Showing papers in "Defence Science Journal in 2007"
Journal Article•
TL;DR: Hargittai et al. as mentioned in this paper found that people search for content in a myriad of ways and there is a large variance in whether people are able to find various types of content on the Web and how long they take to complete online tasks.
Abstract: Much of the existing literature on the digital divide – the differences between the haves and have nots regarding access to the Internet – limits its scope to a binary classification of technology use by only considering whether someone does or does not use the Internet. To remedy this shortcoming, in this paper I look at the differences in people’s online skills. In order to measure people’s online ability, I assigned search tasks to a random sample of Internet users from a suburban county. Findings suggest that people search for content in a myriad of ways and there is a large variance in whether people are able to find various types of content on the Web and how long they take to complete online tasks. Age is negatively associated with one’s level of Internet skill, experience with the technology is positively related to online skill, and differences in gender do little to explain the variance in people’s ability to find content online. * I would like to thank Paul DiMaggio for his insightful comments throughout this project, Stan Katz for his ongoing support, and Erica Field, Hank Farber and members of the 2001/2002 Princeton Sociology Dissertation Support Group for helpful discussions. I am also grateful to Edward Freeland, James Chu, Carolyn Mordas, Jeremy Davis-Turak, and Inna Barmash for their assistance with various components of the project. Generous support from the Markle Foundation is kindly acknowledged. The project has also been supported in part by NSF grant #SES9819907, a grant from the Russell Sage Foundation, and through a grant from the Pew Charitable Trusts to the Center for Arts and Cultural Policy Studies, Princeton University. I am also grateful to the Fellowship of Woodrow Wilson Scholars at Princeton University. ** Sociology Department, Wallace Hall, Princeton University, Princeton, NJ 08544. Tel: 1-609258-6915; Fax: 1-609-258-2180; Email: papers-at-eszter-dot-com Eszter Hargittai -First Monday -Second-Level Digital Divide :: 2 Introduction: Inequalities in Internet Use Much of the literature documenting the Internet’s spread across the population has focused on the differences among those who have access to the Internet and those who do not, or the differences among those who use it and those who do not. Since the National Telecommunications Information Administration published its first report “Falling Through the Net: A Survey of the Have Nots in Rural and Urban America” in 1995, many analyses have been written on the inequalities of access to and use of the medium. Existing studies of differential Internet access and use document inequalities among various segments of the population (Bucy 2000) with particular attention to education (NTIA 2000) race (Hoffman 1999), gender (Bimber 2000), age (Loges and Jung 2001), income (Benton 1998) and rural residence (Strover 1999). These studies have been essential in understanding inequalities in access to the Internet, or what has come to be known as the “digital divide”. Here, I argue that as the medium spreads to a majority of the population (NTIA 2002) it is increasingly important to look at not only who uses the Internet, but also to distinguish among people’s varying levels of online skills. Skill, in this context, is defined as the ability to efficiently and effectively find information on the Web. By exploring the differences in how people use the Web for information retrieval, we can discern if there is a “second-level digital divide” in the making as the Web spreads to the majority of the American population. To explore this question, I report findings from a project that explores people’s ability to locate content online. Documenting differences in people’s Web use skills allows us to distinguish between how different kinds of people are able to take advantage of the medium in varying ways. Refining the current approach to the digital divide While most reports identify differences among various segments of the population, over time studies emphasize the increasing diffusion of the medium among the population at large (Howard, Rainie and Jones 2001; Katz and Rice 2002; NTIA 2000; 2002; Pew Internet and American Life Project 2000). As more people start using the Web for communication and information retrieval, it becomes less useful to merely look at binary classifications of who is online when discussing questions of inequality in relation to the Internet (DiMaggio and Hargittai 2001). Eszter Hargittai -First Monday -Second-Level Digital Divide :: 3 Rather, we need to start looking at differences in how those who are online use the medium, that is, differences in people’s online skills. It is important to consider more than mere access to the network when studying the differential spread of the Internet across the population and inequalities in people’s use of the medium. Given the increasing spread of the medium, it is important to expand the research agenda to allow analyses of the differences among Internet users. That is, how can we talk about the Internet’s effect on political participation if a user does not possess the skills to find political information? Similarly, how can the Internet prove to be a useful link between government and citizens if people are unable to find official documents online? Information about people’s online skills tells us to what extent they are able to use the medium in ways of most interest to them and in ways that are most useful to their particular needs. The ability to find different types of information online allows people to use the medium to their maximum benefit. If users often give up in frustration and confusion then merely having access does not mean that a digital divide has been solved because a divide remains in their capacity for effective use of the Internet. As Kiesler et al. (2000) note, the computer – currently the basis of most users’ Internet access in the United States – is still not an appliance with obvious directions when something does not seem to go as expected. By measuring users’ Internet skills, we can bridge the gap in the literature between mere structural measures of access and descriptions of what people do online to account for what different people are able to do online.
