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  • Articles  (16)
  • Other Sources
  • PACS. 75.10.Jm Quantized spin models
  • controllability
  • Springer  (16)
  • American Geophysical Union
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  • American Meteorological Society
  • American Physical Society
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  • International Union of Crystallography (IUCr)
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  • 2000-2004  (12)
  • 1995-1999  (4)
  • 1945-1949
  • Physics  (11)
  • Electrical Engineering, Measurement and Control Technology  (5)
  • Natural Sciences in General
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  • Articles  (16)
  • Other Sources
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  • Springer  (16)
  • American Geophysical Union
  • American Institute of Physics (AIP)
  • American Meteorological Society
  • American Physical Society
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  • 2000-2004  (12)
  • 1995-1999  (4)
  • 1945-1949
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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    The European physical journal 31 (2003), S. 63-67 
    ISSN: 1434-6036
    Keywords: PACS. 75.10.Jm Quantized spin models
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: We investigate an extended spin ladder with diagonal frustrated exchanges in a wide parameter regime. By representing the model as a sum of semidefinite positive projection operators, we prove that this model has exactly a dimer ground state. Smoothly changing parameters may lead the model cover several exactly known models. Starting from this ladder model, we proposed two two-dimensional net models with exact ground states. The quantum phase transition of the ground state, due to the change of exchange strengths along perpendicular rungs, is also discussed.
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  • 2
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    Springer
    The European physical journal 31 (2003), S. 209-216 
    ISSN: 1434-6036
    Keywords: PACS. 75.10.Jm Quantized spin models
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: We investigate a large class of antiferromagnetic spin-1 chains with nearest neighbour interaction and exactly known matrix product ground state. The spectrum of low-lying excitations is calculated numerically by DMRG and exact diagonalisation. Spin liquid behaviour with an excitation gap is observed meeting the Haldane scenario. Further, we compare properties of the anisotropic model with the well-known isotropic AKLT model and use the analytical single mode approximation to obtain a quantitative understanding of the excitation gap. The low-lying excited states can be interpreted in terms of a magnon-like elementary excitation.
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  • 3
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    Springer
    The European physical journal 29 (2002), S. 15-18 
    ISSN: 1434-6036
    Keywords: PACS. 75.10.Jm Quantized spin models
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: We generalize the Shastry-Sutherland model to three dimensions. By representing the model as a sum of the semidefinite positive projection operators, we exactly prove that the model has exact dimer ground state. Several schemes for constructing the three-dimensional Shastry-Sutherland model are proposed.
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  • 4
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    Springer
    Journal of electronic testing 6 (1995), S. 179-190 
    ISSN: 1573-0727
    Keywords: behavioral testing ; feed-forward neural networks ; controllability ; observability ; neural error models
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: Abstract Testability analysis of neural architectures can be performed at a very high abstraction level on the computational paradigm. In this paper, we consider the case of feed-forward multi-layered neural networks. We introduce a behavioral error model which allows good mapping of the physical faults in widely different implementations. Conditions for error controllability, observability and global testability are analytically derived; their purpose is that of verifying whether it is possible to excite all modeled errors and to propagate the error's effects to the primary outputs (actual test vectors being then technological-dependent). Mapping of physical faults onto behavioral errors is performed for some representative, architectures.
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Applied mathematics and mechanics 17 (1996), S. 999-1008 
    ISSN: 1573-2754
    Keywords: fibre bundle ; controllability ; observability ; minimality
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Mathematics , Physics
    Notes: Abstract The definition of nonlinear control systems on fibre bundles proposed by Brockett and Willems is incomplete from the mathematical view. A new geometric framework is proposed and a minimal realization theory is developed for nonlinear control systems on fibre bundles which is elaborated as a natural generalization of Sussmann's theory and differs essentially from Van der Schaft's approach. Limitations of realization theory given by Van der Schaft are also discussed.
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  • 6
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    Applied mathematics and mechanics 24 (2003), S. 1063-1074 
    ISSN: 1573-2754
    Keywords: hybrid dynamic system ; switched linear system ; time-delay ; controllability ; controllable set ; switching sequence ; switching path ; TP13 ; TP273 ; O317 ; 93B05 ; 93B27 ; 93C99
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Mathematics , Physics
    Notes: Abstract The controllability for switched linear systems with time-delay in controls is first investigated. The whole work contains three parts. This is the third part. The definition and determination of controllability of switched linear systems with multiple time-delay in control functions is mainly investigated. The sufficient and necessary conditions for the one-periodic, multiple-periodic controllability of periodic-type systems and controllability of aperiodic systems are presented, respectively. Finally, the case of distinct delays is discussed, it is shown that the controllability is independent of the size of delays.
