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Entropy generation in bypass transitional boundary layer flows

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Journal of Hydrodynamics 2014年第5期26卷 669-680页

作者： GEOrGE Joseph owen Landon D. XING Tao MCELIGOT Donald M. CrEPEAU john C. BUDWIG ralph S. NOLAN Kevin P. Department of Mechanical Engineering College of EngineeringUniversity of IdahoMoscowIdaho 83843USA University of Idaho Idaho FallsIdaho 83402USA University of Idaho BoiseIdaho 83702USA Imperial College London London SW7-28ZUK

The primary objective of this study is to evaluate the accuracy of using computational fluid dynamics （CFD） turbulence models to predict entropy generation rates in bypass transitional boundary layers flows under zero and adverse pressure gradients. Entropy generation rates in such flows are evaluated employing the commercial CFD software, ANSYS FLUENT. Various turbulence and transitional models are assessed by comparing their results with the direct numerical simulation （DNS） data and two recent CFD studies. A solution verification study is conducted on three systematically refined meshes. The factor of safety method is used to estimate the numerical error and grid uncertainties. Monotonic convergence is achieved for all simulations. The reynolds number based on momentum thickness, reo, skin-friction coefficient, Cf, approximate entropy generation rates, S, dissipation coefficient, Cd , and the intermittency, y, are calculated for bypass transition simulations. All reynolds averaged Navier-Stokes （rANS） turbulence and transitional models show improvement over previous CFD results in predicting onset of transition. The transition SST k - ω 4 equation model shows closest agreement with DNS data for all flow conditions in this study due to a much finer grid and more accurate inlet boundary conditions. The other rANS models predict an early onset of transition and higher boundary layer entropy generation rates than the DNS shows.

关键词： entropy generation bypass transition reynolds averaged Navier-Stokes (rANS) transitional boundary layer turbulence models

A Survey of Language-Based Approaches to Cyber-Physical and Embedded System Development

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Tsinghua Science and Technology 2015年第2期20卷 130-141页

作者： Paul Soulier Depeng Li john r. Williams University of Hawaii Massachusetts Institute of Technology(MIT)

As computers continue to advance, they are becoming more capable of sensing, interacting, and communicating with the physical and cyber world. Medical devices, electronic braking systems in automotive applications, and industrial control systems are examples of the many Cyber-Physical Systems （CPS） that utilize these computing capabilities. Given the potential consequences of software related failures in such systems, a high degree of safety, security, and reliability is often required. Programming languages are important tools used by programmers to develop CPS. They provide a programmer with the ability to transform designs into machine code. Of equal importance is their ability to detect and avoid programming mistakes. The development of CPS has predominantly been accomplished using the C programming language. Although C is a powerful language, it lacks features present in other languages that facilitate the development of reliable systems. This has prompted research into language-based alternatives for improving program quality through the use of programming languages. This paper presents an overview of the characteristics of embedded and cyber-physical systems and the associated requirements imposed on programming languages. This is followed by a survey of relevant research into language- based methods for creating safe, reliable, and robust software for CPS.

关键词： cyber-physical systems embedded systems programming languages type systems

Hydrodynamics and solids mixing in fluidized beds with inclined-hole distributors

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Particuology 2019年第2期17卷 19-28页

作者： Alhussain Bakhurji Xiaotao Bi john r. Grace Fluidization research Centre Department of Chemical and Biological Engineering University of British Columbia Vancouver V6TJZ3 Canada

Experimental fluidization results were compared for three gas distributors with the same opening ratio but different orifice in clinations (30,45 , and 90 ). Hydrodynamic studies were con ducted with glass beads (diameter 154p.m) to evaluate the impacts of orifice inclination and static bed depth on pressure drop, pressure drop fluctuations, bed expansion, and minimum fluidization velocity. Solids residence time distributions were determined using phosphoresce nt tracer particles (mea n diameter 76 pm), activated by ultraviolet light. The bed pressure drop was higher with the inclined-hole distributors and increased with static bed height. In a shallow bed, the inclined-hole distributors gave less expansion;however, in deep beds, the orifice angle had negligible influence on bed expansion. The minimum fluidization velocity varied with static bed height for the inclined-hole distributors and was higher for steeper angles. The turnover time estimated using bubbling-bed equations matched the experimental results well for vertical mixing. Probes and ports at the walls of the fluidization column reduced the dense-phase downward velocity by up to 40%. The tangential particle velocity was highest for the 30 -hole distributor and decreased with increasing orifice angle. Tangential mixing was described by a dispersion model;the dispersion coefficient for the inclined-hole distributors was approximately twice that for the 90 -hole distributor in a shallow bed.

关键词： Swirling fluidized bed Fluidization Solids mixing Inclined-hole distributor

Photonics for net zero

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Advanced Photonics 2022年第1期4卷 2-4页

作者： john r.Lincoln Photonics Leadership Group and Harlin Ltd. SalisburyUnited Kingdom

Achieving net zero will be the biggest technological challenge of the 21^(st)century.A truly global,all-pervasive challenge impacting every application,market,and *** are no guidelines,instructions,or silver bullets that provide overnight *** net zero will be a sum of countless innovations across energy generation,resource efficiency,and waste *** will have a pivotal role in all of these;directly,by reducing the carbon impact from using light-based technologies;and indirectly,through increased use of photonics in monitoring and reduction in greenhouse gasses across a vast range of industries.

