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2011

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Articles 1 - 30 of 7060

Full-Text Articles in Engineering

Identification And Thermochemical Analysis Of High-Lignin Feedstocks For Biofuel And Biochemical Production, Venugopal Mendu, Anne Harman-Ware, Mark Crocker, Jungho Jae, Jozsef Stork, Samuel Morton, Andrew Placido, George Huber, Seth Debolt Dec 2015

Identification And Thermochemical Analysis Of High-Lignin Feedstocks For Biofuel And Biochemical Production, Venugopal Mendu, Anne Harman-Ware, Mark Crocker, Jungho Jae, Jozsef Stork, Samuel Morton, Andrew Placido, George Huber, Seth Debolt

Samuel A Morton

Background - Lignin is a highly abundant biopolymer synthesized by plants as a complex component of plant secondary cell walls. Efforts to utilize lignin-based bioproducts are needed. Results - Herein we identify and characterize the composition and pyrolytic deconstruction characteristics of high-lignin feedstocks. Feedstocks displaying the highest levels of lignin were identified as drupe endocarp biomass arising as agricultural waste from horticultural crops. By performing pyrolysis coupled to gas chromatography-mass spectrometry, we characterized lignin-derived deconstruction products from endocarp biomass and compared these with switchgrass. By comparing individual pyrolytic products, we document higher amounts of acetic acid, 1-hydroxy-2-propanone, acetone and furfural in switchgrass ...


An Optimal-Model Of Entry, Ticketing And Seating Of Neyland Stadium, Isaac Atuahene, Rupy Sawhney, Xueping Li, Charles Aikens Oct 2013

An Optimal-Model Of Entry, Ticketing And Seating Of Neyland Stadium, Isaac Atuahene, Rupy Sawhney, Xueping Li, Charles Aikens

Isaac Atuahene

No abstract provided.


Simulated Annealing Technique To Design Minimum Cost Exchanger, Nadeem Muhammed Khalfe, Sandip K. Lahiri, Shiv K. Wadhwa Dec 2011

Simulated Annealing Technique To Design Minimum Cost Exchanger, Nadeem Muhammed Khalfe, Sandip K. Lahiri, Shiv K. Wadhwa

Nadeem Khalfe

Owing to the wide utilization of heat exchangers in industrial processes, their cost minimization is an important target for both designers and users. Traditional design approaches are based on iterative procedures which gradually change the design and geometric parameters to satisfy a given heat duty and constraints. Although well proven, this kind of approach is time consuming and may not lead to cost effective design as no cost criteria are explicitly accounted for. The present study explores the use of non-traditional optimization technique called simulated annealing (SA), for design optimization of shell and tube heat exchangers from an economic point ...


Thermodynamic Analysis And Evaluation Of Heat Recovery Through A Canopus Heat Exchanger For Vapour Compression Refrigeration (Vcr) System., Kaushik Sc, Panwar Nl, Siva Reddy V Dec 2011

Thermodynamic Analysis And Evaluation Of Heat Recovery Through A Canopus Heat Exchanger For Vapour Compression Refrigeration (Vcr) System., Kaushik Sc, Panwar Nl, Siva Reddy V

Dr. V. Siva Reddy

This communication deals with the waste heat recovery from the industrial refrigeration and air-conditioning system by introducing Canopus heat exchanger. There is a considerable amount of low-grade heat available in large-capacity systems. To recover this low-grade heat, a Canopus heat exchanger is introduced between compressor and condenser components. The system feasibility is studied with various operating parameters and its effect on heat recovery factor and overall COP of the system. The parametric results obtained for different eco-friendly working fluids, such as R-134a and R-507a, have been presented. It is found that, in general, overall COP of the system is improved ...


Sustainable Development With Renewable Energy Resources: A Review, Panwar Nl, Siva Reddy V, Ranjan Kr Dec 2011

Sustainable Development With Renewable Energy Resources: A Review, Panwar Nl, Siva Reddy V, Ranjan Kr

Dr. V. Siva Reddy

No abstract provided.


