003597   Patro P K;Kulkarni A R;Gupta S M;Harendranath C S (NO, Indian Institute of Technology Bombay, Mumbai-400 076) : Effect of homogeniety on microstructure, dielectric, and ferroelectric properties of strontium barium niobate. Def Sci J 2007, 57(1), 79-87.

Strontium barium niobate (SBN) is tetragonal tungsten bronze structured ferroelectric material. It is one of the few lead-free ferroelectrics in the fore-front of environment-friendly electroceramic research and development. The unusual sintering behaviour of SBN exhibits abnormal grain growth, duplex microstructure, and low density that has plagued commercial exploitation of SBN. The formation of duplex microstructure becomes more prominent when synthesised by conventional solid-state approach. Compositional inhomogeneity is believed to be the key player of such ambiguity. Will homogeneous mixing eliminate this problem? To answer this question, first SBN was synthesised by conventional solid-state technique, then coprecipitation technique, a wet chemical route, was employed for synthesis of SBN. In coprecipitate route, the precursors were mixed at the molecular level. It is thought that the improved composition uniformity might help in eliminating microstructure-related problems with improved dielectric properties. The findings in this connection on microstructure, dielectric, and ferroelectric properties of SBN when synthesised by conventional solid-state route as well as coprecipitation route have been discussed.

10 illus, 13 ref

003596   Patro P K (Metallurgical Engineering and Materials Science Dep, Indian Institute of Technology Bombay, Mumbai-400 076, Email: pankajpatro@iitb.ac.in) : Control of abnormal grain growth and dielectric properties of ferroelectric strontium barium niobate. Trans Indian Inst Metals 2006, 59(2), 229-35.

Strontium Barium Niobate (SBN) is a tetragonal tungsten bronze structured ferroelectric material. The unusual sintering behavior of SBN exhibits abnormal grain growth, duplex microstructure and low density that has plagued commercial exploitation of SBN. The formation of duplex microstructure becomes more prominent when synthesized by conventional solid-state approach. Although the exact reason of duplex microstructure is not known, it is believed that composition inhomogeneity is one of the reasons of such ambiguity. Will homogeneous mixing will eliminate this problem? To answer this question, coprecipitation a wet chemical route, has been employed for synthesis of SBN; in this route, the precursors are mixed in the molecular level. It is thought that the improved composition uniformity might help in eliminating microstructure related problems with improved dielectric properties. The findings in this connection on microstructure dielectric and ferroelectric properties are discussed.

7 illus, 13 ref

003595   Patil B M;Srinivasa R S;Dharwadkar S R (Chemistry Dep, The Institute of Science, 15, Madam Cama Road, Mumbai-400 032, Email: srdharwadkar@hotmail.com) : Synthesis of CaTiO₃ from calcium titanyl oxalate hexahydrate (CTO) as precursor employing microwave heating technique. Bull Mater Sci 2007, 30(3), 225-9.

Calcium titanate, CaTiO₃, an important microwave dielectric material and one of major phases in syn-roc (synthetic rock), a titanate ceramic with potential application for fixation of high level nuclear waste was synthesized from calcium titanyl oxalate [CaTiO (C₂O₄)₂ 6H₂O] (CTO) by employing microwave heating techni-que. CTO heated in microwave heating system in air at 500°C for 1 h gave a perovskite, CaTiO₃. The product obtained by heating of CTO in the same system at 700°C for the same duration was however, much more crystalline. CaTiO₃ obtained by the present method was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and BET surface area measurement.

4 illus, 23 ref

003594   Nayak S S;Kim D H;Pabi S K;Murty B S (Center for Noncrystalline Materials, Yonsei University, Seoul 120-749, South Korea, Email: sashank@metal.iitkgp.ernet.in) : Aluminium-based nanocomposites by non-equilibrium processing routes. Trans Indian Inst Metals 2006, 59(2), 193-8.

Successful synthesis of Al-based nanocomposites by mechanical alloying (MA) and rapid solidification processing (RSP) with functional mechanical properties, in Al-Fe and Al-Ti systems, has been reported. In melt spun Al-Fe ribbons fine cellular structure, dendritic structure, fine dispersion of second phase particle and particle segregations at α-Al grain boundaries were observed depending on compositions. In Al-Ti system only a two phase mixture forms irrespective of the composition. The volume fraction of Ll₂-Al₃ Ti i precipitates in Al- Ti alloys is more in as spun ribbons compared to MA powders. MA shows improved hardness value, which further increases with annealing temperature.

6 illus, 7 ref

003593   Nayak P S;Singh B K (Chemistry Dep, Govt. M.H. College of Home Science and Science for Women, Jabalpur-482 002, Email: preetisagarnayak@rediffmail.com) : Instrumental characterization of clay by XRF, XRD and FTIR. Bull Mater Sci 2007, 30(3), 235-8.

Instrumental characterizations of the clay were performed by different techniques such as XRF, XRD and FTIR. XRF shows the chemical compositions of the clay where AI-oxide and silica oxide are present in major quantity whereas XRD confirms the presence of these minerals in clay. FTIR studies show the presence of quartz, alumina, haematite and different mineral matters.

4 tables, 28 ref

003592   Narayankhedkar K G (Mechanical Engineering Dep, Indian Institute of Technology Bombay, Powai, Mumbai-400 076) : Advances in stirling type pulse tube cryocoolers. Indian J Cryogenics 2005, 30(1), 16-22.

Recent advances in cryocoolers are beginning to alleviate problems such as poor reliability and increased cost. For space applications the additional requirement of high efficiency is needed, whereas for commercial applications low cost is a primary factor. The lack of a suitable cryocooler to meet the requirements of a particular application has hampered the advancement of many applications. The main problems associated with cryocoolers are: un reliability, inefficiency, size, weight, vibration, and cost. The seriousness of each of these problems depends on the application. A significant amount of cryocooler development in the last 10 years has been focused on space applications. Cryocoolers find applications in Military, Police and Security, Environmental, Commercial, Medical, Transportation, Energy, Agriculture and Biology. Developments on pulse tube cryocoolers eliminate the moving displacer in Stirling and Gifford-McMahon cryocoolers. The use of new high heat capacity materials allows Gifford-McMahon and Pulse Tube cryocoolers to reach temperatures below 4 K. A detailed review of Pulse Tube cryocoolers and indigenous developments are presented.

