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 2521 - 2550 of 3295

Full-Text Articles in Engineering

Service-Oriented Computing: Key Concepts And Principles, Michael N. Huhns, Munindar P. Singh Jan 2005

Service-Oriented Computing: Key Concepts And Principles, Michael N. Huhns, Munindar P. Singh

Faculty Publications

Traditional approaches to software development - the ones embodied in CASE tools and modeling frameworks - are appropriate for building individual software components, but they are not designed to face the challenges of open environments. Service-oriented computing provides a way to create a new architecture that reflects components' trends toward autonomy and heterogeneity. We thus emphasize SOC concepts instead of how to deploy Web services in accord with current standards. To begin the series, we describe the key concepts and abstractions of SOC and the elements of a corresponding engineering methodology.

Go to article

Tunable Multiferroic Properties In Nanocomposite Pbtio3-Cofe2O4 Epitaxial Thin Films, M. Murakami, K.-S. Chang, M. A. Aronova, C.-L. Lin, Ming H. Yu, Jason R. Hattrick-Simpers, M. Wuttig, I. Takeuchi, C. Gao, B. Hu, S. E. Lofland, L. A. Knauss, L. A. Bendersky Jan 2005

Tunable Multiferroic Properties In Nanocomposite Pbtio3-Cofe2O4 Epitaxial Thin Films, M. Murakami, K.-S. Chang, M. A. Aronova, C.-L. Lin, Ming H. Yu, Jason R. Hattrick-Simpers, M. Wuttig, I. Takeuchi, C. Gao, B. Hu, S. E. Lofland, L. A. Knauss, L. A. Bendersky

Faculty Publications

We report on the synthesis of PbTiO3–CoFe2O4 multiferroic nanocomposites and continuous tuning of their ferroelectric and magnetic properties as a function of the average composition on thin-film composition spreads. The highest dielectric constant and nonlinear dielectric signal was observed at (PbTiO3)85–(CoFe2O4)15, where robust magnetism was also observed. Transmission electron microscopy revealed a pancake-shaped epitaxial nanostructure of PbTiO3 on the order of 30 nm embedded in the matrix of CoFe2O4 at this composition. Composition dependent ferroics properties observed here indicate that there …

Go to article

Mechanics Of Composite Materials In Fuel Cell Systems, Kenneth Reifsnider, Xinyu Huang, G. Ju, Matthew Feshler, K. An Jan 2005

Mechanics Of Composite Materials In Fuel Cell Systems, Kenneth Reifsnider, Xinyu Huang, G. Ju, Matthew Feshler, K. An

Faculty Publications

The science and technology that are fundamental to the concept of composite materials are also the foundation for the construction and function of fuel cells and fuel cell systems. The present paper outlines this relationship in the context of the physics and chemistry that are enabled by the specific selection and arrangement of constituents of the “functional composite” fuel cell. General principles of operation are described, and fundamental issues are defined that must be addressed by the composites community if the fuel cell science and engineering is to advance. Examples of several types of functional composite fuel cells are presented, …

Go to article

Effects Of Dynamic Fluid Pressure On Chondrocytes Cultured In Biodegradable Poly(Glycolic Acid) Fibrous Scaffolds, Lichun Lu, Xun Zhu, Larry G. Pederson, Esmaiel Jabbari, Bradford Currier, Shawn O'Driscoll, Michael Yaszemski Jan 2005

Effects Of Dynamic Fluid Pressure On Chondrocytes Cultured In Biodegradable Poly(Glycolic Acid) Fibrous Scaffolds, Lichun Lu, Xun Zhu, Larry G. Pederson, Esmaiel Jabbari, Bradford Currier, Shawn O'Driscoll, Michael Yaszemski

Faculty Publications

No abstract provided.