Enhanced Microbial Utilization Of Recalcitrant Cellulose By An Ex Vivo Cellulosome-Microbe Complex, Chun You, Xiao-Zhou Zhang, Noppadon Sathitsuksanoh, Lee R. Lynd Dec 2011

Enhanced Microbial Utilization Of Recalcitrant Cellulose By An Ex Vivo Cellulosome-Microbe Complex, Chun You, Xiao-Zhou Zhang, Noppadon Sathitsuksanoh, Lee R. Lynd

Open Dartmouth: Peer-reviewed articles by Dartmouth faculty

A cellulosome-microbe complex was assembled ex vivo on the surface of Bacillus subtilis displaying a miniscaffoldin that can bind with three dockerin-containing cellulase components: the endoglucanase Cel5, the processive endoglucanase Cel9, and the cellobiohydrolase Cel48. The hydrolysis performances of the synthetic cellulosome bound to living cells, the synthetic cellulosome, a noncomplexed cellulase mixture with the same catalytic components, and a commercial fungal enzyme mixture were investigated on low-accessibility recalcitrant Avicel and high accessibility regenerated amorphous cellulose (RAC). The cellbound cellulosome exhibited 4.5- and 2.3-fold-higher hydrolysis ability than cell-free cellulosome on Avicel and RAC, respectively. The cellulosome-microbe synergy was ...


Cyber-Physical Modeling Of Implantable Cardiac Medical Devices, Zhihao Jiang, Miroslav Pajic, Rahul Mangharam Dec 2011

Cyber-Physical Modeling Of Implantable Cardiac Medical Devices, Zhihao Jiang, Miroslav Pajic, Rahul Mangharam

Real-Time and Embedded Systems Lab (mLAB)

The design of bug-free and safe medical device software is challenging, especially in complex implantable devices that control and actuate organs in unanticipated contexts. Safety recalls of pacemakers and implantable cardioverter defibrillators between 1990 and 2000 affected over 600,000 devices. Of these, 200,000 or 41%, were due to firmware issues and their effect continues to increase in frequency. There is currently no formal methodology or open experimental platform to test and verify the correct operation of medical device software within the closed-loop context of the patient. To this effect, a real-time Virtual Heart Model (VHM) has been developed ...


Cluster Control Of Automated Surface Vessels, Paul David Mahacek Dec 2011

Cluster Control Of Automated Surface Vessels, Paul David Mahacek

Mechanical Engineering Senior Theses

This research focuses on the design and control of a fleet of robotic kayaks, and presents experimental data regarding the functionality and performance of the system. One of the key technical challenges in fielding multi-robot systems for real-world applications is the coordination and relative motion control of the individual units. Coordinated formation control of the fleet is implemented through the use of the cluster space control architecture, which is a full-order controller that treats the fleet as a virtual, articulating, kinematic mechanism. The resulting system is capable of autonomous navigation utilizing a centralized controller, currently implemented via a shore-based computer ...


Use Of The Richtmyer-Meshkov Instability To Infer Yield Stress At High-Energy Densities, Guy Dimonte, G. Terrones, F. J. Cherne, T. C. Germann, Virginie Dupont, K. Kadau, W. T. Buttler, D. M. Oro, C. Morris, D. L. Preston Dec 2011

Use Of The Richtmyer-Meshkov Instability To Infer Yield Stress At High-Energy Densities, Guy Dimonte, G. Terrones, F. J. Cherne, T. C. Germann, Virginie Dupont, K. Kadau, W. T. Buttler, D. M. Oro, C. Morris, D. L. Preston

Aerospace Engineering - Daytona Beach

We use the Richtmyer-Meshkov instability (RMI) at a metal-gas interface to infer the metal’s yield stress (Y) under shock loading and release. We first model how Y stabilizes the RMI using hydrodynamics simulations with a perfectly plastic constitutive relation for copper (Cu). The model is then tested with molecular dynamics (MD) of crystalline Cu by comparing the inferred Y from RMI simulations with direct stress-strain calculations, both with MD at the same conditions. Finally, new RMI experiments with solid Cu validate our simulation-based model and infer Y~0.47 GPa for a 36 GPa shock.


Geometrical Frustration In Nanowire Growth, K. W. Schwarz, J. Tersoff, S. Kodambaka, Y.C. Chou, F. M. Ross Dec 2011

Geometrical Frustration In Nanowire Growth, K. W. Schwarz, J. Tersoff, S. Kodambaka, Y.C. Chou, F. M. Ross

Birck and NCN Publications

Idealized nanowire geometries assume stable sidewalls at right angles to the growth front. Here we report growth simulations that include a mix of nonorthogonal facet orientations, as for Au-catalyzed Si. We compare these with in situ microscopy observations, finding striking correspondences. In both experiments and simulations, there are distinct growth modes that accommodate the lack of right angles in different ways-one through sawtooth-textured sidewalls, the other through a growth front at an angle to the growth axis. Small changes in conditions can reversibly switch the growth between modes. The fundamental differences between these modes have important implications for control of ...


