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Articles 1 - 30 of 14292

Full-Text Articles in Physical Sciences and Mathematics

Stomatal Conductance Measurement For Toxicity Assessment In Zero-Effluent Constructed Wetlands: Effects Of Landfill Leachate On Hydrophytes, Andrzej Białowiec, Jacek A. Koziel, Piotr Manczarski Feb 2019

Stomatal Conductance Measurement For Toxicity Assessment In Zero-Effluent Constructed Wetlands: Effects Of Landfill Leachate On Hydrophytes, Andrzej Białowiec, Jacek A. Koziel, Piotr Manczarski

Agricultural and Biosystems Engineering Publications

In this research, we explore for the first time the use of leaf stomatal conductance (gs) for phytotoxicity assessment. Plants respond to stress by regulating transpiration. Transpiration can be correlated with stomatal conductance when the water vapor pressure gradient for transpiration is constant. Thus, our working hypothesis was that the gs measurement could be a useful indicator of the effect of toxic compounds on plants. This lab-scale study aimed to test the measurement of gs as a phytotoxicity indicator. Our model plants were two common hydrophytes used in zero-effluent constructed wetlands for treating landfill leachate. The toxic influence of two ...


Modeling Solid-Phase Microextraction Of Volatile Organic Compounds By Porous Coatings Using Finite Element Analysis, Bulat Kenessov, Miras Derbissalin, Jacek A. Koziel, Dmitry S. Kosyakov Jan 2019

Modeling Solid-Phase Microextraction Of Volatile Organic Compounds By Porous Coatings Using Finite Element Analysis, Bulat Kenessov, Miras Derbissalin, Jacek A. Koziel, Dmitry S. Kosyakov

Agricultural and Biosystems Engineering Publications

Experimental optimization of analytical methods based on solid-phase microextraction (SPME) is a complex and labor-intensive process associated with uncertainties. Using theoretical basics of SPME and finite element analysis software for the optimization proved to be an efficient alternative. In this study, an improved finite element analysis-based model for SPME of volatile organic compounds (VOCs) by porous coatings was developed mainly focussing on the mass transport in coatings. Benzene and the Carboxen/polydimethylsiloxane (Car/PDMS) coating were used as the model VOC and a porous SPME coating, respectively. It has been established that in the coating, volumetric fractions of Carboxen, PDMS ...


On The Role Of Composition And Processing Parameters On The Microstructure Evolution Of Ti-Xmo Alloys, Michael Y. Mendoza, Peyman Samimi, David A. Brice, Iman Ghamarian, Matt Rolchigo, Richard Lesar, Peter Collins Jan 2019

On The Role Of Composition And Processing Parameters On The Microstructure Evolution Of Ti-Xmo Alloys, Michael Y. Mendoza, Peyman Samimi, David A. Brice, Iman Ghamarian, Matt Rolchigo, Richard Lesar, Peter Collins

Materials Science and Engineering Publications

Laser Engineered Net Shaping (LENS™) was used to produce a compositionally graded Ti-xMo (0 ≤ x ≤ 12 wt %) specimen and nine Ti-15Mo (fixed composition) specimens at different energy densities to understand the composition–processing–microstructure relationships operating using additive manufacturing. The gradient was used to evaluate the effect of composition on the prior-beta grain size. The specimens deposited using different energy densities were used to assess the processing parameters influence the microstructure evolutions. The gradient specimen did not show beta grain size reduction with the Mo content. The analysis from the perspective of the two grain refinement mechanisms based on a ...


