Effect of Drag Reducing Polymer and Suspended Solid on the Rate of Diffusion Controlled Corrosion in 90° Copper Elbow

NASA Astrophysics Data System (ADS)

Fouad, Mohamed Ahmed; Zewail, Taghreed Mohamed; Amine, Nieven Kamal Abbes

2017-06-01

Rate of diffusion controlled corrosion in 90° Copper Elbow acidified dichromate has been investigated in relation to the following parameters: effect of solution velocity in the absence and presence of drag- reducing polymer on the rate of diffusion controlled corrosion, and effect of the presence of suspended solids on the rate of diffusion controlled corrosion. It was found that the presence of drag reducing polymer inhibited the rate of mass transfer, while the presence of suspended solid increased significantly the rate of mass transfer.

The 300 Area Integrated Field Research Challenge Quality Assurance Project Plan

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

Fix, N. J.

Pacific Northwest National Laboratory and a group of expert collaborators are using the U.S. Department of Energy Hanford Site 300 Area uranium plume within the footprint of the 300-FF-5 groundwater operable unit as a site for an Integrated Field-Scale Subsurface Research Challenge (IFRC). The IFRC is entitled Multi-Scale Mass Transfer Processes Controlling Natural Attenuation and Engineered Remediation: An IFRC Focused on the Hanford Site 300 Area Uranium Plume Project. The theme is investigation of multi-scale mass transfer processes. A series of forefront science questions on mass transfer are posed for research that relate to the effect of spatial heterogeneities; themore » importance of scale; coupled interactions between biogeochemical, hydrologic, and mass transfer processes; and measurements/approaches needed to characterize and model a mass transfer-dominated system. This Quality Assurance Project Plan provides the quality assurance requirements and processes that will be followed by the 300 Area IFRC Project. This plan is designed to be used exclusively by project staff.« less

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

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.

A model for heat and mass input control in GMAW

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

Smartt, H.B.; Einerson, C.J.

1993-05-01

This work describes derivation of a control model for electrode melting and heat and mass transfer from the electrode to the work piece in gas metal arc welding (GMAW). Specifically, a model is developed which allows electrode speed and welding speed to be calculated for given values of voltage and torch-to-base metal distance, as a function of the desired heat and mass input to the weldment. Heat input is given on a per unit weld length basis, and mass input is given in terms of transverse cross-sectional area added to the weld bead (termed reinforcement). The relationship to prior workmore » is discussed. The model was demonstrated using a computer-controlled welding machine and a proportional-integral (PI) controller receiving input from a digital filter. The difference between model-calculated welding current and measured current is used as controller feedback. The model is calibrated for use with carbon steel welding wire and base plate with Ar-CO[sub 2] shielding gas. Although the system is intended for application during spray transfer of molten metal from the electrode to the weld pool, satisfactory performance is also achieved during globular and streaming transfer. Data are presented showing steady-state and transient performance, as well as resistance to external disturbances.« less

Thrust vector control of upper stage with a gimbaled thruster during orbit transfer

NASA Astrophysics Data System (ADS)

Wang, Zhaohui; Jia, Yinghong; Jin, Lei; Duan, Jiajia

2016-10-01

In launching Multi-Satellite with One-Vehicle, the main thruster provided by the upper stage is mounted on a two-axis gimbal. During orbit transfer, the thrust vector of this gimbaled thruster (GT) should theoretically pass through the mass center of the upper stage and align with the command direction to provide orbit transfer impetus. However, it is hard to be implemented from the viewpoint of the engineering mission. The deviations of the thrust vector from the command direction would result in large velocity errors. Moreover, the deviations of the thrust vector from the upper stage mass center would produce large disturbance torques. This paper discusses the thrust vector control (TVC) of the upper stage during its orbit transfer. Firstly, the accurate nonlinear coupled kinematic and dynamic equations of the upper stage body, the two-axis gimbal and the GT are derived by taking the upper stage as a multi-body system. Then, a thrust vector control system consisting of the special attitude control of the upper stage and the gimbal rotation of the gimbaled thruster is proposed. The special attitude control defined by the desired attitude that draws the thrust vector to align with the command direction when the gimbal control makes the thrust vector passes through the upper stage mass center. Finally, the validity of the proposed method is verified through numerical simulations.

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.

Controlling Mass Transport in Microfluidic Devices

PubMed Central

Kuo, Jason S.; Chiu, Daniel T.

2017-01-01

Microfluidic platforms offer exquisite capabilities in controlling mass transport for biological studies. In this review, we focus on recent developments in manipulating chemical concentrations at the microscale. Some techniques prevent or accelerate mixing, whereas others shape the concentration gradients of chemical and biological molecules. We also highlight several in vitro biological studies in the areas of organ engineering, cancer, and blood coagulation that have benefited from accurate control of mass transfer. PMID:21456968

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).

Bubble coalescence suppression driven carbon monoxide (CO)-water mass transfer increase by electrolyte addition in a hollow fiber membrane bioreactor (HFMBR) for microbial CO conversion to ethanol.

PubMed

Jang, Nulee; Yasin, Muhammad; Kang, Hyunsoo; Lee, Yeubin; Park, Gwon Woo; Park, Shinyoung; Chang, In Seop

2018-05-04

This study investigated the effects of electrolytes (CaCl 2 , K 2 HPO 4 , MgSO 4 , NaCl, and NH 4 Cl) on CO mass transfer and ethanol production in a HFMBR. The hollow fiber membranes (HFM) were found to generate tiny gas bubbles; the bubble coalescence was significantly suppressed in electrolyte solution. The volumetric gas-liquid mass transfer coefficients (k L a) increased up to 414% compared to the control. Saturated CO (C ∗ ) decreased as electrolyte concentrations increased. Overall, the maximum mass transfer rate (R max ) in electrolyte solution ranged from 106% to 339% of the value obtained in water. The electrolyte toxicity on cell growth was tested using Clostridium autoethanogenum. Most electrolytes, except for MgSO 4 , inhibited cell growth. The HFMBR operation using a medium containing 1% MgSO 4 achieved 119% ethanol production compared to that without electrolytes. Finally, a kinetic simulation using the parameters got from the 1% MgSO 4 medium predicted a higher ethanol production compared to the control. Copyright © 2018 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.

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.

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

Quantification of the Mass Transfer at Fluid Interfaces in Microfluidic Channels

NASA Astrophysics Data System (ADS)

Wismeth, Carina; Manhart, Michael; Niessner, Reinhard; Baumann, Thomas

2017-04-01

Mass transfer rates at interfaces in a complex porous media are relevant in many environmental applications and control the functions of natural filter systems in subsurface environments. The mass transfer at fluid interfaces is associated with interface convection caused by local inhomogeneities in interface tension and hydrodynamic instabilities at the interface. If there is a surface tension gradient along the surface a shear stress jump is generated that results in fluid motion along the surface that is called Marangoni effect. These spontaneous convection currents can lead to an increased mass transfer of the transition component at the phase boundary and to an increased mixing of the phases. Therefore compensatory currents at the interface can have a significant influence on the subsurface transport of contaminants in the groundwater area, especially in the vadose zone. Using microfluidic channels and advanced experimental techniques it is possible to measure the fluid flow and mass transfer rates directly and to quantify the effect of the Marangoni convection on the mass transfer at interfaces between a non-aqueous liquid and water with high temporal and spatial resolution. The use of fluorescent particles as well as the recording and analysis of their trajectories is intended to visualize interfacial processes and to quantify the mass transfer at fluid phase boundaries. Concentration gradients at the interface are analysed by spectroscopic methods and allow an assessment of the enrichment and depletion at the phase boundaries. Extensive test series provide the experimental basis for quantifying and analysing the impact of the Marangoni effect on the mass transfer rates at interfaces in porous media in subsurface aquatic environments. Within this research project we concentrate on the effect of Marangoni convection on the mass transfer near an 1-octanol-water interface, which serves as a well defined proxy for non-aqueous phase liquids in porous media. Experiments and a numerical simulation are closely coupled to provide a generic data set with high reproducibility and used to obtain highly resolved three-dimensional data of mass transfer in two- and three-phase systems to foster the understanding of subsurface transport, especially in the vadose zone.

A new active variable stiffness suspension system using a nonlinear energy sink-based controller

NASA Astrophysics Data System (ADS)

Anubi, Olugbenga Moses; Crane, Carl D.

2013-10-01

This paper presents the active case of a variable stiffness suspension system. The central concept is based on a recently designed variable stiffness mechanism which consists of a horizontal control strut and a vertical strut. The horizontal strut is used to vary the load transfer ratio by actively controlling the location of the point of attachment of the vertical strut to the car body. The control algorithm, effected by a hydraulic actuator, uses the concept of nonlinear energy sink (NES) to effectively transfer the vibrational energy in the sprung mass to a control mass, thereby reducing the transfer of energy from road disturbance to the car body at a relatively lower cost compared to the traditional active suspension using the skyhook concept. The analyses and simulation results show that a better performance can be achieved by subjecting the point of attachment of a suspension system, to the chassis, to the influence of a horizontal NES system.

MHD Forced Convective Laminar Boundary Layer Flow from a Convectively Heated Moving Vertical Plate with Radiation and Transpiration Effect

PubMed Central

Uddin, Md. Jashim; Khan, Waqar A.; Ismail, A. I. Md.

2013-01-01

A two-dimensional steady forced convective flow of a Newtonian fluid past a convectively heated permeable vertically moving plate in the presence of a variable magnetic field and radiation effect has been investigated numerically. The plate moves either in assisting or opposing direction to the free stream. The plate and free stream velocities are considered to be proportional to whilst the magnetic field and mass transfer velocity are taken to be proportional to where is the distance along the plate from the leading edge of the plate. Instead of using existing similarity transformations, we use a linear group of transformations to transform the governing equations into similarity equations with relevant boundary conditions. Numerical solutions of the similarity equations are presented to show the effects of the controlling parameters on the dimensionless velocity, temperature and concentration profiles as well as on the friction factor, rate of heat and mass transfer. It is found that the rate of heat transfer elevates with the mass transfer velocity, convective heat transfer, Prandtl number, velocity ratio and the magnetic field parameters. It is also found that the rate of mass transfer enhances with the mass transfer velocity, velocity ratio, power law index and the Schmidt number, whilst it suppresses with the magnetic field parameter. Our results are compared with the results existing in the open literature. The comparisons are satisfactory. PMID:23741295

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.

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.

Determination of beam-position dependent transfer functions of LCR-G gravimeters by means of moving mass calibration device in the Mátyáshegy Gravity and Geodynamical Observatory, Budapest

NASA Astrophysics Data System (ADS)

Koppán, András; Kis, Márta; Merényi, László; Papp, Gábor; Benedek, Judit; Meurers, Bruno

2017-04-01

In this presentation authors propose a method for the determination of transfer characteristics and fine calibration of LCR relative gravimeters used for earth-tide recordings, by means of the moving-mass gravimeter calibration device of Budapest-Mátyáshegy Gravity and Geodynamical Observatory. Beam-position dependent transfer functions of four relative LCR G type gravimeters were determined and compared. In order to make these instruments applicable for observatory tidal recordings, there is a need for examining the unique characteristics of equipments and adequately correcting these inherent distorting effects. Thus, the sensitivity for the tilting, temporal changes of scale factors and beam-position dependent transfer characteristics are necessary to be determined for observatory use of these instruments. During the calibration a cylindrical ring of 3200 kg mass is vertically moving around the equipment, generating gravity variations. The effect of the moving mass can be precisely calculated from the known mass and geometrical parameters. The maximum theoretical gravity variation produced by the vertical movement of the mass is ab. 110 microGal, so it provides excellent possibility for the fine calibration of gravimeters in the tidal range. Magnetic experiments were also carried out on the pillar of the calibration device as well, in order to analyse the magnetic effect of the moving stainless steel-mass. According to the magnetic measurements, a correction for the magnetic effect was applied on the measured gravimetric data series. The calibration process is aided by intelligent controller electronics. A PLC-based system has been developed to allow easy control of the movement of the calibrating mass and to measure the mass position. It enables also programmed steps of movements (waiting positions and waiting times) for refined gravity changes. All parameters (position of the mass, CPI data, X/Y leveling positions) are recorded with 1/sec. sampling rate. The system can be controlled remotely through the internet. Authors wish to express their thanks to OTKA (Hungarian Scientific Research Fund) for their support (OTKA-K101603, OTKA K109060).

Geochemistry of spring water, southeastern Uinta Basin, Utah and Colorado

USGS Publications Warehouse

Kimball, Briant A.

1981-01-01

The chemical quality of water in the southeastern Uinta Basin, Utah and Colorado, is important to the future development of the abundant oil-shale resources of the area. This report examines the observed changes in chemistry as water circulates in both shallow and deep ground-water systems. Mass-balance and mass- transfer calculations are used to define reactions that simulate the observed water chemistry in the mixed sandstone, siltstone, and carbonate lithology of the Green River Formation of Tertiary age.The mass-transfer calculations determine a reaction path particular to this system. The early dominance of calcite dissolution produces a calcium carbonate water. After calcite saturation, deeper circulation and further rock-water interaction cause the reprecipitation of calcite, the dissolution of dolomite and plagioclase, and the oxidation of pyrite; all combining to produce a calcium magnesium sodium bicarbonate sulfate water. The calculations suggest that silica concentrations are controlled by a kaolinite-Ca-montmorillonite phase boundary. Close agreement of mineral-saturation indices calculated by both an aqueous-equilibrium model and the mass-transfer model support the selection of reactions from the mass-transfer calculations.

Preliminary characterization of carbon dioxide transfer in a hollow fiber membrane module as a possible solution for gas-liquid transfer in microgravity conditions

NASA Astrophysics Data System (ADS)

Farges, Bérangère; Duchez, David; Dussap, Claude-Gilles; Cornet, Jean-François

2012-01-01

In microgravity, one of the major challenge encountered in biological life support systems (BLSS) is the gas-liquid transfer with, for instance, the necessity to provide CO2 (carbon source, pH control) and to recover the evolved O2 in photobioreactors used as atmosphere bioregenerative systems.This paper describes first the development of a system enabling the accurate characterization of the mass transfer limiting step for a PTFE membrane module used as a possible efficient solution to the microgravity gas-liquid transfer. This original technical apparatus, together with a technical assessment of membrane permeability to different gases, is associated with a balance model, determining thus completely the CO2 mass transfer problem between phases. First results are given and discussed for the CO2 mass transfer coefficient kLCO obtained in case of absorption experiments at pH 8 using the hollow fiber membrane module. The consistency of the proposed method, based on a gas and liquid phase balances verifying carbon conservation enables a very accurate determination of the kLCO value as a main limiting step of the whole process. Nevertheless, further experiments are still needed to demonstrate that the proposed method could serve in the future as reference method for mass transfer coefficient determination if using membrane modules for BLSS in reduced or microgravity conditions.

Heat transfer in a microvascular network: the effect of heart rate on heating and cooling in reptiles (Pogona barbata and Varanus varius).

PubMed

Seebacher, F

2000-03-21

Thermally-induced changes in heart rate and blood flow in reptiles are believed to be of selective advantage by allowing animal to exert some control over rates of heating and cooling. This notion has become one of the principal paradigms in reptilian thermal physiology. However, the functional significance of changes in heart rate is unclear, because the effect of heart rate and blood flow on total animal heat transfer is not known. I used heat transfer theory to determine the importance of heat transfer by blood flow relative to conduction. I validated theoretical predictions by comparing them with field data from two species of lizard, bearded dragons (Pogona barbata) and lace monitors (Varanus varius). Heart rates measured in free-ranging lizards in the field were significantly higher during heating than during cooling, and heart rates decreased with body mass. Convective heat transfer by blood flow increased with heart rate. Rates of heat transfer by both blood flow and conduction decreased with mass, but the mass scaling exponents were different. Hence, rate of conductive heat transfer decreased more rapidly with increasing mass than did heat transfer by blood flow, so that the relative importance of blood flow in total animal heat transfer increased with mass. The functional significance of changes in heart rate and, hence, rates of heat transfer, in response to heating and cooling in lizards was quantified. For example, by increasing heart rate when entering a heating environment in the morning, and decreasing heart rate when the environment cools in the evening a Pogona can spend up to 44 min longer per day with body temperature within its preferred range. It was concluded that changes in heart rate in response to heating and cooling confer a selective advantage at least on reptiles of mass similar to that of the study animals (0. 21-5.6 kg). Copyright 2000 Academic Press.

An environmental transfer hub for multimodal atom probe tomography.

