bluuebunny/crossref_metadata_2025 huggingface dataset:
Studies on Friction Stir Welding of Al-Cu-Li (AA2195) Alloy
Authors: Agilan M. , Anbukkarasi R. , Venkateswran T. , Panicker Paul G. , Kailas Sathish V. , Sivakumar D. , Pant Bhanu
Published: September 2015

For aerospace applications, Al-Cu-Li alloys are more attractive than conventional aluminum alloys due to their low density, high modulus and high strength. AA2195 is a third generation Al-Li alloy, developed with improved weldability. In this study, AA2195 alloy of 5mm thick sheets were welded by friction stir welding process (FSW). Tool rotational speed was varied from 400 rpm to 1000 rpm at constant travel speed of 60mm/min. Optimum tool rotation speed was identified and defect free weld coupons were processed with optimized parameter. Mechanical properties and micro structural characterization have been conducted on FSW welds.
Vacuum Brazing of Molybdenum – Kovar and Evaluation of its Joint Strength
Authors: Kumar Sandeep , Upadhyay Abhishek , Dinesh Kumar Pal , Agarwal Arun
Published: September 2015

This paper explains the technique of vacuum brazing for joining Molybdenum and Kovar. Joining of Molybdenum and Kovar is difficult because of difference in their mechanical properties and Melting Points. Kovar is an alloy of Fe, Ni , Co (composition : Ni 29% , Co 17% , rest Iron) . Molybdenum is a refractory material and its joint with Kovar is used for high temperature applications. Various parameters affecting the vacuum brazing process , vacuum furnace and factors affecting joint strength are discussed.Vacuum brazing of Molybdenum and Kovar samples was carried out inside vacuum brazing furnace using Copper a filler material. Vacuum level of furnace hot zone was maintained better than 10-6 mbar. The joint-strength was evaluated in Universal testing machine with the help of fixtures as per AWS C 3.2 Standard for testing strength of brazed joints. Ram tensile test was conducted. Factors affecting the joint strength of brazed joints like external compressive weight, diffusion of filler material into the parent materials, surface roughness of parent materials, surface flatness have been discussed. Joint strength of 75 MPa is obtained. Failure was found at the brazed joint interface.
Wetting Kinetics and Joint Strength of Sn-0.3Ag-0.7Cu Lead-Free Solder Alloy on Copper Substrate as a Function of Reflow Time
Authors: Sona Mrunali , Narayan Prabhu K.
Published: September 2015

Solder plays a vital role in the interconnection of electronic devices in electronic assemblies. As an interconnection material, the solder joint executes electrical, mechanical and thermal functions. The use of lead bearing solders in electronic products is banned due to the toxicity and environmental risks coupled with lead. In the present study, wetting kinetics, interfacial reactions and the formation of intermetallic compounds (IMCs) during solidification of Sn-0.3Ag-0.7Cu solder alloy on Cu substrate and the corresponding joint strength were studied as a function of reflow time. Experiments were carried out at various reflow times of 10, 100, 300 and 500s. The reflow temperature was maintained at 270°C. The solder alloy showed enhanced wettability on the substrate at longer reflow times. The thickness of IMC layer formed during a reflow time of 10s was 1.67μm and the thickness increased to 2.20μm, 2.85μm, 2.91μm during 100s, 300s and 500s of reflow time respectively. The joint shear test was performed to assess the integrity of Sn-0.3Ag-0.7Cu solder solidified on Cu substrates using Nordson DAGE 4000 Plus bond tester. The joint strength increased with the increase in reflow time up to 300s and the maximum joint strength was observed for samples reflowed for 300s. Although the samples reflowed for 500s samples showed good wettability, they exhibited lowest joint strength.
Effect of Brazing and Heat Treatment Cycle on the Mechanical Properties of Base Materials
Authors: Dileep Kumar N. , Thomas Tharian K. , Isaac Aby , Venkitakrishnan P.V.
Published: September 2015

Brazing is extensively used in liquid rocket engines for realizing various subsystems. In the case of cryogenic engines, brazing operation is done to realize the gas generator. Gas Generator is one of the major systems of cryogenic engine. It generates and supplies hot gases required for running turbine of main turbo pump. This uses liquid oxygen and gaseous hydrogen as propellant combination. Combustion chamber of Gas Generator is of double walled construction with the cylindrical outer shell of transition class ICSS-0716-301 austenitic-martensitic stainless steel and inner shell of ICSS-1218 321, aTi stabilized austenitic stainless steel material brazed together with Fe-Ni-Mn type braze alloy at a temperature of 1180°C. This temperature can cause the grain growth and related issues to the base material. Thus the present work focuses on the effect of the brazing/thermal cycle on mechanical properties and microstructure of the base materials in post braze condition. The results obtained on metallurgical/mechanical behavior of the material showed the different grain growth patterns in inner and outer shell materials. This helped in understanding the effect of brazing condition on the changes in mechanical properties of base materials.
Determination of Instability in Zr-2.5Nb-0.5Cu Using Lyapunov Function
Authors: Saxena Kuldeep Kumar , Pancholi Vivek , Srivastava Dinesh , Dey G.K. , Jha Sanjay K. , Saibaba Nudurupati
Published: September 2015