Go to article

Transient Analysis Of A Porous Electrode, Sheba Devan, Venkat R. Subramanian, Ralph E. White Jan 2005

Transient Analysis Of A Porous Electrode, Sheba Devan, Venkat R. Subramanian, Ralph E. White

Faculty Publications

An analytical expression is presented for the voltage response including the transient voltage for a simple (i.e., no concentration gradients) porous electrode model subject to a sinusoidal input current density. The transient voltage response as a function of the frequency, exchange current density, and double layer capacitance is studied independent of the periodic (steady state) voltage response. The change in the voltage response in the transient region is compared to that of the periodic voltage response with respect to the parameters. The physical properties of the porous electrode can be estimated using the voltage response in the transient …

Go to article

Cubic Spline Regression For The Open-Circuit Potential Curves Of A Lithium-Ion Battery, Qingzhi Guo, Ralph E. White Jan 2005

Cubic Spline Regression For The Open-Circuit Potential Curves Of A Lithium-Ion Battery, Qingzhi Guo, Ralph E. White

Faculty Publications

A cubic spline regression model was used to fit the experimental open-circuit potential (OCP) curves of two intercalation electrodes of a lithium-ion battery. All the details of an OCP curve were accurately predicted by the resulting model. The number of regression intervals used to fit an OCP curve was determined in a way such that in each regression interval the OCP exhibits a profile predictable by a third-order polynomial. The locations of the data points used to separate regression intervals were optimized. Compared to a polynomial model with the same number of fitting parameters, the cubic spline regression model is …

Go to article

A Mathematical Model For A Lithium-Ion Battery/Electrochemical Capacitor Hybrid System, Godfrey Sikha, Ralph E. White, Branko N. Popov Jan 2005

A Mathematical Model For A Lithium-Ion Battery/Electrochemical Capacitor Hybrid System, Godfrey Sikha, Ralph E. White, Branko N. Popov

Faculty Publications

A one-dimensional model for predicting the performance of a battery/electrochemical capacitor-hybrid system has been developed. Simulation results are presented for a LiCoO2|LiPF6 ethylene carbonate/dimethyl carbonate|carbon battery system and a Maxwell PC 10F carbon double-layer electrochemical capacitor. The current shared between the battery and the electrochemical capacitor at very short times depends on the ohmic resistances of the battery and the capacitor. As the discharge proceeds, the operating conditions such as frequency, duty ratio, and peak pulse discharge current control the current shared among parallel circuits. These parameters also determine the extent of the run time increase of …

Go to article

Autonomous Vehicle Technologies For Small Fixed-Wing Uavs, Randal Beard, Derek Kingston, Morgan Quigley, Deryl Snyder, Reed Christiansen, Walt Johnson, Timothy Mclain, Michael A. Goodrich Jan 2005

Autonomous Vehicle Technologies For Small Fixed-Wing Uavs, Randal Beard, Derek Kingston, Morgan Quigley, Deryl Snyder, Reed Christiansen, Walt Johnson, Timothy Mclain, Michael A. Goodrich

Faculty Publications

The objective of this paper is to describe the design and implementation of a small semi-autonomous fixed-wing unmanned air vehicle. In particular we describe the hardware and software architectures used in the design. We also describe a low weight, low cost autopilot developed at Brigham Young University and the algorithms associated with the autopilot. Novel PDA and voice interfaces to the UAV are described. In addition, we overview our approach to real-time path planning, trajectory generation, and trajectory tracking. The paper is augmented with movie files that demonstrate the functionality of the UAV and its control software.

Go to article

Incorporating The Impact Of Engineering Solutions On Society Into Technical Engineering Courses, Nicole Dejong-Okamoto, Jinny Rhee, Nikos J. Mourtos Jan 2005

Incorporating The Impact Of Engineering Solutions On Society Into Technical Engineering Courses, Nicole Dejong-Okamoto, Jinny Rhee, Nikos J. Mourtos

Faculty Publications

In the era of market and workforce globalisation, engineers need a solid understanding of the impact that their products have locally, as well as globally. This is why the US Accreditation Board for Engineering and Technology (ABET) recently put a new spin on this requirement in engineering education. Specifically, outcome 3h of Engineering Criteria 2000 states that engineering graduates must have the broad education to understand the impact of engineering solutions in a global/ societal context. This outcome may be one of the most difficult to achieve, since it requires not only a strong technical understanding, but also an informed …

