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Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Study of Pre-Shearing Protocol and Rheological Parameters of Shear Thickening Fluids Containing Nano Particles
No full textSuspensions having viscoelastic property are ubiquitous and find applications in
variety of fields. One such suspension is that of the shear thickening fluid, which is non-
Newtonian in nature and shows an increase in viscosity when subjected to shear. Thus, these
fluids have the ability to change from liquid to solid phase when they undergo shear and then
return back to their original state when the shear is released. This reversible nature is highly
useful in defence applications. Previous studies show that the shear thickening fluids have the
potential of impact and stab resistance and can be used as a coating material on Kevlar fabric
to be used as a soft body armour. With modifications in the fluids, these armours can be made
more durable and light weight, which will help in increasing the flexibility of the soldier.
Like most of the viscoelastic materials, shear thickening fluids are also made up of
polymers, and have a tendency to store its previous shear history, thereby making it a memory
fluid. In the present work, a protocol has been developed in order to remove this shear history
from the fluids and thus enhance its properties. The shear thickening fluid for which such
protocol has been developed is a bi-dispersed mixture of fumed silica (11 nm) and simple
silica (400 nm). The past history was removed using the pre-shearing technique. Such
technique has been used for the first time for any such bi-dispersed suspension composed of
different sized particles. The rheological protocol developed for such a shear thickening fluid
is quite different from that reported in the past. Using this method it can be observed how
much initial shear and rest period is required by the sample so as to become stable and
provide reproducible rheological results. The outcomes have been found to indicate a
significant increase in critical viscosity of the material.
Another important feature which affects the thickening behaviour of these
fluids is the particle shape. Elongated particles provide high viscosity to the fluid whereas
spherical particles show thickening behaviour at higher shear rates. Thus, composite shear
thickening fluid was prepared using halloysite nanotubes (rods) and fumed silica (spheres)
and its rheological properties were studied. A better non-flocculated structure was obtained at
1% halloysite and 20% fumed silica composition compared to that of only spherical particle
STF. The oscillatory tests showed that this composition was also suitable as a high impact
resistant material as no gel formation takes place rather the fluid behaves like a dispersed sol.
Furthermore, composites having higher percentages of halloysite nanotubes were also
prepared and a comparison of the rheological properties of the three halloysite nanotubesfumed
silica composites was done
Preparation and Characterization of PDLLA-PCL-Starch Blends Processed Under Microwave Radiation
No full textM.Tech. (Chemical)Properties of biodegradable polymers like PDLLA and PCL can be modified by blending them with each other and with other polymers like Starch. In the present study we have prepared blends pf PDLLA, PCL and Starch in different proportions and then subjected to microwave radiation. Using microwave time of reaction has been reduced to 3-30 min as microwave is associated with more even distribution of heat. To characterize the blends various techniques like FTIR has been used. On blending PDLLA, PCL and starch in various ratios using chloroform as a solvent and subjecting the mixtures to microwave radiation, it becomes clear from FTIR spectra that O-H and C=O regions of the blend show significant variance after microwave irradiation compaired to the parent polymers. The results indicate a direct linkage between the polymers indicating the formation of a chemical linkage between the two molecules as opposed to just a phyical blend
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Design and Development of Load Bearing Composite Scaffolds for Bone Implants
Full text linkDoctor of Philosophy- Mechanical EngineeringBiocomposites mimicking hard tissue in the process of bone repair and regeneration have been in development for several decades. Contributions of several researchers in selection of materials, development of preparation routes, conduct of post surgery response studies and clinical trials for continual developments are commendable. Among several disciplines involved in this process, engineers’ role has been identified vital in materials and their processing.
Natural bone made up of Collagen and reinforcement ceramic phase, has dense structure at the middle of the bone and porous structure at the ends. Damaged or diseased bone needs regeneration with implant reinforcements for load sharing during healing process. Essential requirement of an implant is to share the load and to stimulate the bone growth by proper mechanics. Structural point of view, mechanical properties of an ideal implant shall match native bone properties.
Known the properties of Hydroxyapatite (HA), Ca10 (PO4)6 (OH)2 in bone applications for its bio active, bio conductive and bio inductive nature, it was chosen as bone material. Hydroxyapatite (HA) being ceramic, it suffers from low strength, low toughness and low tensile properties. In order to overcome the structural weaknesses of HA, Polyetheretherketone (PEEK-polymer) matrix was chosen to match the properties of Collagen.
The polymer part of composite, PEEK, by brand name VESTKEEP 2000FP, a non-medical grade polymer is a justified selection due to its inherent superior properties such as- semi-crystalline, high strength, temperature resistant, chemically inert, bio inert, bio conductive, radiolucent, clinically proven and approved by Food and Drug Administration (FDA)-U S A.
Hydroxyapatite, the reinforcing ceramic powder was extracted from chicken egg shells. Thoroughly washed egg shells were heated through predefined thermal cycles for the formation of CaO. Obtained CaO after thermal treatment has been chemically treated with tri-calcium phosphate (TCP) in wet condition at temperatures 10000C and above for the formation of HA. After ball milling and sieve separation, the obtained HA powder was characterized at International Advanced Research Centre for Powder Metallurgy and New Materials (ARCI), Hyderabad
For better bone native tissue interaction, HA was extracted from chicken eggshells. Fragile nature of HA had limited its content to a maximum of 40% in total biocomposite. Biocomposite with PEEK and egg shell extracted HA was synthesized and processed for i) dense composite through compression molding to mimic cortical bone and ii) porous structure through polymeric sponge method to mimic Cancellous bone.
