Open Access. Powered by Scholars. Published by Universities.®

Engineering Commons™

Open Access. Powered by Scholars. Published by Universities.®

Clemson University

Discipline
Keyword
Publication Year
Publication
Publication Type
File Type

Articles 1801 - 1830 of 2584

Full-Text Articles in Engineering

In Vitro Study Of Fluid Diodes In The Pulmonary Valve Position, John Porcher Dec 2011

In Vitro Study Of Fluid Diodes In The Pulmonary Valve Position, John Porcher

All Theses

Every year many people suffer from severe chronic pulmonary insufficiency. Problems that can be incurred include the valve becoming stenotic, where it inhibits antegrade flow, and incompetent, allowing retrograde flow. When either of these conditions occurs with great severity, it is often necessary for the native valve to be replaced. There are no acceptable, permanent solutions currently available for a pulmonary valve replacement. Previous research, based on regurgitant fraction and transvalvular gradient, has indicated that a fluid diode could possibly serve as a permanent valve replacement solution. This study investigated the effectiveness of a diode to reduce the workload of …

Go to article

An Early Warning Monitoring System For Cnc Spindle Bearing Failure, Andrew Werner Dec 2011

An Early Warning Monitoring System For Cnc Spindle Bearing Failure, Andrew Werner

All Theses

Equipment employed in a manufacturing environment must be able to operate as long as possible having as little downtime as possible. Therefore, maintenance is crucial in order to allow for the equipment to perform its designated tasks without failure, especially on critical systems. In a CNC machine, if the spindle fails, the machine is useless. Having the ability to detect spindle degradation to the point where a replacement spindle installation can be planned, via condition monitoring, is invaluable to a manufacturer who utilizes these types of machines.
An early warning monitoring system for CNC spindle bearing failure has been developed …

Go to article

Measuring Digital System Latency From Sensing To Actuation At Continuous 1 Millisecond Resolution, Weixin Wu Dec 2011

Measuring Digital System Latency From Sensing To Actuation At Continuous 1 Millisecond Resolution, Weixin Wu

All Theses

This thesis describes a new method for measuring the end-to-end latency between sensing and actuation in a digital computing system. Compared to previous work, which generally measures the latency at 16-33 ms intervals or at discrete events separated by hundreds of ms, our new method measures the latency continuously at 1 millisecond resolution. This allows for the observation of variations in latency over sub 1 s periods, instead of relying upon averages of measurements. We have applied our method to two systems, the ?rst using a camera for sensing and an LCD monitor for actuation, and the second using an …

Go to article

Printing Carbon Nanotube Based Supercapacitors For Packaging, Alexandra Hartman Dec 2011

Printing Carbon Nanotube Based Supercapacitors For Packaging, Alexandra Hartman

All Theses

Living in a world full of portable electronics, there is great need for energy storage devices. Currently, limitations for storage involve power inefficiencies as well as bulkiness. This is why printable charge storage devices that display good electrochemical performance are needed. It is for this reason that research into the production and packaging of carbon nanotube based super capacitors was carried out.
A super capacitor can be built by using high surface area multi-walled carbon nanotubes suspended in an ionic liquid. The two active electrodes are made from a combination of the multi-walled carbon nanotubes and an ionic liquid, ground …

Go to article

The Design Of A Haptic Device For Training And Evaluating Surgeon And Novice Laparoscopic Movement Skills, Ryan Bontreger Dec 2011

The Design Of A Haptic Device For Training And Evaluating Surgeon And Novice Laparoscopic Movement Skills, Ryan Bontreger

All Theses

As proper levels of force application are necessary to ensure patient safety, and training hours with an expert on live subjects are difficult, enhanced computer-based training is needed to teach the next generation of surgeons. Considering the role of touch in surgery, there is a need for a device capable of discerning the haptic ability of surgical trainees. This need is amplified by minimally invasive surgical techniques where a surgeon's sense of tissue properties comes not directly through their own hands but indirectly through the tools. A haptic device capable of producing a realistic range of forces and motions that …

Go to article

New Analytical Bounds On The Probability Of Code-Word Error For Convolution Codes With Viterbi Decoding, Shweta Tomar Dec 2011