Go to article

A Suboptimal Receiver With Turbo Block Coding For Ultra-Wideband Communications, Robert H. Morelos-Zaragoza, Timothy Becker, Sim Aquino Jan 2005

A Suboptimal Receiver With Turbo Block Coding For Ultra-Wideband Communications, Robert H. Morelos-Zaragoza, Timothy Becker, Sim Aquino

Faculty Publications

In this paper, the performance of adaptive equalization and turbo product coding is investigated for pulse-based UWB communications in short-range indoor environments. The sensitivity of adaptive LMS linear and nonlinear (decision-feedback) equalizers with respect to the number of training symbols and number of taps is considered. To reduce the error performance variation with respect to changing channel conditions, a turbo product code (TPC) with two component (31,26,3) Hamming codes is proposed. We report simulation results showing that channel coding not only improves error performance, but also reduces significantly the sensitivity of UWB systems in short-range indoor wireless communications.

Go to article

Mechanism Of Targeted Chemotherapeutic Delivery Using Ultrasound, Thaidra A. Gaufin, Byron K. Murray, Seiga Ohmine, Kim L. O'Neill, William G. Pitt, Briant S. Stringham Jan 2005

Mechanism Of Targeted Chemotherapeutic Delivery Using Ultrasound, Thaidra A. Gaufin, Byron K. Murray, Seiga Ohmine, Kim L. O'Neill, William G. Pitt, Briant S. Stringham

Faculty Publications

Ultrasound (US) is used to enhance and target delivery of drugs and genes to cancer tissues. The advantages of focused delivery to select tissues are manifold, but the exact mechanisms are largely unknown and need clarification to optimize delivery. The present study further defined the role of collapse cavitation in US-induced permeabilization of cell membranes and subsequent drug or gene uptake by the cell. Cavitation, defined as the collapse of micro-bubbles, produces high shear stresses and shock waves that may transiently puncture cell membranes and has been suggested as the cause of increased permeability. The hypothesis that collapsing bubbles permeabilize …

Go to article

Polymerization Kinetics Of Peo-B-Pnipaam Block Copolymers, William G. Pitt, Yi Zeng Jan 2005

Polymerization Kinetics Of Peo-B-Pnipaam Block Copolymers, William G. Pitt, Yi Zeng

Faculty Publications

Our research in ultrasonic activated drug delivery motivated us to develop polymeric micelles that sequester hydrophobic drugs (Fig. 1) until they are sheared open by cavitation events produced by low frequency ultrasound (Fig. 2). [1] Using this type of drug delivery system, micelles sequestering drug can circulate freely without releasing their drug until they flow through a tumor or other tissue insonated by low frequency ultrasound. There they release part of their drug (Fig. 3). [2,3] This drug delivery technology was used to reduce tumors in a rat model [4] using block copolymers of PEO and PPO. However, we are …

Go to article

Efficient Capacity-Based Antenna Selection For Mimo Systems, Michael A. Jensen, Matthew L. Morris Jan 2005

Efficient Capacity-Based Antenna Selection For Mimo Systems, Michael A. Jensen, Matthew L. Morris

Faculty Publications

The achieved capacity of the multiple-input-multiple-output wireless channel is typically dependent on the array configurations at the transmitter and receiver. Maximizing system capacity or throughput therefore requires that the arrays adapt to changing channel conditions, which may be accomplished by selecting an appropriate subset of available antenna elements for connection to the electronic transmit and receive modules. This work presents algorithms, derived using relatively straightforward information theoretic considerations, for efficiently and effectively selecting the antenna elements. Computational examples using a realistic channel model for indoor environments illustrate the performance of the techniques.