PubMed

Perea, Daniel E; Gerstl, Stephan S A; Chin, Jackson; Hirschi, Blake; Evans, James E

2017-01-01

Environmental control during transfer between instruments is required for samples sensitive to air or thermal exposure to prevent morphological or chemical changes prior to analysis. Atom probe tomography is a rapidly expanding technique for three-dimensional structural and chemical analysis, but commercial instruments remain limited to loading specimens under ambient conditions. In this study, we describe a multifunctional environmental transfer hub allowing controlled cryogenic or room-temperature transfer of specimens under atmospheric or vacuum pressure conditions between an atom probe and other instruments or reaction chambers. The utility of the environmental transfer hub is demonstrated through the acquisition of previously unavailable mass spectral analysis of an intact organic molecule made possible via controlled cryogenic transfer into the atom probe using the hub. The ability to prepare and transfer specimens in precise environments promises a means to access new science across many disciplines from untainted samples and allow downstream time-resolved in situ atom probe studies.

The Multi-Scale Mass Transfer Processes Controlling Natural Attenuation and Engineered Remediation: An IFC Focused on Hanford’s 300 Area Uranium Plume Quality Assurance Project Plan

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

Fix, N. J.

The purpose of the project is to conduct research at an Integrated Field-Scale Research Challenge Site in the Hanford Site 300 Area, CERCLA OU 300-FF-5 (Figure 1), to investigate multi-scale mass transfer processes associated with a subsurface uranium plume impacting both the vadose zone and groundwater. The project will investigate a series of science questions posed for research related to the effect of spatial heterogeneities, the importance of scale, coupled interactions between biogeochemical, hydrologic, and mass transfer processes, and measurements/approaches needed to characterize a mass-transfer dominated system. The research will be conducted by evaluating three (3) different hypotheses focused onmore » multi-scale mass transfer processes in the vadose zone and groundwater, their influence on field-scale U(VI) biogeochemistry and transport, and their implications to natural systems and remediation. The project also includes goals to 1) provide relevant materials and field experimental opportunities for other ERSD researchers and 2) generate a lasting, accessible, and high-quality field experimental database that can be used by the scientific community for testing and validation of new conceptual and numerical models of subsurface reactive transport.« less

Understanding Recent Mass Balance Changes of the Greenland Ice Sheet

NASA Technical Reports Server (NTRS)

vanderVeen, Cornelius

2003-01-01

The ultimate goal of this project is to better understand the current transfer of mass between the Greenland Ice Sheet, the world's oceans and the atmosphere, and to identify processes controlling the rate of this transfer, to be able to predict with greater confidence future contributions to global sea level rise. During the first year of this project, we focused on establishing longer-term records of change of selected outlet glaciers, reevaluation of mass input to the ice sheet and analysis of climate records derived from ice cores, and modeling meltwater production and runoff from the margins of the ice sheet.

Mathematical Simulation of the Process of Aerobic Treatment of Wastewater under Conditions of Diffusion and Mass Transfer Perturbations

NASA Astrophysics Data System (ADS)

Bomba, A. Ya.; Safonik, A. P.

2018-05-01

A mathematical model of the process of aerobic treatment of wastewater has been refined. It takes into account the interaction of bacteria, as well as of organic and biologically nonoxidizing substances under conditions of diffusion and mass transfer perturbations. An algorithm of the solution of the corresponding nonlinear perturbed problem of convection-diffusion-mass transfer type has been constructed, with a computer experiment carried out based on it. The influence of the concentration of oxygen and of activated sludge on the quality of treatment is shown. Within the framework of the model suggested, a possibility of automated control of the process of deposition of impurities in a biological filter depending on the initial parameters of the water medium is suggested.

Mathematical Simulation of the Process of Aerobic Treatment of Wastewater under Conditions of Diffusion and Mass Transfer Perturbations

NASA Astrophysics Data System (ADS)

Bomba, A. Ya.; Safonik, A. P.

2018-03-01

A mathematical model of the process of aerobic treatment of wastewater has been refined. It takes into account the interaction of bacteria, as well as of organic and biologically nonoxidizing substances under conditions of diffusion and mass transfer perturbations. An algorithm of the solution of the corresponding nonlinear perturbed problem of convection-diffusion-mass transfer type has been constructed, with a computer experiment carried out based on it. The influence of the concentration of oxygen and of activated sludge on the quality of treatment is shown. Within the framework of the model suggested, a possibility of automated control of the process of deposition of impurities in a biological filter depending on the initial parameters of the water medium is suggested.

A Reaction Between High Mn-High Al Steel and CaO-SiO2-Type Molten Mold Flux: Part II. Reaction Mechanism, Interface Morphology, and Al2O3 Accumulation in Molten Mold Flux

NASA Astrophysics Data System (ADS)

Kang, Youn-Bae; Kim, Min-Su; Lee, Su-Wan; Cho, Jung-Wook; Park, Min-Seok; Lee, Hae-Geon

2013-04-01

Following a series of laboratory-scale experiments, the mechanism of a chemical reaction 4[{Al}] + 3({SiO}_2) = 3[{Si}] + 2({Al}_2{O}_3) between high-alloyed TWIP (TWin-Induced Plasticity) steel containing Mn and Al and molten mold flux composed mainly of CaO-SiO2 during the continuous casting process is discussed in the present article in the context of kinetic analysis, morphological evolution at the reaction interface. By the kinetic analysis using a two-film theory, a rate-controlling step of the chemical reaction at the interface between the molten steel and the molten flux is found to be mass transport of Al in a boundary layer of the molten steel, as long as the molten steel and the molten flux phases are concerned. Mass transfer coefficient of the Al in the boundary layer (k_{{Al}}) is estimated to be 0.9 to 1.2 × 10-4 m/s at 1773 K (1500 ^{circ}C). By utilizing experimental data at various temperatures, the following equation is obtained for the k_{{Al}}; ln k_{{Al}} = -14,290/T - 1.1107. Activation energy for the mass transfer of Al in the boundary layer is 119 kJ/mol, which is close to a value of activation energy for mass transfer in metal phase. The composition evolution of Al in the molten steel was well explained by the mechanism of Al mass transfer. On the other hand, when the concentration of Al in the steel was high, a significant deviation of the composition evolution of Al in the molten steel was observed. By observing reaction interface between the molten steel and the molten flux, it is thought that the chemical reaction controlled by the mass transfer of Al seemed to be disturbed by formation of a solid product layer of MgAl2O4. A model based on a dynamic mass balance and the reaction mechanism of mass transfer of Al in the boundary layer for the low Al steel was developed to predict (pct Al2O3) accumulation rate in the molten mold flux.

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.

Optical mass memory system (AMM-13). AMM/DBMS interface control document

NASA Technical Reports Server (NTRS)

Bailey, G. A.

1980-01-01

The baseline for external interfaces of a 10 to the 13th power bit, optical archival mass memory system (AMM-13) is established. The types of interfaces addressed include data transfer; AMM-13, Data Base Management System, NASA End-to-End Data System computer interconnect; data/control input and output interfaces; test input data source; file management; and facilities interface.

Investigations of the Controlling Factors for Air Emissions Associated With the Dredging of Indiana Harbor and Canal (IHC) and CDF Operations

DTIC Science & Technology

2008-04-01

concepts of a transient toxic constituent loss and transport model for both solids and chemical incorporating a kinetic approach rather than equilibrium...to air. A transient kinetic mass-transfer model was applied to the data and it was found that the TSS level was the most critical parameter for...measured (Thibodeaux et al. 2004). The transient behavior followed the expected theory of the mass-transfer kinetic, but the conventional LEA model

Performance Modeling of Network-Attached Storage Device Based Hierarchical Mass Storage Systems

NASA Technical Reports Server (NTRS)

Menasce, Daniel A.; Pentakalos, Odysseas I.

1995-01-01

Network attached storage devices improve I/O performance by separating control and data paths and eliminating host intervention during the data transfer phase. Devices are attached to both a high speed network for data transfer and to a slower network for control messages. Hierarchical mass storage systems use disks to cache the most recently used files and a combination of robotic and manually mounted tapes to store the bulk of the files in the file system. This paper shows how queuing network models can be used to assess the performance of hierarchical mass storage systems that use network attached storage devices as opposed to host attached storage devices. Simulation was used to validate the model. The analytic model presented here can be used, among other things, to evaluate the protocols involved in 1/0 over network attached devices.

Mixing-controlled reactive transport on travel times in heterogeneous media

NASA Astrophysics Data System (ADS)

Luo, J.; Cirpka, O.

2008-05-01

Modeling mixing-controlled reactive transport using traditional spatial discretization of the domain requires identifying the spatial distributions of hydraulic and reactive parameters including mixing-related quantities such as dispersivities and kinetic mass-transfer coefficients. In most applications, breakthrough curves of conservative and reactive compounds are measured at only a few locations and models are calibrated by matching these breakthrough curves, which is an ill posed inverse problem. By contrast, travel-time based transport models avoid costly aquifer characterization. By considering breakthrough curves measured on different scales, one can distinguish between mixing, which is a prerequisite for reactions, and spreading, which per se does not foster reactions. In the travel-time based framework, the breakthrough curve of a solute crossing an observation plane, or ending in a well, is interpreted as the weighted average of concentrations in an ensemble of non-interacting streamtubes, each of which is characterized by a distinct travel-time value. Mixing is described by longitudinal dispersion and/or kinetic mass transfer along individual streamtubes, whereas spreading is characterized by the distribution of travel times which also determines the weights associated to each stream tube. Key issues in using the travel-time based framework include the description of mixing mechanisms and the estimation of the travel-time distribution. In this work, we account for both apparent longitudinal dispersion and kinetic mass transfer as mixing mechanisms, thus generalizing the stochastic-convective model with or without inter-phase mass transfer and the advective-dispersive streamtube model. We present a nonparametric approach of determining the travel-time distribution, given a breakthrough curve integrated over an observation plane and estimated mixing parameters. The latter approach is superior to fitting parametric models in cases where the true travel-time distribution exhibits multiple peaks or long tails. It is demonstrated that there is freedom for the combinations of mixing parameters and travel-time distributions to fit conservative breakthrough curves and describe the tailing. Reactive transport cases with a bimolecular instantaneous irreversible reaction and a dual Michaelis-Menten problem demonstrate that the mixing introduced by local dispersion and mass transfer may be described by apparent mean mass transfer with coefficients evaluated by local breakthrough curves.

Optimal orbit transfer suitable for large flexible structures

NASA Technical Reports Server (NTRS)

Chatterjee, Alok K.

1989-01-01

The problem of continuous low-thrust planar orbit transfer of large flexible structures is formulated as an optimal control problem with terminal state constraints. The dynamics of the spacecraft motion are treated as a point-mass central force field problem; the thrust-acceleration magnitude is treated as an additional state variable; and the rate of change of thrust-acceleration is treated as a control variable. To ensure smooth transfer, essential for flexible structures, an additional quadratic term is appended to the time cost functional. This term penalizes any abrupt change in acceleration. Numerical results are presented for the special case of a planar transfer.

Hydrodynamic fabrication of structurally gradient ZnO nanorods.

PubMed

Kim, Hyung Min; Youn, Jae Ryoun; Song, Young Seok

2016-02-26

We studied a new approach where structurally gradient nanostructures were fabricated by means of hydrodynamics. Zinc oxide (ZnO) nanorods were synthesized in a drag-driven rotational flow in a controlled manner. The structural characteristics of nanorods such as orientation and diameter were determined by momentum and mass transfer at the substrate surface. The nucleation of ZnO was induced by shear stress which plays a key role in determining the orientation of ZnO nanorods. The nucleation and growth of such nanostructures were modeled theoretically and analyzed numerically to understand the underlying physics of the fabrication of nanostructures controlled by hydrodynamics. The findings demonstrated that the precise control of momentum and mass transfer enabled the formation of ZnO nanorods with a structural gradient in diameter and orientation.

Study of acetic acid production by immobilized acetobacter cells: oxygen transfer

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

Ghommidh, C.; Navarro, J.M.; Durand, G.

1982-03-01

The immobilization of living Acetobacter cells by adsorption onto a large-surface-area ceramic support was studied in a pulsed flow reactor. The high oxygen transfer capability of the reactor enabled acetic acid production rates up to 10.4 g/L/h to be achieved. Using a simple mathematical model incorporating both internal and external mass transfer coefficients, it was shown that oxygen transfer in the microbial film controls the reactor productivity. (Refs. 10).

A theoretical study of the spheroidal droplet evaporation in forced convection

NASA Astrophysics Data System (ADS)

Li, Jie; Zhang, Jian

2014-11-01

In many applications, the shape of a droplet may be assumed to be an oblate spheroid. A theoretical study is conducted on the evaporation of an oblate spheroidal droplet under forced convection conditions. Closed-form analytical expressions of the mass evaporation rate for an oblate spheroid are derived, in the regime of controlled mass-transfer and heat-transfer, respectively. The variation of droplet size during the evaporation process is presented in the regime of shrinking dynamic model. Comparing with the droplets having the same surface area, an increase in the aspect ratio enhances the mass evaporation rate and prolongs the burnout time.

Controls of sediment transfers, sedimentary budgets and relief development in cold environments: Results from four catchment systems in Iceland, Swedish Lapland and Finnish Lapland

NASA Astrophysics Data System (ADS)

Beylich, A. A.

2012-04-01

By the combined, longer-term and quantitative recording of relevant denudative slope processes and stream work in four selected catchment systems in sub-arctic oceanic Eastern Iceland (Hrafndalur and Austdalur), arctic-oceanic Swedish Lapland (Latnjavagge) and sub-arctic oceanic Finnish Lapland (Kidisjoki), information on the absolute and relative importance of the different denudative processes is collected. Direct comparison of the four catchment geo-systems (the catchment sizes range from 7 km2 to 23 km2) allows conclusions on major controls of sediment transfers, sedimentary budgets and relief development in theses cold climate environments. To allow direct comparison of the different processes, all mass transfers are calculated as tonnes multiplied by meter per year, i.e. as the product of the annually transferred mass and the corresponding transport distance. Ranking the different processes according to their annual mass transfers shows that stream work dominates over slope denudation. For Hrafndalur (Eastern Iceland) the following order of denudative processes is found after nine years of process studies (2001 - 2010): (1) Fluvial suspended sediment plus bedload transport, (2) Fluvial solute transport, (3) Rock falls plus boulder falls, (4) Chemical slope denudation, (5) Mechanical fluvial slope denudation (slope wash), (6) Creep processes, (7) Avalanches, (8) Debris flows, (9) Translation slides, (10) Deflation. Compared to that, in Austdalur the following ranking is given after fourten years of process studies (1996 - 2010): (1) Fluvial suspended sediment plus bedload transport, (2) Fluvial solute transport, (3) Mechanical fluvial slope denudation (slope wash), (4) Chemical slope denudation, (5) Avalanches, (6) Rock falls plus boulder falls, (7) Creep processes, (8) Debris flows, (9) Deflation, (10) Translation slides. In the Latnjavagge catchment (Swedish Lapland) the ranking is (eleven-years period of studies, 1999 - 2010): (1) Fluvial solute transport, (2) Fluvial suspended sediment plus bedload transport, (3) Rock falls plus boulder falls, (4) Chemical slope denudation, (5) Mechanical fluvial slope denudation (slope wash), (6) Avalanches, (7) Creep processes and solifluction, (8) Slush flows, (9) Debris flows, (10) Translation slides, (11) Deflation. In Kidisjoki (Finnish Lapland) the order of processes, as determined after a nine-years period (2001 - 2010) of geomorphic process studies, is: (1) Fluvial solute transport, (2) Chemical slope denudation, (3) Fluvial suspended sediment plus bedload transport, (4) Mechanical fluvial slope denudation, (5) Creep processes, (6) Avalanches and slush flows, (7) Debris flows and slides, (8) Rock and boulder falls, (9) Deflation. As a result, in all four selected cold climate study areas the intensity of contemporary denudative processes and mass transfers is altogether rather low, which is in opposition to the earlier postulated oppinion of a generally high intensity of geomorphic processes in cold climate environments. A direct comparison of the annual mass transfers summarises that there are differences between process intensities and the relative importance of different denudative processes within the four study areas. The major controls of these detected differences are: (i) Climate: The higher annual precipitation along with the larger number of extreme rainfall events and the higher frequency of snowmelt and rainfall generated peak runoff events in Eastern Iceland as compared to Swedish Lapland and Finnish Lapland lead to higher mass transfers, (ii) Lithology: The low resistance of rhyolites in Hrafndalur causes especially high weathering rates and connected mass transfers in this catchment. Due to the lower resistance of the rhyolites as compared to the basalts found in Austdalur Postglacial modification of the glacially formed relief is clearly further advanced in Hrafndalur as compared to Austdalur, (iii) Relief: The greater steepness of the Icelandic catchments leads to higher mass transfers here as compared to Latnjavagge and Kidisjoki, (iv) Vegetation cover: The significant disturbance of the vegetation cover by human impacts in Easter Iceland causes higher mass transfers (slope wash) whereas restricted sediment availability is a main reason for lower mass transfers in Swedish Lapland and Finnish Lapland. The applied catchment-based approach seems to be effective for analysing sediment budgets and trends of Postglacial relief development in selected study areas with given environmental settings. Direct comparison of investigated catchments will improve possibilities to model relief development as well as possible effects of projected climate change in cold climate environments.