Pre-Methylation Of Lignin To Improve Storage Stability Of Oil Produced By Solvent Liquefaction, Jae-Young Kim, Parinaz Hafezi-Sefat, Sarah D. Cady, Ryan G. Smith, Robert C. Brown Jan 2019

Pre-Methylation Of Lignin To Improve Storage Stability Of Oil Produced By Solvent Liquefaction, Jae-Young Kim, Parinaz Hafezi-Sefat, Sarah D. Cady, Ryan G. Smith, Robert C. Brown

Mechanical Engineering Publications

In this study, we methylated hydroxyl groups (phenolic hydroxyl: Phe-OH and aliphatic hydroxyl: Aliph-OH) in soda lignin (SL) prior to solvent liquefaction to improve storage stability of the resulting oil. We investigated two methylating reagents, dimethyl sulfate (DMS) and dimethyl carbonate (DMC), for selective Phe-OH and total hydroxyl group (Phe-OH and Aliph-OH) blocking. Samples of SL, DMS-SL, and DMC-SL were depolymerized into oils under supercritical ethanol (350 °C). Both methylated lignins produced higher amounts of oils and smaller amounts of char compared to untreated SL due to suppressed charring reactions. Oil produced from SL had relatively higher functional group contents ...


Development Of Time-Weighted Average Sampling Of Odorous Volatile Organic Compounds In Air With Solid-Phase Microextraction Fiber Housed Inside A Gc Glass Liner: Proof Of Concept, Madina Tursumbayeva, Jacek A. Koziel, Devin L. Maurer, Bulat Kenessov, Somchai Rice Jan 2019

Development Of Time-Weighted Average Sampling Of Odorous Volatile Organic Compounds In Air With Solid-Phase Microextraction Fiber Housed Inside A Gc Glass Liner: Proof Of Concept, Madina Tursumbayeva, Jacek A. Koziel, Devin L. Maurer, Bulat Kenessov, Somchai Rice

Agricultural and Biosystems Engineering Publications

Finding farm-proven, robust sampling technologies for measurement of odorous volatile organic compounds (VOCs) and evaluating the mitigation of nuisance emissions continues to be a challenge. The objective of this research was to develop a new method for quantification of odorous VOCs in air using time-weighted average (TWA) sampling. The main goal was to transform a fragile lab-based technology (i.e., solid-phase microextraction, SPME) into a rugged sampler that can be deployed for longer periods in remote locations. The developed method addresses the need to improve conventional TWA SPME that suffers from the influence of the metallic SPME needle on the ...


Enhancing The Co-Utilization Of Biomass-Derived Mixed Sugars By Yeasts, Meirong Gao, Deon Ploessl, Zengyi Shao Jan 2019

Enhancing The Co-Utilization Of Biomass-Derived Mixed Sugars By Yeasts, Meirong Gao, Deon Ploessl, Zengyi Shao

Chemical and Biological Engineering Publications

Plant biomass is a promising carbon source for producing value-added chemicals, including transportation biofuels, polymer precursors, and various additives. Most engineered microbial hosts and a select group of wild-type species can metabolize mixed sugars including oligosaccharides, hexoses, and pentoses that are hydrolyzed from plant biomass. However, most of these microorganisms consume glucose preferentially to non-glucose sugars through mechanisms generally defined as carbon catabolite repression. The current lack of simultaneous mixed-sugar utilization limits achievable titers, yields, and productivities. Therefore, the development of microbial platforms capable of fermenting mixed sugars simultaneously from biomass hydrolysates is essential for economical industry-scale production, particularly for ...


Random Models Of Idempotent Linear Maltsev Conditions. I. Idemprimality, Clifford Bergman, Agnes Szendrei Jan 2019

Random Models Of Idempotent Linear Maltsev Conditions. I. Idemprimality, Clifford Bergman, Agnes Szendrei

Mathematics Publications

We extend a well-known theorem of Murski\v{\i} to the probability space of finite models of a system M of identities of a strong idempotent linear Maltsev condition. We characterize the models of M in a way that can be easily turned into an algorithm for producing random finite models of M, and we prove that under mild restrictions on M, a random finite model of M is almost surely idemprimal. This implies that even if such an M is distinguishable from another idempotent linear Maltsev condition by a finite model A of M, a random search for a ...


