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Full-Text Articles in Engineering

Research Article| December 30 2005 Analysis Of Shea Nut Shells By X-Ray Photoelectron Spectroscopy, Guilin Jiang, Ghaleb A. Husseini, Larry Lin Baxter, Matthew R. Linford Dec 2005

Research Article| December 30 2005 Analysis Of Shea Nut Shells By X-Ray Photoelectron Spectroscopy, Guilin Jiang, Ghaleb A. Husseini, Larry Lin Baxter, Matthew R. Linford

Faculty Publications

Determining the chemical structure and composition of biomass fuels using x-ray photoelectron spectroscopy (XPS) can provide fundamental knowledge of their structures that is useful in understanding and predicting their combustion behavior. Shea nut shells are an example of an agricultural residue (byproduct of food and feed production) of potential interest for biomass combustion. The XPS spectra of shea nut shells provide both its elemental composition and indications of its bonding. Traditional fuel analyses of this fuel are also provided. These include: ultimate analysis — the elemental composition of the overall fuel (C, H, N, S, and O); chlorine analysis — …

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Analysis Of Grain Screenings By X-Ray Photoelectron Spectroscopy, Guilin Jiang, Ghaleb A. Husseini, Larry Lin Baxter, Matthew R. Linford Dec 2005

Analysis Of Grain Screenings By X-Ray Photoelectron Spectroscopy, Guilin Jiang, Ghaleb A. Husseini, Larry Lin Baxter, Matthew R. Linford

Faculty Publications

Determining the chemical structure and composition of biomass fuels using x-ray photoelectron spectroscopy XPS can provide fundamental knowledge of their structures that is useful in understanding and predicting their combustion behavior. Grain screenings are an example of an agricultural residue byproduct of food and feed production of potential interest for biomass combustion. The XPS spectra of grain screenings provide both its elemental composition and indications of its bonding. Traditional fuel analyses of this fuel are also provided. These include: ultimate analysis — the elemental composition of the overall fuel C, H, N, S, and O; chlorine analysis — reported here …

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Analysis Of Sawdust By X-Ray Photoelectron Spectroscopy, Guilin Jiang, Ghaleb A. Husseini, Larry Lin Baxter, Matthew R. Linford Dec 2005

Analysis Of Sawdust By X-Ray Photoelectron Spectroscopy, Guilin Jiang, Ghaleb A. Husseini, Larry Lin Baxter, Matthew R. Linford

Faculty Publications

Determining the chemical structure and composition of biomass fuels using x-ray photoelectron spectroscopy XPS can provide fundamental knowledge of their structures that is useful in understanding and predicting their combustion behavior. Sawdust is an example of a forest product residue byproduct of paper and lumber production of potential interest for biomass combustion. The XPS spectra of sawdust provide both its elemental composition and indications of its bonding. Traditional fuel analyses of this fuel are also provided. These include: ultimate analysis — the elemental composition of the overall fuel C, H, N, S, and O; chlorine analysis — reported here as …

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Analysis Of Straw By X-Ray Photoelectron Spectroscopy, Guilin Jiang, Ghaleb A. Husseini, Larry Lin Baxter, Matthew R. Linford Dec 2005

Analysis Of Straw By X-Ray Photoelectron Spectroscopy, Guilin Jiang, Ghaleb A. Husseini, Larry Lin Baxter, Matthew R. Linford

Faculty Publications

Determining the chemical structure and composition of biomass fuels using x-ray photoelectron spectroscopy XPS can provide fundamental knowledge of their structures that is useful in understanding and predicting their combustion behavior. Straw is an example of an agricultural residue byproduct of food and feed production of potential interest for biomass combustion. The XPS spectra of straw provide both its elemental composition and indications of its bonding. Traditional fuel analyses of this fuel are also provided. These include: ultimate analysis — the elemental composition of the overall fuel C, H, N, S, and O; chlorine analysis — reported here as part …

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Top-Down Structure And Device Fabrication Using In Situ Nanomachining, Xiaodong Li, Xinnan Wang, Qihua Xiong, Peter C. Eklund Dec 2005

Top-Down Structure And Device Fabrication Using In Situ Nanomachining, Xiaodong Li, Xinnan Wang, Qihua Xiong, Peter C. Eklund

Faculty Publications

We demonstrate the potential of an alternative tool for the fabrication of nanoscale structures and devices. A nanoindenter integrated with an atomic force microscope is shown to be a powerful machine tool for cutting precise length nanowires or nanobelts and for manipulating the shortened wires. We also demonstrate its utility in cutting grooves and fabricating dents (or periodic arrays of dents) in ZnSnanobelts. This approach permits the direct mechanical machining of nanodevices that are supported on a substrate without the inherent complications of e beam or photolithography.

