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作者： Grybos, Pawel Maj, Piotr Ramello, Luciano Swientek, Krzysztof IEEE Faculty of Electrical Engineering Automatics Computer Science and Electronics Department of Measurement and Instrumentation AGH University of Science and Technology 30-059 Cracow Poland Dipartamento di Scienze e Tecnologie Avanzate Universita del Piemonte Orientale INFN 15100 Alessandria Italy Faculty of Physics and Applied Computer Science AGH University of Science and Technology 30-059 Cracow Poland

We present the measurements of matching and high count rate performance of a 64 channel readout ASIC called DEDIX for high count rate position-sensitive measurements using semiconductor detectors. The ASIC is designed in 0.35 μm CMOS process and its total area is 3900 × 5000 μm2. The DEDIX has a binary readout architecture. Each channel is built of a charge sensitive amplifier (CSA) with a pole-zero cancellation circuit, a shaper, two independent discriminators and two independent 20-bit counters. The size of the input device in CSA has been optimized for a detector capacitance in the range of 1-3 pF per strip. An equivalent noise charge of 110 el rms has been achieved for a total detector capacitance of 1 pF at the shaper peaking time of 160 ns. Internal correction DAC implemented in each channel independently ensures a low spread of discriminator effective threshold, namely 0.4 mV at one sigma level. The mean gain in the multichannel ASIC is 54 μV/el, with a good uniformity from channel-to-channel (sd/mean 0.8%). Low noise performance and high rate capability have been demonstrated by the measurement up to and above 1 MHz average rate of input signals. © 2007 IEEE.

关键词： Image matching

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A Diophantine Frequency Synthesizer for the Examination of High Spectral Purity

A Diophantine Frequency Synthesizer for the Examination of H...

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IEEE International Frequency Control Symposium

作者： Paul P. Sotiriadis Gregory L. Weaver Electrical and Computer Engineering Johns Hopkins University Baltimore MD USA Space Department Johns Hopkins University-Applied Physics Laboratory Baltimore MD USA

Diophantine frequency synthesis (DFS), a number theoretic approach to the design of very high resolution and agile frequency synthesizers was introduced at the IEEE frequency control symposium of 2006, [1]. Since DFS uses frequency addition (and/or subtraction), concerns for the impact of mixing spurs in the spectral purity was raised. Further work has been performed to address this issue and is reported in this paper. The focus has been on basic DFS architecture targeting micro-phase type applications. The design goal has been to achieve 100 dB spurious free dynamic range (SPFD) with minimal circuit complexity. The results of the examination demonstrate that the use of DFS does not impart any extraordinary design constraints to spectral purity from that of other topology choices. In fact, the flexibility of the design technique from its applied math basis allows this demonstration synthesizer to be realized with simple and expedient construction.

关键词： Frequency synthesizers Signal resolution Dynamic range Digital modulation Frequency conversion Phase locked loops Frequency synchronization Optical transmitters Optical receivers Quality of service

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Chip Discrimination for UWB Impulse Radio Networks in Multipath Channels

Chip Discrimination for UWB Impulse Radio Networks in Multip...

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MILCOM, Military Communications Conference

作者： J. R. Ward J. Keith Townsend Applied Physics Laboratory Johns Hopkins University Laurel MD USA Department of Electrical and Computer Engineering North Carolina State University Raleigh NC USA

In this paper we present a technique that eliminates the need for centralized power control in ultrawideband (UWB) radio networks in multipath channel environments. The technique we call chip-discrimination, exploits the low duty cycle waveform of UWB impulse radio to mitigate the effects of high power interference using locally measured information at the receiver. Chip discrimination has been applied to UWB systems in non-multipath channels with matched filter reception. Here we develop a chip discrimination technique for multipath channels with RAKE receivers. A chip discriminator located at each RAKE finger selectively removes interfering pulses that exceed a dynamic threshold for each received multipath component. computer simulation is used to demonstrate the effectiveness of the technique using the IEEE 802.15.3a channel model under the assumptions of both perfect and imperfect channel estimation using maximal ratio combining (MRC).