28 ref

003591   Naidu V P S;Raol J R (NO, National Aerospace Laboratories, Bangalore-560 017) : Target tracking with multi acoustic array sensors data. Def Sci J 2007, 57(3), 289-303.

Acoustic array sensor along with Root-MUSIC algorithm is used to estimate the direction of arrival of the acoustic signal emitted by an acoustic target. Three architectures are used to track the target in Cartesian coordinates: (i) digital filter with least square estimation, (ii) linear Kalman filter with least square estimation, and (iii) extended Kalman filter. A comparative evaluation of the three architectures in terms of performance metrics is presented.

10 illus, 1 table, 11 ref

003590   Naidu V P S;Girija G;Raol J R (NO, National Aerospace Laboratories, Bangalore-560 017) : Data fusion for identity estimation and tracking of centroid using imaging sensor data. Def Sci J 2007, 57(5), 639-52.

Two aspects involved in automatic target recognition namely, (i) Location and identity estimation (LIE) of a target by fusing infrared (IR) and acoustic sensor data, and (ii) centroid tracking for target state estimation using IR sensor data are discussed. The LIE has been achieved using a combination of Bayesian fusion and one of the three search algorithms namely, metropolis hastings (MH), simulated annealing (SA) and gradual greedy (GG). It was observed that the performance of the GG search algorithms was better in terms of success rate which has been evaluated through Monte Carlo simulations. For tracking of the centroid, an algorithm, where the centroid of the gray level image is tracked using probabilistic data association filter, has been implemented. Simulated data results indicate good tracking performance of this algorithm. For robust tracking of centroid, the track from the imaging sensor was fused with the track from ground-based radar using state vector fusion. It was observed that fusion generates robust tracks even when there is data loss in one of the sensors.

12 illus, 2 tables, 11 ref

003589   Muthurajan H;Kumar H H;Kharat D K (NO, Armament Research and Development Establishment, Pune-411 021) : Computer-controlled sophisticated ultrasonic cleaner. Def Sci J 2007, 57(1), 105-8.

Significant advantage of ultrasonic cleaning technique is the abilities to clean the delicate and complex shape materials without damaging their surfaces quickly. Ultrasonic cleaners have found increasing applications in a variety of industries because these offer an environmentally good alternative to ozone-depleting compounds and hazardous solvents. Also, ultrasonic vibration is one of the methods for chemical synthesis (chemical reaction) and of yield enhancement of chemical engineering process. Consequently, there is a need to develop multipurpose ultrasonic cleaner/vibrator using computer control, which can be used to set the various performance parameter of ultrasonic vibrator such as frequency, duty cycle, continuous/pulsed mode, duration of operation, and thermal profile of tank during the process. An ultrasonic cleaner was developed using an oscillator circuit and the duration of oscillator circuit functioning can be set through the computer. Computerised ultrasonic cleaner using indigenously made piezoceramic transducers and their advantages over the conventional ultrasonic cleaners are discussed.

3 illus, 11 ref

003588   Muthuraj R;Srinivas S (NO, Arulmigu Meenakshi Amman College of Engineering, Kanchipuram, Tamil Nadu) : Flow of a thermoviscous fluid through an annular tube with constriction. Def Sci J 2007, 57(5), 653-9.

Flow of thermoviscous fluid within the annulus of circular cylinders with a local constriction at the outer wall is investigated analytically, assuming that the constriction is nonªsymmetric wrt the radial distance. Analytical solutions for velocity and temperature fields have been obtained. The effect of the shape parameter of the constriction on velocity, temperature, Nusselt number, and flow rate are illustrated graphically and discussed.

7 illus, 15 ref

003587   Moulick S K;Dewangan M L (NO, Bhilai Institute of Technology, Durg-491 001) : Use of catalytic converter for two wheelers. Appl Sci Period 2006, 8(2), 110-15.

Feasibility of using catalytic converters to reduce HC and CO emissions form 2-stroke engine. It was found that it is possible to reduce emissions significantly by installing catalytic converters at a proper location in the exhaust pipe. It can reduce the pollution to some extent. A power loss of <60> was also met with catalytic converters.

4 illus, 3 tables, 5 ref

003586   Mokadam A M;Sapkal R S;Khairnar S M (Civil Engineering Dep, Government College of Engienering, Amravati-444 604) : Aeration performance of stepped cascades for Municipal wastewater. Appl Sci Period 2006, 8(2), 116-22.

High level of dissolved oxygen is important for maintenance of healthy streams and rivers. Structures like stepped cascades can increase dissolved oxygen level by creating turbulence condition. Aeration properties of weirs and cascades have been studied widely in the laboratory and field over numbers of years for water. Rare attention Is received in this context for wastewater. Describes a laboratory investigation of aeration properties of stepped cascades for municipal wastewater. It is demonstrated that height of fall and discharge are important factors which affects the aeration of cascades.

4 illus, 6 ref

003585   Mohapatra S;Ram S (NO, Indian Institute of Technology, Kharagpur-721 302) : Synthesis of lithium-doped zirconia nanoceramics of controlled oxygen vacancies. Def Sci J 2007, 57(1), 41-6.

Doping of lithium (Li⁺) cations results in stabilised zirconia, especially in tetragonal (t) crystal structure, i.e.; Li⁺: t-ZrO₂ It is useful to vary oxygen vacancies in Li⁺: ZrO₂ powders. The Li⁺: t-ZrO₂ powder having 1-5 mol per cent Lⁱ⁺, are obtained by using a novel chemical method of a polymer precursor, which consists of Li⁺ and Zr⁴⁺ cations capping in polymer molecules of polyvinyl alcohol (PVA) and sucrose. The results are analysed in terms of XRD and microstructure of Li⁺: t-ZrO₂ powders prepared under specific conditions of heating the precursor in air at elevated temperatures. The polymer precursor consists of fibrils of average 120 m length and 0.5-1.0 m dia. A refined Li⁺: t-ZrO₂ powder (15-25 nm crystallite size) occurs after heating the precursor at 500-600°C for 2 h in air.

