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- Mechanical and Materials Engineering Faculty Publications and Presentations (90)
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Articles 61 - 90 of 109
Full-Text Articles in Engineering
High-Performance Self-Powered Photodetectors Based On Zno/Zns Core-Shell Nanorod Arrays, Hailing Lin, Lin Wei, Cuncun Wu, Yanxue Chen, Shishen Yan, Liangmo Mei, Jun Jiao
High-Performance Self-Powered Photodetectors Based On Zno/Zns Core-Shell Nanorod Arrays, Hailing Lin, Lin Wei, Cuncun Wu, Yanxue Chen, Shishen Yan, Liangmo Mei, Jun Jiao
Mechanical and Materials Engineering Faculty Publications and Presentations
In recent years, there is an urgent demand for high-performance ultraviolet photodetectors with high photosensitivity, fast responsivity, and excellent spectral selectivity. In this letter, we report a self-powered photoelectrochemical cell-type UV detector using the ZnO/ZnS core-shell nanorod array as the active photoanode and deionized water as the electrolyte. This photodetector demonstrates an excellent spectral selectivity and a rapid photoresponse time of about 0.04 s. And the maximum responsivity is more than 0.056 (A/W) at 340 nm, which shows an improvement of 180 % compared to detectors based on the bare ZnO nanorods. This improved photoresponsivity can be understood from the …
Study Design Of A Cluster-Randomized Controlled Trial To Evaluate A Large-Scale Distribution Of Cook Stoves And Water Filters In Western Province, Rwanda, Corey L. Nagel, Miles Kirby, Laura D. Zambrano, Ghislaine Rosa, Christina K. Barstow, Evan A. Thomas, Thomas Clasen
Study Design Of A Cluster-Randomized Controlled Trial To Evaluate A Large-Scale Distribution Of Cook Stoves And Water Filters In Western Province, Rwanda, Corey L. Nagel, Miles Kirby, Laura D. Zambrano, Ghislaine Rosa, Christina K. Barstow, Evan A. Thomas, Thomas Clasen
Mechanical and Materials Engineering Faculty Publications and Presentations
Background: In Rwanda, pneumonia and diarrhea are the first and second leading causes of death, respectively, among children under five. Household air pollution (HAP) resultant from cooking indoors with biomass fuels on traditional stoves is a significant risk factor for pneumonia, while consumption of contaminated drinking water is a primary cause of diarrheal disease. To date, there have been no largescale effectiveness trials of programmatic efforts to provide either improved cookstoves or household water filters at scale in a low-income country. In this paper we describe the design of a clusterrandomized trial to evaluate the impact of a national-level program …
Column-Grid-Array (Cga) Versus Ball-Grid-Array (Bga): Boardlevel Drop Test And The Expected Dynamic Stress In The Solder Material, Ephraim Suhir, Reza Ghaffarian
Column-Grid-Array (Cga) Versus Ball-Grid-Array (Bga): Boardlevel Drop Test And The Expected Dynamic Stress In The Solder Material, Ephraim Suhir, Reza Ghaffarian
Mechanical and Materials Engineering Faculty Publications and Presentations
Board level drop test is considered with an objective to develop a physically meaningful analytical predictive model for the evaluation of the expected impactinduced dynamic stresses in the solder material. Ball-gridarray (BGA) and column-grid-array (CGA) designs are addressed. Intuitively it is felt that while the application of the CGA technology to relieve thermal stresses in the solder material might be quite effective (owing to the greater interfacial compliance of the CGA in comparison with the BGA), the situation might be quite different when the PCB/package experiences dynamic loading. This is because the mass of the CGA joints exceeds considerably that …
Stabilization Of Vegetable Oil-Based Quenchants To Thermal-Oxidative Degradation: Experimental Strategy And Effect Of Oxidation On Quenching Performance, Éder Cícero Adão Simêncio, Rosa Lúcia Simêncio Otero, Lauralice De Campos Franceschini Canale, George E. Totten
Stabilization Of Vegetable Oil-Based Quenchants To Thermal-Oxidative Degradation: Experimental Strategy And Effect Of Oxidation On Quenching Performance, Éder Cícero Adão Simêncio, Rosa Lúcia Simêncio Otero, Lauralice De Campos Franceschini Canale, George E. Totten
Mechanical and Materials Engineering Faculty Publications and Presentations
