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Strong Stability Of A Class Of Difference Equations Of Continuous Time And Structured Singular Value Problem, Qian Ma, Keqin Gu, Narges Choubedar 2018 Nanjing University of Science and Technology

Strong Stability Of A Class Of Difference Equations Of Continuous Time And Structured Singular Value Problem, Qian Ma, Keqin Gu, Narges Choubedar

SIUE Faculty Research, Scholarship, and Creative Activity

This article studies the strong stability of scalar difference equations of continuous time in which the delays are sums of a number of independent parameters tau_i, i = 1, 2, . . . ,K. The characteristic quasipolynomial of such an equation is a multilinear function of exp(-tau_i s). It is known that the characteristic quasipolynomial of any difference equation set in the form of one-delayper- scalar-channel (ODPSC) model is also in such a multilinear form. However, it is shown in this article that some multilinear forms of quasipolynomials are not characteristic quasipolynomials of any ODPSC difference equation set. The equivalence between local strong ...


Measurement Of Speed Of Sound Profile Using Laaces Balloon, Zhuang Li, Brett Schaefer, Brian Schaefer, William Dever, Tyler Morgan, Matthew Foltz 2017 McNeese State University

Measurement Of Speed Of Sound Profile Using Laaces Balloon, Zhuang Li, Brett Schaefer, Brian Schaefer, William Dever, Tyler Morgan, Matthew Foltz

2017 Academic High Altitude Conference

The goal of this mission is to test the speed of sound at different altitudes and ultimately at a maximum height of 100,000 feet (30 km). In conjunction with this testing, environmental parameters including temperature, pressure, and humidity are measured and used to calculate the speed of sound to compare to the measured results. The team constructed the payload “Dorothy” using polystyrene foam due to its lightweight and thermal isolation property. An ultrasonic sensor with a reflection mirror were installed outside payload box to measure speed of sound. All the sensors were calibrated. Software for the project was developed ...


Detection Of 4-Point Bend Induced Micro-Cracks In Cfrp Laminates Via Coda Wave Nde, Richard Livings, Dan Barnard, Vinay Dayal 2017 Iowa State University

Detection Of 4-Point Bend Induced Micro-Cracks In Cfrp Laminates Via Coda Wave Nde, Richard Livings, Dan Barnard, Vinay Dayal

Vinay Dayal

Although coda wave NDE has been shown to have some sensitivity to realistic damage in concrete structures, the technique’s capability for detecting micro-cracks in fibrous composite materials has yet to be evaluated. This paper reports on the first investigation of realistic damage, specifically micro-cracks, in fibrous composite materials using coda wave differential signal features. Micro-cracks were generated in CFRP samples using the 4-point bending configuration shown in Fig. 1. The damage was monitored during loading with Acoustic Emission, and the loading was stopped after each significant damage event. The damage was then examined with coda wave NDE, immersion UT ...


Dissertation Xu V1.Pdf, Jiawen Xu 2017 University of Connecticut - Storrs

Dissertation Xu V1.Pdf, Jiawen Xu

Jiawen Xu

The objective of this dissertation research is on the designing and optimization of promising wave guiding and energy manipulation approach.  Specifically address above-mentioned issues of modeling and application of piezoelectric metamaterials and energy harvesting.  The first research task is to develop fundamental modeling and understanding of piezoelectric metamaterial integrated with LC shunts to create local resonances.  We establish the lumped-parameter model of the piezoelectric metamaterial.  Transverse wave is considered throughout the modeling and analysis, and the lumped parameters are derived based on the wavenumber involved.  Taking advantage of the model, we identify the influence of a key parameter, the system-level ...


Dynamic Characterization Of Periodic Lattice Of Elastically-Connected Bi-Stable Elements Under Seismic Excitation, Lingwei Meng, Myungwon Hwang, Andres F. Arrieta Ph.D. 2017 Purdue University

Dynamic Characterization Of Periodic Lattice Of Elastically-Connected Bi-Stable Elements Under Seismic Excitation, Lingwei Meng, Myungwon Hwang, Andres F. Arrieta Ph.D.

The Summer Undergraduate Research Fellowship (SURF) Symposium

Metamaterials are engineered materials, typically in periodic arrangements, which exhibit unconventional or extreme properties not found in nature. Understanding the dynamics of metamaterials enables the design of structures with specific functionalities. The dynamics of metamaterials in linear regime has been relatively well studied in recent years, however the unique phenomena arising from nonlinearities in metamaterials are yet to be explored. In this paper, we focus on an array of bi-stable elements connected by elastic springs under various forms of external excitations acting on the entire system. The general equations of motion are derived to handle any degree-of-freedom (DoF) systems of ...