High Throughput, Automated Prediction Of Focusing Patterns For Inertial Microfluidics, Aditya Kommajosula, Jeong-Ah Kim, Wonhee Lee, Baskar Ganapathysubramanian Jan 2019

High Throughput, Automated Prediction Of Focusing Patterns For Inertial Microfluidics, Aditya Kommajosula, Jeong-Ah Kim, Wonhee Lee, Baskar Ganapathysubramanian

Mechanical Engineering Publications

Visual inspections for identifying focusing points in inertial microfluidic flows are prone to misinterpreting stable locations and focusing shifts in the case of non-trivial focusing patterns. We develop and deploy an approach for automating the calculation of focusing patterns for a general channel geometry, and thereby reduce the dependence on empirical/visual procedures to confirm the presence of stable locations. We utilize concepts from interpolation theory (to represent continuous force-fields using discrete points), and stability theory to identify "basins of attraction" and quantitatively identify stable equilibrium points. Our computational experiments reveal that predicting equilibrium points accurately requires upto ×10-20 times ...


Notes On The Gridlab-D Household Equivalent Thermal Parameter Model, Leigh Tesfatsion, Swathi Battula Jan 2019

Notes On The Gridlab-D Household Equivalent Thermal Parameter Model, Leigh Tesfatsion, Swathi Battula

Economics Working Papers

GridLab-D (GLD) is an agent-based platform, developed by researchers at Pacific Northwest National Laboratory, that permits users to accurately simulate the state dynamics of power distribution systems at time scales ranging from sub-seconds to years. The purpose of this study is to present, in careful comprehensive form, a complete analytical state-space control representation for a version of the GLD Household Equivalent Thermal Parameter Model as support documentation for model users. This model is a physically-based implementation of a household with multiple price-responsive and conventional appliances whose thermal dynamics are determined over successive days by resident appliance usage and external weather ...


A Latent Spatial Piecewise Exponential Model For Interval-Censored Disease Surveillance Data With Time-Varying Covariates And Misclassification, Yaxuan Sun, Chong Wang, William Q. Meeker, Max Morris, Marisa L. Rotolo, Jeffery Zimmerman Jan 2019

A Latent Spatial Piecewise Exponential Model For Interval-Censored Disease Surveillance Data With Time-Varying Covariates And Misclassification, Yaxuan Sun, Chong Wang, William Q. Meeker, Max Morris, Marisa L. Rotolo, Jeffery Zimmerman

Veterinary Diagnostic and Production Animal Medicine Publications

Understanding the dynamics of disease spread is critical to achieving effective animal disease surveillance. A major challenge in modeling disease spread is the fact that the true disease status cannot be known with certainty due to the imperfect diagnostic sensitivity and specificity of the tests used to generate the disease surveillance data. Other challenges in modeling such data include interval censoring, relating disease spread to distance between units, and incorporating time-varying covariates, which are the unobserved disease statuses. We propose a latent spatial piecewise exponential model (PEX) with misclassification of events to address the challenges in modeling such disease surveillance ...


Effects Of Harvest Time On The Aroma Of White Wines Made From Cold-Hardy Brianna And Frontenac Gris Grapes Using Headspace Solid-Phase Microextraction And Gas Chromatography-Mass Spectrometry-Olfactometry, Somchai Rice, Madina Tursumbayeva, Matthew Clark, David Greenlee, Murlidhar Dharmadhikari, Anne Fennell, Jacek A. Koziel Jan 2019

Effects Of Harvest Time On The Aroma Of White Wines Made From Cold-Hardy Brianna And Frontenac Gris Grapes Using Headspace Solid-Phase Microextraction And Gas Chromatography-Mass Spectrometry-Olfactometry, Somchai Rice, Madina Tursumbayeva, Matthew Clark, David Greenlee, Murlidhar Dharmadhikari, Anne Fennell, Jacek A. Koziel

Agricultural and Biosystems Engineering Publications

The Midwest wine industry has shown a marked increase in growers, hectares planted, wineries, and wine production. This growth coincides with the release of cold-hardy cultivars such as Brianna and Frontenac gris, in 2001 and 2003, respectively. These white grape varieties account for one-third of the total area grown in the state of Iowa. It is generally accepted that the wine aroma profile plays a crucial role in developing a local, sustainable brand. However, the identity of Brianna/Frontenac Gris-based wine aromas and their link to the grape berry chemistry at harvest is unknown. This study aims to preliminarily characterize ...


