Open Access. Powered by Scholars. Published by Universities.®

Engineering Commons™

Open Access. Powered by Scholars. Published by Universities.®

Faculty Publications

Discipline
Institution
Keyword
Publication Year
File Type

Articles 2821 - 2850 of 3294

Full-Text Articles in Engineering

Enhanced Luminescence In Ingan Multiple Quantum Wells With Quaternary Alingan Barriers, Jianping Zhang, J. Yang, Grigory Simin, M. Shatalov, M. Asif Khan, M. S. Shur, R. Gaska Oct 2000

Enhanced Luminescence In Ingan Multiple Quantum Wells With Quaternary Alingan Barriers, Jianping Zhang, J. Yang, Grigory Simin, M. Shatalov, M. Asif Khan, M. S. Shur, R. Gaska

Faculty Publications

We report on the comparative photoluminescence studies of AlGaN/GaN, GaN/InGaN, and AlInGaN/InGaN multiple quantum well(MQW) structures. The study clearly shows the improvement in materials quality with the introduction of indium. Our results point out the localized state emission mechanism for GaN/InGaN structures and the quantum well emission mechanism for AlInGaN/InGaN structures. The introduction of indium is the dominant factor responsible for the observed differences in the photoluminescence spectra of these MQW structures.

Go to article

High Electron Mobility In Algan/Gan Heterostructures Grown On Bulk Gan Substrates, E. Frayssinet, W. Knap, P. Lorenzini, N. Grandjean, J. Massies, C. Skierbiszewski, T. Suski, I. Grzegory, S. Porowski, Grigory Simin, X. Hu, M. Asif Khan, M. S. Shur, R. Gaska, D. Maude Oct 2000

High Electron Mobility In Algan/Gan Heterostructures Grown On Bulk Gan Substrates, E. Frayssinet, W. Knap, P. Lorenzini, N. Grandjean, J. Massies, C. Skierbiszewski, T. Suski, I. Grzegory, S. Porowski, Grigory Simin, X. Hu, M. Asif Khan, M. S. Shur, R. Gaska, D. Maude

Faculty Publications

Dislocation-free high-quality AlGaN/GaN heterostructures have been grown by molecular-beam epitaxy on semi-insulating bulk GaN substrates. Hall measurements performed in the 300 K–50 mK range show a low-temperature electron mobility exceeding 60 000 cm2/V s for an electron sheet density of 2.4×1012 cm−2. Magnetotransport experiments performed up to 15 T exhibit well-defined quantum Hall-effect features. The structures corresponding to the cyclotron and spin splitting were clearly resolved. From an analysis of the Shubnikov de Hass oscillations and the low-temperature mobility we found the quantum and transport scattering times to be 0.4 and 8.2 ps, respectively. The …

Go to article

Preparation Of Mesoporous Sno2-Sio2 Composite As Electrodes For Lithium Batteries, Fanglin Chen, Zhong Shi, Meilin Liu Oct 2000

Preparation Of Mesoporous Sno2-Sio2 Composite As Electrodes For Lithium Batteries, Fanglin Chen, Zhong Shi, Meilin Liu

Faculty Publications

Mesoporous SnO2–SiO2 composite stable up to 600 °C with a BET surface area of 350 m2 g-1 and an average pore size of 3.4 nm is successfully prepared, which exhibits promising cycling properties as anodes for lithium batteries

Go to article

Preparation Of Mesoporous Yttria-Stabilized Zirconia (Ysz) And Ysz-Nio Using A Triblock Copolymer As Surfactant, Fanglin Chen, Meilin Liu Oct 2000

Preparation Of Mesoporous Yttria-Stabilized Zirconia (Ysz) And Ysz-Nio Using A Triblock Copolymer As Surfactant, Fanglin Chen, Meilin Liu

Faculty Publications

Mesoporous yttria-stabilized zirconia (YSZ) and YSZ-NiO have been prepared for the first time using Pluronic P103 as a structure-directing agent and inorganic chlorides as precursors in a nonaqueous medium. After being fired at 500°C for 2 h, mesostructured YSZ has a BET surface area of about 146 m2 g-1, with an average pore size of 3.8 nm, while mesostructured YSZ-NiO has a BET surface area of about 108 m2 g-1, with an average pore size of 4.5 nm.

