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Articles 1 - 30 of 1819

Full-Text Articles in Engineering

Deep Ocean Vector Sensor Array Performance Metrics, Gabriel Kniffin, Lisa Zurk Jul 2017

Deep Ocean Vector Sensor Array Performance Metrics, Gabriel Kniffin, Lisa Zurk

Lisa M. Zurk

Recent work in passive sonar has drawn interest in the potential for vertical line arrays (VLAs) deployed below the critical depth—the depth inthe deep ocean at which the sound speed below the channel axis reaches the sound speed near the surface. Such arrays can take advantage of propagation via the reliable acoustic path (RAP), which has been shown to improve thesignal-to-noise ratio (SNR) of received signals from sources at or near the surface at moderate ranges.


Volume Holographic Optical Elements, Ching-Cherng Sun, Partha P. Banerjee Apr 2016

Volume Holographic Optical Elements, Ching-Cherng Sun, Partha P. Banerjee

Partha Banerjee

The final two papers are concerned with the analysis of novel holograms. Banerjee et al. investigate holographic recording and reconstruction for edge-lit holograms recorded in a 90-degree geometry. Various cases of recording and readout that incorporate propagational diffraction have been modeled. It is shown that the 90-degree geometry can result in beam shaping, as evidenced through preliminary experimental results with photorefractive lithium niobate. Nguyen et al. propose a new approach for designing computer-generated holograms. An artificial neural network is used to initiate the genetic algorithm so that the high computation cost of genetic algorithms for synthesizing holograms is significantly reduced ...


Chemical Dynamics Of Aluminum Nanoparticles In Ammonium Nitrate And Ammonium Perchlorate Matrices: Enhanced Reactivity Of Organically Capped Aluminum, William K. Lewis, Barbara A. Harruff-Miller, Joseph R. Gord, Andrew T. Rosenberger, Thomas M. Sexton, Elena A. Guliants, Christopher E. Bunker Apr 2016

Chemical Dynamics Of Aluminum Nanoparticles In Ammonium Nitrate And Ammonium Perchlorate Matrices: Enhanced Reactivity Of Organically Capped Aluminum, William K. Lewis, Barbara A. Harruff-Miller, Joseph R. Gord, Andrew T. Rosenberger, Thomas M. Sexton, Elena A. Guliants, Christopher E. Bunker

Elena A. Guliants

Aluminum nanoparticles have been a subject of active investigation in recent years because of their potential to enhance the energy content of energetic materials. The associated kinetics of the chemical reaction and energy release are, in many cases, governed by the properties of the passivation layer protecting the particle rather than those of the underlying metal core. The passivation layer of Al particles is typically an oxide shell several nanometers thick, but other possibilities are now available. We have previously developed synthesis routes to produce air-stable Al nanoparticles that are capped by oleic acid. In the present study, we examine ...


Carbon Nanoparticles As Visible-Light Photocatalysts For Efficient Co2 Conversion And Beyond, Li Cao, Sushant Sahu, Parambath Anilkumar, Christopher E. Bunker, Juan Xu, K. A. Shiral Fernando, Ping Wang, Elena A. Guliants, Kenneth N. Tackett Ii, Ya-Ping Sun Apr 2016

Carbon Nanoparticles As Visible-Light Photocatalysts For Efficient Co2 Conversion And Beyond, Li Cao, Sushant Sahu, Parambath Anilkumar, Christopher E. Bunker, Juan Xu, K. A. Shiral Fernando, Ping Wang, Elena A. Guliants, Kenneth N. Tackett Ii, Ya-Ping Sun

Elena A. Guliants

Increasing atmospheric CO2 levels have generated much concern, driving the ongoing carbon sequestration effort. A compelling CO2 sequestration option is its photocatalytic conversion to hydrocarbons, for which the use of solar irradiation represents an ultimate solution. Here we report a new strategy of using surface-functionalized small carbon nanoparticles to harvest visible photons for subsequent charge separation on the particle surface in order to drive the efficient photocatalytic process. The aqueous solubility of the catalysts enables photoreduction under more desirable homogeneous reaction conditions. Beyond CO2 conversion, the nanoscale carbon-based photocatalysts are also useful for the photogeneration of H2 from water under ...


