Scholarly Works, Electrical and Computer Engineering

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Research articles, presentations, and other scholarship

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Application of Cybernetics and Control Theory for a New Paradigm in Cybersecurity
Adams, Michael D.; Hitefield, Seth D.; Hoy, Bruce; Fowler, Michael C.; Clancy, Thomas Charles III (Virginia Tech, 2013-11-01)
A significant limitation of current cyber security research and techniques is its reactive and applied nature. This leads to a continuous ‘cyber cycle’ of attackers scanning networks, developing exploits and attacking systems, with defenders detecting attacks, analyzing exploits and patching systems. This reactive nature leaves sensitive systems highly vulnerable to attack due to un-patched systems and undetected exploits. Some current research attempts to address this major limitation by introducing systems that implement moving target defense. However, these ideas are typically based on the intuition that a moving target defense will make it much harder for attackers to find and scan vulnerable systems, and not on theoretical mathematical foundations. The continuing lack of fundamental science and principles for developing more secure systems has drawn increased interest into establishing a ‘science of cyber security’. This paper introduces the concept of using cybernetics, an interdisciplinary approach of control theory, systems theory, information theory and game theory applied to regulatory systems, as a foundational approach for developing cyber security principles. It explores potential applications of cybernetics to cyber security from a defensive perspective, while suggesting the potential use for offensive applications. Additionally, this paper introduces the fundamental principles for building non-stationary systems, which is a more general solution than moving target defenses. Lastly, the paper discusses related works concerning the limitations of moving target defense and one implementation based on non-stationary principles.
Atomic Layer Deposited Tantalum Silicate on Crystallographically-Oriented Epitaxial Germanium: Interface Chemistry and Band Alignment
Clavel, Michael B.; Bhattacharya, Shuvodip; Hudait, Mantu K. (Royal Society of Chemistry, 2022-05-13)
The interface chemistry and energy band alignment properties of atomic layer deposited (ALD) tantalum silicate (TaSiOx) dielectrics on crystallographically-oriented, epitaxial (001)Ge, (110)Ge, and (111)Ge thin-films, grown on GaAs substrates by molecular beam epitaxy, were investigated. The ALD process, consisting of a 6 : 1 Ta : Si precursor super-cycle, was analyzed via sputter depth-dependent elemental analysis utilizing X-ray photoelectron spectroscopy (XPS). The XPS investigations revealed uniform Si incorporation throughout the TaSiOx dielectric, and a measurable amount of cross-diffusion between Ge and Ta atomic species in the vicinity of the oxide/semiconductor heterointerface. The formation of a thin SiO2 interfacial oxide, through the intentional pre-pulsing of the Si precursor prior to the Si : Ta super-cycle process, was observed via cross-sectional transmission electron microscopy analysis. Moreover, the bandgap of Ta-rich Ta0.8Si0.2Ox dielectrics, analyzed using the photoelectron energy loss technique centered on the O 1s binding energy spectra, was determined to be in the range of 4.62 eV-4.66 eV (±0.06 eV). Similarly, the XPS-derived valence band and conduction band offsets (ΔEV and ΔEC, respectively) were found to be ΔEV > 3.0 ± 0.1 eV and ΔEC > 0.6 ± 0.1 eV for the (001)Ge, (110)Ge, and (111)Ge orientations, promoting the increased carrier confinement necessary for reducing operational and off-state leakage current in metal-oxide-semiconductor devices. Thus, the empirical TaSiOx/Ge interfacial energy band offsets, coupled with the uniform dielectric deposition observed herein, provides key guidance for the integration of TaSiOx dielectrics with Ge-based field-effect transistors targeting ultra-low power logic applications.
