Classical Fourier-Bessel methodology fails when used to reconstruct helical structures with severe Bessel overlap on the layer lines. In the reconstruction of a peculiar type of double-layered helical tube of GDP-tubu...
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Classical Fourier-Bessel methodology fails when used to reconstruct helical structures with severe Bessel overlap on the layer lines. In the reconstruction of a peculiar type of double-layered helical tube of GDP-tubulin, we face the problem of Bessel overlap on all the layer lines due to the superposition of the Fourier components from the inner and outer layers of the tube. In order to decompose the Fourier terms of the inner and outer layers more than one image of the tubes must be combined and the orientations of their inner and outer layer helices must be determined. While there is no direct analytical method to determine these orientational parameters, we have devised all iterative Fourier-Bessel algorithm to calculate the correct orientations and thus allow us to obtain a reconstruction from multiple images of the double-layered tubes. The algorithm successfully works for the reconstruction of computer-modeled double-layered helical tubes as well as with real images obtained by cryo-electron microscopy. The algorithm has also been applied with very satisfactory results to the reconstruction of 13-protofilament microtubules, which is another helical structure that suffer Bessel overlap, suggesting its generality. (C) 2004 Elsevier Inc. All rights reserved.
In order to assess a large number of diverse projects as fairly and rapidly as possible, a procedure often adopted is to use a panel consisting of a large number of experts, only a small number of whom assess each pro...
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In order to assess a large number of diverse projects as fairly and rapidly as possible, a procedure often adopted is to use a panel consisting of a large number of experts, only a small number of whom assess each project. Since no one expert assesses all the projects, conscious or unconscious bias regarding overall standards by any expert will advantage or disadvantage the projects assessed by that particular expert. This paper presents an iterative algorithm that has been used successfully to detect and correct for such biases. Each expert's assessments are modeled as differing from the ideal as a result of a shift of mean and having a standard deviation that is too low or too high. This model is used in conjunction with the concept of "paired assessments" to account for individual projects being of unusually high or low quality and so to evaluate the discrepancy from the ideal marks. The same computer program also has applications in the peer-review or expert-evaluation of research proposals, and any other situation involving subjective assessments by a restricted number of persons.
In orthogonal frequency-division multiplex access (OFDMA) uplink, it is admitted that the carrier-frequency offsets (CFOs) between multi-transmitter and receiver introduce intercarrier interference (ICI) and cause sev...
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ISBN:
(纸本)0780391527
In orthogonal frequency-division multiplex access (OFDMA) uplink, it is admitted that the carrier-frequency offsets (CFOs) between multi-transmitter and receiver introduce intercarrier interference (ICI) and cause severe performance loss. In this paper, with reference to a detailed analysis of the ICI caused by CFOs, we propose a novel low-complexity iterative ICI cancellation algorithm, which is based on the perfect estimation of each user's CFO. Moreover, the convergence behaviors of the iterations are studied with three theorems, and the user-interleaving patterns suitable for this algorithm are presented. In accordance with the simulation results, we come to the conclusion that the low-complexity iterative algorithm can effectively suppress and cancel the ICI due to CFOs.
While calculating the aggregate proportion in the ratio of mixture design by normal equation method, the value of solution may be negative, or the result gradation of the compound may go beyond the standard range. By ...
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While calculating the aggregate proportion in the ratio of mixture design by normal equation method, the value of solution may be negative, or the result gradation of the compound may go beyond the standard range. By iterative algorithm, the gradation data calculated by normal equation method was used as initial target value, setting the gradation to the boundary value if the sieving data goes beyond limits, and canceling the relevant aggregate if the result of proportion was negative. According to the adjusted object value, using the normal equation method again, the new aggregate proportion and the new gradation of the compound will come into being as well as the next target value. Finally, the accurate result which was up to the mustard can be found by iterative calculation. Although the principle of the iterative method was simple, it had excellent characteristics, such as good astringency, stability, convenience, and applicability in the engineering.
Passage-time densities are important for the detailed performance analysis of distributed computer and communicating systems. We provide a proof and demonstration of a practical iterative algorithm for extracting comp...
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Passage-time densities are important for the detailed performance analysis of distributed computer and communicating systems. We provide a proof and demonstration of a practical iterative algorithm for extracting complete passage-time densities from expressive semi-Markov systems. We end by showing its application to a distributed web-server cluster model of 15.9 million states. (c) 2004 Elsevier B.V. All rights reserved.
In this paper, we study a class of mixed quasi-variational-like inclusion with a bifunction in reflexive Banach spaces. By applying a minimax inequality due to the first author, some existence and uniqueness theorems ...