关键词： technology silver Photonics

Sperm cell biology： current perspectives and future prospects

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Asian Journal of Andrology 2011年第1期13卷 3-5页

作者： r john Aitken ralf r Henkel Discipline of Biological Sciences University of Newcastle Newcastle NSW 2308 Australia Department of Medical Biosdences University of the Western Cape Bellville 7535 South Africa

Major advances in biomolecular techniques as well as in the sensitivity and accuracy of mass spectrometers are transforming the scientific landscape by fueling unprecedented advances in analytical biochemistry--the ＇... 详细信息

关键词： Sperm cell biology perspectives

An interferometric ex vivo study of corneal biomechanics under physiologically representative loading,highlighting the role of the limbus in pressure compensation

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Eye and Vision 2020年第5期7卷 412-422页

作者： Abby Wilson john Jones john rTyrer john Marshall Wolfson School of Mechanical Manufacturing and Electrical EngineeringLoughborough UniversityLoughboroughUK Laser Optical Engineering Ltd. DerbyshireUK Institute of Ophthalmology UCLLondonUK

Background:The mechanical properties of the cornea are complex and regionally *** paper uses an original method to investigate the biomechanics of the cornea in response to hydrostatic loading over the typical physiological range of intra-ocular pressure(IOP)fluctuations thereby increasing understanding of clinically relevant corneal biomechanical properties and their contributions to the refractive properties of the ***:Displacement speckle pattern interferometry(DSPI)was used to measure the total surface displacement of 40 porcine and 6 human corneal-scleral specimens in response to pressure variations up to 1 mmHg from a baseline of 16.5 *** specimens were mounted in a modified artificial anterior chamber(AAC)and loaded *** of high strain in response to loading were identified by comparing the displacements across different ***:The nature of the response of the corneal surface to loading demonstrated high regional topographic *** properties were shown to be asymmetrical,and deformation of the limbal and pre-limbal regions dominated these responses respectively with over 90%(N-T)and 60%(S-I)of the total maximum displacement occurring in these regions indicating *** contrast,the curvature of the central cornea remained relatively unchanged merely translating in ***:The limbal and pre-limbal regions of the cornea appear to be fundamental to the absorption of small pressure fluctuations facilitating the curvature of the central cornea to remain relatively *** differential mechanical properties of this region could have important implications for the application of corneal surgery and corneal crosslinking,warranting further investigation.

关键词： Cornea Biomechanics Interferometry Limbus Topography

A Study of the Velocity Field during Evaporation of Sessile Water and Water/Ethanol Drops

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Journal of Bionic Engineering 2010年第4期7卷 321-328页

作者： john r.E.Christy Khellil Sefiane Euan Munro School of Engineering University of Edinburgh

Many studies have investigated evaporation of sessile drops in an attempt to understand the effect of wetting on theevaporation *** interest has also increased in the deposition of particles from such drops,with evaporative massflux being deemed to be responsible for ring-like deposits,and counteraction of the mass flux by Marangoni convection explainingmore uniform deposition *** of such deposition processes is important in biological applications,such as the Litos test-system endorsed by the russian Ministry of Health for diagnosis of urolithiasis and the evaporation ofcolloidal drops for depositing and organizing proteins and *** most cases where deposition from evaporating drops hasbeen studied,velocity information is inferred from the final deposition pattern or from mathematical modeling based on simplifiedmodels of the physics of the evaporation *** this study we have directly measured the flow velocities in the baseof sessile drops,using micro particle image velocimetry,viewing the drop from below,through the cover *** water drops,a radial pattern of flow was observed with a maximum velocity close to but not at the pinned outer *** ‘azeotropic’ethanol/water mixtures,the velocity field is more chaotic to begin with,passing through a phase involving three or four recirculationcells and finally having the same radial pattern as for water drops.

关键词： evaporation sessile drop velocimetry particle deposition μPIV

Coping with the environmental effects of point-source discharges

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Journal of Environmental Sciences 1992年第1期4卷 1-9页

作者： john Caims B.r.Niederlehner University Center for Environmental and Hazardous Materials Studies Virginia Polytechnic Institute and State University Blacksburg Virginia 24061-0415 USAUniversity Center for Environmental and Hazardous Materials Studies Virginia Polytechnic Institute and State University Blacksburg Virginia 24061-0415 USA Jr

Current methods for assessing the environmental impact of point source discharges in the United States are reviewed. The emphasis of many assessments of damage from pollution is shifting from chemical or technological standards to biological standards, i.e., the protection of biological integrity in the receiving system. The importance of integrating information from chemical measurements, toxicity tests, and field surveys in impact assessment is re-emphasized. Ways in which environmental professionals can improve methods for assessing damage from pollution and its control are discussed.

关键词： effluents biological integrity environmental assessment toxicity tests water pollution.

The Potential for Genotype-by-Environment Interactions to Maintain Genetic Variation in a Model Legume–rhizobia Mutualism

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Plant Communications 2020年第6期1卷 100-111页

作者： Priya Vaidya john r.Stinchcombe Department of Ecology and Evolutionary Biology University of TorontoTorontoON M5S3B2Canada Koffler Scientific reserve at Joker’s Hill University of TorontoTorontoON M5S3B2Canada

The maintenance of genetic variation in mutualism-related traits is key for understanding mutualism evolution,yet the mechanisms maintaining variation remain *** asked whether genotype-byenvironment(G3E)interaction is a potential mechanism maintaining variation in the model legume–rhizobia system,Medicago truncatula–Ensifer *** planted 50 legume genotypes in a greenhouse under ambient light and shade to reflect reduced carbon availability for *** found an expected reduction under shaded conditions for plant performance traits,such as leaf number,aboveground and belowground biomass,and a mutualism-related trait,nodule *** also found G3E for nodule number,with83%of this interaction due to shifts in genotype fitness rank order across light environments,coupled with strong positive directional selection on nodule number regardless of light *** results suggest that G3E can maintain genetic variation in a mutualism-related trait that is under consistent positive directional selection across light environments.

关键词： mutualism evolution genetic variation genotype-by-environment interaction Medicago truncatula light availability partner quality