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  • Articles  (2,915)
  • Springer  (2,915)
  • National Academy of Sciences
  • 1995-1999  (1,833)
  • 1975-1979  (1,082)
  • 1999  (1,833)
  • 1978  (1,082)
  • Electrical Engineering, Measurement and Control Technology  (2,915)
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  • Articles  (2,915)
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Publisher
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  • 1995-1999  (1,833)
  • 1975-1979  (1,082)
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  • 1
    Electronic Resource
    Electronic Resource
    Stress wave propagation when the elastic coefficients vary with depth (1999)
    Springer
    Circuits, systems and signal processing 18 (1999), S. 27-42 
    Details
    ISSN: 1531-5878
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: Abstract Of concern is the propagation of distortionless surface waves in a medium that may be nonuniform relative to depth. Distortionless wave propagation in inhomogeneous media was discussed by V. Burke, R. J. Duffin and D. Hazony, inQuart. Appl. Math., 183–194 (1976). Accordingly, the media could be modeled by a distributed electrical ladder network, nonuniform along the axis. We give a two-dimensional development based on Hooke's law and Newton's law which leads to the well-known case of Rayleigh waves in homogeneous media. It will be seen that the available pool of propagation modes greatly increases when high-pass propagation is included. The emphasis is on media where the elastic coefficients track one another as a function of depth. Special cases are studied in detail showing that as a disturbance travels along the surface, it may assume a broadband phase change, which translates into a shape distortion in the time domain, which is periodic with distance. Applications may be found in acousto-optics, in situ monitoring of elongated bodies, high-frequency SAW filters, microstrips, and any situations where surface waves are used in an environment of high precision or relatively large distances.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01206543
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  • 2
    Electronic Resource
    Electronic Resource
    Linear stabilizing controllers for electrically driven flexible-joint robots with uncertain parameters (1999)
    Springer
    Circuits, systems and signal processing 18 (1999), S. 131-147 
    Details
    ISSN: 1531-5878
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: Abstract This study presents a linear output-based controller for stabilizing a rigid-link flexible-joint electrically driven (RLFJED) robot manipulator. The proposed controller ensures local exponential stability under some uncertainty conditions. It is assumed that the velocity signals from the link side are not measurable. The controller is analyzed by using tools for pole placement by an output-feedback in the framework of the linear system theory. Some useful structural properties of the systems under consideration have been studied. Applications of the results to the set-point regulation control problem are considered.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01206679
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  • 3
    Electronic Resource
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    Optimality of a direct adaptive controller in the presence of model mismatch and bounded disturbances (1999)
    Springer
    Circuits, systems and signal processing 18 (1999), S. 205-223 
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    ISSN: 1531-5878
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: Abstract In this paper we consider an adaptive controller with vanishing gain and excitation of the reference signal. We use the burst recovery concept to show that all signals in the adaptive loop remain uniformly bounded. We also show that the mean-square performance converges so that the adaptive system is optimal in the sense that the parameter estimation error and the one-step ahead prediction error are uncorrelated in the mean despite the presence of the unmodeled dynamics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01225695
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  • 4
    Electronic Resource
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    Cycloid decompositions of finite Markov chains (1999)
    Springer
    Circuits, systems and signal processing 18 (1999), S. 191-204 
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    ISSN: 1531-5878
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: Abstract Finite homogeneous Markov chains ξ, which admit invariant probability distributions, can be defined by the cycloids { $$\bar C_k $$ } (closed polygonal lines whose consecutive edges have various orientations that do not necessarily determine a common direction for $$\bar C_k $$ ) occurring in their graphs. These Markov chains are called cycloid chains, and the corresponding finite-dimensional distributions are linear expressions on the cycloids { $$\bar C_k $$ } with the real coefficients αk. Then the collection {{ $$\bar C_k $$ }, {αk}}, called the cycloid decomposition of ξ, gives a minimal description of the finite-dimensional distributions that, except for a choice of the maximal tree, uniquely determines the chain ξ. Furthermore, the cycloid decompositions have an interpretation in terms of the transition probability functions expressing the same essence as the known Chapman-Kolmogorov equations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01225694
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  • 5
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    Linear systems in a saturated mode and convergence as gain becomes large of asymptotically stable equilibrium points of neural nets (1999)
    Springer
    Circuits, systems and signal processing 18 (1999), S. 241-267 
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    ISSN: 1531-5878
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: Abstract We study solutions of the “linear system in a saturated mode” $$\begin{array}{*{20}c} {(M)} & {x' \in Tx + c - \partial I_{D^n } x.} \\ \end{array} $$ We show that a trajectory is in a constant face of the cubeD n on some interval (0,d]. We answer a question about comparing the two systems: (M) and $$\begin{array}{*{20}c} {(H)} & {\begin{array}{*{20}c} {Cu' = T\upsilon + c - R^{ - 1} u,} & {\upsilon = G(\lambda } \\ \end{array} u)} \\ \end{array} $$ . As λ→∞, limits ofv corresponding to asymptotically stable equilibrium points of (H) are asymptotically stable equilibrium points of (M), and the converse is also true. We study the assumptions to see which are required and which may be weakened.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01225697
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  • 6
    Electronic Resource
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    A numerical algorithm for the diffusion equation using 3D FEM and the Arnoldi method (1999)
    Springer
    Circuits, systems and signal processing 18 (1999), S. 291-314 
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    ISSN: 1531-5878
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: Abstract In this paper we introduce a new computational method for solving the diffusion equation. In particular, we construct a “generalized” state-space system and compute the impulse response of an equivalent truncated state-space system. In this effort, we use a 3D finite element method (FEM) to obtain the state-space system. We then use the Arnoldi iteration to approximate the state impulse response by projecting on the dominant controllable subspace. The idea exploited here is the approximation of the impulse response of the linear system. We study the homogeneous and heterogeneous cases and discuss the approximation error. Finally, we compare our computational results to our experimental setup.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01225699
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  • 7
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    On singular nonlinearH ∞ control: A state-space approach (1999)
    Springer
    Circuits, systems and signal processing 18 (1999), S. 351-364 
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    ISSN: 1531-5878
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: Abstract A simple state-space approach for the four-block singular nonlinearH ∞ control problem is proposed in this paper. This approach combines a (J, J′)-lossless and a class of conjugate (J, J′)-expansive systems to yield a family of nonlinearH ∞ output feedback controllers. The singular nonlinearH ∞ control problem is thus transformed into a simple lossless network problem that is easy to deal with in a network-theory context.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01200787
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  • 8
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    Stabilization of Subba Rao-Liporace models (1999)
    Springer
    Circuits, systems and signal processing 18 (1999), S. 395-406 
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    ISSN: 1531-5878
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: Abstract The stability of time-varying autoregressive (TVAR) models is an important issue in many applications such as time-varying spectral estimation, EEG simulation and analysis, and time-varying linear prediction coding (TVLPC). For stationary AR models there are methods that guarantee stability, but the for nonadaptive time-varying approaches there are no such methods. On the other hand, in some situations, such as in EEG analysis, the models that temporarily exhibit roots with almost unit moduli are difficult to use. Thus we may need a tighter stability condition such as stability with margin 1−ϱ. In this paper we propose a method for the estimation of TVAR models that guarantees stability with margin 1−ϱ, that is, the moduli of the roots of the time-varying characteristic polynomial are less than or equal to some arbitrary positive number ϱ for every time instant. The model class is the Subba Rao-Liporace class, in which the time-varying coefficients are constrained to a subspace of the coefficient time evolutions. The method is based on sequential linearization of the associated nonlinear constraints and the subsequent use of a Gauss-Newton-type algorithm. The method is also applied to a simulated autoregressive process.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01200790
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  • 9
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    Call for papers (1999)
    Springer
    Circuits, systems and signal processing 18 (1999), S. 443-443 
    Details
    ISSN: 1531-5878
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01200793
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  • 10
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    Minimax controller design using rate feedback (1999)
    Springer
    Circuits, systems and signal processing 18 (1999), S. 17-25 
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    ISSN: 1531-5878
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: Abstract A complete analytic characterization and solution construction (done either explicitly or by recursion) for the minimax control problem using optimal rate feedback is given for the case when the plant consists of a known fixed set of coupled oscillators of cardinality not exceeding three. When this is not the case, the problem appears to be analytically intractable, and suboptimal solutions based on numerical techniques are currently the only recourse.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01206542
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  • 11
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    Constructing analytical energy functions for lossless network-reduction power system models: Framework and new developments (1999)
    Springer
    Circuits, systems and signal processing 18 (1999), S. 1-16 
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    ISSN: 1531-5878
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: Abstract The task of constructing an energy function is essential for direct stability analysis of electric power systems. This paper presents a general procedure for constructing analytical energy functions for detailed lossless network-reduction power system stability models. This paper primarily (i) develops canonical representations for lossless networkreduction power system models and shows that such canonical representations cover existing stability models, (ii) derives theoretical results regarding the existence of analytical energy functions for the canonical representations, and (iii) presents a systematic procedure to construct corresponding energy functions.
