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Full-Text Articles in Mechanical Engineering

Multiple Scales Of Beach Morphodynamic Processes: Measurements And Modelling, Jun Cheng Nov 2015

Multiple Scales Of Beach Morphodynamic Processes: Measurements And Modelling, Jun Cheng

Graduate Theses and Dissertations

Multiple scales of beach morphodynamic processes ranging from those of wave-breaking induced turbulence, individual wave, storm, seasonal, to inter-annual are examined in this dissertation based on both laboratory and field data. These processes were simulated using process-based numerical models and data-driven models.

At a microscale, separating turbulence from orbital motion under breaking waves in the surf zone is essential to understanding wave-energy dissipation. Velocity data under monochromatic and random waves in the large-scale sediment transport facility (LSTF) were analyzed. Moving averaging provides a simple method for extracting turbulence from velocity measurements under random breaking waves collected at a reasonably high ...


Corrosion Of Steel In Submerged Concrete Structures, Michael Thomas Walsh Nov 2015

Corrosion Of Steel In Submerged Concrete Structures, Michael Thomas Walsh

Graduate Theses and Dissertations

This investigation determined that severe corrosion of steel can occur in the submerged portions of reinforced concrete structures in marine environments. Field studies of decommissioned pilings from actual bridges revealed multiple instances of strong corrosion localization, showing appreciable local loss of steel cross-section. Quantitative understanding of the phenomenon and its causes was developed and articulated in the form of a predictive model. The predictive model output was consistent with both the corrosion rate estimates and the extent of corrosion localization observed in the field observations. The most likely explanation for the observed phenomena that emerged from the understanding and modeling ...


Kinematic Control Of Redundant Mobile Manipulators, Mustafa Mashali Nov 2015

Kinematic Control Of Redundant Mobile Manipulators, Mustafa Mashali

Graduate Theses and Dissertations

A mobile manipulator is a robotic arm mounted on a robotic mobile platform. In such a system, the degrees of freedom of the mobile platform are combined with that of the manipulator. As a result, the workspace of the manipulator is substantially extended. A mobile manipulator has two trajectories: the end-effector trajectory and the mobile platform trajectory. Typically, the mobile platform trajectory is not defined and is determined through inverse kinematics. But in some applications it is important to follow a specified mobile platform trajectory. The main focus of this work is to determine the inverse kinematics of a mobile ...


Heat Transfer Analysis Of Slot Jet Impingement Onto Roughened Surfaces, Rashid Ali Alshatti Nov 2015

Heat Transfer Analysis Of Slot Jet Impingement Onto Roughened Surfaces, Rashid Ali Alshatti

Graduate Theses and Dissertations

The effect of surface roughness on jet impingement heat transfer was investigated in this research. A numerical analysis was conducted for free surface slot jet impinging normally onto a heated plate. Six different geometries and three different plate materials were investigated. The cooling fluid used for the analysis was water, and the flow was laminar with a range of Reynolds number (Re) from 500 to 1000. Temperature distribution, local and average heat transfer coefficient, and local and average Nusselt number were presented for each case.

The steady state heat transfer results show that the increase in Reynolds number (Re) increases ...


Use Of Fdm Components For Ion Beam And Vacuum Applications, Eric Miguel Tridas Nov 2015

Use Of Fdm Components For Ion Beam And Vacuum Applications, Eric Miguel Tridas

Graduate Theses and Dissertations

This study focuses on novel approaches to the modeling and construction of devices used in ion beam and vacuum systems. Turbulent computational fluid dynamics simulations were performed to model the air flow into an ion funnel system. The results of these simulations were coupled one-way with electrodynamics simulations of the fields generated by the ion funnel. Using the turbulence kinetic energy (k), a spatially varying estimation of the fluctuating component of the velocity field was calculated. These resulting simulations more accurately predicted the ion transmission through the system. Using fused deposition modeling (FDM) novel construction methods for the ion funnel ...


