bluuebunny/crossref_metadata_2025 huggingface dataset:
Quality of Service and Radio Management in Biomedical Wireless Sensor Networks
Authors: Abreu Carlos , Miranda Francisco , Mendes Paulo M.
Published: September 2015

Biomedical wireless sensor networks enable the development of real time patient monitoring systems, either to monitor chronically ill persons in their homes or to monitor patients in step-down hospital units. However, due to the critical nature of medical data, these networks have to meet demanding quality of service requirements, ensuring high levels of confidence to their users. These goals depend on several factors, such as the characteristics of the network deployment area or the network topology. In such context, this chapter surveys the main applications of biomedical wireless sensor networks, taking into account the key quality of service requirements of each one of them. Finally, it presents an analytic method, and its experimental validation, to help engineers managing the radio power of the network nodes in order to improve the communications and the quality of service provided by the network while minimising the energy consumption and, thus, maximising the network lifetime.
Scenarios and Modeling of Land Use and Cover Changes in Portugal from 1980 to 2040
Authors: Santos Sara , Cabral Pedro , Zamyatin Alexander
Published: September 2015

In this study, land use and cover changes in continental Portugal are analyzed for years 1980, 1995 and 2010 using samples of the Landyn research project. The modeling approach includes testing the hypothesis that land cover changes are generated by a first-order Markov process. Results show that the changes in land use and cover are dependent of the previous moment in time, i.e., they follow a Markov process. Accordingly, multi-decadal land cover projections of Landyn simplified land cover classes are legitimately presented and analyzed for continental Portugal and its regions for years 2020, 2030 and 2040. To make these results spatially explicit, a modelling approach which combines Markov chains with cellular automata is carried out using hypothetical scenarios. The quantitative and spatially explicit information provided by this study enables a better understanding of tendencies in land cover change and may be useful for territorial planning and management.
Comparing the MLC and JavaNNS Approaches in Classifying Multi-Temporal LANDSAT Satellite Imagery over an Ephemeral River Area
Authors: Tarantino Eufemia , Novelli Antonio , Aquilino Mariella , Figorito Benedetto , Fratino Umberto
Published: September 2015

This paper analyzes two pixel-based classification approaches to support the analysis of land cover transformations based on multitemporal LANDSAT sensor data covering a time space of about 24 years. The research activity presented in this paper was carried out using Lama San Giorgio (Bari, Italy) catchment area as a study case, being this area prone to flooding as proved by its geological and hydrological characteristics and by the significant number of floods occurred in the past. Land cover classes were defined in accordance with on the CN method with the aim of characterizing land use based on attitude to generate runoff. Two different classifiers, i.e. Maximum Likelihood Classifier (MLC) and Java Neural Network Simulator (JavaNNS) models, were compared. The Artificial Neural Networks (ANN) approach was found to be the most reliable and efficient when lacking ground reference data and a priori knowledge on input data distribution.
An Enactivist Approach to Web-based Learning
Authors: De Simone Giuseppe , Di Gennaro Diana Carmela , Fragnito Riccardo
Published: September 2015

In the Web-based learning era, the possibility to use the online network for learning activities, studies and research has brought about a revolution in the educational processes and the emergence of a new culture characterized by the idea that knowledge is not closed and defined, but open and accessible to all. Within a perspective in which knowledge is generated by the interaction of the individual with the environment, the socio-constructivist approach paved the way to new theoretical frameworks that, starting from the social dimension of learning, acknowledge and embrace the biological aspects of learning processes, thus offering interesting reflections on the web-learning phenomenon. Stemming from these assumptions, LiveCampus was created; a social learning environment aimed at fostering a synergistic integration between the dimensions of formal and informal knowledge.
A Scalable Big Stream Cloud Architecture for the Internet of Things
Authors: Belli Laura , Cirani Simone , Davoli Luca , Ferrari Gianluigi , Melegari Lorenzo , Montón Màrius , Picone Marco
Published: September 2015

The Internet of Things (IoT) will consist of billions (50 billions by 2020) of interconnected heterogeneous devices denoted as “Smart Objects:” tiny, constrained devices which are going to be pervasively deployed in several contexts. To meet low-latency requirements, IoT applications must rely on specific architectures designed to handle the gigantic stream of data coming from Smart Objects. This paper propose a novel Cloud architecture for Big Stream applications that can efficiently handle data coming from Smart Objects through a Graph-based processing platform and deliver processed data to consumer applications with low latency. The authors reverse the traditional “Big Data” paradigm, where real-time constraints are not considered, and introduce the new “Big Stream” paradigm, which better fits IoT scenarios. The paper provides a performance evaluation of a practical open-source implementation of the proposed architecture. Other practical aspects, such as security considerations, and possible business oriented exploitation plans are presented.
A Review of the Effect of Process Parameters on the Performance of Plastic Injection Molding Process to Control the Warpage in Plastics
Authors: Singh Gurjeet , Pradhan Mohan Kumar , Verma Ajay
Published: September 2015

Quality control is important aspect of manufacturing process. The quality of product in injection moulding is influenced by injection moulding process parameter. A study of the influence of process parameters on the injection moulding process is presented. Statistically based model approach were studied. In this the process parameter that affect the injection moulding process are like injection time, injection pressure, packing pressure, packing time, cooling time, coolant temperature mold temperature, melt temperature are studied and compared. This paper deals with design of experiment approach to fine out optimal parameter setting. The comparison shows effect of parameters on injection moulding process.Key words: Plastic injection moulding, Orthogonal array, Cycle time
Heat Treatment Studies on 50CrV4 Spring Steel
Authors: Anil Kumar V. , Karthikeyan M.K. , Gupta R.K. , Ramkumar P. , Uday Prakash M.
Published: September 2015