Averting Hiv Infections In New York City: A Modeling Approach Estimating The Future Impact Of Additional Behavioral And Biomedical Hiv Prevention Strategies, Jason Kessler, Julie E. Myers, Kimberly A. Nucifora, Nana Mensah, Alexis Kowalski, Monica Sweeney, Christopher Toohey, Amin Khademi, Colin Shepard, Blayne Cutler, R. Scott Braithwaite Apr 2016

Averting Hiv Infections In New York City: A Modeling Approach Estimating The Future Impact Of Additional Behavioral And Biomedical Hiv Prevention Strategies, Jason Kessler, Julie E. Myers, Kimberly A. Nucifora, Nana Mensah, Alexis Kowalski, Monica Sweeney, Christopher Toohey, Amin Khademi, Colin Shepard, Blayne Cutler, R. Scott Braithwaite

Amin Khademi

Background: New York City (NYC) remains an epicenter of the HIV epidemic in the United States. Given the variety of evidence-based HIV prevention strategies available and the significant resources required to implement each of them, comparative studies are needed to identify how to maximize the number of HIV cases prevented most economically.

Methods: A new model of HIV disease transmission was developed integrating information from a previously validated micro-simulation HIV disease progression model. Specification and parameterization of the model and its inputs, including the intervention portfolio, intervention effects and costs were conducted through a collaborative process between the academic modeling ...


Spatio-Spectral Sampling And Color Filter Array Design, Keigo Hirakawa, Patrick Wolfe Mar 2016

Spatio-Spectral Sampling And Color Filter Array Design, Keigo Hirakawa, Patrick Wolfe

Keigo Hirakawa

Owing to the growing ubiquity of digital image acquisition and display, several factors must be considered when developing systems to meet future color image processing needs, including improved quality, increased throughput, and greater cost-effectiveness. In consumer still-camera and video applications, color images are typically obtained via a spatial subsampling procedure implemented as a color filter array (CFA), a physical construction whereby only a single component of the color space is measured at each pixel location. Substantial work in both industry and academia has been dedicated to post-processing this acquired raw image data as part of the so-called image processing pipeline ...


An Overview Of The Low-Cost Carrier Model In The Russian Market, Tamilla Curtis, Dawna Rhoades Mar 2016

An Overview Of The Low-Cost Carrier Model In The Russian Market, Tamilla Curtis, Dawna Rhoades

Dr. Tamilla Curtis

This study provides an overview of the low-cost carrier (LCC) model in the Russian market. The LCC model seeks to achieve a competitive advantage through the reduction of operating costs, below the traditional airline model. Since Russia is an emerging and developing economy, airlines face a high level of uncertainty. Despite the fact that the Russian aviation market is dominated by a few large carriers, Russian lowcost airlines such as SkyExpress and Avianova have been growing rapidly since starting their operations. While Russian LCCs follow the traditional LCC model, some differences are apparent as a result of the specifics of ...


Platform-Specific Code Generation From Platform-Independent Timed Models, Baekgyu Kim, Lu Feng, Oleg Sokolsky, Insup Lee Mar 2016

Platform-Specific Code Generation From Platform-Independent Timed Models, Baekgyu Kim, Lu Feng, Oleg Sokolsky, Insup Lee

Oleg Sokolsky

Many safety-critical real-time embedded systems need to meet stringent timing constraints such as preserving delay bounds between input and output events. In model-based development, a system is often implemented by using a code generator to automatically generate source code from system models, and integrating the generated source code with a platform. It is challenging to guarantee that the implemented systems preserve required timing constraints, because the timed behavior of the source code and the platform is closely intertwined. In this paper, we address this challenge by proposing a model transformation approach for the code generation. Our approach compensates the platform-processing ...