Generation Of Inhomogeneous Acoustic Waves Using An Array Of Loudspeakers, Samuel E. Wonfor, Trevor A. Kyle, J. Stuart Bolton, Jeffrey F. Rhoads 2017 Purdue University

Generation Of Inhomogeneous Acoustic Waves Using An Array Of Loudspeakers, Samuel E. Wonfor, Trevor A. Kyle, J. Stuart Bolton, Jeffrey F. Rhoads

The Summer Undergraduate Research Fellowship (SURF) Symposium

In previous studies it has been shown that pressure fields created by inhomogeneous sound waves (waves which decay in a direction perpendicular to their propagation direction) are able to transmit energy into objects more effectively than ones created by conventional sound waves. This behavior may be useful in the detection of hidden explosive threats. To explore this, a device capable of constructing inhomogeneous waves is being developed. The proposed device is an acoustic array consisting of several high-frequency speakers. The speakers are independently driven to construct a desired inhomogeneous pressure field on a target surface. Inhomogeneous pressure fields were reconstructed ...


Examination Of Ordering Effects In Sound Evaluations, Yiyun Zhang, Patricia Davies, Daniel Carr 2017 Purdue University

Examination Of Ordering Effects In Sound Evaluations, Yiyun Zhang, Patricia Davies, Daniel Carr

The Summer Undergraduate Research Fellowship (SURF) Symposium

It is difficult to predict sound annoyance responses because annoyance is an inherently subjective concept and the evaluation standard could be different from each person. Usually, annoyance models are functions of strengths of sound characteristics only, and these models can help engineers to improve sounds that machines make and minimize annoyance levels, but other factors can also influence annoyance ratings of products. The main goal of this research was to investigate ordering effects in sound evaluations when people are hearing a set of sounds in sequence. Of particular interest is how the response to a sound influences the response to ...


Stability Analysis Of A Flexible Vehicle Model Controlled By Human Pilot Models, Abhishek Ajmani, Anil Bajaj 2017 Purdue University

Stability Analysis Of A Flexible Vehicle Model Controlled By Human Pilot Models, Abhishek Ajmani, Anil Bajaj

The Summer Undergraduate Research Fellowship (SURF) Symposium

There is a constant race among automobile manufactures to design safer vehicles while minimizing weight to reduce power consumption. Additionally, organizations like NASA and SpaceX are persistently working toward creating reliable, lightweight rovers to be used on the surface of Mars. However, the lightweight requirement often increases vehicle flexibility, which further develops a tendency toward instability in the lateral (sideways) direction. This investigation develops a mathematical model that represents the dynamics of a flexible vehicle in forward motion, and a heuristic human pilot model is proposed which controls the vehicle. Following such formulation, the combined vehicle and pilot model is ...


The Influence Of Macroscale Stress Concentrations On The Near-Resonant Thermomechanics Of Mock Energetic Materials, Lauren A. Cooper, Allison R. Range, Jeffrey F. Rhoads 2017 Western Kentucky University

The Influence Of Macroscale Stress Concentrations On The Near-Resonant Thermomechanics Of Mock Energetic Materials, Lauren A. Cooper, Allison R. Range, Jeffrey F. Rhoads

The Summer Undergraduate Research Fellowship (SURF) Symposium

The characterization of particulate composite energetic materials, both with and without stress concentration, is currently of great interest to the defense community. This work seeks to further characterize the self-heating effect of composite energetic plates, particularly around regions of high stress, when subjected to harmonic excitation near resonance. Mock energetic plates with macroscale stress concentrations are prepared in various compositions based on the PBXN-109 formulation, and are tested near the first resonant frequency using an electrodynamic shaker. The resulting mechanical and thermal responses are recorded using a laser Doppler vibrometer and an infrared camera, respectively. Upon comparison between the regions ...


Cyber-Physical System Characterization And Co-Regulation Of A Quadrotor Uas, Seth E. Doebbeling 2017 University of Nebraska - Lincoln

Cyber-Physical System Characterization And Co-Regulation Of A Quadrotor Uas, Seth E. Doebbeling

Mechanical (and Materials) Engineering -- Dissertations, Theses, and Student Research

An Unmanned Aircraft System (UAS) is a Cyber-Physical System (CPS) in which a host of real-time computational tasks contending for shared resources must be cooperatively managed to obtain mission objectives. Traditionally, control of the UAS is designed assuming a fixed, high sampling rate in order to maintain reliable performance and margins of stability. But emerging methods challenge this design by dynamically allocating resources to computational tasks, thereby affecting control and mission performance. To apply these emerging strategies, a characterization and understanding of the effects of timing on control and trajectory following performance is required. Going beyond traditional control evaluation techniques ...


