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Articles 1 - 30 of 30
Full-Text Articles in Mechanical Engineering
Promoting Electrocatalytic Activity Of A Composite Sofc Cathode La0.8Sr0.2Mno3+Δ/Ce0.8Gd0.2O2-Δ With Molten Carbonates, Yunhui Gong, Xue Li, Lingling Zhang, Whitney Tharp, Changyong Qin, Kevin Huang
Promoting Electrocatalytic Activity Of A Composite Sofc Cathode La0.8Sr0.2Mno3+Δ/Ce0.8Gd0.2O2-Δ With Molten Carbonates, Yunhui Gong, Xue Li, Lingling Zhang, Whitney Tharp, Changyong Qin, Kevin Huang
Faculty Publications
The effect of molten carbonates (MCs) on polarization resistance (RP), a direct measure of oxygen reduction reaction (ORR) activity, of a composite La0.8Sr0.2MnO3+δ/Ce0.8Gd0.2O2-δ (LSM/GDC) solid oxide fuel cell (SOFC) cathode has been systematically investigated in this study over a temperature range of 550–650°C and partial pressure of oxygen (pO2) span of 10−3 ∼ 1 atm. It is shown that the LSM/GDC cathode, either in the pristine or MC-modified states, can be generally modeled by two consecutive parallel circuits consisting of a resistance and a …
Enhanced Reversibility And Durability Of A Solid Oxide Fe–Air Redox Battery By Carbothermic Reaction Derived Energy Storage Materials, Xuan Zhao, Xue Li, Yunhui Gong, Kevin Huang
Enhanced Reversibility And Durability Of A Solid Oxide Fe–Air Redox Battery By Carbothermic Reaction Derived Energy Storage Materials, Xuan Zhao, Xue Li, Yunhui Gong, Kevin Huang
Faculty Publications
The recently developed solid oxide metal–air redox battery is a new technology capable of high-rate chemistry. Here we report that the performance, reversibility and stability of a solid oxide iron–air redox battery can be significantly improved by nanostructuring energy storage materials from a carbothermic reaction.
A New Solid Oxide Molybdenum–Air Redox Battery, Xuan Zhao, Yunhui Gong, Xue Li, Nansheng Xu, Kevin Huang
A New Solid Oxide Molybdenum–Air Redox Battery, Xuan Zhao, Yunhui Gong, Xue Li, Nansheng Xu, Kevin Huang
Faculty Publications
A new type of rechargeable molybdenum–air battery based on the technologies of reversible solid oxide fuel cells and chemical looping is reported in this study. The reversible solid oxide fuel cell serves as the electrical unit to realize the charging and discharging cycles while a pair of Mo/MoO2 redox couple integrated with the reversible solid oxide fuel cell stores electrical energy via an H2–H2O oxygen shuttle. The specific charge of the new battery reaches 1117 A h per kg-Mo at 550°C, which is 45% higher than the non-rechargeable Mo–air battery. The corresponding discharge specific energy is 974 W h per …
Enhanced Reducibility And Conductivity Of Na/K-Doped Srti0.8Nb0.2O3, Guoliang Xiao, Sirikanda Nuansaeng, Lei Zhang, Suwit Suthirakun, Andreas Heyden, Hans-Conrad Zur Loye, Fanglin Chen
Enhanced Reducibility And Conductivity Of Na/K-Doped Srti0.8Nb0.2O3, Guoliang Xiao, Sirikanda Nuansaeng, Lei Zhang, Suwit Suthirakun, Andreas Heyden, Hans-Conrad Zur Loye, Fanglin Chen
Faculty Publications
