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Articles 151 - 180 of 452

Full-Text Articles in Mechanical Engineering

Physics And Applications Of A Pdms Based Centrifugal Microfluidic System, Ziliang Cai Jan 2015

Physics And Applications Of A Pdms Based Centrifugal Microfluidic System, Ziliang Cai

LSU Doctoral Dissertations

The objective of this research work is to develop a centrifugal microfluidic system for general purposes based on microfabrication technologies including SU-8 photolithography, polydimethylsiloxane (PDMS) casting. The main contribution of this research is to integrate a flyball governor system into the polymer based centrifugal microfluidic platform. A series of function units are developed based on this unique mechanism. In the first part, three pinch valve systems were designed and tested. The first one is based on the magnetic force and the second one is on the basis of spring force and the last one is a membrane valve. All valving …


Healing-On-Demand Polymer Composites Based On Shape Memory Polyurethane Fibers And Polymeric Artificial Muscles, Pengfei Zhang Jan 2015

Healing-On-Demand Polymer Composites Based On Shape Memory Polyurethane Fibers And Polymeric Artificial Muscles, Pengfei Zhang

LSU Doctoral Dissertations

In this dissertation, the healing-on-demand polymer composites based on shape memory polyurethane fibers and artificial muscles are investigated, for understanding and developing a novel healing-on-demand composite so that it would be used for industrial applications that could heal structural-length scale damage and leaking autonomously, repeatedly, efficiently, timely, and molecularly. Firstly, the structural relaxation behavior of shape memory polyurethane (SMPU) fiber was studied by theoretical analysis and experimental test. Then, a self-healing composite based on cold-drawn short SMPU fiber was prepared and tested for evaluating its crack-healing performance. After that, polymer artificial muscle based healing-on-demand composite was developed and characterized. Based …


Heat Transfer And Film Cooling On A Gas Turbine Blade And Shroud, Onieluan Tamunobere Jan 2015

Heat Transfer And Film Cooling On A Gas Turbine Blade And Shroud, Onieluan Tamunobere

LSU Doctoral Dissertations

At a fixed pressure ratio, the thermodynamic efficiency and net power output of a gas turbine engine increases with an increase in the turbine inlet temperature. Cooling is necessary because of the thermal limits of the engine materials. This research studies through experimentation, the heat transfer and cooling of critical gas turbine components including the shroud and blade tip. In the first phase, the shroud heat transfer behavior and the effectiveness of shroud cooling under the conditions of rotation is undertaken in a single stage turbine at a design rotation speed of 550 rpm, at off-design speeds and for varying …


Modeling Two-Phase Flow And Heat Transfer In Polygonal Microchannels, Sai Sashankh Rao Jan 2015

Modeling Two-Phase Flow And Heat Transfer In Polygonal Microchannels, Sai Sashankh Rao

LSU Doctoral Dissertations

Microfluidics is a burgeoning research area with applications ranging from microfluidic cooling to biomolecule synthesis. Here we study two problems to gain an improved understanding of two-phase flow and heat transfer in microfluidic devices. We also study a third problem on boundary layer flow out of theoretical interest. In the first problem, we study the heat and mass transfer in polygonal micro heat pipes under small imposed temperature differences. A micro heat pipe, used in electronics cooling, consists of a closed polygonal microchannel filled with a wetting liquid and a long vapor bubble. We model the evaporation, fluid flow, and …


Fabrication And Characterization Of Miniaturized Components Based On Extruded Ceramic-Filled Polymer Blends, Khurshida Sharmin Jan 2015

Fabrication And Characterization Of Miniaturized Components Based On Extruded Ceramic-Filled Polymer Blends, Khurshida Sharmin

LSU Doctoral Dissertations

The objective of this work is to develop an improved manufacturing process for microstructured ceramic components that is based on co-extrusion. Co-extrusion of structured feedrods holds promise for development of multi-layered, functionally graded and/or textured structures. However, it requires a polymer binder that is difficult to remove before structures can be sintered to full density. A two-step debinding is introduced to eliminate debinding defects that are commonly observed in thermal debinding (TD). Cracking is a major issue due to a lack of pore spaces for outgassing of pyrolysis products in traditional TD. In two-step debinding, a soluble binder is removed …


