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Articles 1 - 22 of 22
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Investigating Co2 Removal By Ca- And Mg-Based Sorbents With Application To Indoor Air Treatment, Elliott T. Gall, Cem Sonat, William W. Nazaroff, Cise Unluer
Investigating Co2 Removal By Ca- And Mg-Based Sorbents With Application To Indoor Air Treatment, Elliott T. Gall, Cem Sonat, William W. Nazaroff, Cise Unluer
Mechanical and Materials Engineering Faculty Publications and Presentations
Indoor carbon dioxide (CO 2 ) levels serve as an indicator of ventilation sufficiency in relation to metabolic effluents. Recent evidence suggests that elevated CO 2 exposure (with or without other bioeffluents) may cause adverse cognitive effects. In shelter-in-place (SIP) facilities, indoor CO 2 levels may become particularly elevated. This study evaluates four low-cost alkaline earth metal oxides and hydroxides as CO 2 sorbents for potential use in indoor air cleaning applications. Sorbents studied were MgO, Mg(OH) 2 , Ca(OH) 2 and commercially available soda lime. Uncarbonated sorbents characterized with nitrogen adsorption porosimetry showed BET surface areas in the 5.6–27 …
Focused-Based Multifractal Analysis Of The Wake In A Wind Turbine Array Utilizing Proper Orthogonal Decomposition, Naseem Ali, Hawwa Falih Kadum, Raúl Bayoán Cal
Focused-Based Multifractal Analysis Of The Wake In A Wind Turbine Array Utilizing Proper Orthogonal Decomposition, Naseem Ali, Hawwa Falih Kadum, Raúl Bayoán Cal
Mechanical and Materials Engineering Faculty Publications and Presentations
Hot-wire anemometry measurements have been performed in a 3×3 wind turbine array to study the multifractality of the turbulent kinetic energy dissipation. A multifractal spectrum and Hurst exponents are determined at nine locations downstream of the hub height, bottom and top tips. Higher multifractality is found at 0.5D and 1D downstream of the bottom tip and hub height. The second order of the Hurst exponent and combination factor shows the ability to predict the flow state in terms of its development. Snapshot proper orthogonal decomposition (POD) is used to identify the coherent and incoherent structures and to reconstruct the stochastic …
Comparing Sanitation Delivery Modalities In Urban Informal Settlement Schools: A Randomized Trial In Nairobi, Kenya, Kate Bohnert, Anna N. Chard, Alex Mwaki, Amy E., Kirby, Richard Muga, Corey L. Nagel, Evan A. Thomas, Matthew C. Freeman
Comparing Sanitation Delivery Modalities In Urban Informal Settlement Schools: A Randomized Trial In Nairobi, Kenya, Kate Bohnert, Anna N. Chard, Alex Mwaki, Amy E., Kirby, Richard Muga, Corey L. Nagel, Evan A. Thomas, Matthew C. Freeman
Mechanical and Materials Engineering Faculty Publications and Presentations
The provision of safely managed sanitation in informal settlements is a challenge, especially in schools that require durable, clean, sex-segregated facilities for a large number of children. In informal settlements in Nairobi, school sanitation facilities demand considerable capital costs, yet are prone to breakage and often unhygienic. The private sector may be able to provide quality facilities and services to schools at lower costs as an alternative to the sanitation that is traditionally provided by the government. We conducted a randomized trial comparing private sector service delivery (PSSD) of urine-diverting dry latrines with routine waste collection and maintenance and government …
Bioaerosol Deposition On An Air-Conditioning Cooling Coil, Yan Wu, Ailu Chen, Irvan Luhung, Elliott T. Gall, Qingliang Cao, Victor Wei-Chung Chang, William W. Nazaroff
Bioaerosol Deposition On An Air-Conditioning Cooling Coil, Yan Wu, Ailu Chen, Irvan Luhung, Elliott T. Gall, Qingliang Cao, Victor Wei-Chung Chang, William W. Nazaroff
Mechanical and Materials Engineering Faculty Publications and Presentations
This study is concerned with the role of a fin-and-tube heat exchanger in modifying microbial indoor air quality. Specifically, depositional losses of ambient bioaerosols and particles onto dry (not cooled) and wet (cool) coil surfaces were measured for different airspeeds passing through the test coil. Total, bacterial and fungal DNA concentrations in condensate water produced by a wet coil were also quantified by means of fluorescent dsDNA-binding dye and qPCR assays. Results revealed that the deposition of bioaerosols and total particles is substantial on coil surfaces, especially when wet and cool. The average deposition fraction was 0.14 for total DNA, …
Distribution Of Mean Kinetic Energy Around An Isolated Wind Turbine And A Characteristic Wind Turbine Of A Very Large Wind Farm, Gerard Cortina, Marc Calaf, Raul Bayoan Cal
Distribution Of Mean Kinetic Energy Around An Isolated Wind Turbine And A Characteristic Wind Turbine Of A Very Large Wind Farm, Gerard Cortina, Marc Calaf, Raul Bayoan Cal
Mechanical and Materials Engineering Faculty Publications and Presentations
