PVA/Chitosan/Silver Nanoparticles Electrospun Nanocomposites: Molecular Relaxations Investigated by Modern Broadband Dielectric Spectroscopy

In this study, we used broadband dielectric spectroscopy to analyze polymer nanofibers of poly(vinyl alcohol)/chitosan/silver nanoparticles. We also studied the effect of incorporating silver nanoparticles in the polymeric mat, on the chain motion dynamics and their interactions with chitosan nanofibers, and we calculated the activation energies of the sub-Tg relaxation processes. Results revealed the existence of two sub-Tg relaxations, the first gets activated at very low temperature (−90 °C) and accounts for motions of the side groups within the repeating unit such as –NH2, –OH, and –CH2OH in chitosan and poly(vinyl alcohol). The second process gets activated around −10 °C and it is thought to be related to the local main chain segments’ motions that are facilitated by fluctuations within the glycosidic bonds of chitosan. The activation energy for the chitosan/PVA/AgNPs nanocomposite nanofibers is much higher than that of the chitosan control film due to the presence of strong interactions between the amine groups and the silver nanoparticles. Kramers–Krönig integral transformation of the ε′′ vs. f spectra in the region of the chitosan Tg helped resolve this relaxation and displayed the progress of its maxima with increasing temperature in the regular manner

Polymer chain dynamics in epoxy based composites as investigated by broadband dielectric spectroscopy

Epoxy networks of the diglycidyl ether of bisphenol A (DGEBA) were prepared using 3,3′- and 4,4′-diaminodiphenyl sulfone isomer crosslinkers. Secondary relaxations and the glass transitions of resultant networks were probed using broadband dielectric spectroscopy (BDS). A sub-Tgγ relaxation peak for both networks shifts to higher frequencies (f) with increasing temperature in Arrhenius fashion, both processes having the same activation energy and being assigned to phenyl ring flipping in DGEBA chains. A β relaxation is assigned to local motions of dipoles that were created during crosslinking reactions. 4,4′-based networks exhibited higher Tg relative to 3,3′-based networks as per dynamic mechanical as well as BDS analyses. The Vogel–Fulcher–Tammann–Hesse equation fitted well to relaxation time vs. temperature data and comparison of Vogel temperatures suggests lower free volume per mass for the 3,3′-based network. The Kramers–Krönig transformation was used to directly calculate dc-free ɛ″ vs. f data from experimental ɛ′ vs. f data. Distribution of relaxation times (DRT) curves are bi-modal for the 3,3′-crosslinked resin suggesting large-scale microstructural heterogeneity as opposed to homogeneity for the 4,4′-based network whose DRT consists of a single peak.U.S. Office of Naval Research, Award N00014-07-1-1057 and fellowship support from the Department of Education Graduate Assistance in Areas of National Need Award P200A090066. Qatar University's Center for Advanced Materials' Start-Up grant

Interactive Visualization and Analysis of Hurricane Data

We present a novel methodology to process hurricane data to be ready for display in Microsoft Live Labs Pivot. We describe the complexity of hurricane data files, which makes gleaning information out of them difficult. Hurricane data files contain a significant amount of information pertaining to hurricanes, however it is a poor representation of data. We present an algorithm for a parser to extract information out of data files and generate a CXML formatted file compatible with Microsoft Live Labs Pivot for a more appealing and therefore more useful statistical representation. We show how historical data from past hurricanes can be modified for representation. © 2011 IEEE

A Near-Zero Run-Time Energy Overhead Within a Computation Outsourcing Framework For Energy Management In Mobile Devices

