Dynamics of Phase Transitions in a Snow Mass Containing Water-Soluble Salt Particles

NASA Astrophysics Data System (ADS)

Zelenko, V. L.; Heifets, L. I.; Orlov, Yu. N.; Voskresenskiy, N. M.

2018-07-01

A macrokinetic approach is used to describe the dynamics of phase transitions in a snow mass containing water-soluble salt particles. Equations are derived that describe the rate of salt granule dissolution and the change in the phase composition and temperature of a snow mass under the conditions of heat transfer with an isothermal surface. An experimental setup that models the change in the state of a snow mass placed on an isothermal surface is created to verify theoretical conclusions. Experimental observations of the change in temperature of the snow mass are compared to theoretical calculations. The mathematical model that is developed can be used to predict the state of a snow mass on roads treated with a deicing agent, or to analyze the state of snow masses containing water-soluble salt inclusions and resting on mountain slopes.

Heat Transfer in a Superelliptic Transition Duct

NASA Technical Reports Server (NTRS)

Poinsatte, Philip; Thurman, Douglas; Hippensteele, Steven

2008-01-01

Local heat transfer measurements were experimentally mapped using a transient liquid-crystal heat transfer technique on the surface of a circular-to-rectangular transition duct. The transition duct had a length-to-diameter ratio of 1.5 and an exit-plane aspect ratio of 3. The crosssectional geometry was defined by the equation of a superellipse. The cross-sectional area was the same at the inlet and exit but varied up to 15 percent higher through the transition. The duct was preheated to a uniform temperature (nominally 64 C) before allowing room temperature air to be suddenly drawn through it. As the surface cooled, the resulting isothermal contours on the duct surface were revealed using a surface coating of thermochromic liquid crystals that display distinctive colors at particular temperatures. A video record was made of the surface temperature and time data for all points on the duct surfaces during each test. Using this surface temperature-time data together with the temperature of the air flowing through the model and the initial temperature of the model wall, the heat transfer coefficient was calculated by employing the classic one-dimensional, semi-infinite wall heat transfer conduction model. Test results are reported for inlet diameter-based Reynolds numbers ranging from 0.4x106 to 2.4x106 and two grid-generated freestream turbulence intensities of about 1 percent, which is typical of wind tunnels, and up to 16 percent, which may be more typical of real engine conditions.

Mass transfer from an oscillating microsphere.

PubMed

Zhu, Jiahua; Zheng, Feng; Laucks, Mary L; Davis, E James

2002-05-15

The enhancement of mass transfer from single oscillating aerocolloidal droplets having initial diameters approximately 40 microm has been measured using electrodynamic levitation to trap and oscillate a droplet evaporating in nitrogen gas. The frequency and amplitude of the oscillation were controlled by means of ac and dc fields applied to the ring electrodes of the electrodynamic balance (EDB). Elastic light scattering was used to size the droplet. It is shown that the mass transfer process for a colloidal or aerocolloidal particle oscillating in the Stokes flow regime is governed by a Peclet number for oscillation and a dimensionless oscillation parameter that represents the ratio of the diffusion time scale to the oscillation time scale. Evaporation rates are reported for stably oscillating droplets that are as much as five times the rate for evaporation in a stagnant gas. The enhancement is substantially larger than that predicted by quasi-steady-flow mass transfer.

Modelling mass transfer during venting/soil vapour extraction: Non-aqueous phase liquid/gas mass transfer coefficient estimation

NASA Astrophysics Data System (ADS)

Esrael, D.; Kacem, M.; Benadda, B.

2017-07-01

We investigate how the simulation of the venting/soil vapour extraction (SVE) process is affected by the mass transfer coefficient, using a model comprising five partial differential equations describing gas flow and mass conservation of phases and including an expression accounting for soil saturation conditions. In doing so, we test five previously reported quations for estimating the non-aqueous phase liquid (NAPL)/gas initial mass transfer coefficient and evaluate an expression that uses a reference NAPL saturation. Four venting/SVE experiments utilizing a sand column are performed with dry and non-saturated sand at low and high flow rates, and the obtained experimental results are subsequently simulated, revealing that hydrodynamic dispersion cannot be neglected in the estimation of the mass transfer coefficient, particularly in the case of low velocities. Among the tested models, only the analytical solution of a convection-dispersion equation and the equation proposed herein are suitable for correctly modelling the experimental results, with the developed model representing the best choice for correctly simulating the experimental results and the tailing part of the extracted gas concentration curve.

Modeling of the heat transfer in bypass transitional boundary-layer flows

NASA Technical Reports Server (NTRS)

Simon, Frederick F.; Stephens, Craig A.

1991-01-01

A low Reynolds number k-epsilon turbulence model and conditioned momentum, energy and turbulence equations were used to predict bypass transition heat transfer on a flat plate in a high-disturbance environment with zero pressure gradient. The use of conditioned equations was demonstrated to be an improvement over the use of the global-time-averaged equations for the calculation of velocity profiles and turbulence intensity profiles in the transition region of a boundary layer. The approach of conditioned equations is extended to include heat transfer and a modeling of transition events is used to predict transition onset and the extent of transition on a flat plate. The events, which describe the boundary layer at the leading edge, result in boundary-layer regions consisting of: (1) the laminar, (2) pseudolaminar, (3) transitional, and (4) turbulent boundary layers. The modeled transition events were incorporated into the TEXSTAN 2-D boundary-layer code which is used to numerically predict the heat transfer. The numerical predictions in general compared well with the experimental data and revealed areas where additional experimental information is needed.

Noise Levels Associated With New York City's Mass Transit Systems

PubMed Central

Gershon, Robyn R. M.; Zeltser, Marina; Canton, Allison; Akram, Muhammad

2009-01-01

Objectives. We measured noise levels associated with various forms of mass transit and compared them to exposure guidelines designed to protect against noise-induced hearing loss. Methods. We used noise dosimetry to measure time-integrated noise levels in a representative sample of New York City mass transit systems (subways, buses, ferries, tramway, and commuter railways) aboard transit vehicles and at vehicle boarding platforms or terminals during June and July 2007. Results. Of the transit types evaluated, subway cars and platforms had the highest associated equivalent continuous average (Leq) and maximum noise levels. All transit types had Leq levels appreciably above 70 A-weighted decibels, the threshold at which noise-induced hearing loss is considered possible. Conclusions. Mass transit noise exposure has the potential to exceed limits recommended by the World Health Organization and the US Environmental Protection Agency and thus cause noise-induced hearing loss among riders of all forms of mass transit given sufficient exposure durations. Environmental noise–control efforts in mass transit and, in cases in which controls are infeasible, the use of personal hearing protection would benefit the ridership's hearing health. PMID:19542046

Convective mass transfer around a dissolving bubble

NASA Astrophysics Data System (ADS)

Duplat, Jerome; Grandemange, Mathieu; Poulain, Cedric

2017-11-01

Heat or mass transfer around an evaporating drop or condensing vapor bubble is a complex issue due to the interplay between the substrate properties, diffusion- and convection-driven mass transfer, and Marangoni effects, to mention but a few. In order to disentangle these mechanisms, we focus here mainly on the convective mass transfer contribution in an isothermal mass transfer problem. For this, we study the case of a millimetric carbon dioxide bubble which is suspended under a substrate and dissolved into pure liquid water. The high solubility of CO2 in water makes the liquid denser and promotes a buoyant-driven flow at a high (solutal) Rayleigh number (Ra˜104 ). The alteration of p H allows the concentration field in the liquid to be imaged by laser fluorescence enabling us to measure both the global mass flux (bubble volume, contact angle) and local mass flux around the bubble along time. After a short period of mass diffusion, where the boundary layer thickens like the square root of time, convection starts and the CO2 is carried by a plume falling at constant velocity. The boundary layer thickness then reaches a plateau which depends on the bubble cross section. Meanwhile the plume velocity scales like (dV /d t )1 /2 with V being the volume of the bubble. As for the rate of volume loss, we recover a constant mass flux in the diffusion-driven regime followed by a decrease in the volume V like V2 /3 after convection has started. We present a model which agrees well with the bubble dynamics and discuss our results in the context of droplet evaporation, as well as high Rayleigh convection.

23 CFR 810.210 - Authorization for use and occupancy by mass transit.

Code of Federal Regulations, 2011 CFR

2011-04-01

... 23 Highways 1 2011-04-01 2011-04-01 false Authorization for use and occupancy by mass transit. 810... TRANSPORTATION MASS TRANSIT AND SPECIAL USE HIGHWAY PROJECTS Making Highway Rights-of-Way Available for Mass Transit Projects § 810.210 Authorization for use and occupancy by mass transit. (a) Upon being authorized...

Roughness induced transition and heat transfer augmentation in hypersonic environments

NASA Astrophysics Data System (ADS)

Wassel, A. T.; Shih, W. C. L.; Courtney, J. F.

Boundary layer transition and surface heating distributions on graphite, fine weave carbon-carbon, and metallic nosetip materials were derived from surface temperature responses measured in nitrogen environments during both free-flight and track-guided testing in hypersonic environments. Innovative test procedures were developed, and heat transfer results were validated against established theory through experiments using a super-smooth tungsten model. Quantitative definitions of mean transition front locations were established by deriving heat flux distributions from measured temperatures, and comparisons made with existing nosetip transition correlations. Qualitative transition locations were inferred directly from temperature distributions to investigate preferred orientations on fine weave nosetips. Levels of roughness augmented heat transfer were generally shown to be below values predicted by state-of-the-art methods.

Local Mass and Heat Transfer on a Turbine Blade Tip

DOE PAGES

Jin, P.; Goldstein, R. J.

2003-01-01

Locmore » al mass and heat transfer measurements on a simulated high-pressure turbine blade-tip surface are conducted in a linear cascade with a nonmoving tip endwall, using a naphthalene sublimation technique. The effects of tip clearance (0.86–6.90% of chord) are investigated at various exit Reynolds numbers (4–7 × 10 5 ) and turbulence intensities (0.2 and 12.0%). The mass transfer on the tip surface is significant along its pressure edge at the smallest tip clearance. At the two largest tip clearances, the separation bubble on the tip surface can cover the whole width of the tip on the second half of the tip surface. The average mass-transfer rate is highest at a tip clearance of 1.72% of chord. The average mass-transfer rate on the tip surface is four and six times as high as on the suction and the pressure surface, respectively. A high mainstream turbulence level of 12.0% reduces average mass-transfer rates on the tip surface, while the higher mainstream Reynolds number generates higher local and average mass-transfer rates on the tip surface.« less

Using White Dwarf Companions of Blue Stragglers to Constrain Mass Transfer Physics

NASA Astrophysics Data System (ADS)

Gosnell, Natalie M.; Leiner, Emily; Geller, Aaron M.; Knigge, Christian; Mathieu, Robert D.; Sills, Alison; Leigh, Nathan

2018-06-01

Complete membership studies of old open clusters reveal that 25% of the evolved stars follow pathways in stellar evolution that are impacted by binary evolution. Recent studies show that the majority of blue straggler stars, traditionally defined to be stars brighter and bluer than the corresponding main sequence turnoff, are formed through mass transfer from a giant star onto a main sequence companion, resulting in a white dwarf in a binary system with a blue straggler. We will present constraints on the histories and mass transfer efficiencies for two blue straggler-white dwarf binaries in open cluster NGC 188. The constraints are a result of measuring white dwarf cooling temperatures and surface gravities with HST COS far-ultraviolet spectroscopy. This information sets both the timeline for mass transfer and the stellar masses in the pre-mass transfer binary, allowing us to constrain aspects of the mass transfer physics. One system is formed through Case C mass transfer, leaving a CO-core white dwarf, and provides an interesting test case for mass transfer from an asymptotic giant branch star in an eccentric system. The other system formed through Case B mass transfer, leaving a He-core white dwarf, and challenges our current understanding of the expected regimes for stable mass transfer from red giant branch stars.

23 CFR 810.204 - Application by mass transit authority.

Code of Federal Regulations, 2010 CFR

2010-04-01

... 23 Highways 1 2010-04-01 2010-04-01 false Application by mass transit authority. 810.204 Section 810.204 Highways FEDERAL HIGHWAY ADMINISTRATION, DEPARTMENT OF TRANSPORTATION PUBLIC TRANSPORTATION... rail or other nonhighway public mass transit facility may submit an application therefor to the State...

Mass transfer parameters of celeriac during vacuum drying

NASA Astrophysics Data System (ADS)

Beigi, Mohsen

2017-04-01

An accurate prediction of moisture transfer parameters is very important for efficient mass transfer analysis, accurate modelling of drying process, and better designing of new dryers and optimization of existing drying process. The present study aimed to investigate the influence of temperature (e.g., 55, 65 and 75 °C) and chamber pressure (e.g., 0.1, 3, 7, 10, 13 and 17 kPa) on effective diffusivity and convective mass transfer coefficient of celeriac slices during vacuum drying. The obtained Biot number indicated that the moisture transfer in the celeriac slices was controlled by both internal and external resistance. The effective diffusivity obtained to be in the ranges of 7.5231 × 10-10-3.8015 × 10-9 m2 s-1. The results showed that the diffusivity increased with increasing temperature and decreasing pressure. The mass transfer coefficient values varied from 4.6789 × 10-7 to 1.0059 × 10-6 m s-1, and any increment in drying temperature and pressure caused an increment in the coefficient.

Devices with extended area structures for mass transfer processing of fluids

DOEpatents

TeGrotenhuis, Ward E.; Wegeng, Robert S.; Whyatt, Greg A.; King, David L.; Brooks, Kriston P.; Stenkamp, Victoria S.

2009-04-21

A microchannel device includes several mass transfer microchannels to receive a fluid media for processing at least one heat transfer microchannel in fluid communication with a heat transfer fluid defined by a thermally conductive wall, and at several thermally conductive fins each connected to the wall and extending therefrom to separate the mass transfer microchannels from one another. In one form, the device may optionally include another heat transfer microchannel and corresponding wall that is positioned opposite the first wall and has the fins and the mass transfer microchannels extending therebetween.

Mass Transfer Cooling Near The Stagnation Point

NASA Technical Reports Server (NTRS)

Roberts, Leonard

1959-01-01

A simplified analysis is made of mass transfer cooling, that is, injection of a foreign gas, near the stagnation point for two-dimensional and axisymmetric bodies. The reduction in heat transfer is given in terms of the properties of the coolant gas and it is shown that the heat transfer may be reduced considerably by the introduction of a gas having appropriate thermal and diffusive properties. The mechanism by which heat transfer is reduced is discussed.

An advanced model of heat and mass transfer in the protective clothing - verification

NASA Astrophysics Data System (ADS)

Łapka, P.; Furmański, P.

2016-09-01

The paper presents an advanced mathematical and numerical models of heat and mass transfer in the multi-layers protective clothing and in elements of the experimental stand subjected to either high surroundings temperature or high radiative heat flux emitted by hot objects. The model included conductive-radiative heat transfer in the hygroscopic porous fabrics and air gaps as well as conductive heat transfer in components of the stand. Additionally, water vapour diffusion in the pores and air spaces as well as phase transition of the bound water in the fabric fibres (sorption and desorption) were accounted for. The thermal radiation was treated in the rigorous way e.g.: semi-transparent absorbing, emitting and scattering fabrics were assumed a non-grey and all optical phenomena at internal or external walls were modelled. The air was assumed transparent. Complex energy and mass balance as well as optical conditions at internal or external interfaces were formulated in order to find exact values of temperatures, vapour densities and radiation intensities at these interfaces. The obtained highly non-linear coupled system of discrete equation was solve by the in-house iterative algorithm which was based on the Finite Volume Method. The model was then successfully partially verified against the results obtained from commercial software for simplified cases.

23 CFR 810.308 - Approval of urban system nonhighway public mass transit projects.

Code of Federal Regulations, 2011 CFR

2011-04-01

... 23 Highways 1 2011-04-01 2011-04-01 false Approval of urban system nonhighway public mass transit... PUBLIC TRANSPORTATION MASS TRANSIT AND SPECIAL USE HIGHWAY PROJECTS Federal-Aid Urban System Nonhighway Public Mass Transit Projects § 810.308 Approval of urban system nonhighway public mass transit projects...

Impact of kinetic mass transfer on free convection in a porous medium

NASA Astrophysics Data System (ADS)

Lu, Chunhui; Shi, Liangsheng; Chen, Yiming; Xie, Yueqing; Simmons, Craig T.

2016-05-01

We investigate kinetic mass transfer effects on unstable density-driven flow and transport processes by numerical simulations of a modified Elder problem. The first-order dual-domain mass transfer model coupled with a variable-density-flow model is employed to describe transport behavior in porous media. Results show that in comparison to the no-mass-transfer case, a higher degree of instability and more unstable system is developed in the mass transfer case due to the reduced effective porosity and correspondingly a larger Rayleigh number (assuming permeability is independent on the mobile porosity). Given a constant total porosity, the magnitude of capacity ratio (i.e., immobile porosity/mobile porosity) controls the macroscopic plume profile in the mobile domain, while the magnitude of mass transfer timescale (i.e., the reciprocal of the mass transfer rate coefficient) dominates its evolution rate. The magnitude of capacity ratio plays an important role on the mechanism driving the mass flux into the aquifer system. Specifically, for a small capacity ratio, solute loading is dominated by the density-driven transport, while with increasing capacity ratio local mass transfer dominated solute loading may occur at later times. At significantly large times, however, both mechanisms contribute comparably to solute loading. Sherwood Number could be a nonmonotonic function of mass transfer timescale due to complicated interactions of solute between source zone, mobile zone and immobile zone in the top boundary layer, resulting in accordingly a similar behavior of the total mass. The initial assessment provides important insights into unstable density-driven flow and transport in the presence of kinetic mass transfer.

State of the Art of Current Practices for Transit Transfers.

DOT National Transportation Integrated Search

1981-07-01

The major objectives of the study are to: (1) describe and summarize the transfer policies currently in use on U.S. transit properties; (2) identify reasons why properties use or do not use particular transfer policies; (3) determine the consequences...

Flavin Charge Transfer Transitions Assist DNA Photolyase Electron Transfer

NASA Astrophysics Data System (ADS)

Skourtis, Spiros S.; Prytkova, Tatiana; Beratan, David N.

2007-12-01

This contribution describes molecular dynamics, semi-empirical and ab-initio studies of the primary photo-induced electron transfer reaction in DNA photolyase. DNA photolyases are FADH--containing proteins that repair UV-damaged DNA by photo-induced electron transfer. A DNA photolyase recognizes and binds to cyclobutatne pyrimidine dimer lesions of DNA. The protein repairs a bound lesion by transferring an electron to the lesion from FADH-, upon photo-excitation of FADH- with 350-450 nm light. We compute the lowest singlet excited states of FADH- in DNA photolyase using INDO/S configuration interaction, time-dependent density-functional, and time-dependent Hartree-Fock methods. The calculations identify the lowest singlet excited state of FADH- that is populated after photo-excitation and that acts as the electron donor. For this donor state we compute conformationally-averaged tunneling matrix elements to empty electron-acceptor states of a thymine dimer bound to photolyase. The conformational averaging involves different FADH--thymine dimer confromations obtained from molecular dynamics simulations of the solvated protein with a thymine dimer docked in its active site. The tunneling matrix element computations use INDO/S-level Green's function, energy splitting, and Generalized Mulliken-Hush methods. These calculations indicate that photo-excitation of FADH- causes a π→π* charge-transfer transition that shifts electron density to the side of the flavin isoalloxazine ring that is adjacent to the docked thymine dimer. This shift in electron density enhances the FADH--to-dimer electronic coupling, thus inducing rapid electron transfer.

Improving the quality of transition and transfer of care in young adults with congenital heart disease.

PubMed

Everitt, Ian K; Gerardin, Jennifer F; Rodriguez, Fred H; Book, Wendy M

2017-05-01

The transition and transfer from pediatric to adult care is becoming increasingly important as improvements in the diagnosis and management of congenital heart disease allow patients to live longer. Transition is a complex and continuous process that requires careful planning. Inadequate transition has adverse effects on patients, their families and healthcare delivery systems. Currently, significant gaps exist in patient care as adolescents transfer to adult care and there are little data to drive the informed management of transition and transfer of care in adolescent congenital heart disease patients. Appropriate congenital heart disease care has been shown to decrease mortality in the adult population. This paper reviews the transition and transfer of care processes and outlines current congenital heart disease specific guidelines in the United States and compares these recommendations to Canadian and European guidelines. It then reviews perceived and real barriers to successful transition and identifies predictors of success during transfer to adult congenital heart disease care. Lastly, it explores how disease-specific markers of outcomes and quality indicators are being utilized to guide transition and transfer of care in other chronic childhood illnesses, and identifies existing knowledge gaps and structural impediments to improving the management of transition and transfer among congenital heart disease patients. © 2017 Wiley Periodicals, Inc.

Heat and Mass Transfer in an L Shaped Porous Medium

NASA Astrophysics Data System (ADS)

Salman Ahmed, N. J.; Azeem; Yunus Khan, T. M.

2017-08-01

This article is an extension to the heat transfer in L-shaped porous medium by including the mass diffusion. The heat and mass transfer in the porous domain is represented by three coupled partial differential equations representing the fluid movement, energy transport and mass transport. The equations are converted into algebraic form of equations by the application of finite element method that can be conveniently solved by matrix method. An iterative approach is adopted to solve the coupled equations by setting suitable convergence criterion. The results are discussed in terms of heat transfer characteristics influenced by physical parameters such as buoyancy ratio, Lewis number, Rayleigh number etc. It is found that these physical parameters have significant effect on heat and mass transfer behavior of L-shaped porous medium.

Alternative Fuels Data Center: Mass Transit

Science.gov Websites

traveled and fuel used by private vehicles. Vehicle fleet managers, corporate decision makers, and public effective incentives for fleet managers and corporate decision makers to build mass transit ridership

Saponification reaction system: a detailed mass transfer coefficient determination.

PubMed

Pečar, Darja; Goršek, Andreja

2015-01-01

The saponification of an aromatic ester with an aqueous sodium hydroxide was studied within a heterogeneous reaction medium in order to determine the overall kinetics of the selected system. The extended thermo-kinetic model was developed compared to the previously used simple one. The reaction rate within a heterogeneous liquid-liquid system incorporates a chemical kinetics term as well as mass transfer between both phases. Chemical rate constant was obtained from experiments within a homogeneous medium, whilst the mass-transfer coefficient was determined separately. The measured thermal profiles were then the bases for determining the overall reaction-rate. This study presents the development of an extended kinetic model for considering mass transfer regarding the saponification of ethyl benzoate with sodium hydroxide within a heterogeneous reaction medium. The time-dependences are presented for the mass transfer coefficient and the interfacial areas at different heterogeneous stages and temperatures. The results indicated an important role of reliable kinetic model, as significant difference in k(L)a product was obtained with extended and simple approach.

Rethinking Transfer: Learning from CALL Teacher Education as Consequential Transition

ERIC Educational Resources Information Center

Chao, Chin-chi

2015-01-01

Behind CALL teacher education (CTE) there is an unproblematized consensus of transfer, which suggests a positivist and tool-centered view of learning gains that differs from the sociocultural focus of recent teacher education research. Drawing on Beach's (2003) conceptualization of transfer as "consequential transition," this qualitative…

Incomplete mass transfer processes in 28Si +93Nb reaction

NASA Astrophysics Data System (ADS)

Tripathi, R.; Sodaye, S.; Ramachandran, K.; Sharma, S. K.; Pujari, P. K.

Cross sections of reaction products were measured in 28Si +93Nb reaction using recoil catcher technique involving by off-line gamma-ray spectrometry at beam energies of 105 and 155MeV. At Elab = 155MeV, the contribution from different incomplete mass transfer processes is investigated. Results of the present studies show the contribution from deep inelastic collision (DIC), massive transfer or incomplete fusion (ICF) and quasi-elastic transfer (QET). The contribution from massive transfer reactions was confirmed from the fractional yield of the reaction products in the forward catcher foil. The present results are different from those from the reactions with comparatively higher entrance channel mass asymmetry with lighter projectiles, for which dominant transfer processes are ICF and QET which involve mass transfer predominantly from projectile to target. The N/Z values of the products close to the target mass were observed to be in a wide range, starting from N/Z of the target (93Nb) and extending slightly below the N/Z of the composite system, consistent with the contribution from DIC and QET reactions. At Elab = 105MeV, a small contribution from QET was observed in addition to complete fusion.

Mass fractionation processes of transition metal isotopes

NASA Astrophysics Data System (ADS)

Zhu, X. K.; Guo, Y.; Williams, R. J. P.; O'Nions, R. K.; Matthews, A.; Belshaw, N. S.; Canters, G. W.; de Waal, E. C.; Weser, U.; Burgess, B. K.; Salvato, B.

2002-06-01

Recent advances in mass spectrometry make it possible to utilise isotope variations of transition metals to address some important issues in solar system and biological sciences. Realisation of the potential offered by these new isotope systems however requires an adequate understanding of the factors controlling their isotope fractionation. Here we show the results of a broadly based study on copper and iron isotope fractionation during various inorganic and biological processes. These results demonstrate that: (1) naturally occurring inorganic processes can fractionate Fe isotope to a detectable level even at temperature ˜1000°C, which challenges the previous view that Fe isotope variations in natural system are unique biosignatures; (2) multiple-step equilibrium processes at low temperatures may cause large mass fractionation of transition metal isotopes even when the fractionation per single step is small; (3) oxidation-reduction is an importation controlling factor of isotope fractionation of transition metal elements with multiple valences, which opens a wide range of applications of these new isotope systems, ranging from metal-silicate fractionation in the solar system to uptake pathways of these elements in biological systems; (4) organisms incorporate lighter isotopes of transition metals preferentially, and transition metal isotope fractionation occurs stepwise along their pathways within biological systems during their uptake.

Mass transit and appropriate technology

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bell, L.

1978-06-01

Population pressures, dwinding fossil-fuel reserves, and new technological developments will make mass transet more and more competitive with private automobiles in the future. But future transit systems require a combination of high and low technologies--automated subways and conventional sidewalks. Buses and taxicabs may still be the answer in some cities, because more-sophisticated technologies may cause more problems than they solve. Larry Bell reviews information on some of the more advanced transit systems--those in service, proposed, and defunct. He concludes that the most appropriate thechnology for each problem will be found by aiming at balanced, integrated solutions that consider all responablemore » options. (MCW)« less

Determination of the mass-transfer coefficient in liquid phase in a stream-bubble contact device

NASA Astrophysics Data System (ADS)

Dmitriev, A. V.; Dmitrieva, O. S.; Madyshev, I. N.

2016-09-01

One of the most effective energy saving technologies is the improvement of existing heat and mass exchange units. A stream-bubble contact device is designed to enhance the operation efficiency of heat and mass exchange units. The stages of the stream-bubble units that are proposed by the authors for the decarbonization process comprise contact devices with equivalent sizes, whose number is determined by the required performance of a unit. This approach to the structural design eliminates the problems that arise upon the transition from laboratory samples to industrial facilities and makes it possible to design the units of any required performance without a decrease in the effectiveness of mass exchange. To choose the optimal design that provides the maximum effectiveness of the mass-exchange processes in units and their intensification, the change of the mass-transfer coefficient is analyzed with the assumption of a number of parameters. The results of the study of the effect of various structural parameters of a stream-bubble contact device on the mass-transfer coefficient in the liquid phase are given. It is proven that the mass-transfer coefficient increases in the liquid phase, in the first place, with the growth of the level of liquid in the contact element, because the rate of the liquid run-off grows in this case and, consequently, the time of surface renewal is reduced; in the second place, with an increase in the slot diameter in the downpipe, because the jet diameter and, accordingly, their section perimeter and the area of the surface that is immersed in liquid increase; and, in the third place, with an increase in the number of slots in the downpipe, because the area of the surface that is immersed in the liquid of the contact element increases. Thus, in order to increase the mass-transfer coefficient in the liquid phase, it is necessary to design the contact elements with a minimum width and a large number of slots and their increased diameter; in

Suicide and Mass Urban Transit.

ERIC Educational Resources Information Center

Berman, Alan L., Ed.

1991-01-01

Presents case consultation in which consultants respond to issues of urban planning for mass transit (subway) system and how to maximize prevention of intentional injury within subway stations. Also asks what type of research study should be used and what type of data collected once system is operating. Case is discussed by Morton M. Silverman and…

Crashworthiness evaluation of mass transit buses.

DOT National Transportation Integrated Search

2008-11-01

Mass transit bus systems are an integral part of the national transportation network, serving more than 20.6 billion passenger-miles per year with a relatively low fatality rate. Bus occupant injuries are evenly distributed among crashes on all sides...

The Role of "Creative Transfer" in Professional Transitions

ERIC Educational Resources Information Center

Triantafyllaki, Angeliki

2016-01-01

This paper discusses the concept of "knowledge transfer" in terms of expansion of prior knowledge, creativity and approaches to generating new knowledge. It explores professional transitions in which knowledge restructuring and identity reformation are pathways into greater work flexibility and adjustment. Two studies, exploring…

LUT Reveals a New Mass-transferring Semi-detached Binary

NASA Astrophysics Data System (ADS)

Qian, S.-B.; Zhou, X.; Zhu, L.-Y.; Zejda, M.; Soonthornthum, B.; Zhao, E.-G.; Zhang, J.; Zhang, B.; Liao, W.-P.

2015-12-01

GQ Dra is a short-period eclipsing binary in a double stellar system that was discovered by Hipparcos. Complete light curves in the UV band were obtained with the Lunar-based Ultraviolet Telescope in 2014 November and December. Photometric solutions are determined using the W-D (Wilson and Devinney) method. It is discovered that GQ Dra is a classical Algol-type semi-detached binary where the secondary component is filling the critical Roche lobe. An analysis of all available times of minimum light suggests that the orbital period is increasing continuously at a rate of \\dot{P}=+3.48(+/- 0.23)× {10}-7 days yr-1. This could be explained by mass transfer from the secondary to the primary, which is in agreement with the semi-detached configuration with a lobe-filling secondary. By assuming a conservation of mass and angular momentum, the mass transfer rate is estimated as \\dot{m}=9.57(+/- 0.63)× {10}-8 {M}⊙ {{yr}}-1. All of these results reveal that GQ Dra is a mass-transferring semi-detached binary in a double system that was formed from an initially detached binary star. After the massive primary evolves to fill the critical Roche lobe, the mass transfer will be reversed and the binary will evolve into a contact configuration with two sub-giant or giant component stars.

Mass transfer resistance in ASFF reactors for waste water treatment.

PubMed

Ettouney, H M; Al-Haddad, A A; Abu-Irhayem, T M

1996-01-01

Analysis of mass transfer resistances was performed for an aerated submerged fixed-film reactor (ASFF) for the treatment of waste water containing a mixture of sucrose and ammonia. Both external and internal mass transfer resistances were considered in the analysis, and characterized as a function of feed flow-rate and concentration. Results show that, over a certain operating regime, external mass transfer resistance in the system was greater for sucrose removal than ammonia. This is because the reaction rates for carbon removal were much larger than those of nitrogen. As a result, existence of any form of mass transfer resistance caused by inadequate mixing or diffusion limitations, strongly affects the overall removal rates of carbon more than nitrogen. Effects of the internal måss transfer resistance were virtually non-existent for ammonia removal. This behaviour was found over two orders of magnitude range for the effective diffusivity for ammonia, and one order of magnitude for the film specific surface area. However, over the same parameters' range, it is found that sucrose removal was strongly affected upon lowering its effective diffusivity and increasing the film specific surface area.

Environmental Energy and Mass Transfer: Key to Understanding Catchment Evolution (Invited)

NASA Astrophysics Data System (ADS)

Troch, P. A.; Rasmussen, C.; Broxton, P. D.; Heidbuechel, I.

2010-12-01

While a lot is now known about catchment behavior of many study sites around the world, the ability to generalize these findings for predictions in unmonitored sites remains difficult. This is largely due to the fact that the link between climate, hydrologic response and how the landscape is structured is poorly understood. Notwithstanding, such understanding is fundamental to advancing new hydrological theory and useful model structures that can be used in ungauged sites. In this paper we will present a theoretical framework based on open systems thermodynamics to study catchment evolution. This framework is referred to as Environmental Energy and Mass Transfer (EEMT) and relates long-term energy and mass fluxes through the catchment to its internal structure and functioning. We will illustrate this concept using recent results from field investigations in two semi-arid environments in southwest USA:, the Valles Caldera National Preserve (VCNP) near Los Alamos, NM and the Santa Catalina Mountains (SCM) near Tucson, AZ. In VCNP we have designed an experiment that involves calculating transit times for a number of catchments that drain from a large dome called Redondo Peak. These catchments have different orientations and therefore receive different amounts of solar radiation. In general, we found that there was a correlation between mean transit times and aspect for these streams. At the same time, other topographic characteristics, which are typically considered as controls over catchment mean transit times, such as catchment area, elevation, and the ratio of flowpath length to slope gradient, exhibit limited predictive power with respect to mean transit times. The relationship between mean transit times and aspect suggests that in the Valles Caldera, transit times might be affected by a variety of features that are influenced by aspect, such as slope steepness, vegetation patterns, and soil depth. In SCM we have monitored the hydrological response in two

Mass Transfer Limited Enhanced Bioremediation at Dnapl Source Zones: a Numerical Study

NASA Astrophysics Data System (ADS)

Kokkinaki, A.; Sleep, B. E.

2011-12-01

The success of enhanced bioremediation of dense non-aqueous phase liquids (DNAPLs) relies on accelerating contaminant mass transfer from the organic to the aqueous phase, thus enhancing the depletion of DNAPL source zones compared to natural dissolution. This is achieved by promoting biological activity that reduces the contaminant's aqueous phase concentration. Although laboratory studies have demonstrated that high reaction rates are attainable by specialized microbial cultures in DNAPL source zones, field applications of the technology report lower reaction rates and prolonged remediation times. One possible explanation for this phenomenon is that the reaction rates are limited by the rate at which the contaminant partitions from the DNAPL to the aqueous phase. In such cases, slow mass transfer to the aqueous phase reduces the bioavailability of the contaminant and consequently decreases the potential source zone depletion enhancement. In this work, the effect of rate limited mass transfer on bio-enhanced dissolution of DNAPL chlorinated ethenes is investigated through a numerical study. A multi-phase, multi-component groundwater transport model is employed to simulate DNAPL mass depletion for a range of source zone scenarios. Rate limited mass transfer is modeled by a linear driving force model, employing a thermodynamic approach for the calculation of the DNAPL - water interfacial area. Metabolic reductive dechlorination is modeled by Monod kinetics, considering microbial growth and self-inhibition. The model was utilized to identify conditions in which mass transfer, rather than reaction, is the limiting process, as indicated by the bioavailability number. In such cases, reaction is slower than expected, and further increase in the reaction rate does not enhance mass depletion. Mass transfer rate limitations were shown to affect both dechlorination and microbial growth kinetics. The complex dynamics between mass transfer, DNAPL transport and distribution, and

Vertical mass transfer in open channel flow

USGS Publications Warehouse

Jobson, Harvey E.

1968-01-01

The vertical mass transfer coefficient and particle fall velocity were determined in an open channel shear flow. Three dispersants, dye, fine sand and medium sand, were used with each of three flow conditions. The dispersant was injected as a continuous line source across the channel and downstream concentration profiles were measured. From these profiles along with the measured velocity distribution both the vertical mass transfer coefficient and the local particle fall velocity were determined.The effects of secondary currents on the vertical mixing process were discussed. Data was taken and analyzed in such a way as to largely eliminate the effects of these currents on the measured values. A procedure was developed by which the local value of the fall velocity of sand sized particles could be determined in an open channel flow. The fall velocity of the particles in the turbulent flow was always greater than their fall velocity in quiescent water. Reynolds analogy between the transfer of momentum and marked fluid particles was further substantiated. The turbulent Schmidt number was shown to be approximately 1.03 for an open channel flow with a rough boundary. Eulerian turbulence measurements were not sufficient to predict the vertical transfer coefficient. Vertical mixing of sediment is due to three semi-independent processes. These processes are: secondary currents, diffusion due to tangential velocity fluctuations and diffusion due to the curvature of the fluid particle path lines. The diffusion coefficient due to tangential velocity fluctuations is approximately proportional to the transfer coefficient of marked fluid particles. The proportionality constant is less than or equal to 1.0 and decreases with increasing particle size. The diffusion coefficient due to the curvature of the fluid particle path lines is not related to the diffusion coefficient for marked fluid particles and increases with particle size, at least for sediment particles in the sand size

23 CFR 810.210 - Authorization for use and occupancy by mass transit.

Code of Federal Regulations, 2010 CFR

2010-04-01

... 23 Highways 1 2010-04-01 2010-04-01 false Authorization for use and occupancy by mass transit. 810.210 Section 810.210 Highways FEDERAL HIGHWAY ADMINISTRATION, DEPARTMENT OF TRANSPORTATION PUBLIC TRANSPORTATION MASS TRANSIT AND SPECIAL USE HIGHWAY PROJECTS Making Highway Rights-of-Way Available for Mass...

Mass Transit: Actions Needed for the BART Airport Extension

DOT National Transportation Integrated Search

1996-05-31

The Bay Area Rapid Transit District (BART) intends to spend over $1.1 billion, including $750 million in federal funds, to extend mass transit service to the San Francisco International Airport. The project is controversial, encountering both widespr...

Review and Evaluation of Wireless Power Transfer (WPT) for Electric Transit Applications

DOT National Transportation Integrated Search

2014-08-01

This research report provides a status review of emerging and existing Wireless Power Transfer (WPT) technologies applicable to electric bus (EB) and rail transit. The WPT technology options discussed, especially Inductive Power Transfer (IPT), enabl...

Mass transit ridership and self-reported hearing health in an urban population.

PubMed

Gershon, Robyn R M; Sherman, Martin F; Magda, Lori A; Riley, Halley E; McAlexander, Tara P; Neitzel, Richard

2013-04-01

Information on prevalence and risk factors associated with self-reported hearing health among mass transit riders is extremely limited, even though evidence suggests mass transit may be a source of excessive exposure to noise. Data on mass transit ridership were collected from 756 study participants using a self-administered questionnaire. Hearing health was measured using two symptom items (tinnitus and temporary audiometric threshold shift), two subjective measures (self-rated hearing and hearing ability), and two medical-related questions (hearing testing and physician-diagnosed hearing loss). In logistic regression analyses that controlled for possible confounders, including demographic variables, occupational noise exposure, nonoccupational noise exposure (including MP3 player use) and use of hearing protection, frequent and lengthy mass transit (all forms) ridership (1,100 min or more per week vs. 350 min or less per week) was the strongest predictor of temporary threshold shift symptoms. Noise abatement strategies, such as engineering controls, and the promotion of hearing protection use should be encouraged to reduce the risk of adverse impacts on the hearing health of mass transit users.

An Entrance Region Mass Transfer Experiment.

ERIC Educational Resources Information Center

Youngquist, G. R.

1979-01-01

This paper describes an experiment designed to reveal the consequences of the development of a concentration boundary layer. The rate of a mass transfer limited electrochemical reaction is measured and used to obtain the dependence of average Sherwood number on Reynolds number and entrance length. (Author/BB)

Disentangling oil weathering using GC x GC. 2. Mass transfer calculations.

PubMed

Arey, J Samuel; Nelson, Robert K; Plata, Desiree L; Reddy, Christopher M

2007-08-15

Hydrocarbon mass transfers to the atmosphere and water column drive the early weathering of oil spills and also control the chemical exposures of many coastal wildlife species. However, in the field, mass transfer rates of individual hydrocarbons to air and water are often uncertain. In the Part 1 companion to this paper, we used comprehensive two-dimensional gas chromatography (GC x GC) to identify distinct signatures of evaporation and dissolution encoded in the compositional evolution of weathered oils. In Part 2, we further investigate patterns of mass removal in GC x GC chromatograms using a mass transfer model. The model was tailored to conditions at a contaminated beach on Buzzards Bay, MA, after the 2003 Bouchard 120 oil spill. The model was applied to all resolved hydrocarbon compounds in the C11-C24 boiling range, based on their GC x GC-estimated vapor pressures and aqueous solubilities. With no fitted parameters, the model successfully predicted GC x GC chromatogram patterns of mass removal associated with evaporation, water-washing, and diffusion-limited transport. This enabled a critical field evaluation of the mass transfer model and also allowed mass apportionment estimates of hundreds of individual hydrocarbon compounds to air and water. Ultimately, this method should improve assessments of wildlife exposures to oil spill hydrocarbons.

Rock mass classification system : transition from RMR to GSI.

DOT National Transportation Integrated Search

2013-11-01

The AASHTO LRFD Bridge Design Specifications is expected to replace the rock mass rating : (RMR) system with the Geological Strength Index (GSI) system for classifying and estimating : engineering properties of rock masses. This transition is motivat...

LUT observations of the mass-transferring binary AI Dra

NASA Astrophysics Data System (ADS)

Liao, Wenping; Qian, Shengbang; Li, Linjia; Zhou, Xiao; Zhao, Ergang; Liu, Nianping

2016-06-01

Complete UV band light curve of the eclipsing binary AI Dra was observed with the Lunar-based Ultraviolet Telescope (LUT) in October 2014. It is very useful to adopt this continuous and uninterrupted light curve to determine physical and orbital parameters of the binary system. Photometric solutions of the spot model are obtained by using the W-D (Wilson and Devinney) method. It is confirmed that AI Dra is a semi-detached binary with secondary component filling its critical Roche lobe, which indicates that a mass transfer from the secondary component to the primary one should happen. Orbital period analysis based on all available eclipse times suggests a secular period increase and two cyclic variations. The secular period increase was interpreted by mass transfer from the secondary component to the primary one at a rate of 4.12 ×10^{-8}M_{⊙}/yr, which is in agreement with the photometric solutions. Two cyclic oscillations were due to light travel-time effect (LTTE) via the presence of two cool stellar companions in a near 2:1 mean-motion resonance. Both photometric solutions and orbital period analysis confirm that AI Dra is a mass-transferring binary, the massive primary is filling 69 % of its critical Roche lobe. After the primary evolves to fill the critical Roche lobe, the mass transfer will be reversed and the binary will evolve into a contact configuration.

Electron transfer by excited benzoquinone anions: slow rates for two-electron transitions.

PubMed

Zamadar, Matibur; Cook, Andrew R; Lewandowska-Andralojc, Anna; Holroyd, Richard; Jiang, Yan; Bikalis, Jin; Miller, John R

2013-09-05

Electron transfer (ET) rate constants from the lowest excited state of the radical anion of benzoquinone, BQ(-•)*, were measured in THF solution. Rate constants for bimolecular electron transfer reactions typically reach the diffusion-controlled limit when the free-energy change, ΔG°, reaches -0.3 eV. The rate constants for ET from BQ(-•)* are one-to-two decades smaller at this energy and do not reach the diffusion-controlled limit until -ΔG° is 1.5-2.0 eV. The rates are so slow probably because a second electron must also undergo a transition to make use of the energy of the excited state. Similarly, ET, from solvated electrons to neutral BQ to form the lowest excited state, is slow, while fast ET is observed at a higher excited state, which can be populated in a transition involving only one electron. A simple picture based on perturbation theory can roughly account for the control of electron transfer by the need for transition of a second electron. The picture also explains how extra driving force (-ΔG°) can restore fast rates of electron transfer.

Prediction of mass transfer coefficient in rotating bed contactor (Higee) using artificial neural network

NASA Astrophysics Data System (ADS)

Saha, Dipendu

2009-02-01

The feasibility of drastically reducing the contactor size in mass transfer processes utilizing centrifugal field has generated a lot of interest in rotating packed bed (Higee). Various investigators have proposed correlations to predict mass transfer coefficients in Higee, but, none of the correlations was more than 20-30% accurate. In this work, artificial neural network (ANN) is employed for predicting mass transfer coefficient data. Results show that ANN provides better estimation of mass transfer coefficient with accuracy 5-15%.

Recent advances in transition metal-catalyzed N -atom transfer reactions of azides

PubMed Central

Driver, Tom G.

2011-01-01

Transition metal-catalyzed N-atom transfer reactions of azides provide efficient ways to construct new carbon–nitrogen and sulfur–nitrogen bonds. These reactions are inherently green: no additive besides catalyst is needed to form the nitrenoid reactive intermediate, and the by-product of the reaction is environmentally benign N2 gas. As such, azides can be useful precursors for transition metal-catalyzed N-atom transfer to sulfides, olefins and C–H bonds. These methods offer competitive selectivities and comparable substrate scope as alternative processes to generate metal nitrenoids. PMID:20617243

Influence of drying air parameters on mass transfer characteristics of apple slices

NASA Astrophysics Data System (ADS)

Beigi, Mohsen

2016-10-01

To efficiently design both new drying process and equipment and/or to improve the existing systems, accurate values of mass transfer characteristics are necessary. The present study aimed to investigate the influence of drying air parameters (i.e. temperature, velocity and relative humidity) on effective diffusivity and convective mass transfer coefficient of apple slices. The Dincer and Dost model was used to determine the mass transfer characteristics. The obtained Biot number indicated that the moisture transfer in the apple slices was controlled by both internal and external resistance. The effective diffusivity and mass transfer coefficient values obtained to be in the ranges of 7.13 × 10-11-7.66 × 10-10 and 1.46 × 10-7-3.39 × 10-7 m s-1, respectively and the both of them increased with increasing drying air temperature and velocity, and decreasing relative humidity. The validation of the model showed that the model predicted the experimental drying curves of the samples with a good accuracy.

Simultaneous Heat and Mass Transfer Model for Convective Drying of Building Material

NASA Astrophysics Data System (ADS)

Upadhyay, Ashwani; Chandramohan, V. P.

2018-04-01

A mathematical model of simultaneous heat and moisture transfer is developed for convective drying of building material. A rectangular brick is considered for sample object. Finite-difference method with semi-implicit scheme is used for solving the transient governing heat and mass transfer equation. Convective boundary condition is used, as the product is exposed in hot air. The heat and mass transfer equations are coupled through diffusion coefficient which is assumed as the function of temperature of the product. Set of algebraic equations are generated through space and time discretization. The discretized algebraic equations are solved by Gauss-Siedel method via iteration. Grid and time independent studies are performed for finding the optimum number of nodal points and time steps respectively. A MATLAB computer code is developed to solve the heat and mass transfer equations simultaneously. Transient heat and mass transfer simulations are performed to find the temperature and moisture distribution inside the brick.

Heat transfer and fluid mechanics measurements in transitional boundary layer flows

NASA Technical Reports Server (NTRS)

Wang, T.; Simon, T. W.; Buddhavarapu, J.

1985-01-01

Experimental results are presented to document hydrodynamic and thermal development of flat-plate boundary layers undergoing natural transition. Local heat transfer coefficients, skin friction coefficients and profiles of velocity, temperature and Reynolds normal and shear stresses are presented. A case with no transition and transitional cases with 0.68% and 2.0% free-stream disturbance intensities were investigated. The locations of transition are consistent with earlier data. A late-laminar state with significant levels of turbulence is documented. In late-transitional and early-turbulent flows, turbulent Prandtl number and conduction layer thickness values exceed, and the Reynolds analogy factor is less than, values previously measured in fully turbulent flows.

Model for heat and mass transfer in freeze-drying of pellets.

PubMed

Trelea, Ioan Cristian; Passot, Stéphanie; Marin, Michèle; Fonseca, Fernanda

2009-07-01

Lyophilizing frozen pellets, and especially spray freeze-drying, have been receiving growing interest. To design efficient and safe freeze-drying cycles, local temperature and moisture content in the product bed have to be known, but both are difficult to measure in the industry. Mathematical modeling of heat and mass transfer helps to determine local freeze-drying conditions and predict effects of operation policy, and equipment and recipe changes on drying time and product quality. Representative pellets situated at different positions in the product slab were considered. One-dimensional transfer in the slab and radial transfer in the pellets were assumed. Coupled heat and vapor transfer equations between the temperature-controlled shelf, the product bulk, the sublimation front inside the pellets, and the chamber were established and solved numerically. The model was validated based on bulk temperature measurement performed at two different locations in the product slab and on partial vapor pressure measurement in the freeze-drying chamber. Fair agreement between measured and calculated values was found. In contrast, a previously developed model for compact product layer was found inadequate in describing freeze-drying of pellets. The developed model represents a good starting basis for studying freeze-drying of pellets. It has to be further improved and validated for a variety of product types and freeze-drying conditions (shelf temperature, total chamber pressure, pellet size, slab thickness, etc.). It could be used to develop freeze-drying cycles based on product quality criteria such as local moisture content and glass transition temperature.

The role of intra-NAPL diffusion on mass transfer from MGP residuals

NASA Astrophysics Data System (ADS)

Shafieiyoun, Saeid; Thomson, Neil R.

2018-06-01

An experimental and computational study was performed to investigate the role of multi-component intra-NAPL diffusion on NAPL-water mass transfer. Molecular weight and the NAPL component concentrations were determined to be the most important parameters affecting intra-NAPL diffusion coefficients. Four NAPLs with different viscosities but the same quantified mass were simulated. For a spherical NAPL body, a combination of NAPL properties and interphase mass transfer rate can result in internal diffusion limitations. When the main intra-NAPL diffusion coefficients are in the range of self-diffusion coefficients (10-5 to 10-6 cm2/s), dissolution is not limited by internal diffusion except for high mass transfer rate coefficients (>180 cm/day). For a complex and relatively high viscous NAPL (>50 g/(cm s)), smaller intra-NAPL diffusion coefficients (<10-8) are expected and even low mass transfer rate coefficients ( 6 cm/day) can result in diffusion-limited dissolution.

Supporting the Transition of Sophomores, Transfers, and Seniors: Opportunities for Residence Life Professionals

ERIC Educational Resources Information Center

Kranzow, Jeannine; Foote, Stephanie M.; Hinkle, Sara E.

2015-01-01

College students transitioning to their sophomore year, those transferring to a new institution, and seniors transitioning out of higher education face various challenges and struggles. The literature on the transitions associated with these student populations indicates that they need sustained support in a few key areas that include student and…

Coloration of tyrosine by organic-semiconductor interfacial charge-transfer transitions

NASA Astrophysics Data System (ADS)

Fujisawa, Jun-ichi; Kikuchi, Natsumi; Hanaya, Minoru

2016-11-01

L-tyrosine (Tyr) plays a crucial role as a proteinogenic amino acid and also as a precursor to several neurotransmitters and hormones. Here we demonstrate coloration of Tyr based on organic-semiconductor interfacial charge-transfer (ICT) transitions. The ICT transitions from Tyr to TiO2 are induced by the chemisorption of Tyr on TiO2 surfaces via the hydroxy group of the phenol moiety. Because other amino acids possess no chemical group to induce ICT transitions, this coloration method enables to detect Tyr selectively without drastic structural change in contrast to the conventional coloration methods.

Influence of the boundary conditions on heat and mass transfer in spacer-filled channels

NASA Astrophysics Data System (ADS)

Ciofalo, M.; La Cerva, M. F.; Di Liberto, M.; Tamburini, A.

2017-11-01

The purpose of this study is to discuss some problems which arise in heat or mass transfer in complex channels, with special reference to the spacer-filled channels adopted in membrane processes. Among the issues addressed are the consistent definition of local and mean heat or mass transfer coefficients; the influence of the wall boundary conditions; the influence of one-side versus two-side heat/mass transfer. Most of the results discussed were obtained by finite volume CFD simulations concerning heat transfer in Membrane Distillation or mass transfer in Electrodialysis and Reverse Electrodialysis, but many of the conclusions apply also to different processes involving geometrically complex channels

The effects of dual-domain mass transfer on the tritium-helium-3 dating method.

PubMed

Neumann, Rebecca B; Labolle, Eric M; Harvey, Charles F

2008-07-01

Diffusion of tritiated water (referred to as tritium) and helium-3 between mobile and immobile regions in aquifers (mass transfer) can affect tritium and helium-3 concentrations and hence tritium-helium-3 (3H/3He) ages that are used to estimate aquifer recharge and groundwater residence times. Tritium and helium-3 chromatographically separate during transport because their molecular diffusion coefficients differ. Simulations of tritium and helium-3 transport and diffusive mass transfer along stream tubes show that mass transfer can shift the 3H/3He age of the tritium and helium-3 concentration ([3H + 3He]) peak to dates much younger than the 1963 peak in atmospheric tritium. Furthermore, diffusive mass-transfer can cause the 3H/3He age to become younger downstream along a stream tube, even as the mean water-age must increase. Simulated patterns of [3H + 3He] versus 3H/3He age using a mass transfer model appear consistent with a variety of field data. These results suggest that diffusive mass transfer should be considered, especially when the [3H + 3He] peak is not well defined or appears younger than the atmospheric peak. 3H/3He data provide information about upstream mass-transfer processes that could be used to constrain mass-transfer models; however, uncritical acceptance of 3H/3He dates from aquifers with immobile regions could be misleading.

Mass Transfer Testing of a 12.5-cm Rotor Centrifugal Contactor

DOE Office of Scientific and Technical Information (OSTI.GOV)

D. H. Meikrantz; T. G. Garn; J. D. Law

2008-09-01

TRUEX mass transfer tests were performed using a single stage commercially available 12.5 cm centrifugal contactor and stable cerium (Ce) and europium (Eu). Test conditions included throughputs ranging from 2.5 to 15 Lpm and rotor speeds of 1750 and 2250 rpm. Ce and Eu extraction forward distribution coefficients ranged from 13 to 19. The first and second stage strip back distributions were 0.5 to 1.4 and .002 to .004, respectively, throughout the dynamic test conditions studied. Visual carryover of aqueous entrainment in all organic phase samples was estimated at < 0.1 % and organic carryover into all aqueous phase samplesmore » was about ten times less. Mass transfer efficiencies of = 98 % for both Ce and Eu in the extraction section were obtained over the entire range of test conditions. The first strip stage mass transfer efficiencies ranged from 75 to 93% trending higher with increasing throughput. Second stage mass transfer was greater than 99% in all cases. Increasing the rotor speed from 1750 to 2250 rpm had no significant effect on efficiency for all throughputs tested.« less

Effect of operating temperature on styrene mass transfer characteristics in a biotrickling filter.