On An Effective Submodeling Procedure For Stresses Determined With Finite Element Analysis, Ajay Ashok Kardak Jan 2015

On An Effective Submodeling Procedure For Stresses Determined With Finite Element Analysis, Ajay Ashok Kardak

LSU Doctoral Dissertations

Submodeling can enable stress analysts using finite elements to focus analysis on a subregion containing the stress concentration of interest, with consequent computational savings. Such benefits are only truly realized if the boundary conditions on the edges of the subregion that were originally contained within the global region are sufficiently accurate. These boundary conditions are drawn from initial global finite element analysis (FEA), and consequently themselves have errors that in turn lead to errors in the stresses sought. When these last boundary-condition errors are controlled, and the discretization errors incurred by the FEA of ensuing submodels are also controlled, submodeling …


Multiscale Modeling Of Smart Materials Under Static And Dynamic Thermo-Mechanical Loading, Soodabeh Sharafi Jan 2015

Multiscale Modeling Of Smart Materials Under Static And Dynamic Thermo-Mechanical Loading, Soodabeh Sharafi

LSU Master's Theses

Engineering material systems with tailored capabilities are a topic trend in plethora of research. Polymer based Artificial Muscle, PAM, and Shape memory polymer fiber, SMPF, enable structural engineers to incorporate smartness functionality into their design through programming cycles. Smartness functionality leads to the production of artificial muscles with different load carrying capability. SMPF is another category of smart materials, which are capable of being micro-structurally engineered to isolate vibration at different temperature and frequency conditions. The smartness functionality offers the adjustment between inherent properties of these materials with their industrial applications through modeling techniques. Mixture of phenomenological, numerical, mathematical models …


An Analytic Solution Of The Thermal Boundary Layer At The Leading Edge Of A Heated Semi-Infinite Flat Plate Under Forced Uniform Flow, Robert Jessee Jan 2015

An Analytic Solution Of The Thermal Boundary Layer At The Leading Edge Of A Heated Semi-Infinite Flat Plate Under Forced Uniform Flow, Robert Jessee

LSU Master's Theses

Abstract The heated flat plate under uniform flow has been vastly studied, with the Blasius and Pohlhausen solutions developed over 100 years ago. These solutions are numerical in nature. Here, an analytic solution is found for the temperature and velocity profiles at the leading edge of a heated flat plate under forced uniform flow. By defining a similarity variable the governing equations are reduced to a dimensionless equation with an analytic solution at the leading edge. This report gives justification for the similarity variable via scaling analysis, details the process of converting to similarity form, and presents a similarity solution. …


Study Of Active Vibration Control Using The Method Of Receptances, Amit Maha Jan 2015

Study Of Active Vibration Control Using The Method Of Receptances, Amit Maha

LSU Doctoral Dissertations

Using the Method of Receptance, it is possible in general to assign 2_x0002_ poles (i.e. n conjugate pairs) of an axially vibrating rod of variable cross section by sensing the state at _x0002_ points along the rod. Using the sensor data, closed loop feedback control gains can be calculated by solving a simple set of linear equations. The feedback gains can be applied to generate the required control force using an actuator. This partial pole assignment can be done without continuous or discrete analytical modeling. Therefore, the physical parameters such as the rigidity, the density, and the variable cross-sectional area …


The Effects Of Work Zone Configurations On Physiological And Subjective Workload, Mahmoud Shakouri Hassanabadi Jan 2015

The Effects Of Work Zone Configurations On Physiological And Subjective Workload, Mahmoud Shakouri Hassanabadi

LSU Master's Theses

There is a dearth of research on the effect of driving through work zones on physiological and subjective workload of drivers. The objectives of this research were to (a) study the effect of work zones and traffic density on physiological measures of workload, subjective workload and performance variables (b) study the relationship between physiological measures of workload, subjective workload and performance variables. Conventional lane merge (CLM), joint lane merge (JLM) and a road without a work zone (control) were modeled with high and low traffic density by using a full-size driving simulator. 13 female and 17 male students volunteered to …


