Group photo of Ph.D. graduates and faculty from commencement.

Our research addresses areas across physical acoustics, computational modeling of physical systems, stochastic modeling, data analytics and engineering education. We explore problems through an interdisciplinary lens with researchers from physical sciences, social-science, education and business management. Some of these topics are described here. Two recently funded NSF projects address Graduate Education in Cyber-Physical Systems Engineering and the Design of AI-assisted Augmented Reality based Education and Training Systems.

Acoustic Streaming in the Inner Ear

The cochlea of the inner ear is a small fluid-filled chamber responsible for converting acoustically induced mechanical vibrations into the neural signals that we use to interpret sound. The internal sensory structures within the cochlea can be excited by air and bone conduction. The mechanical process of bone conduction hearing is shown in Fig. 1. The arrows in the figure denote relative velocity directions of the tympanic membrane (TM), oval window (O), and round window (R).

The mechanical features of bone conduction are shown in the Figure. In contrast to air conduction, sound induces vibration of the otic capsule, the bony outer wall of the inner ear that includes the cochlea. Due to the incompressible behavior of the enclosed fluid in the cochlea, the sum of the volume velocities at the oval and the round windows must equal the time-rate of change of the volume of fluid in the cochlea. In this research acoustic streaming resulting from the time-harmonic compression of the cochlear capsule is examined.

Bone conduction hearing mechanisms: C, cochlea (uncoiled); O, oval window; R, round window; TM, tympanic membrane (eardrum); SCC, semicircular canal; V, vestibule; VA, vestibular aqueduct. (a) Air conduction (arrows), (b) bone conduction (arrows). Reprinted with permission from Ho, Neuroimaging Clin. N. Am. 29, 57-92. (2019).

Bone conduction hearing mechanisms: C, cochlea (uncoiled); O, oval window; R, round window; TM, tympanic membrane (eardrum); SCC, semicircular canal; V, vestibule; VA, vestibular aqueduct. (a) Air conduction (arrows), (b) bone conduction (arrows). Reprinted with permission from Ho, Neuroimaging Clin. N. Am. 29, 57-92. (2019).

Passive Radio Frequency Excited Acoustic Transduction

In this work, the physical processes that govern the operation of a passive acoustic transducer, shown if Fig 1, are analyzed and modeled. The wireless battery-free transducer derives its power from an externally applied electromagnetic field generated by a radio transmitter. The audio signal is encoded in the backscattered electromagnetic field. Electro-mechano-acoustical analogies are developed and presented. Power generation, sound transduction, and radio frequency backscatter transmission of the audio signal are analyzed.

Introduction to the special issue on the theory and applications of acoustofluidics

J. Friend, C. Thompson, K. Chitala and M. Denis. The Journal of the Acoustical Society of America 150, 4558 (2021);

Acoustofluidics is a burgeoning field that applies ultrasound to micro-scale to nano-scale fluidic systems. The discovery of the ability to effectively manipulate fluids and particles at small scales has yielded results that are superior to other approaches and has been built into a diverse range of research. Recasting the fundamentals of acoustics from the past to include new phenomena observed in recent years has allowed acoustical systems to impact new areas, such as drug delivery, diagnostics, and enhanced chemical processes. The contributions in this special issue address a diverse range of research topics in acoustofluidics. Topics include acoustic streaming, flows induced by bubbles, manipulation of particles using acoustic radiation forces, fluid and structural interactions, and contributions suggesting a natural limit to the particle velocity, the ability to deliver molecules to human immune T cells, and microdroplet generation via nozzle-based acoustic atomization.

Padé approximants and their application to scattering from fluid media

In this work, a numerical method for modeling the scattered acoustic pressure from fluid occlusions is described. The method is based on the asymptotic series expansion of the pressure expressed in terms of sound speed contrast between the host medium and entrained fluid occlusions. Padé approximants are used to extend the applicability of the result for larger values of sound speed contrast. For scattering from a circular cylinder, an improvement in convergence between the exact and numerical solutions is demonstrated. In the case of scattering from an inhomogeneous medium, a numerical solution with reduced order of Padé approximants is presented.