Exploitation Of Unintentional Information Leakage From Integrated Circuits, William E. Cobb Dec 2011

Exploitation Of Unintentional Information Leakage From Integrated Circuits, William E. Cobb

Theses and Dissertations

Unintentional electromagnetic emissions are used to recognize or verify the identity of a unique integrated circuit (IC) based on fabrication process-induced variations in a manner analogous to biometric human identification. The effectiveness of the technique is demonstrated through an extensive empirical study, with results presented indicating correct device identification success rates of greater than 99:5%, and average verification equal error rates (EERs) of less than 0:05% for 40 near-identical devices. The proposed approach is suitable for security applications involving commodity commercial ICs, with substantial cost and scalability advantages over existing approaches. A systematic leakage mapping methodology is also ...


A Review Of Baobab (Adansonia Digitata) Products: Effect Of Processing Techniques, Medicinal Properties And Uses, Donatien Kabore, Hagrétou Sawadogo-Lingani, Bréhima Diawara, Clarise Compaoré, Mamoudou H. Dicko Prof., Mogens Jacobsen Dec 2011

A Review Of Baobab (Adansonia Digitata) Products: Effect Of Processing Techniques, Medicinal Properties And Uses, Donatien Kabore, Hagrétou Sawadogo-Lingani, Bréhima Diawara, Clarise Compaoré, Mamoudou H. Dicko Prof., Mogens Jacobsen

Pr. Mamoudou H. DICKO, PhD

A general literature review including the effect of processing techniques, medicinal value and uses of baobab tree is reported in this manuscript. Baobab tree has multi-purpose uses, as it produces food and non-food products such as medicines, fuel, timber, fodder. Every part of the baobab tree is reported to be useful. The seeds, leaves, roots, flowers, fruit pulp and bark of baobab are edible. Baobab leaves are used in the preparation of soup. Seeds are used as a thickening agent in soups, but they can be fermented and used as a flavouring agent or roasted and eaten as snacks. The ...


Gene Selection And Classification For Cancer Microarray Data Based On Machine Learning And Similarity Measures, Qingzhong Liu, Andrew H. Sung, Zhongxue Chen, Jianzhong Liu, Lei Chen, Mengyu Qiao, Zhaohui Wang, Xudong Huang, Youping Deng Dec 2011

Gene Selection And Classification For Cancer Microarray Data Based On Machine Learning And Similarity Measures, Qingzhong Liu, Andrew H. Sung, Zhongxue Chen, Jianzhong Liu, Lei Chen, Mengyu Qiao, Zhaohui Wang, Xudong Huang, Youping Deng

Lei Chen

Background: Microarray data have a high dimension of variables and a small sample size. In microarray data analyses, two important issues are how to choose genes, which provide reliable and good prediction for disease status, and how to determine the final gene set that is best for classification. Associations among genetic markers mean one can exploit information redundancy to potentially reduce classification cost in terms of time and money.

Results: To deal with redundant information and improve classification, we propose a gene selection method, Recursive Feature Addition, which combines supervised learning and statistical similarity measures. To determine the final optimal ...


Computer-Aided, Multi-Modal, And Compression Diffuse Optical Studies Of Breast Tissue, David R. Busch Jr Dec 2011

Computer-Aided, Multi-Modal, And Compression Diffuse Optical Studies Of Breast Tissue, David R. Busch Jr

Publicly Accessible Penn Dissertations

Diffuse Optical Tomography and Spectroscopy permit measurement of important physiological parameters non-invasively through ~10 cm of tissue. I have applied these techniques in measurements of human breast and breast cancer. My thesis integrates three loosely connected themes in this context: multi-modal breast cancer imaging, automated data analysis of breast cancer images, and microvascular hemodynamics of breast under compression. As per the first theme, I describe construction, testing, and the initial clinical usage of two generations of imaging systems for simultaneous diffuse optical and magnetic resonance imaging. The second project develops a statistical analysis of optical breast data from many spatial ...