The Development Of A Fluorescence-Based Reverse Flow Injection Analysis (Rfia) Method For Quantifying Ammonium At Nanomolar Concentrations In Oligotrophic Seawater, William Abbott Nov 2015

The Development Of A Fluorescence-Based Reverse Flow Injection Analysis (Rfia) Method For Quantifying Ammonium At Nanomolar Concentrations In Oligotrophic Seawater, William Abbott

Graduate Theses and Dissertations

The goal of this thesis was to adopt a reverse flow injection analysis (rFIA) technique to the fluorometric analysis of the reaction o-phthaldialdehyde (OPA) with ammonium, allowing accurate measurements of ammonium concentrations lower than the detection limit of the widely used indophenol blue (IPB) colorimetric method while accounting for the background fluorescence of seawater. Ammonium is considered an essential nutrient for primary productivity, especially in the nutrient depleted surface ocean where as the most reduced form of dissolved inorganic nitrogen, it is readily assimilated via metabolic pathways. Challenges in the quantification of ammonium require more sensitive analytical techniques for ...


Design, Fabrication And Analysis Of A Paver Machine Push Bar Mechanism, Mahendra Palnati Nov 2015

Design, Fabrication And Analysis Of A Paver Machine Push Bar Mechanism, Mahendra Palnati

Graduate Theses and Dissertations

Now-a-days, the major challenge that’s being faced by the concrete industry is the cleaning of concrete handling equipment. Concrete consists of aggregates, which harden with time, and the transportation of concrete mixture within the plant is a significant problem. This will not only increase the overall maintenance cost, but will lead to loss of raw materials, affect the rate of production, and reduce the lifetime of concrete handling equipment.

The present study focuses on the design and implementation of an adaptive cleaning mechanism in the concrete industry and its importance in achieving efficient cleaning, which is tested to verify ...


Passive Symmetry In Dynamic Systems And Walking, Haris Muratagic Oct 2015

Passive Symmetry In Dynamic Systems And Walking, Haris Muratagic

Graduate Theses and Dissertations

The ubiquitous nature of symmetry lends itself to be taken for granted, however the breath of research on symmetry encompasses several disciplines. In engineering, studies centered on symmetry often address issues in dynamic systems theory, robotics, and gait rehabilitation. This thesis presents findings on two specific topics dealing with passively induced symmetry; dissimilar rotating systems and human gait. Past studies on passive symmetry in dynamic systems often incorporate physical coupling or a controller. This thesis presents a technique to passively induce symmetry between two dissimilar systems that are not physically connected. This work also presents a human gait study consisting ...


Measuring Polydimethylsiloxane (Pdms) Mechanical Properties Using Flat Punch Nanoindentation Focusing On Obtaining Full Contact, Federico De Paoli Oct 2015

Measuring Polydimethylsiloxane (Pdms) Mechanical Properties Using Flat Punch Nanoindentation Focusing On Obtaining Full Contact, Federico De Paoli

Graduate Theses and Dissertations

In this research, the materials used were the Polydimethylsiloxane (PDMS) polymers. PDMS mechanicals properties were measured using a customized version of the nanoindentation test using a flat punch tip. The method is proposed in Chapter 3 and it is used to calculate the elastic modulus of different PDMS samples. The samples tested were both produced specifically for this research and available in the laboratory’s storage. They all present different levels of cross-linking degree.

It is quite common to not have full contact between the cylindrical flat punch and the sample because of the unavoidable tilt. The new method guarantees ...


Design Of Shape Morphing Structures Using Bistable Elements, Ahmad Alqasimi Oct 2015

Design Of Shape Morphing Structures Using Bistable Elements, Ahmad Alqasimi

Graduate Theses and Dissertations

This dissertation presents new concepts and methodology in designing shape-morphing structures using bistable elements. Developed using the Pseudo-Rigid-Body Model (PRBM), linear bistable compliant mechanism elements produce predictable and controllable length changes. Step-by-step design procedures are developed to guide the design process of these bistable elements. Two different examples of Shape-Morphing Space Frames (SMSFs) were designed and prototyped utilizing the bistable linear elements in a single-layer grid, in addition to flexures and rigid links, to morph a cylindrical space frame into both a hyperbolic and a spherical space frame. Moreover, bistable unit-cell compliant-mechanism elements were also developed to morph a compact ...


