Polarisation optical time domain reflectometry for statistical evaluation of polarisation mode dispersion

The authors shows that a commercial optical time domain reflectometer can be modified to measure the statistical nature of polarisation mode dispersion along the length of a communications grade fibre with short-length PMDs<4 ps/km.<>     

DDFSGEN

This paper presents a functional compiler for the automatic design of Direct Digital Frequency Synthesizer (DDFS) integrated circuits (ICs) using a ROM based table look-up architecture. The compiler allows the user to specify high-level specifications such as the acceptable spurious response and it generates the IC architecture, floorplan, and layout. To construct the layout for different specifications, a library of parameterized macrocells has been developed in 1.2 m CMOS technology.A test chip with a quadrature DDFS module has been generated, using the compiler, and fabricated. The chip has two input signals: one is for frequency control while the other is for phase initialization. Input and output word lengths are 16 bits and 6 bits respectively. The chip complexity is approximately 12,000 transistors (DDFS core) and the die size is 4.8×2.9mm ². A maximum sample rate of 80 MHz has been attained implying a maximum sine (cosine) output frequency of 40 MHz and a frequency resolution of 1.22 kHz. The maximum spurious level measured is –46 dB.     

A 533-MHz BiCMOS superscalar RISC microprocessor

This 533-MHz BiCMOS very large scale integration (VLSI) implementation of the PowerPC architecture contains three pipelines and a large on-chip secondary cache to achieve a peak performance of 1600 MIPS. The 15 mm×10 mm die contains 2.7 M transistors (2M CMOS and 0.7 M bipolar) and dissipates less than 85 W. The die is fabricated in a six-level metal, 0.5-μm BiCMOS process and requires 3.6 and 2.1 V power supplies     

Harnessing “Click”‐Type Chemistry for the Preparation of Novel Electronic Materials

Sequence‐independent or “click”‐type chemistry is applied for the preparation of novel π‐conjugated oligomers. A variety of bi‐functional monomers for Wittig–Horner olefination are developed and applied in a sequential protection–deprotection process for the preparation of structurally similar π‐conjugated oligomers. Selected oligomers are incorporated as the organic semiconductors in light‐emitting diodes and a field‐effect transistor, demonstrating the potential of the approach.     

Generalization of the Gram-Charlier/Edgeworth Series and Application to Time-Frequency Analysis

We derive a general equation relating probability densities and as special cases we the obtain Gram-Charlier and Edgeworth series. This allows us to generalize these methods and clarify a number of issues pertaining to both probability theory and time-frequency analysis. In particular we show how the Gram-Charlier and Edgeworth series are related to the kernel method of time-frequency analysis. The approach allows us to construct densities that satisfy given constraints such as joint moments or conditional moments. Also, we show that the kernel has to be signal dependent and that to obtain a proper distribution it should be the ratio of two characteristic functions.     

An efficient approach to ARMA modeling of biological systems withmultiple inputs and delays

Presents a new approach to AutoRegressive Moving Average (ARMA or ARX) modeling which automatically seeks the best model order to represent investigated linear, time invariant systems using their input/output data. The algorithm seeks the ARMA parameterization,which accounts for variability in the output of the system due to input activity and contains the fewest number of parameters required to do so. The unique characteristics of the proposed system identification algorithm are its simplicity and efficiency in handling systems with delays and multiple inputs. The authors present results of applying the algorithm to simulated data and experimental biological data. In addition, a technique for assessing the error associated with the impulse responses calculated from estimated ARMA parameterizations is presented. The mapping from ARMA coefficients to impulse response estimates is nonlinear, which complicates any effort to construct confidence bounds for the obtained impulse responses. Here a method for obtaining a linearization of this mapping is derived, which leads to a simple procedure to approximate the confidence bounds     

A general approach for obtaining joint representations in signalanalysis. II. General class, mean and local values, and bandwidth

For pt.I see ibid., vol.44, no.5, p.1080-90 (1996). Using the method developed in Cohen (1996) (Part I), the concepts of instantaneous frequency and group delay are generalized to arbitrary variables; in addition, new expressions for mean values and bandwidths are obtained. The kernel method is used to define a general class for arbitrary variables. As in the time-frequency case, the general class generates all possible distributions. The method is also formulated in terms of the local autocorrelation function     

Large Nonclassical Electrostriction in (Y,Nb)‐Stabilized δ‐Bi2O3

Classical electrostriction, describing a second‐order electromechanical response of insulating solids, scales with elastic compliance, S, and inversely with dielectric susceptibility, ε. This behavior, first noted 20 years ago by Robert Newnham, is shown to apply to a wide range of electrostrictors including polymers, glasses, crystalline linear dielectrics, and relaxor ferroelectrics. Electrostriction in fluorite ceramics of (Y, Nb)‐stabilized δ‐Bi₂O₃ is examined with 16%–23% vacant oxygen sites. Given the values of compliance and dielectric susceptibility, the electrostriction coefficients are orders of magnitude larger than those expected from Newnham's scaling law. In ambient temperature nanoindentation measurements, (Y, Nb)‐stabilized δ‐Bi₂O₃ displays primary creep. These findings, which are strikingly similar to those reported for Gd‐doped ceria, support the suggestion that ion conducting ceramics with the fluorite structure, a large concentration of anion vacancies and anelastic behavior, may constitute a previously unknown class of electrostrictors.     

A new approach of geodesic reconstruction for drusen segmentationin eye fundus images

Segmentation of bright blobs in an image is an important problem in computer vision and particularly in biomedical imaging. In retinal angiography, segmentation of drusen, a yellowish deposit located on the retina, is a serious challenge in proper diagnosis and prevention of further complications. Drusen extraction using classic segmentation methods does not lead to good results. We present a new segmentation method based on new transformations we introduced in mathematical morphology. It is based on the search for a new class of regional maxima components of the image. These maxima correspond to the regions inside the drusen. We present experimental results for drusen extraction using images containing examples having different types and shapes of drusen. We also apply our segmentation technique to two important cases of dynamic sequences of drusen images. The first case is for tracking the average gray level of a particular drusen in a sequence of angiographic images during a fluorescein exam. The second case is for registration and matching of two angiographic images from widely spaced exams in order to characterize the evolution of drusen.