રાજકોટ શહેરમાં ટેલિકોમ્યુનિકેશનની સેવા પુરી પાડનાર ખાનગી અને જાહેર ક્ષેત્રનો તુલનાત્મક અભ્યાસ

Not availabl

Preparation of Erosion Susceptibility Map of Dhaman Khadi Sub-Watershed in Eastern Gujarat Using ArcGIS Interface

An attempt has been made to model land degradation in term of water erosion of selected Dhaman Khadi sub-watershed (7710.64 ha.) in Eastern Gujarat, India through Revised Universal Soil Loss Equation using ArcGIS interface. The average erosivity of 30 years (1986-2015) annual rainfall using standard formula was estimated to be 480.63 MJ mm ha?1 hr?1 per year. The erodibility factor K was computed as 0.236 and 0.177 mt?hr MJ?1 mm?1 per unit R respectively for clay loam and clay soils using modified formula.. 20 m Digital Elevation Model was prepared from Toposheet No. F43N10 by using ‘Topo to Raster’ interpolation method. The slope length factor L was derived from DEM using Unit Stream Power Erosion and Deposition (USPED) Model. The raster layers of slope steepness factor for slope having < 9 % and ? 9 % was prepared separately to form final slope steepness factor map. Cover management factor map was derived based on cropping pattern for the various land cover categories of the study area. The standard conservation practice factor values for cross-sloped agricultural lands were assigned to the attribute table of the intersected map of LU/LC and slope maps to prepare the P factor map. Average gross soil erosion was minimum for evergreen forest while maximum for wasteland without scrub. Highest area covered by agricultural land (i. e. 41.54) of Dhaman Khadi sub-watershed having 33.28 tons/ha/yr gross soil erosion needs immediatetreatment to prevent land degradation. Soil loss tolerance limit of study area was used to derive erosion susceptibility map in order to identify the priority of conservation programs. As all the factors of RUSLE was estimated precisely at sub-watershed level, the study could help for rapid and reliable planning of watershed development programs in combination with the use of RS and GIS technology

NICFD and the PIV technique: Feasibility in low speed and high speed flows

The growing interest in organic Rankine Cycle (ORC) based power systems has encouraged ample amount of literature on the design methodologies for unconventional turbo-machinery. These machines generally operate in the so-called Non-Ideal Compressible Fluid Dynamic (NICFD) region of the working fluid where the thermophysical properties and transport properties models, and optical properties are experimentally unexplored. Therefore, these design methods need to be validated using state-of-the-art measurement techniques like Particle Image Velocimetry (PIV). PIV has not been implemented to study the non-ideal behaviour of such fluids, and therefore a feasibility study of PIV in these unconventional media is required. This work deals with exploring the possible challenges that could occur while applying the PIV technique to measure the flow comprising of non-ideal fluids in low speed and high-speed regime.The fluids for which the feasibility is studied are Octamethylcyclotetrasiloxane (D4) and Hexamethyldisiloxane (MM) which are frequently used working fluids for ORC power systems. The equation of state used to calculate thermo-physical properties of these fluids is briefly discussed. The viscosity of these fluids is calculated to assess the tracer particle response characteristics and check for large variations of viscosity with the thermodynamic variables. To be able perform optical diagnostics, one also has to explore the optical properties of the working fluid --- especially the refractive index. Therefore, a theoretical study of refractive index and influence of thermodynamic properties on the refractive index is studied. Conventional seeding techniques are reviewed and its feasibility for the fluids of interest is discussed.A test facility called the Non-Intrusive Vapour Analyser (NIVA) was designed to conduct PIV in low speed vapour flows induced by a rotating disk. A suspension of D4 and 170 nm titania particles was evaporated to obtain a seeded volume of D4 vapour, on which PIV can be performed. The signal-to-noise ratio (SNR) was calculated to verify sufficient light scattering property of the titania particles. The seeding technique of evaporating the suspension of D4 + titania yields sufficiently homogeneous seeding distribution. Mean velocity fields of the vapour flow in the NIVA at different disk rotation speeds could be measured with acceptable uncertainties. Considering a vast difference in flow conditions at high-speeds, a theoretical study of high-speed MM flow in a de-Laval nozzle is done to explore challenges that could occur in application of PIV. Large gradients in density are typical of dense gas expansions. This subsequently results in large gradients in optical properties like refractive index. Challenges to particle imaging due to inhomogeneous refraction of light are investigated by preliminary estimation of position error and velocity error along the nozzle axis. A conceptual design of the seeding system is proposed that can operate at high-pressures and does not risk contamination of the working fluid.It was concluded from the experimental results in NIVA that PIV is feasible in low-speed vapour flows and can measure velocity fields with an average uncertainty of less than 1%. Also, refractive index gradients in high-speed vapour flows could cause unacceptable errors of greater than 1% in PIV measurements. These errors depend on the complexity of the fluid and the distance between the measurement plane and nozzle wall. Aerospace Engineerin

Anchoring Effect on the Mechanical Properties of CNTs Grown Carbon Fiber/Polymer Matrix Multi-Scale Composites

Carbon fibers were uniformly coated with carbon nanotubes by catalytic decomposition of acetylene using thermal chemical vapor deposition technique at 700 degrees C. The nanotube coated fibers were employed for the fabrication of unidirectional multi-scale composites with epoxy matrix. As the carbon nanotubes were directly grown on carbon fibers they remain firmly attached with the fiber substrate therefore they are anticipated to modify the interfacial characteristics of the composites and in turn considerably alter the mechanical behavior. Moreover, the direct growth of carbon nanotubes on fiber facilitates uniform distribution of carbon nanotubes in the polymer matrix. The composite specimens made of carbon nanotubes coated fibers showed a significant enhancement of 48% and 85% in the tensile and flexure strength respectively as compared to composites made of carbon fibers undergone similar thermal cycle but without carbon nanotubes growth. The morphology of carbon nanotubes coating on carbon fibers was examined at nano-level using high resolution TEM which showed growth of carbon nanotubes with different morphology and diameter ranging from 5-50 nm. Specimens failed in tensile were further investigated for fractographic analysis using SEM which showed improved fiber/matrix interfacial bonding indicated by less fiber pull out