Hot workability of Zr-2.5Nb-0.5Cu alloy has been investigated by means of hot compression test using Gleeble-3800®, in the temperature and strain rate range of 700 to 925°C and 0.01-10s-1, respectively. Deformation behavior was characterized in terms of flow instability using peak stress with the help of Lyapunov Function. The true stress-strain curves shows that softening occurs at all lower temperature and for entire strain rates of deformation. The instable flow was suggested by negative m value at deformation condition of 700°C (5 and 10 s-1), while s value at 925°C (10 s-1). The combined result of rate of change of m and s with respect to log strain rate suggest that the deformation condition ranges from 725-780°C (10-2- 10-1 s-1) and 700°C (1-10 s-1) representing safe domain for stable flow.
Effect of Grain Size on Deformation Twinning Behavior of Ti6Al4V Alloy
Authors: Kumar Saxena Ashish , Anupoju Manikanta , Tewari Asim , Pant Prita
Published: September 2015

An understanding of the plastic deformation behavior of Ti6Al4V (Ti64) is of great interest because it is used in aerospace applications due to its high specific strength. In addition, Ti alloys have limited slip systems due to hexagonal crystal structure; hence twinning plays an important role in plastic deformation. The present work focuses upon the grain size effect on plastic deformation behaviour of Ti64. Various microstructures with different grain size were developed via annealing of Ti64 alloy in α-β phase regime (825°C and 850°C) for 4 hours followed by air cooling. The deformation behavior of these samples was investigated at various deformation temperature and strain rate conditions. Detailed microstructure studies showed that (i) smaller grains undergoes twinning only at low temperature and high strain rate, (ii) large grain samples undergo twinning at all temperatures & strain rates, though the extent of twinning varied.
Microstructure Control and Mechanical Property Correlation in Titanium Alloy Ti-6Al-4V Fasteners for Space Applications
Authors: Narayana Murty S.V.S. , Manwatkar Sushant , Ramesh Narayanan P.
Published: September 2015

High strength fasteners of Titanium alloy Ti-6Al-4V are widely used in both launch vehicle and satellite structures. Ti-6Al-4V fasteners having three different types of microstructures were analysed for mechanical properties to understand the role of two phase α+β or transformed β phase in the head region. Based on the microstructure-mechanical property correlations, it was concluded that the presence of transformed beta phase will not affect the strength properties, but will produce scatter in percentage elongation, percentage reduction in area and failure torque values. Therefore, it is recommended that the microstructure of aerospace titanium alloy Ti-6Al-4V fasteners should contain homogeneous two phase α+β throughout.
Characteristics of Functionally Graded Bimetallic Aluminium Alloys by Sequential Casting Technique
Authors: Karun Akhil S. , Sanil Hari , Rajan T.P.D. , Pillai Uma Thanu Subramonia , Pai B.C.
Published: September 2015

Light weight aluminium alloys and low-density materials have drawn the attention of researchers as potential structural materials for transportation sector due to the requirement of effective reduction in fuel consumption, stringent emission norms and higher payload capacity. Functionally Graded Materials (FGM) provides variation in properties and better functional performance within a component. Sequential casting is fairly a new technique to produce functionally graded materials and components by controlled mould filling process. Bimetallics of aluminium alloys are prepared by sequential casting using A390-A319 alloy (cast-cast alloy) and A390-A6061 alloy (cast-wrought alloy) combination and solidified under gravity. The effect of temperature of the two melts and gap between pouring of the melts on microstructure and properties of the bimetals are investigated. The microstructures show good interface bonding between the two different alloy metals. The hardness testing shows higher hardness at hypereutectic alloy region. The process described in this study shows potential and effective approach to create good bonding between two different aluminium alloys to develop advanced functional and structural materials which can be used in various automobile components to reduce the overall weight of the vehicle, by which better fuel efficiency and performance can be achieved.
Characterization of the Electrical Discharge Machined M300 Maraging Steel Flexures Using Nanoindentation
Authors: Srinath J. , Sudarshan Rao G. , Nagamalleswara Rao G. , Chaman Joji J. , Ramesh Narayanan P. , Sharma S.C. , George Koshy M.
Published: September 2015

Gyroscope is an orientation determining sensor whose performance is mainly dependant on one of the critical element called the gimbal flexure. Thinner the flexure, better is the performance. To have sufficient strength, M300 maraging steel is used to fabricate the thin flexures machined by Electrical Discharge Machining (EDM) process down to the required thickness of 0.05 mm in various stages. After the EDM processing, the recast layer formed can cause degradation in the microstructure and mechanical properties. Micro-abrasive machining was carried out to remove the recast layer.
An attempt was made to understand the changes that occurred after EDM and after micro-abrasive machining with respect to the microstructure using optical and Scanning Electron Microscopy (SEM) and with respect to mechanical properties using nanoindentation. Nanoindentation technique was adopted as the recast layer was just few microns thick. Indentations were carried out on the base material, as EDM cut flexure, and the micro-abrasive machined EDM cut flexure to obtain elastic modulus and hardness values for each condition and the results were analyzed.
Characterization of ZnO Films Produced by Thermal Evaporation and Oxidation
Authors: Prabukumar C. , Jayalakshmi M. , Udaya Bhat K.
Published: September 2015