Although petroleum oils continue to be the dominant type of basestock for the formulation of vaporizable quenchants, there is increasing pressure to identify an alternative basestock to address the limitations to their continued use because they are not a renewable basestock and they possess generally poor toxicity and biodegradability properties. Currently the most often cited alternative basestocks are those based on seed oils since they are renewable and usually non-toxic but especially because they are typically readily biodegradable. However, they suffer a critically important deficiency in that they are also typically much less stable to thermal-oxidative degradation than petroleum oils. …
More Investigations In Capillary Fluidics Using A Drop Tower, Andrew Paul Wollman, Mark M. Weislogel, Brentley M. Wiles, Donald Pettit, Trevor Snyder
More Investigations In Capillary Fluidics Using A Drop Tower, Andrew Paul Wollman, Mark M. Weislogel, Brentley M. Wiles, Donald Pettit, Trevor Snyder
Mechanical and Materials Engineering Faculty Publications and Presentations
A variety of contemplative demonstrations concerning intermediate-to-large length scale capillary fluidic phenomena were made possible by the brief weightless environment of a drop tower (Wollman and Weislogel in Exp Fluids 54(4):1, 2013). In that work, capillarity-driven flows leading to unique spontaneous droplet ejections, bubble ingestions, and multiphase flows were introduced and discussed. Such efforts are continued herein. The spontaneous droplet ejection phenomena (auto-ejection) is reviewed and demonstrated on earth as well as aboard the International Space Station. This technique is then applied to novel low-g droplet combustion where soot tube structures are created in the wakes of burning drops. …
Semiconductor Film Grown On A Circular Substrate: Predictive Modeling Of Lattice-Misfit Stresses, Ephraim Suhir, Johann Nicolics, G. Khatibi, M. Lederer
Semiconductor Film Grown On A Circular Substrate: Predictive Modeling Of Lattice-Misfit Stresses, Ephraim Suhir, Johann Nicolics, G. Khatibi, M. Lederer
Mechanical and Materials Engineering Faculty Publications and Presentations
effective and physically meaningful analytical predictive model is developed for the evaluation the lattice-misfit stresses (LMS) in a semiconductor film grown on a circular substrate (wafer). The two-dimensional (plane-stress) theory-of-elasticity approximation (TEA) is employed in the analysis. The addressed stresses include the interfacial shearing stress, responsible for the occurrence and growth of dislocations, as well as for possible delaminations and the cohesive strength of a buffering material, if any. Normal radial and circumferential (tangential) stresses acting in the film cross-sections and responsible for its short- and long-term strength (fracture toughness) are also addressed. The analysis is geared to the GaN …
Structure Functions, Scaling Exponents And Intermittency In The Wake Of A Wind Turbine Array, Naseem Ali, Aleksandr Sergeyevich Aseyev, Raúl Bayoán Cal
Structure Functions, Scaling Exponents And Intermittency In The Wake Of A Wind Turbine Array, Naseem Ali, Aleksandr Sergeyevich Aseyev, Raúl Bayoán Cal
Mechanical and Materials Engineering Faculty Publications and Presentations
Hot-wire measurements obtained in a 3 × 3 wind turbine array boundary layer are utilized to analyze high order structure functions, intermittency effects as well as the probability density functions of velocity increments at different scales within the energy cascade. The intermittency exponent is found to be greater in the far-wake region in comparison with the near-wake. At hub height, the intermittency exponent is found to be null. Extended self-similarity scaling exponents of the second, fourth, and fifth order structure functions remain relatively constant as a function of height in the far-wake; whereas in the near-wake, these are highly affected …
Complex Capillary Fluidic Phenomena For Passive Control Of Liquids In Low-Gravity Environments, Logan Torres
Complex Capillary Fluidic Phenomena For Passive Control Of Liquids In Low-Gravity Environments, Logan Torres
Undergraduate Research & Mentoring Program
