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

Engineering Commons™

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

Faculty Publications

Discipline
Institution
Keyword
Publication Year
File Type

Articles 2221 - 2250 of 3295

Full-Text Articles in Engineering

A Systematic Approach For Securing Our Space Assets, Heather Yates, Michael R. Grimaila Feb 2008

A Systematic Approach For Securing Our Space Assets, Heather Yates, Michael R. Grimaila

Faculty Publications

We are surrounded by the use of space assets, but for the most part are unaware of their impact on our lives. On a daily basis, space assets contribute to our well-being and others around the world. Space activities have enhanced security, monitored the environment, improved and increased information growth and flow, created economic growth, and changed the way people around the world live and work.[1] Since the 1991 Gulf War, we have also come to understand how much the US military depends on space. Military forces use satellite information for communications, intelligence, surveillance, reconnaissance, warning, weather, navigation, and timing. …

Go to article

Mpsa Effects On Copper Electrodeposition Investigated By Molecular Dynamics Simulations, John N. Harb, Richard L. Rowley, Dean R. Wheeler, Clint G. Guymon Jan 2008

Mpsa Effects On Copper Electrodeposition Investigated By Molecular Dynamics Simulations, John N. Harb, Richard L. Rowley, Dean R. Wheeler, Clint G. Guymon

Faculty Publications

In superconformal filling of copper-chip interconnects, organic additives are used to fill high-aspect-ratio trenches or vias from the bottom up. In this study we report on the development of intermolecular potentials and use molecular dynamics simulation.

Go to article

Expanded Mathematical Treatment For "Spectral Bias In Adaptive Beamforming With Narrowband Interference'', Brian D. Jeffs, Karl F. Warnick Jan 2008

Expanded Mathematical Treatment For "Spectral Bias In Adaptive Beamforming With Narrowband Interference'', Brian D. Jeffs, Karl F. Warnick

Faculty Publications

This technical note presents extended versions of some mathematical derivations found in the paper Spectral Bias in Adaptive Beamforming with Narrowband Interference which is under review for publication in IEEE Signal Processing Letters. Though the SP Letters paper is self contained and complete, this note provides intermediate steps for some of the equation derivations to assist the interested readers who would like to re-create the results.

Go to article

Air-Trench Splitters For Ultra-Compact Ring Resonators In Low Refractive Index Contrast Waveguides, Seunghyun Kim, Gregory P. Nordin, Yongbin Lin, Nazli Rahmanian Jan 2008

Air-Trench Splitters For Ultra-Compact Ring Resonators In Low Refractive Index Contrast Waveguides, Seunghyun Kim, Gregory P. Nordin, Yongbin Lin, Nazli Rahmanian

Faculty Publications

We demonstrate air-trench splitters in low index contrast perfluorocyclobutyl (PFCB) waveguides. Splitters are fabricated by etching 800 nm wide high aspect ratio (18:1) trenches. The measured optical loss is 0.4 dB/splitter. The reflection/transmission splitting ratio is 0.859/0.141, which closely matches two-dimensional finite difference time domain (2DFDTD) simulation results. Air-trench splitters and bends are used to demonstrate an ultra-compact ring resonator (RR) with a size reduction of 1,700 compared to a RR based on traditional curved waveguides in the same material system. A comparison between the RR’s measured and analytically calculated performance shows close agreement when splitter and bend losses are …

Go to article

Pid Parameter Optimization Of An Uav Longitudinal Flight Control System, Kamran Turkoglu, Ugur Ozdemir, Melike Nikbay, Elbrous Jafarov Jan 2008

Pid Parameter Optimization Of An Uav Longitudinal Flight Control System, Kamran Turkoglu, Ugur Ozdemir, Melike Nikbay, Elbrous Jafarov

Faculty Publications

In this paper, an automatic control system design based on Integral Squared Error (ISE) parameter optimization technique has been implemented on longitudinal flight dynamics of an UAV. It has been aimed to minimize the error function between the reference signal and the output of the plant. In the following parts, objective function has been defined with respect to error dynamics. An unconstrained optimization problem has been solved analytically by using necessary and sufficient conditions of optimality, optimum PID parameters have been obtained and implemented in control system dynamics.