ZnO nanostructures such as nanowires and nanorods are beneficial in solar energy harvesting because they provide a structure with a large surface area. Also, they provide a direct pathway to electron transportation, eliminating the scope for grain boundary scattering. In this investigation, thin ZnO films were prepared by thermal evaporation of the Zn metal, which was followed by oxidation. Evaporation parameters and oxidation temperatures were fixed. The oxidation duration was the variable. The effect of oxidation time, on the morphology and structural properties were studied by using scanning electron microscopy and X-ray diffractometry. The study shows that with increase in oxidation time, the morphology changed to nanorods from initial flake morphology. As a function of oxidation time, the crystallinity and texture became more dominant. By using, I-V characteristic curves, it was found that the morphology changes alter the surface electrical conductivity of the prepared ZnO films.
Development of a Novel Ablative Composite Tape Layup Technology for Solid Rocket Motor Nozzle and Liquid Engine Liners
Authors: Mohan Kumar L. , Usha K.M. , Anandapadmanabhan E.N. , Chakravarthy P.
Published: September 2015

Solid rocket motor nozzles and liquid engine throats use ablative composite materials to protect the structures from the extremely severe operating conditions of high temperature, pressure and particle impingement. These ablative nozzle liners are processed from carbon phenolic/silica phenolic prepregs using a complex processing cycle. The process starts from impregnating the fibres with phenolic resin followed by either moulding or wrapping/winding prepreg tapes over metallic mandrels followed by polymerization under pressure. Traditionally, prepreg is cut into straight tapes and wound on mandrels to form the divergents. For throats and convergents, prepreg patterns are cut and stacked for curing. Plies of shape conforming to the development of base cone are cut from the prepreg and wound on the mandrel. After polymerization, the final required configuration is machined from this cylindrical blank after the liners are cured. The new method, described in this paper, replaces the straight-cut prepreg tapes by bias-cut prepreg tapes. These can be used for ablative liners in which the plies are at an angle to the direction of the flow. Bias tapes are cut at 45° to the warp and weft directions of the fabric to the required width and formed to the required frustum of cone. Since the cone is formed from straight cut bias tape, the fibre construction will be uniform around the circumference unlike the pattern cut tape. The efficiency of this process depends on the wrapping ratio which is in turn a function of the diameter, ply angle and tape width. To get the best wrapping ratio, shaped mandrels are used which brings down the material wastage and machining allowances. This paper describes the attempts to develop the Bias wrapping technology for angle wound liners. The details of process trials, challenges faced and how they were overcome, advantages of the process over conventional process etc are explained. Exhaustive material characterization of the material was done. Property comparison and validation of performance in subscale tests and a full scale static test are also discussed. The analysis indicates that this new technology has good potential in replacing the traditional tape-winding technology for rocket motor nozzle liners.
Development of Patch Antenna Substrate in BaO-4.TiO2 System
Authors: Sreemoolanadhan Hariharan , Masin Basheer , Mathew Mariamma , Sharma S.C.
Published: September 2015

BaTi4O9(BT4), has dielectric constant (εr)≈36 and unloaded Q-factor (Qf) >35,000GHz, but has temperature coefficient of frequency (τf~16-20ppm/°C). Ba2Ti9O20(B2T9), very near to BT4 in the BaO-TiO2phase diagram, has εr~38, Qf~35,000GHz and τf<4ppm/°C. Though this phase is selected for most of the applications, there are many challenges like slow formation, decomposition, reaction with substrate etc. But, BT4 formed quickly and densified easily, but only high τf precluded it from many practical applications. Most of the literature on the modification of BT4 decreased the εr≤35. Here, the preparation and properties of ZnO/ZnTiO3added BaTi4O9ceramics are reported. The ceramics have been prepared by the solid state method. Raw materials have been homogenized and calcined at 1125°C. Calcined powders are ball-milled, compacted and sintered in 1275−1350°C to get dense ceramics with ρ=4.38-4.44 g/cc (TD>97.5%). XRD analysis has confirmed the BaTi4O9phase formation along with secondary phases. FeSEM microstructures show liquid phase assisted sintering leading to fused grains and exaggerated grain growth. The dielectric properties have been measured near 4GHz by standard rod resonator methods using cylindrical specimens. The ceramics have εr36.5−38, τf<11ppm/°C and Qf>17THz. It is possible to further improve the Qf of these ceramics by controlling the processing.
Processing and Characterization of Hypoeutectic Functionally Graded Aluminum – SiC Metal Matrix Composites
Authors: Jayakumar E. , Jacob Jibin C. , Rajan T.P.D. , Joseph M.A. , Pai B.C.
Published: September 2015

The present study describes the processing and characterization of hypoeutectic A319 functionally graded Aluminium metal matrix composite (FGMMC) reinforced with 10 weight percentage SiCp particles of 23 μm size. FGMMC’s are processed by liquid stir casting method followed by vertical centrifugal casting. Metallographic analysis of FGMMC casting reveals the influence of the centrifugal force on the gradation of various phases in the matrix and an increasing gradient distribution of SiC reinforcements gradually from inner towards the outer periphery forming different zones. Tensile and the compressive tests show that the variation in properties are structure sensitive and is confirmed by the dry wear tests. The study clearly depicts the gradient nature in the structure and mechanical properties of the FGM castings produced by centrifugal casting method.
Effect of Ultrasonic Treatment on Microstructure and Mechanical Property of In Situ Al/2TiB Particulate Composites
Authors: Nampoothiri Jayakrishnan , Raj Baldev , Ravi K.R.
Published: September 2015