Deep Ocean Vector Sensor Array Performance Metrics, Gabriel Kniffin, Lisa Zurk 2017 Portland State University

Deep Ocean Vector Sensor Array Performance Metrics, Gabriel Kniffin, Lisa Zurk

Lisa M. Zurk

Recent work in passive sonar has drawn interest in the potential for vertical line arrays (VLAs) deployed below the critical depth—the depth inthe deep ocean at which the sound speed below the channel axis reaches the sound speed near the surface. Such arrays can take advantage of propagation via the reliable acoustic path (RAP), which has been shown to improve thesignal-to-noise ratio (SNR) of received signals from sources at or near the surface at moderate ranges.


Performance Metrics For Depth-Based Signal Separation Using Deep Vertical Line Arrays, Gabriel Paul Kniffin, John Kenneth Boyle, Lisa Zurk, Martin Siderius 2017 Portland State University

Performance Metrics For Depth-Based Signal Separation Using Deep Vertical Line Arrays, Gabriel Paul Kniffin, John Kenneth Boyle, Lisa Zurk, Martin Siderius

Lisa M. Zurk

A recent publication by McCargar and Zurk [(2013). J. Acoust. Soc. Am. 133(4), EL320–EL325] introduced a modified Fourier transform-based method for passive source depth estimation using vertical line arrays deployed below the critical depth in the deep ocean. This method utilizes the depth-dependent modulation caused by the interference between the direct and surface-reflected acoustic arrivals, the observation of which is enhanced by propagation through the reliable acoustic path. However, neither the performance of this method nor its limits of applicability have yet been thoroughly investigated. This paper addresses both of these issues; the first by identifying and analyzing ...


Probability Distribution Of Multiple-Target Data Snapshots Applied To Large-Aperture Array Processing, Jorge E. Quijano, Lisa Zurk 2017 University of Victoria

Probability Distribution Of Multiple-Target Data Snapshots Applied To Large-Aperture Array Processing, Jorge E. Quijano, Lisa Zurk

Lisa M. Zurk

We consider sonar array target detection and azimuth estimation in experimental scenarios consisting of large-aperture horizontal line arrays of hydrophones in the water column.


The Impact Of Three Interfaces For 360-Degree Video On Spatial Cognition, Wutthigrai Boonsuk, Stephen B. Gilbert, Jonathan W. Kelly 2017 Iowa State University

The Impact Of Three Interfaces For 360-Degree Video On Spatial Cognition, Wutthigrai Boonsuk, Stephen B. Gilbert, Jonathan W. Kelly

Jonathan W. Kelly

In this paper, we describe an experiment designed to evaluate the effectiveness of three interfaces for surveillance or remote control using live 360-degree video feeds from a person or vehicle in the field. Video feeds are simulated using a game engine. While locating targets within a 3D terrain using a 2D 360-degree interface, participants indicated perceived egocentric directions to targets and later placed targets on an overhead view of the terrain. Interfaces were compared based on target finding and map placement performance. Results suggest 1) non-seamless interfaces with visual boundaries facilitate spatial understanding, 2) correct perception of self-to-object relationships is ...


Incorporation Of Composite Defects From Ultrasonic Nde Into Cad And Fe Models, Onur Rauf Bingol, Bryan Schiefelbein, Robert J. Grandin, Stephen D. Holland, Adarsh Krishnamurthy 2017 Iowa State University

Incorporation Of Composite Defects From Ultrasonic Nde Into Cad And Fe Models, Onur Rauf Bingol, Bryan Schiefelbein, Robert J. Grandin, Stephen D. Holland, Adarsh Krishnamurthy

Stephen D. Holland

Fiber-reinforced composites are widely used in aerospace industry due to their combined properties of high strength and low weight. However, owing to their complex structure, it is difficult to assess the impact of manufacturing defects and service damage on their residual life. While, ultrasonic NDE is the preferred method to identify the presence of defects (such as delaminations) in composites, there are no reasonable ways to model the damage and evaluate the structural integrity of composites. Hence, a framework to incorporate flaws and known damage models automatically into a finite element analysis (FEA) of composites will aid in accessing their ...