Celebrate the 10th Anniversary of IEEE Electrification Magazine and Embrace a New Era
Rahman, Saifur (IEEE, 2023-09)
Dusty space plasma diagnosis using temporal behavior of polar mesospheric summer echoes during active modification
Mahmoudian, A.; Scales, Wayne A.; Kosch, M. J.; Senior, A.; Rietveld, Michael T. (Copernicus Publications, 2011)
The objective of this paper is to study the effect of different plasma and dust parameters on Polar Mesospheric Summer Echoes (PMSE) temporal behavior after turn-on and turn-off of radio wave heating and to use these responses to diagnose the properties of the dust layer. The threshold radar frequency and dust parameters for the enhancement or suppression of radar echoes after radio wave heating turn-on are investigated for measured mesospheric plasma parameters. The effect of parameters such as the electron temperature enhancement during heating, dust density, dust charge polarity, ion-neutral collision frequency, electron density and dust radius on the temporal evolution of electron irregularities associated with PMSE are investigated. The possible diagnostic information for various charged dust and background plasma quantities using the temporal behavior of backscattered radar power in active experiments is discussed. The computational results are used to make predictions for PMSE active modification experiments at 7.9, 56, 139, 224 and 930 MHz corresponding to existing radar facilities. Data from a 2009 VHF (224 MHz) experiment at EISCAT is compared with the computational model to obtain dust parameters in the PMSE.
Editorial on Special Issue “Holography, 3-D Imaging and 3-D Display”
Poon, Ting-Chung; Zhang, Yaping; Cao, Liangcai; Yoshikawa, Hiroshi (MDPI, 2020-10-11)
Modern holographic techniques have been successfully applied in many important areas, such as 3D inspection, 3D microscopy, metrology and profilometry, augmented reality, and industrial informatics [...]
Environmental Information Improves Robotic Search Performance
Yetkin, Harun; Lutz, Collin C.; Stilwell, Daniel J. (Virginia Tech, 2016)
We address the problem where a mobile search agent seeks to find an unknown number of stationary objects distributed in a bounded search domain, and the search mission is subject to time/distance constraint. Our work accounts for false positives, false negatives and environmental uncertainty. We consider the case that the performance of a search sensor is dependent on the environment (e.g., clutter density), and therefore sensor performance is better in some locations than in others. For applications where environmental information can be acquired, we derive a decision-theoretic cost function to compute the locations where the environmental information should be acquired. We address the cases where environmental characterization is performed either by a separate vehicle or by the same vehicle that performs the search task.
GPS phase scintillation and proxy index at high latitudes during a moderate geomagnetic storm
Prikryl, P.; Ghoddousi-Fard, R.; Kunduri, B. S. R.; Thomas, E. G.; Coster, A. J.; Jayachandran, P. T.; Spanswick, E.; Danskin, D. W. (Copernicus Publications, 2013)
The amplitude and phase scintillation indices are customarily obtained by specialised GPS Ionospheric Scintillation and TEC Monitors (GISTMs) from L1 signal recorded at the rate of 50 Hz. The scintillation indices S-4 and sigma(Phi) are stored in real time from an array of high-rate scintillation receivers of the Canadian High Arctic Ionospheric Network (CHAIN). Ionospheric phase scintillation was observed at high latitudes during a moderate geomagnetic storm (Dst = -61 nT) that was caused by a moderate solar wind plasma stream compounded with the impact of two coronal mass ejections. The most intense phase scintillation (sigma(Phi) similar to 1 rad) occurred in the cusp and the polar cap where it was co-located with a strong ionospheric convection, an extended tongue of ionisation and dense polar cap patches that were observed with ionosondes and HF radars. At sub-auroral latitudes, a sub-auroral polarisation stream that was observed by mid-latitude radars was associated with weak scintillation (defined arbitrarily as sigma(Phi) < 0.5 rad). In the auroral zone, moderate scintillation coincided with auroral breakups observed by an all-sky imager, a riometer and a magnetometer in Yellowknife. To overcome the limited geographic coverage by GISTMs other GNSS data sampled at 1 Hz can be used to obtain scintillation proxy indices. In this study, a phase scintillation proxy index (delta phase rate, DPR) is obtained from 1-Hz data from CHAIN and other GPS receivers. The 50-Hz and 1-Hz phase scintillation indices are correlated. The percentage occurrences of sigma(Phi) > 0.1 rad and DPR > 2mm s(-1), both mapped as a function of magnetic latitude and magnetic local time, are very similar.
