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- Fiber reinforced plastics (4)
- Composite construction (3)
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- Laminated wood (2)
- Piezoelectric devices (2)
- Viscoelasticity (2)
- Absorption (1)
- Acoustic surface wave devices (1)
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- Actuators (1)
- Amines (1)
- Anisotropy (1)
- Bolted joints (1)
- Bridges - Design and construction - Materials (1)
- Brunswick (1)
- Cluster analysis (1)
- Copper (1)
- Creep (1)
- Cylindrical bending vibrations (1)
- Engineered wood (1)
- Fluid dynamics (1)
- Frost Heave (1)
- Gene expression (1)
- Guard fences (1)
- Hafnium oxide (1)
- Hardwoods (1)
- Ligands; Organic compounds (1)
- Lignin oxidation (1)
Articles 1 - 20 of 20
Full-Text Articles in Engineering
The Rate Of Fluid Absorption In Porous Media, Ran Wei Rioux
The Rate Of Fluid Absorption In Porous Media, Ran Wei Rioux
Electronic Theses and Dissertations
Fluid flow in porous media is an important process for many applications such as oil recovery, packed bed absorption colun~ns and filtration. Short time fluid uptake is important for processes such as textile sizing, paper coating and printing. But more work is needed to characterize the parameters that determine the absorption rate. This work is focused on short time absorption rate on uncoated and coated paper. Absorption rate is measured with a Bristow Wheel device for seven different uncoated papers and eleven coated papers. Gloss dynamics of freshly printed samples and tack dynamics are measured with two novel devices. Various …
Oxygen Delignification Kinetics And Selectivity Improvement, Steven M. Violette
Oxygen Delignification Kinetics And Selectivity Improvement, Steven M. Violette
Electronic Theses and Dissertations
Pulp strength loss during oxygen delignification is caused by cellulose chain cleavage resulting fiom attack by oxygen-based radicals generated through reactions with lignin. The objective of this research was to improve the lignin-to-cellulose selectivity during oxygen delignification by using radical-scavenging polymeric additives that adsorb on the cellulose surfaces where protection fiom radicals is needed. Among the polymers evaluated were starch, carboxymethyl-cellulose, galactomannan, xylan, and glucomannan. Oxygen delignification experiments were conducted on Northeast softwood Kraft pulps at different temperatures, sodium hydroxide charges, reaction times, and pretreatments. The effect of polymer additives on the selectivity and kinetics was studied. Polymer adsorption on …
Relationship Between Alkaline Pulp Yield And The Mass Fraction And Degree Of Polymerization Of Cellulose In Pulp, Mehmet Sefik Tunc
Relationship Between Alkaline Pulp Yield And The Mass Fraction And Degree Of Polymerization Of Cellulose In Pulp, Mehmet Sefik Tunc
Electronic Theses and Dissertations
Wood as a raw material is generally the dominant cost factor for the production of chemical pulp. Therefore, an increase in pulp yield has a major impact on the competitiveness of a mill. In order to optimize pulp yield, for example by changing operating conditions, a mill must be able to monitor the yield accurately. However, an accurate "real-time" pulp yield measurement method is not available at the present time. Pulping yield is presently measured from the amount of pulp produced from a given quantity of wood consumed over a 3 to 6 month time frame. This method is obviously …
Viscoelastic Roll Coating Flows, Mitchell A. Johnson
Viscoelastic Roll Coating Flows, Mitchell A. Johnson
Electronic Theses and Dissertations
The physics of a fluid flow between two rotating cylinders is important in processes such as bearing lubrication, roll coating, and printing. A small amount of dissolved polymer in the fluid can have a large impact on the behavior of the process. Viscoelasticity affects the stability of application and metering processes, and reduces the maximum speed at which a uniform film can be coated onto a substrate. The goal of this work is to characterize the effect of viscoelasticity on the forward roll coating operation. A bench-top apparatus simulated the process. Measurements of the gap between the roll surfaces, pressure …
A Surface Acoustic Wave Mercury Vapor Sensor, Reichl B. Haskell
A Surface Acoustic Wave Mercury Vapor Sensor, Reichl B. Haskell
Electronic Theses and Dissertations
An ST cut quartz 261 MHz surface acoustic wave (SAW) delay line mercury vapor sensor was designed, fabricated, and tested. A gold sensing film was sputtered onto the delay path of a SAW device to collect mercury for detection. The sensor's ability to detect mercury was due to the strong interaction between gold and mercury, known as amalgamation. In the present work, a large number of gold films of various thicknesses were exposed to low concentrations of gaseous mercury. It was shown for thinner films (i.e. 25A) the total amount of mercury that could be absorbed was limited; however, the …
