Engineering Commons^™

Simulations Of Diffusion Driven Phase Evolution In Heterogenous Solids, Subramanya Gautam Sadasiva

Open Access Dissertations

With reduction in size, ever greater operational demands are placed on electronics components at all levels of the device, starting from the transistor level to the level of the package and the solder interconnects. Concurrently, there has been a move to more complicated materials systems in order to meet health and environmental guidelines. These trends of reducing size, increasing loads have increased the necessity to understand the mechanisms of the failure. ^ As the length scales are reduced, it becomes increasingly important to consider interfacial and micro-structural effects that can be safely ignored at larger length scales owing to the …

Designing A Sustainable And Transferable Inventory Management System For Small Healthcare Facilities, Shree Frazier

Open Access Theses

Managing the costs of supplies within healthcare facilities has been a task that has plagued the health industry for many years. Many facilities are accustomed to using a par system approach. This involves bringing an inventory item to an amount sufficient for daily operation. This method often requires daily inspection by a healthcare worker, which reduces his/her time spent performing value added tasks. Employees at small healthcare facilities have multiple responsibilities, therefore they cannot afford to spend much time on inventory management. A proposed approach is the Kanban method, which allows for strict monitoring of inventory items without the need …

Heavy Vehicle Rollover Propensity At Roundabouts On Highspeed Roads, Thomas M. Hall

Open Access Theses

There is a recent trend of building roundabouts on high-speed roads, often with significant heavy vehicle traffic. With the increased presence of trucks on roundabouts, the issue of rollover has become a concern. Geometric features that allow excessive speed on the approach and entry have been connected to rollover, as well as sudden changes in crossfall and radius. However, the effect on the rollover threshold of changing the roundabout's circulatory superelevation is not fully understood. The impact of aggressive driving behaviors, as displayed by high driver speed far from the roundabout, as well as errors that are manifested by the …

Studies Of Systems With Nonholonomic Constraints: The Segway And The Chaplygin Sleigh, Joseph Troy Lee Tuttle

Open Access Theses

In this thesis, two systems with nonholonomic systems are investigated: the Segway and the Chaplygin sleigh. Using Lagrangian mechanics, the constrained nonlinear equations of motion for both systems are derived. By use of the nullspace of the constraint matrices, the unconstrained equations of motion can be obtained. For the Segway, these equations are linearized about a zero equilibrium state, placed into state space form and decoupled. A feedback controller is designed about the velocity and heading angle rate reference commands. To compare to the real data from the built Segway, measurement noise was also included in the model. Experimental data …

Piston / Cylinder Interface Of Axial Piston Machines – Effect Of Piston Micro-Surface Shaping, Ashley M. Wondergem

Open Access Theses

Axial piston machines are widely used in current industries such as aerospace, agriculture, automotive, heavy machinery, military, etc. Thus new cost-effective and highly efficient designs with better performance and reliability are needed. These new, high efficient pumps and motors will also aid in new applications such as hybrid hydrostatic transmissions and displacement controlled actuation. The aim of this work is to study how to reduce the energy dissipation (increase efficiency) while also improving the load carrying ability of the fluid film between the piston and the cylinder through surface shaping of the piston over a wide range of operating conditions. …

Measurements Of Entropy-Layer Instabilities Over Cone-Ogive-Cylinders At Mach 6, Roger T Greenwood

Open Access Dissertations

Predicting the onset of boundary layer transition is critical in hypersonic flight. To improve transition prediction methods, it is necessary to understand the underlying instability mechanisms that cause transition. Entropy-layer instabilities are of particular interest in the design of blunt reentry vehicles and other blunt supersonic and hypersonic vehicles. Entropy-layer instabilities from outside the boundary layer may enter the boundary layer and have a significant effect on transition. There is little experimental data for entropy-layer instabilities. ^ Experimental measurements of what appear to be entropy-layer instabilities have been made in the Boeing/AFOSR Mach-6 Quiet Tunnel (BAM6QT) using surface pressure transducers …

Indoor Acoustic Mapping And Geolocation, Thomas Shyy

Open Access Theses

The Global Positioning System (GPS) is widely used in navigations of flights, vehicles and travelers nowadays. However, the signals are not always available and there are some cases where the receptions of the GPS signal can be lost because of the presence of urban canyons, buildings, tunnels and forests. Another down side for the GPS is that indoor positioning can be really difficult because of the greater signal interference from the indoor.

