Propylene polymerization — a computer efficient algorithm with orthogonal collocation

This paper presents a new approach to the modelling of solid catalyzed Ziegler-Natta polymerization of propylene, using orthogonal collocation technique. It is shown that this model can predict the width of the molar mass distribution (MWD) of the product polymer. Its computation time is much shorter compared to other models. An interesting feature of the model is that it considers the discrete nature of the microcatalyst particles and takes advantage of solving a smaller number of stiff differential equations by choosing the number of internal collocation points judiciously. In addition, pseudo-steady state approximation (QSSA) is applied to some of the moment generating equations.     

Using the matrix pencil method to estimate the parameters of a sumof complex exponentials

The approximation of a function by a sum of complex exponentials is a problem that is at least two centuries old. Fundamentally, all techniques discussed in this article proceed from using the same sequence of data samples and vary only, but importantly, in how those samples are used in achieving the parameter estimation. All of these techniques, in other words, seek the same quantitative parameters to represent the sampled data, but use different routes to get there. The techniques for estimating the parameters are either linear or nonlinear. The linear techniques are emphasized in this presentation. In particular, the matrix pencil method is described, which is more robust to noise in the sampled data. The matrix pencil approach has a lower variance of the estimates of the parameters of interest than a polynomial-type method (Prony's method belongs to this category), and is also computationally more efficient. A bandpass version of the matrix pencil can be implemented in hardware, utilizing an AT&T DSP32C chip operating in real time. A copy of the computer program implementing the matrix pencil technique is given in the appendix     

An appreciation of J.C. Bose's pioneering work in millimeter waves

The pioneering work in the area of millimeter waves, performed by J. C. Bose, a physicist from Calcutta, India, during 1894-1900, is reviewed and appraised. Various measurement techniques and circuit components, developed by him a hundred years ago, are still being used. The development of the electromagnetic horn, the point-contact detector, and the galena (semiconductor) detector of electromagnetic waves are attributed to the original research of J.C. Bose     

A MRF model-based segmentation approach to classification formultispectral imagery

An unsupervised segmentation approach to classification of multispectral image is suggested here in Markov random field (MRF) frame work. This work generalizes the work of Sarkar et al. (2000) on gray value images for multispectral images and is extended for landuse classification. The essence of this approach is based on capturing intrinsic characters of tonal and textural regions of any multispectral image. The approach takes an initially oversegmented image and the original. multispectral image as the input and defines a MRF over region adjacency graph (RAG) of the initially segmented regions. Energy function minimization associated with the MRF is carried out by applying a multivariate statistical test. A cluster validation scheme is outlined after obtaining optimal segmentation. Quantitative evaluation of classification accuracy of test data for three illustrations are shown and compared with conventional maximum likelihood procedure. Comparison of the proposed methodology with a recent work of texture segmentation in the literature has also been provided. The findings of the proposed method are found to be encouraging     

A note on the Cramer-Rao bound for 2-D direction finding based on2-D array

The authors present explicit expressions for the Cramer-Rao bound (CRB) for estimating the two-dimensional (2-D) direction of a single source based on 2-D arrays of identical omnidirectional sensors. Two commonly used models, random wave and unknown wave, are compared. It is shown that the CRBs for the two models have the same dependency on the array structure. A specialization of the CRB to two orthogonal uniform linear arrays (ULAs) is discussed. It is found that the joint CRBs of the direction angles based on the two orthogonal ULAs can be as low as one quarter (for a random waveform model with a large number of snapshots and low SNR) or one half (for both models with high SNR) of the CRBs based on each ULA     

Analysis of arbitrarily shaped microstrip patch antennas using the Sommerfeld formulation

Triangular patch modeling is used for analysis of arbitrarily shaped microstrip patch antennas over a single lossy dielectric medium. Since the Sommerfeld formulation is used, both the single dielectric layer (over which the microstrip patch is located) and the ground plane are considered to be infinitely wide. Typical numerical results are presented for rectangular, circular, semicircular, pentagonal, and triangular patch antennas. © 1992 John Wiley & Sons, Inc.     

Static and impact fatigue behaviour of borosilicate glass

Failure of a borosilicate glass as a result of repeated impact has been studied. Impact fatigue study was conducted in an improved pendulum type repeated impact apparatus specially designed and fabricated for determining single and repeated impact strength. For elimination of the effect of humidity, repeated impact tests were carried out under liquid nitrogen. Quasi-static measurements were determined under four-point bending. Using a square waveform as applicable to the present impact tests and fracture mechanics interpretation, the number of cycles to failure during impact fatigue tests were predicted from quasi-static fatigue measurements. It has been shown that repeated impact loading has a deleterious effect on the failure cycles compared to slow stressing. The role of an added mechanical effect during repeated impacts has been suggested in controlling the cyclic fatigue behaviour. Paper presented at the poster session of MRSI AGM VI, Kharagpur, 1995     

Microstructural studies on lattice imperfections in irradiated titanium and Ti-5 Pct Ta-2 Pct Nb by X-ray diffraction line-profile analysis

Microstructural parameters such as the average domain size, effective domain size at a particular crystallographic direction, and microstrain within the domains of titanium and Ti-5 pct Ta-2 pct Nb, irradiated with 116 MeV O⁵⁺ ion, have been characterized as a function of dose by X-ray diffraction line-profile analysis (XRDLPA) using different model-based approaches. The dislocation density and stacking-fault probabilities have also been estimated from the analysis. The analysis revealed that there was a significant decrease of the average domain size with dose as compared to the unirradiated sample. The estimated values of dislocation density increased significantly for the irradiated samples and were found to be an order of magnitude more as compared to the unirradiated one. However, the dislocation density became saturated with an increase in dose. The deformation (stacking-fault) probabilities were found to be negligible even with the increase in dose of irradiation.