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  • Articles  (13,844)
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  • Springer  (11,963)
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  • 1995-1999  (13,844)
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  • 1999  (13,844)
  • Chemistry and Pharmacology  (10,774)
  • Electrical Engineering, Measurement and Control Technology  (3,269)
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  • Articles  (13,844)
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  • 1995-1999  (13,844)
  • 1955-1959
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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
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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.
    Type of Medium: Electronic Resource
    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.
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    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.
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    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.
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    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.
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    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.
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    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
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    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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    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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    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)
    Springer
    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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    URL: http://dx.doi.org/10.1007/BF01206544
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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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    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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    URL: http://dx.doi.org/10.1007/BF01387471
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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
    Source: Springer Online Journal Archives 1860-2000
    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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    Orientation and crystallisation mechanisms during fast drawing of poly(ethylene terephthalate) (1999)
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    Polymer bulletin 42 (1999), S. 357-363 
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    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary Synchrotron radiation has been used to record the diffraction patterns from Poly(ethylene terephthalate) for a range of draw rates (0.1 to 10sec−1) and temperatures (90 to 120°C). The patterns were analysed to derive the development of the 〈P 2(cosθ)〉 order parameter and the rates of crystallisation. The effects of temperature and draw rate can be unified with a WLF time-temperature shift factor. Comparison with estimates of chain relaxation processes show that, when the draw rate is faster than the chain retraction process, the onset of crystallisation is delayed until the end of drawing. Crystallisation is very sensitive to both temperature and orientation and has an approximate 4th power dependence on 〈P2(cosθ)〉.
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    Poly(2,6-dimethyl-1,4-phenylene oxide)/polystyrene blends: thermodynamic interactions from glass transition data (1999)
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    Polymer bulletin 42 (1999), S. 441-448 
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    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary The glass transition temperatures of several blends of poly(2,6-dimethyl-1,4-phenylene oxide) and polystyrene have been measured by DSC, and the T g -composition data have been described on the basis of a thermodynamic treatment. A negative enthalpy of mixing and a positive entropy of mixing have been found, in agreement with the well known miscibility of the blend. The presence of a singolarity point in the T g -composition plot has been evidenced and considered at the light of a theoretical treatment recently proposed.
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    Synthesis and properties of new AB-type semi-crystalline poly(ether imide)s (1999)
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    Polymer bulletin 43 (1999), S. 157-163 
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    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary Two AB-type poly(ether imide)s were prepared by one-pot polyimidization in N-methyl-2-pyrrolidone(NMP)/pyridine or N,N-dimethylacetamide(DMAc)/Et3N solution in the presence of triphenylphosphite(TPP) activator. The polymers were obtained with inherent viscosities of 1.16(5a) and 0.54(5b) dL/g and were highly thermostable up to at least 552°C with 5% weight loss. The polymers showed chemical resistance against chloroform even at higher temperature but could readily be dissolved in m-cresol and concentrated sulfuric acid. Wide-angle X-ray diffractograms revealed that the polymers were semi-crystalline.
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    Synthesis of novel organocobalt poly(arylene-vinylene)s containing (cyclobutadiene)cobalt moieties in the main chain (1999)
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    Polymer bulletin 43 (1999), S. 165-170 
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    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary Organocobalt poly(arylene-vinylene)s composed of 1,2- or 1,3- linkage at their cyclobutadiene moieties (3 and 4, respectively) were prepared by the Heck reaction of p-divinylbenzene with (cyclobutadiene)cobalt-containing monomers having two aryl bromide moieties (1 and 2, respectively). The number average molecular weights (M n) of the obtained organocobalt poly(arylene-vinylene)s (3 and 4) were 4,100 and 4,000, respectively (GPC, on the basis of polystyrene). UV-vis spectra of 3 and 4 exhibited main π-π* absorption peaks at 362 and 397 nm, respectively, which were ca. 60 nm bathochromically shifted from those of the corresponding monomeric units. Both polymers were found to show thermotropic liquid crystallinity in the range of room temperature to ca. 80 °C by employing differential scanning calorimetry (DSC) and the optical measurement using crossed polarizers.
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    Vinyltrimethoxysilane-co-2-vinylpyridine copolymer Synthesis and monomer reactivity ratios (1999)
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    Polymer bulletin 43 (1999), S. 171-175 
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    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary Copolymers containing vinyltrimethoxysilane (VTMOS) and 2-vinylpyridine (2VPy) at different compositions were synthesized and characterized. The monomer reactivity ratios r1 and r2 were estimated by using the classical Fineman-Ross and Kelen Tüdos linear fitting procedures. Moreover, these parameters were also estimated using a nonlinear computational fitting known as Reactivity Ratios Error in Variable Method (RREVM). Attempts to obtain the corresponding copolymer with vinyltrimethylsilane (VTMS) were performed but only hompolymerization 2VPy is observed due to the non-reactivity of VTMS under this conditions. The results were analysed in terms of the relative comonomeric structures and compared with similar related systems. The reactivities are interpreted in terms of the resonance and stabilization effects together with the chemical structure.
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    Synthesis of alkoxycarbene-containing polymers and their application as polymeric catalysts for phenylacetylene polymerization (1999)
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    Polymer bulletin 43 (1999), S. 177-182 
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    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary Polymers having Fischer-type alkoxycarbenes in the side chain were synthesized by the reaction of pendant hydroxy groups with pentacarbonyltungsten acetoxyphenylcarbene [(CO)5W=C(Ph)O2CCH3, 2]. Namely, copolymers of methyl methacrylate with 4-hydroxybutyl methacrylate [poly(MMA-co-HBMA), 3b] were prepared and subjected to the reaction with 2 derived from tetramethylammonium salt of pentacarbonyltungsten hydroxyphenylcarbene [(CO)5W=C(Ph)ON(CH3)4, 1] with acetyl chloride. Soluble copolymers (4b) with pendant metal-carbene segments were obtained, and 1H NMR and UV spectroscopic analyses indicated that the metal-carbene moiety was introduced onto 20–70% of hydroxy groups of the copolymers. In contrast, the introduction of carbene moiety into a copolymer of MMA with 2-hydroxyethyl methacrylate [poly(MMA-co-HEMA), 3a] was unsuccessful because no reaction with 2 took place. The formed polymer (4b) served as a polymeric catalyst for the polymerization of phenylacetylene under the photo-irradiation.