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Fully Compliant Tensural Bistable Micro-Mechanisms (Ftbm), D. L. Wilcox, Larry L. Howell Dec 2005

Fully Compliant Tensural Bistable Micro-Mechanisms (Ftbm), D. L. Wilcox, Larry L. Howell

Faculty Publications

A new class of bistable mechanisms, the fully compliant tensural bistable micromechanism (FTBM) class, is introduced. The class consists of linear bistable micromechanisms that undergo tension loads, in addition to the bending loads present, through their range of motion. Proof-of-concept designs fabricated in two different microelectromechanical systems (MEMS) surface micromachining processes were demonstrated. Three sets of refined designs within the FTBM class were designed using optimization methods linked with nonlinear finite element analysis (FEA), then fabricated and tested. Measured force and displacement performance are compared to values obtained by FEA. On-chip actuation of the bistable mechanisms was achieved using thermomechanical …

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Performance Analysis Of Common Detectors For Shaped Offset Qpsk And Feher's Qpsk, Tom Nelson, Michael D. Rice, Erik Perrins Dec 2005

Performance Analysis Of Common Detectors For Shaped Offset Qpsk And Feher's Qpsk, Tom Nelson, Michael D. Rice, Erik Perrins

Faculty Publications

Sponsorship: US Air Force Grant FA9302-05-C-0001. A detector architecture capable of detecting both shaped offset quadrature phase shift keying (SOQPSK-TG) and Feher's quadrature phase shift keying (FQPSK-JR) is developed and analyzed. Both modulations are embodied as fully interoperable modulations in the Interrange Instrumentation Group (IRIG) standard IRIG-106. It is shown that the common detector achieves near optimal bit error rate performance without knowledge of which modulation is used by the transmitter. The detection techniques are based on a common trellis-coded modulation representation and a common continuous phase modulation (CPM) representation for these two modulations. In addition the common pulse amplitude …

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Loss Aware Rate Allocations In H.263 Coded Video Transmissions, Xiao Su, Benjamin Wah Dec 2005

Loss Aware Rate Allocations In H.263 Coded Video Transmissions, Xiao Su, Benjamin Wah

Faculty Publications

For packet video, information loss and bandwidth limitation are two factors that affect video playback quality. Traditional rate allocation approaches have focused on optimizing video quality under bandwidth constraint alone. However, in the best-effort Internet, packets carrying video data are susceptible to losses, which need to be reconstructed at the receiver side. In this paper, we propose loss aware rate allocations in both group-of-block (GOB) level and macroblock level, given that certain packets are lost during transmissions and reconstructed using simple interpolation methods at the receiver side. Experimental results show that our proposed algorithms can produce videos of higher quality …

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Modeling Microwave Emissions Of Erg Surfaces In The Sahara Desert, David G. Long, Haroon Stephen Dec 2005

Modeling Microwave Emissions Of Erg Surfaces In The Sahara Desert, David G. Long, Haroon Stephen

Faculty Publications

Sand seas (ergs) of the Sahara are the most dynamic parts of the desert. Aeolian erosion, transportation, and deposition continue to reshape the surface of the ergs. The large-scale features (dunes) of these bedforms reflect the characteristics of the sand and the long-term wind. Radiometric emissions from the ergs have strong dependence on the surface geometry. We model the erg surface as composed of tilted rough facets. Each facet is characterized by a tilt distribution dependent upon the surface roughness of the facet. The radiometric temperature (Tb) of ergs is then the weighted sum of the Tb from all the …

