Engineering Commons^™

Silver Photodiffusion Into Ge-Rich Amorphous Germanium Sulfide—Neutron Reflectivity Study, Y. Sakaguchi, H. Asaoka, M. Mitkova

Electrical and Computer Engineering Faculty Publications and Presentations

Silver diffuses into chalcogenide films upon light exposure, and the kinetics of photodiffusion has been a subject of various investigations because of the difficulties in the in situ determination of the time-dependent Ag reaction and diffusion development in the chalcogenide layers. In this paper, we report the results of time-resolved neutron reflectivity measurement of Ag/Ge₄₀S₆₀/Si substrates under light exposure to clarify the kinetics of Ag photodiffusion into Ge-rich Ge chalcogenides. It reveals that Ag ions diffuse all over the Ge chalcogenide host layer once Ag dissolves into the layer without forming a metastable reaction layer unlike …

Memetic-Based Schedule Synthesis For Communication On Time-Triggered Embedded Systems, Heyuan Shi, Kun Tang, Chengbao Lio, Xiaoyu Song, Chao Hu, Jiaguang Sun

Electrical and Computer Engineering Faculty Publications and Presentations

ime-triggered systems play an important role in industrial embedded systems. The time-triggered network is deployed on the time-triggered network-on-chip implementation. It ensures the safety-critical industrial communication for real-time embedded multiprocessor systems. To guarantee the safety-critical requirements for communication, each message is transmitted by a predefined static schedule. However, synthesizing a feasible schedule is a challenge because both spatial and temporal constraints should be considered. This article presents a novel memetic-based schedule synthesis algorithm to derive a feasible schedule by determining the offset of messages on the time-triggered network-on-chip. Memetic-based schedule synthesis algorithm is based on memetic algorithm, which incorporates local …

On Dual-Band Amplifications Using Dual Two-Tones: Clarifications And Discussion, Siyuan Yan, Xianzhen Yang, Xiao Li, Fu Lo

Electrical and Computer Engineering Faculty Publications and Presentations

A significant development of recent research in nonlinear distortion is the expansion of the conventional two-tone test for power amplifiers to the concurrent dual-band transmitters, by Amin et al. A general framework using dual two-tones is developed, which shows that the output signal is affected not only by intermodulation (IM) products but also by cross-modulation (CM) products. In this paper, we will make a number of clarifications to Amin et al.'s paper. The effects of IM and CM in passband will be discussed, IM represents a reduction for compressive devices, and CM reflects an interference caused by the signal from …

Chiral Metamaterial-Based Microwave Sensors, Nantakan Wongkasem, Amornthep Sonsilphong, Mario Gonzalez

Electrical and Computer Engineering Faculty Publications and Presentations

A significant resonance shift is found in both reflection and transmission coefficients from both parallel and perpendicular excitations in a helical structure. The responses from the perpendicular excitation show better sensitivity than those from the parallel excitation at 480 MHz-560 MHz for 0.2 circumference difference. Additional electromagnetic properties of a helical structure, such as chirality, optical rotatory dispersion and circular dichroism can also further combine to enhance the sensing performance.

A Fast Fpga Implementation For Triple Des Encryption Scheme, Edni Del Rosal, Sanjeev Kumar

Electrical and Computer Engineering Faculty Publications and Presentations

In cryptography, the Triple DES (3DES, TDES or officially TDEA) is a symmetric-key block cipher which applies the Data Encryption Standard (DES) cipher algorithm three times to each data block. Electronic payment systems are known to use the TDES scheme for the encryption/decryption of data, and hence faster implementations are of great significance. Field Programmable Gate Arrays (FPGAs) offer a new solution for optimizing the performance of applications meanwhile the Triple Data Encryption Standard (TDES) offers a mean to secure information. In this paper we present a pipelined implementation in VHDL, in Electronic Code Book (EBC) mode, of this commonly …

Feedforward Chemical Neural Network: An In Silico Chemical System That Learns Xor, Drew Blount, Peter Banda, Christof Teuscher, Darko Stefanovic

Electrical and Computer Engineering Faculty Publications and Presentations

Inspired by natural biochemicals that perform complex information processing within living cells, we design and simulate a chemically implemented feedforward neural network, which learns by a novel chemical-reaction-based analogue of backpropagation. Our network is implemented in a simulated chemical system, where individual neurons are separated from each other by semipermeable cell-like membranes. Our compartmentalized, modular design allows a variety of network topologies to be constructed from the same building blocks. This brings us towards general-purpose, adaptive learning in chemico: wet machine learning in an embodied dynamical system.