50CrV4 spring steel is a tough, shock resisting, shallow hardening chromium vanadium steel having high fatigue and impact resistance in the heat treated condition. It is used extensively in gears, pinions, springs, shafts, axles, pins, bolts, etc., which require high modulus of resilience. The alloy was realised through conventional melt route of electric arc furnace (EAF) followed by ESR. The application of the alloy is limited to a section thickness of 15mm [1]. Hence obtaining optimum mechanical properties becomes a challenging task. In this study, the hardening as well as tempering operations were limited to 15mm thickness. The samples from the alloy were subjected to hardening at 860°C for 1.25 h. and oil quenching to room temperature followed by tempering at four different temperatures of 250, 300, 370 & 450°C for 3 h. each with oil quenching to room temperature. It was found that the alloy exhibited good combination of strength and ductility when tempered at 450°C. Microstructural study revealed the presence of fine tempered lath martensite along with the presence of a very small amount of delta ferrite along prior austenitic grain boundaries.
Assessment of Wetting Kinematics and Cooling Performance of Select Vegetable Oils and Mineral-Vegetable Oil Blend Quench Media
Authors: Pranesh Rao K.M. , Prabhu K.N.
Published: September 2015

Quench hardening is a process where an alloy is heated to solutionizing temperature and held for a definite period, and then rapidly cooled in a quenching medium. Selection of quenchant that can yield desired properties is essential as it governs heat extraction process during quenching. In the present work, the cooling performance of vegetable oil and mineral-vegetable oil blend quench media was assessed. The vegetable oils used in this work were olive oil, canola oil and rice bran oil. The mineral-vegetable oil blends were prepared by blending 10 and 20 vol. % of rice bran and canola oil in mineral oil. Inconel probe of 12.5mm diameter and 60mm height, instrumented with thermocouples were used to characterize quenchants. The probe was heated to 850°C and quenched in the oil medium. The cooling curves at different locations in the probe were used to study wetting kinematics. Inverse modelling technique was used to estimate spatially dependent metal-quenchant interfacial heat flux. It was found that the vegetable oils exhibited very short vapour blanket stage compared to mineral oil and blends. Faster wetting kinematics obtained with blends resulted in uniform heat transfer compared to that of mineral oil. The temperature distribution in the probe quenched in vegetable oils and blends was more uniform compared to that in mineral oil. It is expected that the parts quenched in vegetable oils and blends would lead to better hardness distribution compared to mineral oils.
On the Anomalous Coffin-Manson Behavior Observed under Elevated Temperature Ratcheting in Type 316LN SS
Authors: Sarkar Aritra , Atikukke Nagesha , Sandhya R. , Laha K.
Published: September 2015

Ratcheting is the progressive directional accumulation of deformation due to asymmetric loading in structures. Coffin-Manson plots derived from ratcheting experiments conducted at temperatures over the range, 823-923 K showed anomalous behavior at 873 K and 923 K in the form of dual slope and positive slope respectively, which was attributed to a change in the deformation mechanism during ratcheting in the above temperature domain. This was also reflected in the transition in the fracture mode from fatigue to creep at 873 and 923 K.
Material Characterisation and Constitutive Modelling of a Copper Alloy and Stainless Steel at Cryogenic and Elevated Temperatures
Authors: Asraff A.K. , Sheela S. , Jayamani Krishnajith , Chandran Nair S. Sarath , Muthukumar R.
Published: September 2015

High performance rockets are developed using cryogenic technology. High thrust cryogenic rocket engines operating at elevated temperatures and pressures are the backbone of such rockets. The thrust chamber of such engines, which produce the thrust for the propulsion of the rocket, can be considered as structural elements. Often double walled construction is employed for these chambers for better cooling and enhanced performance. The thrust chamber investigated here has its hot inner wall fabricated out of a high conductivity high ductility copper alloy and outer wall made of a ductile stainless steel. The engine is indigenously designed and developed by ISRO and is undergoing hot tests. Inner wall is subjected to high thermal and pressure loads during operation of engine due to which it will be in the plastic regime. Evaluation of tensile properties of the copper alloy and stainless steel up to fracture, at cryogenic, ambient and elevated temperatures in parent metal and welded forms is of paramount importance for its constitutive modelling and thermo structural analysis of the thrust chamber.
Study on Dissimilar Butt Joining of Aluminum Alloy, AA5052 and High Strength Low Alloy Steel through a Modified FSW Process
Authors: Ramachandran K.K. , Murugan N. , Shashi Kumar S.
Published: September 2015

In the preset investigation, aluminum alloy, AA5052 and HSLA steel are successfully butt welded using a modified FSW process wherein the work pieces submerged in a liquid medium are stirred by the FSW tool. The trials are conducted by varying the tool rotational speed from 400 rpm to 900 rpm while keeping the other parameters constant. The welded joints are tested for ultimate tensile strength (UTS) and the joint interface microstructure is analyzed using SEM and EDS. The results show that when compared to the normal FSW process, the peak value of UTS is marginally low but the range of tool rotational speed that could produce defect free joints with good joint strength is almost doubled in the modified FSW process.
Prediction of Temperature Profile in the HAZ of Maraging Steel GTAW Weldments
Authors: Arpan K.S. , Niladri M. , Venkateswaran T. , Chakravarthy P. , Singh Gurpreet , Sivakumar D.
Published: September 2015

