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Articles 1921 - 1950 of 2359

Full-Text Articles in Engineering

Accelerated Testing Method For Pem Fuel Cell Based Uninterrupted Power Supply Systems, Xinyu Huang, Xiaofeng Wang Jan 2007

Accelerated Testing Method For Pem Fuel Cell Based Uninterrupted Power Supply Systems, Xinyu Huang, Xiaofeng Wang

Faculty Publications

Proton exchange membrane fuel cell based power systems are on the verge of commercialization for a number of niche applications where batteries are traditionally used. Uninterrupted power supply (UPS) for wireless communication towers and broadband network relay utilities is one of the targeted application of fuel cell power systems with capacity ranging from one to serveral kilowatts. It is believed that fuel cell based UPS systems can offer considerable advantage when extended backup time is desirable. In order to replace the well-known battery based UPS systems, the reliability and perofrmance of fuel cell based UPS system need to be thoroughly …

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Demonstration Of Magnetoelectric Scanning Probe Microscopy, Jason R. Hattrick-Simpers, Liyang Dai, Manfred Wuttig, Ichiro Takeuchi, Eckhard Quandt Jan 2007

Demonstration Of Magnetoelectric Scanning Probe Microscopy, Jason R. Hattrick-Simpers, Liyang Dai, Manfred Wuttig, Ichiro Takeuchi, Eckhard Quandt

Faculty Publications

A near-field room temperature scanning magnetic probe microscope has been developed using a laminated magnetoelectric sensor. The simple trilayer longitudinal-transverse mode sensor, fabricated using Metglas as the magnetostrictive layer and polyvinylidene fluoride as the piezoelectric layer, shows an ac field sensitivity of 467±3μV∕Oe in the measured frequency range of 200Hz–8kHz. The microscope was used to image a 2mm diameter ring carrying an ac current as low as 10−5A. ac fields as small as 3×10−10T have been detected.

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Rapid Structural Mapping Of Ternary Metallic Alloy Systems Using The Combinatorial Approach And Cluster Analysis, C. J. Long, Jason R. Hattrick-Simpers, M. Murakami, R. C. Srivastava, I. Takeuchi, V. L. Karen, X. Li Jan 2007

Rapid Structural Mapping Of Ternary Metallic Alloy Systems Using The Combinatorial Approach And Cluster Analysis, C. J. Long, Jason R. Hattrick-Simpers, M. Murakami, R. C. Srivastava, I. Takeuchi, V. L. Karen, X. Li

Faculty Publications

We are developing a procedure for the quick identification of structural phases in thin film composition spread experiments which map large fractions of compositional phase diagrams of ternary metallic alloy systems. An in-house scanning x-ray microdiffractometer is used to obtain x-ray spectra from 273 different compositions on a single composition spread library. A cluster analysissoftware is then used to sort the spectra into groups in order to rapidly discover the distribution of phases on the ternary diagram. The most representative pattern of each group is then compared to a database of known structures to identify known phases. Using this method, …

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Short-Time Transient Analysis Of Intercalation Of An Ion Into A Sphere, Sheba Devan, Ralph E. White Jan 2007

Short-Time Transient Analysis Of Intercalation Of An Ion Into A Sphere, Sheba Devan, Ralph E. White

Faculty Publications

A short-time transient analysis is presented for a sinusoidal input potential for a spherical particle. The objective of this work was to extract accurate values of the parameters associated with an intercalation into a spherical particle. These parameters are exchange current density, double-layer capacitance, and diffusion coefficient. The effects of these parameters on the response were examined using a sensitivity analysis, which indicated that optimum frequency values of the input perturbation exist for estimation of these parameters. A procedure is presented to obtain all these parameters using the short-time response. The results show that the short-time analysis is a useful …

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Analytical Expression For The Impedance Response Of An Insertion Electrode Cell, Godfrey Sikha, Ralph E. White Jan 2007

Analytical Expression For The Impedance Response Of An Insertion Electrode Cell, Godfrey Sikha, Ralph E. White