New Analytical Bounds On The Probability Of Code-Word Error For Convolution Codes With Viterbi Decoding, Shweta Tomar

All Theses

New analytical bounds are developed for the probability of code-word error in a communication system with convolutional coding and soft-decision Viterbi decoding. The bounds are applicable to communications in channels with asynchronous interferers which are modeled as independent, partial-time white Gaussian interference sources. This model is often used in simulations to reflect the circumstances encountered in many packet radio communication networks. The new results include both purely analytical bounds and offline-simulation-aided bounds that permit implementation of accurate communication-link models with much lower online computational and storage requirements than are required with traditional Monte Carlo simulations of link performance. They significantly …

Go to article

Analysis And Parameterization Of The Flight Of Ember Generation Experiments, Hillary Harris Dec 2011

Analysis And Parameterization Of The Flight Of Ember Generation Experiments, Hillary Harris

All Theses

This thesis presents a study on ember flight modeling based on a series of wind tunnel experiments. The purpose of these experiments and the data collected was to provide the input conditions for an ember flight model in order to compare and validate the model predictions. An analysis was performed which determined the sensitivity of model predictions of downwind mass distribution to uncertainties in the model input parameters.
From the wind tunnel experiments, flight distances were measured and characteristic ember size distributions were obtained from the collected data. A flight model was developed based on standard models published in the …

Go to article

The Performance Of Serial, Matched-Filter Packet Acquisition Using Transmit And Receive Antenna Diversity, Shivram Ramanathan Dec 2011

The Performance Of Serial, Matched-Filter Packet Acquisition Using Transmit And Receive Antenna Diversity, Shivram Ramanathan

All Theses

The performance of serial, matched-filter acquisition is evaluated for asynchronous packet radio communications using transmit or receive antenna diversity. Transmit diversity is achieved using dual antenna transmissions of orthogonal preamble sequences and receive diversity is achieved using dual antenna reception of a single preamble sequence. Sequential test statistics are formed using non-coherent combining of the outputs from the orthogonal preamble matched-filters if transmitter diversity is used; the test statistics are formed using non coherent combining of the outputs from the preamble matched-filter in each receiver chain if receiver diversity is used. Threshold-based acquisition of the test statistics using both fixed …

Go to article

Robust Design And Monitoring Tools For Sustainable And Resilient Structural Design And Infrastructure Management, Sarah Dalton Dec 2011

Robust Design And Monitoring Tools For Sustainable And Resilient Structural Design And Infrastructure Management, Sarah Dalton

All Theses

Structural systems are subject to inherent uncertainties due to the variability in many hard-to-control `noise factors' that include but are not limited to external loads, material properties, and construction workmanship. Two design methodologies have been widely accepted in the practicing engineering realm to manage the variability associated with operational structures: Allowable Stress Design (ASD) and Load and Resistance Factor Design (LRFD). These traditional approaches explicitly recognize the presence of uncertainty; however, they do not take robustness against this uncertainty into consideration. Overlooking this robustness against uncertainty in the structural design process has two drawbacks. First, the design may not satisfy …

Go to article

The Effects Of Solvent Mixture On The Thermal And Mechanical Properties Of Solvent Cast Poly-Lactic Acid (Pla) Film, Jeremy Hughes Dec 2011

The Effects Of Solvent Mixture On The Thermal And Mechanical Properties Of Solvent Cast Poly-Lactic Acid (Pla) Film, Jeremy Hughes

All Theses

CH 1 ABSTRACT
The objective of this study was to investigate the effects of various solvents on the crystallinity and thermal expansion stability of PLA film. Three different PLA films were produced by the solvent casting technique; PLA in chloroform (PLA-C), PLA in methylene chloride (PLA-M), and PLA in methylene chloride: acetonitrile = 50: 50 (PLA-MA). The PLA-MA had higher % crystallinity, 46.15, than the PLA-C, 24.03, and the PLA-M, 14.25. With this increase in crystallinity, the PLA-MA had improved thermal expansion stability as shown by very low accumulated dimensional changes at 20-100 ¡C. Wide angle x-ray diffraction identified multiple …