This paper discusses the modeling of gas-tungsten arc welding (GTAW) process being adopted for maraging steel plates used in aerospace applications. Primary objective of this work is to predict the temperature profile of heat affected zone in a maraging steel weld. Finite element modeling was done utilizing a gaussian heat flux distribution on a weldment. Model also incorporated a moving heat source along with provision for heat sinks in the form of copper backup plates. For validating the model, welding experiments were conducted on 2 mm and 8 mm thick 250 grade maraging steel plates. Thermal profiles were acquired at different locations of heat affected zone using thermocouples and compared with the predictions from the model.
Processing and Characterization of Superinvar for Space Application
Authors: Gupta Rohit Kumar , Varma Praveen , Anil Kumar V. , Sarkar P. , Desai Jaimin , Ramkumar P.
Published: September 2015

Material with ultra-low coefficient of thermal expansion (CTE) is required for mounting camera and other optical elements in satellite systems. Invar (64 Fe 36Ni) has been the work-horse material for this purpose. In recent years, modified version of conventional invar i.e. Superinvar with 5% cobalt (replacing 5% nickel) is being used to further bring down the errors in camera mountings due to thermal expansion. Processing of this alloy poses many challenges due to its requirement of ultra-low CTE. In the present work, melting and thermomechanical processing parameters were selected to meet the specified requirement of the alloy. The alloy was melted through vacuum induction melting process to obtain uniform and homogeneous chemistry and properties. Virgin raw material was used to achieve lowest carbon and manganese contents. Chemical composition thus obtained is found to be within the specification.
Material was hot worked to refine the microstructure. Three different sizes of forged blocks were produced. Hot worked material was heat treated to obtain desirable and stable microstructure. Heat treatment cycle for stabilization was selected and used to retain carbon in the solution and minimize temporal growth. Mechanical properties (tensile strength and modulus of elasticity) and physical properties (CTE, thermal conductivity) were evaluated. Properties were found to be meeting the specification. It is observed that the material shows uniform single phase austenitic microstructure. The paper presents details of the process selection and challenges in processing of this alloy to obtain the targeted CTE < 0.6x10-6 per °C in the temperature range of 25°C to 150°C along with other desired mechanical properties.
Experimental Study on the Effect of Tool Pin Profile on Aluminium AA6063 Friction Stir Welded Butt Joint
Authors: Manikkavasagan P. , Rajamurugan G. , Kumar K. Satheesh , Yuvaraj D.
Published: September 2015

In this study, aluminium AA6063 6mm thickness plate were welded by friction stir butt joint, the friction stir welding process is an emerging solid state joining processes in which the material that is being welded does not melt. This process uses a non consumable tool to generate a welding. The welding parameter such as tool rotational speed, welding speed, axial force and tool pin profile play a major role in deciding the joint properties. Two different tool pin profiles (Square and pentagon) have been used to fabricate the joints at constant rotational speed 1500rpm. The effect of welding parameter was evaluated in different mechanical properties of hardness distribution and tensile properties for axial weld zone.
Assessment of Latent Heat and Solid Fraction of Al-22Si Alloy Using Newtonian and Fourier Analysis Techniques
Authors: Vijayan Vijeesh , Prabhu K.N.
Published: September 2015

Computer aided cooling curve analysis (CACCA) is an online prediction tool for the determination of solidification characteristics of metals or alloys. The results of CACCA can be used to accurately determine latent heat and solid fraction needed for modeling of the solidification process. Newtonian and Fourier analysis techniques adopt a data base line fitting technique to the first derivative curve for calculation of the solid fraction and latent heat of solidification. This paper describes the theoretical and experimental procedures involved Newtonian and Fourier analysis techniques with reference to an Al-22% Si alloy. The correlations between the solid fraction and temperature/time for the alloy were determined.
Characterization of Hot Workability of Boron-Added Modified 9Cr-1Mo Steel (P91B) Using Dynamic Materials Model
Authors: Arvinth Davinci Marimuthu , Samantaray Dipti , Borah Utpal , Albert Shaju K. , Bhaduri A.K.
Published: September 2015

Elevated temperature workability of Boron added modified 9Cr-1Mo steel is studied in temperature range 1223-1473K and strain rates of 0.001-10s-1 using Dynamic Materials Model. Towards this end hot isothermal compression tests are carried out and the experimental results are used to obtain processing map. Extensive microstructural investigation is carried out to validate different domains of processing map. On the basis of the microstructurally validated processing map, parameters for the thermomechanical processing of P91B are recommended.
Dry Sliding Wear Behavior of Ti-6Al-4V Alloy
Authors: Anandajothi M. , Ramanathan S.
Published: September 2015

Titanium and its alloys exhibit a unique combination of physical and corrosion resistance properties which make them ideal materials for space flight engine component such as disks and blades of compressor, marine applications, chemical industries and many bio medical applications. However the use of these materials is limited due to its poor tribological properties. Dry sliding wear tests were performed on Ti-6Al-4V using a pin-on-disc (EN31 steel) configuration. Wear rates were measured with different load and sliding velocity at a constant sliding distance. Microstructures of worn surfaces were characterized by scanning electron microscope (SEM) and energy dispersive spectrometer (EDS).
The Effect of Magnesium on the Modifying Efficiency of Strontium in A356 Alloy
Authors: Chacko Anil , Shaji M.C. , Golla Brahma Raju
Published: September 2015