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    Synthesis of poly(N,N-dimethylcarbamoylmethylene) as a polymer homolog of N,N-dimethylacetamide (1999)
    Springer
    Polymer bulletin 43 (1999), S. 183-190 
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    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary A novel polymer homolog of N,N-dimethylacetamide (DMAc) having amide groups on all main chain carbons, poly(N,N-dimethylcarbamoylmethylene) 1, was prepared by heating poly(di-t-butyl fumarate) 2 at 180 °C for 2 hours followed by treatment with hexamethylphosphoramide at 180 °C for 5 hours. The structure of the obtained polymer 1 was confirmed by 1H-, 13C-NMR and IR spectroscopy. The polymer 1 actually showed the properties based on its repeating structures. 1 had the amphiphilicity and was soluble both in protic and aprotic solvents. Furthermore, 1 showed the miscibility with commodity polymers such as poly(N-vinylpyrrolidone), poly(vinyl alcohol) and poly(vinyl chloride). In comparison with another polymer homolog of DMAc, poly(2-methyl-2-oxazoline), the polymer 1 exhibited better miscibility with poly(N-vinylpyrrolidone).
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    Polyamides containing α-aminoacids and hydrophilic oxyethylene groups along the chain (1999)
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    Polymer bulletin 43 (1999), S. 191-198 
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    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary Biocompatible and potentially biodegradable polyamides (PAs) containing in the chain both peptide bonds and hydrophilic triethyleneoxide segments have been prepared by interfacial polycondensation of sebacoyl dichloride with amide-diamines derived from the 4,7,10-trioxa-1,13-tridecanediamine and α-aminoacids such as glycine, L-valine and L-phenylalanine. These PAs exhibit moderate inherent viscosity values and show limited solubilities in CHCl3, DMF and DMSO. 1H-NMR and FTIR spectroscopy analysis confirmed the expected structures. DSC and X-rays diffraction spectra indicated crystallinity degrees from 19 to 31%. The melting temperatures range between 135–238 °C. Liquid water absorption measurements indicate a high equilibrium weight-uptake when a glycine residue is present in the amide-diamine moiety. In vitro tests carried out using cultures of human fibroblasts showed the biocompatibility of the prepared PAs.
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    New catalyst systems for polymerization of substituted acetylenes: W(NO)2(O2CR)2-MCl4(M=Ti, Sn) (1999)
    Springer
    Polymer bulletin 43 (1999), S. 199-206 
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    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary W(NO)2(O2CR)2 - Lewis acid (LA) catalysts (LA=TiCl4, SnCl4; R=-CH(C2H5)(CH2)3CH3) induce substituted acetylenes (phenylacetylene, propargyl ether, 1,6-heptadiyne, diphenylacetylene) to polymerize or oligomerize. Their catalytic ability strongly depends on the Lewis acid and solvent. The polymerization reactions of phenylacetylene always accompany the cycolotrimerization reactions. In the system with TiCl4 in CH2Cl2 the yield of polymer equals to 56% at 80% conversion of a monomer. However, in the system with SnCl4 in benzene, 42% cyclotrimers arise at 57% conversion of phenylacetylene. The mechanism of these reactions as well as the structure of the obtained polymers were determined.
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    Catalyst effect on the transesterification reactions between polycarbonate and polycaprolactone-B-polydimethylsiloxane triblock copolymers (1999)
    Springer
    Polymer bulletin 43 (1999), S. 207-214 
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    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary Transesterification reactions between bisphenol-A polycarbonate and polydimethylsiloxane-polycaprolactone block copolymers were studied in melt at 270°C. Influence of the composition of reaction mixture and the catalyst type on the formation and properties of the products obtained were investigated by spectroscopic, chromatographic and thermal methods. Both of the catalysts used, zinc acetate and lanthanum acetylacetonate are very efficient transesterification catalysts for the system studied. GPC and DSC results clearly show the formation of novel polymers displaying combined properties of the polycarbonate and the silicone-ester copolymer.
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    Termination mechanism of polymethyl methacrylate and polystyrene studied by ultrasonic degradation technique (1999)
    Springer
    Polymer bulletin 43 (1999), S. 215-222 
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    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary A new method for determining the dominant termination mechanism in radical polymerization based on ultrasonic scission of long chains is used to study the termination of polystyrene and polymethyl methacrylate. The method is extended to obtain the disproportionation/combination ratio. Long dead polymer chains in solution were broken by ultrasound. The chain radicals thus formed were then allowed to terminate in the presence and absence of a chain terminating agent (radical trap). The resulting molecular weights are compared to find the dominant termination mechanism. It is found that the dominant mechanism in polystyrene is combination and that in polymethyl methacrylate is disproportionation. These results are in accordance with those quoted in the literature and obtained by other methods.The effectiveness of the radical trap used (2-chloroethyl benzene) was tested by NMR and it was found that when the trapping agent is present it terminates 100% of the polymethyl methacrylate chains. The time evolution of the degree of polymerization was compared to simulations based on Schmid's model. The disproportionation/combination ratios were found for polymethyl methacrylate as 2 and for polystyrene as 1/7 respectively through simulation studies.
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  • 57
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    Poly(β-malic acid) derivatives with non-charged hydrophilic lateral groups: synthesis and characterization (1999)
    Springer
    Polymer bulletin 43 (1999), S. 297-304 
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    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary Poly((3-hydroxypropyl β malate) has been synthesized starting from aspartic acid and benzyloxy-1-propanol as precursors. This new polymer was characterized by 1H and 13C NMR, size exclusion chromatography and differential scanning calorimetry. Homopolymer is soluble in water. Two kinds of amphiphilic copolymers were also prepared and characterized. Such polymers have been synthesized with a view to preparing non-charged degradable associating networks or drug carriers.