In an effort to further apply the recent results of puddle jumping research, we seek to expand the oblique droplet impact studies of others by exploiting large liquid droplets in the near weightless environment of a drop tower. By using the spontaneous puddle jump mechanism, droplets of volumes 1 mL ≤ V ≤ 3 mL with corresponding Weber numbers of We ≈ 1 are impinged on surfaces inclined in the range 40° ≤ α ≤ 80° (measured from the horizontal plane). Impact surface wetting characteristics exhibit static contact angles θstatic = 165 ± 5°. All impacts result in complete rebound. …
Quantum Yield Optimization For Semiconductor Photocatalysis Systems, Ryan Catabay
Quantum Yield Optimization For Semiconductor Photocatalysis Systems, Ryan Catabay
Undergraduate Research & Mentoring Program
The utilization of photocatalysis has a well-known potential for mineralizing organic contaminants in water purification processes. A continuous flow photocatalytic reactor was developed in order to test the quantum yield of titanium dioxide, a semiconductor material well known for its photocatalytic properties. In order to build this reactor, multiple manufacturing methods were performed: manual and CNC machining, laser cutting, waterjet cutting, and chemical synthesis. A continuous flow reactor was particularly designed for a controlled, variable radiant flux of ultraviolet light. This continuous UV radiation excites the photocatalyst, generating electron hole pairs that form hydroxyl radicals, which in turn mineralize organic …
Design For Fractal Grid Generated Turbulence, Moira Gion
Design For Fractal Grid Generated Turbulence, Moira Gion
Undergraduate Research & Mentoring Program
Fractal geometry can be used to find organization or order in something that appears to be in disorder, or chaos. Turbulence is viewed as one place where fractal geometry can be found in nature. The irregularity in fluid flow is dependent on the initial conditions. In the past, the idea of self-similarity has been used to develop statistical theories of energy cascade in a turbulent flow. Recent studies have done experiments on obstructing flows with fractal objects to observe intermittency, (or self-similarity) within a turbulent flow. Experiments on fractal grid generated turbulence has been performed by other research groups, so …
Engineered Mushing Cooker, Aimee Ritter
Engineered Mushing Cooker, Aimee Ritter
Undergraduate Research & Mentoring Program
This project revolves around building methanol cookers for dog mushers in the Iditarod and for the Denali Park Ranger Kennel in Denali National Park, Alaska. Traditional cookers are bulky, slow to burn, and use up a lot of fuel. Our goal has been to revolutionize the way mushing cookers look and perform. Our cookers are built to pack well in the sleds, heat up to 3 gallons of snowmelt, perform in arctic climates, use methanol (specifically HEET) for fuel, and be lightweight. A traditional cooker would use 3 to 4 bottles or more of HEET (36-48+oz.) and take at least …
Real-Time Monitoring Of Personal Exposures To Carbon Dioxide, Elliott T. Gall, Toby Cheung, Irvan Luhung, Stefano Schiavon, William W. Nazaroff
Real-Time Monitoring Of Personal Exposures To Carbon Dioxide, Elliott T. Gall, Toby Cheung, Irvan Luhung, Stefano Schiavon, William W. Nazaroff
Mechanical and Materials Engineering Faculty Publications and Presentations
Elevated indoor CO2 levels are indicative of insufficient ventilation in occupied spaces and correlate with elevated concentrations of pollutants of indoor origin. Adverse health and well-being outcomes associated with elevated indoor CO2 levels are based on CO2 as a proxy, although some emerging evidence suggests CO2 itself may impact human cognition. Using portable monitors, we conducted an exposure study with 16 subjects in Singapore to understand the levels, dynamics and influencing factors of personal exposure to CO2. Participants carried a CO2 monitor continuously for 7-day periods recording their exposure levels at 1-min intervals. …
Comparative Estimates Of Anthropogenic Heat Emission In Relation To Surface Energy Balance Of A Subtropical Urban Neighborhood, Changhyoun Park, Gunnar W. Schade, Nicholas D. Werner, David J. Sailor, Cheolhee Kim
Comparative Estimates Of Anthropogenic Heat Emission In Relation To Surface Energy Balance Of A Subtropical Urban Neighborhood, Changhyoun Park, Gunnar W. Schade, Nicholas D. Werner, David J. Sailor, Cheolhee Kim
