Synthesis and characterization of bulk and thin film antimony-selenium phase change alloys

Phase change alloys have recently gained increasing attention due to their application in developing phase change random memory (PRAM) devices, as Flash memory based devices are rapidly approaching their technological limitations. The most dominant features of PRAM devices are its non-volatile nature, compatible with present day IC\u27s manufacturing process, high density, fast operation, low power consumption etc; Devices built on binary alloys such as Antimony - Selenium (SbSe) exhibit certain superior properties such as fast operation, reduced power consumption, economical etc. compared to that of ternary alloy (GST). In order to understand this behavior in detail, bulk SbxSe 100-x (40 ≤ x ≤ 70) alloys are synthesized and deposited as thin films on silicon (100) plane substrate. Series of experiments such as X-ray diffraction analysis (XRD), Energy dispersive X-ray diffraction (EDAX), Spectroscopic Ellipsometer, Hall test experiments are carried out to characterize both the bulk and thin films. EDAX experiments show the deviation between bulk and thin films compositions is less than 10%. Diffraction patterns of bulk exhibit orthorhombic structure, i.e., Sb2Se3 type where as thin films demonstrate amorphous behavior. Impact of annealing on thin films is studied by heating the films to 170°C under argon (Ar) ambience. Post annealing results of Sb40Se60 thin films show the crystal structure is orthorhombic and crystallization temperature (Tc) increases with increase in Sb content of the compound. Ellipsometry and Hall measurements of annealed films exhibit high refractive index (n), low extinction coefficient (k) and high carrier concentration with associated low carrier mobility. Further the conductivity of annealed Sb40Se60 thin films switches from p to n type

Development of multi-functional streetscape green infrastructure using a performance index approach

The file attached to this record is the author's final peer reviewed version. The Publisher's final version can be found by following the DOI link.This paper presents a performance evaluation framework for streetscape vegetation. A performance index (PI) is conceived using the following seven traits, specific to the street environments – Pollution Flux Potential (PFP), Carbon Sequestration Potential (CSP), Thermal Comfort Potential (TCP), Noise Attenuation Potential (NAP), Biomass Energy Potential (BEP), Environmental Stress Tolerance (EST) and Crown Projection Factor (CPF). Its application is demonstrated through a case study using fifteen street vegetation species from the UK, utilising a combination of direct field measurements and inventoried literature data. Our results indicate greater preference to small-to-medium size trees and evergreen shrubs over larger trees for streetscaping. The proposed PI approach can be potentially applied two-fold: one, for evaluation of the performance of the existing street vegetation, facilitating the prospects for further improving them through management strategies and better species selection; two, for planning new streetscapes and multi-functional biomass as part of extending the green urban infrastructure

Electrochemical kinetics and dimensional considerations at the nanoscale

It is shown that the consideration of the density of states variation in nanoscale electrochemical systems yields modulations in the rate constant and concomitant electrical currents. The proposed models extend the utility of Marcus-Hush-Chidsey (MHC) kinetics to a larger class of materials and could be used as a test of dimensional character. The implications of the study are of much significance to an understanding and modulation of charge transfer nanostructured electrodes.Comment: 15 pages, 6 figure

Enhanced voltage generation through electrolyte flow on liquid-filled surfaces.

The generation of electrical voltage through the flow of an electrolyte over a charged surface may be used for energy transduction. Here, we show that enhanced electrical potential differences (i.e., streaming potential) may be obtained through the flow of salt water on liquid-filled surfaces that are infiltrated with a lower dielectric constant liquid, such as oil, to harness electrolyte slip and associated surface charge. A record-high figure of merit, in terms of the voltage generated per unit applied pressure, of 0.043 mV Pa-1 is obtained through the use of the liquid-filled surfaces. In comparison with air-filled surfaces, the figure of merit associated with the liquid-filled surface increases by a factor of 1.4. These results lay the basis for innovative surface charge engineering methodology for the study of electrokinetic phenomena at the microscale, with possible application in new electrical power sources

Cost effective prevention of reflective cracking in composite pavements

Louisiana had experimented with various techniques and treatments to control reflection cracking since the 1970s; however, the cost-effectiveness and performance of these methods had not been reliably evaluated. In addition, scientific evaluation and testing of these treatment methods was not performed on many projects. To ensure successful control of this distress and effective allocation of maintenance funds, there is a critical need to assess the performance of pavement sections across the state built with various treatment methods and to determine the most cost-effective techniques to delay or to prevent reflection cracking in composite pavements. The objective of this study is to evaluate and compare different reflection cracking control treatments by evaluating the performance, constructability, and cost-effectiveness of pavements built with these treatments across the state. To achieve this objective, a survey of current state practices identified the treatment methods that are used or that had been used to delay and mitigate reflection cracking in composite pavements. Based on this survey and a thorough review of LADOTD databases, pavement sections in which reflective crack control treatment methods were used, were identified. Projects with sufficient years in service and with available untreated segments were selected for detailed performance and economic evaluation. In total, the performance of 50 different sites that were constructed with various treatments was monitored for a period ranging from four to 18 years. Results of this analysis assessed the benefits of these crack control techniques in terms of performance, economic worthiness, constructability, and long-term benefits. Among various treatments that were analyzed, saw and seal, and chip seal as an interlayer provided with the most promising results in terms of performance and economic worthiness. However, the cost-effectiveness of fiber-glass grid was not validated as compared to regular HMA overlays. Stress absorbing membrane interlayer and high strain asphalt crack relief interlayer (STRATA®) showed mixed results in terms of performance and cost effectiveness. In addition, there were an insufficient number of projects for stress absorbing membrane interlayer, paving fabrics and high strain asphalt reflective crack relief interlayer to allow for drawing conclusions on the effectiveness of these treatment methods

