Computer Sciences Commons^™

Privacy Preservation Using Spherical Chord, Doyal Tapan Mukherjee

Masters Theses

"Structured overlay networks are primarily used in data storage and data lookup, but they are vulnerable against many kinds of attacks. Within the realm of security, overlay networks have demonstrated applicability in providing privacy, availability, integrity, along with scalability. The thesis first analyses the Chord and the SALSA protocols which are organized in structured overlays to provide data with a certain degree of privacy, and then defines a new protocol called Spherical Chord which provides data lookup with privacy, while also being scalable, and addresses critical existing weaknesses in Chord and SALSA protocols. Spherical Chord is a variant of the …

Hidden Markov Model With Information Criteria Clustering And Extreme Learning Machine Regression For Wind Forecasting, Dao Lam, Shuhui Li, Donald C. Wunsch

Electrical and Computer Engineering Faculty Research & Creative Works

This paper proposes a procedural pipeline for wind forecasting based on clustering and regression. First, the data are clustered into groups sharing similar dynamic properties. Then, data in the same cluster are used to train the neural network that predicts wind speed. For clustering, a hidden Markov model (HMM) and the modified Bayesian information criteria (BIC) are incorporated in a new method of clustering time series data. to forecast wind, a new method for wind time series data forecasting is developed based on the extreme learning machine (ELM). the clustering results improve the accuracy of the proposed method of wind …

Impact Of Loss Synchronization On Reliable High Speed Networks: A Model Based Simulation, Suman Kumar, Lin Xue, Seung Jong Park

Computer Science Faculty Research & Creative Works

Contemporary nature of network evolution demands for simulation models which are flexible, scalable, and easily implementable. In this paper, we propose a fluid-based model for performance analysis of reliable high-speed networks. In particular, this paper aims to study the dynamic relationship between congestion control algorithms and queue management schemes, in order to develop a better understanding of the causal linkages between the two. We propose a loss synchronization module which is user configurable. We validate our model through simulations under controlled settings. Also, we present a performance analysis to provide insights into two important issues concerning 10 Gbps high speed …

Impact Of Location History Collection Schemes On Observed Human Mobility Features, Alicia Rodriguez-Carrion, Sajal K. Das, Celeste Campo, Carlos Garcia-Rubio

Computer Science Faculty Research & Creative Works

Human mobility knowledge is key for urban planning or mobility model's design. Therefore, estimating reliable mobility parameters is crucial to lay an unbiased foundation. However, most works estimating such features rely on datasets made up of the history of mobile network cells where the user is located when she makes active use of the network, known as Call Data Records (CDRs), or every time their device connects to a new cell, without taking into account cell changes not caused by movement. Could we accurately characterize human mobility with such datasets? In this work we consider three approaches to collect network-based …

Cross-Layer Schemes For Performance Optimization In Wireless Networks, Quanmin Ye

Doctoral Dissertations

"Wireless networks are undergoing rapid progress and inspiring numerous applications. As the application of wireless networks becomes broader, they are expected to not only provide ubiquitous connectivity, but also support end users with certain service guarantees.

End-to-end delay is an important Quality of Service (QoS) metric in multihop wireless networks. This dissertation addresses how to minimize end-to-end delay through joint optimization of network layer routing and link layer scheduling. Two cross-layer schemes, a loosely coupled cross-layer scheme and a tightly coupled cross-layer scheme, are proposed. The two cross-layer schemes involve interference modeling in multihop wireless networks with omnidirectional antenna. In …

Energy Aware And Privacy Preserving Protocols For Ad Hoc Networks With Applications To Disaster Management, Mayank Raj

Doctoral Dissertations

"Disasters can have a serious impact on the functioning of communities and societies. Disaster management aims at providing efficient utilization of resources during pre-disaster (e.g. preparedness and prevention) and post-disaster (e.g. recovery and relief) scenarios to reduce the impact of disasters. Wireless sensors have been extensively used for early detection and prevention of disasters. However, the sensor's operating environment may not always be congenial to these applications. Attackers can observe the traffic flow in the network to determine the location of the sensors and exploit it. For example, in intrusion detection systems, the information can be used to identify coverage …

Foundations Of Coverage Algorithms In Autonomic Mobile Sensor Networks, Mark Edward Snyder

Doctoral Dissertations

"Drones are poised to become a prominent focus of advances in the near future as hardware platforms manufactured via mass production become accessible to consumers in higher quantities at lower costs than ever before. As more ways to utilize such devices become more popular, algorithms for directing the activities of mobile sensors must expand in order to automate their work.