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An Analysis Of Seawinds-Based Rain Retrieval In Severe Weather Events, David G. Long, Jeffrey R. Allen Dec 2005

An Analysis Of Seawinds-Based Rain Retrieval In Severe Weather Events, David G. Long, Jeffrey R. Allen

Faculty Publications

The Ku-band SeaWinds scatterometer estimates near-surface ocean wind vectors by relating measured backscatter to a geophysical model function for the near-surface vector wind. The conventional wind retrieval algorithm does not explicitly account for SeaWinds' sensitivity to rain, resulting in rain-caused wind retrieval error. A new retrieval method, termed "simultaneous wind/rain retrieval," that estimates both wind and rain from rain-contaminated measurements has been previously proposed and validated with Tropical Rain Measuring Mission data. Here, the accuracy of rains retrieved by the new method is validated through comparison with the Next Generation Weather Radar (NEXRAD) in coastal storm events. The rains detected …

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Recovery Of The Grain Boundary Character Distribution Through Oblique Double-Sectioning, Brent L. Adams, David T. Fullwood, E. R. Homer Nov 2005

Recovery Of The Grain Boundary Character Distribution Through Oblique Double-Sectioning, Brent L. Adams, David T. Fullwood, E. R. Homer

Faculty Publications

This work was supported primarily by the MRSEC program of the National Science Foundation under DMR-0079996. A method for the retrieval of the complete grain boundary character distribution by oblique double-sectioning is proposed. The method, which is similar to the recovery of the orientation distribution from sets of incomplete pole-figures, is efficient and provides many advantages as compared to calibrated serial sectioning. As compared to standard stereological approaches, the new methodology retains the advantage of direct measurement of the grain boundary inclination parameters. Solutions to the fundamental equation of oblique double-sectioning are provided in the Fourier space, and some specifics …

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Highly Efficient Fluorescence Detection In Picoliter Volume Liquid-Core Waveguides, Aaron R. Hawkins, John P. Barber, Dongliang Yin Nov 2005

Highly Efficient Fluorescence Detection In Picoliter Volume Liquid-Core Waveguides, Aaron R. Hawkins, John P. Barber, Dongliang Yin

Faculty Publications

We report loss improvement and fluorescence detection in integrated antiresonant reflecting optical waveguides with liquid cores. The minimum waveguide loss is reduced to 0.33/cm by compensating for thickness variations in the fabrication process. We demonstrate fluorescence detection from as few as 490 molecules in a 57 pl core using these optimized waveguides. We measure angular fluorescence collection factors as high as 15% per facet in good agreement with theory. This demonstrates the potential of integrated hollow-core waveguides as optical sensors for single-molecule spectroscopy.

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Effects Of Ebg Reflection Phase Profiles On The Input Impedance And Bandwidth Of Ultrathin Directional Dipoles, M. Faisal Abedin, Mohammod Ali Nov 2005

Effects Of Ebg Reflection Phase Profiles On The Input Impedance And Bandwidth Of Ultrathin Directional Dipoles, M. Faisal Abedin, Mohammod Ali

Faculty Publications

A comprehensive study of the effects of the reflection phase profiles on dipole antennas is presented with the ultimate objective of designing ultrathin printed dipoles (as thin as one hundredth of the wavelength). Dipole driving-point impedance and bandwidth are studied as function of various electromagnetic bandgap (EBG) reflection phase profiles. It is demonstrated that although many different reflection phase profiles can be generated for a certain antenna height, it is the profile that satisfies a specific range of reflection phase angles that is required to achieve good antenna performance. Such optimum EBG phase profiles are generated for a number of …

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Asynchronous Ds-Ss Cdma Random Spreading Code Correlation Statistics In The Presence Of Timing Error, David W. Matolak Nov 2005

Asynchronous Ds-Ss Cdma Random Spreading Code Correlation Statistics In The Presence Of Timing Error, David W. Matolak

Faculty Publications

We quantify the effect of timing tracking errors upon 2nd order correlation statistics of random binary spreading codes and, in so doing, fill a gap in the literature. Using a Gaussian model for timing tracking error, new expressions for autocorrelation statistics are derived. For crosscorrelations, we show that a zero mean Gaussian timing error has no effect upon 2nd order crosscorrelation statistics.

