An Energy Efficient Clustered Gravitational and Fuzzy Based Routing Algorithm in WSNs

Wireless Personal Communications - Wireless sensor networks consist of many tiny sensor nodes which are deployed in various geographical locations for sensing the normal spectacles and also to...     

Design and development of a novel high-transconductance pH-ISFET (ion-sensitive field-effect transistor)-based glucose biosensor

A glucose biosensor based on a high-transconductance ISFET transduction element with aspect ratio (channel width/length) of 400 has been developed. This biosensor is an N-channel enhancement mode device with interdigitated drain-source geometry, fabricated by the NMOS process, in which glucose oxidase (GOD) enzyme has been immobilized over the silicon dioxide-silicon nitride dual-dielectric gate. The device has been operated in the active mode by applying a gate voltage through Ag/AgCl reference electrode. Electrical characterization has been performed in terms of I-V characteristics like output characteristics and leakage current. The pH response characteristics have been measured and the pH sensitivity factor has been found to be?≥?50?mV/decade. Device characterization has also been performed by a signal conditioning circuit developed for direct readout of pH from the ISFET device. Temperature behaviour and drift phenomenon have been investigated.

The glucose response characteristics of the ISFET have been determined, without and with the glucose oxidase enzyme layer. Improvement of the glucose sensitivity by deposition of the enzyme layer has been studied and cross-sensitivity of the device towards urea has been examined. The advantage of the high transconductance was evident from the ability of the sensor to detect small glucose concentrations without the enzyme layer. The paper describes the design, fabrication and characterization of the sensor.     

Thermal Stability of Nitride-Based Diffusion Barriers for Ohmic Contacts to <Emphasis Type="Italic">n</Emphasis>-GaN

The use of TaN, TiN, and ZrN diffusion barriers for Ti/Al-based contacts on n-GaN (n ∼ 3 × 10¹⁷ cm⁻³) is reported. The annealing temperature (600–1,000°C) dependence of the Ohmic contact characteristics using a Ti/Al/X/Ti/Au metallization scheme, where X is TaN, TiN, or ZrN, deposited by sputtering was investigated by contact resistance measurements and Auger electron spectroscopy (AES). The as-deposited contacts were rectifying and transitioned to Ohmic behavior for annealing at ≥600°C. A minimum specific contact resistivity of ∼6 × 10⁻⁵ Ω-cm⁻² was obtained after annealing over a broad range of temperatures (600–900°C for 60 s), comparable to that achieved using a conventional Ti/Al/Pt/Au scheme on the same samples. The contact morphology became considerably rougher at the high end of the annealing range. The long-term reliability of the contacts at 350°C was examined; each contact structure showed an increase in contact resistance by a factor of three to four over 24 days at 350°C in air. AES profiling showed that the aging had little effect on the contact structure of the nitride stacks.     

Influence of chemical compositions of slag and graphite on the phenomena occurring in the graphite/slag interfacial region

Silica reduction reactions taking place in the slag/carbon interfacial region were investigated for synthetic/natural graphite in the temperature range 1500 °C to 1700 °C. Two silica-rich blast furnace slags, with low levels of iron oxide, were used in this study. Silica concentration in these slags, labeled as 1 and 2, was 30.80 pct and 36.80 pct with a respective basicity of 1.67 and 1.22. Reaction rate investigations were supplemented with wettability measurements on these systems with an aim to probe a possible interdependence between wetting characteristics and reaction rates of silica reduction. Wettability and slag/carbon reactions were studied in a horizontal tube resistance furnace in argon atmosphere, using the sessile drop approach. While the contact angles were measured by recording live images of the assembly with a charge-coupled device camera, the volumes of CO and CO₂ evolved were obtained from an analysis of off-gases with the help of a mass spectrometer. Reaction rates for silica reduction showed a wide variation for different systems. Synthetic graphite showed nonwetting behavior with both slags. Natural graphite, however, showed dynamic wetting with slag 2, resulting in low contact angles. This is attributed to the difference in the deposition of Si-based reaction products in the interfacial region, which in turn influences wettability. Temperature had a significant effect on both the wettability and silica reduction rate of the graphite/slag system. Activation energies for silica reduction in slags 1 and 2 with natural graphite were estimated to be 253 and 241 kJ/mol, respectively. Chemical composition of carbonaceous materials and slags were found to play a very important role in dictating overall reaction rates and wetting characteristics.     

Residual stresses and sliding wear

The residual stresses that develop during the wear of AISI-SAE 1018 and 4340 steels have been examined. The entire three-dimensional stress tensor was obtained. A normal stress perpendicular to the surface, predicted by theory, has been found, but its magnitude is too small to affect the wear rate. There are also significant shear stresses. The wear process rapidly alters any initial stress distribution produced by heat treatment or peening to such a degree that the wear rate is not affected by these stresses, unless they are initially larger than those that can be produced by the wear parameters.     

Room temperature-vulcanized silicone elastomer: Effect of curing conditions and the nature of filler on mechanical and thermal properties

Linear poly(dimethylsiloxane diol) of about 650 D.P. was synthesized by hydrolytic condensation of dimethyldichlorosilane in a saturated solution of sodium chloride. The polymer was then compounded with various fillers, Cab-O-Sil, Dicalite, and titanium dioxide, and cured at room temperature in the presence of tin salt and tri- or tetrafunctional silane. The tensile strength and elongation of the unfilled rubber were found to be 0.8 kg/cm² and 320%, respectively. However, Dicalite White (100 phr)-reinforced elastomer showed a tensile strength of 40 kg/cm². Crosslink density was determined from the swelling studies. Thermal aging at 150, 200, and 250°C was also studied.     

Limiting capacities of drainage stack in tall buildings

Inter-relationships developed previously between negative pressure produced in a stack and flow rate to stack diameter ratio have provided a simple procedure for designing both vented and unvented drainage systems in tall buildings. These studies have, however, disregarded existing suctions in the stack.The present work relates to a performance study of Single Stack and Modified One-pipe systems of drainage for existing suctions in the stack, a condition closer to the actual situation in tall buildings. The results of this investigation have been reported in terms of permissible stack capacities and are in close agreement with the recommendations of B.R.E. (U.K.).