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Articles 1 - 25 of 25
Full-Text Articles in Engineering
Friction Of Soft Elastomeric Surfaces With A Defect, Charles J. Rand, Alfred Crosby
Friction Of Soft Elastomeric Surfaces With A Defect, Charles J. Rand, Alfred Crosby
Alfred Crosby
We consider a simple problem that provides insight into the building blocks of friction for topographically patternedsurfaces and fundamental understanding into the general friction of coatings. The problem focuses on the effect of a line defect, such as a pattern’s edge, on the lateral force of a sliding soft interface. The line defect presents a discontinuity in the stress at the sliding interface, changing the lateral stiffness and decreasing the sliding force. We relate the decrease in sliding shear force to the changes in lateral stiffness through relationships that account for contact splitting and lateral confinement effects.
Burrowing In Marine Muds By Crack Propagation: Kinematics And Forces, Sanjay Raja Arwade, Kelly M. Dorgan, Peter A. Jumars
Burrowing In Marine Muds By Crack Propagation: Kinematics And Forces, Sanjay Raja Arwade, Kelly M. Dorgan, Peter A. Jumars
Sanjay Raja Arwade
The polychaete Nereis virens burrows through muddy sediments by exerting dorsoventral forces against the walls of its tongue-depressor-shaped burrow to extend an oblate hemispheroidal crack. Stress is concentrated at the crack tip, which extends when the stress intensity factor (KI) exceeds the critical stress intensity factor (KIc). Relevant forces were measured in gelatin, an analog for elastic muds, by photoelastic stress analysis, and were 0.015±0.001 N (mean ± s.d.; N=5). Measured elastic moduli (E) for gelatin and sediment were used in finite element models to convert the forces in gelatin to those required in muds to maintain the same body …
Crumpled Surface Structures, Douglas P. Holmes, Michal Ursiny, Alfred Crosby
Crumpled Surface Structures, Douglas P. Holmes, Michal Ursiny, Alfred Crosby
Alfred Crosby
We present a scalable patterning method based on surface plate buckling, or crumpling, to generate a variety of topographies that can dynamically change shape and aspect ratio in response to stimuli.
Delay And Energy Tradeoff In Multi-State Wireless Sensor Networks, W. L. Leow, H. Pishro-Nik, Daiheng Ni
Delay And Energy Tradeoff In Multi-State Wireless Sensor Networks, W. L. Leow, H. Pishro-Nik, Daiheng Ni
Daiheng Ni
This paper discusses a first attempt to investigate, using analytic means, the transmission delay and energy char- acteristics of a multi-state wireless sensor network. For such a network with n nodes, where each node can be active, resting or sleeping, a model that describes the transition of a node from one state to another and the probability associated with each state is proposed. Asymptotic analyses of transmission delay and energy are presented. We report the presence of a threshold for the arrival rate of data packets that decides which energy component dominates. The transmission delay-energy tradeoff is presented for the …
Development Of A Prototype Intersection Collision Avoidance System Under Vii, Daiheng Ni, Hossein Pishro-Nik, Richa Prasad, Mohammed Raza Kanjee, Hui Zhu, Thai Nguyen
Development Of A Prototype Intersection Collision Avoidance System Under Vii, Daiheng Ni, Hossein Pishro-Nik, Richa Prasad, Mohammed Raza Kanjee, Hui Zhu, Thai Nguyen
Daiheng Ni
Vehicle collisions at in tersections account for a large percen tage of overall traffic accidents, a good portion of which are fatal. A large number of these accidents can be avoided by a warning system which makes a driver aware of potential collisions on the road, thus allowing the driver enough time to preven t such situations. This pape r presents the design of a prototype intersection collision warning system based on Vehicle Infrastructure Integration (VII). Underlying the system are wireless communications, positioning technology, and information technology that ensure accu rate and timely safety information.
