thessaloniki, Greece, in 1979, and his M.S. and Ph.D degrees both in Electrical Engineering from the University of Connecticut, in 1981 and 1986, respectively. From 1986 to 1987 he was Research Assistant Professor at the University of Virginia, Charlottesville. In 1987 he joined IBM T. J. Watson Research Center, Yorktown Heights as a Research Staff Member. Since October 1995, he has been with the Telecommunications Department of Aristotle University, Thessaloniki, Greece. His interests are in the area of wireless networks, high speed networks, routing, scheduling, congestion control, modeling and performance analysis. 相似文献
Leonidas GeorgiadisEmail: |
Nikos G. Argiriou received the Diploma degree in Electrical Engineering from the Department of Electrical Engineering, Telecommunication Division, Aristotle University of Thessaloniki, Greece, in 1996. He worked as a researcher, on secure medical image transmission over networks, at the Image Processing Lab at the same university during 1996–1997. During 1998–2000 he was a researcher for the European Project Esprit Catserver concerning the use of advanced Quality of Service techniques in CATV networks. He received his Ph.D. degree at Aristotle University of Thessaloniki in 2007. His current research interests are in the development and implementation of QoS techniques for wired and wireless networks. Leonidas Georgiadis received the Diploma degree in Electrical Engineering from Aristotle University, Thessaloniki, Greece, in 1979, and his M.S. and Ph.D degrees both in Electrical Engineering from the University of Connecticut, in 1981 and 1986, respectively. From 1986 to 1987 he was Research Assistant Professor at the University of Virginia, Charlottesville. In 1987 he joined IBM T. J. Watson Research Center, Yorktown Heights as a Research Staff Member. Since October 1995, he has been with the Telecommunications Department of Aristotle University, Thessaloniki, Greece. His interests are in the area of wireless networks, high speed networks, routing, scheduling, congestion control, modeling and performance analysis. 相似文献