PubMed

Parnian, Parham; Zamir, Seyed Morteza; Shojaosadati, Seyed Abbas

2017-05-01

To study the effect of operating temperature on styrene mass transfer from gas to liquid phase in biotrickling filters (BTFs), overall mass transfer coefficient (K L a) was calculated through fitting test data to a general mass balance model under abiotic conditions. Styrene was used as the volatile organic compound and the BTF was packed with a mixture of pall rings and pumice. Operating temperature was set at 30°C and 50°C for mesophilic and thermophilic conditions, respectively. K L a values increased from 54 to 70 h -1 at 30°C and from 60 to 90 h -1 at 50°C, respectively, depending on the countercurrent gas to liquid flow ratio that varied in the range of 7.5-32. Evaluation of styrene mass transfer capacity (MTC) showed that liquid-phase mass transfer resistance decreased as the flow ratio increased at constant temperature. MTC also decreased with an increase in operating temperature. Both gas-liquid partition coefficient and K L a increased with increasing temperature; however the effect on gas-liquid partition coefficient was more significant and served to increase mass transfer limitations. Thermophilic biofiltration on the one hand increases mass transfer limitations, but on the other hand may enhance the biodegradation rate in favor of enhancing BTFs' performance.

Mass transit : project management oversight benefits and future funding requirements

DOT National Transportation Integrated Search

2000-09-01

To meet the nation's transportation needs, many states, cities, and localities are building or planning mass transit projects to replace aging infrastructure or add new capacity. These transit projects are very costly and require large investments of...

Thermal Timescale Mass Transfer In Binary Population Synthesis

NASA Astrophysics Data System (ADS)

Justham, S.; Kolb, U.

2004-07-01

Studies of binary evolution have, until recently, neglected thermal timescale mass transfer (TTMT). Recent work has suggested that this previously poorly studied area is crucial in the understanding of systems across the compact binary spectrum. We use the state-of-the-art binary population synthesis code BiSEPS (Willems and Kolb, 2002, MNRAS 337 1004-1016). However, the present treatment of TTMT is incomplete due to the nonlinear behaviour of stars in their departure from gravothermal `equilibrium'. Here we show work that should update the ultrafast stellar evolution algorithms within BiSEPS to make it the first pseudo-analytic code that can follow TTMT properly. We have generated fits to a set of over 300 Case B TTMT sequences with a range of intermediate-mass donors. These fits produce very good first approximations to both HR diagrams and mass-transfer rates (see figures 1 and 2), which we later hope to improve and extend. They are already a significant improvement over the previous fits.

Student Transitions Project: Mobility of Transfer Students Sub-Committee Terms of Reference

ERIC Educational Resources Information Center

Ministry of Advanced Education, 2007

2007-01-01

The Student Transitions Project Steering Committee's terms of reference allow it to appoint sub-committees to provide advice. Recently, the committee appointed a Mobility of Transfer Students Sub-Committee (formerly the Enrolment Planning Data Sub-Committee, a sub-committee of the British Columbia Council on Admissions and Transfer). The…

Mass transfer in a 1370 C (2500 F) lithium thermal convection loop

NASA Technical Reports Server (NTRS)

Scheuermann, C. M.

1974-01-01

Experimental results from a test to evaluate interstitial element mass transfer effects on T-111, ASTAR 811C, and ASTAR 1211C after 5000 hours in flowing lithium at 1370 C (2500 F) are presented. No gross corrosion effects were observed. However, hafnium and nitrogen transfer to cooler regions within the loop were noted. Oxygen was in general removed from test specimens, but there was no evidence to indicate that it was a major factor in the mass transfer process. Carbon and hydrogen transfer were not detected.

Heat Transfer in Conical Corner and Short Superelliptical Transition Ducts

NASA Technical Reports Server (NTRS)

Poinsatte, Philip; Thurman, Douglas; Hippensteele, Steven

2008-01-01

Local surface heat transfer measurements were experimentally mapped using a transient liquid-crystal heat-transfer technique on the surface of two circular-to-rectangular transition ducts. One has a transition cross section defined by conical corners (Duct 1) and the other by an elliptical equation with changing coefficients (Duct 2). Duct 1 has a length-to-diameter ratio of 0.75 and an exit plane aspect ratio of 1.5. Duct 2 has a length-to-diameter ratio of 1.0 and an exit plane aspect ratio of 2.9. Test results are reported for various inlet-diameter-based Reynolds numbers ranging from 0.45 106 to 2.39 106 and two freestream turbulence intensities of about 1 percent, which is typical of wind tunnels, and up to 16 percent, which may be more typical of real engine conditions.

Mass transfer apparatus and method for separation of gases

DOEpatents

Blount, Gerald C.

2015-10-13

A process and apparatus for separating components of a source gas is provided in which more soluble components of the source gas are dissolved in an aqueous solvent at high pressure. The system can utilize hydrostatic pressure to increase solubility of the components of the source gas. The apparatus includes gas recycle throughout multiple mass transfer stages to improve mass transfer of the targeted components from the liquid to gas phase. Separated components can be recovered for use in a value added application or can be processed for long-term storage, for instance in an underwater reservoir.

Mass transfer apparatus and method for separation of gases

DOE Office of Scientific and Technical Information (OSTI.GOV)

Blount, Gerald C.; Gorensek, Maximilian Boris; Hamm, Luther L.

A process and apparatus for separating components of a source gas is provided in which more soluble components of the source gas are dissolved in an aqueous solvent at high pressure. The system can utilize hydrostatic pressure to increase solubility of the components of the source gas. The apparatus includes gas recycle throughout multiple mass transfer stages to improve mass transfer of the targeted components from the liquid to gas phase. Separated components can be recovered for use in a value added application or can be processed for long-term storage, for instance in an underwater reservoir.

Mass Transfer via Low-Velocity Rebound in a Microgravity Environment

NASA Astrophysics Data System (ADS)

Jarmak, S. G.; Colwell, J. E.; Brisset, J.; Dove, A.; Brown, A. Q.

2017-12-01

Observations of low-velocity collisions (< 1 m/s) between μm to cm-size particles in a microgravity environment are crucial to an understanding of the surface properties of small, airless bodies as well as the processes that lead to their formation. The COLLIDE (Collisions Into Dust Experiment) and PRIME (Physics of Regolith Impacts in Microgravity Experiment) programs created impacts into simulated planetary regolith with cm-scale impactors to observe ejecta production and coefficients of restitution in microgravity. These experiments were carried out on orbit (COLLIDE, COLLIDE-2), in suborbital space (COLLIDE-3), and on parabolic airplane flights (PRIME) under vacuum. Some impacts at speeds less than 40 cm/s resulted in mass transfer from the target regolith onto the impactor. To study these mass-transfer collisions in more detail without the cost or time requirements of spaceflight or parabolic flights, we developed an experimental apparatus in a laboratory drop tower (free-fall time 0.75 s) and performed experiments at standard pressure. The impactor is suspended from a spring and remains in contact with the bed of regolith until free-fall allows the spring to retract and pull the impactor upwards. This method allowed us to simulate the rebound portion of a low-velocity collision in a laboratory microgravity environment. We achieved rebound velocities of 10 - 60 cm/s, and we observed mass transfer events with rebound speeds below 40 cm/s. The amount of mass transfer produced was more significant than a monolayer of granular material, but less than the amount observed in the COLLIDE and PRIME experiments. These mass-transfer collisions may play a role in the growth of planetesimals. We will present the results of our laboratory-based studies where we vary impact velocity and target material, and discuss implications for collisional evolution in the protoplanetary disk and planetary rings.

An Algorithm to Compress Line-transition Data for Radiative-transfer Calculations

NASA Astrophysics Data System (ADS)

Cubillos, Patricio E.

2017-11-01

Molecular line-transition lists are an essential ingredient for radiative-transfer calculations. With recent databases now surpassing the billion-line mark, handling them has become computationally prohibitive, due to both the required processing power and memory. Here I present a temperature-dependent algorithm to separate strong from weak line transitions, reformatting the large majority of the weaker lines into a cross-section data file, and retaining the detailed line-by-line information of the fewer strong lines. For any given molecule over the 0.3-30 μm range, this algorithm reduces the number of lines to a few million, enabling faster radiative-transfer computations without a significant loss of information. The final compression rate depends on how densely populated the spectrum is. I validate this algorithm by comparing Exomol’s HCN extinction-coefficient spectra between the complete (65 million line transitions) and compressed (7.7 million) line lists. Over the 0.6-33 μm range, the average difference between extinction-coefficient values is less than 1%. A Python/C implementation of this algorithm is open-source and available at https://github.com/pcubillos/repack. So far, this code handles the Exomol and HITRAN line-transition format.

OT1_ipascucc_1: Understanding the Origin of Transition Disks via Disk Mass Measurements

NASA Astrophysics Data System (ADS)

Pascucci, I.

2010-07-01

Transition disks are a distinguished group of few Myr-old systems caught in the phase of dispersing their inner dust disk. Three different processes have been proposed to explain this inside-out clearing: grain growth, photoevaporation driven by the central star, and dynamical clearing by a forming giant planet. Which of these processes lead to a transition disk? Distinguishing between them requires the combined knowledge of stellar accretion rates and disk masses. We propose here to use 43.8 hours of PACS spectroscopy to detect the [OI] 63 micron emission line from a sample of 21 well-known transition disks with measured mass accretion rates. We will use this line, in combination with ancillary CO millimeter lines, to measure their gas disk mass. Because gas dominates the mass of protoplanetary disks our approach and choice of lines will enable us to trace the bulk of the disk mass that resides beyond tens of AU from young stars. Our program will quadruple the number of transition disks currently observed with Herschel in this setting and for which disk masses can be measured. We will then place the transition and the ~100 classical/non-transition disks of similar age (from the Herschel KP "Gas in Protoplanetary Systems") in the mass accretion rate-disk mass diagram with two main goals: 1) reveal which gaps have been created by grain growth, photoevaporation, or giant planet formation and 2) from the statistics, determine the main disk dispersal mechanism leading to a transition disk.

Improving the Transition of Care in Patients Transferred Through the Ochsner Medical Center Transfer Center

PubMed Central

Amedee, Ronald G.; Maronge, Genevieve F.; Pinsky, William W.

2012-01-01

Background Patient transfers from other hospitals within the Ochsner Health System to the main campus are coordinated through a Transfer Center that was established in fall 2008. We analyzed the transfer process to assess distinct opportunities to enhance the overall transition of patient care. Methods We surveyed internal medicine residents and nocturnists to determine their satisfaction with transfers in terms of safety, efficiency, and usefulness of information provided at the time of transfer. After a kaizen event at which complementary goals for the institution and members of the study team were recognized and implemented, we resurveyed the group to evaluate improvement in the transfer process. Results The preintervention average satisfaction score was 1.18 (SD=0.46), while the postintervention score was 3.7 (SD=1.01). A t test showed a significant difference in the average scores between the preintervention and postintervention surveys (P<0.0001). Conclusions By including residents in the transfer calls (a result of the kaizen event), data were collected that facilitated fewer and higher quality handoffs that were performed in less time. In addition, the process resulted in increased awareness of the value of resident participation in institutional quality improvement projects. PMID:23267257

Improving the transition of care in patients transferred through the ochsner medical center transfer center.

PubMed

Amedee, Ronald G; Maronge, Genevieve F; Pinsky, William W

2012-01-01

Patient transfers from other hospitals within the Ochsner Health System to the main campus are coordinated through a Transfer Center that was established in fall 2008. We analyzed the transfer process to assess distinct opportunities to enhance the overall transition of patient care. We surveyed internal medicine residents and nocturnists to determine their satisfaction with transfers in terms of safety, efficiency, and usefulness of information provided at the time of transfer. After a kaizen event at which complementary goals for the institution and members of the study team were recognized and implemented, we resurveyed the group to evaluate improvement in the transfer process. The preintervention average satisfaction score was 1.18 (SD=0.46), while the postintervention score was 3.7 (SD=1.01). A t test showed a significant difference in the average scores between the preintervention and postintervention surveys (P<0.0001). By including residents in the transfer calls (a result of the kaizen event), data were collected that facilitated fewer and higher quality handoffs that were performed in less time. In addition, the process resulted in increased awareness of the value of resident participation in institutional quality improvement projects.

Direct Numerical Simulation of Fluid Flow and Mass Transfer in Particle Clusters

PubMed Central

2018-01-01

In this paper, an efficient ghost-cell based immersed boundary method is applied to perform direct numerical simulation (DNS) of mass transfer problems in particle clusters. To be specific, a nine-sphere cuboid cluster and a random-generated spherical cluster consisting of 100 spheres are studied. In both cases, the cluster is composed of active catalysts and inert particles, and the mutual influence of particles on their mass transfer performance is studied. To simulate active catalysts the Dirichlet boundary condition is imposed at the external surface of spheres, while the zero-flux Neumann boundary condition is applied for inert particles. Through our studies, clustering is found to have negative influence on the mass transfer performance, which can be then improved by dilution with inert particles and higher Reynolds numbers. The distribution of active/inert particles may lead to large variations of the cluster mass transfer performance, and individual particle deep inside the cluster may possess a high Sherwood number. PMID:29657359

A super-Earth transiting a nearby low-mass star.

PubMed

Charbonneau, David; Berta, Zachory K; Irwin, Jonathan; Burke, Christopher J; Nutzman, Philip; Buchhave, Lars A; Lovis, Christophe; Bonfils, Xavier; Latham, David W; Udry, Stéphane; Murray-Clay, Ruth A; Holman, Matthew J; Falco, Emilio E; Winn, Joshua N; Queloz, Didier; Pepe, Francesco; Mayor, Michel; Delfosse, Xavier; Forveille, Thierry

2009-12-17

A decade ago, the detection of the first transiting extrasolar planet provided a direct constraint on its composition and opened the door to spectroscopic investigations of extrasolar planetary atmospheres. Because such characterization studies are feasible only for transiting systems that are both nearby and for which the planet-to-star radius ratio is relatively large, nearby small stars have been surveyed intensively. Doppler studies and microlensing have uncovered a population of planets with minimum masses of 1.9-10 times the Earth's mass (M[symbol:see text]), called super-Earths. The first constraint on the bulk composition of this novel class of planets was afforded by CoRoT-7b (refs 8, 9), but the distance and size of its star preclude atmospheric studies in the foreseeable future. Here we report observations of the transiting planet GJ 1214b, which has a mass of 6.55M[symbol:see text]), and a radius 2.68 times Earth's radius (R[symbol:see text]), indicating that it is intermediate in stature between Earth and the ice giants of the Solar System. We find that the planetary mass and radius are consistent with a composition of primarily water enshrouded by a hydrogen-helium envelope that is only 0.05% of the mass of the planet. The atmosphere is probably escaping hydrodynamically, indicating that it has undergone significant evolution during its history. The star is small and only 13 parsecs away, so the planetary atmosphere is amenable to study with current observatories.

Assessing the comparative efficiency of urban mass transit systems in Ohio : longitudinal analysis.

DOT National Transportation Integrated Search

2013-12-01

A mass transit system not only improves passenger mobility, it also affects the level of economic activities (e.g., working and shopping). Thus, changes wrought by mass transit service planning can heavily influence regional economic growth. This pla...

Nuclear quantum shape-phase transitions in odd-mass systems

NASA Astrophysics Data System (ADS)

Quan, S.; Li, Z. P.; Vretenar, D.; Meng, J.

2018-03-01

Microscopic signatures of nuclear ground-state shape-phase transitions in odd-mass Eu isotopes are explored starting from excitation spectra and collective wave functions obtained by diagonalization of a core-quasiparticle coupling Hamiltonian based on energy density functionals. As functions of the physical control parameter—the number of nucleons—theoretical low-energy spectra, two-neutron separation energies, charge isotope shifts, spectroscopic quadrupole moments, and E 2 reduced transition matrix elements accurately reproduce available data and exhibit more-pronounced discontinuities at neutron number N =90 compared with the adjacent even-even Sm and Gd isotopes. The enhancement of the first-order quantum phase transition in odd-mass systems can be attributed to a shape polarization effect of the unpaired proton which, at the critical neutron number, starts predominantly coupling to Gd core nuclei that are characterized by larger quadrupole deformation and weaker proton pairing correlations compared with the corresponding Sm isotopes.

Local endwall heat/mass-transfer distributions in pin fin channels

NASA Astrophysics Data System (ADS)

Lau, S. C.; Kim, Y. S.; Han, J. C.

1987-10-01

Naphthalene sublimination experiments were conducted to study the effects of the pin configuration, the pin length-to-diameter ratio, and the entrance length on local endwall heat/mass transfer in a channel with short pin fins (pin length-to-diameter ratios of 0.5 and 1.0). The detailed distributions of the local endwall heat/mass-transfer coefficient were obtained for staggered and aligned arrays of pin fins, for the spanwise pin spacing-to-diameter ratio of 2.5, and for streamwise pin spacing-to-diameter ratios of 1.25 and 2.5. The Reynolds numbers were kept at about 33,000. Overall- and row-averaged Nusselt numbers compared very well with those from previous heat-transfer studies.

Mass Transit: Status of New Starts Transit Projects With Full Funding Grant Agreements

DOT National Transportation Integrated Search

1999-08-19

Since the early 1970s, the federal government has provided a large share of the nation's capital investment in urban mass transportation. Much of this investment has come through the Federal Transit Administration's (FTA) "new starts" program, which ...

Ozone mass transfer behaviors on physical and chemical absorption for hollow fiber membrane contactors.

PubMed

Zhang, Yong; Li, Kuiling; Wang, Jun; Hou, Deyin; Liu, Huijuan

2017-09-01

To understand the mass transfer behaviors in hollow fiber membrane contactors, ozone fluxes affected by various conditions and membranes were investigated. For physical absorption, mass transfer rate increased with liquid velocity and the ozone concentration in the gas. Gas flow rate was little affected when the velocity was larger than the critical value, which was 6.1 × 10 -3 m/s in this study. For chemical absorption, the flux was determined by the reaction rate between ozone and the absorbent. Therefore, concentration, species, and pH affected the mass transfer process markedly. For different absorbents, the order of mass transfer rate was the same as the reaction rate constant, which was phenol, sodium nitrite, hydrogen peroxide, and oxalate. Five hydrophobic membranes with various properties were employed and the mass transfer behavior can be described by the Graetz-Lévèque equation for the physical absorption process. The results showed the process was controlled by liquid film and the gas phase conditions, and membrane properties did not affect the ozone flux. For the chemical absorption, gas film, membrane and liquid film affected the mass transfer together, and none of them were negligible.

Evaporative mass transfer behavior of a complex immiscible liquid.

PubMed

McColl, Colleen M; Johnson, Gwynn R; Brusseau, Mark L

2008-09-01

A series of laboratory experiments was conducted with a multiple-component immiscible liquid, collected from the Picillo Farm Superfund Site in Rhode Island, to examine liquid-vapor mass-transfer behavior. The immiscible liquid, which comprises solvents, oils, pesticides, PCBs, paint sludges, explosives, and other compounds, was characterized using gas chromatography and gas chromatography/mass spectrometry to determine mole fractions of selected constituents. Batch experiments were conducted to evaluate equilibrium phase-partitioning behavior. Two sets of air-stripping column studies were conducted to examine the mass-transfer dynamics of five selected target compounds present in the immiscible-liquid mixture. One set of column experiments was designed to represent a system with free-phase immiscible liquid present; the other was designed to represent a system with a residual phase of immiscible liquid. Initial elution behavior of all target components generally appeared to be ideal for both systems, as the initial vapor-phase concentrations were similar to vapor-phase concentrations measured for the batch experiment and those estimated using Raoult's law (incorporating the immiscible-liquid composition data). Later-stage removal of 1,2-dichlorobenzene appeared to be rate limited for the columns containing free-phase immiscible liquid and no porous medium. Conversely, evaporative mass transfer appeared to be ideal throughout the experiment conducted with immiscible liquid distributed relatively uniformly as a residual phase within a sandy porous medium.

Evaporative Mass Transfer Behavior of a Complex Immiscible Liquid

PubMed Central

McColl, Colleen M.; Johnson, Gwynn R.; Brusseau, Mark L.

2010-01-01

A series of laboratory experiments was conducted with a multiple-component immiscible liquid, collected from the Picillo Farm Superfund Site in Rhode Island, to examine liquid-vapor mass-transfer behavior. The immiscible liquid, which comprises solvents, oils, pesticides, PCBs, paint sludges, explosives, and other compounds, was characterized using gas chromatography and gas chromatography/mass spectrometry to determine mole fractions of selected constituents. Batch experiments were conducted to evaluate equilibrium phase-partitioning behavior. Two sets of air-stripping column studies were conducted to examine the mass-transfer dynamics of five selected target compounds present in the immiscible-liquid mixture. One set of column experiments was designed to represent a system with free-phase immiscible liquid present; the other was designed to represent a system with a residual phase of immiscible liquid. Initial elution behavior of all target components generally appeared to be ideal for both systems, as the initial vapor-phase concentrations were similar to vapor-phase concentrations measured for the batch experiment and those estimated using Raoult’s law (incorporating the immiscible-liquid composition data). Later-stage removal of 1,2-dichlorobenzene appeared to be rate limited for the columns containing free-phase immiscible liquid and no porous medium. Conversely, evaporative mass transfer appeared to be ideal throughout the experiment conducted with immiscible liquid distributed relatively uniformly as a residual phase within a sandy porous medium. PMID:18614196

Mass transfer equation for proteins in very high-pressure liquid chromatography.

PubMed

Gritti, Fabrice; Guiochon, Georges

2009-04-01

The mass transfer kinetics of human insulin was investigated on a 50 mm x 2.1 mm column packed with 1.7 microm BEH-C(18) particles, eluted with a water/acetonitrile/trifluoroacetic acid (TFA) (68/32/0.1, v/v/v) solution. The different contributions to the mass transfer kinetics, e.g., those of longitudinal diffusion, eddy dispersion, the film mass transfer resistance, cross-particle diffusivity, adsorption-desorption kinetics, and transcolumn differential sorption, were incorporated into a general mass transfer equation designed to account for the mass transfer kinetics of proteins under high pressure. More specifically, this equation includes the effects of pore size exclusion, pressure, and temperature on the band broadening of a protein. The flow rate was first increased from 0.001 to 0.250 mL/min, the pressure drop increasing from 2 to 298 bar, and the column being placed in stagnant air at 296.5 K, in order to determine the effective diffusivity of insulin through the porous particles, the mass transfer rate constants, and the adsorption equilibrium constant in the low-pressure range. Then, the column inlet pressure was increased by using capillary flow restrictors downstream the column, at the constant flow rate of 0.03 mL/min. The column temperature was kept uniform by immersing the column in a circulating water bath thermostatted at 298.7 and 323.15 K, successively. The results showed that the surface diffusion coefficient of insulin decreases faster than its bulk diffusion coefficient with increasing average column pressure. This is consistent with the adsorption energy of insulin onto the BEH-C(18) surface increasing strongly with increasing pressure. In contrast, given the precision of the height equivalent to a theoretical plate (HETP) measurement (+/-12%), the adsorption kinetics of insulin appears to be rather independent of the pressure. On average, the adsorption rate constant of insulin is doubled from about 40 to 80 s(-1) when the temperature

Geoelectrical inference of mass transfer parameters using temporal moments

USGS Publications Warehouse

Day-Lewis, Frederick D.; Singha, Kamini

2008-01-01

We present an approach to infer mass transfer parameters based on (1) an analytical model that relates the temporal moments of mobile and bulk concentration and (2) a bicontinuum modification to Archie's law. Whereas conventional geochemical measurements preferentially sample from the mobile domain, electrical resistivity tomography (ERT) is sensitive to bulk electrical conductivity and, thus, electrolytic solute in both the mobile and immobile domains. We demonstrate the new approach, in which temporal moments of collocated mobile domain conductivity (i.e., conventional sampling) and ERT‐estimated bulk conductivity are used to calculate heterogeneous mass transfer rate and immobile porosity fractions in a series of numerical column experiments.

Fem Formulation for Heat and Mass Transfer in Porous Medium

NASA Astrophysics Data System (ADS)

Azeem; Soudagar, Manzoor Elahi M.; Salman Ahmed, N. J.; Anjum Badruddin, Irfan

2017-08-01

Heat and mass transfer in porous medium can be modelled using three partial differential equations namely, momentum equation, energy equation and mass diffusion. These three equations are coupled to each other by some common terms that turn the whole phenomenon into a complex problem with inter-dependable variables. The current article describes the finite element formulation of heat and mass transfer in porous medium with respect to Cartesian coordinates. The problem under study is formulated into algebraic form of equations by using Galerkin's method with the help of two-node linear triangular element having three nodes. The domain is meshed with smaller sized elements near the wall region and bigger size away from walls.

Numerical study of heat and mass transfer in inertial suspensions in pipes.

NASA Astrophysics Data System (ADS)

Niazi Ardekani, Mehdi; Brandt, Luca

2017-11-01

Controlling heat and mass transfer in particulate suspensions has many important applications such as packed and fluidized bed reactors and industrial dryers. In this work, we study the heat and mass transfer within a suspension of spherical particles in a laminar pipe flow, using the immersed boundary method (IBM) to account for the solid fluid interactions and a volume of fluid (VoF) method to resolve temperature equation both inside and outside of the particles. Tracers that follow the fluid streamlines are considered to investigate mass transfer within the suspension. Different particle volume fractions 5, 15, 30 and 40% are simulated for different pipe to particle diameter ratios: 5, 10 and 15. The preliminary results quantify the heat and mass transfer enhancement with respect to a single-phase laminar pipe flow. We show in particular that the heat transfer from the wall saturates for volume fractions more than 30%, however at high particle Reynolds numbers (small diameter ratios) the heat transfer continues to increase. Regarding the dispersion of tracer particles we show that the diffusivity of tracers increases with volume fraction in radial and stream-wise directions however it goes through a peak at 15% in the azimuthal direction. European Research Council, Grant No. ERC-2013-CoG- 616186, TRITOS; SNIC (the Swedish National Infrastructure for Computing).

23 CFR 810.308 - Approval of urban system nonhighway public mass transit projects.

Code of Federal Regulations, 2010 CFR

2010-04-01

... 23 Highways 1 2010-04-01 2010-04-01 false Approval of urban system nonhighway public mass transit projects. 810.308 Section 810.308 Highways FEDERAL HIGHWAY ADMINISTRATION, DEPARTMENT OF TRANSPORTATION PUBLIC TRANSPORTATION MASS TRANSIT AND SPECIAL USE HIGHWAY PROJECTS Federal-Aid Urban System Nonhighway...

Pore-scale supercritical CO 2 dissolution and mass transfer under drainage conditions

DOE PAGES

Chang, Chun; Zhou, Quanlin; Oostrom, Mart; ...

2016-12-05

Recently, both core- and pore-scale imbibition experiments have shown non-equilibrium dissolution of supercritical CO 2 (scCO 2) and a prolonged depletion of residual scCO 2. In this paper, pore-scale scCO 2 dissolution and mass transfer under drainage conditions were investigated using a two-dimensional heterogeneous micromodel and a novel fluorescent water dye with a sensitive pH range between 3.7 and 6.5. Drainage experiments were conducted at 9 MPa and 40 °C by injecting scCO 2 into the sandstone-analogue pore network initially saturated by water without dissolved CO 2 (dsCO 2). During the experiments, time-lapse images of dye intensity, reflecting water pH,more » were obtained. These images show non-uniform pH in individual pores and pore clusters, with average pH levels gradually decreasing with time. Further analysis on selected pores and pore clusters shows that (1) rate-limited mass transfer prevails with slowly decreasing pH over time when the scCO 2-water interface area is low with respect to the volume of water-filled pores and pore clusters, (2) fast scCO 2 dissolution and phase equilibrium occurs when scCO 2 bubbles invade into water-filled pores, significantly enhancing the area-to-volume ratio, and (3) a transition from rate-limited to diffusion-limited mass transfer occurs in a single pore when a medium area-to-volume ratio is prevalent. The analysis also shows that two fundamental processes – scCO 2 dissolution at phase interfaces and diffusion of dsCO 2 at the pore scale (10–100 µm) observed after scCO 2 bubble invasion into water-filled pores without pore throat constraints – are relatively fast. The overall slow dissolution of scCO 2 in the millimeter-scale micromodel can be attributed to the small area-to-volume ratios that represent pore-throat configurations and characteristics of phase interfaces. Finally, this finding is applicable for the behavior of dissolution at pore, core, and field scales when water-filled pores and pore

Pore-scale supercritical CO 2 dissolution and mass transfer under drainage conditions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chang, Chun; Zhou, Quanlin; Oostrom, Mart

Recently, both core- and pore-scale imbibition experiments have shown non-equilibrium dissolution of supercritical CO 2 (scCO 2) and a prolonged depletion of residual scCO 2. In this paper, pore-scale scCO 2 dissolution and mass transfer under drainage conditions were investigated using a two-dimensional heterogeneous micromodel and a novel fluorescent water dye with a sensitive pH range between 3.7 and 6.5. Drainage experiments were conducted at 9 MPa and 40 °C by injecting scCO 2 into the sandstone-analogue pore network initially saturated by water without dissolved CO 2 (dsCO 2). During the experiments, time-lapse images of dye intensity, reflecting water pH,more » were obtained. These images show non-uniform pH in individual pores and pore clusters, with average pH levels gradually decreasing with time. Further analysis on selected pores and pore clusters shows that (1) rate-limited mass transfer prevails with slowly decreasing pH over time when the scCO 2-water interface area is low with respect to the volume of water-filled pores and pore clusters, (2) fast scCO 2 dissolution and phase equilibrium occurs when scCO 2 bubbles invade into water-filled pores, significantly enhancing the area-to-volume ratio, and (3) a transition from rate-limited to diffusion-limited mass transfer occurs in a single pore when a medium area-to-volume ratio is prevalent. The analysis also shows that two fundamental processes – scCO 2 dissolution at phase interfaces and diffusion of dsCO 2 at the pore scale (10–100 µm) observed after scCO 2 bubble invasion into water-filled pores without pore throat constraints – are relatively fast. The overall slow dissolution of scCO 2 in the millimeter-scale micromodel can be attributed to the small area-to-volume ratios that represent pore-throat configurations and characteristics of phase interfaces. Finally, this finding is applicable for the behavior of dissolution at pore, core, and field scales when water-filled pores and pore

Pore-scale supercritical CO 2 dissolution and mass transfer under drainage conditions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chang, Chun; Zhou, Quanlin; Oostrom, Mart

Abstract: Recently, both core- and pore-scale imbibition experiments have shown non-equilibrium dissolution of supercritical CO 2 (scCO 2) and a prolonged depletion of residual scCO 2. In this study, pore-scale scCO 2 dissolution and mass transfer under drainage conditions were investigated using a two-dimensional heterogeneous micromodel and a novel fluorescent water dye with a sensitive pH range between 3.7 and 6.5. Drainage experiments were conducted at 9 MPa and 40 °C by injecting scCO 2 into the sandstone-analogue pore network initially saturated by water without dissolved CO 2 (dsCO 2). During the experiments, time-lapse images of dye intensity, reflecting watermore » pH, were obtained. These images show non-uniform pH in individual pores and pore clusters, with average pH levels gradually decreasing with time. Further analysis on selected pores and pore clusters shows that (1) rate-limited mass transfer prevails with slowly decreasing pH over time when the scCO 2-water interface area is low with respect to the volume of water-filled pores and pore clusters, (2) fast scCO 2 dissolution and phase equilibrium occurs when scCO 2 bubbles invade into water-filled pores, significantly enhancing the area-to-volume ratio, and (3) a transition from rate-limited to diffusion-limited mass transfer occurs in a single pore when a medium area-to-volume ratio is prevalent. The analysis also shows that two fundamental processes – scCO 2 dissolution at phase interfaces and diffusion of dsCO 2 at the pore scale (10-100 µm) observed after scCO 2 bubble invasion into water-filled pores without pore throat constraints – are relatively fast. The overall slow dissolution of scCO 2 in the millimeter-scale micromodel can be attributed to the small area-to-volume ratios that represent pore-throat configurations and characteristics of phase interfaces. This finding is applicable for the behavior of dissolution at pore, core, and field scales when water-filled pores and pore

About Mass Transfer in Capillaries of Biological Systems under Influence of Vibrations

NASA Astrophysics Data System (ADS)

Prisniakov, K.

Vibrations accompany the flight of the manned spacecraft both at a stage of a orbital injection to an orbit, and during long flights (as noise), rendering undesirable physiological influence on crew, reducing serviceability and creating constant discomfort. The report represents attempt to predict a state of the cosmonaut in conditions of influence of vibrations for the period of start and stay in Space, being based on researches of mass transfer processes in capillary systems. For this purpose the original researches on heat and mass transfer processes with evaporation of liquids in capillary - porous structures in conditions of vibration actions and changes of a direction of action of gravitation are generalized. Report demonstrates the existence of modes at which increased or lowered mass transfer is achieved on border of separation "liquid - gas". The possible mechanism of influence of vibrations on evaporation of a liquid in capillaries is examined. The magnitudes of frequencies and amplitudes are submitted at which minimax characteristics are observed. The opportunity of application of the developed mathematical model of heat and mass transfer in capillary - porous structures to forecasting influence of vibrations for biological processes in capillaries of alive essences is analyzed. Such approach is justified on the mechanical nature of harmful influence of vibrations on an organism of the person. In addition the range of vibration frequencies which arise during space flights, corresponds to own resonant frequencies of a human body and his separate organs. Comparison of these resonant frequencies of a body of the person (5-80 Hertz) with vibration frequencies of optimum modes of heat and mass transfer in capillary - porous structures (20-40 Hertz) is shown their ranges of coverage. It gives the basis to assume existence of similar effects in capillaries of human body. It is supposed, that the difficulty of breath, change of a rhythm of breath, the subsequent

Combined heat and mass transfer device for improving separation process

DOEpatents

Tran, Thanh Nhon

1999-01-01

A two-phase small channel heat exchange matrix simultaneously provides for heat transfer and mass transfer between the liquid and vapor phases of a multi-component mixture at a single, predetermined location within a separation column, significantly improving the thermodynamic efficiency of the separation process. The small channel heat exchange matrix is composed of a series of channels having a hydraulic diameter no greater than 5.0 millimeters for conducting a two-phase coolant. In operation, the matrix provides the liquid-vapor contacting surfaces within the separation column, such that heat and mass are transferred simultaneously between the liquid and vapor phases. The two-phase coolant allows for a uniform heat transfer coefficient to be maintained along the length of the channels and across the surface of the matrix. Preferably, a perforated, concave sheet connects each channel to an adjacent channel to facilitate the flow of the liquid and vapor phases within the column and to increase the liquid-vapor contacting surface area.

Combined heat and mass transfer device for improving separation process

DOEpatents

Tran, T.N.

1999-08-24

A two-phase small channel heat exchange matrix simultaneously provides for heat transfer and mass transfer between the liquid and vapor phases of a multi-component mixture at a single, predetermined location within a separation column, significantly improving the thermodynamic efficiency of the separation process. The small channel heat exchange matrix is composed of a series of channels having a hydraulic diameter no greater than 5.0 millimeters for conducting a two-phase coolant. In operation, the matrix provides the liquid-vapor contacting surfaces within the separation column, such that heat and mass are transferred simultaneously between the liquid and vapor phases. The two-phase coolant allows for a uniform heat transfer coefficient to be maintained along the length of the channels and across the surface of the matrix. Preferably, a perforated, concave sheet connects each channel to an adjacent channel to facilitate the flow of the liquid and vapor phases within the column and to increase the liquid-vapor contacting surface area. 12 figs.

Improving mass transfer to soften tissues by pulsed electric fields: fundamentals and applications.

PubMed

Puértolas, E; Luengo, E; Álvarez, I; Raso, J

2012-01-01

The mass transfer phenomenon occurs in many operations of the food industry with the purpose of obtaining a given substance of interest, removing water from foods, or introducing a given substance into the food matrix. Pretreatments that modify the permeability of the cell membranes, such as grinding, heating, or enzymatic treatment, enhance the mass transfer. However, these techniques may require a significant amount of energy and can cause losses of valuable food compounds. Pulsed electric field (PEF) technology is a nonthermal processing method that causes permeabilization of cell membranes using low energy requirements and minimizing quality deterioration of the food compounds. Many practical applications of PEF for enhancing mass transfer in the food industry have been investigated. The purpose of this chapter is to give an overview of the state of the art of application of PEF for improving mass transfer in the food industry.

Heat and Mass Transfer Model in Freeze-Dried Medium

NASA Astrophysics Data System (ADS)

Alfat, Sayahdin; Purqon, Acep

2017-07-01

There are big problems in agriculture sector every year. One of the major problems is abundance of agricultural product during the peak of harvest season that is not matched by an increase in demand of agricultural product by consumers, this causes a wasted agricultural products. Alternative way was food preservation by freeze dried method. This method was already using heat transfer through conduction and convection to reduce water quality in the food. The main objective of this research was to design a model heat and mass transfer in freeze-dried medium. We had two steps in this research, the first step was design of medium as the heat injection site and the second was simulate heat and mass transfer of the product. During simulation process, we use physical property of some agriculture product. The result will show how temperature and moisture distribution every second. The method of research use finite element method (FEM) and will be illustrated in three dimensional.

Determination of external and internal mass transfer limitation in nitrifying microbial aggregates.

PubMed

Wilén, Britt-Marie; Gapes, Daniel; Keller, Jürg

2004-05-20

In this article we present a study of the effects of external and internal mass transfer limitation of oxygen in a nitrifying system. The oxygen uptake rates (OUR) were measured on both a macro-scale with a respirometric reactor using off-gas analysis (Titrimetric and Off-Gas Analysis (TOGA) sensor) and on a micro-scale with microsensors. These two methods provide independent, accurate measurements of the reaction rates and concentration profiles around and in the granules. The TOGA sensor and microsensor measurements showed a significant external mass transfer effect at low dissolved oxygen (DO) concentrations in the bulk liquid while it was insignificant at higher DO concentrations. The oxygen distribution with anaerobic or anoxic conditions in the center clearly shows major mass transfer limitation in the aggregate interior. The large drop in DO concentration of 22-80% between the bulk liquid and aggregate surface demonstrates that the external mass transfer resistance is also highly important. The maximum OUR even for floccular biomass was only attained at much higher DO concentrations (approximately 8 mg/L) than typically used in such systems. For granules, the DO required for maximal activity was estimated to be >20 mg/L, clearly indicating the effects of the major external and internal mass transfer limitations on the overall biomass activity. Smaller aggregates had a larger volumetric OUR indicating that the granules may have a lower activity in the interior part of the aggregate. Copyright 2004 Wiley Periodicals, Inc.

Modeling of the Inter-phase Mass Transfer during Cosolvent-Enhanced NAPL Remediation

NASA Astrophysics Data System (ADS)

Agaoglu, B.; Scheytt, T. J.; Copty, N. K.

2012-12-01

This study investigates the factors influencing inter-phase mass transfer during cosolvent-enhanced NAPL remediation and the ability of the REV (Representative Elementary Volume) modeling approach to simulate these processes. The NAPLs considered in this study consist of pure toluene, pure benzene and known mixtures of these two compounds, while ethanol-water mixtures were selected as the remedial flushing solutions. Batch tests were performed to identify both the equilibrium and non-equilibrium properties of the multiphase system. A series of column flushing experiments involving different NAPLs were conducted for different ethanol contents in the flushing solution and for different operational parameters. Experimental results were compared to numerical simulations obtained with the UTCHEM multiphase flow simulator (Delshad et al., 1996). Results indicate that the velocity of the flushing solution is a major parameter influencing the inter-phase mass transport processes at the pore scale. Depending on the NAPL composition and porous medium properties, the remedial solution may follow preferential flow paths and be subject to reduced contact with the NAPL. This leads to a steep decrease in the apparent mass transfer coefficient. Correlations of the apparent time-dependent mass transfer coefficient as a function of flushing velocity are developed for various porous media. Experimental results also show that the NAPL mass transfer coefficient into the cosolvent solution increases when the NAPL phase becomes mobile. This is attributed to the increase in pore scale contact area between NAPL and the remedial solution when NAPL mobilization occurs. These results suggest the need to define a temporal and spatially variable mass transfer coefficient of the NAPL into the cosolvent solution to reflect the occurrence of subscale preferential flow paths and the transient bypassing of the NAPL mass. The implications of these findings on field scale NAPL remediation with

Modelling mass and heat transfer in nano-based cancer hyperthermia.

PubMed

Nabil, M; Decuzzi, P; Zunino, P

2015-10-01

We derive a sophisticated mathematical model for coupled heat and mass transport in the tumour microenvironment and we apply it to study nanoparticle delivery and hyperthermic treatment of cancer. The model has the unique ability of combining the following features: (i) realistic vasculature; (ii) coupled capillary and interstitial flow; (iii) coupled capillary and interstitial mass transfer applied to nanoparticles; and (iv) coupled capillary and interstitial heat transfer, which are the fundamental mechanisms governing nano-based hyperthermic treatment. This is an improvement with respect to previous modelling approaches, where the effect of blood perfusion on heat transfer is modelled in a spatially averaged form. We analyse the time evolution and the spatial distribution of particles and temperature in a tumour mass treated with superparamagnetic nanoparticles excited by an alternating magnetic field. By means of numerical experiments, we synthesize scaling laws that illustrate how nano-based hyperthermia depends on tumour size and vascularity. In particular, we identify two distinct mechanisms that regulate the distribution of particle and temperature, which are characterized by perfusion and diffusion, respectively.

Assessing the efficiency of mass transit systems in the United States.

DOT National Transportation Integrated Search

2017-04-01

Frustrated with increased parking problems, unstable gasoline prices, and stifling traffic congestion, a growing number of : metropolitan city dwellers consider utilizing the mass transit system. Reflecting this sentiment, a ridership of the mass tra...

Low floor mass transit vehicle

DOEpatents

Emmons, J Bruce [Beverly Hills, MI; Blessing, Leonard J [Rochester, MI

2004-02-03

A mass transit vehicle includes a frame structure that provides an efficient and economical approach to providing a low floor bus. The inventive frame includes a stiff roof panel and a stiff floor panel. A plurality of generally vertical pillars extend between the roof and floor panels. A unique bracket arrangement is disclosed for connecting the pillars to the panels. Side panels are secured to the pillars and carry the shear stresses on the frame. A unique seating assembly that can be advantageously incorporated into the vehicle taking advantage of the load distributing features of the inventive frame is also disclosed.

Mass and heat transfer model of Tubular Solar Still

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ahsan, Amimul; Fukuhara, Teruyuki

2010-07-15

In this paper, a new mass and heat transfer model of a Tubular Solar Still (TSS) was proposed incorporating various mass and heat transfer coefficients taking account of the humid air properties inside the still. The heat balance of the humid air and the mass balance of the water vapor in the humid air were formulized for the first time. As a result, the proposed model enabled to calculate the diurnal variations of the temperature, water vapor density and relative humidity of the humid air, and to predict the hourly condensation flux besides the temperatures of the water, cover andmore » trough, and the hourly evaporation flux. The validity of the proposed model was verified using the field experimental results carried out in Fukui, Japan and Muscat, Oman in 2008. The diurnal variations of the calculated temperatures and water vapor densities had a good agreement with the observed ones. Furthermore, the proposed model can predict the daily and hourly production flux precisely. (author)« less

Study on transfer optimization of urban rail transit and conventional public transport

NASA Astrophysics Data System (ADS)

Wang, Jie; Sun, Quan Xin; Mao, Bao Hua

2018-04-01

This paper mainly studies the time optimization of feeder connection between rail transit and conventional bus in a shopping center. In order to achieve the goal of connecting rail transportation effectively and optimizing the convergence between the two transportations, the things had to be done are optimizing the departure intervals, shorting the passenger transfer time and improving the service level of public transit. Based on the goal that has the minimum of total waiting time of passengers and the number of start of classes, establish the optimizing model of bus connecting of departure time. This model has some constrains such as transfer time, load factor, and the convergence of public transportation grid spacing. It solves the problems by using genetic algorithms.

Numerical Simulations of Dynamical Mass Transfer in Binaries

NASA Astrophysics Data System (ADS)

Motl, P. M.; Frank, J.; Tohline, J. E.

1999-05-01

We will present results from our ongoing research project to simulate dynamically unstable mass transfer in near contact binaries with mass ratios different from one. We employ a fully three-dimensional self-consistent field technique to generate synchronously rotating polytropic binaries. With our self-consistent field code we can create equilibrium binaries where one component is, by radius, within about 99 of filling its Roche lobe for example. These initial configurations are evolved using a three-dimensional, Eulerian hydrodynamics code. We make no assumptions about the symmetry of the subsequent flow and the entire binary system is evolved self-consistently under the influence of its own gravitational potential. For a given mass ratio and polytropic index for the binary components, mass transfer via Roche lobe overflow can be predicted to be stable or unstable through simple theoretical arguments. The validity of the approximations made in the stability calculations are tested against our numerical simulations. We acknowledge support from the U.S. National Science Foundation through grants AST-9720771, AST-9528424, and DGE-9355007. This research has been supported, in part, by grants of high-performance computing time on NPACI facilities at the San Diego Supercomputer Center, the Texas Advanced Computing Center and through the PET program of the NAVOCEANO DoD Major Shared Resource Center in Stennis, MS.

Ultrasound in gas-liquid systems: effects on solubility and mass transfer.

PubMed

Laugier, F; Andriantsiferana, C; Wilhelm, A M; Delmas, H

2008-09-01

The effect of ultrasound on the pseudo-solubility of nitrogen in water and on gas-liquid mass transfer kinetics has been investigated in an autoclave reactor equipped with a gas induced impeller. In order to use organic liquids and to investigate the effect of pressure, gas-liquid mass transfer coefficient was calculated from the evolution of autoclave pressure during gas absorption to avoid any side-effects of ultrasound on the concentrations measurements. Ultrasound effect on the apparent solubility is very low (below 12%). Conversely ultrasound greatly improves gas-liquid mass transfer, especially below gas induction speed, this improvement being boosted by pressure. In typical conditions of organic synthesis: 323 K, 1100 rpm, 10 bar, k(L).a is multiplied by 11 with ultrasound (20 kHz/62.6 W). The impact of sonication is much higher on gassing out than on gassing in. In the same conditions, this enhancement is at least five times higher for degassing.

Effect of acoustic streaming on the mass transfer from a sublimating sphere

NASA Astrophysics Data System (ADS)

Kawahara, N.; Yarin, A. L.; Brenn, G.; Kastner, O.; Durst, F.

2000-04-01

The effect of the acoustic streaming on the mass transfer from the surface of a sphere positioned in an ultrasonic acoustic levitator is studied both experimentally and theoretically. Acoustic levitation using standing ultrasonic waves is an experimental tool for studying the heat and mass transfer from small solid or liquid samples, because it allows an almost steady positioning of a sample at a fixed location in space. However, the levitator introduces some difficulties. One of the main problems with acoustic levitation is that an acoustic streaming is induced near the sample surface, which affects the heat and mass transfer rates, as characterized by increased Nusselt and Sherwood numbers. The transfer rates are not uniform along the sample surface, and the aim of the present study is to quantify the spatial Sherwood number distribution over the surface of a sphere. The experiments are based on the measurement of the surface shape of a sphere layered with a solid substance as a function of time using a charge-coupled device (CCD) camera with backlighting. The sphere used in this research is a glass sphere layered with a volatile solid substance (naphthalene or camphor). The local mass transfer from the surface both with and without an ultrasonic acoustic field is investigated in order to evaluate the effect of the acoustic streaming. The experimental results are compared with predictions following from the theory outlined [A. L. Yarin, M. Pfaffenlehner, and C. Tropea, J. Fluid Mech. 356, 65 (1998); A. L. Yarin, G. Brenn, O. Kastner, D. Rensink, and C. Tropea, ibid. 399, 151 (1999)] which describes the acoustic field and the resulting acoustic streaming, and the mass transfer at the surface of particles and droplets located in an acoustic levitator. The results are also compared with the experimental data and with the theoretical predictions of Burdukov and Nakoryakov [J. Appl. Mech. Tech. Phys. 6, 51 (1965)], which are valid only in the case of spherical

Metal-to-metal charge transfer transitions - Interpretation of visible-region spectra of the moon and lunar materials

NASA Technical Reports Server (NTRS)

Loeffler, B. M.; Burns, R. G.; Tossell, J. A.

1975-01-01

Prominent bands in the spectral profiles of Fe-Ti phases in lunar samples have been attributed to charge-transfer transitions between Fe and Ti cations, and a model is presented for calculating charge transfer energies from energy levels computed by the SCF-X(alpha) scattered wave molecular orbital method for isolated MO6 octahedral coordination clusters containing Fe(2+), Fe(3+), Ti(3+), and Ti(4+) cations. The calculated charge transfer energy for the Fe(2+) to Ti(4+) transition correlates well with a measured spectral feature around 0.6 micron in ilmenite, and, since ilmenite is a major constituent of mare basalts and dark-mantling material, the observed darkness and blueness of the regolith in lunar black spots is attributed primarily to this transition. The Ti(3+) to Ti(4+) transition is thought to contribute to some phases.

Measurement of the oxygen mass transfer through the air-water interface.

PubMed

Mölder, Erik; Mashirin, Alelxei; Tenno, Toomas

2005-01-01

Gas mass transfer through the liquid-gas interface has enormous importance in various natural and industrial processes. Surfactants or insoluble compounds adsorbed onto an interface will inhibit the gas mass transfer through the liquid-gas surface. This study presents a technique for measuring the oxygen mass transfer through the air-water interface. Experimental data obtained with the measuring device were incorporated into a novel mathematical model, which allowed one to calculate diffusion conduction of liquid surface layer and oxygen mass transfer coefficient in the liquid surface layer. A special measurement cell was constructed. The most important part of the measurement cell is a chamber containing the electrochemical oxygen sensor inside it. Gas exchange between the volume of the chamber and the external environment takes place only through the investigated surface layer. Investigated liquid was deoxygenated, which triggers the oxygen mass transfer from the chamber through the liquid-air interface into the liquid phase. The decrease of oxygen concentration in the cell during time was measured. By using this data it is possible to calculate diffusional parameters of the water surface layer. Diffusion conduction of oxygen through the air-water surface layer of selected wastewaters was measured. The diffusion conduction of different wastewaters was about 3 to 6 times less than in the unpolluted water surface. It was observed that the dilution of wastewater does not have a significant impact on the oxygen diffusion conduction through the wastewater surface layer. This fact can be explained with the presence of the compounds with high surface activity in the wastewater. Surfactants achieved a maximum adsorption and, accordingly, the maximum decrease of oxygen permeability already at a very low concentration of surfactants in the solution. Oxygen mass transfer coefficient of the surface layer of the water is found to be Ds/ls = 0.13 x 10(-3) x cm/s. A simple

A mass transfer origin for blue stragglers in NGC 188 as revealed by half-solar-mass companions.

PubMed

Geller, Aaron M; Mathieu, Robert D

2011-10-19

In open star clusters, where all members formed at about the same time, blue straggler stars are typically observed to be brighter and bluer than hydrogen-burning main-sequence stars, and therefore should already have evolved into giant stars and stellar remnants. Correlations between blue straggler frequency and cluster binary star fraction, core mass and radial position suggest that mass transfer or mergers in binary stars dominates the production of blue stragglers in open clusters. Analytic models, detailed observations and sophisticated N-body simulations, however, argue in favour of stellar collisions. Here we report that the blue stragglers in long-period binaries in the old (7 × 10(9)-year) open cluster NGC 188 have companions with masses of about half a solar mass, with a surprisingly narrow mass distribution. This conclusively rules out a collisional origin, as the collision hypothesis predicts a companion mass distribution with significantly higher masses. Mergers in hierarchical triple stars are marginally permitted by the data, but the observations do not favour this hypothesis. The data are highly consistent with a mass transfer origin for the long-period blue straggler binaries in NGC 188, in which the companions would be white dwarfs of about half a solar mass.

Influence of mass transfer on bubble plume hydrodynamics.

PubMed

Lima Neto, Iran E; Parente, Priscila A B

2016-03-01

This paper presents an integral model to evaluate the impact of gas transfer on the hydrodynamics of bubble plumes. The model is based on the Gaussian type self-similarity and functional relationships for the entrainment coefficient and factor of momentum amplification due to turbulence. The impact of mass transfer on bubble plume hydrodynamics is investigated considering different bubble sizes, gas flow rates and water depths. The results revealed a relevant impact when fine bubbles are considered, even for moderate water depths. Additionally, model simulations indicate that for weak bubble plumes (i.e., with relatively low flow rates and large depths and slip velocities), both dissolution and turbulence can affect plume hydrodynamics, which demonstrates the importance of taking the momentum amplification factor relationship into account. For deeper water conditions, simulations of bubble dissolution/decompression using the present model and classical models available in the literature resulted in a very good agreement for both aeration and oxygenation processes. Sensitivity analysis showed that the water depth, followed by the bubble size and the flow rate are the most important parameters that affect plume hydrodynamics. Lastly, dimensionless correlations are proposed to assess the impact of mass transfer on plume hydrodynamics, including both the aeration and oxygenation modes.

Health care providers' attitudes towards transfer and transition in young persons with long term illness- a web-based survey.

PubMed

Sparud-Lundin, Carina; Berghammer, Malin; Moons, Philip; Bratt, Ewa-Lena

2017-04-11

Transition programs in health care for young persons with special health care needs aim to maximize lifelong functioning. Exploring health care professionals' perspective may increase the possibility of successful implementation of transition programs. The aim was to survey health care professionals' attitudes towards components and barriers on transition and transfer in young people with long-term medical conditions with special health care needs. A cross-sectional web-based survey was sent by e-mail to 529 physicians and nurses in Swedish pediatric and adult outpatient clinics. Response rate was 38% (n = 201). The survey consisted of 59 questions regarding different aspects of components and barriers on transition and transfer. Descriptive statistics were computed to summarize demographic data and categorized responses. The Chi square test was used for comparison between proportions of categories. Most respondents agreed on the destinations of care for adolescents within their specialty. Age and psychosocial aspects such as maturity and family situations were considered the most important initiators for transfer. Joint meeting with the patient (82%); presence of a transition coordinator (76%) and a written individualized transfer plan (55%) were reported as important transition components. Pediatric care professionals found the absence of a transition coordinator to be more of a transition barrier than adult care professionals (p = 0.018) and also a more important transfer component (p = 0.017). Other barriers were lack of funding (45%) and limited clinical space (19%). Transition programs were more common in university hospitals than in regional hospitals (12% vs 2%, p = <0.001) as well as having a transition coordinator (12% vs 3%, p = 0.004). The findings highlight a willingness to work on new transition strategies and provide direction for improvement, taking local transition components as well as potential barriers into consideration when

Influence of indoor environmental factors on mass transfer parameters and concentrations of semi-volatile organic compounds.

