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Articles 31 - 60 of 1132
Full-Text Articles in Engineering
The Australian Long Term Power Quality Survey Project Update, Sean Elphick, V. Smith, Victor Gosbell, Robert Barr
The Australian Long Term Power Quality Survey Project Update, Sean Elphick, V. Smith, Victor Gosbell, Robert Barr
Robert Barr
The Australian Long Term National Power Quality Survey (LTNPQS) is a large multi-utility power quality survey which has now been in operation for 8 years. This paper details the latest innovative developments in the reporting and analysis procedures developed for the LTNPQS. The paper also highlights the key power quality issues affecting Australian electricity networks at the present time. These include high voltage levels at LV sites and difficulties in measurement of voltage unbalance. The longevity of the survey has allowed better understanding of disturbance trend levels. Interesting results include an apparent reduction in harmonic levels in the past couple …
Prediction Of Organic Droplet Behavior On A Solid Surface As Influenced By Aqueous Surfactant Solutions, Samuel Morton
Prediction Of Organic Droplet Behavior On A Solid Surface As Influenced By Aqueous Surfactant Solutions, Samuel Morton
Samuel A Morton
This dissertation presents a model capable of predicting equilibrium oil droplet contact angles on a solid surface immersed in surfactant solution, a thorough discussion of the effects of surfactant concentration and salt addition on contact angles, and an experimental investigation into the impact of voltage application to the solid surface on oil droplet shape in an aqueous/organic/solid system. The work contained in this dissertation resulted in five journal articles and numerous presentations. The model applies current theories of surfactant self-assembly, the quasi-chemical approximation for solid surface adsorption, and various aqueous/organic/solid system properties to determine organic droplet contact angles. The computational …
Green Credits Versus Environmentally Sustainable Traffic Operations:A Comparison Of Contributions To Energy And Emissions Reductions, Yan Zhou, Lee Tupper, Mashrur Chowdhury, Leidy Klotz
Green Credits Versus Environmentally Sustainable Traffic Operations:A Comparison Of Contributions To Energy And Emissions Reductions, Yan Zhou, Lee Tupper, Mashrur Chowdhury, Leidy Klotz
Leidy E. Klotz
Although society is facing a variety of environmental issues, including the depletion of energy resources, and has a much greater awareness of climate change and its serious related social impacts, transportation systems have been pushed to increasingly greater limits because of the dramatic growth in traffic demand. A case study was performed to compare the contributions of green construction credits and those of environmentally sustainable traffic operations to reducing energy use and emissions. The study measured the impacts of green credits by using the Carnegie Mellon University economic input-output life-cycle assessment model. These impacts were compared with those achieved through …
Women As Sustainability Leaders In Engineering: Evidence From Industry And Academia In The U.S., Jennilee Harrison, Leidy Klotz
Women As Sustainability Leaders In Engineering: Evidence From Industry And Academia In The U.S., Jennilee Harrison, Leidy Klotz
Leidy E. Klotz
Women are underrepresented in engineering education and practice, which limits the quality of the engineering workforce. One way to increase the participation of women in engineering is to emphasize subjects that appeal to them and require skills at which they are especially adept. A subject that may fit this description is sustainability. To examine whether the subject of sustainability may help increase the participation of women in engineering, the purpose of this research is to compare the percentage of women in selected sustainable engineering leadership positions with the percentage of women in general engineering leadership positions. Gender data were collected …
Can Declared Strategy Voting Be An Effective Instrument For Group Decision-Making?, Lorrie Cranor
Can Declared Strategy Voting Be An Effective Instrument For Group Decision-Making?, Lorrie Cranor
Lorrie F Cranor
The goal of this research is to determine whether declared strategy voting can be an effective tool for group decision-making. Declared strategy voting is a novel group decision-making procedure in which preference is specified using voting strategies - first-order mathematical functions that specify a choice in terms of zero or more parameters. This research will focus on refining the declared strategy voting concept, developing an accessible implementation of declared strategy voting that can be used for mock elections, assessing the potential impacts of declared strategy voting, and evaluating the effectiveness of declared strategy voting for group decision-making. This proposal describes …
