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2008

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Articles 211 - 240 of 7321

Full-Text Articles in Physical Sciences and Mathematics

The Adaptability Of Langmuir Probes To The Pico-Satellite Regime, Andrew Jay Auman Dec 2008

The Adaptability Of Langmuir Probes To The Pico-Satellite Regime, Andrew Jay Auman

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

The purpose of this thesis is to investigate whether it is feasible to use Langmuir probes on pico-satellites flying in low Earth orbit over mid- to low-latitude geographic regions. Following chapters on the expected ionospheric conditions and an overview of Langmuir probe theory, a chapter addressing the difficulties involved with pico-satellite Langmuir probes is presented. Also, the necessary satellite-to-probe surface area requirements in order to achieve confidence in pico-satellite Langmuir probe data, for the orbital regions of interest to this thesis, are stated.

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The Möbius Geometry Of Hypersurfaces, Michael Bolt Dec 2008

The Möbius Geometry Of Hypersurfaces, Michael Bolt

University Faculty Publications and Creative Works

No abstract provided.

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Synthesis And Characterization Of Biodegradable Polyurethanes For Biomedical Application, Changhong Zhang Dec 2008

Synthesis And Characterization Of Biodegradable Polyurethanes For Biomedical Application, Changhong Zhang

All Dissertations

This dissertation constitutes the studies about the biomedical materials research of novel polyurethanes. These elastic and degradable polyurethanes exhibited the potential for drug delivery, scaffold fabrication by novel ink-jet printing technology or other biomedical applications. This dissertation includes two parts about two different types of polyurethanes.
In the first part of this dissertation, we studied a polyurethane that was synthesized from methylene di-p-phenyl-diisocyanate (MDI), polycaprolactone diol (PCL-diol) and N, N-bis (2-hydorxyethyl)-2-aminoethane-sulfonic acid (BES). MDI, PCL-diol and BES were polymerized into polyurethane and served as the hard segment, soft segment and chain extender respectively. The effects of the chain extender BES …

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Fabrication And Optical Properties Of Noble Metal Nanostructures, Mark Kinnan Dec 2008

Fabrication And Optical Properties Of Noble Metal Nanostructures, Mark Kinnan

All Dissertations

Experimental and theoretical results are presented in Chapters 2, 3, and 4 on the effects of dielectric medium, particle size, and interparticle distance, respectively, on plasmon coupling in two-dimensional arrays of silver nanoparticles. The arrays were fabricated via the self-assembly of single crystal particles from c.a. 46 nm to 287 nm on PVP-modified glass substrates. Spin-coated poly(methylmethacrylate) layers were used to immobilize the particles and prevent their surface aggregation. Varying the thickness of the PMMA layer made it possible to change the average dielectric medium between the particles. UV-Visible spectra of different arrays were compared to the corresponding electron microscope …

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Calculations Of Diffusion In Fcc Binary Alloys Using On-The-Fly Kinetic Monte Carlo, Erdi Bleda Dec 2008

Calculations Of Diffusion In Fcc Binary Alloys Using On-The-Fly Kinetic Monte Carlo, Erdi Bleda

All Dissertations

With the recent advancements in computer technologies and the improvements in simulation algorithms, along with the theories, has allowed scientists to carry out diffusion calculations more efficiently, especially for the cases where either the diffusion itself takes longer, or there is no available isotope to carry out the diffusion experiments such as tracer diffusion.
In this work, we present a systematic approach to diffusion in intermetallic alloys such as weakly clustered Cu — Ni and weakly ordered Au — Ag. We use Accelerated Molecular Dynamics (AMD) combined with the Embedded Atom Method (EAM) to find the necessary saddlepoint energies. With …

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Fluorescent Conjugated Polymer Dots For Single Molecule Imaging And Sensing Applications, Changfeng Wu Dec 2008

Fluorescent Conjugated Polymer Dots For Single Molecule Imaging And Sensing Applications, Changfeng Wu