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    URL: http://dx.doi.org/10.1007/s002890050614
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  • 58
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    Synthesis and properties of poly(phenylacetylene)s with pendant imino groups (1999)
    Springer
    Polymer bulletin 43 (1999), S. 305-310 
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    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary Polymerization of phenylacetylenes containing imino groups with a variety of transition metal catalysts was investigated. The monomers employed were N-(4-ethynylbenzylidene)aniline (1), N-(3-ethynylbenzylidene)aniline (2), N-(4-ethynylbenzylidene)-2,6-diisopropylaniline (3), N-(4-ethynylbenzylidene)-4-hexylaniline (4), N-(4-ethynylbenzylidene)butylamine (5), and N-(4-ethynylbenzylidene)octylamine (6). All of the monomers smoothly polymerized with [(nbd)RhCl]2-Et3N to give polymers in excellent yields, whereas no polymerization took place with W, Mo, and Fe catalysts. The produced polymers were orange to red solids and soluble in common organic solvents except for poly(1). UV-vis spectra of the polymers indicated that the main chains possess a similar degree of conjugation to that of poly(phenylacetylene). However, the stability of polymer backbone toward oxidative cleavage in solution remarkably improved, which is contributed by the electron-withdrawing character of imino groups.
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    URL: http://dx.doi.org/10.1007/s002890050615
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    Controlled polymerization of methylmethacrylate and ethylacrylate using tris(4,4'-dimethyl-2,2'-bipyridine) copper(II) hexafluorophosphate complexes and aluminium isopropoxide (1999)
    Springer
    Polymer bulletin 43 (1999), S. 319-326 
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    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary The radical polymerization of methylmethacrylate and ethylacrylate was carried out in the presence of tris(4,4'-dimethyl-2,2'-bipyridine) copper(II) hexafluorophosphate complexes and aluminium isopropoxide. The molecular weight of the synthesized polyethylacrylates increased proportionally with conversion, whereas the polymerization of methylmethacrylate revealed a nonlinear behavior. The polydispersities of the molecular weight distributions observed were between 1.09 and 1.34. Poly(styrene-block-polymethylmethacrylate) was synthesized by sequential monomer addition.
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    Synthesis and the properties of novel cycloaliphatic-aromatic polyamides having pendent N,N'-diphenyl imido groups (1999)
    Springer
    Polymer bulletin 43 (1999), S. 311-318 
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    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: ABSTRACT : We have investigated a novel monomer having two pendent phenyl imido groups for preparing new cycloaliphatic-aromatic polyamides. Novel polyamides were synthesized by direct polycondensation reaction of N,N'-diphenyl-2,3,5,6-diimido cyclohexane-1,4-dicarboxylic acid(PICA) and various aromatic diamines such as p-phenylene diamine, 4,4'-oxydianiline and 4,4'-methylene dianiline. A direct polycondensation was carried out by a Yamazaki method which is typical of using triphenyl phosphite, lithium chloride, and pyridine. Inherent viscosity of these resulting polyamides are ranged 0.20 ∼ 0.45 dl/g. A transparent flexible and tough film was casted. The glass transition temperature of the polyamide from the PICA and 4,4'-oxydianiline is 147 °C. The decomposition temperature of these polyamides are ranged from 350 ∼ 360 °C and the ash contents of them orders MDA 〉 p-PDA 〉 ODA according to kinds of the using diamines. And the solubilities of these polyamides are good in aprotic solvents such as DMAc, NMP, DMF.
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    Chain transfer reaction in metallocene catalyzed ethylene copolymerization with allyltrimethylsilane (1999)
    Springer
    Polymer bulletin 43 (1999), S. 333-340 
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    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary In order to investigate the polymerization behavior of allytrimethylsilane as a comonomer, ethylene was copolymerized with allyltrimethylsilane at 80°C in toluene using methylaluminoxane (MAO) activated metallocene catalysts. The catalytic activity of the polymerization strongly depended on both the type of the catalysts and the concentration of allyltrimethylsilane. End group analysis of the copolymers by means of 1H and 13C NMR spectroscopy revealed that allyltrimethylsilane rather act as a chain transfer agent in the copolymerization, even though considerable amount of allyltrimethylsilane was incorporated in the polymer chain with rac-Et(Ind)2ZrCl2 catalysts. The chain transfer reaction influence strongly the molecular weight and comonomer content of the copolymers.
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    Poly[N-(hydroxyethyl)ethyleneimine-co-phenyl succinic anhydride] Synthesis and structure (1999)
    Springer
    Polymer bulletin 43 (1999), S. 341-347 
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    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary Five copolymers from N-(hydroxyethyl)ethyleneimine as nucleophilic monomer and phenylsuccinic anhydride (PhSAn) as electrophilic monomer, were synthesized according to the spontaneous copolymerization concept. These copolymers were characterized by elemental analysis, FT-IR, 1H-NMR, and 13C-NMR spectroscopy. The copolymer composition determined from the 1H-NMR spectra showed that the copolymers are not alternating. According to all the data, it was suggested a copolymer structure which includes ester and anhydride bonds. The molecular weights determined by vapor pressure osmometry ranged between 5.100 and 6.100 g/mol.
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    Comparison of the photopolymerization kinetics of triethyleneglycol dimethacrylate initiated by camphorquinone/N-phenylglycine and camphorquinone/D,L-α-phenylglycine (1999)
    Springer
    Polymer bulletin 43 (1999), S. 349-355 
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    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary This work describes the kinetics of triethyleneglycol dimethacrylate (TEGDM) polymerization, photoinitiated by camphorquinone (CQ) / N-phenylglycine (NPG) and CQ /D,L α-phenylglycine (α-PG), in air and/or in N2. The rates of polymerization (Rp), double bond conversion (p), monomer conversion (pmax), at different concentration of NPG and α-PG were measured and analysed. It was found that CQ/NPG is much more effective photoinitiator system than CQ/α-PG, regarding to the different their chemical structure and H-atom donor ability.
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    URL: http://dx.doi.org/10.1007/s002890050621
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    Thermal properties and flammability of acrylic nanocomposites based upon organophilic layered silicates (1999)
    Springer
    Polymer bulletin 43 (1999), S. 395-402 
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    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary Thermal and mechanical properties of poly(methylmethacrylate-co-dodecylmethacrylate) nanocomposites based upon exfoliated organophilic layered silicates, were investigated as a function of the silicate and comonomer content. Layered silicates such as sodium bentonite were rendered organophilic by means of ion-exchanging sodium cations for N,N,N,N-dioctadecyl-dimethyl-ammonium cations. Silicate exfoliation was enhanced by means of 5 and 10 wt.-% dodecyl-methacrylate (LMA) addition to afford translucent reinforced acrylic nanocomposites. In contrast to conventional filled acrylic polymers, only 10 wt.-% organophilic silicate was sufficient to increase Young's modulus from 2200 to 4030 MPa, glass temperature from 72 to 80 °C and degradation temperature from 220 to 256 °C with respect to the neat MMA/LMA (90 wt.-%/10 wt.-%) copolymer. Flammability studies, performed on a cone calorimeter, revealed that the maximum heat release rate of MMA/LMA copolymer nanocomposite decreased from 837 kW/m2 to 566 kW/m2. The nanocomposite morphology was examined by means of transmission electron microscopy (TEM).
