Engineering Commons^™

Stable Thermally-Modulated Nanodroplet Ultrasound Contrast Agents, Anastasiia Vasiukhina, Javad Estraghi, Adib Ahmadzadegan, Craig J. Goergen, Pavlov P. Vlachos, Luis Solorio

School of Mechanical Engineering Faculty Publications

Liquid perfluorocarbon-based nanodroplets are stable enough to be used in extravascular imaging, but provide limited contrast enhancement due to their small size, incompressible core, and small acoustic impedance mismatch with biological fluids. Here we show a novel approach to overcoming this limitation by using a heating–cooling cycle, which we will refer to as thermal modulation (TM), to induce echogenicity of otherwise stable but poorly echogenic nanodroplets without triggering a transient phase shift. We apply thermal modulation to high-boiling point tetradecafluorohexane (TDFH) nanodroplets stabilized with a bovine serum albumin (BSA) shell. BSA-TDFH nanodroplets with an average diameter under 300 nanometers showed …

Breakage Modeling Of Needle-Shaped Particles Using The Discrete Element Method, Rohit Kumar, William Ketterhagen, Avik Sarkar, Jennifer S. Curtis, Carl Wassgren

School of Mechanical Engineering Faculty Publications

This paper models the breakage of large aspect ratio particles in an attrition cell using discrete element method (DEM) and population balance (PB) models. The particles are modeled in DEM as sphero-cylinders. The stresses within each particle are calculated along the particle length using beam theory and the particle breaks into two parts if the stress exceeds a critical value. Thus, the size distribution changes with time within the DEM model. The DEM model is validated against previously published experimental data.

The simulations demonstrate that particle breakage occurs primarily in front of the attrition cell blades, with the breakage rate …

Improving Human-Machine Collaboration Through Transparency-Based Feedback – Part I: Human Trust And Workload Model, Kumar Akash, Katelyn Polson, Neera Jain

School of Mechanical Engineering Faculty Publications

In this paper, we establish a partially observable Markov decision process(POMDP) model framework that captures dynamic changes in human trust and workload for contexts that involve interactions between humans and intelligent decision-aid systems. We use a reconnaissance mission study to elicit a dynamic change in human trust and workload with respect to the system’s reliability and user interface transparency as well as the presence or absence of danger. We use human subject data to estimate transition and observation probabilities of the POMDP model and analyze the trust-workload behavior of humans. Our results indicate that higher transparency is more likely to …

Improving Human-Machine Collaboration Through Transparency-Based Feedback – Part Ii: Control Design And Synthesis, Kumar Akash, Tahira Reid, Neera Jain

School of Mechanical Engineering Faculty Publications

To attain improved human-machine collaboration, it is necessary for autonomous systems to infer human trust and workload and respond accordingly. In turn, autonomous systems require models that capture both human trust and workload dynamics. In a companion paper, we developed a trust-workload partially observable Markov decision process (POMDP) model framework that captured changes in human trust and workload for contexts that involve interaction between a human and an intelligent decision-aid system. In this paper, we defne intuitive reward functions and show that these can be readily transformed for integration with the proposed POMDP model. We synthesize a near-optimal control policy …

Additive Manufacturing Of Ti6al4v Alloy: A Review, Shunyu Liu, Yung C. Shin

School of Mechanical Engineering Faculty Publications

In this paper, the recent progress on Ti6Al4V fabricated by three mostly developed additive manufacturing (AM) techniques-directed energy deposition (DED), selective laser melting (SLM) and electron beammelting (EBM)-is thoroughly investigated and compared. Fundamental knowledge is provided for the creation of links between processing parameters, resultant microstructures and associated mechanical properties. Room temperature tensile and fatigue properties are also reviewed and compared to traditionally manufactured Ti6Al4V parts. The presence of defects in as-builtAMTi6Al4V components and the influences of these defects on mechanical performances are also critically discussed.