Metabolic Engineering For Biocatalyst Robustness To Organic Inhibitors, Liam Royce, Laura R. Jarboe Jan 2019

Metabolic Engineering For Biocatalyst Robustness To Organic Inhibitors, Liam Royce, Laura R. Jarboe

Chemical and Biological Engineering Publications

Microbial production of biorenewable fuels and chemicals is often limited by inhibition of the biocatalyst, either by increasing concentrations of the product compound or by contaminant compounds in the biomass‐derived sugars. This inhibition can interfere with economically viable production. Here we discuss typical mechanisms of inhibition and methods for improving biocatalyst robustness. Inhibition often takes the form of inhibition of enzyme activity, depletion of cofactor pools, and membrane damage; methods are discussed for mitigating each of these types of inhibition. Various evolutionary schemes have been developed and implemented on a variety of inhibitory compounds, including butanol, acetic acid, furfural ...


Fish Growth Changes Over Time In A Midwestern Usa Lake, Eric D. Katzenmeyer, Michael E. Colvin, Timothy W. Stewart, Clay L. Pierce, Scott E. Grummer Jan 2019

Fish Growth Changes Over Time In A Midwestern Usa Lake, Eric D. Katzenmeyer, Michael E. Colvin, Timothy W. Stewart, Clay L. Pierce, Scott E. Grummer

Natural Resource Ecology and Management Publications

Growth of Walleye Sander vitreus, Yellow Bass Morone mississippiensis, Common Carp Cyprinus carpio, and Black Bullhead Ameiurus melas was assessed in Clear Lake, Iowa, USA, over several decades and in relation to environmental variables. Growth of Common Carp was positively correlated with phytoplankton concentration. Recent Black Bullhead growth was faster than in the 1950s and 1990s, which may be a consequence of their recent decline in abundance. Growth of Common Carp and Yellow Bass was faster in the 1940s than in more recent time periods. Relative to their entire range, Common Carp first year growth was below average whereas length ...


Collaborative Efforts To Forecast Seasonal Influenza In The United States, 2015–2016, Craig J. Mcgowan, Jarad Niemi, Nehemias Ulloa, Katie Will, Et Al. Jan 2019

Collaborative Efforts To Forecast Seasonal Influenza In The United States, 2015–2016, Craig J. Mcgowan, Jarad Niemi, Nehemias Ulloa, Katie Will, Et Al.

Statistics Publications

Since 2013, the Centers for Disease Control and Prevention (CDC) has hosted an annual influenza season forecasting challenge. The 2015–2016 challenge consisted of weekly probabilistic forecasts of multiple targets, including fourteen models submitted by eleven teams. Forecast skill was evaluated using a modified logarithmic score. We averaged submitted forecasts into a mean ensemble model and compared them against predictions based on historical trends. Forecast skill was highest for seasonal peak intensity and short-term forecasts, while forecast skill for timing of season onset and peak week was generally low. Higher forecast skill was associated with team participation in previous influenza ...


Effect Of (Poly)Electrolytes On The Interfacial Assembly Of Peg Functionalized Gold Nanoparticles, Srikanth Nayak, Max Fieg, Wenjie Wang, Wei Bu, Surya Mallapragada, David Vaknin Jan 2019

Effect Of (Poly)Electrolytes On The Interfacial Assembly Of Peg Functionalized Gold Nanoparticles, Srikanth Nayak, Max Fieg, Wenjie Wang, Wei Bu, Surya Mallapragada, David Vaknin

Chemical and Biological Engineering Publications

We report on the effect of interpolymer complexes (IPCs) of poly(acrylic acid) (PAA) with poly(ethylene glycol) functionalized Au nanoparticles (PEG-AuNPs) as they assemble at the vapor-liquid interface, using surface sensitive synchrotron X-ray scattering techniques. Depending on the suspension pH, PAA functions both as a weak polyelectrolyte and a hydrogen bond donor, and these two roles affect the interfacial assembly of PEG-AuNPs differently. Above its isoelectric point, we find that PAA leads to the formation of a PEG-AuNPs monolayer at the interface with hexagonal structure. In the presence of high concentration of HCl (i.e., below the isoelectric point ...