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    A synthesis of O-diethylaminoethyl chitosan and its binding ability of cholate and deoxycholate anion in vitro (1999)
    Springer
    Polymer bulletin 42 (1999), S. 25-32 
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    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary The aim of this study was to investigate the bile salts adsorption behavior of the diethylaminoethyl (DEAE)-chitosan, in vitro. In order to prepare the DEAE-chitosan, where the DEAE groups are specifically introduced onto 6-OH groups of chitosan with minimal by-product, DEAE-chitin was prepared by reacting chitin with N,N-diethylaminoethyl chloride, and direct N-deacetylation of DEAE-chitin was carried out in 10% of an aqueous sodium hydroxide solution containing sodium borohydride. DEAE chitosan samples were incubated with cholic acid sodium salt and deoxycholic acid sodium salt in a tromethane buffer solution (pH 7.5) for 1 hour, and the bile salts adsorption performances of the samples were examined by HPLC. The modified chitosan samples showed improved bile salts adsorption performances compared to chitosan, and the absorption amount of bile salt to the samples increased with increase in the DEAE groups introduced. In most cases, the adsorption amount of deoxycholate to the samples was greater than that of cholate.
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    The ambient temperature synthesis and characterization of bile acid polymers (1999)
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    Polymer bulletin 42 (1999), S. 41-46 
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    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary Room temperature polymerization of three naturally occurring bile acids, cholic, lithocholic and deoxycholic, was carried out using a mixture of diisopropyl carbodiimide (DIPC), and a 1:1 salt of dimethyl amino pyridine and p-toluenesulfonic acid (DMAP/PTSA). The corresponding polymers were characterized by IR, NMR, Thermal Analysis and X-ray diffraction. Molecular weights were calculated by gel permeation chromatography in the range 50,000–60,000, using polystyrene standards. The polymers were also characterized by mass spectrometry, using matrix assisted laser desorption ionization-time of flight, MALDI-TOF.
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    Synthesis and properties of poly(phenylacetylene)s having dialkylamino groups (1999)
    Springer
    Polymer bulletin 42 (1999), S. 55-60 
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    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary Poly(phenylacetylene)s bearing dialkylamino groups were prepared by the polymerization of p-(N,N-dialkylamino)phenylacetylenes with [Rh(nbd)Cl]2, and their electrochemical behavior was examined. Rh-catalyzed polymerization of p-(N,N-diethylamino)phenylacetylene (DEAPA) and p-(N,N-di-n-butylamino)phenylacetylene (DBAPA) in toluene in the presence of triethylamine gave good yields of the polymers (86 and 90%, respectively). Poly(DEAPA) was soluble in chloroform and dichloromethane, and poly(DBAPA) dissolved in various solvents such as toluene, THF, dichloromethane and chloroform. Poly(DEAPA) and poly(DBAPA) showed onset temperatures at 248 and 190°C, respectively, and absorptions around 300–400 nm. Electrochemical doping of the polymer films resulted in the shift of the absorptions to a region around 680 nm, which accompanied a color change of the polymer films from green ocher to deep blue.
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    Hydrogenation of poly(vinyl cinnamate) thin layer (1999)
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    Polymer bulletin 42 (1999), S. 149-152 
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    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary Hydrogenation of poly(vinyl cinnamate) was performed with RhH(CO)(PPh3)3 catalyst with intent to clarify the photoalignment mechanism of liquid crystals on poly(vinyl cinnamate) alignment layer. The hydrogenated cinnamate side group shows the characteristic peaks at 2.9 ppm and 2.5 ppm in 1H-NMR spectrum, and a decreasing peak at 280 nm in UV spectrum. This reaction can reveal the role of dimerized or residual cinnamate groups in the applications of the polymeric layer for electronic devices.
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    Ru(0) complex catalyzed polyaddition New synthesis of poly(alkylenebenzoxazole) and poly(alkylenebenzimidazole) (1999)
    Springer
    Polymer bulletin 42 (1999), S. 141-147 
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    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary The reactions of α,ω-diyne, HC≡C(CH2)mC≡CH (m = 6 and 8), with 3,3'-diaminobenzidine and with 3,3'-diamino-4,4'-dihydroxybiphenyl in the presence of RU3(CO)12-PPh3 catalyst give the corresponding poly(alkylenebenzoxazole)s and poly(alkylenebenzimidazole)s, respectively. The former polymers obtained from the equimolar reaction of the monomers are partly soluble in polar organic solvents such as DMF, DMSO, and NMP, while the poly(benzimidazole)s are soluble in these solvents. GPC measurement shows the molecular weights of the polymers, M n of 4.8−14.1×103 and M w of 6.4−19.7×103.
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    On the preparation and characterization of chitosan hydrochloride (1999)
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    Polymer bulletin 42 (1999), S. 159-166 
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    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary The procedures for the purification of commercial chitosan samples as hydrochlorides and in the neutralized form are described. Thermal analysis reveals that, independently of the purification method, all samples are highly pure. The agreement between values of degrees of acetylation determined by conductimetric titrations and by 1H nmr spectroscopy is very good. The aqueous solutions of both forms of purified chitosan were free of aggregation as evaluated by their Huggins constants. The potential use of solutions of chitosan hydrochloride in acid-free aqueous NaCl for the studies aiming to characterize the solution behavior of chitosan is demonstrated.
