Reduced-resolution synthetic-discriminant-function design by multiresolution wavelet analysis

Several approaches to the design of reduced-resolution synthetic discriminant functions (SDF's) using multiresolution wavelet analysis (MWA) techniques are investigated. In the first approach, reducedresolution approximations of a full-resolution SDF are obtained by MWA. In the second approach, reduced-resolution approximations of the training-image Fourier transforms are obtained by MWA, and a reduced-resolution SDF is obtained directly by training on these. For both approaches, reducedresolution MICE-SDF filters were designed with MWA and conventional down-sampling techniques. Simulations showed that filters designed by the second approach with MWA techniques permitted reductions in the number of filter pixels from 128 × 128 to 32 × 32, while still satisfying the design constraints. In comparison, the performances of 32 × 32 filters designed by conventional downsampling techniques were significantly degraded.     

Error-reduction techniques and error analysis for fully phase- and amplitude-based encryption

The performance of fully phase- and amplitude-based encryption processors is analyzed. The effects of noise perturbations on the encrypted information are considered. A thresholding method of decryption that further reduces the mean-squared error (MSE) for the fully phase- and amplitude-based encryption processes is provided. The proposed thresholding scheme significantly improves the performance of fully phase- and amplitude-based encryption, as measured by the MSE metric. We obtain analytical MSE bounds when thresholding is used for both decryption methods, and we also present computer-simulation results. These results show that the fully phase-based method is more robust. We also give a formal proof of a conjecture about the decrypted distribution of distorted encrypted information. This allows the analytical bounds of the MSE to be extended to more general non-Gaussian, nonadditive, nonstationary distortions. Computer simulations support this extension.     

我国R22逐步禁用和替代物的现状与进展

简要回顾了国际上保护臭氧层行动,阐述了国际上以及我国最近对R22的逐步禁用日程.介绍了R22替代物研究现状和进展.最后提出了作者的几点看法.     

Quantitative security evaluation of optical encryption using hybrid phase- and amplitude-modulated keys

In the increasing number of system approaches published in the field of optical encryption, the security level of the system is evaluated by qualitative and empirical methods. To quantify the security of the optical system, we propose to use the equivalent of the key length routinely used in algorithmic encryption. We provide a calculation method of the number of independent keys and deduce the binary key length for optical data encryption. We then investigate and optimize the key length of the combined phase- and amplitude-modulated key encryption in the holographic storage environment, which is one of the promising solutions for the security enhancement of single- and double-random phase-encoding encryption and storage systems. We show that a substantial growth of the key length can be achieved by optimized phase and amplitude modulation compared to phase-only encryption. We also provide experimental confirmation of the model results.     

Adaptive laser beam projection on an extended target: phase- and field-conjugate precompensation

The problem of adaptive laser beam projection onto an extended object (target) having a randomly rough surface in an optically inhomogeneous medium (atmosphere) is analyzed. Outgoing beam precompensation is considered through conjugation of either the target-return wave phase or the complex field. It is shown that in the presence of "frozen" turbulence, both phase-conjugate (PC) and field-conjugate (FC) precompensation can result in a superfocusing effect, which suggests the possibility of achieving a brighter target hit spot in volume turbulence than in vacuum. This superfocusing effect is significantly more distinct for FC precompensation. In the quasi-stationary case (slowly moving turbulence or target), PC and FC beam control lead to enhanced intensity fluctuations at the target surface associated with intermittent formation and disintegration of bright target hit spots that sporadically attach to the extended target surface. This intensity fluctuation level exceeds intensity fluctuations in the absence of beam control and is higher for FC precompensation. In the nonstationary case, both PC and FC lead to an increase of beam width and centroid wander at the extended target surface compared with conventional projection of a collimated or focused beam.     

MTL代数的蕴涵滤子与正蕴涵滤子

在MTL代数M上引入了蕴涵滤子、正蕴涵滤子的概念,研究了它们的性质,给出了M的非空子集成为蕴涵滤子及正蕴涵滤子的充要条件和M的蕴涵滤子成为正蕴涵滤子的充要条件.讨论了蕴涵滤子与正蕴涵滤子的关系,得到了M的每一个正蕴涵滤子都是蕴涵滤子,但反之不真.     

Multilevel isotrigon textures

To date a small palette of isotrigon textures have been available to study how the brain uses higher-order spatial correlation information. We introduce several hundred new isotrigon textures. Special modulation properties are illustrated that can be used to extract neural responses to higher-order spatial correlations. We also ask how many textures make an adequate training set and how representative individual examples are of their texture class. Human discrimination of 90 of these patterns was quantified. Modeling those responses shows that humanlike performance can be obtained providing a fourth-order classifier is used, although more than one mechanism is required.     

