A note on the application of edge-elements for modelingthree-dimensional inhomogeneously-filled cavities

The application of edge-elements for modeling three-dimensional inhomogeneously filled cavities is presented. Explicit representations for the two element matrices [S]_e and [T] _e, are provided in order to facilitate the implementation of the FEM formulation. Also included are the results of a numerical experiment that investigates the rate of convergence of the computations of the dominant resonance frequency of a rectangular cavity when the edge-element formulation is used     

A note on filter application in averaging of samples

In this contribution, the capability of filters to suppress random parts of a signal is treated in terms of their impulse and step responses. The idea is based on weighted averaging of digital data, and makes use of statistical moments of the random part of the signal and corresponding entropical uncertainty. This is illustrated by considering a low-pass FIR filter as an example. As a result, a simple recommendation is given for completing the computer-aided filter design which may be significant in measurements or communication.     

D-S规则推广及其在飞机目标识别中的应用研究

在多传感器特征信息融合算法中,D-S理论得到了广泛应用,但该理论在处理多特征冲突问题时识别效果不十分理想。针对这种情况,本文推广了D-S规则,得出了一种处理冲突信息的新方法。在分析推广规则受融合顺序影响的基础上,提出了最佳融合顺序,较好地利用了冲突信息,并通过仿真比较了D-S规则和推广规则应用于飞机目标识别的效果。结果表明:本文提出的D-S理论推广规则能有效解决多特征冲突的飞机目标识别难题。     

A note on the superposition principle

Two theorems concerning the superposition principle are stated and proved. These theorems are useful in the computation of total power dissipated in a network.     

A fuzzy rule-based iterative learning control method with application to hydroforming processes

A pressure tracking control of hydroforming processes which is used for precision forming of sheet metals is considered in this paper. In this process, forming pressure of the process needs to be strictly controlled to ensure the high quality of the forming products. However, satisfactory control performance is often difficult to achieve using conventional control methods due to the complexities and the uncertainties of the process. To overcome the problems, a fuzzy rule-based learning control scheme is proposed. In the proposed scheme, a fuzzy rule base constructed from expert knowledge is adopted to generate an appropriate control input which will provide satisfactory pressure tracking performance of the hydroforming process. A series of experiments was performed to show the effectiveness of the proposed control scheme and to investigate the design parameters of the proposed algorithm. The experimental results show that the proposed fuzzy rule-based learning controller can guarantee good tracking performance and, thus, high quality of the products even when only a vague, imprecise and fragmentary knowledge of the process is available.     

A note on the anatomy of federation

Federation can be perceived as a security foundation accommodating federated identity management solutions. In this paper we analyse the structure and function of federations with the aim of revealing the essential elements and architecture principles of federation models. Firstly, we identify some fundamental concepts that underpin the structure and operation of a trust realm. Then we analyse how these aggregate to provide for identity management and trust brokerage in a federation. We then explain various federation models in terms of these concepts. Finally, we examine the current state of Web-based federation standards and products, indicate specific research challenges for the next generation of federation-enabling technology. The paper targets an audience of research professionals and practitioners with some security and software engineering background who wish to find out more about federation models, and it can also be useful to (security) architects and consultants who are considering different federation architecture options for their projects.     

The interpretation and application of Rent's rule

This paper provides a review of both Rent's rule and the placement models derived from it. It is proposed that the power-law form of Rent's rule, which predicts the number of terminals required by a group of gates for communication with the rest of the circuit, is a consequence of a statistically homogeneous circuit topology and gate placement. The term “homogeneous” is used to imply that quantities such as the average wire length per gate and the average number of terminals per gate are independent of the position within the circuit. Rent's rule is used to derive a variety of net length distribution models and the approach adopted in this paper is to factor the distribution function into the product of an occupancy probability distribution and a function which represents the number of valid net placement sites. This approach places diverse placement models under a common framework and allows the errors introduced by the modeling process to be isolated and evaluated. Models for both planar and hierarchical gate placement are presented     

A new iterative soft-output Viterbi algorithm and its application to the “dicode” channel

We present an iterative soft-output decoding algorithm for serially concatenated coding systems. It has better performance than the conventional noniterative decoding algorithm. When applied together with an outer convolutional code to the dicode channel with partial response (1 — D), we obtain an additional coding gain of about 1 dB at a bit-error rate of 10^-4 after two iterations. This new algorithm can also be applied advantageously to satellite communication and fading channels.     

Comments on and extensions of "A note on the application of edge-elements for modeling three-dimensional inhomogeneously-filled cavities"

For the original paper see ibid., vol. 40, no. 9, p. 1767-1773 (1992). Some comments are made on the aforementioned paper and a typographical error is corrected. Eigenvalue solutions for three-dimensional (3-D) cavities computed using an independently implemented finite-element code using edge-based elements are reported as verification of the tabulated formulas in this paper. The question of "trivial" eigenvalues is briefly addressed. The extension of the tabulated formulas to diagonally anisotropic media is presented; it is shown to be very straightforward. Such media currently have significant applications as artificial absorbers in finite-element meshes.     