Go to article

Evaluating The Usability Of System-Generated And User-Generated Passwords Of Approximately Minimum Equal Security, Sourav Bhuyan Dec 2011

Evaluating The Usability Of System-Generated And User-Generated Passwords Of Approximately Minimum Equal Security, Sourav Bhuyan

All Theses

System-generated or user-generated text-based passwords are commonly used by the users to authenticate access to their electronic assets. These passwords may vary in usability and memorability depending on the type of password generation, composition and length. However, little past research has compared usability and memorability of passwords, satisfying minimum entropy for a secure password. This study compared three password policy conditions, assigning/generating passwords of approximately equal minimum security, i.e. 6-character alphanumeric system-generated passwords, minimum 8-character restricted user-generated passwords and minimum 16-character unrestricted user-generated passwords.
The study involved 54 participants, equally divided into three groups, 18 in each password policy condition. …

Go to article

Effect Of Selected Phase Change Materials Concentration And Manufacturing Process On The Properties Of Plaster Mixture Systems, Rong Cui Dec 2011

Effect Of Selected Phase Change Materials Concentration And Manufacturing Process On The Properties Of Plaster Mixture Systems, Rong Cui

All Theses

Phase change materials (PCM) are generally used in building construction materials for their ability to absorb and release large amounts of energy when their phase change happens at their specific melting temperature. This results in a significant increase in thermal mass of the building, a reduction in temperature fluctuations and therefore a reduction in heating and cooling loads. However, in order to properly select a PCM and optimize its integration in a specific building, the properties of building construction materials enhanced with PCM must be known. This research focuses on studying the effects of the concentration of a micro-encapsulated PCM …

Go to article

Chlorine Absorption Utilizing Caustic Sodium Sulfite, Henry Mcdonald Dec 2011

Chlorine Absorption Utilizing Caustic Sodium Sulfite, Henry Mcdonald

All Theses

A scrubber was required to abate a waste stream containing chlorine gas created in the electrolytic dissolution step of the aqueous polishing process at the Mixed Oxides Fuel Fabrication Facility at Savannah River Site, South Carolina. A method of absorption that utilized caustic sodium sulfite as the scrubbing agent was studied for implementation in the process. This method was found to be highly efficient with respect to process requirements, and it was also found to provide enhanced performance over the more conventional method of chlorine scrubbing which uses only aqueous sodium hydroxide as a reagent. Sulfite provides an additional advantage …

Go to article

Fabrication And Characterization Of Multi-Functional Non-Spherical Particles Via Mechanical Deformation, Venkata Shilpa Varahagiri Dec 2011

Fabrication And Characterization Of Multi-Functional Non-Spherical Particles Via Mechanical Deformation, Venkata Shilpa Varahagiri

All Theses

Nanoparticles bridge the gap between bulk materials and molecules. They possess exciting but contrasting mechanical, chemical, magnetic and optical properties when compared to their bulk counterparts due to their shape and size. When the size of noble metal nanoparticles is reduced to less than the wavelength of light, the particles intensely absorb and scatter light at wavelengths that depend on the particle size, shape, and local dielectric environment due to Localized Surface Plasmon Resonance (LSPR) modes. Recently, plasmonic particles have been used in a wide variety of sensor and optical device applications including immunoassays and surface enhanced Raman spectroscopy substrates. …

Go to article

An Investigation Of The Application Of Phase Change Materials In Practical Thermal Management Systems, David Ewing Dec 2011

An Investigation Of The Application Of Phase Change Materials In Practical Thermal Management Systems, David Ewing

All Dissertations

This work investigates the application of alternative cooling techniques to thermal management. In the first section, this work presents models and extensive simulation studies on an alternative cooling strategy based upon phase change materials (PCMs) for the thermal management system of a LED headlight assembly. These studies have shown that properly chosen PCMs, when suspended in metal foam matrices, increased the thermal conductivity of the PCM. The increased thermal conductivity can enhance the cooling characteristics of a practical thermal management system for a LED headlight system. To further enhance the advantages of using PCMs, nanoparticle enhanced fluids (nanofluids) are desirable …

Go to article

Optimization-Based Power Management Of Hybrid Power Systems With Applications In Advanced Hybrid Electric Vehicles And Wind Farms With Battery Storage, Hoseinali Borhan Dec 2011