This study was undertaken to investigate the effect of different concentrations of magnesium (0.2%, 0.3%, and 0.4%) on the modifying efficiency of Sr in aluminium alloy A356. Both sand casting and gravity die castings were taken for the same composition. Modifying efficiency was studied quantitatively by measuring the size and shape of Si eutectic particles by using ImageJ image analyser and giving a Modification Rating (MR), developed by American Foundrymen’s Society (AFS), for each microstructure ranging from 1 to 6, 1 being unmodified and 6 being completely modified very fine structures. Characterisation was done with optical microscope and SEM equipped with EDS and XRD. Mechanical testing involved hardness test in both as cast and standard T6 condition.
Investigation of High Temperature Compatibility between Ferroboron and 9Cr-Based Ferritic Steel towards the Development of Indigenous Shield Material for Fast Reactor Applications
Authors: Arun Kumar Rai , Raju Subramanian , Saroja S. , Jayakumar Tammana
Published: September 2015

The feasibility of employing the indigenously developed Ferroboron alloy as an alternate neutron shield material in combination with 9Cr-based ferritic steel clad in future Indian Fast Breeder Reactors (FBR), has been investigated from a metallurgical perspective. In this regard, extensive studies have been undertaken to estimate quantitatively the nature of interaction between Ferroboron and P91-ferritic steel at high temperatures. It is found that in the temperature range 550 to 600°C, 9Cr-based ferritic steel is fully compatible with Ferroboron. However, at higher temperatures, Feroboron interacts with ferritic steel; but the maximum estimated loss of clad thickness is restricted to about 250 μm for 60 years of service.
Electron Microscopic Study of Nodules Formed during Electrodeposition of Copper on Aluminium
Authors: Augustin Arun , Bhat K. Udaya , Udupa K. Rajendra , Hegde Ampar Chitharanjan
Published: September 2015

Copper thin film was deposited on double zincated aluminium using electrodeposition route. To understand the growth behavior of copper nodules, deposition was done by varying coating current density. The topography and cross section of the coating was analyzed by using SEM. The structural details of copper nodules were studied by using TEM. Deposited copper thin film was made up of pomegranate like nodules with size varying from 5 μm to 8 μm, varying as a function of coating current density. At higher current density, the coating was made up of multiple layers of nodules having defects like twins, dislocations and stacking faults. The nodules had fine crystallites of size in the range of 50 nm.
Effect of Si on the Microstructure and Mechanical Properties of Mg-2Sb Alloy
Authors: Rajeshkumar Ramasubbu , Josheph Prince , Srinivasan Amirthalingam , Pillai Uma Thanu Subramonia , Pai Bellambettu Chandrasekhara
Published: September 2015

In the present work the effects of Si (0.5, 1, 1.5 wt%) on the as cast microstructure of Mg-2Sb alloy have been investigated. Si addition forms new Mg-Sb-Si ternary compound in Mg-Sb alloys besides the morphology of Mg3Sb2 changes from needle to chinese scripted and polygonal shaped Mg-Sb-Si ternary compound. The improved room temperature tensile properties are obtained with Mg-2Sb-1Si alloy which is due to the presence of polygonal shaped Mg-Sb-Si ternary compound.
An Experimental Study on Thermal Stability of Age-Hardenable Aluminium Alloys Modified by Scandium Inoculation
Authors: Mandal P.K.
Published: September 2015

The Al-Zn-Mg system is a familiar age-hardenable 7xxx series of aluminium alloy. Aluminium alloys are gaining wide popularity in aeronautical, automotive, and transportation industries. Scandium (Sc) has the ability to refine grain size of cast aluminium structure. It has been possible to achieve an ideal combination of strength, density, and thermal stability because of the unique age-hardening characteristics of Sc. Moreover, low solid solubility of Sc in aluminium is responsible for the improvement of the microstructure and mechanical properties when added in small amounts (≤0.6 wt.%). Further, inoculation is an effective means of grain refinement in liquid state of as-castaluminium alloys. So, density of GP zones formation and early stage of ageing effects assessment main priority in the present work. However, coherent precipitates like ScAl3are finely dispersed to provide thermal stability by increasing recrystallization temperature. Hence, the improvement in the high temperature stability of aluminium alloys (7xxx series) may be attributed to the grain boundary pinning (e.g. Zenerdrag mechanism) by the fine precipitates.In this paper, the relationship between the mechanical behavior and microstructure characteristics of Al-Zn-Mg-Sc based alloys are investigated to understand the thermal stability mechanism of grain refinement and dispersive precipitation.
Effect of Electromagnetic Stirring on the Reciprocating Wear Characteristics of A390 Alloy
Authors: Aswinikumar G.L. , Rajeev V.R. , Jayaraj K. , Ashok Kumar A. , Emmanuvel Bibin , Jose Jeswin
Published: September 2015