Design And Implementation Of A Practical Security-Conscious Electronic Polling System, Lorrie Cranor, Ron Cytron
Design And Implementation Of A Practical Security-Conscious Electronic Polling System, Lorrie Cranor, Ron Cytron
Lorrie F Cranor
We present the design and implementation of Sensus, a practical, secure and private system for conducting surveys and elections over computer networks. Expanding on the work of Fujioka, Okamoto, and Ohta, Sensus uses blind signatures to ensure that only registered voters can vote and that each registered voter only votes once, while at the same time maintaining voters' privacy. Sensus allows voters to verify independently that their votes were counted correctly, and anonymously challenge the results should their votes be miscounted. We outline seven desirable properties of voting systems and show that Sensus satisfied these properties well, in some cases …
Market Analysis For Small And Mid-Size Commercial Turboprop Aircraft, Vitaly Guzhva, Tamilla Curtis, Vladislav Borodulin
Market Analysis For Small And Mid-Size Commercial Turboprop Aircraft, Vitaly Guzhva, Tamilla Curtis, Vladislav Borodulin
Dr. Tamilla Curtis
Recent fuel price volatility and growing concerns about the efficiency of regional jets have led to a revival of large turboprop aircraft as efficient passenger carriers on short-haul regional routes. However, the overall market for smaller turboprops is much less defined as it is characterized by a plethora of small commuter and niche operators in addition to regional carriers. Since most small and mid-size turboprop manufacturers have gone bankrupt or discontinued production due to some other reasons, current operators of this aircraft class are left with aging fleets that would need to be replaced by 2020-2030. This paper assesses the …
A Nonasymptotic Homogenization Theory Of Electromagnetic Metamaterials, Igor Tsukerman, Vadim Markel
A Nonasymptotic Homogenization Theory Of Electromagnetic Metamaterials, Igor Tsukerman, Vadim Markel
Igor Tsukerman
We propose a new homogenization methodology for periodic electromagnetic structures (photonic crystals and metamaterials). The physical essence of this methodology is in seeking effective material parameters that provide, in some sense, the best approximation of Bloch impedances as well as dispersion relations over an ensemble of physical modes in the structure. Mathematically, the homogenization problem is solved by approximating the fields on the fine and coarse scales with the respective eigenmodes that satisfy Maxwell's equations and boundary conditions as accurately as possible.
Trefftz Absorbing Boundary Conditions In Analytical, Discontinuous Galerkin And Finite Difference Form, Fritz Kretzschmar, Farzad Ahmadi, Nabil Nowak, Sascha Schnepp, Igor Tsukerman, Herbert Egger, Thomas Weiland
Trefftz Absorbing Boundary Conditions In Analytical, Discontinuous Galerkin And Finite Difference Form, Fritz Kretzschmar, Farzad Ahmadi, Nabil Nowak, Sascha Schnepp, Igor Tsukerman, Herbert Egger, Thomas Weiland
Igor Tsukerman
We explore a novel avenue for generating absorbing boundary conditions for wave problems. The key part of our approach is Trefftz approximations of the solution, i.e. approximations by functions satisfying locally the underlying wave equation. Trefftz functions include outgoing waves only (and possibly evanescent waves), but no incoming waves. We show how this idea can be applied in three different contexts: analytical, Discontinuous Galerkin, and finite difference.
Imaging Diffractometer With Holographic Encoding Enhancements For Laser Sensing And Characterization, Joesph Binford, Bradley Duncan, Jack Parker, Elizabeth Beecher, Mark Delong
Imaging Diffractometer With Holographic Encoding Enhancements For Laser Sensing And Characterization, Joesph Binford, Bradley Duncan, Jack Parker, Elizabeth Beecher, Mark Delong
Bradley D. Duncan
What is believed to be a novel holographic optical encoding scheme has been developed to enhance the performance of laser sensors designed for the measurement of wavelength and angular trajectory. A prototype holographic imaging diffractometer has been created to reconstruct holographic cueing patterns superimposed in the focal plane of wide-angle scene imagery. Based on experimental pattern metric measurements at the focal plane, a theoretical model is used to compute the laser source wavelength and its apparent propagation direction within the sensor's field of view. The benefits of incorporating holographic enhancements within an imager-based sensor architecture are discussed.