Patient specific scaffold to repair damaged bone with precise geometry was successfully demonstrated in present work. CT/ MRI scan data in DICOM format was taken from KD Hospitals, Ambala (Haryana state), India. The obtained 2D images were converted in to 3D surface modeled at Central Tool Room (CTRL), Luthiana (Punjab) using 3D Doctor Software. 3D surface data was imported through IGES exchange protocol to PRO/E WF 3. Volume model of human pelvis was generated and exported in stl format to VANGUARD HS Selective Laser Sintering (SLS) machine. Scaled human pelvis was printed in Acrylonitrile-Butadiene-Styrene (ABS) material at CTRL, India.
Taguchi’s orthogonal approach was used in design of experiments of dense specimens for effective and quicker experimentation. After several trials in arriving at the specimen formation, three influencing factors (or processing parameters) were identified viz., the constituent composition of PEEK and HA, the sintering temperature or maximum temperature and the rate of heating. Three fine levels of each processing parameters were arrived at after comprehending the properties of biocomposite components from literature and delimiting studies on dense specimens.
Two different sets of samples were prepared, the first one with PEEK/ HA (natural or eggshell extracted HA) and the second one with PEEK/ HA (synthetic or commercial, purchased from Clarion pharmaceuticals, New Delhi). Dense specimens mimicking cortical bone structure were produced in powder metallurgy route. Mechanical properties of dense specimens viz., flexure strength and Young’s modulus of biocomposite were established through three point bend test as per ASTM D790 at Central Institute of Plastics Engineering& Technology, Hyderabad. The test results were revealing superior interaction of natural HA with PEEK.
Porous specimens to mimic Cancellous bone were prepared through Polymeric sponge method. A nylon mesh of 10 pores per inch was impregnated in Alumina slurry for preparation of template. Alumina template was used for preparation PEEK/HA porous specimens with porosities 41%, 45% and 51%. First set of porous specimens as sintered were tested in unconstrained compression test to establish the mechanical properties. Second set of porous specimens exposed to artificial sea water for 25 days at 370C were tested in unconstrained compression to establish degradation of mechanical properties invitro. PEEK/HA composite was concluded to be hydrophobic as the degradation effect was minimal.
Thermal stability study was conducted on biocomposite to pave guide lines for processing of the material to ensure bone in-situ applications Higher contents of HA in PEEK was found to be delaying the degradation of the composite. Weight loss of composite was found to be negligible even at 5000C. This test was establishing safe processing temperature of PEEK/HA could be as high as 3500C.
Finally an effort was made to extrapolate the porous scaffold’s mechanical behavior using DEFORM 3D software. Three sets of porosity (75%, 82% & 89%) in two different constituent percentages (PEEK/HA 70/30 and 80/20) were analyzed for load - deformation behaviour.
The total work entitled ‘Design and development of load bearing composite scaffolds for bone implants’ has been concluded as the dense and porous specimens were found prospective at load bearing sites with appropriate selection
Fabrication and Property Evaluation of a Epoxy-Clay-PET Nanocomposite System
No full textME, MEDNanocomposites are reported to be the materials of 21st century in the view of their unusual
properties and unique design possibilities that are not exhibited by conventional composites.
The objective of this work is to gain insight with regards to properties of nanocomposites
mainly comprising of Polyethylene terephthalate (PET) as fiber, montmorillonite (MMT) clay
as nano-filler and Epoxy as the matrix.
Nano–particles and nano–layers have very high surface–to–volume and aspect ratios and this
makes them ideal for use in polymeric materials. Such structures combine the best properties
of each component to possess enhanced mechanical and superconducting properties for
advanced applications. The physical, chemical and biological properties of nano materials
differ from the properties of individual atoms and molecules or bulk matter. By creating nano
particles, it is possible to control the fundamental properties of materials, such as their melting
temperature, magnetic properties, charge capacity and even their color without changing the
materials chemical compositions.
The present work describes the fabrication, characterization and subsequent mechanical testing
of a nanocomposite system containing both nano (clay) and micro (PET fibers) fillers. The
experimental work describes the sequence of processing steps required to prepare
nanocomposites. The study evaluates the effect of change in filler concentration on the tensile
strength, bending strength and flexural modulus of nanocomposites. The study also describes
the surface modification procedure for PET fibers to achieve enhanced interfacial bonding
between these micro fillers and the epoxy matrix. Fibers have been treated in an alkaline
solution of fixed concentration subjected to different treatment time and temperature
conditions. The work also compares the properties of the nanocomposites with the treated
fibers under the selected treatment conditions with those with untreated fibers
Mechanical Properties of Glass Fiber Reinforced Epoxy Nanocomposites: Effect of Different Nanoclays
No full textME, MEDIn this work, E glass fiber reinforced nanocomposites are manufactured with epoxy matrix modified with two different nanoclays: Cloisite 30B® and Cloisite 15A®. The nanoclays are dispersed in epoxy resin in different concentrations (1 wt.% and 2 wt.%). Two ply fibers (±45 stacking sequence) reinforced composites are manufactured using modified epoxy by
vacuum assisted resin infusion moudling (VARIM). The baseline data for comparison is generated by carrying out test on neat epoxy glass fiber composite i.e. without nanoclay. Xray diffraction indicates that an intercalated nanoclay epoxy composite is obtained. Elastic
modulus, flexural strength and micro-hardness are improved with incorporation of nanoclays.
Highest improvement in flexural strength, tensile modulus and micro-hardness obtained at 2 wt.% Cloisite 30B® nanoclay. The flexural strength and tensile modulus of E glass epoxy composite increased by 59% and 69.8% with 2 wt.% Cloisite 30B
® nanoclay. The improvement in the properties may be attributed to the high aspect ratio, contact surface and
reinforcing effects of nanoclays
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