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    URL: http://dx.doi.org/10.1007/BF01206541
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  • 12
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    Finding all the DC solutions of a certain class of piecewise-linear circuits (1999)
    Springer
    Circuits, systems and signal processing 18 (1999), S. 89-110 
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    ISSN: 1531-5878
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: Abstract The problem of finding all the DC solutions of a certain class of piecewise-linear electronic circuits containing locally passive and locally active one-ports is considered in this paper. An effective method enabling us to locate the solutions is developed. The method constitutes the crucial point of an algorithm based on the idea of successive contraction, division, and elimination that is capable of determining all the solutions. Several numerical examples are given, and some comparison analyses are performed confirming the usefulness of the proposed approach.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01206677
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  • 13
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    On Kalman's controllability and observability criteria for singular systems (1999)
    Springer
    Circuits, systems and signal processing 18 (1999), S. 269-290 
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    ISSN: 1531-5878
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: Abstract The controllability and observability properties of a singular system are extensively studied. The definitions of controllability,R-controllability, and impulse controllability are introduced via characteristics of the original state vector. Analogous definitions are presented for the case of observability. The criteria established for controllability and observability are simple rank criteria related to the Markov parameters from the inputs to the states and from the initial conditions to the outputs, respectively. The present results can be considered as the direct extension of Kalman's controllability and observability criteria to the case of singular systems. Finally, the controllability and observability subspaces are derived from the image and the kernel of the controllability and the observability matrices, respectively.
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    URL: http://dx.doi.org/10.1007/BF01225698
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  • 14
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    Spectral mimicry: A method of synthesizing matching time series with different Fourier spectra (1999)
    Springer
    Circuits, systems and signal processing 18 (1999), S. 431-442 
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    ISSN: 1531-5878
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: Abstract Given a stationary time seriesX and another stationary time seriesY (with a different power spectral density), we describe an algorithm for constructing a stationary time series Z that contains exactly the same values asX permuted in an order such that the power spectral density ofZ closely resembles that ofY. We call this methodspectral mimicry. We prove (under certain restrictions) that, if the univariate cumulative distribution function (CDF) ofX is identical to the CDF ofY, then the power spectral density ofZ equals the power spectral density ofY. We also show, for a class of examples, that when the CDFs ofX andY differ modestly, the power spectral density ofZ closely approximates the power spectral density ofY. The algorithm, developed to design an experiment in microbial population dynamics, has a variety of other applications.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01200792
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  • 15
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    On the direction estimation Cramér-Rao bounds in the presence of uncorrelated unknown noise (1999)
    Springer
    Circuits, systems and signal processing 18 (1999), S. 479-487 
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    ISSN: 1531-5878
    Keywords: Cramér-Rao bounds ; direction-of-arrival estimation ; unknown noise
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: Abstract The deterministic and stochastic direction estimation Cramér-Rao bounds (CRBs) are studied in the presence of one signal and spatially uncorrelated sensor noise with unknown nonequal variances in array sensors. The explicit CRB expressions are obtained, and their relationship is studied showing some typical properties inherent in the nonidentical noise case.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01387467
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  • 16
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    A method for defining analog circuits for the minimization of discrete functionals: An image processing application (1999)
    Springer
    Circuits, systems and signal processing 18 (1999), S. 457-477 
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    ISSN: 1531-5878
    Keywords: Nonlinear circuit theory ; co-content ; functional minimization ; image processing
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: Abstract The solutions of many physical-mathematical problems can be obtained by minimizing proper functionals. In the literature, some methods for the synthesis of analog circuits (mainly cellular neural networks) are presented that find the solution of some of these problems by implementing the discretized Euler-Lagrange equations associated with the pertinent functionals. In this paper, we propose a method for defining analog circuits that directly minimize (in a parallel way) a class of discretized functionals in the frequently occurring case where the solution depends on two spatial variables. The method is a generalization of the one presented in Parodi et al.,Internat. J. Circuit Theory Appl., 26, 477–498, 1998. The analog circuits consist of both a (nonlinear) resistive part and a set of linear capacitors, whose steady-state voltages represent the discrete solution to the problem. The method is based on the potential (co-content) functions associated with voltage-controlled resistive elements. es an example, we describe an application in the field of image processing: the restoration of color images corrupted by additive noise.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01387466
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  • 17
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    Editorial announcement (1999)
    Springer
    Circuits, systems and signal processing 18 (1999), S. i 
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    ISSN: 1531-5878
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology
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    URL: http://dx.doi.org/10.1007/BF01206540
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  • 18
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    A concurrent system for the computation of higher-order moments (1999)
    Springer
    Circuits, systems and signal processing 18 (1999), S. 111-130 
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    ISSN: 1531-5878
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: Abstract The cumulants defined in terms of moments are basic to the study of higher-order statistics (HOS) of a stationary stochastic process. This paper presents a concurrent systolic array system for the computation of higher-order moments. The system allows for the simultaneous computation of the second-, third-, and fourth-order moments. The architecture achieves good speedup through its excellent exploitation of parallelism, pipelining, and reusability of some intermediate results. The computational complexity and system performance issues related to the architecture are discussed. The concurrent system is designed with the CMOS VLSI technology and is capable of operating at 3.9 MHz.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01206678
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  • 19
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    The invertibility of operators and contraction mappings (1999)
    Springer
    Circuits, systems and signal processing 18 (1999), S. 183-187 
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    ISSN: 1531-5878
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: Abstract Necessary and sufficient conditions for the invertibility of a (not necessarily linear) operatorN between normed linear spaces are given. It is shown thatN is invertible precisely if a certain operator associated withN is a contraction.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01206682
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  • 20
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    Function emulation using MVQ neural networks (1999)
    Springer
    Circuits, systems and signal processing 18 (1999), S. 315-329 
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    ISSN: 1531-5878
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: Abstract In earlier studies a multiclass vector quantization (MVQ)-based neural network design was explored for pattern classification. We reconsider that design here in the context of function emulation. With proper adjustment, the MVQ design demonstrates excellent performance. Moreover, the design algorithms sense discontinuities in the data and replicate them in the network.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01200785
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  • 21
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    The approximating capability of fast forms (1999)
    Springer
    Circuits, systems and signal processing 18 (1999), S. 365-376 
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    ISSN: 1531-5878
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: Abstract In earlier studies the concept of a fast form was generalized to a format that unified such discrete transform examples as the FFT, the FCT, the FST, and the FHT. In this study we consider the approximation of arbitrary linear maps by fast forms. Using simulation we evaluate the approximation capabilities of the generalized fast form.
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    URL: http://dx.doi.org/10.1007/BF01200788
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  • 22
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    Real-time FFT algorithm applied to on-line spectral analysis (1999)
    Springer
    Circuits, systems and signal processing 18 (1999), S. 377-393 
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    ISSN: 1531-5878
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: Abstract On-line running spectral analysis is of considerable interest in many electrophysiological signals, such as the EEG (electroencephalograph). This paper presents a new method of implementing the fast Fourier transform (FFT) algorithm. Our “real-time FFT algorithm” efficiently utilizes computer time to perform the FFT computation while data acquisition proceeds so that local butterfly modules are built using the data points that are already available. The real-time FFT algorithm is developed using the decimation-in-time split-radix FFT (DIT sr-FFT) butterfly structure. In order to demonstate the synchronization ability of the proposed algorithm, the authors develop a method of evaluating the number of arithmetic operations that it requires. Both the derivation and the experimental result show that the real-time FFT algorithm is superior to the conventional whole-block FFT algorithm in synchronizing with the data acquisition process. Given that the FFT sizeN=2 r , real-time implementation of the FFT algorithm requires only 2/r the computational time required by the whole-block FFT algorithm.
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    URL: http://dx.doi.org/10.1007/BF01200789
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  • 23
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    Special issue on Advanced Signal/Image Reconstruction (1999)
    Springer
    Circuits, systems and signal processing 18 (1999), S. 523-523 
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    ISSN: 1531-5878
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01387470
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  • 24
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    Envelope-constrained H2 FIR filter design (1999)
    Springer
    Circuits, systems and signal processing 18 (1999), S. 539-551 
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    ISSN: 1531-5878
    Keywords: H 2 deconvolution filter ; envelope-constrained filter ; finite impulse response filter ; linear matrix inequality
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: Abstract In this paper, we consider an envelope-constrained (EC)H 2 optimal finite impulse response (FIR) filtering problem. Our aim is to design a filter such that theH 2 norm of the filtering error transfer function is minimized subject to the constraint that the filter output with a given input to the signal system is contained or bounded by a prescribed envelope. The filter design problem is formulated as a standard optimization problem with linear matrix inequality (LMI) constraints. Furthermore, by relaxing theH 2 norm constraint, we propose a robust ECFIR filter design algorithm based on the LMI approach.
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    URL: http://dx.doi.org/10.1007/BF01269915
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  • 25
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    Two-dimensional discrete-continuous model conversion (1999)
    Springer
    Circuits, systems and signal processing 18 (1999), S. 565-585 
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    ISSN: 1531-5878
    Keywords: Two-dimensional system ; model conversion ; Roesser's model
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: Abstract This paper presents a geometric-series method for finding two-dimensional (2D) discrete-time (continuous-time) state-space models from 2D continuous-time (discretetime) systems. This method allows the use of well-developed theorems and algorithms in the 2D discrete-time (continuous-time) domain to indirectly carry out analysis and design of hybrid 2D composite systems.