Optical Sparse Aperture Imaging, Nicholas Miller, Matthew Dierking, Bradley Duncan
Optical Sparse Aperture Imaging, Nicholas Miller, Matthew Dierking, Bradley Duncan
Bradley D. Duncan
The resolution of a conventional diffraction-limited imaging system is proportional to its pupil diameter. A primary goal of sparse aperture imaging is to enhance resolution while minimizing the total light collection area; the latter being desirable, in part, because of the cost of large, monolithic apertures. Performance metrics are defined and used to evaluate several sparse aperture arrays constructed from multiple, identical, circular subapertures. Subaperture piston and∕or tilt effects on image quality are also considered. We selected arrays with compact nonredundant autocorrelations first described by Golay. We vary both the number of subapertures and their relative spacings to arrive at …
Monte Carlo Simulation Of Multiple Photon Scattering In Sugar Maple Tree Canopies, Michael Greiner, Bradley Duncan, Matthew Dierking
Monte Carlo Simulation Of Multiple Photon Scattering In Sugar Maple Tree Canopies, Michael Greiner, Bradley Duncan, Matthew Dierking
Bradley D. Duncan
Detecting objects hidden beneath forest canopies is a difficult task for optical remote sensing systems. Rather than relying upon the existence of gaps between leaves, as other researchers have done, our ultimate goal is to use light scattered by leaves to image through dense foliage. Herein we describe the development of a Monte Carlo model for simulating the scattering of light as it propagates through the leaves of an extended tree canopy. We measured several parameters, including the gap fraction and maximum leaf-area density, of a nearby sugar maple tree grove and applied them to our model. We report the …
Improving Mid-Frequency Contrast In Sparse Aperture Optical Imaging Systems Based Upon The Golay-9 Array, Andrew Stokes, Bradley Duncan, Matthew Dierking
Improving Mid-Frequency Contrast In Sparse Aperture Optical Imaging Systems Based Upon The Golay-9 Array, Andrew Stokes, Bradley Duncan, Matthew Dierking
Bradley D. Duncan
Sparse aperture imaging systems are capable of producing high resolution images while maintaining an overall light collection area that is small compared to a fully filled aperture yielding the same resolution. This is advantageous for applications where size, volume, weight and/or cost are important considerations. However, conventional sparse aperture systems pay the penalty of reduced contrast at midband spatial frequencies. This paper will focus on increasing the midband contrast of sparse aperture imaging systems based on the Golay-9 array. This is one of a family of two-dimensional arrays we have previously examined due to their compact, non-redundant autocorrelations. The modulation …
Periodic, Pseudo-Noise Waveforms For Multi-Function Coherent Ladar, Matthew Dierking, Bradley Duncan
Periodic, Pseudo-Noise Waveforms For Multi-Function Coherent Ladar, Matthew Dierking, Bradley Duncan
Bradley D. Duncan
We report the use of periodic, pseudonoise waveforms in a multifunction coherent ladar system. We exploit the Doppler sensitivity of these waveforms, as well as agile processing, to enable diverse ladar functions, including high range resolution imaging, macro-Doppler imaging, synthetic aperture ladar, and range-resolved micro-Doppler imaging. We present analytic expressions and simulations demonstrating the utility of pseudonoise waveforms for each of the ladar modes. We also discuss a laboratory pseudonoise ladar system that was developed to demonstrate range compression and range-resolved micro-Doppler imaging, as well as the phase recovery common to each of the coherent modes.