Bree's Diagram Of A Functionally Graded Thick-Walled Cylinder Under Thermo-Mechanical Loading Considering Nonlinear Kinematic Hardening, Mohsen Damadam, Reza Moheimani, Hamid Dalir

School of Mechanical Engineering Faculty Publications

n this paper, elasto-plastic analysis of a thick-walled cylinder made of functionally graded materials (FGMs) subjected to constant internal pressure and cyclic temperature gradient loading is carried out using MATLAB. The material is assumed to be isotropic and independent of tem- perature with constant Poisson's ratio and the material properties vary radially based on a power law volume function relation. The Von Mises’ yield criterion and the Armstrong-Frederick non- linear kinematic hardening model were implemented in this investigation. To obtain the incre- mental plastic strain, return mapping algorithm (RMA) was used. At the end, the Bree's inter- action diagram is …

Real-Time Sensing Of Trust In Human-Machine Interactions, Wan-Lin Hu, Kumar Akash, Neera Jain, Tahira Reid

School of Mechanical Engineering Faculty Publications

Human trust in automation plays an important role in successful interactions between humans and machines. To design intelligent machines that can respond to changes in human trust, real-time sensing of trust level is needed. In this paper, we describe an empirical trust sensor model that maps psychophysiological measurements to human trust level. The use of psychophysiological measurements is motivated by their ability to capture a human's response in real time. An exhaustive feature set is considered, and a rigorous statistical approach is used to determine a reduced set of ten features. Multiple classification methods are considered for mapping the reduced …

The Relationship Between Intermittent Limit Cycles And Postural Instability Associated With Parkinson’S Disease, James R. Chagdes, Jessica E. Huber, Meredith Saletta, Meghan Darling-White, Arvind Raman, Shirley Rietdyk, Howard N. Zelaznik, Jeffrey M. Haddad

School of Mechanical Engineering Faculty Publications

Background: Many disease-specifc factors such as muscular weakness, increased muscle stiffness, varying postural strategies, and changes in postural refexes have been shown to lead to postural instability and fall risk in people with Parkinson’s disease (PD). Recently, analytical techniques, inspired by the dynamical systems perspective on movement control and coordination, have been used to examine the mechanisms underlying the dynamics of postural declines and the emergence of postural instabilities in people with PD. Methods: A wavelet-based technique was used to identify limit cycle oscillations (LCOs) in the anterior–posterior (AP) postural sway of people with mild PD (n = 10) compared …

Implementation Of A Novel Hydraulic Hybrid Powertrain In A Sports Utility Vehicle, Michael Sprengel, Tyler Bleazard, Hiral Haria, Monika Ivantysynova

School of Mechanical Engineering Faculty Publications

Hydraulic hybrid transmissions offer an efficient and high performance alternative to electric hybrid transmission in on-road vehicles. One of the principle benefits of hydraulic over electric hybrids is the higher power density offered by their energy storage media. This enables hydraulic hybrids to capture virtually all of the available kinetic energy from braking. In contrast electric hybrids are often forced to dissipate part of this energy through friction brakes due to the lower power density inherent in their energy storage media. To date various hydraulic hybrid architectures have been investigated and put into production. However as is typically true there …

Strain Modulations As A Mechanism To Reduce Stress Relaxation In Laryngeal Tissues, Eric J. Hunter, Thomas Siegmund, Roger W. Chan

School of Mechanical Engineering Faculty Publications

Vocal fold tissues in animal and human species undergo deformation processes at several types of loading rates: a slow strain involved in vocal fold posturing (on the order of 1 Hz or so), cyclic and faster posturing often found in speech tasks or vocal embellishment (1–10 Hz), and shear strain associated with vocal fold vibration during phonation (100 Hz and higher). Relevant to these deformation patterns are the viscous properties of laryngeal tissues, which exhibit non-linear stress relaxation and recovery. In the current study, a large strain time-dependent constitutive model of human vocal fold tissue is used to investigate effects …

The Anisotropic Hyperelastic Biomechanical Response Of The Vocal Ligament And Implications For Frequency Regulation: A Case Study, Jordan E. Kelleher, Thomas Siegmund, Mindy Du, Elhum Naseri, Roger W. Chan

School of Mechanical Engineering Faculty Publications

No abstract provided.

