Acoustics, Dynamics, and Controls Commons^™

Streaming Potential Generated By A Pressure-Driven Flow Over Superhydrophobic Stripes, Hui Zhao

Mechanical Engineering Faculty Research

The streaming potential generated by a pressure-driven flow over a weakly charged slip-stick surface [the zeta potential of the surface is smaller than the thermal potential (25 mV)] with an arbitrary double layer thickness is theoretically studied by solving the Debye–Huckel equation and Stokes equation. A series solution of the streaming potential is derived. Approximate expressions for the streaming potential in the limits of thin double layers and thick double layers are also given in excellent agreement with the full solution. To understand the impact of the slip, the streaming potential is compared against that over a homogeneously charged smooth …

Parallel-Sparse Symmetrical/Unsymmetrical Finite Element Domain Decomposition Solver With Multi-Point Constraints For Structural/Acoustic Analysis, Siroj Tungkahotara, Willie R. Watson, Duc T. Nguyen, Subramaniam D. Rajan

Civil & Environmental Engineering Faculty Publications

Details of parallel-sparse Domain Decomposition (DD) with multi-point constraints (MPC) formulation are explained. Major computational components of the DD formulation are identified. Critical roles of parallel (direct) sparse and iterative solvers with MPC are discussed within the framework of DD formulation. Both symmetrical and unsymmetrical system of simultaneous linear equations (SLE) can be handled by the developed DD formulation. For symmetrical SLE, option for imposing MPC equations is also provided.

Large-scale (up to 25 million unknowns involving complex numbers) structural and acoustic Finite Element (FE) analysis are used to evaluate the parallel computational performance of the proposed DD implementation using …

Motorcycle Data Acquisition System, Jonathan Luke Harmse

Biomedical Engineering

No abstract provided.

Stochastic Optimal Control In Nonlinear Systems, Celestin Nkundineza

Department of Mechanical and Materials Engineering: Dissertations, Theses, and Student Research

Stochastic control is an important area of research in engineering systems that undergo disturbances. Controlling individual states in such systems is critical. The present investigation is concerned with the application of the stochastic optimal control strategy developed by To (2010) and its implementation as well as providing computed results of linear and nonlinear systems under stationary and nonstationary random excitations. In the strategy the feedback matrix is designed based on the achievement of the objectives for individual states in the system through the application of the Lyapunov equation for the system. Each diagonal element in the gain or associated gain …

Modeling Acoustic Scattering From The Seabed Using Transport Theory, Jorge Quijano, Lisa M. Zurk

Electrical and Computer Engineering Faculty Publications and Presentations

Radiative Transfer (RT) theory has established itself as an important tool for electromagnetic remote sensing in parallel plane geometries with random distributions of scatterers, and most recently it has also been proposed as a model for the propagation of elastic waves in layered ocean sediments. In this work the capabilities of this model are illustrated, as the RT method is used to predict backscattering strength from laboratory models of random media. The RT model is characterized by its flexibility on accommodating scatterers in a broad variety of sizes, shapes, and acoustic contrast relative to the background media. Additionally, this formulation …

Intelligibility Of Electrolarynx Speech Using A Novel Actuator, Brian Madden, Mark Nolan, Ted Burke, James Condron, Eugene Coyle

Conference Papers

During voiced speech, the larynx provides quasi-periodic acoustic excitation of the vocal tract. Following a laryngectomy, some people speak using an electrolarynx which replaces the excitatory function of the absent larynx. Drawbacks of conventional electrolarynx designs include the buzzing monotonic sound emitted, the need for a free hand to operate the device, and difficulty experienced by many laryngectomees in adapting to its use. Despite these shortcomings, it remains the preferred method of speech rehabilitation for a substantial minority of laryngectomees. In most electrolarynxes, mechanical vibrations are produced by a linear electromechanical actuator, the armature of which percusses against a metal …

Final Design Report: Vibration Table For Cvbt- Vt4 Design Team, Thomas Bevan, Matthew Laurino

Mechanical Engineering

CVBT (Center for Vocational Building Technology) teaches villagers in Northeastern Thailand how to make various concrete products. Many of these products require the use of a vibration table in order to remove air and water trapped within the concrete. Removal of these voids improves the outside surface of the molded concrete, and also allows the use of a lower water to cement ratio, allowing a much stronger finished product. The currently used vibration table (VT3) has several disadvantages associated with it, which the new table (VT4) eliminates. Compared with the VT3, the VT4 has a more rigid tabletop and improved …

Adaptive Cutting Force Control For Process Stability Of Micro Ultrasonic Machining, Ala'a M. Al-Okaily

Department of Industrial and Management Systems Engineering: Dissertations, Theses, and Student Research

The growing demand for miniaturized products motivates the advancement in micromanufacturing processes research and development. Micro Ultrasonic Machining (Micro USM) is a downscaled version of a macro USM process that is developed to fabricate complex features in chemically inert, nonconductive, hard, brittle materials such as quartz, glass, and ceramics. These materials have many applications in various fields such as optics, electronics, MEMS, and biotechnology. The micro USM process stability is hard to accomplish, because it is highly influenced by the accuracy of the machining system and the variation of the process control parameters. The repeatability of micro USM machined features …

Increasing The Sensitivity Of Surface Acoustic Wave (Saw) Chemical Sensors And Other Chemical Sensing Investigations, Nina R. Smith