Self-Assembly Of Nanoparticles At Interfaces, Alexander Böker, Jinbo He, Thomas P. Russell, Todd S. Emrick
Self-Assembly Of Nanoparticles At Interfaces, Alexander Böker, Jinbo He, Thomas P. Russell, Todd S. Emrick
Todd S. Emrick
Developments in the assembly of nanoparticles at liquid–liquid interfaces are reviewed where the assemblies can be controlled by tuning the size of the nanoparticles and the chemical characteristics of the ligands. Both synthetic and biological nanoparticles are discussed. By controlling the type of ligands, uniform and Janus-type nanoparticles can be produced where, at liquid–liquid interfaces, subsequent reactions of the ligands can be used to generate crosslinked sheets of nanoparticles at the interface that have applications including novel encapsulants, filtration devices with well-defined porosities, and controlled release materials. By controlling the size and volume fraction of the nanoparticles and the chemical …
Forty-Fifth Annual Allerton Conference On Communication, Control, And Computing, H. Pishro-Nik, A. Ganz, Daiheng Ni
Forty-Fifth Annual Allerton Conference On Communication, Control, And Computing, H. Pishro-Nik, A. Ganz, Daiheng Ni
Daiheng Ni
This paper initiates the study of scaling laws for vehicular ad hoc networks (VANET)s. It provides a general framework to study VANETs. The fundamental capacity limits of these networks are investigated and we show how the road geometry affects this capacity. The VANET capacity is calculated for different road structures. The need for new capacity metrics is dis- cussed. These results are obtained by combining geomet- rical analysis, network flow arguments, and probabilistic study of VANETs.
Genome-Scale Analysis Of Saccharomyces Cerevisiae Metabolism And Ethanol Production In Fed-Batch Culture, Radhakrishnan Mahadevan, Michael A. Henson
Genome-Scale Analysis Of Saccharomyces Cerevisiae Metabolism And Ethanol Production In Fed-Batch Culture, Radhakrishnan Mahadevan, Michael A. Henson
Michael A Henson
A dynamic flux balance model based on a genome-scale metabolic network reconstruction is developed for in silico analysis of Saccharomyces cerevisiae metabolism and ethanol production in fed-batch culture. Metabolic engineering strategies previously identified for their enhanced steady-state biomass and/or ethanol yields are evaluated for fed-batch performance in glucose and glucose/xylose media. Dynamic analysis is shown to provide a single quantitative measure of fed-batch ethanol productivity that explicitly handles the possible tradeoff between the biomass and ethanol yields. Productivity optimization conducted to rank achievable fed-batch performance demonstrates that the genetic manipulation strategy and the fed-batch operating policy should be considered simultaneously. …
Quantum Dots Coordinated With Conjugated Organic Ligands: New Nanomaterials With Novel Photophysics, Nathan L. Hammer, Todd S. Emrick, Michael D. Barnes
Quantum Dots Coordinated With Conjugated Organic Ligands: New Nanomaterials With Novel Photophysics, Nathan L. Hammer, Todd S. Emrick, Michael D. Barnes
Todd S. Emrick
CdSe quantum dots functionalized with oligo-(phenylene vinylene) (OPV) ligands (CdSe-OPV nanostructures) represent a new class of composite nanomaterials with significantly modified photophysics relative to bulk blends or isolated components. Singlemolecule spectroscopy on these species have revealed novel photophysics such as enhanced energy transfer, spectral stability, and strongly modified excited state lifetimes and blinking statistics. Here, we review the role of ligands in quantum dot applications and summarize some of our recent efforts probing energy and charge transfer in hybrid CdSe-OPV composite nanostructures
A Molecular Model For Intercellular Synchronization In The Mammalian Circadian Clock, Tsz-Leung To, Michael A. Henson, Erik D. Herzog, Francis J. Doyle Iii
A Molecular Model For Intercellular Synchronization In The Mammalian Circadian Clock, Tsz-Leung To, Michael A. Henson, Erik D. Herzog, Francis J. Doyle Iii
Michael A Henson
The mechanisms and consequences of synchrony among heterogeneous oscillators are poorly understood in biological systems. We present a multicellular, molecular model of the mammalian circadian clock that incorporates recent data implicating the neurotransmitter vasoactive intestinal polypeptide (VIP) as the key synchronizing agent. The model postulates that synchrony arises amongcircadian neurons because they release VIP rhythmically on a daily basis and in response to ambient light. Two basic cell types, intrinsically rhythmic pacemakers and damped oscillators, are assumed to arise from a distribution of Period gene transcription rates. Postsynaptic neurons show time-of-day dependent responses to VIP binding through a signaling cascade …
Designing Model Systems For Enhanced Adhesion, Al Crosby
Designing Model Systems For Enhanced Adhesion, Al Crosby
Alfred Crosby