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In this paper, we study a class of mixed quasi-variational-like inclusion with a bifunction in reflexive Banach spaces. By applying a minimax inequality due to the first author, some existence and uniqueness theorems of solutions for the mixed quasi-variational-like inclusions are proved. Next, by applying the auxiliary variational inequality technique, we suggest an iterative algorithm to compute the approximate solutions of the mixed quasi-variational-like inclusions. The convergence criteria of the algorithm is studied under quite mild conditions. Our results represent improvement and generalization of the previously known results in literature. (c) 2005 Elsevier Ltd. All rights reserved.
Modeling of the bidirectional reflectance of thin-film coatings on rough surfaces has been an important and challenging problem. In the past, there have been studies that use thin-film optics to take account of the co...
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Modeling of the bidirectional reflectance of thin-film coatings on rough surfaces has been an important and challenging problem. In the past, there have been studies that use thin-film optics to take account of the coating-induced interference effects and the geometric optics approximation to model the surface roughness. In an effort to delineate the validity regime of the hybrid method, the predicted bidirectional reflectance is compared with that obtained from the rigorous electromagnetic-wave solution for one-dimensional rough surfaces, considering the effect of coating thickness and roughness parameters. Two hybrid models are implemented using the Monte Carlo ray-tracing algorithm: the surface generation method and microfacet slope method. The former relies on statistically generated surfaces according to the root-mean-square roughness and the autocorrelation length, whereas the latter uses the microfacet whose orientation is stochastically determined, when a ray hits the surface, according to the slope distribution without creating deterministic rough surfaces a priori. The validity regimes of the hybrid models are established for silicon dioxide films on silicon substrates. The advantages and disadvantages of each hybrid model are discussed. Some useful guidelines are provided for the simulation of optical scattering from coated rough surfaces.
This article presents and examines a new algorithm for solving a score equation for the maximum likelihood estimate in certain problems of practical interest. The method circumvents the need to compute second-order de...
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This article presents and examines a new algorithm for solving a score equation for the maximum likelihood estimate in certain problems of practical interest. The method circumvents the need to compute second-order derivatives of the full likelihood function. It exploits the structure of certain models that yield a natural decomposition of a very complicated likelihood function. In this decomposition, the first part is a log-likelihood from a simply analyzed model, and the second part is used to update estimates from the first part. Convergence properties of this iterative (fixed-point) algorithm are examined, and asymptotics are derived for estimators obtained using only a finite number of iterations. Illustrative examples considered in the article include multivariate Gaussian copula models, nonnormal random-effects models, generalized linear mixed models, and state-space models. Properties of the algorithm and of estimators are evaluated in simulation studies on a bivariate copula model and a nonnormal linear random-effects model.
In this paper, we study the influence of the M-2 quality factor of an incident beam on the reconstruction performance of a computer generated hologram (CGH). We use a statistical method to analyze the evolution of dif...
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In this paper, we study the influence of the M-2 quality factor of an incident beam on the reconstruction performance of a computer generated hologram (CGH). We use a statistical method to analyze the evolution of different quality criteria such as diffraction efficiency, root mean square error, illumination uniformity or correlation coefficient calculated in the numerical reconstruction versus the increasing M-2 quality factor. The simulation results show us that this factor must always be taken into account in the CGH design when the M-2 value is bigger than 2. (c) 2004 Elsevier B.V. All rights reserved.
We have developed a computational framework for iterative cone-beam micro-CT reconstruction. When applied to small animal imaging and other high-resolution applications, iterative algorithms pose significant implement...
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We have developed a computational framework for iterative cone-beam micro-CT reconstruction. When applied to small animal imaging and other high-resolution applications, iterative algorithms pose significant implementation difficulties due to the associated high computational burden. To address this burden, we use threads and message passing (MPI) to facilitate multiprocessor cluster computing. The system matrix can be either precomputed or calculated on-the-fly. Additionally, the system matrix can be based on trilinear interpolation or volumetric intersection methods. In the case of storing the system matrix, we exploit symmetries in the cone-beam geometry to reduce the storage requirements by a factor of nearly eight. We chose simultaneous iterative reconstruction technique (SIRT) to demonstrate the framework, although other algorithms are easily implemented. When precomputing the system matrix, each iteration of SIRT completes several times faster than when using an on-the-fly system matrix computation. The precomputed method remains faster when implementing ordered subsets, but the performance advantage diminishes as the number of subsets increases. We present reconstructions of the three-dimensional (3-D) Shepp-Logan head phantom as well as mouse data acquired by a small animal X-ray CT scanner.
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