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Full-Text Articles in Mechanical Engineering

Interpretable Deep Learning For Guided Microstructure-Property Explorations In Photovoltaics, Balaji Sesha Sarath Pokuri, Sambuddha Ghosal, Apurva Kokate, Soumik Sarkar, Baskar Ganapathysubramanian Oct 2019

Interpretable Deep Learning For Guided Microstructure-Property Explorations In Photovoltaics, Balaji Sesha Sarath Pokuri, Sambuddha Ghosal, Apurva Kokate, Soumik Sarkar, Baskar Ganapathysubramanian

Baskar Ganapathysubramanian

The microstructure determines the photovoltaic performance of a thin film organic semiconductor film. The relationship between microstructure and performance is usually highly non-linear and expensive to evaluate, thus making microstructure optimization challenging. Here, we show a data-driven approach for mapping the microstructure to photovoltaic performance using deep convolutional neural networks. We characterize this approach in terms of two critical metrics, its generalizability (has it learnt a reasonable map?), and its intepretability (can it produce meaningful microstructure characteristics that influence its prediction?). A surrogate model that exhibits these two features of generalizability and intepretability is particularly useful for subsequent design exploration ...


Encoding Invariances In Deep Generative Models, Viraj Shah, Ameya Joshi, Sambuddha Ghosal, Balaji Pokuri, Soumik Sarkar, Baskar Ganapathysubramanian, Chinmay Hegde Jun 2019

Encoding Invariances In Deep Generative Models, Viraj Shah, Ameya Joshi, Sambuddha Ghosal, Balaji Pokuri, Soumik Sarkar, Baskar Ganapathysubramanian, Chinmay Hegde

Baskar Ganapathysubramanian

Reliable training of generative adversarial networks (GANs) typically require massive datasets in order to model complicated distributions. However, in several applications, training samples obey invariances that are \textit{a priori} known; for example, in complex physics simulations, the training data obey universal laws encoded as well-defined mathematical equations. In this paper, we propose a new generative modeling approach, InvNet, that can efficiently model data spaces with known invariances. We devise an adversarial training algorithm to encode them into data distribution. We validate our framework in three experimental settings: generating images with fixed motifs; solving nonlinear partial differential equations (PDEs); and ...


Call For Abstracts - Resrb 2019, July 8-9, Wrocław, Poland, Wojciech M. Budzianowski Dec 2018

Call For Abstracts - Resrb 2019, July 8-9, Wrocław, Poland, Wojciech M. Budzianowski

Wojciech Budzianowski

No abstract provided.


Ionic And Electronic Conductivities Of Atomic Layer Deposition Thin Film Coated Lithium Ion Battery Cathode Particles, Rajankumar L. Patel, Jonghyun Park, Xinhua Liang Sep 2018

Ionic And Electronic Conductivities Of Atomic Layer Deposition Thin Film Coated Lithium Ion Battery Cathode Particles, Rajankumar L. Patel, Jonghyun Park, Xinhua Liang

Xinhua Liang

It is imperative to ascertain the ionic and electronic components of the total conductivity of an electrochemically active material. A blocking technique, called the “Hebb-Wagner method”, is normally used to explain the two components (ionic and electronic) of a mixed conductor, in combination with the complex ac impedance method and dc polarization measurements. CeO2 atomic layer deposition (ALD)-coated and uncoated, LiMn2O4 (LMO) and LiMn1.5Ni0.5O4 (LMNO) powders were pressed into pellets and then painted with silver to act as a blocking electrode. The electronic conductivities were derived from the ...


Prediction Of Solid Oxide Fuel Cell Performance Using Artificial Neural Network, M. A. Rafe Biswas, Kamwana N. Mwara Oct 2017

Prediction Of Solid Oxide Fuel Cell Performance Using Artificial Neural Network, M. A. Rafe Biswas, Kamwana N. Mwara

M. A. Rafe Biswas

NASA’s Johnson Space Center has recently begun efforts to eventually integrate air-independent Solid Oxide Fuel Cell (SOFC) systems, with landers that can be propelled by LOX-CH4, for long duration missions. Using landers that utilize such propellants, provides the opportunity to use SOFCs as a power option, especially since they are able to process methane into a reactant through fuel reformation. Various lead-up activities, such as hardware testing and computational modelling, have been initiated to assist with this developmental effort.
One modeling approach, currently being explored to predict SOFC behavior, involves the usage of artificial neural networks (ANN). Since SOFC ...