Challenges Towards Structural Integrity And Performance Improvement Of Welded Structures, Mohammad Washim Dewan Jan 2015

Challenges Towards Structural Integrity And Performance Improvement Of Welded Structures, Mohammad Washim Dewan

LSU Doctoral Dissertations

Welding is a fabrication process that joint materials, is extensively utilized in almost every field of metal constructions. Heterogeneity in mechanical properties, metallurgical and geometrical defects, post-weld residual stresses and distortion due to non-linear welding processes are prime concerns for performance reduction and failures of welded structures. Consequently, structural integrity analysis and performance improvement of weld joints are important issues that must be considered for structural safety and durability under loading. In this study, an extensive experimental program and analysis were undertaken on the challenges towards structural integrity analysis and performance improvement of different welded joints. Two widely used welding …


Fixed Platform Crane For Equipment Access, Carlos Gonzalez, Steven Hollander, Yue Zhao, Jared Pellegrin, Travis Odom May 2014

Fixed Platform Crane For Equipment Access, Carlos Gonzalez, Steven Hollander, Yue Zhao, Jared Pellegrin, Travis Odom

Honors Capstones

No abstract provided.


Tomographic Imaging Of Combustion Zones Using Tunable Diode Laser Absorption Spectroscopy (Tdlas), Avishek Guha Jan 2014

Tomographic Imaging Of Combustion Zones Using Tunable Diode Laser Absorption Spectroscopy (Tdlas), Avishek Guha

LSU Doctoral Dissertations

This work concentrates on enabling the usage of a specific variant of tunable diode laser absorption spectroscopy (abbr. TDLAS) for tomogaphically reconstructing spatially varying temperature and concentrations of gases with as few reconstruction artifacts as possible. The specific variant of TDLAS used here is known as wavelength modulation with second harmonic detection (abbr. WMS-2f) which uses the wavelength dependent absorbance information of two different spectroscopic transitions to determine temperature and concentration values. Traditionally, WMS-2f has generally been applied to domains where temperature although unknown, was spatially largely invariant while concentration was constant and known to a reasonable approximation (_x0006_+/- 10% …


Meso-Scale Analysis Of Deformation Induced Heating In Granular Metalized Explosives By Piston Supported Waves, Sunada Srinath Nagamani Chakravarthy Jan 2014

Meso-Scale Analysis Of Deformation Induced Heating In Granular Metalized Explosives By Piston Supported Waves, Sunada Srinath Nagamani Chakravarthy

LSU Doctoral Dissertations

Shock sensitivity of heterogeneous explosive composites is dependent on the formation of hot-spots which are small regions of elevated temperatures within the material. Changes in the initial meso-structure (i.e. packing density, composition, particle size and shapes) of the explosives can significantly alter the hot-spot fields in the material and thereby affect its shock sensitivity. In this study, an explicit, 2D, Lagrangian finite and discrete element technique is used to numerically simulate the deformation induced heating of granular mixtures of explosive (HMX), and metal (Al) particles due to piston supported uniaxial deformation waves (400 ≤ Up ≤ 800 m/s). A number …


Association Of Lean Implementation On Perceived Organizational Maturity Levels Of Managers And Staff In The Public Sector, Patrick Eduardo O'Mara Jan 2014

Association Of Lean Implementation On Perceived Organizational Maturity Levels Of Managers And Staff In The Public Sector, Patrick Eduardo O'Mara

LSU Master's Theses

Extensive research has shown the impact of Lean implementation at the process level of an organization to increase quality, reduce cycle time, and reduce operational costs. However, little research has been done to associate Lean with improvement at the strategic level of an organization. The objectives of the present research were to (a) study the association of Lean implementation with maturity levels of employees (b) study the relationship between Lean implementation in the levels of agreement with cohesion between managers and staff in evaluating perceived current state and desired state of organizational practices (c) identify potential barriers of Lean implementation …


Using A Sleep And Activity Monitor To Operationalize Fatigue Risk Management, Vanessa Bégat Seitz Jan 2014

