An image processing IC for backprojection and spatial histogrammingin a pipelined array

The first VLSI digital signal processor that performs both high-precision image backprojection and spatial histogram calculations at raster-scan rates as high as 30 MHz is described. Realized in 1 μm CMOS technology, this 13.3 mm×13.3 mm chip is designed to handle images as large as 1024×1024 12 b pixels. Loadable coefficients and a unified architecture allow this IC to be used with a variety of computed-tomography scanners for image reconstructions, including fan- and parallel-beam reconstruction. This chip also computes the forward Radon transform, which is a spatial histogram, permitting it to be used for iterative reconstruction algorithms. The bit lengths in the fixed-point architecture assure 12 b reconstruction accuracy     

The role of multilateral institutions

In line with its mission of alleviating poverty through support for environmentally and socially sustainable economic development, The World Bank (along with some other multilateral development banks) is working to help developing countries capture a share of the emerging global market in greenhouse-gas-emissions reductions ('carbon trading'). Under the Kyoto Protocol of the United Nations Framework Convention on Climate Change (UNFCCC), the Joint Implementation instrument and the Clean Development Mechanism now provide an opening for substantial international resource transfers and potential for supporting sustainable development through the transfer of cleaner technologies or sustainable forestry and agro-forestry practices. For example, carbon sequestration represents a non-extractive non-consumptive sustainable use of living natural resources that can be incorporated within a multiple-use 'integrated ecosystem management' approach. The World Bank initiated the Prototype Carbon Fund (PCF) in April 2000, to help spur the development of a global carbon market and to 'learn by doing' how to use carbon-purchase transactions across a range of energy-sector technologies (and some forestry applications) to achieve environmentally credible and cost-effective emissions reductions that benefit developing countries and economies in transition. Building on the success of the PCF ($145 million raised from public and private-sector investors), The World Bank expects to launch two new funds in 2002: the Biocarbon Fund and the Community Development Carbon Fund. These funds will target synergies between carbon markets and objectives such as biodiversity conservation, combating desertification and small-scale community-driven development. Experience from the PCF shows that developing countries can have a comparative advantage in supplying this global market, as emissions reductions can be achieved in developing countries in the range of $3-$5 per ton of CO(2) equivalent, compared with a marginal abatement cost of $10-$15 per ton of CO(2) equivalent in most countries within the Organization for Economic Cooperation and Development. However, realizing this economic potential over the next decade, and targeting the market to the rural poor, will require substantial assistance with project development and government legal and institutional capacity building. Specific needs include raising awareness of the potential of carbon markets at all levels (particularly in energy and land-use sectors), clarifying property rights, particularly in the case of communally held land and resources, ensuring the existence of an attractive investment climate, eliminating policies that create perverse incentives and constraints, and mitigating logistical, political and 'reputational' risks that could deter private-sector investors. It will also be necessary to find ways to reconcile the short-term needs of the rural poor and the typically long-term revenue stream associated with carbon sequestration.     

Metallic inductive and capacitive grids: theory and experiment

We present theoretical modeling and experimental validation of both capacitive (dot) and inductive (hole) metallic crossed gratings in the mid-infrared (2-5 microm). The gratings are fabricated by use of interferometric lithography and modeled by use of rigorous coupled-wave analysis. Our experimental and numerical investigations of the transmittance spectra of these gratings suggest that, as in inductive grids, the behavior of capacitive grids is described by the coupling of the incident light into surface plasma waves.     

Picosecond-pulse and millimeter-wave spectroscopy of barium ferrite

Transmission measurements of a barium ferrite pressed-powder sample have been made with an optically switched picosecond-pulse spectrometer. By comparison to millimeter-wave spectroscopy of the same sample, features related to the ferrimagnetic resonance have been identified in the pulse spectrum. Time-domain spectra predicted from models of the permeability indicate significant discrepancies with the experimental short-pulse line shape     

The effects of an electromagnetic crystal substrate on a microstrippatch antenna

The effects of a two-dimensional (2D) electromagnetic bandgap substrate on the performance of a microstrip patch antenna are investigated. The microstrip patch antenna is placed on a defect in the electromagnetic bandgap substrate that localizes the energy under the antenna. Finite-difference time-domain calculations are employed to determine the effects of the substrate. The excitation frequency of the antenna near the resonance frequency of the defect mode can be used to control the coupling between antennas that are placed in an array     

Design of ultrawideband photonic crystals for broadband antennaapplications

Face-centred-cubic photonic crystals with overlapping stop bands are stacked in tandem to obtain an ultrawideband photonic crystal. This crystal has a stop band that extends from 16 to at least 25 GHz and has a minimum rejection of ~7 dB at normal incidence. Different stacking configurations have been studied, and cavity modes between nonadjacent crystals with overlapping stop bands have been observed     

Characterization of layered dielectrics with short electromagneticpulses

The use of picosecond duration bursts of electromagnetic radiation to study short-pulse wave propagation in layered dieletric materials is discussed. The radiation is generated using planar antennas that are switched photoconductively. The measurements are compared with time- and frequency-domain theoretical data. Issues associated with the windowing of time-domain results for highly resonant structures are addressed, as well as how the derived frequency domain data are influenced by the windowed Fourier transform. The accuracy of the time-domain results suggest that this technique may be a useful tool for characterizing layered materials     

An evaluation of Radon transform computations using DSP chips

The Radon transform and its inverse (a filtered backprojection) are receiving increasing attention for applications in image reconstruction. As data collection capabilities and image reconstruction algorithms have become more sophisticated, the computational intensity of these problems has drastically increased. Parallel processing techniques are being used to implement highspeed hardware designs that will speed up this computationally burdensome task. Parallel arrays of digital signal processing (DSP) chips may be used to compute the Radon transform and back-projection for high-speed image reconstruction. In this paper we describe computation of the Radon transform and back-projection using a parallel pipelined processor architecture of DSP chips and evaluate the accuracy of the computations and quality of reconstructed images. To justify the computational approach selected, alternative procedures for computation of the Radon transform and back-projection are described and their performance using the 32-bit fixed-point arithmetic of the selected DSP chips are compared. We present, evaluate, and compare the simulated performances of implementations of these procedures on two fixed-point DSP chips: the TI TMS32020 and the AT&T DSP16.     

Strategy for kinetic parameter estimation—Thermal degradation of polyurethane elastomers

The kinetics of the thermal degradation of polyurethane (PU) elastomers based on poly(ether polyol) soft segments and an aromatic type of diisocyanate were investigated by thermogravimetric analysis (TGA) under a nitrogen atmosphere employing four heating rates. The corresponding kinetic parameters of the two degradation stages were estimated by minimizing the output error functional and by the Kissinger method. In evaluating the kinetic parameters of the two‐step PU thermal decomposition, a differential thermogravimetry curve was applied as an objective functional in a regression procedure. Parameter estimation was obtained by minimizing the weighted quadratic output error functional with the modified Nelder–Mead simplex search algorithm. The confidence regions in the preexponential factor‐activation energy space were established for both the first and second stages of degradation. The effect of the molecular weight of the soft segment and the content of the hard segment on the activation energy of the degradation process was constructed by response surface methodology. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 764–772, 2007