Al/2TiB2in-situ composite was fabricated using salt-melt reaction method. Subsequently, it was re-melted and treated with high intensity ultrasonic waves for various time intervals. Substantial reduction in TiB2 particle size down to ~ 300 nm along with significant improvement in dispersion is achieved with the aid of ultrasonic treatment. Ultrasonic treatment has resulted significant increase in hardness of Al/2TiB2in-situ composite.
Hydrophobic Silica Aerogels by Ambient Pressure Drying
Authors: Nagapriya Srinivasan , Ajith M.R. , Sreemoolanadhan H. , Mathew Mariamma , Sharma S.C.
Published: September 2015

Silica aerogels have been prepared through sol-gel process by polymerization of TEOS in the presence of NH4F and NH4OH as catalysts. The solvent present in the gel is replaced by ethanol followed by a non-polar solvent such as n-hexane prior to solvent modification step. Gels are made hydrophobic by treating them with HMDZ to prevent rupture during drying, which has been confirmed by FTIR. Gels are then washed and dried carefully in a PID controlled oven at atmospheric pressure. The ageing duration and solvent exchange combinations are optimized to yield crack-free gels prior to drying. Aerogels are characterized for density, specific surface area, pore volume, pore size, thermal stability and contact angle. Hydrophobic, high surface area (570 m2/g), low density (0.07 g/cm3) silica aerogels are synthesized by using optimized mole ratio of precursors and catalysts. Silica aerogel granules (1-3 mm) as well as monoliths (Ф~35 mm) could be produced through ambient pressure drying of gels.
Processing and Characterization of Functionally Graded In Situ Aluminum Composite
Authors: Arsha A.G. , Jayakumar E. , Rajan T.P.D. , Pai Ballembettu Chandrasekhar
Published: September 2015

A390 functionally graded material (FGM) pistons were fabricated by centrifugal casting, where the silicon particles were segregated in the head portion of the pistons by appropriate design and their density differences. Centrifugal casting offers casting of cylindrical structures with gradation in its properties. In centrifugally cast A390, a suitable die design can lead to the formation of hard primary Si particles gradually distributed towards the head region producing a particle rich zone, transition zone and matrix rich zone. Microstructure and chemical composition analysis confirms the composition gradation. Hardness and wear test results revealed that the gradation positively helps to improve the desired properties with the presence of in-situ primary silicon reinforcements.
Green Route Synthesis, Structural and Luminescence Studies of Mg-Doped Y2O3 Nnanophosphor
Authors: Prasannakumar J.B. , Ramgopal G. , Daruka Prasad B. , Basavaraj R.B. , Nagabhushana H. , Anantharaju K.S. , Prashantha S.C.
Published: September 2015

We report the synthesis of Y2O3:Mg2+ (0.5-9mol %) nanoparticles (NPs) with different morphologies via ecofriendly, inexpensive and simple low temperature solution combustion method using Aloe Vera gel as fuel. The formation of different morphologies was characterized by PXRD, SEM, UV-Visible, PL techniques etc. The PXRD data confirms the formation of single phase Y2O3 with cubic crystal structure. The influence of Mg ions concentration on the morphology, UV absorption and PL emission were investigated in detail. NPs exhibit white light emission with CIE chromaticity coordinates (0.317, 0.32 and 0.308, 0.359) and correlated color temperature values 6298 and 6674 respectively. These findings show a great promise of Y2O3: Mg2+ NPs as a phosphor in warm white LEDs.
Structural and Multiferroic Properties of Co0.6Zn0.4Fe2O4 – Pb0.76Ca0.24TiO3 Composite Thin Films
Authors: Thakur Shilpa , Sharma Hakikat , Sharma Sarita , Negi N.S.
Published: September 2015

Co0.6Zn0.4Fe2O4 (CZFO), Pb0.76Ca0.24TiO3 (PCT) thin films and Co0.6Zn0.4Fe2O4 – Pb0.76Ca0.24TiO3(CZFO/PCT) composite thin film were prepared by chemical solution method using metello – organic precursor. Structural and microstructural properties were studied by using XRD and Atomic force microscopy (AFM) respectively. XRD patterns confirme cubic spinel structure for CZFO ferrite and perovskite structure for PCT ferroelectric phase without any impurity phase formation. Grain size and roughness were calculated from AFM images. Grain size and roughness of composite thin film are decreased in comparison to individual phases (CZFO,PCT). Magnetic properties were studied using VSM.
Synthesis, Characterization and Photoluminescence Properties of CdSiO3:Ce3+ Nanophosphors
Authors: Basavaraj R.B. , Amith Yadav H.J. , Nagabhushana H. , Prashantha S.C. , Anantharaju K.S. , Vidya Y.S.
Published: September 2015