Go to article

Network Model For Mimo Systems With Coupled Antennas And Noisy Amplifiers, Michael A. Jensen, Matthew L. Morris Jan 2005

Network Model For Mimo Systems With Coupled Antennas And Noisy Amplifiers, Michael A. Jensen, Matthew L. Morris

Faculty Publications

This work presents a framework for the analysis of mutually-coupled antennas in a multiple-input multiple-output system. The approach uses network theory to formulate the transfer matrix relating the signals input to the transmit antennas to the signals at the output of the receiver front end. This transfer function includes the coupled transmit and receive antennas, the multipath propagation channel, the receiver matching network, and a realistic noise model for the receive amplifiers. Application of the formulation to coupled dipole antennas characterized using full-wave electromagnetic analysis illustrates the performance gains possible from matching the coupled antenna/receive amplifier subsystem for minimum noise …

Go to article

Spatial Resolution And Processing Tradeoffs For Hydros: Application Of Reconstruction And Resolution Enhancement Techniques, David G. Long, Michael W. Spencer, Eni G. Njoku Jan 2005

Spatial Resolution And Processing Tradeoffs For Hydros: Application Of Reconstruction And Resolution Enhancement Techniques, David G. Long, Michael W. Spencer, Eni G. Njoku

Faculty Publications

Recent developments in reconstruction and resolution enhancement for microwave instruments suggest a possible tradeoff between computation, resolution, and downlink data rate based on postcollection reconstruction/resolution enhancement processing. The Hydrospheric State (HYDROS) mission is designed to measure global soil moisture and freeze/thaw state in support of weather and climate prediction, water, energy, and carbon cycle studies, and natural hazards monitoring. It will use an active and passive L-band microwave system that optimizes measurement accuracy, spatial resolution, and coverage. The active channels use synthetic aperture radar-type processing to achieve fine spatial resolution, requiring a relatively high downlink data rate and ground processor …

Go to article

Effects Of Pressure On Coal Pyrolysis And Char Morphology, Dong Zeng, Thomas H. Fletcher Jan 2005

Effects Of Pressure On Coal Pyrolysis And Char Morphology, Dong Zeng, Thomas H. Fletcher

Faculty Publications

A better understanding of high-pressure coal pyrolysis is needed to design advanced coal gasification combined-cycle systems. High-temperature, high-heating-rate, and high-pressure pyrolysis experiments were conducted on three bituminous coals and a lignite, to more fully understand the effects of pressure on resultant char properties. A flat-flame burner was designed and used inside a high-pressure drop-tube reactor to provide a high-temperature, high-heatingrate environment that is representative of industrial processes. Chars were prepared at four different pressures, ranging from 0.85 atm to 15 atm. The measured total volatiles yields compared well with predictions of the Chemical Percolation Devolatilization (CPD) model. The physical properties …

Go to article

Simulated Land-Based Turbine Deposits Generated In An Accelerated Deposition Facility, Jared W. Jensen, Sean W. Squire, Jeffrey P. Bons, Thomas H. Fletcher Jan 2005

Simulated Land-Based Turbine Deposits Generated In An Accelerated Deposition Facility, Jared W. Jensen, Sean W. Squire, Jeffrey P. Bons, Thomas H. Fletcher

Faculty Publications

This report presents a validation of the design and operation of an accelerated testing facility for the study of foreign deposit layers typical to the operation of land-based gas turbines. This facility was designed to produce turbine deposits in a 4-h test that would simulate 10,000 h of turbine operation. This is accomplished by matching the net foreign particulate throughput of an actual gas turbine. Flow Mach number, temperature and particulate impingement angle are also matched. Validation tests were conducted to model the ingestion of foreign particulate typically found in the urban environment. The majority of this particulate is ceramic …

Go to article

Observations Of Flame Behavior In A Laboratory-Scale Premixed Natural Gas/Air Gas Turbine Combustor From Planar Laser Induced Fluorescence Measurements Of Oh, Laser Doppler Anemometer Velocity Measurements, And Coherent Anti-Stokes Roman Spectrometer Temperature Measurements, Thomas H. Fletcher Jan 2005

