Stability Analysis Of A More General Class Of Systems With Delay-Dependent Coefficients, 2019 Laboratoire des Signaux et Syst`emes (L2S) CentraleSup´elec-CNRS-Universit´e Paris Sud, 3 rue Joliot- Curie 91192 Gif-sur-Yvette cedex, France.
Stability Analysis Of A More General Class Of Systems With Delay-Dependent Coefficients, Chi Jin, Keqin Gu, Islam Boussaada, Silviu-Iulian Niculescu
SIUE Faculty Research, Scholarship, and Creative Activity
This paper presents a systematic method to analyse the stability of systems with single delay in which the coefficient polynomials of the characteristic equation depend on the delay. Such systems often arise in, for example, life science and engineering systems. A method to analyze such systems was presented by Beretta and Kuang in a 2002 paper, but with some very restrictive assumptions. This work extends their results to the general case with the exception of some degenerate cases. It is found that a much richer behavior is possible when the restrictive assumptions are removed. The interval of interest for the ...
Analysis Of Dynamic Behaviour Of A Tensioned Carbon Nanotube In Thermal And Pressurized Environments, 2019 University of Lagos
Analysis Of Dynamic Behaviour Of A Tensioned Carbon Nanotube In Thermal And Pressurized Environments, Ahmed Yinusa, Gbeminiyi Sobamowo
Karbala International Journal of Modern Science
In this paper, the dynamic behaviour of a tensioned single-walled carbon nanotubes (SWCNT) in thermal and pressurized environments is investigated analytically. With the applications of Bernoulli-Euler and thermal elasticity mechanics theories, the governing equation of motion are developed and solved using Laplace and Fourier transforms. The results of the close form solution in this work are in excellent agreements with past results in literature. From the parametric studies, it is established that as the magnitude of the pressure distribution at the surface increases, the deflection associated with the nanotube increases at any mode of vibration. However, a corresponding increase in ...
Bouncing Dynamics Of A Class Of Mem/Nem Switching Systems, 2019 The University of Western Ontario
Bouncing Dynamics Of A Class Of Mem/Nem Switching Systems, Mohamed Bognash
Electronic Thesis and Dissertation Repository
The aim of the present research is to understand the bouncing dynamic behavior of NEM/MEM switches in order to improve the switch performance and reliability. It is well known that the bouncing can dramatically degrade the switch performance and life; hence, in the present study, bouncing dynamics of a cantilever-based NME/MEM switch has been studied in detail. To this end, a model of a MEM switch that incorporates electrostatic force, squeeze film air damping force as well as asperity-based contact force has been proposed for an electrostatically actuated switch. An actuation force due to piezoelectric effects is further ...
Optical Micro-Seismometer Based On Evanescent Field Perturbation Of Whispering Gallery Modes, 2018 Southern Methodist University
Optical Micro-Seismometer Based On Evanescent Field Perturbation Of Whispering Gallery Modes, Jaime Da Silva
Mechanical Engineering Research Theses and Dissertations
This thesis proposes a light-weight, compact, and accurate optical micro-seismometer that could be used in many applications, such as planetary exploration. The sensor proposed here is based on the principle of whispering gallery optical mode (WGM) resonance shifts of a dielectric micro-resonator due to disturbances of its evanescent field. The micro-seismometer could be used in place of the traditional bulky seismometers. The design of a waveguide-resonator and mechanical structure to disturb the evanescent field are presented. A proof-of-concept a seismometer model that uses a 5µm ring resonator is numerically tested with actual seismic data. The results show that a WGM-based ...
Variable Input Observer For Nonstationary High-Rate Dynamic Systems, 2018 Iowa State University
Variable Input Observer For Nonstationary High-Rate Dynamic Systems, Jonathan Hong, Simon Laflamme, Liang Cao, Jacob Dodson, Bryan Joyce
Civil, Construction and Environmental Engineering Publications
Engineering systems experiencing events of amplitudes higher than 100 gn for a duration under 100 ms, here termed high-rate dynamics, can undergo rapid damaging effects. If the structural health of such systems could be accurately estimated in a timely manner, preventative measures could be employed to minimize adverse effects. For complex high-rate problems, adaptive observers have shown promise due to their capability to deal with nonstationary, noisy, and uncertain systems. However, adaptive observers have slow convergence rates, which impede their applicability to the high-rate problems. To improve on the convergence rate, we propose a variable input space concept for ...