Go to article

Microfluidic Devices For Terahertz Spectroscopy Of Biomolecules, P. A. George, W. Hui, F. Rana, Benjamin G. Hawkins, A. E. Smith, B. J. Kirby Jan 2008

Microfluidic Devices For Terahertz Spectroscopy Of Biomolecules, P. A. George, W. Hui, F. Rana, Benjamin G. Hawkins, A. E. Smith, B. J. Kirby

Faculty Publications

We demonstrate microfluidic devices for terahertz spectroscopy of biomolecules in aqueous solutions. The devices are fabricated out of a plastic material that is both mechanically rigid and optically transparent with near-zero dispersion in the terahertz frequency range. Using a low-power terahertz time-domain spectrometer, we experimentally measure the absorption spectra of the vibrational modes of bovine serum albumin from 0.5–2.5 THz and find good agreement with previously reported data obtained using large-volume solutions and a high-power free-electron laser. Our results demonstrate the feasibility of performing high sensitivity terahertz spectroscopy of biomolecules in aqueous solutions with detectable molecular quantities as small as …

Go to article

Acceptor Levels In Gase:In Crystals Investigated By Deep-Level Transient Spectroscopy And Photoluminescence, Y. Cui, R. Dupere, A. Burger, D. Johnstone, K. C. Mandal, S. A. Payne Jan 2008

Acceptor Levels In Gase:In Crystals Investigated By Deep-Level Transient Spectroscopy And Photoluminescence, Y. Cui, R. Dupere, A. Burger, D. Johnstone, K. C. Mandal, S. A. Payne

Faculty Publications

No abstract provided.

Go to article

Combinatorial Investigation Of Magnetostriction In Fe-Fa And Fe-Ga-Al, Jason R. Hattrick-Simpers, Dwight Hunter, Corneliu M. Craciunescu, Kyu Sung Jang, Makoto Murakami, James Cullen, Manfred Wuttig, Ichiro Takeuchi, Samuel E. Lofland, Leonid Bendersky, Noble Woo, Robert Bruce Vandover, Toshiya Takahashi, Yasubumi Furuya Jan 2008

Combinatorial Investigation Of Magnetostriction In Fe-Fa And Fe-Ga-Al, Jason R. Hattrick-Simpers, Dwight Hunter, Corneliu M. Craciunescu, Kyu Sung Jang, Makoto Murakami, James Cullen, Manfred Wuttig, Ichiro Takeuchi, Samuel E. Lofland, Leonid Bendersky, Noble Woo, Robert Bruce Vandover, Toshiya Takahashi, Yasubumi Furuya

Faculty Publications

A high-throughput high-sensitivity optical technique for measuringmagnetostriction of thin-film composition-spread samples has been developed. It determines the magnetostriction by measuring the induced deflection of micromachined cantilever unimorph samples. Magnetostrictionmeasurements have been performed on as-deposited Fe–Ga and Fe–Ga–Al thin-film composition spreads. The thin-film Fe–Ga spreads display a similar compositional variation of magnetostriction as bulk. A previously undiscovered peak in magnetostriction at low Ga content was also observed and attributed to a maximum in the magnetocrystalline anisotropy. Magnetostrictive mapping of the Fe–Ga–Al ternary system reveals the possibility of substituting up to 8at.%Al in Fe70Ga30 without significant degradation of magnetostriction.

Go to article

High-Throughput Screening Of Shape Memory Alloy Thin-Film Spreads Using Nanoindentation, Arpit Dwivedi, Thomas J. Wyrobek, Oden L. Warren, Jason R. Hattrick-Simpers, Olubenga O. Famodu, Ichiro Takeuchi Jan 2008

High-Throughput Screening Of Shape Memory Alloy Thin-Film Spreads Using Nanoindentation, Arpit Dwivedi, Thomas J. Wyrobek, Oden L. Warren, Jason R. Hattrick-Simpers, Olubenga O. Famodu, Ichiro Takeuchi