关键词： Radio network Multipath channels Power control Ultra wideband technology Interference Power measurement Semiconductor device measurement RAKE receivers Matched filters Fading

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Lattice Boltzmann algorithms for fluid turbulence

Lattice Boltzmann algorithms for fluid turbulence

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department of Defense - HPCMP Users Group Conference 2007;High Performance Computing Modernization program: A Bridge to Future Defense, DoD HPCMP UGC

作者： Vahala, George Yepez, Jeffrey Soe, Min Vahala, Linda Ziegeler, Sean Department of Physics College of William and Mary Williamsburg VA United States Hanscom Field MA United States Department of Mathematics and Science Rogers State University Claremore OK United States Department of Electrical and Computer Engineering Old Dominion University Norfolk VA United States High Performance Computing Modernization Program Mississippi State University MS United States

ISBN: (纸本)0769530885

Lattice Boltzmann algorihms are a mesoscopic representation of nonlinear continuum physics (like Navier-Stokes, magnetohydrodynamics (MHD), Gross-Pitaevskii equations) which are ideal for parallel supercomputers because they transform the difficult nonlinear convective macroscopic derivatives into purely local moments of distribution functions. The macroscopic nonlinearities are recovered by relaxation distribution functions in the collision operator whose dependence on the macroscopic velocity is algebraically nonlinear and thus purely local. Unlike standard computational fluid dynamics codes, there is no loss in parallelization in handling arbitrary geometric boundaries, e.g., using bounce-back rules from kinetic theory. By encoding detailed balance into the collision operator through the introduction of discrete H-function, the lattice Boltzmann algorithm can be made unconditionally stable for arbitrary high Reynolds numbers. It is shown that this approach is a special case of a quantum lattice Boltzmann algorithm that entangles local qubits through unitary collision operators and which is ideally parallelized on quantum computer architectures. Here we consider turbulence simulations using 2,048 PEs on a 1,6003-spatial grid. A connection is found between the rate of change of enstrophy and the onset of laminar-to-turbulent flows. © 2007 IEEE.

关键词： Magnetohydrodynamics

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A machine learning approach for finding hyperspectral endmembers

A machine learning approach for finding hyperspectral endmem...

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IEEE International Symposium on Geoscience and Remote Sensing (IGARSS)

作者： Amit Banerjee Philippe Burlina Joshua Broadwater Applied Physics Laboratory Johns Hopkins University Laurel MD USA Department of Electrical and Computer Engineering Center for Automation Research University of Maryland College Park MD USA

A support vector algorithm for detecting endmembers in a hyperspectral image is introduced. It is a novel method for finding the spectral convexities in a high-dimensional space which addresses several limitations of previous endmember methods. A new approach for estimating the number of endmembers using rate-distortion theory is also presented. It is based upon the observation that the endmembers form a set of basis vectors for the hyperspectral datacube using the linear mixture model. The result is a fully-automatic method for endmember detection. Experimental results using the Cuprite datacube are presented.

关键词： Machine learning Hyperspectral imaging Vectors Data mining Rate-distortion Principal component analysis Automation Educational institutions Distributed computing Classification algorithms

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Kernel fully constrained least squares abundance estimates

Kernel fully constrained least squares abundance estimates

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IEEE International Symposium on Geoscience and Remote Sensing (IGARSS)

作者： Joshua Broadwater Rama Chellappa Amit Banerjee Philippe Burlina Applied Physics Laboratory Johns Hopkins University Laurel MD USA Department of Electrical and Computer Engineering Center for Automation Research University of Maryland College Park MD USA

A critical step for fitting a linear mixing model to hyperspectral imagery is the estimation of the abundances. The abundances are the percentage of each end member within a given pixel; therefore, they should be non-negative and sum to one. With the advent of kernel based algorithms for hyperspectral imagery, kernel based abundance estimates have become necessary. This paper presents such an algorithm that estimates the abundances in the kernel feature space while maintaining the non-negativity and sum-to-one constraints. The usefulness of the algorithm is shown using the AVIRIS Cuprite, Nevada image.

关键词： Kernel Least squares approximation Hyperspectral imaging Vectors Laboratories physics computing Automation Educational institutions Classification algorithms Data mining

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Enhancement of Light Extraction in GaInN Light-Emitting Diodes with Graded-Index Indium Tin Oxide Layer

Enhancement of Light Extraction in GaInN Light-Emitting Diod...

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Conference on Lasers and Electro-Optics (CLEO)

作者： Jong Kyu Kim Martin F. Schubert J.-Q. Xi Frank Mont E. Fred Schubert Electrical Computer and Systems Engineering Department Rensselaer Polytechnic Institute Troy NY USA Department of Physics Applied Physics and Astronomy Rensselaer Polytechnic Institute Troy NY USA Electrical Computer and Systems Engineering Dept. Rensselaer Polytechnic Institute 110 Eighth St. Troy NY 12180 USA Dept. of Physics Applied Physics and Astronomy Rensselaer Polytechnic Institute 110 Eighth St. Troy NY 12180 USA

Enhancement of light extraction in a GaInN light-emitting diode employing a graded-refractive index ITO anti-reflection coating deposited by oblique-angle electron-beam evaporation is presented.