Faculty Publications

An analytical expression for the impedance response of an insertion cathode/separator/foil anode cell sandwich is presented. The analytical expression includes the impedance contributions from interfacial kinetics, double-layer adsorption, and solution-phase and solid-phase diffusion processes. The validity of the analytical solution is ascertained by comparison with the numerical solution obtained for a LiCoO2 /polypropylene/lithium metal cell. The flexibility of the analytical solution is utilized to analyze various limiting conditions. An expression to estimate solid-phase diffusion coefficient of insertion species in a porous electrode influenced by the solution-phase diffusion process is also derived

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Simulation Of Polarization Curves For Oxygen Reduction Reaction In 0.5 M H2So4 At A Rotating Ring Disk Electrode, Qingbo Dong, Shriram Santhanagopalan, Ralph E. White Jan 2007

Simulation Of Polarization Curves For Oxygen Reduction Reaction In 0.5 M H2So4 At A Rotating Ring Disk Electrode, Qingbo Dong, Shriram Santhanagopalan, Ralph E. White

Faculty Publications

A cylindrical two-dimensional model based on the Nernst–Planck equations, the Navier–Stokes equation, and the continuity equation is used to simulate the oxygen reduction reaction in 0.5MH2SO4 at a rotating ring disk electrode. Concentration distributions and a potential profile are obtained as a function of the axial and radial distances from the center of the electrode surface. Polarization curves are simulated to interpret experimental results by studying various reaction mechanisms, i.e., the four-electron-transfer reduction of oxygen, the two-electron-transfer reduction of oxygen, a combination of the above two reactions, mechanisms with reduction of peroxide to water, and/or the heterogeneous …

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Moving Boundary Model For The Discharge Of A Licoo2 Electrode, Qi Zhang, Ralph E. White Jan 2007

Moving Boundary Model For The Discharge Of A Licoo2 Electrode, Qi Zhang, Ralph E. White

Faculty Publications

A moving boundary model in a spherical LiCoO2 particle is presented to account for the diffusion controlled phase transition in LiCoO2 solid particles, and this model is incorporated into a porous electrode model for the LiCoO2 electrode. The simulation results agree well with the experimental data of a LiCoO2 electrode. A study of the flux distribution in the porous electrode shows that the phase transition phenomenon in the LiCoO2particles has a significant effect on the flux distribution by changing the solid phase diffusion resistance in the particles.

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Parameter Estimation And Model Discrimination For A Lithium-Ion Cell, Shriram Santhanagopalan, Qingzhi Guo, Ralph E. White Jan 2007

Parameter Estimation And Model Discrimination For A Lithium-Ion Cell, Shriram Santhanagopalan, Qingzhi Guo, Ralph E. White

Faculty Publications

Two different models were used to obtain transport and kinetic parameters using nonlinear regression from experimental charge/discharge curves of a lithium-ion cell measured at 35°C under four rates, C/5, C/2, 1C, and 2C, where the C rate is 1.656A . The Levenberg-Marquardt method was used to estimate parameters in the models such as the diffusion of lithium ions in the positive electrode. A confidence interval for each parameter was also presented. The parameter values lie within their confidence intervals. The use of statistical weights to correct for the scatter in experimental data as well as to treat one set of …

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Effect Of Water On The Electrochemical Oxidation Of Gas-Phase So2 In A Pem Electrolyzer For H2 Production, John Staser, Ramaraja P. Ramasamy, Premkumar Sivasubramanian, John W. Weidner Jan 2007

Effect Of Water On The Electrochemical Oxidation Of Gas-Phase So2 In A Pem Electrolyzer For H2 Production, John Staser, Ramaraja P. Ramasamy, Premkumar Sivasubramanian, John W. Weidner

Faculty Publications

Water plays a critical role in producing hydrogen from the electrochemical oxidation of SO2 in a proton exchange membrane (PEM) electrolyzer. Not only is water needed to keep the membrane hydrated, but it is also a reactant. One way to supply water is to dissolve SO2 in sulfuric acid and feed that liquid to the anode, but this process results in significant diffusion resistance for the SO2. Alternatively, we have developed a process where SO2 is fed as a gas to the anode compartment and reacts with water crossing the membrane to produce sulfuric acid. There was concern that the …