190 citations
TL;DR: In this article, a comparison of classical detection methods with biosensors is also given, where a comparison between classical detection method with biosensor is also made, and a comparison with classical detection techniques with biophysical transducers is made.
Abstract: Biological warfare agents (BWA) such as Bacillus anthracis, Francisella tularensis, Yersinia pestis or butulotoxin represent one of possibilities exploitable by military or terrorists. Rapid detection of BWA is one of the most important presumptions prerequisities for successful defence agai nst t hem. The det ection devices–bi osensors–can be divided accordi ng to t heir physicochemical transducers to electrochemical, optical, and piezoelectric groups. A comparison of classical detection methods with biosensors is also given.
52 citations
TL;DR: In this article, the authors obtained creep stresses and strain rates for a thin rotating disc with inclusion using Seth's transition theory and showed that the rotating disc is likely to fracture by cleavage close to the inclusion at the bore.
Abstract: Creep stresses and strain rates have been obtained for a thin rotating disc with inclusionusing Seth’s transition theory. Results have been discussed numerically and depicted graphically.It has been observed that radial stress has maximum value at the internal surface of the rotatingdisc made of incompressible material as compared to circumferential stress and this value ofradial stress further increases with the increase in angular speed. Strain rates have maximumvalues at the internal surface for compressible material. Rotating disc is likely to fracture bycleavage close to the inclusion at the bore
39 citations
TL;DR: In this paper, an attempt has been made to address important applications of sol-gel technology, particularly in sensing techniques from the defence perspective, and several products are already commercially available for applications in optical coatings, nanocomposites and public healthcare.
Abstract: Sol-gel processes refer to the transition of predefined compositions of inorganic alkoxidesprecursors from liquid sol phase to solid gel phase. The phenomenon of sol-gel was known tomankind for more than 150 years. It is because of concerted efforts of researchers frommultidisciplinary fields, sol-gel science transformed to technology. Several products are alreadycommercially 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 toaddress important applications of sol-gel technology, particularly in sensing techniques fromthe defence perspective.
39 citations
TL;DR: In this paper, a human pulse detection and processing system has been developed using a piezoelectric sensor and signal provessing circuit consisting of signal amplifier, filters, and noise-reduction circuit.
Abstract: Diagnosis according to Ayurveda is to find the root cause of a disease. Out of eight differentkinds of examinations, nadi-pariksha is very important. By checking the pulse, the Ayurvedicphysician finds the predominant dosha out of the three - vata, pitta and kapha. Nadi-parikshais done at the root of the thumb by examining the radial artery. Presently, this technique issubjective and the accuracy of the diagnosis depends upon the expertise of the Ayurvedicphysician. As a first step towards making the diagnosis by nadi-pariksha objective, humanpulse detection and processing system has been developed.Piezoelectric sensor was used for human pulse detection. The pulse signals obtained fromthe piezoelectric sensor were processed through signal processing circuitry. The signal provessingcircuit consists of signal amplifier, filters, and noise-reduction circuit. The signal processingcircuit has been designed, built, and tested. The performance of the developed system wasevaluated 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 beenpresented and analysed.
31 citations
TL;DR: In this paper, a typical mix was carried out with 86 percent solid loading and toluene diisocynate (TDI) as curator to study the rheological properties and the flow behavior of HTPB-based compositepropellant, and the data were analyzed using power law fluid equation to determine the viscosity index(K) and pseudoplasticity index (m).