Creating A Computational Tool To Simulate Vibration Control For Piezoelectric Devices, 2018 Western Kentucky University
Creating A Computational Tool To Simulate Vibration Control For Piezoelectric Devices, Ahmet Ozkan Ozer, Emma J. Moore
Piezoelectric materials have the unique ability to convert electrical energy to mechanical vibrations and vice versa. This project takes a stab to develop a reliable computational tool to simulate the vibration control of a novel “partial differential equation” model for a piezoelectric device, which is designed by integrating electric conducting piezoelectric layers constraining a viscoelastic layer to provide an active and lightweight intelligent structure. Controlling unwanted vibrations on piezoelectric devices (or harvesting energy from ambient vibrations) through piezoelectric layers has been the major focus in cutting-edge engineering applications such as ultrasonic welders and inchworms. The corresponding mathematical models for piezoelectric ...
Ultrasonic Sensing And Actuation In Laminate Structures Using Bondline-Embedded D35 Piezoelectric Sensors, 2018 University of Wisconsin-Milwaukee
Ultrasonic Sensing And Actuation In Laminate Structures Using Bondline-Embedded D35 Piezoelectric Sensors, Hussain Ahmed Altammar, Anoop K. Dhingra, Nathan P. Salowitz
Mechanical Engineering Faculty Articles
Ultrasonic systems employing embedded piezoelectric transducers have seen increased interest in recent years. The ability to sense, actuate, and analyze the wave propagation modes in engineering structures has been fundamental to the advancement of ultrasonic structural health monitoring (SHM). This paper presents a study into the sensing and actuation properties of shear-mode (d35) piezoelectric transducers made of lead zirconate titanate (PZT) that are internally embedded in the bondline of laminate structures. The manuscript presents analytical analysis, finite element simulation, and experimental validation building from an individual piezoelectric element to a full laminate structure. The validated model was then used to ...
Acoustic Source Localization With A Vtol Suav Deployable Module, 2018 University of South Florida
Acoustic Source Localization With A Vtol Suav Deployable Module, Kory Olney
Graduate Theses and Dissertations
A real time acoustic direction-finding module has been developed to estimate the ele- vation and azimuth of an impulsive event while function aboard a small unmanned air- craft vehicle. The generalized cross-correlation with phase transform method was used to estimate time differences of arrival in an 8 channel microphone array. A linear least squares approach was used to calculate an estimate for the direction of arrival. In order to accomplish this task, a vertical takeoff and landing small unmanned aircraft system was assembled to host the direction finding module. The module itself is made up of an eight-channel synchronous analog-to-digital ...
3d Numerical Study Of Multiphase Counter-Current Flow Within A Packed Bed For Post Combustion Carbon Dioxide Capture, 2018 China University of Mining and Technology, China
3d Numerical Study Of Multiphase Counter-Current Flow Within A Packed Bed For Post Combustion Carbon Dioxide Capture, Li Yang, Fang Liu, Zhengchang Song, Kunlei Liu, Kozo Saito
Mechanical Engineering Faculty Publications
The hydrodynamics within counter-current flow packed beds is of vital importance to provide insight into the design and operational parameters that may impact reactor and reaction efficiencies in processes used for post combustion CO2 capture. However, the multiphase counter-current flows in random packing used in these processes are complicated to visualize. Hence, this work aimed at developing a computational fluid dynamics (CFD) model to study more precisely the complex details of flow inside a packed bed. The simulation results clearly demonstrated the development of, and changes in, liquid distributions, wetted areas, and film thickness under various gas and liquid ...
Development Of A Fully Instrumented, Resonant Tensegrity Strut, 2018 Union College
Development Of A Fully Instrumented, Resonant Tensegrity Strut, Kentaro Barhydt
A tensegrity is a structure composed of a series of rigid members connected in static equilibrium by tensile elements. A vibrating tensegrity robot is an underactuated system in which a set of its struts are vibrated at certain frequency combinations to achieve various locomotive gaits. Evolutionary robotics research lead by Professor John Rieffel focuses on exploiting the complex dynamics of tensegrity structures to control locomotion in vibrating tensegrity robots by finding desired gaits using genetic algorithms. A current hypothesis of interest is that the optimal locomotive gaits of a vibrating tensegrity exist at its resonant frequencies.