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Effect Of Diphenyl Siloxane On The Catalytic Activity Of Pt On Carbon, Vijay A. Sethuraman, John W. Weidner, Lesia V V. Protsailo Jan 2007

Effect Of Diphenyl Siloxane On The Catalytic Activity Of Pt On Carbon, Vijay A. Sethuraman, John W. Weidner, Lesia V V. Protsailo

Faculty Publications

The effect of silicone on the catalytic activity of Pt for oxygen reduction and hydrogen adsorption was studied using diphenyl siloxane as a source compound at a rotating disk electrode (RDE). Diphenyl siloxane did not affect the catalytic activity of Pt when it was injected into the electrolyte. However, it blocked the oxygen reduction reaction when it was premixed with the catalyst. Proton transport was not blocked in either case. We postulate that diphenyl siloxane induces hydrophobicity and causes local water starvation, thereby blocking oxygen transport. Hence, the slow leaching of silicone seals in a fuel cell could cause silicon …

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Low-Temperature Synthesis Of A Ptru/Nb0.1ti0.9o2 Electrocatalyst For Methanol Oxidation, Brenda L. García, Roderick Fuentes, John W. Weidner Jan 2007

Low-Temperature Synthesis Of A Ptru/Nb0.1ti0.9o2 Electrocatalyst For Methanol Oxidation, Brenda L. García, Roderick Fuentes, John W. Weidner

Faculty Publications

Niobium was doped into anatase TiO2 support at 10 mol % (Nb0.1Ti0.9O2) using sol-gel chemistry. A PtRu/Nb0.1Ti0.9O2 catalyst was synthesized by LiBH4 reduction in tetrahydrofuran. The methanol electro-oxidation activity of the catalyst shows that this oxide support was electrically conductive. The current (A/gPt) was 6% higher on the PtRu/Nb0.1Ti0.9O2 catalyst compared to a commercial PtRu/C catalyst at 25°C. The electrochemically active surface area of the PtRu/C was 94% higher than PtRu/Nb0.1Ti0.9O2, thus the current per active site was 100% higher on PtRu/Nb0.1Ti0.9O2. A membrane electrode assembly with PtRu/Nb0.1Ti0.9O2 had 46% higher current (A/gPt) than an equivalent E-TEK membrane electrode assembly …

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Exafs Characterization Of Dendrimer-Derived Pt/Γ-Al2o3, A. Siani, O. S. Alexeev, C. T. Williams, Harry J. Ploehn, M. D. Amiridis Jan 2007

Exafs Characterization Of Dendrimer-Derived Pt/Γ-Al2o3, A. Siani, O. S. Alexeev, C. T. Williams, Harry J. Ploehn, M. D. Amiridis

Faculty Publications

The various steps involved in the preparation of a Pt/-Al2O3 material using hydroxyl-terminated generation four (G4OH) PAMAM dendrimers as templates were monitored by EXAFS. The results indicate that Cl ligands in the Pt precursors (H2PtCl6 and K2PtCl4) were partially replaced by aquo ligands upon hydrolysis to form [PtCl3(H2O)3]+ and [PtCl2(H2O)2] species. After interaction of such species with G4OH, Cl ligands from the first coordination shell of Pt were further replaced by nitrogen atoms from the dendrimer interior, …

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Fabrication And Characterization Of Poly(Propylene Fumarate) Scaffolds With Controlled Pore Structures Using 3-Dimensional Printing And Injection Molding, Kee-Won Lee, Shanfeng Wang, Lichun Lu, Esmaiel Jabbari, Bradford L. Currier, Michael J. Yaszemski Oct 2006

Fabrication And Characterization Of Poly(Propylene Fumarate) Scaffolds With Controlled Pore Structures Using 3-Dimensional Printing And Injection Molding, Kee-Won Lee, Shanfeng Wang, Lichun Lu, Esmaiel Jabbari, Bradford L. Currier, Michael J. Yaszemski

