A probabilistic approach to run-to-run control

This paper considers model uncertainty in the run-to-run control problem from a probabilistic viewpoint. The methodology assumes that the model parameters are stochastic and uses experimental input-output data off-line to characterize the probability distribution of the model parameters. This naturally leads to the notions of probability of stability and probability of performance as a means of evaluating run-to-run controllers. Analytic formulas for the probability of stability are given for the particular case of an EWMA controller. When considering a more general notion of performance, the Monte Carlo method is used to approximate the probability of performance to a high degree of confidence. This probabilistic approach to run-to-run control is then illustrated on a virtual plasma etching reactor. Finally, the reliability of the method is investigated     

A probabilistic approach to some asymptotics in noiselesscommunication

Renewal theory is a powerful tool in the analysis of source codes. We use renewal theory to obtain some asymptotic properties of finite-state noiseless channels. We discuss the relationship between these results and earlier uses of renewal theory to analyze the Lempel-Ziv (1977, 1978) codes and the Tunstall (1967) code. As a new application of our results, we provide the asymptotic performance of two of the Perl, Garey and Even (1975) prefix condition codes     

A flexible approach to emitter-coupled logic arrays

The ECCSL arrays have been successfully fabricated using two levels of metalization on 120 by 120-mil chips. The yield, fabrication, and performance studies of these arrays, while not yet complete, indicate that current mode logic arrays of 10 to 30 gates are entirely feasible. This is especially true if the size of the chips are reduced as much as possible (preferably below 0.10 by 0.10 inch.) Indications are that arrays with relatively low gate counts (10 to 30 gates) greatly reduce the testing problems usually associated with array technology.     

Element pattern for circular arrays of axial slits on large conducting cylinders

The element pattern for circular arrays of axial slits on large perfectly conducting cylinders is derived. Its properties are examined and compared with those of similar planar arrays. Implications for circular array design are deduced.     

An approach for low sidelobe beamforming in uniform concentric circular arrays

In this paper, a new tapered beamforming function for sidelobe reduction in the uniform concentric circular arrays (UCCA) is proposed. This technique is based on tapering the current amplitudes of the rings in the array, where all elements in an individual ring are weighted in amplitude by the same value and the weight values of different rings are determined by a function that has a normalized-gaussian probability density function variation. This novel tapering window is optimized in its parameters to have the lowest possible sidelobe level that may reach 43 dB below the main lobe and these optimum weights are found to be function of the number of elements of the innermost ring and the number of rings in the array. The proposed tapering window can be modified to compensate the gain reduction due to tapering when compared with the uniform feeding case.     

A probabilistic approach to fault diagnosis in linear lightwavenetworks

The application of probabilistic reasoning to fault diagnosis in linear lightwave networks (LLNs) is investigated. The LLN inference model is represented by a Bayesian network (or causal network). An inference algorithm is proposed that is capable of conducting fault diagnosis (inference) with incomplete evidence and on an interactive basis. Two belief updating algorithms are presented which are used by the inference algorithm for performing fault diagnosis. The first belief updating algorithm is a simplified version of the one proposed by Pearl (1988) for singly connected inference models. The second belief updating algorithm applies to multiply connected inference models and is more general than the first. The authors also introduce a t-fault diagnosis system and an adaptive diagnosis system to further reduce the computational complexity of the fault diagnosis process     

A probabilistic approach to the single-point, single-dose problem

A general probabilistic approach is applied to the single-point, single-dose method for estimating individual infusion rates and serum drug concentrations. By using transformations of probability density functions, the effects of variations in the elimination rate constant upon pharmacokinetic variables may be studied and optimal sampling times may be chosen. Although this study treats the case of error-free sampling in a single-compartment model with a normal distribution of rate constants, the methods presented can be extended to more general situations.     

Element pattern for circular arrays of waveguide-fed axial slits on large conducting cylinders

Analytical and numerical results are presented for the array element pattern of axial slits in conducting cylinders. The slits are fed by parallel-plate guides in the TEM mode and are matched to free space. Both harmonic series and integral representation for the far-field patterns are obtained and numerically evaluated as a function ofkr_{0}and spacing. The integral representation is treated asymptotically for large values ofkr_{0}. The element patterns exhibit two characteristic features: a dip off broadside and a ripple in the main beam near broadside, the level of both beingkr_{0}dependent. While the harmonic series offers no basis for an explanation of these effects, the asymptotics clearly demonstrates that the pattern can be decomposed into two parts: 1) a space wave contribution which can be directly obtained by substituting the circular array "admittance crater" into the appropriate planar array formulas and exhibits a dip analogous to a grating lobe effect; 2) a set of creeping waves which, unlike the more common type, contribute significantly in the forward region and, by interfering with the space wave, cause the ripple near broadside. These creeping waves are the fast (usuallyn = -1) space harmonics (grating lobes) of the fundamental, slightly slow set, and their presence does not seem to have been recognized in the literature.     

A probabilistic model-based approach to consistent white matter tract segmentation

Since the invention of diffusion magnetic resonance imaging (dMRI), currently the only established method for studying white matter connectivity in a clinical environment, there has been a great deal of interest in the effects of various pathologies on the connectivity of the brain. As methods for in vivo tractography have been developed, it has become possible to track and segment specific white matter structures of interest for particular study. However, the consistency and reproducibility of tractography-based segmentation remain limited, and attempts to improve them have thus far typically involved the imposition of strong constraints on the tract reconstruction process itself. In this work we take a different approach, developing a formal probabilistic model for the relationships between comparable tracts in different scans, and then using it to choose a tract, a posteriori, which best matches a predefined reference tract for the structure of interest. We demonstrate that this method is able to significantly improve segmentation consistency without directly constraining the tractography algorithm.     

