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Mechanical Engineering

2019

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Interface Facilitated Reorientation Of Mg Nanolayers In Mg-Nb Nanolaminates, Y. Chen, Mingyu Gong, N. A. Mara, Jian Wang Jan 2019

Interface Facilitated Reorientation Of Mg Nanolayers In Mg-Nb Nanolaminates, Y. Chen, Mingyu Gong, N. A. Mara, Jian Wang

Mechanical & Materials Engineering Faculty Publications

Mg/Nb nanolaminates synthesized through vapor deposition techniques exhibit high flow strength without conventional twinning in Mg. In this work, we investigated the influence of laminated microstructures on deformation mechanisms of Mg nanolayers. Using molecular dynamics simulations, we explored that (0001)-oriented Mg layers transform or re-orient to {10¯10}-oriented Mg layers through nucleation and growth of {10¯12} twins by atomic shuffling, instead of conventional {10¯12} twinning shear. Such a reorientation accommodates in-plane compressive strain and out-of-plane tensile strain when Mg/Nb laminates are subjected to compression parallel to the Mg/Nb interfaces. The nucleation of {10 ...


The Role Of Low-Level Image Features In The Affective Categorization Of Rapidly Presented Scenes, L. Jack Rhodes, Matthew Rios, Jacob M. Williams, Gonzalo Quinones, Prahalada K. Rao, Vladimir Miskovic Jan 2019

The Role Of Low-Level Image Features In The Affective Categorization Of Rapidly Presented Scenes, L. Jack Rhodes, Matthew Rios, Jacob M. Williams, Gonzalo Quinones, Prahalada K. Rao, Vladimir Miskovic

Mechanical & Materials Engineering Faculty Publications

It remains unclear how the visual system is able to extract affective content from complex scenes even with extremely brief (< 100 millisecond) exposures. One possibility, suggested by findings in machine vision, is that low-level features such as unlocalized, two-dimensional (2-D) Fourier spectra can be diagnostic of scene content. To determine whether Fourier image amplitude carries any information about the affective quality of scenes, we first validated the existence of image category differences through a support vector machine (SVM) model that was able to discriminate our intact aversive and neutral images with ~ 70% accuracy using amplitude-only features as inputs. This model allowed us to confirm that scenes belonging to different affective categories could be mathematically distinguished on the basis of amplitude spectra alone. The next question is whether these same features are also exploited by the human visual system. Subsequently, we tested observers’ rapid classification of affective and neutral naturalistic scenes, presented briefly (~33.3 ms) and backward masked with synthetic textures. We tested categorization accuracy across three distinct experimental conditions, using: (i) original images, (ii) images having their amplitude spectra swapped within a single affective image category (e.g., an aversive image whose amplitude spectrum has been swapped with another aversive image) or (iii) images having their amplitude spectra swapped between affective categories (e.g., an aversive image containing the amplitude spectrum of a neutral image). Despite its discriminative potential, the human visual system does not seem to use Fourier amplitude differences as the chief strategy for affectively categorizing scenes at a glance. The contribution of image amplitude to affective categorization is largely dependent on interactions with the phase spectrum, although it is impossible to completely rule out a residual role for unlocalized 2-D amplitude measures.


Monolithic Heat-Transfer Device, Sidy Ndao, George Gogos, Dennis Alexander, Troy Anderson, Craig Zuhlke Jan 2019

Monolithic Heat-Transfer Device, Sidy Ndao, George Gogos, Dennis Alexander, Troy Anderson, Craig Zuhlke

Mechanical & Materials Engineering Faculty Publications

A monolithic heat-transfer device can include a container wall configured to retain a working fluid, where the container wall is formed of a single material. The container wall also includes an interior surface configured to be in fluid communication with the working fluid. The monolithic heat-transfer device also includes a channel disposed in the interior surface of the container wall, where the channel comprises a microstructure and a nanostructure. The microstructure and the nanostructure are materially contiguous with the single material forming the container wall. In some embodiments, the nanostructure comprises one or more layers of nanoparticles. The monolithic heat-transfer ...