Optimization-Based Power Management Of Hybrid Power Systems With Applications In Advanced Hybrid Electric Vehicles And Wind Farms With Battery Storage, Hoseinali Borhan

All Dissertations

Modern hybrid electric vehicles and many stationary renewable power generation systems combine multiple power generating and energy storage devices to achieve an overall system-level efficiency and flexibility which is higher than their individual components. The power or energy management control, ``brain' of these ``hybrid' systems, determines adaptively and based on the power demand the power split between multiple subsystems and plays a critical role in overall system-level efficiency. This dissertation proposes that a receding horizon optimal control (aka Model Predictive Control) approach can be a natural and systematic framework for formulating this type of power management controls. More importantly the …

Go to article

Interfacial Force Field Parameterization Using The Dual Force Field Charmm Program For The Accurate Simulation Of Peptide-Surface Interaction, Nadeem Vellore Dec 2011

Interfacial Force Field Parameterization Using The Dual Force Field Charmm Program For The Accurate Simulation Of Peptide-Surface Interaction, Nadeem Vellore

All Dissertations

Protein adsorption to solid material surfaces is a complex phenomenon and various factors play a role in controlling these processes. Inherent limitations to understand these biological interactions using experimental approaches alone have led to the possibility of exploring these systems using computational molecular simulation methodologies. Before confidence can be placed on these computational protocols, however, rigorous validation of the applicability of these methods to accurately represent protein adsorption processes is needed. In this research, we evaluated the use of all-atom empirical force field (FF) based simulations using the CHARMM simulation program and FF for the study of peptide adsorption processes …

Go to article

Radio Frequency Micro/Nano-Fluidic Devices For Microwave Dielectric Property Characterizations, Chunrong Song Dec 2011

Radio Frequency Micro/Nano-Fluidic Devices For Microwave Dielectric Property Characterizations, Chunrong Song

All Dissertations

In this dissertation, a number of different topics in microwave dielectric property measurements have been covered by a systematic approach to the goals of development of dielectric spectroscopy and study of its high electric field effects with integrated on-chip microwave microfluidic / nanofluidic devices.
A method of parasitic effects cancellation for dielectric property measurement is proposed, analyzed, and experimentally evaluated for microwave characterization of small devices and materials that yield low intensity signals. The method dramatically reduces parasitic effects to uncover the otherwise buried signals. A high-sensitive radio frequency (RF) device is then developed and fabricated to detect small dielectric …

Go to article

Light-Emitting Nanocomposites And Novel Amorphous Polymers For Optical Applications, Kyle Gipson Dec 2011

Light-Emitting Nanocomposites And Novel Amorphous Polymers For Optical Applications, Kyle Gipson

All Dissertations

Polymeric optical materials generally are comprised of amorphous polymers that are transparent in at visible wavelengths but exhibit strong absorption bands in the near-infrared making them less useful for many optical applications. Attenuation, which is the absorption per unit length, largely results from the high vibrational energy associated with carbon-hydrogen bonds contained in the polymer backbone. Attenuation can be mitigated by optical amplification utilizing light emitting additives. Investigated in this dissertation are synthesis techniques for the fabrication of light-emitting polymer nanocomposites and their resultant thermal and rheological characteristics for potential use as polymer optical fibers or films.
Inorganic nanocrystals doped …

Go to article

Quantitative Analysis And Structural Characterization Of Carbonaceous Pitches, Sourabh Kulkarni Dec 2011

Quantitative Analysis And Structural Characterization Of Carbonaceous Pitches, Sourabh Kulkarni

All Dissertations

Both petroleum pitches and pitches derived from pure polycyclic aromatic hydrocarbons (PAHs) are oligomeric materials that can serve as precursors for a wide variety of advanced carbon materials. The goal of this study was the structural characterization and quantitative analysis of the dominant constituent oligomers and species present in these pitches.
A key requirement for such work is the ability to fractionate these complex mixtures into samples of narrow molecular weight distribution (mol wt; MWD) that can be used as standards. To this end, semicontinuous (or semibatch) dense-gas/supercritical extraction (DGE/SCE) was used to produce monomer, dimer, and trimer fractions of …