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Social Utility Functions-Part Ii: Applications, Wynn C. Stirling, Richard L. Frost Nov 2005

Social Utility Functions-Part Ii: Applications, Wynn C. Stirling, Richard L. Frost

Faculty Publications

Social utilities account for agent preferences and, thus, can characterize complex interrelationships, such as cooperation, compromise, negotiation, and altruism, that can exist between agents. Satisficing game theory, which is based on social utilities, offers a framework within which to design sophisticated multiagent systems. Key features of this approach are: a) an N-agent system may be represented by a 2N-dimensional Bayesian network, called a praxeic network; b) the theory accommodates a notion of situational altruism (a willingness to defer to others in a controlled way if so doing would actually benefit others under the condition that others wish to take advantage …

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A Compliant Contact-Aided Revolute Joint, Jessie R. Cannon, Larry L. Howell Nov 2005

A Compliant Contact-Aided Revolute Joint, Jessie R. Cannon, Larry L. Howell

Faculty Publications

This paper presents the compliant contact-aided revolute (CCAR) joint, a planar mechanism capable of performing the functions of a bearing and a spring. The pseudo-rigid-body model is used to predict the behavior of the CCAR joint, and this model is validated through the use of finite element analysis and prototype testing. The CCAR joint is shown to have high maximum rotation and lateral stiffness. A case study is presented, and manufacturing considerations are discussed for the macro, meso, and micro scales.

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A Compliant Contact-Aided Revolute Joint, Jessie R. Cannon, Larry L. Howell Nov 2005

A Compliant Contact-Aided Revolute Joint, Jessie R. Cannon, Larry L. Howell

Faculty Publications

This paper presents the compliant contact-aided revolute (CCAR) joint, a planar mechanism capable of performing the functions of a bearing and a spring. The pseudo-rigid-body model is used to predict the behavior of the CCAR joint, and this model is validated through the use of finite element analysis and prototype testing. The CCAR joint is shown to have high maximum rotation and lateral stiffness. A case study is presented, and manufacturing considerations are discussed for the macro, meso, and micro scales.

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Social Utility Functions-Part I: Theory, Wynn C. Stirling Nov 2005

Social Utility Functions-Part I: Theory, Wynn C. Stirling

Faculty Publications

The dominant approaches to utility-based multiagent decision theory rely on the premise of individual rationality-the doctrine that each individual is committed to achieving the best outcome for itself, regardless of the effect doing so has on others. This fundamentally asocial concept is the basis of conventional von Neumann-Morgenstern (vN-M) utilities but is inadequate to characterize truly cooperative artificial systems. Social utility functions differ from conventional vN-M utilities in that they are functions of multiple decision-maker preferences, rather than actions, and thus permit individuals to expand their spheres of interest beyond the self. A logical basis for coherent reasoning in multiagent …

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Terahertz Studies Of The Dielectric Response And Second-Order Phonons In A Gase Crystal, B. L. Yu, F. Zeng, V. Kartazayev, R. R. Alfano, K. C. Mandal Oct 2005

Terahertz Studies Of The Dielectric Response And Second-Order Phonons In A Gase Crystal, B. L. Yu, F. Zeng, V. Kartazayev, R. R. Alfano, K. C. Mandal

Faculty Publications

No abstract provided.

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The Role Of Cavitation In Acoustically Activated Drug Delivery, Mario A. Diaz, Ghaleb A. Husseini, William G. Pitt, Eric S. Richardson, Douglas A. Christensen Oct 2005

The Role Of Cavitation In Acoustically Activated Drug Delivery, Mario A. Diaz, Ghaleb A. Husseini, William G. Pitt, Eric S. Richardson, Douglas A. Christensen

Faculty Publications

The triblock copolymer, Pluronic P105, has been found to be an ideal ultrasonically activated drug delivery vehicle because it forms micelles with hydrophobic polypropylene oxide cores that sequester hydrophobic drugs (Fig. 1). These micelles release their contents upon the application of low frequency ultrasound [1]such that drugs can be released specifically at the ultrasonicated region (Fig. 2). Such ultrasonically controlled release has been effective against cancer cells in vitro [2] and in vivo [3]. This poster presents our results showing that collapse cavitation is associated with drug release. Cavitation is generally divided into two types of behavior. Stable cavitation is …