Using A Sleep And Activity Monitor To Operationalize Fatigue Risk Management, Vanessa Bégat Seitz

LSU Master's Theses

When a person continues to work despite being fatigued, an accident may occur or productivity may decrease. Reducing fatigue related accidents is complicated due to the subjective nature and pervasiveness of the feeling of fatigue. Because finding one universal definition or measure of fatigue is problematic, fatigue is typically measured by a combination of factors such as amount of sleep obtained, physical or cognitive work performed, or sleepiness which can then be related back to a measure of performance. Until recently, sleep measurement was restricted to a lab setting; however, with the emergence of actigraph devices, it is now possible …


Assessing The Effects Of Work Zone Configurations On Drivers' Visual Attention, Karthy Punniaraj Jan 2014

Assessing The Effects Of Work Zone Configurations On Drivers' Visual Attention, Karthy Punniaraj

LSU Master's Theses

This study assessed the effects of two different work zone configurations on driver’s visual attention by eye movement monitoring. A driving simulator study was conducted with thirty participants. Variations in traffic density and warning sign placement distance were added to the merge configurations to simulate the real time situation. A 2 x 2 x 3 within-subjects factorial design was used for this research. The independent variables used in this study were (1) merge configuration [(i) Conventional Lane Merge (CLM) and (ii) Joint Lane Merge (JLM)], (2) traffic density [(i) high and (ii) low] and (3) distance between traffic signs [(i) …


Age, Performance And Retention Interval Effects On Acceptance Of A Consumer Health Information Technology System, Stephen Andrew Ford Jan 2014

Age, Performance And Retention Interval Effects On Acceptance Of A Consumer Health Information Technology System, Stephen Andrew Ford

LSU Master's Theses

The older adult population will continue to place pressure on the financial and resource allocation of the healthcare industry as the over 65 population continues to grow. Health care expenditures to treat the aging population will continue to rise as older adults are more likely to have expensive chronic conditions. The future may lay with Consumer Health Information Technology which may allow the patients to have more control of their treatment schedule and self-management of their health and chronic conditions. However, older adults may exhibit cognitive declines that prohibit the learning and proper use of technology, and this assumption is …


A Parametric Investigation Of A Novel, Modular, Gasketless, Microfluidic Interconnect Using Parallel Superhydrophobic Surfaces, Christopher Ramsey Brown Jan 2014

A Parametric Investigation Of A Novel, Modular, Gasketless, Microfluidic Interconnect Using Parallel Superhydrophobic Surfaces, Christopher Ramsey Brown

LSU Master's Theses

The gasketless microfluidic interconnect has the potential to offer a standardized approach to interconnects between modular microfluidic components. This strategy uses parallel superhydrophobic surfaces (contact angle ≥ 150ᴼ) to passively seal adjacent, concentric, microfluidic ports separated by an air gap using a liquid bridge created between the chips. The parallel superhydrophobic surfaces do not require the addition of a gasket or other additional components so that the assembly process scales favorably with an increasing number of fluidic interconnects. The gasketless seal does not contribute to geometric constraint between the component chips which allows alignment between chips to scale favorably with …


An Experimental Investigation Of Corrosion Fatigue Life Via Thermographic Method, Richard Wayne Purvis Jan 2014

An Experimental Investigation Of Corrosion Fatigue Life Via Thermographic Method, Richard Wayne Purvis

LSU Master's Theses

The effect of prior corrosion fatigue damage on the thermographic response of 1018 low carbon steel is investigated. Specimens were subject to rotating bending fatigue at 38 Hz loading frequency while being exposed to a 3.5% NaCl and distilled water solution. Some specimens were subject to corrosion fatigue for part of their fatigue life and then their thermographic response measured under fatigue in air at 62 Hz loading frequency. Fatigue tests in air with thermographic measurement were performed as a comparison. It was observed that the initial temperature rise after corrosion fatigue fits the previously proposed model for air fatigue, …


A Thermographic Method For Remaining Fatigue Life Prediction Of Welded Joints, Paul Thomas Williams Jan 2014