PubMed

Wei, Wenjuan; Mandin, Corinne; Ramalho, Olivier

2018-03-01

Semi-volatile organic compounds (SVOCs) in indoor environments can partition among the gas phase, airborne particles, settled dust, and available surfaces. The mass transfer parameters of SVOCs, such as the mass transfer coefficient and the partition coefficient, are influenced by indoor environmental factors. Subsequently, indoor SVOC concentrations and thus occupant exposure can vary depending on environmental factors. In this review, the influence of six environmental factors, i.e., indoor temperature, humidity, ventilation, airborne particle concentration, source loading factor, and reactive chemistry, on the mass transfer parameters and indoor concentrations of SVOCs was analyzed and tentatively quantified. The results show that all mass transfer parameters vary depending on environmental factors. These variations are mostly characterized by empirical equations, particularly for humidity. Theoretical calculations of these parameters based on mass transfer mechanisms are available only for the emission of SVOCs from source surfaces when airborne particles are not present. All mass transfer parameters depend on the temperature. Humidity influences the partition of SVOCs among different phases and is associated with phthalate hydrolysis. Ventilation has a combined effect with the airborne particle concentration on SVOC emission and their mass transfer among different phases. Indoor chemical reactions can produce or eliminate SVOCs slowly. To better model the dynamic SVOC concentration indoors, the present review suggests studying the combined effect of environmental factors in real indoor environments. Moreover, interactions between indoor environmental factors and human activities and their influence on SVOC mass transfer processes should be considered. Copyright © 2017 Elsevier Ltd. All rights reserved.

The integrated contaminant elution and tracer test toolkit, ICET3, for improved characterization of mass transfer, attenuation, and mass removal

NASA Astrophysics Data System (ADS)

Brusseau, Mark L.; Guo, Zhilin

2018-01-01

It is evident based on historical data that groundwater contaminant plumes persist at many sites, requiring costly long-term management. High-resolution site-characterization methods are needed to support accurate risk assessments and to select, design, and operate effective remediation operations. Most subsurface characterization methods are generally limited in their ability to provide unambiguous, real-time delineation of specific processes affecting mass-transfer, transformation, and mass removal, and accurate estimation of associated rates. An integrated contaminant elution and tracer test toolkit, comprising a set of local-scale groundwater extraction-and injection tests, was developed to ameliorate the primary limitations associated with standard characterization methods. The test employs extended groundwater extraction to stress the system and induce hydraulic and concentration gradients. Clean water can be injected, which removes the resident aqueous contaminant mass present in the higher-permeability zones and isolates the test zone from the surrounding plume. This ensures that the concentrations and fluxes measured within the isolated area are directly and predominantly influenced by the local mass-transfer and transformation processes controlling mass removal. A suite of standard and novel tracers can be used to delineate specific mass-transfer and attenuation processes that are active at a given site, and to quantify the associated mass-transfer and transformation rates. The conceptual basis for the test is first presented, followed by an illustrative application based on simulations produced with a 3-D mathematical model and a brief case study application.

Bibliography on augmentation of convective heat and mass transfer

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bergles, A.E.; Webb, R.L.; Junkhan, G.H.

1979-05-01

Heat transfer augmentation has developed into a major specialty area in heat transfer research and development. A bibliography of world literature on augmentation is presented. The literature is classified into passive augmentation techniques, which require no external power, and active techniques, which do require external power. The fourteen techniques are grouped in terms of their application to the various modes of heat transfer. Mass transfer is included for completeness. Key words are included with each citation for technique/mode identification. The total number of publications cited is 1,967, including 75 surveys of various techniques and 42 papers on performance evaluation ofmore » passive techniques. Patents are not included as they will be the subject of a future topical report.« less

Mass transfer coefficient in ginger oil extraction by microwave hydrotropic solution

NASA Astrophysics Data System (ADS)

Handayani, Dwi; Ikhsan, Diyono; Yulianto, Mohamad Endy; Dwisukma, Mandy Ayulia

2015-12-01

This research aims to obtain mass transfer coefficient data on the extraction of ginger oil using microwave hydrotropic solvent as an alternative to increase zingiberene. The innovation of this study is extraction with microwave heater and hydrotropic solvent,which able to shift the phase equilibrium, and the increasing rate of the extraction process and to improve the content of ginger oil zingiberene. The experiment was conducted at the Laboratory of Separation Techniques at Chemical Engineering Department of Diponegoro University. The research activities carried out in two stages, namely experimental and modeling work. Preparation of the model postulated, then lowered to obtain equations that were tested and validated using data obtained from experimental. Measurement of experimental data was performed using microwave power (300 W), extraction temperature of 90 ° C and the independent variable, i.e.: type of hydrotropic, the volume of solvent and concentration in order, to obtain zingiberen levels as a function of time. Measured data was used as a tool to validate the postulation, in order to obtain validation of models and empirical equations. The results showed that the mass transfer coefficient (Kla) on zingiberene mass transfer models ginger oil extraction at various hydrotropic solution attained more 14 ± 2 Kla value than its reported on the extraction with electric heating. The larger value of Kla, the faster rate of mass transfer on the extraction process. To obtain the same yields, the microwave-assisted extraction required one twelfth time shorter.

Nonequilibrium transition induced by mass media in a model for social influence

NASA Astrophysics Data System (ADS)

González-Avella, J. C.; Cosenza, M. G.; Tucci, K.

2005-12-01

We study the effect of mass media, modeled as an applied external field, on a social system based on Axelrod’s model for the dissemination of culture. The numerical simulations show that the system undergoes a nonequilibrium phase transition between an ordered phase (homogeneous culture) specified by the mass media and a disordered (culturally fragmented) one. The critical boundary separating these phases is calculated on the parameter space of the system, given by the intensity of the mass media influence and the number of options per cultural attribute. Counterintuitively, mass media can induce cultural diversity when its intensity is above some threshold value. The nature of the phase transition changes from continuous to discontinuous at some critical value of the number of options.

Heat And Mass Transfer Analysis of a Film Evaporative MEMS Tunable Array

NASA Astrophysics Data System (ADS)

O'Neill, William J.

This thesis details the heat and mass transfer analysis of a MEMs microthruster designed to provide propulsive, attitude control and thermal control capabilities to a cubesat. This thruster is designed to function by retaining water as a propellant and applying resistive heating in order to increase the temperature of the liquid-vapor interface to either increase evaporation or induce boiling to regulate mass flow. The resulting vapor is then expanded out of a diverging nozzle to produce thrust. Because of the low operating pressure and small length scale of this thruster, unique forms of mass transfer analysis such as non-continuum gas flow were modeled using the Direct Simulation Monte Carlo method. Continuum fluid/thermal simulations using COMSOL Multiphysics have been applied to model heat and mass transfer in the solid and liquid portions of the thruster. The two methods were coupled through variables at the liquid-vapor interface and solved iteratively by the bisection method. The simulations presented in this thesis confirm the thermal valving concept. It is shown that when power is applied to the thruster there is a nearly linear increase in mass flow and thrust. Thus, mass flow can be regulated by regulating the applied power. This concept can also be used as a thermal control device for spacecraft.

Analysis of mass transfer characteristics in a tubular membrane using CFD modeling.

PubMed

Yang, Jixiang; Vedantam, Sreepriya; Spanjers, Henri; Nopens, Ingmar; van Lier, Jules B

2012-10-01

In contrast to the large amount of research into aerobic membrane bioreactors, little work has been reported on anaerobic membrane bioreactors (AMBRs). As to the application of membrane bioreactors, membrane fouling is a key issue. Membrane fouling generally occurs more seriously in AMBRs than in aerobic membrane bioreactors. However, membrane fouling could be managed through the application of suitable shear stress that can be introduced by the application of a two-phase flow. When the two-phase flow is applied in AMBRs, little is known about the mass transfer characteristics, which is of particular importance, in tubular membranes of AMBRs. In our present work, we have employed fluid dynamic modeling to analyze the mass transfer characteristics in the tubular membrane of a side stream AMBR in which, gas-lift two-phase flow was applied. The modeling indicated that the mass transfer capacity at the membrane surface at the noses of gas bubbles was higher than the mass transfer capacity at the tails of the bubbles, which is in contrast to the results when water instead of sludge is applied. At the given mass transfer rate, the filterability of the sludge was found to have a strong influence on the transmembrane pressure at a steady flux. In addition, the model also showed that the shear stress in the internal space of the tubular membrane was mainly around 20 Pa but could be as high as about 40 Pa due to gas bubble movements. Nonetheless, at these shear stresses a stable particle size distribution was found for sludge particles. Copyright © 2012 Elsevier Ltd. All rights reserved.

Carbon monoxide mass transfer for syngas fermentation in a stirred tank reactor with dual impeller configurations.

PubMed

Ungerman, Andrew J; Heindel, Theodore J

2007-01-01

This study compares the power demand and gas-liquid volumetric mass transfer coefficient, kLa, in a stirred tank reactor (STR) (T = 0.211 m) using different impeller designs and schemes in a carbon monoxide-water system, which is applicable to synthesis gas (syngas) fermentation. Eleven different impeller schemes were tested over a range of operating conditions typically associated with the "after large cavity" region (ALC) of a Rushton-type turbine (D/T = 0.35). It is found that the dual Rushton-type impeller scheme exhibits the highest volumetric mass transfer rates for all operating conditions; however, it also displays the lowest mass transfer performance (defined as the volumetric mass transfer coefficient per unit power input) for all conditions due to its high power consumption. Dual impeller schemes with an axial flow impeller as the top impeller show improved mass transfer rates without dramatic increases in power draw. At high gas flow rates, dual impeller schemes with a lower concave impeller have kLa values similar to those of the Rushton-type dual impeller schemes but show improved mass transfer performance. It is believed that the mass transfer performance can be further enhanced for the bottom concave impeller schemes by operating at conditions beyond the ALC region defined for Rushton-type impellers because the concave impeller can handle higher gas flow rates prior to flooding.

Transition Heat Transfer Modeling Based on the Characteristics of Turbulent Spots

NASA Technical Reports Server (NTRS)

Simon, Fred; Boyle, Robert

1998-01-01

While turbulence models are being developed which show promise for simulating the transition region on a turbine blade or vane, it is believed that the best approach with the greatest potential for practical use is the use of models which incorporate the physics of turbulent spots present in the transition region. This type of modeling results in the prediction of transition region intermittency which when incorporated in turbulence models give a good to excellent prediction of the transition region heat transfer. Some models are presented which show how turbulent spot characteristics and behavior can be employed to predict the effect of pressure gradient and Mach number on the transition region. The models predict the spot formation rate which is needed, in addition to the transition onset location, in the Narasimha concentrated breakdown intermittency equation. A simplified approach is taken for modeling turbulent spot growth and interaction in the transition region which utilizes the turbulent spot variables governing transition length and spot generation rate. The models are expressed in terms of spot spreading angle, dimensionless spot velocity, dimensionless spot area, disturbance frequency and Mach number. The models are used in conjunction with a computer code to predict the effects of pressure gradient and Mach number on the transition region and compared with VKI experimental turbine data.

Vibrational energy transfer dynamics in ruthenium polypyridine transition metal complexes.

PubMed

Fedoseeva, Marina; Delor, Milan; Parker, Simon C; Sazanovich, Igor V; Towrie, Michael; Parker, Anthony W; Weinstein, Julia A

2015-01-21

Understanding the dynamics of the initial stages of vibrational energy transfer in transition metal complexes is a challenging fundamental question which is also of crucial importance for many applications, such as improving the performance of solar devices or photocatalysis. The present study investigates vibrational energy transport in the ground and the electronic excited state of Ru(4,4'-(COOEt)2-2,2-bpy)2(NCS)2, a close relative of the efficient "N3" dye used in dye-sensitized solar cells. Using the emerging technique of ultrafast two-dimensional infrared spectroscopy, we show that, similarly to other transition-metal complexes, the central Ru heavy atom acts as a "bottleneck" making the energy transfer from small ligands with high energy vibrational stretching frequencies less favorable and thereby affecting the efficiency of vibrational energy flow in the complex. Comparison of the vibrational relaxation times in the electronic ground and excited state of Ru(4,4'-(COOEt)2-2,2-bpy)2(NCS)2 shows that it is dramatically faster in the latter. We propose to explain this observation by the intramolecular electrostatic interactions between the thiocyanate group and partially oxidised Ru metal center, which increase the degree of vibrational coupling between CN and Ru-N modes in the excited state thus reducing structural and thermodynamic barriers that slow down vibrational relaxation and energy transport in the electronic ground state. As a very similar behavior was earlier observed in another transition-metal complex, Re(4,4'-(COOEt)2-2,2'-bpy)(CO)3Cl, we suggest that this effect in vibrational energy dynamics might be common for transition-metal complexes with heavy central atoms.

The Colorado Ultraviolet Transit Experiment (CUTE): Observing Mass Loss on Short-Period Exoplanets

NASA Astrophysics Data System (ADS)

Egan, Arika; Fleming, Brian; France, Kevin

2018-06-01

The Colorado Ultraviolet Transit Experiment (CUTE) is an NUV spectrograph packaged into a 6U CubeSat, designed to characterize the interaction between exoplanetary atmospheres and their host stars. CUTE will conduct a transit spectroscopy survey, gathering data over multiple transits on more than 12 short-period exoplanets with a range of masses and radii. The instrument will characterize the spectral properties of the transit light curves to < 1% depth sensitivity. The NUV is host to several high oscillator strength atomic and molecular absorption features predicted to exist in the upper atmospheres of these planets, including Mg I, Mg II, Fe II, and OH. The shape and evolution of these spectral light curves will be used to quantify mass loss rates, the stellar drives of that mass loss, and the possible existence of exoplanetary magnetic fiends. This poster presents the science motivation for CUTE, planned observation and data analysis methods, and expected results.

Heat and Mass Transfer Processes in Scrubber of Flue Gas Heat Recovery Device

NASA Astrophysics Data System (ADS)

Veidenbergs, Ivars; Blumberga, Dagnija; Vigants, Edgars; Kozuhars, Grigorijs

2010-01-01

The paper deals with the heat and mass transfer process research in a flue gas heat recovery device, where complicated cooling, evaporation and condensation processes are taking place simultaneously. The analogy between heat and mass transfer is used during the process of analysis. In order to prepare a detailed process analysis based on heat and mass process descriptive equations, as well as the correlation for wet gas parameter calculation, software in the Microsoft Office Excel environment is being developed.

Influence of relative air/water flow velocity on oxygen mass transfer in gravity sewers.

PubMed

Carrera, Lucie; Springer, Fanny; Lipeme-Kouyi, Gislain; Buffiere, Pierre

2017-04-01

Problems related to hydrogen sulfide may be serious for both network stakeholders and the public in terms of health, sustainability of the sewer structure and urban comfort. H 2 S emission models are generally theoretical and simplified in terms of environmental conditions. Although air transport characteristics in sewers must play a role in the fate of hydrogen sulfide, only a limited number of studies have investigated this issue. The aim of this study was to better understand H 2 S liquid to gas transfer by highlighting the link between the mass transfer coefficient and the turbulence in the air flow and the water flow. For experimental safety reasons, O 2 was taken as a model compound. The oxygen mass transfer coefficients were obtained using a mass balance in plug flow. The mass transfer coefficient was not impacted by the range of the interface air-flow velocity values tested (0.55-2.28 m·s -1 ) or the water velocity values (0.06-0.55 m·s -1 ). Using the ratio between k L,O 2 to k L,H 2 S , the H 2 S mass transfer behavior in a gravity pipe in the same hydraulic conditions can be predicted.

Transitional and turbulent boundary layer with heat transfer

NASA Astrophysics Data System (ADS)

Wu, Xiaohua; Moin, Parviz

2010-08-01

We report on our direct numerical simulation of an incompressible, nominally zero-pressure-gradient flat-plate boundary layer from momentum thickness Reynolds number 80-1950. Heat transfer between the constant-temperature solid surface and the free-stream is also simulated with molecular Prandtl number Pr=1. Skin-friction coefficient and other boundary layer parameters follow the Blasius solutions prior to the onset of turbulent spots. Throughout the entire flat-plate, the ratio of Stanton number and skin-friction St/Cf deviates from the exact Reynolds analogy value of 0.5 by less than 1.5%. Mean velocity and Reynolds stresses agree with experimental data over an extended turbulent region downstream of transition. Normalized rms wall-pressure fluctuation increases gradually with the streamwise growth of the turbulent boundary layer. Wall shear stress fluctuation, τw,rms'+, on the other hand, remains constant at approximately 0.44 over the range, 800transfer experiments. In the transitional region, turbulent spots are tightly packed with numerous hairpin vortices. With the advection and merging of turbulent spots, these young isolated hairpin forests develop into the downstream turbulent region. Isosurfaces of temperature up to Reθ=1900 are found to display well-resolved signatures of hairpin vortices, which indicates the persistence of the hairpin forests.

Investigation of mass transfer intensification under power ultrasound irradiation using 3D computational simulation: A comparative analysis.

PubMed

Sajjadi, Baharak; Asgharzadehahmadi, Seyedali; Asaithambi, Perumal; Raman, Abdul Aziz Abdul; Parthasarathy, Rajarathinam

2017-01-01

This paper aims at investigating the influence of acoustic streaming induced by low-frequency (24kHz) ultrasound irradiation on mass transfer in a two-phase system. The main objective is to discuss the possible mass transfer improvements under ultrasound irradiation. Three analyses were conducted: i) experimental analysis of mass transfer under ultrasound irradiation; ii) comparative analysis between the results of the ultrasound assisted mass transfer with that obtained from mechanically stirring; and iii) computational analysis of the systems using 3D CFD simulation. In the experimental part, the interactive effects of liquid rheological properties, ultrasound power and superficial gas velocity on mass transfer were investigated in two different sonicators. The results were then compared with that of mechanical stirring. In the computational part, the results were illustrated as a function of acoustic streaming behaviour, fluid flow pattern, gas/liquid volume fraction and turbulence in the two-phase system and finally the mass transfer coefficient was specified. It was found that additional turbulence created by ultrasound played the most important role on intensifying the mass transfer phenomena compared to that in stirred vessel. Furthermore, long residence time which depends on geometrical parameters is another key for mass transfer. The results obtained in the present study would help researchers understand the role of ultrasound as an energy source and acoustic streaming as one of the most important of ultrasound waves on intensifying gas-liquid mass transfer in a two-phase system and can be a breakthrough in the design procedure as no similar studies were found in the existing literature. Copyright © 2016. Published by Elsevier B.V.

The Influence of Oscillatory Fractions on Mass Transfer of Non-Newtonian Fluid in Wavy-Walled Tubes for Pulsatile Flow

NASA Astrophysics Data System (ADS)

Zhu, Donghui; Bian, Yongning

2018-03-01

The shape of pipeline structure, fluid medium and flow state have important influence on the heat transfer and mass effect of fluid. In this paper, we investigated the mass transfer behavior of Non-Newtonian fluid CMC solution with 700ppm concentration in five different-sized axisymmetric wave-walled tubes for pulsatile flow. It is revealed that the effect of mass transfer is enhanced with the increase of oscillatory fractions P based on the PIV measurements. Besides, mass transfer rate was measured by the electrochemical method in the larger oscillatory points rate range. It is observed that mass transfer rate increases with the increase in P and reached the maximum mass transfer rate at the most optimal oscillatory fractions P opt. After reaching the optimal oscillatory fractions P opt, the mass transfer rate decreases with increasing P.

Shift in Mass Transfer of Wastewater Contaminants from Microplastics in the Presence of Dissolved Substances.

PubMed

Seidensticker, Sven; Zarfl, Christiane; Cirpka, Olaf A; Fellenberg, Greta; Grathwohl, Peter

2017-11-07

In aqueous environments, hydrophobic organic contaminants are often associated with particles. Besides natural particles, microplastics have raised public concern. The release of pollutants from such particles depends on mass transfer, either in an aqueous boundary layer or by intraparticle diffusion. Which of these mechanisms controls the mass-transfer kinetics depends on partition coefficients, particle size, boundary conditions, and time. We have developed a semianalytical model accounting for both processes and performed batch experiments on the desorption kinetics of typical wastewater pollutants (phenanthrene, tonalide, and benzophenone) at different dissolved-organic-matter concentrations, which change the overall partitioning between microplastics and water. Initially, mass transfer is externally dominated, while finally, intraparticle diffusion controls release kinetics. Under boundary conditions typical for batch experiments (finite bath), desorption accelerates with increasing partition coefficients for intraparticle diffusion, while it becomes independent of partition coefficients if film diffusion prevails. On the contrary, under field conditions (infinite bath), the pollutant release controlled by intraparticle diffusion is not affected by partitioning of the compound while external mass transfer slows down with increasing sorption. Our results clearly demonstrate that sorption/desorption time scales observed in batch experiments may not be transferred to field conditions without an appropriate model accounting for both the mass-transfer mechanisms and the specific boundary conditions at hand.

Mathematical simulation of convective-radiative heat transfer in a ventilated rectangular cavity with consideration of internal mass transfer

NASA Astrophysics Data System (ADS)

Sheremet, M. A.; Shishkin, N. I.

2012-07-01

Mathematical simulation of the nonstationary regimes of heat-and-mass transfer in a ventilated rectangular cavity with heat-conducting walls of finite thickness in the presence of a heat-generating element of constant temperature has been carried out with account for the radiative heat transfer in the Rosseland approximation. As mechanisms of energy transfer in this cavity, the combined convection and the thermal radiation in the gas space of the cavity and the heat conduction in the elements of its fencing solid shell were considered. The mathematical model formulated in the dimensionless stream function-vorticity vector-temperature-concentration variables was realized numerically with the use of the finite-difference method. The streamline, temperature-field, and concentration distributions reflecting the influence of the Rayleigh number (Ra = 104, 105, 106), the nonstationarity (0 < τ ≤ 1000), and the optical thickness of the medium (τλ = 50, 100, 200) on the regimes of the gas flow and the heat-and-mass transfer in the cavity have been obtained.

Mass transfer in thin films under counter-current gas: experiments and numerical study

NASA Astrophysics Data System (ADS)

Lucquiaud, Mathieu; Lavalle, Gianluca; Schmidt, Patrick; Ausner, Ilja; Wehrli, Marc; O Naraigh, Lennon; Valluri, Prashant

2016-11-01

Mass transfer in liquid-gas stratified flows is strongly affected by the waviness of the interface. For reactive flows, the chemical reactions occurring at the liquid-gas interface also influence the mass transfer rate. This is encountered in several technological applications, such as absorption units for carbon capture. We investigate the absorption rate of carbon dioxide in a liquid solution. The experimental set-up consists of a vertical channel where a falling film is sheared by a counter-current gas flow. We measure the absorption occurring at different flow conditions, by changing the liquid solution, the liquid flow rate and the gas composition. With the aim to support the experimental results with numerical simulations, we implement in our level-set flow solver a novel module for mass transfer taking into account a variant of the ghost-fluid formalism. We firstly validate the pure mass transfer case with and without hydrodynamics by comparing the species concentration in the bulk flow to the analytical solution. In a final stage, we analyse the absorption rate in reactive flows, and try to reproduce the experimental results by means of numerical simulations to explore the active role of the waves at the interface.

Conjugate heat and mass transfer in the lattice Boltzmann equation method.

PubMed

Li, Like; Chen, Chen; Mei, Renwei; Klausner, James F

2014-04-01

An interface treatment for conjugate heat and mass transfer in the lattice Boltzmann equation method is proposed based on our previously proposed second-order accurate Dirichlet and Neumann boundary schemes. The continuity of temperature (concentration) and its flux at the interface for heat (mass) transfer is intrinsically satisfied without iterative computations, and the interfacial temperature (concentration) and their fluxes are conveniently obtained from the microscopic distribution functions without finite-difference calculations. The present treatment takes into account the local geometry of the interface so that it can be directly applied to curved interface problems such as conjugate heat and mass transfer in porous media. For straight interfaces or curved interfaces with no tangential gradient, the coupling between the interfacial fluxes along the discrete lattice velocity directions is eliminated and thus the proposed interface schemes can be greatly simplified. Several numerical tests are conducted to verify the applicability and accuracy of the proposed conjugate interface treatment, including (i) steady convection-diffusion in a channel containing two different fluids, (ii) unsteady convection-diffusion in the channel, (iii) steady heat conduction inside a circular domain with two different solid materials, and (iv) unsteady mass transfer from a spherical droplet in an extensional creeping flow. The accuracy and order of convergence of the simulated interior temperature (concentration) field, the interfacial temperature (concentration), and heat (mass) flux are examined in detail and compared with those obtained from the "half-lattice division" treatment in the literature. The present analysis and numerical results show that the half-lattice division scheme is second-order accurate only when the interface is fixed at the center of the lattice links, while the present treatment preserves second-order accuracy for arbitrary link fractions. For curved

Dynamics of Mass Transfer in Wide Symbiotic Systems

NASA Astrophysics Data System (ADS)

de Val-Borro, Miguel; Karovska, M.; Sasselov, D.

2010-01-01

We investigate the formation of accretion disks around the secondary in detached systems consisting of an Asymptotic Giant Branch (AGB) star and a compact accreting companion as a function of mass loss rate and orbital parameters. In particular, we study winds from late-type stars that are gravitationally focused by a companion in a wide binary system using hydrodynamical simulations. For a typical slow and massive wind from an evolved star there is a stream flow between the stars with accretion rates of a few percent of the mass loss from the primary. Mass transfer through a focused wind is an important mechanism for a broad range of interacting binary systems and can explain the formation of Barium stars and other chemically peculiar stars.

Ultrafast Interlayer Electron Transfer in Incommensurate Transition Metal Dichalcogenide Homobilayers.

PubMed

Li, Yuanyuan; Cui, Qiannan; Ceballos, Frank; Lane, Samuel D; Qi, Zeming; Zhao, Hui

2017-11-08

Two-dimensional materials, such as graphene, transition metal dichalcogenides, and phosphorene, can be used to construct van der Waals multilayer structures. This approach has shown potentials to produce new materials that combine novel properties of the participating individual layers. One key requirement for effectively harnessing emergent properties of these materials is electronic connection of the involved atomic layers through efficient interlayer charge or energy transfer. Recently, ultrafast charge transfer on a time scale shorter than 100 fs has been observed in several van der Waals bilayer heterostructures formed by two different materials. However, information on the transfer between two atomic layers of the same type is rare. Because these homobilayers are essential elements in constructing multilayer structures with desired optoelectronic properties, efficient interlayer transfer is highly desired. Here we show that electron transfer between two monolayers of MoSe 2 occurs on a picosecond time scale. Even faster transfer was observed in homobilayers of WS 2 and WSe 2 . The samples were fabricated by manually stacking two exfoliated monolayer flakes. By adding a graphene layer as a fast carrier recombination channel for one of the two monolayers, the transfer of the photoexcited carriers from the populated to the drained monolayers was time-resolved by femtosecond transient absorption measurements. The observed efficient interlayer carrier transfer indicates that such homobilayers can be used in van der Waals multilayers to enhance their optical absorption without significantly compromising the interlayer transport performance. Our results also provide valuable information for understanding interlayer charge transfer in heterostructures.

Investigations of effect of phase change mass transfer rate on cavitation process with homogeneous relaxation model

DOE Office of Scientific and Technical Information (OSTI.GOV)

He, Zhixia; Zhang, Liang; Saha, Kaushik

The super high fuel injection pressure and micro size of nozzle orifice has been an important development trend for the fuel injection system. Accordingly, cavitation transient process, fuel compressibility, amount of noncondensable gas in the fuel and cavitation erosion have attracted more attention. Based on the fact of cavitation in itself is a kind of thermodynamic phase change process, this paper takes the perspective of the cavitation phase change mass transfer process to analyze above mentioned phenomenon. The two-phase cavitating turbulent flow simulations with VOF approach coupled with HRM cavitation model and U-RANS of standard k-ε turbulence model were performedmore » for investigations of cavitation phase change mass transfer process. It is concluded the mass transfer time scale coefficient in the Homogenous Relaxation Model (HRM) representing mass transfer rate should tend to be as small as possible in a condition that ensured the solver stable. At very fast mass transfer rate, the phase change occurs at very thin interface between liquid and vapor phase and condensation occurs more focused and then will contribute predictably to a more serious cavitation erosion. Both the initial non-condensable gas in fuel and the fuel compressibility can accelerate the cavitation mass transfer process.« less

Length-mass relationships for transitional water benthic macroinvertebrates in Mediterranean and Black Sea ecosystems

NASA Astrophysics Data System (ADS)

Rosati, I.; Barbone, E.; Basset, A.

2012-11-01

Length-mass relationships are potentially useful tools to estimate individual biomass, assuming a relative invariance within and among populations and, sometimes, among species pertaining to a same family or order. Here, we present a field test of these assumptions in guilds of benthic macroinvertebrates colonising transitional water ecosystems. To this aim, we are analysing length-mass relationships of benthic macroinvertebrates of transitional water ecosystems and assessing their variability among populations of a same species and among species of a same family and/or order. Data are from synoptic studies carried out at four oligohaline transitional water ecosystems, from the Southern Italy and the Danube delta ecoregions; they refer to 40 macroinvertebrate taxa selected from the overall species pool according to absolute and relative density requirements. Species composition differed widely among ecoregions while length-mass relationships of the species occurring in both ecoregions did not; the variability of length-mass parameters of these species among ecosystems was lower than 10%. Length-mass regressions were relatively conservative also with respect to taxonomic resolution; significant differences were observed among species within 5 out of the 7 orders tested but differences in slopes and intercepts were on average lower than 15%. Therefore, our results, representing one of the first efforts to catalogue length-mass relationships for benthic macroinvertebrates in transitional waters, support the assumption of relative invariance of length-mass relationships and their use in studies where gross estimates of population biomasses are required.

IR, 1H NMR, mass, XRD and TGA/DTA investigations on the ciprofloxacin/iodine charge-transfer complex.

PubMed

Refat, Moamen S; El-Hawary, W F; Moussa, Mohamed A A

2011-05-01

The charge-transfer complex (CTC) of ciprofloxacin drug (CIP) as a donor with iodine (I(2)) as a sigma acceptor has been studied spectrophotometrically in CHCl(3). At maximum absorption bands, the stoichiometry of CIP:iodine system was found to be 1:1 ratio according to molar ratio method. The essential spectroscopic data like formation constant (K(CT)), molar extinction coefficient (ɛ(CT)), standard free energy (ΔG°), oscillator strength (f), transition dipole moment (μ), resonance energy (R(N)) and ionization potential (I(D)) were estimated. The spectroscopic techniques such as IR, (1)H NMR, mass and UV-vis spectra and elemental analyses (CHN) as well as TG-DTG and DTA investigations were used to characterize the chelating behavior of CIP/iodine charge-transfer complex. The iodine CT interaction was associated with a presence of intermolecular hydrogen bond. The X-ray investigation was carried out to investigate the iodine doping in the synthetic CT complex. Copyright © 2011 Elsevier B.V. All rights reserved.

The use of transition region characteristics to improve the numerical simulation of heat transfer in bypass transitional flows

NASA Technical Reports Server (NTRS)

Simon, Frederick F.

1993-01-01

A method is presented for improving the numerical prediction of bypass transition heat transfer on a flat plate in a high-disturbance environment with zero or favorable pressure gradient. The method utilizes low Reynolds number k-epsilon turbulence models in combination with the characteristic parameters of the transition region. The parameters representing the characteristics of the transition region used are the intermittency, transition length and turbulent spot properties. An analysis is made of the transition length in terms of turbulent spot variables. The nondimensional spot formation rate, required for the prediction of the transition length, is shown by the analysis to be a function of the spot spreading angle, the dimensionless spot velocity ratio and the dimensionless spot area ratio. The intermittency form of the k-epsilon equations were derived from conditionally averaged equations which have been shown to be an improvement over global-time-averaged equations for the numerical calculation of the transition region. The numerical predictions are in general good agreement with the experimental data and indicate the potential use of the method in accelerating flows. Turbulence models of the k-epsilon type are known to underpredict the transition length. The present work demonstrates how incorporating transition region characteristics improves the ability of two-equation turbulence models to simulate bypass transition for flat plates with potential application to turbine vanes and blades.

Masses of Kepler-46b, c from Transit Timing Variations

NASA Astrophysics Data System (ADS)

Saad-Olivera, Ximena; Nesvorný, David; Kipping, David M.; Roig, Fernando

2017-04-01

We use 16 quarters of the Kepler mission data to analyze the transit timing variations (TTVs) of the extrasolar planet Kepler-46b (KOI-872). Our dynamical fits confirm that the TTVs of this planet (period P={33.648}-0.005+0.004 days) are produced by a non-transiting planet Kepler-46c (P={57.325}-0.098+0.116 days). The Bayesian inference tool MultiNest is used to infer the dynamical parameters of Kepler-46b and Kepler-46c. We find that the two planets have nearly coplanar and circular orbits, with eccentricities ≃ 0.03 somewhat higher than previously estimated. The masses of the two planets are found to be {M}b={0.885}-0.343+0.374 and {M}c={0.362}-0.016+0.016 Jupiter masses, with M b being determined here from TTVs for the first time. Due to the precession of its orbital plane, Kepler-46c should start transiting its host star a few decades from now.

Couette flow of an incompressible fluid in a porous channel with mass transfer

NASA Astrophysics Data System (ADS)

Niranjana, N.; Vidhya, M.; Govindarajan, A.

2018-04-01

The present discussion deals with the study of couette flow through a porous medium of a viscous incompressible fluid between two infinite horizontal parallel porous flat plates with heat and mass transfer. The stationary plate and the plate in uniform motion are subjected to transverse sinusoidal injection and uniform suction of the fluid. Due to this type of injection velocity, the flow becomes three dimensional. The analytical solutions of the nonlinear partial differential equations of this problem are obtained by using perturbation technique. Expressions for the velocity, temperature fields and the rate of heat and mass transfers are obtained. Effects of the following parameters Schmidt number (Sc), Modified Grashof number (Gm) on the velocity, temperature and concentration fields are obtained numerically and depicted through graphs. The rate of heat and mass transfer are also analyzed.

Drop mass transfer in a microfluidic chip compared to a centrifugal contactor

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nemer, Martin B.; Roberts, Christine C.; Hughes, Lindsey G.

2014-06-13

A model system was developed for enabling a multiscale understanding of centrifugal-contactor liquid–liquid extraction.The system consisted of Nd(III) + xylenol orange in the aqueous phase buffered to pH =5.5 by KHP, and dodecane + thenoyltrifluroroacetone (HTTA) + tributyphosphate (TBP) in the organic phase. Diffusion constants were measured for neodymium in both the organic and aqueous phases, and the Nd(III) partition coefficients were measured at various HTTA and TBP concentrations. A microfluidic channel was used as a high-shear model environment to observe mass-transfer on a droplet scale with xylenol orange as the aqueous-phase metal indicator; mass-transfer rates were measured quantitatively inmore » both diffusion and reaction limited regimes on the droplet scale. Lastly, the microfluidic results were comparable to observations made for the same system in a laboratory scale liquid–liquid centrifugal contactor, indicating that single drop microfluidic experiments can provide information on mass transfer in complicated flows and geometries.« less

Method and system for simulating heat and mass transfer in cooling towers

DOEpatents

Bharathan, Desikan; Hassani, A. Vahab

1997-01-01

The present invention is a system and method for simulating the performance of a cooling tower. More precisely, the simulator of the present invention predicts values related to the heat and mass transfer from a liquid (e.g., water) to a gas (e.g., air) when provided with input data related to a cooling tower design. In particular, the simulator accepts input data regarding: (a) cooling tower site environmental characteristics; (b) cooling tower operational characteristics; and (c) geometric characteristics of the packing used to increase the surface area within the cooling tower upon which the heat and mass transfer interactions occur. In providing such performance predictions, the simulator performs computations related to the physics of heat and mass transfer within the packing. Thus, instead of relying solely on trial and error wherein various packing geometries are tested during construction of the cooling tower, the packing geometries for a proposed cooling tower can be simulated for use in selecting a desired packing geometry for the cooling tower.

Transitioning and Transfer of Adolescents and Young Adults with Pediatric Onset Chronic Disease: The Patient and Parent Perspective

PubMed Central

Fernandes, Susan M.; O’Sullivan-Oliveira, Joanne; Landzberg, Michael J.; Khairy, Paul; Melvin, Patrice; Sawicki, Gregory S.; Ziniel, Sonja; Kenney, Lisa B.; Garvey, Katharine C.; Sobota, Amy; O’Brien, Rebecca; Nigrovic, Peter A.; Sharma, Niraj; Fishman, Laurie N

2017-01-01

Purpose To determine patients’ and parents’ perceptions of transitioning education as well as their attitudes and perceived barriers to transfer to adult oriented care. Methods A self-report survey was administered to patients (16–25 years old) with various childhood onset chronic diseases. A similar survey was administered to their parents/guardians. Results A total of 155 patients and 104 parents participated in the study. The mean age of patients was 18.9±2.3 years; 57% were female. Although most patients and parents reported receiving information and training about their medical condition, significant gaps in “transitioning education” were identified. These included stated deficiencies in education regarding unprotected intercourse, health of future offspring, birth control, pregnancy, illicit drug use, and future career or vocation counseling. Commonly named barriers to transfer were emotional attachments and lack of adult medicine specialty providers; however, the majority anticipated being ready to transfer to adult oriented care by age 25 years. Conclusion Current transitioning education delivery appears to result in significant gaps in transfer of information and training, as perceived by patients and their parents. Standardization of transitioning education may help ensure that patients obtain the necessary skills for self-care in adulthood and successful transfer to adult oriented care. PMID:24919937

Mathematical modeling heat and mass transfer processes in porous media

NASA Astrophysics Data System (ADS)

Akhmed-Zaki, Darkhan

2013-11-01

On late development stages of oil-fields appears a complex problem of oil-recovery reduction. One of solution approaches is injecting of surfactant together with water in the form of active impurities into the productive layer - for decreasing oil viscosity and capillary forces between ``oil-water'' phases system. In fluids flow the surfactant can be in three states: dissolved in water, dissolved in oil and adsorbed on pore channels' walls. The surfactant's invasion into the reservoir is tracked by its diffusion with reservoir liquid and mass-exchange with two phase (liquid and solid) components of porous structure. Additionally, in this case heat exchange between fluids (injected, residual) and framework of porous medium has practical importance for evaluating of temperature influences on enhancing oil recovery. Now, the problem of designing an adequate mathematical model for describing a simultaneous flowing heat and mass transfer processes in anisotropic heterogeneous porous medium -surfactant injection during at various temperature regimes has not been fully researched. In this work is presents a 2D mathematical model of surfactant injections into the oil reservoir. Description of heat- and mass transfer processes in a porous media is done through differential and kinetic equations. For designing a computational algorithm is used modify version of IMPES method. The sequential and parallel computational algorithms are developed using an adaptive curvilinear meshes which into account heterogeneous porous structures. In this case we can evaluate the boundaries of our process flows - fronts (``invasion'', ``heat'' and ``mass'' transfers), according to the pressure, temperature, and concentration gradient changes.

Determination of the mass transfer limiting step of dye adsorption onto commercial adsorbent by using mathematical models.

PubMed

Marin, Pricila; Borba, Carlos Eduardo; Módenes, Aparecido Nivaldo; Espinoza-Quiñones, Fernando R; de Oliveira, Silvia Priscila Dias; Kroumov, Alexander Dimitrov

2014-01-01

Reactive blue 5G dye removal in a fixed-bed column packed with Dowex Optipore SD-2 adsorbent was modelled. Three mathematical models were tested in order to determine the limiting step of the mass transfer of the dye adsorption process onto the adsorbent. The mass transfer resistance was considered to be a criterion for the determination of the difference between models. The models contained information about the external, internal, or surface adsorption limiting step. In the model development procedure, two hypotheses were applied to describe the internal mass transfer resistance. First, the mass transfer coefficient constant was considered. Second, the mass transfer coefficient was considered as a function of the dye concentration in the adsorbent. The experimental breakthrough curves were obtained for different particle diameters of the adsorbent, flow rates, and feed dye concentrations in order to evaluate the predictive power of the models. The values of the mass transfer parameters of the mathematical models were estimated by using the downhill simplex optimization method. The results showed that the model that considered internal resistance with a variable mass transfer coefficient was more flexible than the other ones and this model described the dynamics of the adsorption process of the dye in the fixed-bed column better. Hence, this model can be used for optimization and column design purposes for the investigated systems and similar ones.

The mass of the Mars-sized exoplanet Kepler-138 b from transit timing.

PubMed

Jontof-Hutter, Daniel; Rowe, Jason F; Lissauer, Jack J; Fabrycky, Daniel C; Ford, Eric B

2015-06-18

Extrasolar planets that pass in front of their host star (transit) cause a temporary decrease in the apparent brightness of the star, providing a direct measure of the planet's size and orbital period. In some systems with multiple transiting planets, the times of the transits are measurably affected by the gravitational interactions between neighbouring planets. In favourable cases, the departures from Keplerian orbits (that is, unaffected by gravitational effects) implied by the observed transit times permit the planetary masses to be measured, which is key to determining their bulk densities. Characterizing rocky planets is particularly difficult, because they are generally smaller and less massive than gaseous planets. Therefore, few exoplanets near the size of Earth have had their masses measured. Here we report the sizes and masses of three planets orbiting Kepler-138, a star much fainter and cooler than the Sun. We determine that the mass of the Mars-sized inner planet, Kepler-138 b, is 0.066(+0.059)(-0.037) Earth masses. Its density is 2.6(+2.4)(-1.5) grams per cubic centimetre. The middle and outer planets are both slightly larger than Earth. The middle planet's density (6.2(+5.8)(-3.4) grams per cubic centimetre) is similar to that of Earth, and the outer planet is less than half as dense at 2.1(+2.2)(-1.2) grams per cubic centimetre, implying that it contains a greater portion of low-density components such as water and hydrogen.

Strangers headed to a strange land? A pilot study of using a transition coordinator to improve transfer from pediatric to adult services.

PubMed

Annunziato, Rachel A; Baisley, Margaret C; Arrato, Nicole; Barton, Codette; Henderling, Fiona; Arnon, Ronen; Kerkar, Nanda

2013-12-01

To compare the impact of a transition coordinator on outcomes for pediatric liver transplant recipients vs a historical comparison group. To examine the utility of a transition coordinator, medication adherence, as measured by SDs of tacrolimus blood levels (Tacrolimus SD), was compared between the "transition coordinator group" (20 transplant recipients transferred between 2007 and 2012) and comparison group for 1 year before and after transfer. Measures of health care management, quality of life, and acceptability were administered to the transition coordinator group as well. A repeated measures ANOVA was used to compare adherence values between the transition coordinator group and the comparison group. During the year before transfer, for the transition coordinator group, Tacrolimus SD was 1.98 (SD = 1.05) vs 3.25 (SD = 1.19) for comparison patients, F(1,25) = 4.77, P = .04. After transfer, levels remained stable for the transition coordinator group, Tacrolimus SD = 1.88 (SD = 1.57), but increased for comparison patients, Tacrolimus SD = 4.36 (SD = 0.99), F(1,25) = 6.99, P = .01. Psychosocial outcomes remained stable during the transfer period and acceptability was high. Our findings, although limited by a small sample size, suggest that a transition coordinator is a promising method to improve this process. Copyright © 2013 Mosby, Inc. All rights reserved.

High School Transfer Students and the Transition to College: Timing and the Structure of the School Year

PubMed Central

Sutton, April; Muller, Chandra; Langenkamp, Amy G.

2013-01-01

The timing of a high school transfer may shape students’ transitions to college through its (mis)alignment with the structure of the school year. A transfer that occurs during the summer interrupts the four-year high school career, whereas a transfer that occurs midyear disrupts both the four-year high school career and the structure of the school year. Using the Education Longitudinal Study of 2002 (ELS), the investigators find that the penalty suffered after the transfer depends on the degree to which students’ high school pathways synchronize with the curricular and extracurricular structure of the school year. Midyear transfer students appear to suffer the greatest postsecondary matriculation penalty. Students who transfer midyear are less likely to attend a four-year college compared with nontransfer and summer transfer students, whereas summer transfer students are less likely to attend a highly selective four-year college compared with their nontransfer counterparts. Curricular and extracurricular disruptions that transfer students experience after their school move explain some, but not all, of the negative associations observed between transferring and the transition to college. Directions for future research and the theoretical and policy implications of the results are discussed. PMID:24683277

A comparison of mass transfer coefficients between trickle-bed, hollow fiber membrane and stirred tank reactors.

PubMed

Orgill, James J; Atiyeh, Hasan K; Devarapalli, Mamatha; Phillips, John R; Lewis, Randy S; Huhnke, Raymond L

2013-04-01

Trickle-bed reactor (TBR), hollow fiber membrane reactor (HFR) and stirred tank reactor (STR) can be used in fermentation of sparingly soluble gasses such as CO and H2 to produce biofuels and bio-based chemicals. Gas fermenting reactors must provide high mass transfer capabilities that match the kinetic requirements of the microorganisms used. The present study compared the volumetric mass transfer coefficient (K(tot)A/V(L)) of three reactor types; the TBR with 3 mm and 6 mm beads, five different modules of HFRs, and the STR. The analysis was performed using O2 as the gaseous mass transfer agent. The non-porous polydimethylsiloxane (PDMS) HFR provided the highest K(tot)A/V(L) (1062 h(-1)), followed by the TBR with 6mm beads (421 h(-1)), and then the STR (114 h(-1)). The mass transfer characteristics in each reactor were affected by agitation speed, and gas and liquid flow rates. Furthermore, issues regarding the comparison of mass transfer coefficients are discussed. Copyright © 2013 Elsevier Ltd. All rights reserved.

[Correlation of molecular weight and nanofiltration mass transfer coefficient of phenolic acid composition from Salvia miltiorrhiza].

PubMed

Li, Cun-Yu; Wu, Xin; Gu, Jia-Mei; Li, Hong-Yang; Peng, Guo-Ping

2018-04-01

Based on the molecular sieving and solution-diffusion effect in nanofiltration separation, the correlation between initial concentration and mass transfer coefficient of three typical phenolic acids from Salvia miltiorrhiza was fitted to analyze the relationship among mass transfer coefficient, molecular weight and concentration. The experiment showed a linear relationship between operation pressure and membrane flux. Meanwhile, the membrane flux was gradually decayed with the increase of solute concentration. On the basis of the molecular sieving and solution-diffusion effect, the mass transfer coefficient and initial concentration of three phenolic acids showed a power function relationship, and the regression coefficients were all greater than 0.9. The mass transfer coefficient and molecular weight of three phenolic acids were negatively correlated with each other, and the order from high to low is protocatechualdehyde >rosmarinic acid> salvianolic acid B. The separation mechanism of nanofiltration for phenolic acids was further clarified through the analysis of the correlation of molecular weight and nanofiltration mass transfer coefficient. The findings provide references for nanofiltration separation, especially for traditional Chinese medicine with phenolic acids. Copyright© by the Chinese Pharmaceutical Association.

Mess in mass transit: though demand is up, the service is down

DOE Office of Scientific and Technical Information (OSTI.GOV)

Not Available

1979-07-16

Mass transit systems (bus and rail), in poor mechanical and physical condition, are facing an economic crisis. Most industries that had been constructing new rail or bus equipment have now quit production completely or nearly so. San Diego is buying trolleys for its 16-mile line to the Mexican border, on which construction will begin in late 1979, from a West German supplier. The background of how the US got into this situation is reviewed. American's love affair with the automobile put the transit systems in financial trouble with poor ridership, and now the companies are afraid to reconstruct, thinking perhapsmore » Americans will revert to the automobile if gasoline again becomes plentiful. As the US attempts to remedy the transit situation, there should be a burden sharing between local and Federal governments. Local transit authorities should carry the operating costs, but even if they are heavily traveled, fares meet only 48% of operating costs. Therefore, communities will have to find ways to raise money in order to keep the systems running. The Carter Administration did not seize on mass transit as a means of conserving gasoline, but President Carter did say that part of the windfall tax on oil companies would be set aside for mass transport. But some progress is noted: Baltimore is digging its first subway; Buffalo began construction of a 6.5-mile subway and elevated-transit system; and Atlanta put into operation the first 6.7-mile segment of MARTA. Improvisions in many cities are noted, such as, leasing commercial buses and pressing school buses into operation. (MCW)« less

Bibliography on augmentation of convective heat and mass transfer-II

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bergles, A.E.; Nirmalan, V.; Junkhan, G.H.

1983-12-01

Heat transfer augmentation has developed into a major specialty area in heat transfer research and development. This report presents and updated bibliography of world literature on augmentation. The literature is classified into passive augmentation techniques, which require no external power, and active techniques, which do require external power. The fifteen techniques are grouped in terms of their applications to the various modes of heat transfer. Mass transfer is included for completeness. Key words are included with each citation for technique/mode identification. The total number of publications cited is 3045, including 135 surveys of various techniques and 86 papers on performancemore » evaluation of passive techniques. Patents are not included, as they are the subject of a separate bibliographic report.« less

Mathematical model of mass transfer at electron beam treatment

NASA Astrophysics Data System (ADS)

Konovalov, Sergey V.; Sarychev, Vladimir D.; Nevskii, Sergey A.; Kobzareva, Tatyana Yu.; Gromov, Victor E.; Semin, Alexander P.

2017-01-01

The paper proposes a model of convective mass transfer at electron beam treatment with beams in titanium alloys subjected to electro-explosion alloying by titanium diboride powder. The proposed model is based on the concept that treatment with concentrated flows of energy results in the initiation of vortices in the melted layer. The formation mechanism of these vortices rooted in the idea that the availability of temperature drop leads to the initiation of the thermo-capillary convection. For the melted layer of metal the equations of the convective heat transfer and boundary conditions in terms of the evaporated material are written. The finite element solution of these equations showed that electron-beam treatment results in the formation of multi-vortex structure that in developing captures all new areas of material. It leads to the fact that the strengthening particles are observed at the depth increasing many times the depth of their penetration according to the diffusion mechanism. The distribution of micro-hardness at depth and the thickness of strengthening zone determined from these data supported the view that proposed model of the convective mass transfer describes adequately the processes going on in the treatment with low-energy high-current electron beam.

Diffusive transfer to membranes as an effective interface between gel electrophoresis and mass spectrometry

NASA Astrophysics Data System (ADS)

Ogorzalek Loo, Rachel R.; Mitchell, Charles; Stevenson, Tracy I.; Loo, Joseph A.; Andrews, Philip C.

1997-12-01

Diffusive transfer was examined as a blotting method to transfer proteins from polyacrylamide gels to membranes for ultraviolet matrix-assisted laser desorption ionization (MALDI) mass spectrometry. The method is well-suited for transfers from isoelectric focusing (IEF) gels. Spectra have been obtained for 11 pmol of 66 kDa albumin loaded onto an IEF gel and subsequently blotted to polyethylene. Similarly, masses of intact carbonic anhydrase and hemoglobin were obtained from 14 and 20 pmol loadings. This methodology is also compatible with blotting high molecular weight proteins, as seen for 6 pmol of the 150 kDa monoclonal antibody anti-[beta]-galactosidase transferred to Goretex. Polypropylene, Teflon, Nafion and polyvinylidene difluoride (PVDF) also produced good spectra following diffusive transfer. Only analysis from PVDF required that the membrane be kept wet prior to application of matrix. Considerations in mass accuracy for analysis from large-area membranes with continuous extraction and delayed extraction were explored, as were remedies for surface charging. Vapor phase CNBr cleavage was applied to membrane-bound samples for peptide mapping.

Precise masses for the transiting planetary system HD 106315 with HARPS

NASA Astrophysics Data System (ADS)

Barros, S. C. C.; Gosselin, H.; Lillo-Box, J.; Bayliss, D.; Delgado Mena, E.; Brugger, B.; Santerne, A.; Armstrong, D. J.; Adibekyan, V.; Armstrong, J. D.; Barrado, D.; Bento, J.; Boisse, I.; Bonomo, A. S.; Bouchy, F.; Brown, D. J. A.; Cochran, W. D.; Collier Cameron, A.; Deleuil, M.; Demangeon, O.; Díaz, R. F.; Doyle, A.; Dumusque, X.; Ehrenreich, D.; Espinoza, N.; Faedi, F.; Faria, J. P.; Figueira, P.; Foxell, E.; Hébrard, G.; Hojjatpanah, S.; Jackman, J.; Lendl, M.; Ligi, R.; Lovis, C.; Melo, C.; Mousis, O.; Neal, J. J.; Osborn, H. P.; Pollacco, D.; Santos, N. C.; Sefako, R.; Shporer, A.; Sousa, S. G.; Triaud, A. H. M. J.; Udry, S.; Vigan, A.; Wyttenbach, A.

2017-12-01

Context. The multi-planetary system HD 106315 was recently found in K2 data. The planets have periods of Pb 9.55 and Pc 21.06 days, and radii of rb = 2.44 ± 0.17 R⊕ and rc = 4.35 ± 0.23 R⊕ . The brightness of the host star (V = 9.0 mag) makes it an excellent target for transmission spectroscopy. However, to interpret transmission spectra it is crucial to measure the planetary masses. Aims: We obtained high precision radial velocities for HD 106315 to determine the mass of the two transiting planets discovered with Kepler K2. Our successful observation strategy was carefully tailored to mitigate the effect of stellar variability. Methods: We modelled the new radial velocity data together with the K2 transit photometry and a new ground-based partial transit of HD 106315c to derive system parameters. Results: We estimate the mass of HD 106315b to be 12.6 ± 3.2 M⊕ and the density to be 4.7 ± 1.7 g cm-3, while for HD 106315c we estimate a mass of 15.2 ± 3.7 M⊕ and a density of 1.01 ± 0.29 g cm-3. Hence, despite planet c having a radius almost twice as large as planet b, their masses are consistent with one another. Conclusions: We conclude that HD 106315c has a thick hydrogen-helium gaseous envelope. A detailed investigation of HD 106315b using a planetary interior model constrains the core mass fraction to be 5-29%, and the water mass fraction to be 10-50%. An alternative, not considered by our model, is that HD 106315b is composed of a large rocky core with a thick H-He envelope. Transmission spectroscopy of these planets will give insight into their atmospheric compositions and also help constrain their core compositions. Based on observations collected at the European Organisation for Astronomical Research in the Southern Hemisphere under ESO programme 198.C-0168.