From Requirements To Code: Model Based Development Of A Medical Cyber Physical System, Anitha Murugesan, Mats Heimdahl, Michael Whalen, Sanjai Rayadurgam, John Komp, Lian Duan, Baekgyu Kim, Oleg Sokolsky, Insup Lee Mar 2016

From Requirements To Code: Model Based Development Of A Medical Cyber Physical System, Anitha Murugesan, Mats Heimdahl, Michael Whalen, Sanjai Rayadurgam, John Komp, Lian Duan, Baekgyu Kim, Oleg Sokolsky, Insup Lee

Oleg Sokolsky

The advanced use of technology in medical devices has improved the way health care is delivered to patients. Unfortunately, the increased complexity of modern medical devices poses challenges for development, assurance, and regulatory approval. In an e ort to improve the safety of advanced medical devices, organizations such as FDA have supported exploration of techniques to aid in the development and regulatory approval of such systems. In an ongoing research project, our aim is to provide effective development techniques and exemplars of system development artifacts that demonstrate state of the art development techniques.

In this paper we present an end-to-end ...


Verified Ros-Based Deployment Of Platform-Independent Control Systems, Wenrui Meng, Junkil Park, Oleg Sokolsky, Stephanie Weirich, Insup Lee Mar 2016

Verified Ros-Based Deployment Of Platform-Independent Control Systems, Wenrui Meng, Junkil Park, Oleg Sokolsky, Stephanie Weirich, Insup Lee

Oleg Sokolsky

The paper considers the problem of model-based deployment of platform-independent control code on a specific platform. The approach is based on automatic generation of platform-specific glue code from an architectural model of the system. We present a tool, ROSGen, that generates the glue code based on a declarative specification of platform interfaces. Our implementation targets the popular Robot Operating System (ROS) platform. We demonstrate that the code generation process is amenable to formal verification. The code generator is implemented in Coq and relies on the infrastructure provided by the CompCert and VST tool. We prove that the generated code always ...


Verified Ros-Based Deployment Of Platform-Independent Control Systems, Wenrui Meng, Junkil Park, Oleg Sokolsky, Stephanie Weirich, Insup Lee Mar 2016

Verified Ros-Based Deployment Of Platform-Independent Control Systems, Wenrui Meng, Junkil Park, Oleg Sokolsky, Stephanie Weirich, Insup Lee

Oleg Sokolsky

The paper considers the problem of model-based deployment of platform-independent control code on a specific platform. The approach is based on automatic generation of platform-specific glue code from an architectural model of the system. We present a tool, ROSGen, that generates the glue code based on a declarative specification of platform interfaces. Our implementation targets the popular Robot Operating System (ROS) platform. We demonstrate that the code generation process is amenable to formal verification. The code generator is implemented in Coq and relies on the infrastructure provided by the CompCert and VST tool. We prove that the generated code always ...


Automatic Verification Of Linear Controller Software, Miroslav Pajic, Junkil Park, Insup Lee, George Pappas, Oleg Sokolsky Mar 2016

Automatic Verification Of Linear Controller Software, Miroslav Pajic, Junkil Park, Insup Lee, George Pappas, Oleg Sokolsky

Oleg Sokolsky

We consider the problem of verification of software implementations of linear time-invariant controllers. Commonly, different implementations use different representations of the controller’s state, for example due to optimizations in a third-party code generator. To accommodate this variation, we exploit input-output controller specification captured by the controller’s transfer function and show how to automatically verify correctness of C code controller implementations using a Frama-C/Why3/Z3 toolchain. Scalability of the approach is evaluated using randomly generated controller specifications of realistic size.


From Requirements To Code: Model Based Development Of A Medical Cyber Physical System, Anitha Murugesan, Mats Heimdahl, Michael Whalen, Sanjai Rayadurgam, John Komp, Lian Duan, Baekgyu Kim, Oleg Sokolsky, Insup Lee Mar 2016

From Requirements To Code: Model Based Development Of A Medical Cyber Physical System, Anitha Murugesan, Mats Heimdahl, Michael Whalen, Sanjai Rayadurgam, John Komp, Lian Duan, Baekgyu Kim, Oleg Sokolsky, Insup Lee

Oleg Sokolsky

The advanced use of technology in medical devices has improved the way health care is delivered to patients. Unfortunately, the increased complexity of modern medical devices poses challenges for development, assurance, and regulatory approval. In an e ort to improve the safety of advanced medical devices, organizations such as FDA have supported exploration of techniques to aid in the development and regulatory approval of such systems. In an ongoing research project, our aim is to provide effective development techniques and exemplars of system development artifacts that demonstrate state of the art development techniques.