Donor and acceptor co-doped SrTiO3 materials have shown interesting features in their conductivity and reducibility. In this work, 10 mol% Na+ or K+ as acceptor dopants have been introduced into the A-site of donor-doped strontium titanate, SrTi0.8Nb0.2O3, and the doping impact on their properties has been studied. By doping with Na or K, the sinterability of SrTi0.8Nb0.2O3 in reducing atmospheres has been improved. Na0.1Sr0.9Ti0.8Nb0.2O3 and K0.1Sr0.9Ti0.8Nb0.2O3 show metallic …
Cyclic Durability Of A Solid Oxide Fe-Air Redox Battery Operated At 650°C, Xuan Zhao, Yunhui Gong, Xue Li, Nansheng Xu, Kevin Huang
Cyclic Durability Of A Solid Oxide Fe-Air Redox Battery Operated At 650°C, Xuan Zhao, Yunhui Gong, Xue Li, Nansheng Xu, Kevin Huang
Faculty Publications
The recently developed rechargeable solid oxide metal-air redox battery has shown a great potential for applications in mid- to large-scale stationary energy storage. Cyclic durability is one of the most important requirements for stationary energy storage. In this study, we report the cyclic durability of a solid oxide Fe-air redox battery operated at 650°C. The battery was continuously cycled 100 times under a current density of 50 mA/cm2 with rather flat performance, producing an average specific energy of 760 Wh/kg-Fe at a round-trip efficiency of 55.5%. The post-test examination indicated that the performance losses could arise from the fuel-electrode …
Cyclic Durability Of A Solid Oxide Fe-Air Redox Battery Operated At 650°C, Xuan Zhao, Yunhui Gong, Xue Li, Nansheng Xu, Kevin Huang
Cyclic Durability Of A Solid Oxide Fe-Air Redox Battery Operated At 650°C, Xuan Zhao, Yunhui Gong, Xue Li, Nansheng Xu, Kevin Huang
Faculty Publications
The recently developed rechargeable solid oxide metal-air redox battery has shown a great potential for applications in mid- to large-scale stationary energy storage. Cyclic durability is one of the most important requirements for stationary energy storage. In this study, we report the cyclic durability of a solid oxide Fe-air redox battery operated at 650◦C. The battery was continuously cycled 100 times under a current density of 50 mA/cm2 with rather flat performance, producing an average specific energy of 760 Wh/kg-Fe at a round-trip efficiency of 55.5%. The post-test examination indicated that the performance losses could arise from the fuel-electrode of …
Non-Redundant Sensor Fault Detection Using An Improved Dynamic Model, Brandon Cannon, Robert C. Leishman, Timothy W. Mclain, Joseph Jackson, Jovan Boskovic
Non-Redundant Sensor Fault Detection Using An Improved Dynamic Model, Brandon Cannon, Robert C. Leishman, Timothy W. Mclain, Joseph Jackson, Jovan Boskovic
Faculty Publications
This paper proposes a method of detecting faults in non-redundant sensors. Such a method is advantageous for small unmanned aerial vehicles (UAVs), which are prevented from carrying redundant sensors due to size, weight, and power constraints. The method we propose uses a multiplicative extended Kalman lter (MEKF) for estimation and employs hypothesis testing to detect faults. This method has been shown to detect bias, drift, and increased noise in a non-redundant sensor real-time on board an autonomous rotorcraft.