A Method For Measuring Programmatic Dependency And Interdependency Between Dod Acquisition Programs, Matthew B. Christensen Dec 2011

A Method For Measuring Programmatic Dependency And Interdependency Between Dod Acquisition Programs, Matthew B. Christensen

Theses and Dissertations

There is currently no accepted method for quantitative measurement of acquisition program interdependency. While some methods exist for measuring dependency or interdependency at the component or system level, these methods do not translate well to program interdependency measurement. The objective of this thesis is to provide a model for measuring acquisition program interdependency accurately and quantitatively. The model presented in this thesis uses four Interdependency Factors to identify dependency relationships between programs. Specific Interdependency Levels are then used to measure the strengths of those dependencies. The model also accounts for measurement of dependencies upon programs that are not directly connected ...


Rapid Development: A Content Analysis Comparison Of Literature And Purposive Sampling Of Afrl Rapid Reaction Projects, Andrew R. Smith Dec 2011

Rapid Development: A Content Analysis Comparison Of Literature And Purposive Sampling Of Afrl Rapid Reaction Projects, Andrew R. Smith

Theses and Dissertations

In the current environment of military operations requesting faster delivery schedules to counter insurgent tactics, the engineering team often searches for how to quickly deliver the 80% solution, typically in 6-12 months. These are labeled rapid development projects. A content analysis of best practices in commercial product development literature, where time to market is often a driving factor, was accomplished showing varying emphasis of systems engineering technical and technical management processes. Technical Planning, Stakeholders Requirements Development, and Architecture Design were identified as important processes. This analysis confirms preconceived notions of plan upfront and early by emphasizing the SE processes of ...


Link Performance Analysis For A Proposed Future Architecture Of The Air Force Satellite Control Network, Eric W. Nelson Dec 2011

Link Performance Analysis For A Proposed Future Architecture Of The Air Force Satellite Control Network, Eric W. Nelson

Theses and Dissertations

The Air Force Satellite Control Network (AFSCN) is a worldwide network of ground stations that support a wide variety of users from the National Aeronautics and Space Administration (NASA) to the National Reconnaissance Office (NRO). The network performs tracking, telemetry, and commanding (TT&C) for these varied users. Users, located at Satellite Operations Centers (SOC), must compete for time on the AFSCN. This thesis demonstrates how to predict satellite link performance, specifically by users of the AFSCN. It will also demonstrate how users might use this capability to save spacecraft power. A tool was created called the AFSCN Link Predictor ...


Linear-Quadratic Control Of A Mems Micromirror Using Kalman Filtering, Jamie P. Schnapp Dec 2011

Linear-Quadratic Control Of A Mems Micromirror Using Kalman Filtering, Jamie P. Schnapp

Theses and Dissertations

The deflection limitations of electrostatic flexure-beam actuators are well known. Specifically, as the beam is actuated and the gap traversed, the restoring force necessary for equilibrium increases proportionally with the displacement to first order, while the electrostatic actuating force increases with the inverse square of the gap. Equilibrium, and thus stable open-loop voltage control, ceases at one-third the total gap distance, leading to actuator snap-in. A Kalman Filter is designed with an appropriately complex state dynamics model to accurately estimate actuator deflection given voltage input and capacitance measurements, which are then used by a Linear Quadratic controller to generate a ...


Investigation Of Gallium Nitride Transistor Reliability Through Accelerated Life Testing And Modeling, Bradley D. Christiansen Dec 2011

Investigation Of Gallium Nitride Transistor Reliability Through Accelerated Life Testing And Modeling, Bradley D. Christiansen

Theses and Dissertations

Gallium nitride high electron mobility transistors are attractive to the DoD for their ability to operate at high frequencies, voltages, temperatures, and power. Yet, there are concerns about the reliability of these devices. Various degradation mechanisms and their causes are proposed in the literature. A variety of reliability tests were conducted to understand these mechanisms and causes. A multi-stressor experiment revealed different failure mechanisms than are in the literature. In particular, the devices tested at high voltage in the OFF state did not degrade significantly as suggested by others' reports. The validity of temperature-accelerated life testing when applied to GaN ...


Electroluminescence Studies On Longwavelength Indium Arsenide Quantum Dot Microcavities Grown On Gallium Arsenide, John C. Ramsey Dec 2011

Electroluminescence Studies On Longwavelength Indium Arsenide Quantum Dot Microcavities Grown On Gallium Arsenide, John C. Ramsey

Theses and Dissertations

A comprehensive study of the electroluminescence of four GaAs/AlGaAs microcavity devices with InAs/GaInAs quantum dot active regions emitting near 1.3 micrometer was conducted. The four molecular beam epitaxial grown samples with AlAs oxide aperture confinement layers were fabricated, characterized, and optically modeled. Optical power transmission of the samples was modeled using Matlab and compared with measured transmission data. Resonant cavity light emitting diodes (RCLEDs) and three vertical cavity surface emitting laser (VCSEL) samples were fabricated and electro-optically characterized over a range of injection currents and temperatures. Devices achieved continuous wave room temperature lasing at 1.28 micrometer ...