Observations Of Flame Behavior In A Laboratory-Scale Premixed Natural Gas/Air Gas Turbine Combustor From Planar Laser Induced Fluorescence Measurements Of Oh, Laser Doppler Anemometer Velocity Measurements, And Coherent Anti-Stokes Roman Spectrometer Temperature Measurements, Thomas H. Fletcher

Faculty Publications

Instantaneous planar laser induced fluorescence (PLIF) images of OH, simultaneous axial/radial and axial/tangential velocity measurements with an LDA (laser Doppler anemometer), and instantaneous gas temperature measurements using a coherent anti- Stokes Raman spectrometer (CARS) were obtained in a pre-mixed, swirl-stabilized laboratory-scale combustor, fired with natural gas. Four operating conditions were examined (two swirl conditions and equivalence ratios of 0.80 and 0.65). The instantaneous PLIF images of OH illustrate the chaotic nature of the turbulent flame eddies. Mean and standard deviations of each variable were measured at different locations in the flame, along with probability density functions. Stability of the flame …

Go to article

Swelling Properties And Intrinsic Reactivities Of Coal Chars Produced At Elevated Pressures And High Heating Rates, Dong Zeng, Michael Clark, Todd Gunderson, William C. Hecker, Thomas H. Fletcher Jan 2005

Swelling Properties And Intrinsic Reactivities Of Coal Chars Produced At Elevated Pressures And High Heating Rates, Dong Zeng, Michael Clark, Todd Gunderson, William C. Hecker, Thomas H. Fletcher

Faculty Publications

A high-temperature, high-pressure flat-flame burner reactor was developed to prepare char at different pressures. This system achieves particle heating rates of 105 K/s, which better mimics industrial conditions than conventional drop tube or radiative flow reactors. Previous data at atmospheric pressure demonstrated a significant decrease in particle swelling during devolatilization as heating rates increased from 104 K/s (the typical drop tube heating rate) to 105 K/s. Pyrolysis experiments were performed at pressures from 1 to 15 atm at 1300 C for two bituminous coals and a lignite. Average swelling was determined from a combination of the mass …

Go to article

Coordination Variables, Coordination Functions, And Cooperative Timing Missions, Randal Beard, Timothy W. Mclain Jan 2005

Coordination Variables, Coordination Functions, And Cooperative Timing Missions, Randal Beard, Timothy W. Mclain

Faculty Publications

Sponsorship: AFOSR, DARPA. This paper presents a solution strategy for achieving cooperative timing among teams of vehicles. Based on the notion of coordination variables and coordination functions, the strategy facilitates cooperative timing by requiring acceptably low levels of communication and computation. The application of the coordination variable/function approach to trajectory planning problems for teams of unmanned air vehicles with timing constraints is described. Three types of timing constraints are considered: simultaneous arrival, tight sequencing, and loose sequencing. Simulation results demonstrating the viability of the approach are presented.

Go to article

Automatic Generation Of Social Network Data From Electronic-Mail Communications, Jason Yee, Robert F. Mills, Gilbert L. Peterson, Summer E. Bartczack Jan 2005

Automatic Generation Of Social Network Data From Electronic-Mail Communications, Jason Yee, Robert F. Mills, Gilbert L. Peterson, Summer E. Bartczack

Faculty Publications

Most organizations have formal and informal elements. Formal structures are usually documented in organizational charts showing chain of command, levels of authority, and personnel resources. The actual effectiveness of the organization or specific individuals may actually depend on informal structures and internal communication networks. These are by definition personality-dependent and may provide significant insight into how work actually gets done within the organization. Effective leaders will want insight into these informal structures for various reasons. Inefficient decision-making or staffing processes may result in unnecessary or redundant communications, chokepoints, or single points of failure, each of which can either delay decisions …

Go to article

Failure In Internally Pressurized Bent Tubes, Robin Stevenson, Boon-Chai Ng, Peter Polidoro Dec 2004