Predictive Peridynamic 3d Models Of Pitting Corrosion In Stainless Steel With Formation Of Lacy Covers, Siavash Jafarzadeh, Florin Bobaru, Ziguang Chen Jan 2019

Predictive Peridynamic 3d Models Of Pitting Corrosion In Stainless Steel With Formation Of Lacy Covers, Siavash Jafarzadeh, Florin Bobaru, Ziguang Chen

Mechanical & Materials Engineering Faculty Publications

In this work, the peridynamic corrosion model is used for 3D simulation of pitting corrosion in stainless steel. Models for passivation and salt layer formation are employed to predict detailed characteristics of pit growth kinetic in stainless steels, such as lacy cover formation on top of the pit, and the diffusion-controlled regime at the pit bottom. The model is validated against an experimentally grown pit on 316L stainless steel in NaCl solution. Lacy covers in this model are formed autonomously during the simulation process. They are remarkably similar to the covers observed on top of the real pits.


Higher-Order Overtone Thickness-Shear Vibrations Of Multilayered Thin-Film Acoustic Wave Resonators And Angular Rate Sensing, Hui Chen, Ji Wang, Jianke Du, Jiashi Yang Jan 2019

Higher-Order Overtone Thickness-Shear Vibrations Of Multilayered Thin-Film Acoustic Wave Resonators And Angular Rate Sensing, Hui Chen, Ji Wang, Jianke Du, Jiashi Yang

Mechanical & Materials Engineering Faculty Publications

We propose a new structure for piezoelectric gyroscopes. It is made from multilayered thin films of AlN or ZnO with alternating c-axes along the film thickness. It is shown theoretically that when such a film is electrically driven into higher-order overtone thickness-shear vibration in one of the two in-plane directions of the film and is rotating about the film normal, the Coriolis force due to the rotation causes a higher-order overtone thicknessshear vibration in a perpendicular direction with an electrical output that can be used to measure the angular rate of the rotation. Different from existing thickness-shear mode piezoelectric gyroscopes ...


3d Printing Of Hybrid Mos2-Graphene Aerogels As Highly Porous Electrode Materials For Sodium Ion Battery Anodes, Emery Brown, Pengli Yan, Halil Tekik, Ayyappan Elangovan, Jian Wang, Dong Lin, Jun Li Jan 2019

3d Printing Of Hybrid Mos2-Graphene Aerogels As Highly Porous Electrode Materials For Sodium Ion Battery Anodes, Emery Brown, Pengli Yan, Halil Tekik, Ayyappan Elangovan, Jian Wang, Dong Lin, Jun Li

Mechanical & Materials Engineering Faculty Publications

This study reports a 3D freeze-printing method that integrates inkjet printing and freeze casting to control both the microstructure and macroporosity via formation of ice microcrystals during printing. A viscous aqueous ink consisting of a molecular MoS2 precursor (ammonium thiomolybdate) mixed with graphene oxide (GO) nanosheets is used in the printing process. Post-treatments by freeze-drying and reductive thermal annealing convert the printed intermediate mixture into a hybrid structure consisting of MoS2 nanoparticles anchored on the surface of 2D rGO nanosheets in a macroporous framework, which is fully characterized with FESEM, TEM, XRD, Raman spectroscopy and TGA. The resulting ...


Glocal Integrity In 420 Stainless Steel By Asynchronous Laser Processing, Michael P. Sealy, Haitham Hadidi, Cody Kanger, X. L. Yan, Bai Cui, J. A. Mcgeough Jan 2019

Glocal Integrity In 420 Stainless Steel By Asynchronous Laser Processing, Michael P. Sealy, Haitham Hadidi, Cody Kanger, X. L. Yan, Bai Cui, J. A. Mcgeough

Mechanical & Materials Engineering Faculty Publications

Cold working individual layers during additive manufacturing (AM) by mechanical surface treatments, such as peening, effectively “prints” an aggregate surface integrity that is referred to as a glocal (i.e., local with global implications) integrity. Printing a complex, pre-designed glocal integrity throughout the build volume is a feasible approach to improve functional performance while mitigating distortion. However, coupling peening with AM introduces new manufacturing challenges, namely thermal cancellation, whereby heat relaxes favorable residual stresses and work hardening when printing on a peened layer. Thus, this work investigates glocal integrity formation from cyclically coupling LENS® with laser peening on 420 stainless ...