In this paper we present an end-to-end ...


Platform-Specific Code Generation From Platform-Independent Timed Models, Baekgyu Kim, Lu Feng, Oleg Sokolsky, Insup Lee Mar 2016

Platform-Specific Code Generation From Platform-Independent Timed Models, Baekgyu Kim, Lu Feng, Oleg Sokolsky, Insup Lee

Oleg Sokolsky

Many safety-critical real-time embedded systems need to meet stringent timing constraints such as preserving delay bounds between input and output events. In model-based development, a system is often implemented by using a code generator to automatically generate source code from system models, and integrating the generated source code with a platform. It is challenging to guarantee that the implemented systems preserve required timing constraints, because the timed behavior of the source code and the platform is closely intertwined. In this paper, we address this challenge by proposing a model transformation approach for the code generation. Our approach compensates the platform-processing ...


A Data-Driven Behavior Modeling And Analysis Framework For Diabetic Patients On Insulin Pumps, Sanjian Chen, Lu Feng, Michael Rickels, Amy Peleckis, Oleg Sokolsky, Insup Lee Mar 2016

A Data-Driven Behavior Modeling And Analysis Framework For Diabetic Patients On Insulin Pumps, Sanjian Chen, Lu Feng, Michael Rickels, Amy Peleckis, Oleg Sokolsky, Insup Lee

Oleg Sokolsky

About 30%-40% of Type 1 Diabetes (T1D) patients in the United States use insulin pumps. Current insulin infusion systems require users to manually input meal carb count and approve or modify the system-suggested meal insulin dose. Users can give correction insulin boluses at any time. Since meal carbohydrates and insulin are the two main driving forces of the glucose physiology, the user-specific eating and pump-using behavior has a great impact on the quality of glycemic control.

In this paper, we propose an “Eat, Trust, and Correct” (ETC) framework to model the T1D insulin pump users’ behavior. We use machine ...


Tribological Performance Of Hybrid Filtered Arc-Magnetron Coatings: Part I: Coating Deposition Process And Basic Coating Properties Characterization, Vladimir Gorokovsky, Chris Bowman, Paul Gannon, David Vanvorous, Andrey Voevodin, Adam Rutkowski, Christopher Muratore, Richard Smith, Asghar Kayani, David Gelles, Vaithiyalingam Shutthanandan, Boris Trusov Mar 2016

Tribological Performance Of Hybrid Filtered Arc-Magnetron Coatings: Part I: Coating Deposition Process And Basic Coating Properties Characterization, Vladimir Gorokovsky, Chris Bowman, Paul Gannon, David Vanvorous, Andrey Voevodin, Adam Rutkowski, Christopher Muratore, Richard Smith, Asghar Kayani, David Gelles, Vaithiyalingam Shutthanandan, Boris Trusov

Christopher Muratore

Aircraft propulsion applications require low-friction and wear resistant surfaces that operate under high contact loads in severe environments. Recent research on supertough and low friction nanocomposite coatings produced with hybrid plasma deposition processes was demonstrated to have a high potential for such demanding applications. However, industrially scalable hybrid plasma technologies are needed for their commercial realization. The Large area Filtered Arc Deposition (LAFAD) process provides atomically smooth coatings at high deposition rates over large surface areas. The LAFAD technology allows functionally graded, multilayer, super-lattice and nanocomposite architectures of multi-elemental coatings via electro-magnetic mixing of two plasma flows composed of different ...


Progress In The Development Of Adaptive Nitride-Based Coatings For High Temperature Tribological Applications, Samir Aouadi, Brandon Luster, Punit Kohli, Christopher Muratore, Andrey Voevodin Mar 2016

Progress In The Development Of Adaptive Nitride-Based Coatings For High Temperature Tribological Applications, Samir Aouadi, Brandon Luster, Punit Kohli, Christopher Muratore, Andrey Voevodin

Christopher Muratore

Adaptive tribological coatings were recently developed as a new class of smart materials that were designed to adjust their surface chemical composition and structure as a function of changes in the working environment to minimize friction coefficient and wear between contact surfaces. This paper provides an overview of the current research developments in this field, including: (1) Chameleon nanocomposite coatings which are produced by depositing a multi-phase structure whereby some of the phases provide mechanical strength and others are lubricious; (2) Micro- and nano-textured coatings which consist of hard nitride films with highly ordered micropores and nanopores that are subsequently ...