Planting Date, Hybrid Maturity, And Weather Effects On Maize Yield And Crop Stage, M. E. Baum, S. V. Archontoulis, M. A. Licht Jan 2019

Planting Date, Hybrid Maturity, And Weather Effects On Maize Yield And Crop Stage, M. E. Baum, S. V. Archontoulis, M. A. Licht

Agronomy Publications

Unfavorable weather conditions frequently cause farmers to plant maize (Zea mays L.) outside the optimum planting timeframe. We analyzed maize yield and phenology from a multilocation, year, hybrid relative maturity, and planting date experiment performed in Iowa, USA. Our objectives were to determine the optimum combination of planting date and relative maturity to maximize maize grain yield per environment and to elucidate the risk associated with the use of “full-season hybrids” when planting occurs beyond the optimum planting date. Analysis of variance (ANOVA) attributed 70% of the variability in grain yield to planting date and only 10% to relative maturity ...


Analysis Of Mitochondrial Genomes Resolves The Phylogenetic Position Of Chinese Freshwater Mussels (Bivalvia, Unionidae), Rui-Wen Wu, Xiong-Jun Liu, Sa Wang, Kevin J. Roe, Shan Ouyang, Xiao-Ping Wu Jan 2019

Analysis Of Mitochondrial Genomes Resolves The Phylogenetic Position Of Chinese Freshwater Mussels (Bivalvia, Unionidae), Rui-Wen Wu, Xiong-Jun Liu, Sa Wang, Kevin J. Roe, Shan Ouyang, Xiao-Ping Wu

Natural Resource Ecology and Management Publications

The Yangtze River basin is one of the most species-rich regions for freshwater mussels on Earth, but is gravely threatened by anthropogenic activities. However, conservation planning and management of mussel species has been hindered by a number of taxonomic uncertainties. In order to clarify the taxonomic status and phylogenetic position of these species, mitochondrial genomes of four species (Acuticosta chinensis, Schistodesmus lampreyanus, Cuneopsis heudei and Cuneopsis capitatus) were generated and analyzed along with data from 43 other mitogenomes. The complete F-type mitogenomes of A. chinensis, S. lampreyanus, C. heudei, and C. capitatus are 15652 bp, 15855 bp, 15892 bp, and ...


Leaf Nutrients, Not Specific Leaf Area, Are Consistent Indicators Of Elevated Nutrient Inputs, Jennifer Firn, Kimberly J. La Pierre, Lori Biederman, Et Al. Jan 2019

Leaf Nutrients, Not Specific Leaf Area, Are Consistent Indicators Of Elevated Nutrient Inputs, Jennifer Firn, Kimberly J. La Pierre, Lori Biederman, Et Al.

Ecology, Evolution and Organismal Biology Publications

Leaf traits are frequently measured in ecology to provide a ‘common currency’ for predicting how anthropogenic pressures impact ecosystem function. Here, we test whether leaf traits consistently respond to experimental treatments across 27 globally distributed grassland sites across 4 continents. We find that specific leaf area (leaf area per unit mass)—a commonly measured morphological trait inferring shifts between plant growth strategies—did not respond to up to four years of soil nutrient additions. Leaf nitrogen, phosphorus and potassium concentrations increased in response to the addition of each respective soil nutrient. We found few significant changes in leaf traits when ...


