Vortex reconnections between coreless vortices in binary condensates

Vortex reconnections plays an important role in the turbulent flows associated with the superfluids. To understand the dynamics, we examine the reconnections of vortex rings in the superfluids of dilute atomic gases confined in trapping potentials using Gross-Petaevskii equation. Furthermore we study the reconnection dynamics of coreless vortex rings, where one of the species can act as a tracer.Comment: 9 pages, Proceeding from International Conference On Complex Processes in Plasmas and Nonlinear Dynamical Systems, Gandhinagar, India (November 2012

Characterization of polybenzimidazole (PBI) film at high temperatures

Polybenzimidazole, a linear thermoplastic polymer with excellent thermal stability and strength retention over a wide range of temperatures, was evaluated for its potential use as the main dielectric in high temperature capacitors. The film was characterized in terms of its dielectric properties in a frequency range of 50 Hz to 100 kilo-Hz. These properties, which include the dielectric constant and dielectric loss, were also obtained in a temperature range from 20 C to 300 C with an electrical stress of 60 Hz, 50 V/mil present. The alternating and direct current breakdown voltages of silicone oil impregnated films as a function of temperature were also determined. The results obtained indicate that while the film remained relatively stable up to 200 C, it exhibited an increase in its dielectric properties as the temperature was raised to 300 C. It was also found that conditioning of the film by heat treatment at 60 C for six hours tended to improve its dielectric and breakdown properties. The results are discussed and conclusions made concerning the suitability of the film as a high temperature capacitor dielectric

Role of Second Formant Frequency( F2) in Forensic Speaker Identification

Identification of a speaker specific feature is an almost impossible task because of the enormous number of features which can affect a single voice utterance.F2, (marker of vowel position) plays an important role in vowel identification. The present study is an statistical analysis conducted on the 16 speakers’ F2, F2- F1 and F3-F2 values for the vowels; “/a:/, /i:/ and /u:/. Vowel /a/ showed considerable height difference in Known sample (where the researcher knew the Speaker) and Unknown sample (someone else collected the sample)

Vehicle simulations of fuel economy for an automatic transmission and a ratio limited continuously variable transmission

An automatic transmission (AT) of a vehicle was compared with a ratio limited Continuously Variable Transmission (CVT). Dynamic model of a passenger car was simulated to compare the overall efficiency of the vehicle equipped with these different types of transmissions. The overall efficiencies were calculated in terms of fuel consumption of the vehicle. The results are based on the Environmental Protection Agency\u27s (EPA) city and highway driving cycles. A Modular approach is taken to model an existing vehicle. The complete model is subdivided into an engine model, road load model, throttle and brake pedal models, and a transmission model. The model is simulated in MATLAB/Simulink software. The automatic transmission model was then replaced by a CVT model and simulated under similar conditions to compare the overall gain in the fuel economy. The simulation results for the automatic transmission closely match with the data obtained from the EPA. The results for the ratio limited CVT indicate improvement in the fuel economy of the vehicle under both the urban and highway driving cycles

Optimal Battery Operations and Design Considering Capacity Fade Mechanisms

Safely and capacity fade are the key issues that restrict the use of the lithium-ion battery for many applications. These issues are being tackled in a variety of ways. This dissertation focuses on using detailed continuum-level electrochemical models to study transport, kinetics, and mechanical processes in the lithium-ion batteries. These models can be used to quantify the effect of capacity fade mechanisms (side reactions and mechanical degradation) and improve the safety aspects of the lithium ion batteries. Three capacity-fade mechanisms—solid electrolyte interface side reaction, lithium-plating side reaction and mechanical degradation due to intercalation-induced stresses—are considered in the dissertation. Monitoring and control of plating side reaction is also very critical for battery safety. Two main focus areas of the dissertation are: 1) Optimal battery operation (design of charging/discharging protocols) considering three capacity fade mechanisms mentioned previously along with safety issues 2) Rational battery design (choice of porosity, thicknesses of electrodes, etc.) considering discharge capacity and capacity fade mechanism

