Mechanical Engineering Commons^™

Low-Voltage Closed Loop Mems Actuators, Shahrzad Towfighian, Glenn Heppler, Eihab Abdel-Rahman

Mechanical Engineering Faculty Scholarship

An efficient electrostatic resonator is designed by adding a low voltage controller to an electrostatic actuator. The closedloop actuator shows stable, and bi-sable behaviors with bounded chaotic oscillations as large as 117% of the capacitor gap. The controller voltage is decreased from a previously designed resonator to less than 9 V thereby reducing the load on the controller circuit components. Bifurcation diagrams are obtained showing the frequency and magnitude of AC voltage required for chaotic oscillations to develop. The information entropy, a measure of chaotic characteristic, is calculated for the micro-resonator and is found to be 0.732.

Lattice Boltzmann Simulation Of Binary Drop Coalescence At Low Weber Number, Lina Baroudi

Dissertations and Theses

"A numerical study has been performed using a lattice Boltzmann method (LBM) for an incompressible binary fluid based on the Cahn-Hilliard diffuse interface approach to investigate the early-time coalescence dynamics of two liquid drops. The two drops approach each other at a very low Weber number (We) and the coalescence process is driven by surface tension. When the two drops come into contact, the curvature diverges and causes infinitely large surface tension forces, leading to the formation of a rapidly growing liquid bridge. Depending on the forces that govern the widening of the liquid bridge, the coalescence dynamics can be …

Formulation & Thermophysical Analysis Of A Beeswax Microemulsion & The Experimental Calculation Of Its Heat Transfer Coefficient, Ravi Ramnanan-Singh

Dissertations and Theses

Experimentation and implementation of Phase Change Materials (PCM) as suitable Thermal Energy Storage (TES) mediums has garnered greater attention in recent decades. PCMs have the ability to not only store Sensible Heat (SH) within a given temperature range, but also store large amounts of Latent Heat (LH) as they undergo a phase change, whether it is from solid to liquid or liquid to gas. This investigation examines the preparation of a beeswax microemulsion, the analysis of its thermophysical properties, and the experimental method to calculate its heat transfer coefficient under laminar flow conditions. First, the beeswax microemulsion was formulated to …

Feasibility Analysis Of Estrification Systems With Entrainers, Kang Wook Lee

Dissertations and Theses

(Ethyl Acetate) and IPA (Isopropyl Acetate) production systems are studied in terms of the feasibility analysis. It is not feasible to retrieve pure products by a simple reactive distillation for IPA production system because CCR (Critical Composition Region) covers the entire desired binary edge for IPA system. On the other hand, even though CCR does not cover the entire desired binary edge of the EA system completely, internal reflux ratio (IRR) analysis does not allow the production of the pure product via reactive distillation for EA production system. To overcome the restraints, external entrainers are utilized to take advantage of …

Exploration Of The Endothermic And Exothermic Reactions Of Calcium Oxide And Magnesium Oxide And Design Of A Vessel For A Thermochemical Heat Storage System, Jorge Pulido

Dissertations and Theses

A high temperature Thermal Energy Storage (TES) system has been investigated for use in solar thermal power plants or in vehicles to preheat the engine and/or the cabin in cold weather. The idea is to store surplus thermal energy and then release it on demand to heat a working fluid. The stored heat can be used to generate electricity after sunset or to meet the peak loads. These would lead to an improvement in energy efficiency, reductions in energy imports from foreign sources and total energy-related emissions. The basic operating principle involved in the TES system is a thermochemical reaction …

The Effect Of Time-Delay Feedback Controller On An Electrically Actuated Resonator, S. Shao, K. M. Masri, Mohammad I. Younis

Mechanical Engineering Faculty Scholarship

This paper presents a study of the effect of a time-delay feedback controller on the dynamics of a Microelectromechanical systems (MEMS) capacitor actuated by DC and AC voltages. It is shown that negative time-delay feedback control gain can lead to an unstable system, even if AC voltage is relatively small compared to DC voltage. Perturbation method is utilized to present analytically the nonlinear dynamic characteristics of the MEMS capacitor. Agreements among the results of a shooting technique, long-time integration, basin of attraction analysis with the perturbation method are achieved.

