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2006

Mechanical Engineering

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Including Embodied Energy Considerations At The Conceptual Stage Of Building Design, Y. Yohanis, Brian Norton Jan 2006

Including Embodied Energy Considerations At The Conceptual Stage Of Building Design, Y. Yohanis, Brian Norton

Articles

Elevated operating temperatures reduce the solar to electrical conversion efficiency of building integrated photovoltaic devices (BIPV). Phase change materials (PCM) can be used to passively limit this temperature rise although their effectiveness is limited by their low thermal conductivities and by crystallization segregation during solidification. This paper presents an experimental evaluation of the effects of convection and crystalline segregation in a PCM as a function of efficiency of heat transfer within the finned PV/PCM system. The thermal performances of bulk PCM with crystallization segregation for different internal fin arrangements are presented. It is noted that the addition of internal ...


Generating Random Surfaces With Desired Autocorrelation Length, Yilei Zhang, Sriram Sundararajan Jan 2006

Generating Random Surfaces With Desired Autocorrelation Length, Yilei Zhang, Sriram Sundararajan

Mechanical Engineering Publications

A versatile surface processing method based on electrostatic deposition of particles and subsequent dry etching is shown to be able to tailor the autocorrelation length of a random surface by varying particle size and coverage. An explicit relation between final autocorrelation length, surface coverage of the particles, particle size, and etch depth is built. The autocorrelation length of the final surface closely follows a power law decay with particle coverage, the most significant processing parameter. Experimental results on silicon substrates agree reasonably well with model predictions.


A Multiscale Model For Dilute Turbulent Gas-Particle Flows Based On The Equilibration Of Energy Concept, Ying Xu, Shankar Subramaniam Jan 2006

A Multiscale Model For Dilute Turbulent Gas-Particle Flows Based On The Equilibration Of Energy Concept, Ying Xu, Shankar Subramaniam

Mechanical Engineering Publications

The objective of this study is to improve Eulerian-Eulerian models of particle-laden turbulent flow. We begin by understanding the behavior of two existing models—one proposed by Simonin [von Kármán Institute of Fluid Dynamics Lecture Series, 1996], and the other by Ahmadi [Int. J. Multiphase Flow16, 323 (1990)]—in the limiting case of statistically homogeneous particle-laden turbulent flow. The decay of particle-phase and fluid-phase turbulent kinetic energy (TKE) is compared with direct numerical simulation results. Even this simple flow poses a significant challenge to current models, which have difficulty reproducing important physical phenomena such as the variation of turbulent kinetic ...


Femtosecond Coherent Anti-Stokes Raman Scattering Measurement Of Gas Temperatures From Frequency-Spread Dephasing Of The Raman Coherence, Robert P. Lucht, Sukesh Roy, Terrence R. Meyer, James R. Gord Jan 2006

Femtosecond Coherent Anti-Stokes Raman Scattering Measurement Of Gas Temperatures From Frequency-Spread Dephasing Of The Raman Coherence, Robert P. Lucht, Sukesh Roy, Terrence R. Meyer, James R. Gord

Mechanical Engineering Publications

Gas-phase temperatures and concentrations are measured from the magnitude and decay of the initial Raman coherence in femtosecond coherent anti-Stokes Raman scattering (CARS). A time-delayed probe beam is scattered from the Raman polarization induced by pump and Stokes beams to generate CARS signal; the dephasing rate of this initial coherence is determined by the temperature-sensitive frequency spread of the Raman transitions. Temperature is measured from the CARS signal decrease with increasing probe delay. Concentration is found from the ratio of the CARS and nonresonant background signals. Collision rates do not affect the determination of these quantities.


Effect Of Sample Aging On The Accuracy Of The International Energy Agency's Tar Measurement Protocol, Ming Xu, Robert C. Brown, Glenn Norton Jan 2006

Effect Of Sample Aging On The Accuracy Of The International Energy Agency's Tar Measurement Protocol, Ming Xu, Robert C. Brown, Glenn Norton

Mechanical Engineering Publications

The Working Group of the Biomass Gasification Task of the International Energy Agency (IEA) Bioenergy Agreement has developed a protocol for sampling and analysis of tar and particulates from biomass gasifiers, which is commonly accepted as a standard for reliable measurement of tar in producer gas. The methodology is dependent upon dissolving tar in a solvent for subsequent recovery by evaporation or distillation. This paper investigates whether storage of the tar/solvent sample prior to analysis affects the accuracy of the tar measurement. On the basis of the results of this study, we recommend that samples be analyzed within a ...