Go to article

Optical Bandgap Formation In Alingan Alloys, G. Tamulaitis, K. Kazlauskas, S. Juršėnas, A. Žukauskas, M. A. Khan, J. W. Yang, J. Zhang, Grigory Simin, M. S. Shur, R. Gaska Oct 2000

Optical Bandgap Formation In Alingan Alloys, G. Tamulaitis, K. Kazlauskas, S. Juršėnas, A. Žukauskas, M. A. Khan, J. W. Yang, J. Zhang, Grigory Simin, M. S. Shur, R. Gaska

Faculty Publications

We report on the spectral dynamics of the reflectivity, site-selectively excited photoluminescence,photoluminescence excitation, and time-resolved luminescence in quaternary AlInGaN epitaxial layers grown on GaN templates. The incorporation of a few percents of In into AlGaN causes significant smoothening of the band-bottom potential profile in AlInGaN layers owing to improved crystal quality. An abrupt optical bandgap indicates that a nearly lattice-matched AlInGaN/GaN heterostructure with large energy band offsets can be grown for high-efficiency light-emitting devices.

Go to article

A Dynamic Optimal Trajectory Generator For Cartesian Path Following, Edward Red Sep 2000

A Dynamic Optimal Trajectory Generator For Cartesian Path Following, Edward Red

Faculty Publications

This paper considers a dynamic and adaptive trajectory generator for negotiating paths using S-curves. Applying constant jerk transitions between the constant acceleration and deceleration periods of the trajectory, the trajectory will optimally transition to the desired speed setting. Optimal is defined to be the minimum time to transition from the current speed to the set speed for the move segment when jerk and acceleration are limited. The S-curve equations will adapt to instantaneous changes in speed setting and path length. An integrated motion planner will determine allowable speeds and transitional profiles based on the remaining move distance.

Go to article

Algan/Gan Metal-Oxide-Semiconductor Heterostructure Field-Effect Transistors On Sic Substrates, M. Asif Khan, X. Hu, A. Tarakji, Grigory Simin, J. Yang, R. Gaska, M. S. Shur Aug 2000

Algan/Gan Metal-Oxide-Semiconductor Heterostructure Field-Effect Transistors On Sic Substrates, M. Asif Khan, X. Hu, A. Tarakji, Grigory Simin, J. Yang, R. Gaska, M. S. Shur

Faculty Publications

We report on AlGaN/GaN metal–oxide–semiconductor heterostructurefield-effect transistors (MOS-HFETs) grown over insulating 4H–SiC substrates. We demonstrate that the dc and microwave performance of the MOS-HFETs is superior to that of conventional AlGaN/GaN HFETs, which points to the high quality of SiO2/AlGaNheterointerface. The MOS-HFETs could operate at positive gate biases as high as +10 V that doubles the channel current as compared to conventional AlGaN/GaN HFETs of a similar design. The gate leakage current was more than six orders of magnitude smaller than that for the conventional AlGaN/GaN HFETs. The MOS-HFETs exhibited stable operation at elevated temperatures up to 300 …

Go to article

Sio2-Passivated Lateral-Geometry Gan Transparent Schottky-Barrier Detectors, V. Adivarahan, Grigory Simin, J. W. Yang, A. Lunev, M. Asif Khan, M. Pala, M. Shur, R. Gaska Aug 2000

Sio2-Passivated Lateral-Geometry Gan Transparent Schottky-Barrier Detectors, V. Adivarahan, Grigory Simin, J. W. Yang, A. Lunev, M. Asif Khan, M. Pala, M. Shur, R. Gaska

Faculty Publications

We report on a transparent Schottky-barrierultraviolet detector on GaN layers over sapphire substrates. Using SiO2 surface passivation, reverse leakage currents were reduced to a value as low as 1 pA at 5 V reverse bias for 200 μm diameter device. The device exhibits a high internal gain, about 50, at low forward biases. The response time (about 15 ns) is RC limited, even in the internal gain regime. A record low level of the noise spectral density, 5×10−23 A2/Hz, was measured at 10 Hz. We attribute this low noise level to the reduced reverse leakage current.