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    Synthesis and properties of nonlinear optical chromophores and polymers containing 6-nitroquinoline as π-electron acceptor (1999)
    Springer
    Polymer bulletin 42 (1999), S. 175-181 
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    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary Two nonlinear optical (NLO) methacrylate monomers, 2-methyl-acrylic acid 2-(ethyl-{4-[2-(6-nitro-quinolin-2-yl)-vinyl]-phenyl}-amino)-ethyl ester (5) and 2-methyl-acrylic acid 6-{3-[2-(6-nitro-quinolin-2-yl)-vinyl]-carbazol-9-yl}-hexyl ester (7) were newly synthesized and copolymerized with methylmethacrylate to give NLO polymers, P1 and P2. These polymers were well soluble in organic solvents and showed glass transition temperatures at 145 °C and 114 °C, respectively. The number average molecular weights (Mn) were 26,600 for P1 and 9,300 for P2. The SHG coefficients (d33) of corona-poled films of P1 and P2 measured with 1.064 μm Nd-YAG laser were 32.2 pm/V and 17.6 pm/V, respectively.
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    A novel π-conjugated polymer : poly(3,4-bis(phenylene)-3-cyclobutene-1,2-dione) (1999)
    Springer
    Polymer bulletin 42 (1999), S. 183-190 
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    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: ABSTRACT: We have investigated a new 1,2-type aromatic dibromide monomer for preparing a modified π -conjugated poly(p-phenylenevinylene). A novel π -conjugated poly(p-phenylenevinylene) was prepared by dehalogenation polycondensation of a dibromoaromatic compound with a squaric unit as a monomer with zerovalent nickel [Ni(0)] complex. The monomer and the polymer were characterized by FT-IR, 1H-NMR, Elemental Anaylsis, TGA, DSC, GPC and UV-Visible. The resultant polymer had good solubility to polar aprotic, solvents, e.g. DMF, DMAc, DMSO and NMP and solvatochromism in DMAc.
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    Mechanochemical synthesis and characterization of poly(vinyl chloride)-block-poly(vinyl alcohol) copolymers by ultrasonic irradiation (1999)
    Springer
    Polymer bulletin 42 (1999), S. 197-204 
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    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Mechanical degradation and mechanochemical reaction in heterogeneous systems of the solid poly(vinyl chloride)-poly(vinyl alcohol) aqueous solutions have been studied by ultrasonic irradiation at 30 °C. The rate of decrease in the viscosity-average degree of polymerization of the degraded poly(vinyl chloride) was much faster than that of the degraded poly(vinyl alcohol). Mechanochemical reaction occurred by free radicals produced from the chain scissions of both polymers by ultrasonic waves. The copolymer was obtained and the molar ratio of the vinyl chloride and the vinyl alcohol units in its copolymer can be determined. In addition, the changes in the composition of the total block copolymer, the unreacted poly(vinyl chloride), and the unreacted poly(vinyl alcohol) were obtained.
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    Fracture toughness of polysulfone/epoxy semi-IPN with morphology spectrum (1999)
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    Polymer bulletin 42 (1999), S. 221-227 
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    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The fracture toughness of the semi-IPN's of crosslinked epoxy and linear polysulfone(PSf) having morphology spectrum was investigated. The epoxy resin was based on diglycidyl ether of bisphenol A(DGEBA) and diaminodiphenylsulfone(DDS). The morphology spectrum, which has the gradual change of the morphological feature resulting from the concentration gradient of PSf in the epoxy resin can be obtained by inserting a PSf film in DGEBA/DDS mixture before cure. The relative rate of the dissolution of the PSf in the epoxy oligomer and the rate of curing reaction determine the concentration gradient of the PSf. In the region where the PSf concentration is less then 5%, sea(epoxy)-island(PSf) morphology is observed. As the concentration of PSf increases, the morphology changes to nodular structure, inverted sea-island, and PSf/epoxy homogeneous phase. Up to overall 10wt% of PSf, the fracture toughness of the PSf modified epoxy with morphology spectrum was higher than that of the counterpart with uniform concentration of PSf. These results were ascribed to the plastic deformation of the continuous PSf rich phase which was present in the morphology spectrum.
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    URL: http://dx.doi.org/10.1007/s002890050456
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    Polymerization of allylbenzene with metallocene catalysts (1999)
    Springer
    Polymer bulletin 42 (1999), S. 265-272 
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    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary Homopolymerization of allylbenzene was carried out with various metallocene/methylaluminoxane (MAO) catalysts. Different polymerization behavior was observed depending upon the catalysts empolyed. rac-Et(Ind)2ZrCl2 and rac-Me2Si(Ind)2ZrCl2 gave semicrystalline polyallylbenzenes while i-Pr(CpFlu)ZrCl2 and CpTiCl3 did not give any polymeric product. The Cp2ZrCl2 gave amorphous polyallylbenzene with low molecular weight. The effect of temperature on the polymerization was investigated with a constant Al/Zr ratio. The temperature showing maximum catalyst activity is higher for the ansa metallocene catalysts than Cp2ZrCl2 catalyst. The IR and NMR spectra indicated that the polyallylbenzene consisted of allylbenzene repeating unit and no isomerization occurred.
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    URL: http://dx.doi.org/10.1007/s002890050462
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    Synthesis of poly(ethyl vinyl ethers) containing two dipolar electronic systems and their properties (1999)
    Springer
    Polymer bulletin 42 (1999), S. 237-244 
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    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary 5-Nitro-2-(2′-vinyloxyethoxy)benzylidenemalononitrile (2a), methyl 5-nitro-2-(2′-vinyloxyethoxy)benzylidenecyanoacetate (2b), 3-nitro-4-(2′-vinyloxyethoxy)benzylidenemalononitrile (4a), and methyl 3-nitro-4-(2′-vinyloxyethoxy)benzylidenecyanoacetate (4b) were prepared by the condensation of 5-nitro-2-(2′-vinyloxyethoxy)benzaldehyde (1) and 3-nitro-4-(2′-vinyloxyethoxy)benzaldehyde (3) with malononitrile or methyl cyanoacetate, respectively. Vinyl ether monomers 2a-b and 4a-b were polymerized with boron trifluoride etherate as a cationic initiator to yield poly(vinyl ethers) 5-6 having nitrooxybenzylidenemalononitrile and nitrooxycyanocinnamate, which is effective chromophore for second-order nonlinear optical applications. Polymers 5-6 were soluble in common organic solvents such as acetone and DMSO. T g values of the resulting polymer were in the range of 70–81°C. Electrooptic coefficient (r33) of the poled polymer films were in the range of 19–27 pm/V, which was improved by introducing of nitro group. Polymers 5–6 showed a thermal stability up to 300°C in TGA thermograms, which is acceptable for NLO device applications.