This work explores algorithms used to direct the behavior of networks of autonomous mobile sensors, and in particular how such networks can operate to achieve coverage of a field using mobility. We focus special attention to the way limited mobility …

Analysis And Optimization Of A Protocol For Mobile Element Discovery In Sensor Networks, Francesco Restuccia, Giuseppe Anastasi, Marco Conti, Sajal K. Das

Computer Science Faculty Research & Creative Works

Recent studies have demonstrated that mobile elements (MEs) are an efficient solution to help decrease dramatically energy consumption in wireless sensor networks (WSNs). However, in most of cases, sensors use duty cycle schemes to save energy, and unless the ME mobility pattern is deterministic, each sensor node has to discover the presence of the ME in the nearby area before starting to exchange data with it. Therefore, in such wireless sensor networks with mobile elements (in short, WSN-MEs), the definition and analysis of a protocol for efficient ME discovery becomes of fundamental importance. In this paper, we propose an extensive …

Exploring Optimization And Caching For Efficient Collection Operations, Venkata Krishna Suhas Nerella, Swetha Surapaneni, Sanjay K. Madria, Thomas Weigert

Computer Science Faculty Research & Creative Works

Many large programs operate on collection types. Extensive libraries are available in many programming languages, such as the C++ Standard Template Library, which make programming with collections convenient. Extending programming languages to provide collection queries as first-class constructs in the language would not only allow programmers to write queries explicitly in their programs but it would also allow compilers to leverage the wealth of experience available from the database domain to optimize such queries. This paper describes an approach to reduce the run time of programs involving explicit collection queries by performing run time query optimization that is effective for …

Event-Triggered Optimal Regulation Of Uncertain Linear Discrete-Time Systems By Using Q-Learning Scheme, Avimanyu Sahoo, S. Jagannathan

Electrical and Computer Engineering Faculty Research & Creative Works

In this paper, an event-triggered optimal adaptive regulation of an uncertain linear discrete time system is proposed. This scheme solves the optimal control in a forward in- time and online manner by using both dynamic programming and Q learning. First, the time varying action dependent value or the Q-function is estimated online by an adaptive value function estimator (VFE) with event-based state vector and a time dependent basis function. The estimated value function parameters are subsequently used to generate the optimal control gain matrix. Further, aperiodic tuning law for the VFE parameters is proposed not only to estimate the parameters …

A Fault Prediction Scheme For Takagi-Sugeno Fuzzy Systems With Immeasurable Premise Variables And Disturbance, Balaje T. Thumati, Jagannathan Sarangapani

Electrical and Computer Engineering Faculty Research & Creative Works

As explained in the literature, it is very hard to measure premise variables of a Takagi-Sugeno (TS) fuzzy system. Therefore, in this paper, a fault detection and prediction (FDP) scheme is designed for a class of TS fuzzy systems with immeasurable (unknown) premise variables and external disturbances. A fault detection (FD) observer is designed to approximate the system output and the premise variables. Subsequently, a FD residual is generated by comparing the observer output with respect to the system output. The FD residual is evaluated to detect any faults in the system. Further, time-to-failure (TTF) of the TS fuzzy system …

Localization And Tracking Of Objects Using Cross-Correlation Of Shadow Fading Noise, M. R. Basheer, S. Jagannathan

Electrical and Computer Engineering Faculty Research & Creative Works

Multipath and shadow fading are the primary cause for positioning errors in a Received Signal Strength Indicator (RSSI) based localization scheme. While fading, in general, is detrimental to localization accuracy, cross-correlation and divergence properties of shadow fading residuals may be utilized to improve localization and tracking accuracy of mobile IEEE 802.15.4 transmitters. Therefore, this paper begins by presenting a stochastic filter that models the fast-changing multipath fading as a mean reverting Ornstein-Uhlenbeck (OU) process followed by a Generalized Auto Regressive Conditional Heteroskedasticity (GARCH) filtering to isolate the slow changing shadow fading residuals from measured RSSI values. Subsequently, a novel wireless …

Nonlinear Development And Secondary Instability Of Traveling Crossflow Vortices, Fei Li, Meelan M. Choudhari, Lian Duan, Chau-Lyan Chang

