A microstrip wideband bandpass filter based on λ/2 stub with spurious passband suppression scheme

In the design of bandpass filters, the use of λ/2 stubs of shunt configuration had been mostly unacceptable due to their effect of narrow stopband bandwidths in the ensuing filters. The design of bandpass filter presented in this article introduces 360° series transmission line segments to increase the stopband bandwidths to an acceptable level without affecting the wide passband. This designed filter has low insertion loss of less than –1.98 dB and a fractional bandwidth of 50% at 6 GHz mid-band frequency. A sharp rejection in the stopband is observed. To further widen the bandwidth of stopbands, a series capacitor and a shunt stub are used. The transmission line model of the filter is in good agreement with measured results. The filter is planar and is fabricated on FR-4 substrate which makes it cost-effective and easy to fabricate.     

STUDY OF THERMOELASTIC WAVE PROPAGATION IN A HALF-SPACE USING GN THEORY

Thermoelastic interactions in an isotropic homogeneous elastic half-space are studied using mathematical methods under the purview of the GN model of linear theory of generalized thermoelasticity. Of specific concern here is the propagation of waves owing to ramp-type heating of the bounding surface, which is either (i) traction-free or (ii) held rigidly fixed whereby the displacement is constrained. Using the integral transform approach, approximate solutions valid in the small time range are obtained for the situation when Fourier conductivity is dominant. Also exact solutions for temperature, displacement, and stress fields are obtained for the same problem for cases where conductivity is ignorable. Numerical estimates are also obtained for a particular example.     

Rapid melting and solidification of a surface layer

Metallurgical and Materials Transactions B - A one-dimensional computer heat flow model is used to investigate the effect of high intensity heat fluxes,e.g. those achieved via continuous CO2 laser...     

Microstructural studies of glass-metal composites produced by ion-exchange and hydrogen treatments

Detailed electron micrographic studies have been carried out on float glass surface subjected to sodium ? copper ion-exchange in molten salts followed by a reduction treatment in hydrogen. Spherical copper particles of diameters ranging from 50 to 300 å are formed in the glass matrix depending on the ion-exchange and reduction temperatures. The nucleus density of these particles is maximum at around 450?C. Phase separation in glasses whether incipient or induced by ion-exchange, increases considerably the nucleus density when such samples are subsequently reduced. This is ascribed to the increase in the number of copper atoms surrounding the nucleation sites in the phase separated glasses. The optical absorption spectra of the glass-metal composites show two bands, namely at 17 400 cm^?1 and 23 000 cm^?1 respectively. The absorption maxima for both the bands occur for specimens reduced at temperatures between 450 and 500? C corresponding to the temperature of maximum nucleus density. The bands at 17 400 cm^?1 and 23 000 cm^?1 are assigned to the conduction resonance and plasma resonance respectively as predicted by Maxwell-Garnet theory on aggregated metal systems dispersed in a dielectric matrix.     

Glass-metal particulate composites

Oxide glasses containing ultrafine metal particles have interesting physical properties and have been widely used in practical systems. The various preparational techniques developed so far for making these materials are discussed. Electrical conduction in these composites is controlled by electron tunnelling between the metal islands. At high electric fields certain glasses containing bismuth granules show a memory switching effect. The latter has been explained by a particle stretching model. Optical absorption characteristics of these composites can be explained on the basis of various effective medium theories developed so far for inhomogeneous materials. Glasses containing ferromagnetic metal grains show a superparamagnetic behaviour with a transition temperature below 300 K. Improvement in the mechanical properties of glasses can be achieved by incorporating metal particles of suitable characteristics within them. In this paper the present state of understanding of all these properties is reviewed.     

Mechanical properties of glass fibres containing aluminium dispersoids

Glass fibres containing metallic aluminium dispersoids up to 7.5 at% AI have been made using ceramic bushings. The metallic granules have diameters ranging from 5 to 40 nm. A new technique based on strength-strain regression analysis has been used to determine the Young's moduli of the glass fibres. The Weibull parameters have been evaluated by both the graphical regression (GRE) and maximum likelihood (MLE) techniques. Fracture studies have also been carried out. The presence of aluminium particles increases the Young's modulus of the fibres but reduces the strength. The latter arises due to the metallic particles acting as stress concentrators within the glass matrix.     

A mobile bazaar for wide-area wireless services

We introduce MoB, an infrastructure for collaborative wide-area wireless data services. MoB proposes to change the current model of data services in the following fundamental ways: (1) it decouples infrastructure providers from services providers and enables fine-grained competition, (2) it allows service interactions on arbitrary timescales, and, (3) it promotes flexible composition of these fine-grained service interactions based on user and application needs. At the heart of MoB is an open market architecture in which mobile users can opportunistically trade various services with each other in a flexible manner. In this paper we first describe the overall architecture of MoB including various enablers like user reputation management, incentive management, and accounting services. We next present our experience from both simulations as well as our prototype implementation of MoB in enhancing application performance in multiple different scenarios—file transfers, web browsing, media streaming, and location-enhanced services. This work is supported in part by NSF grants CNS-0520152, CNS-0639434, CNS-0627589 and CNS-0627102. Rajiv Chakravorty received the B.E. degree from Nagpur University, Nagpur, India, in 1997 and the M.Tech. degree form the Indian Institute of Technology, Delhi in 1999. He is working towards the Ph.D. degree at the Computer Laboratory, University of Cambridge, U.K. In 2005 he was a visiting research scholar in the Department of Computer Sciences, University of Wisconsin, Madison. He has worked with Philips Research, ASA Laboratories, Eindhoven, The Netherlands. He also pursued research at ComNets, RWTH-Aachen, Germany. His current interests include mobile and wireless systems, and networking. He is a recipient of DAAD Scholarship Award from Germany, and the Sun Microsystems Scholarship and the Hughes Hall Commonwealth scholarhip from Cambridge Univeristy. Sulabh Agarwal received the B.Tech. degree in Computer Science and Engineering from Indian Institute of Technology, Delhi in 2000, and the M.S. degree in Computer Science from University of Maryland, College Park in 2002. His research interest is in the area of computer networking. Suman Banerjee received the B.Tech. degree in Computer Science and Engineering from Indian Institute of Technology, Kanpur in 1996, and the M.S. and the Ph.D. degrees in Computer Science from University of Maryland, College Park in 1999 and 2003 respectively. He is an Assistant Professor of Computer Sciences at University of Wisconsin-Madison and heads the Wisconsin Wireless and NetworkinG Systems (WiNGS) laboratory. His broad research interests are in the areas of networking and distributed systems with a special focus in the area of wireless and mobile networking systems. Ian Pratt received the Ph.D. in Computer Science from University of Cambridge, Cambridge, U.K. He was elected a Fellow of King’s College, Cambridge, U.K., in 1996. He is a Senior Faculty member at the Computer Loboratory, University of Cambridge, Cambridge, U.K. He is a a leader of the Systems Research Group, where he has been architect of a number of influential projects, including the Desk Area Network workstation, the Cambridge Open Mobile System, the Xen Virtual Machine Monitor, and the XenoServer infrastructure for global computing. His research interests cover a broad range if systems topics, including computer architecture, operating system design, mobile systems, and networking.