^ssc3 illus, 2 tables, 14 ref

003584   Miyahara H;Maruno Y;Nishihata Y;Keisaku OGI (Materials Science and Engineering Dep, Faculty of Engineering, Kyushu University, 6-10-1 Hakozaki, Higashi-Ku, Fukuoka 812-8581, Japan, Email: miyahara@zaiko.kyushu-u.ac.jp) : Influence of reinforcements on solidification microstructure and fatigue properteis of cast aluminum alloy composites. Trans Indian Inst Metals 2006, 59(2), 235-61.

Influences of reinforcements on crystal growth of matrix alloy in cast composites were investigated, and an advantage of reinforcements on rotating bending fatigue belabor were examined. In the composite specimens, the alpha dendrite is deformed during solidification, and the eutectic structure is distributed around fibers. The solutal diffusion field around dendrite tip governs the tip undercooling. The fatigue strength of composites specimens is influenced by the cluster of reinforcement particles rather than the matrix structure. The clusters of particles introduce the cracks but also interrupt the crack propagation. Therefore, reinforcement particles eventually better the fatigue properties of notched specimens.

9 illus, 18 ref

003583   Misra A K;Mathur R (NO, Central Road Research Institute, New Delhi-110 020, Email: akmishra.crri@nic.in) : Magnesium oxychloride cement concrete. Bull Mater Sci 2007, 30(3), 239-46.

Scope of magnesium oxychloride (MOC) cement in concrete works has been evaluated. MOC . cement concrete compositions of varying strengths having good placing and finishing characteristics were prepared and investigated for their compressive and flexural strengths, E-values, abrasion resistance etc. The durability of MOC concrete compositions against extreme environmental conditions viz. heating-cooling, freezing-thawing, wetting-drying and penetration and deposition of salts etc were investigated. The results reveal that MOC concrete has high compressive strength associated with high flexural strength and the ratio of compressive to flexural strength varies between 6 and 8. The elastic moduli of the compositions studied are found to be 23-85 GPa and the abrasion losses between 0-11 and 0-20%. While alternate heating-cooling cycles have no adverse effect on MOC concrete, it can be made durable against freezing-thawing and the excessive exposure to water and salt attack by replacing 10% magnesium chloride solution by magnesium sulphate solution of the same concentration.

2 illus, 13 tables, 16 ref

003582   Kulkarni A V (NO, Indian Institute of Technology, Kanpur-208 016) : Electrochemical discharge machining process. Def Sci J 2007, 57(5), 765-70.

Electrochemical discharge machining process is evolving as a promising micromachining process. The experimental investigations in the work substantiate this trend. In the work, in situ, synchronised, transient temperature and current measurements have been carried out. The need for the transient measurements arose due to the time-varying nature of the discharge formation and time varying circuit current. Synchronised and transient measurements revealed the discrete nature of the process. It also helped in formulating the basic mechanism for the discharge formation and the material removal in the process. Temperature profile on workpiece and in electrochemical discharge machining cell is experimentally measured using pyrometer, and two varieties of K-type thermocouples. Surface topography of the discharge-affected zones on the workpiece has been carried out using scanning electron microscope. Measurements and surface topographical studies reveal the potential use of this process for machining in micron regime. With careful experimental set-up design, suitable supply voltage and its polarity, the process can be applied for both micromachining and micro-deposition. It can be extended for machining and or deposition of wide range of materials.

4 illus, 22 ref

003581   Krishnardula V G;Sofyan N I;Gale W F;Fergus J W (Materials Research and Education Center, Auburn University, Alabama 36849, U.S.A, Email: krishvg@auburn.edu) : Joining of ferritic oxide dispersion strengthened alloys. Trans Indian Inst Metals 2006, 59(2), 199-203.

Oxide dispersion strengthened (ODS) alloys exhibit superior high temperature properties compared to conventional alloys. Joining of these ODS alloys poses a challenge and limits their application in the industry. The transient liquid phase (TLP) bonding technique was employed in the present study to join two ferritic ODS alloys, MA956 and PM2000, using physical vapor deposited thin-film boron as an interlayer. Successful bonds with minimal disruption of the substrate microstructure and limited second phase precipitation at the bond-line were achieved when substrates were joined in the fine grained condition, under an applied bonding stress, with substrate orientation parallel to the extrusion direction.

4 illus, 10 ref

003580   Khare S;Negi S S (NO, Instrument Research and Development Establishment, Dehradun-248 008) : Thermal (Infrared) imaging sensors. Def Sci J 2007, 57(3), 173-83.

Recent developments in improved type of infrared detector technologies focal plane arrays, signal processing techniques, and innovative optical designs have enabled thermal imaging technology to undergo revolutionary advancement, leading to realisation of high performance and compact thermal cameras for surveillance, target acquisition, tracking, and guidance. Instruments Research and Development Establishment (IRDE), Dehradun, has designed and developed a variety of thermal imaging sights for different ongoing programmes/projects. In the present paper, an overview of thermal imaging systems, different generations and classification of thermal imaging systems is described. Presents salient features/specifications of thermal imaging systems developed by IRDE together with the images recorded in actual field trials.

^iia13 illus, 11 tables

003579   Kharat D K;Mitra S;Akhtar S;Vijai Kumar (NO, Armament Research and Development Establishment, Pune-411 021) : Polymeric piezoelectric transducers for hydrophone applications. Def Sci J 2007, 57(1), 7-22.

Conventional ceramic piezoelectric materials have been used in hydrophones for sonar applications since 1940's. In the last few years since the discovery of polymeric piezoelectric hydrophones, the technology has matured, applications have emerged in extraordinary number of cases such as underwater navigation, biomedical applications, biomimetics, etc. Hydrophones are used underwater at high hydrostatic pressures. In the presence of hydrostatic pressures, the anisotropic piezoelectric response of ceramic materials is such that it has poor hydrophone performance characteristics whereas polymeric piezoelectric materials show enough hydrostatic piezoelectric coefficients. Moreover, piezoelectric polymers have low acoustic impedance, which is only 2-6 time that of water, whereas in piezoelectric ceramics, it is typically II-time greater than that of water. A close impedance match permits efficient transduction of acoustic signals in water and tissues. Newly developed hydrostatic-mode polyvinylidene flouride (PVDF) hydrophones use a pressure-release system to achieve improved sensitivity. Recently, voided PVDF materials have been used for making hydrophones having higher sensitivity and figure of merit than unvoided PVDF materials.