Abstract: To study the rheological properties and the flow behaviour of HTPB based compositepropellant, a typical mix was carried out with 86 per cent solid loading and toluene diisocynate(TDI) as curator. Viscosity of the propellant slurry was measured at different shear rates overa range of temperature from 40 oC to 60 oC at various time intervals up to five hours from endof mix. The data are analysed using power law fluid equation to determine the viscosity index(K) and pseudoplasticity index (m). From these, optimum casting temperature and useful pot lifewas evaluated. Casting rates at different temperatures were determined by Haegen-Poisseuilleequation modified for non-Newtonian fluid flow, using K and m.
30 citations
TL;DR: Recently, voided PVDF materials have been used for making Hydrostatic-mode polyvinylidene flouride (PVDF) hydrophones using a pressure-releasesystem to achieve improved sensitivity as mentioned in this paper.
Abstract: Conventional ceramic piezoelectric materials have been used in hydrophones for sonarapplications since 1940's. In the last few years since the discovery of polymeric piezoelectrichydrophones, the technology has matured, applications have emerged in extraordinary number ofcases such as underwater navigation, biomedical applications, biomimetics, etc. Hydrophones areused underwater at high hydrostatic pressures. In the presence of hydrostatic pressures, theanisotropic piezoelectric response of ceramic materials is such that it has poor hydrophone performancecharacteristics whereas polymeric piezoelectric materials show enough hydrostatic piezoelectriccoefficients. Moreover, piezoelectric polymers have low acoustic impedance, which is only 2-6 timethat of water, whereas in piezoelectric ceramics, it is typically 11-time greater than that of water. Aclose impedance match permits efficient transduction of acoustic signals in water and tissues. Newlydeveloped hydrostatic-mode polyvinylidene flouride (PVDF) hydrophones use a pressure-releasesystem to achieve improved sensitivity. Recently, voided PVDF materials have been used for makinghydrophones having higher sensitivity and figure of merit than unvoided PVDF materials.
21 citations
TL;DR: In this article, a comprehensive compilation of relevant information on the techniques is presented, and their maturity levels, shortcomings, and difficulties faced are highlighted, and a comprehensive effort has been made to review the techniques so far available based on explosive vapour detection especially to detect the landmines.
Abstract: Large quantity of explosive is manufactured worldwide for use in various types of ammunition,arms, and mines, and used in armed conflicts. During manufacturing and usage of the explosiveequipment, some of the explosive residues are released into the environment in the form ofcontaminated effluents, unburnt explosives fumes and vapours. Limited but uncontrolledcontinuous release of trace vapours also takes place when explosive-laden landmines are deployedin the field. One of the major technological challenges in post-war scenario worldwide is thedetection of landmines using these trace vapour signatures and neutralising them safely. Differenttypes of explosives are utilised as the main charge in antipersonnel and antitank landmines. Inthis paper, an effort has been made to review the techniques so far available based on explosivevapour detection especially to detect the landmines. A comprehensive compilation of relevantinformation on the techniques is presented, and their maturity levels, shortcomings, and difficultiesfaced are highlighted.
21 citations
TL;DR: An overview of airborne IRST as a system has been presented with detailed comparative simulation results of different detectionitracking algorithms and the present status of airborneIRSTs.
Abstract: Infrared search and track (IRST) systems are required for fighter aircraft to enable them to passively search, detect, track, classify, and prioritise multiple airborne targets under all aspects, look-up, look-down, and co-altitude conditions and engage them at as long ranges as possible. While the IRST systems have been proven in performance for ground-based and naval-based platforms, it is still facing some technical problems for airborne applications. These problems arise from uncertainty in target signature, atmospheric effects, background clutter (especially dense and varying clouds), signal and data processing algorithms to detect potential targets at long ranges and some hardware limitations such as large memory requirement to store and process wide field of view data. In this paper, an overview of airborne IRST as a system has been presented with detailed comparative simulation results of different detectionitracking algorithms and the present status of airborne IRSTs
20 citations
TL;DR: In this article, the authors give an insight into the piezoelectric gyro sensor technology including the principle of operation, performance-limiting phenomenon, etc., including the performance of various forms of vibrating structure gyros.
Abstract: This paper gives an insight into the piezoelectric gyro sensor technology including theprinciple of operation, performance-limiting phenomenon, etc. With a brief account ofconventional gyro sensor technologies, a detailed discussion on piezoelectric vibrating structuregyro sensor technology has been given. The performance of various forms of vibrating structurepiezoelectric gyros, including future trends, has been highlighted.