Chaotic Motion in Oscillatory Flows

Over the last 150 years, the problem of oscillatory motion of fluids has been examined by numerous investigators. However, only recently have some of the causes for instability and chaotic motion in such flows been uncovered. Chaotic oscillations in wall-bounded oscillatory flows have been linked to the nonlinear growth of vortical disturbances introduced into the viscous boundary layer. The temporal evolution of these disturbances gives rise to the basic features evident in the resulting chaotic fluid motion. Disturbances are generated by the environment and consequently are comprised of numerous modes having a varied spatial wave number and amplitude. Once the fluid motion becomes unstable, according to linear theory, the least linearly stable mode will prevail and chaotic oscillation will ensue at a threshold value of the controlling parameter. Nonlinear amplitude growth can yield alternative solutions, which display chaotic oscillations at lower threshold values. To determine the least stable disturbance, the sensitivity of the fluid motion to the wave number composition and amplitude of an imposed disturbance must be understood. The figure depicts the state space trajectory of the kinetic energy of a chaotic three-dimensional disturbance in an oscillatory boundary layer. The orbits demonstrate an exponential sensitivity to initial conditions. The feature indicates the presence of chaotic oscillations.

Network Traffic and Channel Characterization

Internet traffic resulting from world-wide-web access is increasing at exponential rates and resulting in congested networks. At the same time, Internet voice and video applications are being seen as a cost-effective means of communication for both residential and corporate users. The end- to-end delay, delay variation and packet losses are traffic impairments that influence the audio and visual quality of packet voice and video applications. The characterization of Internet traffic and traffic impairments is therefore an important problem for the testing and implementation of protocols that support real-time applications. This research is focused on developing probabilistic models that can predict the delay and loss experienced by packet streams arising from real-time applications. These models are based on the analysis of measurements of delay and packet loss experienced by probe packets sent out at periodic intervals over the Internet. These measurements provide the seasonal time-of-day patterns of delay and delay variation. The figure depicts the time-of-day variation of the average round-trip delay experienced by a fifteen-minute constant bit rate packet stream when traversing a sequence of fourteen hops between the source and destination on the Internet. The maximum delay typically occur during peak occurs of 10-12 am and 2-5 PM. Predictive models of such patterns comprising of a deterministic cyclic behavior superimposed by stochastic disturbances are being investigated.

Spectrum Sharing

This work examines the blocking performance of narrow-band (NB) and wideband (WB) sources that access a shared pool of wireless channels. The NB sources utilize a single channel, whereas WB sources access simultaneously a larger group of channels. This system is analyzed in the context of maximizing the utilization of spectrum that is allocated to the WB system by allowing NB sources random access to the same spectrum. The performance measure to be controlled is the blocking experienced by WB sources. A queueing model of this system is proposed that allows evaluation of the impact of NB sources on WB performance. Assuming Poisson arrival process models and negative exponential distributions for the channel holding times, the dependence of the blocking probability of the WB source is derived as a function of the NB utilization factor. In an uncontrolled NB access scheme, the WB blocking is lower bounded by the blocking probability experienced by NB sources. The performance improvement afforded by adding extra NB channels and by controlling the access rates of the NB source for finite population WB sources is presented. The analysis presented here provides an assessment of some of the emerging paradigms for adaptive spectrum allocation. Of particular interest are the criteria under which spectrum agile, cognitive and software radios functioning in an opportunistic fashion can access unused spectrum allocated to a primary system without adversely affecting the performance of the primary system.

Innovative Graduate Educational Models and Undergraduate Bridge Programs

Engaging graduate students as co-creators of educational modules on an interdisciplinary topic [to appear ASEE 2022]

Co-creation in higher education is the process where students collaborate with instructors in designing the curriculum and associated educational material. This can take place in different scenarios, such as integrating co-creation into an ongoing course, modifying a previously taken course, or while creating a new course. In this work, we investigate training and formative assessment models for preparing graduate students in engineering to participate as co-creators of educational material on an interdisciplinary topic. The topic of cyber-physical systems engineering and product lifecycle management with application to structural health monitoring is considered in this co-creation project. This entails not only topics from different disciplines of Civil, Computer, Electrical and Environmental engineering, Business and Information Sciences, but also humanistic issues of sustainability, environment, ethical and legal concerns in data-driven decision-making that support the control of cyber-physical systems.