In order to support run-time computation outsourcing to save energy, a certain amount of overhead has to be incurred to facilitate appropriate communication. As computation outsourcing is a methodology for saving energy on mobile devices, the amount of overhead incurred must be kept to a minimum. In this work, we support our compile-time methodology to facilitate the outsourcing of intensive computation with a run-time monitoring system that consumes an extremely low amount of energy (near-Zero). This near-Zero overhead resulted from analyzing the code at compile-time rather than run-time execution and profiling. The compile-time strategy utilized in our work analyzes the code at multiple levels of abstraction (High, Medium, and Low). The result of the analysis, which takes advantage of a real-time systems technique that calculates the maximum number of loop iterations, hence giving us a worst-case execution time for each loop within the benchmark application, allows for a fine-grain analysis of our benchmark. Resulting from analyzing the code, a client/server version of the applications is produced. As a result of producing this client/server version, certain runtime support has to take place on both the machine executing the client (the mobile device) as the machine executing the server. Our experimental results as performed on a Sharp Zaurus, utilizing Wi-Fi as a means of communication, showed tremendous energy saving while incurring a near-Zero run-time overhead. © 2008 IEEE

Advancing the Layered Approach to Agent-Based Crowd Simulation

We adapt a scalable layered intelligence technique from the game industry, for agent-based crowd simulation. We extend this approach for planned movements, pursuance of assignable goals, and avoidance of dynamically introduced obstacles/threats, while keeping the system scalable with the number of agents. We exploit parallel processing for expediting the pre-processing step that generates the path-plans offline. We demonstrate the various behaviors in a hall-evacuation scenario, and experimentally establish the scalability of the frame-rates with increasing number of agents

Advancing the Layered Approach to Agent-Based Crowd Simulation

Abstract We adapt a scalable layered intelligence technique from the game industry, for agent-based crowd simulation. We extend this approach for planned movements, pursuance of assignable goals, and avoidance of dynamically introduced obstacles/threats, while keeping the system scalable with the number of agents. We exploit parallel processing for expediting the pre-processing step that generates the path-plans offline. We demonstrate the various behaviors in a hall-evacuation scenario, and experimentally establish the scalability of the frame-rates with increasing number of agents

Energy Management for Mobile Devices through Computation Outsourcing within Pervasive Smart Spaces

Abstract — In this work we explore the opportunity Pervasive Spaces could provide as supplemental energy sources. We utilize the nature of pervasive smart spaces to outsource computation that would normally be performed on a mobile device to a surrogate server within the smart space. The decision to outsource a computation depends on whether its energy cost on the device is larger than the cost of communicating its data to the surrogate and receiving the results back. We propose an approach by which the outsourcing decision is made at runtime, while the intelligence that makes that decision is inserted at compile-time as logic that modifies the application code. The merit of our approach is that it is application-independent and requires minimal programmer energy awareness. We utilized a methodology from real-time systems to aid us in constructing the decision making logic. Additionally, we implemented a runtime support on top of Linux to facilitate for testing and experimenting with the client/server outsourcing approach. Our experimental validation and benchmarks shows significant energy saving on the mobile device, which validates our approach as a viable and novel approach to power saving and management for mobile devices

Layered Intelligence for Agent-based Crowd Simulation

We adapt a scalable layered intelligence technique from the game industry, for agent-based crowd simulation. We extend this approach for planned movements, pursuance of assignable goals, and avoidance of dynamically introduced obstacles/threats as well as congestions, while keeping the system scalable with the number of agents. We demonstrate the various behaviors in hall-evacuation scenarios, and experimentally establish the scalability of the frame rates with increasing numbers of agents

Broadband Dielectric Spectroscopic Studies of Molecular Motions in a Nafion® Membrane vs. Annealing Time and Temperature

The dynamics of macromolecular motions as coupled to proton migration in annealed Nafion® membranes were explored at temperatures above 100 °C using broadband dielectric spectroscopy. Loss permittivity vs. frequency spectra of both β and α relaxations showed increased relaxation times with annealing which was rationalized in terms of water de-sorption and diminished free volume. The α relaxation time increases with increased annealing temperature. A parameter N reflecting connectedness of charge hopping pathways was extracted and indicated that the conductivity network accumulates more charge traps, presumably due to free volume decrease, with increased annealing time. Conductivity increases with increased annealing time at all temperatures despite the decrease in N; this suggests a change in the nature of proton hopping on annealing at high temperatures to be between sulfonic acid groups rather than by hopping across H2OH+—OH2 bonds