Surrogate Modeling Of Ultrasonic Testing Simulations Using Variable-Fidelity Models And Data-Driven Methods, Robert Grandin, Leifur Leifsson 2017 Iowa State University

Surrogate Modeling Of Ultrasonic Testing Simulations Using Variable-Fidelity Models And Data-Driven Methods, Robert Grandin, Leifur Leifsson

Robert Grandin

Ultrasonic testing (UT) is used to detect internal flaws in materials or to characterize material properties [1]. Computational simulations are an important part of the UT process. Having fast surrogate models for ultrasonic testing (UT) simulations is key for inverse analysis and model-assisted probability of detection (MAPOD) in the field of nondestructive evaluation. In fact, it is impractical to perform the aforementioned tasks in a timely manner using current simulation models directly. Fast surrogate models can make these processes computationally tractable. This paper presents investigations of using surrogate modeling techniques to create fast approximate models of UT simulator responses. In ...


Modeling For Ut Inspection Of Anisotropic Materials, Robert A. Roberts, Robert Grandin, Andrew Downs 2017 Iowa State University

Modeling For Ut Inspection Of Anisotropic Materials, Robert A. Roberts, Robert Grandin, Andrew Downs

Robert Grandin

This presentation reports on the extension of an established CNDE ultrasound beam transmission model to accommodate transmission in generally anisotropic materials. Using principles of elastodynamic reciprocity, the model expresses the internal wave field as a surface integral over the radiating transducer, employing the full Green function (point force response function) for the combined body under inspection and the coupling medium. The model evaluates the Green function asymptotically for short wavelength, and is therefore referred to as an asymptotic Green function model (AGF). The integrand of the transducer integral is projected on to a discretely orthogonal Gaussian basis, leading to a ...


Ultrasound Scatter In Heterogeneous 3d Microstructures, Brady Engle, Ronald A. Roberts, Robert Grandin 2017 Iowa State University

Ultrasound Scatter In Heterogeneous 3d Microstructures, Brady Engle, Ronald A. Roberts, Robert Grandin

Robert Grandin

This paper reports on a computational study of ultrasound propagation in heterogeneous metal microstructures. Random spatial fluctuations in elastic properties over a range of length scales relative to ultrasound wavelength can give rise to scatter-induced attenuation, backscatter noise, and phase front aberration. It is of interest to quantify the dependence of these phenomena on the microstructure parameters, for the purpose of quantifying deleterious consequences on flaw detectability, and for the purpose of material characterization. Valuable tools for estimation of microstructure parameters (e.g. grain size) through analysis of ultrasound backscatter have been developed based on approximate weak-scattering models. While useful ...


Incorporation Of Composite Defects From Ultrasonic Nde Into Cad And Fe Models, Onur Rauf Bingol, Bryan Schiefelbein, Robert J. Grandin, Stephen D. Holland, Adarsh Krishnamurthy 2017 Iowa State University

Incorporation Of Composite Defects From Ultrasonic Nde Into Cad And Fe Models, Onur Rauf Bingol, Bryan Schiefelbein, Robert J. Grandin, Stephen D. Holland, Adarsh Krishnamurthy

Robert Grandin

Fiber-reinforced composites are widely used in aerospace industry due to their combined properties of high strength and low weight. However, owing to their complex structure, it is difficult to assess the impact of manufacturing defects and service damage on their residual life. While, ultrasonic NDE is the preferred method to identify the presence of defects (such as delaminations) in composites, there are no reasonable ways to model the damage and evaluate the structural integrity of composites. Hence, a framework to incorporate flaws and known damage models automatically into a finite element analysis (FEA) of composites will aid in accessing their ...


Validation Of Utsim2, A New Ultrasonic Simulation Package, Robert Grandin, Timothy Gray 2017 Iowa State University

Validation Of Utsim2, A New Ultrasonic Simulation Package, Robert Grandin, Timothy Gray

Robert Grandin

The Center for NDE (CNDE) at Iowa State University has a long history of developing physics models for NDE and packaging these models into simulation tools which make the modeling capabilities accessible to CNDE’s industrial sponsors. Recent work at CNDE has led to the development of a new ultrasonic simulation package, UTSim2, which aims to continue this tradition of supporting industrial application of CNDE models. In order to meet this goal, UTSim2 has been designed as an extensible software package which can support previously-developed physics models as well as future models yet to be developed. Initial work has focused ...


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