Construction Of Mse Wall Using Tire Shred-Sand Mixture As Backfill (Spr-3470), Monica Prezzi, Varenya Kumar Duvvuru Mohan Dec 2011

Construction Of Mse Wall Using Tire Shred-Sand Mixture As Backfill (Spr-3470), Monica Prezzi, Varenya Kumar Duvvuru Mohan

JTRP Other Publications and Reports

A large number of waste tires are generated each year throughout the world. Instead of disposing these tires in landfills, they can be used beneficially in road construction, MSE walls or structural fills that require large quantities of material. Such use of tires not only saves the costs of landfilling, but also provides certain desirable mechanical properties. The focus of this research was on determining important geotechnical properties of tire shred-sand mixtures required for their use as a lightweight backfill for MSE walls. Accordingly, the shear strength and pullout characteristics of tire shred-sand mixtures at various mixing ratios were determined ...


Economics Of Spectrum Allocation In Cognitive Radio Networks, Gaurav S. Kasbekar Dec 2011

Economics Of Spectrum Allocation In Cognitive Radio Networks, Gaurav S. Kasbekar

Publicly Accessible Penn Dissertations

Cognitive radio networks (CRNs) are emerging as a promising technology for the efficient use of radio spectrum. In these networks, there are two levels of networks on each channel, primary and secondary, and secondary users can use the channel whenever the primary is not using it. Spectrum allocation in CRNs poses several challenges not present in traditional wireless networks; the goal of this dissertation is to address some of the economic aspects thereof. Broadly, spectrum allocation in CRNs can be done in two ways- (i) one-step allocation in which the spectrum regulator simultaneously allocates spectrum to primary and secondary users ...


Plasmon Enhanced Photoconduction In Porphyrin-Gold Nanoparticle Assemblies, David Conklin Dec 2011

Plasmon Enhanced Photoconduction In Porphyrin-Gold Nanoparticle Assemblies, David Conklin

Publicly Accessible Penn Dissertations

This thesis describes a series of experiments to both determine the origins of charge transport and enhanced photoconduction in metal nanoparticle arrays linked with zinc-porphyrin complexes, but to also determine the nucleation and growth mechanisms related to Ferroelectric Nanolithography (FNL) as a platform for hybrid devices. The development of test structures on glass substrates was undertaken to not only allow the study of the mechanisms controlling charge transport but the photoconduction of zinc-porphyrin linked gold nanoparticle (AuNP) arrays. In this study, the dominate charge transport mechanism was determined to be thermally assisted tunneling and the origins of enhanced photoconduction in ...


Dynamic Vertical Climbing: Bioinspiration, Design, And Analysis, Goran Lynch Dec 2011

Dynamic Vertical Climbing: Bioinspiration, Design, And Analysis, Goran Lynch

Publicly Accessible Penn Dissertations

Biologists have proposed a pendulous climbing model, the Full-Goldman (F-G) template, that abstracts remarkable similarities in dynamic wall scaling behavior exhibited by radically different animal species. This thesis presents a progression of work related to dynamic vertical climbing based on that model.

We begin by describing the inspiration, design, implementation of and experimentation with the first dynamical vertical climbing robot. We study numerically a version of the pendulous climbing template dynamically re-scaled for applicability to utilitarian payloads with conventional electronics and actuation, revealing that the incorporation of passive compliance can compensate for an artifact’s poorer power density and scale ...


Enhancing Meniscus Repair Through Biomaterial Design, Lara Ionescu Silverman Dec 2011

Enhancing Meniscus Repair Through Biomaterial Design, Lara Ionescu Silverman

Publicly Accessible Penn Dissertations

The knee meniscus is prone to damage, which leads to pain and inhibits mobility in the joint long term. Due to the minimal vascularity, low cellularity and large mechanical forces imparted on the meniscus with normal use, endogenous repair is limited. Resection of the damaged region of the tissue (meniscectomy) remains the most common treatment for a torn meniscus, but this procedure results in cartilage degradation and other adverse changes in the knee joint. Given the prevalence of meniscus damage, there is thus a pressing need for novel approaches to meniscus repair. To address this issue, this thesis developed in ...