High carrier lifetimes in epitaxial germanium-tin/Al(In)As heterostructures with variable tin composition
Hudait, Mantu K.; Johnston, Steven W.; Clavel, Michael B.; Bhattacharya, Shuvodip; Karthikeyan, Sengunthar; Joshi, Rutwik (Royal Society of Chemistry, 2022-06-23)
Group IV-based germanium-tin (Ge1−ySny) compositional materials have recently shown great promise for infrared detection, light emission and ultra-low power transistors. High carrier lifetimes are desirable for enhancing the detection limit and efficiency of photodetectors, low threshold current density in lasers, and low tunneling barrier height by lowering defects and dislocations at the heterointerface of a source and a channel. Here, carrier lifetimes in epitaxial germanium (Ge) and variable tin (Sn) compositional Ge1−ySny materials were experimentally determined on GaAs substrates using the contactless microwave photoconductive decay (μ-PCD) technique at an excitation wavelength of 1500 nm. Sharp (2 × 2) reflection high energy electron diffraction patterns and low surface roughness were observed from the surface of the Ge0.97Sn0.03 epilayer. X-ray rocking curves from Ge0.97Sn0.03 and Ge0.94Sn0.06 layers demonstrated the pseudomorphic and lattice-matched growth on AlAs and In0.12Al0.88As buffers, respectively, further substantiated by reciprocal space maps and abrupt heterointerfaces evident from the presence of Pendellösung oscillations. High effective carrier lifetimes of 150 ns to 450 ns were measured for Ge1−ySny epilayers as a function of Sn composition, surface roughness, growth temperature, and layer thickness. The observed increase in the carrier lifetime with an increasing Ge layer thickness and a reducing surface roughness, by incorporating Sn, were explained. The enhancement of the carrier lifetime with an increasing Sn concentration was achieved by controlling the defects with lattice-matched Ge0.94Sn0.06/In0.12Al0.88As heterointerfaces or the pseudomorphic growth of Ge0.94Sn0.06 on GaAs. Therefore, our monolithic integration of variable Sn alloy compositional Ge1−ySny materials with high carrier lifetimes opens avenues to realize electronic and optoelectronic devices.
Imitation Learning with Stability and Safety Guarantees
Yin, He; Seiler, Peter; Jin, Ming; Arcak, Murat (IEEE, 2022-01-01)
A method is presented to learn neural network (NN) controllers with stability and safety guarantees through imitation learning (IL). Convex stability and safety conditions are derived for linear time-invariant systems with NN controllers by merging Lyapunov theory with local quadratic constraints to bound the activation functions in the NN. These conditions are incorporated in the IL process, which minimizes the IL loss, and maximizes the volume of the region of attraction associated with the NN controller simultaneously. An alternating direction method of multipliers based algorithm is proposed to solve the IL problem. The method is illustrated on a vehicle lateral control example.
New Way of Generating Electromagnetic Waves
Hosseini-Fahraji, Ali; Manteghi, Majid; Ngo, Khai D. T. (2020-05)
This paper presents a new method for generating low-frequency electromagnetic waves for navigation and communication in challenging environments, such as underwater and underground. The main idea is to store magnetic energy in two different spaces using the interaction between a permanent magnet and a magnetic material. The magnetic reluctance of the medium around the permanent magnet is modulated to change the magnetic flux path. The nonlinear properties of magnetic material as a critical phenomenon are used for effective modulation. As a result, a time-variant field is generated by the modulation of the permanent magnet flux. This non-resonant time-variant characterization means that the transmitter is not bound to the fundamental limits of the antennas and can transmit higher data rates. A prototype transmitter as a prove-of-concept is designed and tested based on the proposed idea. Compared to the rotating magnet, the prototyped transmitter can modulate $50\%$ of the stored energy of the permanent magnet with much lower power consumption.