Reducing Energy Costs By Optimizing Controller Tuning, Aidan O'Dwyer Jan 2006

Reducing Energy Costs By Optimizing Controller Tuning, Aidan O'Dwyer

Conference papers

The proportional integral derivative (PID) controller is the most dominant form of automatic controller in industrial use today. With this technique, it is necessary to adjust the controller parameters according to the nature of the process. This tailoring of controller to process is known as controller tuning. Controller tuning is easily and effectively performed using tuning rules (i.e. formulae for controller tuning, based on process information). Such tuning rules allow the easy set up of controllers to achieve optimum performance at commissioning. Importantly, they allow ease of re-commissioning if the characteristics of the process change. The paper outlines the ...


A Numerical Acoustic Fluid-Structure Model Of A Therapeutic Ultrasound Angioplasty Device, Graham Gavin, M.S. J. Hashmi, Finbar Dolan, Garrett Mcguinness Jan 2006

A Numerical Acoustic Fluid-Structure Model Of A Therapeutic Ultrasound Angioplasty Device, Graham Gavin, M.S. J. Hashmi, Finbar Dolan, Garrett Mcguinness

Conference Papers

Ultrasonic angioplasty involves the use of ultrasonic vibrations delivered to the distal-tip of small diameter wire waveguides and is an emerging technology the may have potential use in the treatment of complicated atherosclerotic plaques during cardiovascular surgery. Complicated plaques, including chronic total occlusions and calcified lesions, seriously reduce success rates during standard intervention involving guidewire access, followed by balloon dilation or stent delivery. The large amplitude (0-150 μm) wire waveguide distal-tip displacements in the low-frequency ultrasonic (18-45 kHz) range have been shown to disrupt plaque material by direct contact ablation and cavitation, acoustic streaming and pressure wave components in adjacent ...


The Role And Future Of Nanotechnology In Research, Industry And Education, David Kennedy Jan 2006

The Role And Future Of Nanotechnology In Research, Industry And Education, David Kennedy

Conference Papers

Major developments in Nanotechnology have taken place across the world
over the last few years. From a humble beginning, Ireland inc. became a leader in the Microelectronics industry and now has to face the challenge of developing a strategic plan to maintain its lead position in the nano field which in most cases will supersede the micro phase. Most countries are taking a similar path of development all be it alone or in collaboration with other countries. This process is expensive and requires market drivers and experts to lead and deliver demands from the industries of the future. The approach ...


Grain Boundary Property Determination Through Measurement Of Triple Junction Geometry And Crystallography, Brent L. Adams, D. Casasent, M. Demirel, Bassem S. El-Dasher, D. Kinderlehrer, C. Liu, I. Livshits, F. Manolache, D. Mason, A. Morawiec, W. W. Mullins, S. Ozdemir, Gregory S. Rohrer, Anthony D. Rollett, David M. Saylor, Shlomo Ta'asan, A. Talukder, Chialin T. Wu, C. C. Yang, W. Yang Jan 2006

Grain Boundary Property Determination Through Measurement Of Triple Junction Geometry And Crystallography, Brent L. Adams, D. Casasent, M. Demirel, Bassem S. El-Dasher, D. Kinderlehrer, C. Liu, I. Livshits, F. Manolache, D. Mason, A. Morawiec, W. W. Mullins, S. Ozdemir, Gregory S. Rohrer, Anthony D. Rollett, David M. Saylor, Shlomo Ta'asan, A. Talukder, Chialin T. Wu, C. C. Yang, W. Yang

Faculty Publications

This work was supported primarily by the MRSEC program of the National Science Foundation under Award Number DMR-0079996. Microstructure controls the properties of most useful materials. Thus an ability to control microstructure through the processing of materials is a key to optimization of materials performance. Most materials are polycrystalline and their grain structure is a very important aspect of their microstructure. Thanks to their complexity there is a great variety of grain boundary types even in relatively isotropic materials such as the cubic metals. Simply describing the crystallography requires five (macroscopic) parameters (e.g. disorientation and inclination). Evidently, acquiring a ...


Robustness And Control Of A Magnetically Levitated Transportation System, Grzegorz Oleszczuk Jan 2006

Robustness And Control Of A Magnetically Levitated Transportation System, Grzegorz Oleszczuk

Mechanical & Aerospace Engineering Theses & Dissertations

Electromagnetic suspension of Magnetic Levitation Vehicles (Maglev) has been studied for many years as an alternative to wheel-on rail transportation systems. In this work, design and implementation of control systems for a Maglev laboratory experiment and a Maglev vehicle under development at Old Dominion University are described. Both plants are modeled and simulated with consideration of issues associated with system non-linearity, structural flexibility and electromagnetic force modeling. Discussion concerning different control strategies, namely centralized and decentralized approaches are compared and contrasted in this work. Different types of electromagnetic non-linearities are considered and described to establish a convenient method for modeling ...