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Analysis Of Gaits For A Rotating Tripedal Robot, Damian M. Lyons, Kiran Pamnany Oct 2005

Analysis Of Gaits For A Rotating Tripedal Robot, Damian M. Lyons, Kiran Pamnany

Faculty Publications

A goal of robotics has been to develop mechanisms that have the efficiency and speed of wheeled robots with the terrain flexibility of legged robots. In previous work, we have proposed a unique three-legged mechanism, the rotopod, designed to integrate these two useful approaches to locomotion. In this paper, we present an analysis of the variety of gaits that can be exhibited by the rotopod. We present examples of many of these gaits and discuss their potential use. A trajectory generation algorithm is presented that can be used to generate point to point trajectories using one of three different styles …

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Ontologies In Web Personalization, Magdalini Eirinaki, Michalis Vazirgiannis Oct 2005

Ontologies In Web Personalization, Magdalini Eirinaki, Michalis Vazirgiannis

Faculty Publications

No abstract provided.

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Mechanism Of Current Collapse Removal In Field-Plated Nitride Hfets, Alexei Koudymov, V. Adivarahan, Jinwei Yang, Grigory Simin, Asif Khan Oct 2005

Mechanism Of Current Collapse Removal In Field-Plated Nitride Hfets, Alexei Koudymov, V. Adivarahan, Jinwei Yang, Grigory Simin, Asif Khan

Faculty Publications

An experimental study of the mechanism of RF current collapse removal in high-power nitride-based HFETs is presented. The results show that the conductivity of the dielectric material under the field plate plays a crucial role in the current collapse removal. Identical geometry field plated HFETs differing only in the FP dielectric conductivity show varying degree of current collapse removal. Devices with semiconducting dielectric layers exhibit perfectly linear RF power - drain bias dependence with the output powers of 20 W/mm at 55 V drain bias with essentially no current collapse. A trapped charge discharging model is presented to explain the …

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Structure Of Human Thymidylate Synthase Under Low-Salt Conditions, Leslie L. Lovelace, Wladek Minor, Lukasz Lebioda Sep 2005

Structure Of Human Thymidylate Synthase Under Low-Salt Conditions, Leslie L. Lovelace, Wladek Minor, Lukasz Lebioda

Faculty Publications

Human thymidylate synthase, a target in cancer chemotherapy, was crystallized from PEG 3350 with 30 mM ammonium sulfate (AS) in the crystallization medium. The crystals are isomorphous with the high-salt crystals (~2.0 M AS) and the structure has been solved and refined (R = 22.6%, Rfree = 24.3%) at 1.8 Å resolution. The high- and low-AS-concentration structures are quite similar, with loop 181-197 is in the inactive conformation. Also, residues 95-106 and 129-135 (eukaryotic inserts region) show high mobility as assessed by poor electron density and high values of crystallographic temperature factors (residues 1-25 and 108-129 are disordered in both …

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Superdirectivity In Mimo Systems, Michael A. Jensen, Matthew L. Morris, Jon W. Wallace Sep 2005

Superdirectivity In Mimo Systems, Michael A. Jensen, Matthew L. Morris, Jon W. Wallace

Faculty Publications

Multiantenna systems such as devices for multiple-input-multiple-output (MIMO) communication can theoretically use array superdirectivity to optimally exploit the propagation channel. In traditional analyses of MIMO systems, such superdirectivity is not observed due to the commonly applied constraint that limits the excitation current magnitudes. However, when an electromagnetically appropriate constraint on the power radiated by the array is applied, the computed capacity can include effects of transmit superdirectivity. A similar result occurs at the receiver for spatially colored noise. This paper formulates the MIMO system capacity under these circumstances and provides a framework for computing this capacity when the level of …

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Static And Dynamic Obstacle Avoidance For Miniature Air Vehicles, Jeffery Brian Saunders, Brandon Call, Andrew Curtis, Randal W. Beard, Timothy W. Mclain Sep 2005