Accounting for the Effect of Noncondensing Gases on Interphasic Heat and Mass Transfer in the Two-Fluid Model Used in the KORSAR Code

NASA Astrophysics Data System (ADS)

Yudov, Yu. V.

2018-03-01

A model is presented of the interphasic heat and mass transfer in the presence of noncondensable gases for the KORSAR/GP design code. This code was developed by FGUP NITI and the special design bureau OKB Gidropress. It was certified by Rostekhnadzor in 2009 for numerical substantiation of the safety of reactor installations with VVER reactors. The model is based on the assumption that there are three types of interphasic heat and mass transfer of the vapor component: vapor condensation or evaporation on the interphase under any thermodynamic conditions of the phases, pool boiling of the liquid superheated above the saturation temperature at the total pressure, and spontaneous condensation in the volume of gas phase supercooled below the saturation temperature at the vapor partial pressure. Condensation and evaporation on the interphase continuously occur in a two-phase flow and control the time response of the interphase heat and mass transfer. Boiling and spontaneous condensation take place only at the metastable condition of the phases and run at a quite high speed. The procedure used for calculating condensation and evaporation on the interphase accounts for the combined diffusion and thermal resistance of mass transfer in all regimes of the two-phase flow. The proposed approach accounts for, in a natural manner, a decrease in the rate of steam condensation (or generation) in the presence of noncondensing components in the gas phase due to a decrease (or increase) in the interphase temperature relative to the saturation temperature at the vapor partial pressure. The model of the interphase heat transfer also accounts for the processes of dissolution or release of noncondensing components in or from the liquid. The gas concentration at the interphase and on the saturation curve is calculated by the Henry law. The mass transfer coefficient in gas dissolution is based on the heat and mass transfer analogy. Results are presented of the verification of the interphase heat and mass transfer used in the KORSAR/GP code based on the data on film condensation of steam-air flows in vertical pipes. The proposed model was also tested by solving a problem of nitrogen release from a supersaturated water solution.

Low-thrust orbit transfer optimization with refined Q-law and multi-objective genetic algorithm

NASA Technical Reports Server (NTRS)

Lee, Seungwon; Petropoulos, Anastassios E.; von Allmen, Paul

2005-01-01

An optimization method for low-thrust orbit transfers around a central body is developed using the Q-law and a multi-objective genetic algorithm. in the hybrid method, the Q-law generates candidate orbit transfers, and the multi-objective genetic algorithm optimizes the Q-law control parameters in order to simultaneously minimize both the consumed propellant mass and flight time of the orbit tranfer. This paper addresses the problem of finding optimal orbit transfers for low-thrust spacecraft.

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.

Use of magnetic nanoparticles to enhance bioethanol production in syngas fermentation.

PubMed

Kim, Young-Kee; Lee, Haryeong

2016-03-01

The effect of two types of nanoparticles on the enhancement of bioethanol production in syngas fermentation by Clostridium ljungdahlii was examined. Methyl-functionalized silica and methyl-functionalized cobalt ferrite-silica (CoFe2O4@SiO2-CH3) nanoparticles were used to improve syngas-water mass transfer. Of these, CoFe2O4@SiO2-CH3 nanoparticles showed better enhancement of syngas mass transfer. The nanoparticles were recovered using a magnet and reused five times to evaluate reusability, and it was confirmed that their capability for mass transfer enhancement was maintained. Both types of nanoparticles were applied to syngas fermentation, and production of biomass, ethanol, and acetic acid was enhanced. CoFe2O4@SiO2-CH3 nanoparticles were more efficient for the productivity of syngas fermentation due to improved syngas mass transfer. The biomass, ethanol, and acetic acid production compared to a control were increased by 227.6%, 213.5%, and 59.6%, respectively by addition of CoFe2O4@SiO2-CH3 nanoparticles. The reusability of the nanoparticles was confirmed by reuse of recovered nanoparticles for fermentation. Copyright © 2016 Elsevier Ltd. All rights reserved.

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.

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.

Biofilms in 3D porous media: Delineating the influence of the pore network geometry, flow and mass transfer on biofilm development.

PubMed

Carrel, Maxence; Morales, Verónica L; Beltran, Mario A; Derlon, Nicolas; Kaufmann, Rolf; Morgenroth, Eberhard; Holzner, Markus

2018-05-01

This study investigates the functional correspondence between porescale hydrodynamics, mass transfer, pore structure and biofilm morphology during progressive biofilm colonization of a porous medium. Hydrodynamics and the structure of both the porous medium and the biofilm are experimentally measured with 3D particle tracking velocimetry and micro X-ray Computed Tomography, respectively. The analysis focuses on data obtained in a clean porous medium after 36 h of biofilm growth. Registration of the particle tracking and X-ray data sets allows to delineate the interplay between porous medium geometry, hydrodynamic and mass transfer processes on the morphology of the developing biofilm. A local analysis revealed wide distributions of wall shear stresses and concentration boundary layer thicknesses. The spatial distribution of the biofilm patches uncovered that the wall shear stresses controlled the biofilm development. Neither external nor internal mass transfer limitations were noticeable in the considered system, consistent with the excess supply of nutrient and electron acceptors. The wall shear stress remained constant in the vicinity of the biofilm but increased substantially elsewhere. Copyright © 2018 Elsevier Ltd. All rights reserved.

Use of a parallel artificial membrane system to evaluate passive absorption and elimination in small fish.

PubMed

Kwon, Jung-Hwan; Katz, Lynn E; Liljestrand, Howard M

2006-12-01

A parallel artificial lipid membrane system was developed to mimic passive mass transfer of hydrophobic organic chemicals in fish. In this physical model system, a membrane filter-supported lipid bilayer separates two aqueous phases that represent the external and internal aqueous environments of fish. To predict bioconcentration kinetics in small fish with this system, literature absorption and elimination rates were analyzed with an allometric diffusion model to quantify the mass transfer resistances in the aqueous and lipid phases of fish. The effect of the aqueous phase mass transfer resistance was controlled by adjusting stirring intensity to mimic bioconcentration rates in small fish. Twenty-three simple aromatic hydrocarbons were chosen as model compounds for purposes of evaluation. For most of the selected chemicals, literature absorption/elimination rates fall into the range predicted from measured membrane permeabilities and elimination rates of the selected chemicals determined by the diffusion model system.

Some Biological Hints on the Control of Heat and Mass Transfer

NASA Astrophysics Data System (ADS)

Hagiwara, Yoshimichi

This review paper explores the possibilities of the control of heat and mass transfer associated with drought tolerance and freeze tolerance. The accumulation of some metabolites, such as proline and trehalose, are effective for drought tolerance. The special microstructures on the surfaces of some plants and insects in deserts are effective for collecting moisture in the air. Methods of preserving crops will be improved by the mimetic of the drought tolerance. Calcium ions and a protein are effective for the retrieval of damaged cell membrane due to ice formation. Ice crystal growth is inhibited by some substances such as antifreeze proteins. The cryopreservation of foods and organs will be improved by the mimetic of the freeze tolerance.

Lattice Boltzmann simulation of the gas-solid adsorption process in reconstructed random porous media.

PubMed

Zhou, L; Qu, Z G; Ding, T; Miao, J Y

2016-04-01

The gas-solid adsorption process in reconstructed random porous media is numerically studied with the lattice Boltzmann (LB) method at the pore scale with consideration of interparticle, interfacial, and intraparticle mass transfer performances. Adsorbent structures are reconstructed in two dimensions by employing the quartet structure generation set approach. To implement boundary conditions accurately, all the porous interfacial nodes are recognized and classified into 14 types using a proposed universal program called the boundary recognition and classification program. The multiple-relaxation-time LB model and single-relaxation-time LB model are adopted to simulate flow and mass transport, respectively. The interparticle, interfacial, and intraparticle mass transfer capacities are evaluated with the permeability factor and interparticle transfer coefficient, Langmuir adsorption kinetics, and the solid diffusion model, respectively. Adsorption processes are performed in two groups of adsorbent media with different porosities and particle sizes. External and internal mass transfer resistances govern the adsorption system. A large porosity leads to an early time for adsorption equilibrium because of the controlling factor of external resistance. External and internal resistances are dominant at small and large particle sizes, respectively. Particle size, under which the total resistance is minimum, ranges from 3 to 7 μm with the preset parameters. Pore-scale simulation clearly explains the effect of both external and internal mass transfer resistances. The present paper provides both theoretical and practical guidance for the design and optimization of adsorption systems.

Lattice Boltzmann simulation of the gas-solid adsorption process in reconstructed random porous media

NASA Astrophysics Data System (ADS)

Zhou, L.; Qu, Z. G.; Ding, T.; Miao, J. Y.

2016-04-01

The gas-solid adsorption process in reconstructed random porous media is numerically studied with the lattice Boltzmann (LB) method at the pore scale with consideration of interparticle, interfacial, and intraparticle mass transfer performances. Adsorbent structures are reconstructed in two dimensions by employing the quartet structure generation set approach. To implement boundary conditions accurately, all the porous interfacial nodes are recognized and classified into 14 types using a proposed universal program called the boundary recognition and classification program. The multiple-relaxation-time LB model and single-relaxation-time LB model are adopted to simulate flow and mass transport, respectively. The interparticle, interfacial, and intraparticle mass transfer capacities are evaluated with the permeability factor and interparticle transfer coefficient, Langmuir adsorption kinetics, and the solid diffusion model, respectively. Adsorption processes are performed in two groups of adsorbent media with different porosities and particle sizes. External and internal mass transfer resistances govern the adsorption system. A large porosity leads to an early time for adsorption equilibrium because of the controlling factor of external resistance. External and internal resistances are dominant at small and large particle sizes, respectively. Particle size, under which the total resistance is minimum, ranges from 3 to 7 μm with the preset parameters. Pore-scale simulation clearly explains the effect of both external and internal mass transfer resistances. The present paper provides both theoretical and practical guidance for the design and optimization of adsorption systems.

CARBON DIOXIDE REDUCTION CONTACTORS IN SPACE VEHICLES AND OTHER ENCLOSED STRUCTURES,

DTIC Science & Technology

CONTROLLED ATMOSPHERES, CARBON DIOXIDE, REMOVAL, LIFE SUPPORT SYSTEMS, SPACE ENVIRONMENTS, CONFINED ENVIRONMENTS, OXYGEN CONSUMPTION, REGENERATION(ENGINEERING), CHEMISORPTION, MASS TRANSFER, FLUID MECHANICS, CENTRIFUGES .

Mass transfer inside a flux hood for the sampling of gaseous emissions from liquid surfaces - Experimental assessment and emission rate rescaling

NASA Astrophysics Data System (ADS)

Prata, Ademir A.; Lucernoni, Federico; Santos, Jane M.; Capelli, Laura; Sironi, Selena; Le-Minh, Nhat; Stuetz, Richard M.

2018-04-01

This study assesses the mass transfer of compounds inside the US EPA flux hood, one of the enclosure devices most commonly employed for the direct measurement of atmospheric emissions from liquid surfaces in wastewater treatment plants (WWTPs). Experiments comprised the evaporation of water and the volatilisation of a range of volatile organic compounds (VOCs). Special attention was given to the evaluation of the mass transfer coefficients in the microenvironment created by the flux hood and the effects of concentration build up in the hood's headspace. The VOCs emission rates and the water evaporation rates generally increased with the sweep air flow rate, as did the mass transfer coefficients for all compounds. The emission of compounds whose volatilisation is significantly influenced by the gas phase was greatly affected by concentration build up, whereas this effect was not significant for liquid phase-controlled compounds. The gas-film mass transfer coefficient (kG) estimated inside the US EPA flux hood was of the same order as the respective kG reported in the literature for wind tunnel-type devices, but the emission rates measured by the flux hood can be expected to be lower, due to the concentration build-up. Compared against an emission model for the passive surfaces in WWTPs, the mass transfer of acetic acid (representing a gas phase-dominated compound) inside the US EPA flux hood was equivalent to conditions of wind speeds at 10 m height (U10) of 0.27, 0.51 and 0.99 m s-1, respectively, for sweep air flow rates of 2, 5 and 10 L min-1. On the other hand, for higher wind speeds, the emission rates of gas phase-controlled compounds obtained with the flux hood can be considerably underestimated: for instance, at U10 = 5 m s-1, the emission rates of acetic acid inside the flux hood would be approximately 23, 12 and 6 times lower than the emission rates in the field, for sweep air flow rates of 2, 5 and 10 L min-1, respectively. A procedure is presented in order to scale the emission rates of these compounds measured with the flux hood to field conditions of higher winds.

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.

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.

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.

Optimization of transfer trajectories to the Apophis asteroid for spacecraft with high and low thrust

NASA Astrophysics Data System (ADS)

Ivashkin, V. V.; Krylov, I. V.

2014-03-01

The problem of optimization of a spacecraft transfer to the Apophis asteroid is investigated. The scheme of transfer under analysis includes a geocentric stage of boosting the spacecraft with high thrust, a heliocentric stage of control by a low thrust engine, and a stage of deceleration with injection to an orbit of the asteroid's satellite. In doing this, the problem of optimal control is solved for cases of ideal and piecewise-constant low thrust, and the optimal magnitude and direction of spacecraft's hyperbolic velocity "at infinity" during departure from the Earth are determined. The spacecraft trajectories are found based on a specially developed comprehensive method of optimization. This method combines the method of dynamic programming at the first stage of analysis and the Pontryagin maximum principle at the concluding stage, together with the parameter continuation method. The estimates are obtained for the spacecraft's final mass and for the payload mass that can be delivered to the asteroid using the Soyuz-Fregat carrier launcher.

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.

Magnetically Suspended Linear Pulse Motor for Semiconductor Wafer Transfer in Vacuum Chamber

NASA Technical Reports Server (NTRS)

Moriyama, Shin-Ichi; Hiraki, Naoji; Watanabe, Katsuhide; Kanemitsu, Yoichi

1996-01-01

This paper describes a magnetically suspended linear pulse motor for a semiconductor wafer transfer robot in a vacuum chamber. The motor can drive a wafer transfer arm horizontally without mechanical contact. In the construction of the magnetic suspension system, four pairs of linear magnetic bearings for the lift control are used for the guidance control as well. This approach allows us to make the whole motor compact in size and light in weight. The tested motor consists of a double-sided stator and a transfer arm with a width of 50 mm and a total length of 700 mm. The arm, like a ladder in shape, is designed as the floating element with a tooth width of 4 mm (a tooth pitch of 8 mm). The mover mass is limited to about 1.6 kg by adopting such an arm structure, and the ratio of thrust to mover mass reaches to 3.2 N/kg under a broad air gap (1 mm) between the stator teeth and the mover teeth. The performance testing was carried out with a transfer distance less than 450 mm and a transfer speed less than 560 mm/s. The attitude of the arm was well controlled by the linear magnetic bearings with a combined use, and consequently the repeatability on the positioning of the arm reached to about 2 micron. In addition, the positioning accuracy was improved up to about 30 micron through a compensation of the 128-step wave current which was used for the micro-step drive with a step increment of 62.5 micron.

Laboratory Experiments and Modeling of Pooled NAPL Dissolution in Porous Media

NASA Astrophysics Data System (ADS)

Copty, N. K.; Sarikurt, D. A.; Gokdemir, C.

2017-12-01

The dissolution of non-aqueous phase liquids (NAPLs) entrapped in porous media is commonly modeled at the continuum scale as the product of a chemical potential and an interphase mass transfer coefficient, the latter expressed in terms of Sherwood correlations that are related to flow and porous media properties. Because of the lack of precise estimates of the interface area separating the NAPL and aqueous phase, numerous studies have lumped the interfacial area into the interphase mass transfer coefficient. In this paper controlled dissolution experiments from a pooled NAPL were conducted. The immobile NAPL mass is placed at the bottom of a flow cell filled with porous media with water flowing on top. Effluent aqueous phase concentrations were measured for a wide range of aqueous phase velocities and for two types of porous media. To interpret the experimental results, a two-dimensional pore network model of the NAPL dissolution was developed. The well-defined geometry of the NAPL-water interface and the observed effluent concentrations were used to compute best-fit mass transfer coefficients and non-lumped Sherwood correlations. Comparing the concentrations predicted with the pore network model to simple previously used one-dimensional analytic solutions indicates that the analytic model which ignores the transverse dispersion can lead to over-estimation of the mass transfer coefficient. The predicted Sherwood correlations are also compared to previously published data and implications on NAPL remediation strategies are discussed.