Optimization And Translation Of Msc-Based Hyaluronic Acid Hydrogels For Cartilage Repair, Isaac E. Erickson Dec 2011

Optimization And Translation Of Msc-Based Hyaluronic Acid Hydrogels For Cartilage Repair, Isaac E. Erickson

Publicly Accessible Penn Dissertations

Traumatic injury and disease disrupt the ability of cartilage to carry joint stresses and, without an innate regenerative response, often lead to degenerative changes towards the premature development of osteoarthritis. Surgical interventions have yet to restore long-term mechanical function. Towards this end, tissue engineering has been explored for the de novo formation of engineered cartilage as a biologic approach to cartilage repair. Research utilizing autologous chondrocytes has been promising, but clinical limitations in their yield have motivated research into the potential of mesenchymal stem cells (MSCs) as an alternative cell source. MSCs are multipotent cells that can differentiate towards a ...


The Nanoaquarium: A Nanofluidic Platform For In Situ Transmission Electron Microscopy In Liquid Media, Joseph M. Grogan Dec 2011

The Nanoaquarium: A Nanofluidic Platform For In Situ Transmission Electron Microscopy In Liquid Media, Joseph M. Grogan

Publicly Accessible Penn Dissertations

There are many scientifically interesting and technologically relevant nanoscale phenomena that take place in liquid media. Examples include aggregation and assembly of nanoparticles; colloidal crystal formation; liquid phase growth of structures such as nanowires; electrochemical deposition and etching for fabrication processes and battery applications; interfacial phenomena; boiling and cavitation; and biological interactions. Understanding of these fields would benefit greatly from real-time, in situ transmission electron microscope (TEM) imaging with nanoscale resolution. Most liquids cannot be imaged by traditional TEM due to evaporation in the high vacuum environment and the requirement that samples be very thin. Liquid-cell in situ TEM has ...


Mind Economy: Dynamic Graph Analysis Of Communications, Alexy Khrabrov Dec 2011

Mind Economy: Dynamic Graph Analysis Of Communications, Alexy Khrabrov

Publicly Accessible Penn Dissertations

Social networks are growing in reach and impact but little is known about their structure, dynamics, or users’ behaviors. New techniques and approaches are needed to study and understand why these networks attract users’ persistent attention, and how the networks evolve. This thesis investigates questions that arise when modeling human behavior in social networks, and its main contributions are:

• an infrastructure and methodology for understanding communication on graphs;

• identification and exploration of sub-communities;

• metrics for identifying effective communicators in dynamic graphs;

• a new definition of dynamic, reciprocal social capital and its iterative computation

• a methodology to study influence in social ...


Starting Radial Subdiffusion From A Central Point Through A Diverging Medium (A Sphere): Heat-Balance Integral Method, Jordan Hristov Dec 2011

Starting Radial Subdiffusion From A Central Point Through A Diverging Medium (A Sphere): Heat-Balance Integral Method, Jordan Hristov

Jordan Hristov

The work presents an integral solution of the time-fractional subdiffusion equation as alternative approach to those employing hypergeometric functions. The integral solution suggests a preliminary defined profile with unknown coefficients and the concept of penetration (boundary layer) well known from the heat diffusion and hydrodynamics. The profile satisfies the boundary conditions imposed at the boundary of the boundary layer that allows its coefficients to be expressed through the boundary layer depth as unique parameter describing the profile. The technique is demonstrated by a solution of a time fractional radial equation concerning anomalous diffusion from a central point source in a ...


Self-Regenerating Nanotips For Low-Power Electric Propulsion (Ep) Cathodes, Lyon Bradley King Dec 2011

Self-Regenerating Nanotips For Low-Power Electric Propulsion (Ep) Cathodes, Lyon Bradley King

Michigan Tech Patents

Spindt-type field-emission cathodes for use in electric propulsion (EP) systems having self-assembling nanostructures that can repeatedly regenerate damaged cathode emitter nanotips. A nanotip is created by applying a negative potential near the surface of a liquefied base metal to create a Taylor cone converging to a nanotip, and solidifying the Taylor cone for use as a field-emission cathode. When the nanotip of the Taylor cone becomes sufficiently blunted or damaged to affect its utility, the base metal is re-liquefied by application of a heat source, a negative potential is reapplied to the surface of the base metal to recreate the ...