Conjugate heat and mass transfer in the lattice Boltzmann equation method

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, LK; Chen, C; Mei, RW

2014-04-22

An interface treatment for conjugate heat and mass transfer in the lattice Boltzmann equation method is proposed based on our previously proposed second-order accurate Dirichlet and Neumann boundary schemes. The continuity of temperature (concentration) and its flux at the interface for heat (mass) transfer is intrinsically satisfied without iterative computations, and the interfacial temperature (concentration) and their fluxes are conveniently obtained from the microscopic distribution functions without finite-difference calculations. The present treatment takes into account the local geometry of the interface so that it can be directly applied to curved interface problems such as conjugate heat and mass transfer inmore » porous media. For straight interfaces or curved interfaces with no tangential gradient, the coupling between the interfacial fluxes along the discrete lattice velocity directions is eliminated and thus the proposed interface schemes can be greatly simplified. Several numerical tests are conducted to verify the applicability and accuracy of the proposed conjugate interface treatment, including (i) steady convection-diffusion in a channel containing two different fluids, (ii) unsteady convection-diffusion in the channel, (iii) steady heat conduction inside a circular domain with two different solid materials, and (iv) unsteady mass transfer from a spherical droplet in an extensional creeping flow. The accuracy and order of convergence of the simulated interior temperature (concentration) field, the interfacial temperature (concentration), and heat (mass) flux are examined in detail and compared with those obtained from the "half-lattice division" treatment in the literature. The present analysis and numerical results show that the half-lattice division scheme is second-order accurate only when the interface is fixed at the center of the lattice links, while the present treatment preserves second-order accuracy for arbitrary link fractions. For

Search for light curve modulations among Kepler candidates. Three very low-mass transiting companions

NASA Astrophysics Data System (ADS)

Lillo-Box, J.; Ribas, A.; Barrado, D.; Merín, B.; Bouy, H.

2016-07-01

Context. Light curve modulations in the sample of Kepler planet candidates allows the disentangling of the nature of the transiting object by photometrically measuring its mass. This is possible by detecting the effects of the gravitational pull of the companion (ellipsoidal modulations) and in some cases, the photometric imprints of the Doppler effect when observing in a broad band (Doppler beaming). Aims: We aim to photometrically unveil the nature of some transiting objects showing clear light curve modulations in the phase-folded Kepler light curve. Methods: We selected a subsample among the large crop of Kepler objects of interest (KOIs) based on their chances to show detectable light curve modulations, I.e., close (a< 12 R⋆) and large (in terms of radius, according to their transit signal) candidates. We modeled their phase-folded light curves with consistent equations for the three effects, namely, reflection, ellipsoidal and beaming (known as REB modulations). Results: We provide detailed general equations for the fit of the REB modulations for the case of eccentric orbits. These equations are accurate to the photometric precisions achievable by current and forthcoming instruments and space missions. By using this mathematical apparatus, we find three close-in very low-mass companions (two of them in the brown dwarf mass domain) orbiting main-sequence stars (KOI-554, KOI-1074, and KOI-3728), and reject the planetary nature of the transiting objects (thus classifying them as false positives). In contrast, the detection of the REB modulations and transit/eclipse signal allows the measurement of their mass and radius that can provide important constraints for modeling their interiors since just a few cases of low-mass eclipsing binaries are known. Additionally, these new systems can help to constrain the similarities in the formation process of the more massive and close-in planets (hot Jupiters), brown dwarfs, and very low-mass companions.

Heat and mass transfer correlations for liquid droplet of a pure fuel in combustion

NASA Astrophysics Data System (ADS)

Dgheim, J.; Chesneau, X.; Pietri, L.; Zeghmati, B.

The authors report a numerical analysis of heat and mass transfers, which govern the combustion of a fuel droplet assimilated to a sphere. The results are presented in the form of temperature, mass-fraction, Nusselt and Sherwood number profiles. The following heat and mass transfers correlations are developed: ; , which account for the effects of natural convection and the physical properties of the gas phase. These correlations agree with the results of detailed numerical analysis as well as the experimental data involving a single droplet.

Influences of Altered River Geomorphology on Channel-Floodplain Mass and Momentum Transfer

NASA Astrophysics Data System (ADS)

Byrne, C. F.; Stone, M. C.

2017-12-01

River management strategies, including both river engineering and restoration, have altered river geomorphology and associated lateral channel-floodplain connectivity throughout the world. This altered connectivity is known to drive changes in ecologic and geomorphic processes during floods, however, quantification of altered connectivity is difficult due to the highly dynamic spatial and temporal nature of flood wave conditions. The objective of this research was to quantify the physical processes of lateral mass and momentum transfer at the channel-floodplain interface. The objective was achieved with the implementation of novel scripting and high-resolution, two-dimensional hydrodynamic modeling techniques under unsteady flow conditions. The process-based analysis focused on three geomorphic feature types within the Middle Rio Grande, New Mexico, USA: (1) historical floodplain surfaces, (2) inset floodplain surfaces formed as a result of channel training and hydrologic alteration, and (3) mechanically restored floodplain surfaces. Results suggest that inset floodplain feature types are not only subject to greater mass and momentum transfer magnitudes, but those connections are also more heterogeneous in nature compared with historical feature types. While restored floodplain feature types exhibit transfer magnitudes and heterogeneity comparable to inset feature types, the surfaces are not of great enough spatial extent to substantially influence total channel-floodplain mass and momentum transfer. Mass and momentum transfer also displayed differing characteristic changes as a result of increased flood magnitude, indicating that linked hydrodynamic processes can be altered differently as a result of geomorphic and hydrologic change. The results display the potential of high-resolution modeling strategies in capturing the spatial and temporal complexities of river processes. In addition, the results have implications for other fields of river science including

Computer program (POWREQ) for power requirements of mass transit vehicles

DOT National Transportation Integrated Search

1977-08-01

This project was performed to develop a computer program suitable for use in systematic analyses requiring estimates of the energy requirements of mass transit vehicles as a function of driving schedules and vehicle size, shape, and gross weight. The...

Transitional Disks Associated with Intermediate-Mass Stars: Results of the SEEDS YSO Survey

NASA Technical Reports Server (NTRS)

Grady, C.; Fukagawa, M.; Maruta, Y.; Ohta, Y.; Wisniewski, J.; Hashimoto, J.; Okamoto, Y.; Momose, M.; Currie, T.; McElwain, M.;

A Review of Interventions Aimed at Facilitating Successful Transition Planning and Transfer to Adult Care Among Youth with Chronic Illness.

PubMed

Weissberg-Benchell, Jill; Shapiro, Jenna B

2017-05-01

This article reviews studies that developed interventions aimed at facilitating the transition process and/or the transfer of youth with chronic illness to adult programs during the past decade. Three key intervention approaches have been studied. Data assessing the impact of transition coordinators suggest that the most successful outcomes occur when coordinators meet with patients prior to the transfer of care, support them as they negotiate the adult programs, and facilitate appointment keeping. Data assessing the impact of transition clinics suggest that the key to positive outcomes is helping patients develop a trusting relationship with the adult providers before fully transferring their care to the adult clinic. Similar conclusions can be drawn for transition programs, where it appears that the opportunity to discuss and plan transition with a pediatric provider over time and to meet with both the pediatric and adult providers simultaneously are beneficial for facilitating successful transfer to adult care. Although aspects of these care processes appear promising for improving transition success, this review identifies areas that need further study. We argue that studies are needed that examine individual patient and family-focused interventions as well as looking at other potential interventions in the health care system. [Pediatr Ann. 2017;46(5):e182-e187.]. Copyright 2017, SLACK Incorporated.

Unit operations for gas-liquid mass transfer in reduced gravity environments

NASA Technical Reports Server (NTRS)

Pettit, Donald R.; Allen, David T.

1992-01-01

Basic scaling rules are derived for converting Earth-based designs of mass transfer equipment into designs for a reduced gravity environment. Three types of gas-liquid mass transfer operations are considered: bubble columns, spray towers, and packed columns. Application of the scaling rules reveals that the height of a bubble column in lunar- and Mars-based operations would be lower than terrestrial designs by factors of 0.64 and 0.79 respectively. The reduced gravity columns would have greater cross-sectional areas, however, by factors of 2.4 and 1.6 for lunar and Martian settings. Similar results were obtained for spray towers. In contract, packed column height was found to be nearly independent of gravity.

Temperature-dependent vibrational spectroscopy to study order-disorder transitions in charge transfer complexes

NASA Astrophysics Data System (ADS)

Isaac, Rohan; Goetz, Katelyn P.; Roberts, Drew; Jurchescu, Oana D.; McNeil, L. E.

2018-02-01

Charge-transfer (CT) complexes are a promising class of materials for the semiconductor industry because of their versatile properties. This class of compounds shows a variety of phase transitions, which are of interest because of their potential impact on the electronic characteristics. Here temperature-dependent vibrational spectroscopy is used to study structural phase transitions in a set of organic CT complexes. Splitting and broadening of infrared-active phonons in the complex formed between pyrene and pyromellitic dianhydride (PMDA) confirm the structural transition is of the order-disorder type and complement previous x-ray diffraction (XRD) results. We show that this technique is a powerful tool to characterize transitions, and apply it to a range of binary CT complexes composed of polyaromatic hyrdocarbons (anthracene, perylene, phenanthrene, pyrene, and stilbene) and PMDA. We extend the understanding of transitions in perylene-PMDA and pyrene-PMDA, and show that there are no order-disorder transitions present in anthracene-PMDA, stilbene-PMDA and phenanthrene-PMDA in the temperature range investigated here.

Transition-density-fragment interaction combined with transfer integral approach for excitation-energy transfer via charge-transfer states

NASA Astrophysics Data System (ADS)

Fujimoto, Kazuhiro J.

2012-07-01

A transition-density-fragment interaction (TDFI) combined with a transfer integral (TI) method is proposed. The TDFI method was previously developed for describing electronic Coulomb interaction, which was applied to excitation-energy transfer (EET) [K. J. Fujimoto and S. Hayashi, J. Am. Chem. Soc. 131, 14152 (2009)] and exciton-coupled circular dichroism spectra [K. J. Fujimoto, J. Chem. Phys. 133, 124101 (2010)]. In the present study, the TDFI method is extended to the exchange interaction, and hence it is combined with the TI method for applying to the EET via charge-transfer (CT) states. In this scheme, the overlap correction is also taken into account. To check the TDFI-TI accuracy, several test calculations are performed to an ethylene dimer. As a result, the TDFI-TI method gives a much improved description of the electronic coupling, compared with the previous TDFI method. Based on the successful description of the electronic coupling, the decomposition analysis is also performed with the TDFI-TI method. The present analysis clearly shows a large contribution from the Coulomb interaction in most of the cases, and a significant influence of the CT states at the small separation. In addition, the exchange interaction is found to be small in this system. The present approach is useful for analyzing and understanding the mechanism of EET.

Space-to-Space Power Beaming Enabling High Performance Rapid Geocentric Orbit Transfer

NASA Technical Reports Server (NTRS)

Dankanich, John W.; Vassallo, Corinne; Tadge, Megan

2015-01-01

The use of electric propulsion is more prevalent than ever, with industry pursuing all electric orbit transfers. Electric propulsion provides high mass utilization through efficient propellant transfer. However, the transfer times become detrimental as the delta V transitions from near-impulsive to low-thrust. Increasing power and therefore thrust has diminishing returns as the increasing mass of the power system limits the potential acceleration of the spacecraft. By using space-to-space power beaming, the power system can be decoupled from the spacecraft and allow significantly higher spacecraft alpha (W/kg) and therefore enable significantly higher accelerations while maintaining high performance. This project assesses the efficacy of space-to-space power beaming to enable rapid orbit transfer while maintaining high mass utilization. Concept assessment requires integrated techniques for low-thrust orbit transfer steering laws, efficient large-scale rectenna systems, and satellite constellation configuration optimization. This project includes the development of an integrated tool with implementation of IPOPT, Q-Law, and power-beaming models. The results highlight the viability of the concept, limits and paths to infusion, and comparison to state-of-the-art capabilities. The results indicate the viability of power beaming for what may be the only approach for achieving the desired transit times with high specific impulse.

Barriers to Physical Activity in a Mass Transit Population: A Qualitative Study.

PubMed

Das, Bhibha M; Petruzzello, Steven J

2016-01-01

The physical inactivity epidemic continues be one of the greatest public health challenges in contemporary society in the United States. The transportation industry is at greater risk of physical inactivity, compared with individuals in other sectors of the workforce. The aim of this study was to use the Nominal Group Technique, a focus group technique, to examine mass transit employees' perceptions of the barriers to physical activity at their worksite. Three focus groups (n = 31) were conducted to examine mass transit employees' perceptions of barriers to physical activity at the worksite. Salient barriers included (1) changing work schedules, (2) poor weather conditions, and (3) lack of scheduled and timely breaks. Findings were consistent with previous research demonstrating shift work, poor weather, and lack of breaks can negatively impact mass transit employees' ability to be physically active. Although physical activity barriers for this population have been consistent for the last 20 years, public health practice and policy have not changed to address these barriers. Future studies should include conducing focus groups stratified by job classification (eg, operators, maintenance, and clerical) along with implementing and evaluating worksite-based physical activity interventions and policy changes.

The effects of recirculation flows on mass transfer from the arterial wall to flowing blood.

PubMed

Zhang, Zhiguo; Deng, Xiaoyan; Fan, Yubo; Guidoin, Robert

2008-01-01

Using a sudden tubular expansion as a model of an arterial stenosis, the effect of disturbed flow on mass transfer from the arterial wall to flowing blood was studied theoretically and tested experimentally by measuring the dissolution rate of benzoic acid disks forming the outer tube of a sudden tubular expansion. The study revealed that mass transfer from vessel wall to flowing fluid in regions of disturbed flow is independent of wall shear rates. The rate of mass transfer is significantly higher in regions of disturbed flow with a local maximum around the reattachment point where the wall shear rate is zero. The experimental study also revealed that the rate of mass transfer from the vessel wall to a flowing fluid is much higher in the presence of microspheres (as models of blood cells) in the flowing fluid and under the condition of pulsatile flow than in steady flow. These results imply that flow disturbance may enhance the transport of biochemicals and macromolecules, such as plasma proteins and lipoproteins synthesized within the blood vessel wall, from the blood vessel wall to flowing blood.

Facilitating transitions. Nursing support for parents during the transfer of preterm infants between neonatal nurseries.

PubMed

Rowe, Jennifer; Jones, Liz

2008-03-01

Transfers between neonatal units are significant transitional experiences for parents of preterm infants. The study aimed to investigate practices that nurses identify as supportive to parents during preterm infants' transfers. It explored the influence of organisational context on practice and what strategies nurses perceive would help them to provide supportive care. Parents' experiences of neonatal nurseries, their stressors and needs have been well documented. The powerful position of nurses in influencing parenting experience is also recognised. However, nurses' understanding of the transfer process, their roles in supporting parents through this and the organisational context influencing practice have not been explored. A focus group design was used composed of registered nurses from two neonatal units who met for a series of group interviews. Eleven registered nurses participated. They explored and critiqued their current practices and then established aims and strategies for practice development. A qualitative content analysis was conducted. Participants identified validation, empowerment and communication as critical to effective practice. They identified a range of organisational dynamics, from logistical issues to nursing authority and scope of practice, as these influenced practice. They presented strategies for practice development, including staff education and the development of nurse practitioner roles. This study explores nurses' understanding and insights into transitions for parents of preterm infants. It shows a congruence between nurses' perceptions of parents' experiences and needs and those reported by parents in previous studies. It articulates the way nurses practice in response to these perceptions, and the manner in which organisational dynamics influence their ability to facilitate transitions. The need to invest in transitions and invest in nurses to facilitate transitions is proposed, ultimately by increasing their clinical authority

Evaluation of Outcomes in Adolescent Inflammatory Bowel Disease Patients Following Transfer From Pediatric to Adult Health Care Services: Case for Transition.

PubMed

Cole, Rebecca; Ashok, Dhandapani; Razack, Abdul; Azaz, Amer; Sebastian, Shaji

2015-08-01

We aimed to evaluate the impact of a transition service on clinical and developmental outcomes in adolescent Inflammatory Bowel Disease (IBD) patients on transfer to adult health care services. We reviewed the records of IBD patients diagnosed in pediatric care following their transfer/attendance to the adult IBD service. The data on patients who attended the transition service were compared with those who did not pass through the transition service. Seventy-two patients were included in the study 41M and 31F. Forty-four patients went through the transition system (Group A), and 28 had no formalized transition arrangement before transfer (Group B). A significantly higher number of Group B patients needed surgery within 2 years of transfer when compared with patients in Group A (46% vs. 25%, p = .01). Sixty-one percent of patients in Group B needed at least one admission within 2 years of transfer when compared with 29% of Group A patients (p = .002). Nonattendance at clinics was higher in Group B patients with 78% having at least one nonattendance, whereas 29% of Group A failed to attend at least one appointment (p = .001). In addition, drug compliance rates were higher in the transition group when compared with Group B (89% and 46%, respectively; p = .002). A higher proportion of transitioned patients achieved their estimated maximum growth potential when completing adolescence. There was a trend toward higher dependence on opiates and smoking in Group B patients. In adolescent IBD patients, transition care is associated with better disease specific and developmental outcomes. Prospective studies of different models of transition care in IBD are needed. Copyright © 2015 Society for Adolescent Health and Medicine. Published by Elsevier Inc. All rights reserved.

High School Transfer Students and the Transition to College: Timing and the Structure of the School Year

ERIC Educational Resources Information Center

Sutton, April; Muller, Chandra; Langenkamp, Amy G.

2013-01-01

The timing of a high school transfer may shape students' transitions to college through its (mis)alignment with the structure of the school year. A transfer that occurs during the summer interrupts the four-year high school career, whereas a transfer that occurs midyear disrupts both the four-year high school career and the structure of the school…

Flow boiling heat transfer of R134a and R404A in a microfin tube at low mass fluxes and low heat fluxes

NASA Astrophysics Data System (ADS)

Spindler, Klaus; Müller-Steinhagen, Hans

2009-05-01

An experimental investigation of flow boiling heat transfer in a commercially available microfin tube with 9.52 mm outer diameter has been carried out. The microfin tube is made of copper with a total fin number of 55 and a helix angle of 15°. The fin height is 0.24 mm and the inner tube diameter at fin root is 8.95 mm. The test tube is 1 m long and is electrically heated. The experiments have been performed at saturation temperatures between 0 and -20°C. The mass flux was varied between 25 and 150 kg/m2s, the heat flux from 15,000 W/m2 down to 1,000 W/m2. All measurements have been performed at constant inlet vapour quality ranging from 0.1 to 0.7. The measured heat transfer coefficients range from 1,300 to 15,700 W/m2K for R134a and from 912 to 11,451 W/m2K for R404A. The mean heat transfer coefficient of R134a is in average 1.5 times higher than for R404A. The mean heat transfer coefficient has been compared with the correlations by Koyama et al. and by Kandlikar. The deviations are within ±30% and ±15%, respectively. The influence of the mass flux on the heat transfer is most significant between 25 and 62.5 kg/m2s, where the flow pattern changes from stratified wavy flow to almost annular flow. This flow pattern transition is shifted to lower mass fluxes for the microfin tube compared to the smooth tube.

Implementation of a Transition Model in a NASA Code and Validation Using Heat Transfer Data on a Turbine Blade

NASA Technical Reports Server (NTRS)

Ameri, Ali A.

2012-01-01

The purpose of this report is to summarize and document the work done to enable a NASA CFD code to model laminar-turbulent transition process on an isolated turbine blade. The ultimate purpose of the present work is to down-select a transition model that would allow the flow simulation of a variable speed power turbine to be accurately performed. The flow modeling in its final form will account for the blade row interactions and their effects on transition which would lead to accurate accounting for losses. The present work only concerns itself with steady flows of variable inlet turbulence. The low Reynolds number k- model of Wilcox and a modified version of the same model will be used for modeling of transition on experimentally measured blade pressure and heat transfer. It will be shown that the k- model and its modified variant fail to simulate the transition with any degree of accuracy. A case is thus made for the adoption of more accurate transition models. Three-equation models based on the work of Mayle on Laminar Kinetic Energy were explored. The three-equation model of Walters and Leylek was thought to be in a relatively mature state of development and was implemented in the Glenn-HT code. Two-dimensional heat transfer predictions of flat plate flow and two-dimensional and three-dimensional heat transfer predictions on a turbine blade were performed and reported herein. Surface heat transfer rate serves as sensitive indicator of transition. With the newly implemented model, it was shown that the simulation of transition process is much improved over the baseline k- model for the single Reynolds number and pressure ratio attempted; while agreement with heat transfer data became more satisfactory. Armed with the new transition model, total-pressure losses of computed three-dimensional flow of E3 tip section cascade were compared to the experimental data for a range of incidence angles. The results obtained, form a partial loss bucket for the chosen blade

Interferometric study on the mass transfer in cryogenic distillation under magnetic field

NASA Astrophysics Data System (ADS)

Bao, S. R.; Zhang, R. P.; Y Rong, Y.; Zhi, X. Q.; Qiu, L. M.

2017-12-01

Cryogenic distillation has long been used for the mass production of industrial gases because of its features of high efficiency, high purity, and capability to produce noble gases. It is of great theoretical and practical significance to explore methods to improve the mass transfer efficiency in cryogenic distillation. The negative correlation between the susceptibility of paramagnetic oxygen and temperature provides a new possibility of comprehensive utilization of boiling point and susceptibility differences in cryogenic distillation. Starting from this concept, we proposed a novel distillation intensifying method by using gradient magnetic field, in which the magnetic forces enhance the transport of the oxygen molecules to the liquid phase in the distillation. In this study, a cryogenic testbed was designed and fabricated to study the diffusion between oxygen and nitrogen under magnetic field. A Mach-Zehnder interferometer was used to visualize the concentration distribution during the diffusion process. The mass transfer characteristics with and without magnetic field, in the chamber filled with the magnetized medium, were systematically studied. The concentration redistribution of oxygen was observed, and the stable stratified diffusion between liquid oxygen and nitrogen was prolonged by the non-uniform magnetic field. The experimental results show that the magnetic field can efficiently influence the mass transfer in cryogenic distillation, which can provide a new mechanism for the optimization of air separation process.

The ultrasonic-enhanced factor of mass-transfer coefficient in the supercritical carbon dioxide extraction

NASA Astrophysics Data System (ADS)

Luo, Benyi; Lu, Yigang

2008-10-01

Based on several hypotheses about the process of supercritical carbon dioxide extraction, the onflow around the solute granule is figured out by the Navier-Stocks equation. In combination with the Higbie’s solute infiltration model, the link between the mass-transfer coefficient and the velocity of flow is found. The mass-transfer coefficient with the ultrasonical effect is compared with that without the ultrasonical effect, and then a new parameter named the ultrasonic-enhanced factor of mass-transfer coefficient is brought forward, which describes the mathematical model of the supercritical carbon dioxide extraction process enhanced by ultrasonic. The model gives out the relationships among the ultrasonical power, the ultrasonical frequency, the radius of solute granule and the ultrasonic-enhanced factor of mass-transfer coefficient. The results calculated by this model fit well with the experimental data, including the extraction of Coix Lacryma-jobi Seed Oil (CLSO) and Coix Lacryma-jobi Seed Ester (CLSE) from coix seeds and the extraction of Eicosapentaenoic Acid (EPA) and Docosahexaenoic Acid (DHA) from the alga by means of the ultrasonic-enhanced supercritical carbon dioxide extraction (USFE) and the supercritical carbon dioxide extraction (SFE) respectively. This proves the rationality of the ultrasonic-enhanced factor model. The model provides a theoretical basis for the application of ultrasonic-enhanced supercritical fluid extraction technique.

An internet-based communication network for information transfer during patient transitions from skilled nursing facility to the emergency department.

PubMed

Hustey, Fredric M; Palmer, Robert M

2010-06-01

To determine whether the implementation of an Internet-based communication system improves the amount of essential information conveyed between a skilled nursing facility (SNF) and the emergency department (ED) during patient care transitions. Interventional; before and after. ED of an urban teaching hospital with approximately 55,000 visits per year and a 55-bed subacute free-standing rehabilitation facility (the SNF). All patients transferred from the SNF to the ED over 16 months. An Internet-based communication network with SNF-ED transfer form for communication during patient care transitions. Nine elements of patient information assessed before and after intervention through chart review. changes in efficiency of information transfer and staff satisfaction. Two hundred thirty-four of 237 preintervention and all 276 postintervention care transitions were reviewed. The Internet communication network was used in 78 (26%) of all care transitions, peaking at 40% by the end of the study. There was more critical patient information (1.85 vs 4.29 of 9 elements; P<.001) contained within fewer pages of transfer documents (24.47 vs 5.15; P<.001) after the intervention. Staff satisfaction with communication was higher among ED physicians after the intervention. The use of an Internet-based system increased the amount of information communicated during SNF-ED care transitions and significantly reduced the number of pages in which this information was contained.

Reduction of benzene and naphthalene mass transfer from crude oils by aging-induced interfacial films.

PubMed

Ghoshal, Subhasis; Pasion, Catherine; Alshafie, Mohammed

2004-04-01

Semi-rigid films or skins form at the interface of crude oil and water as a result of the accumulation of asphaltene and resin fractions when the water-immiscible crude oil is contacted with water for a period of time or "aged". The time varying patterns of area-independent mass transfer coefficients of two compounds, benzene and naphthalene, for dissolution from crude oil and gasoline were determined. Aqueous concentrations of the compounds were measured in the eluent from flow-through reactors, where a nondispersed oil phase and constant oil-water interfacial area were maintained. For Brent Blend crude oil and for gasoline amended with asphaltenes and resins, a rapid decrease in both benzene and naphthalene mass transfer coefficients over the first few days of aging was observed. The mass transfer coefficients of the two target solutes were reduced by up to 80% over 35 d although the equilibrium partition coefficients were unchanged. Aging of gasoline, which has negligible amounts of asphaltene and resin, did not result in a change in the solute mass transfer coefficients. The study demonstrates that formation of crude oil-water interfacial films comprised of asphaltenes and resins contribute to time-dependent decreases in rates of release of environmentally relevant solutes from crude oils and may contribute to the persistence of such solutes at crude oil-contaminated sites. It is estimated that the interfacial film has an extremely low film mass transfer coefficient in the range of 10(-6) cm/min.

On the role of heat and mass transfer into laser processability during selective laser melting AlSi12 alloy based on a randomly packed powder-bed

NASA Astrophysics Data System (ADS)

Wang, Lianfeng; Yan, Biao; Guo, Lijie; Gu, Dongdong

2018-04-01

A newly transient mesoscopic model with a randomly packed powder-bed has been proposed to investigate the heat and mass transfer and laser process quality between neighboring tracks during selective laser melting (SLM) AlSi12 alloy by finite volume method (FVM), considering the solid/liquid phase transition, variable temperature-dependent properties and interfacial force. The results apparently revealed that both the operating temperature and resultant cooling rate were obviously elevated by increasing the laser power. Accordingly, the resultant viscosity of liquid significantly reduced under a large laser power and was characterized with a large velocity, which was prone to result in a more intensive convection within pool. In this case, the sufficient heat and mass transfer occurred at the interface between the previously fabricated tracks and currently building track, revealing a strongly sufficient spreading between the neighboring tracks and a resultant high-quality surface without obvious porosity. By contrast, the surface quality of SLM-processed components with a relatively low laser power notably weakened due to the limited and insufficient heat and mass transfer at the interface of neighboring tracks. Furthermore, the experimental surface morphologies of the top surface were correspondingly acquired and were in full accordance to the calculated results via simulation.

Transition of young people with chronic conditions: a cross-sectional study of patient perceptions before and after transfer from pediatric to adult health care.

PubMed

Rutishauser, Christoph; Sawyer, Susan M; Ambresin, Anne-Emmanuelle

2014-08-01

The aim of this study was to compare perceived barriers to and the most preferred age for successful transition to adult health care between young people with chronic disorders who had not yet transferred from pediatric to adult health care (pre-transfer) and those who had already transferred (post-transfer). In a cross-sectional study, we compared 283 pre-transfer with 89 post-transfer young people, using a 28-item questionnaire that focused on perceived barriers to transition and beliefs about the most preferred age to transfer. Feeling at ease with the pediatrician was the most important barrier to successful transition in both groups, but was rated significantly higher in the pre-transfer compared to the post-transfer group (OR = 2.03, 95 %CI 1.12-3.71). Anxiety and lack of information were the next most important barriers, rated equally highly by the two groups (OR = 0.67, 95 %CI 0.35-1.28 and OR = 0.71, 95 %CI 0.36-1.38, respectively). More than 80 % of the respondents in both groups reported that 16-19 years was the most preferred age to transfer; more than half of all the respondents reported 18-19 years and older as the most preferred age. Better transition planning through the provision of regular and more detailed information about adult health-care providers and the transition process could reduce anxiety and contribute to a more positive attitude to overcome perceived barriers to transition from young people's perspective. Young people's preferences about transferring to adult health care provide a challenge to those children's hospitals that transfer to adult health care at a younger age.

Upward and downward heat and mass transfer with miniature periodically operating loop thermosyphons

NASA Astrophysics Data System (ADS)

Fantozzi, Fabio; Filippeschi, Sauro; Latrofa, Enrico Maria

2004-03-01

Upward and downward two-phase heat and mass transfer has been considered in the present paper. The heat and mass transfer with the condenser located below the evaporator has been obtained by inserting an accumulator tank in the liquid line of a loop thermosyphon and enforcing a pressure pulsation. In previous papers these heat transfer devices have been called pulsated two phase thermosyphons (PTPT). A mini PTPT has been experimentally investigated. It has shown a stable periodic heat transfer regime weakly influenced by the position of the condenser with respect to the evaporator. In contrast a classical loop mini thermosyphon (diameter of connecting pipes 4 mm) did not achieve a stable functioning for the investigated level differences between evaporator and condenser lower than 0.37 m. The present study shows that the functioning of a PTPT device does not directly depend on the level difference or the presence of noncondensable gas. In order to obtain a natural circulation in mini or micro loops, a periodically operating heat transfer regime should therefore be considered.

Heat and Mass Transfer of Ammonia Gas Absorption into Falling Liquid Film on a Horizontal Tube

NASA Astrophysics Data System (ADS)

Inoue, Norihiro; Yabuuchi, Hironori; Goto, Masao; Koyama, Shigeru

Heat and mass transfer coefficients during ammonia gas absorption into a falling liquid film formed by distilled water on a horizontal tube were obtained experimentally. The test absorber consists of 200 mm i.d., 600 mm long stainless steel shell, a 1 7.3 mm o.d., 14.9 mm i.d. stainless steel test tube with 600 mm working length mounted along the axis of shell, and a 12.7 mm o.d. pipe manifold of supplying the absorbent. In this paper, it was clear that heat and mass transfer coefficient could be enhanced by increasing the flow rate of absorbent and temperature difference between inlet absorbent and ammonia gas, also heat driven by the temperature difference have an effect on heat transfer of the fa1ling liquid film and mass transfer of vapor side. And the new correlation of heat transfer in dimensionless form was proposed by the temperature difference which was considered heat driven of vapor and liquid film side using a interface temperature of vapor and liquid phase. The new correlations of mass transfer on a interface of vapor and liquid phase in dimensionless form were proposed by using effect factors could be suppose from absorption phenomena.

Acoustic Streaming and Heat and Mass Transfer Enhancement

NASA Technical Reports Server (NTRS)

Trinh, E. H.; Gopinath, A.

1996-01-01

A second order effect associated with high intensity sound field, acoustic streaming has been historically investigated to gain a fundamental understanding of its controlling mechanisms and to apply it to practical aspects of heat and mass transfer enhancement. The objectives of this new research project are to utilize a unique experimental technique implementing ultrasonic standing waves in closed cavities to study the details of the generation of the steady-state convective streaming flows and of their interaction with the boundary of ultrasonically levitated near-spherical solid objects. The goals are to further extend the existing theoretical studies of streaming flows and sample interactions to higher streaming Reynolds number values, for larger sample size relative to the wavelength, and for a Prandtl and Nusselt numbers parameter range characteristic of both gaseous and liquid host media. Experimental studies will be conducted in support to the theoretical developments, and the crucial impact of microgravity will be to allow the neglect of natural thermal buoyancy. The direct application to heat and mass transfer in the absence of gravity will be emphasized in order to investigate a space-based experiment, but both existing and novel ground-based scientific and technological relevance will also be pursued.

Direct geoelectrical evidence of mass transfer at the laboratory scale

NASA Astrophysics Data System (ADS)

Swanson, Ryan D.; Singha, Kamini; Day-Lewis, Frederick D.; Binley, Andrew; Keating, Kristina; Haggerty, Roy

2012-10-01

Previous field-scale experimental data and numerical modeling suggest that the dual-domain mass transfer (DDMT) of electrolytic tracers has an observable geoelectrical signature. Here we present controlled laboratory experiments confirming the electrical signature of DDMT and demonstrate the use of time-lapse electrical measurements in conjunction with concentration measurements to estimate the parameters controlling DDMT, i.e., the mobile and immobile porosity and rate at which solute exchanges between mobile and immobile domains. We conducted column tracer tests on unconsolidated quartz sand and a material with a high secondary porosity: the zeolite clinoptilolite. During NaCl tracer tests we collected nearly colocated bulk direct-current electrical conductivity (σb) and fluid conductivity (σf) measurements. Our results for the zeolite show (1) extensive tailing and (2) a hysteretic relation between σf and σb, thus providing evidence of mass transfer not observed within the quartz sand. To identify best-fit parameters and evaluate parameter sensitivity, we performed over 2700 simulations of σf, varying the immobile and mobile domain and mass transfer rate. We emphasized the fit to late-time tailing by minimizing the Box-Cox power transformed root-mean square error between the observed and simulated σf. Low-field proton nuclear magnetic resonance (NMR) measurements provide an independent quantification of the volumes of the mobile and immobile domains. The best-fit parameters based on σf match the NMR measurements of the immobile and mobile domain porosities and provide the first direct electrical evidence for DDMT. Our results underscore the potential of using electrical measurements for DDMT parameter inference.

Direct geoelectrical evidence of mass transfer at the laboratory scale

USGS Publications Warehouse

Swanson, Ryan D.; Singha, Kamini; Day-Lewis, Frederick D.; Binley, Andrew; Keating, Kristina; Haggerty, Roy

2012-01-01

Previous field-scale experimental data and numerical modeling suggest that the dual-domain mass transfer (DDMT) of electrolytic tracers has an observable geoelectrical signature. Here we present controlled laboratory experiments confirming the electrical signature of DDMT and demonstrate the use of time-lapse electrical measurements in conjunction with concentration measurements to estimate the parameters controlling DDMT, i.e., the mobile and immobile porosity and rate at which solute exchanges between mobile and immobile domains. We conducted column tracer tests on unconsolidated quartz sand and a material with a high secondary porosity: the zeolite clinoptilolite. During NaCl tracer tests we collected nearly colocated bulk direct-current electrical conductivity (σb) and fluid conductivity (σf) measurements. Our results for the zeolite show (1) extensive tailing and (2) a hysteretic relation between σf and σb, thus providing evidence of mass transfer not observed within the quartz sand. To identify best-fit parameters and evaluate parameter sensitivity, we performed over 2700 simulations of σf, varying the immobile and mobile domain and mass transfer rate. We emphasized the fit to late-time tailing by minimizing the Box-Cox power transformed root-mean square error between the observed and simulated σf. Low-field proton nuclear magnetic resonance (NMR) measurements provide an independent quantification of the volumes of the mobile and immobile domains. The best-fit parameters based on σf match the NMR measurements of the immobile and mobile domain porosities and provide the first direct electrical evidence for DDMT. Our results underscore the potential of using electrical measurements for DDMT parameter inference.

Calibration of mass transfer-based models to predict reference crop evapotranspiration

NASA Astrophysics Data System (ADS)

Valipour, Mohammad

2017-05-01

The present study aims to compare mass transfer-based models to determine the best model under different weather conditions. The results showed that the Penman model estimates reference crop evapotranspiration better than other models in most provinces of Iran (15 provinces). However, the values of R 2 were less than 0.90 for 24 provinces of Iran. Therefore, the models were calibrated, and precision of estimation was increased (the values of R 2 were less than 0.90 for only ten provinces in the modified models). The mass transfer-based models estimated reference crop evapotranspiration in the northern (near the Caspian Sea) and southern (near the Persian Gulf) Iran (annual relative humidity more than 65 %) better than other provinces. The best values of R 2 were 0.96 and 0.98 for the Trabert and Rohwer models in Ardabil (AR) and Mazandaran (MZ) provinces before and after calibration, respectively. Finally, a list of the best performances of each model was presented to use other regions and next studies according to values of mean, maximum, and minimum temperature, relative humidity, and wind speed. The best weather conditions to use mass transfer-based equations are 8-18 °C (with the exception of Ivanov), <25.5 °C, <15 °C, >55 % for mean, maximum, and minimum temperature, and relative humidity, respectively.

Energy transfer enhancement by oxygen perturbation of spin-forbidden electronic transitions in aromatic systems

NASA Astrophysics Data System (ADS)

Monguzzi, A.; Tubino, R.; Salamone, M. M.; Meinardi, F.

2010-09-01

Triplet-triplet energy transfer in multicomponent organic systems is usually entirely ascribed to a Dexter-type mechanism involving only short-range donor/acceptor interactions. We demonstrate that the presence of molecular oxygen introduces a perturbation to the electronic structure of one of the involved moieties which can induce a large increase in the spin-forbidden transition oscillator strength so that the otherwise negligible Förster contribution dominates the overall energy transfer rate.

Tensor form factor for the D → π(K) transitions with Twisted Mass fermions.

NASA Astrophysics Data System (ADS)

Lubicz, Vittorio; Riggio, Lorenzo; Salerno, Giorgio; Simula, Silvano; Tarantino, Cecilia

2018-03-01

We present a preliminary lattice calculation of the D → π and D → K tensor form factors fT (q2) as a function of the squared 4-momentum transfer q2. ETMC recently computed the vector and scalar form factors f+(q2) and f0(q2) describing D → π(K)lv semileptonic decays analyzing the vector current and the scalar density. The study of the weak tensor current, which is directly related to the tensor form factor, completes the set of hadronic matrix element regulating the transition between these two pseudoscalar mesons within and beyond the Standard Model where a non-zero tensor coupling is possible. Our analysis is based on the gauge configurations produced by the European Twisted Mass Collaboration with Nf = 2 + 1 + 1 flavors of dynamical quarks. We simulated at three different values of the lattice spacing and with pion masses as small as 210 MeV and with the valence heavy quark in the mass range from ≃ 0.7 mc to ≃ 1.2mc. The matrix element of the tensor current are determined for a plethora of kinematical conditions in which parent and child mesons are either moving or at rest. As for the vector and scalar form factors, Lorentz symmetry breaking due to hypercubic effects is clearly observed in the data. We will present preliminary results on the removal of such hypercubic lattice effects.

Care Transitions After Acute Myocardial Infarction for Transferred-In Versus Direct-Arrival Patients.

PubMed

Vora, Amit N; Peterson, Eric D; Hellkamp, Anne S; Sutton, Nadia R; Panacek, Edward; Thomas, Laine; de Lemos, James A; Wang, Tracy Y

2016-03-01

Many patients in the United States require transfer from one hospital to another for acute myocardial infarction (MI) care. How well these transferred-in patients are transitioned back to their local community is unknown. We used linked Medicare claims data to examine postdischarge outcomes of 39 136 patients with acute MI aged ≥65 years discharged alive from 451 US hospitals in Acute Coronary Treatment and Intervention Outcomes Network Registry-Get With the Guidelines. Multivariable Cox modeling was used to compare the likelihood of outpatient clinic follow-up and risks of all-cause mortality and all-cause or cardiovascular readmission at 30 days post MI between transferred-in and direct-arrival patients. From 2007 to 2010, 14 060 of 39 136 patients (36%) required interhospital transfer for acute MI care, traveling a median of 43 miles (interquartile range, 27-68 miles; 77.6 km [interquartile range, 48.2-122.6 km]). Compared with those arriving directly, transferred-in patients with MI were slightly younger (median age, 73 versus 74; P<0.01) but less likely to have previous MI, heart failure, and previous revascularization than direct-arrival patients. Relative to direct-arrival patients, those transferred-in had a lower likelihood of outpatient follow-up within 30 days post discharge (risk-adjusted incidence, 69.9% versus 78.2%; hazard ratio [HR], 0.90; 95% confidence interval, 0.87-0.92) and higher adjusted 30-day all-cause and cardiovascular readmission risks (14.5% versus 14.0%; HRall-cause, 1.08; 95% confidence interval, 1.01-1.15 and 9.5% versus 9.1%; HRcardiovascular, 1.13; 95% confidence interval, 1.04-1.22). In contrast, risk-adjusted 30-day mortality was similar between transferred-in and direct arrivals (1.6% versus 1.6%; HR, 1.05; 95% confidence interval, 0.86-1.27). Transferred-in patients with acute MI are less likely to have outpatient clinic follow-up within 30 days and more likely to be readmitted within the first 30 days post discharge compared

Mass transfer study on the electrochemical removal of copper ions from synthetic effluents using reticulated vitreous carbon.

PubMed

Britto-Costa, Pedro H; Ruotolo, Luís Augusto M

2013-01-01

Porous electrodes have been successfully used for metal electrodeposition from diluted aqueous solution due to their high porosity and specific surface area, which lead to high mass transfer rates. This work studies the mass transfer of copper electrodeposition on reticulated vitreous carbon in a flow reactor without membrane. The flow configuration, otherwise the filter-press electrochemical reactors, was designed in order to minimize the pressure drop. The mass transfer coefficient was determined by voltammetric and galvanostatic electrodeposition. In the voltammetric experiments a Luggin capillary was used to measure the current-potential curves and to determine the limiting current (and, consequently, the mass transfer coefficient). In the galvanostatic experiments the concentration-time curves were obtained and considering a limiting current kinetics model, the mass transfer coefficient (k(m)) was determined for different flow velocities. The results showed that both methods give similar values of k(m), thus the voltammetric method can be recommended because it is faster and simpler. Finally, the reactor performance was compared with others from literature, and it was observed that the proposed reactor design has high Sherwood numbers similar to other reactor configurations using membranes and reticulated vitreous carbon electrodes.

Heat and mass transfer in flames

NASA Technical Reports Server (NTRS)

Faeth, G. M.

1986-01-01

Heat- and mass-transfer processes in turbulent diffusion flames are discussed, considering turbulent mixing and the structure of single-phase flames, drop processes in spray flames, and nonluminous and luminous flame radiation. Interactions between turbulence and other phenomena are emphasized, concentrating on past work of the author and his associates. The conserved-scalar formalism, along with the laminar-flamelet approximation, is shown to provide reasonable estimates of the structure of gas flames, with modest levels of empiricism. Extending this approach to spray flames has highlighted the importance of drop/turbulence interactions; e.g., turbulent dispersion of drops, modification of turbulence by drops, etc. Stochastic methods being developed to treat these phenomena are yielding encouraging results.

Advection modes by optimal mass transfer

NASA Astrophysics Data System (ADS)

Iollo, Angelo; Lombardi, Damiano

2014-02-01

Classical model reduction techniques approximate the solution of a physical model by a limited number of global modes. These modes are usually determined by variants of principal component analysis. Global modes can lead to reduced models that perform well in terms of stability and accuracy. However, when the physics of the model is mainly characterized by advection, the nonlocal representation of the solution by global modes essentially reduces to a Fourier expansion. In this paper we describe a method to determine a low-order representation of advection. This method is based on the solution of Monge-Kantorovich mass transfer problems. Examples of application to point vortex scattering, Korteweg-de Vries equation, and hurricane Dean advection are discussed.

From bosonic topological transition to symmetric fermion mass generation

NASA Astrophysics Data System (ADS)

You, Yi-Zhuang; He, Yin-Chen; Vishwanath, Ashvin; Xu, Cenke

2018-03-01

A bosonic topological transition (BTT) is a quantum critical point between the bosonic symmetry-protected topological phase and the trivial phase. In this work, we investigate such a transition in a (2+1)-dimensional lattice model with the maximal microscopic symmetry: an internal SO (4 ) symmetry. We derive a description for this transition in terms of compact quantum electrodynamics (QED) with four fermion flavors (Nf=4 ). Within a systematic renormalization group analysis, we identify the critical point with the desired O (4 ) emergent symmetry and all expected deformations. By lowering the microscopic symmetry, we recover the previous Nf=2 noncompact QED description of the BTT. Finally, by merging two BTTs we recover a previously discussed theory of symmetric mass generation, as an SU (2 ) quantum chromodynamics-Higgs theory with Nf=4 flavors of SU (2 ) fundamental fermions and one SU (2 ) fundamental Higgs boson. This provides a consistency check on both theories.

Three-dimensional Hydrodynamical Simulations of Mass Transfer in Binary Systems by a Free Wind

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, Zheng-Wei; Stancliffe, Richard J.; Abate, Carlo

A large fraction of stars in binary systems are expected to undergo mass and angular momentum exchange at some point in their evolution, which can drastically alter the chemical and dynamical properties and fates of the systems. Interaction by stellar wind is an important process in wide binaries. However, the details of wind mass transfer are still not well understood. We perform three-dimensional hydrodynamical simulations of wind mass transfer in binary systems to explore mass-accretion efficiencies and geometries of mass outflows, for a range of mass ratios from 0.05 to 1.0. In particular, we focus on the case of amore » free wind, in which some physical mechanism accelerates the expelled wind material balancing the gravity of the mass-losing star with the wind velocity comparable to the orbital velocity of the system. We find that the mass-accretion efficiency and accreted specific angular momentum increase with the mass ratio of the system. For an adiabatic wind, we obtain that the accretion efficiency onto the secondary star varies from about 0.1% to 8% for mass ratios between 0.05 and 1.0.« less

Modeling CO2 mass transfer in amine mixtures: PZ-AMP and PZ-MDEA.

PubMed

Puxty, Graeme; Rowland, Robert

2011-03-15

The most common method of carbon dioxide (CO(2)) capture is the absorption of CO(2) into a falling thin film of an aqueous amine solution. Modeling of mass transfer during CO(2) absorption is an important way to gain insight and understanding about the underlying processes that are occurring. In this work a new software tool has been used to model CO(2) absorption into aqueous piperazine (PZ) and binary mixtures of PZ with 2-amino-2-methyl-1-propanol (AMP) or methyldiethanolamine (MDEA). The tool solves partial differential and simultaneous equations describing diffusion and chemical reaction automatically derived from reactions written using chemical notation. It has been demonstrated that by using reactions that are chemically plausible the mass transfer in binary mixtures can be fully described by combining the chemical reactions and their associated parameters determined for single amines. The observed enhanced mass transfer in binary mixtures can be explained through chemical interactions occurring in the mixture without need to resort to using additional reactions or unusual transport phenomena such as the "shuttle mechanism".

Measurement and modeling of CO2 mass transfer in brine at reservoir conditions

NASA Astrophysics Data System (ADS)

Shi, Z.; Wen, B.; Hesse, M. A.; Tsotsis, T. T.; Jessen, K.

2018-03-01

In this work, we combine measurements and modeling to investigate the application of pressure-decay experiments towards delineation and interpretation of CO2 solubility, uptake and mass transfer in water/brine systems at elevated pressures of relevance to CO2 storage operations in saline aquifers. Accurate measurements and modeling of mass transfer in this context are crucial to an improved understanding of the longer-term fate of CO2 that is injected into the subsurface for storage purposes. Pressure-decay experiments are presented for CO2/water and CO2/brine systems with and without the presence of unconsolidated porous media. We demonstrate, via high-resolution numerical calculations in 2-D, that natural convection will complicate the interpretation of the experimental observations if the particle size is not sufficiently small. In such settings, we demonstrate that simple 1-D interpretations can result in an overestimation of the uptake (diffusivity) by two orders of magnitude. Furthermore, we demonstrate that high-resolution numerical calculations agree well with the experimental observations for settings where natural convection contributes substantially to the overall mass transfer process.

A rocky planet transiting a nearby low-mass star.

PubMed

Berta-Thompson, Zachory K; Irwin, Jonathan; Charbonneau, David; Newton, Elisabeth R; Dittmann, Jason A; Astudillo-Defru, Nicola; Bonfils, Xavier; Gillon, Michaël; Jehin, Emmanuël; Stark, Antony A; Stalder, Brian; Bouchy, Francois; Delfosse, Xavier; Forveille, Thierry; Lovis, Christophe; Mayor, Michel; Neves, Vasco; Pepe, Francesco; Santos, Nuno C; Udry, Stéphane; Wünsche, Anaël

2015-11-12

M-dwarf stars--hydrogen-burning stars that are smaller than 60 per cent of the size of the Sun--are the most common class of star in our Galaxy and outnumber Sun-like stars by a ratio of 12:1. Recent results have shown that M dwarfs host Earth-sized planets in great numbers: the average number of M-dwarf planets that are between 0.5 to 1.5 times the size of Earth is at least 1.4 per star. The nearest such planets known to transit their star are 39 parsecs away, too distant for detailed follow-up observations to measure the planetary masses or to study their atmospheres. Here we report observations of GJ 1132b, a planet with a size of 1.2 Earth radii that is transiting a small star 12 parsecs away. Our Doppler mass measurement of GJ 1132b yields a density consistent with an Earth-like bulk composition, similar to the compositions of the six known exoplanets with masses less than six times that of the Earth and precisely measured densities. Receiving 19 times more stellar radiation than the Earth, the planet is too hot to be habitable but is cool enough to support a substantial atmosphere, one that has probably been considerably depleted of hydrogen. Because the host star is nearby and only 21 per cent the radius of the Sun, existing and upcoming telescopes will be able to observe the composition and dynamics of the planetary atmosphere.

Mass transfer characteristics during convective, microwave and combined microwave-convective drying of lemon slices.

PubMed

Sadeghi, Morteza; Mirzabeigi Kesbi, Omid; Mireei, Seyed Ahmad

2013-02-01

The investigation of drying kinetics and mass transfer phenomena is important for selecting optimum operating conditions, and obtaining a high quality dried product. Two analytical models, conventional solution of the diffusion equation and the Dincer and Dost model, were used to investigate mass transfer characteristics during combined microwave-convective drying of lemon slices. Air temperatures of 50, 55 and 60 °C, and specific microwave powers of 0.97 and 2.04 W g(-1) were the process variables. Kinetics curves for drying indicated one constant rate period followed by one falling rate period in convective and microwave drying methods, and only one falling rate period with the exception of a very short accelerating period at the beginning of microwave-convective treatments. Applying the conventional method, the effective moisture diffusivity varied from 2.4 × 10(-11) to 1.2 × 10(-9) m(2) s(-1). The Biot number, the moisture transfer coefficient, and the moisture diffusivity, respectively in the ranges of 0.2 to 3.0 (indicating simultaneous internal and external mass transfer control), 3.7 × 10(-8) to 4.3 × 10(-6) m s(-1), and 2.2 × 10(-10) to 4.2 × 10(-9) m(2) s(-1) were also determined using the Dincer and Dost model. The higher degree of prediction accuracy was achieved by using the Dincer and Dost model for all treatments. Therefore, this model could be applied as an effective tool for predicting mass transfer characteristics during the drying of lemon slices. Copyright © 2012 Society of Chemical Industry.

Heat and mass transfer in vertical porous medium due to partial heating

NASA Astrophysics Data System (ADS)

Salman Ahmed N., J.; Khan, T. M. Yunus; Ahamad, N. Ameer; Kamangar, Sarfaraz

2018-05-01

The investigation of heat and mass transfer adjacent to vertical plate subjected to partial heating of plate in multiple segments is carried out. A section of the plate is heated with isothermal temperature Th and the far away condition is maintained at ambient temperature T∞.. The vertical plate is maintained at constant concentration Ch as opposed to lowest concentration at far away condition. Finite element method is used and governing equations are converted into simple form of equations using Galerkin approach. The results are discussed in terms of contour plots. Study is carried out with respect to various physical parameters. The heat and mass transfer rate found to increase with increase in Rayleigh number.

Effect of Reynolds number on flow and mass transfer characteristics of a 90 degree elbow

NASA Astrophysics Data System (ADS)

Fujisawa, Nobuyuki; Ikarashi, Yuya; Yamagata, Takayuki; Taguchi, Syoichi

2016-11-01

The flow and mass transfer characteristics of a 90 degree elbow was studied experimentally by using the mass transfer measurement by plaster dissolution method, the surface flow visualization by oil film method and stereo PIV measurement. The experiments are carried out in a water tunnel of a circular pipe of 56mm in diameter with a working fluid of water. The Reynolds number was varied from 30000 to 200000. The experimental result indicated the change of the mass transfer coefficient distribution in the elbow with increasing the Reynolds number. This phenomenon is further examined by the surface flow visualization and measurement of secondary flow pattern in the elbow, and the results showed the suggested change of the secondary flow pattern in the elbow with increasing the Reynolds numbers.

Heat and mass transfer and hydrodynamics in swirling flows (review)

NASA Astrophysics Data System (ADS)

Leont'ev, A. I.; Kuzma-Kichta, Yu. A.; Popov, I. A.

2017-02-01

Research results of Russian and foreign scientists of heat and mass transfer in whirling flows, swirling effect, superficial vortex generators, thermodynamics and hydrodynamics at micro- and nanoscales, burning at swirl of the flow, and technologies and apparatuses with the use of whirling currents for industry and power generation were presented and discussed at the "Heat and Mass Transfer in Whirling Currents" 5th International Conference. The choice of rational forms of the equipment flow parts when using whirling and swirling flows to increase efficiency of the heat-power equipment and of flow regimes and burning on the basis of deep study of the flow and heat transfer local parameters was set as the main research prospect. In this regard, there is noticeable progress in research methods of whirling and swirling flows. The number of computational treatments of swirling flows' local parameters has been increased. Development and advancement of the up to date computing models and national productivity software are very important for this process. All experimental works are carried out with up to date research methods of the local thermoshydraulic parameters, which enable one to reveal physical mechanisms of processes: PIV and LIV visualization techniques, high-speed and infrared photography, high speed registration of parameters of high-speed processes, etc. There is a problem of improvement of researchers' professional skills in the field of fluid mechanics to set adequately mathematics and physics problems of aerohydrodynamics for whirling and swirling flows and numerical and pilot investigations. It has been pointed out that issues of improvement of the cooling system and thermal protection effectiveness of heat-power and heat-transfer equipment units are still actual. It can be solved successfully using whirling and swirling flows as simple low power consumption exposing on the flow method and heat transfer augmentation.