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Building upon the prior research targeting the laminar breakdown mechanisms associated with stationary crossflow instability over a swept-wing configuration, this paper investigates the secondary instability of traveling crossflow modes as an alternate scenario for transition. For the parameter range investigated herein, this alternate scenario is shown to be viable unless the initial amplitudes of the traveling crossflow instability are lower than those of the stationary modes by considerably more than one order of magnitude. The linear growth predictions based on the secondary instability theory are found to agree well with both parabolized stability equations and direct numerical simulation, and the …

Crystallization In Nano-Confinement Seeded By A Nanocrystal -- A Molecular Dynamics Study, Heng Pan, Costas Grigoropoulos

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Seeded crystallization and solidification in nanoscale confinement volumes have become an important and complex topic. Due to the complexity and limitations in observing nanoscale crystallization, computer simulation can provide valuable details for supporting and interpreting experimental observations. In this article, seeded crystallization from nano-confined liquid, as represented by the crystallization of a suspended gold nano-droplet seeded by a pre-existing gold nanocrystal seed, was investigated using molecular dynamics simulations in canonical (NVT) ensemble. We found that the crystallization temperature depends on nano-confinement volume, crystal orientation, and seed size as explained by classical two-sphere model and Gibbs-Thomson effect.

Near Optimal Boundary Control Of Distributed Parameter Systems Modeled As Parabolic Pdes By Using Finite Difference Neural Network Approximation, Behzad Talaei, Hao Xu, S. Jagannathan

Electrical and Computer Engineering Faculty Research & Creative Works

This paper develops a novel neural network (NN) based near optimal boundary control scheme for distributed parameter systems (DPS) governed by semi linear parabolic partial differential equations (PDE) in the presence of control constraints and unknown system dynamics. First, finite difference method (FDM) is utilized to develop a reduced order system which represents the discretized dynamics of PDE system. Subsequently, a near optimal control scheme is proposed for the discretized system by using NN based approximate dynamic programming (ADP). To relax the requirement of system dynamics, a NN identifier is utilized. Moreover, a second NN is proposed to estimate a …

Extremum-Seeking For Nonlinear Discrete-Time Systems With Application To Hcci Engines, H. Zargarzadeh, S. Jagannathan, J. A. Drallmeier

Electrical and Computer Engineering Faculty Research & Creative Works

For many control applications, identifying an optimal operating point by maximizing/minimizing a performance function is important. This paper applies the extremum-seeking method to nonaffine, nonlinear discrete-time systems stabilized by an optimal adaptive controller. First, a novel averaging method is used for the nonlinear discrete-time systems to show that their output unique extrema are stable equilibrium points. Then, a singular perturbation method in discrete time is employed to show that the overall closed loop system will dynamically converge to the extremum. The applicability of this scheme is numerically verified on a Homogeneous Charge Compression Ignition (HCCI) model validated experimentally and expressed …

A Model-Based Fault Detection And Prognostics Scheme For Takagi-Sugeno Fuzzy Systems, Balaje T. Thumati, Miles A. Feinstein, S. Jagannathan

Electrical and Computer Engineering Faculty Research & Creative Works

In this paper, a novel model-based fault detection (FD) and prediction scheme is developed for a class of Takagi-Sugeno (T-S) fuzzy systems. Unlike other FD schemes, in the proposed design, an FD observer with online fault learning capability is utilized to generate a residual which is obtained by comparing the system output with respect to the observer output. A fault is declared active if the generated residual exceeds an a priori chosen threshold. Subsequently, the fault magnitude is estimated online by using a suitable parameter update law. Upon detection, the online estimate of the fault magnitude is used in a …

Neural Network-Based Finite-Horizon Approximately Optimal Control Of Uncertain Affine Nonlinear Continuous-Time Systems, Hao Xu, Qiming Zhao, Travis Dierks, S. Jagannathan

Electrical and Computer Engineering Faculty Research & Creative Works

This paper develops a novel neural network (NN) based finite-horizon approximate optimal control of nonlinear continuous-time systems in affine form when the system dynamics are complete unknown. First an online NN identifier is proposed to learn the dynamics of the nonlinear continuous-time system. Subsequently, a second NN is utilized to learn the time-varying solution, or referred to as value function, of the Hamilton-Jacobi-Bellman (HJB) equation in an online and forward in time manner. Then, by using the estimated time-varying value function from the second NN and control coefficient matrix from the NN identifier, an approximate optimal control input is computed. …