Particle breakage in sand blasting due to impact on ductile materials

Cleaning of rust, paint or removing burrs and many other such applications are done by several processes. Sand blasting is one of them, where a stream of sand particles is forcefully projected onto a surface, with compressed air or steam. These sand particles break up into very small pieces upon impact, which are inhaled by workers to cause silicosis. While much research has been done on the surface being impacted, very little research has been done on the particle itself. Hence, proper analytical modeling of the sand blasting process from the particle perspective, validated by experimental results, is required to predict the sand particle breakage.;In the present thesis, a finite element model of the sand particle is developed in LS-INGRID and a transient dynamic analysis is performed in LS-DYNA3D. This study focuses mainly on the propagation of stress waves and the volume loss of the sand particle upon impacting an aluminum plate. Three different shapes of the sand particle and five different sizes with varying impact angles and particle velocities were chosen to analyze the influence of impact. The results of the model showed close correlation with the experimental results of A. J. Sparks and I. M. Hutchings. These results were presented in the form of graphs of dependencies between volume loss and other parameters affecting the impact. It was concluded that 100mum size is the optimum size of the sand particle that increases the safety of the workers performing sandblasting due to its lesser volume loss

Algorithms for LiDAR Based Traffic Tracking: Development and Demonstration

The current state of the art of traffic tracking is based on the use of video, and requires extensive manual intervention for it to work, including hours of painstaking human examination of videos frame by frame which also make the acquisition of data extremely expensive. Fundamentally, this is because we do not have observability of the actual scene from a camera which captures a 2D projection of the 3D world. Even if video were to be automated, it would involve such algorithms as RANSACK for outlier elimination while matching features across frames or across multiple cameras. This results in algorithms without stationary relationships between input and output statistics, i.e., between sensing resolution and error and estimated positions and velocities. LiDAR directly provides 3D point clouds, giving a one-one mapping between the scene from the physical world and data. However, available eye-safe lidars have been developed for autonomous vehicles, and provide only sparse point clouds when used for longer range data acquisition. Our experimental results use the Velodyne HDL 64E lidar. The sparse nature of data points returned by the Velodyne LiDAR rendered most of the algorithms for object identification and tracking using 3D point clouds at the point cloud library (PCL), a leading multi-agency open source research initiative focused on 3D point cloud processing ineffective for our work. Hence I developed a comprehensive set of algorithms developed to identify and remove background; detect objects through clustering of remaining points; associate detected objects across frames, track the detected objects, and estimate the dimension of objects. Two different complementary algorithms based on, surface equation (in 3D Cartesian coordinates) and LiDAR spherical coordinates were developed for background identification and removal. Delaunay triangulation based clustering is performed to identify objects. Kalman filter and Hungarian assignment algorithm are used in tandem to track multiple objects simultaneously. A novel bounding box algorithm was devised taking advantage of the way LiDAR scans the environment to predict the orientation and estimate dimension of objects. Trajectory analysis is performed to identify and split any wrong associations, join trajectories belonging to same object and stitch partial trajectories. Finally, the results are stored in a format usable by various transportation or traffic engineering applications. The algorithms were tested by peers with data collected at three intersections. Detection rate and counting accuracy are above 95% which is on par with commercial video solutions that employ humans to varying degrees. While prototyping for the algorithms was done it MATLAB, preliminary tests of conversion to C++ showed that the developed algorithms can be executed in real time on standard computer hardware

Design of Multilevel Inverter Driven Induction Machine

Multilevel inverters have gained interest in recent years in high-power medium-voltage industry. This paper considered the most popular structure among the transformer-less voltage source multilevel inverters, the diode-clamped inverter based on the neutral point converter. This paper proposes a single carrier multi-modulation SVPWM technique with conventional space vector switching sequence. Simulation results presents comparison of single and multicarrier conventional space vector switching sequence with general switching sequence of nine-level diode-clamped inverter for stator currents, electromagnetic torque and speed for constant modulation index and for constant V/f control method. Simulation is carried out in MATLAB-Simulink software. Keywords- Multilevel inverter, APODC, SVPWM, total harmonic distortion, Diode-clamped inverter, SCMMOS, MCMMOS, Induction machine, synchronously rotating reference fram

Optimized SVPWM for Multilevel Inverter

Multilevel inverters have gained interest in recent years in high-power medium-voltage industry. This paper considered the most popular structure among the transformer-less voltage source multilevel inverters, the diode-clamped converter based on the neutral point converter. This paper proposes a single carrier multi-modulation SVPWM technique with an optimized space vector switching sequence. Simulation results presents comparison of single and multicarrier optimized space vector switching sequence with general switching sequence of nine-level diode-clamped inverter for the parameter total harmonic distortion and fundamental component of voltage