Aside from the objective of creating modules accessible to students with different levels of disciplinary knowledge, the goal of this research is to investigate if the co-creation process and the resulting modules also promote interest and engagement in interdisciplinary research. A literature survey of effective training approaches for co-creation and associated educational theories is summarized. For students, essential training components include providing (i) opportunities to align their interests, knowledge, skills and values with the topic presented; (ii) experiential learning on the topic to help develop and enhance critical thinking and question posing skills, and (iii) safe spaces to reflect, voice their opinions, concerns and suggestions. In this research we investigate the adaption of project-based learning (PjBL) strategies and practices to support (i) and (ii) and focus groups for participatory action research (PAR) as safe spaces for reflection, feedback and action in item (iii). The co-creation process will be assessed through qualitative analysis of data collected through the PjBL activities and PAR focus groups and other qualitative data (i.e., focus group transcripts, interview transcripts, project materials, fieldnotes, etc.). The outcome of the co-creation process is an on-line course module that is designed to be integrated in existing engineering graduate and undergraduate courses at four different institutions, that includes two state universities and two that are historically black colleges and universities.

Engaging Women Engineering Undergraduates as Peer Facilitators in Participatory Action Research Focus Group [ASEE 2021]

This study is part of a longitudinal research project examining the design of summer bridge and subsequent undergraduate engineering programs in the College of Engineering at University of Massachusetts Lowell, with the long-term view of how these programs can create more supportive, inclusive environments for women to become engaged as leaders in their educational pathways and future careers. A summer bridge program prepares first-year women engineering students for the academic and cultural opportunities and challenges they may face. Through an immersion in focus groups constructed for participatory action research (PAR), students learn to use their voices for change and also to lead in taking action to improve their experiences in the program. This summer experience is leveraged in the academic year by additional training for a small group of women participants from the summer program to facilitate focus groups open to all undergraduate students in the college of engineering. Using PAR and an asset-based approach emphasizing listening and learning from student voices, this study suggests how engaging women as peer facilitators in PAR focus groups builds leadership and communication skills, as well as increases understanding of student perceptions and experiences in their engineering majors. Further, using the results of a survey administered to all engineering students in their Junior and Senior years on their experiences in their majors, the responses from participants in the summer program are compared with those from students who did not have this opportunity. Women engineering students in the summer program were statistically more likely to see themselves as having stronger critical thinking and communication skills than women who did not participate in this program, but differences between these two groups in perceptions of sense of belonging and leadership skills were not statistically significant.

Participatory Action Research (PAR) as Formative Assessment of a STEM Summer Bridge Program (ASEE 2021 )

Research, Academics and Mentoring Pathways (RAMP) is a six-week summer bridge program offered to incoming female undergraduate engineering students. Initiated in 2018, the goal of this program is to increase the enrollment, retention, and success of female engineering students as they enter the College of Engineering, continue with their studies, and graduate into the workforce. The objectives are to encourage research participation, improve student content knowledge in gateway courses such as Calculus, and increase their sense of belonging, preparedness, and self-efficacy. To understand student perspectives and experiences, we utilized Participatory Action Research (PAR) to construct a series of formative assessments prioritizing the views and participation of the RAMP students themselves. PAR was selected as a research and assessment strategy due to its emphasis on student participation and empowerment linked with action for positive change. Online surveys and four focus groups involved the students in topics geared towards developing a psychologically safe space for sharing experiences, providing feedback on program activities, and reflecting on personal goals, values, and aspirations.

Analysis of the assessment data from these activities and surveys in 2018 revealed concrete suggestions that were used to improve the RAMP program in 2019. Changes made included using peer facilitators for the focus groups, providing workshops in a variety of locations, including more interactive research-based projects, using undergraduates for project support, and retaining several aspects of the 2018 program that were highly rated, such as industry visits, kayaking trips, and financial aid workshops. This iterative process of listening to student feedback and using their suggestions to make program changes was repeated in RAMP 2019, and will be continued in RAMP 2020. Based on our findings, we will identify the insights learned from using PAR as a formative assessment and explain why this approach may be especially helpful in creating more supportive and beneficial environments for women in engineering education.