Effects of heat and mass transfer on unsteady boundary layer flow of a chemical reacting Casson fluid

NASA Astrophysics Data System (ADS)

Khan, Kashif Ali; Butt, Asma Rashid; Raza, Nauman

2018-03-01

In this study, an endeavor is to observe the unsteady two-dimensional boundary layer flow with heat and mass transfer behavior of Casson fluid past a stretching sheet in presence of wall mass transfer by ignoring the effects of viscous dissipation. Chemical reaction of linear order is also invoked here. Similarity transformation have been applied to reduce the governing equations of momentum, energy and mass into non-linear ordinary differential equations; then Homotopy analysis method (HAM) is applied to solve these equations. Numerical work is done carefully with a well-known software MATHEMATICA for the examination of non-dimensional velocity, temperature, and concentration profiles, and then results are presented graphically. The skin friction (viscous drag), local Nusselt number (rate of heat transfer) and Sherwood number (rate of mass transfer) are discussed and presented in tabular form for several factors which are monitoring the flow model.

A research program for improving heat transfer prediction for the laminar to turbulent transition region of turbine vanes/blades

NASA Technical Reports Server (NTRS)

Simon, Frederick F.

1993-01-01

A program sponsored by NASA for the investigation of the heat transfer in the transition region of turbine vanes and blades with the objective of improving the capability for predicting heat transfer is described. The accurate prediction of gas-side heat transfer is important to the determination of turbine longevity, engine performance, and developmental costs. The need for accurate predictions will become greater as the operating temperatures and stage loading levels of advanced turbine engines increase. The present methods for predicting transition shear stress and heat transfer on turbine blades are based on incomplete knowledge and are largely empirical. To meet the objective of the NASA program, a team approach consisting of researchers from government, universities, a research institute, and a small business is presented. The research is divided into the areas of experiments, direct numerical simulations (DNS), and turbulence modeling. A summary of the results to date is given for the above research areas in a high-disturbance environment (bypass transition) with a discussion of the model development necessary for use in numerical codes.

Mass and energy transfer across the Earth's magnetopause caused by vortex-induced reconnection: Mass and energy transfer by K-H vortex

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nakamura, T. K. M.; Eriksson, S.; Hasegawa, H.

When the interplanetary magnetic field (IMF) is strongly northward, a boundary layer that contains a considerable amount of plasma of magnetosheath origin is often observed along and earthward of the low-latitude magnetopause. Such a pre-existing boundary layer, with a higher density than observed in the adjacent magnetosphere, reduces the local Alfvén speed and allows the Kelvin-Helmholtz instability (KHI) to grow more strongly. We employ a three-dimensional fully kinetic simulation to model an event observed by the Magnetospheric Multiscale (MMS) mission in which the spacecraft detected substantial KH waves between a pre-existing boundary layer and the magnetosheath during strong northward IMF.more » Initial results of this simulation [Nakamura et al., 2017] have successfully demonstrated ion-scale signatures of magnetic reconnection induced by the non-linearly developed KH vortex, which are quantitatively consistent with MMS observations. Furthermore, we quantify the simulated mass and energy transfer processes driven by this vortex-induced reconnection (VIR) and show that during this particular MMS event (i) mass enters a new mixing layer formed by the VIR more efficiently from the pre-existing boundary layer side than from the magnetosheath side, (ii) mixed plasmas within the new mixing layer convect tailward along the magnetopause at more than half the magnetosheath flow speed, and (iii) energy dissipation in localized VIR dissipation regions results in a strong parallel electron heating within the mixing layer. Finally, the quantitative agreements between the simulation and MMS observations allow new predictions that elucidate how the mass and energy transfer processes occur near the magnetopause during strong northward IMF.« less

Mass and energy transfer across the Earth's magnetopause caused by vortex-induced reconnection: Mass and energy transfer by K-H vortex

DOE PAGES

Nakamura, T. K. M.; Eriksson, S.; Hasegawa, H.; ...

2017-10-23

When the interplanetary magnetic field (IMF) is strongly northward, a boundary layer that contains a considerable amount of plasma of magnetosheath origin is often observed along and earthward of the low-latitude magnetopause. Such a pre-existing boundary layer, with a higher density than observed in the adjacent magnetosphere, reduces the local Alfvén speed and allows the Kelvin-Helmholtz instability (KHI) to grow more strongly. We employ a three-dimensional fully kinetic simulation to model an event observed by the Magnetospheric Multiscale (MMS) mission in which the spacecraft detected substantial KH waves between a pre-existing boundary layer and the magnetosheath during strong northward IMF.more » Initial results of this simulation [Nakamura et al., 2017] have successfully demonstrated ion-scale signatures of magnetic reconnection induced by the non-linearly developed KH vortex, which are quantitatively consistent with MMS observations. Furthermore, we quantify the simulated mass and energy transfer processes driven by this vortex-induced reconnection (VIR) and show that during this particular MMS event (i) mass enters a new mixing layer formed by the VIR more efficiently from the pre-existing boundary layer side than from the magnetosheath side, (ii) mixed plasmas within the new mixing layer convect tailward along the magnetopause at more than half the magnetosheath flow speed, and (iii) energy dissipation in localized VIR dissipation regions results in a strong parallel electron heating within the mixing layer. Finally, the quantitative agreements between the simulation and MMS observations allow new predictions that elucidate how the mass and energy transfer processes occur near the magnetopause during strong northward IMF.« less

Ice Generation and the Heat and Mass Transfer Phenomena of Introducing Water to a Cold Bath of Brine.

PubMed

Yun, Xiao; Quarini, Giuseppe L

2017-03-13

We demonstrate a method for the study of the heat and mass transfer and of the freezing phenomena in a subcooled brine environment. Our experiment showed that, under the proper conditions, ice can be produced when water is introduced to a bath of cold brine. To make ice form, in addition to having the brine and water mix, the rate of heat transfer must bypass that of mass transfer. When water is introduced in the form of tiny droplets to the brine surface, the mode of heat and mass transfer is by diffusion. The buoyancy stops water from mixing with the brine underneath, but as the ice grows thicker, it slows down the rate of heat transfer, making ice more difficult to grow as a result. When water is introduced inside the brine in the form of a flow, a number of factors are found to influence how much ice can form. Brine temperature and concentration, which are the driving forces of heat and mass transfer, respectively, can affect the water-to-ice conversion ratio; lower bath temperatures and brine concentrations encourage more ice to form. The flow rheology, which can directly affect both the heat and mass transfer coefficients, is also a key factor. In addition, the flow rheology changes the area of contact of the flow with the bulk fluid.

An assessment of the impact of transition on advanced winged entry vehicle thermal protection system mass

NASA Technical Reports Server (NTRS)

Wurster, K. E.

1981-01-01

This study examines the impact of turbulent heating on thermal protection system (TPS) mass for advanced winged entry vehicles. Four basic systems are considered: insulative, metallic hot structures, metallic standoff, and hybrid systems. TPS sizings are performed using entry trajectories tailored specifically to the characteristics of each TPS concept under consideration. Comparisons are made between systems previously sized under the assumption of all laminar heating and those sized using a baseline estimate of transition and turbulent heating. The relative effect of different transition criteria on TPS mass requirements is also examined. Also investigated are entry trajectories tailored to alleviate turbulent heating. Results indicate the significant impact of turbulent heating on TPS mass and demonstrate the importance of both accurate transition criteria and entry trajectory tailoring.

Molecular orbital (SCF-Xα-SW) theory of metal-metal charge transfer processes in minerals - II. Application to Fe2+ --> Ti4+ charge transfer transitions in oxides and silicates

USGS Publications Warehouse

Sherman, David M.

1987-01-01

A molecular orbital description, based on Xα-Scattered wave calculations on a (FeTiO10)14− cluster, is given for Fe2+ → Ti4+ charge transfer transitions in minerals. The calculated energy for the lowest Fe2+ → Ti4+ metal-metal charge transfer transition is 18040 cm−1 in reasonable agreement with energies observed in the optical spectra of Fe-Ti oxides and silicates. As in the case of Fe2+ → Fe3+ charge transfer in mixed-valence iron oxides and silicates, Fe2+ → Ti4+ charge transfer is associated with Fe-Ti bonding across shared polyhedral edges. Such bonding results from the overlap of the Fe(t 2g ) and Ti(t 2g ) 3d orbitals.

Jahn-Teller effects in transition-metal compounds with small charge-transfer energy

NASA Astrophysics Data System (ADS)

Mizokawa, Takashi

2013-04-01

We have studied Jahn-Teller effects in Cs2Au2Br6, ACu3Co4O12(A=Ca or Y), and IrTe2 in which the ligand p-to-transition-metal d charge-transfer energy is small or negative. The Au+/Au3+ charge disproportionation of Cs2Au2Br6 manifests in Au 4f photoemission spectra. In Cs2Au2Br6 with negative Δ and intermediate U, the charge disproportionation can be described using effective d orbitals constructed from the Au 5d and Br 4p orbitals and is stabilized by the Jahn-Teller distortion of the Au3+ site with low-spin d8 configuration. In ACu3Co4O12, Δs for Cu3+ and Co4+ are negative and Us are very large. The Zhang-Rice picture is valid to describe the electronic state, and the valence change from Cu2+/Co4+ to Cu3+/Co3+ can be viewed as the O 2p hole transfer from Co to Cu or d9 + d6L → d9L + d6. In IrTe2, both Δ and U are small and the Ir 5d and Te 5p electrons are itinerant to form the multi-band Fermi surfaces. The ideas of band Jahn-Teller transition and Peierls transition are useful to describe the structural instabilities.

Fine structure in the transition region: reaction force analyses of water-assisted proton transfers.

PubMed

Yepes, Diana; Murray, Jane S; Santos, Juan C; Toro-Labbé, Alejandro; Politzer, Peter; Jaque, Pablo

2013-07-01

We have analyzed the variation of the reaction force F(ξ) and the reaction force constant κ(ξ) along the intrinsic reaction coordinates ξ of the water-assisted proton transfer reactions of HX-N = Y (X,Y = O,S). The profile of the force constant of the vibration associated with the reactive mode, k ξ (ξ), was also determined. We compare our results to the corresponding intramolecular proton transfers in the absence of a water molecule. The presence of water promotes the proton transfers, decreasing the energy barriers by about 12 - 15 kcal mol(-1). This is due in part to much smaller bond angle changes being needed than when water is absent. The κ(ξ) profiles along the intrinsic reaction coordinates for the water-assisted processes show striking and intriguing differences in the transition regions. For the HS-N = S and HO-N = S systems, two κ(ξ) minima are obtained, whereas for HO-N = O only one minimum is found. The k ξ (ξ) show similar behavior in the transition regions. We propose that this fine structure reflects the degree of synchronicity of the two proton migrations in each case.

Mass transit : bus rapid transit shows promise

DOT National Transportation Integrated Search

2001-09-17

The U. S. General Accounting Office (GAO) was asked to (1) examine the federal role in supporting Bus Rapid Transit; (2) compare the capital costs, operating costs, and performance characteristics of Bus Rapid Transit and Light Rail systems; and (3) ...

Toward a universal mass-momentum transfer relationship for predicting nutrient uptake and metabolite exchange in benthic reef communities

NASA Astrophysics Data System (ADS)

Falter, James L.; Lowe, Ryan J.; Zhang, Zhenlin

2016-09-01

Here we synthesize data from previous field and laboratory studies describing how rates of nutrient uptake and metabolite exchange (mass transfer) are related to form drag and bottom stresses (momentum transfer). Reanalysis of this data shows that rates of mass transfer are highly correlated (r2 ≥ 0.9) with the root of the bottom stress (τbot0.4) under both waves and currents and only slightly higher under waves (~10%). The amount of mass transfer that can occur per unit bottom stress (or form drag) is influenced by morphological features ranging anywhere from millimeters to meters in scale; however, surface-scale roughness (millimeters) appears to have little effect on actual nutrient uptake by living reef communities. Although field measurements of nutrient uptake by natural reef communities agree reasonably well with predictions based on existing mass-momentum transfer relationships, more work is needed to better constrain these relationships for more rugose and morphologically complex communities.

The simultaneous mass and energy evaporation (SM2E) model.

PubMed

Choudhary, Rehan; Klauda, Jeffery B

2016-01-01

In this article, the Simultaneous Mass and Energy Evaporation (SM2E) model is presented. The SM2E model is based on theoretical models for mass and energy transfer. The theoretical models systematically under or over predicted at various flow conditions: laminar, transition, and turbulent. These models were harmonized with experimental measurements to eliminate systematic under or over predictions; a total of 113 measured evaporation rates were used. The SM2E model can be used to estimate evaporation rates for pure liquids as well as liquid mixtures at laminar, transition, and turbulent flow conditions. However, due to limited availability of evaporation data, the model has so far only been tested against data for pure liquids and binary mixtures. The model can take evaporative cooling into account and when the temperature of the evaporating liquid or liquid mixture is known (e.g., isothermal evaporation), the SM2E model reduces to a mass transfer-only model.

Controlling the column spacing in isothermal magnetic advection to enable tunable heat and mass transfer.

DOE PAGES

Solis, Kyle Jameson; Martin, James E.

2012-11-01

Isothermal magnetic advection is a recently discovered method of inducing highly organized, non-contact flow lattices in suspensions of magnetic particles, using only uniform ac magnetic fields of modest strength. The initiation of these vigorous flows requires neither a thermal gradient nor a gravitational field and so can be used to transfer heat and mass in circumstances where natural convection does not occur. These advection lattices are comprised of a square lattice of antiparallel flow columns. If the column spacing is sufficiently large compared to the column length, and the flow rate within the columns is sufficiently large, then one wouldmore » expect efficient transfer of both heat and mass. Otherwise, the flow lattice could act as a countercurrent heat exchanger and only mass will be efficiently transferred. Although this latter case might be useful for feeding a reaction front without extracting heat, it is likely that most interest will be focused on using IMA for heat transfer. In this paper we explore the various experimental parameters of IMA to determine which of these can be used to control the column spacing. These parameters include the field frequency, strength, and phase relation between the two field components, the liquid viscosity and particle volume fraction. We find that the column spacing can easily be tuned over a wide range, to enable the careful control of heat and mass transfer.« less

Discrete multi-physics simulations of diffusive and convective mass transfer in boundary layers containing motile cilia in lungs.

PubMed

Ariane, Mostapha; Kassinos, Stavros; Velaga, Sitaram; Alexiadis, Alessio

2018-04-01

In this paper, the mass transfer coefficient (permeability) of boundary layers containing motile cilia is investigated by means of discrete multi-physics. The idea is to understand the main mechanisms of mass transport occurring in a ciliated-layer; one specific application being inhaled drugs in the respiratory epithelium. The effect of drug diffusivity, cilia beat frequency and cilia flexibility is studied. Our results show the existence of three mass transfer regimes. A low frequency regime, which we called shielding regime, where the presence of the cilia hinders mass transport; an intermediate frequency regime, which we have called diffusive regime, where diffusion is the controlling mechanism; and a high frequency regime, which we have called convective regime, where the degree of bending of the cilia seems to be the most important factor controlling mass transfer in the ciliated-layer. Since the flexibility of the cilia and the frequency of the beat changes with age and health conditions, the knowledge of these three regimes allows prediction of how mass transfer varies with these factors. Copyright © 2018 Elsevier Ltd. All rights reserved.

Temperature-difference-driven mass transfer through the vapor from a cold to a warm liquid.

PubMed

Struchtrup, Henning; Kjelstrup, Signe; Bedeaux, Dick

2012-06-01

Irreversible thermodynamics provides interface conditions that yield temperature and chemical potential jumps at phase boundaries. The interfacial jumps allow unexpected transport phenomena, such as the inverted temperature profile [Pao, Phys. Fluids 14, 306 (1971)] and mass transfer from a cold to a warm liquid driven by a temperature difference across the vapor phase [Mills and Phillips, Chem. Phys. Lett. 372, 615 (2002)]. Careful evaluation of the thermodynamic laws has shown [Bedeaux et al., Physica A 169, 263 (1990)] that the inverted temperature profile is observed for processes with a high heat of vaporization. In this paper, we show that cold to warm mass transfer through the vapor from a cold to a warm liquid is only possible when the heat of evaporation is sufficiently small. A necessary criterium for the size of the mass transfer coefficient is given.

Improving polio vaccination during supplementary campaigns at areas of mass transit in India

PubMed Central

2010-01-01

Background In India, children who are traveling during mass immunization campaigns for polio represent a substantial component of the total target population. These children are not easily accessible to health workers and may thus not receive vaccine. Vaccination activities at mass transit sites (such as major intersections, bus depots and train stations), can increase the proportion of children vaccinated but the effectiveness of these activities, and factors associated with their success, have not been rigorously evaluated. Methods We assessed data from polio vaccination activities in Jyotiba Phule Nagar district, Uttar Pradesh, India, conducted in June 2006. We used trends in the vaccination results from the June activities to plan the timing, locations, and human resource requirements for transit vaccination activities in two out of the seven blocks in the district for the July 2006 supplementary immunization activity (SIA). In July, similar data was collected and for the first time vaccination teams also recorded the proportion of children encountered each day who were vaccinated (a new monitoring system). Results In June, out of the 360,937 total children vaccinated, 34,643 (9.6%) received vaccinations at mass transit sites. In the July SIA, after implementation of a number of changes based on the June monitoring data, 36,475 children were vaccinated at transit sites (a 5.3% increase). Transit site vaccinations in July increased in the two intervention blocks from 18,194 to 21,588 (18.7%) and decreased from 16,449 to 14,887 (9.5%) in the five other blocks. The new monitoring system showed the proportion of unvaccinated children at street intersection transit sites in the July campaign decreased from 24% (1,784/7,405) at the start of the campaign to 3% (143/5,057) by the end of the SIA, consistent with findings from the more labor-intensive post-vaccination coverage surveys routinely performed by the program. Conclusions Analysis of vaccination data from

Mass Transfer Coefficientin Stirred Tank for p-Cresol Extraction Process from Coal Tar

NASA Astrophysics Data System (ADS)

Fardhyanti, D. S.; Tyaningsih, D. S.; Afifah, S. N.

2017-04-01

Indonesia is a country that has a lot of coal resources. The Indonesian coal has a low caloric value. Pyrolysis is one of the process to increase the caloric value. One of the by-product of the pyrolysis process is coal tar. It contains a lot of aliphatic or aromatic compounds such asp-cresol (11% v/v). It is widely used as a disinfectant. Extractionof p-Cresol increases the economic value of waste of coal. The aim of this research isto study about mass tranfer coefficient in the baffled stirred tank for p-Cresolextraction from coal tar. Mass transfer coefficient is useful for design and scale up of industrial equipment. Extraction is conducted inthe baffled stirred tank equipped with a four-bladed axial impeller placed vertically in the vessel. Sample for each time processing (5, 10, 15, 20, 25 and 30minutes) was poured into a separating funnel, settled for an hour and separated into two phases. Then the two phases were weighed. The extract phases and raffinate phases were analyzed by Spectronic UV-Vis. The result showed that mixing speed of p-Cresol extraction increasesthe yield of p-Cresol and the mass transfer coefficient. The highest yield of p-Cresol is 49.32% and the highest mass transfer coefficient is 4.757 x 10-6kg/m2s.

Investigating mass transfer in symbiotic systems with hydrodynamic simulations

NASA Astrophysics Data System (ADS)

de Val-Borro, Miguel; Karovska, Margarita; Sasselov, Dimitar D.

2014-06-01

We investigate gravitationally focused wind accretion in binary systems consisting of an evolved star with a gaseous envelope and a compact accreting companion. We study the mass accretion and formation of an accretion disk around the secondary caused by the strong wind from the primary late-type component using global 2D and 3D hydrodynamic numerical simulations. In particular, the dependence on the mass accretion rate on the mass loss rate, wind temperature and orbital parameters of the system is considered. For a typical slow and massive wind from an evolved star the mass transfer through a focused wind results in rapid infall onto the secondary. A stream flow is created between the stars with accretion rates of a 2-10% percent of the mass loss from the primary. This mechanism could be an important method for explaining periodic modulations in the accretion rates for a broad range of interacting binary systems and fueling of a large population of X-ray binary systems. We test the plausibility of these accretion flows indicated by the simulations by comparing with observations of the symbiotic CH Cyg variable system.

Heat and mass transfer in wooden dowels during a simulated fire: an experimental and analytical study

Treesearch

J. A. Mardini; A. S. Lavine; V. K. Dhir

1996-01-01

Abstract--An experimental and analytical study of heat and mass transfer in wooden dowels during a simulated fire is presented in this paper. The goal of this study is to understand the processes of heat and mass transfer in wood during wildland fires. A mathematical model is developed to describe the processes of heating, drying and pyrolysis of wood until ignition...

Effect of Schmidt number on mass transfer across a sheared gas-liquid interface in a wind-driven turbulence.

PubMed

Takagaki, Naohisa; Kurose, Ryoichi; Kimura, Atsushi; Komori, Satoru

2016-11-14

The mass transfer across a sheared gas-liquid interface strongly depends on the Schmidt number. Here we investigate the relationship between mass transfer coefficient on the liquid side, k L , and Schmidt number, Sc, in the wide range of 0.7 ≤ Sc ≤ 1000. We apply a three-dimensional semi direct numerical simulation (SEMI-DNS), in which the mass transfer is solved based on an approximated deconvolution model (ADM) scheme, to wind-driven turbulence with mass transfer across a sheared wind-driven wavy gas-liquid interface. In order to capture the deforming gas-liquid interface, an arbitrary Lagrangian-Eulerian (ALE) method is employed. Our results show that similar to the case for flat gas-liquid interfaces, k L for the wind-driven wavy gas-liquid interface is generally proportional to Sc -0.5 , and can be roughly estimated by the surface divergence model. This trend is endorsed by the fact that the mass transfer across the gas-liquid interface is controlled mainly by streamwise vortices on the liquid side even for the wind-driven turbulence under the conditions of low wind velocities without wave breaking.

Effect of Schmidt number on mass transfer across a sheared gas-liquid interface in a wind-driven turbulence

PubMed Central

Takagaki, Naohisa; Kurose, Ryoichi; Kimura, Atsushi; Komori, Satoru

2016-01-01

The mass transfer across a sheared gas-liquid interface strongly depends on the Schmidt number. Here we investigate the relationship between mass transfer coefficient on the liquid side, kL, and Schmidt number, Sc, in the wide range of 0.7 ≤ Sc ≤ 1000. We apply a three-dimensional semi direct numerical simulation (SEMI-DNS), in which the mass transfer is solved based on an approximated deconvolution model (ADM) scheme, to wind-driven turbulence with mass transfer across a sheared wind-driven wavy gas-liquid interface. In order to capture the deforming gas-liquid interface, an arbitrary Lagrangian-Eulerian (ALE) method is employed. Our results show that similar to the case for flat gas-liquid interfaces, kL for the wind-driven wavy gas-liquid interface is generally proportional to Sc−0.5, and can be roughly estimated by the surface divergence model. This trend is endorsed by the fact that the mass transfer across the gas-liquid interface is controlled mainly by streamwise vortices on the liquid side even for the wind-driven turbulence under the conditions of low wind velocities without wave breaking. PMID:27841325

Hydride Transfer in DHFR by Transition Path Sampling, Kinetic Isotope Effects, and Heavy Enzyme Studies

PubMed Central

Wang, Zhen; Antoniou, Dimitri; Schwartz, Steven D.; Schramm, Vern L.

2016-01-01

Escherichia coli dihydrofolate reductase (ecDHFR) is used to study fundamental principles of enzyme catalysis. It remains controversial whether fast protein motions are coupled to the hydride transfer catalyzed by ecDHFR. Previous studies with heavy ecDHFR proteins labeled with 13C, 15N, and nonexchangeable 2H reported enzyme mass-dependent hydride transfer kinetics for ecDHFR. Here, we report refined experimental and computational studies to establish that hydride transfer is independent of protein mass. Instead, we found the rate constant for substrate dissociation to be faster for heavy DHFR. Previously reported kinetic differences between light and heavy DHFRs likely arise from kinetic steps other than the chemical step. This study confirms that fast (femtosecond to picosecond) protein motions in ecDHFR are not coupled to hydride transfer and provides an integrative computational and experimental approach to resolve fast dynamics coupled to chemical steps in enzyme catalysis. PMID:26652185

On the importance of the heat and mass transfer resistances in internally-cooled liquid desiccant dehumidifiers and regenerators

DOE PAGES

Woods, Jason; Kozubal, Eric

2018-02-06

Liquid desiccant heat and mass exchangers are a promising technology for efficient humidity control in buildings. Many researchers have investigated these exchangers, often using numerical models to predict their performance. However, there is a lack of information in the literature on the magnitude of the heat and mass transfer resistances, both for the dehumidifier (which absorbs moisture from the air) and the regenerator (which heats the liquid desiccant to re-concentrate it). This article focuses on internally-cooled, 3-fluid exchangers in a parallel plate geometry. Water heats or cools a desiccant across a plate, and the desiccant absorbs or releases water intomore » an airstream through a membrane. A sensitivity analysis was used to estimate the importance of each of the heat and mass transfer resistances (air, membrane, desiccant, plate, water), and how it changes with different design geometries. The results show that, for most designs, the latent and sensible heat transfer of the dehumidifier is dominated by the air mass transfer resistance and air heat transfer resistance, respectively. The air mass transfer resistance is also important for the regenerator, but much less so; the change in the desiccant equilibrium humidity ratio due to a change in either temperature or desiccant mass fraction is much higher at the regenerator's higher temperatures. This increases the importance of (1) getting heat from the water to the desiccant/membrane interface, and (2) diffusing salt ions quickly away from the desiccant/membrane interface. The membrane heat transfer and water heat transfer resistances were found to be the least important. These results can help inform decisions about what simplifying assumptions to make in numerical models, and can also help in designing these exchangers by understanding which resistances are most important.« less

On the importance of the heat and mass transfer resistances in internally-cooled liquid desiccant dehumidifiers and regenerators

DOE Office of Scientific and Technical Information (OSTI.GOV)

Woods, Jason; Kozubal, Eric

Liquid desiccant heat and mass exchangers are a promising technology for efficient humidity control in buildings. Many researchers have investigated these exchangers, often using numerical models to predict their performance. However, there is a lack of information in the literature on the magnitude of the heat and mass transfer resistances, both for the dehumidifier (which absorbs moisture from the air) and the regenerator (which heats the liquid desiccant to re-concentrate it). This article focuses on internally-cooled, 3-fluid exchangers in a parallel plate geometry. Water heats or cools a desiccant across a plate, and the desiccant absorbs or releases water intomore » an airstream through a membrane. A sensitivity analysis was used to estimate the importance of each of the heat and mass transfer resistances (air, membrane, desiccant, plate, water), and how it changes with different design geometries. The results show that, for most designs, the latent and sensible heat transfer of the dehumidifier is dominated by the air mass transfer resistance and air heat transfer resistance, respectively. The air mass transfer resistance is also important for the regenerator, but much less so; the change in the desiccant equilibrium humidity ratio due to a change in either temperature or desiccant mass fraction is much higher at the regenerator's higher temperatures. This increases the importance of (1) getting heat from the water to the desiccant/membrane interface, and (2) diffusing salt ions quickly away from the desiccant/membrane interface. The membrane heat transfer and water heat transfer resistances were found to be the least important. These results can help inform decisions about what simplifying assumptions to make in numerical models, and can also help in designing these exchangers by understanding which resistances are most important.« less

The Cryogenic Propellant Storage and Transfer Technology Demonstration Mission:. [Progress and Transition

NASA Technical Reports Server (NTRS)

Meyer, Michael L.; Taylor, William J.; Ginty, Carol A.; Melis, Matthew E.

2014-01-01

This presentation provides an overview of the Cryogenic Propellant Storage and Transfer (CPST) Mission from formulation through Systems Requirements Review and into preparation for Preliminary Design Review. Accomplishments of the technology maturation phase of the project are included. The presentation then summarizes the transition, due to Agency budget constraints, of CPST from a flight project into a ground project titled evolvable Cryogenics (eCryo).

New method for mass transfer across the surface of non-spherical particles in turbulence

NASA Astrophysics Data System (ADS)

Oehmke, T.; Variano, E. A.

2016-12-01

We present a method for making model particles that allow for the interfacial mass transfer rate to be measured. This is similar to traditional use of gypsum plaster used to measure erosion rates on the timescale of weeks to years. Our new method is useful for measuring erosion rates on the timescale of minutes. We use this to measure the manner in which particle shape affects its rate of dissolution in turbulent flow. The related questions are relevant to mass transfer in turbulence, e.g. in cases of marine biology and pollution by microplastics.

Heat and Mass Transfer Measurements for Tray-Fermented Fungal Products

NASA Astrophysics Data System (ADS)

Jou, R.-Y.; Lo, C.-T.

2011-01-01

In this study, heat and mass transfer in static tray fermentation, which is widely used in solid-state fermentation (SSF) to produce fungal products, such as enzymes or koji, is investigated. Specifically, kinetic models of transport phenomena in the whole-tray chamber are emphasized. The effects of temperature, moisture, and humidity on microbial growth in large-scale static tray fermentation are essential to scale-up SSF and achieve uniform fermentation. In addition, heat and mass transfer of static tray fermentation of Trichoderma fungi with two tray setups—traditional linen coverings and stacks in a temperature-humidity chamber is examined. In both these setups, the following factors of fermentation were measured: air velocity, air temperature, illumination, pH, carbon dioxide (CO2) concentration, and substrate temperature, and the effects of bed height, moisture of substrate, and relative humidity of air are studied. A thin (1 cm) bed at 28 °C and 95 % relative humidity is found to be optimum. Furthermore, mixing was essential for achieving uniform fermentation of Trichoderma fungi. This study has important applications in large-scale static tray fermentation of fungi.

Modifier mass transfer kinetic effect in the performance of solvent gradient simulated moving bed (SG-SMB) process

NASA Astrophysics Data System (ADS)

Câmara, L. D. T.

2015-09-01

The solvent-gradient simulated moving bed process (SG-SMB) is the new tendency in the performance improvement if compared to the traditional isocratic solvent conditions. In such SG-SMB separation process the modulation of the solvent strength leads to significant increase in the purities and productivity followed by reduction in the solvent consumption. A stepwise modelling approach was utilized in the representation of the interconnected chromatographic columns of the system combined with lumped mass transfer models between the solid and liquid phase. The influence of the solvent modifier was considered applying the Abel model which takes into account the effect of modifier volume fraction over the partition coefficient. The modelling and simulations were carried out and compared to the experimental SG-SMB separation of the amino acids phenylalanine and tryptophan. A lumped mass transfer kinetic model was applied for both the modifier (ethanol) as well as the solutes. The simulation results showed that such simple and global mass transfer models are enough to represent all the mass transfer effect between the solid adsorbent and the liquid phase. The separation performance can be improved reducing the interaction or the mass transfer kinetic effect between the solid adsorbent phase and the modifier. The simulations showed great agreement fitting the experimental data of the amino acids concentrations both at the extract as well as at the raffinate.

A Research Program for Improving Heat Transfer Prediction Capability for the Laminar to Turbulent Transition Region of Turbine Vanes/Blades

NASA Technical Reports Server (NTRS)

Simon, Frederick F.

2007-01-01

A program sponsored by the National Aeronautics and Space Administration (NASA) for the investigation of the heat transfer in the transition region of turbine vanes and blades with the object of improving the capability for predicting heat transfer is described,. The accurate prediction of gas-side heat transfer is important to the determination of turbine longevity, engine performance and developmental costs. The need for accurate predictions will become greater as the operating temperatures and stage loading levels of advanced turbine engines increase. The present methods for predicting transition shear stress and heat transfer on turbine blades are based on incomplete knowledge and are largely empirical. To meet the objectives of the NASA program, a team approach consisting of researchers from government, universities, a research institute, and a small business is presented. The research is divided into areas of experimentation, direct numerical simulation (DNS) and turbulence modeling. A summary of the results to date is given for the above research areas in a high-disturbance environment (bypass transition) with a discussion of the model development necessary for use in numerical codes.

Chemical Evolution of Groundwater Near a Sinkhole Lake, Northern Florida: 2. Chemical Patterns, Mass Transfer Modeling, and Rates of Mass Transfer Reactions

NASA Astrophysics Data System (ADS)

Katz, Brian G.; Plummer, L. Niel; Busenberg, Eurybiades; Revesz, Kinga M.; Jones, Blair F.; Lee, Terrie M.

1995-06-01

Chemical patterns along evolutionary groundwater flow paths in silicate and carbonate aquifers were interpreted using solute tracers, carbon and sulfur isotopes, and mass balance reaction modeling for a complex hydrologic system involving groundwater inflow to and outflow from a sinkhole lake in northern Florida. Rates of dominant reactions along defined flow paths were estimated from modeled mass transfer and ages obtained from CFC-modeled recharge dates. Groundwater upgradient from Lake Barco remains oxic as it moves downward, reacting with silicate minerals in a system open to carbon dioxide (CO2), producing only small increases in dissolved species. Beneath and downgradient of Lake Barco the oxic groundwater mixes with lake water leakage in a highly reducing, silicate-carbonate mineral environment. A mixing model, developed for anoxic groundwater downgradient from the lake, accounted for the observed chemical and isotopic composition by combining different proportions of lake water leakage and infiltrating meteoric water. The evolution of major ion chemistry and the 13C isotopic composition of dissolved carbon species in groundwater downgradient from the lake can be explained by the aerobic oxidation of organic matter in the lake, anaerobic microbial oxidation of organic carbon, and incongruent dissolution of smectite minerals to kaolinite. The dominant process for the generation of methane was by the CO2 reduction pathway based on the isotopic composition of hydrogen (δ2H(CH4) = -186 to -234‰) and carbon (δ13C(CH4) = -65.7 to -72.3‰). Rates of microbial metabolism of organic matter, estimated from the mass transfer reaction models, ranged from 0.0047 to 0.039 mmol L-1 yr-1 for groundwater downgradient from the lake.

Mass Transfer Study of Chlorine Dioxide Gas Through Polymeric Packaging Materials

USDA-ARS?s Scientific Manuscript database

A continuous system for measuring the mass transfer of gaseous chlorine dioxide (ClO2), a strong oxidizing agent and used in food and pharmaceutical packaging, through 10 different types of polymeric packaging material was developed utilizing electrochemical sensor as a detector. Permeability, diff...

Fluid Flow and Mass Transfer in Micro/Nano-Channels

NASA Astrophysics Data System (ADS)

Conlisk, A. T.; McFerran, Jennifer; Hansford, Derek; Zheng, Zhi

2001-11-01

In this work the fluid flow and mass transfer due to the presence of an electric field in a rectangular channel is examined. We consider a mixture of water or other neutral solvent and a salt compound such as sodium chloride for which the ionic species are entirely dissociated. Results are produced for the case where the channel height is much greater than the electric double layer(EDL)(microchannel) and for the case where the channel height is of the order or somewhat greater than the width of the EDL(nanochannel). For the electroosmotic flow so induced, the velocity field and the potential are similar. The fluid is assumed to behave as a continuum and the Boltzmann distribution for the mole fractions of the ions emerges from the classical dilute mass transfer equation in the limiting case where the EDL thickness is much less than the channel height. Depending on the relative magnitude of the mole fractions at the walls of the channel, both forward and reversed flow may occur. The volume flow rate is observed to vary linearly with channel height for electrically driven flow in contrast to pressure driven flow which varies as height cubed. This means that power requirements for small channels are much greater for pressure driven flow. Supported by DARPA

Endocytic pathway rapidly delivers internalized molecules to lysosomes: an analysis of vesicle trafficking, clustering and mass transfer.

PubMed

Pangarkar, Chinmay; Dinh, Anh-Tuan; Mitragotri, Samir

2012-08-20

Lysosomes play a critical role in intracellular drug delivery. For enzyme-based therapies, they represent a potential target site whereas for nucleic acid or many protein drugs, they represent the potential degradation site. Either way, understanding the mechanisms and processes involved in routing of materials to lysosomes after cellular entry is of high interest to the field of drug delivery. Most therapeutic cargoes other than small hydrophobic molecules enter the cells through endocytosis. Endocytosed cargoes are routed to lysosomes via microtubule-based transport and are ultimately shared by various lysosomes via tethering and clustering of endocytic vesicles followed by exchange of their contents. Using a combined experimental and numerical approach, here we studied the rates of mass transfer into and among the endocytic vesicles in a model cell line, 3T3 fibroblasts. In order to understand the relationship of mass transfer with microtubular transport and vesicle clustering, we varied both properties through various pharmacological agents. At the same time, microtubular transport and vesicle clustering were modeled through diffusion-advection equations and the Smoluchowski equations, respectively. Our analysis revealed that the rate of mass transfer is optimally related to microtubular transport and clustering properties of vesicles. Further, the rate of mass transfer is highest in the innate state of the cell. Any perturbation to either microtubular transport or vesicle aggregation led to reduced mass transfer to lysosome. These results suggest that in the absence of an external intervention the endocytic pathway appears to maximize molecular delivery to lysosomes. Strategies are discussed to reduce mass transfer to lysosomes so as to extend the residence time of molecules in endosomes or late endosomes, thus potentially increasing the likelihood of their escape before disposition in the lysosomes. Copyright © 2012 Elsevier B.V. All rights reserved.

Determination of mass and heat transfer parameters during freeze-drying cycles of pharmaceutical products.

PubMed

Hottot, A; Vessot, S; Andrieu, J

2005-01-01

The principal aim of this study was to evaluate the water vapour mass transfer resistance of the dried layer and the vial heat transfer coefficient values of a pharmaceutical product during the primary drying period. First, overall vial heat transfer coefficient values, Kv, were determined by a gravimetric method based on pure ice sublimation experiments. Thus, it was possible to set up a map of the total heat flux received by each vial throughout the plate surface of our pilot scale freeze-dryer. Important heterogeneities were observed for the vials placed at the plate edges and for the vials placed at the center of the plate. As well, the same gravimetric method was also used to precisely determine the influence of main lyophilization operating parameters (shelf temperature and gas total pressure) or the vial types and sizes on these overall heat transfer coefficient values. A semi-empirical relationship as a function of total gas pressure was proposed. The transient method by pressure rise analysis (PRA method) after interrupting the water vapour flow between the sublimation chamber and the condenser, previously set up and validated in our laboratory, was then extensively used with an amorphous BSA-based formulation to identify the dried layer mass transfer resistance values, Rp, the ice front temperature, and the total heat transfer coefficient values, Kv, with or without annealing treatment. It was proved that this method gave accurate and coherent data only during the first half of the sublimation period when the totality of the vials of the set was still sublimating. Thus, this rapid method allowed estimation of, on line and in situ, the sublimation front temperature and the characterization of the morphology and structure of the freeze-dried layer, all along the first part of the sublimation period. The estimated sublimation temperatures shown by the PRA model were about 2 degrees C lower than the experimental values obtained using thermocouples inserted

Substrate mass transfer: analytical approach for immobilized enzyme reactions

NASA Astrophysics Data System (ADS)

Senthamarai, R.; Saibavani, T. N.

2018-04-01

In this paper, the boundary value problem in immobilized enzyme reactions is formulated and approximate expression for substrate concentration without external mass transfer resistance is presented. He’s variational iteration method is used to give approximate and analytical solutions of non-linear differential equation containing a non linear term related to enzymatic reaction. The relevant analytical solution for the dimensionless substrate concentration profile is discussed in terms of dimensionless reaction parameters α and β.

Dynamic Mass Transfer of Hemoglobin at the Aqueous/Ionic-Liquid Interface Monitored with Liquid Core Optical Waveguide.

PubMed

Chen, Xuwei; Yang, Xu; Zeng, Wanying; Wang, Jianhua

2015-08-04

Protein transfer from aqueous medium into ionic liquid is an important approach for the isolation of proteins of interest from complex biological samples. We hereby report a solid-cladding/liquid-core/liquid-cladding sandwich optical waveguide system for the purpose of monitoring the dynamic mass-transfer behaviors of hemoglobin (Hb) at the aqueous/ionic liquid interface. The optical waveguide system is fabricated by using a hydrophobic IL (1,3-dibutylimidazolium hexafluorophosphate, BBimPF6) as the core, and protein solution as one of the cladding layer. UV-vis spectra are recorded with a CCD spectrophotometer via optical fibers. The recorded spectra suggest that the mass transfer of Hb molecules between the aqueous and ionic liquid media involve accumulation of Hb on the aqueous/IL interface followed by dynamic extraction/transfer of Hb into the ionic liquid phase. A part of Hb molecules remain at the interface even after the accomplishment of the extraction/transfer process. Further investigations indicate that the mass transfer of Hb from aqueous medium into the ionic liquid phase is mainly driven by the coordination interaction between heme group of Hb and the cationic moiety of ionic liquid, for example, imidazolium cation in this particular case. In addition, hydrophobic interactions also contribute to the transfer of Hb.

Would Current International Space Station (ISS) Recycling Life Support Systems Save Mass on a Mars Transit?

NASA Technical Reports Server (NTRS)

Jones, Harry W.

2017-01-01

The oxygen and water are recycled on the International Space Station (ISS) to save the cost of launching their mass into orbit. Usually recycling systems are justified by showing that their launch mass would be much lower than the mass of the oxygen or water they produce. Short missions such as Apollo or space shuttle directly provide stored oxygen and water, since the needed total mass of oxygen and water is much less than that of there cycling equipment. Ten year or longer missions such as the ISS or a future moon base easily save mass by recycling while short missions of days or weeks do not. Mars transit and long Mars surface missions have an intermediate duration, typically one to one and a half years. Some of the current ISS recycling systems would save mass if used on a Mars transit but others would not.

Mass transfer from a circular cylinder: Effects of flow unsteadiness and slight nonuniformities

NASA Technical Reports Server (NTRS)

Marziale, M. L.; Mayle, R. E.

1984-01-01

Experiments were performed to determine the effect of periodic variations in the angle of the flow incident to a turbine blade on its leading edge heat load. To model this situation, measurements were made on a circular cylinder oscillating rotationally in a uniform steady flow. A naphthalene mass transfer technique was developed and used in the experiments and heat transfer rates are inferred from the results. The investigation consisted of two parts. In the first, a stationary cylinder was used and the transfer rate was measured for Re = 75,000 to 110,000 and turbulence levels from .34 percent to 4.9 percent. Comparisons with both theory and the results of others demonstrate that the accuracy and repeatability of the developed mass transfer technique is about + or - 2 percent, a large improvement over similar methods. In the second part identical flow conditions were used but the cylinder was oscillated. A Strouhal number range from .0071 to .1406 was covered. Comparisons of the unsteady and steady results indicate that the magnitude of the effect of oscillation is small and dependent on the incident turbulence conditions.

Prediction of mass transfer coefficients in non-Newtonian fermentation media using first-principles methods.

PubMed

Radl, Stefan; Khinast, Johannes G

2007-08-01

Bubble flows in non-Newtonian fluids were analyzed using first-principles methods with the aim to compute and predict mass transfer coefficients in such fermentation media. The method we used is a Direct Numerical Simulation (DNS) of the reactive multiphase flow with deformable boundaries and interfaces. With this method, we are able for the first time to calculate mass transfer coefficients in non-Newtonian liquids of different rheologies without any experimental data. In the current article, shear-thinning fluids are considered. However, the results provide the basis for further investigations, such as the study of viscoelastic fluids. (c) 2007 Wiley Periodicals, Inc.

Parents in transition: Experiences of parents of young people with a liver transplant transferring to adult services.

PubMed

Wright, J; Elwell, L; McDonagh, J E; Kelly, D A; Wray, J

2017-02-01

Predictors of successful transition from pediatric to adult services include ability to self-manage and engage with healthcare services. Parents have a key role in healthcare management throughout childhood and adolescence including encouraging development of self-management skills in their children. Transition to adult services can be challenging for parents and young people, yet parents' views regarding transition remain largely unexplored. Nine parents of pediatric liver transplant recipients (15.2-25.1 yr) participated in semistructured interviews. Interviews were analyzed using IPA. Analysis revealed three key themes: "emotional impact of transplantation," "protection vs. independence," and "ending relationships and changing roles." Parents expressed the dichotomous nature of the desire to promote independence in their child while still maintaining control and protection, and discussed how changing roles and relationships were difficult to navigate. Parents are important facilitators of young people's development of self-management skills for successful transfer to adult services. Parents should be supported to move from a "managerial" to a "supervisory" role during transition to help young people engage independently with the healthcare team. Findings support the development of interventions for parents to emphasize their role in transition and guide the transfer of self-management skills from parent to young person. © 2016 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

Transition boiling heat transfer and the film transition regime

NASA Technical Reports Server (NTRS)

Ramilison, J. M.; Lienhard, J. H.

1987-01-01

The Berenson (1960) flat-plate transition-boiling experiment has been recreated with a reduced thermal resistance in the heater, and an improved access to those portions of the transition boiling regime that have a steep negative slope. Tests have been made in Freon-113, acetone, benzene, and n-pentane boiling on horizontal flat copper heaters that have been mirror-polished, 'roughened', or teflon-coated. The resulting data reproduce and clarify certain features observed by Berenson: the modest surface finish dependence of boiling burnout, and the influence of surface chemistry on both the minimum heat flux and the mode of transition boiling, for example. A rational scheme of correlation yields a prediction of the heat flux in what Witte and Lienhard (1982) previously identified as the 'film-transition boiling' region. It is also shown how to calculate the heat flux at the boundary between the pure-film, and the film-transition, boiling regimes, as a function of the advancing contact angle.

Mass transfer in supercritical fluids instancing selected fluids in supercritical carbon dioxide

NASA Astrophysics Data System (ADS)

Hu, Miao; Benning, Rainer; Delgado, Antonio; Ertunc, Oezguer

The research interests lie in a deeper understanding of the mechanisms of diffusion and nucle-ation of organic solutes in near-and supercritical state of a solvent, which count as important means of mass transfer in the process engineering industry. The use of supercritical fluids in industrial processes, such as extraction and particle handling, has become a more and more popular method. Take a closer look at the two processes one would find that there are obviously two sub-processes involved in each of the process, namely the diffusion/nucleation as well as a phase transition procedure. Because of the operational limitations in the practice, this phase transition can-not be neglected. So it is also included in the theoretical approach. Classically to deduce conclusions from experiment results, mathematical/physical models outlining property changes and summarizing characteristics of the two processes are expected. In order to become an insight of these phenomena from the origin, and also to serve as a fundamental attribute for the numerical simulation later, the theories of statistical thermodynamics are adopted here as a proper means to describe the behaviors of the two processes. As the diffusion coefficients of the samples in our case are only of an order of approx. 10-8m2s-1, it can be assumed that the processes are in equilibrium (local changes are neglectably small), a model can be built on a general macroscopic approach for equilibrium systems, namely the Boltzmann-Gibbs distri-bution. And some rather general methods e.g. linear response theory can be applied. But as the transfer phenomena are genuinely not equilibrium systems, from this aspect a model can also be built based on the microscopic description -the kinetic theory of the behaviors of the particles of this non-equilibrium system. The characteristics under compensated gravity are also to be considered in the models. The differences and constraints between the models are to be compared and

Back Disorder Intervention Strategies for Mass Transit Operators Exposed to Whole-Body VIBRATION—COMPARISON of Two Transit System Approaches and Practices

NASA Astrophysics Data System (ADS)

Johanning, E.

1998-08-01

Occupational long-term whole-body vibration (WBV) has been recognized as a major risk factor for low back disorders, one of the most important reasons for medical impairment and early permanent disability among mass transit operators. Although no firm health and safety vibration exposure threshold limits have been established, the available data suggests that rail vehicle operators would probably fall under the proposed WBV “action levels” of the EU directive provisions for protection from physical hazards. This provision calls for technical, administrative and medical controls. This paper examines and compares the current conditions, provisions and plans of two major mass transit systems, the New Yorker MTA and the Munich MVV. The available data, information and publications (English/German) on working conditions, vibration exposure, epidemiology and intervention strategies (primary and secondary prevention) for rail bound mass transit workers were reviewed. Results strongly suggest that the MTA transit system has currently and in the near future no effective and meaningful controls in place to significantly reduce the WBV exposure of subway operators. It appears that the MVV system has more and better control measures in place to reduce harmful effects of WBV. Results of a scientific evaluation of a participatory, collaborative project in the MVV system suggest that the MVV may have developed a successful method of a “condition prevention” (Verhältnisprävention)—and “behavioral prevention” (Verhaltensprävention) intervention strategy, which appears beneficial for WBV exposed workers with existing low back pain. Long-term outcomes and benefits need to be assessed further.

Optical backbone-sidechain charge transfer transitions in proteins sensitive to secondary structure and modifications.

PubMed

Mandal, I; Paul, S; Venkatramani, R

2018-04-17

The absorption of light by proteins can induce charge transfer (CT) transitions in the UV-visible range of the electromagnetic spectrum. Metal-ligand complexes or active site prosthetic groups which absorb in the visible region exhibit prominent CT transitions. Furthermore, the protein backbone also exhibits CT transitions in the far UV range. In this manuscript, we present a detailed computational study of new near UV-visible CT transitions that involve amino acids with charged side chains. Specifically, using time dependent density functional theory calculations, we examine the absorption spectra of naturally charged amino acids (Lys, Glu, Arg, Asp and His), extracted from solution phase protein structures generated by classical molecular dynamics simulations, and phosphorylated amino acids (Tyr, Thr and Ser) from experimentally determined protein structures. We show that amino acids with charged sidechains present a directed electronic donor-bridge-acceptor paradigm, with the lowest energy optical excitations demonstrating peptide backbone-sidechain charge separations. The UV-visible spectral range of the backbone-sidechain CT transitions is determined by the chemical nature of the donor, bridge and acceptor groups within each amino acid, amino acid conformation and the protein secondary structure where the amino acids are located. Photoinduced CT occurs in opposite directions for the anionic and cationic amino acids along the ground state dipole moment vector for the chromophores. We find that photoinduced charge separation is more facile for the anionic amino acids (Asp, Glu, pSer, pThr and pTyr) relative to that for the cationic amino acids (Lys, Arg and Hsp). Our results provide a foundation for the development of spectroscopic markers based on the recently proposed Protein Charge Transfer Spectra (ProCharTS) which are relevant for the study of DNA-binding or intrinsically disordered proteins that are rich in charged amino acids.

Analysis of transition-metal acetylacetonate complexes by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry.

PubMed

Wyatt, Mark F; Havard, Stephen; Stein, Bridget K; Brenton, A Gareth

2008-01-01

Transition-metal acetylacetonate complexes of the form Metal(acac)(2), where Metal = Fe(II), Co(II), Ni(II), Cu(II), and Zn(II), and Metal(acac)(3), where Metal = V(III), Cr(III), Mn(III), Fe(III), and Co(III), were investigated by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOFMS). The data was acquired using the aprotic, electron transfer matrix, 2-[(2E)-3-(4-tert-butylphenyl)-2-methylprop-2-enylidene]malononitrile (DCTB), and the observation of positive radical ions is shown clearly to depend on the metal element and the oxidation state it occupies. The ionization energy of DCTB was calculated to be 8.08 eV by density functional theory methods, which is notably lower than the experimental value, but within the range of other computational values. This value is very close to those of the analytes, so the existing electron transfer mechanism which is based on the ionization energies of the matrix and analyte, cannot be used predictively. Similarly, the data neither proves nor disproves the validity of the existing electron transfer ionization mechanism, with respect to metal coordination complexes without strong chromophores. In this case, periodic trends may be more useful in explaining the observed species and the prediction of species from sets of similar complexes. The addition of a sodium salt benefits the MALDI-TOFMS characterization of certain compounds studied, but the benefit of the addition of ammonium or silver salts is negligible.

Quantitative and Qualitative Aspects of Gas-Metal-Oxide Mass Transfer in High-Temperature Confocal Scanning Laser Microscopy

NASA Astrophysics Data System (ADS)

Piva, Stephano P. T.; Pistorius, P. Chris; Webler, Bryan A.

2018-05-01

During high-temperature confocal scanning laser microscopy (HT-CSLM) of liquid steel samples, thermal Marangoni flow and rapid mass transfer between the sample and its surroundings occur due to the relatively small sample size (diameter around 5 mm) and large temperature gradients. The resulting evaporation and steel-slag reactions tend to change the chemical composition in the metal. Such mass transfer effects can change observed nonmetallic inclusions. This work quantifies oxide-metal-gas mass transfer of solutes during HT-CSLM experiments using computational simulations and experimental data for (1) dissolution of MgO inclusions in the presence and absence of slag and (2) Ca, Mg-silicate inclusion changes upon exposure of a Si-Mn-killed steel to an oxidizing gas atmosphere.

Effects of partial slip boundary condition and radiation on the heat and mass transfer of MHD-nanofluid flow

NASA Astrophysics Data System (ADS)

Abd Elazem, Nader Y.; Ebaid, Abdelhalim

2017-12-01

In this paper, the effect of partial slip boundary condition on the heat and mass transfer of the Cu-water and Ag-water nanofluids over a stretching sheet in the presence of magnetic field and radiation. Such partial slip boundary condition has attracted much attention due to its wide applications in industry and chemical engineering. The flow is basically governing by a system of partial differential equations which are reduced to a system of ordinary differential equations. This system has been exactly solved, where exact analytical expression has been obtained for the fluid velocity in terms of exponential function, while the temperature distribution, and the nanoparticles concentration are expressed in terms of the generalized incomplete gamma function. In addition, explicit formulae are also derived from the rates of heat transfer and mass transfer. The effects of the permanent parameters on the skin friction, heat transfer coefficient, rate of mass transfer, velocity, the temperature profile, and concentration profile have been discussed through tables and graphs.

Verification and validation of an advanced model of heat and mass transfer in the protective clothing

NASA Astrophysics Data System (ADS)

Łapka, Piotr; Furmański, Piotr

2018-04-01

The paper presents verification and validation of an advanced numerical model of heat and moisture transfer in the multi-layer protective clothing and in components of the experimental stand subjected to either high surroundings temperature or high radiative heat flux emitted by hot objects. The developed model included conductive-radiative heat transfer in the hygroscopic porous fabrics and air gaps as well as conductive heat transfer in components of the stand. Additionally, water vapour diffusion in the pores and air spaces as well as phase transition of the bound water in the fabric fibres (sorption and desorption) were accounted for. All optical phenomena at internal or external walls were modelled and the thermal radiation was treated in the rigorous way, i.e., semi-transparent absorbing, emitting and scattering fabrics with the non-grey properties were assumed. The air was treated as transparent. Complex energy and mass balances as well as optical conditions at internal or external interfaces were formulated in order to find values of temperatures, vapour densities and radiation intensities at these interfaces. The obtained highly non-linear coupled system of discrete equations was solved by the Finite Volume based in-house iterative algorithm. The developed model passed discretisation convergence tests and was successfully verified against the results obtained applying commercial software for simplified cases. Then validation was carried out using experimental measurements collected during exposure of the protective clothing to high radiative heat flux emitted by the IR lamp. Satisfactory agreement of simulated and measured temporal variation of temperature at external and internal surfaces of the multi-layer clothing was attained.