Robust Motion Estimation With Rgb-D Cameras, Robert C. Leishman, Daniel Koch, Timothy W. Mclain
Robust Motion Estimation With Rgb-D Cameras, Robert C. Leishman, Daniel Koch, Timothy W. Mclain
Faculty Publications
Estimating vehicle motion using vision sensors in real time has been greatly explored in the past few years due to speed improvements and advances in computer hardware. Six degree of freedom motion estimation using vision information is desirable due to a vision sensors low cost, low power requirements and light weight and for the quality of the solutions that can be obtained using few assumptions about the environment. However, cameras have the downside of not providing good estimates when visual features are sparse or not available. Also, there are problems with changes in lighting and when light is low or …
Unveiling The Roles Of Binder In The Mechanical Integrity Of Electrodes For Lithium-Ion Batteries, Jianchao Chen, Jianyong Liu, Yue Qi, Tao Sun, Xiaodong Li
Unveiling The Roles Of Binder In The Mechanical Integrity Of Electrodes For Lithium-Ion Batteries, Jianchao Chen, Jianyong Liu, Yue Qi, Tao Sun, Xiaodong Li
Faculty Publications
In lithium-ion secondary batteries research, binders have received the least attention, although the electrochemical performance of Li-ion batteries such as specific capacity and cycle life cannot be achieved if the adhesion strengths between electrode particles and between electrode films and current collectors are insufficient to endure charge-discharge cycling. In this paper, the roles of binders in the mechanical integrity of electrodes for lithium-ion batteries were studied by coupled microscratch and digital image correlation (DIC) techniques. A microscratch based composite model was developed to decouple the carbon particle/particle cohesion strength from the electrode-film/copper-current-collector adhesion strength. The dependences of microscratch coefficient of …
Inviscid Analysis Of Extended Formation Flight, James Kless, Michael Aftosmis, Andrew Ning, Marian Nemec
Inviscid Analysis Of Extended Formation Flight, James Kless, Michael Aftosmis, Andrew Ning, Marian Nemec
Faculty Publications
Flying airplanes in extended formations, with separation distances of tens of wingspans, significantly improves safety while maintaining most of the fuel savings achieved in close formations. The present study investigates the impact of roll trim and compressibility at a fixed lift coefficient on the benefits of extended formation flight. An Euler solver with adjoint-based mesh refinement combined with a wake propagation model is used to analyze a two-body echelon formation at a separation distance of 30 spans. Two geometries are examined: a simple wing and a wing-body geometry. Energy savings, quantified by both formation drag fraction and span efficiency factor, …
Numerical Simulation Of Convection In Triangular Cavities To Predict Solar Still Performance, Jeremy D. Lefevre, W. Jerry Bowman, Matthew R. Jones
Numerical Simulation Of Convection In Triangular Cavities To Predict Solar Still Performance, Jeremy D. Lefevre, W. Jerry Bowman, Matthew R. Jones
Faculty Publications
To improve modeling of solar still behavior, the convection correlations currently used need to be improved upon. Variations in operating parameters and cover geometries make it difficult to use a single correlation to describe the operation of all solar stills. In this work, three right triangles (representing covers at 15, 30, and 45 deg) were modeled, meshed, and solved to predict the convection heat transfer inside for a variety of operating conditions. For a correlation of the form Nu = C · Ran, it was found that C = 1.1, 0.60, and 0.71, and n = 0.19, 0.24, …
First Spectroscopic Identification Of Pyrocarbonate For High Co2 Flux Membranes Containing Highly Interconnected Three Dimensional Ionic Channels, Lingling Zhang, Xinyu Huang, Changyong Qin, Kyle Brinkman, Yunhui Gong, Siwei Wang, Kevin Huang
First Spectroscopic Identification Of Pyrocarbonate For High Co2 Flux Membranes Containing Highly Interconnected Three Dimensional Ionic Channels, Lingling Zhang, Xinyu Huang, Changyong Qin, Kyle Brinkman, Yunhui Gong, Siwei Wang, Kevin Huang
Faculty Publications
Identification of the existence of pyrocarbonate ion C2O52− in molten carbonates exposed to a CO2 atmosphere provides key support for a newly established bi-ionic transport model that explains the mechanisms of high CO2 permeation flux observed in mixed oxide-ion andcarbonate-ion conducting (MOCC) membranes containing highly interconnected three dimensional ionic channels. Here we report the first Raman spectroscopic evidence of C2O52− as an active species involved in the CO2-transport process of MOCC membranes exposed to a CO2atmosphere. The two new broad peaks centered at 1317 cm−1 …
Performance Of Solid Oxide Iron-Air Battery Operated At 550°C, Xuan Zhao, Yunhui Gong, Xue Li, Nansheng Xu, Kevin Huang
Performance Of Solid Oxide Iron-Air Battery Operated At 550°C, Xuan Zhao, Yunhui Gong, Xue Li, Nansheng Xu, Kevin Huang
Faculty Publications