Sherwood correlation for dissolution of pooled NAPL in porous media

NASA Astrophysics Data System (ADS)

Aydin Sarikurt, Derya; Gokdemir, Cagri; Copty, Nadim K.

2017-11-01

The rate of interphase mass transfer from non-aqueous phase liquids (NAPLs) entrapped in the subsurface into the surrounding mobile aqueous phase is commonly expressed in terms of Sherwood (Sh) correlations that are expressed as a function of flow and porous media properties. Because of the lack of precise methods for the estimation of the interfacial area separating the NAPL and aqueous phases, most studies have opted to use modified Sherwood expressions that lump the interfacial area into the interphase mass transfer coefficient. To date, there are only two studies in the literature that have developed non-lumped Sherwood correlations; however, these correlations have undergone limited validation. In this paper controlled dissolution experiments from pooled NAPL were conducted. The immobile NAPL mass is placed at the bottom of a flow cell filled with porous media with water flowing horizontally on top. Effluent aqueous phase concentrations were measured for a wide range of aqueous phase velocities and for two different porous media. To interpret the experimental results, a two-dimensional pore network model of the NAPL dissolution kinetics and aqueous phase transport was developed. The observed effluent concentrations were then used to compute best-fit mass transfer coefficients. Comparison of the effluent concentrations computed with the two-dimensional pore network model to those estimated with one-dimensional analytical solutions indicates that the analytical model which ignores the transport in the lateral direction can lead to under-estimation of the mass transfer coefficient. Based on system parameters and the estimated mass transfer coefficients, non-lumped Sherwood correlations were developed and compared to previously published data. The developed correlations, which are a significant improvement over currently available correlations that are associated with large uncertainties, can be incorporated into future modeling studies requiring non-lumped Sh expressions.

Digital control algorithms for microgravity isolation systems

NASA Technical Reports Server (NTRS)

Sinha, Alok; Wang, Yung-Peng

1992-01-01

New digital control algorithms were developed to achieve the desired acceleration transmissibility function. The attractive electromagnets have been taken as actuators. The relative displacement and the acceleration of the mass were used as feedback signals. Two approaches were developed to find that controller transfer function in Z-domain, which yields the desired transmissibility at each frequency. In the first approach, the controller transfer function is obtained by assuming that the desired transmissibility is known in Z-domain. Since the desired transmissibility H sub d(S) = 1/(tauS+1)(exp 2) is given in S-domain, the first task is to obtain the desired transmissibility in Z-domain. There are three methods to perform this task: bilinear transformation, and backward and forward rectangular rules. The bilinear transformation and backward rectangular rule lead to improper controller transfer functions, which are physically not realizable. The forward rectangular rule does lead to a physically realizable controller. However, this controller is found to be marginally stable because of a pole at Z=1. In order to eliminate this pole, a hybrid control structure is proposed. Here the control input is composed of two parts: analog and digital. The analog input simply represents the velocity (or the integral of acceleration) feedback; and the digital controller which uses only relative displacement signal, is then obtained to achieve the desired closed-loop transfer function. The stability analysis indicates that the controller transfer function is stable for typical values of sampling period. In the second approach, the aforementioned hybrid control structure is again used. First, an analog controller transfer function corresponding to relative displacement feedback is obtained to achieve the transmissibility as 1/(tauS+1)(exp 2). Then the transfer function for the digital control input is obtained by discretizing this analog controller transfer function via bilinear transformation. The stability of the resulting Z-domain closed loop system is analyzed. Also, the frequency response of the Z-domain closed-loop transfer function is determined to evaluate the performance of the control system.

Mass Transfer with Chemical Reaction.

ERIC Educational Resources Information Center

DeCoursey, W. J.

1987-01-01

Describes the organization of a graduate course dealing with mass transfer, particularly as it relates to chemical reactions. Discusses the course outline, including mathematics models of mass transfer, enhancement of mass transfer rates by homogeneous chemical reaction, and gas-liquid systems with chemical reaction. (TW)

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.

43 CFR 3106.4-3 - Mass transfers.

Code of Federal Regulations, 2011 CFR

2011-10-01

... 43 Public Lands: Interior 2 2011-10-01 2011-10-01 false Mass transfers. 3106.4-3 Section 3106.4-3... or Otherwise § 3106.4-3 Mass transfers. (a) A mass transfer may be utilized in lieu of the provisions... large number of Federal leases to the same transferee. (b) Three originally executed copies of the mass...

Fuel Reforming Technologies (BRIEFING SLIDES)

DTIC Science & Technology

2009-09-01

Heat and Mass Transfer , Catalysis...Gallons Of Fuel/Day/1100men Deployment  To Reduce Noise/Thermal Signature And 4 Environmental Emissions Advanced Heat and Mass Transfer 5 Advanced... Heat and Mass & Transfer Technologies Objective Identify And Develop New Technologies To Enhance Heat And Mass Transfer In Deployed Energy

Diagonalizing controller for a superconducting six-axis accelerometer

NASA Astrophysics Data System (ADS)

Bachrach, B.; Canavan, E. R.; Levine, W. S.

A relatively simple MIMO (multiple input, multiple output) controller which converts an instrument with a nondiagonally dominant transfer function matrix into a strongly diagonally dominant device is developed. The instrument, which uses inductance bridges to sense the position of a magnetically levitated superconducting mass, has very lightly damped resonances and fairly strong cross coupling. By taking advantage of the particular structure of the instrument's transfer function matrix, it is possible to develop a relatively simple controller which achieves the desired decoupling. This controller consists of two parts. The first part cancels the nondiagonal terms of the open-loop transfer function matrix, while the second part is simply a set of SISO (single input, single output) controllers. The stability of the closed-loop system is studied using Rosenbrock's INA (inverse Nyguist array) technique, which produces a simple set of conditions guaranteeing stability. Simulation of the closed-loop system indicates that it should easily achieve its performance goals.

Transfer of obturator nerve for femoral nerve injury: an experiment study in rats.

PubMed

Meng, Depeng; Zhou, Jun; Lin, Yaofa; Xie, Zheng; Chen, Huihao; Yu, Ronghua; Lin, Haodong; Hou, Chunlin

2018-07-01

Quadriceps palsy is mainly caused by proximal lesions in the femoral nerve. The obturator nerve has been previously used to repair the femoral nerve, although only a few reports have described the procedure, and the outcomes have varied. In the present study, we aimed to confirm the feasibility and effectiveness of this treatment in a rodent model using the randomized control method. Sixty Sprague-Dawley rats were randomized into two groups: the experimental group, wherein rats underwent femoral neurectomy and obturator nerve transfer to the femoral nerve motor branch; and the control group, wherein rats underwent femoral neurectomy without nerve transfer. Functional outcomes were measured using the BBB score, muscle mass, and histological assessment. At 12 and 16 weeks postoperatively, the rats in the experimental group exhibited recovery to a stronger stretch force of the knee and higher BBB score, as compared to the control group (p < 0.05). The muscle mass and myofiber cross-sectional area of the quadriceps were heavier and larger than those in the control group (p < 0.05). A regenerated nerve with myelinated and unmyelinated fibers was observed in the experimental group. No significant differences were observed between groups at 8 weeks postoperatively (p > 0.05). Obturator nerve transfer for repairing femoral nerve injury was feasible and effective in a rat model, and can hence be considered as an option for the treatment of femoral nerve injury.

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%.

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.

Investigation of the kinetic mechanism of the demanganization reaction between carbon-saturated liquid iron and CaF2-CaO-SiO2-based slags

NASA Astrophysics Data System (ADS)

Duan, Sheng-chao; Li, Chuang; Guo, Han-jie; Guo, Jing; Han, Shao-wei; Yang, Wen-sheng

2018-04-01

The demanganization reaction kinetics of carbon-saturated liquid iron with an eight-component slag consisting of CaO-SiO2-MgO-FeO-MnO-Al2O3-TiO2-CaF2 was investigated at 1553, 1623, and 1673 K in this study. The rate-controlling step (RCS) for the demanganization reaction with regard to the hot metal pretreatment conditions was studied via kinetics analysis based on the fundamental equation of heterogeneous reaction kinetics. From the temperature dependence of the mass transfer coefficient of a transition-metal oxide (MnO), the apparent activation energy of the demanganization reaction was estimated to be 189.46 kJ·mol-1 in the current study, which indicated that the mass transfer of MnO in the molten slag controlled the overall rate of the demanganization reaction. The calculated apparent activation energy was slightly lower than the values reported in the literature for mass transfer in a slag phase. This difference was attributed to an increase in the "specific reaction interface" (SRI) value, either as a result of turbulence at the reaction interface or a decrease of the absolute amount of slag phase during sampling, and to the addition of calcium fluoride to the slag.

Heat and mass transfer during the cryopreservation of a bioartificial liver device: a computational model.

PubMed

Balasubramanian, Saravana K; Coger, Robin N

2005-01-01

Bioartificial liver devices (BALs) have proven to be an effective bridge to transplantation for cases of acute liver failure. Enabling the long-term storage of these devices using a method such as cryopreservation will ensure their easy off the shelf availability. To date, cryopreservation of liver cells has been attempted for both single cells and sandwich cultures. This study presents the potential of using computational modeling to help develop a cryopreservation protocol for storing the three dimensional BAL: Hepatassist. The focus is upon determining the thermal and concentration profiles as the BAL is cooled from 37 degrees C-100 degrees C, and is completed in two steps: a cryoprotectant loading step and a phase change step. The results indicate that, for the loading step, mass transfer controls the duration of the protocol, whereas for the phase change step, when mass transfer is assumed negligible, the latent heat released during freezing is the control factor. The cryoprotocol that is ultimately proposed considers time, cooling rate, and the temperature gradients that the cellular space is exposed to during cooling. To our knowledge, this study is the first reported effort toward designing an effective protocol for the cryopreservation of a three-dimensional BAL device.

Development of model for studies on momentum transfer in electrochemical cells with entry region coil as turbulence promoter

NASA Astrophysics Data System (ADS)

Penta Rao, Tamarba; Rajendra Prasad, P.

2018-04-01

Entry region swirl promoters gain importance in industry because of its effectiveness in augmentation of mass and heat transfer augmentation. Design of equipment needs momentum transfer data along with mass or heat transfer data. Hence an experimental investigation was carried out with coaxially placed entry region spiral coil as turbulence promoters on momentum transfer in forced convection flow of electrolyte in circular conduits. Aqueous solution of sodium hydroxide and 0.01 M equimolal Ferri-ferro cyanide system was chosen for the study. The study covered parameters like effect of pitch of the coil, effect of length of the coil, diameter of the coil, diameter of the coil wire, diameter of the annular rod. The promoter is measured by limiting current technique using diffusion controlled electrochemical reactions. The study comprises of evaluation of momentum transfer rates at the outer wall of the electrochemical cell. Pressure drop measurements were also made to obtain the energy consumption pattern. Within the range of variables covered. The results are correlated by the momentum transfer similarity function. Momentum transfer coefficients were evaluated from measured limiting currents. Effect of each parameter was studied in terms of friction factor. A model was developed for momentum transfer. The experimental data on momentum transfer was modeled in terms of momentum transfer function and Reynolds number, geometric parameters.

On the possibility of control restoration in some inverse problems of heat and mass transfer

NASA Astrophysics Data System (ADS)

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

2016-11-01

The hypersonic aircraft permeable surfaces effective heat protection problems are considered. The physic-chemical processes (the dissociation and the ionization) in laminar boundary layer of compressible gas are appreciated in mathematical model. The statements of direct problems of heat and mass transfer are given: according to preset given controls it is necessary to compute the boundary layer mathematical model parameters and determinate the local and total heat flows and friction forces and the power of blowing system. The A.A.Dorodnicyn's generalized integral relations method has been used as calculation basis. The optimal control - the blowing into boundary layer (for continuous functions) was constructed as the solution of direct problem in extreme statement with the use of this approach. The statement of inverse problems are given: the control laws ensuring the preset given local heat flow and local tangent friction are restored. The differences between the interpolation and the approximation statements are discussed. The possibility of unique control restoration is established and proved (in the stagnation point). The computational experiments results are presented.

Headspace screening of fluid obtained from the gut during colonoscopy and breath analysis by proton transfer reaction-mass spectrometry: A novel approach in the diagnosis of gastro-intestinal diseases

NASA Astrophysics Data System (ADS)

Lechner, M.; Colvin, H. P.; Ginzel, C.; Lirk, P.; Rieder, J.; Tilg, H.

2005-05-01

Background: The diagnosis of many gastro-intestinal diseases is difficult and can often be confirmed only by using invasive diagnostic means. In contrast, the headspace screening of fluid obtained from the gut during colonoscopy and the analysis of exhaled air may be a novel approach for the diagnosis of these diseases.Materials and methods: The screening was performed by using proton transfer reaction-mass spectrometry (PTR-MS) which allows rapid and sensitive measurement. Fluid samples obtained from the gut during colonoscopy were collected from 76 and breath samples from 70 subjects. Mass spectra of healthy controls were created. Afterwards these spectra were compared with those of patients suffering from inflammatory bowel diseases (IBD; Crohn's disease and ulcerative colitis; n = 10) and irritable bowel syndrome (IBS; n = 7).Results: Significant differences in the mass spectra could be observed both in the headspace of the fluid and in the exhaled air comparing patients with healthy controls.Conclusions: This study is the first describing headspace screening of fluid obtained from the gut during colonoscopy, possibly presenting a novel diagnostic tool in the differential diagnosis of gastro-intestinal diseases.

Analysis of an electrohydraulic aircraft control surface servo and comparison with test results

NASA Technical Reports Server (NTRS)

Edwards, J. W.

1972-01-01

An analysis of an electrohydraulic aircraft control-surface system is made in which the system is modeled as a lumped, two-mass, spring-coupled system controlled by a servo valve. Both linear and nonlinear models are developed, and the effects of hinge-moment loading are included. Transfer functions of the system and approximate literal factors of the transfer functions for several cases are presented. The damping action of dynamic pressure feedback is analyzed. Comparisons of the model responses with results from tests made on a highly resonant rudder control-surface servo indicate the adequacy of the model. The effects of variations in hinge-moment loading are illustrated.

Mathematical Investigation of Fluid Flow, Mass Transfer, and Slag-steel Interfacial Behavior in Gas-stirred Ladles

NASA Astrophysics Data System (ADS)

Cao, Qing; Nastac, Laurentiu

2018-06-01

In this study, the Euler-Euler and Euler-Lagrange modeling approaches were applied to simulate the multiphase flow in the water model and gas-stirred ladle systems. Detailed comparisons of the computational and experimental results were performed to establish which approach is more accurate for predicting the gas-liquid multiphase flow phenomena. It was demonstrated that the Euler-Lagrange approach is more accurate than the Euler-Euler approach. The Euler-Lagrange approach was applied to study the effects of the free surface setup, injected bubble size, gas flow rate, and slag layer thickness on the slag-steel interaction and mass transfer behavior. Detailed discussions on the flat/non-flat free surface assumption were provided. Significant inaccuracies in the prediction of the surface fluid flow characteristics were found when the flat free surface was assumed. The variations in the main controlling parameters (bubble size, gas flow rate, and slag layer thickness) and their potential impact on the multiphase fluid flow and mass transfer characteristics (turbulent intensity, mass transfer rate, slag-steel interfacial area, flow patterns, etc.,) in gas-stirred ladles were quantitatively determined to ensure the proper increase in the ladle refining efficiency. It was revealed that by injecting finer bubbles as well as by properly increasing the gas flow rate and the slag layer thickness, the ladle refining efficiency can be enhanced significantly.

Mass transfer in white dwarf-neutron star binaries

NASA Astrophysics Data System (ADS)

Bobrick, Alexey; Davies, Melvyn B.; Church, Ross P.