Factors Influencing Fish Mercury Concentrations In Iowa Rivers, Nathan Mills, Michael J. Weber, Clay L. Pierce, Darcy Cashatt Jan 2019

Factors Influencing Fish Mercury Concentrations In Iowa Rivers, Nathan Mills, Michael J. Weber, Clay L. Pierce, Darcy Cashatt

Natural Resource Ecology and Management Publications

Fish mercury concentrations have received considerable attention due to human health implications. Fish mercury concentrations are variable within and among systems due to a suite of biotic and abiotic influences that vary among regions and are difficult to predict. Understanding factors associated with variability in fish mercury concentrations would help guide consumption advisories. Mercury concentrations in channel catfish (Ictalurus punctatus, n = 205), flathead catfish (Pylodictis olivaris, n = 123), northern pike (Esox lucius, n = 60), smallmouth bass (Micropterus dolomieu, n = 176), and walleye (Sander vitreus, n = 176) were assessed in ten Iowa rivers and relationships with land use, water chemistry, and ...


Waste To Carbon: Influence Of Structural Modification On Voc Emission Kinetics From Stored Carbonized Refuse-Derived Fuel, Andrzej Białowiec, Monika Micuda, Antoni Szumny, Jacek Łyczko, Jacek A. Koziel Jan 2019

Waste To Carbon: Influence Of Structural Modification On Voc Emission Kinetics From Stored Carbonized Refuse-Derived Fuel, Andrzej Białowiec, Monika Micuda, Antoni Szumny, Jacek Łyczko, Jacek A. Koziel

Agricultural and Biosystems Engineering Publications

The torrefaction of municipal solid waste is one of the solutions related to the Waste to Carbon concept, where high-quality fuel—carbonized refuse-derived fuel (CRDF)—is produced. An identified potential problem is the emission of volatile organic compounds (VOCs) during CRDF storage. Kinetic emission parameters have not yet been determined. It was also shown that CRDF can be pelletized for energy densification and reduced volume during storage and transportation. Thus, our working hypothesis was that structural modification (via pelletization) might mitigate VOC emissions and influence emission kinetics during CRDF storage. Two scenarios of CRDF structural modification on VOC emission kinetics ...


Torrefaction Of Sewage Sludge: Kinetics And Fuel Properties Of Biochars, Jakub Pulka, Piotr Manczarski, Jacek A. Koziel, Andrzej Białowiec Jan 2019

Torrefaction Of Sewage Sludge: Kinetics And Fuel Properties Of Biochars, Jakub Pulka, Piotr Manczarski, Jacek A. Koziel, Andrzej Białowiec

Agricultural and Biosystems Engineering Publications

We propose a ‘Waste to Carbon’ thermal transformation of sewage sludge (SS) via torrefaction to a valuable product (fuel) with a high content of carbon. One important, technological aspect to develop this concept is the determination of activation energy needed for torrefaction. Thus, this research aimed to evaluate the kinetics of SS torrefaction and determine the effects of process temperature on fuel properties of torrefied products (biochars). Torrefaction was performed using high ash content SS at six (200~300 °C) temperatures and 60 min residence (process) time. Mass loss during torrefaction ranged from 10~20%. The resulting activation energy for ...


Camr: Coded Aggregated Mapreduce, Konstantinos Konstantinidis, Aditya Ramamoorthy Jan 2019

Camr: Coded Aggregated Mapreduce, Konstantinos Konstantinidis, Aditya Ramamoorthy

Electrical and Computer Engineering Publications

Many big data algorithms executed on MapReduce-like systems have a shuffle phase that often dominates the overall job execution time. Recent work has demonstrated schemes where the communication load in the shuffle phase can be traded off for the computation load in the map phase. In this work, we focus on a class of distributed algorithms, broadly used in deep learning, where intermediate computations of the same task can be combined. Even though prior techniques reduce the communication load significantly, they require a number of jobs that grows exponentially in the system parameters. This limitation is crucial and may diminish ...