All Dissertations

While single molecule imaging and sensing hold the promise of providing unprecedented detail about cellular processes, many advanced applications are limited by the lack of appropriate fluorescence probes. In many cases, currently available fluorescent labels are not sufficiently bright and photostable to overcome the background associated with various autofluorescence and scattering processes. This dissertation describes research efforts focused on the development of a novel class of fluorescent nanoparticles called conjugated polymers dots (CPdots) for single molecule fluorescence detection. The CPdots contain highly fluorescent π-conjugated polymers that have been refined over the last decades as the active material in polymer light-emitting …

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Synthesis, Characterization, And Application Of Ag Nanostructures, Stephen Hudson Dec 2008

Synthesis, Characterization, And Application Of Ag Nanostructures, Stephen Hudson

All Dissertations

Noble metal nanoparticles (NPs) have been used for many centuries; however their properties were not truly scrutinized until Michael Farady's investigations in the 1850's. Advances in the field of nanotechnology over the last three decades have enabled insights into the properties of materials as their dimensions are reduced to the nanoscale. The repercussions of these insights are seen in many modern applications.
In this dissertation, properties of novel nanostructures based on Ag NPs are presented and discussed. The exceptional optical properties of Ag NPs stem from the collective oscillations of the conduction electrons known as plasmon resonances. The excitation of …

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Two Categories Of Refutation Decision Procedures For Classical And Intuitionistic Propositional Logic, Edward Doyle Dec 2008

Two Categories Of Refutation Decision Procedures For Classical And Intuitionistic Propositional Logic, Edward Doyle

All Dissertations

An automatic theorem prover is a computer program that proves theorems without the assistance of a human being. Theorem proving is an important basic tool in proving theorems in mathematics, establishing the correctness of computer programs, proving the correctness of communication protocols, and verifying integrated circuit designs.
This dissertation introduces two new categories of theorem provers, one for classical propositional logic and another for intuitionistic propositional logic. For each logic a container property and generalized algorithm are introduced.
Many methods have been developed over the years to prove theorems in propositional logic. This dissertation describes and presents example proofs for …

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Novel Lactide Derived Polymers; Synthesis, Properties And Applications, Dahlia Haynes Dec 2008

Novel Lactide Derived Polymers; Synthesis, Properties And Applications, Dahlia Haynes

All Dissertations

This dissertation primarily encompasses the synthesis, characterization, properties and discussion of applications for lactide derived polymers. The methodology focuses on altering polylactide's (PLA's) dynamic and physical properties increasing its broad market utility in both traditional and non-traditional applications. The fundamentals of this work include understanding and enhancing the polymer chemistry and materials related processes through the use of copolymerization, fluorination, composite chemistry and materials science.
The first chapter discusses the important of this research with emphasis on current world issues that focuses on the feasibility of renewable resources and sustainability implementation. Modification of renewable resource materials like lactic acid is …

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Hybrid Bond-Order Potential For Silicon, Suleiman Oloriegbe Dec 2008

Hybrid Bond-Order Potential For Silicon, Suleiman Oloriegbe

All Dissertations

ABSTRACT
A new hybrid bond-order potential for silicon is developed. The functional form of the potential is derived from hybrid of expressions from empirical bond-order formalism and first principles approximations. The total energy is expressed as the sum of attractive, repulsive and promotion energies. By introducing a screening function derived from approximations to first principles expressions, the potential is made long-ranged by allowing covalent interactions beyond the first nearest neighbor shell of atoms in agreement with quantum mechanical descriptions of the bonding in silicon. Environment-dependent promotion energy is introduced that accurately accounts for energetic interactions due to changes in hybridization …

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Digital Image Ballistics From Jpeg Quantization: A Followup Study, Hany Farid Dec 2008

Digital Image Ballistics From Jpeg Quantization: A Followup Study, Hany Farid

Computer Science Technical Reports

The lossy JPEG compression scheme employs a quantization table that controls the amount of compression achieved. Because different cameras typically employ different tables, a comparison of an image's quantization scheme to a database of known cameras affords a simple technique for confirming or denying an image's source. This report describes the analysis of quantization tables extracted from 1,000,000 images downloaded from Flickr.com.

