Data Exploration Interface for Digital Forensics

The fast capacity growth of cheap storage devices presents an ever-growing problem of scale for digital forensic investigations. One aspect of scale problem in the forensic process is the need for new approaches to visually presenting and analyzing large amounts of data. Current generation of tools universally employ three basic GUI components—trees, tables, and viewers—to present all relevant information. This approach is not scalable as increasing the size of the input data leads to a proportional increase in the amount of data presented to the analyst. We present an alternative approach, which leverages data visualization techniques to provide a more intuitive interface to explore the forensic target. We use tree visualization techniques to give the analyst both a high-level view of the file system and an efficient means to drill down into the details. Further, we provide means to search for keywords and filter the data by time period

Capillary Break-up Rheometry of Low-Viscosity Elastic Fluids

Submitted to Applied Rheology, August 2004We investigate the dynamics of the capillary thinning and break-up process for low viscosity elastic fluids such as dilute polymer solutions. Standard measurements of the evolution of the midpoint diameter of the necking fluid filament are augmented by high speed digital video images of the break up dynamics. We show that the successful operation of a capillary thinning device is governed by three important time scales (which characterize the relative importance of inertial, viscous and elastic processes), and also by two important length scales (which specify the initial sample size and the total stretch imposed on the sample). By optimizing the ranges of these geometric parameters, we are able to measure characteristic time scales for tensile stress growth as small as 1 millisecond for a number of model dilute and semi-dilute solutions of polyethylene oxide (PEO) in water and glycerin. If the aspect ratio of the sample is too small, or the total axial stretch is too great, measurements are limited, respectively, by inertial oscillations of the liquid bridge or by the development of the well-known beads-on-a-string morphology which disrupt the formation of a uniform necking filament. By considering the magnitudes of the natural time scales associated with viscous flow, elastic stress growth and inertial oscillations it is possible to construct an “operability diagram” characterizing successful operation of a capillary break-up extensional rheometer. For Newtonian fluids, viscosities greater than approximately 70 mPa.s are required; however for dilute solutions of high molecular weight polymer the minimum viscosity is substantially lower due to the additional elastic stresses arising from molecular extension. For PEO of molecular weight 106 g/mol, it is possible to measure relaxation times of order 1 ms in dilute polymer solutions of viscosity 2 – 10 mPa.s.NS

Microdevices for extensional rheometry of low viscosity elastic liquids : a review

Extensional flows and the underlying stability/instability mechanisms are of extreme relevance to the efficient operation of inkjet printing, coating processes and drug delivery systems, as well as for the generation of micro droplets. The development of an extensional rheometer to characterize the extensional properties of low viscosity fluids has therefore stimulated great interest of researchers, particularly in the last decade. Microfluidics has proven to be an extraordinary working platform and different configurations of potential extensional microrheometers have been proposed. In this review, we present an overview of several successful designs, together with a critical assessment of their capabilities and limitations

The Inertio-Elastic Planar Entry Flow of Low-Viscosity Elastic Fluids in Micro-fabricated Geometries

The non-Newtonian flow of dilute aqueous polyethylene oxide (PEO) solutions through microfabricated planar abrupt contraction-expansions is investigated. The contraction geometries are fabricated from a high-resolution chrome mask and cross-linked PDMS gels using the tools of soft-lithography. The small length scales and high deformation rates in the contraction throat lead to significant extensional flow effects even with dilute polymer solutions having time constants on the order of milliseconds. The dimensionless extra pressure drop across the contraction increases by more than 200% and is accompanied by significant upstream vortex growth. Streak photography and videomicroscopy using epifluorescent particles shows that the flow ultimately becomes unstable and three-dimensional. The moderate Reynolds numbers (0.03 ⤠Re ⤠44) associated with these high Deborah number (0 ⤠De ⤠600) microfluidic flows results in the exploration of new regions of the Re-De parameter space in which the effects of both elasticity and inertia can be observed. Understanding such interactions will be increasingly important in microfluidic applications involving complex fluids and can best be interpreted in terms of the elasticity number, El = De/Re, which is independent of the flow kinematics and depends only on the fluid rheology and the characteristic size of the device.NS

Formulation, characterisation and flexographic printing of novel Boger fluids to assess the effects of ink elasticity on print uniformity

Model elastic inks were formulated, rheologically characterised in shear and extension, and printed via flexography to assess the impact of ink elasticity on print uniformity. Flexography is a roll-to-roll printing process with great potential in the mass production of printed electronics for which understanding layer uniformity and the influence of rheology is of critical importance. A new set of flexo-printable Boger fluids was formulated by blending polyvinyl alcohol and high molecular weight polyacrylamide to provide inks of varying elasticity. During print trials, the phenomenon of viscous fingering was observed in all prints, with those of the Newtonian ink exhibiting a continuous striping in the printing direction. Increasing elasticity significantly influenced this continuity, disrupting it and leading to a quantifiable decrease in the overall relative size of the printed finger features. As such, ink elasticity was seen to have a profound effect on flexographic printing uniformity, showing the rheological tuning of inks may be a route to obtaining specific printed features

Power sensitive algorithms and protocols for wireless cellular and Ad Hoc networks

A suite of distributed power control schemes with active link protection (DPC/ALP) is studied in this thesis for Ad Hoc and cellular network scenarios. --Abstract, page iii

Active Link Protection with Distributed Power Control of Wireless Networks

A suite of distributed power control schemes (DPC) with active link protection (ALP) is studied in this paper for cellular networks. The DPC/ALP scheme protects the active links and ensures that they sustain their quality through out their transmission. The DPC/ALP either admits or rejects new links gaining access to the network while maintaining the quality of service (QoS) defined in terms of Signal to Noise Ratio (SIR). The DPC/ALP schemes operate only using local measurements. A networking approach to power control is taken here based on the concept of active link protection, which naturally supports the implementation of admission control. The convergence of all the schemes is shown analytically. Simulation experiments are designed to explore the network dynamics and operational effects. The proposed schemes are demonstrated on uplink power control scenarios in the case of cellular networks focusing mainly on CDMA systems. Results indicate that our scheme uses least possible transmission power for each user, converges in lesser number of iterations, and accommodates more users thus increasing network capacity or spatial re-use

Investigation of the layering mechanism of agglomerate growth during drum pelletization

Conventional drum pelletization circuits exhibit undesirable surging behavior that is known to result from uncontrolled occurrence of the mechanisms of nucleation, coalescence and layering. This study was undertaken to investigate the mechanism of pellet growth by layering. Several laboratory experiments were carried out to delineate the effect of feed moisture content and feed quantity. This paper presents an analysis of the experimental results and a simple model to describe the layering process. (C) 2002 Published by Elsevier Science B.V