Static And Dynamic Obstacle Avoidance For Miniature Air Vehicles, Jeffery Brian Saunders, Brandon Call, Andrew Curtis, Randal W. Beard, Timothy W. Mclain

Faculty Publications

Small unmanned air vehicles are limited in sensor weight and power such that detection and avoidance of unknown obstacles during flight is difficult. This paper presents a low power low weight method of detection using a laser range finder. In addition, a rapidly-exploring random tree algorithm to generate waypoint paths around obstacles known a priori is presented, and a dynamic geometric algorithm to generate paths around detected obstacles is derived. The algorithms are demonstrated in simulation and in flight tests on a fixed-wing miniature air vehicle (MAV).

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Embedded Slanted Grating Coupler For Vertical Coupling Between Fibers And Silicon-On-Insulator Planar Waveguides, Gregory P. Nordin, J. Jiang, B. Wang Sep 2005

Embedded Slanted Grating Coupler For Vertical Coupling Between Fibers And Silicon-On-Insulator Planar Waveguides, Gregory P. Nordin, J. Jiang, B. Wang

Faculty Publications

We propose a compact and efficient grating coupler for vertical coupling between optical fibers and planar waveguides. A grating with a parallelogram shape is designed to be etched through the entire high-index waveguide core. The coupler is optimized using a microgenetic algorithm coupled with a two-dimensional finite-difference time-domain method. Simulations show that up to 75.8% coupling efficiency can be obtained between a single-mode fiber and a 240-nm-thick silicon-on-insulator planar waveguide.

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Impact Of Receive Amplifier Signal Coupling On Mimo System Performance, Michael A. Jensen, Matthew L. Morris Sep 2005

Impact Of Receive Amplifier Signal Coupling On Mimo System Performance, Michael A. Jensen, Matthew L. Morris

Faculty Publications

This paper uses a detailed model of multiple input multiple output (MIMO) systems to explore the impact of signal coupling in the receiver front end on communication capacity. The model is applied to assess the performance of a MIMO system with two transmit and receive antennas in a simulated multipath environment for different amplifier coupling levels. The results show that in practical scenarios where simple impedance matching techniques are used, the circuit coupling can reduce the signal-to-noise ratio at the receiver and therefore degrade the achievable MIMO capacity.

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A Global Regulatory Role Of Gluconeogenic Genes In Escherichia Coli Revealed By Transcriptome Network Analysis, Katy Kao, Linh Tran, James Liao Aug 2005

A Global Regulatory Role Of Gluconeogenic Genes In Escherichia Coli Revealed By Transcriptome Network Analysis, Katy Kao, Linh Tran, James Liao

Faculty Publications

In bacterial adaptation to the dynamic environment, metabolic genes are typically thought to be the executors, whereas global transcription regulators are regarded as the decision makers. Although the feedback from metabolic consequence is believed to be important, much less is understood. This work demonstrates that the gluconeogenic genes in Escherichia coli, ppsA, sfcA, and maeB, provide a feedback loop to the global regulator, cAMP receptor protein (CRP), in carbon source transition. Disruption of one of the gluconeogenic pathways has no phenotype in balanced growth, but causes a significant delay in the diauxic transition from glucose to acetate. To investigate the …

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Navigation And Control Technologies For Autonomous Micro Vehicles, Randal Beard, Timothy W. Mclain Aug 2005

Navigation And Control Technologies For Autonomous Micro Vehicles, Randal Beard, Timothy W. Mclain

Faculty Publications

Sponsorship: Air Force Research Laboratory / Munitions Directorate. During this project we focused on four primary objectives which are listed below. 1. Magnetometer Integration. Integrate and flight test magnetometers with the current version of the autopilot (Spiral 1). 2. Height-Above-Ground Sensor Integration. Integrate and flight test height-above-ground sensors with the current version of the autopilot (Spiral 1). 3. Automatic Gain Adjustment. Develop and flight test automatic gain adjustment algorithms that automatically tune the servo loops of the autopilot. 4. Automatic Trim Seeking. Develop and flight test automatic trim seeking algorithms to recursively estimate the trim values of the UAV.

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