Mechanical and Materials Engineering Faculty Publications and Presentations
Long-term eddy covariance measurements have been conducted in a subtropical urban area, an older neighborhood north of downtown Houston. The measured net radiation (Q*), sensible heat flux (H) and latent heat flux (LE) showed typical seasonal diurnal variations in urban areas: highest in summer; lowest in winter. From an analysis of a subset of the first two years of measurements, we find that approximately 42% of Q* is converted into H, and 22% into LE during daytime. The local anthropogenic heat emissions were estimated conventionally using the long-term residual method and the heat emission inventory approach. We also …
Effect Of Nano-Oxide Particle Size On Radiation Resistance Of Ironechromium Alloys, Weizong Xu, Lulu Li, James A. Valdez, Mostafa Saber, Yuntian Zhu, Carl C. Koch, Ronald O. Scattergood
Effect Of Nano-Oxide Particle Size On Radiation Resistance Of Ironechromium Alloys, Weizong Xu, Lulu Li, James A. Valdez, Mostafa Saber, Yuntian Zhu, Carl C. Koch, Ronald O. Scattergood
Mechanical and Materials Engineering Faculty Publications and Presentations
Radiation resistance of Fe-14Cr alloys under 200 keV He irradiation at 500 *C was systematically investigated with varying sizes of nano oxide Zr, Hf and Cr particles. It is found that these nano oxide particles acted as effective sites for He bubble formation. By statistically analyzing 700-1500 He bubbles at the depth of about 150-700 nm from a series of HRTEM images for each sample, we established the variation of average He bubble size, He bubble density, and swelling percentage along the depth, and found them to be consistent with the He concentration profile calculated from the SIRM program. Oxide …
Ozone Reaction With Interior Building Materials: Influence Of Diurnal Ozone Variation, Temperature And Humidity, Donghyun Rim, Elliott T. Gall, Randy L. Maddalena, William W. Nazaroff
Ozone Reaction With Interior Building Materials: Influence Of Diurnal Ozone Variation, Temperature And Humidity, Donghyun Rim, Elliott T. Gall, Randy L. Maddalena, William W. Nazaroff
Mechanical and Materials Engineering Faculty Publications and Presentations
Elevated tropospheric ozone concentrations are associated with increased morbidity and mortality. Indoor ozone chemistry affects human exposure to ozone and reaction products that also may adversely affect health and comfort. Reactive uptake of ozone has been characterized for many building materials; however, scant information is available on how diurnal variation of ambient ozone influences ozone reaction with indoor surfaces. The primary objective of this study is to investigate ozone-surface reactions in response to a diurnally varying ozone exposure for three common building materials: ceiling tile, painted drywall, and carpet tile. A secondary objective is to examine the effects of air …
Long-Term Stability Of 14yt-4sc Alloy At High Temperature, Lulu Li, Weizong Xu, Mostafa Saber, Yuntian Zhu, Carl C. Koch, Ronald O. Scattergood
Long-Term Stability Of 14yt-4sc Alloy At High Temperature, Lulu Li, Weizong Xu, Mostafa Saber, Yuntian Zhu, Carl C. Koch, Ronald O. Scattergood
Mechanical and Materials Engineering Faculty Publications and Presentations
14YT alloy (Fe-14Cr-0.25wt.%Y2O3-0.4wt.%Ti) with 4 at.% Sc addition was previously reported to exhibit a nanoscale microstructure and high strength when annealed at temperatures up to 1000 °C (0.65Tm) for 1 hour. Here we report that the microstructure and mechanical behavior of 14YT-4Sc alloy after long-term annealing for up to 60 hours at 1000 °C. FIB analysis shows abnormal grain growth with annealing time, while a large fraction of the matrix still consists of nanoscale grains. TEM images reveal a slight growth of nano grains, with estimated grain growth exponent, n, to be 0.29. Sc-Ti-Y-O enriched nano oxide particles (nm) were …
Development Of A National Anthropogenic Heating Database With An Extrapolation For International Cities, David J. Sailor, Matei Georgescu, Jeffrey M. Milne, Melissa A. Hart
Development Of A National Anthropogenic Heating Database With An Extrapolation For International Cities, David J. Sailor, Matei Georgescu, Jeffrey M. Milne, Melissa A. Hart