Holographic Aperture Ladar, Bradley Duncan, Matthew Dierking
Holographic Aperture Ladar, Bradley Duncan, Matthew Dierking
Bradley D. Duncan
Holographic aperture ladar is a variant of synthetic aperture ladar that seeks to increase cross-range scene resolution by synthesizing a large effective aperture through the motion of a smaller receiver and through the subsequent proper phasing and correlation of the detected signals in postprocessing. Unlike in conventional synthetic aperture ladar, however, holographic aperture ladar makes use of a two- dimensional translating sensor array, not simply a translating point detector. Also unlike in conventional synthetic aperture ladar, holographic aperture images will be formed in the two orthogonal cross-range dimensions parallel and perpendicular to the sensor platform’s direction of motion. The central …
Experimental Demonstration Of A Stripmap Holographic Aperture Ladar System, Jason Stafford, Bradley Duncan, Matthew Dierking
Experimental Demonstration Of A Stripmap Holographic Aperture Ladar System, Jason Stafford, Bradley Duncan, Matthew Dierking
Bradley D. Duncan
By synthesizing large effective apertures through the translation of a smaller imaging sensor and the subsequent proper phasing and correlation of detected signals in postprocessing, holographic aperture ladar (HAL) systems seek to increase the resolution of remotely imaged targets. The stripmap HAL process was demonstrated in the laboratory, for the first time to our knowledge. Our results show that the stripmap HAL transformation can precisely account for off-axis transmitter induced phase migrations. This in turn allows multiple pupil plane field segments, sequentially collected across a synthetic aperture, to be coherently mosaiced together. As a direct consequence, we have been able …
Effects Of Spatial Modes On Ladar Vibration Signature Estimation, Douglas Jameson, Matthew Dierking, Bradley Duncan
Effects Of Spatial Modes On Ladar Vibration Signature Estimation, Douglas Jameson, Matthew Dierking, Bradley Duncan
Bradley D. Duncan
Ladar-based vibrometry has been shown to be a powerful technique in enabling the plant identification of machines. Rather than sensing the geometric shape of a target laser vibrometers sense motions of the target induced by moving parts within the system. Since the target need not be spatially resolved, vibration can be sensed reliably and provide positive identification at ranges beyond the imaging limits of the aperture. However, as the range of observation increases, the diffraction-limited beam size on the target increases as well, and may encompass multiple vibrational modes on the target's surface. As a result, vibration estimates formed from …
Bidirectional Scattering Distribution Functions Of Maple And Cottonwood Leaves, Michael Greiner, Bradley Duncan, Matthew Dierking
Bidirectional Scattering Distribution Functions Of Maple And Cottonwood Leaves, Michael Greiner, Bradley Duncan, Matthew Dierking
Bradley D. Duncan
We present our investigations into the optical scattering properties of both sugar maple (Acer saccarum) and eastern cottonwood (Populus deltoides) leaves in the near-IR wavelength regime. The bidirectional scattering distribution function (BSDF) describes the fractions of light reflected by and transmitted through a leaf for a given set of illumination and observation angles. Experiments were performed to measure the BSDF of each species at a discrete set of illumination and observation angles. We then modeled the BSDFs in such a way that other researchers may interpolate their values for scattering in any direction under illumination at any angle.
Demonstrated Resolution Enhancement Capability Of A Stripmap Holographic Aperture Ladar System, Samuel Venable, Bradley Duncan, Matthew Dierking, David Rabb
Demonstrated Resolution Enhancement Capability Of A Stripmap Holographic Aperture Ladar System, Samuel Venable, Bradley Duncan, Matthew Dierking, David Rabb
Bradley D. Duncan
Holographic aperture ladar (HAL) is a variant of synthetic aperture ladar (SAL). The two processes are related in that they both seek to increase cross-range (i.e., the direction of the receiver translation) image resolution through the synthesis of a large effective aperture. This is in turn achieved via the translation of a receiver aperture and the subsequent coherent phasing and correlation of multiple received signals. However, while SAL imaging incorporates a translating point detector, HAL takes advantage of a two-dimensional translating sensor array. For the research presented in this article, a side-looking stripmap HAL geometry was used to sequentially image …
Saturated Semiconductor Optical Amplifier Phase Modulation For Long Range Laser Radar Applications, Jennifer Carns, Bradley Duncan, Matthew Dierking
Saturated Semiconductor Optical Amplifier Phase Modulation For Long Range Laser Radar Applications, Jennifer Carns, Bradley Duncan, Matthew Dierking
Bradley D. Duncan
We investigate the use of a semiconductor optical amplifier operated in the saturation regime as a phase modulator for long range laser radar applications. The nature of the phase and amplitude modulation resulting from a high peak power Gaussian pulse, and the impact this has on the ideal pulse response of a laser radar system, is explored. We also present results of a proof-of-concept laboratory demonstration using phase-modulated pulses to interrogate a stationary target.
Metal Wear Detection Apparatus And Method Employing Microfluidic Electronic Device, Jiang Zhe, Li Du, Joan Carletta, Robert Veillette
Metal Wear Detection Apparatus And Method Employing Microfluidic Electronic Device, Jiang Zhe, Li Du, Joan Carletta, Robert Veillette
Robert Veillette
An apparatus and a method for detection of wear particles in a lubricant are disclosed. The apparatus includes a microfluidic device including a microchannel sized for a lubricant containing wear particles to pass therethrough and first and second electrodes extending into the microchannel. A detection system is coupled with the electrodes for detection of wear particles passing through the microchannel, based on a change in capacitance of the electrodes.