On The Generation And Detection Of Ultrasonic Plate Waves In Microporous Polymeric Material, Lin Lin
On The Generation And Detection Of Ultrasonic Plate Waves In Microporous Polymeric Material, Lin Lin
Electronic Theses and Dissertations
Membranes are among the most important engineering components in use in many process industries. Examples of uses for membranes include water purification, industrial effluent treatment, recovery of volatile organic compounds, protein recovery, bio-separations and many others. Polymeric membranes are the most commonly used membranes. Membranes act as a barrier through which fluids and solutes are selectively transported. Quality assurance is a critical aspect of membrane module fabrication. In other materials, ultrasound has been widely used for materials characterization as well as flaw detection. Recently ultrasonic techniques have been used to detect the presence of defects in membranes. This thesis describes …
Active Vibration Suppression Of Smart Structures Using Piezoelectric Shear Actuators, Brian P. Baillargeon
Active Vibration Suppression Of Smart Structures Using Piezoelectric Shear Actuators, Brian P. Baillargeon
Electronic Theses and Dissertations
Active vibration damping using piezoelectric materials integrated with structural systems has found widespread use in engineering applications. Current vibration suppression systems usually consist of piezoelectric extension actuators bonded to the surface or embedded within the structure. The use of piezoelectric shear actuators/sensors has been proposed as an alternative, where the electric field is applied perpendicular to the direction of polarization to cause shear deformation of the material. We present an exact analysis and active vibration suppression of laminated composite plates and cylindrical shells with embedded piezoelectric shear actuators and sensors. Suitable displacement and electric potential fknctions are utilized to identically …
Determination Of The Viscoelastic Properties Of General Anisotropic Materials, Anish Sen Senan
Determination Of The Viscoelastic Properties Of General Anisotropic Materials, Anish Sen Senan
Electronic Theses and Dissertations
Elastic properties are rarely sufficient in order to evaluate the condition of a composite material. Knowledge of the viscoelastic properties is very critical for design purposes, for they directly characterize damping. Damping related measurements in the material provides information about the degree of cross-linking and crystallinity of the polymer. For metals, damping may be related to dislocation motion among other characteristics. For composite materials, in general the interphase and the matrix dominate the damping of the material. Ultrasonic measurement of damping gives a non- destructive measure of strength of composite materials. This thesis considers damping characteristics of polymer matrix composites …
Influence Of Stress Relaxation On Watertight Integrity Of Hybrid Bolted Joints, Keith N. Pelletier
Influence Of Stress Relaxation On Watertight Integrity Of Hybrid Bolted Joints, Keith N. Pelletier
Electronic Theses and Dissertations
Stress relaxation and creep are major concerns when loading composite materials. Due to the viscoelactic nature of the matrix material, composite materials tend to lose initial loads at a decreasing rate. This is especially true through the thickness of the material, where the behavior of the material is dominated by the matrix. Of particular interest to the current study presented in this thesis is the investigation of stress relaxation in bolted composite/metal hybrid connections. It is ultimately desired to be able to use bolted composite/metal hybrid connections for naval applications, where it is important to maintain as much of the …
Fatigue And Fracture Of The Frp-Wood Interface: Experimental Characterization And Performance Limits, Yong Hong
Fatigue And Fracture Of The Frp-Wood Interface: Experimental Characterization And Performance Limits, Yong Hong
Electronic Theses and Dissertations
A performance-based material evaluation methodology was developed to qualify FRP composite reinforcement bonded to glulam structural members for highway bridge applications. The objectives of this thesis are: a) to implement and correlate two methods to evaluate the fatigue and fracture performance of FRP-wood interfaces with associated performance limits; and b) to provide data and recommendations necessary to develop performance-based material specifications. The first method is based on evaluating the apparent shear strength in a single-lap shear test by fatigue tension loading. The second method is based on evaluating the interface fracture toughness in Mode I or opening-mode using fracture mechanics. …