High Strength, Deformable Nanotwinned Al–Co Alloys, S. Xue, Qiang Li, D. Y. Xie, Y. F. Zhang, Han Wang, Haiyan Wong, J. Wang, Xinghang Zhang Jan 2019

High Strength, Deformable Nanotwinned Al–Co Alloys, S. Xue, Qiang Li, D. Y. Xie, Y. F. Zhang, Han Wang, Haiyan Wong, J. Wang, Xinghang Zhang

Mechanical & Materials Engineering Faculty Publications

Aluminum (Al) alloys have been widely used in the transportation industry. However, most highstrength Al alloys to date have limited mechanical strength, on the order of a few hundred MPa, which is much lower than the flow stress of high-strength steels. In this study, we show the fabrication of nanocrystalline Al alloys with high-density growth twins enabled by a few atomic percent of Co solute. In situ uniaxial compression tests show that the flow stress of Al–Co solid solution alloys exceeds 1.5 GPa, while good work hardening capability is maintained. This study provides a new perspective on the ...


Resistance To Helium Bubble Formation In Amorphous Sioc/Crystalline Fe Nanocomposite, Qing Su, Tianyao Wang, Jonathan Gigax, Lin Shao, Michael Nastasi Jan 2019

Resistance To Helium Bubble Formation In Amorphous Sioc/Crystalline Fe Nanocomposite, Qing Su, Tianyao Wang, Jonathan Gigax, Lin Shao, Michael Nastasi

Mechanical & Materials Engineering Faculty Publications

The management of radiation defects and insoluble He atoms represent key challenges for structural materials in existing fission reactors and advanced reactor systems. To examine how crystalline/amorphous interface, together with the amorphous constituents affects radiation tolerance and He management, we studied helium bubble formation in helium ion implanted amorphous silicon oxycarbide (SiOC) and crystalline Fe composites by transmission electron microscopy (TEM). The SiOC/Fe composites were grown via magnetron sputtering with controlled length scale on a surface oxidized Si (100) substrate. These composites were subjected to 50 keV He+ implantation with ion doses chosen to produce a 5 at ...


A Sensorless Force-Feedback System For Robot-Assisted Laparoscopic Surgery, Baoliang Zhao, Carl A. Nelson Jan 2019

A Sensorless Force-Feedback System For Robot-Assisted Laparoscopic Surgery, Baoliang Zhao, Carl A. Nelson

Mechanical & Materials Engineering Faculty Publications

The existing surgical robots for laparoscopic surgery offer no or limited force feedback, and there are many problems for the traditional sensor-based solutions. This paper builds a teleoperation surgical system and validates the effectiveness of sensorless force feedback. The tool-tissue interaction force at the surgical grasper tip is estimated using the driving motor’s current, and fed back to the master robot with a position-force bilateral control algorithm. The stiffness differentiation experiment and tumor detection experiment were conducted. In the stiffness differentiation experiment, 43 out of 45 pairs of ranking relationships were identified correctly, yielding a success rate of 96 ...


Mechanical Characterizations Of 3d-Printed Plla/Steel Particle Composites, Hozhabr Mozafari, Pengfei Dong, Haitham Hadidi, Michael P. Sealy, Linxia Gu Jan 2019

Mechanical Characterizations Of 3d-Printed Plla/Steel Particle Composites, Hozhabr Mozafari, Pengfei Dong, Haitham Hadidi, Michael P. Sealy, Linxia Gu

Mechanical & Materials Engineering Faculty Publications

The objective of this study is to characterize the micromechanical properties of poly-L-lactic acid (PLLA) composites reinforced by grade 420 stainless steel (SS) particles with a specific focus on the interphase properties. The specimens were manufactured using 3D printing techniques due to its many benefits, including high accuracy, cost effectiveness and customized geometry. The adopted fused filament fabrication resulted in a thin interphase layer with an average thickness of 3 μm. The mechanical properties of each phase, as well as the interphase, were characterized by nanoindentation tests. The effect of matrix degradation, i.e., imperfect bonding, on the elastic modulus ...