A Thermographic Method For Remaining Fatigue Life Prediction Of Welded Joints, Paul Thomas Williams

LSU Master's Theses

A non-destructive thermographic technique is adapted and applied to study the fatigue life and behavior of welded specimens made from two different materials. Results show good agreement between experimental predictions of consumed fatigue life and predicted fatigue life. Further, the thermal evolution of the specimens is used to calculate Damage Parameter, which is also used to make fatigue life predictions with promising results. To gain further insight Buckingham Pi theorem is also applied to determine the role of the important parameters involved in a dimensionless form. For this purpose, a series of experiments were performed and used for the analysis …


Fabrication And Enhancement Of Aluminum-Based Microchannel Devices, Paul Joseph Hymel Jan 2014

Fabrication And Enhancement Of Aluminum-Based Microchannel Devices, Paul Joseph Hymel

LSU Master's Theses

Microscale molding replication and transient liquid phase (TLP) bonding were used to fabricate Al-based microchannel heat exchangers (MHEs) and micro gas chromatograph (mGC) columns. Metal-based microchannel heat exchangers often experience corrosion as a result of their operating conditions. To address this problem, an internal anodization method was developed in Al microtubes by pulsing the flow of electrolyte through a microtube when the current dropped below a set value. The anodic aluminum oxide (AAO) films were characterized by scanning electron microscopy (SEM), focused ion beam (FIB) cross sections, and X-ray energy dispersive spectroscopy (EDS) to determine their growth rate and morphology. …


Using Eye-Tracking To Investigate Strategy And Performance Of Expert And Novice Control Room Operators, Christina Marie Koffskey Jan 2014

Using Eye-Tracking To Investigate Strategy And Performance Of Expert And Novice Control Room Operators, Christina Marie Koffskey

LSU Master's Theses

There is lacking research within the Petrochemical Industry that uses eye-tracking to explore the differences between the strategies of expert and novice control room operators as they monitor and address process parameters that could be used to improve novice training programs and interface design. Scan paths and three eye-tracking metrics (Fixation Frequency, Gaze Duration Mean, and Gaze Percentage) were used to investigate the differences in eye behavior of three expert control room operators and six novice students as they monitored and corrected a Crude Refinement simulation. A 2x2x2 mixed factor design was used to explore the effects that expertise (expert …


Minimization Of Transportation, Installation And Maintenance Operations Costs For Offshore Wind Turbines, Tasnim Ibn Faiz Jan 2014

Minimization Of Transportation, Installation And Maintenance Operations Costs For Offshore Wind Turbines, Tasnim Ibn Faiz

LSU Master's Theses

Although it is a sustainable source and there is abundant potential for energy, cost of energy generated from offshore wind is still high compared to other sustainable energy sources. Apart from the manufacturing cost of turbines, cost of energy is significantly affected by costs of transportation and installation operations of wind turbines and maintenance operations of turbine components. Through optimum selection of decision variables, such as turbine installation method and rated power output of each turbine, cost of transportation and installation operations can be minimized. The first model in this study investigates the impact of these decision variables and effect …


Analyses Of Online Monitoring Signals For A Gmaw Process Before And After Improvement, Aniruddha Joshi Jan 2014

Analyses Of Online Monitoring Signals For A Gmaw Process Before And After Improvement, Aniruddha Joshi

LSU Master's Theses

The ability to detect the onset of welding instability is a very powerful tool in welding process monitoring and control. Toward this goal, this study investigates a gas metal arc welding (GMAW) process by analyzing online monitoring signals. Two separate data sets are obtained from the process, which correspond to (a) a stable process after improvement and (b) a relatively unstable process which tends to exhibit spatter and poor weld bead geometry. Voltage, current, wire-feeding speed and line speed signals for both data sets are analysed and features are extracted from the raw signals using different signal processing techniques. Specifically, …


The Effects Of Asymmetric Micro Ratchets On Pool Boiling Performance, Lance Austin Brumfield Jan 2014

The Effects Of Asymmetric Micro Ratchets On Pool Boiling Performance, Lance Austin Brumfield