A Vision For Health Informatics: Introducing The Sked Framework, Elizabeth D. Trippe, Jacob B. Aguilar, Yi H. Yan, Mustafa V. Nural, Jessica A. Brady, Mehdi Assefi, Saeid Safaei, Mehdi Allahyari, Seyedamin Pouriyeh, Mary R. Galinski, Jessica C. Kissinger, Juan B. Gutierrez Jun 2017

A Vision For Health Informatics: Introducing The Sked Framework, Elizabeth D. Trippe, Jacob B. Aguilar, Yi H. Yan, Mustafa V. Nural, Jessica A. Brady, Mehdi Assefi, Saeid Safaei, Mehdi Allahyari, Seyedamin Pouriyeh, Mary R. Galinski, Jessica C. Kissinger, Juan B. Gutierrez

Mehdi Allahyari

The goals of the Triple Aim of health care and the goals of P4 medicine outline objectives that require a significant health informatics component. However, the goals do not provide specifications about how all of the new individual patient data will be combined in meaningful ways and with data from other sources, like epidemiological data, to promote the health of individuals and society. We seem to have more data than ever before but few resources and means to use it efficiently. We need a general, extensible solution that integrates and homogenizes data of disparate origin, incompatible formats, and multiple spatial ...


Nonlinear Development And Secondary Instability Of Traveling Crossflow Vortices, Fei Li, Meelan M. Choudhari, Lian Duan, Chau-Lyan Chang Mar 2017

Nonlinear Development And Secondary Instability Of Traveling Crossflow Vortices, Fei Li, Meelan M. Choudhari, Lian Duan, Chau-Lyan Chang

Lian Duan

Building upon the prior research targeting the laminar breakdown mechanisms associated with stationary crossflow instability over a swept-wing configuration, this paper investigates the secondary instability of traveling crossflow modes as an alternate scenario for transition. For the parameter range investigated herein, this alternate scenario is shown to be viable unless the initial amplitudes of the traveling crossflow instability are lower than those of the stationary modes by considerably more than one order of magnitude. The linear growth predictions based on the secondary instability theory are found to agree well with both parabolized stability equations and direct numerical simulation, and the ...


High-Frequency Instabilities Of Stationary Crossflow Vortices In A Hypersonic Boundary Layer, Fei Li, Meelan Choudhari, Pedro Paredes-Gonzalez, Lian Duan Mar 2017

High-Frequency Instabilities Of Stationary Crossflow Vortices In A Hypersonic Boundary Layer, Fei Li, Meelan Choudhari, Pedro Paredes-Gonzalez, Lian Duan

Lian Duan

Hypersonic boundary layer flows over a circular cone at moderate incidence angle can support strong crossflow instability in between the windward and leeward rays on the plane of symmetry. Due to more efficient excitation of stationary crossflow vortices by surface roughness, such boundary layer flows may transition to turbulence via rapid amplification of the high-frequency secondary instabilities of finite-amplitude stationary crossflow vortices. The amplification characteristics of these secondary instabilities are investigated for crossflow vortices generated by an azimuthally periodic array of roughness elements over a 7° half-angle circular cone in a Mach 6 free stream. The analysis is based on ...


Ionic And Electronic Conductivities Of Atomic Layer Deposition Thin Film Coated Lithium Ion Battery Cathode Particles, Rajankumar L. Patel, Jonghyun Park, Xinhua Liang Mar 2017

Ionic And Electronic Conductivities Of Atomic Layer Deposition Thin Film Coated Lithium Ion Battery Cathode Particles, Rajankumar L. Patel, Jonghyun Park, Xinhua Liang

Jonghyun Park

It is imperative to ascertain the ionic and electronic components of the total conductivity of an electrochemically active material. A blocking technique, called the “Hebb-Wagner method”, is normally used to explain the two components (ionic and electronic) of a mixed conductor, in combination with the complex ac impedance method and dc polarization measurements. CeO2 atomic layer deposition (ALD)-coated and uncoated, LiMn2O4 (LMO) and LiMn1.5Ni0.5O4 (LMNO) powders were pressed into pellets and then painted with silver to act as a blocking electrode. The electronic conductivities were derived from the ...