18 citations
TL;DR: In this paper, in situ, synchronised, transient temperature and current measurements have been carried out, and the surface topography of the dischargeaffected zones on the workpiece has been analyzed using scanning electron microscope.
Abstract: Electrochemical discharge machining process is evolving as a promising micromachiningprocess. The experimental investigations in the present work substantiate this trend. In the presentwork, in situ, synchronised, transient temperature and current measurements have been carriedout. The need for the transient measurements arose due to the time-varying nature of the dischargeformation and time varying circuit current. Synchronised and transient measurements revealedthe discrete nature of the process. It also helped in formulating the basic mechanism for thedischarge formation and the material removal in the process. Temperature profile on workpieceand in electrochemical discharge machining cell is experimentally measured using pyrometer,and two varieties of K-type thermocouples. Surface topography of the discharge-affected zoneson the workpiece has been carried out using scanning electron microscope. Measurements andsurface topographical studies reveal the potential use of this process for machining in micronregime. With careful experimental set-up design, suitable supply voltage and its polarity, theprocess can be applied for both micromachining and micro-deposition. It can be extended formachining and or deposition of wide range of materials.
TL;DR: In this article, the structural and piezoelectric properties of PbNi1/3Nb2/3 PbZrO3-PbTiO3 system were studied on mechano-chemically processed powder.
Abstract: Sintering temperatures affect the structural and piezoelectric properties of PbNi1/3Nb2/3-PbZrO3-PbTiO3 system considerably; therefore the effect has been studied on mechano-chemicallyprocessed powder. This process involves activating mixed oxides of PbO, NiO, Nb2O5, ZrO2 andTiO2, and in the present study, calcination steps at an intermediate temperatures were skippedwhich are usually required in conventional solid state reaction methods and chemical routes.Single-phase formation was confirmed from XRD patterns which shows rhombohedral structureat higher sintering temperature. Investigations of the microstructure indicate almost linear increasein grain size from 0.98 m to 2.56 m when the sintering temperature was varied from 1050 oC to1150 °C. A high value of planar coupling factor (kp) = 67 per cent and piezoelectric charge coefficient(d 33 ~ 750 pm/V; (as determined from strain versus electric field curve at low field) were obtainedfor the ceramic specimens sintered at 1100 °C. The maximum strain was observed ~ 0.21 per centat 40 kV/cm applied field for the sample sintered at 1100 °C for 4 h.
TL;DR: Percutaneous administration of sulphur mustardinduces oxidative stress and quercetin can protect it as a prophylactic agent, in a dose-dependent manner.
Abstract: Sulphur mustard (SM) is a chemical warfare agent that causes serious blisters upon contactwith human skin. SM alkylates DNA and several other macromolecules, and also induces oxidativestress. Quercetin, a bioflavonoid has wide pharmacological actions. The protective efficacy ofquercetin (100 mg/kg, i.p. and 200 mg/kg, i.p.) was studied by administering three doses in miceagainst SM. The first dose was administered at 30 min prior, simultaneous, 2 h post or 24 h post,and two more doses on the next two days. SM was administered (in PEG 300) percutaneouslyat varying doses for survival and protection studies. SM was also administered at a dose of2 LD50 (19.3 mg/kg) with and without quercetin treatment and various biochemical markers wereestimated 7 days after SM administration. Histological examinations of vital organs were alsocarried out. The animals administered with SM died at various days depending upon the dose.The body weight decreased significantly. Quercetin protected the mice significantly, in a dose-dependent manner. The protection was better when the first dose of quercetin administered was30 min prior or simultaneously. A significant decrease in reduced as well as oxidised glutathioneand an increase in malondialdehyde, WBC count, RBC count, and haemoglobin were observedwith 2 LD50 SM. Quercetin at 100 mg/kg and 200 mg/kg doses significantly protected the biochemicalmarkers when the first dose of quercetin administered was 30 min prior or as simultaneoustreatment. The histological lesions induced by sulphur mustard on liver, spleen, and skin werealso significantly protected by quercetin when the first dose was administered 30 min prior oras simultaneous treatment. The present study shows that percutaneous administration of SMinduces oxidative stress and quercetin can protect it as a prophylactic agent.
