An oxidative cross-dehydrogenative-coupling reaction in water using molecular oxygen as the oxidant: vanadium catalyzed indolation of tetrahydroisoquinolines

An aerobic oxidative cross-dehydrogenative coupling reaction between sp(3) C-H and sp(2) C-H bonds is developed by employing a vanadium catalyst (10 mol%) in an aqueous medium using molecular oxygen as the oxidant. This environmentally benign strategy exhibits larger substrate scope and shows high regioselectivity.

Coupling of High Voltage AC Power Line Fields to Metallic Pipelines

In the recent years, there has been a trend to run metallic pipelines carrying petroleum products and high voltage AC power lines parallel to each other in a relatively narrow strip of land. Due to this sharing of the right-of-way, verhead AC power line electric field may induce voltages on the metallic pipelines running in close vicinity leading to serious adverse effects. In this paper, the induced voltages on metallic pipelines running in close vicinity of high voltage power transmission lines have been computed. Before computing the induced voltages, an optimum configuration of the phase conductors based on the lowest conductor surface gradient and field under transmission line has been arrived at. This paper reports the conductor surface field gradients calculated for the various configurations. Also the electric fields under transmission line, for single circuit and double circuit (various phase arrangements) have been analyzed. Based on the above results, an optimum configuration giving the lowest field under the power line as well as the lowest conductor surface gradient has been arrived at and for this configuration, induced voltage on the pipeline has been computed using the Charge Simulation Method (CSM). For comparison, induced voltages on the pipeline has been computed for the various other phase configurations also.

Modeling of active fiber composite for delamination sensing

In order to demonstrate the feasibility of Active Fiber Composites (AFC) as sensors for detecting damage, a pretwisted strip made of AFC with symmetric free-edge delamination is considered in this paper. The strain developed on the top/bottom of the strip is measured to detect and assess delamination. Variational Asymptotic Method (VAM) is used in the development of a non-classical non-linear cross sectional model of the strip. The original three dimensional (3D) problem is simplified by the decomposition into two simpler problems: a two-dimensional (2D) problem, which provides in a compact form the cross-sectional properties using VAM, and a non-linear one-dimensional (1D) problem along the length of the beam. This procedure gives the non-linear stiffnesses, which are very sensitive to damage, at any given cross-section of the strip. The developed model is used to study a special case of cantilevered laminated strip with antisymmetric layup, loaded only by an axial force at the tip. The charge generated in the AFC lamina is derived in closed form in terms of the 1D strain measures. It is observed that delamination length and location have a definite influence on the charge developed in the AFC lamina. Also, sensor voltage output distribution along the length of the beam is obtained using evenly distributed electrode strip. These data could in turn be used to detect the presence of damage.

Structural Health Monitoring (SHM) Using Strain Gauges, PVDF Film and Fiber Bragg Grating (FBG) Sensors: A Comparative Study

The term Structural Health Monitoring has gained wide acceptance in the recent pastas a means to monitor a structure and provide an early warning of an unsafe conditionusing real-time data. Utilization of structurally integrated, distributed sensors tomonitor the health of a structure through accurate interpretation of sensor signals andreal-time data processing can greatly reduce the inspection burden. The rapidimprovement of the Fiber Bragg Grating sensor technology for strain, vibration andacoustic emission measurements in recent times make them a feasible alternatives tothe traditional strain gauges transducers and conventional Piezoelectric sensors usedfor Non Destructive Evaluation (NDE) and Structural Health Monitoring (SHM).Optical fiber-based sensors offers advantages over conventional strain gauges, PVDFfilm and PZT devices in terms of size, ease of embedment, immunity fromelectromagnetic interference(EMI) and potential for multiplexing a number ofsensors. The objective of this paper is to demonstrate the feasibility of Fiber BraggGrating sensor and compare its utility with the conventional strain gauges and PVDFfilm sensors. For this purpose experiments are being carried out in the laboratory on acomposite wing of a mini air vehicle (MAV). In this paper, the results obtained fromthese preliminary experiments are discussed.

Measurement of Electron Spin Lifetime and Optical Orientation Efficiency in Germanium Using Electrical Detection of Radio Frequency Modulated Spin Polarization

We propose and demonstrate a technique for electrical detection of polarized spins in semiconductors in zero applied magnetic fields. Spin polarization is generated by optical injection using circularly polarized light which is modulated rapidly using an electro-optic cell. The modulated spin polarization generates a weak time-varying magnetic field which is detected by a sensitive radio-frequency coil. Using a calibrated pickup coil and amplification electronics, clear signals were obtained for bulk GaAs and Ge samples from which an optical spin orientation efficiency of 4.8% could be determined for Ge at 1342 nm excitation wavelength. In the presence of a small external magnetic field, the signal decayed according to the Hanle effect, from which a spin lifetime of 4.6 +/- 1.0 ns for electrons in bulk Ge at 127 K was extracted.