Failure In Internally Pressurized Bent Tubes, Robin Stevenson, Boon-Chai Ng, Peter Polidoro

Faculty Publications

The analysis and modeling of tube-hydroformed components is more complicated than that employed for sheet-metal panels, due to the lengthier process sequence and variable strain path - from flat-rolled sheet to tube; from straight tube to bent tube; and from bent tube to hydroformed component. These additional process steps make it difficult to determine whether post mortem analyses of tube failure during hydroforming can, and should, be conducted with the same tools and databases as used for simple stampings. To provide a partial answer, the properties of commercially fabricated welded straight tubes were evaluated using a free-expansion internal pressure test …

Go to article

The Effect Of Gas Pressure On No Conversion Energy Efficiency In Nonthermal Nitrogen Plasma, Morris D. Argyle, Gui-Bing Zhao, S.V.B. Janardhan Garikipati, Xudong Hu, Maciej Radosz Nov 2004

The Effect Of Gas Pressure On No Conversion Energy Efficiency In Nonthermal Nitrogen Plasma, Morris D. Argyle, Gui-Bing Zhao, S.V.B. Janardhan Garikipati, Xudong Hu, Maciej Radosz

Faculty Publications

This work explores the effect of gas pressure on the rate of electron collision reactions and energy consumption for NO conversion in N2 in a pulsed corona discharge reactor. A previous study showed that the rate constant of electron collision reactions, multiplied by the electron concentration, can be expressed as k[e] = βα−0.5P−0.5W0.75exp(−αP/W). The model parameter α remains constant with increasing gas pressure, which verifies the previous assumption that the electron temperature is inversely proportional to gas pressure. However, the model parameter β decreases with increasing gas pressure, which indicates that the rate constant of electron collision reactions decreases with …

Go to article

Kalman Consensus Strategies And Their Application To Cooperative Control, Randal Beard, Derek Kingston, Wei Ren Nov 2004

Kalman Consensus Strategies And Their Application To Cooperative Control, Randal Beard, Derek Kingston, Wei Ren

Faculty Publications

Sponsorship: AFOSR, NSF. In this paper, we propose discrete-time and continuous-time consensus update schemes motivated by the discrete-time and continuous-time Kalman filters. With certainty information encoded into each agent, the proposed consensus schemes explicitly account for relative confidence in the information that is communicated from each agent in the team. We show mild sufficient conditions under which consensus can be achieved using the proposed schemes in the presence of switching interaction topologies. The Kalman consensus scheme is shown to be input-to-state stable. We show how to exploit this fact in multi-agent cooperative control scenarios.

Go to article

Simulation Of Gate Lag And Current Collapse In Gallium Nitride Field-Effect Transistors, N. Braga, R. Mickevicius, R. Gaska, M. S. Shur, M. Asif Khan, Grigory Simin Nov 2004

Simulation Of Gate Lag And Current Collapse In Gallium Nitride Field-Effect Transistors, N. Braga, R. Mickevicius, R. Gaska, M. S. Shur, M. Asif Khan, Grigory Simin

Faculty Publications

Results of two-dimensional numerical simulations of gate lag and current collapse in GaN heterostructurefield-effect transistors are presented. Simulation results clearly show that current collapse takes place only if an enhanced trapping occurs under the gate edges. Hot electrons play an instrumental role in the collapse mechanism. The simulation results also link the current collapse with electrons spreading into the buffer layer and confirm that a better electron localization (as in a double heterostructurefield-effect transistor) can dramatically reduce current collapse.