“Metal-air” batteries have garnered much attention in recent years due to their high intrinsic specific energy and use of inexhaustible and storage-free oxygen source -air- for the “metal-oxygen” reaction. In this study, we report theperformance of a new type of all solid-state “iron-air” battery operated at 550°C. The results show that CeO2 nanoparticles incorporated into the Fe-Fe3O4 redox-couple can improve the specific energy (Wh/kg) and round trip efficiency by 15% and 29%, respectively, over the baseline Fe-Fe3O4 battery. Use of supported Fe-Fe3O4 nanoparticles as the redox couple can increase the …
Micro Modeling Study Of Cathode/Electrolyte Interfacial Stresses For Solid Oxide Fuel Cells, Xinfang Jin, Xingjian Xue
Micro Modeling Study Of Cathode/Electrolyte Interfacial Stresses For Solid Oxide Fuel Cells, Xinfang Jin, Xingjian Xue
Faculty Publications
Delamination of the cathode/electrolyte interface is an important degradation phenomenon in solid oxide fuel cells (SOFCs). While the thermal stress has been widely recognized as one of the major reasons for such delamination failures, the role of chemical stress does not receive too much attention. In this paper, a micro-model is developed to study the cathode/electrolyte interfacial stresses, coupling oxygen ion transport process with structural mechanics. Results indicate that the distributions of chemical stress are very complicated at the cathode/electrolyte interface and show different patterns from those of thermal stress. The maximum principal stresses take place at the cathode/electrolyte interface …
Floating Electrode Electrowetting On Hydrophobic Dielectric With An Sio2 Layer, Mehdi Khodayari, Benjamin Hahne, Nathan B. Crane, Alex A. Volinsky
Floating Electrode Electrowetting On Hydrophobic Dielectric With An Sio2 Layer, Mehdi Khodayari, Benjamin Hahne, Nathan B. Crane, Alex A. Volinsky
Faculty Publications
Floating electrode electrowetting is caused by dc voltage applied to a liquid droplet on the Cytop surface, without electrical connection to the substrate. The effect is caused by the charge separation in the floating electrode. A highly-resistive thermally-grown SiO2 layer underneath the Cytop enables the droplet to hold charges without leakage, which is the key contribution. Electrowetting with an SiO2 layer shows a memory effect, where the wetting angle stays the same after the auxiliary electrode is removed from the droplet in both conventional and floating electrode electrowetting. Floating electrode electrowetting provides an alternative configuration for developing advanced electrowetting-based devices.
Analysis Of An Improved Imu-Based Observer For Multirotor Helicopters, John Charles Macdonald, Robert C. Leishman, Randal W. Beard, Timothy W. Mclain
Analysis Of An Improved Imu-Based Observer For Multirotor Helicopters, John Charles Macdonald, Robert C. Leishman, Randal W. Beard, Timothy W. Mclain
Faculty Publications
Multirotor helicopters are increasingly popular platforms in the robotics community. Making them fully autonomous requires accurate state estimation. We review an improved dynamic model for multirotor helicopters and analyze the observability properties of an estimator based on this model. The model allows better use of IMU data to facilitate accurate state estimates even when updates from a sensor measuring position become less frequent and less accurate. We demonstrate that the position update rate can be cut in half versus typical approaches while maintaining the same accuracy. We also find that velocity estimates are at least twice as accurate no matter …
Relative Navigation Approach For Vision-Based Aerial Gps-Denied Navigation, Robert C. Leishman, Timothy Mclain, Randal W. Beard
Relative Navigation Approach For Vision-Based Aerial Gps-Denied Navigation, Robert C. Leishman, Timothy Mclain, Randal W. Beard
Faculty Publications
GPS-denied aerial flight is a popular research topic. The problem is challenging and requires knowledge of complex elements from many distinct disciplines. Additionally, aerial vehicles can present challenging constraints such as stringent payload limitations and fast vehicle dynamics. In this paper we propose a new architecture to simplify some of the challenges that constrain GPS-denied aerial flight. At the core, the approach combines visual graph-SLAM with a multiplicative extended Kalman filter. More importantly, for the front end we depart from the common practice of estimating global states and instead keep the position and yaw states of the MEKF relative to …
A High Energy Density All Solid-State Tungsten-Air Battery, Xuan Zhao, Xue Li, Yunhui Gong, Nansheng Xu, Kevin Gregory Romito, Kevin Huang
A High Energy Density All Solid-State Tungsten-Air Battery, Xuan Zhao, Xue Li, Yunhui Gong, Nansheng Xu, Kevin Gregory Romito, Kevin Huang
Faculty Publications
An all solid-state tungsten–air battery using solid oxide–ion electrolyte is demonstrated as a new chemistry for advanced energy storage. The unique design of separated energy storage from the electrodes allows for free volume expansion–contraction during electrical cycles and new metal–air chemistry to be explored conveniently.