ISBN: (纸本)9781424435906

Enhancement of light extraction in a GaInN light-emitting diode employing a graded-refractive index ITO anti-reflection coating deposited by oblique-angle electron-beam evaporation is presented.

关键词： Light emitting diodes Indium tin oxide Coatings Refractive index Gallium nitride Optical films Reflectivity physics Optical refraction Optical variables control

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Nonlinear Quantum Cascade Lasers: Toward Broad Tunability and Short-Wavelength Operation

Nonlinear Quantum Cascade Lasers: Toward Broad Tunability an...

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Conference on Lasers and Electro-Optics (CLEO)

作者： Feng Xie Don Smith V.R. Chaganti A. Belyanin Dan Wasserman Claire Gmachl Junichiro Kono Mikhail Belkin Federico Capasso Department of Physics and Astronomy Texas A and M University College Station TX USA Department of Electrical Engineering PRISM and MIRTHE Princeton University Princeton NJ USA Department of Electrical and Computer Engineering Rice University Houston TX USA Division of Engineering and Applied Sciences Harvard University Cambridge MA USA

We propose new designs for quantum-cascade lasers integrated with resonant intersubband nonlinearities, which promise ultra-broad spectral tuning and room-temperature operation in the hard-to-reach short-wavelength ra... 详细信息

ISBN: (纸本)1557528349

关键词： Quantum cascade lasers Laser tuning Laser transitions Pump lasers Nonlinear optics Frequency conversion Optical mixing Semiconductor lasers Optical tuning Optical pumping

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A comparison between traditional shift-and-add (SAA) and point-by-point back projection (BP) - Relevance to morphology of microcalcifications for isocentric motion in Digital Breast tomosynthesis (DBT)

A comparison between traditional shift-and-add (SAA) and poi...

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7th IEEE International Conference on Bioinformatics and Bioengineering, BIBE

作者： Chen, Ying Lo, Joseph Y Dobbins III, James T. Department of Electrical and Computer Engineering Southern Illinois University Carbondale Carbondale IL 62901 United States Department of Biomedical Engineering Duke University Duke University Medical Center Durham NC 27710 United States Duke Advanced Imaging Laboratories Duke University Duke University Medical Center Durham NC 27710 United States Medical Physics Graduate Program Duke University Duke University Medical Center Durham NC 27710 United States

ISBN: (纸本)1424415098

Digital breast tomosynthesis (DBT) is a three-dimensional imaging technique providing an arbitrary set of reconstruction planes in the breast with limited series of projection images. This paper describes a comparison between traditional shift-and-add (SAA) and point-by-point back projection (BP) algorithms by impulse response and modulation transfer function (MTF) analysis. Due to the partial isocentric motion of the x-ray tube in DBT, structures such as microcalcifications appear slightly blurred in traditional shift-and-add (SAA) images in the direction perpendicular to the direction of tube 's motion. Point-by-point BP improved rendition of microcalcifications. The sharpness and morphology of calcifications were improved in a human subject images. A Filtered Back Projection (FBP) deblurring approach was used to demonstrate deblurred point-by-point BP tomosynthesis images. The point-by-point BP rather than traditional SAA should be considered as the foundation of further deblurring algorithms for DBT reconstruction. ©2007 IEEE.

关键词： Impulse response

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High refractive index nanoparticle-loaded encapsulants for light-emitting diodes

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Proceedings of SPIE - The International Society for Optical engineering 2007年 6486卷

作者： Mont, Frank W. Kim, Jong Kyu Schubert, Martin F. Luo, Hong Schubert, E. Fred Siegel, Richard W. Future Chips Constellation Rensselaer Polytechnic Institute Troy NY 12180 Department of Electrical Computer and Systems Engineering Rensselaer Polytechnic Institute Troy NY 12180 Department of Physics Applied Physics and Astronomy Rensselaer Polytechnic Institute Troy NY 12180 Department of Materials Science and Engineering Rensselaer Nanotechnology Center Rensselaer Polytechnic Institute Troy NY 12180

ISBN: (纸本)0819465992;9780819465993

TiO2 nanoparticle-loaded epoxy for light-emitting diode (LED) encapsulation is demonstrated to have a refractive index of n = 1.68, higher than that of pure epoxy (n = 1.53). The dispersion of surfactant-coated TiO 2 nanoparticles into epoxy is shown to reduce the number and size of TiO2 agglomerates compared to uncoated TiO2 nanoparticle-loaded epoxy. The scattering of nanoparticle-loaded media is highly dependent on nanoparticle size and loading factor. A multilayer graded refractive index structure for LED encapsulants with layer thicknesses less than the calculated mean optical scattering length is therefore proposed. The graded-index structure shows increasing optical transmittance as the number of layers increases.

关键词： Light emitting diodes

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