Mechanical and Materials Engineering Faculty Publications and Presentations
Given increasing utility of numerical models to examine urban impacts on meteorology and climate, there exists an urgent need for accurate representation of seasonally and diurnally varying anthropogenic heating data, an important component of the urban energy budget for cities across the world. Incorporation of anthropogenic heating data as inputs to existing climate modeling systems has direct societal implications ranging from improved prediction of energy demand to health assessment, but such data are lacking for most cities. To address this deficiency we have applied a standardized procedure to develop a national database of seasonally and diurnally varying anthropogenic heating profiles …
Capillary Channel Flow (Ccf) Eu2-02 On The International Space Station (Iss): An Experimental Investigation Of Passive Bubble Separations In An Open Capillary Channel, Mark M. Weislogel, Andrew P. Wollman, Ryan M. Jenson, John T. Geile, John F. Tucker, Brentley M. Wiles, Andy L. Trattner, Claire Devoe, Lauren M. Sharp, Peter J. Canfield, Jörg Klatte, Michael E. Dreyer
Capillary Channel Flow (Ccf) Eu2-02 On The International Space Station (Iss): An Experimental Investigation Of Passive Bubble Separations In An Open Capillary Channel, Mark M. Weislogel, Andrew P. Wollman, Ryan M. Jenson, John T. Geile, John F. Tucker, Brentley M. Wiles, Andy L. Trattner, Claire Devoe, Lauren M. Sharp, Peter J. Canfield, Jörg Klatte, Michael E. Dreyer
Mechanical and Materials Engineering Faculty Publications and Presentations
It would be signicantly easier to design fluid systems for spacecraft if the fluid phases behaved similarly to those on earth. In this research an open 15:8 degree wedge-sectioned channel is employed to separate bubbles from a two-phase flow in a microgravity environment. The bubbles appear to rise in the channel and coalesce with the free surface in much the same way as would bubbles in a terrestrial environment, only the combined effects of surface tension, wetting, and conduit geometry replace the role of buoyancy. The host liquid is drawn along the channel by a pump and noncondensible gas bubbles …
Anisotropy Of The Reynolds Stress Tensor In The Wakes Of Wind Turbine Arrays In Cartesian Arrangements With Counter-Rotating Rotors, Nicholas Hamilton, Raúl Bayoán Cal
Anisotropy Of The Reynolds Stress Tensor In The Wakes Of Wind Turbine Arrays In Cartesian Arrangements With Counter-Rotating Rotors, Nicholas Hamilton, Raúl Bayoán Cal
Mechanical and Materials Engineering Faculty Publications and Presentations
A 4 × 3 wind turbine array in a Cartesian arrangement was constructed in a wind tunnel setting with four configurations based on the rotational sense of the rotor blades. The fourth row of devices is considered to be in the fully developed turbine canopy for a Cartesian arrangement. Measurements of the flow field were made with stereo particle-image velocimetry immediately upstream and downstream of the selected model turbines. Rotational sense of the turbine blades is evident in the mean spanwise velocity W and the Reynolds shear stress −vw. The flux of kinetic energy is shown to be of greater …
Phase Transitions And In Situ Dynamics Of Crystal Grain Formation Of Alumina Nanotubes Templated By Vertically Aligned Carbon Nanotubes, L. F. Lampert, A. Barnum, S. W. Smith, J. F. Conley, Jun Jiao
Phase Transitions And In Situ Dynamics Of Crystal Grain Formation Of Alumina Nanotubes Templated By Vertically Aligned Carbon Nanotubes, L. F. Lampert, A. Barnum, S. W. Smith, J. F. Conley, Jun Jiao
Mechanical and Materials Engineering Faculty Publications and Presentations
Phase transitions of amorphous alumina (a-alumina) nanotubes grown by atomic layer deposition and templated by carbon nanotubes were investigated with thermal annealing, transmitted Kikuchi electron diffraction, electron-irradiation-induced crystallization, X-ray diffraction, and X-ray photoelectron spectroscopy. The resulting, engineered alumina nanotube arrays demonstrate a large range of tunable phases that are vital for understanding how alumina nanotube arrays can be applied for uses within biotechnology, catalysis, and other academic and industrial uses.