^iia1 table, 60 ref

003578   Kaynakli O;Yamankaradeniz R (Mechancial Engineering Dep, Faculty of Engineering and Agriculture, Uludag University, TR-16059, Bursa, Turkey) : Thermodynamic analysis of absorption refrigeration system based on entropy generation. Curr Sci 2007, 92(4), 472-9.

First and second law thermodynamic analysis of a single-stage absorption refrigeration cycle with water/lithium bromide as working fluid pair is perªformed. Thermodynamic properties of each point in the cycle are calculated using related equations of state. Heat transfer rate of each component in the cycle and some performance parameters are calculated from the first law analysis. From the second law analysis, the entropy generation of each component (S^._j) and the total entropy generation of all the system components (S^._i) are obtained. Variation of the performance and entropy generation of the system are examined at various opªerating conditions. The results show that high coeffiªcient of performance (COP) value is obtained at high generator and evaporator temperatures, and also at low condenser and absorber temperatures. With inªcreasing generator temperature, total entropy generation of the system decreases. Whereas maximum entropy generation occurs in the generator at various operatªing conditions, entropy generation in the refrigerant heat exchanger, expansion valve and solution pump is negligibly small.

12 illus, 1 table, 30 ref

003577   Kaushik H B;Rai D C;Jain S K (Civil Engineering Dep, Indian Institute of Technology Kanpur, Kanpur-208 016) : Uniaxial compressive stress-strain model for clay brick masonry. Curr Sci 2007, 92(4), 497-501.

Material stress-strain properties are required in the nonlinear analyses of structures. Stress-strain relationships for some construction materials such as conªcrete and steel are available in the literature and design codes. However, such relationships are not easily available for one of the most widely used construction material, i.e. masonry. In the comprehensive experimental study, compressive stress-strain relationships for masonry are determined by testing 84 masonry prism specimens constructed using bricks from four different manufacturers and three mortar grades. By regression analysis of experimental data, analytical expressions are proposed to estimate the modulus of elasticity of masonry. An analytical model is proposed to adequately plot the stress-strain curves for masonry using six control points on the curves. A simplified analytical model is also proposed that can be conveniently used in finite element analysis programs.

6 illus, 2 tables, 10 ref

003576   Kalange A E;Gangal S A (NO, University of Pune, Pune-411 007) : Piezoelectric sensor for human pulse detection. Def Sci J 2007, 57(1), 109-14.

Piezoelectric sensor was used for human pulse detection. The pulse signals obtained from the piezoelectric sensor were processed through signal processing circuitry. The signal processing circuit consists of signal amplifier, filters, and noise-reduction circuit. The signal processing circuit has been designed, built, and tested. The performance of the developed system was evaluated by recording the pulses of people (subject) having different doshas. Pulse shapes, repetition rate, amplitude were found to be different for people having different doshas. Performance of the signal processing circuit and the pulse waveforms obtained have been presented and analysed.

^ssc6 illus, 5 ref

003575   Kal S (Advanced Technology Centre, Indian Institute of Technology, Kharagpur-721 302) : Microelectromechanical systems and microsensors. Def Sci J 2007, 57(3), 209-24.

Highly promising technology that is set to revolutionise nearly every product category is microelectromechanical systems (MEMS). MEMS specifically are the integration of mechanical elements, sensors, actuators, and electronics on a common silicon substrate through the utilization of microfabrication technology. Silicon and quartz are now household names to consumers of electronic products, computers and automated appliances. Silicon is the material of microchips or very large scale integrated (VLSI) circuits. Quartz, a piezoelectric crystal made of silicon and oxygen atoms, provides stable clock pulses to the chips. These materials are also being used to fabricate micromachines and microelectromechanical structures and systems for a wide variety of applications for sensing and actuation. Extensive research and development work has been going on in the Microelectronics Laboratory, Advanced Technology Centre of IIT Kharagpur on both microelectronics and MEMS technology since last five years. Some of the MEMS-based microsensors develoed are silicon MEMS accelerometers, flow sensors, thermal detectors, pressure sensors, micro-thrusters and quartz MEMS gyro and accelerometers. An overview of micromaching and MEMS technologies developed at IIT Kharagpur along with the development of various silicon and quartz-based micro sensors are described.

^iia17 illus, 40 ref

003574   Joshi B P;Joshi A;Gangal S A (NO, Armament Research and Development Establishment, Pune-411 021) : Performance improvisation of cantilever-type silicon micro acceleration sensors using stress concentration regions technique. Def Sci J 2007, 57(3), 271-9.

Presents a concept of creating stress concentration regions (SCRs) on the cantilever for enhancing its sensitivity. Five types of structures were simulated to study the behaviour of piezoresistive sensors with SCRs implementation. Use of SCRs results in substantial increase in the sensitivity, which is of the order of 1.85 times the nominal sensitivity. It was aimed at maximising sensor's performance factor, which is the product of sensor bandwidth and sensitivity. This study gives new dimension to the ways of improving performance of cantileverª type inertial piezoresistive sensor.

7 illus, 3 tables, 20 ref

003573   Joshi B P;Chaware A S;Gangal S A (NO, Armament Research and Development Establishment, Pune-411 021) : Optimising performance of a cantilever-type Micro accelerometer sensor. Def Sci J 2007, 57(3), 261-9.

Technique for optimising performance of cantilever-type micro acceleration sensor has been developed. Performance of a sensor is judged mainly by its sensitivity and bandwidth. Maximising product of these two important parameters of inertial sensors helps to optimise the sensor performance. It is observed that placement of a lumped mass (add-mass) on the sensor's proof-mass helps to control both sensitivity and the first resonant frequency of the cantilever structure to the designer's choice. Simulation and modelling of various dimensions of rectangular structures for acceleration sensor with this novel add-mass technique are discussed. Coventorware MEMSCAD has been used to model, simulate, and carry out FEM analysis. A simple analytical model is discussed to elaborate the mechanics of cantilever-type micro accelerometer. The comparison of the results obtained from analytical model and the finite element simulations reveal these to be in good agreement. The advantages of this technique for choosing the two most important sensor parameters (i.e., sensitivity and bandwidth) of an inertial sensor are brought out.