2017-05-01

We perform hydrodynamic simulations of mass transfer in binaries that contain a white dwarf and a neutron star (WD-NS binaries), and measure the specific angular momentum of material lost from the binary in disc winds. By incorporating our results within a long-term evolution model, we measure the long-term stability of mass transfer in these binaries. We find that only binaries containing helium white dwarfs (WDs) with masses less than a critical mass of MWD, crit = 0.2 M⊙ undergo stable mass transfer and evolve into ultracompact X-ray binaries. Systems with higher mass WDs experience unstable mass transfer, which leads to tidal disruption of the WD. Our low critical mass compared to the standard jet-only model of mass-loss arises from the efficient removal of angular momentum in the mechanical disc winds, which develop at highly super-Eddington mass-transfer rates. We find that the eccentricities expected for WD-NS binaries when they come into contact do not affect the loss of angular momentum, and can only affect the long-term evolution if they change on shorter time-scales than the mass-transfer rate. Our results are broadly consistent with the observed numbers of both ultracompact X-ray binaries and radio pulsars with WD companions. The observed calcium-rich gap transients are consistent with the merger rate of unstable systems with higher mass WDs.

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.

Biocatalytic coatings for air pollution control: a proof of concept study on VOC biodegradation.

PubMed

Estrada, José M; Bernal, Oscar I; Flickinger, Michael C; Muñoz, Raúl; Deshusses, Marc A

2015-02-01

Although biofilm-based biotechnologies exhibit a large potential as solutions for off-gas treatment, the high water content of biofilms often causes pollutant mass transfer limitations, which ultimately limit their widespread application. The present study reports on the proof of concept of the applicability of bioactive latex coatings for air pollution control. Toluene vapors served as a model volatile organic compound (VOC). The results showed that Pseudomonas putida F1 cells could be successfully entrapped in nanoporous latex coatings while preserving their toluene degradation activity. Bioactive latex coatings exhibited toluene specific biodegradation rates 10 times higher than agarose-based biofilms, because the thin coatings were less subject to diffusional mass transfer limitations. Drying and pollutant starvation were identified as key factors inducing a gradual deterioration of the biodegradation capacity in these innovative coatings. This study constitutes the first application of bioactive latex coatings for VOC abatement. These coatings could become promising means for air pollution control. © 2014 Wiley Periodicals, Inc.

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

Heat and mass transfer scale-up issues during freeze-drying, III: control and characterization of dryer differences via operational qualification tests.

PubMed

Rambhatla, S; Tchessalov, S; Pikal, Michael J

2006-04-21

The objective of this research was to estimate differences in heat and mass transfer between freeze dryers due to inherent design characteristics using data obtained from sublimation tests. This study also aimed to provide guidelines for convenient scale-up of the freeze-drying process. Data obtained from sublimation tests performed on laboratory-scale, pilot, and production freeze dryers were used to evaluate various heat and mass transfer parameters: nonuniformity in shelf surface temperatures, resistance of pipe, refrigeration system, and condenser. Emissivity measurements of relevant surfaces such as the chamber wall and the freeze dryer door were taken to evaluate the impact of atypical radiation heat transfer during scale-up. "Hot" and "cold" spots were identified on the shelf surface of different freeze dryers, and the impact of variation in shelf surface temperatures on the primary drying time and the product temperature during primary drying was studied. Calculations performed using emissivity measurements on different freeze dryers suggest that a front vial in the laboratory lyophilizer received 1.8 times more heat than a front vial in a manufacturing freeze dryer operating at a shelf temperature of -25 degrees C and a chamber pressure of 150 mTorr during primary drying. Therefore, front vials in the laboratory are much more atypical than front vials in manufacturing. Steady-state heat and mass transfer equations were used to study a combination of different scale-up issues pertinent during lyophilization cycles commonly used for the freeze-drying of pharmaceuticals.

The COLD-SAT Experiment for Cryogenic Fluid Management Technology

NASA Technical Reports Server (NTRS)

Schuster, J. R.; Wachter, J. P.; Vento, D. M.

1990-01-01

Future national space transportation missions will depend on the use of cryogenic fluid management technology development needs for these missions. In-space testing will be conducted in order to show low gravity cryogenic fluid management concepts and to acquire a technical data base. Liquid H2 is the preferred test fluid due to its propellant use. The design of COLD-SAT (Cryogenic On-orbit Liquid Depot Storage, Acquisition, and Transfer Satellite), an Expendable Launch Vehicle (ELV) launched orbital spacecraft that will perform subcritical liquid H2 storage and transfer experiments under low gravity conditions is studied. An Atlas launch vehicle will place COLD-SAT into a circular orbit, and the 3-axis controlled spacecraft bus will provide electric power, experiment control, and data management, attitude control, and propulsive accelerations for the experiments. Low levels of acceleration will provide data on the effects that low gravity might have on the heat and mass transfer processes used. The experiment module will contain 3 liquid H2 tanks; fluid transfer, pressurization and venting equipment; and instrumentation.

A driven active mass damper by using output of a neural oscillator (effects of position control system changes on vibration mitigation performance)

NASA Astrophysics Data System (ADS)

Hongu, J.; Iba, D.; Sasaki, T.; Nakamura, M.; Moriwaki, I.

2015-03-01

In this paper, a design method for a PD controller, which is a part of a new active mass damper system using a neural oscillator for high-rise buildings, is proposed. The new system mimicking the motion of bipedal mammals is a quite simple system, which has the neural oscillator synchronizing with the acceleration response of the structure. The travel distance and direction of the auxiliary mass of the active mass damper is decided by the output of the neural oscillator, and then, the auxiliary mass is transferred to the decided location by using the PD controller. Therefore, the performance of the PD controller must be evaluated by the vibration energy absorbing efficiency by the system. In order to bring the actual path driven by the PD controller in closer alignment with the ideal path, which is assumed to be a sinusoidal wave under resonance, firstly, the path of the auxiliary mass driven by the PD controller is analytically derived, and the inner product between the vector of ideal and analytical path is evaluated. And then, the PD gain is decided by the maximum value of the inner product. Finally, numerical simulations confirm the validity of the proposed design method of the PD controller.

Development of an intelligent system for cooling rate and fill control in GMAW

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

Einerson, C.J.; Smartt, H.B.; Johnson, J.A.

1992-09-01

A control strategy for gas metal arc welding (GMAW) is developed in which the welding system detects certain existing conditions and adjusts the process in accordance to pre-specified rules. This strategy is used to control the reinforcement and weld bead centerline cooling rate during welding. Relationships between heat and mass transfer rates to the base metal and the required electrode speed and welding speed for specific open circuit voltages are taught to a artificial neural network. Control rules are programmed into a fuzzy logic system. TRADITOINAL CONTROL OF THE GMAW PROCESS is based on the use of explicit welding proceduresmore » detailing allowable parameter ranges on a pass by pass basis for a given weld. The present work is an exploration of a completely different approach to welding control. In this work the objectives are to produce welds having desired weld bead reinforcements while maintaining the weld bead centerline cooling rate at preselected values. The need for this specific control is related to fabrication requirements for specific types of pressure vessels. The control strategy involves measuring weld joint transverse cross-sectional area ahead of the welding torch and the weld bead centerline cooling rate behind the weld pool, both by means of video (2), calculating the required process parameters necessary to obtain the needed heat and mass transfer rates (in appropriate dimensions) by means of an artificial neural network, and controlling the heat transfer rate by means of a fuzzy logic controller (3). The result is a welding machine that senses the welding conditions and responds to those conditions on the basis of logical rules, as opposed to producing a weld based on a specific procedure.« less

Development of an intelligent system for cooling rate and fill control in GMAW. [Gas Metal Arc Welding (GMAW)

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

Einerson, C.J.; Smartt, H.B.; Johnson, J.A.

1992-01-01

A control strategy for gas metal arc welding (GMAW) is developed in which the welding system detects certain existing conditions and adjusts the process in accordance to pre-specified rules. This strategy is used to control the reinforcement and weld bead centerline cooling rate during welding. Relationships between heat and mass transfer rates to the base metal and the required electrode speed and welding speed for specific open circuit voltages are taught to a artificial neural network. Control rules are programmed into a fuzzy logic system. TRADITOINAL CONTROL OF THE GMAW PROCESS is based on the use of explicit welding proceduresmore » detailing allowable parameter ranges on a pass by pass basis for a given weld. The present work is an exploration of a completely different approach to welding control. In this work the objectives are to produce welds having desired weld bead reinforcements while maintaining the weld bead centerline cooling rate at preselected values. The need for this specific control is related to fabrication requirements for specific types of pressure vessels. The control strategy involves measuring weld joint transverse cross-sectional area ahead of the welding torch and the weld bead centerline cooling rate behind the weld pool, both by means of video (2), calculating the required process parameters necessary to obtain the needed heat and mass transfer rates (in appropriate dimensions) by means of an artificial neural network, and controlling the heat transfer rate by means of a fuzzy logic controller (3). The result is a welding machine that senses the welding conditions and responds to those conditions on the basis of logical rules, as opposed to producing a weld based on a specific procedure.« less

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.

Crystallization kinetics of the borax decahydrate

NASA Astrophysics Data System (ADS)

Ceyhan, A. A.; Sahin, Ö.; Bulutcu, A. N.

2007-03-01

The growth and dissolution rates of borax decahydrate have been measured as a function of supersaturation for various particle sizes at different temperature ranges of 13 and 50 °C in a laboratory-scale fluidized bed crystallizer. The values of mass transfer coefficient, K, reaction rate constant, kr and reaction rate order, r were determined. The relative importances of diffusion and integration resistance were described by new terms named integration and diffusion concentration fraction. It was found that the overall growth rate of borax decahydrate is mainly controlled by integration (reaction) steps. It was also estimated that the dissolution region of borax decahydrate, apart from other materials, is controlled by diffusion and surface reaction. Increasing the temperature and particle size cause an increase in the values of kinetic parameters ( Kg, kr and K). The activation energies of overall, reaction and mass transfer steps were determined as 18.07, 18.79 and 8.26 kJmol -1, respectively.

The Effect of Thermophoresis on Unsteady Oldroyd-B Nanofluid Flow over Stretching Surface

PubMed Central

Awad, Faiz G.; Ahamed, Sami M. S.; Sibanda, Precious; Khumalo, Melusi

2015-01-01

There are currently only a few theoretical studies on convective heat transfer in polymer nanocomposites. In this paper, the unsteady incompressible flow of a polymer nanocomposite represented by an Oldroyd-B nanofluid along a stretching sheet is investigated. Recent studies have assumed that the nanoparticle fraction can be actively controlled on the boundary, similar to the temperature. However, in practice, such control presents significant challenges and in this study the nanoparticle flux at the boundary surface is assumed to be zero. We have used a relatively novel numerical scheme; the spectral relaxation method to solve the momentum, heat and mass transport equations. The accuracy of the solutions has been determined by benchmarking the results against the quasilinearisation method. We have conducted a parametric study to determine the influence of the fluid parameters on the heat and mass transfer coefficients. PMID:26312754

Methods to control phase inversions and enhance mass transfer in liquid-liquid dispersions

DOEpatents

Tsouris, Constantinos; Dong, Junhang

2002-01-01

The present invention is directed to the effects of applied electric fields on liquid-liquid dispersions. In general, the present invention is directed to the control of phase inversions in liquid-liquid dispersions. Because of polarization and deformation effects, coalescence of aqueous drops is facilitated by the application of electric fields. As a result, with an increase in the applied voltage, the ambivalence region is narrowed and shifted toward higher volume fractions of the dispersed phase. This permits the invention to be used to ensure that the aqueous phase remains continuous, even at a high volume fraction of the organic phase. Additionally, the volume fraction of the organic phase may be increased without causing phase inversion, and may be used to correct a phase inversion which has already occurred. Finally, the invention may be used to enhance mass transfer rates from one phase to another through the use of phase inversions.

Synthesis of Cobalt Powder by Reduction of Cobalt Oxide with Ethanol

NASA Astrophysics Data System (ADS)

Cetinkaya, S.; Eroglu, S.

2018-03-01

In this study, ethanol (C2H5OH) was used as a reducing agent for Co powder synthesis from Co3O4. It aimed to investigate the effects of temperature (700-900 K), reaction time (0-60 min), and gas flow rate on the reaction behavior of Co3O4 in ethanol flow. Mass measurement, x-ray diffraction, and scanning electron microscopy techniques were used to characterize the products. Single-phase Co powders with mean particle sizes of 0.51 μm and 0.70 μm were obtained within 10 min at 800 K and 900 K, respectively. Above 800 K, external mass transfer controlled the reduction process (Q a = 0.52 kJ/mole). Below 800 K, the process (Q a = 20.17 kJ/mole) was partly controlled by external mass transfer and partly by intrinsic chemical reaction kinetics. Significant C uptake was observed at 700 K and 750 K within 60 min. The reactions were discussed in the light of thermodynamic results, which predicted Co formation from Co3O4 and C2H5OH.

Seismic design of passive tuned mass damper parameters using active control algorithm

NASA Astrophysics Data System (ADS)

Chang, Chia-Ming; Shia, Syuan; Lai, Yong-An

2018-07-01

Tuned mass dampers are a widely-accepted control method to effectively reduce the vibrations of tall buildings. A tuned mass damper employs a damped harmonic oscillator with specific dynamic characteristics, thus the response of structures can be regulated by the additive dynamics. The additive dynamics are, however, similar to the feedback control system in active control. Therefore, the objective of this study is to develop a new tuned mass damper design procedure based on the active control algorithm, i.e., the H2/LQG control. This design facilitates the similarity of feedback control in the active control algorithm to determine the spring and damper in a tuned mass damper. Given a mass ratio between the damper and structure, the stiffness and damping coefficient of the tuned mass damper are derived by minimizing the response objective function of the primary structure, where the structural properties are known. Varying a single weighting in this objective function yields the optimal TMD design when the minimum peak in the displacement transfer function of the structure with the TMD is met. This study examines various objective functions as well as derives the associated equations to compute the stiffness and damping coefficient. The relationship between the primary structure and optimal tuned mass damper is parametrically studied. Performance is evaluated by exploring the h2-and h∞-norms of displacements and accelerations of the primary structure. In time-domain analysis, the damping effectiveness of the tune mass damper controlled structures is investigated under impulse excitation. Structures with the optimal tuned mass dampers are also assessed under seismic excitation. As a result, the proposed design procedure produces an effective tuned mass damper to be employed in a structure against earthquakes.

Aeration and mass transfer optimization in a rectangular airlift loop photobioreactor for the production of microalgae.

PubMed

Guo, Xin; Yao, Lishan; Huang, Qingshan

2015-08-01

Effects of superficial gas velocity and top clearance on gas holdup, liquid circulation velocity, mixing time, and mass transfer coefficient are investigated in a new airlift loop photobioreactor (PBR), and empirical models for its rational control and scale-up are proposed. In addition, the impact of top clearance on hydrodynamics, especially on the gas holdup in the internal airlift loop reactor, is clarified; a novel volume expansion technique is developed to determine the low gas holdup in the PBR. Moreover, a model strain of Chlorella vulgaris is cultivated in the PBR and the volumetric power is analyzed with a classic model, and then the aeration is optimized. It shows that the designed PBR, a cost-effective reactor, is promising for the mass cultivation of microalgae. Copyright © 2015 Elsevier Ltd. All rights reserved.

Analysis of heat and mass transfer during condensation over a porous substrate.

PubMed

Balasubramaniam, R; Nayagam, V; Hasan, M M; Khan, L

2006-09-01

Condensing heat exchangers are important in many space applications for thermal and humidity control systems. The International Space Station uses a cooled fin surface to condense moisture from humid air that is blown over it. The condensate and the air are "slurped" into a system that separates air and water by centrifugal forces. The use of a cooled porous substrate is an attractive alternative to the fin where condensation and liquid/gas separation can be achieved in a single step. We analyze the heat and mass transfer during condensation of moisture from flowing air over such a cooled, flat, porous substrate. A fully developed regime is investigated for coupled mass, momentum and energy transport in the gas phase, and momentum and energy transport in the condensate layer on the porous substrate and through the porous medium.

Suitability of the first-order mass transfer concept for describing cyclic diffusive mass transfer in stagnant zones

NASA Astrophysics Data System (ADS)

Griffioen, Jasper

1998-10-01

The concept of first-order mass transfer between mobile and immobile regions, which mathematically simplifies the concept of Fickian diffusion in stagnant areas, has often been used to describe physical nonequilibrium transport of solutes into natural porous media. This study compares the two concepts, using analytical expressions describing cyclic mass transfer into and out of stagnant layers. The results show that the first-order mass transfer concept cannot describe continuous diffusion into the immobile zone during period of net outward diffusion if the immobile zone has not filled completely during the period of net inward diffusion. This sets phenomenological limitations to the first-order mass transfer concept when short periods of relative time are involved; these limitations have to be compared with the practical limitations to the Fickian diffusion concept.

Molecular dynamics modeling of bonding two materials by atomic scale friction stir welding at different process parameters

NASA Astrophysics Data System (ADS)

Konovalenko S., Iv.; Psakhie, S. G.