Processing And Characterization Of High Performance Structural Nanocomposites, Dennis C. Working Jan 2006

Processing And Characterization Of High Performance Structural Nanocomposites, Dennis C. Working

Mechanical & Aerospace Engineering Theses & Dissertations

Carbon nanotubes are considered to be a revolutionary material breakthrough due to their unique combination of properties. While many applications for SWCNTs have been projected, realization of these potential uses have been hampered by the high cost of limited supplies of high quality SWCNTs and the difficulty in the development of a suitable processing method that does not damage the filler thus diminishing the desirable properties of this material. In spite of these technical challenges, their potential to enable the fabrication of multifunctional materials is being investigated in earnest. The goal of this thesis is to investigate the feasibility of ...


Techniques In The Design Of Thermomechanical Microactuators, Larry L. Howell, Timothy W. Mclain, Michael S. Baker, Christian D. Lott Jan 2006

Techniques In The Design Of Thermomechanical Microactuators, Larry L. Howell, Timothy W. Mclain, Michael S. Baker, Christian D. Lott

Faculty Publications

The purpose of this chapter is to provide fundamental background for the design of thermomechanical microactuators. Actuation has been a particularly challenging aspect of microsystem development. Many actuation approaches used at the macro level, such as hydraulics, pneumatics, electric motors, internal combustion engines and turbines, are either too difficult to fabricate at the micro level or do not work well at that scale. Electrostatic attraction is one approach that has been widely used for actuation of microsystems; however, electrostatic actuators tend to have high voltage requirements and low output force capabilities. While electrostatic actuation is suitable for many applications, some ...


An Experimental Investigation Of Guided Wave Propagation In Corrugated Plates Showing Stop Bands And Pass Bands, Tribikram Kundu, Sourav Banerjee, Kumar V. Jata Jan 2006

An Experimental Investigation Of Guided Wave Propagation In Corrugated Plates Showing Stop Bands And Pass Bands, Tribikram Kundu, Sourav Banerjee, Kumar V. Jata

Faculty Publications

Nonplanar surfaces are often encountered in engineering structures. In aerospace structures, periodically corrugated boundaries are formed by friction-stir-welding. In civil engineering structures, rebars used in reinforced concrete beams and slabs have periodic surface. Periodic structures are also being used to create desired acoustic band gaps. For health monitoring of these structures, a good understanding of the elastic wave propagation through such periodic structures is necessary. Although a number of research papers on the wave propagation in periodic structures are available in the literature, no one experimentally investigated the guided wave propagation through plates with periodic boundaries and compared the experimental ...


Elastic Wave Propagation In Sinusoidally Corrugated Waveguides, Sourav Banerjee, Tribikram Kundu Jan 2006

Elastic Wave Propagation In Sinusoidally Corrugated Waveguides, Sourav Banerjee, Tribikram Kundu

Faculty Publications

The ultrasonicwave propagation in sinusoidally corrugated waveguides is studied in this paper. Periodically corrugated waveguides are gaining popularity in the field of vibration control and for designing structures with desired acoustic band gaps. Currently only numerical method (Boundary Element Method or Finite Element Method) based packages (e.g., PZFlex) are in principle capable of modeling ultrasonic fields in complex structures with rapid change of curvatures at the interfaces and boundaries but no analyses have been reported. However, the packages are very CPU intensive; it requires a huge amount of computation memory and time for its execution. In this paper a ...


Extending Taylor Plasticity Theory For Microscopic Slip Transfer Conditions, Brent L. Adams, Ray M. Merrill, John A. Basinger, Bassem S. El-Dasher Jan 2006

Extending Taylor Plasticity Theory For Microscopic Slip Transfer Conditions, Brent L. Adams, Ray M. Merrill, John A. Basinger, Bassem S. El-Dasher

Faculty Publications

This work was supported primarily by the MRSEC Program of the National Science Foundation under DMR-0079996. Most studies in crystal plasticity are based upon Taylor's original 1938 work. Within Taylor's framework the dependence of yield strength on microstructure, beyond lattice orientation, is carried within the critical resolved shear stress for slip. Thus, as the grain size decreases, the critical resolved shear stress is required to increase. This increase in critical resolved shear stress is applied, uniformly across the entire interior of the slipping grains according to the basic assumption of the model (uniform plastic strain or strain rate ...