In order to observe ...
Mobile Opera Backdrop, 2018 California Polytechnic State University, San Luis Obispo
Mobile Opera Backdrop, Juan Villalobos, Robbie Behlman, Kevin Valencia
Opera San Luis Obispo requires an acoustically projecting stage backdrop for their future plan of deploying a mobile opera house. The custom stage backdrop must be low-cost, easy to assemble and must project the performance sound to outdoor audiences. Other design requirements include being transportable in a step van, the ability to be assembled quickly by a crew of two, resistance to various outdoor conditions, the ability to mount accessories from the walls, and should meet a budget of $5,000. With the scope of the project understood, the three-quarter project is outlined. During the first quarter, the main deliverables ...
A Microresonator-Based Laser Doppler Velocity Sensor For Interplanetary Atmospheric Re-Entry, 2018 Southern Methodist University
A Microresonator-Based Laser Doppler Velocity Sensor For Interplanetary Atmospheric Re-Entry, Benjamin Wise
Mechanical Engineering Research Theses and Dissertations
In this thesis, a laser velocity sensor concept based on optical microresonators is presented and the application to spacecraft atmospheric entry is explored. The concept is based on the measurement of Doppler shift of back-scattered laser light. Specifically, the Doppler shift is detected by observing the whispering gallery optical modes (WGM) of a dielectric microresonator excited by the back scattered light from particulates and gas molecules. The microresonator replaces the typical Fabry-Perot interferometer and CCD camera system, thereby significantly reducing the size and weight of the overall detection system. This thesis presents proof-of-concept results for this measurement approach. The Doppler ...
Soft-Microrobotics: The Manipulation Of Alginate Artificial Cells, 2018 Southern Methodist University
Soft-Microrobotics: The Manipulation Of Alginate Artificial Cells, Samuel Sheckman
Mechanical Engineering Research Theses and Dissertations
In this work, the approach to the manipulation of alginate artificial cell soft-microrobots, both individually and in swarms is shown. Fabrication of these artificial cells were completed through centrifugation, producing large volumes of artificial cells, encapsulated with superparamagnetic iron oxide nanoparticles; these artificial cells can be then externally stimulated by an applied magnetic field. The construction of a Permeant Magnet Stage (PMS) was produced to manipulate the artificial cells individually and in swarms. The stage functionalizes the permanent magnet in the 2D xy-plane. Once the PMS was completed, Parallel self-assembly (Object Particle Computation) using swarms of artificial cells in complex ...
Modeling Of Swimming Cells From Nano-Scale To Micro-Scale, 2018 Washinton University in St. Louis
Modeling Of Swimming Cells From Nano-Scale To Micro-Scale, Yicheng Zhao
Engineering and Applied Science Theses & Dissertations
Certain human genetic diseases -- primary ciliary dyskinesia, infertility, and hydrocephalus -- are characterized by changes in beat frequency and waveform of cilia and flagella. Chlamydomonas reinhardtii, which is a single-cell green alga about ten micrometers in diameter that swims with two flagella, serves as an excellent biological model because its flagella share the same structure and genetic background as mammalian cilia and flagella. This study uses the finite element method to investigate the behavior of C. reinhardtii swimming from nano-scale to micro-scale. At the device-level, micro-scale modeling indicates that well-designed acoustic microfluidic devices can be used to trap groups of C ...
Effects Of Tension On Resonant Frequencies Of Strings, 2018 Linfield College
Effects Of Tension On Resonant Frequencies Of Strings, Blake Burnett
This project tests and explores resonance of strings. Since all materials and mechanisms are affected by vibrations, it is important to know the frequencies at which resonance occurs. To explore this subject, strings were used as a model material to test the effect tension has on resonance. The fundamental frequencies and the corresponding modes of resonance were used to analyze the data. The results of this experiment show that increasing tension on a string increases its resonance frequency. Understanding the physics behind resonance frequency allows systems to be designed to take advantage of resonance properties, or to avoid resonance where ...