TL;DR: In this article, the characteristics of these temperature sensors have been discussed in detail with their operating range, sensitivity, and accuracy, and other properties likeinterchangeability, effect of thermal cycling, effects of ionizing radiation ( neutron or gamma ray), effect of magnetic field has also been described.
Abstract: This paper describes the different cryogenic temperature sensors used at cryogenictemperatures down to 1 K. The characteristics of these temperature sensors have been discussedin detail with their operating range, sensitivity, and accuracy. Other properties likeinterchangeability, effect of thermal cycling, effect of ionizing radiation ( neutron or gamma ray),effect of magnetic field has also been described. It is extremely important to choose the righttemperature sensor for right kind of application in a specific operating environment. This papergives an overview of some of the most widely used cryogenic temperature sensors.
TL;DR: In this paper, a new series of composite propellant compositions, based on ammonium perchlorate, hydroxy-terminated polybutadiene and having metallic fuel as aluminium powder, have been developed.
Abstract: A new series of composite propellant compositions, based on ammonium perchlorate,hydroxy-terminated polybutadiene and having metallic fuel as aluminium powder, have beendeveloped. Pressure cast-cum-cured compositions have also been developed with toluenediisocyanate (TDI), isophorone diisocyanate (IPDI), and a mixture of both curatives, i.e., TDIand IPDI, respectively, to study their effect on processibility, mechanical and ballistic propertiesof the compositions. The data indicate that the compositions based on bicurative have a potlife of 7 - 8 h, viscosity build up is from 13280 poise to 14080 poise after 4 h, and the smoothprocessibility of the slurry is enhanced. Further, the mechanical properties are in the range12.2 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.
TL;DR: This paper demonstrates the use of intelligent agent-based team behaviour modelling concepts in simulating the armoured tanks in a tactical masking scenario.
Abstract: Realistic military simulations are needed for analysis, planning, and training. Intelligentagent technology is a valuable software concept with the potential of being widely used inmilitary simulation applications. They provide a powerful abstraction mechanism required fordesigning simulations of complex and dynamic battlefields. Their ability to model the tacticaldecision-making behaviour of simulated battlefield entities gives them an edge over othertechniques. During battlefield simulation, these entities generally represent individualisticbehaviour, taking operational order from higher control and executing relevant plans. However,since a complex battlefield scenario typically involves thousands of entities, their coordinatedteam behaviour should also be considered to make the simulation more realistic. This paperdemonstrates the use of intelligent agent-based team behaviour modelling concepts in simulatingthe armoured tanks in a tactical masking scenario.
TL;DR: In this article, the satellite data of SSM/I sensor has been used to develop new algorithms usingbrightness temperature for snow water equivalent (SWE) and snow depth that will suit theIndian Himalayan conditions.
Abstract: The study of snow characteristics using conventional techniques for vast, rugged andremote snow covered areas of Himalayas is very difficult. In the present study, the satellite dataof SSM/I sensor has been used. Changes in snow accumulation result in related variations inpassive microwave brightness temperature. This study attempts to develop new algorithms usingbrightness temperature for snow water equivalent (SWE) and snow depth that will suit theIndian Himalayan conditions. The snow and meteorological data recorded in the field is usedto determine the empirical coefficients, which have been further used in the algorithmdevelopment. The parameters evaluated can be used as the input for the avalanche risk analysis,as one can estimate average snow depth and SWE of the area which are main input for avalancheforecasting. Algorithms are further used for the prediction of snow depth and SWE for subsequentwinters using the brightness temperature. A good correlation was found between the predictedand the observed values from the ground observatory data.
TL;DR: In this paper, a 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.
Abstract: A 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 unsprungmasses respectively. Road-following springs are applied for the sprung mass to follow the trendof 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 andspring constant to achieve an optimum trade off among ride comfort, handling quality, andsuspension stroke simultaneously for random input. Computer simulations are performed usingMATLAB software to verify the proposed control scheme and effectiveness of the appliedgenetic algorithm.
TL;DR: Tensile strength of snow was determined using indigenously developed automated centrifugal machine as discussed by the authors, which was conducted on sieved snow at four temperature levels of 0 °C, -3 °c, -6 °C and -9 °C at density ranging from 200-460 kg/m 3.