Ductility And Use Of Titanium Alloy And Stainless Steel Aerospace Fasteners, Jarrod Talbott Whittaker Sep 2015

Ductility And Use Of Titanium Alloy And Stainless Steel Aerospace Fasteners, Jarrod Talbott Whittaker

Graduate Theses and Dissertations

The main purpose of this thesis is to investigate the ductility and application of titanium alloys, like titanium 6Al-4V, when used in aerospace fasteners compared to more conventional stainless steel aerospace fasteners such as A286. There have been concerns raised about the safe usability of titanium 6-4 in the aerospace industry due to its lack of strain hardening. However, there is a lack of data pertaining to this concern of safe usage which this thesis aims to address. Tensile tests were conducted to find the ductility indexes of these fasteners which quantify the amount of plastic to elastic elongation. From ...


Dual 7-Degree-Of-Freedom Robotic Arm Remote Teleoperation Using Haptic Devices, Yu-Cheng Wang Sep 2015

Dual 7-Degree-Of-Freedom Robotic Arm Remote Teleoperation Using Haptic Devices, Yu-Cheng Wang

Graduate Theses and Dissertations

A teleoperated system of dual redundant manipulator will be controlled in this thesis. The robot used with the dual redundant manipulator in this thesis is Baxter. Baxter’s redundant robot arms are 7-degree-of-freedom arms. The problem that will be solved in this thesis is optimization of the 7-degree-of-freedom robot arms. The control algorithm of the 7-degree-of-freedom robot arms will be discussed and built. A simulation program will be built to test the control algorithm. Based on the control algorithm, a teleoperation system will be created for Baxter. The controller used is Omni, which is a six-joint haptic device. Omni will ...


Nanomechanical And Nanotribological Characterization Of Sub-Micron Polymeric Spheres, Himanshu Kumar Verma Sep 2015

Nanomechanical And Nanotribological Characterization Of Sub-Micron Polymeric Spheres, Himanshu Kumar Verma

Graduate Theses and Dissertations

Friction between nanoscale objects has been a subject of great interest and intense research effort for the last two decades. However, the vast majority of the work done in this area has focused upon the sliding friction between two rigid, atomically smooth surfaces. Thus the parameter most explored has been the corrugation in the atomic potentials and how this affects the force required to slide one object across another. In truth, many nanoscale objects whose translation force is of practical interest are more spherical in nature. We hypothesize that the factors that determine the translation force will be related, not ...


Mechanical Properties Of Laser-Sintered-Nylon Diamond Lattices, Clayton Neff Jul 2015

Mechanical Properties Of Laser-Sintered-Nylon Diamond Lattices, Clayton Neff

Graduate Theses and Dissertations

Additive manufacturing offers a manufacturing technique to produce complex geometry prototypes at a rapid pace and low cost. These advantages advocate additive manufacturing for the design and production of cellular structures. Cellular structures are interesting because they contain a large amount of porosity (void space of air) to manifest a lightweight structure. Designs of cellular structures generate a periodic pattern; often of complex geometry, called a lattice.

There has been a significant amount of research to maximize specific stiffness of lattice structures but little to evaluate low-stiffness lattices. Low-stiffness structures benefit energy absorbance through bending of the lattice. This research ...


An Experimental Study On Passive Dynamic Walking, Philip Andrew Hatzitheodorou Mar 2015

An Experimental Study On Passive Dynamic Walking, Philip Andrew Hatzitheodorou

Graduate Theses and Dissertations

In this study, a previously designed passive dynamic walker (PDW) is built out of aluminum and plastic. The aim of the study was to produce an asymmetrical PDW and to compare the results to a computer simulation to validate the mathematical model. It also aimed at identifying the limitations of using additive manufacturing to create components for a PDW as well as gain insights on asymmetric systems.

Beginning with a five mass kneed model, parameters were varied to produce up to a nine mass kneed model solution. The nine mass model allows more variability in added mass locations and separates ...