Relative Contributions Of Intracranial Pressure And Intraocular Pressure On Lamina Cribrosa Behavior, Junfei Tong, Deepta Ghate, Sachin Kedar, Linxia Gu Jan 2019

Relative Contributions Of Intracranial Pressure And Intraocular Pressure On Lamina Cribrosa Behavior, Junfei Tong, Deepta Ghate, Sachin Kedar, Linxia Gu

Mechanical & Materials Engineering Faculty Publications

Purpose. To characterize the relative contributions of intraocular pressure (IOP) and intracranial pressure (ICP) on lamina cribrosa (LC) behavior, specifically LC depth (LCD) and LC peak strain. Methods. An axially symmetric finite element model of the posterior eye was constructed with an elongated optic nerve and retro-orbital subarachnoid space ensheathed by pia and dura mater. -e mechanical environment in LC was evaluated with ICP ranging from 5 to 15mmHg and IOP from 10 to 45 mmHg. LCD and LC peak strains at various ICP and IOP levels were estimated using full factorial experiments. Multiple linear regression analyses were then applied ...


Unveiling The Operation Mechanism Of Layered Perovskite Solar Cells, Yun Lin, Yanjun Fang, Jingjing Zhao, Yuchuan Shao, Samuel J. Stuard, Masrur Morshed Nahid, Harald Ade, Qi Wang, Jeffrey E. Shield, Ninghao Zhou, Andrew M. Moran, Jinsong Huang Jan 2019

Unveiling The Operation Mechanism Of Layered Perovskite Solar Cells, Yun Lin, Yanjun Fang, Jingjing Zhao, Yuchuan Shao, Samuel J. Stuard, Masrur Morshed Nahid, Harald Ade, Qi Wang, Jeffrey E. Shield, Ninghao Zhou, Andrew M. Moran, Jinsong Huang

Mechanical & Materials Engineering Faculty Publications

Layered perovskites have been shown to improve the stability of perovskite solar cells while its operation mechanism remains unclear. Here we investigate the process for the conversion of light to electrical current in high performance layered perovskite solar cells by examining its real morphology. The layered perovskite films in this study are found to be a mixture of layered and three dimensional (3D)-like phases with phase separations at micrometer and nanometer scale in both vertical and lateral directions. This phase separation is explained by the surface initiated crystallization process and the competition of the crystallization between 3D-like and layered ...


Predictive Peridynamic 3d Models Of Pitting Corrosion In Stainless Steel With Formation Of Lacy Covers, Siavash Jafarzadeh, Florin Bobaru, Ziguang Chen Jan 2019

Predictive Peridynamic 3d Models Of Pitting Corrosion In Stainless Steel With Formation Of Lacy Covers, Siavash Jafarzadeh, Florin Bobaru, Ziguang Chen

Mechanical & Materials Engineering Faculty Publications

In this work, the peridynamic corrosion model is used for 3D simulation of pitting corrosion in stainless steel. Models for passivation and salt layer formation are employed to predict detailed characteristics of pit growth kinetic in stainless steels, such as lacy cover formation on top of the pit, and the diffusion-controlled regime at the pit bottom. The model is validated against an experimentally grown pit on 316L stainless steel in NaCl solution. Lacy covers in this model are formed autonomously during the simulation process. They are remarkably similar to the covers observed on top of the real pits.


Three-Dimensional Character Of The Deformation Twin In Magnesium, Y. Liu, P.Z. Tang, M.Y. Gong, R.J. Mccabe, J. Wang, C.N. Tome Jan 2019

Three-Dimensional Character Of The Deformation Twin In Magnesium, Y. Liu, P.Z. Tang, M.Y. Gong, R.J. Mccabe, J. Wang, C.N. Tome

Mechanical & Materials Engineering Faculty Publications

Deformation twins are three-dimensional domains, traditionally viewed as ellipsoids because of their two-dimensional lenticular sections. In this work, we performed statistical analysis of twin shapes viewing along three orthogonal directions: the ‘dark side’ (DS) view along the twin shear direction (η1), the twinning plane normal (TPN) view (k1) and the ‘bright side’ (BS) view along the direction λ(=k1 × η1). Our electron back-scatter diffraction results show that twins in the DS and BS views normally exhibit a lenticular shape, whereas they show an irregular shape in the TPN view. Moreover, the findings in the TPN view revealed that twins grow ...