    • 1992 Kavitha Chandra Asymptotic solutions and probabilistic characterization for ultrasonic scattering in biological media,(Thompson, eece)
    • 1992 Ifen Yang Globally synchronized distributed first-in first-out protocols for high-speed networks. (Kim, cs)
    • 1993 Geol-u Ryu Output locality switch (OLS) for ATM networks,(Kim, cs)
    • 1993 Iiyoung Chong ATM traffic control at burst level (Kim, cs)
    • 1993 Himanshu Bhatnagar NCLIPS: An architecture that integrates neural networks and rule-based knowledge representation,(Steele, cs)
    • 1993 Ali Rafieymehr Integrating visualization into massively parallel environments(Steele, cs)
    • 1993 Jie Yao On computations and algorithms for the Gabor transform (Steele, cs)
    • 1993 Paul E. Kenison RESLOG: Logic programming with resolution. (Gumb, cs)
    • 1994 Arun Mulpur Modeling and control of optical fiber variations (Thompson, eece)
    • 1994 Edward Riley CASYS: An object-oriented CASE tool for developing high-reliability software. (Steele, cs)
    • 1995 Kamonpet Patiwat Probabilistic image reconstructions from noisy and incomplete projections. (Krishnan, eece)
    • 1996 Ping Wang Computational algorithms for cell loss ratio in ATM networks with bursty source. (Kim, cs)
    • 1996 Vineet Mehta Instability and chaotic motion in an oscillatory boundary layer. (Thompson, eece)
    • 1996 Sylvia Isler Modeling and simulation of ultrasonic wave propagation. (Thompson, cs)
    • 1997 Ling Xu Probabilistic reconstruction of tomographic images – a statistical approach. (Krishnan, eece)
    • 1997 Bongseog Jang Threshold autoregressive models with application to video traffic. (Thompson, eece)
    • 1997 Eduardo J. Urbina EGA: A pattern recognition architecture to perform empirical goal analysis. (Steele,cs)
    • 1997 Enrique Alvare Intelligent connectionist pattern recognition system: The partial implementation of Expert Netvis a user-driven data exploration system. (Steele, cs)
    • 1998 Anthony Kozloff Improved acoustic scattering model for medical imaging. (Thompson, eece)
    • 1998 Bo-Kyoung Kim Optimal feedback control of ABR traffic in ATM networks. (Thompson, cs)
    • 1998 Sudha Mulpur Adaptive traffic shaping for multiplexed variable bit rate video traffic. (Thompson, cs)
    • 1998 Luis E. Valles Inspection intelligent agent to establish equipment and component optimum replacement in productive process. (Steele, cs)
    • 1999 Yeong-Min Jang Predictive traffic management and buffer dimensioning in broadband wireless networks. (Kim, cs)
    • 2000 Andres A. Monterrosas DYCOCOP: Dynamic Congestion Control Protocol for ATM. ( Kim, cs)
    • 2000 Jimmie Davis Performance models for correlated traffic data. (Krishnan, eece)
    • 2001 Hsin-Chun Yu Reinforcement learning based admission control in wireless CDMA networks. ( Kim, cs)
    • 2002 Younheon Kim Adaptive hybrid ARQ using convolutional and turbo codes on fading channels, and its application to the third-generation wireless communications. ( Kim, cs)
    • 2003 Hark-Sang Kim Measurement and model based characterization of indoor wireless channels. (Chandra, eece)
    • 2003 Prachee Sharma Predictive models for wireless fading channels. (Chandra, cs)
    • 2004 Hanjoon Cho Development of OFDM PAR reduction technique and application on STC-OFDM via tone reservation. ( Kim, cs)
    • 2005 Jung-Rim Hyun Optimal rate control and source estimation. (Kim-Thompson, cs)
    • 2005 Sei-Hyung Selection of Gaussian kernel widths and fast cluster labeling for support vector clustering. (Daniels, cs)
    • 2006 Mital Parikh Characterizing node availabbility and connectivity of a hybrid optical/rf airbone network. (Chandra, eece)
    • 2008 Miroslava Raspopovic Performance models for shared radio spectrum. (Thompson, Chandra eece)
    • 2009 Jing Tsui Analysis of beam steering by diffraction and the scattering of light by turbulence. (Thompson, eece)