Plasma Enhanced Surface Treatments Using Electron Beam-Generated Plasmas, Darrin Leonhardt, Christopher Muratore, Scott Walton, Robert Meger Mar 2016

Plasma Enhanced Surface Treatments Using Electron Beam-Generated Plasmas, Darrin Leonhardt, Christopher Muratore, Scott Walton, Robert Meger

Christopher Muratore

NRL has developed a ‘large area plasma processing system’ (LAPPS) utilizing a high energy (∼2 keV) modulated electron beam to drive the plasma ionization. This system has been shown to be (1) efficient at producing plasma in any gas composition, (2) capable of producing low temperature plasma electrons (9–1012 cm−3) and (3) scalable to large area (square meters). In this work, the progress of a number of applications using LAPPS is discussed. Nitride growth in stainless steel was investigated, which demonstrated high rates (up to 20 μm/h1/2) at low temperatures (≤462 °C). Complementary mass ...


Molybdenum Disulfide As A Lubricant And Catalyst In Adaptive Nanocomposite Coatings, Christopher Muratore, Andrey Voevodin Mar 2016

Molybdenum Disulfide As A Lubricant And Catalyst In Adaptive Nanocomposite Coatings, Christopher Muratore, Andrey Voevodin

Christopher Muratore

Nanocomposite YSZ–Ag–Mo–MoS2 coatings with different MoS2 additions (0–100 at.%) were deposited with a hybrid pulsed laser/magnetron sputtering/filtered cathodic arc process. Wear testing was performed from 25 to 700 °C for each of the coatings. Electron microscopy and other characterization techniques were used to examine the surfaces and wear tracks of the coatings and to determine the mechanisms resulting in the measured tribological properties. Adaptive coatings containing 8 at.% MoS2demonstrated a friction coefficient of 0.2 throughout the temperature range examined here, compared to 0.4 for YSZ–Ag–Mo with ...


In Situ Studies Of Tic1−X N X Hard Coating Tribology, Marisa Rebelo De Figueiredo, Christopher Muratore, Robert Franz, Richard Chromik, Kathryn Wahl, Andrey Voevodin, Michel O'Sullivan, Markus Lechthaler, Christian Mitterer Mar 2016

In Situ Studies Of Tic1−X N X Hard Coating Tribology, Marisa Rebelo De Figueiredo, Christopher Muratore, Robert Franz, Richard Chromik, Kathryn Wahl, Andrey Voevodin, Michel O'Sullivan, Markus Lechthaler, Christian Mitterer

Christopher Muratore

TiC1−x N x hard coatings present time-dependent tribological behavior with an initial running-in period (500–2000 cycles) marked by an elevated friction coefficient, followed by >10000 cycles with low-friction and wear at room temperature (RT) in ambient air. The mechanisms behind this behavior are not completely understood. Tribological tests performed at RT and at different relative humidity (RH) levels revealed that a minimum value between 15 and 25% RH is needed to trigger the low-friction regime at a sliding speed of 100 mm s−1. By in situ observations of transfer film growth, it could be observed that third ...


Adaptive Nanocomposite Coatings With A Titanium Nitride Diffusion Barrier Mask For High-Temperature Tribological Applications, Christopher Muratore, Jianjun Hu, Andrey Voevodin Mar 2016

Adaptive Nanocomposite Coatings With A Titanium Nitride Diffusion Barrier Mask For High-Temperature Tribological Applications, Christopher Muratore, Jianjun Hu, Andrey Voevodin

Christopher Muratore

Adaptive nanocomposite coatings that demonstrate low friction throughout broad ranges of temperature, wear, humidity and other environments are currently in development. One effective temperature adaptation mechanism at temperatures ≤ 500 °C is diffusion of noble metal to the coating surface, providing a low shear strength interface at the friction contact supported by a hard surface underneath. To prolong the wear lifetime of chameleon coatings relying upon this mechanism for low friction, a coating architecture incorporating a diffusion barrier mask to inhibit noble metal diffusion was employed. The diffusion barrier-capped coating provided lubrication at 500 °C over ten times longer than the ...