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    URL: http://dx.doi.org/10.1007/BF01269917
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  • 26
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    Optimal design of nonuniform multirate filter banks (1999)
    Springer
    Circuits, systems and signal processing 18 (1999), S. 505-521 
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    ISSN: 1531-5878
    Keywords: Multirate systems ; multirate signal processing ; filter banks ; optimal design
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: Abstract The design of general nonuniform filter banks is studied. Contrary to uniform filter banks, in nonuniform filter banks, it may not be possible to achieve perfect reconstruction, but in some cases by using optimization techniques, we can design acceptable filter banks. Here, the initial finite impulse response (FIR) analysis filters are designed according to the characteristics of the input. By the design procedure, the FIR synthesis filters are found so that theH-norm of an error system is minimized over all synthesis filters that have a prespecified order. Then, the synthesis filters obtained in the previous step are fixed, and the analysis filters are found similarly. By iteration, theH-norm of the error system decreases until it converges to its final value. At each iteration, the coefficients of the analysis or synthesis filters are obtained by finding the least squares solution of a system of linear equations. If necessary, the frequency characteristics of the filters can be altered by adding penalty terms to the objective function.
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    URL: http://dx.doi.org/10.1007/BF01387469
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  • 27
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    Call for papers (1999)
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    Circuits, systems and signal processing 18 (1999), S. 617-617 
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    ISSN: 1531-5878
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology
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    URL: http://dx.doi.org/10.1007/BF01269919
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  • 28
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    Stability analysis of a class of nonlinear multirate digital control systems (1999)
    Springer
    Circuits, systems and signal processing 18 (1999), S. 43-57 
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    ISSN: 1531-5878
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: Abstract We consider multirate digital control systems that consist of an interconnection of a continuous-time nonlinear plant (described by ordinary differential equations) and a digital lifted controller (described by ordinary difference equations). The input to the digital controller consists of the multirate sampled output of the plant, and the input to the continuous-time plant consists of the multirate hold output of the digital controller. In this paper we show that when quantizer nonlinearities are neglected, then under reasonable conditions (which exclude the critical cases), the stability properties (in the Lyapunov sense) of the trivial solution of the nonlinear multirate digital control system can be deduced from the stability properties of the trivial solution of its linearization. We also point out that certain results involving quantization effects and stabilizing controllers can be established which are in the spirit of some existing results.
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    Spread-spectrum signals and the chaotic logistic map (1999)
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    Circuits, systems and signal processing 18 (1999), S. 59-73 
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    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: Abstract Chaotic systems provide a simple means of generating deterministic signals that resemble white noise. It is this noise-like property that provides the potential for applying chaotic systems in communications. In this work, we report a detailed study of the logistic map for use as direct-sequence spread-spectrum (DS/SS) codes. The advantages of the chaotic DS/SS codes are the almost unlimited number of distinct sequences of arbitrary lengths, the ease of generating these sequences, and the increased privacy afforded by the noise-like appearance of these sequences. Some design criteria are provided from the correlation properties of these sequences, and bit-error rate (BER) results are generated by Monte Carlo simulations.
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    Asymptotic behavior of block floating-point digital filters (1999)
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    Circuits, systems and signal processing 18 (1999), S. 75-84 
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    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: Abstract The asymptotic behavior of block floating-point and floating-point digital filters is analyzed. As a result, mantissa wordlength conditions are derived guaranteeing the absence of limit cycles in the regular dynamic range. Explicitly, the requirements are given for block floating-point state space filters with different quantization formats. Although these conditions are only sufficient, examples are given in which they are also necessary. In most cases the conditions are easily satisfied.
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    Comments on “Invariance property of Gaussian signals: A new interpretation, extension and applications” (1999)
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    Circuits, systems and signal processing 18 (1999), S. 85-85 
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    Topics: Electrical Engineering, Measurement and Control Technology
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    Author's reply (1999)
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    Circuits, systems and signal processing 18 (1999), S. 87-88 
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    Topics: Electrical Engineering, Measurement and Control Technology
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    Errata (1999)
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    Circuits, systems and signal processing 18 (1999), S. 189-190 
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    URL: http://dx.doi.org/10.1007/BF01206683
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    On nonparametric spectral estimation (1999)
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    Circuits, systems and signal processing 18 (1999), S. 169-181 
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    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: Abstract In this paper the Cramér-Rao bound (CRB) for a general nonparametric spectral estimation problem is derived under a local smoothness condition (more exactly, the spectrum is assumed to be well approximated by a piecewise constant function). Further-more, it is shown that under the aforementioned condition the Thomson method (TM) and Daniell method (DM) for power spectral density (PSD) estimation can be interpreted as approximations of the maximum likelihood PSD estimator. Finally the statistical efficiency of the TM and DM as nonparametric PSD estimators is examined and also compared to the CRB for autoregressive moving-average (ARMA)-based PSD estimation. In particular for broadband signals, the TM and DM almost achieve the derived nonparametric performance bound and can therefore be considered to be nearly optimal.
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    Stabilization of third-order, single-stage Sigma-Delta modulators (1999)
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    Circuits, systems and signal processing 18 (1999), S. 149-168 
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    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: Abstract The issue of stability of higher-order, single-stage Sigma-Delta (ΣΔ) modulators is addressed using a method from nonlinear system theory. As a result, theoretical bounds for the quantizer input of the modulators are derived. A new method for stabilizing the ΣΔ modulators is then presented. It uses the quantizer input bound for possible instability detection. Upon detection of such a state, the highest-order integrator is cut off, effectively reducing the order of the modulator, and thus resulting in a stable system. The method is easily implemented and results in a very good signal-to-noise ratio (SNR) and fast return to normal operation compared to other stabilization methods.
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    Uncorrelated component analysis for blind source separation (1999)
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    Circuits, systems and signal processing 18 (1999), S. 225-239 
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    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: Abstract The uncorrelated component analysis (UCA) of a stationary random vector process consists of searching for a linear transformation that minimizes the temporal correlation between its components. Through a general analysis we show that under practically reasonable and mild conditions UCA is a solution for blind source separation. The theorems proposed in this paper for UCA provide useful insights for developing practical algorithms. UCA explores the temporal information of the signals, whereas independent component analysis (ICA) explores the spatial information; thus UCA can be applied for source separation in some cases where ICA cannot. For blind source separation, combining ICA and UCA may give improved performance because more information can be utilized. The concept of single UCA (SUCA) is also proposed, which leads to sequential source separation.
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    Call for papers (1999)
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    Circuits, systems and signal processing 18 (1999), S. i 
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    Topics: Electrical Engineering, Measurement and Control Technology
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    Stability analysis for rotating stall dynamics in axial flow compressors (1999)
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    Circuits, systems and signal processing 18 (1999), S. 331-350 
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    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: Abstract This paper analyzes the nonlinear phenomenon of rotating stall via the methods of projection [Elementary Stability and Bifurcation Theory, G. Iooss and D. D. Joseph, Springer-Verlag, 1980] and Lyapunov [J.-H. Fu,Math. Control Signal Systems, 7, 255–278, 1994]. A compressor model of Moore and Greitzer is adopted in which rotating stall dynamics are associated with Hopf bifurcations. Local stability for each pair of the critical modes is studied and characterized. It is shown that local stability of individual pairs of the critical modes determines collectively local stability of the compressor model. Explicit conditions are obtained for local stability of rotating stall which offer new insight into the design, and active control of axial flow compressors.
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    An adaptive Gauss-Newton algorithm for training multilayer nonlinear filters that have embedded memory (1999)
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    Circuits, systems and signal processing 18 (1999), S. 407-429 
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    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: Abstract We describe herein a new means of training dynamic multilayer nonlinear adaptive filters, orneural networks. We restrict our discussion to multilayer dynamic Volterra networks, which are structured so as to restrict their degrees of computational freedom, based on a priori knowledge about the dynamic operation to be emulated. The networks consist of linear dynamic filters together with nonlinear generalized single-layer subnets. We describe how a Newton-like optimization strategy can be applied to these dynamic architectures and detail a newmodified Gauss-Newton optimization technique. The new training algorithm converges faster and to a smaller value of cost than backpropagation-through-time for a wide range of adaptive filtering applications. We apply the algorithm to modeling the inverse of a nonlinear dynamic tracking system. The superior performance of the algorithm over standard techniques is demonstrated.
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    Linear phase FIR approximation of magnitude response |1/ω| for maximal flatness at an arbitrary frequency ω0, 0〈ω0〈π* (1999)
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    Circuits, systems and signal processing 18 (1999), S. 445-455 
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    Keywords: Linear-phase digital filters ; FIR integrators
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    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: Abstract In many signal processing situations, the desired (ideal) magnitude response of the filter is a rational function: $$\tilde H(\omega ) = |1/\omega |$$ (a digital integrator). The requirements of a linear phase response and guaranteed stable performance limit the design to a finite impulse response (FIR) structure. In many applications we require the FIR filter to yield a highly accurate magnitude response for a narrow band of frequencies with maximal flatness at an arbitrary frequencyω 0 in the spectrum (0, π). No techniques for meeting such requirements with respect to approximation of $$\tilde H(\omega )$$ are known in the literature. This paper suggests a design by which the linear phase magnitude response $$|\tilde H(\omega )|$$ can be approximated by an FIR configuration giving a maximally flat (in the Butterworth sense) response at an arbitrary frequency ω0, 0〈ω0〈π*. A technique to compute exact weights for the design has also been given.