2017-12-01

Using the molecular dynamics method, we simulated the atomic scale butt friction stir welding on two crystallites and varied the onset FSW tool plunge depth. The effects of the plunge depth value on the thermomechanical evolution of nanosized crystallites and mass transfer in the course of FSW have been studied. The increase of plunge depth values resulted in more intense heating and reducing the plasticized metal resistance to the tool movement. The mass transfer intensity was hardly dependent on the plunge depth value. The plunge depth was recommended to be used as a FSW process control parameter in addition to the commonly used ones.

Mechanistic investigations in sono-hybrid techniques for rice straw pretreatment.

PubMed

Suresh, Kelothu; Ranjan, Amrita; Singh, Shuchi; Moholkar, Vijayanand S

2014-01-01

This paper reports comparative study of two chemical techniques (viz. dilute acid/alkali treatment) and two physical techniques (viz. hot water bath and autoclaving) coupled with sonication, termed as sono-hybrid techniques, for hydrolysis of rice straw. The efficacy of each sono-hybrid technique was assessed on the basis of total sugar and reducing sugar release. The system of biomass pretreatment is revealed to be mass transfer controlled. Higher sugar release is obtained during dilute acid treatment than dilute alkali treatment. Autoclaving alone was found to increase sugar release marginally as compared to hot water bath. Sonication of the biomass solution after autoclaving and stirring resulted in significant rise of sugar release, which is attributed to strong convection generated during sonication that assists effective transport of sugar molecules. Discrimination between individual contributions of ultrasound and cavitation to mass transfer enhancement reveals that contribution of ultrasound (through micro-streaming) is higher. Micro-turbulence as well as acoustic waves generated by cavitation did not contribute much to enhancing of mass transfer in the system. Copyright © 2013 Elsevier B.V. All rights reserved.

Finite element solutions of free convective Casson fluid flow past a vertically inclined plate submitted in magnetic field in presence of heat and mass transfer

NASA Astrophysics Data System (ADS)

Raju, R. Srinivasa; Reddy, B. Mahesh; Reddy, G. Jithender

2017-09-01

The aim of this research work is to study the influence of thermal radiation on steady magnetohydrodynamic-free convective Casson fluid flow of an optically thick fluid over an inclined vertical plate with heat and mass transfer. Combined phenomenon of heat and mass transfer is considered. Numerical solutions in general form are obtained by using the finite element method. The sum of thermal and mechanical parts is expressed as velocity of fluid. Corresponding limiting solutions are also reduced from the general solutions. It is found that the obtained numerical solutions satisfy all imposed initial and boundary conditions and reduce to some known solutions from the literature as special cases. Numerical results for the controlling flow parameters are drawn graphically and discussed in detail. In some special cases, the obtained numerical results are compared and found to be in good agreement with the previously published results which are available in literature. Applications of this study includes laminar magneto-aerodynamics, materials processing and magnetohydrodynamic propulsion thermo-fluid dynamics, etc.

kLa of stirred tank bioreactors revisited.

PubMed

Schaepe, S; Kuprijanov, A; Sieblist, C; Jenzsch, M; Simutis, R; Lübbert, A

2013-12-01

By means of improved feedback control kLa measurements become possible at a precision and reproducibility that now allow a closer look at the influences of power input and aeration rate on the oxygen mass transfer. These measurements are performed online during running fermentations without a notable impact on the biochemical conversion processes. A closer inspection of the mass transfer during cultivations showed that at least the number of impellers influences mass transfer and mixing: On the laboratory scale, two hollow blade impellers clearly showed a larger kLa than the usually employed three impeller versions when operated at the same agitation power and aeration rate. Hollow blade impellers are preferable under most operational conditions because of their perfect gas handling capacity. Mixing time studies showed that these two impeller systems are also preferable with respect to mixing. Furthermore the widths of the baffle bars depict a significant influence on the kLa. All this clearly supports the fact that it is not only the integral power density that finally determines kLa. Copyright © 2013 Elsevier B.V. All rights reserved.

Aseismic creep along the North Anatolian Fault quantified by coupling microstructural strain and chemical analyses

NASA Astrophysics Data System (ADS)

Kaduri, Maor; Gratier, Jean-Pierre; Renard, François; Çakir, Ziyadin; Lasserre, Cécile

2017-04-01

In the last decade aseismic creep has been noted as one of the key processes along tectonic plate boundaries. It contributes to the energy budget during the seismic cycle, delaying or triggering the occurrence of large earthquakes. Several major continental active faults show spatial alternation of creeping and locked segments. A great challenge is to understand which parameters control the transition from seismic to aseismic deformation in fault zones, such as the lithology, the degree of deformation from damage rocks to gouge, and the stress driven fault architecture transformations at all scales. The present study focuses on the North Anatolian Fault (Turkey) and characterizes the mechanisms responsible for the partition between seismic and aseismic deformation. Strain values were calculated using various methods, e.g. Fry, R-φs from microstructural measurements in gouge and damage samples collected on more than 30 outcrops along the fault. Maps of mineral composition were reconstructed from microprobe measurements of gouge and damage rock microstructure, in order to calculate the relative mass changes due to stress driven processes during deformation. Strain values were extracted, in addition to the geometrical properties of grain orientation and size distribution. Our data cover subsamples in the damage zones that were protected from deformation and are reminiscent of the host rock microstructure and composition, and subsamples that were highly deformed and recorded both seismic and aseismic deformations. Increase of strain value is linked to the evolution of the orientation of the grains from random to sheared sub-parallel and may be related to various parameters: (1) relative mass transfer increase with increasing strain indicating how stress driven mass transfer processes control aseismic creep evolution with time; (2) measured strain is strongly related with the initial lithology and with the evolution of mineral composition: monomineralic rocks are stronger (less deformed) than polymineralic ones; (3) strain measurements allow to evaluate the cumulated geological displacement accommodated by aseismic creep and the relative ratio between seismic and aseismic displacement for each section of an active fault. These relations allow to quantify more accurately the aseismic creep processes and their evolution with time along the North Anatolian Fault which are controlled by a superposition of two kinds of mechanisms: (1) stress driven mass transfer (pressure solution and metamorphism) that control local and regional mass transfer and associated rheology evolution and (2) grain boundary sliding along weak mineral interfaces (initially weak minerals or more often transformed by deformation-related reactions).

Mass and heat transfer in crushed oil shale

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

Carley, J.F.; Straub, J.S.; Ott, L.L.

1984-04-01

Heat and mass transfer between gases and oil-shale particles are both important for all proposed retorting processes. Past studies of transfer in packed beds, which have disagreed substantially in their results, have nearly all been done with beds of regular particles of uniform size, whereas oil-shale retorting involves particles of diverse shapes and widely ranging sizes. To resolve these questions, we have made 349 runs in which we measured mass-transfer rates from naphthalene particles of diverse shapes buried in packed beds through which air was passed at room temperature. This technique permits calculation of the mass-transfer coefficient for each activemore » particle in the bed rather than, as in most past studies, for the bed as a whole. The data were analyzed in two ways: (1) by the traditional correlation of Colburn j/sub D/ vs Reynolds number and (2) by multiple regression of the mass-transfer coefficient on air rate, traditional correlation of Colburn j/sub D/ vs Reynolds number and (3) by multiple regression of the mass-transfer coefficient on air rate, sizes of active and inert particles, void fraction, and temperature. Principal findings are: (1) local Reynolds number should be based on active particle size rather than average size for the bed; (2) no appreciable differences were seen between shallow beds and deep ones; (3) mass transfer was 26% faster for spheres and lozenges buried in shale than for all-sphere beds; (4) orientation of lozenges in shale beds has little effect on mass-transfer rate; (5) a useful summarizing equation for either mass or heat transfer in shale beds is log j.epsilon = -.0747 - .6344 log Re + .0592 log/sup 2/Re where j = either j/sub D/ or j/sub H/, the Chilton-Colburn j-factors for mass and heat transfer, Re = the Reynolds number defined for packed beds, and epsilon = the void fraction in the bed. 12 references, 15 figures.« less

ChiMS: Open-source instrument control software platform on LabVIEW for imaging/depth profiling mass spectrometers.

PubMed

Cui, Yang; Hanley, Luke

2015-06-01

ChiMS is an open-source data acquisition and control software program written within LabVIEW for high speed imaging and depth profiling mass spectrometers. ChiMS can also transfer large datasets from a digitizer to computer memory at high repetition rate, save data to hard disk at high throughput, and perform high speed data processing. The data acquisition mode generally simulates a digital oscilloscope, but with peripheral devices integrated for control as well as advanced data sorting and processing capabilities. Customized user-designed experiments can be easily written based on several included templates. ChiMS is additionally well suited to non-laser based mass spectrometers imaging and various other experiments in laser physics, physical chemistry, and surface science.

ChiMS: Open-source instrument control software platform on LabVIEW for imaging/depth profiling mass spectrometers

PubMed Central

Cui, Yang; Hanley, Luke

2015-01-01

ChiMS is an open-source data acquisition and control software program written within LabVIEW for high speed imaging and depth profiling mass spectrometers. ChiMS can also transfer large datasets from a digitizer to computer memory at high repetition rate, save data to hard disk at high throughput, and perform high speed data processing. The data acquisition mode generally simulates a digital oscilloscope, but with peripheral devices integrated for control as well as advanced data sorting and processing capabilities. Customized user-designed experiments can be easily written based on several included templates. ChiMS is additionally well suited to non-laser based mass spectrometers imaging and various other experiments in laser physics, physical chemistry, and surface science. PMID:26133872

ChiMS: Open-source instrument control software platform on LabVIEW for imaging/depth profiling mass spectrometers

NASA Astrophysics Data System (ADS)

Cui, Yang; Hanley, Luke

2015-06-01

ChiMS is an open-source data acquisition and control software program written within LabVIEW for high speed imaging and depth profiling mass spectrometers. ChiMS can also transfer large datasets from a digitizer to computer memory at high repetition rate, save data to hard disk at high throughput, and perform high speed data processing. The data acquisition mode generally simulates a digital oscilloscope, but with peripheral devices integrated for control as well as advanced data sorting and processing capabilities. Customized user-designed experiments can be easily written based on several included templates. ChiMS is additionally well suited to non-laser based mass spectrometers imaging and various other experiments in laser physics, physical chemistry, and surface science.

Heat and mass transfer models to understand the drying mechanisms of a porous substrate.

PubMed

Songok, Joel; Bousfield, Douglas W; Gane, Patrick A C; Toivakka, Martti

2016-02-01

While drying of paper and paper coatings is expensive, with significant energy requirements, the rate controlling mechanisms are not currently fully understood. Two two-dimensional models are used as a first approximation to predict the heat transfer during hot air drying and to evaluate the role of various parameters on the drying rates of porous coatings. The models help determine the structural limiting factors during the drying process, while applying for the first time the recently known values of coating thermal diffusivity. The results indicate that the thermal conductivity of the coating structure is not the controlling factor, but the drying rate is rather determined by the thermal transfer process at the structure surface. This underlines the need for ensuring an efficient thermal transfer from hot air to coating surface during drying, before considering further measures to increase the thermal conductivity of porous coatings.

Advances in cryogenic engineering. Volume 27 - Proceedings of the Cryogenic Engineering Conference, San Diego, CA, August 11-14, 1981

NASA Technical Reports Server (NTRS)

Fast, R. W. (Editor)

1982-01-01

Applications of superconductivity are considered, taking into account MHD and fusion, generators, transformers, transmission lines, magnets for physics, cryogenic techniques, electrtronics, and aspects of magnet stability. Advances related to heat transfer in He I are discussed along with subjects related to theat transfer in He II, refrigeration of superconducting systems, refrigeration and liquefaction, dilution and magnetic refrigerators, refrigerators for space applications, mass transfer and flow phenomena, and the properties of fluids. Developments related to cryogenic applications are also explored, giving attention to bulk storage and transfer of cryogenic fluids, liquefied natural gas operations, space science and technology, and cryopumping. Topics related to cryogenic instrumentation and controls include the production and use of high grade silicon diode temperature sensors, the choice of strain gages for use in a large superconducting alternator, microprocessor control of cryogenic pressure, and instrumentation, data acquisition and reduction for a large spaceborne helium dewar.

Towards nanoprinting with metals on graphene.

PubMed

Melinte, G; Moldovan, S; Hirlimann, C; Liu, X; Bégin-Colin, S; Bégin, D; Banhart, F; Pham-Huu, C; Ersen, O

2015-08-28

Graphene and carbon nanotubes are envisaged as suitable materials for the fabrication of the new generation of nanoelectronics. The controlled patterning of such nanostructures with metal nanoparticles is conditioned by the transfer between a recipient and the surface to pattern. Electromigration under the impact of an applied voltage stands at the base of printing discrete digits at the nanoscale. Here we report the use of carbon nanotubes as nanoreservoirs for iron nanoparticles transfer on few-layer graphene. An initial Joule-induced annealing is required to ensure the control of the mass transfer with the nanotube acting as a 'pen' for the writing process. By applying a voltage, the tube filled with metal nanoparticles can deposit metal on the surface of the graphene sheet at precise locations. The reverse transfer of nanoparticles from the graphene surface to the nanotube when changing the voltage polarity opens the way for error corrections.

Towards nanoprinting with metals on graphene

NASA Astrophysics Data System (ADS)

Melinte, G.; Moldovan, S.; Hirlimann, C.; Liu, X.; Bégin-Colin, S.; Bégin, D.; Banhart, F.; Pham-Huu, C.; Ersen, O.

2015-08-01

Graphene and carbon nanotubes are envisaged as suitable materials for the fabrication of the new generation of nanoelectronics. The controlled patterning of such nanostructures with metal nanoparticles is conditioned by the transfer between a recipient and the surface to pattern. Electromigration under the impact of an applied voltage stands at the base of printing discrete digits at the nanoscale. Here we report the use of carbon nanotubes as nanoreservoirs for iron nanoparticles transfer on few-layer graphene. An initial Joule-induced annealing is required to ensure the control of the mass transfer with the nanotube acting as a `pen' for the writing process. By applying a voltage, the tube filled with metal nanoparticles can deposit metal on the surface of the graphene sheet at precise locations. The reverse transfer of nanoparticles from the graphene surface to the nanotube when changing the voltage polarity opens the way for error corrections.

Electric propulsion for geostationary orbit insertion

NASA Technical Reports Server (NTRS)

Oleson, Steven R.; Curran, Francis M.; Myers, Roger M.

1995-01-01

Solar electric propulsion (SEP) technology is already being used for geostationary satellite stationkeeping to increase payload mass. By using this same technology to perform part of the orbit transfer additional increases in payload mass can be achieved. Advanced chemical and N2H4 arcjet systems are used to increase the payload mass by performing stationkeeping and part of the orbit transfer. Four mission options are analyzed which show the impact of either sharing the orbit transfer between chemical and SEP systems or having either complete the transfer alone. Results show that for an Atlas 2AS payload increases in net mass (geostationary satellite mass less wet propulsion system mass) of up to 100 kg can be achieved using advanced chemical for the transfer and advanced N2H4 arcjets for stationkeeping. An additional 100 kg can be added using advanced N2H4 arcjets for part of a 40 day orbit transfer.

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.

Active mass damper system for high-rise buildings using neural oscillator and position controller considering stroke limitation of the auxiliary mass

NASA Astrophysics Data System (ADS)

Hongu, J.; Iba, D.; Nakamura, M.; Moriwaki, I.

2016-04-01

This paper proposes a problem-solving method for the stroke limitation problem, which is related to auxiliary masses of active mass damper systems for high-rise buildings. The proposed method is used in a new simple control system for the active mass dampers mimicking the motion of bipedal mammals, which has a neural oscillator synchronizing with the acceleration response of structures and a position controller. In the system, the travel distance and direction of the auxiliary mass of the active mass damper is determined by reference to the output of the neural oscillator, and then, the auxiliary mass is transferred to the decided location by using a PID controller. The one of the purpose of the previouslyproposed system is stroke restriction problem avoidance of the auxiliary mass during large earthquakes by the determination of the desired value within the stroke limitation of the auxiliary mass. However, only applying the limited desired value could not rigorously restrict the auxiliary mass within the limitation, because the excessive inertia force except for the control force produced by the position controller affected on the motion of the auxiliary mass. In order to eliminate the effect on the auxiliary mass by the structural absolute acceleration, a cancellation method is introduced by adding a term to the control force of the position controller. We first develop the previously-proposed system for the active mass damper and the additional term for cancellation, and verity through numerical experiments that the new system is able to operate the auxiliary mass within the restriction during large earthquakes. Based on the comparison of the proposed system with the LQ system, a conclusion was drawn regarding which the proposed neuronal system with the additional term appears to be able to limit the stroke of the auxiliary mass of the AMD.