8 illus, 15 ref

003572   Jawalkar S N;Mehilal;Kurva R;Singh P P; Bhattacharya B (NO, High Energy Materials Research Lab, Pune-411 021) : Influence of bicurative on processibility of composite propellant. Def Sci J 2007, 57(5), 669-75.

New series of composite propellant compositions, based on ammonium perchlorate, hydroxy-terminated polybutadiene and having metallic fuel as aluminium powder, have been developed. Pressure cast-cum-cured compositions have also been developed with toluene diisocyanate (TDI), isophorone diisocyanate (IPDI), and a mixture of both curatives, i.e., TDI and IPDI, respectively, to study their effect on processibility, mechanical and ballistic properties of the compositions. The data indicate that the compositions based on bicurative have a pot life of 7 - 8 h, viscosity build up is from 13280 poise to 14080 poise after 4 h, and the smooth processibility of the slurry is enhanced. Further, the mechanical properties are in the range 12.2 kg/cm², 40.2 kg/cm², and 40.2 per cent for tensile strength, E-modulus and elongation, respectively, and burn rate is almost the same, i.e., 16 ± 0.5 mm/s.

4 tables, 12 ref

003571   Hurley W J;Andrews W S (NO, Royal Military College of Canada, Ontario K7K7B4) : Normal approximation to a sum of geometric random variables with application to ammunition stockpile planning. Def Sci J 2007, 57(5), 733-7.

Normal approximation for a sum of geometric random variables has been examined. This approximation is relevant to the determination of direct-fire ammunition stockpile levels in a defence setting. Among the methodologies available for this assessment, one is a target-oriented methodology. This approach calculates the number of rounds necessary to destroy a given fraction of the enemy force and infrastructure. The difficulty is that the number of rounds required cannot be determined analytically. An obvious numeric approach is Monte Carlo simulation. Another is the approximation approach which has several advantages like it is easy to implement and is accurate even in the case where the number of targets is low.

^ssc1 illus, 1 table, 3 ref

003570   Harpreet Singh;Puri D;Prakash S (Metallurgical and Materials Engineering Dep, Indian Institute of Technology Roorkee, Roorkee-247 667, Email: hn978dmt@iit.ernet.in) : High temperature oxidation behaviour of plasma sprayed NiCrAlY coatings on Ni-based superalloys in air. Trans Indian Inst Metals 2006, 59(2), 215-27.

Plasma spray coating technologies are capable of depositing a very wide range of compositions without significantly heating the substrate. Investigates NiCrAlY metaIlic coatings were deposited on two Ni-based Superalloys, Superni 75 and Superni 600 by plasma spray process. Oxidation studies were conducted on uncoated as well as plasma spray coated superalloys in air at 900°C under cyclic conditions. Each cycle consisted of one hour heating followed by 20 minutes of cooling in air. The thermogravimetric technique was used to approximate the kinetics of oxidation. All the coated as well as uncoated superalloys nearly followed parabolic rate law. The uncoated Superni 600 showed a minimum weight gain, whereas the NiCr AlY coated Superni 75 a maximum after 50 cycles of exposure among the cases studied. X-Ray Diffraction, SEM/EDAX and EPMA techniques were used to analyse the oxidation products. The main phases analysed for the coated superalloys are oxides of nickel, chromium and aluminium and spinel of nickel and chromium, which are suggested to be responsible for developing oxidation resistance at high temperatures.

11 illus, 36 re

003569   Hanson M P;Driscoll D C;Brown E R;Gossard A C (Materials Dep, University of California, Santa Barbara, Email: micah@engineering.ucsb.edu) : ErSb/GaSb metal/semiconductor nanocomposite grown by molecular beam epitaxy. Trans Indian Inst Metals 2006, 59(2), 167-75.

Effective use of ErSb semimetallic nanoparticles embedded within a semiconducting GaSb matrix, grown by molecular beam epitaxy, to manipulate the electronic and optical properties of the composite material for a variety of applications is demonstrated. The resistivity, optical absorption, and photocarrier lifetimes, are all found to be greatly influenced by the size and density of the ErSb particles: The particle size and density can be controlled by growth parameters resulting in a versatile and highly tunable composite material.

1 table, 14 ref

003568   Hada M K;Menon A;Bhave S Y (NO, Defence Institute of Advanced Technology, Pune-411 025) : Optimisation of an active suspension force controller using genetic algorithm for random input. Def Sci J 2007, 57(5), 691-706.

Novel control scheme for the active suspension in a 4-DOFs half-car model is presented. A force cancellation control scheme is used to isolate the sprung and the unsprung masses. Skyhook damper and virtual damper concepts are employed to stabilise the sprung and unsprung masses respectively. Road-following springs are applied for the sprung mass to follow the trend of the road surface condition and to maintain the suspension stroke within a reasonable range. For efficiency, genetic algorithm is employed to search for the parameters like damping ratio and spring constant to achieve an optimum trade off among ride comfort, handling quality, and suspension stroke simultaneously for random input. Computer simulations are performed using MATLAB software to verify the proposed control scheme and effectiveness of the applied genetic algorithm.

9 illus, 2 tables, 21 ref

003567   Gupta R;Dayal A;Sharma I S (NO, Institute for Systems Studies and Analysis, Delhi-110 054) : Effectiveness of precision-guided munitions on armour systems. Def Sci J 2007, 57(3), 281-7.

Simulation methodology has been used to analyse the effectiveness of multi-barrel rocket launcher system (MBRLs) delivering precision-guided munitions (PGMs) on armour force deployed in concentration areas under various terrain conditions. The methodology considers various aiming strategies, the effectiveness of the sensor and the imprecision in information available about the target to evaluate the effectiveness of the MBRL system.

7 illus, 4 ref

003566   Gupta A K;Khare N (NO, National Physical Laboratory, Dr. K.S. Krishnan Road, New Delhi-110 012) : Fabrication of high-T_c SQUID and its application in measurements of extremely weak magnetic signals. Indian J Cryogenics 2005, 30(1), 1-7.