Distributed Matrix-Vector Multiplication: A Convolutional Coding Approach, Anindya B. Das, Aditya Ramamoorthy Jan 2019

Distributed Matrix-Vector Multiplication: A Convolutional Coding Approach, Anindya B. Das, Aditya Ramamoorthy

Electrical and Computer Engineering Publications

Distributed computing systems are well-known to suffer from the problem of slow or failed nodes; these are referred to as stragglers. Straggler mitigation (for distributed matrix computations) has recently been investigated from the standpoint of erasure coding in several works. In this work we present a strategy for distributed matrix-vector multiplication based on convolutional coding. Our scheme can be decoded using a low-complexity peeling decoder. The recovery process enjoys excellent numerical stability as compared to Reed-Solomon coding based approaches (which exhibit significant problems owing their badly conditioned decoding matrices). Finally, our schemes are better matched to the practically important case ...


Universally Decodable Matrices For Distributed Matrix-Vector Multiplication, Aditya Ramamoorthy, Li Tang, Pascal O. Vontobel Jan 2019

Universally Decodable Matrices For Distributed Matrix-Vector Multiplication, Aditya Ramamoorthy, Li Tang, Pascal O. Vontobel

Electrical and Computer Engineering Publications

Coded computation is an emerging research area that leverages concepts from erasure coding to mitigate the effect of stragglers (slow nodes) in distributed computation clusters, especially for matrix computation problems. In this work, we present a class of distributed matrix-vector multiplication schemes that are based on codes in the Rosenbloom-Tsfasman metric and universally decodable matrices. Our schemes take into account the inherent computation order within a worker node. In particular, they allow us to effectively leverage partial computations performed by stragglers (a feature that many prior works lack). An additional main contribution of our work is a companion matrix-based embedding ...


Stratified Random Sampling From Streaming And Stored Data, Trong Duc Nguyen, Ming-Hung Shih, Divesh Srivastava, Srikanta Tirthapura, Bojian Xu Jan 2019

Stratified Random Sampling From Streaming And Stored Data, Trong Duc Nguyen, Ming-Hung Shih, Divesh Srivastava, Srikanta Tirthapura, Bojian Xu

Electrical and Computer Engineering Conference Papers, Posters and Presentations

Stratified random sampling (SRS) is a widely used sampling technique for approximate query processing. We consider SRS on continuously arriving data streams, and make the following contributions. We present a lower bound that shows that any streaming algorithm for SRS must have (in the worst case) a variance that is Ω(r ) factor away from the optimal, where r is the number of strata. We present S-VOILA, a streaming algorithm for SRS that is locally variance-optimal. Results from experiments on real and synthetic data show that S-VOILA results in a variance that is typically close to an optimal offline algorithm ...


Imaging Stress And Magnetism At High Pressures Using A Nanoscale Quantum Sensor, S. Hsieh, P. Bhattacharyya, C. Zu, T. Mittiga, T. J. Smart, F. Machado, B. Kobrin, T. O. Hohn, N. Z. Rui, Mehdi Kamrani, S. Chatterjee, S. Choi, M. Zaletel, V. V. Struzhkin, J. E. Moore, Valery I. Levitas, R. Jeanloz, N. Y. Yao Dec 2018

Imaging Stress And Magnetism At High Pressures Using A Nanoscale Quantum Sensor, S. Hsieh, P. Bhattacharyya, C. Zu, T. Mittiga, T. J. Smart, F. Machado, B. Kobrin, T. O. Hohn, N. Z. Rui, Mehdi Kamrani, S. Chatterjee, S. Choi, M. Zaletel, V. V. Struzhkin, J. E. Moore, Valery I. Levitas, R. Jeanloz, N. Y. Yao

Aerospace Engineering Publications

Pressure alters the physical, chemical and electronic properties of matter. The development of the diamond anvil cell (DAC) enables tabletop experiments to investigate a diverse landscape of high-pressure phenomena ranging from the properties of planetary interiors to transitions between quantum mechanical phases. In this work, we introduce and utilize a novel nanoscale sensing platform, which integrates nitrogen-vacancy (NV) color centers directly into the culet (tip) of diamond anvils. We demonstrate the versatility of this platform by performing diffraction-limited imaging (~600 nm) of both stress fields and magnetism, up to pressures ~30 GPa and for temperatures ranging from 25-340 K. For ...