Development And Assessment Of A Combined Reu/Ret Program In Materials Science, Noah Salzman, Rick Ubic

Electrical and Computer Engineering Faculty Publications and Presentations

In this paper we present an evaluation and lessons learned from a joint Research Experience for Undergraduates (REU) and Research Experience for Teachers (RET) program focused on energy and sustainability topics within a Materials Science and Engineering program at a public university. This program brought eleven undergraduate science and engineering students with diverse educational and institutional backgrounds and four local middle and high school teachers on campus for an 8-week research experience working in established lab groups at the university.

Using the Qualtrics online survey software, we conducted pre-experience and post-experience surveys of the participants to assess the effects of …

Talking About A Revolution: Overview Of Nsf Red Projects, Noah Salzman

Electrical and Computer Engineering Faculty Publications and Presentations

A significant initiative in engineering education in the U.S. began in 2014 when the National Science Foundation (NSF) initiated the IUSE/PFE: REvolutionizing engineering and computer science Departments (IUSE/PFE: RED) program. The goals of IUSE/PFE: RED (hereinafter referred to as RED) are to “enable engineering and computer science departments to lead the nation by successfully achieving significant sustainable changes necessary to overcome longstanding issues in their undergraduate programs and educate inclusive communities of engineering and computer science students prepared to solve 21st-century challenges.” In 2015, six RED projects were funded followed by seven more in 2016. In addition, NSF funded researchers …

Developing An Instrument To Assess The Effects Of Pre-College Engineering Participation On The Experiences Of First-Year Engineering Students, Noah Salzman, Matthew W. Ohland, Monica E. Cardella

Electrical and Computer Engineering Faculty Publications and Presentations

In this Complete Research paper, we describe the development of a survey instrument to measure the ways that students experience the transition from pre-college engineering activities to first-year engineering programs. As the number of opportunities to study and do engineering prior to matriculation in an undergraduate engineering program increases, first-year engineering students draw from a diverse range of pre-college engineering experiences that affect their transition to studying engineering at a university.

The instrument utilizes a theoretical framework developed via a phenomenographic interview process that identified five distinct ways students experience the transition from pre-college to university engineering. These range from …

Using Ir Cameras Beyond Outreach: Motivational Projects For Engineering Students, Cameron H.G. Wright, Thad B. Welch

Electrical and Computer Engineering Faculty Publications and Presentations

Affordable infrared (IR) cameras provide a unique opportunity to motivate and enhance the education of engineering students. We used both IR and visible images from a FLIR E60 camera as an instructional vehicle in a digital image processing course, where students came from several engineering majors. These IR and visible images were used as the basis for an open-ended final project in the course. Assessment via both pre- and post-project questionnaires showed the project was a positive experience for the students, and helped motivate them to learn the material. This paper discusses the course, the camera, the project, and how …

Elementary School Use Of The Sidekick Basic Kit For Ti Launchpad™, Tara N. Kimmey, Thad B. Welch, Cameron H.G. Wright

Electrical and Computer Engineering Faculty Publications and Presentations

Despite the fact that the Sidekick basic kit for TI LaunchPad™ is intended for a much more experienced group of students, engineers, and makers, we have successfully introduced it into four classes of 5^th grade elementary school students. This system mapped well onto the existing science standards of learning established by the State of Virginia. Additionally, the assessment of this process clearly demonstrated that effective learning is occurring.

Analysis And Testing Of A Coaxial Magnetic Gearbox With Flux Concentration Halbach Rotors, Debarupa Som, Kang Li, Joshua Kadel, Jason Wright, Sina Modaresahmadi, Jonathan Bird, W. William

Electrical and Computer Engineering Faculty Publications and Presentations

Halbach array magnetic gearboxes have been discussed as being able to create high torque density. However, Halbach arrays are difficult to mechanically assembly and often the effective air-gap must be made larger in order to provide space for a retaining sleeve. This paper investigates the benefits of using an additional ferromagnetic retaining pole within the Halbach array structure. It is shown that utilizing this flux concentration ferromagnetic pole improves the torque density and can also help retain the magnets in place.