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    Special issue on Multimedia Communication Services (1999)
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    Circuits, systems and signal processing 18 (1999), S. 524-524 
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    Topics: Electrical Engineering, Measurement and Control Technology
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    A novel algorithm for computing autocorrelation of randomly sampled sequences (1999)
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    Circuits, systems and signal processing 18 (1999), S. 525-537 
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    Keywords: Random sampling, digital signal processing ; spectral estimation ; computational algorithm
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    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: Abstract Random sampling is one of the methods used to achieve sub-Nyquist sampling. This paper proposes a novel algorithm to evaluate the circular autocorrelation of a randomly sampled sequence, from which its power density spectrum can be obtained. With uniform sampling, the size of each lag (the step size) for computing an autocorrelation of a sequence is the same as the sampling period. When random sampling is adopted, the step size should be chosen such that the highest-frequency component of interest contained in a sequence can be accommodated. To find overlaps between a time sequence and its shifted version, an appropriate window is opened in one of the time sequences. To speed up the process, a marker is set to limit the range of searching for overlaps. The proposed method of estimating the power spectrum via autocorrelation is comparable in terms of accuracy and signal-to-noise ratio (SNR) to the conventional point rule. The techniques introduced can also apply to other operations for randomly sampled sequences.
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    Permissively structured transfinite electrical networks (1999)
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    Circuits, systems and signal processing 18 (1999), S. 587-609 
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    Keywords: Transfinite graphs ; infinite electrical networks ; current flows through infinity
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    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: Abstract Transfinite electrical networks of ranks larger than 1 have previously been defined by arbitrarily joining together various infinite extremities through transfinite nodes that are independent of the networks' resistance values. Thus, some or all of those transfinite nodes may remain ineffective in transmitting current “through infinity.” In this paper, transfinite nodes are defined in terms of the paths that permit currents to ”reach infinity.” This is accomplished by defining a suitable metricd v on the node setN S v of eachv-sectionS v, av-section being a maximal subnetwork whose nodes are connected by two-ended paths of ranks no larger thanv. Upon taking the completion ofN S v under that metricd v, we identify those extremities (now calledv-terminals) that are accessible to current flows. These are used to define transfinite nodes that combine such extremities. The construction is recursive and is carried out through all the natural number ranks, and then through the first arrow rank ω and the first limit-ordinal rank ω. The recursion can be carried still further. All this provides a more natural development of transfinite networks and indeed simplifies the theory of electrical behavior for such networks.
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    A new algorithm on multiple unknown source signals estimation and separation in a reverberant space (1999)
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    Circuits, systems and signal processing 18 (1999), S. 489-504 
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    ISSN: 1531-5878
    Keywords: Source separation ; system identification ; pseudo-white noise ; FIR equation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: Abstract In many voice-related applications, the presence of echoes and overlapping speech signals can degrade the quality or intelligibility of a desired speech signal to be processed. It is, therefore, important to cancel the echoes and to separate overlapping speech signals from a mixture of these components, so that a specific function of the system, for instance, transmission, speech identification, or recognition, can be accomplished with better performance. However, in many cases we do not know the properties of the communication channel, and sometimes even the number of speech sources is unknown. In this paper, we propose to use a reference signal to determine the channel characteristics. When the estimated channel parameter matrices are obtained, a recurrence formula can then be used to separate various speech signals including their reverberant counterparts. As a finite impulse response (FIR) model is used to describe the observation model of the sources in the reverberant environment, it is not necessary for the processing speech signals to be uncorrelated. Because it involves only simple computation, our approach can be used in online applications. In this paper, we will investigate the validity of our algorithm and compare it with extended fourth-order blind identification (EFOBI). It is found that our method preserves both signal waveforms and their amplitudes even in a noisy environment, whereas EFOBI has not been able to achieve similar performance.
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    A canonical form for discrete-time systems defined overZ + * (1999)
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    Circuits, systems and signal processing 18 (1999), S. 553-564 
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    Keywords: Canonical forms ; discrete-time systems ; nonlinear systems
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    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: Abstract It is shown that for each memberG of a large class of causal time invariant nonlinear input-output maps, with inputs and outputs defined on the nonnegative integers, there is a functionalA on the input set such that (Gs)(k) has the representationA(F k s) for allk and each inputs, in whichF k is a simple linear map that does not depend onG. More specifically, this holds—with anA that is unique in a certain important sense—for anyG that has approximately finite memory and meets a certain often-satisfied additional condition. Similar results are given for a corresponding continuous-time case in which inputs and outputs are defined on ℝ+. An example shows that the members of a large family of feedback systems have these “A-map” representations.
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    New Algorithms for Polynomial J-Spectral Factorization (1999)
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    Mathematics of control, signals, and systems 12 (1999), S. 24-61 
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    ISSN: 1435-568X
    Keywords: Key words. Polynomial J-spectral factorization, Two-variable polynomial matrix, Quadratic differential form, Dissipativity, Pick matrix.
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    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics , Technology
    Notes: Abstract. In this paper new algorithms are developed for J-spectral factorization of polynomial matrices. These algorithms are based on the calculus of two-variable polynomial matrices and associated quadratic differential forms, and share the common feature that the problem is lifted from the original one-variable polynomial context to a two-variable polynomial context. The problem of polynomial J-spectral factorization is thus reduced to a problem of factoring a constant matrix obtained from the coefficient matrices of the polynomial matrix to be factored. In the second part of the paper, we specifically address the problem of computing polynomial J-spectral factors in the context of H ∞ control. For this, we propose an algorithm that uses the notion of a Pick matrix associated with a given two-variable polynomial matrix.
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    The Realization Problem for Hidden Markov Models (1999)
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    Mathematics of control, signals, and systems 12 (1999), S. 80-120 
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    ISSN: 1435-568X
    Keywords: Key words. Hidden Markov models, Realization, Finite-state Markov process.
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    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics , Technology
    Notes: Abstract. If {X t} is a finite-state Markov process, and {Y t} is a finite-valued output process with Y t+1 depending (possibly probabilistically) on X t, then the process pair is said to constitute a hidden Markov model. This paper considers the realization question: given the probabilities of all finite-length output strings, under what circumstances and how can one construct a finite-state Markov process and a state-to-output mapping which generates an output process whose finite-length strings have the given probabilities? After reviewing known results dealing with this problem involving Hankel matrices and polyhedral cones, we develop new theory on the existence and construction of the cones in question, which effectively provides a solution to the realization problem. This theory is an extension of recent theoretical developments on the positive realization problem of linear system theory.
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    A Global Asymptotic Stability Result for a Class of Totally Asynchronous Discrete Nonlinear Systems (1999)
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    Mathematics of control, signals, and systems 12 (1999), S. 143-166 
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    ISSN: 1435-568X
    Keywords: Key words. Asynchronous systems, Total asynchronism, Regular desynchronization, Global stability, Nonlinear discrete-time systems, Hopfield neural nets.
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    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics , Technology
    Notes: Abstract. This paper proves a global stability result for a class of nonlinear discrete-time systems that are subject to regular desynchronization, also known as total asynchronism. The class of systems studied has its origins in a discrete-time neural net model. The techniques used are of interest in terms of the use of a Lyapunov function for the study of convergence of asynchronous nonlinear dynamical systems and also in terms of applications to neural networks. In the latter context, the main result of this paper strengthens a result of an earlier paper on neural networks, and shows that a class of discrete-time continuous-valued neural nets of the Hopfield type displays global convergence properties even when there exists total asynchronism in the updating of neuron states.
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    Linear Quadratic Optimal Control of Time-Varying Systems with Indefinite Costs on Hilbert Spaces (1999)
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    Mathematics of control, signals, and systems 12 (1999), S. 196-218 
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    Keywords: Key words. Infinite-dimensional system, Time-varying system, Mild evolution operator, Riccati equation, Optimal control problem.
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    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics , Technology
    Notes: Abstract. In this paper we consider time-varying linear systems on Hilbert spaces and study the linear quadratic optimal control problem with an indefinite performance criterion over an infinite time interval. An example shows that in contrast to the finite-dimensional situation, in general, the solvability of the optimal control problem does not imply the solvability of the associated integral Riccati equation. Using an operator theoretic approach towards the time-varying integral Riccati equation, we derive equivalent conditions for the solvability of both problems.
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    Nonsmooth Robust Stabilization of a Class of Two-Dimensional Nonlinear Systems (1999)
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    Mathematics of control, signals, and systems 12 (1999), S. 245-269 
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    ISSN: 1435-568X
    Keywords: Key words. Families of nonlinear systems, Robust stabilization, Nonsmooth state feedback.