Contact Process On Generalized Fibonacci Chains: Infinite-Modulation Criticality And Double-Log Periodic Oscillations, Hatem Barghathi, David Nozadze, Thomas Vojta

Physics Faculty Research & Creative Works

We study the nonequilibrium phase transition of the contact process with aperiodic transition rates using a real-space renormalization group as well as Monte Carlo simulations. The transition rates are modulated according to the generalized Fibonacci sequences defined by the inflation rules A → AB^k and B → A. For k=1 and 2, the aperiodic fluctuations are irrelevant, and the nonequilibrium transition is in the clean directed percolation universality class. For k ≥ 3, the aperiodic fluctuations are relevant. We develop a complete theory of the resulting unconventional "infinite-modulation" critical point, which is characterized by activated dynamical scaling. Moreover, observables …

Dynamical (E,2e) Studies Of Tetrahydropyran And 1,4-Dioxane, J. D. Builth-Williams, G. Da Silva, L. Chiari, D. B. Jones, Hari Chaluvadi, Don H. Madison, M. J. Brunger

Physics Faculty Research & Creative Works

We present experimental and theoretical results for the electron-impact ionization of the highest occupied molecular orbitals of tetrahydropyran and 1,4-dioxane. Using an (e,2e) technique in asymmetric coplanar kinematics, angular distributions of the slow ejected electron, with an energy of 20 eV, are measured when incident electrons at 250 eV ionize the target and scatter through an angle of either -10° or -15°. The data are compared with calculations performed at the molecular 3-body distorted wave level. Fair agreement between the theoretical model and the experimental measurements was observed. The similar structures for these targets provide key insights for assessing the …

Kapitza Resistance Of Si/Sio₂ Interface, Bowen Deng, Aleksandr V. Chernatynskiy, Marat Khafizov, David H. Hurley, Simon R. Phillpot

Physics Faculty Research & Creative Works

A phonon wave packet dynamics method is used to characterize the Kapitza resistance of a Si/SiO₂ interface in a Si/SiO₂/Si heterostructure. By varying the thickness of SiO₂ layer sandwiched between two Si layers, we determine the Kapitza resistance for the Si/SiO ₂ interface from both wave packet dynamics and a direct, non-equilibrium molecular dynamics approach. The good agreement between the two methods indicates that they have each captured the anharmonic phonon scatterings at the interface. Moreover, detailed analysis provides insights as to how individual phonon mode scatters at the interface and their contribution to the Kapitza …

Phonon Thermal Transport Through Tilt Grain Boundaries In Strontium Titanate, Zexi Zheng, Xiang Chen, Bowen Deng, Aleksandr V. Chernatynskiy, Shengfeng Yang, Jinjun Xiong, Youping Chen

Physics Faculty Research & Creative Works

In this work, we perform nonequilibrium molecular dynamics simulations to study phonon scattering at two tilt grain boundaries (GBs) in SrTiO₃. Mode-wise energy transmission coefficients are obtained based on phonon wave-packet dynamics simulations. The Kapitza conductance is then quantified using a lattice dynamics approach. The obtained results of the Kapitza conductance of both GBs compare well with those obtained by the direct method, except for the temperature dependence. Contrary to common belief, the results of this work show that the optical modes in SrTiO₃ contribute significantly to phonon thermal transport, accounting for over 50% of the Kapitza …

Strong-Randomness Infinite-Coupling Phase In A Random Quantum Spin Chain, Fawaz Hrahsheh, José A. Hoyos, Rajesh Narayanan, Thomas Vojta

Physics Faculty Research & Creative Works

We study the ground-state phase diagram of the Ashkin-Teller random quantum spin chain by means of a generalization of the strong-disorder renormalization group. In addition to the conventional paramagnetic and ferromagnetic (Baxter) phases, we find a partially ordered phase characterized by strong randomness and infinite coupling between the colors. This unusual phase acts, at the same time, as a Griffiths phase for two distinct quantum phase transitions, both of which are of infinite-randomness type. We also investigate the quantum multicritical point that separates the two-phase and three-phase regions, and we discuss generalizations of our results to higher dimensions and other …

Triply Differential (E,2e) Studies Of Phenol, Silva G. Da, R. F. Neves, L. Chiari, D. B. Jones, E. Ali, Don H. Madison, C. G. Ning, K. L. Nixon, M. C. Lopes, M. J. Brunger