Passive Bottom Reflection-Loss Estimation Using Ship Noise And A Vertical Line Array, Lanfranco Muzi, Martin Siderius, Christopher M. Verlinden

Electrical and Computer Engineering Faculty Publications and Presentations

An existing technique for passive bottom-loss estimation from natural marine surface noise (generated by waves and wind) is adapted to use noise generated by ships. The original approach—based on beamforming of the noise field recorded by a vertical line array of hydrophones—is retained; however, additional processing is needed in order for the field generated by a passing ship to show features that are similar to those of the natural surface-noise field. A necessary requisite is that the ship position, relative to the array, varies over as wide a range of steering angles as possible, ideally passing directly over the array …

Evolution Of An Introductory Electrical Engineering And Programming Course, Branimir Pejcinovic, Phillip Wong

Electrical and Computer Engineering Faculty Publications and Presentations

Our first year electrical engineering sequence includes two courses that involve programming and hardware interfacing. ECE 102 deals with engineering problem solving and MATLAB, while ECE 103 introduces C programming. We use MATLAB both as a problem solving tool and as an introduction to programming. Students utilize MATLAB to control a data acquisition device, which enables more realistic team-based projects that combine problem-solving, programming, and interfacing. As is widely recognized, these types of courses are important and difficult to teach. We identified areas that needed improvement in ECE 102: a) outdated lecture format, b) not enough timely feedback, c) insufficient …

Low Loss And Low Dispersion Fiber For Transmission Applications In The Terahertz Regime, Sohel Rana, Adnan Siraj Rakin, Harish Subbaraman, Rainer Leonhardt, Derek Abbott

Electrical and Computer Engineering Faculty Publications and Presentations

In this letter we present a novel slotted core fiber incorporating a slotted cladding for the terahertz band. The modal properties of the designed fiber are numerically investigated based on an efficient finite element method (FEM). Simulation results of the fiber exhibit both a low material absorption loss of 0.0103–0.0145 cm^-1 and low dispersion below 0.5 ps/THz/cm within the 0.5–0.9 THz range. Additionally, a number of other features of the fiber have been evaluated.

Inertial And Time-Of-Arrival Ranging Sensor Fusion, Paul Vasilyeav, Sean Pearson, Mahmoud El-Gohary, Mateo Aboy, James Mcnames

Electrical and Computer Engineering Faculty Publications and Presentations

Wearable devices with embedded kinematic sensors including triaxial accelerometers, gyroscopes, and magnetometers are becoming widely used in applications for tracking human movement in domains that include sports, motion gaming, medicine, and wellness. The kinematic sensors can be used to estimate orientation, but can only estimate changes in position over short periods of time. We developed a prototype sensor that includes ultra wideband ranging sensors and kinematic sensors to determine the feasibility of fusing the two sensor technologies to estimate both orientation and position. We used a state space model and applied the unscented Kalman filter to fuse the sensor information. …

Electrodynamic Wheel Magnetic Rolling Resistance, Wei Qin, Jonathan Z. Bird

Electrical and Computer Engineering Faculty Publications and Presentations

In this paper the concept of magnetic rolling resistance (MRR) is introduced. The MRR is particularly useful when trying to characterize maglev devices that operate with a slip. Approaches to minimize the MRR for an electrodynamic wheel magnetic suspension device are discussed. MRR is calculated from the power losses and it is shown that by using MRR a direct performance comparison with existing modes of transportation can be made. The MRR for a number of different maglev designs is calculated.

Fast And Accurate Sparse Coding Of Visual Stimuli With A Simple, Ultra-Low-Energy Spiking Architecture, Walt Woods, Christof Teuscher

Electrical and Computer Engineering Faculty Publications and Presentations

Memristive crossbars have become a popular means for realizing unsupervised and supervised learning techniques. Often, to preserve mathematical rigor, the crossbar itself is separated from the neuron capacitors. In this work, we sought to simplify the design, removing extraneous components to consume significantly lower power at a minimal cost of accuracy. This work provides derivations for the design of such a network, named the Simple Spiking Locally Competitive Algorithm, or SSLCA, as well as CMOS designs and results on the CIFAR and MNIST datasets. Compared to a non-spiking model which scored 33% on CIFAR-10 with a single-layer classifier, this hardware …

A Timed Colored Petri Net Simulation-Based Self-Adaptive Collaboration Method For Production-Logistics Systems, Zhengang Guo, Yingfeng Zhang, Xibin Zhao, Xiaoyu Song