Faculty Publications

We have demonstrated the utility of nanoindentation as a rapid characterization tool for mapping shape memoryalloy compositions in combinatorial thin-film libraries. Nanoindentation was performed on Ni–Mn–Al ternary composition spreads. The indentation hardness and the reduced elastic modulus were mapped across a large fraction of the ternary phase diagram. The large shape memoryalloy composition region, located around the Heusler composition (Ni2MnAl), was found to display significant departure in these mechanical properties from the rest of the composition spread. In particular, the modulus and the hardness values are lower for the martensite region than those of the rest of the …

Go to article

Hydrogen Peroxide Formation Rates In A Pemfc Anode And Cathode: Effect Of Humidity And Temperature, Vijay A. Sethuraman, John W. Weidner, Andrew T. Haug, Sathya Motupally, Lesia V. Protsailo Jan 2008

Hydrogen Peroxide Formation Rates In A Pemfc Anode And Cathode: Effect Of Humidity And Temperature, Vijay A. Sethuraman, John W. Weidner, Andrew T. Haug, Sathya Motupally, Lesia V. Protsailo

Faculty Publications

Hydrogen peroxide (H2O2) formation rates in a proton exchange membrane fuel cell (PEMFC) anode and cathode were estimated as a function of humidity and temperature by studying the oxygen reduction reaction (ORR) on a rotating ring disk electrode. Fuel cell conditions were replicated by depositing a film of Pt/Vulcan XC-72 catalyst onto the disk and by varying the temperature, dissolved O2 concentration, and the acidity levels in hydrochloric acid (HClO4). The HClO4 acidity was correlated to ionomer water activity and hence fuel cell humidity. The H2O2 formation rates showed …

Go to article

Web-Scale Workflow: Integrating Distributed Services, M. Brian Blake, Michael N. Huhns Jan 2008

Web-Scale Workflow: Integrating Distributed Services, M. Brian Blake, Michael N. Huhns

Faculty Publications

Modular applications, components, and services are all ways of describing the product of an organization's efforts to embody its capabilities in autonomous software modules. In fact, the integration of services using well-established workflow paradigms could amplify an organization's capabilities with the creation of a full-blown, inter-organizational system of systems. This is the essence of Web-scale workflows. Considering the recent popularity and acceptance of service-oriented technologies, the application of such distributed systems is only limited by imagination, but it's also important to understand existing research challenges and their implications to various Web-scale workflow domains.

Go to article

Durability Of Perfluorosulfonic Acid And Hydrocarbon Membranes: Effect Of Humidity And Temperature, Vijay A. Sethuraman, John W. Weidner, Andrew T. Haug, Lesia V. Protsailo Jan 2008

Durability Of Perfluorosulfonic Acid And Hydrocarbon Membranes: Effect Of Humidity And Temperature, Vijay A. Sethuraman, John W. Weidner, Andrew T. Haug, Lesia V. Protsailo

Faculty Publications

The effect of humidity on the chemical stability of two types of membranes [i.e., perfluorosulfonic acid type (PFSA, Nafion 112) and biphenyl sulfone hydrocarbon type, (BPSH-35)] was studied by subjecting the membrane electrode assemblies (MEAs) to open-circuit voltage (OCV) decay and potential cycling tests at elevated temperatures and low inlet-gas relative humidities. The BPSH-35 membranes showed poor chemical stability in ex situ Fenton tests compared to that of Nafion membranes. However, under fuel cell conditions, BPSH-35 MEAs outperformed Nafion 112 MEAs in both the OCV decay and potential cycling tests. For both membranes, (i) at a given temperature, …

Go to article

Enhanced Dielectric Properties In Single Crystal-Like Bifeo3 Thin Films Grown By Flux-Mediated Epitaxy, S.-H. Lim, M. Murakami, J. H. Yang, S.-Y. Young, Jason R. Hattrick-Simpers, M. Wuttig, L. G. Salamanca-Riba, I. Takeuchi Jan 2008

Enhanced Dielectric Properties In Single Crystal-Like Bifeo3 Thin Films Grown By Flux-Mediated Epitaxy, S.-H. Lim, M. Murakami, J. H. Yang, S.-Y. Young, Jason R. Hattrick-Simpers, M. Wuttig, L. G. Salamanca-Riba, I. Takeuchi

Faculty Publications

We have fabricated single crystal-like BiFeO3 (BFO) thin films by flux-mediated epitaxy using pulsed laser deposition(PLD). The Bi–Cu–O flux composition and its thickness were optimized using composition spread, thickness gradient, and temperature gradient libraries. The optimized BFO thin films grown with this technique showed larger grain size of ∼2μm and higher dielectric constant in the range of 260–340 than those for standard PLD grown films. In addition, the leakage current density of the films was reduced by two orders of magnitude compared to that of standard PLD grown films.