Faculty Publications

Poly(propylene fumarate) (PPF) is an injectable, biodegradable polymer that has been used for fabricating preformed scaffolds in tissue engineering applications because of in situ crosslinking characteristics. Aiming for understanding the effects of pore structure parameters on bone tissue ingrowth, 3-dimensional (3D) PPF scaffolds with controlled pore architecture have been produced in this study from computer-aided design (CAD) models. We have created original scaffold models with 3 pore sizes (300, 600, and 900 µm) and randomly closed 0%, 10%, 20%, or 30% of total pores from the original models in 3 planes. PPF scaffolds were fabricated by a series steps involving …

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A New Class Of Miniature Embedded Inverted-F Antennas (Ifas) For 2.4 Ghz Wlan Application, Mohammed Z. Azad, Mohammod Ali Sep 2006

A New Class Of Miniature Embedded Inverted-F Antennas (Ifas) For 2.4 Ghz Wlan Application, Mohammed Z. Azad, Mohammod Ali

Faculty Publications

A new class of miniature printed embedded inverted-F antennas are proposed for operation in the 2.4-2.485 GHz wireless local-area network band. One of the proposed antennas on FR4 substrate (dielectric constant = 4.4) measures 9.2 mm by 4.1 mm and has a bandwidth of 3.5%. The peak gain of this antenna is 1.4 dBi. An overall size reduction of 70% is achieved compared to a conventional inverted-F antenna. Effects of dielectric loss tangent and material conductivity on the bandwidth and efficiency of these antennas are also investigated. Finally, two embedded antenna elements are analyzed to demonstrate the feasibility for a …

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The 1.6-Kv Algan/Gan Hfets, N. Tipirneni, Alexei Koudymov, V. Adivarahan, Jinwei Yang, Grigory Simin, Asif Khan Sep 2006

The 1.6-Kv Algan/Gan Hfets, N. Tipirneni, Alexei Koudymov, V. Adivarahan, Jinwei Yang, Grigory Simin, Asif Khan

Faculty Publications

The breakdown voltages in unpassivated nonfield-plated AlGan/GaN HFETs on sapphire substrates were studied. These studies reveal that the breakdown is limited by the surface flashover rather than by the AlGan/GaN channel. after elimination of the surface flashover in air, the breakdown voltage scaled linearly with the gate-drain spacing reaching 1.6 kV at 20 mu m. The corresponding static ON-resistance was as low as 3.4 m Omega(.)cm(2). This translates to a power device figure-of-merit V-BR(2)/R-ON = 7.5 x 10(8) V-2 . n(-1) cm(-2), which, to date, is among the best reported values for an AlGan/GaN HFET.

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A Compact Digitally Controlled Fuel Cell/Battery Hybrid Power Source, Zhenhua Jiang, Roger A. Dougal Aug 2006

A Compact Digitally Controlled Fuel Cell/Battery Hybrid Power Source, Zhenhua Jiang, Roger A. Dougal

Faculty Publications

A compact digitally controlled fuel cell/battery hybrid power source is presented in this paper. The hybrid power source composed of fuel cells and batteries provides a much higher peak power than each component alone while preserving high energy density, which is important and desirable for many modern electronic devices, through an appropriately controlled dc/dc power converter that handles the power flow shared by the fuel cell and the battery. Rather than being controlled to serve only as a voltage or current regulator, the power converter is regulated to balance the power flow to satisfy the load requirements while ensuring the …

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Self-Assembled Composite Nano-/Micronecklaces With Sio2 Beads In Boron Strings, Hai Ni, Xiaodong Li Jul 2006

Self-Assembled Composite Nano-/Micronecklaces With Sio2 Beads In Boron Strings, Hai Ni, Xiaodong Li

Faculty Publications

Nano-/micronecklaces with SiO2 beads in boron strings were synthesized by simply sublimating the desired powders in a sealed quartz tube at high temperature. The boron strings have a rectangular cross section with width varying from 80to1000nm while the SiO2 beads bear either spindle or spherical shape with a size ranging from 100nmto5μm. The spacing between the SiO2 beads is uniform in each boron string. Both the boron strings and the SiO2 beads are amorphous and free of defects. The supersaturated vapors of silicon and oxygen induced the SiO2 bead formation.