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Protecting Critical Infrastructure With Games Technology, Adrian Boeing, Martin Masek, Bill Bailey Dec 2008

Protecting Critical Infrastructure With Games Technology, Adrian Boeing, Martin Masek, Bill Bailey

Australian Information Warfare and Security Conference

It is widely recognised that there is a considerable gap in the protection of the national infrastructure. Trying to identify what is in fact ‘critical’ is proving to be very difficult as threats constantly evolve. An interactive prototyping tool is useful in playing out scenarios and simulating the effect of change, however existing simulators in the critical infrastructure area are typically limited in the visual representation and interactivity. To remedy this we propose the use of games technology. Through its use, critical infrastructure scenarios can be rapidly constructed, tested, and refined. In this paper, we highlight the features of games …

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A Holistic Scada Security Standard For The Australian Context, Christopher Beggs Dec 2008

A Holistic Scada Security Standard For The Australian Context, Christopher Beggs

Australian Information Warfare and Security Conference

Supervisory Control and Data Acquisition (SCADA) systems which control Australia’s critical infrastructure are currently demonstrating signs of vulnerabilities as they are being interconnected to corporate networks, essentially exposing them to malicious threats. This paper discusses the vulnerabilities associated with SCADA systems, as well as discussing various SCADA standards and initiatives that have been developed in recent years to mitigate such threats. The paper presents the requirement for a holistic SCADA security standard that is practical and feasible for each SCADA industry sector.

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Visualisation Of Critical Infrastructure Failure, W D. Wilde, M J. Warren Dec 2008

Visualisation Of Critical Infrastructure Failure, W D. Wilde, M J. Warren

Australian Information Warfare and Security Conference

The paper explores the complexity of critical infrastructure and critical infrastructure failure (CIF), real life examples are used to discuss the complexity involved. The paper then discusses what Visualisation is and how Visualisation can be applied to a security situation, in particular critical infrastructure. The paper concludes by discussing the future direction of the research.

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Media, Government And Manipulation: The Cases Of The Two Gulf Wars, William Hutchinson Dec 2008

Media, Government And Manipulation: The Cases Of The Two Gulf Wars, William Hutchinson

Australian Information Warfare and Security Conference

This paper explores the bias and manipulation of the Western mass media during the Gulf wars of 1991 and 2003. The tactics of compliance and the ethics of the press and journalists are examined. The need for a pluralist press is extolled.

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Homotopy Perturbation Method And Padé Approximants For Solving Flierl-Petviashivili Equation, Syed T. Mohynd-Din, Muhammad A. Noor Dec 2008

Homotopy Perturbation Method And Padé Approximants For Solving Flierl-Petviashivili Equation, Syed T. Mohynd-Din, Muhammad A. Noor

Applications and Applied Mathematics: An International Journal (AAM)

In this paper, we present a reliable combination of homotopy perturbation method and Padé approximants to investigate the Flierl-Petviashivili (FP) equation. The approach introduces a new transformation necessary for the conversion of the Flierl-Petviashivili equation to a first order initial value problem and a reliable framework designed to overcome the difficulty of the singular point at x = 0. The proposed homotopy perturbation method is applied to the reformulated first order initial value problem which leads the solution in terms of transformed variable. The desired series solution is obtained by making use of the inverse transformation. The suggested algorithm may …

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Iphone Forensics Methodology And Tools, Haitham Al-Hajri, Krishnun Sansurooah Dec 2008