Novel Biosensing Approaches for Detection of Exosomal Proteins

Exosomes are endocytic lipid membrane-bound bodies that have been shown to carry proteins associated with cancer and neurodegenerative disease. This has led to an exponential rise in research that looks to incorporate exosomal proteins as disease biomarkers within diagnostic assays. Furthermore, ubiquitous presence of exosomes in nearly all biological fluids creates the possibly of minimally invasive liquid biopsies for the patient. However, the heterogeneity of exosomes and complexity of biological source materials requires a consideration of optimal isolation protocols. More importantly, the development of effective exosome based assays is limited by the scarcity of translational characterization approaches that are capable of determining their molecular composition and physical properties in physiological fluids. The key objectives of this doctoral research was to establish a robust exosome isolation protocol from complex media, prior to sensing the exosomes on an immunosensor transduced by acoustic wave and electrochemical measurements. This work also looked to enhance these platforms from their current baseline performance, through the implementation of various surface structure modifications. A size exclusion chromatography approach was developed for the isolation of exosomes expressing CD63, Alix, CD81 and CD9 proteins, and allowed them to be extracted effectively from cell culture media, human serum and urine. Isolated exosomes were subsequently detected on a quartz crystal microbalance with dissipation (QCM-D) monitoring, after the optimisation of an affinity-based immunofunctionalisation approach. This technique displayed high sensitivity and specificity towards exosomal CD63 at clinically relevant concentrations in complex media. The QCM-D sensor was also used as a working electrode, as part of an electrochemical cell, to enable additional impedance spectroscopy analysis of exosome binding in tandem with the QCM-D response, collectively termed EQCM-D. The combination of these approaches offers a label-free, sensitive and real-time approach to exosome detection. The sensitivity of the EQCM-D platform was improved through surface formation of tuneable gold nanoparticle arrays from selective impregnation of block-copolymer templates, taking advantage of their segregation behaviour. This presented a versatile approach to tune sensor surfaces in order to improve ligand orientation and subsequent analyte binding. Similar advancements were made on silica detection surfaces through the formation of silica inverse opal crystals, with differing thicknesses, using a single-step co-assembly approach that combines a sol-gel matrix with poly(methyl methacrylate) (PMMA) spheres. Porous networks atop the sensors increased the internal surface area significantly, translating to a higher binding capacity of exosomes notwithstanding a higher degree of artefact entrapment. The results achieved through this work offer a potential for multi-modal analysis of exosomal proteins in diagnostics, underpinned by acoustic wave methodologies and nanostructured materials

EFFECT OF GRAPHENE-BASED FILLERS ON THE PROPERTIES OF SUNFLOWER-BASED POLYURETHANE

Polyurethane market majorly depends on synthetic materials which are noxious. This stimulated an idea to replace petrochemical resources with renewable resources for polyurethane production. Keeping this in mind, this research focused on the use of sunflower oil for the preparation of polyol and its use in polyurethane composition. The reaction mechanism of epoxidation and ring-opening was approached for the conversion of sunflower oil to polyol. During the conversion of sunflower oil, unsaturated groups of sunflower oil were converted into hydroxyl groups of polyol. Sunflower oil-based polyol was successfully blended with methylene diphenyl diisocyanate (MDI) to form urethane bonds. Confirmative tests such as fourier transform infrared spectroscopy (FTIR), gel permeation chromatography (GPC), viscosity, and hydroxyl number analysis were performed. Very small amounts of graphene-based fillers such as graphene nanoplatelets (GNPs), graphene nanoribbon (GNR), graphene oxide (GO), and reduced graphene oxide (rGO) were separately dispersed into polyol by ultrasonication method to prepare polyurethane composites to enhance thermal and mechanical strength of the polyurethane. Structure of graphene-based fillers was confirmed by X-ray diffraction study. Film specimens from polyurethane composites were prepared for mechanical tests such as Shore D hardness, tensile and flexural. In the study of tensile strength, the highest tensile strength was recorded 34.9 MPa for polyurethane/graphene nanoplatelet films. For thermal stability analysis, thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and dynamic mechanical analysis (DMA) tests were conducted. Almost all polyurethane composite samples were thermally stable up to 280 oC. The change in thermal stability upon adding graphene-based fillers was analyzed by comparing residual percentages. The surface morphology of the films was studied by water contact angle (WCA), and atomic force microscopy (AFM). The highest WCA was measured at 104.22 for with 0.05 wt.% rGO filler. Hence, this research studied the effect of a very small quantity of graphene-based fillers on the sunflower oil-based polyurethane film

High-speed helical gear design

Call number: LD2668 .R4 1966 S96