Catchment-Scale Phosphorus Export Through Surface And Drainage Pathways, Conrad E. Brendel, Michelle L. Soupir, Leigh Ann M. Long, Matthew J. Helmers, Charles D. Ikenberry, Amy L. Kaleita Dec 2018

Catchment-Scale Phosphorus Export Through Surface And Drainage Pathways, Conrad E. Brendel, Michelle L. Soupir, Leigh Ann M. Long, Matthew J. Helmers, Charles D. Ikenberry, Amy L. Kaleita

Agricultural and Biosystems Engineering Publications

The site-specific nature of P fate and transport in drained areas exemplifies the need for additional data to guide implementation of conservation practices at the catchment scale. Total P (TP), dissolved reactive P (DRP), and total suspended solids (TSS) were monitored at five sites—two streams, two tile outlets, and a grassed waterway—in three agricultural subwatersheds (221.2–822.5 ha) draining to Black Hawk Lake in western Iowa. Median TP concentrations ranged from 0.034 to 1.490 and 0.008 to 0.055 mg P L−1 for event and baseflow samples, respectively. The majority of P ...


Variable Input Observer For Nonstationary High-Rate Dynamic Systems, Jonathan Hong, Simon Laflamme, Liang Cao, Jacob Dodson, Bryan Joyce Dec 2018

Variable Input Observer For Nonstationary High-Rate Dynamic Systems, Jonathan Hong, Simon Laflamme, Liang Cao, Jacob Dodson, Bryan Joyce

Civil, Construction and Environmental Engineering Publications

Engineering systems experiencing events of amplitudes higher than 100 gn for a duration under 100 ms, here termed high-rate dynamics, can undergo rapid damaging effects. If the structural health of such systems could be accurately estimated in a timely manner, preventative measures could be employed to minimize adverse effects. For complex high-rate problems, adaptive observers have shown promise due to their capability to deal with nonstationary, noisy, and uncertain systems. However, adaptive observers have slow convergence rates, which impede their applicability to the high-rate problems. To improve on the convergence rate, we propose a variable input space concept for ...


Quantification Of Voc Emissions From Carbonized Refuse-Derived Fuel Using Solid-Phase Microextraction And Gas Chromatography-Mass Spectrometry, Andrzej Białowiec, Monika Micuda, Antoni Szumny, Jacek Łyczko, Jacek A. Koziel Dec 2018

Quantification Of Voc Emissions From Carbonized Refuse-Derived Fuel Using Solid-Phase Microextraction And Gas Chromatography-Mass Spectrometry, Andrzej Białowiec, Monika Micuda, Antoni Szumny, Jacek Łyczko, Jacek A. Koziel

Agricultural and Biosystems Engineering Publications

In this work, for the first time, the volatile organic compound (VOC) emissions from carbonized refuse-derived fuel (CRDF) were quantified on a laboratory scale. The analyzed CRDF was generated from the torrefaction of municipal waste. Headspace solid-phase microextraction (SPME) and gas chromatography-mass spectrometry (GC-MS) was used to identify 84 VOCs, including many that are toxic, e.g., derivatives of benzene or toluene. The highest emissions were measured for nonanal, octanal, and heptanal. The top 10 most emitted VOCs contributed to almost 65% of the total emissions. The VOC mixture emitted from torrefied CRDF differed from that emitted by other types ...


Pentagons In Triangle-Free Graphs, Bernard Lidicky, Florian Pfender Dec 2018

Pentagons In Triangle-Free Graphs, Bernard Lidicky, Florian Pfender

Mathematics Publications

For all n≥9, we show that the only triangle-free graphs on n vertices maximizing the number 5-cycles are balanced blow-ups of a 5-cycle. This completely resolves a conjecture by Erd\H{o}s, and extends results by Grzesik and Hatami, Hladky, Kral, Norin and Razborov, where they independently showed this same result for large n and for all n divisible by 5.