Nature provides inspiration for enhanced control of adhesion through numerous examples ranging from geckos to jumping spiders. The primary strategy in these examples is the incorporation of patterns, specifically high-aspect-ratio topographic features, to ingeniously maximize adhesion forces while maintaining ease of release. Recently, considerable research efforts have been devoted toward the understanding, development, and optimization of synthetic analogues to these examples in nature. In this article, we provide insight into the mechanisms that lead to enhanced control of interfacial properties through patterning, the strategies that can be used for fabricating synthetic patterns, and an overview of experimental results that have …
Climate Teleconnections To Yangtze River Seasonal Streamflow At The Three Gorges Dam, China, Casey Brown, K. Xu, H.-H. Kwon, U. Lall, J. Zhang, S. Hayashi, Z. Chen
Climate Teleconnections To Yangtze River Seasonal Streamflow At The Three Gorges Dam, China, Casey Brown, K. Xu, H.-H. Kwon, U. Lall, J. Zhang, S. Hayashi, Z. Chen
Casey Brown
In this study, we identify climatic influences on summer monsoon inflow to the Three Gorges Dam (TGD) in the Yangtze River Basin and use indices of these influences to predict streamflow one season ahead. Summer monsoon streamflow at Yichang hydrological station (YHS) was analyzed for the period 1882–2003. Statistical analysis was used to develop a predictive model for summer streamflow using preceding climate variables. Linear correlation maps were constructed using 3-month ahead climate fields to identify regions that exhibit teleconnections with streamflow at Yichang. The analysis revealed regions in the eastern Indian and western Pacific Oceans that influence YHS streamflow. …
Further Studies Of A Simple Atomistic Model Of Silica: Thermodynamic Stability Of Zeolite Frameworks As Silica Polymorphs, Peter A. Monson, S. M. Auerbach, M. H. Ford
Further Studies Of A Simple Atomistic Model Of Silica: Thermodynamic Stability Of Zeolite Frameworks As Silica Polymorphs, Peter A. Monson, S. M. Auerbach, M. H. Ford
Peter A. Monson
We have applied our previously reported model of silica based on low coordination and strong association [ J. Chem. Phys. 121, 8415 (2004) ], to the calculation of phase stability of zeolite frameworks SOD, LTA, MFI, and FAU as silica polymorphs. We applied the method of Frenkel and Ladd for calculating free energies of these solids. Our model predicts that the MFI framework structure has a regime of thermodynamic stability at low pressures and above ∼ 1400 K, relative to dense phases such as quartz. In contrast, our calculations predict that the less dense frameworks SOD, LTA, and FAU exhibit …
Cavitation Rheology For Soft Materials, Jessica A. Zimberlin, Naomi Sanabria-Delong, Gregory N. Tew, Alfred Crosby
Cavitation Rheology For Soft Materials, Jessica A. Zimberlin, Naomi Sanabria-Delong, Gregory N. Tew, Alfred Crosby
Alfred Crosby
To guide the development of tissue scaffolds and the characterization of naturally heterogeneous biological tissues, we have developed a method to determine the local modulus at an arbitrary point within a soft material. The method involves growing a cavity at the tip of a syringe needle and monitoring the pressure of the cavity at the onset of a mechanical instability. This critical pressure is directly related to the local modulus of the material. The results focus on the network development of poly(lactide)–poly(ethylene oxide)–poly(lactide) triblock copolymer and poly(vinyl alcohol) hydrogels. These materials serve as model materials for tissue scaffolds and soft …
Water Hammer Dissipation In Pneumatic Slug Tests, Don Degroot, David W. Ostendorf, Philip J. Dunaj
Water Hammer Dissipation In Pneumatic Slug Tests, Don Degroot, David W. Ostendorf, Philip J. Dunaj
Don DeGroot
We model and measure the dissipation of water hammer induced by well casing and water elasticity with rapid valve opening at the start of a pneumatic slug test. The higher-frequency water hammer can obscure slower, aquifer-controlled, underdamped oscillations of the rigid water column, so a quantitative description of the elastic motion improves the ability of a slug test to calibrate the aquifer permeability k. Internal friction attenuates the water hammer, subject to a known headspace pressure at the air/water interface and equilibrium pressure at the top of the well screen. An analytical elastic solution is presented and matched to an …
Synergies Between Bio- And Oil Refineries For The Production Of Fuels From Biomass, George W. Huber, A. Corma
Synergies Between Bio- And Oil Refineries For The Production Of Fuels From Biomass, George W. Huber, A. Corma
George W. Huber
As petroleum prices continue to increase, it is likely that biofuels will play an ever-increasing role in our energy future. The processing of biomass-derived feedstocks (including cellulosic, starch- and sugar-derived biomass, and vegetable fats) by catalytic cracking and hydrotreating is a promising alternative for the future to produce biofuels, and the existing infrastructure of petroleum refineries is well-suited for the production of biofuels, allowing us to rapidly transition to a more sustainable economy without large capital investments for new reaction equipment. This Review discusses the chemistry, catalysts, and challenges involved in the production of biofuels.