A Total Life Cycle Approach For Developing Predictive Design Methodologies To Optimize Product Performance, Buddhika M. Hapuwatte, Ibrahim S. Jawahir Jan 2019

A Total Life Cycle Approach For Developing Predictive Design Methodologies To Optimize Product Performance, Buddhika M. Hapuwatte, Ibrahim S. Jawahir

Institute for Sustainable Manufacturing Faculty Publications

Sustainable products must be designed by considering how design decisions impact their total life cycle (TLC) sustainability content. Even more so important when designing products to incorporate the technological elements of sustainable manufacturing, the 6Rs (Reduce, Reuse, Recycle, Recover, Redesign and Remanufacture), to achieve Circular Economy (CE). This paper presents the preliminary work of an ongoing research project on developing a novel framework incorporating predictive models with TLC considerations. This unique approach develops and integrates models with associated risks, and optimizes for maximizing the sustainability benefits due to design decisions. Such predictive capability is extremely useful for process planning, where ...


Designing And Redesigning Products, Processes, And Systems For A Helical Economy, Ryan Bradley, Ibrahim S. Jawahir Jan 2019

Designing And Redesigning Products, Processes, And Systems For A Helical Economy, Ryan Bradley, Ibrahim S. Jawahir

Institute for Sustainable Manufacturing Faculty Publications

The Circular Economy (CE) concept has promised to unlock trillions of dollars in business value while driving a significant reduction in the world’s resource consumption and anthropogenic emissions. However, CE mainly lives in ambiguity in the manufacturing domain because CE does not address the changes needed across all of the fundamental elements of manufacturing: products, processes, and systems. Conceptually, CE is grounded in the concept of closed-loop material flows that fit within ecological limits. This grounding translates into a steady state economy, a result that is not an option for the significant portion of the world living in poverty ...


The Effect Of Flinak Molten Salt Corrosion On The Hardness Of Hastelloy N, David Kok Jan 2019

The Effect Of Flinak Molten Salt Corrosion On The Hardness Of Hastelloy N, David Kok

Honors Program Projects

The desire to reduce pollution caused by electricity production has led to a call for the replacement of conventional fossil fuel power plants. In order to fulfill this goal, a large amount of new nuclear reactors is required, and this provides the opportunity to put new and innovative reactor designs into production. The Molten Salt Reactor (MSR) is one of the most promising concepts, but a suitable combination of molten salt and container material needs to be found to reduce the potential for corrosion before the concept can be put into production. FLiNaK molten salt and the nickel-based alloy Hastelloy ...


Rotary Friction Welding Versus Fusion Butt Welding Of Plastic Pipes – Feasibility And Energy Perspective, Ramsey F. Hamade, Tarek R. Andari, Ali H. Ammouri, Ibrahim S. Jawahir Jan 2019

Rotary Friction Welding Versus Fusion Butt Welding Of Plastic Pipes – Feasibility And Energy Perspective, Ramsey F. Hamade, Tarek R. Andari, Ali H. Ammouri, Ibrahim S. Jawahir

Institute for Sustainable Manufacturing Faculty Publications

According to the Plastics Pipe Institute, butt fusion is the most widely used method for joining lengths of PE pipe and pipe to PE fittings “by heat fusion” (https://plasticpipe.org/pdf/chapter09.pdf). However, butt-welding is not energy-cognizant from the point of view of a phase-change fabrication method. This is because the source of heating is external (heater plate). The initial heating and subsequent maintenance at relatively high temperature (above 200 C for welding of high-density polyethylene pipe) is energy intensive. Rotary friction welding, on the other hand focuses the energy where and when as needed because it uses ...