Geometric Consideration Of Nanostructures For Energy Storage Systems, Jonghyun Park, Jie Li, Wei Lu, Ann Marie Sastry Mar 2017

Geometric Consideration Of Nanostructures For Energy Storage Systems, Jonghyun Park, Jie Li, Wei Lu, Ann Marie Sastry

Jonghyun Park

Battery performance and its fade are determined by various aspects such as the transport of ions and electrons through heterogeneous internal structures; kinetic reactions at the interfaces; and the corresponding interplay between mechanical, chemical, and thermal responses. The fundamental factor determining this complex multiscale and multiphysical nature of a battery is the geometry of active materials. In this work, we systematically consider the tradeoffs among a selection of limiting geometries of media designed to store ions or other species via a diffusion process. Specifically, we begin the investigation by considering diffusion in spheres, rods, and plates at the particle level ...


Silicon-Wall Interfacial Free Energy Via Thermodynamics Integration, Wan Shou, Heng Pan Mar 2017

Silicon-Wall Interfacial Free Energy Via Thermodynamics Integration, Wan Shou, Heng Pan

Heng Pan

We compute the interfacial free energy of a silicon system in contact with flat and structured walls by molecular dynamics simulation. The thermodynamics integration method, previously applied to Lennard-Jones potentials [R. Benjamin and J. Horbach, J. Chem. Phys. 137, 044707 (2012)], has been extended and implemented in Tersoff potentials with two-body and three-body interactions taken into consideration. The thermodynamic integration scheme includes two steps. In the first step, the bulk Tersoff system is reversibly transformed to a state where it interacts with a structureless flat wall, and in a second step, the flat structureless wall is reversibly transformed into an ...


Crystallization In Nano-Confinement Seeded By A Nanocrystal -- A Molecular Dynamics Study, Heng Pan, Costas Grigoropoulos Mar 2017

Crystallization In Nano-Confinement Seeded By A Nanocrystal -- A Molecular Dynamics Study, Heng Pan, Costas Grigoropoulos

Heng Pan

Seeded crystallization and solidification in nanoscale confinement volumes have become an important and complex topic. Due to the complexity and limitations in observing nanoscale crystallization, computer simulation can provide valuable details for supporting and interpreting experimental observations. In this article, seeded crystallization from nano-confined liquid, as represented by the crystallization of a suspended gold nano-droplet seeded by a pre-existing gold nanocrystal seed, was investigated using molecular dynamics simulations in canonical (NVT) ensemble. We found that the crystallization temperature depends on nano-confinement volume, crystal orientation, and seed size as explained by classical two-sphere model and Gibbs-Thomson effect.


Parallel Implementation Of A Recursive Least Squares Neural Network Training Method On The Intel Ipsc/2, James Edward Steck, Bruce M. Mcmillin, K. Krishnamurthy, M. Reza Ashouri, Gary G. Leininger Sep 2016

Parallel Implementation Of A Recursive Least Squares Neural Network Training Method On The Intel Ipsc/2, James Edward Steck, Bruce M. Mcmillin, K. Krishnamurthy, M. Reza Ashouri, Gary G. Leininger

K. Krishnamurthy

An algorithm based on the Marquardt-Levenberg least-square optimization method has been shown by S. Kollias and D. Anastassiou (IEEE Trans. on Circuits Syst. vol.36, no.8, p.1092-101, Aug. 1989) to be a much more efficient training method than gradient descent, when applied to some small feedforward neural networks. Yet, for many applications, the increase in computational complexity of the method outweighs any gain in learning rate obtained over current training methods. However, the least-squares method can be more efficiently implemented on parallel architectures than standard methods. This is demonstrated by comparing computation times and learning rates for the ...