On ion gyro-harmonic structuring in the stimulated electromagnetic emission spectrum during second electron gyro-harmonic heating
Samimi, A.; Scales, Wayne A.; Bernhardt, P. A.; Briczinski, S. J.; Selcher, C. A.; McCarrick, M. J. (Copernicus Publications, 2012)
Recent observations show that, during ionospheric heating experiments at frequencies near the second electron gyro-harmonic, discrete spectral lines separated by harmonics of the ion-gyro frequency appear in the stimulated electromagnetic emission (SEE) spectrum within 1 kHz of the pump frequency. In addition to the ion gyro-harmonic structures, on occasion, a broadband downshifted emission is observed simultaneously with these spectral lines. Parametric decay of the pump field into upper hybrid/electron Bernstein (UH/EB) and low-frequency ion Bernstein (IB) and oblique ion acoustic (IA) modes is considered responsible for generation of these spectral features. Guided by predictions of an analytical model, a two-dimensional particle-in-cell (PIC) computational model is employed to study the nonlinear processes during such heating experiments. The critical parameters that affect the spectrum, such as whether discrete gyroharmonic on broadband structures is observed, include angle of the pump field relative to the background magnetic field, pump field strength, and proximity of the pump frequency to the gyro-harmonic. Significant electron heating along the magnetic field is observed in the parameter regimes considered.
Parallelizable synthesis of arbitrary single-qubit gates with linear optics and time-frequency encoding
Henry, Antoine; Raghunathan, Ravi; Ricard, Guillaume; Lefaucher, Baptiste; Miatto, Filippo; Belabas, Nadia; Zaquine, Isabelle; Alleaume, Romain (American Physical Society, 2023-06-26)
We propose methods for the exact synthesis of single-qubit unitaries with high success probability and gate fidelity, considering both time-bin and frequency-bin encodings. The proposed schemes are experimentally implementable with a spectral linear-optical quantum computation (S-LOQC) platform, composed of electro-optic phase modulators and phase-only programmable filters (pulse shapers). We assess the performances in terms of fidelity and probability of the two simplest three-component configurations for arbitrary gate generation in both encodings and give an exact analytical solution for the synthesis of an arbitrary single-qubit unitary in the time-bin encoding, using a single-tone rf driving of the electro-optic modulators. We further investigate the parallelization of arbitrary single-qubit gates over multiple qubits with a compact experimental setup, both for spectral and temporal encodings. We systematically evaluate and discuss the impact of the rf bandwidth, which conditions the number of tones driving the modulators, and of the choice of encoding for different targeted gates. We moreover quantify the number of high-fidelity Hadamard gates that can be synthesized in parallel, with minimal and increasing resources in terms of driving rf tones in a realistic system. Our analysis positions spectral S-LOQC as a promising platform to conduct massively parallel single-qubit operations, with potential applications to quantum metrology and quantum tomography.
Predictive Closed-Loop Service Automation in O-RAN based Network Slicing
Thaliath, Joseph; Niknam, Solmaz; Singh, Sukhdeep; Banerji, Rahul; Saxena, Navrati; Dhillon, Harpreet Singh; Reed, Jeffrey H.; Bashir, Ali Kashif; Bhat, Avinash; Roy, Abhishek (2022-02-03)
Network slicing provides introduces customized and agile network deployment for managing different service types for various verticals under the same infrastructure. To cater to the dynamic service requirements of these verticals and meet the required quality-of-service (QoS) mentioned in the service-level agreement (SLA), network slices need to be isolated through dedicated elements and resources. Additionally, allocated resources to these slices need to be continuously monitored and intelligently managed. This enables immediate detection and correction of any SLA violation to support automated service assurance in a closed-loop fashion. By reducing human intervention, intelligent and closed-loop resource management reduces the cost of offering flexible services. Resource management in a network shared among verticals (potentially administered by different providers), would be further facilitated through open and standardized interfaces. Open radio access network (O-RAN) is perhaps the most promising RAN architecture that inherits all the aforementioned features, namely intelligence, open and standard interfaces, and closed control loop. Inspired by this, in this article we provide a closed-loop and intelligent resource provisioning scheme for O-RAN slicing to prevent SLA violations. In order to maintain realism, a real-world dataset of a large operator is used to train a learning solution for optimizing resource utilization in the proposed closed-loop service automation process. Moreover, the deployment architecture and the corresponding flow that are cognizant of the O-RAN requirements are also discussed.