Physics Faculty Research & Creative Works

We have measured (e,2e) triple differential cross sections (TDCS) for the electron-impact ionisation of phenol with coplanar asymmetrical kinematics for an incident electron energy of 250 eV. Experimental measurements of the angular distribution of the slow outgoing electrons at 20 eV are obtained when the incident electron scatters through angles of -5°, -10°, and -15°, respectively. The TDCS data are compared with calculations performed within the molecular 3-body distorted wave model. In this case, a mixed level of agreement, that was dependent on the kinematical condition being probed, was observed between the theoretical and experimental results in the binary peak …

Multiple Security Domain Nondeducibility In Cyber-Physical Systems, Gerry W. Howser

Doctoral Dissertations

"Cyber-physical Systems (CPS) present special problems for security. This dissertation examines the cyber security problem, the physical security problem, the security problems presented when cyber systems and physical systems are intertwined, and problems presented by the fact that CPS leak information simply by being observed. The issues presented by applying traditional cyber security to CPS are explored and some of the shortcomings of these models are noted. Specific models of a "drive-by-wire'' automobile connected to a road side assistance network, a "Stuxnet type'' attack, the smart grid, and others are presented in detail.

The lack of good tools for CPS …

Proactive Search: Using Outcome-Based Dynamic Nearest-Neighbor Recommendation Algorithms To Improve Search Engine Efficacy, Christopher Shaun Wagner

Doctoral Dissertations

"The explosion of readily available electronic information has changed the focus of data processing from data generation to data discovery. The prevalent use of search engines has generated extensive research into improving the speed and accuracy of searches. The goal of this research is to accurately predict user behavior as a means to proactively improve speed, accuracy, and predictability of search engines. The proactive approach eliminates query entry time and hence reduces the overall processing time, improving speed. Assuming success, the user locates an electronic resource of interest, improving accuracy.

Algorithms that have been shown to predict many vastly different …

A Cloud Brokerage Architecture For Efficient Cloud Service Selection, Venkata Nagarjuna Dondapati

Masters Theses

"The expanding cloud computing services offer great opportunities for consumers to find the best service and best pricing, which however raises new challenges on how to select the best service out of a huge pool. It is obvious time-consuming for consumers to collect the necessary information and analyze all service providers to make the decision. It is also a highly demanding task from a computational perspective, because the same computations may be conducted repeatedly by multiple consumers who have similar requirements. In this paper, we propose a novel brokerage-based architecture in the cloud, where the cloud brokers is responsible for …

Efficient Data Access In Mobile Cloud Computing, Siva Naga Venkata Chaitanya Vemulapalli

Masters Theses

"This thesis focuses on the development of efficient data transfer mechanism among mobile devices using Mobile cloud computing paradigm. Mobile cloud computing is coupling of mobile computing and cloud computing. In the Mobile cloud computing paradigm, users connect to cloud service providers over the Internet and leverage the cloud resources to perform their processing, storage and communication tasks. In this thesis, the focus is on communication tasks among mobile devices performed using Mobile cloud computing paradigm.

Communication or data sharing among mobile devices is often limited by proximity of the devices. This limitation can be removed by employing Mobile cloud …

An Empirical Study On Symptoms Of Heavier Internet Usage Among Young Adults, Saipreethi Vishwanathan

Masters Theses

"Understanding negative consequences of heavy Internet use on mental health is a topic that is gaining significant traction recently. A number of studies have investigated heavy Internet usage, especially among young adults in relation to online games, social media and email. While such studies do provide valuable insights, Internet usage so far has been characterized by means of self-reported surveys only that may suffer from errors and biases. In this paper, we report the findings of a two month empirical study on heavy Internet usage among students conducted at a college campus. The novelty of the study is that it …

Cervical Cancer Histology Image Feature Extraction And Classification, Peng Guo

Masters Theses

"Cervical cancer, the second most common cancer affecting women worldwide and the most common in developing countries can be cured if detected early and treated. Expert pathologists routinely visually examine histology slides for cervix tissue abnormality assessment. In previous research, an automated, localized, fusion-based approach was investigated for classifying squamous epithelium into Normal, CIN1, CIN2, and CIN3 grades of cervical intraepithelial neoplasia (CIN) based on image analysis of 62 digitized histology images obtained through the National Library of Medicine. In this research, CIN grade assessments from two pathologists are analyzed and are used to facilitate atypical cell concentration feature development …