Neural Modeling And Control Of A Distillation Column, James Edward Steck, K. Krishnamurthy, Bruce M. Mcmillin, Gary G. Leininger Sep 2016

Neural Modeling And Control Of A Distillation Column, James Edward Steck, K. Krishnamurthy, Bruce M. Mcmillin, Gary G. Leininger

K. Krishnamurthy

Control of a nine-stage three-component distillation column is considered. The control objective is achieved using a neural estimator and a neural controller. The neural estimator is trained to represent the chemical process accurately, and the neural controller is trained to give an input to the chemical process which will yield the desired output. Training of both the neural networks is accomplished using a recursive least squares training algorithm implemented on an Intel iPSC/2 multicomputer (hypercube). Simulated results are presented for a numerical example.


Identification Of Cutting Force In End Milling Operations Using Recurrent Neural Networks, Q. Xu, K. Krishnamurthy, Bruce M. Mcmillin, Wen Feng Lu Sep 2016

Identification Of Cutting Force In End Milling Operations Using Recurrent Neural Networks, Q. Xu, K. Krishnamurthy, Bruce M. Mcmillin, Wen Feng Lu

K. Krishnamurthy

The problem of identifying the cutting force in end milling operations is considered in this study. Recurrent neural networks are used here and are trained using a recursive least squares training algorithm. Training results for data obtained from a SAJO 3-axis vertical milling machine for steady slot cuts are presented. The results show that a recurrent neural network can learn the functional relationship between the feed rate and steady-state average resultant cutting force very well. Furthermore, results for the Mackey-Glass time series prediction problem are presented to illustrate the faster learning capability of the neural network scheme presented here


A Recursive Least Squares Training Algorithm For Multilayer Recurrent Neural Networks, Q. Xu, K. Krishnamurthy, Bruce M. Mcmillin, Wen Feng Lu Sep 2016

A Recursive Least Squares Training Algorithm For Multilayer Recurrent Neural Networks, Q. Xu, K. Krishnamurthy, Bruce M. Mcmillin, Wen Feng Lu

K. Krishnamurthy

Recurrent neural networks have the potential to perform significantly better than the commonly used feedforward neural networks due to their dynamical nature. However, they have received less attention because training algorithms/architectures have not been well developed. In this study, a recursive least squares algorithm to train recurrent neural networks with an arbitrary number of hidden layers is developed. The training algorithm is developed as an extension of the standard recursive estimation problem. Simulated results obtained for identification of the dynamics of a nonlinear dynamical system show promising results.


Evaluating Cognition In A Workspace Virtually, Chiu-Shui Chan Oct 2015

Evaluating Cognition In A Workspace Virtually, Chiu-Shui Chan

Chiu-Shui Chan

In any built environment, there exist certain subtle stimuli that affect the occupants’ cognitive processes and performance. This research intends to identify: (1) what environmental stimuli an office building would generate that could affect the habitants’ cognitive ability, and (2) how the habitants react to these stimuli. The goals of the study are to develop a new method for using immersive virtual reality to represent a built environment for simulating environmental impact, and to discover factors that could influence habitants’ cognitive performance in a space. It is expected that the discoveries could advance the application of virtual reality to study ...


A System For Rapid Creation And Assessment Of Conceptual Large Vehicle Designs Using Immersive Virtual Reality, Christian Noon, Ruqin Zhang, Eliot H. Winer, James H. Oliver, Brian Gilmore, Jerry Duncan Feb 2015

A System For Rapid Creation And Assessment Of Conceptual Large Vehicle Designs Using Immersive Virtual Reality, Christian Noon, Ruqin Zhang, Eliot H. Winer, James H. Oliver, Brian Gilmore, Jerry Duncan

James H. Oliver

Currently, new product concepts are often evaluated by developing detailed virtual part and assembly models with traditional computer aided design (CAD) tools followed by appropriate analyses (e.g., finite element analysis, computational fluid dynamics, etc.). The creation of these models and analyses are tremendously time consuming. If a number of different conceptual configurations have been determined, it may not be possible to model and analyze each of them due to the complexity of these evaluation processes. Thus, promising concepts might be eliminated based solely on insufficient time and resources for assessment. In addition, the virtual models and analyses performed are ...