Thermodynamic Grain Size Stabilization Models: An Overview, Mostafa Saber, Carl C. Koch, Ronald O. Scattergood
Thermodynamic Grain Size Stabilization Models: An Overview, Mostafa Saber, Carl C. Koch, Ronald O. Scattergood
Mechanical and Materials Engineering Faculty Publications and Presentations
Grain boundaries in a nanocrystalline microstructure produce an increase in the excess free energy of the system. Grain growth is a consequence of the thermodynamic driving force reducing this excess. Thermodynamic stabilization is an approach based on eliminating the driving force by suitable alloy additions that can produce a metastable equilibrium state at the nanoscale grain size, as opposed to kinetic stabilization where the grain growth mobility is restricted by pinning and/or drag mechanisms. The present paper reviews and compares various models proposed for thermodynamic stabilization.
Estimation Of Transient Temperature Distribution During Quenching, Via A Parabolic Model, Diego E. Lozano, Gabriela Martinez-Solis, Rafael David Mercado-Solis, Rafael Colás, George E. Totten
Estimation Of Transient Temperature Distribution During Quenching, Via A Parabolic Model, Diego E. Lozano, Gabriela Martinez-Solis, Rafael David Mercado-Solis, Rafael Colás, George E. Totten
Mechanical and Materials Engineering Faculty Publications and Presentations
A material-independent model to estimate the transient temperature distribution in a test probe quenched by immersion is presented in this study. This model is based on the assumption that, under one-dimensional unsteady heat conduction, the radial temperature distribution at the end of an interval belongs to the equation of a parabola. The model was validated using AISI 304 stainless steel test probes (Φ8×40 mm and Φ12×60 mm) quenched from 850 to 900 °C in water and in water-based NaNO2 solutions at 25 °C and in canola oil at 50 °C. Additionally, square test probes (20×20×100 mm) were quenched from 550 …
A Regression Approach For Estimation Of Anthropogenic Heat Flux Based On A Bottom-Up Air Pollutant Emission Database, Sanghyun Lee, Stuart A. Mckeen, David J. Sailor
A Regression Approach For Estimation Of Anthropogenic Heat Flux Based On A Bottom-Up Air Pollutant Emission Database, Sanghyun Lee, Stuart A. Mckeen, David J. Sailor
Mechanical and Materials Engineering Faculty Publications and Presentations
A statistical regression method is presented for estimating hourly anthropogenic heat flux (AHF) using an anthropogenic pollutant emission inventory for use in mesoscale meteorological and air-quality modeling. Based on bottom-up AHF estimated from detailed energy consumption data and anthropogenic pollutant emissions of carbon monoxide (CO) and nitrogen oxides (NOx) in the US National Emission Inventory year 2005 (NEI-2005), a robust regression relation between the AHF and the pollutant emissions is obtained for Houston. This relation is a combination of two power functions (Y = aXb) relating CO and NOx emissions to AHF, giving a determinant …
Passive Phase Separation Of Microgravity Bubbly Flows Using Conduit Geometry, Ryan M. Jenson, Andrew Paul Wollman, Mark M. Weislogel, Lauren Sharp, Robert Green, Peter J. Canfield, Jörg Klatte, Michael E. Dreyer
Passive Phase Separation Of Microgravity Bubbly Flows Using Conduit Geometry, Ryan M. Jenson, Andrew Paul Wollman, Mark M. Weislogel, Lauren Sharp, Robert Green, Peter J. Canfield, Jörg Klatte, Michael E. Dreyer