Measurement of Stress-Strain Response of A Rammed Earth Prism In Compression Using Fiber Bragg Grating Sensors

A comparative study of strain response and mechanical properties of rammed earth prisms, has been made using Fiber Bragg Grating (FBG) sensors (optical) and clip-on extensometer (electro-mechanical). The aim of this study is to address the merits and demerits of traditional extensometer vis-à-vis FBG sensor; a uni-axial compression test has been performed on a rammed earth prism to validate its structural properties from the stress - strain curves obtained by two different methods of measurement. An array of FBG sensors on a single fiber with varying Bragg wavelengths (..B), has been used to spatially resolve the strains along the height of the specimen. It is interesting to note from the obtained stress-strain curves that the initial tangent modulus obtained using the FBG sensor is lower compared to that obtained using clip-on extensometer. The results also indicate that the strains measured by both FBG and extensometer sensor follow the same trend and both the sensors register the maximum strain value at the same time.

Nanostructuration via solid state transformation as a strategy for improving the thermoelectric efficiency of PbTe alloys

The approach taken in this paper in order to modify the scattering features of electrons and phonons and improve the figure of merit (ZT) of thermoelectric PbTe is to alter the microstructure at constant chemistry. A lamellar pattern of PbTe/GeTe at the nano- and microscale was produced in Pb(0.36)Ge(0.64)Te alloy by the diffusional decomposition of a supersaturated solid solution. The mechanism of nanostructuration is most likely a discontinuous spinodal decomposition. A simple model relating the interface velocity to the observed lamellar spacing is proposed. The effects of nanostructuration in Pb(0.36)Ge(0.64)Te alloy on the electrical and thermal conductivity, thermopower and ZT were investigated. It was shown that nanostructuration through the formation of a lamellar pattern of PbTe/GeTe is unlikely to provide a significant improvement due to the occurrence of discontinuous coarsening. However, the present study allows an analysis of possible strategies to improve thermoelectric materials via optimal design of the microstructure and optimized heat treatment. (C) 2011 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Detection and determination of manganese concentration in water using a fiber Bragg grating coupled with nanotechnology

Through this paper we experimentally demonstrate the fabrication of a fiber Bragg grating (FBG) chemical sensor to detect and determine the manganese concentration in water and compare our results with sophisticated spectroscopic methods, such as atomic absorption spectrometry and the inductively coupled plasma method. Here we propose a simple method to develop a thin layer of gold nanoparticles above the etched grating region to enhance the sensitivity of the reflected spectrum of the FBG. By doing so, we achieve a sensitivity of 1.26 nm/parts per million in determining the trace level of Mn in water. Proper reagents are used to detect manganese in water. (C) 2011 Optical Society of America

Fuel Cell Efficiency Redefined; Carnot Limit Reassessed

There are deficiencies in current definition of thermodynamic efficiency of fuel cells (ηcth = ΔG/ΔH); efficiency greater than unity is obtained when AS for the cell reaction is positive, and negative efficiency is obtained for endothermic reactions. The origin of the flow is identified. A new definition of thennodynamic efficiency is proposed that overcomes these limitations. Consequences of the new definition are examined. Against the conventional view that fuel cells are not Carnot limited, several recent articles have argued that the second law of thermodynamics restricts fuel cell energy conversion in the same way as heat engines. This controversy is critically examined. A resolution is achieved in part from an understanding of the contextual assumptions in the different approaches and in part from identifying some conceptual limitations.

Aerodynamic Load Measurements at Hypersonic Speeds Using Internally Mounted Fiber-Optic Balance System

This paper describes the measurement of aerodynamic loads using fiber-optic strain gauge sensors and associated signal processors at hypersonic speeds in the 300mm hypersonic wind tunnel. at the Department of Aerospace Engineering, Indian Institute of Science. Fiber-optic sensors have been developed in USA since 1990, for variety of applications in experimental stress analysis, skin friction measurement in fluid flows, smart structures, smart materials, sensing of acoustic emission and more recently in the development of compact devices for measurement of displacement, stress/strain, pressure, temperature, acceleration etc. Our group at llSc has been playing a lead role in the use of these fiber - optic sensors for successful measurement of aerodynamic loads in wind tunnels and the first ever six-component wind tunnel strain gauge balance in the world based on fiber optic sensors was built at the Indian Institute of Science in the year 1999. We report here the results of our efforts in the development of an internal strain gauge balance for high-speed wind tunnel applications.