Dielectric waveguides in two-dimensional photonic bandgap materials

We investigate the performance and guiding properties of waveguides fabricated in a finite two-dimensional (2-D) photonic bandgap (PBG) structure. Confinement in the direction perpendicular to the plane of periodicity is achieved by fabricating the 2-D PBG structure in a high dielectric layer enclosed by two lower dielectric layers. Simulations using the finite-difference time-domain (FDTD) method are performed to investigate the energy transport in such waveguides. Good qualitative agreement is found with the experimental observations     

Health and wellness monitoring through wearable and ambient sensors: exemplars from home-based care of elderly with mild dementia

Monitoring and timely intervention are extremely important in the continuous management of health and wellness among all segments of the population, but particularly among those with mild dementia. In relation to this, we prescribe three design principles for the construction of services and applications. These are ambient intelligence, service continuity, and micro-context. In this paper, we provide three exemplars from our research and development activities that illustrate the use of these design principles in the construction of services and applications. All the applications are drawn from the field of care for mild dementia patients in their living quarters.     

Investigation of the interface region produced by molecular beam epitaxial regrowth

The interface region generated by molecular beam epitaxial regrowth has been studied in detail. Regrowth was carried out on epitaxial GaAs after a variety of realistic device processing steps. Combinations of wet chemical etching and ion milling with and without annealing were used with the objective of establishing the best procedure for integrated technologies during regrowth. Capacitance voltage measurements showed perturbations in the carrier profile corresponding to depletion and accumulation regions at the interface which are directly related to interface states at and around the regrowth interface. The measured concentration of the interface states are in the range 1.2 × 10¹⁰ to 7.05 × 10¹¹ cm⁻². The former is one of the lowest reported till date. The concentration of deep traps in the regrown layer and interface, observed by deep level transient spectroscopy, is much lower than the interface state density. Their contribution to carrier perturbation is insignificant, except in one case where an electron trap has a rather high concentration. Results of secondary ion mass spectroscopy indicate that the presence of carbon at the regrown interface is not principally responsible for creating the high resistivity interface region. Our data favor the concept of a disordered region created at the interface during regrowth. Interface state density and trap densities are much larger in the wet chemically etched samples, which is further supported by the results of temporal photoresponse measurements on junction photodiodes. The overall characteristics of the dry etched regrowth interfaces seem to be much more promising than the wet chemical etched ones. On leave from the Institute of Radiophysics and Electronics, The University of Calcutta, Calcutta 700 009, India.     

Shock deformation of coarse grain alumina above Hugoniot elastic limit

Symmetric shock experiments were conducted on a 10 μm grain size coarse alumina ceramic with a gas gun to identify its Hugoniot elastic limit (HEL). To understand the damage initiation and their subsequent growth mechanisms in coarse grain alumina subjected to shock impact at levels much above the HEL, additional asymmetric shock recovery experiments with the same gas gun were then deliberately conducted on the same alumina at shock pressure levels more than three times as high as the HEL and the fragments collected by a dedicated catcher system. Detailed characterization of the shock recovered alumina fragments by X-ray diffraction, nanoindentation, scanning electron microscopy, field emission scanning electron microscopy and transmission electron microscopy were utilized to understand the nature and process of failure initiation, incubational growth, coalescence and propagation leading to fragmentation. Based on these data a new qualitative damage model was developed to explain the deformation mechanism.     

Preparation, structure and electrical conductivity of Pr1−xLaxO2−δ (x = 0.05, 0.1, 0.2)

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

The differential induction machine: Theory and performance

This paper presents the theory and performance of a differential induction machine, which is a special type of induction machine having two shafts projected from the two ends of a single stator. Application of a differential load on the two shafts cause them to run at different speed as a motor, which permits true differential movement and thus can meet the requirements of a differential drive in an electric vehicle. The machine is also capable of regeneration in the differential mode. This paper presents the construction of the above machine and performance of the same based on experimental results from a laboratory prototype. The equivalent circuit of the motor has been presented and verified experimentally.