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    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics , Technology
    Notes: Abstract. In this paper we consider a class of parameterized families of nonlinear systems which cannot be robustly asymptotically stabilized by means of C 1 feedback. We construct C 0 state feedback laws which are smooth away from the origin and which robustly asymptotically stabilize these families of systems. We then show that, in some cases, the regularity of the obtained robust asymptotic stabilizers is “maximum” in the sense that the considered families of systems do not admit any Lipschitz continuous robust asymptotic stabilizer.
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    Orthonormal Basis Functions for Continuous-Time Systems and Lp Convergence (1999)
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    Mathematics of control, signals, and systems 12 (1999), S. 295-305 
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    ISSN: 1435-568X
    Keywords: Key words. Orthonormal basis functions, Continuous-time, Fourier series, Lp convergence.
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    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics , Technology
    Notes: Abstract. In this paper, model sets for linear-time-invariant continuous-time systems that are spanned by fixed pole orthonormal bases are investigated. These bases generalize the well-known Laguerre and two-parameter Kautz cases. It is shown that the obtained model sets are everywhere dense in the Hardy space H 1(Π) under the same condition as previously derived by the authors for the denseness in the (Π is the open right half plane) Hardy spaces H p(Π), 1〈p〈∞. As a further extension, the paper shows how orthonormal model sets, that are everywhere dense in H p(Π), 1≤p〈∞, and which have a prescribed asymptotic order, may be constructed. Finally, it is established that the Fourier series formed by orthonormal basis functions converge in all spaces H p(Π) and (D is the open unit disk) H p(D), 1〈p〈∞. The results in this paper have application in system identification, model reduction, and control system synthesis.
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    Robust Feedback Control of a Single Server Queueing System (1999)
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    Mathematics of control, signals, and systems 12 (1999), S. 307-345 
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    ISSN: 1435-568X
    Keywords: Key words. Robust control, Nonlinear control, Queueing server, Hamilton–Jacobi equation, Traffic signals, Storage function, Bicharacteristics, Boundary dynamics.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics , Technology
    Notes: Abstract. This paper extends previous work of Ball et al. [BDKY] to control of a model of a simple queueing server. There are n queues of customers to be served by a single server who can service only one queue at a time. Each queue is subject to an unknown arrival rate, called a “disturbance” in accord with standard usage from H ∞ theory. An H ∞-type performance criterion is formulated. The resulting control problem has several novel features distinguishing it from the standard smooth case already studied in the control literature: the presence of constraining dynamics on the boundary of the state space to ensure the physical property that queue lengths remain nonnegative, and jump discontinuities in any nonconstant state-feedback law caused by the finiteness of the admissible control set (choice of queue to be served). We arrive at the solution to the appropriate Hamilton–Jacobi equation via an analogue of the stable invariant manifold for the associated Hamiltonian flow (as was done by van der Schaft for the smooth case) and relate this solution to the (lower) value of a restricted differential game, similar to that formulated by Soravia for problems without constraining dynamics. An additional example is included which shows that the projection dynamics used to maintain nonnegativity of the state variables must be handled carefully in more general models involving interactions among the different queues. Primary motivation comes from the application to traffic signal control. Other application areas, such as manufacturing systems and computer networks, are mentioned.
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    Tunnelling rays in graded-index fibres (1978)
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    Optical and quantum electronics 10 (1978), S. 83-93 
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    ISSN: 1572-817X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract An analysis of the role of tunnelling rays in pulse propagation in graded-index fibres is presented. Tunnelling ray attenuation is handled by using the generalized parameter technique which allows attenuation coefficients to be dispensed with and relevant families of tunnelling rays to be identified. Results are given for impulse response pulse widths and shapes. Incorporation of tunnelling ray pulse contributions into the formalism for determining optimum refractive-index profiles is presented. For most cases, tunnelling ray effects are small, but significant corrections may be necessary when measurements are made on short lengths of fibre.
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    Efficient fifth order non-linear process by focused beam in metal vapour (1978)
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    Optical and quantum electronics 10 (1978), S. 131-138 
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    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract Fifth order non-linear processes produced by a focused beam in metal vapour have been investigated experimentally. Evidence of saturation of fifth harmonic generation by picosecond laser pulses is reported.
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    URL: http://dx.doi.org/10.1007/BF00620004
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    Theory of power coupling between multimode optical fibres (1978)
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    Optical and quantum electronics 10 (1978), S. 107-117 
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    Notes: Abstract In this paper power coupling between two multimode optical fibres is investigated. A formalism (based on a geometrical approach) suitable for analysing any coupling configuration between fibres with any index profile and any radiance distribution is presented. The model is applied to obtain coupling losses both in uniformly excited parabolic- and step-index fibres, in the presence of all kinds of coupling errors. Numerical results of extensive utility are shown and useful asymptotic expressions of coupling efficiency, valid for small values of coupling error parameters, are derived together with some practical rules for error combination. Mention is also made of some experimental results we have obtained, which corroborate some previous assertions. The work can supply a useful tool in the design of joints and connectors between single fibres or optical cables.
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    Anomalous polarization dependence of the photon drag and optical rectification fields inn-type gallium phosphide (1978)
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    Optical and quantum electronics 10 (1978), S. 153-161 
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    Notes: Abstract The photon drag and optical rectification response fromn-type gallium phosphide containing 2.4×1016 electrons cm−3 has been studied using laser sources at 10.61 and 2.83μm. By using different contact configurations, the existence of an additional electric field term in the propagation direction has been deduced. This field is shown to arise from the spatial derivatives of the photon drag and optical rectification field components caused by absorption of the radiation. The importance of this effect in detector design is considered.
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    Diffraction efficiency of sequentially stored gratings in reflection volume holograms (1978)
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    Optical and quantum electronics 10 (1978), S. 171-178 
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    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract On the basis of the theory of coupled waves the amplitudes of the first-order diffracted waves and the diffraction efficiency is calculated for sequentially superposed phase gratings stored in dielectric reflection holograms. The investigations are restricted to the case of a fixed reference wave during recording and Bragg-angle incidence. By analogy to the transmission volume grating the coupling effects which appear between incident beams and diffracted waves give the possibility of building up beam-couplers and -splitters with certain coupling parameters determined by the recording process. Moreover, reflection gratings allow a favourable combination between coupling and reflecting properties and avoid the diffraction efficiency oscillations that are characteristic of transmission gratings. The performance of the reconstruction process with several waves simultaneously allows the tuning of the intensities of diffracted waves with dependence on amplitude or phase differences between incident beams.
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    Reversible mirror for real-time holographic interferometry (1978)
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    Optical and quantum electronics 10 (1978), S. 181-183 
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    Topics: Electrical Engineering, Measurement and Control Technology , Physics
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    URL: http://dx.doi.org/10.1007/BF00620010
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    Publisher's Note (1999)
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    Optical and quantum electronics 31 (1999), S. 99-105 
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    Notes: Abstract When the article 'Modification of the finite difference scheme for efficient analysis of thin lossy metal layers in optical devices' by O. Conradi, S. Helfert, and R. Pregla was first published in the Optical Waveguide special issue of Optical and Quantum Electronics (volume 30, nos. 5–6, pages 369–373) the authors' affiliation given was incorrect. The article is printed again in full with the original pagination and credit lines. A misprint in the Results section has been corrected as well: the refractive index of both silver layers is 0.14 − j11.0 at a wavelength of λ = 1523 nm, and not 0.41 − j11.0.
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    Dielectric superlattices for nonlinear optical effects (1999)
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    Optical and quantum electronics 31 (1999), S. 1093-1128 
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    Keywords: nonlinear optical frequency conversion ; optical bistability ; optical superlattice ; quasi-phase-matching
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    Notes: Abstract Dielectric superlattices show a lot of new phenomena that are promising in applications, such as nonlinear optical frequency conversion and optical bistability. This paper reviews the main achievements in this field. Much has been focused on the work done in our Lab. Since 1980, we have extended the concept of superlattice from semiconductor to dielectrics. When quasi-phase-matching technique is introduced into a quasiperiodic dielectric superlattice, more interesting phenomena can occur. For example, multiwavelength second-harmonic generation and coupled parametric processes such as direct third-harmonic generation have been realized with high efficiency. A new mechanism for optical bistability in a 2-dimensional dielectric superlattice, i.e. a 2-dimensional nonlinear photonic crystal, has been proposed theoretically had proved experimentally.
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    Q-switching of a diode cladding-pumped Erbium Fibrelaser at 2.7 μm (1999)
    Springer
    Optical and quantum electronics 31 (1999), S. 1171-1177 
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    Keywords: cladding-pumping ; Q-switching ; fibrelaser ; erbium
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    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract Reliable Q-switched operation of a cladding-pumped 2.7 μm ZBLAN fibre laser in the range of the power limit of self-destruction is shown for the first time. The laser is pumped by a multimode diode. Q-switching is achieved by two different techniques: a rotating mirror and an acousto-optical modulator. Pulse widths of 500 ns with the rotating mirror and 300 ns (FWHM) with the acousto-optical modulator and pulse energies in the μJ range are achieved.