On the other hand, the concept of echolocation has also been used for positioning purposes. Echolocation offers a promising approach to improve the quality of life of people …

Tunable Impedance Matching Network Fundamental Limits And Pracitical Considerations, Wesley N. Allen

Open Access Dissertations

As wireless devices continue to increase in utility while decreasing in dimension, design of the RF front-end becomes more complex. It is common for a single handheld device to operate on a plethora of frequency bands, utilize multiple antennae, and be subjected to a variety of environments. One complexity in particular which arises from these factors is that of impedance mismatch. Recently, tunable impedance matching networks have begun to be implemented to address this problem. ^ This dissertation presents the first in-depth study on the frequency tuning range of tunable impedance matching networks. Both the fundamental limitations of ideal networks …

Thermal Efficiency And Emission Analysis Of Advanced Thermodynamic Strategies In A Multi-Cylinder Diesel Engine Utilizing Valve-Train Flexibility, Chuan Ding

Open Access Dissertations

Stringent emission regulations and a growing demand for fossil fuel drive the development of new technologies for internal combustion engines. Diesel engines are thermally efficient but require complex aftertreatment systems to reduce tailpipe emissions of unburned hydrocarbons (UHC), particulate matter (PM), and nitrogen oxides (NOx). These challenges require research into advanced thermodynamic strategies to improve thermal efficiency, control emission formation and manage exhaust temperature for downstream aftertreatment. The optimal performance for different on-road conditions is analyzed using a fully flexible valve-train on a modern diesel engine. The experimental investigation focuses on thermal management during idling and high-way cruise conditions. In …

A Qualitative Study Of Problematic Reasonings Of Undergraduate Electrical Engineering Students In Continuous Time Signals And Systems Courses, Farrah Fayyaz

Open Access Dissertations

Continuous Time Signals and Systems is a core course in the undergraduate electrical engineering curriculum. The topics covered in this course are difficult to learn conceptually because a significant number of topics are abstract, disconnected from a student's daily life, and make extensive use of mathematical modeling and formulas. Engineering educators have put in significant effort to design effective educational strategies for this course; however, there remained a gap in qualitative understanding of students' reasonings associated with difficulties in conceptual learning of the course content. This study aims to fill this gap by identifying problematic reasonings of undergraduate electrical engineering …

Assessment Of Irrigation Use On Crop Yield And Water Supplies In The Midwestern U.S., Wei-Chih Chen

Open Access Dissertations

Climate plays an important role in many aspects of hydrological and agricultural systems. Temperature and precipitation are usually the main forcing inputs for hydrological and agricultural simulations, while wind effect has generally been neglected in previous research. Wind speed is, however, an important factor for many physical processes, including evaporation from soil, and transpiration from plants. In order to investigate how climate variability impacts agricultural production, there are three hypotheses addressed in this dissertation. Hypothesis 1 is that the representation of changing wind speed will play an important role in the simulation of hydrological processes, and that the effect of …

Algorithm-Circuit Co-Design For Detecting Symptomatic Patterns In Biological Signals, Himanshu Markandeya

Open Access Dissertations

The advancement in scaled Silicon technology has accelerated the development of a wide range of applications in various fields including medical technology. It has immensely contributed to finding solutions for monitoring general health as well as alleviating intractable disorders in the form of implantable and wearable systems. This necessitates the development of energy efficient and functionally efficacious systems. This thesis has explored the algorithm-circuit co-design approach for developing an energy efficient epileptic seizure detection processor which could be used for implantable epilepsy prosthesis. Novel wavelet transform based algorithms are proposed for accurate detection of epileptic seizures. Energy efficient techniques at …