CdSiO3: Ce3+ (1-11mol %) nanophosphors were prepared by low temperature solution combustion method using Oxalyl di-hydrazine (ODH) as fuel. The final products were well characterized by PXRD and SEM. The optical properties of the nanophosphors were investigated by Photoluminescence studies. PXRD results evident that CdSiO3 phosphor shows pure single monoclinic structure. The average crystallite size was calculated using Debye – Scherer’s formula and was found to be in the range of 30-40 nm. The SEM micrographs show phosphors with high porosity and irregular shaped particles. Photoluminescence peaks observed at 454, 563 and 679 nm under 397 nm excitation was due to transition from 5d state to the 2F5/2 and 2F7/2 components of the ground state of Ce3+ in CdSiO3 host material. CdSiO3:Ce3+ nanophosphors show an intense yellow emission with CIE coordinates (0.47, 0.50) with average correlated color temperature value 3284 was within the range of vertical day light. The present study successfully demonstrates solution combustion synthesis of nanophosphors for display applications.
Corrosion and Multi-Scale Mechanical Behaviour of Plasma Electrolytic Oxidation (PEO) and Hard Anodized (HA) Coatings on AA 2219 Aluminum Alloy
Authors: Venugopal A. , Srinath J. , Ramesh Narayanan P. , Sharma S.C. , George Koshy M.
Published: September 2015

The electrochemical corrosion and mechanical properties of ceramic coatings fabricated by plasma electrolytic coating (PEO) and hard anodizing (HA) methods comparatively examined for AA2219. Potentiodynamic polarization results revealed that the corrosion resistance of both coatings are comparable to each other. However, the indentation and scratch testing indicated that the hardness and modulus of the PEO coating was significantly higher when compared to HA coating. The critical load (Lc2) causing adhesive failure of the PEO coating was much high (19N) when compared to HA coating (10N) showing better adhesive strength of the PEO coating.Key words: Plasma electrolytic oxidation (PEO), potentiodynamic polarization, nanoindentation, hard anodizing
Low Temperature Boronizing of Surface Nanostructured Ni-Cr-Mo Steel Using SMAT
Authors: Sreejith G. , Sunny Teotia , Sahu J.N. , Sasikumar Chandrabalan
Published: September 2015

Boronizing is a surface thermochemical treatment in which boron atoms are made to diffuse into a metallic surface at high temperatures. A nano-crystalline surface with larger defect density assists in enhancing the diffusion rate even at low temperatures. In the present work Ni-Cr-Mo steel is subjected to a surface mechanical attrition treatment (SMAT) to activate the surface with nanocrystalline structures and crystal defects. Subsequently the samples were boronized at low temperature regime (400°C - 600°C) for 5 hours using a pack boronizing technique. The microstructure, chemical analysis and hardness of borided layers were investigated using optical microscope, SEM – EDX and Microvicker’s Hardness Tester. The SMAT treated samples showed severe plastic deformation of the surface, nano-structured grains (10-30 nm) and larger defect density illustrating mechanically activated surface for diffusion. The boronizing had clearly demonstrated the diffusion of boron even at 400°C. The thickness of diffused layer was found to be about 20 µm at 400°C and 50 µm at 600°C for SMAT samples while the untreated samples showed practically no diffusion at 400°C and 12 µm at 600°C. The SEM-EDX results had confirmed the presence of boron at the diffused layer; however the hardness was found to be low. A maximum of 650 HV0.3 was achieved by low temperature boronizing of SMAT treated samples.
Optimization and Characterization of Manganese Coating on Cu-Cr-Zr-Ti Alloy
Authors: Venkateswaran T. , Thinesh Babu T. , Agilan M. , Jayan P.K. , Sivakumar D. , Vincent Xavier , Prakher Gupta P. , Anandavel B.
Published: September 2015

In this study, the deposition of Manganese (Mn) on Cu-Cr-Zr-Ti alloy was carried out using electro plating route. The purpose of this coating is to join copper alloys utilizing eutectic reaction between Cu and deposited Mn. Mn coating through electro deposition is difficult due to very high electronegativity. Two different bath compositions have been studied, with and without the addition of sodium selenate (Na2SeO4), where base composition remains same (MnSO4 & (NH4)2SO4). The influence of the bath composition and deposition parameters such as pH, current density, time on the deposition rate of Mn coating was studied. Higher deposition rate of Mn was obtained with lower pH and higher current density (~6 amps/dm2). Time of deposition was optimized to obtain varying thickness, ranging from 10 to 30 microns. Detailed characterization was carried on the Mn coated samples using OM, SEM-EDS and AFM. XRD phase analysis on the coated surface ensures the presence of α-Mn at room temperature. Subsequently, DSC analysis was carried out on the Cu alloy/Mn deposit pair to assess the brazeability temperature window.
Synthesis and Characterization of Silicide Coating on Niobium Alloy Produced Using Molten Salt Method
Authors: Tyagi Megha , Vishwanadh B. , Ghosh Subir Kumar , Tewari R.
Published: September 2015

The main aim of the present work is to develop an oxidation resistant Nb-Si coating on Nb alloys. For this purpose electroless molten salt - method was used, where a selective reaction occurs between NaCl–KCl–NaF–Na2SiF6 and the Si powder. Due to this reaction, oxidation resistant Nb-Si phases forms on the surface of substrate. This paper reports the thickness variation of Nb-Si coating as a function of deposition time. The surface morphology was studied by using scanning electron microscopy (SEM). The various Nb-Si based phases formed on the Nb substrate have been identified using X-ray diffraction (XRD) analysis, supplemented with energy dispersive X-ray spectroscopy results. Based on these results mechanism of silicide coating on Nb alloys has been discussed in detail.
Failure Analysis of Ball-Bearing of Turbo-Pump Used in Liquid Rocket Engine
Authors: Vartha Venkateswarlu , Arun Kumar M.S. , Mathew Saxon , Aneesh Rajan , Bejoy John , Thomas Tharian K. , Shajimon A. Cheriang
Published: September 2015