Abstract: Tensile strength of snow was determined using indigenously developed automated centrifugal machine. Processed snow (sintered at -20 °C for 4 days) samples of dia: 65 mm and height:130 mm were tested using this machine.The experiments were conducted on sieved snow at four temperature levels of 0 °C, -3 °C, -6 °C and -9 °C at density ranging from 200-460 kg/m 3 . Results of these experiments have been compared with the earlier suggested models. Probability distribution of snow strength on the basis of current experimental data has also been presented.
TL;DR: In this paper, the initial stage of fueldispersal was simulated by numerical computation and the simulation result indicated that the distribution of fuel dispersal velocity, when the central HE is ignited at the end, is not the same as that when the center HE was ignited on the axis of the central pipe simultaneously.
Abstract: A fuel-air explosive (FAE) device consists of a shell (top-end cover, bottom-end cover, shell-side wall), a mixed fuel, a central pipe and a burst high-explosive (HE) charged in the central pipe.The mixed fuel is filled in a column structure and dispersed by the explosion drive of central burstHE in the central pipe. The dispersed fuel mixes with air, which produces combustible cloudwhich can be detonated. That is the fuel-air explosive (FAE). The height and ignition positionof the central HE charged column affect the fuel dispersal process. The initial stage of fueldispersal was simulated by numerical computation. The simulation result indicated that thedistribution of fuel dispersal velocity, when the central HE is ignited at the end, is not the sameas that when the central HE is ignited on the axis of the central HE simultaneously. When theratio of the column height of the central HE and that of the FAE device is 0.64~0.73, the distributionof fuel dispersal velocity has little difference when the central HE is ignited at the end of column.But, when the ratio of the column height of the central HE and that of the FAE device is 0.89,the fuel axial dispersal velocity is obviously more than that when the ratio of the column heightof the central HE and that of the FAE device is 0.64~0.73.
TL;DR: In this article, the processing conditions, microstructure, and dielectric properties of strontium bismuthtitanate (SBT) were systematically studied, and a relative density of 90 per cent of the theoretical density was obtained.
Abstract: The processing conditions, microstructure, and dielectric properties of strontium bismuthtitanate (SBT) were systematically studied. The specimen was synthesised by a mechano-chemicalprocessing route using a planetary ball mill. It is important that the action is vigorous enoughto break up loose aggregates and a fine particle size is obtained. The specimen was calcinedat 800 oC for 4 h. The calcined samples were subjected to cold isostatic pressing (CIP) processand finally sintered at 1200 oC for 2 h. A relative density 90 per cent of the theoretical densitywas obtained. Pellets having a diameter of 1cm and thickness of 1 mm were prepared from thesintered compacts for electrical measurements. X-ray diffraction showed that a single phase withthe layered perovskite structure of SBT was formed. Morphological studies were carried out bySEM analysis. Frequency dependence of impedance can provide additional insight intomechanisms controlling the electrical response. Resonance studies were made on poled samplein the frequency range 100 kHz – 20 MHz using an impedance analyser (HP-4294A) interfacedto a computer at room temperature. Dielectric measurements in the frequency range 100 Hz–1 MHz were made using an impedance analyser (HP-4192A) interfaced to a computer and themeasurements were carried out from room temperature to 550 oC. The ferroelectric hysteresis loopwas measured using a standard ferroelectric analyser based on Sawyer-tower circuit. Elasticcompliance (s33, s11) coupling factor (k33, k31)were also obtained. These materials can be utilisedin practical applications as substitutes for lead titanate and lead zirconate titanate (PZT)-basedceramics, where high temperature applications are foreseen.
TL;DR: A variety of aromatic hydrazides have been synthesized by solvent-free hydrazinolysis of corresponding esters with hydrazine hydrate under microwave irradiation as discussed by the authors.
Abstract: A variety of aromatic hydrazides has been synthesised by solvent-free hydrazinolysis ofcorresponding esters with hydrazine hydrate under microwave irradiation.
TL;DR: In this article, the authors presented a concept of creating stress concentration regions (SCRs) on the cantilever for enhancing its sensitivity, which resulted in substantial increase in the sensitivity.