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    URL: http://dx.doi.org/10.1007/s002890050458
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    Coupling reactions of activated oligo(ɛ-caprolactone)s (1999)
    Springer
    Polymer bulletin 42 (1999), S. 257-264 
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    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary Oligo(ɛ-caprolactone)s functionalised with acid groups were prepared by reacting hydroxyl terminated oligo(ɛ-caprolactone)s with succinic anhydride, maleic anhydride or glutaric anhydride. Quantitative conversion of the hydroxyl functionality was achieved in the melt at 130 °C. The resulting acid terminated oligo(ɛ-caprolactone)s were characterised by 1H and 13C NMR spectroscopy. The reactivity of these oligomers was enhanced by conversion of the acid functionality in an acid chloride functionality using thionyl chloride or an anhydride functionality using acetic anhydride. It was shown that these activated oligo(ɛ-caprolactone)s can be used for coupling reactions with compounds containing alcohol- or amino functionalities.
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    Novel non-alternating copolymers synthesized by spontaneous copolymerization of p-chlorophenylmaleimide with 2-methyl-2-oxazoline (1999)
    Springer
    Polymer bulletin 42 (1999), S. 281-286 
    Details
    ISSN: 1436-2449
    Keywords: Keywords: Nucleophilic and electrophilic monomers; spontaneous copolymerization; non-alternating copolymers.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary The copolymerization of p-chlorophenylmaleimide (1) as electrophilic monomer with 2-methyl-2-oxazoline (2) as nucleophilic monomer without initiator in solution under different experimental conditions was investigated. Copolymers were characterized by FT-IR and 1H-NMR spectroscopy. The copolymer composition was determined from 1H-NMR spectra. Molecular weights ranged between 1700 and 5400 g/mol by vapor pressure osmometry.
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    URL: http://dx.doi.org/10.1007/s002890050464
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    Study on the alcoholysis of aromatic polyesters and related esters using a high-pressure calorimeter (1999)
    Springer
    Polymer bulletin 42 (1999), S. 295-300 
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    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary The heat of base-catalyzed alcoholysis of poly(ethylene terephthalate) (PET) and poly(ethylene 2,6-naphthalenedicarboxylate) (PEN) as well as several related aromatic and aliphatic esters has been measured using a high-pressure calorimeter. The process is essentially thermoneutral, and heats of CH3ONa-catalyzed methanolysis of PET and PEN are +1.8±0.6 and +9.3±0.2 kJ/mol-carboxyl group, respectively. Furthermore, the heats of Zn(OCOCH3)2-catalyzed alcoholysis of PET with ethylene glycol and benzyl alcohol are also calculated as +5.8±0.2 and +6.6±0.8 kJ/mol-carboxyl group, respectively. These values are comparable to those for ethyl esters of p-substituted benzoic acids and propionic acid.
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    URL: http://dx.doi.org/10.1007/s002890050466
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  • 80
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    Chain transfer reactions in metallocene catalyzed polymerization of allylbenzene (1999)
    Springer
    Polymer bulletin 42 (1999), S. 301-307 
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    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary Allylbenzene was polymerized in the presence of two types of homogeneous zirconocene catalysts (co-catalyst methylaluiminoxane). Selective chain termination through β-hydride elimination or chain transfer to aluminum was observed depending upon the catalysts employed. The rac-Et(Ind)2ZrCl2, and rac-Me2Si(Ind)2ZrCl2, catalysts gave the polyallylbenzenes with saturated end groups due to chain transfer to aluminum, while the Cp2ZrCl2 catalyst gave the polyallylbenzenes with vinylidene end groups due to β-hydride elimination.
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    Radical polymerization of methacryloyl isocyanate containing 1-adamantanol (1999)
    Springer
    Polymer bulletin 42 (1999), S. 373-378 
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    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary Radical polymerization of the methacryloyl isocyanate containing 1-adamantanol (Ad-MAI) with AIBN in different solvents at 60°C was investigated. It is observed that polymerization is slower in polar solvents than in nonpolar ones. The rate of polymerization for Ad-MAI was found to be slower than those of Adph-MAI and MMA both in photopolymerization and in thermal polymerization. Copolymerization of Ad-MAI (M1) with styrene (M2) in benzene was studied at 60°C. The monomer reactivity ratio was calculated to be r1=1.53 and r2=0.76 according to the method of Fineman-Ross. The prominent glass transition temperature for poly(Ad-MAI) was observed at 142°C from global TSC spectrum.
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    URL: http://dx.doi.org/10.1007/s002890050478
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    Comb-shaped chitosan derivatives having oligo(ethylene glycol) side chains (1999)
    Springer
    Polymer bulletin 42 (1999), S. 387-393 
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    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary Monoaldehydes have been synthesized from tri- and tetra(ethylene glycol) monosubstituted derivatives and introduced into chitosan by the reductive alkylation technique to give comb-shaped polysaccharide hybrids. The reaction of chitosan with the aldehydes in the presence of sodium cyanoborohydride proceeded efficiently to give chitosan derivatives having oligo(ethylene glycol) side chains at the amino groups. The products were characterized by high affinity for organic solvents as well as water in sharp contrast to the original chitin and chitosan. They showed significant adsorption capacity toward metal cations.
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    Synthesis and properties of nonlinear optical polymers based on poly(ether imides) for electrooptical devices (1999)
    Springer
    Polymer bulletin 42 (1999), S. 403-409 
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    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary : Nonlinear optical poly(ether imides) with an adequate thermal stability has been synthesized by direct coupling of hydroxy poly(ether imides) and NLO chromophores with a quantitative yield. The resultant amorphous NLO poly(ether imides) exhibited good solubility in common organic solvents, providing optical-quality thin films by spin coating. The glass transition temperatures of the polymers are at around 180 °C. The electrooptic coefficients (r33, @1.3μm) of PEI-DR1 was 12.3 pm/V with an electrical poling field of 100 V/μm and it decayed about 10 % over 10 months at 90 °C under atmospheric conditions.