Electrical and Computer Engineering Faculty Publications and Presentations

Complex and customized manufacturing requires a high level of collaboration between production and logistics in a flexible production system. With the widespread use of Internet of Things technology in manufacturing, a great amount of real-time and multi-source manufacturing data and logistics data is created, that can be used to perform production-logistics collaboration. To solve the aforementioned problems, this paper proposes a timed colored Petri net simulation-based self-adaptive collaboration method for Internet of Things-enabled production-logistics systems. The method combines the schedule of token sequences in the timed colored Petri net with real-time status of key production and logistics equipment. The key …

Altruistic Punishment Can Help Resolve Tragedy Of The Commons Social Dilemmas, Garrison W. Greenwood

Electrical and Computer Engineering Faculty Publications and Presentations

Social dilemmas force individuals to choose between cooperation, which benefits a group, and defection which benefits the individual. The unfortunate outcome in most social dilemmas is mutual defection where nobody benefits. Researchers frequently use mathematical games such as public goods games to help identify circumstances that might improve cooperation levels within a population. Altruistic punishment has shown promise in these games. Many real-world social dilemmas are expressed via a tragedy of the commons metaphor. This paper describes an investigation designed to see if altruistic punishment might work in tragedy of the commons social dilemmas. Simulation results indicate not only does …

Analysis Of A Magnetically Geared Lead Screw, Mojtaba Bahrami Kouhshahi, Jonathan Bird

Electrical and Computer Engineering Faculty Publications and Presentations

Linear magnetic gearboxes (LMG) and magnetic lead screws (MLS) have been shown to be capable of operating at significantly higher volumetric force densities than traditional electromagnetic linear actuators (ELA). However in both such devices the linear translator must be made of magnet material and therefore if the stroke length of the translator is long the cost of the MLS and LMG will become prohibitively high. In this paper a magnetically geared lead screw (MGLS) is investigated and its performance capability is compared with the LMG and MLS. The advantage of the MGLS is that the translator does not contain magnets.

Ideal Radial Permanent Magnet Coupling Torque Density Analysis, Kang Li, Jonathan Bird, Vedanadam M. Acharya

Electrical and Computer Engineering Faculty Publications and Presentations

This paper derives the closed form 3-D analytical torque equations for an ideal radial Halbach rotor magnetic coupling. The performance of the radial Halbach coupling is then compared with an ideal axial Halbach rotor coupling. The closed form equations and comparison gives insight into the upper torque density limits of Nd-Fe-B based magnetic devices.

A Low Assembly Cost Coaxial Magnetic Gearbox, Kiran Uppalapati, Joshua Kadel, Jason Wright, Kang Li, Wesley Williams, Jonathan Bird

Electrical and Computer Engineering Faculty Publications and Presentations

This paper presents the design investigation and experimental testing of a flux-focusing magnetic gearbox with a three piece laminated rotor structure. Each rotor is made of a single lamination stack held together via thin lamination bridges. It is calculated that mechanical bridges reduces the torque density from 156Nm/L to 139Nm/L (a reduction of 11%). The experimentally measured torque density is shown to be only 95Nm/L because the magnets were demagnetized during testing.

Toward Improving Electrocardiogram (Ecg) Biometric Verification Using Mobile Sensors: A Two-Stage Classifier Approach, Robin Tan, Marek Perkowski

Electrical and Computer Engineering Faculty Publications and Presentations

Electrocardiogram (ECG) signals sensed from mobile devices pertain the potential for biometric identity recognition applicable in remote access control systems where enhanced data security is demanding. In this study, we propose a new algorithm that consists of a two-stage classifier combining random forest and wavelet distance measure through a probabilistic threshold schema, to improve the effectiveness and robustness of a biometric recognition system using ECG data acquired from a biosensor integrated into mobile devices. The proposed algorithm is evaluated using a mixed dataset from 184 subjects under different health conditions. The proposed two-stage classifier achieves a total of 99.52% subject …

Marine Mammal Tracks From Two-Hydrophone Acoustic Recordings Made With A Glider, Elizabeth T. Küsel, Tessa Munoz, Martin Siderius, David K. Mellinger, Sara L. Heimlich