Go to article

Elastic Wave Field Computation In Multilayered Nonplanar Solid Structures: A Mesh-Free Semianalytical Approach, Sourav Banerjee, Tribikram Kundu Jan 2008

Elastic Wave Field Computation In Multilayered Nonplanar Solid Structures: A Mesh-Free Semianalytical Approach, Sourav Banerjee, Tribikram Kundu

Faculty Publications

Multilayered solid structures made of isotropic, transversely isotropic, or general anisotropic materials are frequently used in aerospace, mechanical, and civil structures. Ultrasonic fields developed in such structures by finite size transducers simulating actual experiments in laboratories or in the field have not been rigorously studied. Several attempts to compute the ultrasonic field inside solid media have been made based on approximate paraxial methods like the classical ray tracing and multi-Gaussian beam models. These approximate methods have several limitations. A new semianalytical method is adopted in this article to model elastic wave field in multilayered solid structures with planar or nonplanar …

Go to article

The Role Of Filler-Matrix Interaction On Viscoelastic Response Of Biomimetic Nanocomposite Hydrogels, Alireza S. Sarvestani, Xuezhong He, Esmaiel Jabbari Jan 2008

The Role Of Filler-Matrix Interaction On Viscoelastic Response Of Biomimetic Nanocomposite Hydrogels, Alireza S. Sarvestani, Xuezhong He, Esmaiel Jabbari

Faculty Publications

The effect of a glutamic acid (negatively charged) peptide (Glu6), which mimics the terminal region of the osteonectin glycoprotein of bone on the shear modulus of a synthetic hydorgel/apatite nanocomposite, was investigated. One end of the synthesized peptide was functionalized with an acrylate group (Ac-Glu6) to covalently attach the peptide to the hydrogel phase of the composite matrix. The addition of Ac-Glu6 to hydroxyapatite (HA) nanoparticles (50 nm in size) resulted in significant reinforcement of the shear modulus of the nanocomposite (~100% increase in elastic shear modulus). The reinforcement effect of the Glu6 peptide, a sequence in the terminal region …

Go to article

Parameter Estimation And Life Modeling Of Lithium-Ion Cells, Shriram Santhanagopalan, Qi Zhang, Karthikeyan Kumaresan, Ralph E. White Jan 2008

Parameter Estimation And Life Modeling Of Lithium-Ion Cells, Shriram Santhanagopalan, Qi Zhang, Karthikeyan Kumaresan, Ralph E. White

Faculty Publications

Lithium-ion pouch cells were cycled at five different temperatures (5, 15, 25, 35, and 45°C ), and rate capability studies were performed after every hundred cycles. The data were used with a simple physics-based model to estimate parameters that capture the capacity fade in the cell, with cycling. The weight of active material within each electrode was estimated as a function of time, using rate capability data at the C/33 rate. The C-rate for these cells is 1.656 A. The capacity fade due to the loss of active material and that due to the loss of cyclable lithium …

Go to article

Thermal Model For A Li-Ion Cell, Karthikeyan Kumaresan, Godfrey Sikha, Ralph E. White Jan 2008

Thermal Model For A Li-Ion Cell, Karthikeyan Kumaresan, Godfrey Sikha, Ralph E. White