A note on the multidimensional sampling theorem

The multidimensional sampling theorem is extended to allow nonuniform, but periodic, sampling with explicit and simple reconstruction formulas. The extension is applicable to hexagonal and other nonrectangular lattices; such sampling schemes can be as efficient as rectangular sampling.     

A note on the antenna integral equation

An exact integral equation for a cylindrical antenna having a finite gap at the driving point is presented. By including the integrals of both the electric and magnetic currents flowing at the gap, the external current of the tubular antenna can be calculated separately from the internal current.     

A note on the absolute epsilon entropy

A novel characterization of the absolute epsilon entropy of an ergodic information source is presented. This characterization allows one to derive a new lower bound to this quantity, which is shown to be tight in some interesting special cases     

Constrained iterative speech enhancement with application to speechrecognition

The basis of an improved form of iterative speech enhancement for single-channel inputs is sequential maximum a posteriori estimation of the speech waveform and its all-pole parameters, followed by imposition of constraints upon the sequence of speech spectra. The approaches impose intraframe and interframe constraints on the input speech signal. Properties of the line spectral pair representation of speech allow for an efficient and direct procedure for application of many of the constraint requirements. Substantial improvement over the unconstrained method is observed in a variety of domains. Informed listener quality evaluation tests and objective speech quality measures demonstrate the technique's effectiveness for additive white Gaussian noise. A consistent terminating point of the iterative technique is shown. The current systems result in substantially improved speech quality and linear predictive coding (LPC) parameter estimation with only a minor increase in computational requirements. The algorithms are evaluated with respect to improving automatic recognition of speech in the presence of additive noise and shown to outperform other enhancement methods in this application     

The Philosophy and Mathematics of Bayes' Equation

The rudiments of Bayesian philosophy are introduced, and the mathematics of its application are surveyed; there is no uniformity of thought concerning either. The more extreme Bayesian philosophy, which allows subjective probabilities, is a means of plausible reasoning, or of making inferences, through inductive logic. Because inferences concerning reliability concepts are important in the decision process, this philosophy has a place in the reliability field. The difficulties of interpreting the probability function and of assigning prior distributions restrict the presentation of a unified philosophy. Thus, only techniques for describing prior probabilities under various circumstances can be given. Application of the Bayesian approach depends on how the reliability decision is conceptualized.     

A note on the method of analytical regularization

Many problems of electromagnetics are governed by singular integral equations of the first kind. As discussed by Nosich (1999), it is often possible to obtain a different equation describing the problem by applying the method of analytical regularization, and analytically inverting part of the original equation. The transformed equation is of the second kind. Therefore, as a rule, it is usually preferable to apply a numerical method to the transformed equation than to the original one. What appears to be an exception to that rule is discussed in the present paper: under proper conditions, and for a particular numerical method, results obtained by application to the transformed equation are shown to be identical to those obtained by application to the original equation. Some consequences of this equivalence are discussed     

A note on SAR imagery of the ocean

An example of SAR imagery of the ocean surface including the Gulf Stream Boundary reported by Moskowitz [1] is used to discuss potential mechanisms of SAR image formation of the ocean. It is pointed out that images in addition to those due to modulation of surface scatterer strength may result from organized scatterer motions such as those due to currents or wave orbital velocities. The modulation of scattering cross section by large waves is expected to depend on the magnitude and direction of the wind, making the relationship between image strengths and wave amplitudes rather complicated. It is suggested that the effect of wave orbital accelerations upon azimuthal focus might provide a more direct measure of wave amplitude.     

A note on the performance of ENET II

The performance of the ENET II protocol is discussed and compared to the performance of the commercial Ethernet. Linear network topologies with various number of stations uniformly distributed along the bus are considered. The comparison is based on extensive simulation studies and a recently published performance analysis of ENET II by Y.-C. Liu and G.L. Wise (1987). The experimental results agree with the analysis by Liu and Wise, but they do not confirm the results of M.K. Molloy (1985)     

A note on the limitations of Orchard's method

It has been stated that Orchard's (1985) method for the synthesis of array antennas and its extension to real patterns with real excitations are (a) unable to achieve a ripple level lower than about 0.5 dB when used to obtain shaped beams, and (b) only applicable to arrays of isotropic elements. For the benefit of the unwary, the author points out that neither of these limitations, in fact, applies either to Orchard's original method or to its extensions to real symmetric patterns and real asymmetric patterns     

A note on the Q-factor of microwave resonators

It is shown that the frequency variation of the resonator diaphragms has an effect of the order of 10 % on the calculated Q-factor of a waveguide resonator.     

A note on the predictability of band-limited processes

It is shown that a band-limited process can be expressed in terms of its past samples only, provided that the sampling rate is larger than but can be chosen arbitrarily close to the Nyquist rate.