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Iii-Nitride Transistors With Capacitively Coupled Contacts, Grigory Simin, Z.-J. Yang, A. Koudymov, V. Adivarahan, M. Asif Khan Jul 2006

Iii-Nitride Transistors With Capacitively Coupled Contacts, Grigory Simin, Z.-J. Yang, A. Koudymov, V. Adivarahan, M. Asif Khan

Faculty Publications

AlGaN∕GaNheterostructure field-effect transistor design using capacitively coupled contacts (C3HFET) is presented. Insulated-gate [C3 metal-oxide-semiconductor HFET(C3MOSHFET)] has also been realized. The capacitively coupled source, gate, and drain of C3 device do not require annealedOhmic contacts and can be fabricated using gate alignment-free technology. For typical AlGaN∕GaNheterostructures, the equivalent contact resistance of C3 transistors is below 0.6Ωmm. In rf-control applications, the C3HFET and especially the C3MOSHFET have much higher operating rf powers as compared to HFETs.C3 design is instrumental for studying the two-dimensional electron gas transport in other wide band gap …

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Algan/Gan/Algan Double Heterostructure For High-Power Iii-N Field-Effect Transistors, C. Q. Chen, J. P. Zhang, V. Adivarahan, A. Koudymov, H. Fatima, Grigory Simin, J. Yang, M. Asif Khan Jun 2006

Algan/Gan/Algan Double Heterostructure For High-Power Iii-N Field-Effect Transistors, C. Q. Chen, J. P. Zhang, V. Adivarahan, A. Koudymov, H. Fatima, Grigory Simin, J. Yang, M. Asif Khan

Faculty Publications

We propose and demonstrate an AlGaN/GaN/AlGaN double heterostructure (DH) with significantly improved two-dimensional (2D) confinement for high-power III-N heterostructurefield-effect transistors(HFETs). The DH was grown directly on an AlN buffer over i-SiC substrate. It enables an excellent confinement of the 2D gas and also does not suffer from the parasitic channel formation as experienced in past designs grown over GaN buffer layers. Elimination of the GaN buffer modifies the strain distribution in the DH, enabling Al contents in the barrier region well over 30%. For the AlGaN/GaN/AlGaN DH design, the 2D electron gasmobility achieved was 1150 cm2/V s at …

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Digital Oxide Deposition Of Sio2 Layers For Iii-Nitride Metal-Oxide-Semiconductor Heterostructure Field-Effect Transistors, V. Adivarahan, S. Rai, N. Tipirneni, A. Koudymov, J. Yang, Grigory Simin, M. Asif Khan May 2006

Digital Oxide Deposition Of Sio2 Layers For Iii-Nitride Metal-Oxide-Semiconductor Heterostructure Field-Effect Transistors, V. Adivarahan, S. Rai, N. Tipirneni, A. Koudymov, J. Yang, Grigory Simin, M. Asif Khan

Faculty Publications

We present a digital-oxide-deposition (DOD) technique to deposit high quality SiO2dielectric layers by plasma-enhanced chemical vapor deposition using alternate pulses of silicon and oxygen precursors. The DOD procedure allows for a precise thickness control and results in extremely smooth insulating SiO2 layers. An insulating gate AlGaN∕GaNheterostructurefield-effect transistor(HFET) with 8nm thick DOD SiO2dielectric layer had a threshold voltage of −6V (only 1V higher than that of regular HFET), very low threshold voltage dispersion, and output continuous wave rf power of 15W∕mm at 55V drain bias.

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Erratum: “Terahertz Studies Of The Dielectric Response And Second-Order Phonons In A Gase Crystal” [Appl. Phys. Lett.87, 182104 (2005)], B. L. Yu, F. Zeng, V. Kartazayev, R. R. Alfano, K. C. Mandal Apr 2006

Erratum: “Terahertz Studies Of The Dielectric Response And Second-Order Phonons In A Gase Crystal” [Appl. Phys. Lett.87, 182104 (2005)], B. L. Yu, F. Zeng, V. Kartazayev, R. R. Alfano, K. C. Mandal

Faculty Publications

No abstract provided.