Rolling contact bearings often referred as antifriction bearings are found in many applications where rotating components are involved. Extreme operating conditions, counterfeit or inferior quality bearings, inadequate lubrication, etc often lead to bearing failures. Each rolling contact bearing failure leaves traces of evidences on what caused its failure. Failure analysis of one such bearing is the subject of this paper.One of the engine ground tests was aborted due to the failure of a self-aligning deep groove ball bearing used in turbo-pump of a liquid rocket engine. Series of engine ground tests are conducted as a part of injector acceptance for a liquid rocket engine. The bearing failure occurred in the seventh engine test of one of such series of ground tests. The bearing mentioned here is made of SAE 52100 steel. Post-test hardware inspection revealed that the bearing and the dynamic seals on either side of the bearing are in failed condition. Inner race of bearing was found blackish in appearance with indentation and corrosion marks. Localized black spots were observed in outer race. Bearing balls were found in deformed condition. The paper highlights the failure analysis of the bearing, root cause of the bearing failure and recommendations to avoid such failures.
Use of Cenosphere for Making Metal-Microspheres Syntactic Foam through Powder Metallurgy Route
Authors: Mondal D.P. , Dasgupta R. , Barnwal Ajay Kumar , Pandey Shaily , Jain Hemant
Published: September 2015

Cenospheres are very cheap, and are reasonably strong and thermally stable upto 1200°C. In view of this attempt has been made to use these cenosphere for making Titanium syntactic foams with varying relative densities. Precautions were taken for selecting cold compaction pressure to minimize cenosphere crushing. The sintered samples were then characterized in terms of microstructures primarily to see the extent of cenosphere crushing, distribution of cenosphere, and extent of sintering. The foams made using optimized pressure and sintering parameters, exhibits uniform distribution of cenosphere without any significant crushing. The plateau stress, energy absorption and modulus of these foams are varying with the cenosphere content or the relative density, and these parameters can be engineered by varying cenosphere content in the foam. These foams exhibit considerably higher strength and stiffness than the conventional foam and show the possibility of using them for biomedical and engineering applications.
Analysis of Machining Parameter and Surface Finish of Al-Si Alloys with Grain Refiners and/or Modifier
Authors: Prema Satya , Shreeshail G.Y. , Chandrashekharaiah T.M.
Published: September 2015

The Al-Si alloy is a structural material which generally consists of two or more particulates. However, Al-Si alloys are the most common alloys and commercially available ones due to their economical production. The utilization of Al-Si alloys has given the scope of study to improve in its properties using some grain refiner like Al-5Ti-1B, Al-3B and modifiers like Al-10Sr. The Al alloys were selected based on the economical uses and also, on the basis such that hypoeutectic (i.e., LM-25), eutectic (i.e., LM-6) and hypereutectic (i.e., LM-30). This project aimed to synthesize Al alloys (LM-6, LM-25 and LM-30) by melt stirring method with varying amount of grain refiners and / or modifier. The Prepared composites were characterized for machining properties. Alloys were evaluated for their machining properties which include surface roughness, lathe and drill tool dynamometer and comparing the machining properties with the minor addition of grain refienrs and/or modifier. The study concluded that, the addition of Al-3B to eutectic (i.e., LM-6) alloys has better surface finish.
Design for Manufacturing & Assembly Approach in Realisation of Cryogenic Thrust Chamber
Authors: Singh Alok , Kumar Ravi Ranjan , Pande Ashish Kumar , Venkitakrishnan P.V.
Published: September 2015

In the olden days the motto was "I designed it; you build it!" Design engineers worked alone and Designs were then thrown over the wall leaving manufacturing people with the dilemma how to manufacture. Often this delayed both the product launch and the time to ramp up to full production. In the new good days manufacturability can be assured by developing products in multi-functional teams with early and active participation from Manufacturing, Marketing (and even customers), Finance, Industrial Designers, Quality, Service, Purchasing, Vendors and factory works. The need for a holistic approach between design and manufacturing is required. The two concepts Design for Manufacturing & Design for Assembly has become the need of the hour. The heart of any design for manufacturing system is a group of design principles or guidelines that are structured to help the designer reduce the cost and difficulty of manufacturing an item.Realisation of Cryogenic thrust chamber includes various manufacturing processes like Forming, Welding, Machining and Brazing. During initial stages of Thrust chamber realisation problems like Forming of 1.7m long nozzle divergent from thin sheets, welding of various intricate geometries & assembly of critical parts were observed. Subsequently these problems were studied based on the holistic approach of Design for manufacturing & design for assembly. Improvements based on the above study were considered in design & critical processes modifications resulting in successful and timely realization of the thrust chamber.
Force-Regulated In Situ TCR–Peptide-Bound MHC Class II Kinetics Determine Functions of CD4+ T Cells
Authors: Hong Jinsung , Persaud Stephen P. , Horvath Stephen , Allen Paul M. , Evavold Brian D. , Zhu Cheng
Published: September 2015