Role of power electronics in Grid 3.0
Zhang, Richard (IEEE, 2022-12)
Temperature and Doping-Dependent Interplay between Direct and Indirect Optical Response in Buffer-Mediated Epitaxial Germanium
Hudait, Mantu K.; Meeker, Michael; Liu, Jheng-Sin; Clavel, Michael; Bhattacharya, Shuvodip; Khodaparast, Giti (Elsevier, 2022-09-01)
The structural and optical properties of buffer mediated epitaxial germanium (Ge) layer were investigated and compared with bulk n-type and p-type Ge substrates. An interconnected dual-chamber molecular beam epitaxy (MBE) system was used to grow a 280 nm thin Ge epilayer on (100)GaAs substrate with an intermediate AlAs buffer layer. The lattice-matched, abrupt Ge/AlAs heterointerface was analyzed using cross-sectional transmission electron microscopic analysis, and no elemental interdiffusion was detected via secondary ion mass spectrometry. A strong direct gap transition, compared to the indirect gap transition, and a series of phonon-assisted transitions was observed by photoluminescence (PL) spectroscopy. In addition, the intensity of the direct gap recombination decreases with decreasing PL measurement temperatures, which was ascribed to the reduced density of Γ-valley electrons available for recombination at lower temperature. Furthermore, the intensity ratio between the direct and indirect optical transition drastically decreases with decreasing temperature in both n-type epitaxial and p-type bulk Ge. An empirical relation in both direct and indirect peak position with temperature was established. The observed strong luminescence in 280 nm thick epitaxial Ge at room temperature is vital for Ge-based photonic devices. In addition, the quality of the epitaxial Ge layer grown via MBE is on par with bulk Ge substrates.
Virtual Secure Circuit: Porting Dual-Rail Pre-charge Technique into Software on Multicore
Chen, Zhimin; Schaumont, Patrick R. (Cryptology ePrint Archive, 2010)
This paper discusses a novel direction for multicore cryptographic software, namely the use of multicore to protect a design against side-channel attacks.We present a technique which is based on the principle of dual-rail pre-charge, but which can be completely implemented in software. The resulting protected software is called a Virtual Secure Circuit (VSC). Similar to the dual-rail pre-charge technique, a VSC executes as two complementary programs on two identical processor cores. Our key contributions include (1) the analysis of the security properties of a VSC, (2) the construction of a VSC AES prototype on a dual-PowerPC architecture, (3) the demonstration of VSC’s protection effectiveness with real side-channel attack experiments. The attack results showed that the VSC protected AES needs 80 times more measurements than the unprotected AES to find the first correct key byte. Even one million measurements were not sufficient to fully break VSC protected AES, while unprotected AES was broken using only 40000 measurements. We conclude that VSC can provide a similar side-channel resistance as WDDL, the dedicated hardware equivalent of dual-rail pre-charge. However, in contrast to WDDL, VSC is a software technique, and therefore it is flexible.
Winds and tides in the mid-latitude Southern Hemisphere upper mesosphere recorded with the Falkland Islands SuperDARN radar
Hibbins, R. E.; Freeman, M. P.; Milan, Stephen E.; Ruohoniemi, J. Michael (Copernicus Publications, 2011)
Meteor wind data from the first year of operation of the Falkland Islands SuperDARN radar (52 degrees S, 59 degrees W) are used to characterize the atmospheric tides and background winds in the upper mesosphere above the South Atlantic. Strong (>40 ms(-1)) semidiurnal tides are observed in the winter time and large amplitude (>60 ms(-1)) bursts of quasi two-day wave activity are seen in January 2011. Data are in good agreement with those presented from the SAAMER meteor radar (54 degrees S, 68 degrees W). Comparison with SuperDARN meteor wind data from a geographically similar Northern Hemisphere site at Goose Bay (53 degrees N 60 degrees W) reveal clear interhemispheric differences especially in the semidiurnal and terdiurnal components of the tides. The winter time amplitudes of the tides are much stronger in the Southern Hemisphere than in the north. Background winds are observed to be significantly more polewards and westwards throughout the year than those predicted by the empirical horizontal wind model HWM07.

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