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    A diode-laser pump source with small focus diameter for end- pumped systems (1999)
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    Optical and quantum electronics 31 (1999), S. 173-181 
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    Notes: Abstract A pump source with eight angular multiplexed laser diodes is built. The diode laser emission is collimated and focused using relatively inexpensive aspherical lenses. The maximum output power is 6.3W at 970nm. The overall transmittance of the beam shaping optics is T=85%. The electrical, temporal and spectral properties are studied. The variances of the spatial intensity distribution are Δr0x=99m and Δr0y=85m. The beam propagation factors are M2x=38 and M2y=112. The high intensity in the focus makes this system ideal for end pumping of solid state lasers.
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    Contents to Volume 30 (1999)
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    Optical and quantum electronics 31 (1999), S. 381-387 
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    Topics: Electrical Engineering, Measurement and Control Technology , Physics
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    Semiclassical particle-like description of optical amplifier noise (1999)
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    Optical and quantum electronics 31 (1999), S. 367-376 
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    Notes: Abstract A semiclassical model of optical amplifier noise in terms of photon-particle description and simple calculations is developed. The active-medium amplifier is modelled as a stochastic photon multiplier, whose statistical properties are derived from well-known results about branching processes. The effects on amplifier output noise caused by random amplification of input photons and by spontaneous emission are treated separately, and it is thus possible to ascribe output noise terms to specific physical mechanisms. In view of this, the 3 dB noise figure limit of optical amplifiers can be entirely ascribed to optical gain randomness. Since the results obtained here are coincident with those from quantum theories, it is concluded that the randomness of optical gain in a particle-like description is the correct semiclassical counterpart of vacuum-field amplification in wave-like formulations.
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    Papers presented at the Eleventh Australian Optical Society Conference, University of Adelaide, 10–12 December 1997 (1999)
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    Optical and quantum electronics 31 (1999), S. 389-390 
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    A study of negative index grating growth in germanosilicate planar waveguides (1999)
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    Optical and quantum electronics 31 (1999), S. 469-480 
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    Keywords: germanosilicate planar waveguides ; negative index grating
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    Notes: Abstract Negative index grating growth in germanosilicate planar waveguides fabricated by hollow cathode(HC)-PECVD are characterised in detail. Differences in index modulation growth, both in terms of the grating strength and the rate of negative index change as a function of fluence, are observed. On the other hand, the average index change of the two polarisation states shows the same rate of growth revealing that grating growth is dependent on more than on index change triggered by simple isotropic uv-defect interactions.
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    Precision X-ray optics for fundamental interactions in atomic physics, resolving discrepancies in the X-ray regime (1999)
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    Optical and quantum electronics 31 (1999), S. 495-505 
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    Keywords: accuracy ; complex form factor f ; X-ray optics
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    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract Reliable knowledge of the complex X-ray form factor (Re(f) and f″) is required for many fields including crystallography, medical diagnosis and XAFS studies. However, there are discrepancies between theory and theory, experiment and experiment and theory and experiment of 10% and more, over central X-ray energies. Discrepancies exist for most elements, despite claimed experimental accuracies of 1%. This paper summarises the current variation between experimental and theoretical results, and outlines key issues for obtaining experimental accuracies of 1% in critical wavelength ranges for selected elements to address these issues. This paper critically surveys available experimental data for attenuation coefficients and suggests a procedure for obtaining significantly higher accuracy measurements in the future.
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    Construction of high-quality narrow-band holographic filters (1999)
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    Optical and quantum electronics 31 (1999), S. 535-543 
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    Keywords: dichromated gelatine ; holography ; notch filters
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    Notes: Abstract We have studied the factors limiting the quality of holographic notch filters. We have employed a novel recording scheme in which the sample is translated during exposure, eliminating flare due to reflections at the boundaries, and simultaneously reducing the scatter of the final hologram. We have also refined a gravity-settling dichromated gelatine (DCG) deposition technique and incorporated hardening of the DCG layers during the drying stage. With this, we have produced high optical quality, uniform, flare-free DCG filters with an optical density, OD 〉 5, bandwidth 〈 20 nm and scatter almost as low as that for state of the art dielectric notch filters.
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    A simple high-sensitivity interferometric position sensor for test mass control on an advanced LIGO interferometer (1999)
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    Optical and quantum electronics 31 (1999), S. 571-582 
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    Keywords: high-resolution displacement measurements ; interferometric position sensor
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    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract A small Michelson interferometer has been configured as a tracking mirror displacement sensor in order to achieve both large dynamic range (2.1 mm) and excellent sensitivity $${\rm{(2x10}}^{--{\rm{14}}} {\rm{m/}}\sqrt {{\rm{Hz)}}} {\rm{ }}$$ across a broad frequency range (6Hz–3 kHz). The interferometer is illuminated by a simple LED, uses broadband, non-polarising beamsplitters and contains no lensing optics. A DC-coupled balanced detector provides an error signal that is used to position the tracking mirror of the Michelson interferometer so as to maintain an interferometer operating position close to the centre of a particular fringe. The total interferometric sensor provides a small, simple and cost-effective means of achieving high-resolution displacement measurements.
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    Reconfigurable WDM add/drop multiplexer based on optical switches and fibre Bragg gratings (1999)
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    Optical and quantum electronics 31 (1999), S. 77-83 
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    Notes: Abstract A reconfigurable wavelength-division-multiplexing (WDM) add/drop multiplexer (WADM) is constructed using optical switches (OSWS) and fibre Bragg gratings (FBGs). Selected one or two channel(s) can be added/dropped at the same multiplexer by properly controlling the optical switch pair and fibre Bragg grating arrangement. A␣four-channel system is experimentally demonstrated for a data rate of 2.5 Gb s−1 and a single-mode fibre (SMF) distance of 100km. A negligible maximum power penalty of only 0.3dB is observed when compared with back-to-back transmission.
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    Two-photon absorption and two-photon induced absorption of liquid toluene at 347.15 nm (1999)
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    Optical and quantum electronics 31 (1999), S. 1145-1170 
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    Keywords: excited-state absorption ; excited-state relaxation ; toluene ; two-photon absorption ; two-photon ionization
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    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract Pump pulse transmission and time-delayed probe pulse transmission measurements through liquid toluene were performed with linear and circular polarized second harmonic pulses of a mode-locked ruby laser system. Two-photon absorption and two-photon induced absorption are observed. The induced absorption anisotropy is investigated. A theory of two-photon absorption in isotropic media is presented. The two-photon absorption cross-section components, the effective excited-state absorption cross-section, the absorption anisotropy relaxation time and the excited singlet-state relaxation time are determined.
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    Coherent coupling of diode-pumped solid-state lasers by means of an intracavity Fourier-filter (1999)
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    Optical and quantum electronics 31 (1999), S. 351-357 
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    Notes: Abstract A theoretical model has been developed describing the coherent coupling of two lasers in a common cavity with an internal lens and a Fourier-filter. An analytical expression for the locking range of the lasers was derived which was experimentally proved using two diode- pumped solid-state lasers. By thermally detuning one laser and analysing the far field pattern, the locked and the unlocked state of the lasers were identified.
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    Propagation of chirped nonlinear pulses in a lossy highly birefringent single-mode optical fibre (1999)
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    Optical and quantum electronics 31 (1999), S. 599-604 
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    Keywords: Birefringence ; optical fibre ; soliton
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    Notes: Abstract A new model of the nonlinear propagation of optical solitons with initial linear frequency chirp through lossy highly birefringent fibres, allowing the improvement of the practical results concerning the distortionless signal transmission in ultrahigh-speed communications, is presented within the framework of a system of coupled nonlinear Schroedinger (CNLS) equations. This model demonstrates the existence of bound chirped solitons in a lossy single-mode highly birefringent fibre.
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    Recent progress of integrated optics planar lightwave circuits (1999)
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    Optical and quantum electronics 31 (1999), S. 107-129 
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    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract Planar lightwave circuits (PLCs) are waveguide devices that integrate fiber-matched optical waveguides on silicon or glass substrate to provide an efficient means of interaction for the guided-wave optical signals. PLCs provide various important and functional devices for optical wavelength division multiplexing (WDM), time division multiplexing (TDM) systems and subscriber networks. This paper reviews the recent progress and future prospects of PLC technologies including arrayed-waveguide grating multiplexers, optical add/drop multiplexers, programmable dispersion equalizers and hybrid optoelectronics integration technologies.
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    High-power laser structures incorporating novel curved-gratings (1999)
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    Optical and quantum electronics 31 (1999), S. 215-221 
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    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract We present a theoretical investigation a novel type of distributed feedback laser with a “curved-groove” diffraction grating (c-DFB), which is predicted to give an enhanced spectral and spatial output characteristics.
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    Degree of polarization of non-uniformly partially polarized beams: a proposal (1999)
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    Optical and quantum electronics 31 (1999), S. 223-226 
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    Notes: Abstract Two overall parameters are proposed to characterize the degree of polarization and its uniformity across the transversal section of non-uniformly partially polarized beams. Such parameters can be measured according to the well-known standard methods used to obtain the Stokes parameters, with the addition of a CCD camera to determine the beam intensity at each point of the observation plane.