Go to article

Fuel Saving Strategies For Separated Spacecraft Interferometry, Timothy Mclain, Randal W. Beard, Christopher A. Bailey Aug 2000

Fuel Saving Strategies For Separated Spacecraft Interferometry, Timothy Mclain, Randal W. Beard, Christopher A. Bailey

Faculty Publications

Separated spacecraft interferometry missions will require spacecraft to move in a coordinated fashion to ensure minimal and balanced consumption of fuel. This paper develops strategies for determining interferometry mission plans that result in significant fuel savings over standard approaches. Simulation results demonstrate that valuable reductions in fuel consumption can be realized by combining the retargeting and imaging maneuvers required to image multiple stellar sources. Fuel-optimal imaging strategies have been developed for two-spacecraft interferometry missions similar to the proposed Space Technology 3 mission using chained local optimization methods. Based on these strategies, sampling pattern guidelines for space-borne interferometry missions have been …

Go to article

Trajectory Planning For Coordinated Rendezvous Of Unmanned Air Vehicles, Timothy W. Mclain, Randal W. Beard Aug 2000

Trajectory Planning For Coordinated Rendezvous Of Unmanned Air Vehicles, Timothy W. Mclain, Randal W. Beard

Faculty Publications

A trajectory generation strategy that facilitates the coordination of multiple unmanned air vehicles is developed. Of particular interest is the planning of threat-avoiding trajectories that result in the simultaneous arrival of multiple UAVs at their targets. In this approach, paths to the target are modeled using the physical analogy of a chain. A unique strength of the planning approach is the ability to specify or alter the path length by adding or subtracting links from the chain. Desirable paths to the target are obtained by simulating the dynamics of the chain where threats apply repulsive forces to the chain and …

Go to article

An Iterative Approach To Multisensor Sea Ice Classification, David G. Long, Mark R. Drinkwater, Quinn P. Remund Jul 2000

An Iterative Approach To Multisensor Sea Ice Classification, David G. Long, Mark R. Drinkwater, Quinn P. Remund

Faculty Publications

Characterizing the variability in sea ice in the polar regions is fundamental to an understanding of global climate and the geophysical processes governing climate changes. Sea ice can be grouped into a number of general classes with different characteristics. Multisensor data from NSCAT, ERS-2, and SSM/I are reconstructed into enhanced resolution imagery for use in ice-type classification. The resulting twelve-dimensional data set is linearly transformed through principal component analysis to reduce data dimensionality and noise levels. An iterative statistical data segmentation algorithm is developed using maximum likelihood (ML) and maximum a posteriori (MAP) techniques. For a given ice type, the …

Go to article

Neural Networks Versus Nonparametric Neighbor-Based Classifiers For Semisupervised Classification Of Landsat Thematic Mapper Imagery, Perry J. Hardin Jul 2000

Neural Networks Versus Nonparametric Neighbor-Based Classifiers For Semisupervised Classification Of Landsat Thematic Mapper Imagery, Perry J. Hardin

Faculty Publications

Semisupervised classification is one approach to converting multiband optical and infrared imagery into landcover maps. First, a sample of image pixels is extracted and clustered into several classes. The analyst next combines the clusters by hand to create a smaller set of groups that correspond to a useful landcover classification. The remaining image pixels are then assigned to one of the aggregated cluster groups by use of a per-pixel classifier. Since the cluster aggregation process frequently creates groups with multivariate shapes ill suited for parametric classifiers, there has been renewed interest in nonparametric methods for the task. This research reports …

Go to article

Azimuth Variation In Microwave Scatterometer And Radiometer Data Over Antarctica, David G. Long, Mark R. Drinkwater Jul 2000

Azimuth Variation In Microwave Scatterometer And Radiometer Data Over Antarctica, David G. Long, Mark R. Drinkwater

Faculty Publications

While designed for ocean observation, scatterometer and radiometer data have proven very useful in a variety of cryosphere studies. Over large regions of Antarctica, ice sheet and bedrock topography and the snow deposition, drift, and erosional environment combine to produce roughness on various scales. Roughness ranges from broad, basin-scale ice-sheet topography at 100 km wavelengths to large, spatially coherent dune fields at 10 km wavelength to erosional features on the meter scale known as sastrugi. These roughness scales influence the microwave backscattering and emission properties of the surface, combining to introduce azimuth-angle dependencies in the satellite observation data. In this …