Inductive Coulter Counting: Detection And Differentiation Of Metal Wear Particles In Lubricant, Li Du, Jiang Zhe, Robert Veillette
Inductive Coulter Counting: Detection And Differentiation Of Metal Wear Particles In Lubricant, Li Du, Jiang Zhe, Robert Veillette
Robert Veillette
A device based on an inductive Coulter counting principle for detecting metal particles in lubrication oil is presented. The device detects the passage of ferrous and nonferrous particles by monitoring the inductance change in a coil. First, the sensing principle is demonstrated at the mesoscale using a solenoid. Next, a small planar coil suitable for use in a microscale device is tested. Static tests are conducted on the planar coil using iron and aluminum particles ranging from 80 to 500 µm. The testing results show that the coil can be used to detect and distinguish ferrous and nonferrous metal particles …
A Magnetic Coulter Counting Device For Wear Debris Detection In Lubrication, Li Du, Joan Carletta, Robert Veillette, Jiang Zhe
A Magnetic Coulter Counting Device For Wear Debris Detection In Lubrication, Li Du, Joan Carletta, Robert Veillette, Jiang Zhe
Robert Veillette
A device based on a magnetic Coulter counting principle to detect metal particles in lubrication oil is presented. The device detects the passage of ferrous and non ferrous particles by monitoring inductance change in a coil. First, the sensing principle is demonstrated at the mesoscale using a solenoid. Next, a microscale device is developed using a planar coil. The device is tested using iron and aluminum particles ranging from 100μm to 500μm. The testing results show the device is capable of detecting and distinguishing ferrous and non-ferrous metal particles in lubrication oil. The design concept demonstrated here can be extended …
Real-Time Monitoring Of Wear Debris In Lubrication Oil Using A Microfluidic Inductive Coulter Counting Device, Li Du, Jiang Zhe, Joan Carletta, Robert Veillette, Fred Choy
Real-Time Monitoring Of Wear Debris In Lubrication Oil Using A Microfluidic Inductive Coulter Counting Device, Li Du, Jiang Zhe, Joan Carletta, Robert Veillette, Fred Choy
Robert Veillette
A microfluidic device based on an inductive Coulter counting principle to detect metal wear particles in lubrication oil is presented. The device detects the passage of ferrous and nonferrous particles by monitoring the inductance change of an embedded coil. The device was tested using iron and copper particles ranging in size from 50 to 125 μm. The testing results have demonstrated that the device is capable of detecting and distinguishing ferrous and nonferrous metal particles in lubrication oil; such particles can be indicative of potential machine faults in rotating and reciprocating machinery.
Coupling Efficiencies For General Target Illumination Ladar Systems Incorporating Single Mode Optical Fiber Receivers, Christopher Brewer, Bradley Duncan, Kenneth Barnard, Edward Watson
Coupling Efficiencies For General Target Illumination Ladar Systems Incorporating Single Mode Optical Fiber Receivers, Christopher Brewer, Bradley Duncan, Kenneth Barnard, Edward Watson
Bradley D. Duncan
A rigorous method for modeling received power coupling efficiency (ηF/R) and transmitted power coupling efficiency (ηF/T) in a general-target-illumination ladar system is presented. For our analysis we concentrate on incorporating a single-mode optical fiber into the ladar return signal path. By developing expressions for both ηF/R and ηF/T for a simple, diffuse target, our model allows for varying range, beam size on target, target diameter, and coupling optics. Through numerical analysis ηF/R is shown to increase as the range to target increases and decrease as target diameter increases, and ηF/T is shown to decrease with target range. A baseline signal-to-noise …
Parametric Extension Of The Classical Exposure Schedule Theory For Angle-Multiplexed Photorefractive Recording Using The Common-Aperture Beam Geometry, Mark Delong, Bradley Duncan, Jack Parker
Parametric Extension Of The Classical Exposure Schedule Theory For Angle-Multiplexed Photorefractive Recording Using The Common-Aperture Beam Geometry, Mark Delong, Bradley Duncan, Jack Parker
Bradley D. Duncan
The gradual reorientations in crystal geometry encountered during angle-multiplexed holographic recording with obliquely incident recording beams can create significant parametric exposure-time and recording-angle dependencies in both grating writing- and erasure-time constants. We present a parametric extension of the classically derived backward-recursion algorithm that compensates for the intermingling effects of recording geometry, writing-beam intensity variations, and unique crystal behavior. We present experimental data for a sequence of 301 holograms recorded with the goal of equal hologram strength and, separately, the same sequence recorded with the goal of equal hologram reconstruction intensity—which are different cases for a steeply incident readout beam.