A Technical And Economic Comparative Analysis Of Sensible And Latent Heat Packed Bed Storage Systems For Concentrating Solar Thermal Power Plants, Jamie Trahan Mar 2015

A Technical And Economic Comparative Analysis Of Sensible And Latent Heat Packed Bed Storage Systems For Concentrating Solar Thermal Power Plants, Jamie Trahan

Graduate Theses and Dissertations

Though economically favorable when compared to other renewable energy storage technologies, thermal energy storage systems for concentrating solar thermal power (CSP) plants require additional cost reduction measures to help transition CSP plants to the point of grid-parity. Thermocline packed bed storage is regarded as one potential low cost solution due to the single tank requirement and low cost storage media. Thus sensible heat storage (SHS) and latent heat storage (LHS) packed bed systems, which are two thermocline varieties, are frequently investigated. LHS systems can be further classified as single phase change material (PCM) systems or cascaded systems wherein multiple PCMs ...


Carbon Dioxide (Co2) Emissions, Human Energy, And Cultural Perceptions Associated With Traditional And Improved Methods Of Shea Butter Processing In Ghana, West Africa, Emily Adams Mar 2015

Carbon Dioxide (Co2) Emissions, Human Energy, And Cultural Perceptions Associated With Traditional And Improved Methods Of Shea Butter Processing In Ghana, West Africa, Emily Adams

Graduate Theses and Dissertations

The shea tree is indigenous to 21 countries in Sub-Saharan Africa and provides nuts from which oil (referred to as butter) can be extracted. Shea butter production in the Northern Region of Ghana is of socioeconomic importance to female processors who practice shea production. This study quantified the environmental effects of shea processing from carbon dioxide emissions and the human energy expended through the traditional, improved, and centralized methods of shea processing. Par-boiling accounted for up to 88% of total carbon dioxide emissions throughout the entire shea butter production process. A difference of 2.5(CO2 (kg))/(Shea butter ...


The Development Of An Adaptive Driving Simulator, Sarah Marie Tudor Mar 2015

The Development Of An Adaptive Driving Simulator, Sarah Marie Tudor

Graduate Theses and Dissertations

The ability to drive a car is an important skill for individuals with a spinal cord injury to maintain a high quality of life, particularly their freedom and independence. However, driving with a physical disability often requires the installation of an adaptive driving system to control steering, gas, and braking. The two main types of adaptive driving controls are mechanical and electrical, also known as drive by wire (DBW). DBW controls work by converting electric signals to mechanical actuators. Driving simulators are useful tools for adaptive driving systems because they allow users to test different control devices, to practice driving ...


Viability Of Bismuth As A Green Substitute For Lead In Jacketed .357 Magnum Revolver Bullets, Joel A. Jenkins Mar 2015

Viability Of Bismuth As A Green Substitute For Lead In Jacketed .357 Magnum Revolver Bullets, Joel A. Jenkins

Graduate Theses and Dissertations

In seeking to develop environmentally friendly lead-free non-toxic bullets, the research ballistically evaluated the performance of copper-jacketed handgun bullets containing a pure bismuth core. The lead was first removed from 140 grain HornadyTM XTP® bullets of 38 caliber (.357 diameter) by melting. The empty jackets were then refilled with pure bismuth, including the forming of a correctly sized hollow-point cavity. Due to the lower density of bismuth as compared to lead, the bismuth-cored bullets consistently weighed 125 gains. Conveniently this allowed direct comparison to commercially available 125 grain HornadyTM XTP® lead-cored bullets of 38 caliber. Both bismuth-cored and ...


Synthesis, Characterization, And Electrochemical Properties Of Polyaniline Thin Films, Soukaina Rami Mar 2015

Synthesis, Characterization, And Electrochemical Properties Of Polyaniline Thin Films, Soukaina Rami

Graduate Theses and Dissertations

Conjugated polymers have been used in various applications (battery, supercapacitor, electromagnetic shielding, chemical sensor, biosensor, nanocomposite, light-emitting-diode, electrochromic display etc.) due to their excellent conductivity, electrochemical and optical properties, and low cost. Polyaniline has attracted the researchers from all disciplines of science, engineering, and industry due to its redox properties, environmental stability, conductivity, and optical properties. Moreover, it is a polymer with fast electroactive switching and reversible properties displayed at low potential, which is an important feature in many applications. The thin oriented polyaniline films have been fabricated using self-assembly, Langmuir-Blodgett, in-situ self-assembly, layer-by-layer, and electrochemical technique. The focus of ...