Go to article

Diversity Performance Of Dual-Antenna Handsets Near Operator Tissue, Michael A. Jensen, Bruce M. Green Jul 2000

Diversity Performance Of Dual-Antenna Handsets Near Operator Tissue, Michael A. Jensen, Bruce M. Green

Faculty Publications

This paper presents a computational and experimental study of the diversity performance of two dual-antenna handsets operating indoors in the 902-928 MHz industrial, scientific, and medical (ISM) band. Of particular interest is the effect of the operator tissue on the diversity operation. Key indicators of diversity gain such as branch mean effective gain (MEG) and envelope correlation coefficient are obtained from finite-difference time-domain (FDTD) method simulations as well as from experimental measurements in three different indoor environments. Diversity gain for the handsets is also measured directly. Reasonable agreement is observed between the experimental and simulated results, with both approaches indicating …

Go to article

Gan-Algan Heterostructure Field-Effect Transistors Over Bulk Gan Substrates, M. Asif Khan, J. W. Yang, W. Knap, E. Frayssinet, X. Hu, Grigory Simin, P. Prystawko, M. Leszczynski, I. Grzegory, S. Porowski, R. Gaska, M. S. Shur, B. Beaumont, M. Teisseire, G. Neu Jun 2000

Gan-Algan Heterostructure Field-Effect Transistors Over Bulk Gan Substrates, M. Asif Khan, J. W. Yang, W. Knap, E. Frayssinet, X. Hu, Grigory Simin, P. Prystawko, M. Leszczynski, I. Grzegory, S. Porowski, R. Gaska, M. S. Shur, B. Beaumont, M. Teisseire, G. Neu

Faculty Publications

We report on AlGaN/GaN heterostructures and heterostructurefield-effect transistors(HFETs) fabricated on high-pressure-grown bulk GaN substrates. The 2delectron gas channel exhibits excellent electronic properties with room-temperature electron Hall mobility as high as μ=1650 cm2/V s combined with a very large electron sheet density ns≈1.4×1013 cm−2.The HFET devices demonstrated better linearity of transconductance and low gate leakage, especially at elevated temperatures. We also present the comparative study of high-current AlGaN/GaN HFETs(nsμ>2×1016 V−1 s−1) grown on bulk GaN, sapphire, and SiC substrates under the same conditions. We demonstrate that in …

Go to article

Effectiveness Of A Multimedia General Education Course, Patricia Backer Jun 2000

Effectiveness Of A Multimedia General Education Course, Patricia Backer

Faculty Publications

The current paper describes the design, development, and evaluation of self-paced multimedia modules that are used in an advanced General Education course at San Jose State University. The design and development cycle of these modules began in 1994 and continues to this date. The General Education course, Technology and Civilization (TECH 198), is designed to introduce students to the realm of history and usage of technology in society and to increase their awareness of both the uncertainties as well as the promises of the utilization of technology as a creative human enterprise. During the summer session 1999, the completed modules …

Go to article

Fast Algorithm For Generating Sorted Contour Strings, Norman L. Jones, Michael J. Kennard, Alan K. Zundel Jun 2000

Fast Algorithm For Generating Sorted Contour Strings, Norman L. Jones, Michael J. Kennard, Alan K. Zundel

Faculty Publications

Automatic generation of contours for graphical display and map plotting has been studied extensively since the early days of computing. The individual segments making up a contour line are often determined by subdividing the object of interest into small triangles and computing the contours assuming a linear variation on each triangle. However, efficient storage of contour data and the need to place labels (automatically) or to smooth the contours require that the contours be generated in continuous strings of segments. A simple approach to generate such strings is to sort the randomly generated contour segments. Since sorting can be time-consuming, …

Go to article

Comparison Of Charged Sheets And Corrected 3-D Ewald Calculations Of Long-Range Forces In Slab Geometry Electrolyte Systems With Solvent Molecules, Richard L. Rowley, Paul S. Crozier, Eckhard Spoht, Douglas Henderson Jun 2000