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 influence of mass transfer on solute transport in column experiments with an aggregated soil

NASA Astrophysics Data System (ADS)

Roberts, Paul V.; Goltz, Mark N.; Summers, R. Scott; Crittenden, John C.; Nkedi-Kizza, Peter

1987-06-01

The spreading of concentration fronts in dynamic column experiments conducted with a porous, aggregated soil is analyzed by means of a previously documented transport model (DFPSDM) that accounts for longitudinal dispersion, external mass transfer in the boundary layer surrounding the aggregate particles, and diffusion in the intra-aggregate pores. The data are drawn from a previous report on the transport of tritiated water, chloride, and calcium ion in a column filled with Ione soil having an average aggregate particle diameter of 0.34 cm, at pore water velocities from 3 to 143 cm/h. The parameters for dispersion, external mass transfer, and internal diffusion were predicted for the experimental conditions by means of generalized correlations, independent of the column data. The predicted degree of solute front-spreading agreed well with the experimental observations. Consistent with the aggregate porosity of 45%, the tortuosity factor for internal pore diffusion was approximately equal to 2. Quantitative criteria for the spreading influence of the three mechanisms are evaluated with respect to the column data. Hydrodynamic dispersion is thought to have governed the front shape in the experiments at low velocity, and internal pore diffusion is believed to have dominated at high velocity; the external mass transfer resistance played a minor role under all conditions. A transport model such as DFPSDM is useful for interpreting column data with regard to the mechanisms controlling concentration front dynamics, but care must be exercised to avoid confounding the effects of the relevant processes.

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.

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.

Larger ejaculate volumes are associated with a lower degree of polyandry across bushcricket taxa

PubMed Central

Vahed, Karim

2006-01-01

In numerous insects, including bushcrickets (Tettigoniidae), males are known to transfer substances in the ejaculate that inhibit the receptivity of females to further matings, but it has not yet been established whether these substances reduce the lifetime degree of polyandry of the female. The aim of this study was to test the hypothesis that larger ejaculate volumes should be associated with a lower degree of polyandry across tettigoniid taxa, controlling for male body mass and phylogeny. Data on ejaculate mass, sperm number, nuptial gift mass and male mass were taken primarily from the literature. The degree of polyandry for 14 species of European bushcrickets was estimated by counting the number of spermatodoses within the spermathecae of field-caught females towards the end of their adult lifespans. Data for four further species were obtained from the literature. Data were analysed by using both species regression and independent contrasts to control for phylogeny. Multiple regression analysis revealed that, as predicted, there was a significant negative association between the degree of polyandry and ejaculate mass, relative to male body mass, across bushcricket taxa. Nuptial gift size and sperm number, however, did not contribute further to interspecific variation in the degree of polyandry. A positive relationship was found, across bushcricket taxa, between relative nuptial gift size and relative ejaculate mass, indicating that larger nuptial gifts allow the male to overcome female resistance to accepting large ejaculates. This appears to be the first comparative evidence that males can manipulate the lifetime degree of polyandry of their mates through the transfer of large ejaculates. PMID:16928643

A Cyclic Voltammetry Experiment for the Instrumental Analysis Laboratory.

ERIC Educational Resources Information Center

Baldwin, Richard P.; And Others

1984-01-01

Background information and procedures are provided for experiments that illustrate the nature of cyclic voltammetry and its application in the characterization of organic electrode processes. The experiments also demonstrate the concepts of electrochemical reversibility and diffusion-controlled mass transfer. (JN)

Mass and heat transfer in crushed oil shale

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

Carley, J.F.; Ott, L.L.; Swecker, J.L.

1995-03-01

Studies of heat and mass transfer in packed beds, which disagree substantially in their findings, have nearly all been done with beds of regular particles of uniform size, whereas oil-shale retorting involves particles of diverse irregular shapes and sizes. The authors, in 349 runs, measured mass-transfer rates front naphthalene particles buried in packed beds by passing through air at room temperature. An exact catalog between convection of heat and mass makes it possible to infer heat-transfer coefficients from measured mass-transfer coefficients and fluid properties. Some beds consisted of spheres, naphthalene and inert, of the same, contrasting or distributed sizes. Inmore » some runs, naphthalene spheres were buried in beds of crushed shale, some in narrow screen ranges and others with a wide size range. In others, naphthalene lozenges of different shapes were buried in beds of crushed shale in various bed axis orientations. This technique permits calculation of the mass-transfer coefficient for each active particle in the bed rather than, as in most past studies, for the bed as a whole. The data are analyzed by the traditional correlation of Colburn j{sub D} vs. Reynolds number and by multiple regression of the mass-transfer coefficient on air rate, sizes of active and inert particles, void fraction, and temperature. Principal findings are: local Reynolds number should be based on the active-particle size, not the average for the whole bed; differences between shallow and deep beds are not appreciable; mass transfer is 26% faster for spheres and lozenges buried in shale than in all-sphere beds; orientation of lozenges in shale beds has little or no effect on mass-transfer rate; and for mass or heat transfer in shale beds, log(j{center_dot}{epsilon}) = {minus}0.0747 - 0.6344 log N{sub Re} + 0. 0592 log {sup 2} N{sub Re}.« 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.

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

Sensing of metal-transfer mode for process control of GMAW (gas metal arc welding)

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

Carlson, N.M.; Johnson, J.A.; Smartt, H.B.

1989-01-01

One of the requirements of a sensing system for feedback control of gas metal arc welding (GMAW) is the capability to determine the metal-transfer mode. Because the operating boundary for the desired transfer mode, expressed as a function of mass input and heat input, may vary due to conditions beyond the control of the system, a means of detecting the transfer mode during welding is necessary. A series of sensing experiments was performed during which the ultrasonic emissions, audio emissions, welding current fluctuations and welding voltage fluctuations were recorded as a function of the transfer mode. In addition, high speedmore » movies (5000 frames/s) of the droplet formation and detachment were taken synchronously with the sensing data. An LED mounted in the camera was used to mark the film at the beginning and end of the data acquisition period. A second LED was pulsed at a 1 kHz rate and the pulses recorded on film and with the sensor data. Thus events recorded on the film can be correlated with the sensor data. Data acquired during globular transfer, spray transfer, and stiff spray or streaming transfer were observed to correlate with droplet detachment and arc shorting. The audio, current, and voltage data can be used to discriminate among these different transfer modes. However, the current and voltage data are also dependent on the characteristic of the welding power supply. 5 refs., 3 figs., 1 tab.« less

Low cholesteryl ester transfer protein (CETP) concentration but normal CETP activity in serum from patients with short-term hypothyroidism Lack of relationship to lipoprotein abnormalities.

PubMed

Dedecjus, Marek; Masson, David; Gautier, Thomas; de Barros, Jean-Paul Pais; Gambert, Philippe; Lewinski, Andrzej; Adamczewski, Zbigniew; Moulin, Philippe; Lagrost, Laurent

2003-05-01

Hypothyroidism is associated with a number of abnormalities in lipoprotein metabolism. Although alterations in neutral lipid exchanges among plasma lipoproteins might be one characteristic feature of hypothyroidism, a few human studies of cholesteryl ester transfer protein (CETP) activity have led to heterogeneous and fragmentary observations. The aim of the present study was to analyse the influence of short-term hypothyroidism on CETP activity, as well as on the structure and composition of lipoproteins. PATIENTS, DESIGN AND MEASUREMENTS: Sixty-six thyroidectomized patients were withdrawn from L-thyroxine (L-T4) treatment for 5 weeks. Subsequently, L-T4 therapy was reinstated for 2 months and patients were compared to 61 matched normolipidaemic controls. Serum CETP activity and mass concentration, serum lipids, apolipoproteins and lipoprotein size distribution were determined in the three groups. Serum CETP mass concentration was significantly decreased in short-term hypothyroid patients, as compared to control subjects (3.22 +/- 0.98 vs. 3.79 +/- 1.2 mg/l, respectively; P < 0.001), and the values were normalized during L-T4 therapy. The ability of endogenous serum lipoproteins to interact with CETP was normal in short-term hypothyroid patients. Concordant observations were made regardless of whether neutral lipid transfers were measured from high-density lipoproteins (HDL) toward apo B-containing lipoproteins or from liposomes toward HDL. The size distribution of HDL was significantly different in short-term hypothyroid patients, compared to either the control or treated subgroups, with significant higher proportions of large-sized HDL2b and HDL2a (HDL2b: 13.6 +/- 6.5% before vs. 8.5 +/- 4.2% during L-T4 therapy, P < 0.05; HDL2a, 33.0 +/- 7.0% before vs. 29.3 +/- 6.9% during L-T4 therapy, P < 0.05). Although serum CETP mass concentration correlated negatively with the HDL2 to HDL3 ratio in control subjects (r = -0.588; P < 0.0001), no significant correlations were observed in hypothyroid patients, regardless of whether they were treated or not. Similarly, whereas the previously recognized positive correlation of CETP mass concentration with serum LDL cholesterol levels was found in control subjects (r = 0.264; P < 0.05), no significant correlations appeared in treated and untreated patients. Short-term hypothyroidism may constitute an unique situation in which concomitant alterations in serum cholesteryl ester transfer protein concentration and lipoprotein parameters are disconnected.

Effect of morphology and defect density on electron transfer of electrochemically reduced graphene oxide

NASA Astrophysics Data System (ADS)

Zhang, Yan; Hao, Huilian; Wang, Linlin

2016-12-01

Electrochemically reduced graphene oxide (ERGO) is widely used to construct electrochemical sensors. Understanding the electron transfer behavior of ERGO is essential for its electrode material applications. In this paper, different morphologies of ERGO were prepared via two different methods. Compared to ERGO/GCEs prepared by electrochemical reduction of pre-deposited GO, more exposed edge planes of ERGO are observed on the surface of ERGO-GCE that was constructed by electrophoretic deposition of GO. The defect densities of ERGO were controlled by tuning the mass or concentration of GO. The electron transfer kinetics (k0) of GCE with different ERGOs was comparatively investigated. Owing to increased surface areas and decreased defect density, the k0 values of ERGO/GCE initially increase and then decrease with incrementing of GO mass. When the morphology and surface real areas of ERGO-GCE are the same, an increased defect density induces an accelerated electron transfer rate. k0 valuesof ERGO-GCEs are about 1 order of magnitude higher than those of ERGO/GCEs due to the difference in the amount of edge planes. This work demonstrates that both defect densities and edge planes of ERGO play crucial roles in electron transfer kinetics.

VizieR Online Data Catalog: Adiabatic mass loss in binary stars. II. (Ge+, 2015)

NASA Astrophysics Data System (ADS)

Ge, H.; Webbink, R. F.; Chen, X.; Han, Z.

2016-02-01

In the limit of extremely rapid mass transfer, the response of a donor star in an interacting binary becomes asymptotically one of adiabatic expansion. We survey here adiabatic mass loss from Population I stars (Z=0.02) of mass 0.10M⊙-100M⊙ from the zero-age main sequence to the base of the giant branch, or to central hydrogen exhaustion for lower main sequence stars. The logarithmic derivatives of radius with respect to mass along adiabatic mass-loss sequences translate into critical mass ratios for runaway (dynamical timescale) mass transfer, evaluated here under the assumption of conservative mass transfer. For intermediate- and high-mass stars, dynamical mass transfer is preceded by an extended phase of thermal timescale mass transfer as the star is stripped of most of its envelope mass. The critical mass ratio qad (throughout this paper, we follow the convention of defining the binary mass ratio as q{equiv}Mdonor/Maccretor) above which this delayed dynamical instability occurs increases with advancing evolutionary age of the donor star, by ever-increasing factors for more massive donors. Most intermediate- or high-mass binaries with nondegenerate accretors probably evolve into contact before manifesting this instability. As they approach the base of the giant branch, however, and begin developing a convective envelope, qad plummets dramatically among intermediate-mass stars, to values of order unity, and a prompt dynamical instability occurs. Among low-mass stars, the prompt instability prevails throughout main sequence evolution, with qad declining with decreasing mass, and asymptotically approaching qad=2/3, appropriate to a classical isentropic n=3/2 polytrope. Our calculated qad values agree well with the behavior of time-dependent models by Chen & Han (2003MNRAS.341..662C) of intermediate-mass stars initiating mass transfer in the Hertzsprung gap. Application of our results to cataclysmic variables, as systems that must be stable against rapid mass transfer, nicely circumscribes the range in qad as a function of the orbital period in which they are found. These results are intended to advance the verisimilitude of population synthesis models of close binary evolution. (3 data files).

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.

Irradiation-driven Mass Transfer Cycles in Compact Binaries

NASA Astrophysics Data System (ADS)

Büning, A.; Ritter, H.

2005-08-01

We elaborate on the analytical model of Ritter, Zhang, & Kolb (2000) which describes the basic physics of irradiation-driven mass transfer cycles in semi-detached compact binary systems. In particular, we take into account a contribution to the thermal relaxation of the donor star which is unrelated to irradiation and which was neglected in previous studies. We present results of simulations of the evolution of compact binaries undergoing mass transfer cycles, in particular also of systems with a nuclear evolved donor star. These computations have been carried out with a stellar evolution code which computes mass transfer implicitly and models irradiation of the donor star in a point source approximation, thereby allowing for much more realistic simulations than were hitherto possible. We find that low-mass X-ray binaries (LMXBs) and cataclysmic variables (CVs) with orbital periods ⪉ 6hr can undergo mass transfer cycles only for low angular momentum loss rates. CVs containing a giant donor or one near the terminal age main sequence are more stable than previously thought, but can possibly also undergo mass transfer cycles.

In silico ordinary differential equation/partial differential equation hemodialysis model estimates methadone removal during dialysis.

PubMed

Linares, Oscar A; Schiesser, William E; Fudin, Jeffrey; Pham, Thien C; Bettinger, Jeffrey J; Mathew, Roy O; Daly, Annemarie L

2015-01-01

There is a need to have a model to study methadone's losses during hemodialysis to provide informed methadone dose recommendations for the practitioner. To build a one-dimensional (1-D), hollow-fiber geometry, ordinary differential equation (ODE) and partial differential equation (PDE) countercurrent hemodialyzer model (ODE/PDE model). We conducted a cross-sectional study in silico that evaluated eleven hemodialysis patients. Patients received a ceiling dose of methadone hydrochloride 30 mg/day. Outcome measures included: the total amount of methadone removed during dialysis; methadone's overall intradialytic mass transfer rate coefficient, km ; and, methadone's removal rate, j ME. Each metric was measured at dialysate flow rates of 250 mL/min and 800 mL/min. The ODE/PDE model revealed a significant increase in the change of methadone's mass transfer with increased dialysate flow rate, %Δkm =18.56, P=0.02, N=11. The total amount of methadone mass transferred across the dialyzer membrane with high dialysate flow rate significantly increased (0.042±0.016 versus 0.052±0.019 mg/kg, P=0.02, N=11). This was accompanied by a small significant increase in methadone's mass transfer rate (0.113±0.002 versus 0.014±0.002 mg/kg/h, P=0.02, N=11). The ODE/PDE model accurately predicted methadone's removal during dialysis. The absolute value of the prediction errors for methadone's extraction and throughput were less than 2%. ODE/PDE modeling of methadone's hemodialysis is a new approach to study methadone's removal, in particular, and opioid removal, in general, in patients with end-stage renal disease on hemodialysis. ODE/PDE modeling accurately quantified the fundamental phenomena of methadone's mass transfer during hemodialysis. This methodology may lead to development of optimally designed intradialytic opioid treatment protocols, and allow dynamic monitoring of outflow plasma opioid concentrations for model predictive control during dialysis in humans.