Use Of Anaerobic Adhesive For Prevailing Torque Locking Feature On Threaded Product, Alan Hernandez Jan 2015

Use Of Anaerobic Adhesive For Prevailing Torque Locking Feature On Threaded Product, Alan Hernandez

Graduate Theses and Dissertations

The purpose of this research is to determine if anaerobic adhesive can be used as a prevailing torque locking feature. Maintaining preload in critical joints is the usual standard that anaerobic adhesives are held to in aerospace and other industry. To test if anaerobic adhesive can be used as a prevailing torque locking feature a test procedure was developed and implemented to measure the removal torque of threaded fasteners after an allotted cure time. In total, 191 threaded fasteners of different material and coatings were tested in the unseated and seated states with various strengths and varieties of anaerobic adhesive ...


Experimental Investigation Of Encapsulated Phase Change Materials For Thermal Energy Storage, Tanvir E. Alam Jan 2015

Experimental Investigation Of Encapsulated Phase Change Materials For Thermal Energy Storage, Tanvir E. Alam

Graduate Theses and Dissertations

Thermal energy storage (TES) is one of the most attractive and cost effective solutions to the intermittent generation systems like solar, wind and other renewable sources, compared to alternatives. It creates a bridge between the power supply and demand during peak hours or at times of emergency to ensure the continuous supply of energy. Among all the TES systems, latent heat thermal energy storage (LHTES) draws lots of interests as it has high energy density and can store or retrieve energy isothermally. Two major technical challenges associated with the LHTES are low thermal conductivity of the phase change materials (PCMs ...


A Planar Pseudo-Rigid-Body Model For Cantilevers Experiencing Combined Endpoint Forces And Uniformly Distributed Loads Acting In Parallel, Philip James Logan Jan 2015

A Planar Pseudo-Rigid-Body Model For Cantilevers Experiencing Combined Endpoint Forces And Uniformly Distributed Loads Acting In Parallel, Philip James Logan

Graduate Theses and Dissertations

This dissertation describes the development and effectiveness of a mathematical model used to predict the behavior of cantilever beams whose loading conditions include parallel combinations of evenly distributed loads and endpoint forces. The large deflection of cantilever beams has been widely studied. A number of models and mathematical techniques have been utilized in predicting the endpoint path coordinates and load-deflection relationships of such beams. The Pseudo-Rigid-Body Model (PRBM) is one such method which replaces the elastic beam with rigid links of a parameterized pivot location and torsional spring stiffness. In this paper, the PRBM method is extended to include cases ...


Self-Assembly Kinetics Of Microscale Components: A Parametric Evaluation, Jose Miguel Carballo Jan 2015

Self-Assembly Kinetics Of Microscale Components: A Parametric Evaluation, Jose Miguel Carballo

Graduate Theses and Dissertations

The goal of the present work is to develop, and evaluate a parametric model of a basic microscale Self-Assembly (SA) interaction that provides scaling predictions of process rates as a function of key process variables. At the microscale, assembly by “grasp and release” is generally challenging. Recent research efforts have proposed adapting nanoscale self-assembly (SA) processes to the microscale. SA offers the potential for reduced equipment cost and increased throughput by harnessing attractive forces (most commonly, capillary) to spontaneously assemble components. However, there are challenges for implementing microscale SA as a commercial process. The existing lack of design tools prevents ...


A Numerical And Experimental Investigation Of Flow Induced Noise In Hydraulic Counterbalance Valves, Mutasim Mohamed Elsheikh Jan 2015

A Numerical And Experimental Investigation Of Flow Induced Noise In Hydraulic Counterbalance Valves, Mutasim Mohamed Elsheikh

Graduate Theses and Dissertations

The main objective of this study is to explore the complex fluid flow phenomena that result in the generation of a high frequency noise in counterbalance valves through an experimental and numerical investigation of the flow. Once the influence of the different components involved in noise generation is established, a secondary objective is the introduction of design modifications that eliminate the undesired effect without altering the operation envelope or the performance of the valve.

A hydraulic test bench was used to carry out an experimental investigation of the noise generation process. A computer based data acquisition system was used to ...