Flexible Digital Fringe Projection System For Step‐Height Measurement, Song Zhang, James H. Oliver Feb 2015

Flexible Digital Fringe Projection System For Step‐Height Measurement, Song Zhang, James H. Oliver

James H. Oliver

To circumvent the problems induced by nonlinear gamma of the commercial video projector, we recently developed a flexible method for 3‐D shape measurement that generates sinusoidal fringe patterns for 3‐D shape measurement by defocusing binary structured patterns. However, it can only measure “smooth” objects. In this paper, we propose a technique to generalize this technique for arbitrary step height measurement. In particular, the binary coding method is combined with this technique for point‐by‐point phase unwrapping. Experiments have verified the success of the proposed approach.


Simulation Of Motion Parallax For Monitor-Based Augmented Reality Applications, Rafael Radkowski, James H. Oliver Feb 2015

Simulation Of Motion Parallax For Monitor-Based Augmented Reality Applications, Rafael Radkowski, James H. Oliver

James H. Oliver

The paper presents a method for the simulation of motion parallax for monitor-based Augmented Reality (AR) applications. Motion parallax effects the relative movement between far and close objects: near objects appear moving faster than far objects do. This facilitates the perception of depth, distances, and the structure of geometrically complex objects. Today, industrial AR applications are equipped with monitor-based output devices, e.g., for design reviews. Thus this important depth cue is omitted because all objects appear as one even layer on screen. As a result, the assessment of complex structures becomes more difficult. The method presented in this paper ...


Virtual Reality For Assembly Methods Prototyping: A Review, Abbishek Seth, Judy M. Vance, James H. Oliver Feb 2015

Virtual Reality For Assembly Methods Prototyping: A Review, Abbishek Seth, Judy M. Vance, James H. Oliver

James H. Oliver

Assembly planning and evaluation is an important component of the product design process in which details about how parts of a new product will be put together are formalized. A well designed assembly process should take into account various factors such as optimum assembly time and sequence, tooling and fixture requirements, ergonomics, operator safety, and accessibility, among others. Existing computer-based tools to support virtual assembly either concentrate solely on representation of the geometry of parts and fixtures and evaluation of clearances and tolerances or use simulated human mannequins to approximate human interaction in the assembly process. Virtual reality technology has ...


Virtual Training Simulator For Atomic Force Microscopy, Matthew J. Heying, James H. Oliver, Sriram Sundararajan, Pranav Shrotriya, Qingze Zou Feb 2015

Virtual Training Simulator For Atomic Force Microscopy, Matthew J. Heying, James H. Oliver, Sriram Sundararajan, Pranav Shrotriya, Qingze Zou

James H. Oliver

Training novice users how to operate an Atomic Force Microscope (AFM) is expensive due to the cost of equipment and the time required to train users in a hands-on learning environment. Training large groups of users simultaneously presents a problem because usually only one AFM is available for use. To alleviate this problem, a virtual training simulator for AFM training has been developed. The training simulator is a Windows-based software program designed to allow users to simulate basic AFM operation on a PC. Instructors can use this tool to demonstrate the exact same instruction that a user would receive in ...


Immersive Product Configurator For Conceptual Design, Ruqin Zhang, Christian Noon, Eliot H. Winer, James H. Oliver, Brian Gilmore, Jerry Duncan Feb 2015

Immersive Product Configurator For Conceptual Design, Ruqin Zhang, Christian Noon, Eliot H. Winer, James H. Oliver, Brian Gilmore, Jerry Duncan

James H. Oliver

Currently, new product concepts are evaluated by developing detailed virtual part and assembly models with traditional Computer Aided Design (CAD) tools followed by appropriate analyses (e.g., finite element analysis, computational fluid dynamics, etc.). The creation of these models and analyses are tremendously time consuming. If a number of different conceptual configurations have been determined, it may not be possible to model and analyze each of them. Thus, promising concepts might be eliminated based solely on insufficient time to assess them. In addition, the virtual models and analyses performed are usually of much higher detail and accuracy than what is ...


Zespół Energii Odnawialnej I Zrównoważonego Rozwoju (Eozr), Wojciech M. Budzianowski Dec 2014

Zespół Energii Odnawialnej I Zrównoważonego Rozwoju (Eozr), Wojciech M. Budzianowski

Wojciech Budzianowski

No abstract provided.