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    Modes of open layered anisotropic waveguides: a numerical method with exponential convergence (1999)
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    Optical and quantum electronics 31 (1999), S. 781-796 
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    Keywords: anisotropic media ; numerical methods ; waveguides
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    Notes: Abstract A spectral-element type approach to determine the propagation characteristics of the bound modes of an open planar layered anisotropic waveguide is proposed. The main feature is the expansion of the electromagnetic field in each internal layer on different sets of Legendre polynomials. In the two embedding halfspaces, sets of weighted Laguerre polynomials are used. In this way, the method converges with exponential rate with increasing number of basis functions. No transcendental equation has to be solved and even modes that may exhibit coinciding or very close propagation constants are computed with great accuracy. A detailed analysis of the convergence properties of the algorithm is carried out and a way to estimate and control the error on the propagation constants is discussed.
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    Application of the generalized Douglas scheme to optical waveguide analysis (1999)
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    Optical and quantum electronics 31 (1999), S. 675-687 
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    Keywords: beam-propagation method ; finite-difference method
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    Notes: Abstract The generalized Douglas (GD) scheme is applied to the analysis of various optical waveguides. The GD scheme has an advantage over the conventional finite-difference scheme in that the truncation error can be reduced, while maintaining a tridiagonal matrix. To demonstrate fourth-order accuracy for a three-dimensional problem, a graded-index fiber is analyzed. Furthermore, the coupling length of a rib waveguide directional coupler is analyzed and its convergence behavior is discussed. Application of the GD scheme to a time-domain analysis is also presented.
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    Active nonlinear integrated optical devices: a numerical analysis (1999)
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    Optical and quantum electronics 31 (1999), S. 1073-1084 
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    Keywords: active devices ; beam propagation method ; electromagnetic propagation ; finite element method ; photonics devices
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    Notes: Abstract A finite element beam propagation method to analyze nonlinear active optical waveguides is presented. The model takes into account the mutual coupling among the equations describing the electromagnetic field propagation and the ones governing the signal amplification due to a doped medium. The approach is able to distinguish the different behavior of Ex (quasi-TE) and Ey (quasi-TM) polarizations. The performances of nonlinear and doped couplers are analyzed in detail by varying the input power, the field polarization and the pumping scheme.
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    Room temperature continuous wave visible vertical cavity surface emitting laser (1999)
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    Optical and quantum electronics 31 (1999), S. 303-306 
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    Notes: Abstract Visible VCSEL laser operated at room temperature continuous wave has been achieved by H+ implants using tungsten wires as an implantation mask. The laser wavelength is 650 nm, and the maximum output without heat-sink exceeds 85 μW at CW operation. We also calculated the thermal resistance of the device.
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    VIRGO mirrors: wavefront control (1999)
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    Optical and quantum electronics 31 (1999), S. 507-514 
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    Keywords: VIRGO mirrors ; wavefront control
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    Notes: Abstract The Franco-Italian VIRGO program to detect gravitational waves requires large mirrors whose optical properties are extremely severe: absorption and scattering 〈1ppm at 1064nm, wavefront homogeneity of 9nm RMS on Ø100mm. To achieve this performance on the wavefront, we have developed an experimental method to correct the wavefront shape to be as plane as possible. A thin silica layer is added through a mask by sputtering, where it is necessary on the surface, on the last layer of the multilayer. A phase retardation is produced. The wavefront is measured before and after correction with a Zygo interferometer. The first test has been done on Ø80mm mirror at 633nm. The wavefront peak to valley goes from 34 to 14nm. At this level, we are limited by the interferometer accuracy and repeatability. The optical property modifications due to the corrective coating are small (at 1064nm) or easy to overcome. The corrected wavefront includes at the moment the reference flat of the interferometer, so the measurements are not absolute. But the feasibility of this correction method is proved and it is powerful.
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    Power saturation effects in thick single-element optical limiters (1999)
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    Optical and quantum electronics 31 (1999), S. 555-569 
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    ISSN: 1572-817X
    Keywords: optical limiters ; power saturation effects
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract Optical limiters relying on nonlinear absorption or nonlinear refraction are most effective against an incoming laser beam when the active material is thicker than one Rayleigh length. We have found that a variety of thick optical limiter configurations can be modelled by integrating the formulae for optical transmission by thin media, and that the results are exact to the first order in power or irradiance. The limiter behaviour saturates as the optical power increases. For the case of thick irradiance-dependent absorbers and an incident Gaussian beam model, we have also found that the predictions of a simple saturation formula for the optical transmittance agree well with the transmittance values computed using a numerical technique. Under certain conditions this saturation formula is also suitable for describing the transmission of nonlinear refractors, thereby providing a straight-forward technique for modelling limiters over a broad parameter range.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006935600751
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    Analytical investigations of planar optical waveguides with arbitrary index profile (1999)
    Springer
    Optical and quantum electronics 31 (1999), S. 637-644 
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    ISSN: 1572-817X
    Keywords: Dispersion equation ; index profile ; planar waveguides ; propagation constant
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract We present here an improvement of the existing equivalent attenuated vector (EAV) method. It is shown that our study gives not only analytical dispersion equation with clear physical insight, but also the extremely accurate propagation constants for planar waveguides with arbitrary index profiles.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006983618149
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    Hysteresis phenomena in the light self-diffraction in a dense resonant medium (1999)
    Springer
    Optical and quantum electronics 31 (1999), S. 605-614 
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    ISSN: 1572-817X
    Keywords: Dense resonant medium ; hysteresis ; self-diffraction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract On the basis of the modified Bloch equations a theory is developed of the light self-diffraction in a thin film of a dense resonant medium with allowance for the dipole-dipole interactions of atoms. It is shown that for certain values of intensity of an external field, there occurs in the film the light-induced first-kind phase transition which causes the emergence of regions (domains) with the high excitation of atoms. The switching effects of the system “dense resonant medium + periodically-modulated field” under consideration result in a hysteresis behaviour in the dependence of the diffraction efficiency on the adiabatically changing intensity of the external field. The predicted hysteresis offers additional potentialities in the investigation of the dynamics of the first-kind phase transition in dense media and outlook for usage of the film as a switching logical element.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006907102469
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    A technique for modelling the performance of birefringent wave plates (1999)
    Springer
    Optical and quantum electronics 31 (1999), S. 645-653 
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    ISSN: 1572-817X
    Keywords: Achromatic ; birefringent ; wave plate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract By considering the phase delay introduced by a birefringent wave plate to each frequency component of a finite bandwidth light source we establish the polarisation state of the transmitted light. Realisable designs of achromatic, zero-order and high-order quarter wave and half wave plates are analysed for use with a variety of light sources with different bandwidths.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006979920296
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    Leaky modes of channel waveguides with uniaxial anisotropy (1999)
    Springer
    Optical and quantum electronics 31 (1999), S. 733-749 
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    ISSN: 1572-817X
    Keywords: anisotropy ; Leaky modes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract An exact numerical method for analyzing the propagation properties of leaky modes of inhomogeneous channel optical waveguides with a complex uniaxial diagonal permittivity tensor is developed. The method is based on solving the system of integro-differential equations formulated with respect to transversal components of the magnetic field and the longitudinal component of the electric field. Some results of investigation of leaky modes of diffused channel waveguides in LiNbO3 and LiTaO3 crystals are given.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006978311814
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    Direct computation of higher-order propagation modes using the imaginary-distance beam propagation method (1999)
    Springer
    Optical and quantum electronics 31 (1999), S. 751-761 
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    ISSN: 1572-817X
    Keywords: eigenmodes ; integrated optics ; FD-BPM
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract In this paper we present an extension to the standard method of eigenmode-extraction using the imaginary-distance beam propagation method. We show that it is possible to directly extract higher-order propagation modes of arbitrary shaped waveguide structures by propagating the field along the imaginary axis when the parameters are chosen in an appropriate manner. This method requires an assumption of the propagation constant of the eigenmode. In many cases this value can be determined using fast approximate techniques like the effective index method. Additionally, the approximate mode shape may be introduced as a starting condition and can further accelerate the extraction of the eigenmode. The overall number of propagation steps needed to extract multiple eigenmodes is then significantly smaller than in the case when extracting the modes sequentially with the former method.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006993604488
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    Problem of plane EM wave self-action in multilayer structure: an exact solution (1999)
    Springer
    Optical and quantum electronics 31 (1999), S. 1059-1072 
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    ISSN: 1572-817X
    Keywords: method of single expression ; nonlinear bilayers ; nonlinear boundary problem ; numerical analysis ; wave self-action
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract To solve exactly the problem of plane EM wave interaction with multilayer nonlinear structures a non-traditional theoretical method is applied. Wave equation's solution in each layer of a structure is presented in the special form of a single expression. This form of field presentation does not require the fulfillment of superposition principle, contrary to the traditional approach. Multilayer structures of threefold quarter-wavelength bilayers with alternate linear and nonlinear indices are investigated. Multistable dependences of reflection coefficients on incident electric field amplitude are obtained for negative and positive nonlinearity. The results of investigation not only permits to deeply understand the phenomena of intense electromagnetic wave interaction with multilayer structures but also will be very useful for elaboration of nonlinear devices.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1007024312874
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    Extreme limit in linear polarisation ratio in step-index single- mode fibres with a central dip (1999)
    Springer
    Optical and quantum electronics 31 (1999), S. 53-67 
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    ISSN: 1572-817X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract From Maxwell's equations, using a Fourier expansion, spatial harmonic balance and Green's functions, closed-form expressions are found for the longitudinal electric and magnetic fields, for two orthogonally polarised modes of a birefringent fibre with or without a central index dip. Propagation constants can then be calculated to the desired degree of accuracy. Corrections up to third order are found to be significant. The linear polarisation ratio in the core and in the cladding is almost insensitive to birefringence but exhibits large variations in the central dip, where it deteriorates as the birefringence increases.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006982014596
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    New stigmatic mounting of holographiccylindrical diffraction grating (1999)
    Springer
    Optical and quantum electronics 31 (1999), S. 13-22 
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    ISSN: 1572-817X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract A new stigmatic mounting of a holographic cylindrical diffraction grating has been considered to be used in the field of X-ray and XUV regions. The conditions for zero astigmatism and sagittal coma have been obtained. Astigmatism per unit length has been plotted against wavelength using the design parameters which give zero astigmatism at least at one wavelength.