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    URL: http://dx.doi.org/10.1007/s002890050482
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    A novel gas sensor from crystalline polymer-grafted carbon black: responsibility of electric resistance of composite from crystalline polymer-grafted carbon black against solvent vapor (1999)
    Springer
    Polymer bulletin 42 (1999), S. 425-431 
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    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary Crystalline polymers, such as poly(ɛ-caprolactone) (PCL), poly(ethylene adipate) (PEA), and polyethylene (PE), were successfully grafted onto carbon black surface by direct condensation of terminal groups of these polymers with carboxyl groups on the surface using N,N'-dicyclohexylcarbodiimide as a condensing agent. The electric resistance of a composite prepared from these crystalline polymer-grafted carbon black drastically increased to 104–105 times of initial resistance in good solvent vapor of grafted polymer and returned to initial resistance when it was transferred into dry air. However, the change of electric resistance of the composite hardly observed in poor solvent vapor. These results suggest that these composite can be applied as a novel gas sensor.
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    Corona poling of liquid crystalline polymers with nitroazobenzene side chains (1999)
    Springer
    Polymer bulletin 42 (1999), S. 575-578 
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    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary The orientational behavior of liquid crystalline polymers with para-nitro azobenzene as side chains under electric field was studied by UV-visible spectroscopy. The results showed that λmax of the poled polymer films was around 394nm, compared to that of the unpoled films, the absorption decreased due to poling. The orientational parameters increased linearly with the increase of the electric field. The temporal stability of the poled polymer film is good at room temperature. This kind of materials showed promise application as nonlinear optical component in photorefractive polymers
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    Rheo-optical fourier transform infrared spectroscopy of diol-modified diglycidyl ether of bisphenol-A epoxy resins (1999)
    Springer
    Polymer bulletin 42 (1999), S. 579-586 
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    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary The molecular orientation behaviour of epoxy networks on the basis of the diglycidyl ether of bisphenol-A (DGEBA) and various linear aliphatic diols was studied by rheo-optical FTIR spectroscopy. Uniaxial deformation was performed above and below the glass transition temperature. The influence of diol chain length and molar ratio on the mechanical properties and the orientation parameter will be discussed.
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    Electro-optic studies on novel chiral liquid crystalline polysiloxanes with the N* phase (1999)
    Springer
    Polymer bulletin 42 (1999), S. 603-609 
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    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary The electro-optical response of two novel side chain liquid crystalline polysiloxane copolymers containing chiral pendant groups was investigated. It was found that both copolymers possessed N* phase with a long pitch and therefore the origin of the electro-optical response detected in this phase was considered to be the electroclinic effect.
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    URL: http://dx.doi.org/10.1007/s002890050508
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    Novel blends of alternating propene-carbon monoxide copolymers and styrenic copolymers (1999)
    Springer
    Polymer bulletin 42 (1999), S. 611-618 
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    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary Alternating propene-carbon monoxide copolymers (P-CO) were melt-blended with polystyrene, poly(styrene-co-acrylonitrile) (SAN), and with poly(styrene-co-maleic anhydride) (SMA). P-CO forms homogeneously miscible blends with SAN containing 25 wt% AN at the investigated blend compositions. The transparent blends have single, intermediate glass transition temperatures that fit the Fox equation. The elastic properties of P-CO at room temperature disappear upon blending with SAN because the T g is driven above RT. Polystyrene and SMA are not miscible with P-CO and form heterogeneous blends with two glass transitions. This demonstrates that both the polarity of the styrenic copolymer and the nature of the comonomer govern its phase behavior.
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    Polymerization of methyl methacrylate using organocalcium compounds (1999)
    Springer
    Polymer bulletin 42 (1999), S. 635-639 
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    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary We have studied the polymerization of methyl methacrylate (MMA) using biscyclopentadienylcalcium (Cp2Ca) and bis(pentamethylcyclopentadienyl)calcium (Cp2 *Ca) as initiators. Polymerizations initiated with CP2Ca produced poly(methyl methacrylate), PMMA, with %rr = 80. This polymerization was conducted in 1,2-dimethoxyethane at 0°C; monomer conversion was 57% after 19 h. Lindsell and co-workers reported a much higher syndiotacticity for the same initiator. While 80%rr is higher than a free radical polymerization of MMA at the same temperature, the broad polydispersity and low conversions make this polymerization method unattractive. Use of the more soluble initiator Cp2 *Ca significantly increases monomer conversion but produces PMMA with lower syndiotacticity.
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    Cationic photopolymerisation of divinylethers systems containing hydroxyvinylethers (1999)
    Springer
    Polymer bulletin 42 (1999), S. 641-648 
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    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary Diethyleneglycoldivinylether (DVE2) and triethyleneglycoldivinylether (DVE3) were photopolymerised together with monovinylethers and hydroxyalkylvinylethers, in order to study the curing reaction and to evaluate the properties of the films obtained. In the presence of the monovinylethers, the flexibility of the cured films increased and the Tg values decreased. In the presence of a hydroxyalkylvinyl ether, a stronger plasticisation effect was obtained and attributed to a chain transfer reaction involving -OH groups.
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    Synthesis of Congo Red linked with alkyl amide polymer and its optical ion-sensing property (1999)
    Springer
    Polymer bulletin 42 (1999), S. 655-660 
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    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary The synthesis and metal ion responsive properties of Congo Red-based polyamide are reported. The polymer was prepared by simple interfacial polymerization between Congo Red and sebacoyl chloride. The polymer showed decrease in electronic absorption when exposed to metal ions. The absorbance tends to decrease linearly in a measurable range according to metal ion concentration. It is found that the polymer showed high sensitivity toward Ca2+ and Fe3+.
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    Synthesis and properties of poly(amide-imide)s with different microstructures based on trimellitimide and 4,4'-diphenyl ether (1999)
    Springer
    Polymer bulletin 42 (1999), S. 661-668 
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    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary Poly(amide-imide)s(PAIs) with different microstructures were prepared based on trimellitimide and 4,4'-diphenylether with varying the reaction conditions. The microstructures of PAIs were examined by 500MHz 1H-NMR spectroscopy. The head-to tail (HT-) PAI showed a sharp peak in WAXD curve, a large shift at around 1670 cm−1 for −C=O stretching in FT-IR spectra, and poor solubility in organic solvents, high density, Tg, tensile strength and modulus compared to head-to-head (HH-) PAI and copolymers of HT and HH. These results might be due to the higher packing tendency of the HT PAI than HH PAI or copolymers.