Faculty Publications

A thermal model for a lithium-ion cell is presented and used to predict discharge performance at different operating temperatures. The results from the simulations are compared to experimental data obtained from lithium-ion pouch cells. The model includes a set of parameters (and their concentration and temperature dependencies) that has been obtained for a lithium-ion cell composed of a mesocarbon microbead anode, LiCoO2 cathode in 1 M LiPF6 salt, in a mixture of ethylene carbonate, propylene carbonate, ethyl-methyl carbonate, and diethyl carbonate electrolyte. The parameter set was obtained by comparing the model predictions to the experimental discharge profiles obtained …

Go to article

Analytical Expression For The Impedance Response For A Lithium-Ion Cell, Godfrey Sikha, Ralph E. White Jan 2008

Analytical Expression For The Impedance Response For A Lithium-Ion Cell, Godfrey Sikha, Ralph E. White

Faculty Publications

An analytical expression to predict the impedance response of a dual insertion electrode cell (insertion electrodes separated by an ionically conducting membrane) is presented. The expression accounts for the reaction kinetics and double-layer adsorption processes at the electrode-electrolyte interface, transport of electroactive species in the electrolyte phase, and insertion of species in the solid phase of the insertion electrodes. The accuracy of the analytical expression is validated by comparing the impedance response predicted by the expression to the corresponding numerical solution. The analytical expression is used to predict the impedance response of a lithium-ion cell consisting of a porous LiCoO …

Go to article

A Mathematical Model For A Lithium–Sulfur Cell, Karthikeyan Kumaresan, Yuriy Mikhaylik, Ralph E. White Jan 2008

A Mathematical Model For A Lithium–Sulfur Cell, Karthikeyan Kumaresan, Yuriy Mikhaylik, Ralph E. White

Faculty Publications

A mathematical model is presented for a complete lithium–sulfur cell. The model includes various electrochemical and chemical (precipitation) reactions, multicomponent transport phenomena in the electrolyte, and the charge transfer within and between solid and liquid phases. A change in the porosity of the porous cathode and separator due to precipitation reactions is also included in the model. The model is used to explain the physical reasons for the two-stage discharge profiles that are typically obtained for lithium–sulfur cells.

Go to article

Evolution Of Surface Deposits On A High-Pressure Turbine Blade—Part I: Physical Characteristics, James Edward Wammack, Jared M. Crosby, Daniel Fletcher, Jeffrey P. Bons, Thomas H. Fletcher Jan 2008

Evolution Of Surface Deposits On A High-Pressure Turbine Blade—Part I: Physical Characteristics, James Edward Wammack, Jared M. Crosby, Daniel Fletcher, Jeffrey P. Bons, Thomas H. Fletcher

Faculty Publications

Turbine blade coupons with three different surface treatments were exposed to deposition conditions in an accelerated deposition facility. The facility simulates the flow conditions at the inlet to a first stage high-pressure turbine (T=1150 C, M=0.31). The combustor exit flow is seeded with dust particulate that would typically be ingested by a large utility power plant. The three coupon surface treatments included: (1) bare polished metal; (2) polished thermal barrier coating with bondcoat; and (3) unpolished oxidation resistant bondcoat. Each coupon was subjected to four successive 2 h deposition tests. The particulate loading was scaled to simulate 0.02 parts per …

Go to article

Effects Of Temperature And Particle Size On Deposition In Land Based Turbines, Jared M. Crosby, Scott Lewis, Jeffrey P. Bons, Weiguo Ai, Thomas H. Fletcher Jan 2008

Effects Of Temperature And Particle Size On Deposition In Land Based Turbines, Jared M. Crosby, Scott Lewis, Jeffrey P. Bons, Weiguo Ai, Thomas H. Fletcher

Faculty Publications

Four series of tests were performed in an accelerated deposition test facility to study the independent effects of particle size, gas temperature, and metal temperature on ash deposits from two candidate power turbine synfuels (coal and petcoke). The facility matches the gas temperature and velocity of modern first stage high pressure turbine vanes while accelerating the deposition process. Particle size was found to have a significant effect on capture efficiency with larger particles causing significant thermal barrier coating (TBC) spallation during a 4 h accelerated test. In the second series of tests, particle deposition rate was found to decrease with …

Go to article

Evolution Of Surface Deposits On A High-Pressure Turbine Blade—Part Ii: Convective Heat Transfer, Jeffrey P. Bons, James Edward Wammack, Jared M. Crosby, Daniel Fletcher, Thomas H. Fletcher Jan 2008