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  • 7
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    Springer
    Applied mathematics and mechanics 24 (2003), S. 1051-1062 
    ISSN: 1573-2754
    Keywords: hybrid dynamic system ; switched linear system ; time-delay ; controllability ; controllable set ; switching sequence ; switching path ; TP13 ; TP273 ; O317 ; 93B05 ; 93B27 ; 93C99
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Mathematics , Physics
    Notes: Abstract The controllability for switched linear systems with time-delay in controls is first investigated. The whole work contains three parts. This is the second part. The definition and determination of controllability of switched linear systems with single time-delay in control functions is mainly investigated. The sufficient and necessary conditions for the oneperiodic, multiple-periodic controllability of periodic-type systems and controllability of periodic systems are presented, respectively.
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  • 8
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    Electronic Resource
    Springer
    Journal of dynamical and control systems 6 (2000), S. 159-217 
    ISSN: 1573-8698
    Keywords: controllability ; right-invariant systems ; Lie groups ; solvable
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: Abstract Right-invariant control systems on simply connected solvable Lie groups are studied. A complete and explicit description of controllable single-input right-invariant systems on such Lie groups up to dimension 6 is obtained.
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  • 9
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    Journal of dynamical and control systems 6 (2000), S. 353-363 
    ISSN: 1573-8698
    Keywords: parabolic differential equation ; controllability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: Abstract This paper deals with the approximate controllability problem for a parabolic equation defined for $$x \in \mathbb{R},{\text{ }}t \in \;[0,T]$$ . It is possible to find a sequence of initial conditions with given compact support such that traces at $$x = 0$$ of corresponding solutions converge to the trace of a given solution. We obtain estimates of the rate of this convergence. These estimates are constructed in terms of eigenvalues of certain compact operator.
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  • 10
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    Springer
    Journal of dynamical and control systems 6 (2000), S. 453-459 
    ISSN: 1573-8698
    Keywords: solvable Lie algebras ; systems on Lie groups ; controllability ; maximal semigroups ; hyperplane subalgebras ; metabelian algebras
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: Abstract We call a Lie-algebra $$g$$ SID-controllable if there exist $$A,B \in g$$ such that the invariant control system on the simply connected group G given by $$\dot g = g(A\; + \;uB),\;\;u\;\; \in \;\;\mathbb{R}$$ , is controllable. This is tantamount to saying that the semigroup $$S(A, \pm B) = \langle \exp (\mathbb{R}^ + A + \mathbb{R}B)\rangle \subseteq G$$ is all of G. In his papers [4]–[7] Yu. Sachkov analyzed and characterized solvable SID-controllable Lie algebras. In this paper we improve his results by proving the following simple reduction criterion: a solvable Lie algebra $$g$$ is SID-controllable iff the factor-algebra $$g/D^2 g$$ is SID-controllable. For solvable $$g$$ this reduces the whole problem to metabelian algebras ( $$D^2 g = 0$$ ), a case which is completely solved in Sachkov's work. Our result also generalizes immediately to systems with multiple inputs.
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  • 11
    Electronic Resource
    Electronic Resource
    Springer
    The European physical journal 14 (2000), S. 495-508 
    ISSN: 1434-6036
    Keywords: PACS. 75.10.Jm Quantized spin models
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: An investigation of the spin excitation spectrum of charge ordered (CO) NaV2O5 is presented. We discuss several different exchange models which may be relevant for this compound, namely in-line and zig-zag chain models with weak as well as strong inter-chain coupling and also a ladder model and a CO/MV (mixed valent) model. We put special emphasis on the importance of large additional exchange across the diagonals of V-ladders and the presence of exchange anisotropies on the excitation spectrum. It is shown that the observed splitting of transverse dispersion branches may both be interpreted as anisotropy effect as well as acoustic-optic mode splitting in the weakly coupled chain models. In addition we calculate the field dependence of excitation modes in these models. Furthermore we show that for strong inter-chain coupling, as suggested by recent LDA + U results, an additional high energy optical excitation appears and the spin gap is determined by anisotropies. The most promising CO/MV model predicts a spin wave dispersion perpendicular to the chains which agrees very well with recent results obtained by inelastic neutron scattering.