Theses and Dissertations

The work involves the fabrication and testing of three different surface acoustic wave (SAW) device designs, an investigation of nanowires sensitive to chemicals and preconcentrator prototypes to include with chemical sensors. The SAW chemical sensor designs include modifications to a basic SAW device to see if the sensitivity of the SAW device is increased. The modifications consist of etched trenches along the propagation field, coating the device with carbon nanotubes (CNTs) under the chemically sensitive layer and coating CNTs on top of the chemically sensitive layer. SAW devices are coated with Nafion®, a polymer sensitive to ethanol. The tests indicate …

Adaptive Control Applied To The Cal Poly Spacecraft Attitude Dynamics Simulator, Matthew C. Downs

Master's Theses

The goal of this thesis is to use the Cal Poly Spacecraft Attitude Dynamics Simulator to provide proof of concept of two adaptive control theories developed by former Cal Poly students: Nonlinear Direct Model Reference Adaptive Control and Adaptive Output Feedback Control. The Spacecraft Attitude Dynamics Simulator is a student-built air bearing spacecraft simulator controlled by four reaction wheels in a pyramidal arrangement. Tests were performed to determine the effectiveness of the two adaptive control theories under nominal operating conditions, a “plug-and-play” spacecraft scenario, and under simulated actuator damage. Proof of concept of the adaptive control theories applied to attitude …

Ab-10-C037: Effects Of Noise From Building Mechanical Systems On Elementary School Student Achievement, Lauren M. Ronsse, Lily M. Wang

Durham School of Architectural Engineering and Construction: Faculty Publications

This project seeks to determine what relationship, if any, exists betweenbackground noise levels in elementary classrooms due to the building mechanicalsystems and student performance on achievement tests. Previous research inclassroom acoustics has clearly identified that lower background noise levelsresult in higher speech intelligibility which is crucial for the learning process;however, there is a lack of data correlating lower noise levels to improved studentachievement scores. For this study, background noise level measurements were madein 14 elementary schools in a public school system in Council Bluffs, Iowa, USA.The measurements were made in unoccupied classrooms with the central buildingmechanical systems activated. Second and …

Ab-10-018: The Effects Of Noise From Building Mechanical Systems With Tonal Components On Human Performance And Perception (1322-Rp), Erica E. Ryherd, Lily M. Wang

Durham School of Architectural Engineering and Construction: Faculty Publications

This study investigated the effects of noise from building mechanical systems with tonal components on human task performance and perception. Six different noise conditions based on in-situ measurements were reproduced in an office-like setting; all were set to approximately the same sound level (47 dBA) but could have one particular tonal frequency (120 Hz, 235 Hz, or 595 Hz) at one of two tonal prominence ratios (5 or 9). Thirty participants were asked to complete typing, grammatical reasoning, and math tasks plus subjective questionnaires, while being exposed for approximately 1 hour to each noise condition. Results show that the noise …

Ab-10-017: Combined Effects Of Noise And Temperature On Human Comfort And Performance (1128-Rp), Dale Tiller, Lily M. Wang, Amy Musser, Matthew Radik

Durham School of Architectural Engineering and Construction: Faculty Publications

This paper summarizes results from an experiment designed to investigate the combined effects of noise and temperature on human thermal comfort and task performance. Thirty subjects (16 females, 14 males) were exposed to all combinations of five thermal conditions (PMV +1 [79.6°F:26.4°C], PMV +0.5 [75.8°F:24.3°C], PMV 0 [72.1°F:22.3°C], PMV -0.5 [68.3°F:20.2°C], and PMV -1 [64.6°F:18.1°C]), three RC noise levels (RC-30, RC-40, and RC-50), and two sound qualities (neutral and rumbly): all sounds mimicked noise from building ventilation systems. After a one-hour adaptation period at each condition, subjects rated their thermal comfort using the ASHRAE Thermal Comfort Scale and the Tenant …

Ab-10-019: Human Performance And Perception-Based Evaluations Of Indoor Noise Criteria For Rating Mechanical System Noise With Time-Varying Fluctuations (1322-Rp), Lily M. Wang, Cathleen C. Novak

Durham School of Architectural Engineering and Construction: Faculty Publications

The goal of this study was to investigate the effects of noise from building mechanical systems with time-varying fluctuations on human task performance and perception, and to determine how well current indoor noise rating methods account for this performance and perception. Six different noise conditions with varying degrees of time-varying fluctuations, many focused in the low frequency rumble region, were reproduced in an office-like setting. Thirty participants were asked to complete typing, grammatical reasoning, and math tasks plus subjective questionnaires, while being exposed for approximately one hour to each noise condition. Results show that the noise conditions with higher sound …

Electro-Osmotic Flow Over A Charged Superhydrophobic Surface, Hui Zhao

Mechanical Engineering Faculty Research

Bubbles can be trapped inside textured structures such as grooves, forming a superhydrophobic surface. A superhydrophobic surface has a large effective hydrodynamic slip length compared to a smooth hydrophobic surface and holds the promise of enhancing electrokinetic flows that find many interesting applications in microfluidics. However, recent theoretical studies suggested that electro-osmotic flows over a weakly charged superhydrophobic surface

the zeta potential of the surface is smaller than the thermal potential (25 mV) can only be enhanced when liquid-gas interfaces are charged [T. M. Squires, Phys. Fluids 20, 092105 (2008); Bahga et al., J. Fluid Mech. 644, 245 (2010)]. So …