Electrical and Computer Engineering Faculty Publications and Presentations

A multinational oceanographic and acoustic sea experiment was carried out in the summer of 2014 off the western coast of the island of Sardinia, Mediterranean Sea. During this experiment, an underwater glider fitted with two hydrophones was evaluated as a potential tool for marine mammal population density estimation studies. An acoustic recording system was also tested, comprising an inexpensive, off-the-shelf digital recorder installed inside the glider. Detection and classification of sounds produced by whales and dolphins, and sometimes tracking and localization, are inherent components of population density estimation from passive acoustics recordings. In this work we discuss the equipment used …

Spatio-Temporal Pattern Recognition In Neural Circuits With Memory-Transistor-Driven Memristive Synapses, Kurtis D. Cantley, Robert C. Ivans, Anand Subramaniam, Eric M. Vogel

Electrical and Computer Engineering Faculty Publications and Presentations

Spiking neural circuits have been designed in which the memristive synapses exhibit spike timing-dependent plasticity (STDP). STDP is a learning mechanism where synaptic weight (the strength of the connection between two neurons) depends on the timing of pre-and post-synaptic action potentials. A known capability of networks with STDP is detection of simultaneously recurring patterns within the population of afferent neurons. This work uses SPICE (simulation program with integrated circuit emphasis) to demonstrate the spatio-temporal pattern recognition (STPR) effect in networks with 25 afferent neurons. The neuron circuits are the leaky integrate-and-fire (I&F) type and implemented using extensively validated ambipolar nano-crystalline …

A Cmos Synapse Design Implementing Tunable Asymmetric Spike Timing-Dependent Plasticity, Robert C. Ivans, Kurtis D. Cantley, Justin L. Shumaker

Electrical and Computer Engineering Faculty Publications and Presentations

A CMOS synapse design is presented which can perform tunable asymmetric spike timing-dependent learning in asynchronous spiking neural networks. The overall design consists of three primary subcircuit blocks, and the operation of each is described. Pair-based Spike Timing-Dependent Plasticity (STDP) of the entire synapse is then demonstrated through simulation using the Cadence Virtuoso platform. Tuning of the STDP curve learning window and rate of synaptic weight change is possible using various control parameters. With appropriate settings, it is shown the resulting learning rule closely matches that observed in biological systems.

A Spatial-Spectral Interference Model For Millimeter Wave 5g Applications, Solmaz Niknam, Balasubramaniam Natarajan, Hani Mehrpouyan

Electrical and Computer Engineering Faculty Publications and Presentations

The potential of the millimeter wave (mmWave) band in meeting the ever growing demand for high data rate and capacity in emerging fifth-generation (5G) wireless networks is well-established. Since mmWave systems are expected to use highly directional antennas with very focused beams to overcome severe pathloss and shadowing in this band, the nature of signal propagation in mmWave wireless networks may differ from current networks. One factor that is influenced by such propagation characteristics is the interference behavior, which is also impacted by the simultaneous use of the unlicensed portion of the spectrum by multiple users. Therefore, considering the propagation …

Self-Directed Channel Memristor For High Temperature Operation, Kristy A. Campbell

Electrical and Computer Engineering Faculty Publications and Presentations

Ion-conducting memristors comprised of the layered chalcogenide materials Ge₂Se₃/SnSe/Ag are described. The memristor, termed a self-directed channel (SDC) device, can be classified as a generic memristor and can tolerate continuous high temperature operation (at least 150 °C). Unlike other chalcogenide-based ion conducting device types, the SDC device does not require complicated fabrication steps, such as photodoping or thermal annealing, making these devices faster and more reliable to fabricate. Device pulsed response shows fast state switching in the 10⁻⁹ s range. Device cycling at both room temperature and 140 °C show write endurance of at least …

Residual Self-Interference Cancellation And Data Detection In Full-Duplex Communication Systems, Abbas Koohian, Hani Mehrpouyan, Ali Arshad Nasir, Salman Durrani, Steven D. Blostein

Electrical and Computer Engineering Faculty Publications and Presentations

Residual self-interference cancellation is an important practical requirement for realizing the full potential of full-duplex (FD) communication. Traditionally, the residual selfinterference is cancelled via digital processing at the baseband, which requires accurate knowledge of channel estimates of the desired and self-interference channels. In this work, we consider point-to-point FD communication and propose a superimposed signaling technique to cancel the residual self-interference and detect the data without estimating the unknown channels. We show that when the channel estimates are not available, data detection in FD communication results in ambiguity if the modulation constellation is symmetric around the origin. We demonstrate that …