A probabilistic approach to evaluate the reliability of piezoelectric micro-actuators

In this paper, a probabilistic design approach is presented to evaluate the reliability of piezoelectric micro actuators. Based on the relationship between the lifetime, and degradation mechanism of piezoelectric actuators, and the electric field strength, the concept of "electric strength" is proposed to indicate the electric field strength of the piezoelectric actuators at a specified lifetime. The lifetime (number of cycles to failure) of the piezoelectric actuator, electric strength, and electric load are considered as the random variables; and their probability distributions are discussed. The interference model of electric load, and electric strength is introduced to the reliability design of piezoelectric micro actuators. By this approach, the relationship between the reliability, and the lifetime of the piezoelectric actuator can be given. A case study of the disk drive head positioning system demonstrates the application of the approach.     

A pattern synthesis of circular arrays by phase adjustment

A problem of sidelobe suppression of a uniformly excited circular array of monopoles through the adjustment of the excitation phases is dealt with. For this purpose, the method of approximation programming (MAP) is used to determine the optimum excitation phases which minimize the sidelobe level. Galerkin's method is used to analyze the mutual coupling between array elements. The resulting radiation pattern has equal amplitude sidelobes that are lower than those obtained with a cophasal array. The resulting radiation pattern of a 32-element double-ring array, operating atX-band, was measured and reasonable agreement with theory was obtained.     

Analysis of finite arrays of axially directed printed dipoles on electrically large circular cylinders

Various arrays consisting of finite number of printed dipoles on electrically large dielectric coated circular cylinders are investigated using a hybrid method of moments/Green's function technique in the spatial domain. This is basically an "element by element" approach in which the mutual coupling between dipoles through space as well as surface waves is incorporated. The efficiency of the method comes from the computation of the Green's function, where three types of spatial domain Green's function representations are used interchangeably, based on their computational efficiency and regions where they remain accurate. Numerical results are presented in the form of array current distributions, active reflection coefficient and far-field pattern to indicate the efficiency and accuracy of the method. Furthermore, these results are compared with similar results obtained from finite arrays of printed dipoles on grounded planar dielectric slabs. It is shown that planar approximations, except for small separations, can not be used due to the mutual coupling between the array elements. Consequently, basic performance metrics of printed dipole arrays on coated cylinders show significant discrepancies when compared to their planar counterparts.     

A spherical scatterer inside a circular hollow dielectric waveguide

A theoretical investigation is presented of scattering characteristics of a perfectly conducting spherical object placed inside a quasi-optical transmission line of the millimeter and submillimeter waves in the form of a circular hollow dielectric waveguide (HDW). From the analytical expressions obtained, backscattering and extinction cross sections of this object are derived via the excitation coefficient of the dominantHE ₁₁ mode of the circular HDW and the HDW geometrical parameters. The agreement of the results with the corresponding data for the scattering of a plane homogeneous wave is shown.     

A probabilistic approach to incorporating domain knowledge for closed-room people monitoring

We propose a novel probabilistic approach to recognizing people entering and leaving a closed room in human work place or living environment. Specifically, people in the view of a monitoring camera are first tracked and represented using low-level color features. Based on a new color similarity measure, optimal recognition of people leaving and entering the room is carried out by probabilistic reasoning under the constraints imposed by the domain knowledge, e.g., a person currently inside a room cannot enter again without first leaving it, and vice versa. The novelty of our work mainly lies in the development of a systematic way to incorporate the correlation and constraint among a sequence of people observations, and the optimality of recognition is achieved by maximizing a joint posterior probability of the observations. Experimental results of real and synthetic data are presented to show the efficacy of the proposed approach.     

乳胶模制球面微反镜阵列

英国南安普顿大学的科研人员将研制出一种以球面反射镜阵列构成的阵列器件.该器件包含激光器或由光学活性材料填充的微谐振腔,以金(Au)、铂(Pt)或者其他材料作反射表面.为了制造这种阵列,把含有微型乳胶球的胶体溶液铺在金膜上,在合适的条件下,微乳胶球置于密堆积的单层中.然后把一种金属电镀到球体上,在用溶剂溶解掉微型乳胶球后留下微型凹球面反射镜阵列.     

Near-field analysis of spherical loop arrays

In a recent paper (see ibid., vol.42, p473-7, April 1994), the authors presented the development of an algorithm for the reconstruction of element currents of a spherical loop array given the far-field pattern data in an azimuthal plane, and demonstrated the validity of the method with several computational examples. In this letter, it is shown that the same algorithm can be applied to the reconstruction of the spherical loop-array currents from the near-field data by application of spherical wave expansion of the electric field integral of the array. The main feature of the reconstruction algorithm is that the array currents are obtained recursively through the solution of a triangular equation set     

柔性稀疏阵的稳健波束形成

本文将导向矢量失配时的稳健波束形成问题归结为二次锥规划问题,利用高效的内点法求解。该波束形成器成功地应用于存在阵元位置误差的柔性稀疏阵,相对于经典的对角线加载法、特征空间法,在不同的输入信噪比下获得了更好的输出信号干扰加噪声比。仿真结果表明对超稀疏分布的柔性阵,阵元位置误差对输出SINR起决定性影响,而阵列稀疏程度对其影响不大。