Space-Bandwidth Product Enhancement Of A Monostatic, Multi-Aperture Infrared Image Upconversion Ladar Receiver Incorporating Periodically Polled Linbo3, Christopher Brewer, Bradley Duncan, Phillip Maciejewski, Sean Kirkpatrick, Edward Watson
Space-Bandwidth Product Enhancement Of A Monostatic, Multi-Aperture Infrared Image Upconversion Ladar Receiver Incorporating Periodically Polled Linbo3, Christopher Brewer, Bradley Duncan, Phillip Maciejewski, Sean Kirkpatrick, Edward Watson
Bradley D. Duncan
We investigate the space-bandwidth product of a ladar system incorporating an upconversion receiver. After illuminating a target with an eye-safe beam, we direct the return into a piece of periodically poled LiNbO3 where it is upconverted into the visible spectrum and detected with a CCD camera. The theoretical and experimental transfer functions are then found. We show that the angular acceptance of the upconversion process severely limits the receiver field of regard for macroscopic coupling optics. This limitation is overcome with a pair of microlens arrays, and a 43% increase in the system’s measured space-bandwidth product is demonstrated.
Real-Time Non-Linear Image Processing Using An Active Optical Scanning Technique, Bradley Duncan, Ting-Chung Poon, Ron Piper
Real-Time Non-Linear Image Processing Using An Active Optical Scanning Technique, Bradley Duncan, Ting-Chung Poon, Ron Piper
Bradley D. Duncan
Real-time non-linear image processing has been achieved using an active optical scanning technique. This paper reports experimental results in edge extraction for both binary and grey-scale transmissive objects. Binary edge extraction is achieved using morphological transformations, while grey-scale edge extraction is achieved using a threshold decomposition technique. Advantages and limitation of both techniques are identified.
Optical-Fiber Preamplifiers For Ladar Detection And Associated Measurements For Improving The Signal-To-Noise Ratio, Michael Salisbury, Paul Mcmanamon, Bradley Duncan
Optical-Fiber Preamplifiers For Ladar Detection And Associated Measurements For Improving The Signal-To-Noise Ratio, Michael Salisbury, Paul Mcmanamon, Bradley Duncan
Bradley D. Duncan
In an effort to increase achievable postdetection signal-tonoise ratios (SNRs) of continuous-wave, 1-gm all-solid-state ladar systems, a prototype rare-earth-doped optical-fiber amplifier has been included in the optical return signal path of both a heterodyne and a directdetection ladar system. We provide numerical predictions for SNR increases according to our previously developed theory. We also detail our experimental efforts and provide the results of SNR measurements for four distinct cases: direct ladar detection with and without a fiber amplifier, and heterodyne ladar detection with and without a fiber amplifier. Experimentally measured increases in SNRs for ladar systems incorporating an optical-fiber amplifier …
Volume Holographic Memory For Laser Threat Discrimination, Mark Delong, Bradley Duncan, Jack Parker
Volume Holographic Memory For Laser Threat Discrimination, Mark Delong, Bradley Duncan, Jack Parker
Bradley D. Duncan
Using conventional volume-holographic angle multiplexing in an Fe:LiNbO3 crystal, we have developed a compact laser threat discriminator, intended for aircraft integration, that optically detects laser spatial coherence and angle of arrival while simultaneously rejecting incoherent background sources, such as the Sun. The device is intended for a specific type of psychophysical laser attack against U.S. Air Force pilots, namely, third-world-country exploitation of inexpensive and powerful cw Ar-ion or doubled Nd:YAG lasers in the visible spectrum to blind or disorient U.S. pilots. The component does not solve the general tactical laser weapon situation, which includes identifying precision-guided munitions, range finders, and …