Enhanced Nucleate Boiling On Horizontal Hydrophobic-Hydrophilic Carbon Nanotube Coatings, Xianming Dai, Xinyu Huang, Fanghao Yang, Xiaodong Li, Joshua Sightler, Yingchao Yang, Chen Li
Enhanced Nucleate Boiling On Horizontal Hydrophobic-Hydrophilic Carbon Nanotube Coatings, Xianming Dai, Xinyu Huang, Fanghao Yang, Xiaodong Li, Joshua Sightler, Yingchao Yang, Chen Li
Faculty Publications
Ideal hydrophobic-hydrophilic composite cavities are highly desired to enhance nucleate boiling. However, it is challenging and costly to fabricate these types of cavities by conventional micro/nano fabrication techniques. In this study, a type of hydrophobic-hydrophilic composite interfaces were synthesized from functionalized multiwall carbon nanotubes by introducing hydrophilic functional groups on the pristine multiwall carbon nanotubes. This type of carbon nanotube enabled hydrophobic-hydrophilic composite interfaces were systematically characterized. Ideal cavities created by the interfaces were experimentally demonstrated to be the primary reason to substantially enhance nucleate boiling
A Multiplicative Extended Kalman Filter For Relative Rotorcraft Navigation, Robert C. Leishman, Timothy W. Mclain
A Multiplicative Extended Kalman Filter For Relative Rotorcraft Navigation, Robert C. Leishman, Timothy W. Mclain
Faculty Publications
In this article we detail the fundamentals of a new approach to GPS-denied navigation for aerial vehicles in confined indoor environments. We depart from the common practice of navigating within a globally referenced map, and instead keep the position and yaw states relative to the current node in the map. The approach combines elements of graph SLAM with a multiplicative extended Kalman filter (MEKF). The filter provides quality state estimates at a fast rate and a graph SLAM algorithm maintains a pose graph. We provide specific details for the relative MEKF. We verify the relative estimation approach with hardware flight …
Atomic Layer Deposition On Porous Materials: Problems With Conventional Approaches To Catalyst And Fuel Cell Electrode Preparation, Tzia Ming Onn, Rainer Küngas, Paolo Fornasiero, Kevin Huang, Raymond J. Gorte
Atomic Layer Deposition On Porous Materials: Problems With Conventional Approaches To Catalyst And Fuel Cell Electrode Preparation, Tzia Ming Onn, Rainer Küngas, Paolo Fornasiero, Kevin Huang, Raymond J. Gorte
Faculty Publications
Atomic layer deposition (ALD) offers exciting possibilities for controlling the structure and composition of surfaces on the atomic scale in heterogeneous catalysts and solid oxide fuel cell (SOFC) electrodes. However, while ALD procedures and equipment are well developed for applications involving flat surfaces, the conditions required for ALD in porous materials with a large surface area need to be very different. The materials (e.g., rare earths and other functional oxides) that are of interest for catalytic applications will also be different. For flat surfaces, rapid cycling, enabled by high carrier-gas flow rates, is necessary in order to rapidly grow thicker …
Objectives And Constraints For Wind Turbine Optimization, Andrew Ning, Rick Damiani, Patrick Moriarty
Objectives And Constraints For Wind Turbine Optimization, Andrew Ning, Rick Damiani, Patrick Moriarty
Faculty Publications
Efficient extraction of wind energy is a complex multidisciplinary process. This paper examines common objectives used in wind turbine optimization problems. The focus is not on the specific optimized designs, but rather on understanding when certain objectives and constraints are necessary, and what their limitations are. Maximizing annual energy production, or even using sequential aero/structural optimization, is shown to be significantly suboptimal compared to integrated aero/structural metrics. Minimizing the ratio of turbine mass to annual energy production can be effective for fixed rotor diameter designs, as long as the tower mass is estimated carefully. For variable diameter designs, the predicted …