Present study reports the effect of electromagnetic stirring (EMS) on reciprocating wear characteristics of A390 alloy. The microstructure features showed the refinement of eutectic silicon and reduction in size of primary silicon particles due to the effect of EMS. Hardness of the A390 alloy (100.28 BHN) prepared by EMS was higher than conventional A390 alloy (66.86 BHN). Reciprocating wear tests were carried out at different contact loads (15N to 90N) and speeds (0.2m/s to 1m/s) using pin-on-reciprocating plate tribometer for a constant sliding distance of 500m. As the reciprocating velocity increases from 0.2m/s to 1m/s, the wear loss of both EMS stirred and without stirred A390 alloys were found to decrease gradually up to the critical velocity 0.6m/s. It was noticed that above critical reciprocating velocity 0.6m/s, the wear loss was found to increase abruptly. Also, as the load increases from 15N to 90N, the wear loss of both the alloys were found to increase gradually up to 45N and thereafter abrupt increase in wear loss was noticed up to 90N. This clearly indicates a transition in the mode of wear from mild oxidative to severe metallic wear regime. Wear rate of without stirred A390 alloy in the region 45N to 90N showed predominant increase compared to EMS stirred A390 alloy. This trend suggests that EMS stirred A390 alloy is more coherent and stable under dry sliding wear conditions than without stirred A390 alloy.
Experimental Investigation and Micro-Structural Evolution Analysis of CNT & Fly Ash Reinforced Aluminium Matrix Composites
Authors: Udaya  , Fernandes Peter
Published: September 2015

The paper illustrates Carbon nanotubes reinforced pure Al (CNT/Al) composites and fly ash reinforced pure Al (FA/Al) composites produced by ball-milling and sintering. Microstructures of the fabricated composite were examined and the mechanical properties of the composites were tested and analysed. It was indicated that the CNTs and fly ash were uniformly dispersed into the Al matrix as ball-milling time increased with increase in hardness.
Effect of Ceramic Particles on Microstructure and Mechanical Properties of Aluminium Surface Composite Fabricated Using Friction Stir Processing
Authors: Thangarasu A. , Murugan N.
Published: September 2015

Friction stir processing (FSP) is a novel technique used to fabricate surface composites. This investigation is an attempt to made Al/Al2O3 and Al/SiC surface composite using FSP and compare the mechanical and metallurgical properties influenced by the types of reinforcement particles. Two plates were grooved with 0.8 mm in width, 5 mm in depth and 100 mm in length in the middle of the aluminium plate using wire EDM and compacted with Al2O3 and SiC powder. The FSP was carried out automatically on an indigenously built FSW machine at tool rotational speed of 1200 rpm, processing speed of 60 mm/min and axial force of 10 kN. The optical and Scanning Electron microstructures are precisely revealed the homogeneous distribution of Al2O3 and SiC particles in the stir zone of surface composite layer (SCL). The microhardness was measured across the cross section of SCL layers of Aluminium and Aluminium with SiC and Al2O3. The higher microhardness was obtained in Aluminium with SiC and Al2O3 composites fabricated by FSP. This is because of the higher hardness value of SiC particles than Al2O3 particles.
Permittivities of Ultra-Low Dielectric Silica Beads and Aerogels
Authors: Nagapriya S. , Masin B. , Sreemoolanadhan H. , Ajith M.R. , Mathew Mariamma , Sharma S.C.
Published: September 2015

Materials with relative permittivity or dielectric constant near to that of air (εr~1) are known as ‘ultra-low k’ materials. They find a number of applications in inter-connects of micro-electronic circuits, antennae, high-speed communication substrates etc. Among the inorganic materials, porous silica is the widely studied candidate. Porous silica can be of many types depending upon the extent of porosity and size and connectivity of pores. This paper presents the details of measurement of permittivities and the results of silica beads and silica aerogels. Silica beads, prepared by microwave heating of silica gels, are spherical beads of average 1mm size. Hydrophobic silica aerogels, prepared by ambient pressure drying of silica gels, are irregular chunks of 5-10 mm size. Both are potential bulk fill insulation materials and hence the permittivity can be measured as an aggregate filling a definite volume. The permittivities of these have been measured upto 1 MHz by 3-terminal method using a precision LCR meter and a powder-paste cell as per ASTM-D150-11. The εr values of silica aerogels and silica beads in 20 Hz-1 MHz range could be measured and are less than 1.6 at 1 MHz.
Development of Novel Al-Alloy (Al-5Mg)/10Wt.%TiB2 Metal Matrix Composites by In Situ Reaction Synthesis
Authors: Nimbalkar V.M. , Pandav S.G. , Mohape M.R. , Deshmukh V.P. , Deole S. , Tambavekar A.S. , Baviskar V.R. , Sable S.R. , Chitale M.M.
Published: September 2015

The present paper describes a cost effective route to produce Al alloy-10 wt % TiB2 metal matrix composites by in-situ molten flux assisted reaction synthesis. Now a days main focus is given to aluminium alloy as a matrix material due to its unique combination of good corrosion resistance, low density, superior mechanical properties, good vibration damping, higher wear resistance due to which alloy finds extensive applications in naval applications. With TiB2 as particulate addition in Al-Alloy (Al-5Mg) matrix properties of alloy can greatly be improved.
Enhanced Transport Current in MgB2 Superconducting Wire through Metallic Fe Addition
Authors: Varghese Neson , Kavazhikath Mohandas Devadas , Pillai Mohan Aswathy , Jayakumari Babu Anooja , Raama Varma Manoj , Upendran Syamaprasad
Published: September 2015

The structural and superconducting properties of iron sheathed mono-filamentary superconducting wires of MgB2 with and without Fe addition processed at a relatively low temperature of 600 °C were investigated. The transport critical current density (JC) of the superconducting composite wires is found to increase steadily with an increase in Fe content to an optimum of 10 wt.% is reached. The magnetic JC and flux pinning analysis of the samples carried out up to a field of 9 T also show significant enhancements throughout the entire field of study. Another observation is that the TC of the composites doesn’t vary much, indicating that the added Fe has not gone in to the MgB2 lattice.
Bioactivity of Chemically Modified Porous Titanium
Authors: Dey Reshmi , Nanda Pranjali , Thirugnanam Arunachalam
Published: September 2015