Iphone Forensics Methodology And Tools, Haitham Al-Hajri, Krishnun Sansurooah

Australian Digital Forensics Conference

iPhone mobile devices are rapidly overtaking the new generation of mobile phones market, especially among the young generation. It is also gaining a lot of popularity among security specialists and fancy gadgets for collectors. The device is considered as a “special” mobile phone due to its ability to perform multi-operations if not multitasking. It can therefore be used as a entertainment media device, a camera, a GPS, Internet surfing via Wi-Fi technology, Internet Mobile Edge Services, personal organizer, and finally performing as a cell phone with all the usual services including sms, and so forth. However, the difference between the …

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The Equivariant Chow Rings Of Quot Schemes, T. Braden, Linda Chen, F. Sottile Dec 2008

The Equivariant Chow Rings Of Quot Schemes, T. Braden, Linda Chen, F. Sottile

Mathematics & Statistics Faculty Works

We give a presentation for the (integral) torus-equivariant Chow ring of the quot scheme, a smooth compactification of the space of rational curves of degree d in the Grassmannian. For this presentation, we refine Evain's extension of the method of Goresky, Kottwitz, and MacPherson to express the torus-equivariant Chow ring in terms of the torus-fixed points and explicit relations coming from the geometry of families of torus-invariant curves. As part of this calculation, we give a complete description of the torus-invariant curves on the quot scheme and show that each family is a product of projective spaces.

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Information Sharing: Hackers Vs Law Enforcement, David P. Biros, Mark Weiser, Jim Burkman, Jason Nichols Dec 2008

Information Sharing: Hackers Vs Law Enforcement, David P. Biros, Mark Weiser, Jim Burkman, Jason Nichols

Australian Information Warfare and Security Conference

The fields of information assurance and digital forensics continue to grow in both importance and complexity, spurred on by rapid advancement in digital crime. Contemporary law enforcement professionals facing such issues quickly discover that they cannot be successful while operating in a vacuum and turn to colleagues for assistance. However, there is a clear need for greater IT-based knowledge sharing capabilities amongst law enforcement organizations; an environment historically typified by a silo mentality. A number of efforts have attempted to provide such capabilities, only to be met with limited enthusiasm and difficulties in sustaining continued use. Conversely, the hacker community …

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Security Metrics - A Critical Analysis Of Current Methods, Manwinder Kaur, Andy Jones Dec 2008

Security Metrics - A Critical Analysis Of Current Methods, Manwinder Kaur, Andy Jones

Australian Information Warfare and Security Conference

This paper documents and analyses a number of security metrics currently in popular use. These will include government standards and commercial methods of measuring security on networks. It will conclude with a critical look at some of the problems and challenges faced when using the metrics available today, and also with the development of new metrics.

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Space-Time Regression Modeling Of Tree Growth Using The Skew-T Distribution, Farouk S. Nathoo Dec 2008

Space-Time Regression Modeling Of Tree Growth Using The Skew-T Distribution, Farouk S. Nathoo

COBRA Preprint Series

In this article we present new statistical methodology for the analysis of repeated measures of spatially correlated growth data. Our motivating application, a ten year study of height growth in a plantation of even-aged white spruce, presents several challenges for statistical analysis. Here, the growth measurements arise from an asymmetric distribution, with heavy tails, and thus standard longitudinal regression models based on a Gaussian error structure are not appropriate. We seek more flexibility for modeling both skewness and fat tails, and achieve this within the class of skew-elliptical distributions. Within this framework, robust space-time regression models are formulated using random …

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Interference Effects Due To Projectile Target Nucleus Scattering In Single Ionization Of H₂ By 75-Kev Proton Impact, Jason S. Alexander, Aaron C. Laforge, Ahmad Hasan, Z. S. Machavariani, M. F. Ciappina, R. D. Rivarola, Don H. Madison, Michael Schulz Dec 2008

Interference Effects Due To Projectile Target Nucleus Scattering In Single Ionization Of H₂ By 75-Kev Proton Impact, Jason S. Alexander, Aaron C. Laforge, Ahmad Hasan, Z. S. Machavariani, M. F. Ciappina, R. D. Rivarola, Don H. Madison, Michael Schulz

Physics Faculty Research & Creative Works

Doubly differential cross sections (DDCSs) for single ionization of molecular hydrogen by 75-keV proton impact have been measured and calculated as a function of the projectile scattering angle and energy loss. Interference structures are observed in the scattering angular dependence of the DDCSs, which disappear, however, at electron speeds near the projectile speed. The comparison to our calculations shows that the projectile-target nucleus interaction plays a central role. Furthermore, our data suggest that for a given scattering angle, ionization favors well-defined molecular orientations.