Modeling And Characterization Of Non-Ideal Effects In High-Performance Rf Mems Tuners, Juan Zeng

Open Access Dissertations

The emerging standards for the next-generation wireless communication system demand for multi-band RF front-ends. Reconfigurable RF devices based on MEMS technology have emerged with the potential to significantly reduce the system complexity and cost. Robust operation of RF MEMS tuners under the non-ideal effects due to fabrication uncertainties and environmental variations is critical in achieving reliable RF MEMS reconfigurable devices. Therefore, it is essential to model and characterize these non-ideal effects, and further to alleviate these non-ideal effects by design optimization.^ In this dissertation, the effects of non-perfect anchor support, residual stress, and temperature sensibility of MEMS tuners have been …

Capacity-Related Driver Behavior On Modern Roundabouts Built On High-Speed Roads, Shaikh Ahmad

Open Access Theses

The objective of this thesis was to investigate the factors that affect capacity-related driver behavior on modern roundabouts built on high-speed roads. The capacity of roundabouts is strongly affected by the behavior of drivers as represented by critical headway (critical gap) and follow-up headway (follow-up time). The effects of heavy vehicles (single-unit truck, bus, and semi-trailer) and area type (rural or urban) on roundabout capacity were investigated by comparing the critical headways for roundabouts located on high-speed and low-speed roads. The effects of nighttime conditions (in the presence of street lighting) were also considered. Data were collected using the Purdue …

Strategies For The Replacement Of Historic Bridge Guardrails, Adam J. Clauss

Open Access Theses

Bridges that are designated historic present a special challenge to bridge engineers whenever rehabilitation work or improvements are made to the bridges. Federal and state laws protect historically significant bridges, and railings on these bridges can be subject to protection because of the role they play in aesthetics. Unfortunately, original railings on historic bridges do not typically meet current crash-test requirements and typically do not meet current standards for railing height and size of permitted openings. The objective of this study is to develop strategies that can be used to address existing railings on historic bridges and to develop solutions …

Wi-Fi Real Time Location Systems, Benjamin A. Doll

Open Access Theses

This thesis objective was to determine the viability of utilizing an untrained Wi-Fi real time location system as a GPS alternative for indoor environments. Background research showed that GPS is rarely able to penetrate buildings to provide reliable location data. The benefit of having location information in a facility and how they might be used for disaster or emergency relief personnel and their resources motivated this research. A building was selected with a well-deployed Wi-Fi infrastructure and its untrained location feature was used to determine the distance between the specified test points and the system identified location. It was found …

A Computational Analysis Of The Aerodynamic And Aeromechanical Behavior Of The Purdue Multistage Compressor, David Monk

Open Access Theses

Compressor design programs are becoming more reliant on computational tools to predict and optimize aerodynamic and aeromechanical behavior within a compressor. Recent trends in compressor development continue to push for more efficient, lighter weight, and higher performance machines. To meet these demands, designers must better understand the complex nature of the inherently unsteady flow physics inside of a compressor. As physical testing can be costly and time prohibitive, CFD and other computational tools have become the workhorse during design programs.

The objectives of this research were to investigate the aerodynamic and aeromechanical behavior of the Purdue multistage compressor, as well …

Solar Sail Trajectory Design In The Earth-Moon Circular Restricted Three Body Problem, Ashwati Das

Open Access Theses

The quest to explore the Moon has helped resolve scientific questions, has spurred leaps in technology development, and has revealed Earth's celestial companion to be a gateway to other destinations. With a renewed focus on returning to the Moon in this decade, alternatives to chemical propulsion systems are becoming attractive methods to efficiently use scarce resources and support extended mission durations. Thus, an investigation is conducted to develop a general framework, that facilitates propellant-free Earth-Moon transfers by exploiting sail dynamics in combination with advantageous transfer options offered in the Earth-Moon circular restricted multi-body dynamical model. Both periodic orbits in the …

