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 …

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.

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.

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 …

Electrical Characteristics Of Nanocrystalline Silicon Resistive Memory Devices, Sumedha Gandharava, Catherine Walker, Kurtis D. Cantley

Electrical and Computer Engineering Faculty Publications and Presentations

Resistive memory devices have been studied and fabricated using a wide variety of materials including chalcogenides [1], metal oxides [2], and hydrogenated amorphous silicon (a-Si:H) [3]. The most promising materials seem to be amorphous in nature, with the properties of the atomic lattices being conducive to the physical mechanisms that underlie the subsequent resistive switching. The devices are also finding applications beyond high-density digital memory, such as for electronic synapses in neuromorphic systems [4], [5]. However, a different set of properties is required in the latter case compared to devices that must only store binary values. In addition, it is …

Multi-Relay Communications In The Presence Of Phase Noise And Carrier Frequency Offsets, Omar H. Salim, Ali Arshad Nasir, Hani Mehrpouyan, Wei Xiang

Electrical and Computer Engineering Faculty Publications and Presentations

Impairments like time varying phase noise (PHN) and carrier frequency offset (CFO) result in loss of synchronization and poor performance of multi-relay communication systems. Joint estimation of these impairments is necessary in order to correctly decode the received signal at the destination. In this paper, we address spectrally-efficient multi-relay transmission scenarios where all the relays simultaneously communicate with the destination. We propose an iterative pilot-aided algorithm based on the expectation conditional maximization (ECM) for joint estimation of multipath channels, Wiener PHNs, and CFOs in decode-and-forward (DF) based multi-relay orthogonal frequency division multiplexing (OFDM) systems. Next, a new expression of the …