Study of chemical and mechanical properties of Dharbai fiber reinforced polyester composites

This investigation is focused on identifying a new variety of natural fiber (Dharbai fiber) for reinforcement in polymer matrix composites. An investigation on extraction procedure of Dharbai fibers has been undertaken. The chemical properties of Dharbai fibers were determined experimentally as per TAPPI standards. The FT-IR Spectroscopy was used to study the chemical structure of Dharbai fibers and the tensile properties of these fibers were studied using single filament test. The fibers extracted were reinforced in polyester matrix by varying the fabrication parameters namely fiber weight content (%) and fiber length (mm). The effect of fiber weight content and fiber length on the mechanical properties of Dharbai fiber-polyester composites were evaluated as per ASTM standards. Scanning electron microscope was used to characterize the interfacial bonding between Dharbai fibers and polyester matrix. This study confirmed that, the Dharbai fibers could be used as an effective reinforcement material for making low load bearing polymer composites.     

Impact of Zr content on multiphase zirconium–tungsten oxide (Zr–WO<Subscript>x</Subscript>) films and its MIS structure of Cu/Zr–WO<Subscript>x</Subscript>/p-Si Schottky barrier diodes

Metal–insulator–semiconductor (MIS) structure of Cu/Zr–WO_x/p-Si Schottky diodes with different concentrations (0, 4 and 8 wt%) of Zr content were fabricated. The interfacial layer of zirconium–tungsten oxide (Zr–WO_x) film was grown on p-type silicon (p-Si) wafer using jet nebulizer spray pyrolysis (JNSP) technique at the substrate temperature of 400 °C. After that, the Cu electrode was coated on the Zr–WO_x film via vacuum deposition method. The multiphase (orthorhombic and cubic) crystal structures of Zr–WO_x were revealed by X-ray diffraction (XRD) pattern. The surface morphological analysis using scanning electron microscope (SEM) showed the dissimilar structures of surface and energy dispersive X-ray diffraction (EDX) confirmed the presence of W, Zr and O atoms. Using UV–Visible (UV–Vis) and DC elecrical (I–V) analysis, the minimum band gap energy and average conductivity were obtained for higher concentration (8 wt%) of Zr content. The minimum barrier height (Φ_B) and minimum ideality factor (n) values were attained for 4 wt% of Cu/Zr–WO_x/p-Si Schottky barrier diode (SBD) under illumination condition.     

Ray Tracing Simulation of Images of Dislocations and Inclusions on X-Ray Topographs of GaAs Epitaxial Wafers

In x-ray topography studies, ray tracing simulation has been particularly useful in identifying and characterizing Burgers vectors of dislocations using only one reflection instead of the traditional method of recording at least three reflections and applying $$\vec{g} \cdot \vec{b} = 0$$ and $$\vec{g} \cdot \vec{b} \times \vec{l} = 0$$ criteria. In this study, ray tracing simulation of expected dislocations in (AlxGa(1–x))0.5In0.5P epitaxial layers on GaAs substrates has been carried out by using well-known expressions for displacement fields around dislocations. By comparing the simulated images with observed images on monochromatic x-ray topographs, the Burgers vectors have been characterized. The x-ray topographs from the (AlxGa(1–x))0.5In0.5P epitaxial layers also reveal a unique pattern consisting of a series of circular dark contrast features from inclusions. These dark circles decrease in size as the center of the inclusions is approached. Ray tracing simulated image of an inclusion assuming a spherical strain field matches well with the experimental image, thus providing information on the level of strain around the inclusion.     

PSOBLAP: Particle Swarm Optimization-Based Bandwidth and Link Availability Prediction Algorithm for Multipath Routing in Mobile Ad Hoc Networks

Wireless Personal Communications - In mobile ad hoc network (MANET), optimal path identification is the main problem for implementing the Multipath routing technique. MANET desires an efficient...     

Design of a Buffer Enabled Ad hoc On-demand Multipath Distance Vector Routing Protocol for Improving Throughput in Mobile Ad hoc Networks

Wireless Personal Communications - The buffering in Mobile Ad hoc Networks (MANETs) will depend on end-to-end delay of every user’s information from the arrival time of the resource node...     