Comparison Of Charged Sheets And Corrected 3-D Ewald Calculations Of Long-Range Forces In Slab Geometry Electrolyte Systems With Solvent Molecules, Richard L. Rowley, Paul S. Crozier, Eckhard Spoht, Douglas Henderson

Faculty Publications

Two methods of calculating long-range intermolecular potentials are compared for an approximately 3 M aqueous electrolyte solution confined between two charged surfaces. We investigate the ionic density profiles using the charged-sheets method and the corrected three-dimensional (3D) Ewald method at two different system sizes and also compare the Coulomb forces directly. The corrected 3D Ewald method is recommended for the calculation of long-range potentials in systems of this nature because it is less system size dependent than the charged sheets method and the resultant forces are more consistent with periodic boundaries. However, the charged-sheets method for estimating long-range potentials in …

Go to article

Statistical Continuum Theory For Large Plastic Deformation Of Polycrystalline Materials, Brent L. Adams, S. Ahzi, H. Garmestani, S. Lin Jun 2000

Statistical Continuum Theory For Large Plastic Deformation Of Polycrystalline Materials, Brent L. Adams, S. Ahzi, H. Garmestani, S. Lin

Faculty Publications

This paper focuses on the application of statistical continuum mechanics to the prediction of mechanical response of polycrystalline materials and microstructure evolution under large plastic deformations. A statistical continuum mechanics formulation is developed by applying a Green's function solution to the equations of stress equilibrium in an infinite domain. The distribution and morphology of grains (crystals) in polycrystalline materials is represented by a set of correlation functions that are described by the corresponding probability functions. The elastic deformation is neglected and a viscoplastic power law is employed for crystallographic slip in single crystals. In this formulation, two- and three-point probability …

Go to article

X-Ray Rocking Curve Analysis Of Tetragonally Distorted Ternary Semiconductors On Mismatched (001) Substrates, X. Zhang, David W. Parent, P. Li, A. Rodriguez, G. Zhao, J. Ayers, F. Jain Jun 2000

X-Ray Rocking Curve Analysis Of Tetragonally Distorted Ternary Semiconductors On Mismatched (001) Substrates, X. Zhang, David W. Parent, P. Li, A. Rodriguez, G. Zhao, J. Ayers, F. Jain

Faculty Publications

For ternary heteroepitaxial layers, the independent determination of the composition and state of strain requires x-ray rocking curve measurements for at least two different hkl reflections because the relaxed lattice constant is a function of the composition. The usual approach involves the use of one symmetric reflection and one asymmetric reflection. Two rocking curves are measured at opposing azimuths for each hkl reflection. Thus, it is possible to account for tilting of the hkl planes in the epitaxial layer with respect to the hkl planes in the substrate, by averaging the peak separations obtained at the opposing azimuths. This procedure …

Go to article

Accumulation Hole Layer In P-Gan/Algan Heterostructures, M. S. Shur, A. D. Bykhovski, R. Gaska, J. W. Yang, Grigory Simin, M. A. Khan May 2000

Accumulation Hole Layer In P-Gan/Algan Heterostructures, M. S. Shur, A. D. Bykhovski, R. Gaska, J. W. Yang, Grigory Simin, M. A. Khan

Faculty Publications

We present the results on piezoelectric and pyroelectricdoping in AlGaN-on-GaN and GaN-on-AlGaN heterostructures and demonstrate p-GaN/AlGaN structures with accumulation hole layer. Our results indicate that polarization charge can induce up to 5×1013 cm−2 holes at the AlGaN/GaN heterointerfaces. We show that the transition from three-dimensional (3D) to two-dimensional (2D) hole gas can be only achieved for hole sheet densities on the order of 1013 cm−2 or higher. At lower densities, only 3D-hole accumulation layer may exist. These results suggest that a piezoelectrically induced 2D-hole gas can be used for the reduction of the base spreading resistance …

Go to article

3d Outside Cell Interference Factor For An Air-Ground Cdma ‘Cellular’ System, David W. Matolak May 2000

3d Outside Cell Interference Factor For An Air-Ground Cdma ‘Cellular’ System, David W. Matolak

Faculty Publications

We compute the outside-cell interference factor of a code-division multiple-access (CDMA) system for a three-dimensional (3-D) air-to-ground (AG) "cellular-like" network consisting of a set of uniformly distributed ground base stations and airborne mobile users. The CDMA capacity is roughly inversely proportional to the outside-cell interference factor. It is shown that for the nearly free-space propagation environment of these systems, the outside-cell interference factor can be larger than that for terrestrial propagation models (as expected) and depends approximately logarithmically upon both the cell height and cell radius.