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Power Anomaly Effects And Costs In Low-Voltage Mobile Power Systems, Shengyi Liu, Charles H. Singer, Roger A. Dougal Apr 2006

Power Anomaly Effects And Costs In Low-Voltage Mobile Power Systems, Shengyi Liu, Charles H. Singer, Roger A. Dougal

Faculty Publications

Electric power anomalies or disturbances can disrupt the normal operation of equipment, accelerate aging, or even cause outright failures thus resulting in increased costs of maintenance and reduced system reliability. Past research on the effects caused by power anomalies has been mostly focused on industrial, commercial, or residential systems, or on power distribution equipment. A literature survey reveals that there is no comprehensive review related to low-voltage (LV) power systems and utilization equipment applicable to military combat vehicles, such as aircraft and ships. This paper summarizes the results of a new literature survey that focused on the causes, effects, and …

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Jamming Sensor Networks: Attack And Defense Strategies, Wenyuan Xu, Wade Trappe, Yanyong Zhang Apr 2006

Jamming Sensor Networks: Attack And Defense Strategies, Wenyuan Xu, Wade Trappe, Yanyong Zhang

Faculty Publications

Wireless sensor networks are built upon a shared medium that makes it easy for adversaries to conduct radio interference, or jamming, attacks that effectively cause a denial of service of either transmission or reception functionalities. These attacks can easily be accomplished by an adversary by either bypassing MAC-layer protocols or emitting a radio signal targeted at jamming a particular channel. In this article we survey different jamming attacks that may be employed against a sensor network. In order to cope with the problem of jamming, we discuss a two-phase strategy involving the diagnosis of the attack, followed by a suitable …

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A Reconfigurable Distributed Computing Fabric Exploiting Multilevel Parallelism, Charles L. Cathey, Jason D. Bakos, Duncan A. Buell Apr 2006

A Reconfigurable Distributed Computing Fabric Exploiting Multilevel Parallelism, Charles L. Cathey, Jason D. Bakos, Duncan A. Buell

Faculty Publications

This paper presents a novel reconfigurable data flow processing architecture that promises high performance by explicitly targeting both fine- and course-grained parallelism. This architecture is based on multiple FPGAs organized in a scalable direct network that is substantially more interconnect-efficient than currently used crossbar technology. In addition, we discuss several ancillary issues and propose solutions required to support this architecture and achieve maximal performance for general-purpose applications; these include supporting IP, mapping techniques, and routing policies that enable greater flexibility for architectural evolution and code portability.

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Convergence Of Ipsec In Presence Of Resets, Chin-Tser Huang, Mohamed G. Gouda, E.N. Elnozahy Mar 2006

Convergence Of Ipsec In Presence Of Resets, Chin-Tser Huang, Mohamed G. Gouda, E.N. Elnozahy

Faculty Publications

IPsec is the current security standard for the Internet Protocol IP. According to this standard, a selected computer pair (p, q) in the Internet can be designated a “security association”. This designation guarantees that all sent IP messages whose original source is computer p and whose ultimate destination is computer q cannot be replayed in the future (by an adversary between p and q) and still be received by computer q as fresh messages from p. This guarantee is provided by adding increasing sequence numbers to all IP messages sent from p to q. Thus, p needs to always remember …

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Adaptive Evolution Of Chloroplast Genome Structure Inferred Using A Parametric Bootstrap Approach, Liying Cui, Jim Leebens-Mack, Li-San Wang, Jijun Tang, Linda Rymarquis, David B. Stern, Claude W. Depamphilis Feb 2006

Adaptive Evolution Of Chloroplast Genome Structure Inferred Using A Parametric Bootstrap Approach, Liying Cui, Jim Leebens-Mack, Li-San Wang, Jijun Tang, Linda Rymarquis, David B. Stern, Claude W. Depamphilis

