1,618 research outputs found
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Solid Freeform Fabrication of Functional Silicon Nitride Ceramics by Laminated Object Manufacturing 1
The processing of silicon nitride (Si3N4) structural ceramics by Laminated Object
Manufacturing (LOM) using ceramic tape preforms was investigated. The key processing stages
involved green shape formation (which used the LOM process), followed by the burnout of all
organics, and final densification by pressureless sintering. Two material systems were
considered. These were a) monolithic Si3N4 and b) a preceramic polymer infiltrated Si3N4. The
raw materials for the process were tape preforms of Si3N4, which were fabricated by standard
tape casting techniques.
Mechanical property data obtained for the LOM processed Si3N4 showed high strength and
fracture toughness values. The room temperature and high temperature (1260 o
C) flexural
strengths were in the range of 700-900 MPa and 360-400 MPa, respectively. The fracture
toughness averaged from 5.5-7.5 MPa.m1/2. These strength and fracture toughness values are
comparable to those reported for conventionally prepared Si3N4 ceramics. Thus, this research
demonstrated that the LOM technique is a viable method for preparing functional Si3N4 ceramics
with good physical and mechanical properties.Mechanical Engineerin
Contributions to the theory of generalised hypergeometric series
This thesis deals with various aspects of development in the field of both ordinary and basic hypergeometric functions. It comprises six chapters. The first chapter gives a brief survey of some of the recents developments in this field including the work done in the present thesis. The second chapter gives a systematic study of the transformations connected with the partial sums of generalised hypergeometric series, both ordinary and basic. The main theorem proved in the chapter gives the most general relation of its type. The third chapter is concerned with the development of the transformation theory of bilateral cognate trigonometrical series and generalises all the known results in that field. The fourth chapter gives the integral analogues of some of the transformations of basic series analogous to those for the ordinary series in Chapter VI of Bailey's Cambridge Tract. The fifth chapter deals with a systematic classification and study of two and three term relations between special kinds of well-poised series of the type and gives a new method, by integrals, of deducing these transformations easily. The last and the sixth chapter gives a number of identities involving basic analogues of Appell's hypergeometric functions of two variables and some associated functions.<p
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Fused Deposition of Ceramics (FDC) for Structural Silicon Nitride Components
Fused Deposition of Ceramics is aI! SFF tec~que based on comm~rcial FDMTM ~echno.logy, f?r
fabrication of structural and functIonal cerannc components. ThIS study descnbes, ill detail,
process improvements made in pre-FDC, FDC, and post-FDC fabrication steps to achieve
functional properties in commercial GS-44 silicon nitride ?omponents. . Microstructural
characterization of sintered FDC parts reveals microstructures simllar to convennonally processed
silicon nitride material. Mechanical properties of FDC processed silicon nitride bend bars and
toughness samples were evaluated. These property evaluation studies demonstrate that mechanical
properties similar to commercial GS-44 silicon nitride materials can be achieved using FDC. The
study also describes results achieved on fabrication of complex components from silicon nitride
using FDC.Mechanical Engineerin
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Structural Ceramics by Fused Deposition of Ceramics
Fused Deposition of Ceramics (FDC) is a SFF technique, based on FDMTM technology, for
fabrication of advanced structural ceramics from powderlbinder filaments. In this study, in-situ
reinforced (ISR) Si3N4 powder and polymer/wax based binder systems were used as filament
material for FDC processing using a commercially available FDMTM system, 3D Modeler.
Powderlbinder feedstocks were mixed using a torque rheometer and filaments were fabricated
using a capillary rheometer and twin screw extruder. Green FDC components were built from
these filaments and then characterized for inter-road and inter-layer bonding. Binder removal
procedures were established for FDC green components to yield brown parts without distortion or
shape change. Brown FDC parts were characterized for carbon residue, pore distribution and
dimensional changes. Brown FDC parts were then sintered and the sintered density,
microstructure, and shrinkage anisotropy were studied.Mechanical Engineerin
Cloning and heterologous expression of a gene encoding lycopene-epsilon-cyclase, a precursor of lutein in tea (Camellia sinensis var assamica)
This report describes the cloning and expression of a gene lycopene epsilon cyclase, (LCYE) from Camellia sinensis var assamica which is a precursor of the carotenoid lutein in tea. The 1982 bp cDNA sequence with 1599 bp open reading frame of LCYE was identified from an SSH library constructed for quality trait in tea. 5’ and 3’ RACE (rapid-amplification of cDNA ends) was done to clone the full length cDNA of LCYE. Homology studies showed that the deduced amino acid sequence of LCYE gene had the highest sequence identity of up to 84% with Vitis vinefera. The cloned gene was successfully expressed in a PET based Escherichia coli expression system. The size of the expressed protein was 59615 Daltons. A suppression subtractive library was constructed using a quality clone H3111 (tester) and a garden series clone T3E3 (driver).Key words: Carotenoid, RACE, heterologous expression, lutein, tea
Preliminary comparative RH mapping between river buffalo chromosome 6 (BBU6) and bovine chromosome 3 (BTA3)
The high voltage system for the novel MPGD-based photon detectors of COMPASS RICH-1
The architecture of the novel MPGD-based photon detectors of COMPASS RICH-1
consists in a large-size hybrid MPGD multilayer layout combining two layers of
Thick-GEMs and a bulk resistive MICROMEGAS. Concerning biasing voltage, the
Thick-GEMs are segmented in order to reduce the energy released in case of
occasional discharges, while the MICROMEGAS anode is segmented in pads
individually biased at positive voltage, while the micromesh is grounded. In
total, there are ten different electrode types and more than 20000 electrodes
supplied by more than 100 HV channels. Commercial power supply units are used.
The original elements of the power supply system are the architecture of the
voltage distribution net, the compensation, by voltage adjustment, of the
effects of pressure and temperature variation affecting the detector gain and a
sophisticated control software, which allows to protect the detectors against
errors by the operator, to monitor and log voltages and current at 1 Hz rate
and to automatically react to detector misbehaviors. The HV system and its
performance are described in detail as well as the electrical stability of the
detector during the operation at COMPASS.Comment: 5th international conference on Micro-Pattern Gas Detectors
(MPGD2017),presentation by Silvia Dalla Torr
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