Go to article

Multilevel Coded Modulation For Unequal Error Protection And Multistage Decoding—Part Ii: Asymmetric Constellations, Motohiko Isaka, Marc P. C. Fossorier, Robert H. Morelos-Zaragoza, Shu Lin, Hideki Imai May 2000

Multilevel Coded Modulation For Unequal Error Protection And Multistage Decoding—Part Ii: Asymmetric Constellations, Motohiko Isaka, Marc P. C. Fossorier, Robert H. Morelos-Zaragoza, Shu Lin, Hideki Imai

Faculty Publications

In this paper, multilevel coded asymmetric modulation with multistage decoding and unequal error protection (UEP) is discussed. These results further emphasize the fact that unconventional signal set partitionings are more promising than traditional (Ungerboeck-type) partitionings, to achieve UEP capabilities with multilevel coding and multistage decoding. Three types of unconventional partitionings are analyzed for asymmetric 8-PSK and 16-QAM constellations over the additive white Gaussian noise channel to introduce design guidelines. Generalizations to other PSK and QAM type constellations follow the same lines. Upper bounds on the bit-error probability based on union bound arguments are first derived. In some cases, these bounds …

Go to article

Fuel Optimization For Constrained Rotation Of Satellite Formations, Timothy Mclain, Randal W. Beard, Fred Y. Hadaegh Apr 2000

Fuel Optimization For Constrained Rotation Of Satellite Formations, Timothy Mclain, Randal W. Beard, Fred Y. Hadaegh

Faculty Publications

This paper considers the problem of reorienting a constellation of spacecraft such that the fuel distributed across the constellation is both conserved and expended uniformly. Results are derived for constellations with an arbitrary number of spacecraft, assuming that the constellation is in free space, that the spacecraft mass is time invariant, and that the thrusters can produce thrust in any direction. An open-loop control algorithm is derived by minimizing a cost function that trades off total fuel minimization and fuel equalization. The associated optimization problem is shown to be amenable to standard algorithms. Simulation results using a four-spacecraft constellation are …

Go to article

Unmanned Research Vehicle (Urv): Development, Implementation, & Flight Test Of A Mimo Digital Flight Control System Designed Using Quantitative Feedback Theory, Constantine H. Houpis, Steven J. Rasmussen Apr 2000

Unmanned Research Vehicle (Urv): Development, Implementation, & Flight Test Of A Mimo Digital Flight Control System Designed Using Quantitative Feedback Theory, Constantine H. Houpis, Steven J. Rasmussen

Faculty Publications

The Quantitative Feedback Theory (QFT) design technique, which has the ability to bridge the gap between theory and the real-world control design problem, is utilized in the design of a MIMO digital flight control system for an unmanned research vehicle (URV) that is presented in this paper. The design illustrates how the real-world knowledge of the plant to be controlled and the desired performance specifications can be utilized in trying to achieve a successful robust design for a nonlinear control problem. This paper presents some of the issues involved in developing, implementing, and flight testing a flight control system (FCS) …

Go to article

The Character Of Ash Deposits And The Thermal Performance Of Furnaces, T. F. Wall, S. P. Bhattacharya, Larry Lin Baxter 8507091, G. Richards, J. N. Harb Mar 2000

The Character Of Ash Deposits And The Thermal Performance Of Furnaces, T. F. Wall, S. P. Bhattacharya, Larry Lin Baxter 8507091, G. Richards, J. N. Harb

Faculty Publications

The character of fireside ash deposits depend on the processes by which deposits are formed and subsequent reactions within the deposit and with furnace gases. The properties influencing furnace heat transfer, absorptivity for radiative transfer and thermal conductivity for conductive transfer are shown from many measurements to depend on this character. Illustrative trends in these properties as deposits mature and grow are presented together with their effect on furnace exit temperature and efficiency. The reflective character of initial deposits from particular coals is then considered with predictions and measurements of the spectral character of such deposits, during the first three …