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  • 12
    Electronic Resource
    Electronic Resource
    Springer
    The European physical journal 10 (1999), S. 731-738 
    ISSN: 1434-6036
    Keywords: PACS. 75.10.Jm Quantized spin models
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: We present a class of optimum ground states for quantum spin- models on the Cayley tree with coordination number 3. The interaction is restricted to nearest neighbours and contains 5 continuous parameters. For all values of these parameters the Hamiltonian has parity invariance, spin-flip invariance, and rotational symmetry in the xy-plane of spin space. The global ground states are constructed in terms of a 1-parametric vertex state model, which is a direct generalization of the well-known matrix product ground state approach. By using recursion relations and the transfer matrix technique we derive exact analytical expressions for local fluctuations and longitudinal and transversal two-point correlation functions.
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  • 13
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    Springer
    The European physical journal 14 (2000), S. 91-97 
    ISSN: 1434-6036
    Keywords: PACS. 75.10.Jm Quantized spin models
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: We study the spin ladder model with interactions between spins on neighboring rungs. The model Hamiltonian with the exact singlet ground state degenerated with ferromagnetic state is obtained. The singlet ground state wave function has a special recurrent form and depends on two parameters. Spin correlations in the singlet ground state show double-spiral structure with period of spirals equals to the system size. For special values of parameters they have exponential decay. The spectrum of the model is gapless and there are asymptotically degenerated excited states for special values of parameters in the thermodynamic limit.
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  • 14
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    Journal of electronic testing 13 (1998), S. 93-103 
    ISSN: 1573-0727
    Keywords: high-level test synthesis ; behavioral modification ; controllability ; observability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: Abstract In this study, we present a high-level testability analysis technique that evaluates the testability of a design based on the proposed controllability and observability measures. The control-data flow graph (CDFG) constructed from the VHDL description of a design is first analyzed to identify hard-to-control conditional branches and hard-to-control/observe register transfer statements. After the hard-to-test areas of the design are identified, the proposed testability enhancement methods can be applied to improve the testability of the circuit. Unlike many recent studies in the area of high-level test synthesis (HLTS) that focus on improving the testability of data paths, our approach also improves the testability of synthesized circuits by enhancing the controllability of the control flow. Experimental results on several high-level synthesis benchmarks show that when this approach is used prior to logic synthesis, the test generation complexities are reduced while better fault coverage and ATPG efficiency are often achieved. Implementation of this technique requires minimal logic and performance overheads and allows test vectors to be applied at clock-speed.
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  • 15
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    Electronic Resource
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    Applied mathematics and mechanics 24 (2003), S. 1041-1050 
    ISSN: 1573-2754
    Keywords: hybrid dynamic system ; switched linear system ; time-delay ; controllability ; generalized cyclic invariant subspace ; switching sequence ; switching path ; TP13 ; TP273 ; O317 ; 93B05 ; 93B27 ; 93C99
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Mathematics , Physics
    Notes: Abstract The controllability for switched linear system with time-delay in controls was first investigated. The whole work contains three parts. This is the first part, including problem formulation and some preliminaries. Firstly, the mathematical model of switched linear systems with time-delay in control functions was presented. Secondly, the concept of column space, cyclic invariant subspace and generalized cyclic invariant subspace were introduced. And some basic properties, such as separation lemma, were presented. Finally, a basic lemma was given to reveal the relation between the solution set of a centain integral equations and the generalized cyclic invariant subspace. This lemma will play an important role in the determination of controllability. All these definitions and lemmas are necessary research tools for controllability analysis.
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  • 16
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    Springer
    Applied mathematics and mechanics 21 (2000), S. 1320-1330 
    ISSN: 1573-2754
    Keywords: nonlinear control system ; controllability ; oriented manifold ; invariant manifold ; dynamics of rigid body ; O231
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Mathematics , Physics
    Notes: Abstract The problem of controllability of nonlinear control system is a significant field which has an extensive prospect of application. A. M. Kovalev of Ukraine Academy of Science applied the oriented manifold method developed in dynamics of rigid body to nonlinear control system for the first time and obtained a series of efficient results. Based on Kovalev's oriented manifold method, firstly, by invariant manifold method the problem of controllability of nonlinear control system was studied and the necessary condition of the controllability of a kind of affine nonlinear system was given out. Then the realization of the necessary condition was discussed. At last, the motion of a rigid body with two rotors was investigated and the necessary condition which is satisfied by this system was proved.
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