Abstract: Acceleration sensors find applications in missile and competent munitions subsystems.Cantilever-type sensor's sensitivity and bandwidth are dependant on material properties of thecantilever and structure of proof mass. It is always desired to design a sensor as sensitive aspossible but also maintaining higher bandwidth. In piezoresistive (cantilever-type) accelerometers,various techniques were employed by designers to enhance their sensitivity and bandwidth.Most of these techniques are usually focused on shape and size of either cantilever or proofmass. This paper presents a concept of creating stress concentration regions (SCRs) on thecantilever for enhancing its sensitivity. Five types of structures were simulated to study thebehaviour of piezoresistive sensors with SCRs implementation. Use of SCRs results in substantialincrease in the sensitivity, which is of the order of 1.85 times the nominal sensitivity. It was aimedat maximising sensor's performance factor, which is the product of sensor bandwidth andsensitivity. This study gives new dimension to the ways of improving performance of cantilever-type inertial piezoresistive sensor.
TL;DR: In this paper, the use of stabiliser and doping stabiliser-coated particles with polymerics-substance was adopted to overcome the problem of acid formation in closed-air systems.
Abstract: Red phosphorus (RP) is an essential ingredient to generate smoke for multi-spectralobscuration and is receiving wide attention throughout the world for military applications.However, oxidation of phosphorus occurs in moist air resulting in the formation of variousphosphorus acids and subsequently the evolution of the toxic gas, phosphine (PH3), even inthe sealed systems. Entrapped moisture leads to deterioration of the stores. The commercial-RPat ambient temperature and 95 per cent RH conditions indicates 15 per cent moisture absorptionand 13 per cent acidity development with the generation of more than 100 ppm of phosphinegas. Efforts were made to overcome this problem by suppressing acid formation. The technologyadopted was: (i) use of stabiliser, and (ii) doping stabiliser-coated particles with polymericsubstance. The aim to use metal oxide as stabiliser was to neutralise the phosphorus acids,which are catalysing the phosphine generation. MgO due to its basic nature seems to be fasterthan amphoteric Al2O3, in removing the acid from site of reaction, thus suppressing the phosphinerelease effectively. Though MgCO3 as stabiliser suppresses moisture absorption and aciditydevelopment, phosphine release is not controlled effectively. Study of RP coated with thesematerials independently and monitoring them at different RH conditions indicated superiorityof MgO in suppressing acidity and phosphine formation.
TL;DR: In this paper, the authors presented numerical modeling of turbulent-reacting flow field of supersonic combustion ramjet(scramjet) combustors using an eight-step hydrogen-airchemistry.
Abstract: Numerical modelling of turbulent-reacting flow field of supersonic combustion ramjet(scramjet) combustors are presented. The developed numerical procedure is based on the implicittreatment of chemical source terms by preconditioning and solved along with unstedy turbulentNavier-Stokes equations explicitly. Reaction is modelled using an eight-step hydrogen-airchemistry. Code is validated against a standard wall jet experimental data and is successfullyused to model the turbulent-reacting flow field resulting due to the combustion of hydrogeninjected from diamond-shaped strut and also in the wake region of wedge-shaped strut placedin the heated supersonic airstream. The analysis could demonstrate the effect of interaction ofoblique shock wave with a supersonic stream of hydrogen in its (fuel-air) mixing and reactionfor strut-based scramjet combustors.
TL;DR: In this article, a new formulation of terminal guidance law which controls the impact attitude angle while minimising the miss distance is presented, which does not require linearization of missile-target engagement model.
Abstract: This paper presents a new formulation of terminal guidance law which controls the impact attitude angle while minimising the miss distance. The formulation is based on the fuzzy logiccontrol approach. Unlike many prevalent designs, the proposed guidance law does not require linearisation of missile-target engagement model. Numerical simulation results demonstrate that the proposed guidance law offers satisfactory performance, fulfilling its design goals.
TL;DR: It was found that the response of amperometric sensor is proportional to the logarithmic of ricin concentration from 100 ng/mlto 3200 ng/ ml, while with amperomet immunosensor, one can detect ricin as low as 40 ng-ml within 90 min.