Effect of radiator position and mass flux on the dryer room heat transfer rate

NASA Astrophysics Data System (ADS)

Mirmanto, M.; Sulistyowati, E. D.; Okariawan, I. D. K.

A room radiator as usually used in cold countries, is actually able to be used as a heat source to dry goods, especially in the rainy season where the sun seldom shines due to much rain and cloud. Experiments to investigate effects of radiator position and mass flux on heat transfer rate were performed. This study is to determine the best position of the radiator and the optimum mass flux. The radiator used was a finned radiator made of copper pipes and aluminum fins with an overall dimension of 220 mm × 50 mm × 310 mm. The prototype room was constructed using plywood and wood frame with an overall size of 1000 mm × 1000 mm × 1000 mm. The working fluid was heated water flowing inside the radiator and air circulating naturally inside the prototype room. The nominal mass fluxes employed were 800, 900 and 1000 kg/m2 s. The water was kept at 80 °C at the radiator entrance, while the initial air temperature inside the prototype room was 30 °C. Three positions of the radiator were examined. The results show that the effect of the mass flux on the forced and free convection heat transfer rate is insignificant but the radiator position strongly affects the heat transfer rate for both forced and free convection.

Mass transfer characteristics of bisporus mushroom ( Agaricus bisporus) slices during convective hot air drying

NASA Astrophysics Data System (ADS)

Ghanbarian, Davoud; Baraani Dastjerdi, Mojtaba; Torki-Harchegani, Mehdi

2016-05-01

An accurate understanding of moisture transfer parameters, including moisture diffusivity and moisture transfer coefficient, is essential for efficient mass transfer analysis and to design new dryers or improve existing drying equipments. The main objective of the present study was to carry out an experimental and theoretical investigation of mushroom slices drying and determine the mass transfer characteristics of the samples dried under different conditions. The mushroom slices with two thicknesses of 3 and 5 mm were dried at air temperatures of 40, 50 and 60 °C and air flow rates of 1 and 1.5 m s-1. The Dincer and Dost model was used to determine the moisture transfer parameters and predict the drying curves. It was observed that the entire drying process took place in the falling drying rate period. The obtained lag factor and Biot number indicated that the moisture transfer in the samples was controlled by both internal and external resistance. The effective moisture diffusivity and the moisture transfer coefficient increased with increasing air temperature, air flow rate and samples thickness and varied in the ranges of 6.5175 × 10-10 to 1.6726 × 10-9 m2 s-1 and 2.7715 × 10-7 to 3.5512 × 10-7 m s-1, respectively. The validation of the Dincer and Dost model indicated a good capability of the model to describe the drying curves of the mushroom slices.

Band-to-band transitions, selection rules, effective mass, and excitonic contributions in monoclinic β -Ga2O3

NASA Astrophysics Data System (ADS)

Mock, Alyssa; Korlacki, Rafał; Briley, Chad; Darakchieva, Vanya; Monemar, Bo; Kumagai, Yoshinao; Goto, Ken; Higashiwaki, Masataka; Schubert, Mathias

2017-12-01

We employ an eigenpolarization model including the description of direction dependent excitonic effects for rendering critical point structures within the dielectric function tensor of monoclinic β -Ga2O3 yielding a comprehensive analysis of generalized ellipsometry data obtained from 0.75-9 eV. The eigenpolarization model permits complete description of the dielectric response. We obtain, for single-electron and excitonic band-to-band transitions, anisotropic critical point model parameters including their polarization vectors within the monoclinic lattice. We compare our experimental analysis with results from density functional theory calculations performed using the Gaussian-attenuation-Perdew-Burke-Ernzerhof hybrid density functional. We present and discuss the order of the fundamental direct band-to-band transitions and their polarization selection rules, the electron and hole effective mass parameters for the three lowest band-to-band transitions, and their excitonic contributions. We find that the effective masses for holes are highly anisotropic and correlate with the selection rules for the fundamental band-to-band transitions. The observed transitions are polarized close to the direction of the lowest hole effective mass for the valence band participating in the transition.

Fluid and mass transfer at subduction interfaces-The field metamorphic record

NASA Astrophysics Data System (ADS)

Bebout, Gray E.; Penniston-Dorland, Sarah C.

2016-01-01

The interface between subducting oceanic slabs and the hanging wall is a structurally and lithologically complex region. Chemically disparate lithologies (sedimentary, mafic and ultramafic rocks) and mechanical mixtures thereof show heterogeneous deformation. These lithologies are tectonically juxtaposed at mm to km scales, particularly in more intensely sheared regions (mélange zones, which act as fluid channelways). This juxtaposition, commonly in the presence of a mobile fluid phase, offers up huge potential for mass transfer and related metasomatic alteration. Fluids in this setting appear capable of transporting mass over scales of kms, along flow paths with widely varying geometries and P-T trajectories. Current models of arc magmatism require km-scale migration of fluids from the interface into mantle wedge magma source regions and implicit in these models is the transport of any fluids generated in the subducting slab along and ultimately through the subduction interface. Field and geochemical studies of high- and ultrahigh-pressure metamorphic rocks elucidate the sources and compositions of fluids in subduction interfaces and the interplay between deformation and fluid and mass transfer in this region. Recent geophysical studies of the subduction interface - its thickness, mineralogy, density, and H2O content - indicate that its rheology greatly influences the ways in which the subducting plate is coupled with the hanging wall. Field investigation of the magnitude and styles of fluid-rock interaction in metamorphic rocks representing "seismogenic zone" depths (and greater) yields insight regarding the roles of fluids and elevated fluid pore pressure in the weakening of plate interface rocks and the deformation leading to seismic events. From a geochemical perspective, the plate interface contributes to shaping the "slab signature" observed in studies of the composition of arc volcanic rocks. Understanding the production of fluids with hybridized chemical

Gas hold-up and oxygen mass transfer in three pneumatic bioreactors operating with sugarcane bagasse suspensions.

PubMed

Esperança, M N; Cunha, F M; Cerri, M O; Zangirolami, T C; Farinas, C S; Badino, A C

2014-05-01

Sugarcane bagasse is a low-cost and abundant by-product generated by the bioethanol industry, and is a potential substrate for cellulolytic enzyme production. The aim of this work was to evaluate the effects of air flow rate (QAIR), solids loading (%S), sugarcane bagasse type, and particle size on the gas hold-up (εG) and volumetric oxygen transfer coefficient (kLa) in three different pneumatic bioreactors, using response surface methodology. Concentric tube airlift (CTA), split-cylinder airlift (SCA), and bubble column (BC) bioreactor types were tested. QAIR and %S affected oxygen mass transfer positively and negatively, respectively, while sugarcane bagasse type and particle size (within the range studied) did not influence kLa. Using large particles of untreated sugarcane bagasse, the loop-type bioreactors (CTA and SCA) exhibited higher mass transfer, compared to the BC reactor. At higher %S, SCA presented a higher kLa value (0.0448 s−1) than CTA, and the best operational conditions in terms of oxygen mass transfer were achieved for %S < 10.0 g L−1 and QAIR > 27.0 L min−1. These results demonstrated that pneumatic bioreactors can provide elevated oxygen transfer in the presence of vegetal biomass, making them an excellent option for use in three-phase systems for cellulolytic enzyme production by filamentous fungi.

Effect of mass transfer in a recirculation batch reactor system for immobilized penicillin amidase.

PubMed

Park, J M; Choi, C Y; Seong, B L; Han, M H

1982-10-01

The effect of external mass transfer resistance on the overall reaction rate of the immobilized whole cell penicillin amidase of E. coli in a recirculation batch reactor was investigated. The internal diffusional resistance was found negligible as indicated by the value of effectiveness factor, 0.95. The local environmental change in a column due to the pH drop was successfully overcome by employing buffer solution. The reaction rate was measured by pH-stat method and was found to follow the simple Michaelis-Menten law at the initial stage of the reaction. The values of the net reaction rate experimentally determined were used to calculate the substrate concentration at the external surface of the catalyst pellet and then to calculate the mass transfer coefficient, k(L), at various flow rates and substrate concentrations. The correlation proposed by Chilton and Colburn represented adequately the experimental data. The linear change of log j(D) at low log N(Re) with negative slope was ascribed to the fact that the external mass transfer approached the state of pure diffusion in the limit of zero superficial velocity.

Flow patterns and transition characteristics for steam condensation in silicon microchannels

NASA Astrophysics Data System (ADS)

Ma, Xuehu; Fan, Xiaoguang; Lan, Zhong; Hao, Tingting

2011-07-01

This study investigated the two-phase flow patterns and transition characteristics for steam condensation in silicon microchannels with different cross-sectional geometries. Novel experimental techniques were developed to determine the local heat transfer rate and steam quality by testing the temperature profile of a copper cooler. Flow regime maps for different microchannels during condensation were established in terms of steam mass flux and steam quality. Meanwhile, the correlation for the flow pattern transition was obtained using different geometrical and dimensionless parameters for steam condensation in microchannels. To better understand the flow mechanisms in microchannels, the condensation flow patterns, such as annular flow, droplet flow, injection flow and intermittent flow, were captured and analyzed. The local heat transfer rate showed the nonlinear variations along the axial direction during condensation. The experimental results indicate that the flow patterns and transition characteristics strongly depend on the geometries of microchannels. With the increasing steam mass flux and steam quality, the annular/droplet flow expands and spans over a larger region in the microchannels; otherwise the intermittent flow occupies the microchannels. The dimensionless fitting data also reveal that the effect of surface tension and vapor inertia dominates gravity and viscous force at the specified flow pattern transitional position.

Ground-based Search of Earth-mass Exoplanets using Transit-Timing Variations

NASA Astrophysics Data System (ADS)

Fernandez, J. M.

2010-10-01

This work presents recent results from a ground-based transit follow-up program of the extrasolar planet XO-2b in order to find Earth-mass companions. It also introduces the future use of the MONET 1m-class robotic telescopes as part of the effort to overcome the difficulties of this kind of project.

Complementary Strategies for Directed C(sp3 )-H Functionalization: A Comparison of Transition-Metal-Catalyzed Activation, Hydrogen Atom Transfer, and Carbene/Nitrene Transfer.

PubMed

Chu, John C K; Rovis, Tomislav

2018-01-02

The functionalization of C(sp 3 )-H bonds streamlines chemical synthesis by allowing the use of simple molecules and providing novel synthetic disconnections. Intensive recent efforts in the development of new reactions based on C-H functionalization have led to its wider adoption across a range of research areas. This Review discusses the strengths and weaknesses of three main approaches: transition-metal-catalyzed C-H activation, 1,n-hydrogen atom transfer, and transition-metal-catalyzed carbene/nitrene transfer, for the directed functionalization of unactivated C(sp 3 )-H bonds. For each strategy, the scope, the reactivity of different C-H bonds, the position of the reacting C-H bonds relative to the directing group, and stereochemical outcomes are illustrated with examples in the literature. The aim of this Review is to provide guidance for the use of C-H functionalization reactions and inspire future research in this area. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Simultaneous estimation of local-scale and flow path-scale dual-domain mass transfer parameters using geoelectrical monitoring

USGS Publications Warehouse

Briggs, Martin A.; Day-Lewis, Frederick D.; Ong, John B.; Curtis, Gary P.; Lane, John W.

2013-01-01

Anomalous solute transport, modeled as rate-limited mass transfer, has an observable geoelectrical signature that can be exploited to infer the controlling parameters. Previous experiments indicate the combination of time-lapse geoelectrical and fluid conductivity measurements collected during ionic tracer experiments provides valuable insight into the exchange of solute between mobile and immobile porosity. Here, we use geoelectrical measurements to monitor tracer experiments at a former uranium mill tailings site in Naturita, Colorado. We use nonlinear regression to calibrate dual-domain mass transfer solute-transport models to field data. This method differs from previous approaches by calibrating the model simultaneously to observed fluid conductivity and geoelectrical tracer signals using two parameter scales: effective parameters for the flow path upgradient of the monitoring point and the parameters local to the monitoring point. We use regression statistics to rigorously evaluate the information content and sensitivity of fluid conductivity and geophysical data, demonstrating multiple scales of mass transfer parameters can simultaneously be estimated. Our results show, for the first time, field-scale spatial variability of mass transfer parameters (i.e., exchange-rate coefficient, porosity) between local and upgradient effective parameters; hence our approach provides insight into spatial variability and scaling behavior. Additional synthetic modeling is used to evaluate the scope of applicability of our approach, indicating greater range than earlier work using temporal moments and a Lagrangian-based Damköhler number. The introduced Eulerian-based Damköhler is useful for estimating tracer injection duration needed to evaluate mass transfer exchange rates that range over several orders of magnitude.

Mass transfer of hydrophobic organic chemicals between silicone sheets and through plant leaves and low-density polyethylene.

PubMed

Ahmadi, Hamid; Bolinius, Damien Johann; Jahnke, Annika; MacLeod, Matthew

2016-12-01

Plant leaves play an important role in the fate of hydrophobic organic contaminants (HOCs) in the environment. Yet much remains unknown about the permeability of leaves by HOCs. In this pilot study we measured (i) the kinetics of mass transfer of three polycyclic aromatic hydrocarbons (PAHs) and six polychlorinated biphenyls between a spiked and an unspiked sheet of polydimethylsiloxane (PDMS) in direct contact with each other for 24 h and (ii) kinetics of mass transfer of two PAHs through leaves and low-density polyethylene (LDPE) in a passive dosing experiment by inserting these matrices between the two sheets of PDMS for 48 h. The kinetics of mass transfer of fluoranthene between PDMS sheets in direct contact were a factor of 12 slower than those reported in the literature. The kinetics of mass transfer of fluorene and phenanthrene through leaves were within the range of those previously reported for 2,4-dichlorophenoxyacetic acid through isolated cuticles. Our results provide a proof-of-concept demonstration that the passive dosing method applied in this study can be used to measure the mass transfer coefficients of organic chemicals through leaves. Key recommendations for future experiments are to load the PDMS at the highest feasible concentrations to avoid working at analyte levels close to the limit of detection, to keep the leaves moist and to minimize potential pathways for contamination of the PDMS sheets by exposure to laboratory air. Copyright © 2016 The Authors. Published by Elsevier Ltd.. All rights reserved.

Oxygen mass transfer in a stirred tank bioreactor using different impeller configurations for environmental purposes

PubMed Central

2013-01-01

In this study, a miniature stirred tank bioreactor was designed for treatment of waste gas containing benzene, toluene and xylene. Oxygen mass transfer characteristics for various twin and single-impeller systems were investigated for 6 configurations in a vessel with 10 cm of inner diameter and working volume of 1.77L. Three types of impellers, namely, Rushton turbine, Pitched 4blades and Pitched 2blades impellers with downward pumping have been used. Deionized water was used as a liquid phase. With respect to other independent variables such as agitation speed, aeration rate, type of sparger, number of impellers, the relative performance of these impellers was assessed by comparing the values of (KLa) as a key parameter. Based on the experimental data, empirical correlations as a function of the operational conditions have been proposed, to study the oxygen transfer rates from air bubbles generated in the bioreactor. It was shown that twin Rushton turbine configuration demonstrates superior performance (23% to 77% enhancement in KLa) compared with other impeller compositions and that sparger type has negligible effect on oxygen mass transfer rate. Agitation speeds of 400 to 800 rpm were the most efficient speeds for oxygen mass transfer in the stirred bioreactor. PMID:23369581

Study of the heat-transfer crisis on heat-release surfaces of annular channels with swirl and transit flows

NASA Astrophysics Data System (ADS)

Boltenko, E. A.

2016-10-01

The results of the experimental study of the heat-transfer crisis on heat-release surfaces of annular channels with swirl and transit flow are presented. The experiments were carried out using electric heated annular channels with one and (or) two heat-release surfaces. For the organization of transit flow on a convex heat-release surface, four longitudinal ribs were installed uniformly at its perimeter. Swirl flow was realized using a capillary wound tightly (without gaps) on the ribs. The ratio between swirl and transit flows in the annular gap was varied by applying longitudinal ribs of different height. The experiments were carried out using a closed-type circulatory system. The experimental data were obtained in a wide range of regime parameters. Both water heated to the temperature less than the saturation temperature and water-steam mixture were fed at the inlet of the channels. For the measurement of the temperature of the heat-release surfaces, chromel-copel thermocouples were used. It was shown that the presence of swirl flow on a convex heatrelease surface led to a significant decrease in critical heat flows (CHF) compared to a smooth surface. To increase CHF, it was proposed to use the interaction of swirl flows of the heat carrier. The second swirl flow was transit flow, i.e., swirl flow with the step equal to infinity. It was shown that CHF values for a channel with swirl and transit flow in all the studied range of regime parameters was higher than CHF values for both a smooth annular channel and a channel with swirl. The empirical ratios describing the dependence of CHF on convex and concave heat-release surfaces of annular channels with swirl and transit flow on the geometrical characteristics of channels and the regime parameters were obtained. The experiments were carried out at the pressure p = 3.0-16.0 MPa and the mass velocity ρw = 250-3000 kg/(m2s).

Influence of fluid dynamic conditions on enzymatic hydrolysis of lignocellulosic biomass: Effect of mass transfer rate.

PubMed

Wojtusik, Mateusz; Zurita, Mauricio; Villar, Juan C; Ladero, Miguel; Garcia-Ochoa, Felix

2016-09-01

The effect of fluid dynamic conditions on enzymatic hydrolysis of acid pretreated corn stover (PCS) has been assessed. Runs were performed in stirred tanks at several stirrer speed values, under typical conditions of temperature (50°C), pH (4.8) and solid charge (20% w/w). A complex mixture of cellulases, xylanases and mannanases was employed for PCS saccharification. At low stirring speeds (<150rpm), estimated mass transfer coefficients and rates, when compared to chemical hydrolysis rates, lead to results that clearly show low mass transfer rates, being this phenomenon the controlling step of the overall process rate. However, for stirrer speed from 300rpm upwards, the overall process rate is controlled by hydrolysis reactions. The ratio between mass transfer and overall chemical reaction rates changes with time depending on the conditions of each run. Copyright © 2016 Elsevier Ltd. All rights reserved.

Determination of the profile of DO and its mass transferring coefficient in a biofilm reactor packed with semi-suspended bio-carriers.

PubMed

Tang, Bing; Song, Haoliang; Bin, Liying; Huang, Shaosong; Zhang, Wenxiang; Fu, Fenglian; Zhao, Yiliang; Chen, Qianyu

2017-10-01

The work aims at illustrating the profile of DO and its mass transferring process in a biofilm reactor packed with a novel semi-suspended bio-carrier, and further revealing the main factors that influence the mass transferring coefficient of DO within the biofilm. Results showed that the biofilm was very easy to attach and grow on the semi-suspended bio-carrier, which obviously changed the DO profile inside and outside the biofilm. The semi-suspended bio-carrier caused three different mass transfer zones occurring in the bioreactor, including the zones of bulk solution, boundary layer and biofilm, in which, the boundary layer zone had an obvious higher mass transfer resistance. Increasing the aeration rate might improve the hydrodynamic conditions in the bioreactor and accelerate the mass transfer of DO, but it also detached the biofilm from the surface of bio-carrier, which reduced the consumption of DO, and accordingly, decreased the DO gradient in the bioreactor. Copyright © 2017 Elsevier Ltd. All rights reserved.

Ultrasonic guided wave propagation across waveguide transitions: energy transfer and mode conversion.

PubMed

Puthillath, Padmakumar; Galan, Jose M; Ren, Baiyang; Lissenden, Cliff J; Rose, Joseph L

2013-05-01

Ultrasonic guided wave inspection of structures containing adhesively bonded joints requires an understanding of the interaction of guided waves with geometric and material discontinuities or transitions in the waveguide. Such interactions result in mode conversion with energy being partitioned among the reflected and transmitted modes. The step transition between an aluminum layer and an aluminum-adhesive-aluminum multi-layer waveguide is analyzed as a model structure. Dispersion analysis enables assessment of (i) synchronism through dispersion curve overlap and (ii) wavestructure correlation. Mode-pairs in the multi-layer waveguide are defined relative to a prescribed mode in a single layer as being synchronized and having nearly perfect wavestructure matching. Only a limited number of mode-pairs exist, and each has a unique frequency range. A hybrid model based on semi-analytical finite elements and the normal mode expansion is implemented to assess mode conversion at a step transition in a waveguide. The model results indicate that synchronism and wavestructure matching is associated with energy transfer through the step transition, and that the energy of an incident wave mode in a single layer is transmitted almost entirely to the associated mode-pair, where one exists. This analysis guides the selection of incident modes that convert into transmitted modes and improve adhesive joint inspection with ultrasonic guided waves.

The Transition of NASA EOS Datasets to WFO Operations: A Model for Future Technology Transfer

NASA Technical Reports Server (NTRS)

Darden, C.; Burks, J.; Jedlovec, G.; Haines, S.

2007-01-01

The collocation of a National Weather Service (NWS) Forecast Office with atmospheric scientists from NASA/Marshall Space Flight Center (MSFC) in Huntsville, Alabama has afforded a unique opportunity for science sharing and technology transfer. Specifically, the NWS office in Huntsville has interacted closely with research scientists within the SPORT (Short-term Prediction and Research and Transition) Center at MSFC. One significant technology transfer that has reaped dividends is the transition of unique NASA EOS polar orbiting datasets into NWS field operations. NWS forecasters primarily rely on the AWIPS (Advanced Weather Information and Processing System) decision support system for their day to day forecast and warning decision making. Unfortunately, the transition of data from operational polar orbiters or low inclination orbiting satellites into AWIPS has been relatively slow due to a variety of reasons. The ability to integrate these high resolution NASA datasets into operations has yielded several benefits. The MODIS (MODerate-resolution Imaging Spectrometer ) instrument flying on the Aqua and Terra satellites provides a broad spectrum of multispectral observations at resolutions as fine as 250m. Forecasters routinely utilize these datasets to locate fine lines, boundaries, smoke plumes, locations of fog or haze fields, and other mesoscale features. In addition, these important datasets have been transitioned to other WFOs for a variety of local uses. For instance, WFO Great Falls Montana utilizes the MODIS snow cover product for hydrologic planning purposes while several coastal offices utilize the output from the MODIS and AMSR-E instruments to supplement observations in the data sparse regions of the Gulf of Mexico and western Atlantic. In the short term, these datasets have benefited local WFOs in a variety of ways. In the longer term, the process by which these unique datasets were successfully transitioned to operations will benefit the planning and

Cryogenic two-phase flow during chilldown: Flow transition and nucleate boiling heat transfer

NASA Astrophysics Data System (ADS)

Jackson, Jelliffe Kevin

The recent interest in space exploration has placed a renewed focus on rocket propulsion technology. Cryogenic propellants are the preferred fuel for rocket propulsion since they are more energetic and environmentally friendly compared with other storable fuels. Voracious evaporation occurs while transferring these fluids through a pipeline that is initially in thermal equilibrium with the environment. This phenomenon is referred to as line chilldown. Large temperature differences, rapid transients, pressure fluctuations and the transition from the film boiling to the nucleate boiling regime characterize the chilldown process. Although the existence of the chilldown phenomenon has been known for decades, the process is not well understood. Attempts have been made to model the chilldown process; however the results have been fair at best. A major shortcoming of these models is the use of correlations that were developed for steady, non-cryogenic flows. The development of reliable correlations for cryogenic chilldown has been hindered by the lack of experimental data. An experimental facility was constructed that allows the flow structure, the temperature history and the pressure history to be recorded during the line chilldown process. The temperature history is then utilized in conjunction with an inverse heat conduction procedure that was developed, which allows the unsteady heat transfer coefficient on the interior of the pipe wall to be extracted. This database is used to evaluate present predictive models and correlations for flow regime transition and nucleate boiling heat transfer. It is found that by calibrating the transition between the stratified-wavy and the intermittent/annular regimes of the Taitel and Dukler flow regime map, satisfactory predictions are obtained. It is also found that by utilizing a simple model that includes the effect of flow structure and incorporating the enhancement provided by the local heat flux, significant improvement in the

Adolescents' and young adults' transition experiences when transferring from paediatric to adult care: a qualitative metasynthesis.

PubMed

Fegran, Liv; Hall, Elisabeth O C; Uhrenfeldt, Lisbeth; Aagaard, Hanne; Ludvigsen, Mette Spliid

2014-01-01

The objective of this study was to synthesize qualitative studies of how adolescents and young adults with chronic diseases experience the transition from paediatric to adult hospital care. The review is designed as a qualitative metasynthesis and is following Sandelowski and Barroso's guidelines for synthesizing qualitative research. Literature searches were conducted in the databases PubMed, Ovid, Scopus, Cumulative Index to Nursing and Allied Health Literature (CINAHL), ISI Web of Science, and Nordic and German databases covering the period from 1999 to November 2010. In addition, forward citation snowball searching was conducted in the databases Ovid, CINAHL, ISI Web of Science, Scopus and Google Scholar. Of the 1143 records screened, 18 studies were included. Inclusion criteria were qualitative studies in English, German or Nordic languages on adolescents' and young adults' transition experiences when transferring from paediatric to adult care. There was no age limit, provided the focus was on the actual transfer process and participants had a chronic somatic disease. The studies were appraised as suitable for inclusion using a published appraisal tool. Data were analyzed into metasummaries and a metasynthesis according to established guidelines for synthesis of qualitative research. Four themes illustrating experiences of loss of familiar surroundings and relationships combined with insecurity and a feeling of being unprepared for what was ahead were identified: facing changes in significant relationships, moving from a familiar to an unknown ward culture, being prepared for transfer and achieving responsibility. Young adults' transition experiences seem to be comparable across diagnoses. Feelings of not belonging and of being redundant during the transfer process are striking. Health care professionals' appreciation of young adults' need to be acknowledged and valued as competent collaborators in their own transfer is crucial, and may protect them from

Heat and mass transfer enhancement of nanofluids flow in the presence of metallic/metallic-oxides spherical nanoparticles

NASA Astrophysics Data System (ADS)

Qureshi, M. Zubair Akbar; Ali, Kashif; Iqbal, M. Farooq; Ashraf, Muhammad; Ahmad, Shazad

2017-01-01

The numerical study of heat and mass transfer for an incompressible magnetohydrodynamics (MHD) nanofluid flow containing spherical shaped nanoparticles through a channel with moving porous walls is presented. Further, another endeavour is to study the effect of two types of fluids, namely the metallic nanofluid (Au + water) and metallic-oxides nanofluid (TiO2 + water) are studied. The phenomena of spherical metallic and metallic-oxides nanoparticles have been also mathematically modelled by using the Hamilton-Crosser model. The influence of the governing parameters on the flow, heat and mass transfer aspects of the problem is discussed. The outcome of the investigation may be beneficial to the application of biotechnology and industrial purposes. Numerical solutions for the velocity, heat and mass transfer rate at the boundary are obtained and analysed.

Prediction of Heat and Mass Transfer in a Rotating Ribbed Coolant Passage With a 180 Degree Turn

NASA Technical Reports Server (NTRS)

Rigby, David L.

1999-01-01

Numerical results are presented for flow in a rotating internal passage with a 180 degree turn and ribbed walls. Reynolds numbers ranging from 5200 to 7900, and Rotation numbers of 0.0 and 0.24 were considered. The straight sections of the channel have a square cross section, with square ribs spaced one hydraulic diameter (D) apart on two opposite sides. The ribs have a height of 0.1D and are not staggered from one side to the other. The full three dimensional Reynolds Averaged Navier-Stokes equations are solved combined with the Wilcox k-omega turbulence model. By solving an additional equation for mass transfer, it is possible to isolate the effect of buoyancy in the presence of rotation. That is, heat transfer induced buoyancy effects can be eliminated as in naphthalene sublimation experiments. Heat transfer, mass transfer and flow field results are presented with favorable agreement with available experimental data. It is shown that numerically predicting the reattachment between ribs is essential to achieving an accurate prediction of heat/mass transfer. For the low Reynolds numbers considered, the standard turbulence model did not produce reattachment between ribs. By modifying the wall boundary condition on omega, the turbulent specific dissipation rate, much better agreement with the flow structure and heat/ mass transfer was achieved. It is beyond the scope of the present work to make a general recommendation on the omega wall boundary condition. However, the present results suggest that the omega boundary condition should take into account the proximity to abrupt changes in geometry.

Application research of computational mass-transfer differential equation in MBR concentration field simulation.

PubMed

Li, Chunqing; Tie, Xiaobo; Liang, Kai; Ji, Chanjuan

2016-01-01

After conducting the intensive research on the distribution of fluid's velocity and biochemical reactions in the membrane bioreactor (MBR), this paper introduces the use of the mass-transfer differential equation to simulate the distribution of the chemical oxygen demand (COD) concentration in MBR membrane pool. The solutions are as follows: first, use computational fluid dynamics to establish a flow control equation model of the fluid in MBR membrane pool; second, calculate this model by adopting direct numerical simulation to get the velocity field of the fluid in membrane pool; third, combine the data of velocity field to establish mass-transfer differential equation model for the concentration field in MBR membrane pool, and use Seidel iteration method to solve the equation model; last but not least, substitute the real factory data into the velocity and concentration field model to calculate simulation results, and use visualization software Tecplot to display the results. Finally by analyzing the nephogram of COD concentration distribution, it can be found that the simulation result conforms the distribution rule of the COD's concentration in real membrane pool, and the mass-transfer phenomenon can be affected by the velocity field of the fluid in membrane pool. The simulation results of this paper have certain reference value for the design optimization of the real MBR system.

Development, income transfer strategies, and the nutritional transition in Brazilian children from a rural and remote region.

PubMed

Freitas, D A; Sousa, Á A; Jones, K M

2014-01-01

Global development processes have been associated with the nutritional transition, where undernutrition is replaced by overnutrition. Income transfer policies in Brazil have targeted hunger, but may not address the need for balanced nutrition. Data was collected from government databanks that document the nutritional status of Brazilians applying for social services. This data was analyzed for descriptive statistics. Development and income transfer processes appear to be associated with an increase in overweight children between the years 2008 and 2012. Income transfer programs need to incorporate educational programs that address the need to budget for balanced nutrition.

Influence of blade leading edge geometry and upstream blowing on the heat/mass transfer in a turbine cascade

NASA Astrophysics Data System (ADS)

Papa, Marco

The effect of secondary flows on mass transfer from a simulated gas turbine blade and hubwall is investigated. Measurements performed using naphthalene sublimation provide non-dimensional mass transfer coefficients, in the form of Sherwood numbers, that can be converted to heat transfer coefficients through the use of an analogy. Tests are conducted in a linear cascade composed of five blades having the profile of a first stage rotor blade of a high-pressure turbine aircraft engine. Detailed mass transfer maps on the airfoil and endwall surfaces allow the identification of significant flow features that are in good agreement with existing secondary flow models. These results are well-suited for validation of numerical codes, as they are obtained with an accurate technique that does not suffer from conduction or radiation errors and allows the imposition of precise boundary conditions. The performance of a RANS (Reynolds Averaged Navier-Stokes) numerical code that simulates the flow and heat/mass transfer in the cascade using the SST (Shear Stress Transport) k-o model is evaluated through a comparison with the experimental results. Tests performed with a modified blade leading edge show that the introduction of a fillet at the junction with the endwall reduces the effects of the horseshoe vortex in the first part of the passage, while no measurable changes in mass transfer are observed further downstream. Air injected through a slot located upstream of the cascade simulates the engine wheelspace coolant injection between the stator and the rotor. Local mass transfer data obtained injecting naphthalene-free and naphthalene-saturated air are reduced to derive maps of cooling effectiveness on the blade and endwall. Oil dot tests show the surface flow on the endwall. The surface downstream of the gap is coplanar to the upstream surface in the baseline configuration and is shifted to form a forward and backward facing step to investigate the effects of component

The Study of Micro-Pressure Inner-Loop Bioreactor Oxygen Mass Transfer Characteristics

NASA Astrophysics Data System (ADS)

Wan, L. G.; Lin, Q.; Bian, D. J.; Ren, Q. K.; Xiao, Y. B.; Lu, W. X.

2018-03-01

The oxygen mass transfer characteristics in a Micro-Pressure Inner-Loop bioreactor (MPR) were studied by clean water oxygenation experiment, the results show that when the aeration adopt by 0.1, 0.2, 0.4, 0.6 m3·h-1, respectively, the oxygen mass transfer coefficient KLa(20) in the reactor increases with the increase of the aeration. KLa(20) shows a good linear correlation with the aeration. The rate is 0.2128 h·m-3·min-1 and the correlation coefficient R=0.993. However, the trend of EO2 increases first and then decreases with the increase of aeration. When the aeration increased to 0.4 m3·h-1, the EO2 reaches the maximum. If aeration increases constantly, EO2 begin to decrease excessive aeration may lead to an increase in energy waste during reactor operation.

Influence of mass transfer resistance on overall nitrate removal rate in upflow sludge bed reactors.

PubMed

Ting, Wen-Huei; Huang, Ju-Sheng

2006-09-01

A kinetic model with intrinsic reaction kinetics and a simplified model with apparent reaction kinetics for denitrification in upflow sludge bed (USB) reactors were proposed. USB-reactor performance data with and without sludge wasting were also obtained for model verification. An independent batch study showed that the apparent kinetic constants k' did not differ from the intrinsic k but the apparent Ks' was significantly larger than the intrinsic Ks suggesting that the intra-granule mass transfer resistance can be modeled by changes in Ks. Calculations of the overall effectiveness factor, Thiele modulus, and Biot number combined with parametric sensitivity analysis showed that the influence of internal mass transfer resistance on the overall nitrate removal rate in USB reactors is more significant than the external mass transfer resistance. The simulated residual nitrate concentrations using the simplified model were in good agreement with the experimental data; the simulated results using the simplified model were also close to those using the kinetic model. Accordingly, the simplified model adequately described the overall nitrate removal rate and can be used for process design.

Electronic structure of negative charge transfer CaFeO3 across the metal-insulator transition

NASA Astrophysics Data System (ADS)

Rogge, Paul C.; Chandrasena, Ravini U.; Cammarata, Antonio; Green, Robert J.; Shafer, Padraic; Lefler, Benjamin M.; Huon, Amanda; Arab, Arian; Arenholz, Elke; Lee, Ho Nyung; Lee, Tien-Lin; Nemšák, Slavomír; Rondinelli, James M.; Gray, Alexander X.; May, Steven J.

2018-01-01

We investigated the metal-insulator transition for epitaxial thin films of the perovskite CaFeO3, a material with a significant oxygen ligand hole contribution to its electronic structure. We find that biaxial tensile and compressive strain suppress the metal-insulator transition temperature. By combining hard x-ray photoelectron spectroscopy, soft x-ray absorption spectroscopy, and density functional calculations, we resolve the element-specific changes to the electronic structure across the metal-insulator transition. We demonstrate that the Fe sites undergo no observable spectroscopic change between the metallic and insulating states, whereas the O electronic configuration undergoes significant changes. This strongly supports the bond-disproportionation model of the metal-insulator transition for CaFeO3 and highlights the importance of ligand holes in its electronic structure. By sensitively measuring the ligand hole density, however, we find that it increases by ˜5 -10 % in the insulating state, which we ascribe to a further localization of electron charge on the Fe sites. These results provide detailed insight into the metal-insulator transition of negative charge transfer compounds and should prove instructive for understanding metal-insulator transitions in other late transition metal compounds such as the nickelates.

Numerical Problems and Agent-Based Models for a Mass Transfer Course

ERIC Educational Resources Information Center

Murthi, Manohar; Shea, Lonnie D.; Snurr, Randall Q.

2009-01-01

Problems requiring numerical solutions of differential equations or the use of agent-based modeling are presented for use in a course on mass transfer. These problems were solved using the popular technical computing language MATLABTM. Students were introduced to MATLAB via a problem with an analytical solution. A more complex problem to which no…

A Transition Odyssey: Pupils' Experiences of Transfer to Secondary School across Five Decades

ERIC Educational Resources Information Center

Galton, Maurice; McLellan, Ros

2018-01-01

This article reviews transition from primary to secondary school over the period from the 1970s to the present day. It first considers the evidence from the earlier period and then at the time of the millennium before reporting on a recent investigation undertaken in four secondary schools. Using the 'five bridges model' of transfer, it compares…

Inflow Motions Associated with High-mass Protostellar Objects

NASA Astrophysics Data System (ADS)

Yoo, Hyunju; Kim, Kee-Tae; Cho, Jungyeon; Choi, Minho; Wu, Jingwen; Evans, Neal J., II; Ziurys, L. M.

2018-04-01

We performed a molecular line survey of 82 high-mass protostellar objects in a search for inflow signatures associated with high-mass star formation. Using the H13CO+ (1‑0) line as an optically thin tracer, we detected a statistically significant excess of blue asymmetric line profiles in the HCO+ (1‑0) transition, but nonsignificant excesses in the HCO+ (3‑2) and H2CO (212–111) transitions. The negative blue excess for the HCN (3‑2) transition suggests that the line profiles are affected by dynamics other than inflow motion. The HCO+ (1‑0) transition thus seems to be the suitable tracer of inflow motions in high-mass star-forming regions, as previously suggested. We found 27 inflow candidates that have at least 1 blue asymmetric profile and no red asymmetric profile, and derived the inflow velocities to be 0.23‑2.00 km s‑1 for 20 of them using a simple two-layer radiative transfer model. Our sample is divided into two groups in different evolutionary stages. The blue excess of the group in relatively earlier evolutionary stages was estimated to be slightly higher than that of the other in the HCO+ (1‑0) transition.

QCD phase transition with chiral quarks and physical quark masses.

PubMed

Bhattacharya, Tanmoy; Buchoff, Michael I; Christ, Norman H; Ding, H-T; Gupta, Rajan; Jung, Chulwoo; Karsch, F; Lin, Zhongjie; Mawhinney, R D; McGlynn, Greg; Mukherjee, Swagato; Murphy, David; Petreczky, P; Renfrew, Dwight; Schroeder, Chris; Soltz, R A; Vranas, P M; Yin, Hantao

2014-08-22

We report on the first lattice calculation of the QCD phase transition using chiral fermions with physical quark masses. This calculation uses 2+1 quark flavors, spatial volumes between (4 fm)(3) and (11 fm)(3) and temperatures between 139 and 196 MeV. Each temperature is calculated at a single lattice spacing corresponding to a temporal Euclidean extent of N(t) = 8. The disconnected chiral susceptibility, χ(disc) shows a pronounced peak whose position and height depend sensitively on the quark mass. We find no metastability near the peak and a peak height which does not change when a 5 fm spatial extent is increased to 10 fm. Each result is strong evidence that the QCD "phase transition" is not first order but a continuous crossover for m(π) = 135 MeV. The peak location determines a pseudocritical temperature T(c) = 155(1)(8) MeV, in agreement with earlier staggered fermion results. However, the peak height is 50% greater than that suggested by previous staggered results. Chiral SU(2)(L) × SU(2)(R) symmetry is fully restored above 164 MeV, but anomalous U(1)(A) symmetry breaking is nonzero above T(c) and vanishes as T is increased to 196 MeV.

An Experiment to Introduce Mass Transfer Concepts Using a Commercial Hollow Fiber Blood Oxygenator

ERIC Educational Resources Information Center

McIver, Keith; Merrill, Thomas; Farrell, Stephanie

2017-01-01

A commercial hollow fiber blood oxygenation laboratory experiment was used to introduce lower level engineering students to mass balances in a two-phase system. Using measured values of concentration and flow rate, students calculated the rate of mass transfer from the gas phase and into the liquid phase, and compared the two values to determine…

Vacuum drying of apples (cv. Golden Delicious): drying characteristics, thermodynamic properties, and mass transfer parameters

NASA Astrophysics Data System (ADS)

Nadi, Fatemeh; Tzempelikos, Dimitrios

2018-01-01

In this work, apples of cv. Golden Delicious were cut into slices that were 5 and 7 mm thick and then vacuum dried at 50, 60 and 70 °C and pressure of 0.02 bar. The thin layer model drying kinetics was studied, and mass transfer properties, specifically effective moisture diffusivity and convective mass transfer coefficient, were evaluated using the Fick's equation of diffusion. Also, thermodynamic parameters of the process, i.e. enthalpy (ΔH), entropy (ΔS) and Gibbs free energy (ΔG), were determined. Colour properties were evaluated as one of the important indicators of food quality and marketability. Determination of mass transfer parameters and thermodynamic properties of vacuum dried apple slices has not been discussed much in the literature. In conclusion, the Nadi's model fitted best the observed data that represent the drying process. Thermodynamic properties were determined based on the dependence of the drying constant of the Henderson and Pabis model on temperature, and it was concluded that the variation in drying kinetics depends on the energy contribution of the surrounding environment. The enthalpy and entropy diminished, while the Gibbs free energy increased with the increase of the temperature of drying; therefore, it was possible to verify that variation in the diffusion process in the apple during drying depends on energetic contributions of the environment. The obtained results showed that diffusivity increased for 69%, while the mass transfer coefficient increase was even higher, 75%, at the variation of temperature of 20 °C. The increase in the dimensionless Biot number was 20%.

Vacuum drying of apples (cv. Golden Delicious): drying characteristics, thermodynamic properties, and mass transfer parameters

NASA Astrophysics Data System (ADS)

Nadi, Fatemeh; Tzempelikos, Dimitrios

2018-07-01

In this work, apples of cv. Golden Delicious were cut into slices that were 5 and 7 mm thick and then vacuum dried at 50, 60 and 70 °C and pressure of 0.02 bar. The thin layer model drying kinetics was studied, and mass transfer properties, specifically effective moisture diffusivity and convective mass transfer coefficient, were evaluated using the Fick's equation of diffusion. Also, thermodynamic parameters of the process, i.e. enthalpy ( ΔH), entropy ( ΔS) and Gibbs free energy ( ΔG), were determined. Colour properties were evaluated as one of the important indicators of food quality and marketability. Determination of mass transfer parameters and thermodynamic properties of vacuum dried apple slices has not been discussed much in the literature. In conclusion, the Nadi's model fitted best the observed data that represent the drying process. Thermodynamic properties were determined based on the dependence of the drying constant of the Henderson and Pabis model on temperature, and it was concluded that the variation in drying kinetics depends on the energy contribution of the surrounding environment. The enthalpy and entropy diminished, while the Gibbs free energy increased with the increase of the temperature of drying; therefore, it was possible to verify that variation in the diffusion process in the apple during drying depends on energetic contributions of the environment. The obtained results showed that diffusivity increased for 69%, while the mass transfer coefficient increase was even higher, 75%, at the variation of temperature of 20 °C. The increase in the dimensionless Biot number was 20%.

The mechanism of thermal-gradient mass transfer in the sodium hydroxide-nickel system

NASA Technical Reports Server (NTRS)

May, Charles E

1958-01-01

"Thermal-gradient mass transfer" was investigated in the molten sodium hydroxide-nickel system. Possible mechanisms (physical, electrochemical, and chemical) are discussed in terms of experimental and theoretical evidence. Experimental details are included in appendixes.

The effect of microbubbles on gas-liquid mass transfer coefficient and degradation rate of COD in wastewater treatment.

PubMed

Yao, Kangning; Chi, Yong; Wang, Fei; Yan, Jianhua; Ni, Mingjiang; Cen, Kefa

2016-01-01

A commonly used aeration device at present has the disadvantages of low mass transfer rate because the generated bubbles are several millimeters in diameter which are much bigger than microbubbles. Therefore, the effect of a microbubble on gas-liquid mass transfer and wastewater treatment process was investigated. To evaluate the effect of each bubble type, the volumetric mass transfer coefficients for microbubbles and conventional bubbles were determined. The volumetric mass transfer coefficient was 0.02905 s(-1) and 0.02191 s(-1) at a gas flow rate of 0.67 L min(-1) in tap water for microbubbles and conventional bubbles, respectively. The degradation rate of simulated municipal wastewater was also investigated, using aerobic activated sludge and ozone. Compared with the conventional bubble generator, the chemical oxygen demand (COD) removal rate was 2.04, 5.9, 3.26 times higher than those of the conventional bubble contactor at the same initial COD concentration of COD 200 mg L(-1), 400 mg L(-1), and 600 mg L(-1), while aerobic activated sludge was used. For the ozonation process, the rate of COD removal using microbubble generator was 2.38, 2.51, 2.89 times of those of the conventional bubble generator. Based on the results, the effect of initial COD concentration on the specific COD degradation rate were discussed in different systems. Thus, the results revealed that microbubbles could enhance mass transfer in wastewater treatment and be an effective method to improve the degradation of wastewater.

Mass-transfer limitations for immobilized enzyme-catalyzed kinetic resolution of racemate in a fixed-bed reactor.

PubMed

Xiu, G H; Jiang, L; Li, P

2001-07-05

A mathematical model has been developed for immobilized enzyme-catalyzed kinetic resolution of racemate in a fixed-bed reactor in which the enzyme-catalyzed reaction (the irreversible uni-uni competitive Michaelis-Menten kinetics is chosen as an example) was coupled with intraparticle diffusion, external mass transfer, and axial dispersion. The effects of mass-transfer limitations, competitive inhibition of substrates, deactivation on the enzyme effective enantioselectivity, and the optical purity and yield of the desired product are examined quantitatively over a wide range of parameters using the orthogonal collocation method. For a first-order reaction, an analytical solution is derived from the mathematical model for slab-, cylindrical-, and spherical-enzyme supports. Based on the analytical solution for the steady-state resolution process, a new concise formulation is presented to predict quantitatively the mass-transfer limitations on enzyme effective enantioselectivity and optical purity and yield of the desired product for a continuous steady-state kinetic resolution process in a fixed-bed reactor. Copyright 2001 John Wiley & Sons, Inc.

Finite mass enhancement across bandwidth controlled Mott transition in NiS2-xSex

NASA Astrophysics Data System (ADS)

Han, Garam; Kyung, W. S.; Kim, Y. K.; Cheng, C. M.; Tsuei, K. D.; Lee, K. D.; Hur, N.; Kim, H.-D.; Kim, C.

One of the most important and still debated issues in the strongly correlated electron systems is on the metal insulator transition (MIT) mechanism. In the bandwidth controlled Mott transition (BCMT) scenario, which Mott originally proposed, MIT occurs through a mass divergence in which the effective mass of the quasi-particle (QP) diverges approaching the MIT. The interpretation is supported by dynamic mean field theory (DMFT) model calculations. However, few direct observations have been made yet due to various experimental restrictions. In this talk, I present systematic angle resolved photoemission studies on the MIT in NiS2-xSex, which is a well-known BCMT material. We observed not only the bandwidth shrinkage but also the coherent quasi-particle peak (QP) which is not of the surface origin. In addition, we experimentally showed the mass of the QP remains finite approaching the MIT. This work was supported by IBS-R009-D1.

Photoinduced energy transfer in transition metal complex oligomers

DOE Office of Scientific and Technical Information (OSTI.GOV)

NONE

1997-04-01

The work we have done over the past three years has been directed toward the preparation, characterization and photophysical examination of mono- and bimetallic diimine complexes. The work is part of a broader project directed toward the development of stable, efficient, light harvesting arrays of transition metal complex chromophores. One focus has been the synthesis of rigid bis-bidentate and bis-tridentate bridging ligands. We have managed to make the ligand bphb in multigram quantities from inexpensive starting materials. The synthetic approach used has allowed us prepare a variety of other ligands which may have unique applications (vide infra). We have prepared,more » characterized and examined the photophysical behavior of Ru(II) and Re(I) complexes of the ligands. Energy donor/acceptor complexes of bphb have been prepared which exhibit nearly activationless energy transfer. Complexes of Ru(II) and Re(I) have also been prepared with other polyunsaturated ligands in which two different long lived ( > 50 ns) excited states exist; results of luminescence and transient absorbance measurements suggest the two states are metal-to-ligand charge transfer and ligand localized {pi}{r_arrow}{pi}* triplets. Finally, we have developed methods to prepare polymetallic complexes which are covalently bound to various surfaces. The long term objective of this work is to make light harvesting arrays for the sensitization of large band gap semiconductors. Details of this work are provided in the body of the report.« less

Photoinduced energy transfer in transition metal complex oligomers

DOE Office of Scientific and Technical Information (OSTI.GOV)

NONE

1997-06-01

The work done over the past three years has been directed toward the preparation, characterization and photophysical examination of mono- and bimetallic diimine complexes. The work is part of a broader project directed toward the development of stable, efficient, light harvesting arrays of transition metal complex chromophores. One focus has been the synthesis of rigid bis-bidentate and bis-tridentate bridging ligands. The authors have managed to make the ligand bphb in multigram quantities from inexpensive starting materials. The synthetic approach used has allowed them to prepare a variety of other ligands which may have unique applications (vide infra). They have prepared,more » characterized and examined the photophysical behavior of Ru(II) and Re(I) complexes of the ligands. Energy donor/acceptor complexes of bphb have been prepared which exhibit nearly activationless energy transfer. Complexes of Ru(II) and Re(I) have also been prepared with other polyunsaturated ligands in which two different long lived (> 50 ns) excited states exist; results of luminescence and transient absorbance measurements suggest the two states are metal-to-ligand charge transfer and ligand localized {pi}{r_arrow}{pi}* triplets. Finally, the authors have developed methods to prepare polymetallic complexes which are covalently bound to various surfaces. The long term objective of this work is to make light harvesting arrays for the sensitization of large band gap semiconductors. Details of this work are provided in the body of the report.« less

Prediction and rational correlation of thermophoretically reduced particle mass transfer to hot surfaces across laminar or turbulent forced-convection gas boundary layers

NASA Technical Reports Server (NTRS)

Gokoglu, Suleyman A.; Rosner, Daniel E.

1986-01-01

A formulation previously developed to predict and correlate the thermophoretically-augmented submicron particle mass transfer rate to cold surfaces is found to account for the thermophoretically reduced particle mass transfer rate to overheated surfaces such that thermophoresis brings about a 10-decade reduction below the convective mass transfer rate expected by pure Brownian diffusion and convection alone. Thermophoretic blowing is shown to produce effects on particle concentration boundary-layer (BL) structure and wall mass transfer rates similar to those produced by real blowing through a porous wall. The applicability of the correlations to developing BL-situations is demonstrated by a numerical example relevant to wet-steam technology.

The effect of arsenic chemical form and mixing regime on arsenic mass transfer from soil to magnetite.

PubMed

Yang, Kyung; Kim, Byung-Chul; Nam, Kyoungphile; Choi, Yongju

2017-03-01

This study investigated the effect of chemical forms of arsenic (As) and soil-magnetite mixing regimes on As mass transfer in magnetite-amended soil. Two soil samples with different component ratios of As chemical forms were prepared. In the absence of magnetite, the amount of desorbable As was strongly dependent on the fraction of easily extractable As in soil. Contact of the soils with magnetite in a slurry phase significantly reduced soil As concentration for both soils. Changes in As concentrations in soil, magnetite, and water by the slurry phase contact were simulated using an As mass transfer model. The model parameters were determined independently for each process of As soil desorption and magnetite sorption. The experimentally measured As mass transfer from soil to magnetite was significantly greater than the simulation result. By sequential extraction, it was observed that the soil As concentration was significantly reduced not only for easily extractable As, but also for relatively strongly bound forms of As. Enclosing the magnetite in a dialysis bag substantially limited the As mass transfer from soil to magnetite. These results suggest that improving the mixture between Fe oxides and soils can facilitate the effectiveness of As stabilization using Fe oxides.

Condensation heat transfer and pressure drop of R-410A in a 7.0 mm O.D. microfin tube at low mass fluxes

NASA Astrophysics Data System (ADS)

Kim, Nae-Hyun

2016-12-01

R-410A condensation heat transfer and pressure drop data are provided for a 7.0 mm O.D. microfin tube at low mass fluxes (50-250 kg/m2 s). The heat transfer coefficient of the microfin tube shows a minimum behavior with the mass flux. At a low mass flux, where flow pattern is stratified, condensation induced by surface tension by microfins overwhelms condensation induced by shear, and the heat transfer coefficient decreases as mass flux increases. At a high mass flux, where flow pattern is annular, condensation induced by shear governs the heat transfer, and the heat transfer coefficient increases as mass flux increases. The pressure drop of the microfin tube is larger than that of the smooth tube at the annular flow regime. On the contrary, the pressure drop of the smooth tube is larger than that of the microfin tube at the stratified flow regime.

Experimental assessment of heat and mass transfer of modular nozzles of cooling towers

NASA Astrophysics Data System (ADS)

Merentsov, N. A.; Lebedev, V. N.; Golovanchikov, A. B.; Balashov, V. A.; Nefed'eva, E. E.

2018-01-01

Data of experimental study of hydrodynamics, heat and mass transfer of modular nozzles of cooling towers and some comparative characteristics of the packed device with nozzles, which have wide industrial application, are given in the article.

Photometric Analysis and Modeling of Five Mass-Transferring Binary Systems

NASA Astrophysics Data System (ADS)

Geist, Emily; Beaky, Matthew; Jamison, Kate

2018-01-01

In overcontact eclipsing binary systems, both stellar components have overfilled their Roche lobes, resulting in a dumbbell-shaped shared envelope. Mass transfer is common in overcontact binaries, which can be observed as a slow change on the rotation period of the system.We studied five overcontact eclipsing binary systems with evidence of period change, and thus likely mass transfer between the components, identified by Nelson (2014): V0579 Lyr, KN Vul, V0406 Lyr, V2240 Cyg, and MS Her. We used the 31-inch NURO telescope at Lowell Observatory in Flagstaff, Arizona to obtain images in B,V,R, and I filters for V0579 Lyr, and the 16-inch Meade LX200GPS telescope with attached SBIG ST-8XME CCD camera at Juniata College in Huntingdon, Pennsylvania to image KN Vul, V0406 Lyr, V2240 Cyg, and MS Her, also in B,V,R, and I.After data reduction, we created light curves for each of the systems and modeled the eclipsing binaries using the BinaryMaker3 and PHOEBE programs to determine their fundamental physical parameters for the first time. Complete light curves and preliminary models for each of these neglected eclipsing binary systems will be presented.