An isolated wind turbine and a very large wind farm are introduced into large-eddy simulations of an atmospheric boundary layer. The atmospheric flow is forced with a constant geostrophic wind and a time-varying surface temperature extracted from a selected period of the CASES-99 field experiment. A control volume approach is used to directly compare the transfer of mean kinetic energy around a characteristic wind turbine throughout a diurnal cycle considering both scenarios. For the very large wind farm case, results illustrate that the recovery of mean kinetic energy around a wind turbine is dominated by the vertical flux, regardless of …
Effect Of Fiber Material On Ozone Removal And Carbonyl Production From Carpets, Omed A. Abbass, David J. Sailor, Elliott T. Gall
Effect Of Fiber Material On Ozone Removal And Carbonyl Production From Carpets, Omed A. Abbass, David J. Sailor, Elliott T. Gall
Mechanical and Materials Engineering Faculty Publications and Presentations
Indoor air quality is affected by indoor materials such as carpets that may act as sources and/or sinks of gas-phase air pollutants. Heterogeneous reactions of ozone with carpets may result in potentially harmful products. In this study, indoor residential carpets of varying fiber types were tested to evaluate their ability to remove ozone, and to assess their role in the production of carbonyls when exposed to elevated levels of ozone. Tests were conducted with six types of new unused carpets. Two sets of experiments were conducted, the first measured ozone removal and ozone deposition velocities, and the second measured primary …
Puddle Jumping: Spontaneous Ejection Of Large Liquid Droplets From Hydrophobic Surfaces During Drop Tower Tests, Babek Attari, Mark M. Weislogel, Andrew Paul Wollman, Yongkang Chen, Trevor Snyder
Puddle Jumping: Spontaneous Ejection Of Large Liquid Droplets From Hydrophobic Surfaces During Drop Tower Tests, Babek Attari, Mark M. Weislogel, Andrew Paul Wollman, Yongkang Chen, Trevor Snyder
Mechanical and Materials Engineering Faculty Publications and Presentations
Large droplets and puddles jump spontaneously from sufficiently hydrophobicsurfaces during routine drop tower tests. The simple low-cost passive mechanism can in turn be used as an experimental device to investigate dynamic droplet phenomena for drops up to 104 times larger than their normal terrestrial counterparts. We provide and/or confirm quick and qualitative design guides for such “drop shooters” as employed in drop tower tests including relationships to predict droplet ejection durations and velocities as functions of drop volume, surface texture, surface contour, wettability pattern, and fluid properties including contact angle. The latter is determined via profile image comparisons with numerical …
Inverse Structure Functions In The Canonical Wind Turbine Array Boundary Layer, Bianca Viggiano, Moira Gion, Naseem Ali, Murat Tutkun, Raúl Bayoán Cal
Inverse Structure Functions In The Canonical Wind Turbine Array Boundary Layer, Bianca Viggiano, Moira Gion, Naseem Ali, Murat Tutkun, Raúl Bayoán Cal
Mechanical and Materials Engineering Faculty Publications and Presentations
Wind tunnel measurements for a 3×3 canonical wind turbine array boundary layer are obtained using hot-wire anemometer velocity signals. Two downstream locations are considered, referring to the near- and far-wake, and 21 vertical points are acquired per profile. Velocity increments and exit distances are used to quantify inverse structure functions at both downstream locations. Inverse structure functions in the near-wake show a similar profile for the main vertical locations, but diverge as the moment is increased. In the far-wake, inverse structure functions converge toward a single function for all vertical location and moments. The scaling exponents for inverse structure functions …
Minimum Conditions For Visible Mold Growth, G. A. Tsongas, Frank Riordan
Minimum Conditions For Visible Mold Growth, G. A. Tsongas, Frank Riordan
Mechanical and Materials Engineering Faculty Publications and Presentations
Considerable confusion and misunderstanding exists over the conditions required for visible mold growth at a surface in buildings. That is evident in papers and articles authored by engineers and other scientists, including various ASHRAE, ASTM and Canada Mortgage Housing Corporation publications. One of the major problems is that many HVAC engineers, building scientists, practitioners and others believe there exists a single critical value of the relative humidity (RH) of the indoor or ambient air well away from surfaces, below which mold will not grow on surfaces. However, that is not the case. The purpose of this article is to clarify …
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 …
Assessing Latrine Use In Rural India: A Cross-Sectional Study Comparing Reported Use And Passive Latrine Use Monitors, Antara Sinha, Corey L. Nagel, Evan A. Thomas, Wolf P. Schmidt, Belen Torondel, Sophie Boisson, Thomas Clasen
Assessing Latrine Use In Rural India: A Cross-Sectional Study Comparing Reported Use And Passive Latrine Use Monitors, Antara Sinha, Corey L. Nagel, Evan A. Thomas, Wolf P. Schmidt, Belen Torondel, Sophie Boisson, Thomas Clasen
Mechanical and Materials Engineering Faculty Publications and Presentations