Dynamics Of A Close-Loop Controlled Mems Resonator, Abdulrahman Seleim, Shahrzad Towfighian, Emmanuel Delande, Eihab Abdel-Rahman, Glenn Heppler

Mechanical Engineering Faculty Scholarship

The dynamics of a close-loop electrostatic MEMS resonator, proposed as a platform for ultra sensitive mass sensors, is investigated. The parameter space of the resonator actuation voltage is investigated to determine the optimal operating regions. Bifurcation diagrams of the resonator response are obtained at five different actuation voltage levels. The resonator exhibits bi-stability with two coexisting stable equilibrium points located inside a lower and an upper potential wells. Steady-state chaotic attractors develop inside each of the potential wells and around both wells. The optimal region in the parameter space for mass sensing purposes is determined. In that region, steady-state chaotic …

Geographical Assessment Of Microalgae Biofuels Potential Incorporating Resource Availability, Jason C. Quinn, Kimberly Catton, Sara Johnson, Thomas H. Bradley

Mechanical and Aerospace Engineering Faculty Publications

Previous assessments of the economic feasibility and large-scale productivity of microalgae biofuels have not considered the impacts of land and carbon dioxide (CO2) availability on the scalability of microalgae-based biofuels production. To accurately assess the near-term productivity potential of large-scale microalgae biofuel in the US, a geographically realized growth model was used to simulate microalgae lipid yields based on meteorological data. The resulting lipid productivity potential of Nannochloropsis under large-scale cultivation is combined with land and CO2 resource availability illustrating current geographically feasible production sites and corresponding productivity in the US. Baseline results show that CO2 transport constraints will limit …

Spatially Localized Measurement Of Thermal Conductivity Using A Hybrid Photothermal Technique, Zilong Hua, Heng Ban, Marat Khafizov, Robert Schley, Rory Kennedy, David H. Hurley

Mechanical and Aerospace Engineering Faculty Publications

A photothermal technique capable of measuring thermal conductivity with micrometer lateral resolution is presented. This technique involves measuring separately the thermal diffusivity, D, and thermal effusivity, e, to extract the thermal conductivity, k = (e²/D)^1/2. To generalize this approach, sensitivity analysis is conducted for materials having a range of thermal conductivities. Application to nuclear fuel is consider by performing experimental validation using two materials (CaF₂ and SiO₂) having thermal properties representative of fresh and high burnup nuclear fuel. The measured conductivities compare favorably with literature values.

Parametric Study Of The Frequency-Domain Thermoreflectance Technique, C. Xing, C. Jensen, Z. Hua, Heng Ban, D. H. Hurley, M. Khafizov, J. R. Kennedy

Mechanical and Aerospace Engineering Faculty Publications

Without requiring regression for parameter determination, one-dimensional (1D) analytical models are used by many research groups to extract the thermal properties in frequency-domain thermoreflectance measurements. Experimentally, this approach involves heating the sample with a pump laser and probing the temperature response with spatially coincident probe laser. Micron order lateral resolution can be obtained by tightly focusing the pump and probe lasers. However, small laser beam spot sizes necessarily bring into question the assumptions associated with 1D analytical models. In this study, we analyzed the applicability of 1D analytical models by comparing to 2D analytical and fully numerical models. Specifically, we …

Direct Write Fabrication Of Waveguides And Interconnects For Optical Printed Wiring Boards, Joseph Carl Dingeldein

Dissertations, Master's Theses and Master's Reports - Open

Current copper based circuit technology is becoming a limiting factor in high speed data transfer applications as processors are improving at a faster rate than are developments to increase on board data transfer. One solution is to utilize optical waveguide technology to overcome these bandwidth and loss restrictions. The use of this technology virtually eliminates the heat and cross-talk loss seen in copper circuitry, while also operating at a higher bandwidth. Transitioning current fabrication techniques from small scale laboratory environments to large scale manufacturing presents significant challenges. Optical-to-electrical connections and out-of-plane coupling are significant hurdles in the advancement of optical …

Automated Optimization Of Polymer Extrusion Dies Using Finite Element Analysis, James Allen Peitzmeier

Dissertations, Master's Theses and Master's Reports - Open

An extrusion die is used to continuously produce parts with a constant cross section; such as sheets, pipes, tire components and more complex shapes such as window seals. The die is fed by a screw extruder when polymers are used. The extruder melts, mixes and pressures the material by the rotation of either a single or double screw. The polymer can then be continuously forced through the die producing a long part in the shape of the die outlet. The extruded section is then cut to the desired length. Generally, the primary target of a well designed die is to …

Finite Element Analysis Of 2-D Representative Volume Element, Mandar Kulkarni

Dissertations, Master's Theses and Master's Reports - Open

No abstract provided.

