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Li Jing Li Pei Qian Zhou Xudong Hu Song Gao Chunhui Qi Xiaodong Wen Nan Jia 《Optics Communications》2011,284(13):3428-3432
This paper investigates two key techniques used in 60 GHz Radio over Fiber (RoF) technology for wireless access, namely, the generation of 60 GHz signals and the distribution of 60 GHz local oscillator (LO). In the proposed model, a 60 GHz PSK signal is generated by a heterodyne of two subcarriers with narrow-angle PSK (NA-PSK) modulation, whose phase shift is equal to one half that of a normal PSK signal. Then we use a 60 GHz mixer to frequency mix two PSK signals in two different bands, 60 GHz and baseband. By doing this, the modulation information can be fully eliminated, resulting in a 60 GHz LO. In the wireless terminal, coherent demodulation is realized by a self-mixing of the transmitted 60 GHz PSK signal and LO. Thus no millimeter-wave (mm-wave) band oscillator is needed in the wireless terminal. 相似文献
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Human movement reveals the hall mark characteristics of complex systems: namely, many interacting subsystems, multiple interactions within and between levels of analysis, emergence of movement coordination modes, and the exhibition of varying levels of the complexity of system output that continually evolve with learning and development over the life span. Here we outline how this high or infinitely dimensional complex dynamical system can be modeled by an epigenetic landscape framework—in the sense of Waddington—that captures the key features of the adaptive qualitative and quantitative properties of coordination modes (“order parameters”), the degeneracy of movement organization and the time scales of change. The framework provides some new ways to consider old problems in motor learning and development—such as an explicit and quantitative approach to exploring the concept of motor programs and developmental pathways—and yields new results and insights into the organization of learning during practice and rest times. For instance along one dimension of the landscape most of the changes occur between practice sessions. © 2006 Wiley Periodicals, Inc. Complexity 12: 40–51, 2006 相似文献
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Guisheng Zhai Xuping Xu Hai Lin Anthony N. Michel 《Nonlinear Analysis: Theory, Methods & Applications》2006
In this paper, we study the stability property for a class of switched linear systems whose subsystems are normal. The subsystems can be continuous-time or discrete-time ones. We show that when all the continuous-time subsystems are Hurwitz stable and all the discrete-time subsystems are Schur stable, a common quadratic Lyapunov function exists for the subsystems and thus the switched system is exponentially stable under arbitrary switching. We show that when unstable subsystems are involved, for a desired decay rate of the system, if the activation time ratio between stable subsystems and unstable ones is less than a certain value (calculated using the decay rate), then the switched system is exponentially stable with the desired decay rate. 相似文献
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P. M. FRANK E. ALCORTA GARCIA B. KÖPPEN-SELIGER 《Mathematical and Computer Modelling of Dynamical Systems: Methods, Tools and Applications in Engineering and Related Sciences》2013,19(1):1-17
The main purpose of this paper is to emphasize the particularities of models needed for model-based fault detection and isolation (FDI) in contrast to the models used for control. Of special interest is the question of complexity of the model, which is of great importance for the practical implementation. This, of course, depends basically on the given situation such as the kind of plant, the measurements, the kind and number of faults to be detected and the demands for fault isolation and robustness. However, the paper shows that diagnostic models, in contrast to the wide-spread opinion that those have always to be more complex than the functional models for control, may be even less complex, because they are restricted to only those parts of the system in which the faults occur. The issue of model complexity is discussed in terms of different model-based FDI approaches analytical, knowledge-based and data-based. The ideas are illustrated in a case study, where several types of model-based FDI techniques are compared with the same plant, the amira three tank system. 相似文献
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Farnaz Heidar Zadeh Shant Shahbazian 《International journal of quantum chemistry》2011,111(9):1999-2013
This contribution deals with the subsystem variational procedure within the context of the quantum theory of atoms in positronic molecules (QTAIPM). Before introducing the subsystem energy functional termed as joint subsystem energy functional, a novel notation and the combination strategy are disclosed in detail by restating the positronic subsystem hypervirial theorem. They are employed in proposing the proper subsystem energy functional, the validity of which is checked by various criteria. The zero flux surfaces of the joint density distribution are used to define the topological atoms in the positronic molecules, and they are incorporated into the subsystem variational procedure as proper real space boundary conditions. The variational procedure finally yields the flux of the joint current property density that also appears in the positronic subsystem hypervirial theorem. At every stage, the corresponding equations for the purely electronic systems within the context of the quantum theory of atoms in molecules (QTAIM) are presented to clearly reveal the analogy between these two formalisms and to emphasize the importance of combining the property density distributions in the QTAIPM. The presented material demonstrates the internal consistency of the whole framework and discloses the fact that the QTAIM must be regarded as a variant of the QTAIPM. Furthermore, this formalism promises an extended QTAIM, which is hoped to resolve the issue of molecular structure beyond the clamp nuclei approximation. © 2010 Wiley Periodicals, Inc. Int J Quantum Chem, 2011 相似文献
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Katica Hedrih 《Nonlinear dynamics》2008,51(1-2):127-140
Energy transfer between subsystems coupled by standard light hereditary element in hybrid system is very important for different
engineering applications, especially for dynamical absorption. An analytical study of the energy transfer between coupled
linear and nonlinear oscillators in the free vibrations of a viscoelastically connected double-oscillator system as a new
hybrid nonlinear system with two and half degrees of freedom is pointed out. The analytical study shows that the viscoelastic–hereditary
connection between oscillators causes the appearance of like two-frequency regimes of subsystem's vibrations and that the
energy transfer between subsystems appears.
The Lyapunov exponents corresponding to each of two eigenmodes of the hybrid system, as well as to the subsystems are obtained
and expressed by using energy of the corresponding eigentime components. The Lyapunov exponents are measures of the vibration
processes stability in the hybrid system and in component subsystem vibrations.
In Honor of Giuseppe Rega and Fabrizio Vestroni on the Occasion of their 60th Birthday. 相似文献
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Sebastiano Carpi 《Letters in Mathematical Physics》1998,45(3):259-267
We show that if A is the Haag–Kastler net generated by the energy-momentum tensor in a chiral quantum field theory, then every subsystem B A which is covariant under the action of SL(2,R given on A must coincide with A. The result is valid for all the allowed values of the central charge and is obtained using scaling limit techniques. 相似文献
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Let
be the Haag--Kastler net generated by the
(2) chiral current algebra at level 1. We classify the SL(2,
)-covariant subsystems
by showing that they are all fixed points nets
H
for some subgroup H of the gauge automorphisms group SO(3) of
. Then, using the fact that the net
1 generated by the
(1) chiral current can be regarded as a subsystem of
, we classify the subsystems of
1. In this case, there are two distinct proper subsystems: the one generated by the energy-momentum tensor and the gauge invariant subsystem
. 相似文献