High-T_c rf-SQUID (Superconducting Quantum Interference Device) sensor has been fabricated using natural grain boundary Josephson weak-links in Bi-Sr-Ca-Cu-O film. The film has large grains (<126> 20-30 um) and T_c (R=O) <126> 104K. RF-SQUID sensor has been fabricated by patterning a hole and a microbridge on the film. The rf-SQUID shows good voltage-flux characteristics at 77K. For using SQUID as a magnetometer, it has been operated in flux-locked-loop mode at 77K. The transfer function of the SQUID is 10mV/φ₀ and its field sensitivity <126> 8x10^-12 T/√Hz and 77K. The high-T_c rf-SQUID is used for studying the weak magnetic field from a quartz watch, destabilization of charge ordering in doped rare earth manganite, flux noise due to vortex hopping in MgB₂ superconductor and for non-destructive testing.

13 illus, 11 ref

003565   Gupta A;Ahmad A (NO, Solid State Physics Lab, Delhi-110 054) : Microsensors based on MEMS technology. Def Sci J 2007, 57(3), 225-32.

Sensors play an important role in most of the common activities that occur in the daily lives. They are the building blocks of or microelectromechanical systems (MEMS). This combination of micromechanical structures, sensing elements, and signal conditioning is the beginning of a new era in sensor technology. Sensing systems incorporated with dedicated signal processing functions are called intelligent sensors or smart sensors. The present decade of new millennium will be the decade of smart systems or MEMS. The rapid rise of silicon MEMS recently was due to major advances in silicon microfabrication technology, especially surface micromachining, deep-reactive ion etching, and CMOS-integrated MEMS. An overview of the currently available MEMS sensors, materials for sensors and their processing technologies, together with integration of sensors and electronics is presented.

3 illus, 2 tables, 30 ref

003564   Girija S;Kamachi Mudali U;Shankar V;Dayal R K (Metallurgy and Materials Group, Indira Gandhi Centre for Atomic Research, Kalpakkam-603 102, Email: kamachi@igcar.ernet.in) : Pitting corrosion resistance of AISI type 316 (N) SS weld after various surface treatments and thermal aging. Trans Indian Inst Metals 2006, 59(2), 263-9.

Pitting corrosion resistance of AISI type 316 (N) stainless steel (SS) weld, in neutral sodium chloride environment was investigated after various surface treatments (mechanical and chemical) and thermal aging. Mechanical treatment included lathe turning and wet polishing up to 320-grit emery, and diamond polishing. Chemical treatments included pickling and pickling followed by passivation for the lathe turned surface. The treated specimens were subsequently examined for its pitting corrosion resistance in 0.5M NaCl solution by potentiodynamic anodic polarization method. It was observed that the pitting corrosion resistance was dependant on the surface finish of the material. Chemical treatments like pickling and passivation were found to significantly enhance the pitting corrosion resistance. The weld metal was thermally aged at 1023 K and 1123 K for 100 h each, and evaluated for its pitting corrosion resistance in 0.5M NaCl solution and the results were correlated to the microstructural changes that occurred on thermal aging. The pitting corrosion resistance for the aged weld was found to be much less than that for the as-welded, as a result of transformation of delta ferrite in the weld metal into secondary precipitates. No discernable difference in the pitting corrosion resistance was observed among the thermally aged welds.

5 illus, 3 tables, 34 ref

003563   Ghosh S;Chakrabarty A (NO, Indian Institute of Technology, Kharagpur-721 302) : Performance analysis of different loaded and unloaded wire antennas as EMI sensors. Def Sci J 2007, 57(3), 333-42.

Presents with the performance of different loaded (e.g. inverted L, T, I and C-shaped antennas) and unloaded wire antennas as electromagnetic interference (EMI) sensors. To determine electromagnetic radiation from an electronic component, it is required to evaluate the field strength at a certain distance from it using the sensor. The most common performance descriptor of a sensor is its antenna factor. The method of moments with pulse basis function and point-matching technique has been used to evaluate the current distribution on the antenna surface, and hence, the antenna factor of different wire antennas. The same theory for unloaded antennas has been extended for different loaded-wire antennas. The loaded antennas in transmitting mode are widely used for low-frequency communication. However, while using these antennas as EMI sensors, the extra loading is likely to introduce the reception of cross-polarised component of incident electric field. Highlights the results of the initial investigation on the performance of these loaded antennas as EMI sensors in terms of the antenna factor for the desired and cross-polarised component of incident electric field.

13 illus, 10 ref

003562   Ganguly A;Sharma P (NO, Shri G.S. Institute of Technologhy and Science, Indore-456 003) : Propagation of strong magneto-radiative plane shock wave in a self-gravitating exponentially-decreasing medium. Def Sci J 2007, 57(1), 123-31.

Self-similar theoretical model of propagation of strong plane shock waves in an inhomogeneous, magneto-radiative, self-gravitating atmosphere in the direction of decreasing density is considered. The results discussed depend upon the variations of the flow variables which are displayed graphically and the influences of the gravitation and radiation flux have been studied.

^ssc10 illus, 7 ref

003561   Gajbhiye N S;Pandey P K;George L;Abhishek Kumar (NO, Indian Institute of Technology Kanpur, Kanpur-208 016) : Dielectric properties of nanostructured PZT synthesised by chemical methods. Def Sci J 2007, 57(1), 61-8.

Dielectric behaviour of smart material, lead zirconate tiatanate (PZT), which is important for wide industrial applications, has been explored. Two samples of nanostructured Pb(Zr_0.52Ti_0.48)O₃ ceramic powders were prepared by hydroxide co-precipitation and aqueous solution method (water bath technique). The XRD pattern of the powder exhibited the presence of major tetragonal and minor rhombohedral crystalline phases indicating the mixed-phase composition, which is close to the morphotropic phase boundary (MPB). SEM analysis revealed good homogeneity of the materials. The plot of real part versus imaginary part of the complex impedance was observed nearly a semicircle, indicating that the samples are good dielectric materials, whose resistance decreases considerably with the increase of temperature. Similar to the normal ferroelectric materials, the dielectric constant (∈) of PZT has been found to be increasing gradually with temperature and attains a maxima (∈_max). The detailed analysis for the shift in peak temperature and dielectric constant were carried out.

7 illus, 18 ref

003560   Gaikwad S A;Samuel E P;Patil D S;Gautam D K (Electronics Dep, North Maharashtra Univ, Jalgaon-425 001, Email: israel_jal@sancharnet.in) : Theoretical analysis of effect of temperature on threshold parameters and field intensity in GaN material based heterostructure. Bull Mater Sci 2007, 30(3), 255-61.