Evolution Of Surface Deposits On A High-Pressure Turbine Blade—Part Ii: Convective Heat Transfer, Jeffrey P. Bons, James Edward Wammack, Jared M. Crosby, Daniel Fletcher, Thomas H. Fletcher

Faculty Publications

A thermal barrier coating (TBC)-coated turbine blade coupon was exposed to successive deposition in an accelerated deposition facility simulating flow conditions at the inlet to a first stage high pressure turbine (T=1150 C, M=0.31). The combustor exit flow was seeded with dust particulate that would typically be ingested by a large utility power plant. The turbine coupon was subjected to four successive 2 h deposition tests. The particulate loading was scaled to simulate 0.02 parts per million weight (ppmw) of particulate over 3 months of continuous gas turbine operation for each 2 h laboratory simulation (for a cumulative 1 year …

Go to article

A Survey Of Worm Detection And Containment, Pele Li, M. Salour, Xiao Su Jan 2008

A Survey Of Worm Detection And Containment, Pele Li, M. Salour, Xiao Su

Faculty Publications

Self-duplicating, self-propagating malicious codes known as computer worms spread themselves without any human interaction and launch the most destructive attacks against computer networks. At the same time, being fully automated makes their behavior repetitious and predictable. This article presents a survey and comparison of Internet worm detection and containment schemes. We first identify worm characteristics through their behavior, and then classify worm detection algorithms based on the parameters used in the algorithms. Furthermore, we analyze and compare different detection algorithms with reference to the worm characteristics by identifying the type of worms that can and cannot be detected by these …

Go to article

Socially Rational Models For Autonomous Agents, Wynn C. Stirling, James K. Archibald, Matthew S. Nokleby Jan 2008

Socially Rational Models For Autonomous Agents, Wynn C. Stirling, James K. Archibald, Matthew S. Nokleby

Faculty Publications

Autonomous multi-agent systems that are to coordinate must be designed according to models that accommodate such complex social behavior as compromise, negotiation, and altruism. In contrast to individually rational models, where each agent seeks to maximize its own welfare without regard for others, socially rational agents have interests beyond themselves. Such models require a new type of utility function a social utility to ensure three desirable properties: (a) conditional preferences agents may adjust their preferences to account for the preferences of others; (b) endogeny group preferences are determined internally by interactions between individual agents; (c) framing invariance reformulations of the …

Go to article

Reduced Order Modeling Of Time-Dependent Reflectance Profiles From Purely Scattering Media, R. Scott Larson, Matthew R. Jones Jan 2008

Reduced Order Modeling Of Time-Dependent Reflectance Profiles From Purely Scattering Media, R. Scott Larson, Matthew R. Jones

Faculty Publications

Due to the widespread existence and importance of foam, inverse techniques for characterizing industrial foams are of interest. An essential element in an inverse method used to characterize a foam layer is a model of the time-dependent reflectance of a laser pulse. Monte Carlo methods may be used to accurately model reflectance, but these methods are computationally expensive. Computationally efficient methods based on the diffusion approximation have been developed, but this approach is not sufficiently accurate in many cases of interest. Therefore, a computationally efficient and robust method is desirable. This paper presents a computationally efficient method for modeling the …

Go to article

Characteristics Of Black Liquor Sprays From Gas-Assisted Atomizers In Hightemperature Environments, Andrew J. Mackrory, Dale Tree, Larry L. Baxter Jan 2008

Characteristics Of Black Liquor Sprays From Gas-Assisted Atomizers In Hightemperature Environments, Andrew J. Mackrory, Dale Tree, Larry L. Baxter

Faculty Publications

Black liquor droplets in an entrained-flow gasifier that are too large or too small can cause problems in the chemical recovery process. It is therefore important in gasifier design to understand the nature of the atomized-gas spray. We used high-speed imaging to study black liquor sprays in cold and hot environments. Significant conclusions are that: 1. the droplet size distribution width is linked to the mean droplet size as for other sprays in the literature, necessitating a gasifier design that is tolerant of the distribution width associated with the target droplet size; 2. the shape of black liquor droplets is …