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Spin- And Fine-Structure-Resolved Ionization Of Krypton, S. Bellm, J. Lower, R. P. Mceachran, E. Weigold, Ciarán Ryan-Anderson, Don H. Madison Dec 2008

Spin- And Fine-Structure-Resolved Ionization Of Krypton, S. Bellm, J. Lower, R. P. Mceachran, E. Weigold, Ciarán Ryan-Anderson, Don H. Madison

Physics Faculty Research & Creative Works

The influence of exchange, correlation, and relativistic effects in the ionization of heavy-target atoms can be sensitively probed by kinematically complete studies involving spin-polarized electrons, in particular when the fine structure of the residual ion is resolved. We present spin asymmetries, triple differential cross sections, and branching ratios for the ionization, by 127.5-eV and 114.3-eV electrons, of ground-state krypton atoms leading to the Kr+ 4s 2S1/2, 4p5 2P1/2, and 4p5 2P3/2 states. In order to untangle contributions from different physical effects, the experimental results are compared to those from distorted-wave Born approximation calculations (non- and semirelativistic) in which bound-state and …

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Preparation Of Carboxylic Acid Functionalized Glycopolymers Through Raft And Post-Polymerization Modification For Biomedical Application, Husnu Alp Alidedeoglu Dec 2008

Preparation Of Carboxylic Acid Functionalized Glycopolymers Through Raft And Post-Polymerization Modification For Biomedical Application, Husnu Alp Alidedeoglu

Dissertations

The primary theme of this dissertation involves the synthesis of well-defined primary amine functionalized polymers, subsequent modification of the polymers to produce novel carboxylic acid functionalized glycopolymers and surface polymerization of these systems utilizing controlled polymerization techniques. Additionally, the synthesis of new water-based allylic copolymer latexes is described. Carbohydrates are natural polymers which possess unlimited structural variations. They carry a huge density of information, and play major roles in recognition events and complex biological operations. For example, hyaluronic acid (HA), an anionic glycosaminoglycan, provides lubricating and cushioning properties in the extracellular matrix and has been found to be involved in …

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On Static And Dynamic Partitioning Behavior Of Large-Scale Networks, Zhongmei Yao, Derek Leonard, Xiaoming Wang, Dmitri Loguinov Dec 2008

On Static And Dynamic Partitioning Behavior Of Large-Scale Networks, Zhongmei Yao, Derek Leonard, Xiaoming Wang, Dmitri Loguinov

Computer Science Faculty Publications

In this paper, we analyze the problem of network disconnection in the context of large-scale P2P networks and understand how both static and dynamic patterns of node failure affect the resilience of such graphs. We start by applying classical results from random graph theory to show that a large variety of deterministic and random P2P graphs almost surely (i.e., with probability 1 − o(1)) remain connected under random failure if and only if they have no isolated nodes. This simple, yet powerful, result subsequently allows us to derive in closed-form the probability that a P2P network develops isolated nodes, and …

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Neural-Network-Based State Feedback Control Of A Nonlinear Discrete-Time System In Nonstrict Feedback Form, Pingan He, Jagannathan Sarangapani Dec 2008

Neural-Network-Based State Feedback Control Of A Nonlinear Discrete-Time System In Nonstrict Feedback Form, Pingan He, Jagannathan Sarangapani