The Business School in Transition: New Opportunities in Management Development, Knowledge Transfer and Knowledge Creation

ERIC Educational Resources Information Center

Harrington, Denis; Kearney, Arthur

2011-01-01

Purpose: This paper aims to consider the extent to which business school transition has created new opportunities in management development, knowledge transfer and knowledge creation. Design/methodology/approach: The paper is a critical review of knowledge exchange in a business school context with a particular focus on the "translation or…

Total solids content drives high solid anaerobic digestion via mass transfer limitation.

PubMed

Abbassi-Guendouz, Amel; Brockmann, Doris; Trably, Eric; Dumas, Claire; Delgenès, Jean-Philippe; Steyer, Jean-Philippe; Escudié, Renaud

2012-05-01

The role of the total solids (TS) content on anaerobic digestion was investigated in batch reactors. A range of TS contents from 10% to 35% was evaluated, four replicates were performed. The total methane production slightly decreased with TS concentrations increasing from 10% to 25% TS. Two behaviors were observed at 30% TS: two replicates had similar performances to that at 25% TS; for the two other replicates, the methane production was inhibited as observed at 35% TS. This difference suggested that 30% TS content corresponded to a threshold of the solids content, above which methanogenesis was strongly inhibited. The Anaerobic Digestion Model No. 1 (ADM1) was used to describe the experimental data. The effects of hydrolysis step and liquid/gas mass transfer were particularly investigated. The simulations showed that mass transfer limitation could explain the low methane production at high TS, and that hydrolysis rate constants slightly decreased with increasing TS. Copyright © 2012 Elsevier Ltd. All rights reserved.

The Effects of Reducing the Structural Mass of the Transit Habitat on the Cryogenic Propellant Required for a Human Phobos Mission

NASA Technical Reports Server (NTRS)

Zipay, John Joseph

2016-01-01

A technique for rapidly determining the relationship between the pressurized volume, structural mass and the cryogenic propellant required to be delivered to Earth orbit for a Mars Transit Habitat is provided. This technique is based on assumptions for the required delta-V's, the Exploration Upper Stage performance and the historical structural masses for human spacecraft from Mercury Program through the International Space Station. If the Mars Transit Habitat is constructed from aluminum, structural mass estimates based on the habitat pressurized volume are accurate to within 15%. Other structural material options for the Mars Transit Habitat are also evaluated. The results show that small, achievable reductions in the structural mass of the Transit Habitat can save tens of thousands of pounds of cryogenic propellant that need to be delivered to Earth orbit for a human Phobos Mission.

The Effects of Reducing the Structural Mass of the Transit Habitat on the Cryogenic Propellant Required for a Human Phobos Mission

NASA Technical Reports Server (NTRS)

Zipay, John J.

2016-01-01

A technique for rapidly determining the relationship between the pressurized volume, structural mass and the cryogenic propellant required to be delivered to Earth orbit for a Mars Transit Habitat is provided. This technique is based on assumptions for the required delta-V's, the Exploration Upper Stage performance and the historical structural masses for human spacecraft from Mercury Program through the International Space Station. If the Mars Transit Habitat is constructed from aluminum, structural mass estimates based on the habitat pressurized volume are accurate to within 15 percent. Other structural material options for the Mars Transit Habitat are also evaluated. The results show that small, achievable reductions in the structural mass of the Transit Habitat can save tens of thousands of pounds of cryogenic propellant that need to be delivered to Earth orbit for a human Phobos Mission.

Precise Masses in the WASP-47 Multi-Transiting Hot Jupiter System

NASA Astrophysics Data System (ADS)

Vanderburg, Andrew; Becker, Juliette; Buchhave, Lars A.; Mortier, Annelies; Latham, David W.; Charbonneau, David; Lopez-Morales, Mercedes; HARPS-N Collaboration

2017-06-01

We present precise radial velocity observations of WASP-47, a star known to host a hot Jupiter, a distant Jovian companion, and, uniquely, two additional transiting planets in short-period orbits: a super-Earth in a 19 hour orbit, and a Neptune in a 9 day orbit. We combine our observations, collected with the HARPS-N spectrograph, with previously published data to measure the most precise planet masses yet for this system. When combined with new stellar parameters (from analysis of the HARPS-N spectra) and a reanalysis of the transit photometry, our mass measurements yield strong constraints on the small planets’ compositions. Finally, we probabilistically constrain the orbital inclination of the outer Jovian planet through a dynamical analysis that requires the system reproduce its observed parameters.This work was supported by the National Science Foundation Graduate Research Fellowship Program. HARPS-N was funded by the Swiss Space Office, the Harvard Origin of Life Initiative, the Scottish Universities Physics Alliance, the University of Geneva, the Smithsonian Astrophysical Observatory, the Italian National Astrophysical Institute, the University of St. Andrews, Queens University Belfast, and the University of Edinburgh.

Determination of the external mass transfer coefficient and influence of mixing intensity in moving bed biofilm reactors for wastewater treatment.

PubMed

Nogueira, Bruno L; Pérez, Julio; van Loosdrecht, Mark C M; Secchi, Argimiro R; Dezotti, Márcia; Biscaia, Evaristo C

2015-09-01

In moving bed biofilm reactors (MBBR), the removal of pollutants from wastewater is due to the substrate consumption by bacteria attached on suspended carriers. As a biofilm process, the substrates are transported from the bulk phase to the biofilm passing through a mass transfer resistance layer. This study proposes a methodology to determine the external mass transfer coefficient and identify the influence of the mixing intensity on the conversion process in-situ in MBBR systems. The method allows the determination of the external mass transfer coefficient in the reactor, which is a major advantage when compared to the previous methods that require mimicking hydrodynamics of the reactor in a flow chamber or in a separate vessel. The proposed methodology was evaluated in an aerobic lab-scale system operating with COD removal and nitrification. The impact of the mixing intensity on the conversion rates for ammonium and COD was tested individually. When comparing the effect of mixing intensity on the removal rates of COD and ammonium, a higher apparent external mass transfer resistance was found for ammonium. For the used aeration intensities, the external mass transfer coefficient for ammonium oxidation was ranging from 0.68 to 13.50 m d(-1) and for COD removal 2.9 to 22.4 m d(-1). The lower coefficient range for ammonium oxidation is likely related to the location of nitrifiers deeper in the biofilm. The measurement of external mass transfer rates in MBBR will help in better design and evaluation of MBBR system-based technologies. Copyright © 2015 Elsevier Ltd. All rights reserved.

Intensification of heat and mass transfer by ultrasound: application to heat exchangers and membrane separation processes.

PubMed

Gondrexon, N; Cheze, L; Jin, Y; Legay, M; Tissot, Q; Hengl, N; Baup, S; Boldo, P; Pignon, F; Talansier, E

2015-07-01

This paper aims to illustrate the interest of ultrasound technology as an efficient technique for both heat and mass transfer intensification. It is demonstrated that the use of ultrasound results in an increase of heat exchanger performances and in a possible fouling monitoring in heat exchangers. Mass transfer intensification was observed in the case of cross-flow ultrafiltration. It is shown that the enhancement of the membrane separation process strongly depends on the physico-chemical properties of the filtered suspensions. Copyright © 2014 Elsevier B.V. All rights reserved.

Kinetic model of mass transfer through gas liquid interface in laser surface alloying

NASA Astrophysics Data System (ADS)

Gnedovets, A. G.; Portnov, O. M.; Smurov, I.; Flamant, G.

1997-02-01

In laser surface alloying from gas atmosphere neither surface concentration nor the flux of the alloying elements are known beforehand. They should be determined from the combined solution of heat and mass transfer equations with an account for the kinetics of interaction of a gas with a melt. Kinetic theory description of mass transfer through the gas-liquid interface is applied to the problem of laser surface alloying of iron from the atmosphere of molecular nitrogen. The activation nature of gas molecules dissociation at the surface is considered. It is shown that under pulsed-periodic laser action the concentration profiles of the alloying element have maxima situated close to the surface of the metal. The efficiency of surface alloying increases steeply under laser-plasma conditions which results in the formation of highly supersaturated gas solutions in the metal.

Microbial synthesis gas utilization and ways to resolve kinetic and mass-transfer limitations.

PubMed

Yasin, Muhammad; Jeong, Yeseul; Park, Shinyoung; Jeong, Jiyeong; Lee, Eun Yeol; Lovitt, Robert W; Kim, Byung Hong; Lee, Jinwon; Chang, In Seop

2015-02-01

Microbial conversion of syngas to energy-dense biofuels and valuable chemicals is a potential technology for the efficient utilization of fossils (e.g., coal) and renewable resources (e.g., lignocellulosic biomass) in an environmentally friendly manner. However, gas-liquid mass transfer and kinetic limitations are still major constraints that limit the widespread adoption and successful commercialization of the technology. This review paper provides rationales for syngas bioconversion and summarizes the reaction limited conditions along with the possible strategies to overcome these challenges. Mass transfer and economic performances of various reactor configurations are compared, and an ideal case for optimum bioreactor operation is presented. Overall, the challenges with the bioprocessing steps are highlighted, and potential solutions are suggested. Future research directions are provided and a conceptual design for a membrane-based syngas biorefinery is proposed. Copyright © 2014 Elsevier Ltd. All rights reserved.

Transitional and turbulent flat-plate boundary layers with heat transfer

NASA Astrophysics Data System (ADS)

Wu, Xiaohua; Moin, Parviz

2010-11-01

We report on our direct numerical simulation of two incompressible, nominally zero-pressure-gradient flat-plate boundary layers from momentum thickness Reynolds number 80 to 1950. Heat transfer between the constant-temperature solid surface and the free-stream is also simulated with molecular Prandtl number=1. Throughout the entire flat-plate, the ratio of Stanton number and skin-friction St/Cfdeviates from the exact Reynolds analogy value of 0.5 by less than 1.5%. Turbulent Prandtl number t peaks at the wall. Preponderance of hairpin vortices is observed in both the transitional and turbulent regions of the boundary layers. In particular, the internal structure of merged turbulent spots is hairpin forest; the internal structure of infant turbulent spots is hairpin packet. Numerous hairpin vortices are readily detected in both the near-wall and outer regions of the boundary layers up to momentum thickness Reynolds number 1950. This suggests that the hairpin vortices in the turbulent region are not simply the aged hairpin forests convected from the upstream transitional region. Temperature iso-surfaces in the companion thermal boundary layers are found to be a useful tracer in identifying hairpin vortex structures.

Freeze-drying in novel container system: Characterization of heat and mass transfer in glass syringes.

PubMed

Patel, Sajal M; Pikal, Michael J

2010-07-01

This study is aimed at characterizing and understanding different modes of heat and mass transfer in glass syringes to develop a robust freeze-drying process. Two different holder systems were used to freeze-dry in syringes: an aluminum (Al) block and a plexiglass holder. The syringe heat transfer coefficient was characterized by a sublimation test using pure water. Mannitol and sucrose (5% w/v) were also freeze-dried, as model systems, in both the assemblies. Dry layer resistance was determined from manometric temperature measurement (MTM) and product temperature was measured using thermocouples, and was also determined from MTM. Further, freeze-drying process was also designed using Smart freeze-dryer to assess its application for freeze-drying in novel container systems. Heat and mass transfer in syringes were compared against the traditional container system (i.e., glass tubing vial). In the Al block, the heat transfer was via three modes: contact conduction, gas conduction, and radiation with gas conduction being the dominant mode of heat transfer. In the plexiglass holder, the heat transfer was mostly via radiation; convection was not involved. Also, MTM/Smart freeze-drying did work reasonably well for freeze-drying in syringes. When compared to tubing vials, product temperature decreases and hence drying time increases in syringes. (c) 2010 Wiley-Liss, Inc. and the American Pharmacists Association

Technical characterization of dialysis fluid flow and mass transfer rate in dialyzers with various filtration coefficients using dimensionless correlation equation.

PubMed

Fukuda, Makoto; Yoshimura, Kengo; Namekawa, Koki; Sakai, Kiyotaka

2017-06-01

The objective of the present study is to evaluate the effect of filtration coefficient and internal filtration on dialysis fluid flow and mass transfer coefficient in dialyzers using dimensionless mass transfer correlation equations. Aqueous solution of vitamin B 12 clearances were obtained for REXEED-15L as a low flux dialyzer, and APS-15EA and APS-15UA as high flux dialyzers. All the other design specifications were identical for these dialyzers except for filtration coefficient. The overall mass transfer coefficient was calculated, moreover, the exponents of Reynolds number (Re) and film mass transfer coefficient of the dialysis-side fluid (k D ) for each flow rate were derived from the Wilson plot and dimensionless correlation equation. The exponents of Re were 0.4 for the low flux dialyzer whereas 0.5 for the high flux dialyzers. Dialysis fluid of the low flux dialyzer was close to laminar flow because of its low filtration coefficient. On the other hand, dialysis fluid of the high flux dialyzers was assumed to be orthogonal flow. Higher filtration coefficient was associated with higher k D influenced by mass transfer rate through diffusion and internal filtration. Higher filtration coefficient of dialyzers and internal filtration affect orthogonal flow of dialysis fluid.

Mass Transit: Grants Management Oversight Improving, but Better Follow-Up Needed on Grantees' Noncompliance

DOT National Transportation Integrated Search

1998-04-01

The Department of Transportation's (DOT's) Federal Transit Administration (FTA) administers a multibillion-dollar program of financial assistance for grantees that provide urban and rural public mass transportation. In 1992, the General Accounting Of...

Evaluation of the mass transfer process on thin layer drying of papaya seeds from the perspective of diffusive models

NASA Astrophysics Data System (ADS)

Dotto, Guilherme Luiz; Meili, Lucas; Tanabe, Eduardo Hiromitsu; Chielle, Daniel Padoin; Moreira, Marcos Flávio Pinto

2018-02-01

The mass transfer process that occurs in the thin layer drying of papaya seeds was studied under different conditions. The external mass transfer resistance and the dependence of effective diffusivity ( D EFF ) in relation to the moisture ratio ( \\overline{MR} ) and temperature ( T) were investigated from the perspective of diffusive models. It was verified that the effective diffusivity was affected by the moisture content and temperature. A new correlation was proposed for drying of papaya seeds in order to describe these influences. Regarding the use of diffusive models, the results showed that, at conditions of low drying rates ( T ≤ 70 °C), the external mass transfer resistance, as well as the dependence of the effective diffusivity with respect to the temperature and moisture content should be considered. At high drying rates ( T > 90 °C), the dependence of the effective diffusivity with respect to the temperature and moisture content can be neglected, but the external mass transfer resistance was still considerable in the range of air velocities used in this work.

Heat and Mass Transfer in a Falling Film Evaporator with Aqueous Lithium Bromide Solution

NASA Astrophysics Data System (ADS)

Olbricht, M.; Addy, J.; Luke, A.

2016-09-01

Horizontal tube bundles are often used as falling film evaporators in absorption chillers, especially for systems working at low pressure as H2O/LiBr. Experimental investigations are carried out in a falling film evaporator consisting of a horizontal tube bundle with eighty horizontal tubes installed in an absorption chiller because of a lack of consistent data for heat and mass transfer in the literature. The heat and mass transfer mechanisms and the flow pattern in the falling film are analysed and compared with correlations from literature. The deviations of the experimental data from those of the correlations are within a tolerance of 30%. These deviations may be explained by a change of the flow pattern at a lower Reynolds number than compared to the literature.

Absolute Properties of the Pulsating Post-mass Transfer Eclipsing Binary OO Draconis

NASA Astrophysics Data System (ADS)

Lee, Jae Woo; Hong, Kyeongsoo; Koo, Jae-Rim; Park, Jang-Ho

2018-01-01

OO Dra is a short-period Algol system with a δ Sct-like pulsator. We obtained time-series spectra between 2016 February and May to derive the fundamental parameters of the binary star and to study its evolutionary scenario. The radial velocity (RV) curves for both components were presented, and the effective temperature of the hotter and more massive primary was determined to be {T}{eff,1}=8260+/- 210 K by comparing the disentangling spectrum and the Kurucz models. Our RV measurements were solved with the BV light curves of Zhang et al. using the Wilson-Devinney binary code. The absolute dimensions of each component are determined as follows: M 1 = 2.03 ± 0.06 {M}⊙ , M 2 = 0.19 ± 0.01 {M}⊙ , R 1 = 2.08 ± 0.03 {R}⊙ , R 2 = 1.20 ± 0.02 {R}⊙ , L 1 = 18 ± 2 {L}⊙ , and L 2 = 2.0 ± 0.2 {L}⊙ . Comparison with stellar evolution models indicated that the primary star resides inside the δ Sct instability strip on the main sequence, while the cool secondary component is noticeably overluminous and oversized. We demonstrated that OO Dra is an oscillating post-mass transfer R CMa-type binary; the originally more massive star became the low-mass secondary component through mass loss caused by stellar wind and mass transfer, and the gainer became the pulsating primary as the result of mass accretion. The R CMa stars, such as OO Dra, are thought to have formed by non-conservative binary evolution and ultimately to evolve into EL CVn stars.

Large impact of reorganization energy on photovoltaic conversion due to interfacial charge-transfer transitions.

PubMed

Fujisawa, Jun-ichi

2015-05-14

Interfacial charge-transfer (ICT) transitions are expected to be a novel charge-separation mechanism for efficient photovoltaic conversion featuring one-step charge separation without energy loss. Photovoltaic conversion due to ICT transitions has been investigated using several TiO2-organic hybrid materials that show organic-to-inorganic ICT transitions in the visible region. In applications of ICT transitions to photovoltaic conversion, there is a significant problem that rapid carrier recombination is caused by organic-inorganic electronic coupling that is necessary for the ICT transitions. In order to solve this problem, in this work, I have theoretically studied light-to-current conversions due to the ICT transitions on the basis of the Marcus theory with density functional theory (DFT) and time-dependent DFT (TD-DFT) calculations. An apparent correlation between the reported incident photon-to-current conversion efficiencies (IPCE) and calculated reorganization energies was clearly found, in which the IPCE increases with decreasing the reorganization energy consistent with the Marcus theory in the inverted region. This activation-energy dependence was systematically explained by the equation formulated by the Marcus theory based on a simple excited-state kinetic scheme. This result indicates that the reduction of the reorganization energy can suppress the carrier recombination and enhance the IPCE. The reorganization energy is predominantly governed by the structural change in the chemical-adsorption moiety between the ground and ICT excited states. This work provides crucial knowledge for efficient photovoltaic conversion due to ICT transitions.

Unbiased Inference of the Masses of Transiting Planets from Radial Velocity Follow-up

NASA Astrophysics Data System (ADS)

Montet, Benjamin T.

2018-05-01

Data from the TESS mission will be used to discover hundreds of small planets amenable to radial velocity (RV) followup. Often, RV observations are obtained until a particular fractional precision on the inferred mass is achieved. I show that when the decision to stop collecting RV observations depends on the mass inferred from already-collected data, this will bias mass measurements upward, particularly when the fixed length of RV observing campaigns is considered. I suggest that observing teams should determine their observing strategy for each star before any data are collected, and all stopping criteria should not directly depend on the inferred mass. Observing teams should explicitly publish both their criteria for observing targets and deciding to end their observations, as well as their mass non-detections to avoid introducing biases into the masses---and thus inferences on the densities, compositions, and atmospheres---of transiting planets.

Combined effects of heat and mass transfer to magneto hydrodynamics oscillatory dusty fluid flow in a porous channel

NASA Astrophysics Data System (ADS)

Govindarajan, A.; Vijayalakshmi, R.; Ramamurthy, V.

2018-04-01

The main aim of this article is to study the combined effects of heat and mass transfer to radiative Magneto Hydro Dynamics (MHD) oscillatory optically thin dusty fluid in a saturated porous medium channel. Based on certain assumptions, the momentum, energy, concentration equations are obtained.The governing equations are non-dimensionalised, simplified and solved analytically. The closed analytical form solutions for velocity, temperature, concentration profiles are obtained. Numerical computations are presented graphically to show the salient features of various physical parameters. The shear stress, the rate of heat transfer and the rate of mass transfer are also presented graphically.

Origin of Self-preservation Effect for Hydrate Decomposition: Coupling of Mass and Heat Transfer Resistances

PubMed Central

Bai, Dongsheng; Zhang, Diwei; Zhang, Xianren; Chen, Guangjin

2015-01-01

Gas hydrates could show an unexpected high stability at conditions out of thermodynamic equilibrium, which is called the self-preservation effect. The mechanism of the effect for methane hydrates is here investigated via molecular dynamics simulations, in which an NVT/E method is introduced to represent different levels of heat transfer resistance. Our simulations suggest a coupling between the mass transfer resistance and heat transfer resistance as the driving mechanism for self-preservation effect. We found that the hydrate is initially melted from the interface, and then a solid-like water layer with temperature-dependent structures is formed next to the hydrate interface that exhibits fractal feature, followed by an increase of mass transfer resistance for the diffusion of methane from hydrate region. Furthermore, our results indicate that heat transfer resistance is a more fundamental factor, since it facilitates the formation of the solid-like layer and hence inhibits the further dissociation of the hydrates. The self-preservation effect is found to be enhanced with the increase of pressure and particularly the decrease of temperature. Kinetic equations based on heat balance calculations is also developed to describe the self-preservation effect, which reproduces our simulation results well and provides an association between microscopic and macroscopic properties. PMID:26423519

Origin of Self-preservation Effect for Hydrate Decomposition: Coupling of Mass and Heat Transfer Resistances.

PubMed

Bai, Dongsheng; Zhang, Diwei; Zhang, Xianren; Chen, Guangjin

2015-10-01

Gas hydrates could show an unexpected high stability at conditions out of thermodynamic equilibrium, which is called the self-preservation effect. The mechanism of the effect for methane hydrates is here investigated via molecular dynamics simulations, in which an NVT/E method is introduced to represent different levels of heat transfer resistance. Our simulations suggest a coupling between the mass transfer resistance and heat transfer resistance as the driving mechanism for self-preservation effect. We found that the hydrate is initially melted from the interface, and then a solid-like water layer with temperature-dependent structures is formed next to the hydrate interface that exhibits fractal feature, followed by an increase of mass transfer resistance for the diffusion of methane from hydrate region. Furthermore, our results indicate that heat transfer resistance is a more fundamental factor, since it facilitates the formation of the solid-like layer and hence inhibits the further dissociation of the hydrates. The self-preservation effect is found to be enhanced with the increase of pressure and particularly the decrease of temperature. Kinetic equations based on heat balance calculations is also developed to describe the self-preservation effect, which reproduces our simulation results well and provides an association between microscopic and macroscopic properties.

Near-infrared Variability in the 2MASS Calibration Fields: A Search for Planetary Transit Candidates

NASA Technical Reports Server (NTRS)

Plavchan, Peter; Jura, M.; Kirkpatrick, J. Davy; Cutri, Roc M.; Gallagher, S. C.

2008-01-01

The Two Micron All Sky Survey (2MASS) photometric calibration observations cover approximately 6 square degrees on the sky in 35 'calibration fields,' each sampled in nominal photometric conditions between 562 and 3692 times during the 4 years of the 2MASS mission. We compile a catalog of variables from the calibration observations to search for M dwarfs transited by extrasolar planets. We present our methods for measuring periodic and nonperiodic flux variability. From 7554 sources with apparent K(sub s) magnitudes between 5.6 and 16.1, we identify 247 variables, including extragalactic variables and 23 periodic variables. We have discovered three M dwarf eclipsing systems, including two candidates for transiting extrasolar planets.

Performance Technology Program (PTP-S 2). Volume 9: Evaluation of reentry vehicle nosetip transition and heat transfer in the AEDC hyperballistics track G

NASA Astrophysics Data System (ADS)

Wassel, A. T.; Shih, W. C. L.; Curtis, R. J.

1981-01-01

Boundary layer transition and surface heating distributions on graphite fine weave carbon-carbon, and metallic nosetip materials were derived from surface temperature responses measured in nitrogen environments during both free-flight and track-guided testing in the AEDC Hyperballistics Range/Track G. Innovative test procedures were developed, and heat transfer results were validated against established theory through experiments using a super-smooth tungsten model. Quantitative definitions of mean transition front locations were established by deriving heat flux distributions from measured temperatures, and comparisons made with existing nosetip transition correlations. Qualitative transition locations were inferred directly from temperature distributions to investigate preferred orientations on fine weave nosetips. Levels of roughness augmented heat transfer were generally shown to be below values predicted by state of the art methods.

Advanced subgrid-scale modeling for convection-dominated species transport at fluid interfaces with application to mass transfer from rising bubbles

NASA Astrophysics Data System (ADS)

Weiner, Andre; Bothe, Dieter

2017-10-01

This paper presents a novel subgrid scale (SGS) model for simulating convection-dominated species transport at deformable fluid interfaces. One possible application is the Direct Numerical Simulation (DNS) of mass transfer from rising bubbles. The transport of a dissolving gas along the bubble-liquid interface is determined by two transport phenomena: convection in streamwise direction and diffusion in interface normal direction. The convective transport for technical bubble sizes is several orders of magnitude higher, leading to a thin concentration boundary layer around the bubble. A true DNS, fully resolving hydrodynamic and mass transfer length scales results in infeasible computational costs. Our approach is therefore a DNS of the flow field combined with a SGS model to compute the mass transfer between bubble and liquid. An appropriate model-function is used to compute the numerical fluxes on all cell faces of an interface cell. This allows to predict the mass transfer correctly even if the concentration boundary layer is fully contained in a single cell layer around the interface. We show that the SGS-model reduces the resolution requirements at the interface by a factor of ten and more. The integral flux correction is also applicable to other thin boundary layer problems. Two flow regimes are investigated to validate the model. A semi-analytical solution for creeping flow is used to assess local and global mass transfer quantities. For higher Reynolds numbers ranging from Re = 100 to Re = 460 and Péclet numbers between Pe =104 and Pe = 4 ṡ106 we compare the global Sherwood number against correlations from literature. In terms of accuracy, the predicted mass transfer never deviates more than 4% from the reference values.

Mass Transfer from Gas Bubbles to Impinging Flow of Biological Fluids with Chemical Reaction

PubMed Central

Yang, Wen-Jei; Echigo, R.; Wotton, D. R.; Ou, J. W.; Hwang, J. B.

1972-01-01

The rates of mass transfer from a gas bubble to an impinging flow of a biological fluid such as whole blood and plasma are investigated analytically and experimentally. Gases commonly found dissolved in body fluids are included. Consideration is given to the effects of the chemical reaction between the dissolved gas and the liquid on the rate of mass transfer. Through the application of boundary layer theory the over-all transfer is found to be Sh/(Re)1/2 = 0.845 Sc1/3 in the absence of chemical reaction, and Sh/(Re) 1/2 = F′ (0) in the presence of chemical reaction, where Sh, Re, and Sc are the Sherwood, Reynolds, and Schmidt numbers, respectively, and F′ (0) is a function of Sc and the dimensionless reaction rate constant. Analytical results are also obtained for the bubble lifetime and the bubble radius-time history. These results, which are not incompatible with experimental results, can be applied to predict the dissolution of the entrapped gas emboli in the circulatory system of the human body. PMID:4642218

An inverse gas chromatographic methodology for studying gas-liquid mass transfer.

PubMed

Paloglou, A; Martakidis, K; Gavril, D

2017-01-13

A novel methodology of reversed flow inverse gas chromatography (RF-IGC) is presented. It permits the simultaneous determination of mass transfer coefficients across the gas liquid interface as well as the respective solubility parameters and thermodynamic functions of dissolution of gases into liquids. The standard deviation of the experimentally determined parameters is estimated for first time, which combined with the successful comparison of the values of the present parameters with other literature ones ascertain the reliability of the methodology. Another novelty of the present work is that the chromatographic sampling of the physicochemical phenomena is done without performing the usual flow reversals procedure. Vinyl chloride monomer's (VCM) interaction with various composition liquid foods: orange juice, milk and olive oil was used as model system. The present transfer rates are controlled by the gas film at lower temperatures, but at higher temperatures the resistances in both films tend to become equal. The found liquid diffusivity values express the total mass transfer from the gas phase into the liquid's bulk and they decrease with rising temperature, as the solubilities of gases in liquids do. Solubility, expressed by Henry's law constant and the mean values of interfacial thickness are of the same order of magnitude to literature ones. From the thermodynamic point of view, VCM dissolution in all liquids is accompanied by significant heat release and it is a slightly non-spontaneous process, near equilibrium, while the entropy change values are negative. Copyright © 2016 Elsevier B.V. All rights reserved.

Mixing and solid-liquid mass-transfer rates in a creusot-loire uddeholm vessel: A water model case study

NASA Astrophysics Data System (ADS)

Nyoka, M.; Akdogan, G.; Eric, R. H.; Sutcliffe, N.

2003-12-01

The process of mixing and solid-liquid mass transfer in a one-fifth scale water model of a 100-ton Creusot-Loire Uddeholm (CLU) converter was investigated. The modified Froude number was used to relate gas flow rates between the model and its protoype. The influences of gas flow rate between 0.010 and 0.018 m3/s and bath height from 0.50 to 0.70 m on mixing time were examined. The results indicated that mixing time decreased with increasing gas flow rate and increased with increasing bath height. The mixing time results were evaluated in terms of specific energy input and the following correlation was proposed for estimating mixing times in the model CLU converter: T mix=1.08Q -1.05 W 0.35, where Q (m3/s) is the gas flow rate and W (tons) is the model bath weight. Solid-liquid mass-transfer rates from benzoic acid specimens immersed in the gas-agitated liquid phase were assessed by a weight loss measurement technique. The calculated mass-transfer coefficients were highest at the bath surface reaching a value of 6.40 × 10-5 m/s in the sprout region. Mass-transfer coefficients and turbulence parameters decreased with depth, reaching minimum values at the bottom of the vessel.

Heat transfer investigation of Langley Research Center transition models at a Mach number of 8, volume 2

NASA Technical Reports Server (NTRS)

Matthews, R. K.; Martindale, W. R.; Warmbrod, J. D.; Johnson, C. B.

1972-01-01

The results are presented of a wind tunnel test program to determine aerodynamic heat transfer distributions on delta body and straight body transition models of the space shuttle. Heat transfer rates were determined by the phase-change paint technique on Stycast and RTV models using Tempilag as the surface temperature indicator. The nominal test conditions were: Mach 8, length Reynolds numbers of 5 million and 7.4 million, and angles of attack of 20, 40, and 60 deg. Model details, test conditions, and reduced heat transfer data are included. Data reduction of the phase-change paint photographs was performed by utilizing a new technique.

Experimental investigation of the heat and mass transfer in a tube bundle absorber of an absorption chiller

NASA Astrophysics Data System (ADS)

Olbricht, Michael; Luke, Andrea

2018-05-01

The design of the absorber of absorption chillers is still subject to great uncertainty since the coupled processes of heat and mass transfer as well as the influence of systemic interactions on the absorption process are not fully understood. Unfortunately, only a few investigations on the transport phenomena in the absorber during operation in an absorption chiller are reported in the literature. Therefore, experimental investigations on the heat and mass transfer during falling film absorption of steam in aqueous LiBr-solution are carried out in an absorber installed in an absorption chiller in this work. An improvement of heat and mass transfer due to the increase in convective effects are observed as the Ref number increases. Furthermore, an improvement of the heat transfer in the absorber with increasing coolant temperature can be identified in the systemic context. This is explained by a corresponding reduction in the average viscosity of the solution in the absorber. A comparison with experimental data from literature obtained from so-called absorber-generator test rigs shows a good consistency. Thus, it has been shown that the findings obtained on these simplified experimental setups can be transferred to the absorber in an absorption chiller. However, a comparison with correlations from the literature reveals a strong deviation between experimental and calculated results. Hence, further research activities on the development of better correlations are required in future.

A Search for Transiting Neptune-Mass Extrasolar Planets in High-Precision Photometry of Solar-Type Stars

NASA Technical Reports Server (NTRS)

Henry, Stephen M.; Gillman, Amelie r.; Henry, Gregory W.

2005-01-01

Tennessee State University operates several automatic photometric telescopes (APTs) at Fairborn Observatory in southern Arizona. Four 0.8 m APTs have been dedicated to measuring subtle luminosity variations that accompany magnetic cycles in solar-type stars. Over 1000 program and comparison stars have been observed every clear night in this program for up to 12 years with a precision of approximately 0.0015 mag for a single observation. We have developed a transit-search algorithm, based on fitting a computed transit template for each trial period, and have used it to search our photometric database for transits of unknown companions. Extensive simulations with the APT data have shown that we can reliably recover transits with periods under 10 days as long as the transits have a depth of at least 0.0024 mag, or about 1.6 times the scatter in the photometric observations. Thus, due to our high photometric precision, we are sensitive to transits of possible short-period Neptune-mass planets that likely would have escaped detection by current radial velocity techniques. Our search of the APT data sets for 1087 program and comparison stars revealed no new transiting planets. However, the detection of several unknown grazing eclipsing binaries from among our comparison stars, with eclipse depths of only a few millimags, illustrates the success of our technique. We have used this negative result to place limits on the frequency of Neptune-mass planets in close orbits around solar-type stars in the Sun's vicinity.

Mass correlation between light and heavy reaction products in multinucleon transfer 197Au+130Te collisions

NASA Astrophysics Data System (ADS)

Galtarossa, F.; Corradi, L.; Szilner, S.; Fioretto, E.; Pollarolo, G.; Mijatović, T.; Montanari, D.; Ackermann, D.; Bourgin, D.; Courtin, S.; Fruet, G.; Goasduff, A.; Grebosz, J.; Haas, F.; Jelavić Malenica, D.; Jeong, S. C.; Jia, H. M.; John, P. R.; Mengoni, D.; Milin, M.; Montagnoli, G.; Scarlassara, F.; Skukan, N.; Soić, N.; Stefanini, A. M.; Strano, E.; Tokić, V.; Ur, C. A.; Valiente-Dobón, J. J.; Watanabe, Y. X.

2018-05-01

We studied multinucleon transfer reactions in the 197Au+130Te system at Elab=1.07 GeV by employing the PRISMA magnetic spectrometer coupled to a coincident detector. For each light fragment we constructed, in coincidence, the distribution in mass of the heavy partner of the reaction. With a Monte Carlo method, starting from the binary character of the reaction, we simulated the de-excitation process of the produced heavy fragments to be able to understand their final mass distribution. The total cross sections for pure neutron transfer channels have also been extracted and compared with calculations performed with the grazing code.

Bio-inspired Murray materials for mass transfer and activity

PubMed Central

Zheng, Xianfeng; Shen, Guofang; Wang, Chao; Li, Yu; Dunphy, Darren; Hasan, Tawfique; Brinker, C. Jeffrey; Su, Bao-Lian

2017-01-01

Both plants and animals possess analogous tissues containing hierarchical networks of pores, with pore size ratios that have evolved to maximize mass transport and rates of reactions. The underlying physical principles of this optimized hierarchical design are embodied in Murray's law. However, we are yet to realize the benefit of mimicking nature's Murray networks in synthetic materials due to the challenges in fabricating vascularized structures. Here we emulate optimum natural systems following Murray's law using a bottom-up approach. Such bio-inspired materials, whose pore sizes decrease across multiple scales and finally terminate in size-invariant units like plant stems, leaf veins and vascular and respiratory systems provide hierarchical branching and precise diameter ratios for connecting multi-scale pores from macro to micro levels. Our Murray material mimics enable highly enhanced mass exchange and transfer in liquid–solid, gas–solid and electrochemical reactions and exhibit enhanced performance in photocatalysis, gas sensing and as Li-ion battery electrodes. PMID:28382972

Kinetics and mass-transfer phenomena in anaerobic granular sludge.

PubMed

Gonzalez-Gil, G; Seghezzo, L; Lettinga, G; Kleerebezem, R

2001-04-20

The kinetic properties of acetate-degrading methanogenic granular sludge of different mean diameters were assessed at different up-flow velocities (V(up)). Using this approach, the influence of internal and external mass transfer could be estimated. First, the apparent Monod constant (K(S)) for each data set was calculated by means of a curve-fitting procedure. The experimental results revealed that variations in the V(up) did not affect the apparent K(S)-value, indicating that external mass-transport resistance normally can be neglected. With regard to the granule size, a clear increase in K(S) was found at increasing granule diameters. The experimental data were further used to validate a dynamic mathematical biofilm model. The biofilm model was able to describe reaction-diffusion kinetics in anaerobic granules, using a single value for the effective diffusion coefficient in the granules. This suggests that biogas formation did not influence the diffusion-rates in the granular biomass. Copyright 2001 John Wiley & Sons, Inc.

Bio-inspired Murray materials for mass transfer and activity

NASA Astrophysics Data System (ADS)

Zheng, Xianfeng; Shen, Guofang; Wang, Chao; Li, Yu; Dunphy, Darren; Hasan, Tawfique; Brinker, C. Jeffrey; Su, Bao-Lian

2017-04-01

Both plants and animals possess analogous tissues containing hierarchical networks of pores, with pore size ratios that have evolved to maximize mass transport and rates of reactions. The underlying physical principles of this optimized hierarchical design are embodied in Murray's law. However, we are yet to realize the benefit of mimicking nature's Murray networks in synthetic materials due to the challenges in fabricating vascularized structures. Here we emulate optimum natural systems following Murray's law using a bottom-up approach. Such bio-inspired materials, whose pore sizes decrease across multiple scales and finally terminate in size-invariant units like plant stems, leaf veins and vascular and respiratory systems provide hierarchical branching and precise diameter ratios for connecting multi-scale pores from macro to micro levels. Our Murray material mimics enable highly enhanced mass exchange and transfer in liquid-solid, gas-solid and electrochemical reactions and exhibit enhanced performance in photocatalysis, gas sensing and as Li-ion battery electrodes.

Exposure chamber measurements of mass transfer and partitioning at the plant/air interface.

PubMed

Maddalena, Randy L; McKone, Thomas E; Kado, Norman Y

2002-08-15

Dynamic measures of air and vegetation concentrations in an exposure chamber and a two-box mass balance model are used to quantify factors that control the rate and extent of chemical partitioning between vegetation and the atmosphere. A continuous stirred flow-through exposure chamber was used to investigate the gas-phase transfer of pollutants between air and plants. A probabilistic two-compartment mass balance model of plant/air exchange within the exposure chamber was developed and used with measured concentrations from the chamber to simultaneously evaluate partitioning (Kpa), overall mass transfer across the plant/air interface (Upa), and loss rates in the atmosphere (Ra) and aboveground vegetation (Rp). The approach is demonstrated using mature Capsicum annuum (bell pepper) plants exposed to phenanthrene (PH), anthracene (AN), fluoranthene (FL) and pyrene (PY). Measured values of log Kpa (V[air]/V[fresh plant]) were 5.7, 5.7, 6.0, and 6.2 for PH, AN, FL, and PY, respectively. Values of Upa (m d(-1)) under the conditions of this study ranged from 42 for PH to 119 for FL. After correcting for wall effects, the estimated reaction half-lives in air were 3, 9, and 25 h for AN, FL and PY. Reaction half-lives in the plant compartment were 17, 6, 17, and 5 d for PH, AN, FL, and PY, respectively. The combined use of exposure chamber measurements and models provides a robust tool for simultaneously measuring several different transfer factors that are important for modeling the uptake of pollutants into vegetation.

Primeval very low-mass stars and brown dwarfs - III. The halo transitional brown dwarfs

NASA Astrophysics Data System (ADS)

Zhang, Z. H.; Pinfield, D. J.; Gálvez-Ortiz, M. C.; Homeier, D.; Burgasser, A. J.; Lodieu, N.; Martín, E. L.; Osorio, M. R. Zapatero; Allard, F.; Jones, H. R. A.; Smart, R. L.; Martí, B. López; Burningham, B.; Rebolo, R.

2018-05-01

We report the discovery of an esdL3 subdwarf, ULAS J020858.62+020657.0 and a usdL4.5 subdwarf, ULAS J230711.01+014447.1. They were identified as L subdwarfs by optical spectra obtained with the Gran Telescopio Canarias, and followed up by optical to near infrared spectroscopy with the Very Large Telescope. We also obtained an optical to near infrared spectrum of a previously known L subdwarf, ULAS J135058.85+081506.8, and re-classified it as a usdL3 subdwarf. These three objects all have typical halo kinematics. They have Teff around 2050-2250 K, -1.8 ≤ [Fe/H] ≤-1.5, and mass around 0.0822-0.0833 M⊙, according to model spectral fitting and evolutionary models. These sources are likely halo transitional brown dwarfs with unsteady hydrogen fusions, as their masses are just below the hydrogen-burning minimum mass, which is ˜ 0.0845 M⊙ at [Fe/H] = -1.6 and ˜ 0.0855 M⊙ at [Fe/H] = -1.8. Including these, there are now nine objects in the `halo brown dwarf transition zone', which is a `substellar subdwarf gap' spans a wide temperature range within a narrow mass range of the substellar population.

Examination of the Mass Transfer of Additive Elements in Barium Titanate Ceramics during Sintering Process by Laser Ablation ICP-MS.

PubMed

Sakate, Daisuke; Iwazaki, Yoshiki; Kon, Yoshiaki; Yokoyama, Takaomi; Ohata, Masaki

2018-01-01

The mass transfer of additive elements during the sintering of barium titanate (BaTiO 3 ) ceramic was examined by laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) in the present study. An analytical sample consisting of two pellets of BaTiO 3 with different concentrations of additive elements of manganese (Mn) and holmium (Ho) as well as silicon (Si) as a sintering reagent was prepared and measured by LA-ICP-MS with small laser irradiated diameter of 10 μm to evaluate the distributions and concentrations of additive elements in order to examine their mass transfers. As results, enrichments of Mn and Si as an additive element and a sintering reagent, respectively, were observed on the adhesive surface between two BaTiO 3 pellets, even though Ho did not show a similar phenomenon. The mass transfers of additive elements of Mn and Ho were also examined, and Mn seemed to show a larger mass transfer than that of Ho during the sintering process for BaTiO 3 ceramics. The results obtained in this study shows the effectives of LA-ICP-MS for the future improvement of MLCCs.

On computational experiments in some inverse problems of heat and mass transfer

NASA Astrophysics Data System (ADS)

Bilchenko, G. G.; Bilchenko, N. G.

2016-11-01

The results of mathematical modeling of effective heat and mass transfer on hypersonic aircraft permeable surfaces are considered. The physic-chemical processes (the dissociation and the ionization) in laminar boundary layer of compressible gas are appreciated. Some algorithms of control restoration are suggested for the interpolation and approximation statements of heat and mass transfer inverse problems. The differences between the methods applied for the problem solutions search for these statements are discussed. Both the algorithms are realized as programs. Many computational experiments were accomplished with the use of these programs. The parameters of boundary layer obtained by means of the A.A.Dorodnicyn's generalized integral relations method from solving the direct problems have been used to obtain the inverse problems solutions. Two types of blowing laws restoration for the inverse problem in interpolation statement are presented as the examples. The influence of the temperature factor on the blowing restoration is investigated. The different character of sensitivity of controllable parameters (the local heat flow and local tangent friction) respectively to step (discrete) changing of control (the blowing) and the switching point position is studied.

Identifying and overcoming the effect of mass transfer limitation on decreased yield in enzymatic hydrolysis of lignocellulose at high solid concentrations.

PubMed

Du, Jian; Cao, Yuan; Liu, Guodong; Zhao, Jian; Li, Xuezhi; Qu, Yinbo

2017-04-01

Cellulose conversion decreases significantly with increasing solid concentrations during enzymatic hydrolysis of insoluble lignocellulosic materials. Here, mass transfer limitation was identified as a significant determining factor of this decrease by studying the hydrolysis of delignified corncob residue in shake flask, the most used reaction vessel in bench scale. Two mass transfer efficiency-related factors, mixing speed and flask filling, were shown to correlate closely with cellulose conversion at solid loadings higher than 15% DM. The role of substrate characteristics in mass transfer performance was also significant, which was revealed by the saccharification of two corn stover substrates with different pretreatment methods at the same solid loading. Several approaches including premix, fed-batch operation, and particularly the use of horizontal rotating reactor were shown to be valid in facilitating cellulose conversion via improving mass transfer efficiency at solid concentrations higher than 15% DM. Copyright © 2017 Elsevier Ltd. All rights reserved.

Photocarrier generation from interlayer charge-transfer transitions in WS2-graphene heterostructures

PubMed Central

Yuan, Long; Chung, Ting-Fung; Kuc, Agnieszka; Wan, Yan; Xu, Yang; Chen, Yong P.; Heine, Thomas; Huang, Libai

2018-01-01

Efficient interfacial carrier generation in van der Waals heterostructures is critical for their electronic and optoelectronic applications. We demonstrate broadband photocarrier generation in WS2-graphene heterostructures by imaging interlayer coupling–dependent charge generation using ultrafast transient absorption microscopy. Interlayer charge-transfer (CT) transitions and hot carrier injection from graphene allow carrier generation by excitation as low as 0.8 eV below the WS2 bandgap. The experimentally determined interlayer CT transition energies are consistent with those predicted from the first-principles band structure calculation. CT interactions also lead to additional carrier generation in the visible spectral range in the heterostructures compared to that in the single-layer WS2 alone. The lifetime of the charge-separated states is measured to be ~1 ps. These results suggest that interlayer interactions make graphene–two-dimensional semiconductor heterostructures very attractive for photovoltaic and photodetector applications because of the combined benefits of high carrier mobility and enhanced broadband photocarrier generation. PMID:29423439

Nationwide examples of state and local funds for mass transit : final report, December 2008.

DOT National Transportation Integrated Search

2008-12-04

One of the transportation challenges facing Texas is the identification of adequate funding for : mobility projects. During the 80th Texas Legislature, several proposals were made to address : mass transit funding for the metropolitan areas of the st...

A surface renewal model for unsteady-state mass transfer using the generalized Danckwerts age distribution function.

PubMed

Horvath, Isabelle R; Chatterjee, Siddharth G

2018-05-01

The recently derived steady-state generalized Danckwerts age distribution is extended to unsteady-state conditions. For three different wind speeds used by researchers on air-water heat exchange on the Heidelberg Aeolotron, calculations reveal that the distribution has a sharp peak during the initial moments, but flattens out and acquires a bell-shaped character with process time, with the time taken to attain a steady-state profile being a strong and inverse function of wind speed. With increasing wind speed, the age distribution narrows significantly, its skewness decreases and its peak becomes larger. The mean eddy renewal time increases linearly with process time initially but approaches a final steady-state value asymptotically, which decreases dramatically with increased wind speed. Using the distribution to analyse the transient absorption of a gas into a large body of liquid, assuming negligible gas-side mass-transfer resistance, estimates are made of the gas-absorption and dissolved-gas transfer coefficients for oxygen absorption in water at 25°C for the three different wind speeds. Under unsteady-state conditions, these two coefficients show an inverse behaviour, indicating a heightened accumulation of dissolved gas in the surface elements, especially during the initial moments of absorption. However, the two mass-transfer coefficients start merging together as the steady state is approached. Theoretical predictions of the steady-state mass-transfer coefficient or transfer velocity are in fair agreement (average absolute error of prediction = 18.1%) with some experimental measurements of the same for the nitrous oxide-water system at 20°C that were made in the Heidelberg Aeolotron.

Heat and Mass Transfer in the Over-Shower Zone of a Cooling Tower with Flow Rotation

NASA Astrophysics Data System (ADS)

Kashani, M. M. Hemmasian; Dobrego, K. V.

2013-11-01

The influence of flow rotation in the over-shower zone of a natural draft wet cooling tower (NDCT) on heat and mass transfer in this zone is investigated numerically. The 3D geometry of an actual NDCT and three models of the induced rotation velocity fields are utilized for calculations. Two phases (liquid and gaseous) and three components are taken into consideration. The interphase heat exchange, heat transfer to the walls, condensation-evaporation intensity field, and other parameters are investigated as functions of the induced rotation intensity (the inclination of the velocity vector at the periphery). It is shown that the induced flow rotation intensifies the heat and mass transfer in the over-shower zone of an NDCT. Flow rotation leads to specific redistribution of evaporation-condensation areas in an NDCT and stimulates water condensation near its walls.

Transition and Transfer of Remediated Formerly Utilized Sites Remedial Action Program (FUSRAP) Sites from U.S. Army Corps of Engineers (USACE) to U.S. Department of Energy (DOE)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Carpenter, Cliff; Castillo, Darina; Fatherly, Nicki

The US Department of Energy (DOE) expects to receive the transfer of 10 FUSRAP Sites from the US Army Corps of Engineers (USACE) over the next 10 years; however, the timing of the transfers is highly dependent upon federal funding of the ongoing remedial actions. When remediation for each site is complete and the 2-year operations and maintenance period has concluded, each site will transfer from USACE to DOE for long-term surveillance and maintenance (LTS&M). US DOE’s Office of Legacy Management (LM) will accept program responsibility for these sites and conduct LTS&M activities required to maintain protectiveness, preserve site-specific knowledge,more » and retain the cleanup and stewardship records while keeping stakeholders informed. Since the last FUSRAP site transfer occurred in 2007, LM in coordination with USACE intends to establish a transition process to promote the seamless transfer of sites from the time when the first record of decision is signed to the completion of FUSRAP activities. The approach to transfer active FUSRAP sites to completed sites status has been historically outlined in foundational documents such as the 1999 Memorandum of Understanding and supporting letters of agreement between the two agencies. As more complex FUSRAP sites are completed, this transition process will provide a model between the two agencies to communicate future long-term care liabilities. Ultimately, the FUSRAP transition process is structured to acquire and preserve site knowledge and information necessary for protecting the environment and public health. As of 2015, LM has transitioned and accepted programmatic responsibility for over 90 sites. From LM’s perspective, successful transition of any site includes understanding the long-term environmental liabilities. LM uses site transition framework requirements from past transitions to develop site-specific transition plans. Site-specific transition plans are developed by LM in coordination with USACE and

Magnetic nanoparticles stimulation to enhance liquid-liquid two-phase mass transfer under static and rotating magnetic fields

NASA Astrophysics Data System (ADS)

Azimi, Neda; Rahimi, Masoud

2017-01-01

Rotating magnetic field (RMF) was applied on a micromixer to break the laminar flow and induce chaotic flow to enhance mass transfer between two-immiscible organic and aqueous phases. The results of RMF were compared to those of static magnetic field (SMF). For this purpose, experiments were carried out in a T-micromixer at equal volumetric flow rates of organic and aqueous phases. Fe3O4 nanoparticles were synthesized by co-precipitation technique and they were dissolved in organic phase. Results obtained from RMF and SMF were compared in terms of overall volumetric mass transfer coefficient (KLa) and extraction efficiency (E) at various Reynolds numbers. Generally, RMF showed higher effect in mass transfer characteristics enhancement compared with SMF. The influence of rotational speeds of magnets (ω) in RMF was investigated, and measurable enhancements of KLa and E were observed. In RMF, the effect of magnetic field induction (B) was investigated. The results reveal that at constant concentration of nanoparticles, by increasing of B, mass transfer characteristics will be enhanced. The effect of various nanoparticles concentrations (ϕ) within 0.002-0.01 (w/v) on KLa and E at maximum induction of RMF (B=76 mT) was evaluated. Maximum values of KLa (2.1±0.001) and E (0.884±0.001) were achieved for the layout of RMF (B=76 mT), ω=16 rad/s and MNPs concentration of 0.008-0.01 (w/v).

Mass transit : implementation of FTA's new starts evaluation process and FY 2001 funding proposals

DOT National Transportation Integrated Search

2000-04-01

Since the early 1970s, the federal government has provided a large share of the nation's capital investment in urban mass transportation. Much of this investment has come through the Federal Transit Administration's (FTA) New Starts program, which he...

How changing the particle structure can speed up protein mass transfer kinetics in liquid chromatography.

PubMed

Gritti, Fabrice; Horvath, Krisztian; Guiochon, Georges

2012-11-09

The mass transfer kinetics of a few compounds (uracil, 112 Da), insulin (5.5 kDa), lysozyme (13.4 kDa), and bovine serum albumin (BSA, 67 kDa) in columns packed with several types of spherical particles was investigated under non-retained conditions, in order to eliminate the poorly known contribution of surface diffusion to overall sample diffusivity across the porous particles in RPLC. Diffusivity across particles is then minimum. Based on the porosity of the particles accessible to analytes, it was accurately estimated from the elution times, the internal obstruction factor (using Pismen correlation), and the hindrance diffusion factor (using Renkin correlation). The columns used were packed with fully porous particles 2.5 μm Luna-C(18) 100 Å, core-shell particles 2.6 μm Kinetex-C(18) 100 Å, 3.6 μm Aeris Widepore-C(18) 200 Å, and prototype 2.7 μm core-shell particles (made of two concentric porous shells with 100 and 300 Å average pore size, respectively), and with 3.3 μm non-porous silica particles. The results demonstrate that the porous particle structure and the solid-liquid mass transfer resistance have practically no effect on the column efficiency for small molecules. For them, the column performance depends principally on eddy dispersion (packing homogeneity), to a lesser degree on longitudinal diffusion (effective sample diffusivity along the packed bed), and only slightly on the solid-liquid mass transfer resistance (sample diffusivity across the particle). In contrast, for proteins, this third HETP contribution, hence the porous particle structure, together with eddy dispersion govern the kinetic performance of columns. Mass transfer kinetics of proteins was observed to be fastest for columns packed with core-shell particles having either a large core-to-particle ratio or having a second, external, shell made of a thin porous layer with large mesopores (200-300 Å) and a high porosity (~/=0.5-0.7). The structure of this external shell seems

Development of a Logic Model for a Physical Activity–Based Employee Wellness Program for Mass Transit Workers

PubMed Central

Petruzzello, Steven J.; Ryan, Katherine E.

2014-01-01

Transportation workers, who constitute a large sector of the workforce, have worksite factors that harm their health. Worksite wellness programs must target this at-risk population. Although physical activity is often a component of worksite wellness logic models, we consider it the cornerstone for improving the health of mass transit employees. Program theory was based on in-person interviews and focus groups of employees. We identified 4 short-term outcome categories, which provided a chain of responses based on the program activities that should lead to the desired end results. This logic model may have significant public health impact, because it can serve as a framework for other US mass transit districts and worksite populations that face similar barriers to wellness, including truck drivers, railroad employees, and pilots. The objective of this article is to discuss the development of a logic model for a physical activity–based mass-transit employee wellness program by describing the target population, program theory, the components of the logic model, and the process of its development. PMID:25032838

Development of a logic model for a physical activity-based employee wellness program for mass transit workers.