Temperature dependent analysis to achieve better performance by reducing threshold current requirements and field intensity has been carried out for GaN/AlGaN heterostructure lasers. The mirror loss in the GaN cavity has been obtained as a function of temperature and cavity length. The quantum efficiency has been deduced for different values of cavity length. Dependence of recombination rate on band gap and temperature has been investigated. Threshold current density has been deduced for GaN lasers and effect of temperature on it has been investigated. The near field intensity analysis has been carried out at different temperatures for 10% aluminum mole fraction in GaN/AlGaN heterostructure lasers. Furthermore, the effective index and FWHM of near field has been investigated as a function of temperature. It has been deduced from the analysis that temperature has a dominant effect on the threshold conditions and near field intensity in the wide band gap GaN based lasers.

8 illus, 2 tables, 11 ref

003559   Gadadhar S;Balasubramaniam R (Materials and Metallurgical Engineering Dep, Indian Institute of Technology, Kanpur-208 016, Email: sahoo@iitk.ac.in) : Phosphoric irons for concrete reinforcement applications. Trans Indian Inst Metals 2006, 59(2), 245-53.

Possible use of phosphoric irons for concrete reinforcing applications has been addressed. Three phosphoric irons (Fe-0.llP-0.028C, Fe-0.32P-0.028C and Fe-0.49P-0.028C, wt. %) were ingot melted and forged between 1050°C and ll00°C in the dual phase region to avoid grain boundary embrittlement. The mechanical properties of the phosphoric irons were comparable with that of commercial steel bar. Potentiodynamic polarization and electrochemical spectroscopy (EIS) studies in simulated pore solution (saturated calcium hydroxide of pH 12.5) containing chloride ions indicated that the threshold chloride content for passive film breakdown were higher for phosphoric irons. The improved corrosion resistance of phosphoric irons has been understood based on presence of phosphorus in solid solution.

6 illus, 1 table, 25 ref

003558   Ebenezer D D (NO, Naval Physical and Oceanographic Lab, Kochi-682 021) : Characterisation of piezoelectric ceramics. Def Sci J 2007, 57(1), 69-77.

IEEE standard on piezoelectricity recommends methods to determine the coefficients of piezoelectric ceramics and the sizes of the samples to be used. A method to determine the difference between the actual coefficients and the coefficients determined using the IEEE standard is presented. The difference or error for samples of various shapes and sizes is presented. These errors and manufacturing considerations are used to make recommendations of the actual sizes of piezoceramics in various shapes to be used for material characterisation. Often, the IEEE standard cannot be used to determine the coefficients of piezoceramics used in underwater transducers and other devices because of their shapes and sizes. Radially polarised tubes and axially polarised rings used in hydrophones and projectors, respectively, are the examples. A method to determine some of the complex coefficients of tubes used for quality control during production is presented. Finally, an analytical model that can be used to develop a similar method for rings is presented. Several numerical results are presented to illustrate the methods.

4 illus, 8 tables, 13 ref

003557   Dixit A;Maurya D;Singh D P;Agrawal D C; Mohapatra Y N (NO, Indian Institute of Technology Kanpur, Kanpur-208 016) : Dielectric properties of sol-gel-derived calcium copper titanate and calcium barium copper titanate thin films. Def Sci J 2007, 57(1), 55-60.

Complex perovskite compound CaCu₃Ti₄O₁₂ (CCTO) is of considerable interest because of its anomalously large dielectric response. Dielectric properties of sol-gel-derived thin films of CCTO prepared at various annealing temperatures; 7000 °C, 7200 °C, and 7500°C have been reported. The frequency and temperature-dependent dielectric properties of all these samples have been studied in metal-insulator-metal configuration using an impedance analyser. Dielectric measurements at room temperature show that the dielectric constant increases with the increase in annealing temperature from 700°C-7500°C. High dielectric constant (varying from 600 to 3000 with the change in annealing temperature) has been observed at room temperature at 100 kHz. The dielectric measurements below room temperature do not show any evidence of structural relaxation in CCTO except a little additional tilting of the TiO₆ octahedra with decreasing temperature. The dielectric response of Ba-doped CCTO films has also been reported.

5 illus, 7 ref

003556   Dhokey N B;Sapate S G;Paretkar R K (Metallurgical Engineering Dep, Government College of Engineering, Pune, Maharashtra, Email: nbdhokey@yahoo.co.in) : Evaluation of wear behaviour in copper-SiC reinforced composite by dimensional analysis approach. Trans Indian Inst Metals 2006, 59(2), 283-94.

Approximate generalized experimental model (AGEM) for dry sliding wear developed in earlier studies on sliding wear of copper on the basis of dimensionless analysis was extended tocopper-based composites. These were produced by powder metallurgy route, with the reinforcement of SiC ( 10 to 40% by volume). For wear test, three loads 25, 45 and 65 N and corresponding sliding speeds viz., 0.6 , 1.2 and 1.8 m/s were selected with incremental increase of 10% in sliding speed for obtaining simultaneous variation of load and sliding speed. The wear parameters, viz., dimensionless (Wd) wear rate and normalized (Wn) wear rate parameters were examined in terms of the varying deformation parameter (X) and interface parameter(Y). SEM study of the worn surfaces was done to understand the features of wear behaviour. It was observed that the model based on dimensional analysis for copper alloy could be applied satisfactorily to the composites of copper and SiC, for lower content of SiC.

16 illus, 4 tables, 20 ref

003555   Demirkol A (NO, University of Missouri-Rolla, Rolla MO 65409-0040, USA) : Range density function for active sensor imaging. Def Sci J 2007, 57(3), 305-13.

Generalised target density function (TDF) is studied for active imaging by sensors such as radar. This is achieved by estimating a new TDF which is called range density function (RDF). It is proposed by utilising of a generalised range-angle density function for imaging. While the RDF is developed by a new approach based on inverse Wandermonde matrix computation, it is obtained by considering a new range and scanning angle plane different from the conventional methods.

2 illus, 35 ref

003554   Das S K;Singh R S (NO, Institute for Systems & Studies and Analyses, Delhi-110 054) : Performance modelling of electro-optical devices for military target acquisition. Def Sci J 2007, 57(3), 323-31.