Hydrophobic Hydrogel Caged H3Po4 As A New Class Of High-Temperature Proton Exchange Membranes With Enhanced Acid Retention, Qunwei Tang, Guoging Qian, Kevin Huang
Hydrophobic Hydrogel Caged H3Po4 As A New Class Of High-Temperature Proton Exchange Membranes With Enhanced Acid Retention, Qunwei Tang, Guoging Qian, Kevin Huang
Faculty Publications
We herein report a new class of high-temperature proton exchange membranes comprised of poly(acrylic acid-graft-hexadecyltrimethylammonium bromide) (PAA-g-CTAB) or poly(acrylic acid)-graft-poly(ethylene glycol) (PAA-g-PEG) hydrophobic hydrogel caged H3PO4. The membranes exhibit reasonable proton conductivity, enhanced H3PO4 retention ability and low solubility in water, making them promising as potential high performance and robust electrolytes for high-temperature proton exchange membrane fuel cells. Although the proton conductivity is still lower than that of H3PO4 doped PBI membranes, the new concept provides a different approach to proton exchange membranes for acid retention.
Wave Propagation In Metamaterial Using Multiscale Resonators By Creating Local Anisotropy, Raiz U. Ahmed, Sourav Banerjee
Wave Propagation In Metamaterial Using Multiscale Resonators By Creating Local Anisotropy, Raiz U. Ahmed, Sourav Banerjee
Faculty Publications
Directional guiding, passing or stopping of elastic waves through engineered materials have many applications to the engineering fields. Recently, such engineered composite materials received great attention by the broader research community. In elastic waves, the longitudinal and transverse motion of material particles are coupled, which exhibits richer physics and demands greater attention than electromagnetic waves and acoustic waves in fluids. Waves in periodic media exhibit the property of Bragg scattering and create frequency band gaps in which the energy propagation is prohibited. However, in addition to the Bragg scattering, it has been found that local resonance of artificially designed resonators …
Techno- Economic Analysis Of Wastewater Biosolids Gasification, Jason M. Porter, Nick Lumley, Robert Braun, Tzahi Cath, Ana Prietro, Dotti Ramey, Greta Buschmann
Techno- Economic Analysis Of Wastewater Biosolids Gasification, Jason M. Porter, Nick Lumley, Robert Braun, Tzahi Cath, Ana Prietro, Dotti Ramey, Greta Buschmann
Faculty Publications
Wastewater treatment biosolids, commonly referred to as sludge, is a dilute suspension of micro-organisms, noxious organic matter, and mineral species in up to 99% water. Sludge is produced at about 250 mg/L of mixed municipal and light industrial wastewater treated. Management of this process stream can present a financial and environmental challenge for wastewater treatment plants (WWTPs), accounting for up to 15% of plant energy consumption. Operators of small urban WWTPs see the greatest challenge as their operations do not benefit from economies of scale, which permit larger facilities to absorb the costs or footprint of anaerobic digestion. This work …
Molten Carbonates As An Effective Oxygen Reduction Catalyst For 550–650°C Solid Oxide Fuel Cells, Yunhui Gong, Xue Li, Lingling Zhang, Whitney Tharp, Changyong Qin, Kevin Huang
Molten Carbonates As An Effective Oxygen Reduction Catalyst For 550–650°C Solid Oxide Fuel Cells, Yunhui Gong, Xue Li, Lingling Zhang, Whitney Tharp, Changyong Qin, Kevin Huang
Faculty Publications