Shape-Design For Stabilizing Micro-Particles In Inertial Microfluidic Flows, Aditya Kommajosula, Daniel Stoecklein, Dino Di Carlo, Baskar Ganapathysubramanian Jan 2019

Shape-Design For Stabilizing Micro-Particles In Inertial Microfluidic Flows, Aditya Kommajosula, Daniel Stoecklein, Dino Di Carlo, Baskar Ganapathysubramanian

Mechanical Engineering Publications

Design of microparticles which stabilize at the centerline of a channel flow when part of a dilute suspension is examined numerically for moderate Reynolds numbers (10≤Re≤80). Stability metrics for particles with arbitrary shapes are formulated based on linear-stability theory. Particle shape is parametrized by a compact, Non-Uniform Rational B-Spline (NURBS)-based representation. Shape-design is posed as an optimization problem and solved using adaptive Bayesian optimization. We focus on designing particles for maximal stability at the channel-centerline robust to perturbations. Our results indicate that centerline-focusing particles are families of characteristic "fish"/"bottle"/"dumbbell"-like shapes, exhibiting fore-aft asymmetry. A ...


In Silico Design Of Crop Ideotypes Under A Wide Range Of Water Availability, Talukder Z. Jubery, Baskar Ganapathysubramanian, Matthew E. Gilbert, Daniel Attinger Jan 2019

In Silico Design Of Crop Ideotypes Under A Wide Range Of Water Availability, Talukder Z. Jubery, Baskar Ganapathysubramanian, Matthew E. Gilbert, Daniel Attinger

Mechanical Engineering Publications

Given the changing climate and increasing impact of agriculture on global resources, it is important to identify phenotypes which are global and sustainable optima. Here, an in silico framework is constructed by coupling evolutionary optimization with thermodynamically sound crop physiology, and its ability to rationally design phenotypes with maximum productivity is demonstrated, within well‐defined limits on water availability. Results reveal that in mesic environments, such as the North American Midwest, and semi‐arid environments, such as Colorado, phenotypes optimized for maximum productivity and survival under drought are similar to those with maximum productivity under irrigated conditions. In hot and ...


Propagating, Evanescent, And Complex Wavenumber Guided Waves In High-Performance Composites, Victor Giurgiutiu, Mohammad Faisal Haider Jan 2019

Propagating, Evanescent, And Complex Wavenumber Guided Waves In High-Performance Composites, Victor Giurgiutiu, Mohammad Faisal Haider

Faculty Publications

The study of propagating, evanescent and complex wavenumbers of guided waves (GWs) in high-performance composites using a stable and robust semi-analytical finite element (SAFE) method is presented. To facilitate understanding of the wavenumber trajectories, an incremental material change study is performed moving gradually from isotropic aluminum alloy to carbon fiber reinforced polymer (CFRP) composites. The SAFE results for an isotropic aluminum alloy plate are compared with the exact analytical solutions, which shows that N = 20 SAFE elements across the thickness provides <0.5% error in the highest evanescent wavenumber for the given frequency-wavenumber range. The material change study reveals that reducing the transverse and shear moduli moves the wavenumber solution towards one similar to composite material. The comparison of the propagating, evanescent and complex wavenumber trajectories between composites and aluminum alloy show that antisymmetric imaginary Lamb wave modes always exist in composites although they may not exist in isotropic aluminum alloy at some frequencies. The wavenumber trajectories for a unidirectional CFRP plate show that the range of real wavenumber is much smaller than in the isotropic aluminum alloy. For laminated CFRP composite plates (e.g., unidirectional, off-axis, transverse, cross-ply and quasi-isotropic laminates), the quasi Lamb wave and shear horizontal (SH) wave trajectories are also identified and discussed. The imaginary SH wave trajectories in laminated composites are distorted due to the presence of ±45 plies. The convergence study of the SAFE method in various CFRP laminates indicates that sufficient accuracy can always be achieved by increasing the number of SAFE elements. Future work will address the stress-continuity between composite layers.