Faculty Publications

Background
Genome rearrangements influence gene order and configuration of gene clusters in all genomes. Most land plant chloroplast DNAs (cpDNAs) share a highly conserved gene content and with notable exceptions, a largely co-linear gene order. Conserved gene orders may reflect a slow intrinsic rate of neutral chromosomal rearrangements, or selective constraint. It is unknown to what extent observed changes in gene order are random or adaptive. We investigate the influence of natural selection on gene order in association with increased rate of chromosomal rearrangement. We use a novel parametric bootstrap approach to test if directional selection is responsible for the …

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Elastic Modulus Of Amorphous Sio2 Nanowires, Hai Ni, Xiaodong Li, Hongsheng Gao Jan 2006

Elastic Modulus Of Amorphous Sio2 Nanowires, Hai Ni, Xiaodong Li, Hongsheng Gao

Faculty Publications

Amorphous SiO2 nanowires with diameter ranging from 50 to 100 nm were synthesized using chemical vapor deposition(CVD) under an argon atmosphere at atmospheric pressure. Nanoscale three-point bending tests were performed directly on individual amorphous SiO2 nanowires using an atomic force microscope (AFM).Elastic modulus of the amorphous SiO2 nanowires was measured to be 76.6±7.2GPa, which is close to the reported value of the bulk SiO2 and thermally grown SiO2 thin films, but lower than that of plasma-enhanced CVD SiO2 thin films. The amorphous SiO2 nanowires exhibit brittle fracture failure in bending.

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High-Pressure Torsion-Induced Grain Growth In Electrodeposited Nanocrystalline Ni, X. Z. Liao, A. R. Kilmametov, R. Z. Valiev, Hongsheng Gao, Xiaodong Li, A. K. Mukherjee, J. F. Blingert, Y. T. Zhu Jan 2006

High-Pressure Torsion-Induced Grain Growth In Electrodeposited Nanocrystalline Ni, X. Z. Liao, A. R. Kilmametov, R. Z. Valiev, Hongsheng Gao, Xiaodong Li, A. K. Mukherjee, J. F. Blingert, Y. T. Zhu

Faculty Publications

Deformation-induced grain growth has been reported in nanocrystalline (nc) materials under indentation and severe cyclic loading, but not under any other deformation mode. This raises an issue on critical conditions for grain growth in nc materials. This study investigates deformation-induced grain growth in electrodeposited nc Ni during high-pressure torsion (HPT). Our results indicate that high stress and severe plastic deformation are required for inducing grain growth, and the upper limit of grain size is determined by the deformation mode and parameters. Also, texture evolution suggests that grain-boundary-mediated mechanisms played a significant role in accommodating HPT strain.

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Development Of An Electroless Method To Deposit Corrosion-Resistant Silicate Layers On Metallic Substrates, Swaminatha P. Kumaraguru, Basker Veeraraghavan, Branko N. Popov Jan 2006

Development Of An Electroless Method To Deposit Corrosion-Resistant Silicate Layers On Metallic Substrates, Swaminatha P. Kumaraguru, Basker Veeraraghavan, Branko N. Popov

Faculty Publications

A novel electroless method for depositing corrosion-resistant silicate layers on metallic substrates from aqueous solutions has been developed. The silicate layer was deposited from an aqueous solution of sodium silicate (3.22 weight ratio sodium silicate, 37.5% solution in water from PQ Corporation) and sodium borohydride. The technique is demonstrated by forming a passive film on galvanized steel. Deposition parameters such as concentration of the bath, temperature, and pH have been optimized based on the corrosion characteristics of the final coating. Studies on the coating reveal the formation of a very thin (5 nm) zinc disilicate layer followed by a much …

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Concurrent Multiple- Issue Negotiation For Internet-Based Services, Jiangbo Dang, Michael N. Huhns Jan 2006

Concurrent Multiple- Issue Negotiation For Internet-Based Services, Jiangbo Dang, Michael N. Huhns

Faculty Publications

Negotiation is a technique for reaching a mutually beneficial agreement among autonomous entities. In an Internet-based services context, multiple entities are negotiating simultaneously. The concurrent negotiation protocol extends existing negotiation protocols, letting both service requestors and service providers manage several negotiation processes in parallel. Colored Petri nets, which have greater expressive power than finite state machines and offer support for concurrency, represent the negotiation protocol and facilitate the analysis of desirable properties.

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