The aim of the present investigation is to enhance in-vitro bioactivity and protein adsorption of porous titanium with 3D interconnected pores by various chemical treatments (alkali, dual acid, citric acid and fluoride treatments). The untreated and treated samples were characterized using X-ray powder diffraction (XRD), optical microscopy and scanning electron microscopy (SEM). The protein adsorption study was carried out with Bradford’s reagent using Bovine Serum Albumin (BSA). The optical microscopy reveals that untreated Ti sample exhibited 41.36% surface porosity. The in-vitro bioactivity of the treated and untreated Ti sample was evaluated by immersing them in simulated body fluid (SBF) for different time intervals. The immersed samples were characterized using XRD and SEM to confirm the growth and morphology of apatite. It was observed that apatite deposition of fluoride treated sample was denser than other treated samples for the same period immersed in SBF. All the surface treated samples showed good protein adsorption. The alkali treated sample showed maximum protein adsorption amongst other chemically treated samples which may be due to enhanced micro-roughness and strong electrostatic affinity between the protein and the surface. The enhanced in vitro bioactivity in the surface treated porous titanium indicates that the healing time of the bone and implant in patients can be reduced with good osseointegration.
Fused Silica Filled Silicone Rubber Composites for Flexible Electronic Applications
Authors: Namitha L.K. , Sebastian M.T.
Published: September 2015

Silicone rubber composites filled with fused silica were prepared through sigma mixing followed by hot pressing. Filling fraction of fused silica in the silicone rubber matrix was varied from 0-0.51 volume fraction (Vf) and its effects on dielectric properties at different frequencies, thermal properties and moisture absorption were investigated. The results indicate that with the increase of filler volume fraction the relative permittivity increases and dielectric loss decreases. The coefficient of thermal expansion decreased and the moisture absorption increased marginallyas the filler loading increased.
High Specific Strength Carbon Foam Prepared from Sucrose and Multi-Walled Carbon Nanotube
Authors: Narasimman Rajaram , Vijayan Sujith , Prabhakaran Kuttan
Published: September 2015

Multi-walled carbon nanotube (MWNT) reinforced carbon foams were prepared by thermo-foaming of MWNT dispersions in molten sucrose followed by dehydration and carbonization. The rheological studies showed that the uniform dispersion of MWNT was achieved up to 1.5 wt.%. The carbon foams showed cellular structure. The density of the carbon foams increased with an increase in the MWNT concentration up to 0.25 wt.% and then remained more or less constant. The maximum compressive strength of 4.9 MPa was achieved at the MWNT concentration of 0.5 wt.%.
Potential of Electrospun Graphene Oxide-Gelatin Composite Nanofibers for Biomedical Applications
Authors: Jalaja K , Nirmala R. James
Published: September 2015

Graphene oxide incorporated polymer matrix provides a multifunctional facet due to the reinforcing effect of graphene oxide (GO) with wide range of properties. Nanofibers are fabricated by a versatile technique known as electrospinning. The present study demonstrates the fabrication of gelatin, a protein nanofibers non-covalently functionalized with GO. The effect of GO on gelatin nanofibers in terms of mechanical performance is studied. In order to improve the water resistance of the resulting nanofibers, cross-linking is performed using dextran aldehyde.
Structural and Magnetic Investigation of Cu, Co Substituted NiFe2O4 Thin Films by Scanning Probe Microscopy (AFM, MFM)
Authors: Sharma Hakikat , Negi N.S.
Published: September 2015

In the present study we prepared NiFe2O4, Ni0.95Cu0.05Fe2O4 and Ni0.94Cu0.05Co0.01 Fe2O4 thin films by metallo-organic decomposition method (MOD) using spin coating technique. The samples were characterized by XRD. XRD patterns of thin films confirmed the formation of cubic spinel structure without any secondary phase. For microstructural analysis we characterized samples by Scanning Probe Microscope (SPM). From Atomic force microscopy (AFM), we analyzed surface morphology, calculated grain size, roughness and porosity. It has been found that grain size and roughness affected by Cu, Co substitution. After this we carried out magnetic force microscopy (MFM) on the samples. Effect of substitution on magnetic grains was observed from MFM.
Synthesis and Characterisation of Ternary Nanocomposites as Cathode Material for Lithium-Sulphur Batteries
Authors: Reshma C. , Mary Gladis J.
Published: September 2015

The lithium-sulphur (Li-S) system is one of the most promising candidates for high energy density applications. Sulphur has several drawbacks such as poor conductivity, large volumetric expansion upon lithiation, dissolution of the intermediate polysulfides during charge-discharge processes. The objective of the present work is to prepare a ternary composite of MWCNT/S/conducting polymer system with unique characteristics to be used as a cathode material for lithium sulphur batteries. The synthesis has been carried out in two steps. Sulphur is introduced onto the surface of MWCNT by the chemical reaction between sodium thiosulphate and hydrochloric acid. In the second step, polyindole is produced by insitu reaction from indole monomer by using FeCl3 as oxidising agent. The MWCNT and conducting polymer help to improve the conductivity of sulphur. The composite material is characterised by TGA, FTIR, SEM-EDS and XRD analysis. The polyindole formation is confirmed by using FTIR and SEM-EDS. Electrochemical studies have been performed to demonstrate MWCNT/sulphur/polymer composites as a cathode material for rechargeable lithium –sulphur batteries.
Effect of Micro Arc Oxidation Treatment on the Corrosion and Stress Corrosion Cracking (SCC) Behaviours of AA7020-T6 Aluminum Alloy in 3.5% NaCl Solution
Authors: Venugopal A. , Ramesh Narayanan P. , Sharma S.C. , George Koshy M.
Published: September 2015