We have recently shown that two-dimensional (2D) and force-regulated kinetics of TCR–peptide-bound MHC class I (pMHC-I) interactions predict responses of CD8+ T cells. To test whether these findings are applicable to CD4+ T cells, we analyzed the in situ 3.L2 TCR–pMHC-II interactions for a well-characterized panel of altered peptide ligands on the T cell surface using the adhesion frequency assay with a micropipette and the thermal fluctuation and force-clamp assays with a biomembrane force probe. We found that the 2D effective TCR–pMHC-II affinity and off-rate correlate with, but better predict the T cell response than, the corresponding measurements with the surface plasmon resonance in three dimensions. The 2D affinity of the CD4 for MHC-II was very low, approaching the detection limit, making it one to two orders of magnitude lower than the affinity of CD8 for MHC-I. In addition, the signal-dependent cooperation between TCR and coreceptor for pMHC binding previously observed for CD8 was not observed for CD4. Interestingly, force elicited TCR–pMHC-II catch-slip bonds for agonists but slip-only bonds for antagonists, thereby amplifying the power of discrimination between altered peptide ligands. These results show that the force-regulated 2D binding kinetics of the 3.L2 TCR for pMHC-II determine functions of CD4+ T cells.
Preprocessing Steps for Agilent MicroRNA Arrays: Does the Order Matter
Authors: Qin Li-Xuan , Huang Huei-Chung , Zhou Qin
Published: September 2015

Motivation/Background

Previous publications on microarray preprocessing mostly focused on method development or comparison for an individual preprocessing step. Very few, if any, focused on recommending an effective ordering of the preprocessing steps, in particular, normalization in relationship to log transformation and probe set summarization. In this study, we aim to study how the relative ordering of the preprocessing steps influences differential expression analysis for Agilent microRNA array data.

Methods

A set of 192 untreated primary gynecologic tumor samples (96 endometrial tumors and 96 ovarian tumors) were collected at Memorial Sloan Kettering Cancer Center during the period of 2000–2012. From this same sample set, two datasets were generated: one dataset had no confounding array effects by experimental design and served as the benchmark, and another dataset exhibited array effects and served as the test data. We preprocessed our test dataset using different orderings between the following three steps: quantile normalization, log transformation, and median summarization. Differential expression analysis was performed on each preprocessed test dataset, and the results were compared against the results from the benchmark dataset. True positive rate, false positive rate, and false discovery rate were used to assess the effectiveness of the orderings.

Results

The ordering of log transformation, quantile normalization (on probe-level data), and median summarization slightly outperforms the other orderings.

Conclusion

Our results ease the anxiety over the uncertain effect that the orderings could have on the analysis of Agilent microRNA array data.
Impaired Spatial Learning Memory after Isoflurane Anesthesia or Appendectomy in Aged Mice is Associated with Microglia Activation
Authors: Wang Hui-Lin , Ma Rui-Hua , Fang Hao , Xue Zhang-Gang , Liao Qing-Wu
Published: September 2015

Postoperative cognitive dysfunction (POCD) has been one of the most common problems in elderly patients following surgery. But the specific mechanism of POCD is still not clear. To further understand the reason of these postoperative behavioral deficits, we evaluated the spatial learning memory of both adult (3 months) and aged (18 months) male mice, 3 or 28 days after isoflurane (Iso) exposure for two hours or appendectomy (App). Hippocampal microglia activation and IL-1β, TNF-α, and IFN-γ expression were also evaluated at day 3, day 14 and day 28 after Iso exposure or appendectomy. Results showed that spatial learning memory of aged, but not adult, mice was impaired after Iso exposure or appendectomy, accompanied with more hippocampal microglia activation and IL-1β, TNF-α, and IFN-γ overexpression. These findings suggest that the cognitive deficits of elderly patients who have undergone surgeries are quite possibly caused by hippocampal microglia overactivation and the subsequent inflammation.
Co-creation in Local Public Services Delivery Innovation: Slovak Experience
Authors: Mikusova Merickova Beata , Nemec Juraj , Svidroňová Mária
Published: September 2015

The new approaches to the delivery of local public services include co-creation. In this paper, we focus on two local public service delivery actors: local governments and civil society. Our objective is to identify different types of co-creation in social innovations and the relevant drivers and barriers that account for the success or failure of co-creation processes at the local government level in Slovakia, focusing on the fields of welfare and the environment. The main findings of our analysis are that co-created innovations are mostly initiated by non-governmental actors, and that most local governments have neutral or even negative attitudes to co-created innovations. We provide a positive case study, in which the local government was open to co-creation, and public services were provided in an alternative way. Our study uses a qualitative approach and is based on original survey data from our own research, conducted mainly within the ‘Learning from Innovation in Public Sector Environments’ (LIPSE) research project.
International Aspects of Fiscal Convergences on Regional and Local Level
Authors: Vojinović Borut , Próchniak Mariusz Próchniak , Oplotnik Žan Jan
Published: September 2015

The paper presents the analysis of sigma (σ) and beta (β) convergences of the selected indicators as those that best represent the level of local self-government and fiscal decentralization systems across the selected EU member states. Through research we wanted to establish how EU integration process influenced the area of local self-government in selected EU member states and if we witness also the unification of this aspect among EU member states. Results confirm that convergence really occurred at the significant rate during the whole period 2004 to 2013 and also during the sub periods 2004 to 2009 and further, although in latter period some divergence or slowing down in convergence has been also present. Nevertheless, we can confirm that EU integration process has also influenced the area of local self-government and that EU member countries are converging to the commonly adopted criteria are principles as stated in EU charter of local self-government.
Developmental Dyspraxia and the Play Skills of Children With Autism
Authors: Bodison Stefanie C.
Published: September 2015

OBJECTIVE. This study sought to investigate the impact of developmental dyspraxia on the play skills of children with autism spectrum disorder (ASD).