Optimization Of Turbine Design In Wind Farms With Multiple Hub Heights, Using Exact Analytic Gradients And Structural Constraints, Andrew P.J. Stanley, Andrew Ning, Katherine Dykes Jan 2019

Optimization Of Turbine Design In Wind Farms With Multiple Hub Heights, Using Exact Analytic Gradients And Structural Constraints, Andrew P.J. Stanley, Andrew Ning, Katherine Dykes

Faculty Publications

Wind farms are generally designed with turbines of all the same hub height. If wind farms were designed with turbines of different hub heights, wake interference between turbines could be reduced, lowering the cost of energy (COE). This paper demonstrates a method to optimize onshore wind farms with two different hub heights using exact, analytic gradients. Gradient-based optimization with exact gradients scales well with large problems and is preferable in this application over gradient-free methods. Our model consisted of the following: a version of the FLOw Redirection and Induction in Steady-State wake model that accommodated three- dimensional wakes and calculated ...


A Tunable Electrostatic Mems Pressure Switch, Mark Pallay, Ronald N. Miles, Shahrzad Towfighian Jan 2019

A Tunable Electrostatic Mems Pressure Switch, Mark Pallay, Ronald N. Miles, Shahrzad Towfighian

Mechanical Engineering Faculty Scholarship

We demonstrate a tunable air pressure switch. The switch detects when the ambient pressure drops below a threshold value and automatically triggers without the need for any computational overhead to read the pressure or trigger the switch. The switch exploits the significant fluid interaction of a MEMS beam undergoing a large oscillation from electrostatic levitation to detect changes in ambient pressure. If the oscillation amplitude near the resonant frequency is above a threshold level, dynamic pullin is triggered and the switch is closed. The pressure at which the switch closes can be tuned by adjusting the voltage applied to the ...


Near-Field Electrospinning Of A Polymer/Bioactive Glass Composite To Fabricate 3d Biomimetic Structures, Krishna C. R. Kolan, Jie Li, Sonya Roberts, Julie A. Semon, Jonghyun Park, D. E. Day, Ming-Chuan Leu Jan 2019

Near-Field Electrospinning Of A Polymer/Bioactive Glass Composite To Fabricate 3d Biomimetic Structures, Krishna C. R. Kolan, Jie Li, Sonya Roberts, Julie A. Semon, Jonghyun Park, D. E. Day, Ming-Chuan Leu

Biological Sciences Faculty Research & Creative Works

Bioactive glasses have recently gained attention in tissue engineering and three-dimensional (3D) bioprinting because of their ability to enhance angiogenesis. Some challenges for developing biological tissues with bioactive glasses include incorporation of glass particles and achieving a 3D architecture mimicking natural tissues. In this study, we investigate the fabrication of scaffolds with a polymer/bioactive glass composite using near-field electrospinning (NFES). An overall controlled 3D scaffold with pores, containing random fibers, is created and aimed to provide superior cell proliferation. Highly angiogenic borate bioactive glass (13-93B3) in 20 wt.% is added to polycaprolactone (PCL) to fabricate scaffolds using the NFES ...


A Saddle-Point Dynamical System Approach For Robust Deep Learning, Yasaman Esfandiari, Keivan Ebrahimi, Aditya Balu, Nicola Elia, Umesh Vaidya, Soumik Sarkar Jan 2019

A Saddle-Point Dynamical System Approach For Robust Deep Learning, Yasaman Esfandiari, Keivan Ebrahimi, Aditya Balu, Nicola Elia, Umesh Vaidya, Soumik Sarkar

Electrical and Computer Engineering Publications

We propose a novel discrete-time dynamical system-based framework for achieving adversarial robustness in machine learning models. Our algorithm is originated from robust optimization, which aims to find the saddle point of a min-max optimization problem in the presence of uncertainties. The robust learning problem is formulated as a robust optimization problem, and we introduce a discrete-time algorithm based on a saddle-point dynamical system (SDS) to solve this problem. Under the assumptions that the cost function is convex and uncertainties enter concavely in the robust learning problem, we analytically show that using a diminishing step-size, the stochastic version of our algorithm ...