Mechanical and Materials Engineering Faculty Publications and Presentations
The ability to separate liquid and gas phases in the absence of a gravitational acceleration has proven a challenge to engineers since the inception of space exploration. Due to our singular experience with terrestrial systems, artificial body forces are often imparted in multiphase fluid systems aboard spacecraft to reproduce the buoyancy effect. This approach tends to be inefficient, adding complexity, resources, and failure modes. Ever present in multiphase phenomena, the forces of surface tension can be exploited to aid passive phase separations where performance characteristics are determined solely by geometric design and system wettability. Said systems may be readily designed …
Local Vibrational Modes Competitions In Mn-Doped Zno Epitaxial Films With Tunable Ferromagnetism, Qiang Cao, Maoxiang Fu, Guolei Liu, Huaijin Zhang, Shishen Yan, Yanxue Chen, Liangmo Mei, Jun Jiao
Local Vibrational Modes Competitions In Mn-Doped Zno Epitaxial Films With Tunable Ferromagnetism, Qiang Cao, Maoxiang Fu, Guolei Liu, Huaijin Zhang, Shishen Yan, Yanxue Chen, Liangmo Mei, Jun Jiao
Mechanical and Materials Engineering Faculty Publications and Presentations
We reported spectroscopic investigations of high quality Mn-doped ZnO (ZnMnO) films grown by oxygen plasma-assisted molecular beam epitaxy. Raman scattering spectra revealed two local vibrational modes (LVMs) associated with Mn dopants at 523 and 712cm-1. The LVMs and magnetic properties of ZnMnO films can be synchronously modulated by post annealing processing or by introducing tiny Co. The relative intensity of two LVMs clearly shows competitions arising from uncompensated acceptor and donor defects competition for ferromagnetic and nonmagnetic films. The experimental results indicated that LVM at 523 cm-1 is attributed to Mn—(Zinc-vacancy) complexes, while LVM at 712 cm …
Zno Nanosheet Arrays Constructed On Weaved Titanium Wire For Cds-Sensitized Solar Cells, Cuncun Wu, Lin Wei, Yitan Li, Chang Liu, Jun Jiao, Yanxue Chen, Liangmo Mei
Zno Nanosheet Arrays Constructed On Weaved Titanium Wire For Cds-Sensitized Solar Cells, Cuncun Wu, Lin Wei, Yitan Li, Chang Liu, Jun Jiao, Yanxue Chen, Liangmo Mei
Mechanical and Materials Engineering Faculty Publications and Presentations
Ordered ZnO nanosheet arrays were grown on weaved titanium wires by a low-temperature hydrothermal method. CdS nanoparticles were deposited onto the ZnO nanosheet arrays using the successive ionic layer adsorption and reaction method to make a photoanode. Nanoparticle-sensitized solar cells were assembled using these CdS/ZnO nanostructured photoanodes, and their photovoltaic performance was studied systematically. The best light-to-electricity conversion efficiency was obtained to be 2.17% under 100 mW/cm/cm2 illumination, and a remarkable shortcircuit photocurrent density of approximately 20.1 mA/cm2 was recorded, which could attribute to the relatively direct pathways for transportation of electrons provided by ZnO nanosheet arrays as …
Cds Quantum Dot-Sensitized Solar Cells Based On Nano-Branched Tio2 Arrays, Chang Liu, Yitan Li, Lin Wei, Cuncun Wu, Yanxue Chen, Liangmo Mei, Jun Jiao
Cds Quantum Dot-Sensitized Solar Cells Based On Nano-Branched Tio2 Arrays, Chang Liu, Yitan Li, Lin Wei, Cuncun Wu, Yanxue Chen, Liangmo Mei, Jun Jiao
Mechanical and Materials Engineering Faculty Publications and Presentations