A Simultaneous Increase In The Thermal And Electrical Transport In Carbon Nanotube Yarns Induced By Inter-Tube Metallic Welding, Sabyasachi Ganguli, Amber Reed, Chaminda Jayasinghe, Joe Sprengard, Ajit Roy, Andrey Voevodin, Christopher Muratore Mar 2016

A Simultaneous Increase In The Thermal And Electrical Transport In Carbon Nanotube Yarns Induced By Inter-Tube Metallic Welding, Sabyasachi Ganguli, Amber Reed, Chaminda Jayasinghe, Joe Sprengard, Ajit Roy, Andrey Voevodin, Christopher Muratore

Christopher Muratore

Vertically aligned arrays of multiwall carbon nanotubes (MWCNT) were decorated with gold (Au) nanoparticles of different diameter and areal densities and spun into yarns. The melting point of Au nanoparticles determined by differential scanning calorimetry was approximately 260 °C, well below the oxidation temperature of carbon. A continuous yarn was formed while pulling out a bundle of CNTs from the metalized CNT array. Relatively low temperature (300 °C) thermal processing of the metalized yarn resulted in a 30% improvement in thermal conductivity, 40% increase in electrical conductivity and a 4× increase in elastic modulus. Cross-sections of the yarn were examined ...


Control Of Plasma Flux Composition Incident On Tin Films During Reactive Magnetron Sputtering And The Effect On Film Microstructure, Christopher Muratore, Scott Walton, D. Leonhardt, Richard Fernsler Feb 2016

Control Of Plasma Flux Composition Incident On Tin Films During Reactive Magnetron Sputtering And The Effect On Film Microstructure, Christopher Muratore, Scott Walton, D. Leonhardt, Richard Fernsler

Christopher Muratore

A hybrid plasma enhanced physical vapor deposition (PEPVD) system consisting of an unbalanced dc magnetron and a pulsed electron beam-produced plasma was used to deposit reactively sputteredtitanium nitride thin films. The system allowed for control of the magnitudes of the ion and neutral flux, in addition to the type of nitrogen ions (atomic or molecular) that comprised the flux. For all deposition experiments, the magnitude of the ion flux incident on the substrate was held constant, but the composition of the total flux was varied. X-ray diffraction and atomic force microscopy showed that crystallographic texture and surface morphology of the ...


Temporally And Spatially Resolved Plasma Spectroscopy In Pulsed Laser Deposition Of Ultra-Thin Boron Nitride Films, Nicholas Glavin, Christopher Muratore, Michael Jespersen, Jianjun Hu, Timothy Fisher, Andrey Voevodin Feb 2016

Temporally And Spatially Resolved Plasma Spectroscopy In Pulsed Laser Deposition Of Ultra-Thin Boron Nitride Films, Nicholas Glavin, Christopher Muratore, Michael Jespersen, Jianjun Hu, Timothy Fisher, Andrey Voevodin

Christopher Muratore

Physical vapor deposition (PVD) has recently been investigated as a viable, alternative growth technique for two-dimensional materials with multiple benefits over other vapor deposition synthesis methods. The high kinetic energies and chemical reactivities of the condensing species formed from PVD processes can facilitate growth over large areas and at reduced substrate temperatures. In this study, chemistry, kinetic energies, time of flight data, and spatial distributions within a PVD plasma plume ablated from aboron nitride (BN) target by a KrF laser at different pressures of nitrogen gas were investigated. Time resolved spectroscopy and wavelength specific imaging were used to identify and ...