Go to article

A Formal Representation Of Mechanical Functions To Support Physics-Based Computational Reasoning In Early Mechanical Design, Chiradeep Sen Dec 2011

A Formal Representation Of Mechanical Functions To Support Physics-Based Computational Reasoning In Early Mechanical Design, Chiradeep Sen

All Dissertations

The lack of computational support to the conceptual phase of mechanical engineering design is well recognized. Function-based modeling and thinking is widely recommended in design texts as useful means for describing design concepts and using them in tasks such as solution search, problem decomposition, and design archival. Graph-based function structure models that describe a product as a network of transformative actions of material, energy, and information, are discussed as a potential tool for this purpose, but in the current state of the art, function structures are not formalized as a computational representation. Consequently, no computer tool exists with which a …

Go to article

Effect Of Relative Humidity And Temperature Control On In-Cabin Thermal Comfort State, Ali Alahmer Dec 2011

Effect Of Relative Humidity And Temperature Control On In-Cabin Thermal Comfort State, Ali Alahmer

All Dissertations

This dissertation discusses the effect of manipulating the relative humidity RH levels inside vehicular cabins on the thermal comfort and human occupants' thermal sensation. Three different techniques are used to investigate this effect. Firstly, thermodynamic and psychometric analyses are used to incorporate the effect of changing RH along with the dry bulb temperature on the human comfort window. Specifically, the study computes the effect of changing the relative humidity on the amount of heat rejected from the passenger compartment and the effect on occupants comfort zone. A practical system implementation is also discussed in terms of an evaporative cooler design. …

Go to article

Modeling And Synthesis Of Functionalized Meta-Poly(Phenylene Ethynylene) Helical Structures, Ha Nguyen Dec 2011

Modeling And Synthesis Of Functionalized Meta-Poly(Phenylene Ethynylene) Helical Structures, Ha Nguyen

All Dissertations

The ability of meta-poly(phenylene ethynylene) (mPPE) materials to undergo random coil to helix conformational changes under select conditions affords many opportunities for their use in sensor, separation, catalysis, and bio-related applications. Thus, to advance the development of these materials, a modeling procedure based on replica exchange molecular dynamics (REMD) simulation was developed to reliably assess factors affecting the folding behaviors of functionalized mPPE variants in solution. A combinational modeling study of 20 functionalized mPPEs in five solvent conditions provided insight into how mPPE secondary structure is impacted by the complex relationship between mPPE functional groups and solvent moieties. Further, these …

Go to article

Probabilistic Approaches To Stability And Deformation Problems In Braced Excavation, Zhe Luo Dec 2011

Probabilistic Approaches To Stability And Deformation Problems In Braced Excavation, Zhe Luo

All Dissertations

This dissertation is aimed at applying probabilistic approaches to evaluating the basal-heave stability and the excavation-induced wall and ground movements for serviceability assessment of excavation in clays. The focuses herein are the influence of spatial variability of soil parameters and small sample size on the results of the probabilistic analysis, and Bayesian updating of soil parameters using field observations in braced excavations.
Simplified approaches for reliability analysis of basal-heave in a braced excavation in clay considering the effect of spatial variability in random fields are presented. The proposed approaches employ the variance reduction technique (or more precisely, equivalent variance method) …

Go to article

Highly Conductive Carbon Nanotube Fibers For Biomedical Applications, Vijoya Sa Dec 2011

Highly Conductive Carbon Nanotube Fibers For Biomedical Applications, Vijoya Sa

All Dissertations

We developed a wet spinning process for the formation of polymeric fibers with high loading of single walled carbon nanotubes. The dissertation consists of five chapters. In the first chapter, the research goals were formulated and the art and technologies of fiber spinning from carbon nanotubes were critically analyzed. The next three chapters report the original results. Last chapter summarizes all the findings.
In the second chapter, we describe a surfactant based method of stabilization of carbon nanotube dispersions. The conditions of stability of nanotube dispersions in aqueous solutions of sodium dodecyl sulfate were analyzed. Using surface tension isotherms, the …