Resolving Structure And Mechanical Properties At The Nanoscale Of Viruses With Frequency Modulation Atomic Force Microscopy, David Martinez-Martin, Carolina Carrasco, Mercedes Hernando-Pérez, P. J. De Pablo, Júlio Gómez-Herrero, Rebeca Pérez, Mauricio Garcia Mateu, José López Carrascosa, Daniel Roy Kiracofe, John C. Melcher, Arvind Raman

School of Mechanical Engineering Faculty Publications

Structural Biology (SB) techniques are particularly successful in solving virus structures. Taking advantage of the symmetries, a heavy averaging on the data of a large number of specimens, results in an accurate determination of the structure of the sample. However, these techniques do not provide true single molecule information of viruses in physiological conditions. To answer many fundamental questions about the quickly expanding physical virology it is important to develop techniques with the capability to reach nanometer scale resolution on both structure and physical properties of individual molecules in physiological conditions. Atomic force microscopy (AFM) fulfills these requirements providing images …

Estimating The Yield Strength Of Thin Metal Films Through Elastic-Plastic Buckling-Induced Debonding, S Goyal, K Srinivasan, G Subbarayan, Thomas Siegmund

School of Mechanical Engineering Faculty Publications

In this paper, we propose a procedure to estimate the yield strength of thin films by debonding films from their substrate by elastic-plastic buckling under thermally-induced compressive loading. The out-of-plane displacement of the metal lines under conditions of elastic-plastic buckling is dependent on the yield strength of the film. Thus, an inverse estimate of the yield strength is made from measurements of the out-of-plane displacements of the buckled metal lines. The procedure is demonstrated to estimate the yield strength of aluminum lines consistent with measurements by other techniques.

The Effect Of Polydispersivity On The Thermal Conductivity Of Particulate Thermal Interface Materials, Sasanka Kanuparthi, Ganesh Subbarayan, Thomas Siegmund, Bahgat Sammakia

School of Mechanical Engineering Faculty Publications

A critical need in developing thermal interface materials (TIMs) is an understanding of the effect of particle/matrix conductivities, volume loading of the particles, the size distribution, and the random arrangement of the particles in the matrix on the homogenized thermal conductivity. Commonly, TIM systems contain random spatial distributions of particles of a polydisperse (usually bimodal) nature. A detailed analysis of the microstructural characteristics that influence the effective thermal conductivity of TIMs is the goal of this paper. Random microstructural arrangements consisting of lognormal size-distributions of alumina particles in silicone matrix were generated using a drop-fall-shake algorithm. The generated microstructures were …

Determination Of Superior Surface Strains And Stresses, And Vocal Fold Contact Pressure In A Synthetic Larynx Model Using Digital Image Correlation, Mychal Spencer, Thomas Siegmund, Luc Mongeau

School of Mechanical Engineering Faculty Publications

No abstract provided.

An Efficient Network Model For Determining The Effective Thermal Conductivity Of Particulate Thermal Interface Materials, S Kanuparthi, G Subbarayan, Thomas Siegmund, B Sammakia

School of Mechanical Engineering Faculty Publications

Particulate composites are commonly used in Microelectronics applications. One example of such materials is Thermal Interface Materials (TIMs) that are used to reduce the contact resistance between the chip and the heat sink. The existing analytical descriptions of thermal transport in particulate systems do not accurately account for the effect of inter-particle interactions, especially in the intermediate volume fractions of 30-80%. Another crucial drawback in the existing analytical as well as the network models is the inability to model size distributions (typically bimodal) of the filler material particles that are obtained as a result of the material manufacturing process. While …

A Two-Layer Composite Model Of The Vocal Fol Lamina Propria For Fundamental Frequency Regulation, Kai Zhang, Thomas Siegmund, Roger W. Chan

School of Mechanical Engineering Faculty Publications

No abstract provided.

A Constitutive Model Of The Human Vocal Fold Cover For Fundamental Frequency Regulation, Kai Zhang, Thomas Siegmund, Roger W. Chan

School of Mechanical Engineering Faculty Publications

No abstract provided.

Optimization Of Thermal Interface Materials For Electronics Cooling Applications, Vishal Singhal, Thomas Siegmund, Suresh V. Garimella

School of Mechanical Engineering Faculty Publications

Thermal interface materials (TIMs) are used in electronics cooling applications to decrease the thermal contact resistance between surfaces in contact. A methodology to determine the optimal volume fraction of filler particles in TIMs for minimizing the thermal contact resistance is presented. The method uses finite element analysis to solve the coupled thermo-mechanical problem. It is shown that there exists an optimal filler volume fraction which depends not only on the distribution of the filler particles in a TIM but also on the thickness of the TIM layer, the contact pressure and the shape and the size of the filler particles. …