Abstract: Ricin is a highly toxic plant toxin, which is extracted from the beans of the castor plant,Ricinus communis. Ricin is thousand times more poisonous than cyanide and thirty times morepotent than nerve gases. The toxin (ricin) could be used to contaminate food or water, causingpanic. Attempts were made for the detection of ricin in water samples by utilising amperometricimmunosensors. Single-use screen-printed electrodes were made using polystyrene and graphite.These electrodes were tested for their ability to detect 1-naphthol which is the product of thereaction between 1-naphthyl phosphate and the enzyme alkaline phosphatase conjugate. Anindirect enzyme-linked immunosorbent assay (ELISA) system was used to detect ricin. First,ricin antigen was incubated on the screen-printed electrode. This was followed by blocking withBSA and incubation with antibody raised against ricin in rabbit. The last step wass the incubationwith anti-antibody of rabbit conjugated to enzyme alkaline phosphatase. This electrode is insertedin an electrochemical cell containing diethanolamine buffer and a potential of 0.4 V wrt referenceelectrode (Ag/AgCl) was applied using a potentiostat. Various experiments were carried out foroptimising the conditions like substrate concentration, amount of antibody raised against ricin,anti-antibody alkaline phosphatase conjugate, and blocking agents. It was found that the responseof amperometric sensor is proportional to the logarithmic of ricin concentration from 100 ng/mlto 3200 ng/ml. Using traditional methods, it is possible to detect ricin concentration up to 300ng/ml in 18 h, while with amperometric immunosensor, one can detect ricin as low as 40 ng/mlwithin 90 min. The details of making the screen-printed electrodes, characterisation, optimisationof various conditions for the highest sensitivity have been discussed.
TL;DR: In this article, a simplified point-mass/simple particle trajectory model was proposed to simulate the trajectory elements of a typical spin-stabilised flat-head artillery projectile proof shot.
Abstract: In external ballistics of a conventional spin-stabilised artillery projectile, there are a numberof trajectory models developed for computing trajectory elements having varying degrees ofcomplexity. The present study attempts to propose a single mathematical model, viz., simplifiedpoint-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 andsize, and the complicated nature of air resistance, an accurate mathematical prediction of thetrajectory is difficult. To simplify the computations, the governing equations of motion of theprojectile have been simplified and assumed that the projectile is a particle and the only forcesacting on the projectile are drag and gravity. With this model, trajectory elements have beengenerated and compared with experimental results obtained in the field test. The measuringinstrument used in this case is a Doppler radar.
TL;DR: In this article, a 3D model of the bearing is created using IDEAS software and finite element analysis using contact element has been carried out for finding the deformation and stresses in the webs at variouslocations using ANSYS software.
Abstract: Squirrel cage ball bearings are used in recent aero engines to overcome the vibration andstability problems associated with rotor systems supported by conventional bearings. The criticaldesign feature of squirrel cage bearing is to provide flexible support to rotor system. The outerring of the bearing is configured such that it acts as a flexible bearing support, and hence, weightis minimised. The bearing is mounted directly on a rigid intermediate casing of a gas turbineengine. Finite element analysis helps to obtain a suitable geometry at the design stage. A 3-Dmodel of the bearing is created using IDEAS software. Finite element analysis using contactelement has been carried out for finding the deformation and stresses in the webs at variouslocations using ANSYS software. The deformations are compared with those of experimentalvalues for an axial load. The deformation in the webs is used to check the pressure balance inthe compressor and the load acting on the bearing. Finally, a procedure for doing the finiteelement analysis of ball bearings for combined axial and radial load is laid down.
TL;DR: In this article, a technique for optimising performance of cantilever-type micro acceleration sensor has been developed, where 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 cantileverses to the designer's choice.
Abstract: A technique for optimising performance of cantilever-type micro acceleration sensor hasbeen 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 thesensor performance. It is observed that placement of a lumped mass (add-mass) on the sensor'sproof-mass helps to control both sensitivity and the first resonant frequency of the cantileverstructure to the designer's choice. Simulation and modelling of various dimensions of rectangularstructures for acceleration sensor with this novel add-mass technique are discussed. CoventorwareMEMSCAD has been used to model, simulate, and carry out FEM analysis. A simple analyticalmodel is discussed to elaborate the mechanics of cantilever-type micro accelerometer. Thecomparison of the results obtained from analytical model and the finite element simulations revealthese to be in good agreement. The advantages of this technique for choosing the two mostimportant sensor parameters (i.e., sensitivity and bandwidth) of an inertial sensor are brought out.