Although large-scale programs, like India's Total Sanitation Campaign (TSC), have improved latrine coverage in rural settings, evidence suggests that actual use is suboptimal. However, the reliability of methods to assess latrine use is uncertain. We assessed the reliability of reported use, the standard method, by comparing survey-based responses against passive latrine use monitors (PLUMs) through a cross-sectional study among 292 households in 25 villages in rural Odisha, India, which recently received individual household latrines under the TSC. PLUMs were installed for 2 weeks and householders responded to surveys about their latrine use behavior. Reported use was compared with PLUM results …
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. …
Predicted Stresses In Ball-Grid-Array (Bga) And Column-Grid-Array (Cga) Interconnections In A Mirror-Like Package Design, Ephraim Suhir, Reza Ghaffarian, Johann Nicolics
Predicted Stresses In Ball-Grid-Array (Bga) And Column-Grid-Array (Cga) Interconnections In A Mirror-Like Package Design, Ephraim Suhir, Reza Ghaffarian, Johann Nicolics
Mechanical and Materials Engineering Faculty Publications and Presentations
There is an obvious incentive for using bow-free (temperature change insensitive) assemblies in various areas of engineering, including electron device and electronic packaging fields. The induced stresses in a bow-free assembly could be, however, rather high, considerably higher than in an assembly, whose bow is not restricted. The simplest and trivial case of a bow-free assembly is a tri-component body, in which the inner component is sandwiched between two identical outer components (“mirror” structure), is addressed in our analysis, and a simple and physically meaningful analytical stress model is suggested. It is concluded that if acceptable stresses (below yield stress …
Dynamic Stall Of An Experimental Wind Turbine Blade, Matthew Scott Melius, Raúl Bayoán Cal, Karen Mulleners
Dynamic Stall Of An Experimental Wind Turbine Blade, Matthew Scott Melius, Raúl Bayoán Cal, Karen Mulleners
Mechanical and Materials Engineering Faculty Publications and Presentations
To understand the complex flow phenomena over wind turbine blades during stall development, a scaled three-dimensional non-rotating blade model is designed to be dynamically similar to a rotating full-scale NREL 5 MW wind turbine blade. A time-resolved particle imagevelocimetry(PIV) investigation of flowbehavior during the stall cycle examines the processes of stall development and flow reattachment. Proper orthogonal decomposition (POD) and vortex detection techniques are applied to the PIV fields to quantify relevant flow characteristics such as vortex size, separation angle, and separation point throughout a dynamic pitching cycle. The behavior of the POD coefficients provides time scales for the transitional …
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 …
Micrometeorological Simulations To Predict The Impacts Of Heat Mitigation Strategies On Pedestrian Thermal Comfort In A Los Angeles Neighborhood, Mohammad Taleghani, David J. Sailor, George A. Ban-Weiss
Micrometeorological Simulations To Predict The Impacts Of Heat Mitigation Strategies On Pedestrian Thermal Comfort In A Los Angeles Neighborhood, Mohammad Taleghani, David J. Sailor, George A. Ban-Weiss
Mechanical and Materials Engineering Faculty Publications and Presentations
The urban heat island impacts the thermal comfort of pedestrians in cities. In this paper, the effects of four heat mitigation strategies on micrometeorology and the thermal comfort of pedestrians were simulated for a neighborhood in eastern Los Angeles County. The strategies investigated include solar reflective ‘cool roofs’, vegetative ‘green roofs’, solar reflective ‘cool pavements’, and increased streetlevel trees. Aseries of micrometeorological simulations for an extreme heat day were carried out assuming widespread adoption of each mitigation strategy. Comparing each simulation to the control simulation assuming current land cover for the neighborhood showed that additional street-trees and cool pavements reduced …
Evaluation Of Nitrous Acid Sources And Sinks In Urban Outflow, Elliott T. Gall, Robert J. Griffin, Allison L. Steiner, Jack Dibb, Eric Scheuer, Longwen Gong, Andrew P. Rutter, Basak K. Cevik, Saewung Kim, Barry Lefer, James Flynn
Evaluation Of Nitrous Acid Sources And Sinks In Urban Outflow, Elliott T. Gall, Robert J. Griffin, Allison L. Steiner, Jack Dibb, Eric Scheuer, Longwen Gong, Andrew P. Rutter, Basak K. Cevik, Saewung Kim, Barry Lefer, James Flynn
Mechanical and Materials Engineering Faculty Publications and Presentations
Intensive air quality measurements made from June 22–25, 2011 in the outflow of the Dallas–Fort Worth (DFW) metropolitan area are used to evaluate nitrous acid (HONO) sources and sinks. A two-layer box model was developed to assess the ability of established and recently identified HONO sources and sinks to reproduce observations of HONO mixing ratios. A baseline model scenario includes sources and sinks established in the literature and is compared to scenarios including three recently identified sources: volatile organic compound-mediated conversion of nitric acid to HONO (S1), biotic emission from the ground (S2), and re-emission from a surface nitrite reservoir …
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. …