Application Of Integer Quadratic Programming To Detection Of High-Dimensional Wireless Systems, Jamal Yousuf Alsawalhi

Open Access Dissertations

This work introduces a novel permanent-magnet synchronous machine (PMSM) architecture that employs rotational asymmetry to increase the torque density output in constant power variable speed applications. A population based multi-objective design optimization algorithm is used to design and analyze the new machine topology. A number of design studies are presented to show that the proposed machine structure outperforms a conventional PMSM machine. Validation of the analytical machine design model using a three dimensional finite element analyses is performed and the results are presented. Finally, a case study in which a hybrid electric bus traction motor is designed is presented.

Cnt-Reinforced Polymer Nanocomposite By Molecular Dynamics Simulations, Yaeji Kim

Open Access Dissertations

Polymer matrix composites reinforced with carbon nanotubes (CNTs) have received significant attention due to their potential for exceptional mechanical, electrical, thermal and optical properties. The enhancement of ultimate mechanical properties of CNT reinforced polymer composites is governed not just by the properties of the two phases but by dispersion of the CNTs, interactions in the interfacial region and local molecular changes in polymer due to the vicinity of the CNTs. Strong adhesive interactions between the matrix and CNT leads to good compatibility preventing the aggregation of the reinforcements and results in optimal mechanical response. Even though significant efforts have been …

Solid Amine-Boranes As High Performance Hypergolic Hybrid Rocket Fuels, Mark A. Pfeil

Open Access Dissertations

Hypergolic hybrid rockets have the potential of providing systems that are simple, reliable, have high performance, and allow for energy management. Such a propulsion system can be applied to fields that need a single tactical motor with flexible mission requirements of either high speed to target or extended loitering. They also provide the possibility for alternative fast response dynamic altitude control systems if ignition delays are sufficiently short. ^ Amines are the traditional fuel of choice when selecting a hypergolic combination as these tend to react readily with both nitric acid and dinitrogen tertroxide based oxidizers. It has been found …

Developing A Practical Wireless Monitoring Solution For A Size-Constrained, Low-Power, Biomechanical, Sports Telemetry System, Jeffery Ray King

Open Access Theses

As sport-related concussions become more prevalent, the ability to quickly and reliably assess brain injury risk is increasingly essential. Commercially-available systems exist with the goal of assessing the risk of traumatic brain injury in athletes in real-time. These systems utilize a pre-determined acceleration threshold, discarding all captured information below this arbitrary threshold. The use of an event-based model to assess the risk of traumatic brain injury has been shown to be inadequate. Therefore, these systems falsely promote "accurate" real-time communication of risk. Research conducted by the Purdue Neurotrauma Group (PNG) seeks to advance the field by developing a biomechanical sports …

Experimental Study Of Droplet Capable Conductivity Probe, Yikuan Yan

Open Access Theses

This research focus on experimentally studying the performance of the newly designed Droplet Capable Conductivity Probe (DCCP). ^ A literature review is performed to illustrate the development of current two-fluid model and interfacial area transport equation. Previous conductivity probe instrumentation is also reviewed. The limitations of current conductivity probe design are described and the necessity of developing DCCP is illustrated. ^ The concept of DCCP-2 and DCCP-4 are introduced and experiments are performed to benchmark the capability of DCCP-4.