We report the first study that investigates the use of molten carbonates as an effective catalyst to promote electrochemical oxygen reduction reaction (ORR) at the cathode of intermediate temperature solid oxide fuel cells (IT-SOFCs). A series of binary Li-K carbonate compositions were incorporated into the porous backbones of a commercial cathode assembled in symmetrical impedance cells for electrochemical characterization. Within the temperature range of 550–650◦C, we observed that the polarization and ohmic area-specific resistances of the original sample can be significantly reduced by the introduction of molten carbonates. A new ORR charge-transfer model involving two intermediate species CO5 2− and …
The Effect Of Isostatic Pressing On The Dielectric Properties Of Screen Printed Ba0.5Sr0.5Tio3 Thick Films, Siwei Wang, Lingling Zhang, Jiwei Zhai, Fanglin Chen
The Effect Of Isostatic Pressing On The Dielectric Properties Of Screen Printed Ba0.5Sr0.5Tio3 Thick Films, Siwei Wang, Lingling Zhang, Jiwei Zhai, Fanglin Chen
Faculty Publications
Ba0.5Sr0.5TiO3 thick films with B2O3–Li2O glass sintering aid were prepared by the screen printing method on Al2O3 substrates. A 200 MPa isostatic pressure was applied to the films before sintering. After being sintered at 950∘C, lower porosity and denser microstructure was obtained compared with the films without isostatic pressing. The dielectric constant and dielectric loss were 238 and 0.0028, respectively. A tunability of 61.7% was obtained for the isostatic pressed films, a 27.8% enhancement compared to unpressurized films. These results suggest that isostatic pressing …
Simulation Studying Effects Of Multiple Primary Aberrations On Donut-Shaped Gaussian Beam, Chen Zhang, K. Wang, J. Bai, Y. Liu, Guiren Wang
Simulation Studying Effects Of Multiple Primary Aberrations On Donut-Shaped Gaussian Beam, Chen Zhang, K. Wang, J. Bai, Y. Liu, Guiren Wang
Faculty Publications
In this paper, we demonstrate the variation of donut-shaped depletion pattern which influenced by multiple primary aberrations. The simulation is base on a common stimulation emission of depletion (STED) system composed by Gaussian laser and vortex phase plate. The simulation results are helpful guidelines for analyzing the aberration of depletion patterns in real situations.
Supercritical Co2 Brayton Cycles For Solar-Thermal Energy, Brian D. Iverson, Thomas M. Conboy, James J. Pasch, Alan M. Kruizenga
Supercritical Co2 Brayton Cycles For Solar-Thermal Energy, Brian D. Iverson, Thomas M. Conboy, James J. Pasch, Alan M. Kruizenga
Faculty Publications
Of the mechanisms to improve efficiency for solar-‐thermal power plants, one of the most effective ways to improve overall efficiency is through power cycle improvements. As increases in operating temperature continue to be pursued, supercritical CO2 Brayton cycles begin to look more attractive despite the development costs of this technology. Further, supercritical CO2 Brayton has application in many areas of power generation beyond that for solar energy alone.
One challenge particular to solar-‐thermal power generation is the transient nature of the solar resource. This work illustrates the behavior of developmental Brayton turbomachinery in response to a fluctuating thermal input, much …
Electrochemical Explanation For Asymmetric Electrowetting Response, Mehdi Khodayari, Nathan B. Crane, Alex A. Volinsky
Electrochemical Explanation For Asymmetric Electrowetting Response, Mehdi Khodayari, Nathan B. Crane, Alex A. Volinsky
Faculty Publications
In electrowetting, a droplet/substrate contact angle is modulated by applying a potential difference between the droplet and the substrate. Typically, the droplet potential is changed via an auxiliary electrode dipped in the droplet. Here, it is shown that electrochemical reactions lead to a potential drop on the auxiliary electrode in electrowetting, which degrades the droplet contact angle modulation. The magnitude of this effect depends on the voltage polarity. This problem can be addressed by using a dielectric layer, such as SiO2, which can prevent electrochemical reactions with the electrowetting substrate and the auxiliary electrode.