Electrical and Computer Engineering Faculty Research & Creative Works

In this paper, a suite of adaptive neural network (NN) controllers is designed to deliver a desired tracking performance for the control of an unknown, second-order, nonlinear discrete-time system expressed in nonstrict feedback form. In the first approach, two feedforward NNs are employed in the controller with tracking error as the feedback variable whereas in the adaptive critic NN architecture, three feedforward NNs are used. In the adaptive critic architecture, two action NNs produce virtual and actual control inputs, respectively, whereas the third critic NN approximates certain strategic utility function and its output is employed for tuning action NN weights …

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A Model Based Fault Detection And Prognostic Scheme For Uncertain Nonlinear Discrete-Time Systems, Balaje T. Thumati, Jagannathan Sarangapani Dec 2008

A Model Based Fault Detection And Prognostic Scheme For Uncertain Nonlinear Discrete-Time Systems, Balaje T. Thumati, Jagannathan Sarangapani

Electrical and Computer Engineering Faculty Research & Creative Works

A new fault detection and prognostics (FDP) framework is introduced for uncertain nonlinear discrete time system by using a discrete-time nonlinear estimator which consists of an online approximator. A fault is detected by monitoring the deviation of the system output with that of the estimator output. Prior to the occurrence of the fault, this online approximator learns the system uncertainty. In the event of a fault, the online approximator learns both the system uncertainty and the fault dynamics. A stable parameter update law in discrete-time is developed to tune the parameters of the online approximator. This update law is also …

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Link Rate Allocation Under Bandwidth And Energy Constraints In Sensor Networks, Maggie Cheng, Xuan Gong, Lin Cai Dec 2008

Link Rate Allocation Under Bandwidth And Energy Constraints In Sensor Networks, Maggie Cheng, Xuan Gong, Lin Cai

Computer Science Faculty Research & Creative Works

In sensor networks, both energy and band width are scarce resources. in the past, the energy efficient routing problem has been vastly studied in order to maximize network lifetime, but link bandwidth has been optimistically assumed to be abundant. as energy con straint affects how data should be routed, link bandwidth also affects not just the routing topology but also the allowed data rate on each link, which in turn affects lifetime. Previous works that focus on energy efficient operations in sensor networks with the sole objective of maximizing network lifetime only consider the energy constraint and ignore the bandwidth …

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Ttl Based Packet Marking For Ip Traceback, Vamsi Paruchuri, Arjan Durresi, Sriram Chellappan Dec 2008

Ttl Based Packet Marking For Ip Traceback, Vamsi Paruchuri, Arjan Durresi, Sriram Chellappan

Computer Science Faculty Research & Creative Works

Distributed Denial of Service Attacks continue to pose major threats to the Internet. in order to traceback attack sources (i.e., IP addresses), a well-studied approach is Probabilistic Packet Marking (PPM), where each intermediate router of a packet marks it with a certain probability, enabling a victim host to traceback the attack source. in a recent study, we showed how attackers can take advantage of probabilistic nature of packet markings in existing PPM schemes to create spoofed marks, hence compromising traceback. in this paper, we propose a new PPM scheme called TTL-Based PPM (TPM) scheme, where each packet is marked with …

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Position Transformation: A Location Privacy Protection Method For Moving Objects, Dan Lin, Elisa Bertino, Reynold Cheng, Sunil Prabhakar Dec 2008

Position Transformation: A Location Privacy Protection Method For Moving Objects, Dan Lin, Elisa Bertino, Reynold Cheng, Sunil Prabhakar

Computer Science Faculty Research & Creative Works

The expanding use of location-Based services has profound implications on the privacy of personal information. in this paper, we propose a framework for preserving location privacy based on the idea of sending to the service provider suitably modified location information. Agents execute data transformation, and the service provider directly processes the transformed dataset. Our technique not only prevents the service provider from knowing the exact locations of users, but also protects information about user movements and locations from being disclosed to other users who are not authorized to access this information. We also define a privacy model to analyze our …

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