Active Permanent Magnet Attitude Control For Cubesats Using Mu-Metal Shielding, 2018 University of Arkansas, Fayetteville
Active Permanent Magnet Attitude Control For Cubesats Using Mu-Metal Shielding, Maxwell Martin
Mechanical Engineering Undergraduate Honors Theses
Cube-Satellites (CubeSats) are nanosatellites composed of cube shaped units, each nominally 10cm to a side and around 1kg in mass. Due to their inherent size and weight limitations, it is often impractical to use conventional attitude, or rotational, control methods such as thrusters on these small satellites. Several methods, including magnetorquer rods and small reaction wheels, are often used instead of traditional methods to work around the size and weight limitations. As a new alternative to these methods, a permanent magnet mounted on a rotatable shaft could be used to achieve attitude control. In much the same way that a ...
Reduced Order Modeling For Virtual Building Commissioning, 2018 Boise State University
Reduced Order Modeling For Virtual Building Commissioning, Sean Rosin
Boise State University Theses and Dissertations
Model order reduction can help reduce the time and monetary constraints associated with building commissioning and significantly decrease overall building energy consumption through virtual commissioning. This research aimed to determine the effectiveness of using reduced order models to simulate the overall building energy consumption, and to estimate the energy savings from control-based commissioning recommendations.
A case study building was modeled using a ‘Lumped RC’ thermal model with three thermal resistances and capacitances (3R3C) for the building interior and a 2R1C model describing the building foundation. Due to energy consumption being dependent on building systems, this model was coupled with a ...
Development Of A Model To Predict The Likelihood Of Complaints Due To Assorted Tone-In-Noise Combinations, 2018 University of Nebraska - Lincoln
Development Of A Model To Predict The Likelihood Of Complaints Due To Assorted Tone-In-Noise Combinations, Joonhee Lee, Lily M. Wang
Architectural Engineering -- Faculty Publications
This paper develops a model to predict if listeners would be likely to complain due to annoyance when exposed to a certain noise signal with a prominent tone, such as those commonly produced by heating, ventilation, and air-conditioning systems. Twenty participants completed digit span tasks while exposed in a controlled lab to noise signals with differing levels of tones, ranging from 125 to 1000 Hz, and overall loudness. After completing the digit span tasks under each noise signal, from which task accuracy and speed of completion were captured, subjects were asked to rate level of annoyance and indicate the likelihood ...
Rotordynamic Analysis Of Theoretical Models And Experimental Systems, 2018 California Polytechnic State University - San Luis Obispo
Rotordynamic Analysis Of Theoretical Models And Experimental Systems, Cameron R. Naugle, Cameron Rex Naugle
Master's Theses and Project Reports
This thesis is intended to provide fundamental information for the construction and
analysis of rotordynamic theoretical models, and their comparison the experimental
systems. Finite Element Method (FEM) is used to construct models using Timoshenko
beam elements with viscous and hysteretic internal damping. Eigenvalues
and eigenvectors of state space equations are used to perform stability analysis, produce
critical speed maps, and visualize mode shapes. Frequency domain analysis
of theoretical models is used to provide Bode diagrams and in experimental data
full spectrum cascade plots. Experimental and theoretical model analyses are used
to optimize the control algorithm for an Active Magnetic Bearing ...
High-Resolution Performance Analysis Of A Large Building With Linear Dispersion Ductwork System, 2018 Iowa State University
High-Resolution Performance Analysis Of A Large Building With Linear Dispersion Ductwork System, Anthony Fontanini, Alberto Passalacqua, Umesh Vaidya, Michael Olsen, Baskar Ganapathysubramanian
Buildings consume 40% of the U.S. annual energy usage. The energy usage of building can drastically be reduced by proper management of the thermal load in large interior spaces. A well designed space should include systems that balance both occupant comfort and efficiency. Recently linear dispersion ductwork systems have been shown to be a promising solution for creating both comfortable and efficient spaces. We investigate long-term thermal behavior of a 10,000 ft2 building that utilizes a linear air dispersion system. We optimize the operating point of the HVAC system by utilizing three dimensional Computational Fluid Dynamic (CFD) simulations ...