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    URL: http://dx.doi.org/10.1023/A:1006959311465
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    The inverse TM solution for self-guided dark beams in defocusing non-Kerr media (1999)
    Springer
    Optical and quantum electronics 31 (1999), S. 85-95 
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    ISSN: 1572-817X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract We investigate the TM fields of Tanh shapes propagating in the defocusing non-Kerr dielectrics. These fields are the exact solutions of Maxwell's equations in a specific medium, called the Exponential Integral Medium (EIM). We derive the exact, analytical description of the dielectric permittivity of this medium. The analytical functions expressing both the field components and permittivity of EIM enable us to treat them as a convenient approximation of dark beams both in the Kerr dielectrics and non-Kerr saturable media. We compare the properties of the solutions in the EIM, Kerr and saturable media and discuss the similarity between the fields and permittivity profiles.
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    URL: http://dx.doi.org/10.1023/A:1006996127532
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    Thermal aspects of designing CW-operated nitride VCSELs (1999)
    Springer
    Optical and quantum electronics 31 (1999), S. 1179-1188 
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    ISSN: 1572-817X
    Keywords: CW operation ; nitride lasers ; simulation ; VCSELs
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract A room-temperature (RT) continuous-wave (CW) operation of possible nitride vertical-cavity surface-emitting lasers (VCSELs) is considered in the present paper using a simple VCSEL simulation to give some essential guidelines for their proper designing. It is revealed that a substrate material has a critical influence on a possibility of reaching RT CW thresholds which practically excludes currently used sapphire substrates of relatively low thermal conductivity from this application. SQW nitride VCSELs are found to be very sensitive to an increase in temperature, which is followed by their inappropriate CW-operation characteristics. A moderate increase in a number of quantum wells in VCSEL active regions significantly improves their CW achievements, i.e. decreases RT CW thresholds as well as considerably widens their CW threshold ranges.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1007011009768
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    Quantum-dot superluminescent diode: A proposal for an ultra-wide output spectrum (1999)
    Springer
    Optical and quantum electronics 31 (1999), S. 1235-1246 
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    ISSN: 1572-817X
    Keywords: quantum dot ; SLD ; wide spectrum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract We propose a novel superluminescent diode (SLD) with a quantum dot (QD) active layer, which should give a wider output spectrum than a conventional quantum well SLD. The device makes use of inhomogeneous broadness of gain spectrum resulting from size inhomogeneity of self-assembled quantum dots grown by Stranski– Krastanow mode. Taking a design made out in the InxGa1-xAs/GaAs system for example, the spectrum characteristics of the device are simulated realistically, 100–200 nm full width of half maximum of output spectrum can be obtained. The dependence of the output spectrum on In composition, size distribution and injection current of the dots active region is also elaborated.
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    URL: http://dx.doi.org/10.1023/A:1007030119338
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    Two-photon absorption and two-photon-induced absorption of some organic liquids at 347.15 nm (1999)
    Springer
    Optical and quantum electronics 31 (1999), S. 269-290 
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    ISSN: 1572-817X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract The two-photon absorption cross-sections and effective excited- state absorption cross-sections at 347.15nm of the organic liquids ethylene glycol, methanol, ethanol, tetrahydrofuran, glycerol, cyclohexane, 1,4-dioxane, 1,2-dichloroethane, dichloromethane, chloroform, dimethylsulfoxide, N,N-dimethylformamide, o-xylene, m- xylene, p-xylene and xylene (isomer mixture) have been determined using second harmonic picosecond pulses of a mode-locked ruby laser system. Linear and circular polarized pump pulse transmission measurements were performed to determine the two linear independent two-photon absorption susceptibility components. Linear polarized probe pulse transmission measurements after pump-pulse passage were carried out to determine excited singlet state relaxation times.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006930314475
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    Dynamical gain saturation in Kerr-lens mode-locked CW solid- state lasers (1999)
    Springer
    Optical and quantum electronics 31 (1999), S. 359-365 
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    ISSN: 1572-817X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract It is shown that dynamical gain saturation, usually neglected for solid-state lasers, can contribute significantly to the pulse-shaping mechanism in Kerr-lens mode-locked lasers. In particular, in combination with self-phase modulation it can cause red shifts and blue shifts of the laser spectrum. A control of the reciprocal gain and loss saturation rates using these shifts leads to improved mode- locking stability.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006971007610
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    Thermal stresses in box-type laser packages (1999)
    Springer
    Optical and quantum electronics 31 (1999), S. 293-302 
    Details
    ISSN: 1572-817X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract The effect of Au coating on thermally induced stresses in box-type semiconductor laser packages was investigated by a finite-element method (FEM). The simulated results showed that Invar–Invar joints with Au coating have maximum stresses two times higher than joints without Au coating. This is due to the different coefficients of the thermal expansion (CTE) between dissimilar materials of Invar and Au, resulting in higher stresses. Maximum stresses were also found to be increased as the Au thickness increased. This effect is attributed to the increase in the thermal gradient in the welded region provided by the increased thermal conduction of the thicker Au coating layer. These results suggest that both the difference in CTE between dissimilar materials and higher thermal conduction of Au coating layer have an important impact on thermally induced stresses for optoelectronic packages having laser-welded Au coated materials.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006966021861
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    An all frequency model of optical pulse train noise spectra (1999)
    Springer
    Optical and quantum electronics 31 (1999), S. 431-449 
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    ISSN: 1572-817X
    Keywords: jitter ; laser noise ; optical pulse train
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006915028067
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    Variations of relative line intensity in saturation spectroscopy due to low magnetic fields (1999)
    Springer
    Optical and quantum electronics 31 (1999), S. 391-403 
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    ISSN: 1572-817X
    Keywords: atomic alignment ; atomic physics ; atomic spectroscopy ; hyperfine structure ; rubidium ; saturation spectroscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract We have observed dramatic line intensity variations in the saturation spectrum of Rb85 and Rb87 due to magnetic fields of magnitude on the order of 100 nT. These variations are detected by rotation of the plane of polarisation of the pump beam and probe beam relative to the magnetic field axis. A modified rate equation model is proposed which accounts for all experimentally observed features. Our results may explain some discrepancies between theory and experiment observed by other authors. Furthermore, our study should lead to a better understanding of the processes involved in saturation spectroscopy.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006902725341
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    Micro-electro-mechanical deformable mirrors for aberration control in optical systems (1999)
    Springer
    Optical and quantum electronics 31 (1999), S. 451-468 
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    ISSN: 1572-817X
    Keywords: aberration control ; deformable mirrors ; micro-electro-mechanical systems
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract Controlling optical aberrations is one of the enduring problems in optics. Recent advances in adaptive optics for astronomical applications have shown the promise of adaptive optics technology for controlling aberrations. Micro-electro-mechanical deformable mirrors (MEM-DMs) offer an alternative to conventional adaptive optics which, due to the inexpensive nature of MEM-DM technology, will enable a wide range of commercial and scientific applications for optical wave front control. In this paper we describe MEM-DMs, present results of modelling the performance of an MEM-DM for optical aberration control, and present results of experiments to verify that MEM-DMs can control optical aberrations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006967012137
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  • 100
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    Modelling of multi-line Brillouin/erbium fibre lasers (1999)
    Springer
    Optical and quantum electronics 31 (1999), S. 481-494 
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    ISSN: 1572-817X
    Keywords: Brillouin/erbium fibre laser (BEFL) ; multiple wavelengths
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract Laser sources with unique properties can be produced using a combination of nonlinear Brillouin gain in single-mode optical fibre (SMOF) and gain in erbium-doped fibre (EDF). Narrow bandwidth nonlinear gain from stimulated Brillouin scattering in SMOF determines the wavelength of operation, and gain in EDF allows efficient operation and large power extraction. Various cascading schemes based on the Brillouin/erbium fibre laser (BEFL) as well as distinctive multi-wavelength versions of the BEFL were proposed, being able to produce 10GHz combs of over 30 lines at 1550 nm. These multi-wavelength sources may be of use in future dense wavelength-division multiplexing systems. We explore fundamental aspects of BEFLs configured to generate multiple wavelengths with particular focus on the effects of the Brillouin and EDF pumps on the number of lines and the relationship between the intensities of the individual lines in the comb.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006971213046
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