PubMed

Das, Bhibha M; Petruzzello, Steven J; Ryan, Katherine E

2014-07-17

Transportation workers, who constitute a large sector of the workforce, have worksite factors that harm their health. Worksite wellness programs must target this at-risk population. Although physical activity is often a component of worksite wellness logic models, we consider it the cornerstone for improving the health of mass transit employees. Program theory was based on in-person interviews and focus groups of employees. We identified 4 short-term outcome categories, which provided a chain of responses based on the program activities that should lead to the desired end results. This logic model may have significant public health impact, because it can serve as a framework for other US mass transit districts and worksite populations that face similar barriers to wellness, including truck drivers, railroad employees, and pilots. The objective of this article is to discuss the development of a logic model for a physical activity-based mass-transit employee wellness program by describing the target population, program theory, the components of the logic model, and the process of its development.

Low Reynolds number kappa-epsilon and empirical transition models for oscillatory pipe flow and heat transfer. M.S. Thesis

NASA Technical Reports Server (NTRS)

Bauer, Christopher

1993-01-01

Stirling engine heat exchangers are shell-and-tube type with oscillatory flow (zero-mean velocity) for the inner fluid. This heat transfer process involves laminar-transition turbulent flow motions under oscillatory flow conditions. A low Reynolds number kappa-epsilon model, (Lam-Bremhorst form), was utilized in the present study to simulate fluid flow and heat transfer in a circular tube. An empirical transition model was used to activate the low Reynolds number k-e model at the appropriate time within the cycle for a given axial location within the tube. The computational results were compared with experimental flow and heat transfer data for: (1) velocity profiles, (2) kinetic energy of turbulence, (3) skin friction factor, (4) temperature profiles, and (5) wall heat flux. The experimental data were obtained for flow in a tube (38 mm diameter and 60 diameter long), with the maximum Reynolds number based on velocity being Re(sub max) = 11840, a dimensionless frequency (Valensi number) of Va = 80.2, at three axial locations X/D = 16, 30 and 44. The agreement between the computations and the experiment is excellent in the laminar portion of the cycle and good in the turbulent portion. Moreover, the location of transition was predicted accurately. The Low Reynolds Number kappa-epsilon model, together with an empirical transition model, is proposed herein to generate the wall heat flux values at different operating parameters than the experimental conditions. Those computational data can be used for testing the much simpler and less accurate one dimensional models utilized in 1-D Stirling Engine design codes.

The Spitzer search for the transits of HARPS low-mass planets. II. Null results for 19 planets

NASA Astrophysics Data System (ADS)

Gillon, M.; Demory, B.-O.; Lovis, C.; Deming, D.; Ehrenreich, D.; Lo Curto, G.; Mayor, M.; Pepe, F.; Queloz, D.; Seager, S.; Ségransan, D.; Udry, S.

2017-05-01

Short-period super-Earths and Neptunes are now known to be very frequent around solar-type stars. Improving our understanding of these mysterious planets requires the detection of a significant sample of objects suitable for detailed characterization. Searching for the transits of the low-mass planets detected by Doppler surveys is a straightforward way to achieve this goal. Indeed, Doppler surveys target the most nearby main-sequence stars, they regularly detect close-in low-mass planets with significant transit probability, and their radial velocity data constrain strongly the ephemeris of possible transits. In this context, we initiated in 2010 an ambitious Spitzer multi-Cycle transit search project that targeted 25 low-mass planets detected by radial velocity, focusing mainly on the shortest-period planets detected by the HARPS spectrograph. We report here null results for 19 targets of the project. For 16 planets out of 19, a transiting configuration is strongly disfavored or firmly rejected by our data for most planetary compositions. We derive a posterior probability of 83% that none of the probed 19 planets transits (for a prior probability of 22%), which still leaves a significant probability of 17% that at least one of them does transit. Globally, our Spitzer project revealed or confirmed transits for three of its 25 targeted planets, and discarded or disfavored the transiting nature of 20 of them. Our light curves demonstrate for Warm Spitzer excellent photometric precisions: for 14 targets out of 19, we were able to reach standard deviations that were better than 50 ppm per 30 min intervals. Combined with its Earth-trailing orbit, which makes it capable of pointing any star in the sky and to monitor it continuously for days, this work confirms Spitzer as an optimal instrument to detect sub-mmag-deep transits on the bright nearby stars targeted by Doppler surveys. The photometric and radial velocity time series used in this work are only available at the

A mass transfer model of ethanol emission from thin layers of corn silage

USDA-ARS?s Scientific Manuscript database

A mass transfer model of ethanol emission from thin layers of corn silage was developed and validated. The model was developed based on data from wind tunnel experiments conducted at different temperatures and air velocities. Multiple regression analysis was used to derive an equation that related t...

Operational parameters and their influence on particle-side mass transfer resistance in a packed bed bioreactor.

PubMed

Hussain, Amir; Kangwa, Martin; Yumnam, Nivedita; Fernandez-Lahore, Marcelo

2015-12-01

The influence of internal mass transfer on productivity as well as the performance of packed bed bioreactor was determined by varying a number of parameters; chitosan coating, flow rate, glucose concentration and particle size. Saccharomyces cerevisiae cells were immobilized in chitosan and non-chitosan coated alginate beads to demonstrate the effect on particle side mass transfer on substrate consumption time, lag phase and ethanol production. The results indicate that chitosan coating, beads size, glucose concentration and flow rate have a significant effect on lag phase duration. The duration of lag phase for different size of beads (0.8, 2 and 4 mm) decreases by increasing flow rate and by decreasing the size of beads. Moreover, longer lag phase were found at higher glucose medium concentration and also with chitosan coated beads. It was observed that by increasing flow rates; lag phase and glucose consumption time decreased. The reason is due to the reduction of external (fluid side) mass transfer as a result of increase in flow rate as glucose is easily transported to the surface of the beads. Varying the size of beads is an additional factor: as it reduces the internal (particle side) mass transfer by reducing the size of beads. The reason behind this is the distance for reactants to reach active site of catalyst (cells) and the thickness of fluid created layer around alginate beads is reduced. The optimum combination of parameters consisting of smaller beads size (0.8 mm), higher flow rate of 90 ml/min and glucose concentration of 10 g/l were found to be the maximum condition for ethanol production.

Spin-Polarization-Induced Preedge Transitions in the Sulfur K-Edge XAS Spectra of Open-Shell Transition-Metal Sulfates: Spectroscopic Validation of σ-Bond Electron Transfer.

PubMed

Frank, Patrick; Szilagyi, Robert K; Gramlich, Volker; Hsu, Hua-Fen; Hedman, Britt; Hodgson, Keith O

2017-02-06

Sulfur K-edge X-ray absorption spectroscopy (XAS) spectra of the monodentate sulfate complexes [M II (itao)(SO 4 )(H 2 O) 0,1 ] (M = Co, Ni, Cu) and [Cu(Me 6 tren)(SO 4 )] exhibit well-defined preedge transitions at 2479.4, 2479.9, 2478.4, and 2477.7 eV, respectively, despite having no direct metal-sulfur bond, while the XAS preedge of [Zn(itao)(SO 4 )] is featureless. The sulfur K-edge XAS of [Cu(itao)(SO 4 )] but not of [Cu(Me 6 tren)(SO 4 )] uniquely exhibits a weak transition at 2472.1 eV, an extraordinary 8.7 eV below the first inflection of the rising K-edge. Preedge transitions also appear in the sulfur K-edge XAS of crystalline [M II (SO 4 )(H 2 O)] (M = Fe, Co, Ni, and Cu, but not Zn) and in sulfates of higher-valent early transition metals. Ground-state density functional theory (DFT) and time-dependent DFT (TDDFT) calculations show that charge transfer from coordinated sulfate to paramagnetic late transition metals produces spin polarization that differentially mixes the spin-up (α) and spin-down (β) spin orbitals of the sulfate ligand, inducing negative spin density at the sulfate sulfur. Ground-state DFT calculations show that sulfur 3p character then mixes into metal 4s and 4p valence orbitals and various combinations of ligand antibonding orbitals, producing measurable sulfur XAS transitions. TDDFT calculations confirm the presence of XAS preedge features 0.5-2 eV below the rising sulfur K-edge energy. The 2472.1 eV feature arises when orbitals at lower energy than the frontier occupied orbitals with S 3p character mix with the copper(II) electron hole. Transmission of spin polarization and thus of radical character through several bonds between the sulfur and electron hole provides a new mechanism for the counterintuitive appearance of preedge transitions in the XAS spectra of transition-metal oxoanion ligands in the absence of any direct metal-absorber bond. The 2472.1 eV transition is evidence for further radicalization from copper(II), which

Spin-Polarization-Induced Preedge Transitions in the Sulfur K-Edge XAS Spectra of Open-Shell Transition-Metal Sulfates: Spectroscopic Validation of σ-Bond Electron Transfer

DOE PAGES

Frank, Patrick; Szilagyi, Robert K.; Gramlich, Volker; ...

2017-01-09

Sulfur K-edge X-ray absorption spectroscopy (XAS) spectra of the monodentate sulfate complexes [M II(itao)(SO 4)(H 2O) 0,1] (M = Co, Ni, Cu) and [Cu(Me 6tren)(SO 4)] exhibit well-defined preedge transitions at 2479.4, 2479.9, 2478.4, and 2477.7 eV, respectively, despite having no direct metal–sulfur bond, while the XAS preedge of [Zn(itao)(SO 4)] is featureless. The sulfur K-edge XAS of [Cu(itao)(SO 4)] but not of [Cu(Me 6tren)(SO 4)] uniquely exhibits a weak transition at 2472.1 eV, an extraordinary 8.7 eV below the first inflection of the rising K-edge. Preedge transitions also appear in the sulfur K-edge XAS of crystalline [M II(SO 4)(Hmore » 2O)] (M = Fe, Co, Ni, and Cu, but not Zn) and in sulfates of higher-valent early transition metals. Ground-state density functional theory (DFT) and time-dependent DFT (TDDFT) calculations show that charge transfer from coordinated sulfate to paramagnetic late transition metals produces spin polarization that differentially mixes the spin-up (α) and spin-down (β) spin orbitals of the sulfate ligand, inducing negative spin density at the sulfate sulfur. Ground-state DFT calculations show that sulfur 3p character then mixes into metal 4s and 4p valence orbitals and various combinations of ligand antibonding orbitals, producing measurable sulfur XAS transitions. TDDFT calculations confirm the presence of XAS preedge features 0.5–2 eV below the rising sulfur K-edge energy. The 2472.1 eV feature arises when orbitals at lower energy than the frontier occupied orbitals with S 3p character mix with the copper(II) electron hole. Transmission of spin polarization and thus of radical character through several bonds between the sulfur and electron hole provides a new mechanism for the counterintuitive appearance of preedge transitions in the XAS spectra of transition-metal oxoanion ligands in the absence of any direct metal–absorber bond. The 2472.1 eV transition is evidence for further radicalization from copper(II), which

Gas-liquid mass transfer and flow phenomena in the Peirce-Smith converter: a water model study

NASA Astrophysics Data System (ADS)

Zhao, Xing; Zhao, Hong-liang; Zhang, Li-feng; Yang, Li-qiang

2018-01-01

A water model with a geometric similarity ratio of 1:5 was developed to investigate the gas-liquid mass transfer and flow characteristics in a Peirce-Smith converter. A gas mixture of CO2 and Ar was injected into a NaOH solution bath. The flow field, volumetric mass transfer coefficient per unit volume ( Ak/V; where A is the contact area between phases, V is the volume, and k is the mass transfer coefficient), and gas utilization ratio ( η) were then measured at different gas flow rates and blow angles. The results showed that the flow field could be divided into five regions, i.e., injection, strong loop, weak loop, splashing, and dead zone. Whereas the Ak/V of the bath increased and then decreased with increasing gas flow rate, and η steadily increased. When the converter was rotated clockwise, both Ak/V and η increased. However, the flow condition deteriorated when the gas flow rate and blow angle were drastically increased. Therefore, these parameters must be controlled to optimal conditions. In the proposed model, the optimal gas flow rate and blow angle were 7.5 m3·h-1 and 10°, respectively.

Enhancement of mass transfer by ultrasound: Application to adsorbent regeneration and food drying/dehydration.

PubMed

Yao, Ye

2016-07-01

The physical mechanisms of heat and mass transfer enhancement by ultrasound have been identified by people. Basically, the effect of 'cavitation' induced by ultrasound is the main reason for the enhancement of heat and mass transfer in a liquid environment, and the acoustic streaming and vibration are the main reasons for that in a gaseous environment. The adsorbent regeneration and food drying/dehydration are typical heat and mass transfer process, and the intensification of the two processes by ultrasound is of complete feasibility. This paper makes an overview on recent studies regarding applications of power ultrasound to adsorbent regeneration and food drying/dehydration. The concerned adsorbents include desiccant materials (typically like silica gel) for air dehumidification and other ones (typically active carbon and polymeric resin) for water treatment. The applications of ultrasound in the regeneration of these adsorbents have been proved to be energy saving. The concerned foods are mostly fruits and vegetables. Although the ultrasonic treatment may cause food degradation or nutrient loss, it can greatly reduce the food processing time and decrease drying temperature. From the literature, it can be seen that the ultrasonic conditions (i.e., acoustic frequency and power levels) are always focused on during the study of ultrasonic applications. The increasing number of relevant studies argues that ultrasound is a very promising technology applied to the adsorbent regeneration and food drying/dehydration. Copyright © 2016 Elsevier B.V. All rights reserved.

The impact of viscosity on the combined heat, mass and momentum transfer in laminar liquid falling films

NASA Astrophysics Data System (ADS)

Mittermaier, M.; Ziegler, F.

2018-04-01

In this article we present a model describing a laminar film flow over a vertical isothermal plate whilst heat and mass transfer is occurring. We focus on a formulation where most common assumptions, such as constant property data and constant film thickness, have been cancelled. The hydrodynamic model results in longitudinal and transversal velocity components and their evolution in the entrance region. Heat and mass transfer occurs simultaneously and is modelled with respect to release of differential heat of solution as well as heat flow due to interdiffusion. The numerical solution is obtained by utilising a Newton-Raphson method to solve the finite difference formulation of the governing equations. Mass transfer across the film affects the development of both longitudinal and transversal velocity components. The hydrodynamics are modelled using a boundary layer approximation of the Navier-Stokes equations. The significance of simplifications on the hydrodynamic model are illustrated and discussed using a fully developed velocity profile (Nusselt flow) and a plug flow at the inlet for comparison. Even if a Nusselt profile is assumed, it develops further since mass is absorbed or desorbed. It is found that the onset of absorption occurs at shorter flow length when applying a plug flow at the inlet. If the film is initially in equilibrium, this results in a 9.3% increase in absorbed mass over a length of 0.03 m as compared with the Nusselt flow. A fluid with a viscosity five times the one of lithium bromide solution but sharing comparable properties apart from that, leads to lower overall heat and mass transfer rates. If the respective fluids are saturated at the inlet, the accumulated mass flux absorbed by lithium bromide solution is 2.2 times higher than the one absorbed by a high viscous fluid. However, when a plug flow is applied and the fluid is sub-cooled, ab initio the absorbed mass flux is slightly higher for a high viscous fluid. Assuming a sub

Mass detection in digital breast tomosynthesis: Deep convolutional neural network with transfer learning from mammography.

PubMed

Samala, Ravi K; Chan, Heang-Ping; Hadjiiski, Lubomir; Helvie, Mark A; Wei, Jun; Cha, Kenny

2016-12-01

Develop a computer-aided detection (CAD) system for masses in digital breast tomosynthesis (DBT) volume using a deep convolutional neural network (DCNN) with transfer learning from mammograms. A data set containing 2282 digitized film and digital mammograms and 324 DBT volumes were collected with IRB approval. The mass of interest on the images was marked by an experienced breast radiologist as reference standard. The data set was partitioned into a training set (2282 mammograms with 2461 masses and 230 DBT views with 228 masses) and an independent test set (94 DBT views with 89 masses). For DCNN training, the region of interest (ROI) containing the mass (true positive) was extracted from each image. False positive (FP) ROIs were identified at prescreening by their previously developed CAD systems. After data augmentation, a total of 45 072 mammographic ROIs and 37 450 DBT ROIs were obtained. Data normalization and reduction of non-uniformity in the ROIs across heterogeneous data was achieved using a background correction method applied to each ROI. A DCNN with four convolutional layers and three fully connected (FC) layers was first trained on the mammography data. Jittering and dropout techniques were used to reduce overfitting. After training with the mammographic ROIs, all weights in the first three convolutional layers were frozen, and only the last convolution layer and the FC layers were randomly initialized again and trained using the DBT training ROIs. The authors compared the performances of two CAD systems for mass detection in DBT: one used the DCNN-based approach and the other used their previously developed feature-based approach for FP reduction. The prescreening stage was identical in both systems, passing the same set of mass candidates to the FP reduction stage. For the feature-based CAD system, 3D clustering and active contour method was used for segmentation; morphological, gray level, and texture features were extracted and merged with a

Mass detection in digital breast tomosynthesis: Deep convolutional neural network with transfer learning from mammography

PubMed Central

Chan, Heang-Ping; Hadjiiski, Lubomir; Helvie, Mark A.; Wei, Jun; Cha, Kenny

2016-01-01

Purpose: Develop a computer-aided detection (CAD) system for masses in digital breast tomosynthesis (DBT) volume using a deep convolutional neural network (DCNN) with transfer learning from mammograms. Methods: A data set containing 2282 digitized film and digital mammograms and 324 DBT volumes were collected with IRB approval. The mass of interest on the images was marked by an experienced breast radiologist as reference standard. The data set was partitioned into a training set (2282 mammograms with 2461 masses and 230 DBT views with 228 masses) and an independent test set (94 DBT views with 89 masses). For DCNN training, the region of interest (ROI) containing the mass (true positive) was extracted from each image. False positive (FP) ROIs were identified at prescreening by their previously developed CAD systems. After data augmentation, a total of 45 072 mammographic ROIs and 37 450 DBT ROIs were obtained. Data normalization and reduction of non-uniformity in the ROIs across heterogeneous data was achieved using a background correction method applied to each ROI. A DCNN with four convolutional layers and three fully connected (FC) layers was first trained on the mammography data. Jittering and dropout techniques were used to reduce overfitting. After training with the mammographic ROIs, all weights in the first three convolutional layers were frozen, and only the last convolution layer and the FC layers were randomly initialized again and trained using the DBT training ROIs. The authors compared the performances of two CAD systems for mass detection in DBT: one used the DCNN-based approach and the other used their previously developed feature-based approach for FP reduction. The prescreening stage was identical in both systems, passing the same set of mass candidates to the FP reduction stage. For the feature-based CAD system, 3D clustering and active contour method was used for segmentation; morphological, gray level, and texture features were extracted

Modulated mass-transfer model for superhumps in SU Ursae Majoris stars

NASA Technical Reports Server (NTRS)

Mineshige, Shin

1988-01-01

The response of a circular accretion disk to rapid modulation of the mass-transfer rate into the disk is explored in order to model superhumps in SU UMa stars. It is proposed that periodically enhanced flow may disrupt or heat up the outer disk and produce the dips noted just before the superhump peaks. The elliptical accretion-disk model with extended vertical disk structure can account for the observed characteristics of superhumps in these stars.

Ground-state oxygen holes and the metal–insulator transition in the negative charge-transfer rare-earth nickelates

PubMed Central

Bisogni, Valentina; Catalano, Sara; Green, Robert J.; Gibert, Marta; Scherwitzl, Raoul; Huang, Yaobo; Strocov, Vladimir N.; Zubko, Pavlo; Balandeh, Shadi; Triscone, Jean-Marc; Sawatzky, George; Schmitt, Thorsten

2016-01-01

The metal–insulator transition and the intriguing physical properties of rare-earth perovskite nickelates have attracted considerable attention in recent years. Nonetheless, a complete understanding of these materials remains elusive. Here we combine X-ray absorption and resonant inelastic X-ray scattering (RIXS) spectroscopies to resolve important aspects of the complex electronic structure of rare-earth nickelates, taking NdNiO3 thin film as representative example. The unusual coexistence of bound and continuum excitations observed in the RIXS spectra provides strong evidence for abundant oxygen holes in the ground state of these materials. Using cluster calculations and Anderson impurity model interpretation, we show that distinct spectral signatures arise from a Ni 3d8 configuration along with holes in the oxygen 2p valence band, confirming suggestions that these materials do not obey a conventional positive charge-transfer picture, but instead exhibit a negative charge-transfer energy in line with recent models interpreting the metal–insulator transition in terms of bond disproportionation. PMID:27725665

Another Look at the Mechanisms of Hydride Transfer Enzymes with Quantum and Classical Transition Path Sampling.

PubMed

Dzierlenga, Michael W; Antoniou, Dimitri; Schwartz, Steven D

2015-04-02

The mechanisms involved in enzymatic hydride transfer have been studied for years, but questions remain due, in part, to the difficulty of probing the effects of protein motion and hydrogen tunneling. In this study, we use transition path sampling (TPS) with normal mode centroid molecular dynamics (CMD) to calculate the barrier to hydride transfer in yeast alcohol dehydrogenase (YADH) and human heart lactate dehydrogenase (LDH). Calculation of the work applied to the hydride allowed for observation of the change in barrier height upon inclusion of quantum dynamics. Similar calculations were performed using deuterium as the transferring particle in order to approximate kinetic isotope effects (KIEs). The change in barrier height in YADH is indicative of a zero-point energy (ZPE) contribution and is evidence that catalysis occurs via a protein compression that mediates a near-barrierless hydride transfer. Calculation of the KIE using the difference in barrier height between the hydride and deuteride agreed well with experimental results.

A surface renewal model for unsteady-state mass transfer using the generalized Danckwerts age distribution function

PubMed Central

Horvath, Isabelle R.

2018-01-01

The recently derived steady-state generalized Danckwerts age distribution is extended to unsteady-state conditions. For three different wind speeds used by researchers on air–water heat exchange on the Heidelberg Aeolotron, calculations reveal that the distribution has a sharp peak during the initial moments, but flattens out and acquires a bell-shaped character with process time, with the time taken to attain a steady-state profile being a strong and inverse function of wind speed. With increasing wind speed, the age distribution narrows significantly, its skewness decreases and its peak becomes larger. The mean eddy renewal time increases linearly with process time initially but approaches a final steady-state value asymptotically, which decreases dramatically with increased wind speed. Using the distribution to analyse the transient absorption of a gas into a large body of liquid, assuming negligible gas-side mass-transfer resistance, estimates are made of the gas-absorption and dissolved-gas transfer coefficients for oxygen absorption in water at 25°C for the three different wind speeds. Under unsteady-state conditions, these two coefficients show an inverse behaviour, indicating a heightened accumulation of dissolved gas in the surface elements, especially during the initial moments of absorption. However, the two mass-transfer coefficients start merging together as the steady state is approached. Theoretical predictions of the steady-state mass-transfer coefficient or transfer velocity are in fair agreement (average absolute error of prediction = 18.1%) with some experimental measurements of the same for the nitrous oxide–water system at 20°C that were made in the Heidelberg Aeolotron. PMID:29892429

Transition to turbulence in plane channel flows

NASA Technical Reports Server (NTRS)

Biringen, S.

1984-01-01

Results obtained from a numerical simulation of the final stages of transition to turbulence in plane channel flow are described. Three dimensional, incompressible Navier-Stokes equations are numerically integrated to obtain the time evolution of two and three dimensional finite amplitude disturbances. Computations are performed on CYBER-203 vector processor for a 32x51x32 grid. Results are presented for no-slip boundary conditions at the solid walls as well as for periodic suction blowing to simulate active control of transition by mass transfer. Solutions indicate that the method is capable of simulating the complex character of vorticity dynamics during the various stages of transition and final breakdown. In particular, evidence points to the formation of a lambda-shape vortex and the subsequent system of horseshoe vortices inclined to the main flow direction as the main elements of transition. Calculations involving periodic suction-blowing indicate that interference with a wave of suitable phase and amplitude reduces the disturbance growth rates.

Demonstrating the Effect of Interphase Mass Transfer in a Transparent Fluidized Bed Reactor

ERIC Educational Resources Information Center

Saayman, Jean; Nicol, Willie

2011-01-01

A demonstration experiment is described that employs the ozone decomposition reaction at ambient conditions on Fe2O3 impregnated Fluidized Catalytic Cracking (FCC) catalyst. Using a two-dimensional see-through column the importance of interphase mass transfer is clearly illustrated by the significant difference in ozone conversion between the…

Visualisation of gas-liquid mass transfer around a rising bubble in a quiescent liquid using an oxygen sensitive dye

NASA Astrophysics Data System (ADS)

Dietrich, Nicolas; Hebrard, Gilles

2018-02-01

An approach for visualizing and measuring the mass transfer around a single bubble rising in a quiescent liquid is reported. A colorimetric technique, developed by (Dietrich et al. Chem Eng Sci 100:172-182, 2013) using an oxygen sensitive redox dye was implemented. It was based on the reduction of the colorimetric indicator in presence of oxygen, this reduction being catalysed by sodium hydroxide and glucose. In this study, resazurin was selected because it offered various reduced forms with colours ranging from transparent (without oxygen) to pink (in presence of oxygen). These advantages made it possible to visualize the spatio-temporal oxygen mass transfer around rising bubbles. Images were recorded by a CCD camera and, after post-processing, the shape, size, and velocity of the bubbles were measured and the colours around the bubbles mapped. A calibration, linking the level of colour with the dissolved oxygen concentration, enabled colour maps to be converted into oxygen concentration fields. A rheoscopic fluid was used to visualize the wake of the bubbles. A calculation method was also developed to determine the transferred oxygen fluxes around bubbles of two sizes (d = 0.82 mm and d = 2.12 mm) and the associated liquid-side mass transfer coefficients. The results compared satisfactorily with classical global measurements made by oxygen micro-sensors or from the classical models. This study thus constitutes a striking example of how this new colorimetric method could become a remarkable tool for exploring gas-liquid mass transfer in fluids.

Visualisation of gas-liquid mass transfer around a rising bubble in a quiescent liquid using an oxygen sensitive dye

NASA Astrophysics Data System (ADS)

Dietrich, Nicolas; Hebrard, Gilles

2018-07-01

An approach for visualizing and measuring the mass transfer around a single bubble rising in a quiescent liquid is reported. A colorimetric technique, developed by (Dietrich et al. Chem Eng Sci 100:172-182, 2013) using an oxygen sensitive redox dye was implemented. It was based on the reduction of the colorimetric indicator in presence of oxygen, this reduction being catalysed by sodium hydroxide and glucose. In this study, resazurin was selected because it offered various reduced forms with colours ranging from transparent (without oxygen) to pink (in presence of oxygen). These advantages made it possible to visualize the spatio-temporal oxygen mass transfer around rising bubbles. Images were recorded by a CCD camera and, after post-processing, the shape, size, and velocity of the bubbles were measured and the colours around the bubbles mapped. A calibration, linking the level of colour with the dissolved oxygen concentration, enabled colour maps to be converted into oxygen concentration fields. A rheoscopic fluid was used to visualize the wake of the bubbles. A calculation method was also developed to determine the transferred oxygen fluxes around bubbles of two sizes (d = 0.82 mm and d = 2.12 mm) and the associated liquid-side mass transfer coefficients. The results compared satisfactorily with classical global measurements made by oxygen micro-sensors or from the classical models. This study thus constitutes a striking example of how this new colorimetric method could become a remarkable tool for exploring gas-liquid mass transfer in fluids.

Mass transfer effect of the stalk contraction-relaxation cycle of Vorticella convallaria

NASA Astrophysics Data System (ADS)

Zhou, Jiazhong; Admiraal, David; Ryu, Sangjin

2014-11-01

Vorticella convallaria is a genus of protozoa living in freshwater. Its stalk contracts and coil pulling the cell body towards the substrate at a remarkable speed, and then relaxes to its extended state much more slowly than the contraction. However, the reason for Vorticella's stalk contraction is still unknown. It is presumed that water flow induced by the stalk contraction-relaxation cycle may augment mass transfer near the substrate. We investigated this hypothesis using an experimental model with particle tracking velocimetry and a computational fluid dynamics model. In both approaches, Vorticella was modeled as a solid sphere translating perpendicular to a solid surface in water. After having been validated by the experimental model and verified by grid convergence index test, the computational model simulated water flow during the cycle based on the measured time course of stalk length changes of Vorticella. Based on the simulated flow field, we calculated trajectories of particles near the model Vorticella, and then evaluated the mass transfer effect of Vorticella's stalk contraction based on the particles' motion. We acknowlege support from Laymann Seed Grant of the University of Nebraska-Lincoln.

Modeling the improvement of ultrafiltration membrane mass transfer when using biofiltration pretreatment in surface water applications.

PubMed

Netcher, Andrea C; Duranceau, Steven J

2016-03-01

In surface water treatment, ultrafiltration (UF) membranes are widely used because of their ability to supply safe drinking water. Although UF membranes produce high-quality water, their efficiency is limited by fouling. Improving UF filtrate productivity is economically desirable and has been attempted by incorporating sustainable biofiltration processes as pretreatment to UF with varying success. The availability of models that can be applied to describe the effectiveness of biofiltration on membrane mass transfer are lacking. In this work, UF water productivity was empirically modeled as a function of biofilter feed water quality using either a quadratic or Gaussian relationship. UF membrane mass transfer variability was found to be governed by the dimensionless mass ratio between the alkalinity (ALK) and dissolved organic carbon (DOC). UF membrane productivity was optimized when the biofilter feed water ALK to DOC ratio fell between 10 and 14. Copyright © 2015 Elsevier Ltd. All rights reserved.

An Assessment of the General Applicability of the Relationship Between Nucleation of CO Bubbles and Mass Transfer of Phosphorus in Liquid Iron Alloys

NASA Astrophysics Data System (ADS)

Gu, Kezhuan; Dogan, Neslihan; Coley, Kenneth S.

2018-06-01

The current paper seeks to demonstrate the general applicability of the authors' recently developed treatment of surface renewal during decarburization of Fe-C-S alloys and its effect on the mass transport of phosphorus in the metal phase. The proposed model employs a quantitative model of CO bubble nucleation in the metal to predict the rate of surface renewal, which can then in turn be used to predict the mass-transfer coefficient for phosphorus. A model of mixed transport control in the slag and metal phases was employed to investigate the dephosphorization kinetics between a liquid iron alloy and oxidizing slag. Based on previous studies of the mass-transfer coefficient of FeO in the slag, it was possible to separate the mass transfer coefficient of phosphorus in metal phase, km , from the overall mass-transfer coefficient k_{{o}} . Using this approach, km was investigated under a wide range of conditions and shown to be represented reasonably by the mechanism proposed. The mass-transfer model was tested against results from the literature over a wide range of conditions. The analysis showed that the FeO content in the slag, silicon in the metal and the experimental temperature have strong impact on, km , almost entirely because of their effect on decarburization behavior.

An Assessment of the General Applicability of the Relationship Between Nucleation of CO Bubbles and Mass Transfer of Phosphorus in Liquid Iron Alloys

NASA Astrophysics Data System (ADS)

Gu, Kezhuan; Dogan, Neslihan; Coley, Kenneth S.

2018-02-01

The current paper seeks to demonstrate the general applicability of the authors' recently developed treatment of surface renewal during decarburization of Fe-C-S alloys and its effect on the mass transport of phosphorus in the metal phase. The proposed model employs a quantitative model of CO bubble nucleation in the metal to predict the rate of surface renewal, which can then in turn be used to predict the mass-transfer coefficient for phosphorus. A model of mixed transport control in the slag and metal phases was employed to investigate the dephosphorization kinetics between a liquid iron alloy and oxidizing slag. Based on previous studies of the mass-transfer coefficient of FeO in the slag, it was possible to separate the mass transfer coefficient of phosphorus in metal phase, km , from the overall mass-transfer coefficient k_{{o}} . Using this approach, km was investigated under a wide range of conditions and shown to be represented reasonably by the mechanism proposed. The mass-transfer model was tested against results from the literature over a wide range of conditions. The analysis showed that the FeO content in the slag, silicon in the metal and the experimental temperature have strong impact on, km , almost entirely because of their effect on decarburization behavior.

Transition structures and timing of transfer from paediatric to adult-based care after kidney transplantation in Germany: a qualitative study.

PubMed

Prüfe, Jenny; Dierks, Marie-Luise; Bethe, Dirk; Oldhafer, Martina; Müther, Silvia; Thumfart, Julia; Feldkötter, Markus; Büscher, Anja; Sauerstein, Katja; Hansen, Matthias; Pohl, Martin; Drube, Jens; Thiel, Florian; Rieger, Susanne; John, Ulrike; Taylan, Christina; Dittrich, Katalin; Hollenbach, Sabine; Klaus, Günter; Fehrenbach, Henry; Kranz, Birgitta; Montoya, Carmen; Lange-Sperandio, Bärbel; Ruckenbrod, Bettina; Billing, Heiko; Staude, Hagen; Brunkhorst, Reinhard; Rusai, Krisztina; Pape, Lars; Kreuzer, Martin

2017-06-12

It is known that transition, as a shift of care, marks a vulnerable phase in the adolescents' lives with an increased risk for non-adherence and allograft failure. Still, the transition process of adolescents and young adults living with a kidney transplant in Germany is not well defined. The present research aims to assess transition-relevant structures for this group of young people. Special attention is paid to the timing of the process. In an observational study, we visited 21 departments of paediatric nephrology in Germany. Participants were doctors (n=19), nurses (n=14) and psychosocial staff (n=16) who were responsible for transition in the relevant centres. Structural elements were surveyed using a short questionnaire. The experiential viewpoint was collected by interviews which were transcribedverbatim before thematic analysis was performed. This study highlights that professionals working within paediatric nephrology in Germany are well aware of the importance of successful transition. Key elements of transitional care are well understood and mutually agreed on. Nonetheless, implementation within daily routine seems challenging, and the absence of written, structured procedures may hamper successful transition. While professionals aim for an individual timing of transfer based on medical, social, emotional and structural aspects, rigid regulations on transfer age as given by the relevant health authorities add on to the challenge. ISRCTN Registry no 22988897; results (phase I) and pre-results (phase II). © Article author(s) (or their employer(s) unless otherwise stated in the text of the article) 2017. All rights reserved. No commercial use is permitted unless otherwise expressly granted.

Microscale Enhancement of Heat and Mass Transfer for Hydrogen Energy Storage

DOE Office of Scientific and Technical Information (OSTI.GOV)

Drost, Kevin; Jovanovic, Goran; Paul, Brian

2015-09-30

The document summarized the technical progress associated with OSU’s involvement in the Hydrogen Storage Engineering Center of Excellence. OSU focused on the development of microscale enhancement technologies for improving heat and mass transfer in automotive hydrogen storage systems. OSU’s key contributions included the development of an extremely compact microchannel combustion system for discharging hydrogen storage systems and a thermal management system for adsorption based hydrogen storage using microchannel cooling (the Modular Adsorption Tank Insert or MATI).

Three phase heat and mass transfer model for unsaturated soil freezing process: Part 2 - model validation

NASA Astrophysics Data System (ADS)

Zhang, Yaning; Xu, Fei; Li, Bingxi; Kim, Yong-Song; Zhao, Wenke; Xie, Gongnan; Fu, Zhongbin

2018-04-01

This study aims to validate the three-phase heat and mass transfer model developed in the first part (Three phase heat and mass transfer model for unsaturated soil freezing process: Part 1 - model development). Experimental results from studies and experiments were used for the validation. The results showed that the correlation coefficients for the simulated and experimental water contents at different soil depths were between 0.83 and 0.92. The correlation coefficients for the simulated and experimental liquid water contents at different soil temperatures were between 0.95 and 0.99. With these high accuracies, the developed model can be well used to predict the water contents at different soil depths and temperatures.

Modeling of Heat and Mass Transfer in a TEC-Driven Lyophilizer

NASA Technical Reports Server (NTRS)

Yuan, Zeng-Guang; Hegde, Uday; Litwiller, Eric; Flynn, Michael; Fisher, John

2006-01-01

Dewatering of wet waste during space exploration missions is important for crew safety as it stabilizes the waste. It may also be used to recover water and serve as a preconditioning step for waste compaction. A thermoelectric cooler (TEC)-driven lyophilizer is under development at NASA Ames Research Center for this purpose. It has three major components: (i) an evaporator section where water vapor sublimes from the frozen waste, (ii) a condenser section where this water vapor deposits as ice, and (iii) a TEC section which serves as a heat pump to transfer heat from the condenser to the evaporator. This paper analyses the heat and mass transfer processes in the lyophilizer in an effort to understand the ice formation behavior in the condenser. The analysis is supported by experimental observations of ice formation patterns in two different condenser units.

The effect of surface movements on nitrogen mass transfer in liquid iron

NASA Astrophysics Data System (ADS)

Hirashima, N.; Choo, R. T. C.; Toguri, J. M.; Mukai, K.

1995-10-01

Marangoni convection due to surface tension gradients set up in a nitrogen-liquid iron system at 1873 K has been mathematically simulated and experimentally confirmed by measuring the rate of nitrogen absorption into liquid iron and by observing the free surface motion of liquid iron via zirconium oxide particles using X-ray radiography. This surface flow was created by blowing nitrogen gas through a small lance over the free surface of the liquid iron contained in an alumina boat under resistance heating. Absorption measurements indicated that the mass-transfer coefficient of nitrogen in liquid iron due to Marangoni convection ( k {m/1}>=1.5×10-4 m/s) is slightly less than that due to induction stirring ( k {m/1}=2.1×10-4 to 1.5×10-4 m/s). The free surface velocity induced by the surface tension gradient, with an initial composition difference of 425 to 10 ppm, was found to be of the order of 0.05 to 0.11 m/s. Mathematical modeling was also carried out to determine the velocity and nitrogen concentration profiles in the alumina boat. It was found that Marangoni convection creates mildly turbulent flows in liquid iron. Good agreements between the experimentally obtained data (nitrogen concentration and surface velocity) and the computed results were attained when a constant eddy viscosity which was five times the molecular value was assumed. This prescription allows both the predicted apparent mass-transfer coefficient and the predicted surface velocity to match the experimental results simultaneously. Note that the transport coefficients in the momentum and the convective-diffusive equations are correlated by the turbulent Schmidt number. The dimensionless mass-transfer correlation obtained for the present N-Fe system at 1873 K under resistance heating was found to be Sh=0.104 Re0.7·Sc0.7 with Sc=79.5 (3500

Gas diffusion electrodes improve hydrogen gas mass transfer for a hydrogen oxidizing bioanode

PubMed Central

Rodenas, Pau; Zhu, Fangqi; Sleutels, Tom; Saakes, Michel; Buisman, Cees

2017-01-01

Abstract Background Bioelectrochemical systems (BESs) are capable of recovery of metals at a cathode through oxidation of organic substrate at an anode. Recently, also hydrogen gas was used as an electron donor for recovery of copper in BESs. Oxidation of hydrogen gas produced a current density of 0.8 A m‐2 and combined with Cu2+ reduction at the cathode, produced 0.25 W m‐2. The main factor limiting current production was the mass transfer of hydrogen to the biofilm due to the low solubility of hydrogen in the anolyte. Here, the mass transfer of hydrogen gas to the bioanode was improved by use of a gas diffusion electrode (GDE). Results With the GDE, hydrogen was oxidized to produce a current density of 2.9 A m‐2 at an anode potential of –0.2 V. Addition of bicarbonate to the influent led to production of acetate, in addition to current. At a bicarbonate concentration of 50 mmol L‐1, current density increased to 10.7 A m‐2 at an anode potential of –0.2 V. This increase in current density could be due to oxidation of formed acetate in addition to oxidation of hydrogen, or enhanced growth of hydrogen oxidizing bacteria due to the availability of acetate as carbon source. The effect of mass transfer was further assessed through enhanced mixing and in combination with the addition of bicarbonate (50 mmol L‐1) current density increased further to 17.1 A m‐2. Conclusion Hydrogen gas may offer opportunities as electron donor for bioanodes, with acetate as potential intermediate, at locations where excess hydrogen and no organics are available. © 2017 The Authors. Journal of Chemical Technology & Biotechnology published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry. PMID:29200586

Influence of external mass transfer limitation on apparent kinetic parameters of penicillin G acylase immobilized on nonporous ultrafine silica particles.

PubMed

Kheirolomoom, Azadeh; Khorasheh, Farhad; Fazelinia, Hossein

2002-01-01

Immobilization of enzymes on nonporous supports provides a suitable model for investigating the effect of external mass transfer limitation on the reaction rate in the absence of internal diffusional resistance. In this study, deacylation of penicillin G was investigated using penicillin acylase immobilized on ultrafine silica particles. Kinetic studies were performed within the low-substrate-concentration region, where the external mass transfer limitation becomes significant. To predict the apparent kinetic parameters and the overall effectiveness factor, knowledge of the external mass transfer coefficient, k(L)a, is necessary. Although various correlations exist for estimation of k(L)a, in this study, an optimization scheme was utilized to obtain this coefficient. Using the optimum values of k(L)a, the initial reaction rates were predicted and found to be in good agreement with the experimental data.

Determination of volumetric gas-liquid mass transfer coefficient of carbon monoxide in a batch cultivation system using kinetic simulations.

PubMed

Jang, Nulee; Yasin, Muhammad; Park, Shinyoung; Lovitt, Robert W; Chang, In Seop

2017-09-01

A mathematical model of microbial kinetics was introduced to predict the overall volumetric gas-liquid mass transfer coefficient (k L a) of carbon monoxide (CO) in a batch cultivation system. The cell concentration (X), acetate concentration (C ace ), headspace gas (N co and [Formula: see text] ), dissolved CO concentration in the fermentation medium (C co ), and mass transfer rate (R) were simulated using a variety of k L a values. The simulated results showed excellent agreement with the experimental data for a k L a of 13/hr. The C co values decreased with increase in cultivation times, whereas the maximum mass transfer rate was achieved at the mid-log phase due to vigorous microbial CO consumption rate higher than R. The model suggested in this study may be applied to a variety of microbial systems involving gaseous substrates. Copyright © 2017 Elsevier Ltd. All rights reserved.

Pattern formation and mass transfer under stationary solutal Marangoni instability.

PubMed

Schwarzenberger, Karin; Köllner, Thomas; Linde, Hartmut; Boeck, Thomas; Odenbach, Stefan; Eckert, Kerstin

2014-04-01

According to the seminal theory by Sternling and Scriven, solutal Marangoni convection during mass transfer of surface-active solutes may occur as either oscillatory or stationary instability. With strong support of Manuel G. Velarde, a combined initiative of experimental works, in particular to mention those of Linde, Wierschem and coworkers, and theory has enabled a classification of dominant wave types of the oscillatory mode and their interactions. In this way a rather comprehensive understanding of the nonlinear evolution of the oscillatory instability could be achieved. A comparably advanced state-of-the-art with respect to the stationary counterpart seemed to be out of reach a short time ago. Recent developments on both the numerical and experimental side, in combination with assessing an extensive number of older experiments, now allow one to draw a more unified picture. By reviewing these works, we show that three main building blocks exist during the nonlinear evolution: roll cells, relaxation oscillations and relaxation oscillations waves. What is frequently called interfacial turbulence results from the interaction between these partly coexisting basic patterns which may additionally occur in different hierarchy levels. The second focus of this review lies on the practical importance of such convection patterns concerning their influence on mass transfer characteristics. Particular attention is paid here to the interaction between Marangoni and buoyancy effects which frequently complicates the pattern formation even more. To shed more light on these dependencies, new simulations regarding the limiting case of stabilizing density stratification and vanishing buoyancy are incorporated. Copyright © 2013 Elsevier B.V. All rights reserved.

Mass transfer from a sphere in an oscillating flow with zero mean velocity

NASA Technical Reports Server (NTRS)

Drummond, Colin K.; Lyman, Frederic A.

1990-01-01

A pseudospectral numerical method is used for the solution of the Navier-Stokes and mass transport equations for a sphere in a sinusoidally oscillating flow with zero mean velocity. The flow is assumed laminar and axisymmetric about the sphere's polar axis. Oscillating flow results were obtained for Reynolds numbers (based on the free-stream oscillatory flow amplitude) between 1 and 150, and Strouhal numbers between 1 and 1000. Sherwood numbers were computed and their dependency on the flow frequency and amplitude discussed. An assessment of the validity of the quasi-steady assumption for mass transfer is based on these results.

Nonstationary heat and mass transfer in the multilayer building construction with ventilation channels

NASA Astrophysics Data System (ADS)

Kharkov, N. S.

2017-11-01

Results of numerical modeling of the coupled nonstationary heat and mass transfer problem under conditions of a convective flow in facade system of a three-layer concrete panel for two different constructions (with ventilation channels and without) are presented. The positive effect of ventilation channels on the energy and humidity regime over a period of 12 months is shown. Used new method of replacement a solid zone (requiring specification of porosity and material structure, what complicates process of convergence of the solution) on quasi-solid in form of a multicomponent mixture (with restrictions on convection and mass fractions).

Bifurcations in the theory of current transfer to cathodes of DC discharges and observations of transitions between different modes

NASA Astrophysics Data System (ADS)

Bieniek, M. S.; Santos, D. F. N.; Almeida, P. G. C.; Benilov, M. S.

2018-04-01

General scenarios of transitions between different spot patterns on electrodes of DC gas discharges and their relation to bifurcations of steady-state solutions are analyzed. In the case of cathodes of arc discharges, it is shown that any transition between different modes of current transfer is related to a bifurcation of steady-state solutions. In particular, transitions between diffuse and spot modes on axially symmetric cathodes, frequently observed in the experiment, represent an indication of the presence of pitchfork or fold bifurcations of steady-state solutions. Experimental observations of transitions on cathodes of DC glow microdischarges are analyzed and those potentially related to bifurcations of steady-state solutions are identified. The relevant bifurcations are investigated numerically and the computed patterns are found to conform to those observed in the course of the corresponding transitions in the experiment.

Mass Transfer and Rheology of Fiber Suspensions

NASA Astrophysics Data System (ADS)

Wang, Jianghui

Rheological and mass transfer properties of non-Brownian fiber suspensions are affected by fiber characteristics, fiber interactions, and processing conditions. In this thesis we develop several simulation methods to study the dynamics of single fibers in simple shear flow, as well as the rheology and mass transfer of fiber suspensions. Isolated, rigid, neutrally-buoyant, non-Brownian, slightly curved, nonchiral fibers in simple shear flow of an incompressible Newtonian fluid at low Reynolds number can drift steadily in the gradient direction without external forces or torques. The average drift velocity and direction depend on the fiber aspect ratio, curvature and initial orientation. The drift results from the coupling of rotational and translational dynamics, and the combined effects of flipping, scooping, and spinning motions of the fiber. Irreversible fiber collisions in the suspensions cause shear-induced diffusion. The shear-induced self-diffusivity of dilute suspensions of fibers increases with increasing concentration and increasing static friction between contacts. The diffusivities in both the gradient and vorticity directions are larger for suspensions of curved fibers than for suspensions of straight fibers. For suspensions of curved fibers, significant enhancements in the diffusivity in the gradient direction are attributed to fiber drift in the gradient direction. The shear-induced self-diffusivity of concentrated suspensions of fibers increases with increasing concentration before fiber networks or flocs are formed, after which the diffusivity decreases with increasing concentration. The diffusivity increases with increasing fiber equilibrium bending angle, effective stiffness, coefficient of static friction, and rate of collisions. The specific viscosity of fiber suspensions increases with increasing fiber curvature, friction coefficient between mechanical contacts, and solids concentration. The specific viscosity increases linearly with

Formation of Millisecond Pulsars with Heavy White Dwarf Companions: Extreme Mass Transfer on Subthermal Timescales.

PubMed

Tauris; van Den Heuvel EP; Savonije

2000-02-20

We have performed detailed numerical calculations of the nonconservative evolution of close X-ray binary systems with intermediate-mass (2.0-6.0 M middle dot in circle) donor stars and a 1.3 M middle dot in circle accreting neutron star. We calculated the thermal response of the donor star to mass loss in order to determine its stability and follow the evolution of the mass transfer. Under the assumption of the "isotropic reemission model," we demonstrate that in many cases it is possible for the binary to prevent a spiral-in and survive a highly super-Eddington mass transfer phase (1

Spatial distribution of transferred charges across the heterointerface between perovskite transition metal oxides LaNiO{sub 3} and LaMnO{sub 3}

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kitamura, Miho; Photon Factory, Institute of Materials Structure Science, High Energy Accelerator Research Organization; Horiba, Koji

2016-03-14

To investigate the interfacial charge-transfer phenomena between perovskite transition metal oxides LaNiO{sub 3} (LNO) and LaMnO{sub 3} (LMO), we have performed in situ x-ray absorption spectroscopy (XAS) measurements on LNO/LMO multilayers. The Ni-L{sub 2,3} and Mn-L{sub 2,3} XAS spectra clearly show the occurrence of electron transfer from Mn to Ni ions in the interface region. Detailed analysis of the thickness dependence of these XAS spectra has revealed that the spatial distribution of the transferred charges across the interface is significantly different between the two constituent layers. The observed spatial distribution is presumably described by the charge spreading model that treatsmore » the transfer integral between neighboring transition metal ions and the Coulomb interaction, rather than the Thomas–Fermi screening model.« less

Experimental investigation on the heat transfer characteristics and flow pattern in vertical narrow channels heated from one side

NASA Astrophysics Data System (ADS)

Huang, Lihao; Li, Gang; Tao, Leren

2016-07-01

Experimental investigation for the flow boiling of water in a vertical rectangular channel was conducted to reveal the boiling heat transfer mechanism and flow patterns map aspects. The onset of nucleate boiling went upward with the increasing of the working fluid mass flow rate or the decreasing of the inlet working fluid temperature. As the vapour quality was increased, the local heat transfer coefficient increased first, then decreased, followed by various flow patterns. The test data from other researchers had a similar pattern transition for the bubble-slug flow and the slug-annular flow. Flow pattern transition model analysis was performed to make the comparison with current test data. The slug-annular and churn-annular transition models showed a close trend with current data except that the vapor phase superficial velocity of flow pattern transition was much higher than that of experimental data.

Effect of internal pressure and gas/liquid interface area on the CO mass transfer coefficient using hollow fibre membranes as a high mass transfer gas diffusing system for microbial syngas fermentation.

PubMed

Yasin, Muhammad; Park, Shinyoung; Jeong, Yeseul; Lee, Eun Yeol; Lee, Jinwon; Chang, In Seop

2014-10-01

This study proposed a submerged hollow fibre membrane bioreactor (HFMBR) system capable of achieving high carbon monoxide (CO) mass transfer for applications in microbial synthesis gas conversion systems. Hydrophobic polyvinylidene fluoride (PVDF) membrane fibres were used to fabricate a membrane module, which was used for pressurising CO in water phase. Pressure through the hollow fibre lumen (P) and membrane surface area per unit working volume of the liquid (A(S)/V(L)) were used as controllable parameters to determine gas-liquid volumetric mass transfer coefficient (k(L)a) values. We found a k(L)a of 135.72 h(-1) when P was 93.76 kPa and AS/VL was fixed at 27.5m(-1). A higher k(L)a of 155.16 h(-1) was achieved by increasing AS/VL to 62.5m(-1) at a lower P of 37.23 kPa. Practicality of HFMBR to support microbial growth and organic product formation was assessed by CO/CO2 fermentation using Eubacterium limosum KIST612. Copyright © 2014 Elsevier Ltd. All rights reserved.

Dehydration reactions, mass transfer and rock deformation relationships during subduction of Alpine metabauxites: insights from LIBS compositional profiles between metamorphic veins

NASA Astrophysics Data System (ADS)

Verlaguet, Anne; Brunet, Fabrice; Goffé, Bruno; Menut, Denis; Findling, Nathaniel; Poinssot, Christophe

2013-04-01

In subduction zones, the significant amounts of aqueous fluid released in the course of the successive dehydration reactions occurring during prograde metamorphism are expected to strongly influence the rock rheology, as well as kinetics of metamorphic reactions and mass transfer efficiency. Mineralized veins, ubiquitous in metamorphic rocks, can be seen as preserved witnesses of fluid and mass redistribution that partly accommodate the rock deformation (lateral segregation). However, the driving forces and mechanisms of mass transfer towards fluid-filled open spaces remain somewhat unclear. The aim of this study is to investigate the vein-forming processes and the modalities of mass transfer during local fluid-rock interactions, and their links with fluid production and rock deformation, with new insights from Laser Induced Breakdown Spectroscopy (LIBS) profiles. This study focuses on karstic pockets (metre scale) of Triassic metabauxites embedded in thick carbonate units, that have been isolated from large-scale fluid flow during HP-LT Alpine metamorphism (W. Vanoise, French Alps). These rocks display several generations of metamorphic veins containing various Al-bearing minerals, which give particular insights into mass transfer processes. It is proposed that the internally-derived fluid (~13 vol% produced by successive dehydration reactions) has promoted the opening of fluid-filled open spaces (euhedral habits of vein minerals) and served as medium for diffusive mass transfer from rock to vein. Based on mineralogical and textural features, two vein types can be distinguished: (1) some veins are filled with newly formed products of either prograde (chloritoid) or retrograde (chlorite) metamorphic reactions; in this case, fluid-filled open spaces seem to offer energetically favourable nucleation/growth sites; (2) the second vein type is filled with cookeite (Li-Al-rich chlorite) or pyrophyllite, that were present in the host rock prior to the vein formation. In

An investigation of transition boiling mechanisms of subcooled water under forced convective conditions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kwang-Won, Lee; Sang-Yong, Lee

1995-09-01

A mechanistic model for forced convective transition boiling has been developed to investigate transition boiling mechanisms and to predict transition boiling heat flux realistically. This model is based on a postulated multi-stage boiling process occurring during the passage time of the elongated vapor blanket specified at a critical heat flux (CHF) condition. Between the departure from nucleate boiling (DNB) and the departure from film boiling (DFB) points, the boiling heat transfer is established through three boiling stages, namely, the macrolayer evaporation and dryout governed by nucleate boiling in a thin liquid film and the unstable film boiling characterized by themore » frequent touches of the interface and the heated wall. The total heat transfer rates after the DNB is weighted by the time fractions of each stage, which are defined as the ratio of each stage duration to the vapor blanket passage time. The model predictions are compared with some available experimental transition boiling data. The parametric effects of pressure, mass flux, inlet subcooling on the transition boiling heat transfer are also investigated. From these comparisons, it can be seen that this model can identify the crucial mechanisms of forced convective transition boiling, and that the transition boiling heat fluxes including the maximum heat flux and the minimum film boiling heat flux are well predicted at low qualities/high pressures near 10 bar. In future, this model will be improved in the unstable film boiling stage and generalized for high quality and low pressure situations.« less