    • 2009 Kassiani Kotsidou Acoustical modeling of micro-transducer arrays. (Thompson, eece)
    • 2009 Sania Salahuddin Statistical characterization of an indoor ultra-wideband wireless channel. ( Thompson, cs)
    • 2009 Minsoo Park Reduced alphabet of amino acids and its application to alternative splicing detection. (Kim, cs)
    • 2012 Max Denis A unified treatment of the acoustic and elastic scattered was from fluid-elastic media. (Thompson, eece)
    • 2013 Darlene Fleming Barker An Eulerian path approach to next-generation DNA sequencing with pre-sorted reads. (Kim, cs)
    • 2013 Adam Russell Formulation and application of radial visualization properties (Daniels,cs)
    • 2014 Hengky Susanto Congestion control with QoS through network utility maximization.(Kim,cs)
    • 2015 Ambika Bhatta Acoustic impulse response of a closed empty rectangular room. (Thompson, eece)
    • 2015 Asye Kalkan-Savoy Strain measurement in an ultrasound simulation framework. (Thompson, eece)
    • 2015 Shu Ye Constrained Delaunay meshing for printed circuit board visualization and electromagnetic analysis.(Daniels,cs)
    • 2015 Robert Marceau Partitioning data to minimize cluster overlap using multiple visualization views.(Daniels, cs)
    • 2017 Nicholas Misiunas Synthesis of Non-uniformly Spaced Antenna Arrays Using Data-driven Probabilistic Models.(Chandra, eece)
    • 2017 Hui Zhou Enhancing Convergence of Multipole Expansions at Intermediate Frequency. (Thompson, eece)
    • 2018 Peter Asuzu Millimeter-wave radar investigations of road conditions and their impact on wheel slip. (Thompson, eece)
    • 2018 Barbara Deschamp Analysis mammalian cell culture data. (Chandra, eece)
    • 2018 Elaheh Noursadeghi Distributed Fault Diagnosis for Networked Nonlinear Processes, Multi-Agent Systems, and Source Localization. (Raptis,me)
    • 2018 Mehmet Guney Motion Coordination and Task Planning of Multi-AGV Systems for Warehouse Automation. (Raptis, me)
    • 2021 Lejun Hu Fault Detection in an Interconnected Water Tank System Using Particle Filter (Thompson, Chandra,Levy, eece, Raptis me)
    • 2022 Pratik Gandhi (Chandra, eece)
    • 1989 Martin Manley Stability of Stagnation Flows (Thompson, eece)
    • 1989 Vineet Mehta Fluid motion and hydrodynamic stability of semiconductor melts. (Thompson, eece)
    • 1991 Tham Le Investigation of hidden Markov models for speech recognition. (Thompson, eece)
    • 1991 Ayse Kalkan Neural network coordinate transformer. (Fiddy-Thompson, eece)
    • 1991 Terrence Champion Estimation and synthesis of 2.4 KBPS LPC-10 parameters using sinusoidal transform coder techniques. (Krishnan, eece)
    • 1992 George Tasiopoulos Scientific visualization of two-dimensional time evolving fields. (Thompson, eece)
    • 1992 Chao Hsu Algorithms for scattered ultrasonic fields from inhomogeneous materials (Chandra-Thompson, eece)
    • 1993 Bo-Kyoung Kim Simulation study of weighted round-robin queueing policy (Kim, cs)
    • 1993 Alia Haider Image compression using wavelet transform. (Thompson, eece)
    • 1993 Ajay Muplur Shock propagation models with spectral multi-domain methods and flux-corrected transport. (Thompson, me)
    • 1995 Vardhani Harpanahalli Burst detection in packet data transmission. (Thompson, eece)
    • 1995 Ananda Chakravarty Spatial analysis of stability for disturbances in stagnation flow. (Thompson, eece)
    • 1995 Weihong Gao Image coding using wavelet-based IIR filter banks. (Thompson, eece)
    • 1996 Matthew Bush Modeling and control of a 144 KW dual stage inverter. (Mulpur,Thompson, eece)
    • 1996 Radivojevic Dusan Diffusion corrected optical flow. (Thompson, eece)
    • 1998 Tolga Eren Dynamic analysis of tethered satellite systems. (Chandra, eece)
    • 1998 Nancy Tharakan Acoustic Echo cancellation. (Thompson, eece)
    • 1999 Chun You time series models for internet data traffic. (Chandra, eece)