Multilevel dynamic substructures

The dynamic substructure method is extended to multilevel (recursive) substructures. The obvious distinction of the two approaches is that the stiffness and mass matrices before condensation are no longer frequency independent. The dynamic stiffness matrix at any substructure level is proved to be a function of the vibrating frequency in terms of some constant matrices which are derivable from the dynamic stiffness matrix at one lower substructure level. The method can accurately predict more modes than the number of degrees of freedom retained. The computational procedure, the generalized inverse iteration, the stationary principle of the system natural frequency and the generalized Rayleigh's quotient are derived for the frequency dependent matrices. Numerical examples are given to illustrate some engineering applications. A transcendental dynamic stiffness matrix can be transformed to a more convenient algebraic form by the present method.     

Generalized Aggregation Multilevel solver

The paper presents a Generalized Aggregation Multilevel (GAM) solver, which automatically constructs nearly optimal auxiliary coarse models based on the information available in the source grid only. GAM solver is a hybrid solution scheme where approximation space of each aggregate (group of neighbouring elements) is adaptively and automatically selected depending on the spectral characteristics of individual aggregates. Adaptive features include automated construction of auxiliary aggregated model by tracing ‘stiff’ and ‘soft’ elements, adaptive selection of intergrid transfer operators, and adaptive smoothing. An obstacle test consisting of nine industry problems, such as ring–strut–ring structure, casting setup in airfoil, nozzle for turbines, turbine blade and diffuser casing as well as on poor conditioned shell problems, such as High Speed Civil Transport, automobile body and canoe, was designed to test the performance of GAM solver. Comparison to the state of the art direct and iterative (PCG with Incomplete Cholesky preconditioner) is carried out. Numerical experiments indicate that GAM solver possesses an optimal rate of convergence by which the CPU time grows linearly with the problem size, and at the same time, robustness is not compromised, as its performance is almost insensitive to problem conditioning. © 1997 John Wiley & Sons, Ltd.     

High-temperature superconductive filters and multiplexers

This paper presents measured and computer-simulated results for a number of high-temperature superconductor (HTS) thin filters. The CAD algorithm used to design these filters is described. Experimental results are also presented for an integrated 4-channel C-band multiplexer employing dual-mode hybrid dielectric/HTS thin-film filters. The results presented in this paper demonstrate the feasibility of building C-band superconductive multiplexers that have the potential of large reduction in mass and volume over conventional technologies.     

Magnetically tunable oscillators and filters

Magnetically tunable filters and oscillators can be built throughout the 500-MHz-110-GHz range using a number of ferrite materials and varied geometries. The authors survey current trends and state-of-the-art results for oscillators and filters using YIG spheres _, YIG films, and hexagonal ferrites as the magnetically tunable elements     

Artificial anisotropy and polarizing filters

The calculated spectral transmittance of a multilayer laser mirror is used to determine the effective index of the single layer equivalent to the multilayer stack. We measure the artificial anisotropy of photoresist thin films whose structure is a one-dimensional, subwavelength grating obtained from interference fringes. The limitation of the theory of the first-order effective index homogenization is discussed. We designed normal-incidence, polarizing coating and a polarization rotator by embedding anisotropic films in simple multilayer structures.     

Wiener-like correlation filters

We introduce a new, to our knowledge, design for a Wiener-like correlation filter, which consists of cascading a phase-only filter (POF) with a photorefractive Wiener-like filter. Its performance is compared with that of the POF and the Wiener correlation filter (WCF). Correlation results show that for intermediate and higher levels of noise this correlation filter has a peak-to-noise ratio that is larger than that of either the POF or the WCF while still preserving a correlation peak that is almost as high as that of the POF.     

Algebraic wavelet filters

A method to compute the discrete wavelet transform for certain wavelet filters is proposed that takes advantage of conjugacy properties in number fields. It is shown that wavelet filters derived from compactly supported orthonormal wavelets can be approximated with arbitrary precision by the proposed wavelet filters. © 1996 John Wiley & Sons, Inc.     

Carbon nanotube filters

Over the past decade of nanotube research, a variety of organized nanotube architectures have been fabricated using chemical vapour deposition. The idea of using nanotube structures in separation technology has been proposed, but building macroscopic structures that have controlled geometric shapes, density and dimensions for specific applications still remains a challenge. Here we report the fabrication of freestanding monolithic uniform macroscopic hollow cylinders having radially aligned carbon nanotube walls, with diameters and lengths up to several centimetres. These cylindrical membranes are used as filters to demonstrate their utility in two important settings: the elimination of multiple components of heavy hydrocarbons from petroleum-a crucial step in post-distillation of crude oil-with a single-step filtering process, and the filtration of bacterial contaminants such as Escherichia coli or the nanometre-sized poliovirus ( approximately 25 nm) from water. These macro filters can be cleaned for repeated filtration through ultrasonication and autoclaving. The exceptional thermal and mechanical stability of nanotubes, and the high surface area, ease and cost-effective fabrication of the nanotube membranes may allow them to compete with ceramic- and polymer-based separation membranes used commercially.     

Dichroic rugate filters

We reduce the sidelobes that are present in the bandpass zones of rugate filters, using antireflection coatings to design dichroic rugate filters. Our designs are based on the formalism of equivalent systems that allow us to consider a rugate filter a simple equivalent layer with equivalent optical admittance and equivalent phase thickness functions. Rugate filters with apodization were considered.