Delineation of Groundwater Potential Zones of Coastal Groundwater Basin Using Multi-Criteria Decision Making Technique

Delineation of groundwater potential zones (GWPZ) has been performed for a coastal groundwater basin of eastern India. The groundwater potential zone index (GWPZI) map is generated by using Analytic Hierarchy Process (AHP) from different influencing features, e.g., Land Use/Land Cover (LU/LC), soil (S), geomorphology (GM), hydrogeology (HG), surface geology (SG), recharge rate (RR), drainage density (DD), rainfall (RF), slope (Sl), surface water bodies (SW), lineament density (LD), and Normalized Difference Vegetative Index (NDVI). Recharge rate values are estimated from hydrological water balance model. Overlay weighted sum method is used to integrate all thematic feature maps to generate GWPZ map of the study area. Four zones have been identified for the coastal groundwater basin [very good: 36.39 % (273.53 km², good: 43.57 % (327.47 km²), moderate: 18.27 % (137.30 km²), and poor: 1.77 % (13.27 km²)]. Areas in north to south-west and south-east direction show very good GWPZ due to the presence of low drainage density. GWPZ map and well yield values show good agreement. Sensitivity analysis reveals that exclusion/absence of rainfall and lineament density increases the poor groundwater potential zones. Omission of hydrogeology, soils, surface geology, and NDVI show maximum increase in good GWPZ. Obtained GWPZ map can be utilized effectively for planning of sustainable agriculture. This analysis demonstrates the potential applicability of the methodology for a general coastal groundwater basin.     

Electric field strength effects on time-dependent passivation of metal surfaces

This paper presents further results and extensions of our previous point defect model for time-dependent growth of passive oxide films on metal surfaces. Specifically, by accounting for vacancies as material species rather than just holes in the oxide lattice, the model incorporates more plausible expressions for interfacial reactions and associated kinetic rate expressions. We use the model to explore the general effects of varying metal valence and electrolyte pH on passive film growth. Furthermore, we examine key assumptions concerning the thickness dependence of the electric field within the film. When the electric field inside the film remains constant and the rate constant for oxygen vacancy production varies with applied potential, the model predicts trends in thickness versus potential in reasonable agreement with experimental data for a variety of metal/metal oxide systems. This represents a considerable improvement upon the previous ‘high-field’ form of the model which assumed rate constants independent of potential and electric field in the film varying with thickness.     

Enhancing Quality of Coverage for Target Coverage Problem Using Discrete Haar Wavelet

Quality of coverage is one of the fundamental issues in wireless sensor networks, particularly for the deterministic placement of sensors. One of the methods to improve the quality of coverage is to place the minimum number of sensors in the optimal position to cover the entire target. This paper proposes a discrete Haar wavelet transform for deterministic sensor placement in the target coverage problem. Dilation and translation of Haar wavelet transform are used for identifying the optimal position of sensors. Simulation results validate the performance of discrete Haar wavelet transform better than random placement in terms of optimal placement, quality of coverage and network traffic reduction.     

Mapping of Lattice Strain in 4H-SiC Crystals by Synchrotron Double-Crystal X-ray Topography

The presence of lattice strain in n-doped 4H-SiC substrate crystals grown by a physical vapor transport method can strongly influence the performance of related power devices that are fabricated on them. Information on the level and the variation of lattice strain in these wafer crystals is thus important. In this study, a non-destructive method is developed based on synchrotron double-crystal x-ray topography to map lattice strains in 4H-SiC wafers. Measurements are made on two 4H-SiC substrate crystals—one is an unprocessed commercial wafer while the other was subject to a post-growth high-temperature heat treatment. Maps of different strain components are generated from the equi-misorientation contour maps recorded using synchrotron monochromatic radiation. The technique is demonstrated to be a powerful tool in estimating strain fields in 4H-SiC crystals. Analysis of the strain maps also shows that the normal strain components vary much more significantly than do the shear/rotation components, indicating that lattice dilation/compression rather than lattice tilt is the major type of deformation caused by both the incorporation of nitrogen dopants and the nucleation of basal plane dislocations.