Alumina coating was formed on AA7020 aluminum alloy by micro arc oxidation (MAO) method and its corrosion and stress corrosion cracking (SCC) behaviors were examined in 3.5 wt. % NaCl solution. Potentiodynamic polarization (PP) was used to evaluate the corrosion resistance of the coating and slow strain rate test (SSRT) was used for evaluating the environmental cracking resistance in 3.5% NaCl solution. Results indicated that MAO coating on AA7020 alloy significantly improved the corrosion resistance. However the environmental cracking resistance was found to be only marginal.
Key words: aluminum, micro arc oxidation, x-ray diffraction, stress corrosion cracking
Effect of Process Parameters on Anodization of AA7075
Authors: Chand Sudhanshu , Jalali Koushik , Oommen George , Chakravarthy P. , Murugesan N. , Arun Prakash N.V. , Manickavasagam A.
Published: September 2015

The influence of the major process parameters for anodizing AA7075 is investigated to obtain an anodized layer with minimum porosity with approximately 15μm thickness. Anodization was carried out in a sulphuric acid bath with well-defined process parameters and the anodized layer thickness & Inter pore distance were measured for the chosen process parameter combinations. Porosity index was calculated and an optimized parameter combination was obtained. Voltage was found out to be most influencing parameter in the determination of porosity and thickness. In addition to this, surface finish of the non-anodized and anodized specimens was also compared. It was found out that surface finish of the specimen decreased after anodization. A statistical data model was prepared for thickness and porosity using the data obtained from experiments.
Enhancing Tribological and Corrosion Resistance of Hastelloy C-276 through Laser Surface Treatment
Authors: Hashim M. , Duraiselvam Muthukannan
Published: September 2015

Hastelloy C-276 is a nickel-based super alloy which has inbuilt corrosion resistance and exhibits low wear resistance. In this work, an attempt has been made to improve the tribological properties of this alloy without sacrificing the corrosion properties by laser surface melting in argon atmosphere. The results indicated better grain refinement at optimum laser parameters of 1.5 kW and 300 mm/min thereby exhibiting a maximum hardness of 447 HV.The corrosion rate for the entire laser treated samples showed a decreasing trend with a minimum value of 2.07172 x10-2 mm/year, compared to base alloy. This paper demonstrates that laser surface melting is a viable method to improve the wear and corrosion properties of Hastelloy C-276.
AlN-TiB2 Based Self-Lubricating Ceramic Insert Fabricated by Spark Plasma Sintering for Dry Turning Applications
Authors: Nambiraj K.M. , Rajeswari R. , Madhavan S.
Published: September 2015

This paper reports the development of a cutting tool insert prepared by consolidation, followed by Spark Plasma Sintering (SPS) of TiB2 (Titanium diboride) particles processed through an in-situ reaction and AlN (Aluminium nitride) manufactured by the direct nitridation process. In-situ TiB2 particles, formed during reaction of KBF4 (Potassium tetra Fluoroborate) and K2TiF6 (Potassium Fuorotitanate) with Al alloy, are obtained by dissolving the Al-TiB2 composite in an acidic medium. The extracted TiB2 (30%) particles are blended with AlN and Al2O3 in the weight ratio of 67%-3% and sintered (SPS) at 1440°C with a compaction load of 50 MPa and a total sintering time of 8 minutes. The sintering is carried out in vacuum. The sintered ceramic displays high hardness of nearly 15.5 GPa and extraordinary toughness of 7MPa.m1/2. The inserts are manufactured according to SNGN (Square Double-sided ceramic) configuration. To study its performance, machining is carried out on hardened steel (EN 24). The developed AlN based inserts show increased wear resistance and provide good surface finish when compared with commercially available ceramic inserts (70%Al2O3+30%TiC). Cutting forces are recorded with a Kistler® dynamometer to correlate them with the tool wear. Methods of preparation and comparison of wear resistance and surface finish of the machined material with those pertaining to commercial ceramic inserts are also presented. SEM images are displayed, which support the results.
Ultrasonic-Assisted Electroless Coating of Ni-B Alloy and Composites on Aluminum Alloy Substrates
Authors: Pancrecious Jerin K. , Deepa J.P. , R Ramya , Rajan T.P.D. , Gowd E. Bhoje , Pai B.C.
Published: September 2015

Electroless nickel coating is one of the versatile methods to improve the physical properties of aluminium alloys. The increasing demand for high corrosion resistant surface with improved performance leads to the development of poly-alloy and composite coatings with the aid of ultrasonication. In the present study Ni-B alloy and Ni-B-CeO2 composite coatings were made on 356 aluminium alloy surfaces. The variation in structural and mechanical properties of coatings formed under both ultrasonication and magnetic stirring were investigated. Surface analysis by scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) has shown the formation of more uniform coating under ultrasonication. The electrochemical polarization tests show enhanced corrosion resistance in ultrasonic assisted coatings.
Atomic Oxygen Resistant Polysiloxane Coatings for Low Earth Orbit Space Structures
Authors: Arjun G.N. , Lincy T.L. , Sajitha T.S. , Bhuvaneshwari S. , Deepthi Thomas , Devapal Deepa
Published: September 2015