Accurate predictions of electro-optical imager performance are important for defence decision-making. The predictions serve as a guide for system development and are used in war game, simulations that directly influence engagement tactics. Mathematical models have been developed which involves detection of different military targets using their optoªelectronics properties in different environmental conditions. The method first calculates the signal-to-noise ratio received by the observing sensors reflected from the target by quantifying the light energy in terms of photons, which is used for evaluating the detection probability.

6 illus, 3 tables, 8 ref

003553   Chaudhury N K;Gupta R;Gulia S (NO, Institute of Nuclear Medicine and Allied Sciences, Delhi-110 054) : Sol-gel technology for sensor applications. Def Sci J 2007, 57(3), 241-53.

Sol-gel processes refer to the transition of predefined compositions of inorganic alkoxides precursors from liquid sol phase to solid gel phase. The phenomenon of sol-gel was known to mankind for more than 150 years. It is because of concerted efforts of researchers from multidisciplinary fields, sol-gel science transformed to technology. Several products are already commercially available for applications in optical coatings, nanocomposites, and public healthcare. Potential applications in the areas of biosensors and environmental monitoring are expected. Newer applications with nanotechnology appear too exciting. An attempt has been made to address important applications of sol-gel technology, particularly in sensing techniques from the defence perspective.

^iia1 illus, 83 ref

003552   Chaudhuri D;Savitha D K;Gohri V (NO, Defence Electronics Applications Lab, Dehradun-248 001) : Line pattern removal and enhancement technique for multichannel passive millimeter wave sensor images. Def Sci J 2007, 57(3), 315-21.

Passive millimeter wave (PMMW) imaging systems have attracted an increasing interest over the past years due to their superior poor-weather performance compared with visible and IR systems. In passive imaging, the spatial information acquired is strictly band-limited. A major drawback to PMMW images is their poor angular resolution. Also, another problem of single-channel PMMW imaging systems is the slow response time due to the lack of thermal sensitivity. The imager could operate at TV (television) rates using a number of parallel channels which may reduce the extent of this problem. In multi-channel, differences between the responses of individual channels can introduce noise into the image, which can obscure details of interest. The proposed noise-removal technique is a two-pass combined method of two techniques. One technique is for removing the DC component in the frequency domain and the other one is statistical filtering based on homogeneous region in the image (spatial) domain, followed by high-boost filtering by 3x3 mask for enhancement the image. High quality images are presented to demonstrate the potential of this technique.

2 illus, 15 ref

003551   Chandrasekaran V;Kannan K;Natesan M (Chem Dep, Govt Coll of Engng, Salem-636 011, Email: ikasiamah@yahoo.com) : Synergistic effect of isopropylamine with Cl- and SO₄<. Int J pure appl Chem 2006, 1(1), 101-15.

Synergistic effect ofIsopropylamine with Cl- and SO₄^2- on the inhibition of corrosion of mild steel in phosphoric acid medium has been investigated by using mass loss. potentiostatic polarization and A.C. impedance techniques at 302K. Isopropylamine showed very good inhibition efficiency. It has been found that the inhibition efficiency of the Isopropylamine increased with increase in inhibitor concentration and decreased with increase in acid concentrations. The maximum inhibition efficiency of Isopropylamine in 1N and 5N H₃PO₄ at 2.5% of Isopropylamine were found to be 96.92% and 90.39% respectively. The corrosion rate of mild steel in phosphoric acid has been reduced in the presence of chloride and sulphate ions. Under the synergistic effect. in the presence of 500 ppm of chloride with Isopropylamine inhibition efficiency was 98.24% in IN and 92.03% in 5N phosphoric acid. and in the presence of 500 ppm of sulphate with Isopropylamine. the inhibition efficiency was found to be 97.50% in IN and 91.42% in 5N phosphoric acid. The adsorption of these compounds on the mild steel surface has been found to obey Temkin's adsorption isotherm.

12 illus, 5 tables, 33 ref

003550   Chand K K;Panda H S (NO, Proof and Experimental Establishment, Chandipur, Balasore-756 025) : Mathematical model to simulate the trajectory elements of an artillery projectile proof shot. Def Sci J 2007, 57(1), 139-48.

In external ballistics of a conventional spin-stabilised artillery projectile, there are a number of trajectory models developed for computing trajectory elements having varying degrees of complexity. Attempts to propose a single mathematical model, viz., simplified point-mass/simple particle trajectory model to simulate the trajectory elements of a typical spin-stabilised flat-head artillery projectile proof shot. Due to difficulties in the projectile shape and size, and the complicated nature of air resistance, an accurate mathematical prediction of the trajectory is difficult. To simplify the computations, the governing equations of motion of the projectile have been simplified and assumed that the projectile is a particle and the only forces acting on the projectile are drag and gravity. With this model, trajectory elements have been generated and compared with experimental results obtained in the field test. The measuring instrument used in this case is a Doppler radar.

^ssc14 illus, 3 tables, 11 ref

003549   Chakrapani C et al (NO, Institute of Plasma Research, Bhat, Gandhinagar-382 428) : Performance testing of large scale cryocondensation pump. Indian J Cryogenics 2005, 30(1), 23-9.

6 illus, 2 tables, 3 ref

003548   Chakrabarti D;Davis C L;Strangwood M (Metallurgy and Materials Dep, The University of Birmingham, Edgbaston, Birmingham, B15 2TT UK, Email: c_debalay@yahoo.com) : Effect of precipitate distribution on high strength low alloy (HSLA) steel grain structures. Trans Indian Inst Metals 2006, 59(2), 205-13.

Bimodal grain size distributions were found in continuously cast slab and thermomechanical controlled rolled (TMCR) samples of Nb-microalloyed steel. Scanning electron microscopy (SEM) revealed inhomogeneous distributions of Al- and Nb-containing precipitates, which were found to pin prior austenite grain boundaries during reheating. Fine austenite grain sizes were associated with areas having a higher number density of these precipitates, which correlated with interdendritic regions. The formation of a bimodal grain structure after reheating and rolling could therefore be attributed to the inhomogeneous precipitate distribution, which originates from segregation during continuous casting and is modified during reheating and rolling.

9 illus, 5 tables, 19 ref