Go to article

Modeling The Statistical Time And Angle Of Arrival Characteristics Of An Indoor Multipath Channel, Michael A. Jensen, Brian D. Jeffs, A. Lee Swindlehurst, Quentin H. Spencer Mar 2000

Modeling The Statistical Time And Angle Of Arrival Characteristics Of An Indoor Multipath Channel, Michael A. Jensen, Brian D. Jeffs, A. Lee Swindlehurst, Quentin H. Spencer

Faculty Publications

Most previously proposed statistical models for the indoor multipath channel include only time of arrival characteristics. However, in order to use statistical models in simulating or analyzing the performance of systems employing spatial diversity combining, information about angle of arrival statistics is also required. Ideally, it would be desirable to characterize the full spare-time nature of the channel. In this paper, a system is described that was used to collect simultaneous time and angle of arrival data at 7 GHz. Data processing methods are outlined, and results obtained from data taken in two different buildings are presented. Based on the …

Go to article

Managing Temporal Data In A Comprehensive Modeling Environment, Norman L. Jones, E. James Nelson, Colby T. Manwaring Mar 2000

Managing Temporal Data In A Comprehensive Modeling Environment, Norman L. Jones, E. James Nelson, Colby T. Manwaring

Faculty Publications

Numerous graphical pre- and post-processors have been developed for numerical modeling. Many of these systems support numerical models that can be used for both steady state and transient simulations. Dealing with transient data can be particularly difficult in such an environment due to the differing time scales and units associated with transient field data and boundary conditions. A data model and a set of functions are presented in this paper as a simple, yet powerful strategy for managing temporal data in a comprehensive modeling environment. The strategy makes it possible to seamlessly integrate multiple types of transient data and convert …

Go to article

Pulsed Ultrasound Enhances The Killing Of Escherichia Coli Biofilms By Aminoglycoside Antibiotics In Vivo, Andrea M. Rediske, Beverly L. Roeder, Jared L. Nelson, Rachel L. Robison, Bruce Schaaije, Richard A. Robison, William G. Pitt Mar 2000

Pulsed Ultrasound Enhances The Killing Of Escherichia Coli Biofilms By Aminoglycoside Antibiotics In Vivo, Andrea M. Rediske, Beverly L. Roeder, Jared L. Nelson, Rachel L. Robison, Bruce Schaaije, Richard A. Robison, William G. Pitt

Faculty Publications

Escherichia coli biofilms on two polyethylene disks were implanted subcutaneously into rabbits receiving systemic gentamicin. Ultrasound was applied for 24 h to one disk. Both disks were removed, and viable bacteria were counted. Pulsed ultrasound significantly reduced bacterial viability below that of nontreated biofilms without damage to the skin.

Go to article

Lattice And Energy Band Engineering In Alingan/Ga Heterostructures, M. Asif Khan, J. W. Yang, Grigory Simin, R. Gaska, M. S. Shur, Hans-Conrad Zur Loye, G. Tamulaitis, A. Zukauskas, David J. Smith, D. Chandrasekhar, R. Bicknell-Tassius Feb 2000

Lattice And Energy Band Engineering In Alingan/Ga Heterostructures, M. Asif Khan, J. W. Yang, Grigory Simin, R. Gaska, M. S. Shur, Hans-Conrad Zur Loye, G. Tamulaitis, A. Zukauskas, David J. Smith, D. Chandrasekhar, R. Bicknell-Tassius

Faculty Publications

We report on structural, optical, and electrical properties of AlxInyGa1−x−yNGaNheterostructures grown on sapphire and 6H–SiC substrates. Our results demonstrate that incorporation of In reduces the lattice mismatch, Δa, between AlInGaN and GaN, and that an In to Al ratio of close to 1:5 results in nearly strain-free heterostructures. The observed reduction in band gap,ΔEg, determined from photoluminescence measurements, is more than 1.5 times higher than estimated from the linear dependencies of Δa and ΔEg on the In molar fraction. The incorporation of In and resulting changes in the built-in strain in …

Go to article

First Prev Next Last