Go to article

Coordination Variables And Consensus Building In Multiple Vehicle Systems, Tim Mclain Nov 2004

Coordination Variables And Consensus Building In Multiple Vehicle Systems, Tim Mclain

Faculty Publications

Much of the research focus in the cooperative control community has been on formation control problems. This focus may be due to the fact that the group control problem can be reduced to well-established single-agent control problems by employing a leader-follower type control strategy. For example, single-agent path planning and trajectory generation techniques can be employed for the leader, and conventional trajectory tracking strategies can be employed for the followers. Indeed, formation control problems are much like linear systems theory: we search where the light is the brightest. It can be argued that formation control problems are the simplest type …

Go to article

Evaluation Of Bus And Truck Automation Operations Concepts, H.-S. Jacob Tsao, Lan Zhang, Lin Lin, Deepa Batni Nov 2004

Evaluation Of Bus And Truck Automation Operations Concepts, H.-S. Jacob Tsao, Lan Zhang, Lin Lin, Deepa Batni

Faculty Publications

Traffic congestion will continue to worsen and likely worsen at a faster rate than ever. People throughput and freight throughput have become critical issues for California and the rest of the nation. PATH has funded with approximately $125K a research project entitled “Evaluation of Bus and Truck Automation Scenarios” jointly proposed by Jan Botha (Principal Investigator) of Department of Civil and Environmental Engineering and Jacob Tsao (Co-PI) of Department of Industrial and Systems Engineering at San Jose State University. This report summarizes the major findings of the research conducted by Professor Tsao and his assistants with approximately $44K out of …

Go to article

A Review Of Antennas And Propagation For Mimo Wireless Communications, Michael A. Jensen, Jon W. Wallace Nov 2004

A Review Of Antennas And Propagation For Mimo Wireless Communications, Michael A. Jensen, Jon W. Wallace

Faculty Publications

Multiple-input-multiple-output (MIMO) wireless systems use multiple antenna elements at transmit and receive to offer improved capacity over single antenna topologies in multipath channels. In such systems, the antenna properties as well as the multipath channel characteristics play a key role in determining communication performance. This paper reviews recent research findings concerning antennas and propagation in MIMO systems. Issues considered include channel capacity computation, channel measurement and modeling approaches, and the impact of antenna element properties and array configuration on system performance. Throughout the discussion, outstanding research questions in these areas are highlighted.

Go to article

Resolution Scaling In Noncontact Scanning Impedance Imaging, Benjamin C. Green, Tao Shang, Jacey C. Morine, Hongze Liu, Stephen M. Schultz, Travis E. Oliphant, Aaron R. Hawkins Oct 2004

Resolution Scaling In Noncontact Scanning Impedance Imaging, Benjamin C. Green, Tao Shang, Jacey C. Morine, Hongze Liu, Stephen M. Schultz, Travis E. Oliphant, Aaron R. Hawkins

Faculty Publications

Noncontact scanning impedance imaging has been presented as a method to provide high resolution, high contrast images for a variety of material systems. This technique combines electrical impedance measurements with very high resolution scanning. This article reports on efforts to scale this technique down to the very important single micron range and reveals measurements for both thick and thin samples with a measured minimum resolution below 30 µm. A design for a shielded impedance probe applicable to this process is outlined and probes of several different sizes were made and tested. Fabrication of these impedance probes is explained and a …

Go to article

Integrated Optical Waveguides With Liquid Cores, Aaron R. Hawkins, John P. Barber, Dongliang Yin, D. W. Deamer, Holger Schmidt Oct 2004

Integrated Optical Waveguides With Liquid Cores, Aaron R. Hawkins, John P. Barber, Dongliang Yin, D. W. Deamer, Holger Schmidt

Faculty Publications

We report the design, fabrication, and demonstration of single-mode integrated optical waveguides with liquid cores. The principle of the device is based on antiresonant reflecting optical (ARROW) waveguides with hollow cores. We describe design principles for waveguide loss optimization down to 0.1/cm. Using a fabrication process based on conventional silicon microfabrication and sacrificial core layers, waveguides of varying widths and lengths with volumes covering the pico- to nanoliter range were fabricated. We observe confined mode propagation, measure waveguide losses of 2.4/cm, and demonstrate that the waveguides possess tailorable wavelength selectivity. The potential for highly integrated, sensitive devices based on these …

Go to article

First Prev Next Last