A comparative study of YBCO powders prepared by different processes

Abstracts are not published in this journal This revised version was published online in November 2006 with corrections to the Cover Date.     

An expert system for the design and selection of ball bearing parameters

Artificial Intelligence (AI) is an emerging technology. Research in Al is focused on developing computational approaches to intelligent behaviour.The computer programs with which AI could be associated are primarily processes associated with complexity, ambiguity, indecisiveness, and uncertainty. One of these computer programs is referred to as Knowledge-based Expert System (KBES) as it represents knowledge acquired from various experts in a particular field of interest to the user. The expert system emulates human behaviour in solving problems thought to require experts for their solution by utilizing computer programs that incorporate experts' heuristic reasoning. In this paper, the application of KBES to aid the design of ball and roller bearing is discussed. The precision rolling-element bearing of the twentieth century is a product of exacting technology and sophisticated science. A bearing supports radial and axial loads, at the same time allowing relative motion between two elements of a machine. Various requirements and steps in the design of ball and roller bearings are discussed. Equations are developed for the relevant design parameters and input into the expert system shell called VP-Expert. The expert system rules are also provided.     

InGaAs-InP P-I (MQW)-N surface-normal electroabsorption modulatorsexhibiting better than 8:1 contrast ratio for 1.55-μm applicationsgrown by gas-source MBE

We report growth of In_0.53Ga_0.47 As-InP multiple quantum well (MQW) modulators operating at 1.55 μm for fiber-to-the-home applications. By employing a 200-period InGaAs-InP MQW stack in the intrinsic region of a p-i-n structure and working in reflection, we have been able to realize surface-normal modulator devices that exhibit better than an 8:1 contrast ratio. This is the highest contrast ratio reported to date for this type of device working at this wavelength     

A review on the clad failure studies

In this paper, an attempt has been made to systematically organize the research investigations conducted on clad tube failure, so far. Before presenting the review on the clad failure studies, an introduction to different clad materials has been added, in which the effect of alloying elements on the material properties have been presented. The literature on clad failure has been broadly categorized under the headings LOCA and RIA. The failure mechanisms like creep, corrosion and pellet-clad interaction have been discussed in details. Each subsection of the review has been provided with summary table, in which the studies are arranged in the chronological order. A small section on acceptance criteria for ECCS has also been included. The last section of the review has been dedicated to the core-degradation phenomena.     

Photoluminescence and photoluminescence excitation studies in 80 MeV Ni ion irradiated MOCVD grown GaN

We report damage creation and annihilation under energetic ion bombardment at a fixed fluence. MOCVD grown GaN thin films were irradiated with 80 MeV Ni ions at a fluence of 1 × 10¹³ ions/cm². Irradiated GaN thin films were subjected to rapid thermal annealing for 60 s in nitrogen atmosphere to anneal out the defects. The effects of defects on luminescence were explored with photoluminescence measurements. Room temperature photoluminescence spectra from pristine sample revealed presence of band to band transition besides unwanted yellow luminescence. Irradiated GaN does not show any band to band transition but there is a strong peak at 450 nm which is attributed to ion induced defect blue luminescence. However, irradiated and subsequently annealed samples show improved band to band transitions and a significant decrease in yellow luminescence intensity due to annihilation of defects which were created during irradiation. Irradiation induced effects on yellow and blue emissions are discussed.     

Sources of elastic deformations in steel frame and framed-tube structures: Part 2: Detailed subassemblage models

This paper examines the accuracy of a set of equations for computing Displacement Participation Factors (DPFs) for beam-column subassemblages of steel moment resisting frame buildings. These factors allow the analyst to determine how the entire subassemblage or individual components of a subassemblage contribute to a given structural displacement. Additionally, the component’s contribution to displacement may be evaluated in terms of sources of axial, flexural, or shear deformation.When applied to a set of 12 isolated subassemblages, it was shown in Part 1 of the paper that deformations in the beam-column joint are very significant, and that flexural deformation in the joint, which is often ignored, should be considered in all analyses. The total displacement predicted through the use of the DPFs correlates extremely well with the results of detailed three dimensional finite element analyses of the same subassemblages. However, it was also shown that there is considerable uncertainty in the bending moments and moments of inertia that are used to compute joint flexural deformations.The objective of this paper, which is the second part of a two-part paper, is to further investigate the accuracy of the DPF expressions developed in Part 1. This is done by computing DPFs from the results of detailed three dimensional finite element analysis, and comparing these to those computed through the use of the simple expressions.The results of the analysis show that the joint flexural deformations are accurately predicted by the simple DPF expressions, but that this accuracy arises from compensating “errors” in the simplified analysis. It is also shown that the use of beam flange continuity plates has a marginal effect on computed displacements. The paper ends with recommendations for using the simplified expressions for computing subassemblage deformations, and for including such deformations in structural analysis of steel frame and tube structures.     

1.5 mu m compressive-strained multiquantum-well 20-wavelength distributed-feedback laser arrays

The wide gain spectrum of compressive-strained multiquantum-well active layers was used to fabricate 20-wavelength distributed-feedback laser arrays. A record wide-wavelength span of 131 nm in the 1.5 mu m wavelength region was demonstrated. The maximum intrinsic modulation response, measured by a parasitic-free optical modulation technique, reaches 16 GHz.<>