Optical Properties Of Silicon Core/Multi-Shell Nanowires Using Fdtd And Ema Methods, Tae Kon Kim

Open Access Theses

Semiconductor nanowires are attracting intense interest as a promising material for solar energy conversion for the new-generation photovoltaic (PV) technology. In particular, silicon core/multi-shell nanowires (SiNWs) are under active investigation for PV and solar water splitting applications because they offer novel approaches for solar to electric energy or fuel conversion leading to high efficiency devices. ^ Theoretical studies using the finite-different time-domain method have been performed to investigate the optical properties of many nanostructure arrays, however, they are computationally intensive and require periodic condition, which may not be satisfied with most fabricated samples. In the present study, effective medium approximation …

Modeling Of High Pressure Radial Piston Pumps, Pulkit Agarwal

Open Access Theses

Agarwal, Pulkit. M.S.M.E., Purdue University, December 2014. Modeling of High Pressure Radial Piston Pumps. Major Professor: Andrea Vacca, School of Mechanical Engineering A comprehensive multi-domain simulation tool for investigating the operation of radial piston machines has been developed in the present study. The simulation tool is capable of analyzing the displacing action of the machine parts as well as the power losses occurring in the lubricating interfaces which makes it useful for supporting the design process of radial piston units. The reference machine analyzed in this study is a radial piston pump of rotating cam type design used for high …

Rapid Indirect Trajectory Optimization On Highly Parallel Computing Architectures, Thomas Antony

Open Access Theses

Trajectory optimization is a field which can benefit greatly from the advantages offered by parallel computing. The current state-of-the-art in trajectory optimization focuses on the use of direct optimization methods, such as the pseudo-spectral method. These methods are favored due to their ease of implementation and large convergence regions while indirect methods have largely been ignored in the literature in the past decade except for specific applications in astrodynamics. It has been shown that the shortcomings conventionally associated with indirect methods can be overcome by the use of a continuation method in which complex trajectory solutions are obtained by solving …

Dropwise Condensation Dynamics In Humid Air, Julian Eduardo Castillo Chaco

Open Access Theses

Dropwise condensation of atmospheric water vapor is important in multiple practical engineering applications. The roles of environmental factors and surface morphology/chemistry on the condensation dynamics need to be better understood to enable efficient water-harvesting, dehumidication, and other psychrometric processes. Systems and surfaces that promote faster condensation rates and self-shedding of condensate droplets could lead to improved mass transfer rates and higher water yields in harvesting applications. The thesis presents the design and construction of an experimental facility that allows visualization of the condensation process as a function of relative humidity. Dropwise condensation experiments are performed on a vertically oriented, hydrophobic …

A Dynamic Stochastic Model For Converging Inbound Air Traffic, Jun Chen

Open Access Theses

Weather accounts for the majority of congestion in the National Airspace System which highlights the importance of addressing weather uncertainty to mitigate delays, and this paper presents an effort in this direction. Firstly, a new dynamic stochastic 0-1 Integer Programming (IP) model is proposed, which models the Single Airport Ground Holding Problem (SAGHP) with respect to uncertainty in the separation between flights instead of Airport Acceptance Rate (AAR) or landing capacity. Uncertainty in separation according to different weather conditions is represented through the scenario tree by using stochastic linear programming. Considering time separation constraints instead of AAR constraints, our model …

Impact Of License Selection On Open Source Software Quality, Benjamin J. Cotton

Open Access Theses

Open source software plays an important part in the modern world, powering businesses large and small. However, little work has been done to evaluate the quality of open source software. Two different license paradigms exist within the open source world, and this study examines the difference in software quality between them. In this thesis, the author uses technical debt as a measure of software quality. Eighty open source projects (40 from each paradigm) were downloaded from the popular open source hosting website SourceForge. Using complexity, code duplication, comments, and unit test coverage as inputs to the SonarQube technical debt model, …

Effects Of Hip And Ankle Moments On Running Stability: Simulation Of A Simplified Model, Rubin C. Cholera

Open Access Theses

In human running, the ankle, knee, and hip moments are known to play different roles to influence the dynamics of locomotion. A recent study of hip moments and several hip-based legged robots have revealed that hip actuation can significantly improve the stability of locomotion, whether controlled or uncontrolled. Ankle moments are expected to also significantly affect running stability, but in a different way than hip moments. Here we seek to advance the current theory of dynamic running and associated legged robots by determining how simple open-loop ankle moments could affect running stability. We simulate a dynamical model, and compare it …