Go to article

Network Formation Using Ant Colony Optimization -- A Systematic Review, Steven C. Oimoen, Gilbert L. Peterson, Kenneth M. Hopkinson Jan 2008

Network Formation Using Ant Colony Optimization -- A Systematic Review, Steven C. Oimoen, Gilbert L. Peterson, Kenneth M. Hopkinson

Faculty Publications

A significant area of research in the field of hybrid communications is the Network Design Problem (NDP) [1]. The NDP is an NP complete problem [1] that focuses on identifying the optimal network topology for transmitting commodities between nodes, under constraints such as bandwidth, limited compatible directed channels, and link and commodity costs. The NDP focuses on designing a flexible network while trying to achieve optimal flow or routing. If a link (or arc) is used, then an associated fixed cost of the edge is incurred. In addition, there is a cost for using the arc depending on the flow. …

Go to article

Performance Comparison Of Pb(Zr0.52Ti0.48)O3-Only And Pb(Zr0.52Ti0.48)O3-On-Silicon Resonators, Hengky Chandrahalim, Sunil A. Bhave, Ronald G. Polcawich, Jeff Pulskamp, Dan Judy, Roger Kaul, Madan Dubey Jan 2008

Performance Comparison Of Pb(Zr0.52Ti0.48)O3-Only And Pb(Zr0.52Ti0.48)O3-On-Silicon Resonators, Hengky Chandrahalim, Sunil A. Bhave, Ronald G. Polcawich, Jeff Pulskamp, Dan Judy, Roger Kaul, Madan Dubey

Faculty Publications

This paper provides a quantitative comparison and explores the design space of lead zirconium titanate (PZT)–only and PZT-on-silicon length-extensional mode resonators for incorporation into radio frequency microelectromechanical system filters and oscillators. We experimentally measured the correlation of motional impedance (RX) and quality factor (Q) with the resonators’ silicon layer thickness (tSi). For identical lateral dimensions and PZT-layer thicknesses (tPZT), the PZT-on-silicon resonator has higher resonant frequency (fC), higher Q (5100 versus 140), lower RX (51 Ω versus 205 Ω), and better linearity [third-order input intercept …

Go to article

The Effect Of Contact Length On Adhesion Between Carbon Nanotubes On Silicon Dioxide, Robert C. Davis, Kaylee Mcelroy, Aaron R. Hopkins Dec 2007

The Effect Of Contact Length On Adhesion Between Carbon Nanotubes On Silicon Dioxide, Robert C. Davis, Kaylee Mcelroy, Aaron R. Hopkins

Faculty Publications

The force of adhesion was measured for single walled carbon nanotubes grown over lithographically defined silicon dioxide trenches. We varied contact lengths between the nanotubes and silicon dioxide from 230 to 850 nm. Suspended nanotubes were pushed vertically into the trenches with an atomic force microscope tip, causing them to slip along the surface. Previous work done at shorter contact lengths found that tension was constant with contact length [J. D. Whittaker et al., Nano Lett. 6, 953 (2006)]. This study finds that when the nanotube contact length approaches 1 µm, the tension at which nanotubes slip begins to increase …

Go to article

). Size Dependency Of The Elastic Modulus Of Zno Nanowires: Surface Stress Effect, Guofeng Wang, Xiaodong Li Dec 2007

). Size Dependency Of The Elastic Modulus Of Zno Nanowires: Surface Stress Effect, Guofeng Wang, Xiaodong Li

Faculty Publications

Relation between the elastic modulus and the diameter (D) of ZnOnanowires was elucidated using a model with the calculated ZnOsurface stresses as input. We predict for ZnOnanowires due to surface stress effect: (1) when D>20nm, the elastic modulus would be lower than the bulk modulus and decrease with the decreasing diameter, (2) when 20nm>D>2nm, the nanowires with a longer length and a wurtzite crystal structure could be mechanically unstable, and (3) when D<2nm, the elastic modulus would be higher than that of the bulk value and increase with a decrease in nanowire diameter.

Go to article

First Prev Next Last