Liquid-Phase Catalytic Processing Of Biomass-Derived Oxygenated Hydrocarbons To Fuels And Chemicals, George W. Huber, J. Chheda, J. A. Dumesic
Liquid-Phase Catalytic Processing Of Biomass-Derived Oxygenated Hydrocarbons To Fuels And Chemicals, George W. Huber, J. Chheda, J. A. Dumesic
George W. Huber
Biomass has the potential to serve as a sustainable source of energy and organic carbon for our industrialized society. The focus of this Review is to present an overview of chemical catalytic transformations of biomass-derived oxygenated feedstocks (primarily sugars and sugar-alcohols) in the liquid phase to value-added chemicals and fuels, with specific examples emphasizing the development of catalytic processes based on an understanding of the fundamental reaction chemistry. The key reactions involved in the processing of biomass are hydrolysis, dehydration, isomerization, aldol condensation, reforming, hydrogenation, and oxidation. Further, it is discussed how ideas based on fundamental chemical and catalytic concepts …
Calculation Of Free Energies And Chemical Potentials For Gas Hydrates Using Monte Carlo Simulations, Peter A. Monson, S. J. Wierzchowski
Calculation Of Free Energies And Chemical Potentials For Gas Hydrates Using Monte Carlo Simulations, Peter A. Monson, S. J. Wierzchowski
Peter A. Monson
We describe a method for calculating free energies and chemical potentials for molecular models of gas hydrate systems using Monte Carlo simulations. The method has two components: (i) thermodynamic integration to obtain the water and guest molecule chemical potentials as functions of the hydrate occupancy; (ii) calculation of the free energy of the zero-occupancy hydrate system using thermodynamic integration from an Einstein crystal reference state. The approach is applicable to any classical molecular model of a hydrate. We illustrate the methodology with an application to the structure-I methane hydrate using two molecular models. Results from the method are also used …
Stability And Transient Dynamics Of Thin Liquid Films Flowing Over Locally Heated Surfaces, N Tiwari, Z Mester, Jm Davis
Stability And Transient Dynamics Of Thin Liquid Films Flowing Over Locally Heated Surfaces, N Tiwari, Z Mester, Jm Davis
Jeffrey M. Davis
The dynamics and linear stability of a liquid film flowing over a locally heated surface are studied using a long-wave lubrication analysis. The temperature gradient at the leading edge of the heater induces a gradient in surface tension that opposes the gravitationally driven flow and leads to the formation of a pronounced capillary ridge. The resulting free-surface shapes are computed, and their stability to spanwise perturbations is analyzed for a range of Marangoni numbers, substrate inclination angles, and temperature profiles. Instability is predicted above a critical Marangoni number for a finite band of wave numbers separated from zero, which is …
Cavitation Rheology For Soft Materials, Jessica A. Zimberlin, Naomi Sanabria-Delong, Gregory N. Tewmassachusetts - Amherst, Alfred J. Crosby
Cavitation Rheology For Soft Materials, Jessica A. Zimberlin, Naomi Sanabria-Delong, Gregory N. Tewmassachusetts - Amherst, Alfred J. Crosby
Gregory N. Tew
To guide the development of tissue scaffolds and the characterization of naturally heterogeneous biological tissues, we have developed a method to determine the local modulus at an arbitrary point within a soft material. The method involves growing a cavity at the tip of a syringe needle and monitoring the pressure of the cavity at the onset of a mechanical instability. This critical pressure is directly related to the local modulus of the material. The results focus on the network development of poly(lactide)–poly(ethylene oxide)–poly(lactide) triblock copolymer and poly(vinyl alcohol) hydrogels. These materials serve as model materials for tissue scaffolds and soft …