Nano-branched rutile TiO2 nanorod arrays were grown on F:SnO2 conductive glass (FTO) by a facile, two-step wet chemical synthesis process at low temperature. The length of the nanobranches was tailored by controlling the growth time, after which CdS quantum dots were deposited on the nano-branched TiO2 arrays using the successive ionic layer adsorption and reaction method to make a photoanode for quantum dot-sensitized solar cells (QDSCs). The photovoltaic properties of the CdS-sensitized nano-branched TiO2 solar cells were studied systematically. A short-circuit current intensity of approximately 7 mA/cm2 and a light-to-electricity conversion efficiency of 0.95% were recorded for cells based on …
Zno Nanoneedle/H2o Solid-Liquid Heterojunction-Based Self-Powered Ultraviolet Detector, Qinghao Li, Lin Wei, Yanru Xie, Kai Zhang, Lei Liu, Dapeng Zhu, Jun Jiao, Yanxue Chen, Shishen Yan, Guolei Liu, Liangmo Mei
Zno Nanoneedle/H2o Solid-Liquid Heterojunction-Based Self-Powered Ultraviolet Detector, Qinghao Li, Lin Wei, Yanru Xie, Kai Zhang, Lei Liu, Dapeng Zhu, Jun Jiao, Yanxue Chen, Shishen Yan, Guolei Liu, Liangmo Mei
Physics Faculty Publications and Presentations
ZnO nanoneedle arrays were grown vertically on a fluorine-doped tin oxide-coated glass by hydrothermal method at a relatively low temperature. A self-powered photoelectrochemical cell-type UV detector was fabricated using the ZnO nanoneedles as the active photoanode and H2O as the electrolyte. This solid-liquid heterojunction offers an enlarged ZnO/water contact area and a direct pathway for electron transport simultaneously. By connecting this UV photodetector to an ammeter, the intensity of UV light can be quantified using the output short-circuit photocurrent without a power source. High photosensitivity, excellent spectral selectivity, and fast photoresponse at zero bias are observed in this UV detector. …
Remotely Accessible Instrumented Monitoring Of Global Development Programs: Technology Development And Validation, Evan A. Thomas, Zdenek Zumr, Jodi Graf, Carson A. Wick, James H. Mccellan, Zachary Imam, Christina Barstow, Kelly Spiller, Michael Fleming
Remotely Accessible Instrumented Monitoring Of Global Development Programs: Technology Development And Validation, Evan A. Thomas, Zdenek Zumr, Jodi Graf, Carson A. Wick, James H. Mccellan, Zachary Imam, Christina Barstow, Kelly Spiller, Michael Fleming
Mechanical and Materials Engineering Faculty Publications and Presentations
Many global development agencies self-report their project outcomes, often relying on subjective data that is collected sporadically and communicated months later. These reports often highlight successes and downplay challenges. Instrumented monitoring via distributed data collection platforms may provide crucial evidence to help inform the sector and public on the effectiveness of aid, and the on-going challenges. This paper presents the process of designing and validating an integrated sensor platform with cellular-to-internet reporting purposely targeted at global development programs. The integrated hardware platform has been applied to water, sanitation, energy and infrastructure interventions and validated through laboratory calibration and field observations. …
Energy And Climate Interactions In The Urban Environment, David J. Sailor
Energy And Climate Interactions In The Urban Environment, David J. Sailor
Mechanical and Materials Engineering Faculty Publications and Presentations
This presentation focuses on sustainable design choices and characteristics