Effects Of Frost Heave On A Soil Nail Wall In Brunswick, Maine, Sandra Mcrae Duchesne
Effects Of Frost Heave On A Soil Nail Wall In Brunswick, Maine, Sandra Mcrae Duchesne
Electronic Theses and Dissertations
Soil nail walls have been used as retaining structures worldwide since the early 1970s. The technology is particularly well suited for constructing walls in areas with limited overhead clearance and maneuvering room for heavy equipment, such as highway bridge underpasses. However, designers have been reluctant to experiment with soil nailing in areas with cold-weather climates and frost-susceptible soils, due to the lack of quantifiable data on the behavior of these walls when subjected to freezing conditions. The University of Maine collaborated with the Maine Department of Transportation (MDOT) in a research initiative on the first soil nail wall project in …
Analysis And Structural Health Monitoring Of Composite Plates With Piezoelectric Sensors And Actuators, Richard C. Mewer
Analysis And Structural Health Monitoring Of Composite Plates With Piezoelectric Sensors And Actuators, Richard C. Mewer
Electronic Theses and Dissertations
Structural vibration suppression and health-monitoring have been the focus of intense research over the past decade, and piezoelectric actuators and sensors are particularly well suited to serve in this application. The first part is an analytical investigation into the cylindrical bending vibrations of piezoelectric composite plates. The second part is a fully experimental investigation into various vibration based structural health-monitoring techniques for bolted composites. The analytical solution consists of Fourier basis functions that satisfy the equations of motion and charge equation. The accuracy of the mechanical displacements, electric potential, and stresses are dependent on the number of terms in the …
Measuring The Adhesive Bond Quality Of Vinyl Ester-Glass Composites On Novolak Hmr Treated Wood, Leopold Eisenheld
Measuring The Adhesive Bond Quality Of Vinyl Ester-Glass Composites On Novolak Hmr Treated Wood, Leopold Eisenheld
Electronic Theses and Dissertations
The objectives of this research were to 1) reduce the drying time of novolak-based HMR coupling agent, 2) reinforce wood samples with E-glasslvinyl ester resin composite using the SCRIMPThq process, 3) evaluate the durability and strength properties of the FRP-wood composites, and 4) evaluate the bonding strength of wood-to-wood bonding using vinyl ester resin. To reduce the drying time of HMR-treated wood laminates, a randomized complete three factorial experiment was used to evaluate five HMR drying times, two HMR spread rates, and two HMR solids contents. The experiment evaluated the sensitivity of the HMR treatment process to accelerated drying. The …
Voltammetric Study Of Interaction Of Copper And Model Fungal Secreted Ligands, Ran Liu
Voltammetric Study Of Interaction Of Copper And Model Fungal Secreted Ligands, Ran Liu
Electronic Theses and Dissertations
In lieu of Abstract, excerpt from Conclusion of Voltammetric Study of Interaction of Copper and Model Fungal Secreted Ligands: In summary, the cyclic voltammetry study shows evidence that the chelatormediated Fenton reaction is favored in the wood cell wall, where it may promote the degradation process. Also, reaction mechanisms between Cu(II), 2,3-DHBA and H202 have been proposed which provide at least partial explanations for the H202 cycle, and the mechanism for non-enzymatic, chelator-mediated Fenton reactions in brown rot wood decay processes. Future research in this area should explore cyclic voltarnrnetry analyses of Cu(I1) and ligands secreted by fungi, such as …
Simulation Of The Variability In Microelectronic Capacitors Having Polycrystalline Dielectrics With Columnar Microstructure, Jesse Cousins
Simulation Of The Variability In Microelectronic Capacitors Having Polycrystalline Dielectrics With Columnar Microstructure, Jesse Cousins
Electronic Theses and Dissertations
Increasing circuit densities drive the search for microelectronic capacitors with smaller areas. One solution which reduces capacitor size while leaving capacitance constant is to use a thin film of a high permittivity material such as Ta205, SrTiOy (STO), or (Ba,Sr)Ti03 (BST), whose dielectric constants are much higher than those of currently used dielectrics such as Si02 and Si3N1 One drawback of these dielectric films is that they have a polycrystalline microstructure and the permittivity and leakage current density depend on grain size and orientation. It is unknown how microstructure variations will affect the variability and yield of devices incorporating these …