Control Of Plasma Flux Composition Incident On Tin Films During Reactive Magnetron Sputtering And The Effect On Film Microstructure, Christopher Muratore, Scott Walton, D. Leonhardt, Richard Fernsler Feb 2016

Control Of Plasma Flux Composition Incident On Tin Films During Reactive Magnetron Sputtering And The Effect On Film Microstructure, Christopher Muratore, Scott Walton, D. Leonhardt, Richard Fernsler

Christopher Muratore

A hybrid plasma enhanced physical vapor deposition (PEPVD) system consisting of an unbalanced dc magnetron and a pulsed electron beam-produced plasma was used to deposit reactively sputteredtitanium nitride thin films. The system allowed for control of the magnitudes of the ion and neutral flux, in addition to the type of nitrogen ions (atomic or molecular) that comprised the flux. For all deposition experiments, the magnitude of the ion flux incident on the substrate was held constant, but the composition of the total flux was varied. X-ray diffraction and atomic force microscopy showed that crystallographic texture and surface morphology of the ...


Cross-Plane Thermal Properties Of Transition Metal Dichalcogenides, Christopher Muratore, Vikas Varshney, Jaime Gengler, Jianjun Hu, John Bultman, Timothy Smith, Patrick Shamberger, Bo Qiu, Xiulin Ruan, Ajit Roy, Andrey Voevodin Feb 2016

Cross-Plane Thermal Properties Of Transition Metal Dichalcogenides, Christopher Muratore, Vikas Varshney, Jaime Gengler, Jianjun Hu, John Bultman, Timothy Smith, Patrick Shamberger, Bo Qiu, Xiulin Ruan, Ajit Roy, Andrey Voevodin

Christopher Muratore

In this work, we explore the thermal properties of hexagonal transition metal dichalcogenide compounds with different average atomic masses but equivalent microstructures. Thermal conductivity values of sputtered thin films were compared to bulk crystals. The comparison revealed a >10 fold reduction in thin film thermal conductivity. Structural analysis of the films revealed a turbostratic structure with domain sizes on the order of 5–10 nm. Estimates of phonon scattering lengths at domain boundaries based on computationally derived group velocities were consistent with the observed film microstructure, and accounted for the reduction in thermal conductivity compared to values for bulk crystals.


Estimating The Subsonic Aerodynamic Center And Moment Components For Swept Wings, W. Phillips, Doug Hunsaker, R. Niewoehner Feb 2016

Estimating The Subsonic Aerodynamic Center And Moment Components For Swept Wings, W. Phillips, Doug Hunsaker, R. Niewoehner

Doug Hunsaker

An improved method is presented for estimating the subsonic location of the semispan aerodynamic center of a swept wing and the aerodynamic moment components about that aerodynamic center. The method applies to wings with constant linear taper and constant quarter-chord sweep. The results of a computational fluid dynamics study for 236 wings show that the position of the semispan aerodynamic center of a wing depends primarily on aspect ratio, taper ratio, and quarter-chord sweep angle. Wing aspect ratio was varied from 4.0 to 20, taper ratios from 0.25 to 1.0 were investigated quarter-chord sweep angles were varied ...


Perspectives On Uav Airframe Design, Doug Hunsaker Feb 2016

Perspectives On Uav Airframe Design, Doug Hunsaker

Doug Hunsaker

A perspective on how unmanned airframes may be efficiently and quickly developed as the UAV industry grows.


Pitch Dynamics Of Unmanned Aerial Vehicles, W. Phillips, Doug Hunsaker, N. Alley, R. Niewoehner Feb 2016

Pitch Dynamics Of Unmanned Aerial Vehicles, W. Phillips, Doug Hunsaker, N. Alley, R. Niewoehner

Doug Hunsaker

Dynamic stability requirements for manned aircraft have been in place for many years. However, we cannot expect stability constraints for UAVs to match those for manned aircraft; and dynamic stability requirements specific to UAVs have not been developed. The boundaries of controllability for both remotely-piloted and auto-piloted aircraft must be established before UAV technology can reach its full potential. The development of dynamic stability requirements specific to UAVs could improve flying qualities and facilitate more efficient UAV designs to meet specific mission requirements. As a first step to developing UAV stability requirements in general, test techniques must be established that ...


Smooth-Wall Boundary Conditions For Dissipation-Based Turbulence Models, W. Phillips, Doug Hunsaker, R. Spall Feb 2016

Smooth-Wall Boundary Conditions For Dissipation-Based Turbulence Models, W. Phillips, Doug Hunsaker, R. Spall

Doug Hunsaker

No abstract provided.