Use Of Manual Adaptive Remeshing In The Mechanical Modeling Of An Intraneural Ganglion Cyst, Laura M. Roberts

Dissertations, Master's Theses and Master's Reports - Open

Intraneural Ganglion Cysts expand within in a nerve, causing neurological deficits in afflicted patients. Modeling the propagation of these cysts, originating in the articular branch and then expanding radially outward, will help prove articular theory, and ultimately allow for more purposeful treatment of this condition. In Finite Element Analysis, traditional Lagrangian meshing methods fail to model the excessive deformation that occurs in the propagation of these cysts. This report explores the method of manual adaptive remeshing as a method to allow for the use of Lagrangian meshing, while circumventing the severe mesh distortions typical of using a Lagrangian mesh with …

Methods Of Optimizing The Gas Exchange Process To Improve Fuel Efficiency Of Small Carbureted Spark Ignition Engines, Cory Hannibal Huck

Masters Theses

"Fuel efficiency of internal combustion engines long has been a topic of concern. Much effort has been made to optimize the fuel efficiency of large automotive type engines. However, for small engine manufactures subject to tight cost constraints, this has only recently become an area of great focus. A method by which the fuel efficiency of an engine can be improved is through optimization of the intake process. Specifically, reductions in flow losses and the choice of appropriate valve event timings can provide ways to make gains towards more fuel efficient operation. The challenge arises when the focus is on …

Microlens Array Light Trapping In Cdte/Cds Solar Cells, Patrick Michael Margavio

Masters Theses

"In light of the continued rise in fossil fuel costs, alternative energy sources, such as solar technology, are increasingly important. Concentrating photovoltaic systems are promising for future efficient and cost effective competition with fossil fuels. A microlens array is employed to a CdTe/CdS semiconducting solar cell to increase efficiency via light trapping. Since the microlens array will cause a local increase in incident light intensity, it should cause a corresponding increase in efficiency. The solar cell is deposited layer by layer. The CdS layer is chemically deposited. The CdTe layer is deposited using a novel additive manufacture technique: laser melting …

Prototyping And Testing Of Solar Hybrid Pv-T Panels, Joel Aaron Lamson

Masters Theses

"The combination of photovoltaic and solar thermal (PV-t) systems has been proven to provide greater efficiency than their stand-alone counterparts. Previous studies on hybrid assemblies have found favorable results supporting the combination of both systems. The research presented here builds on the work competed here at Missouri University of Science and Technology (Missouri S&T) yielding favorable results of increased efficiencies as compared to stand-alone systems. The main difference between this experiment and previous research at Missouri S&T is that the hybrid PV-t is unglazed. The effect of an unglazed panel is shown to reduce the thermal output of the PV-t …

Investigating The Effects Of Internally Trapped Residuals On The Performance Of A Homogeneous Charge Compression Ignition (Hcci) Engine, Aaron David Attebery

Masters Theses

"Homogeneous charge compression ignition (HCCI) combustion introduces great opportunity for decreased emissions along with greater engine efficiencies. Implementing an innovative combustion mode such as HCCI presents a great challenge for the engine research community. One such challenge is controlling the innate cyclic variability from this chemical kinetics controlled auto-ignition event when transitioning to or from a SI operating mode. This work includes the study of cycle-to-cycle dynamics that occur within the partial burn regime of an HCCI engine as it approaches the misfire limit. Within this regime there are many successive incomplete combustion events that will impact the next cycle …

Finite Element Analysis Of The Contact Deformation Of Piezoelectric Materials, Ming Liu

Theses and Dissertations--Chemical and Materials Engineering

Piezoelectric materials in the forms of both bulk and thin-film have been widely used as actuators and sensors due to their electromechanical coupling. The characterization of piezoelectric materials plays an important role in determining device performance and reliability. Instrumented indentation is a promising method for probing mechanical as well as electrical properties of piezoelectric materials.

The use of instrumented indentation to characterize the properties of piezoelectric materials requires analytical relations. Finite element methods are used to analyze the indentation of piezoelectric materials under different mechanical and electrical boundary conditions.

For indentation of a piezoelectric half space, a three-dimensional finite element …

Investigation Of A Water Desalination Method Via A Humidification-Dehumidification Process Using Hvac Technology, Juan Antonio Cornejo

Open Access Theses & Dissertations

Potable water is becoming a scarce resource in many arid regions of the world. An experimental unit was designed and constructed to examine and characterize the production capabilities of a humidification-dehumidification (HDH) desalination process. An HDH cycle offers a viable, technologically light, alternative for producing fresh water from brackish water because the low relative humidity air is infused with water vapor through evaporation by means of conventional heating, ventilation and air conditioning (HVAC) components. The evaporation process effectively separates salts and suspended solids from the brackish feed-water. Desalinated water is subsequently recovered by extracting the water vapor from the moist …