Development Of An Frp Reinforced Hardwood Glulam Guardrail, Joshua Keith Botting
Development Of An Frp Reinforced Hardwood Glulam Guardrail, Joshua Keith Botting
Electronic Theses and Dissertations
This study focuses on the development of an aesthetically pleasing, cost effective, timber guardrail system, which utilizes low-grade New England hardwoods such as red maple and beech. This required that several issues be addressed, including structural modeling, rail section design, rail fabrication, evaluation of durability, rail-to-rail field splice connection design, and the evaluation of guardrail system performance under impact loading. The use of glulam beams in infrastructure is increasing rapidly with the reduced availability and increase in cost of high grade solid sawn timber. New techniques allow for increased material usage while maintaining a high strength product. Selective stacking of …
Fatigue Behavior Of Frp-Reinforced Douglas-Fir Glued Laminated Bridge Girders, Matthew Ritchie
Fatigue Behavior Of Frp-Reinforced Douglas-Fir Glued Laminated Bridge Girders, Matthew Ritchie
Electronic Theses and Dissertations
The use of composites in engineered wood products has recently led to the use of fiber-reinforced polymers (FRP) as a reinforcing for glued-laminated (glulam) beams. Bridge girders are among the more common applications of FRP-reinforced glulam beams and therefore the beam is subject to millions of load cycles as well as moisture fluctuations. Significant flexural strength can be gained through the use of such reinforcing, however, the behavior of the wood composite when subject to repeated load cycles and hygrothemal effects is not well understood. In this study, eighteen glulam beams were reinforced in tension with 1.93% E- glass/epoxy reinforcing …
Characterization Of Hfo2 Capacitors, Fan Yang
Characterization Of Hfo2 Capacitors, Fan Yang
Electronic Theses and Dissertations
Hafnium oxide (HfOn) is a promising dielectric for future microelectronic applications. Hf02 thin films (10-75nm) were deposited on Pt/Si02/Si substrates by pulsed DC magnetron reactive sputtering. Top electrodes of Pt were formed by e-beam evapo- ration through an aperture mask on the samples to create MIM (Metal-Insulator-Metal) capacitors. Various processing conditions (Arloz ratio, DC power and deposition rate) and post-deposition annealing conditions (time and temperature) were investigated. The structure of the Hf02 films was characterized by X-ray diffraction (XRD) and the roughness was measured by a profilometer. The electrical properties were characterized in terms of their relative permittivity (E,(T) and …
Adaptive Double Self-Organizing Map For Clustering Gene Expression Data, Dali Wang
Adaptive Double Self-Organizing Map For Clustering Gene Expression Data, Dali Wang
Electronic Theses and Dissertations
This thesis presents a novel clustering technique known as adaptive double self- organizing map (ADSOM) that addresses the issue of identifying the "correct" number of clusters. ADSOM has a flexible topology and performs clustering and cluster visualization simultaneously, thereby requiring no a priori knowledge about the number of clusters. ADSOM combines features of the popular self-organizing map with two- dimensional position vectors, which serve as a visualization tool to decide the number of clusters. It updates its free parameters during training and it allows convergence of its position vectors to a fairly consistent number of clusters provided that its initial …
Effects Of Strand Geometry On Selected Properties Of Long-Stand Structural Composite Lumber Made From Northeastern Hardwoods, Russell Edgar
Effects Of Strand Geometry On Selected Properties Of Long-Stand Structural Composite Lumber Made From Northeastern Hardwoods, Russell Edgar
Electronic Theses and Dissertations
Structural composite lumber (SCL) products often possess significantly higher design values than the top grades of solid lumber, making it a popular choice for both residential and commercial applications. The enhanced mechanical properties of SCL are mainly due to defect randomization and densification of the wood fiber, both largely functions of the size, shape and composition (species) of the wood element. Traditionally, SCL manufacturers have used thin, rectangular elements produced from either moderate density softwoods or low density hardwoods. Higher density hardwood species have been avoided, as they require higher pressures to adequately densify and consolidate the wood furnish. These …