    • 1999 Ping Zhou Delay estimation and control of available bit rate (ABR) sources. (Thompson, Kim, eece)
    • 2000 Gbenga Olowoyeye Workload models for HTTP servers. (Chandra, eece)
    • 2000 Mital Parikh Traffic metrics for adaptive routing. (Chandra, eece)
    • 2000 Parita Amin Infinite impulse response filter based models of room acoustic. (Thompson, eece)
    • 2001 Sa Liu Channel assignment for time-varying demand. (Daniels, cs )
    • 2002 Shekhar S. Kshirsager Feasibility study of soft available bit rate (SABR) routing in Internet. (Kim, cs)
    • 2002 Sintayehu Dehnie TCP performance over wireless fading channels. (Chandra, eece)
    • 2003 Deepak Garg Differentiated services and MPLS integration proposal. 2001-2003. (Kim, cs)
    • 2003 Miroslava Raspopovic Exact image theory for ultra-wideband pulse reflections. (Thompson, eece)
    • 2003 Jing Tsui Network performance of audio streaming servers. ( Thompson, eece )
    • 2003 Jyotsna Basana Asymptotic approximations for the effective bandwidth of a Markovian process. (Thompson, eece)
    • 2004 Vasudevan Vijayakalshmi Wireless channel characterization and modeling. (Chandra, eece)
    • 2003 Rajani Pakalapati Network traffic analysis identifying invariant features in Internet traffic. (Chandra, eece)
    • 2004 Max Denis A model for indoor wireless channels. (Thompson, eece)
    • 2004 Hetalbin Patel A rigid sphere model for the head-related transfer function and its application to audio signal processing. (Thompson, eece)
    • 2004 Estella Pham Indoor Wireless channel estimation. (Chandra, eece)
    • 2005 Sirisha Myneni LAN Traffic analysis and effective bandwidth calculation. (Chandra, eece)
    • 2005 Keyur Joshi TCP performance emulation for lossy communication channels. (Chandra, eece)
    • 2006 Neha Dhar Analysis of channel performance for binary signaling. (Thompson, eece)
    • 2010 Wei-En Hsu Measurement and modeling of ultra-wideband indoor wireless channels. (Chandra, eece)
    • 2010 Lavanya Kakireddy Performance analysis of software defined radio. (Chandra, eece)
    • 2010 Amibka Bhatta An analysis of scattering from a reentrant wedge. (Thompson, eece)
    • 2011 Raji Remany Investigation of pilot tone detection in spectrum sensing (Chandra,Thompson, eece)
    • 2011 Jason M’Sadoques Regarding an alternative method for translational single-item containment (Daniels, cs)
    • 2012 Barbara Deschamp Modeling the mechanical vibration and current flow in carbon nanotubes (Chandra Thompson, eece)
    • 2013 Pratik Gandhi A sensing and transmission model for spectrum sharing (Chandra, eece)
    • 2013 Nicholas Misiunas Spectrum sharing policies with adjacent channel constraints (Chandra, eece)
    • 2013 Megha Sunny Acoustic streaming in a channel bifurcated by an elastic membrane (Thompson, eece)
    • 2013 Dhani Ramya Student analytics for course recommendation (Daniels,cs)
    • 2014 Katherine Aho Fluid motion in the cochlea resulting from bone conducted stimulation (Thompson, eece)
    • 2014 Benjamin Woodward Performance optimization of radial basis function support vector machines (Thompson, eece)
    • 2014 Chisna Nguon Direct Computation of Nonlinear Propagation of Ultrasound in Inhomogeneous Media. (Chandra, eece)
    • 2016 Jenny Au Nonuniformly spaced arrays (Thompson, eece)
    • 2018 James Wigglesworth Conductive Printing via 6-axis Robotic Arm and Monocular Camera System: Control, Tolerance Analysis, and Optimization. (Raptis, me)
    • 2018 Matthew S. Spaziani Design, programming, and control of an autonomous race car. (Raptis, me)
    • 2021 Arielle S. Joasil Simulating the Space-Time Trajectory of Respiratory Droplets and Aerosols. (Chandra, Thompson eece)
    • 2021 Habibat Olaide Alimi Computation of Two-Dimensional Fluid Motion in the Cochlea. (Thompson eece)
    • 2021 Angela Bertolino Source Estimation with Particle Filtering for the Gaussian Plume Model of Pollutant Dispersion. (Chandra eece)
    • 2022 Emi Aoi (Chandra eece)