The Cognitive Implications Of Virtual Locomotion With A Restricted Field Of View, William E. Marsh, Jonathan W. Kelly, Veronica J. Dark, James H. Oliver Oct 2014

The Cognitive Implications Of Virtual Locomotion With A Restricted Field Of View, William E. Marsh, Jonathan W. Kelly, Veronica J. Dark, James H. Oliver

James H. Oliver

A study was conducted to examine the impact, in terms of cognitive demands, of a restricted field of view (FOV) on semi-natural locomotion in virtual reality (VR). Participants were divided into two groups: high-FOV and low-FOV. They were asked to perform basic movements using a locomotion interface while simultaneously performing one of two memory tasks (spatial or verbal) or no memory task. The memory tasks were intended to simulate the competing demands when a user has primary tasks to perform while using an unnatural interface to move through the virtual world. Results show that participants remembered fewer spatial or verbal ...


Sugarmap: Location-Less Coverage For Micro-Aerial Sensing Swarms, Aveek Purohit, Zheng Sun, Pei Zhang Apr 2013

Sugarmap: Location-Less Coverage For Micro-Aerial Sensing Swarms, Aveek Purohit, Zheng Sun, Pei Zhang

Zheng Sun

No abstract provided.


Determination Of Kinetic Parameters From The Thermogravimetric Data Set Of Biomass Samples, Karol Postawa, Wojciech M. Budzianowski Dec 2012

Determination Of Kinetic Parameters From The Thermogravimetric Data Set Of Biomass Samples, Karol Postawa, Wojciech M. Budzianowski

Wojciech Budzianowski

This article describes methods of the determination of kinetic parameters from the thermogravimetric data set of biomass samples. It presents the methodology of the research, description of the needed equipment, and the method of analysis of thermogravimetric data. It describes both methodology of obtaining quantitative data such as kinetic parameters as well as of obtaining qualitative data like the composition of biomass. The study is focused mainly on plant biomass because it is easy in harvesting and preparation. Methodology is shown on the sample containing corn stover which is subsequently pyrolysed. The investigated sample show the kinetic of first order ...


Precis: A Usercentric Word-Length Optimization Tool, Mark Chang, Scott Hauck Jul 2012

Precis: A Usercentric Word-Length Optimization Tool, Mark Chang, Scott Hauck

Mark L. Chang

Translating an algorithm designed for a general-purpose processor into an algorithm optimized for custom logic requires extensive knowledge of the algorithm and the target hardware. Precis lets designers analyze the precision requirements of algorithms specified in Matlab. The design time tool combines simulation, user input, and program analysis to help designers focus their manual precision optimization efforts.


Polaris: Getting Accurate Indoor Orientations For Mobile Devices Using Ubiquitous Visual Patterns On Ceilings, Zheng Sun Feb 2012

Polaris: Getting Accurate Indoor Orientations For Mobile Devices Using Ubiquitous Visual Patterns On Ceilings, Zheng Sun

Zheng Sun

Ubiquitous computing applications commonly use digital compass sensors to obtain orientation of a device relative to the magnetic north of the earth. However, these compass readings are always prone to significant errors in indoor environments due to presence of metallic objects in close proximity. Such errors can adversely affect the performance and quality of user experience of the applications utilizing digital compass sensors.

In this paper, we propose Polaris, a novel approach to provide reliable orientation information for mobile devices in indoor environments. Polaris achieves this by aggregating pictures of the ceiling of an indoor environment and applies computer vision ...


Hydrogen Production From Biogas By Oxy-Reforming: Reaction System Analysis, Aleksandra Terlecka, Wojciech M. Budzianowski Dec 2011

Hydrogen Production From Biogas By Oxy-Reforming: Reaction System Analysis, Aleksandra Terlecka, Wojciech M. Budzianowski

Wojciech Budzianowski

Oxy-reforming is emerging as an interesting alternative to conventional methods of hydrogen generation. The current article characterises this process through analysis of individual reactions: SMR (steam methane reforming), WGS (water gas shift) and CPO (catalytic partial oxidation). Analyses relate to optimisation of thermal conditions thus enabling cost-effectivenes of the process.