METHOD. The praxis abilities of 32 children with ASD (mean age = 7.5 yr) were assessed using two subtests of the Sensory Integration and Praxis Tests and the Planning and Ideas domain of the Sensory Processing Measure Home Form. Play and leisure skills were measured with the Vineland Adaptive Behavior Scales, Second Edition. Utilizing correlation coefficients, we investigated the relationship between developmental dyspraxia and the play skills of children with ASD.

RESULTS. Children with ASD demonstrated definite dysfunction in imitative praxis abilities, the generation of ideas, and participation in age-appropriate play and leisure activities.

CONCLUSION. Praxis problems in children with ASD greatly affect their successful participation in play and leisure activities.
Linking Sensory Factors to Participation: Establishing Intervention Goals With Parents for Children With Autism Spectrum Disorder
Authors: Schaaf Roseann C. , Cohn Ellen S. , Burke Janice , Dumont Rachel , Miller Amy , Mailloux Zoe
Published: September 2015

Parents often focus on independence in activities of daily living and social participation when setting goals for their children with autism spectrum disorders. Occupational therapy practitioners use clinical reasoning to translate these goals to define occupation-based outcomes. This article describes an exploratory analysis of 160 parent-identified goals for children with autism. We identified sensory integrative factors hypothesized to influence each goal and then categorized the goals using the Occupational Therapy Practice Framework: Domain and Process and the International Classification of Functioning, Disability and Health (ICF). Most goals were at the ICF participation and activity levels. Activities of daily living were the most common area of occupation identified, followed by social participation and play. Sensory reactivity and somatopraxis were the most frequently occurring sensory integrative factors. The value of addressing parent goals using a systematic reasoning process to identify factors affecting participation and the importance of measuring participation outcomes are discussed.
Effectiveness of Ayres Sensory Integration® and Sensory-Based Interventions for People With Autism Spectrum Disorder: A Systematic Review
Authors: Watling Renee , Hauer Sarah
Published: September 2015

This systematic review examines the literature published from January 2006 through April 2013 related to the effectiveness of Ayres Sensory Integration® (ASI) and sensory-based interventions (SBIs) within the scope of occupational therapy for people with autism spectrum disorder to improve performance in daily life activities and occupations. Of the 368 abstracts screened, 23 met the inclusion criteria and were reviewed. Moderate evidence was found to support the use of ASI. The results for sensory-based methods were mixed. Recommendations include performing higher level studies with larger samples, using the Fidelity Measure in studies of ASI, and using carefully operationalized definitions and systematic methods in examination of SBIs.
Client Centeredness and Health Reform: Key Issues for Occupational Therapy
Authors: Mroz Tracy M. , Pitonyak Jennifer S. , Fogelberg Donald , Leland Natalie E.
Published: September 2015

Health reform promotes the delivery of patient-centered care. Occupational therapy’s rich history of client-centered theory and practice provides an opportunity for the profession to participate in the evolving discussion about how best to provide care that is truly patient centered. However, the growing emphasis on patient-centered care also poses challenges to occupational therapy’s perspectives on client-centered care. We compare the conceptualizations of client-centered and patient-centered care and describe the current state of measurement of client-centered and patient-centered care. We then discuss implications for occupational therapy’s research agenda, practice, and education within the context of patient-centered care, and propose next steps for the profession.
Assessing the ammonium nitrate formation regime in the Paris megacity and its representation in the CHIMERE model
Authors: Petetin H. , Sciare J. , Bressi M. , Rosso A. , Sanchez O. , Sarda-Estève R. , Petit J.-E. , Beekmann M.
Published: September 2015

Abstract. Secondary inorganic compounds represent a major fraction of fine aerosol in the Paris megacity. The thermodynamics behind their formation is now relatively well constrained, but due to sparse direct measurements of their precursors (in particular NH3 and HNO3), uncertainties remain on their concentrations and variability as well as the formation regime of ammonium nitrate (in terms of limited species, among NH3 and HNO3) in urban environments such as Paris. This study presents the first urban background measurements of both inorganic aerosol compounds and their gaseous precursors during several months within the city of Paris. Intense agriculture-related NH3 episodes are observed in spring/summer while HNO3 concentrations remain relatively low, even during summer, which leads to a NH3-rich regime in Paris. The local formation of ammonium nitrate within the city appears low, despite high NOx emissions. The dataset is also used to evaluate the CHIMERE chemistry-transport model (CTM). Interestingly, the rather good results obtained on ammonium nitrates hide significant errors on gaseous precursors (e.g. mean bias of −75 and +195 % for NH3 and HNO3, respectively). It thus leads to a mis-representation of the nitrate formation regime through a highly underestimated Gas Ratio metric (introduced by Ansari and Pandis, 1998) and a much higher sensitivity of nitrate concentrations to ammonia changes. Several uncertainty sources are investigated, pointing out the importance of better assessing both NH3 emissions and OH concentrations in the future. These results finally remind the caution required in the use of CTMs for emission scenario analysis, highlighting the importance of prior diagnostic and dynamic evaluations.