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    Synthesis of conjugated polyphenylacetylenes with redox active ferrocenyl end-groups (1999)
    Springer
    Polymer bulletin 42 (1999), S. 683-688 
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    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary Metathesis polymerization has been employed for the synthesis of polyphenylacetylene (PPA) containing redox-active ferrocene groups at both ends. Two reversible one electron oxidation waves were detected in CV. The ΔE values decreased with increase in chain length of the polymer, indicating that the metal-metal interaction decreases by increasing the chain length.
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    Preparation and sensor properties of poly (o-toluidine) film (1999)
    Springer
    Polymer bulletin 42 (1999), S. 693-699 
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    ISSN: 1436-2449
    Keywords: Key Words: poly(o-toluidine); enzyme electrode; amperometric biosensor
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary An amperometric biosensor for glucose was constructed in a one-step procedure by the electropolymerization of o-toluidine in the presence of glucose oxidase on Pt substrates in KCl aqueous electrolyte at a potential of 0.5 V vs Ag / AgCl. The amperometric responses of the prepared polymeric biosensor to the glucose were measured at a potential of 0.7 V in PBS solution. Results showed that this polymeric sensor exhibited a fast amperometric response time (4–5 s) and a linear range up to 6 mM glucose with poor stability. Also, it was seen that biosensor responded successfully to glucose injections in the presence of some interfering species such as lactose, sucrose and urea.
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    Study of the miscibility of poly(ethyl methacrylate-co-4-vinylpyridine)/poly(styrene-co-cinnamic acid) blends (1999)
    Springer
    Polymer bulletin 42 (1999), S. 701-708 
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    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary The miscibility of a series of poly(ethyl methacrylate-co-4-vinylpyridine) with poly(styrene-co-cinnamic acid), is investigated by differential scanning calorimetry. The results show that each blend is miscible as ascertained by a single composition dependent glass transition temperature. The Tg's of the blends exhibit positive deviations from the weight average Tg's of the blend components. The thermograms data exploited according to the Kwei and Schneider approaches suggest the occurrence of strong specific intermolecular attractive interactions within the binary systems. The strength of these interactions, as estimated from the Kwei q-values, increases with the proton donor and proton acceptor contents in the copolymers.
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    Thermosensitive networks based on high molecular weight polyoxyethylene and N-isopropylacrylamide (1999)
    Springer
    Polymer bulletin 42 (1999), S. 709-716 
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    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary γ- and UV-irradiation was successfully used for the preparation of mixed networks on the basis of high molecular weight polyoxyethylene (POE) and/or N-isopropylacrylamide and poly(N-isopropylacrylamide) (PNIPAAm). These gels preserve the swelling transition temperature of the pure PNIPAAm and shrink faster above this temperature due to the hydrophilic POE chains. It was found that in a collapsed state these gels retain alkaline organic salts from aqueous solutions.
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    Solid particle erosion of electrically insulating silicon and EPDM rubber compounds (1999)
    Springer
    Polymer bulletin 42 (1999), S. 717-724 
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    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary Jet erosion tests of outdoor insulating silicone and EPDM rubbers were carried out by means of a modified sandblasting equipment. The presence of relatively large, non-reinforcing filler particles increased the erosion rate of the silicone rubber compounds. The erosive wear of highly filled compounds strongly depended on the incident angle of the eroding particles. Rubbers with low amount or very finely dispersed reinforcing filler showed a good resistance to solid particle erosion. The mechanisms of material removal were studied by scanning electron microscopy and discussed.
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  • 98
    Electronic Resource
    Electronic Resource
    Polymerization of cyclic monomers 9. Synthesis and radical polymerization of spirocyclic 2-vinylcyclopropanes (1999)
    Springer
    Polymer bulletin 43 (1999), S. 1-7 
    Details
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary 6,6-Diethyl- (1a) and 6-methyl-6-propyl-5,7-dioxa-4,8-dioxo-1-vinylspiro[2.5]octane (1b) were synthesized by the acetalization of 2-vinylcyclopropane-1,1-dicarboxylic acid with 2- or 3-pentanone. The new monomers were characterized by IR, 1H NMR and 13C NMR spectroscopy. The radical polymerization of the monomers 1a and 1b, in addition of 6,6-methyl-5,7-dioxa-4,8-dioxo-1-vinylspiro[2.5]octane (1c) and (exo/endo)-7-ethoxycarbonyl-2-oxo-7-vinyl-bicyclo[4.1.0]heptane (1d), was carried out in bulk with 2,2`-azoisobutyronitrile (AIBN) as the initiator. The polymer yield with 1d was only low. The polymerization of the monomers 1a and 1c resulted in cross-linked polymers, whereas in case of the polymerization of monomer 1b soluble polymers in a high yield were obtained.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002890050525
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  • 99
    Electronic Resource
    Electronic Resource
    Synthesis of a star-shaped polymer by coordination of 2,2'-bipyridyl-terminated poly(propylene glycol) with ruthenium ion (1999)
    Springer
    Polymer bulletin 43 (1999), S. 9-12 
    Details
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary The Ru(II)-centered star-shaped polymer was prepared by coordination of 2,2'-bipyridyl-terminated poly(propylene glycol) with ruthenium ion. The structure was confirmed by GPC analysis and UV/Vis spectrum. The resulting polymer complex was well-soluble in various organic solvents and water.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002890050526
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  • 100
    Electronic Resource
    Electronic Resource
    Synthesis and properties of poly(p-phenylenevinylene-co-sulfonylene) for a blue light-emitting diode (1999)
    Springer
    Polymer bulletin 43 (1999), S. 13-20 
    Details
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary Novel class of p-phenylenevinylene copolymer with sulfonylene group in the main chain (PPVS) was synthesized through the Wittig reaction of bis(bromomethyl-p-phenyl)-sulfone triphenylphosphonium salt with terephthaldehyde. PPVS was highly soluble in common organic solvents and showed strong blue-shifted fluorescence because the polar sulfonylene group provided better solubility and limited π-conjugation in polymer chain. A single layer device with PPVS sandwiched between indium-tin-oxide (ITO) and aluminum electrodes showed a blue electroluminescence (EL) peaked at 470 nm under the threshold voltage of 14 V. HOMO and LUMO levels of PPVS were found to be 0.46 and 0.28 eV, respectively, lower than those of poly(p-phenylenevinylene) (PPV).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002890050527
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