Go to article

Development Of A Design Method To Reduce Change Propagation Effects, Prabhu Shankar Dec 2011

Development Of A Design Method To Reduce Change Propagation Effects, Prabhu Shankar

All Dissertations

ABSTRACT
This dissertation presents a design method to reduce engineering changes caused due to change propagation effect. The method helps designers to systematically plan a verification, validation, and test (VV&T) plan. The rationale behind such a method is founded on a well-accepted principle that a robust validation plan can reduce design changes. However, such method has not yet been developed in mechanical engineering domain, so a method from software engineering has been adopted and extended to address the limitations in the existing design evaluation tools.
Tools extensively used in industry, such as FMEA, and in academia have been reviewed to …

Go to article

Fabrication Of Grooved Hollow Fiber Membrane For Nerve Regeneration: Process Modeling And Performance Evaluation, Jun Yin Dec 2011

Fabrication Of Grooved Hollow Fiber Membrane For Nerve Regeneration: Process Modeling And Performance Evaluation, Jun Yin

All Dissertations

Nerve injury is a general but intractable disease in traumatic injuries, leading to a significant reduction of functions in the nervous system. Extensive efforts are made on nerve injury rehabilitation. Since the appropriate connections between neurons and their targets are necessary, guiding axonal outgrowth is an essential step for neuron outgrowth in nervous system development, functioning, and regeneration. Besides the direct surgical nerve connection, an artificial means of guiding nerve regeneration called nerve conduits is widely applied in nerve injury rehabilitation. The main function of nerve conduits is to bridge the nerve gap, to help regenerating axons across damaged regions …

Go to article

Fluid Mud Underflows In Coastal Dredge Disposal, Mijanur Chowdhury Dec 2011

Fluid Mud Underflows In Coastal Dredge Disposal, Mijanur Chowdhury

All Dissertations

This manuscript presents the results of a thorough theoretical and experimental investigation on fluid mud underflows generated in a typical coastal dredge disposal operation. The main goal of this investigation is to understand the propagation dynamics of fluid mud underflows that depends upon a number of factors, including: concentrations, rheological properties and released configurations of fluid mud. Laboratory experiments were conducted with different initial fluid mud concentrations in three different experimental set-ups: rectangular flume for constant volume release, rectangular flume for constant flux release, and a square pool for radial constant flux release of fluid mud. The experiments in the …

Go to article

Spectral Engineering Of Optical Fiber Through Active Nanoparticle Doping, Tiffany Lindstrom-James Dec 2011

Spectral Engineering Of Optical Fiber Through Active Nanoparticle Doping, Tiffany Lindstrom-James

All Dissertations

The spectral engineering of optical fiber is a method of intentional doping of the core region in order to absorb/emit specific wavelengths of light therby providing enhanced performance over current fibers. Efforts here focused on developing an understanding of optically active nanoparticles based on alkaline earth fluorides that could be easily and homogeneously incorporated into the core of a silica based optical fiber preform and result in efficient and tailorable spectral emissions.
Doped and undoped calcium, strontium and barium fluoride nanoparticles were successfully synthesized and characterized for their physical, chemical, and optical behavior. Distinct spectroscopic differences as a result of …

Go to article

Development Of A Dynamic In Vitro Model Of A Stented Blood Vessel To Evaluate The Effects Of Stent Strut Material Selection And Surface Coating On Smooth Muscle Cell Response, Bradley Winn Dec 2011

Development Of A Dynamic In Vitro Model Of A Stented Blood Vessel To Evaluate The Effects Of Stent Strut Material Selection And Surface Coating On Smooth Muscle Cell Response, Bradley Winn

All Dissertations

Cardiovascular disease is the leading cause of mortality in The United States and Europe, accounting for approximately half of all deaths. The most common form of cardiovascular disease is atherosclerosis, which is characterized by the formation of fatty atheromatous plaques that can grow to occlude the vessel lumen, thus causing ischemia distal to the occlusion. This is commonly treated using balloon angioplasty, which is usually done in conjunction with the deployment of a stent. Stent deployment helps hold the vessel open following the local injury caused by balloon inflation and prevents elastic recoil and subsequent negative remodeling. Stenting has been …

Go to article

First Prev Next Last