Polysiloxane resin copolymer was synthesized through acid catalyzed hydrolysis of methyl triethoxysilane (MTEOS) and diethoxytetramethyldisiloxane (DEOTMDS). The effect of reaction time on the properties of the polymer was studied and this copolymer was characterized by GPC, 29Si NMR, IR, TGA, viscosity, refractive index, specific gravity and solid content. 29Si NMR and IR showed characteristic signals of Si-O-Si linkage which confirmed the formation of the polymer. GPC and solid content analysis showed an increasing trend in molecular weight with reaction time. Thermo gravimetric analysis showed that the polymer was thermally stable upto ≈ 260°C and all the polymers gave a ceramic residue in the range of 77-80% at 900°C. Siloxane prepared inhouse and methyl phenyl silsequioxane (control) were used as coating materials and atomic oxygen (AO) resistance was evaluated on Al-Kapton, carbon polyimide composite and glass polyimide composite. The mass loss and surface morphology of the coated samples were measured at different time intervals. It is observed that mass loss of polysiloxane coated samples was very less, compared to coated control samples. The morphology of all the samples were studied using FESEM. Erosion kinetics and surface morphology investigation indicate that the polysiloxane coating possesses excellent AO resistance, and displays better cracking resistance on AO exposure.
An Enhancer of the IL-7 Receptor α-Chain Locus Controls IL-7 Receptor Expression and Maintenance of Peripheral T Cells
Authors: Abe Akifumi , Tani-ichi Shizue , Shitara Soichiro , Cui Guangwei , Yamada Hisataka , Miyachi Hitoshi , Kitano Satsuki , Hara Takahiro , Abe Ryo , Yoshikai Yasunobu , Ikuta Koichi
Published: September 2015

The IL-7R plays critical roles in lymphocyte development and homeostasis. Although IL-7R expression is strictly regulated during lymphocyte differentiation and the immune response, little is known regarding its in vivo regulation. To address this issue, we established a mouse line with targeted deletion of the conserved non-coding sequence 1 (CNS1) element found 3.6 kb upstream of the IL-7Rα promoter. We report that IL-7Rα is expressed normally on T and B cells in thymus and bone marrow of CNS1−/− mice except for in regulatory T cells. In contrast, these mice show reduced IL-7Rα expression in conventional CD4 and CD8 T cells as well as regulatory T, NKT, and γδ T cells in the periphery. CD4 T cells of CNS1−/− mice showed IL-7Rα upregulation in the absence of growth factors and IL-7Rα downregulation by IL-7 or TCR stimulation, although the expression levels were lower than those in control mice. Naive CD4 and CD8 T cells of CNS1−/− mice show attenuated survival by culture with IL-7 and reduced homeostatic proliferation after transfer into lymphopenic hosts. CNS1−/− mice exhibit impaired maintenance of Ag-stimulated T cells. Furthermore, IL-7Rα upregulation by glucocorticoids and TNF-α was abrogated in CNS1−/− mice. This work demonstrates that the CNS1 element controls IL-7Rα expression and maintenance of peripheral T cells, suggesting differential regulation of IL-7Rα expression between central and peripheral lymphoid organs.
Delinking CARD9 and IL-17: CARD9 Protects against Candida tropicalis Infection through a TNF-α–Dependent, IL-17–Independent Mechanism
Authors: Whibley Natasha , Jaycox Jillian R. , Reid Delyth , Garg Abhishek V. , Taylor Julie A. , Clancy Cornelius J. , Nguyen M. Hong , Biswas Partha S. , McGeachy Mandy J. , Brown Gordon D. , Gaffen Sarah L.
Published: September 2015

Candida is the third most common cause of bloodstream infections in hospitalized patients. Immunity to C. albicans, the most frequent species to be isolated in candidiasis, involves a well-characterized Dectin-1/caspase-associated recruitment domain adaptor 9 (CARD9)/IL-17 signaling axis. Infections caused by non-albicans Candida species are on the rise, but surprisingly little is known about immunity to these pathogens. In this study, we evaluated a systemic infection model of C. tropicalis, a clinically relevant, but poorly understood, non-albicans Candida. Mice lacking CARD9 were profoundly susceptible to C. tropicalis, displaying elevated fungal burdens in visceral organs and increased mortality compared with wild-type (WT) controls. Unlike C. albicans, IL-17 responses were induced normally in CARD9−/− mice following C. tropicalis infection. Moreover, there was no difference in susceptibility to C. tropicalis infection between WT and IL-23p19−/−, IL-17RA−/−, or Act1−/− mice. However, TNF-α expression was markedly impaired in CARD9−/− mice. Consistently, WT mice depleted of TNF-α were more susceptible to C. tropicalis, and CARD9-deficient neutrophils and monocytes failed to produce TNF-α following stimulation with C. tropicalis Ags. Both neutrophils and monocytes were necessary for defense against C. tropicalis, because their depletion in WT mice enhanced susceptibility to C. tropicalis. Disease in CARD9−/− mice was not due to defective neutrophil or monocyte recruitment to infected kidneys. However, TNF-α treatment of neutrophils in vitro enhanced their ability to kill C. tropicalis. Thus, protection against systemic C. tropicalis infection requires CARD9 and TNF-α, but not IL-17, signaling. Moreover, CARD9-dependent production of TNF-α enhances the candidacidal capacity of neutrophils, limiting fungal disease during disseminated C. tropicalis infection.