Relationship Between Vertical Shear Rate And Kinetic Energy Dissipation Rate In Stably Stratified Flows, Stephen De Bruyn Kops, D. Hebert Dec 2005

Relationship Between Vertical Shear Rate And Kinetic Energy Dissipation Rate In Stably Stratified Flows, Stephen De Bruyn Kops, D. Hebert

Stephen de Bruyn Kops

High resolution direct numerical simulations of strongly stratified turbulence are analyzed in order to investigate the relationship between vertical shearing of horizontal motions and the dissipation rate of kinetic energy. The relative magnitude of each component of the dissipation rate is examined as a function of the Reynolds number and of the buoyancy Reynolds number. From the simulation results, in conjunction with published laboratory results, it is concluded that (1) the simulation results are consistent with the laboratory data but span a much larger range of buoyancy Reynolds number, (2) the ratio of the square of the vertical shear rate ...


Melt Dispersion Mechanism For Fast Reaction Of Nanothermites, Valery I. Levitas, Blaine W. Asay, Steven F. Son, Michelle Pantoya Dec 2005

Melt Dispersion Mechanism For Fast Reaction Of Nanothermites, Valery I. Levitas, Blaine W. Asay, Steven F. Son, Michelle Pantoya

Steven F. Son

An unexpected mechanism for fast oxidation of Alnanoparticles covered by a thin oxide shell (OS) is proposed. The volume change due to melting of Al induces pressures of 0.1–4GPa and causes spallation of the OS. A subsequent unloading wave creates high tensile pressures resulting in dispersion of liquid Al clusters, oxidation of which is not limited by diffusion (in contrast to traditional mechanisms). Physical parameters controlling this process are determined. Methods to promote this melt dispersion mechanism, and consequently, improve efficiency of energetic nanothermites are discussed.


Determination Of Behavior Of Transverse Vibration Of A Timoshenko Beam With An Open Crack Of Uniform Depth, Ermias Koricho, Alem Bazezew Dec 2005

Determination Of Behavior Of Transverse Vibration Of A Timoshenko Beam With An Open Crack Of Uniform Depth, Ermias Koricho, Alem Bazezew

Ermias Koricho

Beams are widely used as structural elements and machine elements in civil, mechanical, naval and aeronautical engineering with quite complex design features. These structural and machine elements are designed for different load conditions, with good range of safety factors, and are inspected regularly. Still, unexpected and sudden failures occur due to the presence of flaws or cracks. This paper discusses the behaviour of a cracked Timoshenko beam under vibration. Particularly, the effect of crack depth and location along the beam length is treated and results obtained by the finite element method are presented. The effect of crack is introduced in ...


30 Adet Pantone Rengin Ink Formulation Programi Kullanilarak Hazirlanmasi, Bilge N. Altay, Nazli Burcu Taklak Dec 2005

30 Adet Pantone Rengin Ink Formulation Programi Kullanilarak Hazirlanmasi, Bilge N. Altay, Nazli Burcu Taklak

Bilge Nazli Altay

Ink Formulation programı kullanılarak formülasyon bileşenleri bulunmak istenen renk, hedef renk olarak tanımlanır ve programa girişi spektral fotometre ile ölçülerek yapılır. Ink Formulation programı tanımlanan hedef rengin üretimi için eldeki mevcut mürekkep ve artık mürekkepleri karıştırarak, hangi mürekkepten ne kadar konulacağını gösterecek şekilde bileşenlerin formülasyon yüzdelerini hesaplayan bir masaüstü yayıncılık programıdır. Bu çalışmanın 1. bölümünde program hakkında bilgi; bölüm 2’de yazılımın kurulumu hakkında bilgi; bölüm 3’de ColorNet yazılımı hakkında bilgi; bölüm 4’de programının yapısı ve görevleri hakkında bilgi; bölüm 5’de programı başlatma hakkında bilgi; bölüm 6’da seçilen bir hedef rengin hesaplanması hakkında bilgi; bölüm 7 ...


Modeling Of The Effects Of Athermal Flow Strength And Activation Energy For Dislocation Glide On The Nanoindentation Creep Of Nickel Thin Film At Room Temperature Dec 2005

Modeling Of The Effects Of Athermal Flow Strength And Activation Energy For Dislocation Glide On The Nanoindentation Creep Of Nickel Thin Film At Room Temperature

A.S. Md Abdul Haseeb

Nanoindentation creep behaviour of nickel at room temperature has been modeled based on the obstacle-controlled dislocation glide mechanism. Using the model, the effects of two important materials parameters viz. the activation free energy required by dislocation to overcome an obstacle without any aid from external stress, ΔF and the athermal flow strength, τ0, which is the flow strength of solids at 0 K are systematically studied. It has been found that ΔF plays a dominant role in room temperature creep properties of nickel. The role of ΔF is particularly dominant in determining the time dependent deformation. On the other hand ...