LSU Doctoral Dissertations

Nucleate boiling is an attractive method for achieving high heat flux at low superheat temperatures. It is frequently used for industrial applications such as heat exchangers and is being considered to cool advanced central processing units (CPU) which produce heat fluxes on the order of 1 MW/m2 and are becoming increasingly less efficient to cool via forced conduction of air. The issue with implementing nucleate boiling as a cooling mechanism lies in the difficulty of quantifying the numerous and complex mechanisms which control the process. A comprehensive nucleate boiling model has yet to be formulated and will be required in …


Hot Corrosion Behaviour Of New Candidates For Thermal Barrier Coatings Application In Turbine Simulated Environments, Mohammad Hamed Habibi Jan 2014

Hot Corrosion Behaviour Of New Candidates For Thermal Barrier Coatings Application In Turbine Simulated Environments, Mohammad Hamed Habibi

LSU Doctoral Dissertations

Thermal barrier coatings (TBCs) are used gas turbine engines. The current material of choice (YSZ) degrades when it contacts with impurities arise from low quality fuels such vanadium and sulfur. YSZ cannot be used in temperature higher than 900˚C. Higher efficiency and performance of gas turbine engines will require a new generation of thermal barrier coatings (TBCs). In current work, hot corrosion behavior of new candidates including Gd2Zr2O7, ZrO2 stabilized with Ta2O5, zirconia stabilized with both Ta2O5 and Y2O3 and zirconia stabilized with CeO2 and TiO2 is investigated. For YSZ case, the reaction between NaVO3 and Y2O3 produces YVO4 and …


Crack Self-Healing In Sic/Spinel Nanocomposite, Fariborz Tavangarian Jan 2014

Crack Self-Healing In Sic/Spinel Nanocomposite, Fariborz Tavangarian

LSU Doctoral Dissertations

Spinel is one of the best known and widely used ceramic materials. It has good thermal shock resistance, high chemical inertness in both acidic and basic environments, excellent optical and dielectric properties, high strength at both elevated and normal temperatures, and has no phase transition up to the melting temperature (2135°C). Spinel is used in the metallurgical, electrochemical, and chemical industrial fields. It has also found some applications in dentistry, catalyst supports, humidity sensors, reinforcing fibers, photoluminescent materials, etc. One of the limitations of spinel ceramic is its brittleness. Furthermore, at high temperature applications, a rapid heating or cooling can …


Applications Of The Variational Approach To Fracture Mechanics, Ataollah Mesgarnejad Jan 2014

Applications Of The Variational Approach To Fracture Mechanics, Ataollah Mesgarnejad

LSU Doctoral Dissertations

In this study we present the variational approach to fracture mechanics as a versatile tool for the modeling of the fracture phenomenon in solids. Variational fracture mechanics restates the problem of initiation and propagation of cracks in solids as an energy minimization problem. The edifice of this energy minimization problem is such that unlike other methods (e.g. extended finite element method XFEM, cohesive-zone methods) the variational approach to fracture mechanics, diminishes the need for an a priori knowledge of the crack path or ad hoc assumptions in the form of path selection laws. We will show applications of the variational …


Novel Syntheses And Surface Modifications Of Electrode Materials For Superior Lithium-Ion Batteries, Jianqing Zhao Jan 2014

Novel Syntheses And Surface Modifications Of Electrode Materials For Superior Lithium-Ion Batteries, Jianqing Zhao

LSU Doctoral Dissertations

Rechargeable lithium-ion battery is one of the most promising energy conversion and storage systems that offers high energy and powder densities, long service life and assuring safety. Performance of lithium-ion batteries crucially relies on electrochemical characteristics of electrode materials, i.e., anode and cathode materials. This dissertation work aims at developing novel electrode materials with high capacity, excellent cycling stability and remarkable rate capability for next-generation lithium-ion batteries. The effects of surface modifications for LiMn2O4 cathode materials are studied by depositing ultrathin conformal amphoteric oxides via atomic layer deposition (ALD). In the case of ZnO coating, the thickness of ZnO ALD …