Activity Of An Antimicrobial Peptide Mimetic Against Planktonic And Biofilm Cultures Of Oral Pathogens, Nicholas Beckloff, Danielle Laube, Tammy Castro, David Furgang, Steven Park, David Perlin, Dylan Clements, Haizhong Tang, Richard W. Scott, Gregory N. Tew, Gill Diamond
Activity Of An Antimicrobial Peptide Mimetic Against Planktonic And Biofilm Cultures Of Oral Pathogens, Nicholas Beckloff, Danielle Laube, Tammy Castro, David Furgang, Steven Park, David Perlin, Dylan Clements, Haizhong Tang, Richard W. Scott, Gregory N. Tew, Gill Diamond
Gregory N. Tew
Antimicrobial peptides (AMPs) are naturally occurring, broad-spectrum antimicrobial agents that have recently been examined for their utility as therapeutic antibiotics. Unfortunately, they are expensive to produce and are often sensitive to protease digestion. To address this problem, we have examined the activity of a peptide mimetic whose design was based on the structure of magainin, exhibiting its amphiphilic structure. We demonstrate that this compound, meta-phenylene ethynylene (mPE), exhibits antimicrobial activity at nanomolar concentrations against a variety of bacterial and Candida species found in oral infections. Since Streptococcus mutans, an etiological agent of dental caries, colonizes the tooth surface and forms …
Water Hammer Dissipation In Pneumatic Slug Tests, David Ostendorf, Don J. Degroot, Philip J. Dunaj
Water Hammer Dissipation In Pneumatic Slug Tests, David Ostendorf, Don J. Degroot, Philip J. Dunaj
David Ostendorf
We model and measure the dissipation of water hammer induced by well casing and water elasticity with rapid valve opening at the start of a pneumatic slug test. The higher-frequency water hammer can obscure slower, aquifer-controlled, underdamped oscillations of the rigid water column, so a quantitative description of the elastic motion improves the ability of a slug test to calibrate the aquifer permeability k. Internal friction attenuates the water hammer, subject to a known headspace pressure at the air/water interface and equilibrium pressure at the top of the well screen. An analytical elastic solution is presented and matched to an …
Modeling Traffic Flow Under Emergency Evacuation Situations: Current Practice And Future Directions, Kevin D. Moriarty, Daiheng Ni, John Collura
Modeling Traffic Flow Under Emergency Evacuation Situations: Current Practice And Future Directions, Kevin D. Moriarty, Daiheng Ni, John Collura
Daiheng Ni
The use of evacuation operations in response to emergency conditions has become commonplace. Until recently, planning and response operations have largely been the concern of emergency management personnel. The reoccurrence of catastrophic events, however, has transp ortation officials becoming in creasingly interested in working to improve evacuation efficiency. Emergency managers and transportation officials have employed the use of traffic simulation software to aid in evacuation planning and to evaluate evacuation operations. Effective emergency simulation software needs to be able to capture the major factors influencing evacuation response. This paper aims to discuss the broad role of transportation and the use …
On Inferring And Characterizing Internet Routing Policies, F Wang, L Gao
On Inferring And Characterizing Internet Routing Policies, F Wang, L Gao
Lixin Gao
No abstract provided.
Prediction-Based Routing For Vehicular Ad Hoc Networks, V Namboodiri, L Gao
Prediction-Based Routing For Vehicular Ad Hoc Networks, V Namboodiri, L Gao
Lixin Gao
No abstract provided.