Enhanced Quantum Dots Spontaneous Emission With Metamaterial Perfect Absorbers, Wei Wang, Xiaodong Yang, Ting S. Luk, Jie Gao Jan 2019

Enhanced Quantum Dots Spontaneous Emission With Metamaterial Perfect Absorbers, Wei Wang, Xiaodong Yang, Ting S. Luk, Jie Gao

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Metamaterial perfect absorbers (PAs) made of a hexagonal array of holes on Ag-SiO 2 -Ag thin films have been realized and utilized to enhance the spontaneous emission rate and photoluminescence intensity of CdSe/ZnS quantum dots (QDs) spin-coated on the absorber top surface. Perfect absorption of incoming light occurs at the wavelength where the impedance is matched to that of the free space. When QDs strongly excite both the electric and magnetic resonances at this perfect absorption wavelength, a significant Purcell effect on the spontaneous emission process and enhanced radiative outcoupling of photoluminescence intensity are expected. For perfect absorbers with ...


Fabrication Of Alcocrfeni High-Entropy Alloy Coating On An Aisi 304 Substrate Via A Cofe₂Ni Intermediate Layer, Wenyuan Cui, Sreekar Karnati, Xinchang Zhang, Elizabeth Burns, Frank W. Liou Jan 2019

Fabrication Of Alcocrfeni High-Entropy Alloy Coating On An Aisi 304 Substrate Via A Cofe₂Ni Intermediate Layer, Wenyuan Cui, Sreekar Karnati, Xinchang Zhang, Elizabeth Burns, Frank W. Liou

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Through laser metal deposition, attempts were made to coat AlCoCrFeNi, a high-entropy alloy (HEA), on an AISI 304 stainless steel substrate to integrate their properties. However, the direct coating of the AlCoCrFeNi HEA on the AISI 304 substrate was found to be unviable due to cracks at the interface between these two materials. The difference in compositional change was suspected to be the source of the cracks. Therefore, a new transition route was performed by coating an intermediate layer of CoFe2Ni on the AISI 304 substrate. Investigations into the microstructure, phase composition, elemental composition and Vickers hardness were ...


Enhanced Electrochemical Biosensor And Supercapacitor With 3d Porous Architectured Graphene Via Salt Impregnated Inkjet Maskless Lithography, John A. Hondred, Igor L. Medintz, Jonathan C. Claussen Jan 2019

Enhanced Electrochemical Biosensor And Supercapacitor With 3d Porous Architectured Graphene Via Salt Impregnated Inkjet Maskless Lithography, John A. Hondred, Igor L. Medintz, Jonathan C. Claussen

Mechanical Engineering Publications

Advances in solution-phase graphene patterning has provided a facile route for rapid, low-cost and scalable manufacturing of electrochemical devices, even on flexible substrates. While graphene possesses advantageous electrochemical properties of high surface area and fast heterogenous charge transport, these properties are attributed to the edge planes and defect sites, not the basal plane. Herein, we demonstrate enhancement of the electroactive nature of patterned solution-phase graphene by increasing the porosity and edge planes through the construction of a multidimensional architecture via salt impregnated inkjet maskless lithography (SIIML) and CO2 laser annealing. Various sized macroscale pores (<25 to ∼250 μm) are patterned directly in the graphene surface by incorporating porogens (i.e., salt crystals) in the ...


Determining The Region Of Origin Of Blood Spatter Patterns Considering Fluid Dynamics, Statistical Uncertainties, Daniel Attinger, Patrick M. Comiskey, Alexander L. Yarin, Kris De Brabanter Jan 2019

Determining The Region Of Origin Of Blood Spatter Patterns Considering Fluid Dynamics, Statistical Uncertainties, Daniel Attinger, Patrick M. Comiskey, Alexander L. Yarin, Kris De Brabanter

Mechanical Engineering Publications

Trajectory reconstruction in bloodstain pattern analysis is currently performed by assuming that blood drop trajectories are straight along directions provided by stain inspection. Recently, several attempts have been made at reconstructing ballistic trajectories backwards, considering the effects of gravity and drag forces. Here, we propose a method to reconstruct the region of origin of impact blood spatter patterns that considers fluid dynamics and statistical uncertainties. The fluid dynamics relies on defining for each stain a range of physically possible trajectories, based on known physics of how drops deform, both in flight and upon slanted impact. Statistical uncertainties are estimated and ...