Exploring the Effects of Atmospheric Forcings on Evaporation: Experimental Integration of the Atmospheric Boundary Layer and Shallow Subsurface

PubMed Central

Smits, Kathleen; Eagen, Victoria; Trautz, Andrew

2015-01-01

Evaporation is directly influenced by the interactions between the atmosphere, land surface and soil subsurface. This work aims to experimentally study evaporation under various surface boundary conditions to improve our current understanding and characterization of this multiphase phenomenon as well as to validate numerical heat and mass transfer theories that couple Navier-Stokes flow in the atmosphere and Darcian flow in the porous media. Experimental data were collected using a unique soil tank apparatus interfaced with a small climate controlled wind tunnel. The experimental apparatus was instrumented with a suite of state of the art sensor technologies for the continuous and autonomous collection of soil moisture, soil thermal properties, soil and air temperature, relative humidity, and wind speed. This experimental apparatus can be used to generate data under well controlled boundary conditions, allowing for better control and gathering of accurate data at scales of interest not feasible in the field. Induced airflow at several distinct wind speeds over the soil surface resulted in unique behavior of heat and mass transfer during the different evaporative stages. PMID:26131928

Application of Transfer Matrix Approach to Modeling and Decentralized Control of Lattice-Based Structures

NASA Technical Reports Server (NTRS)

Cramer, Nick; Swei, Sean Shan-Min; Cheung, Kenny; Teodorescu, Mircea

2015-01-01

This paper presents a modeling and control of aerostructure developed by lattice-based cellular materials/components. The proposed aerostructure concept leverages a building block strategy for lattice-based components which provide great adaptability to varying ight scenarios, the needs of which are essential for in- ight wing shaping control. A decentralized structural control design is proposed that utilizes discrete-time lumped mass transfer matrix method (DT-LM-TMM). The objective is to develop an e ective reduced order model through DT-LM-TMM that can be used to design a decentralized controller for the structural control of a wing. The proposed approach developed in this paper shows that, as far as the performance of overall structural system is concerned, the reduced order model can be as e ective as the full order model in designing an optimal stabilizing controller.

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.

Design Project on Controlled-Release Drug Delivery Devices: Implementation, Management, and Learning Experiences

ERIC Educational Resources Information Center

Xu, Qingxing; Liang, Youyun; Tong, Yen Wah; Wang, Chi-Hwa

2010-01-01

A design project that focuses on the subject of controlled-release drug delivery devices is presented for use in an undergraduate course on mass transfer. The purpose of the project is to introduce students to the various technologies used in the fabrication of drug delivery systems and provide a practical design exercise for understanding the…

Jason Woods | NREL

Science.gov Websites

doctoral student since 2007. Jason's area of expertise is heat and mass transfer, including the design , analysis, and testing of heat and mass transfer devices and processes. Research Interests Membrane Thermal energy storage Heat and mass transfer enhancements Combined cooling, heat, and power (CCHP

The mechanism and theoretical basis of the management of intensity of the heat transfer control through periodic influences on the turbulent boundary layer

NASA Astrophysics Data System (ADS)

Kovalnogov, Vladislav N.; Fedorov, Ruslan V.; Khakhaleva, Larisa V.; Chukalin, Andrey V.; Bondarenko, Aleksandr A.; Kovrizhnykh, Evgeny N.

2017-07-01

Generalization of classical model of a displacement way on the transfer of heat exchange and mass exchange of a stream in the boundary layer, confirmed by the control action of the different nature, is undertaken. Here are given the results of numerical research which have allowed explaining the mechanism, to reveal efficiency and limits of various ways of management of intensity in exchange processes. The possibility of management of intensity in processes of a thermolysis and friction by use of the perforated surface with the damping cavities is analyzed.

Vehicle anti-rollover control strategy based on load transferring rate

NASA Astrophysics Data System (ADS)

Dai, W. T.; Du, H. Q.; Zhang, L.

2018-03-01

When vehicles is drived on a low adhesion road or going on a high speed and sharp turn, it is prone to product some lateral stability problems, such as lateral sideslip or rollover. In order to improve the vehicle anti-rollover stability under these limited conditions, a SUV vehicle model with high mass center was built based on the software of CarSim and the rollover stability controller was designed using the static threshold value method for the lateral load transferring rate (LTR). The simulations are shown that the vehicle anti-rollover stability under limit conditions is improved using the SUV model.

Investigation of Processes Controlling Elution of Solutes from Nonaqueous Phase Liquid (NAPL) Pools into Groundwater

NASA Astrophysics Data System (ADS)

Seyedabbasi, M.; Pirestani, K.; Holland, S. B.; Imhoff, P. T.

2005-12-01

Two major processes influencing the elution of solutes from porous media contaminated with nonaqueous phase liquids (NAPLs) are external mass transfer between the NAPL and groundwater and internal diffusion through NAPL ganglia and pools. There is a relatively large body of literature on the dissolution of single-species NAPLs. Less is known about the rates of elution of compounds dissolving from multicomponent NAPLs. We examined the mass transfer of one solute, 2,3-dimethyl-2-butanol (DMB) - a partitioning tracer, between groundwater and a dense NAPL - trichloroethylene (TCE). Diffusion cell experiments were used to measure the molecular diffusion coefficient of DMB in pure TCE and in porous media contaminated with a TCE pool. Measured diffusion coefficients were compared with empirical correlations (pure TCE) and a parallel resistance model (TCE pool). Based on the results from these analyses, a dimensionless Biot number was derived to express the ratio of the external rate of mass transfer from a NAPL pool to the internal rate of diffusion within the pool, which varies with NAPL saturation and NAPL-water partition coefficient. Biot numbers were then estimated for several laboratory scale experiments involving DMB transport between NAPL pools and groundwater. The estimated Biot numbers were in good agreement with experimental results. The expression for the Biot number developed here may be used to assess the processes controlling the elution of solutes from NAPL pools, which has implications on long-term predictions of solute dissolution from NAPLs in the field.

Modeling Droplet Heat and Mass Transfer during Spray Bar Pressure Control of the Multipurpose Hydrogen Test Bed (MHTB) Tank in Normal Gravity

NASA Technical Reports Server (NTRS)

Kartuzova, O.; Kassemi, M.

2016-01-01

A CFD model for simulating pressure control in cryogenic storage tanks through the injection of a subcooled liquid into the ullage is presented and applied to the 1g MHTB spray bar cooling experiments. An Eulerian-Lagrangian approach is utilized to track the spray droplets and capture the interaction between the discrete droplets and the continuous ullage phase. The spray model is coupled with the VOF model by performing particle tracking in the ullage, removing particles from the ullage when they reach the interface, and then adding their contributions to the liquid. A new model for calculating the droplet-ullage heat and mass transfer is developed. In this model, a droplet is allowed to warm up to the saturation temperature corresponding to the ullage vapor pressure, after which it evaporates while remaining at the saturation temperature. The droplet model is validated against the results of the MHTB spray-bar cooling experiments with 50% and 90% tank fill ratios. The predictions of the present T-sat based model are compared with those of a previously developed kinetic-based droplet mass transfer model. The predictions of the two models regarding the evolving tank pressure and temperature distributions, as well as the droplets' trajectories and temperatures, are examined and compared in detail. Finally, the ullage pressure and local vapor and liquid temperature evolutions are validated against the corresponding data provided by the MHTB spray bar mixing experiment.

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.

International Space Station (ISS) Water Transfer Hardware Logistics

NASA Technical Reports Server (NTRS)

Shkedi, Brienne D.

2006-01-01

Water transferred from the Space Shuttle to the International Space Station (ISS) is generated as a by-product from the Shuttle fuel cells, and is generally preferred over the Progress which has to launch water from the ground. However, launch mass and volume are still required for the transfer and storage hardware. Some of these up-mass requirements have been reduced since ISS assembly began due to changes in the storage hardware (CWC). This paper analyzes the launch mass and volume required to transfer water from the Shuttle and analyzes the up-mass savings due to modifications in the CWC. Suggestions for improving the launch mass and volume are also provided.

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.

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

Geophysical monitoring of solute transport in dual-domain environments through laboratory experiments, field-scale solute tracer tests, and numerical simulation

NASA Astrophysics Data System (ADS)

Swanson, Ryan David

The advection-dispersion equation (ADE) fails to describe non-Fickian solute transport breakthrough curves (BTCs) in saturated porous media in both laboratory and field experiments, necessitating the use of other models. The dual-domain mass transfer (DDMT) model partitions the total porosity into mobile and less-mobile domains with an exchange of mass between the two domains, and this model can reproduce better fits to BTCs in many systems than ADE-based models. However, direct experimental estimation of DDMT model parameters remains elusive and model parameters are often calculated a posteriori by an optimization procedure. Here, we investigate the use of geophysical tools (direct-current resistivity, nuclear magnetic resonance, and complex conductivity) to estimate these model parameters directly. We use two different samples of the zeolite clinoptilolite, a material shown to demonstrate solute mass transfer due to a significant internal porosity, and provide the first evidence that direct-current electrical methods can track solute movement into and out of a less-mobile pore space in controlled laboratory experiments. We quantify the effects of assuming single-rate DDMT for multirate mass transfer systems. We analyze pore structures using material characterization methods (mercury porosimetry, scanning electron microscopy, and X-ray computer tomography), and compare these observations to geophysical measurements. Nuclear magnetic resonance in conjunction with direct-current resistivity measurements can constrain mobile and less-mobile porosities, but complex conductivity may have little value in relation to mass transfer despite the hypothesis that mass transfer and complex conductivity lengths scales are related. Finally, we conduct a geoelectrical monitored tracer test at the Macrodispersion Experiment (MADE) site in Columbus, MS. We relate hydraulic and electrical conductivity measurements to generate a 3D hydraulic conductivity field, and compare to hydraulic conductivity fields estimated through ordinary kriging and sequential Gaussian simulation. Time-lapse electrical measurements are used to verify or dismiss aspects of breakthrough curves for different hydraulic conductivity fields. Our results quantify the potential for geophysical measurements to infer on single-rate DDMT parameters, show site-specific relations between hydraulic and electrical conductivity, and track solute exchange into and out of less-mobile domains.

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.

Monitoring the variations of the oxygen transfer rate in a full scale membrane bioreactor using daily mass balances.

PubMed

Racault, Y; Stricker, A-E; Husson, A; Gillot, S

2011-01-01

Oxygen transfer in biological wastewater treatment processes with high sludge concentration, such as membrane bioreactor (MBR), is an important issue. The variation of alpha-factor versus mixed liquor suspended solids (MLSS) concentration was investigated in a full scale MBR plant under process conditions, using mass balances. Exhaustive data from the Supervisory Control And Data Acquisition (SCADA) and from additional online sensors (COD, DO, MLSS) were used to calculate the daily oxygen consumption (OC) using a non-steady state mass balance for COD and total N on a 24-h basis. To close the oxygen balance, OC has to match the total oxygen transfer rate (OTRtot) of the system, which is provided by fine bubble (FB) diffusers in the aeration tank and coarse bubbles (CB) in separate membrane tanks. First assessing OTR(CB) then closing the balance OC = OTRtot allowed to calculate OTR(FB) and to fit an exponential relationship between OTR(FB) and MLSS. A comparison of the alpha-factor obtained by this balance method and by direct measurements with the off-gas method on the same plant is presented and discussed.

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 dechlorination kinetics were reflected in a transient, spatially heterogeneous bioavailability number and dissolution enhancement. In agreement with the literature, source zone architecture largely determined the impact of mass transfer on potential dissolution enhancement, with bioavailability decreasing the most at high ganglia to pool ratios. The results of this study suggest that if mass transfer rate limitations are not considered in designing bioremediation applications at DNAPL source zones, the enhancement of DNAPL depletion and the overall effectiveness of enhanced bioremediation may be significantly overestimated.

Modeling Nitrogen Fate and Transport at the Sediment-Water Interface

EPA Science Inventory

Diffusive mass transfer at media interfaces exerts control on the fate and transport of pollutants originating from agricultural and urban landscapes and affects the con-ditions of water bodies. Diffusion is essentially a physical process affecting the distribution and fate of va...

Capillary electrophoresis electrospray ionization mass spectrometry interface

DOEpatents

Smith, Richard D.; Severs, Joanne C.

1999-01-01

The present invention is an interface between a capillary electrophoresis separation capillary end and an electrospray ionization mass spectrometry emitter capillary end, for transporting an anolyte sample from a capillary electrophoresis separation capillary to a electrospray ionization mass spectrometry emitter capillary. The interface of the present invention has: (a) a charge transfer fitting enclosing both of the capillary electrophoresis capillary end and the electrospray ionization mass spectrometry emitter capillary end; (b) a reservoir containing an electrolyte surrounding the charge transfer fitting; and (c) an electrode immersed into the electrolyte, the electrode closing a capillary electrophoresis circuit and providing charge transfer across the charge transfer fitting while avoiding substantial bulk fluid transfer across the charge transfer fitting. Advantages of the present invention have been demonstrated as effective in providing high sensitivity and efficient analyses.

Murt user`s guide: A hybrid Lagrangian-Eulerian finite element model of multiple-pore-region solute transport through subsurface media

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

Gwo, J.P.; Jardine, P.M.; Yeh, G.T.

Matrix diffusion, a diffusive mass transfer process,in the structured soils and geologic units at ORNL, is believe to be an important subsurface mass transfer mechanism; it may affect off-site movement of radioactive wastes and remediation of waste disposal sites by locally exchanging wastes between soil/rock matrix and macropores/fractures. Advective mass transfer also contributes to waste movement but is largely neglected by researchers. This report presents the first documented 2-D multiregion solute transport code (MURT) that incorporates not only diffusive but also advective mass transfer and can be applied to heterogeneous porous media under transient flow conditions. In this report, theoreticalmore » background is reviewed and the derivation of multiregion solute transport equations is presented. Similar to MURF (Gwo et al. 1994), a multiregion subsurface flow code, multiplepore domains as suggested by previous investigators (eg, Wilson and Luxmoore 1988) can be implemented in MURT. Transient or steady-state flow fields of the pore domains can be either calculated by MURF or by modelers. The mass transfer process is briefly discussed through a three-pore-region multiregion solute transport mechanism. Mass transfer equations that describe mass flux across pore region interfaces are also presented and parameters needed to calculate mass transfer coefficients detailed. Three applications of MURT (tracer injection problem, sensitivity analysis of advective and diffusive mass transfer, hillslope ponding infiltration and secondary source problem) were simulated and results discussed. Program structure of MURT and functions of MURT subroutiness are discussed so that users can adapt the code; guides for input data preparation are provided in appendices.« less

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.

Phthalates and alternative plasticizers and potential for contact exposure from children's backpacks and toys.

PubMed

Xie, Mingjie; Wu, Yaoxing; Little, John C; Marr, Linsey C

2016-01-01

This work focuses on the mass content of plasticizers in children's backpacks and toys, and their mass transfer from product surfaces to cotton wipes. The mass content of plasticizers in six backpacks and seven toys was measured by extracting them in tetrahydrofuran. Bis(2-ethylhexyl) terephthalate (DEHT) was the most common plasticizer, dominating the composition of plasticizers in four backpacks (average mass content in product polyvinyl chloride, 5.38 ± 1.98%-25.5 ± 3.54%) and six plastic toys (8.17 ± 1.85%-21.2 ± 1.11%). The surface of each product was wiped with three dry and three wet (by isopropanol) cotton wipes, so as to evaluate the mass transfer of plasticizers to clothing and human skin, respectively. DEHT was the most common plasticizer detected on wipe samples. There were strong correlations (backpacks r=0.90; plastic toys r=0.96) between average mass transfer of DEHT to wet wipes and its average mass content in the product. The mass transfers of the five dominant plasticizers in one backpack to both dry and wet wipes were also correlated (both r=1.00) with their mass contents. These results suggest that the mass transfer of plasticizers from products to clothing or human skin is strongly associated with their mass content.

Mass transfer effects in a gasification riser

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

Breault, Ronald W.; Li, Tingwen; Nicoletti, Phillip

2013-07-01

In the development of multiphase reacting computational fluid dynamics (CFD) codes, a number of simplifications were incorporated into the codes and models. One of these simplifications was the use of a simplistic mass transfer correlation for the faster reactions and omission of mass transfer effects completely on the moderate speed and slow speed reactions such as those in a fluidized bed gasifier. Another problem that has propagated is that the mass transfer correlation used in the codes is not universal and is being used far from its developed bubbling fluidized bed regime when applied to circulating fluidized bed (CFB) risermore » reactors. These problems are true for the major CFD codes. To alleviate this problem, a mechanistic based mass transfer coefficient algorithm has been developed based upon an earlier work by Breault et al. This fundamental approach uses the local hydrodynamics to predict a local, time varying mass transfer coefficient. The predicted mass transfer coefficients and the corresponding Sherwood numbers agree well with literature data and are typically about an order of magnitude lower than the correlation noted above. The incorporation of the new mass transfer model gives the expected behavior for all the gasification reactions evaluated in the paper. At the expected and typical design values for the solid flow rate in a CFB riser gasifier an ANOVA analysis has shown the predictions from the new code to be significantly different from the original code predictions. The new algorithm should be used such that the conversions are not over predicted. Additionally, its behaviors with changes in solid flow rate are consistent with the changes in the hydrodynamics.« less

Beyond the standard two-film theory: Computational fluid dynamics simulations for carbon dioxide capture in a wetted wall column

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

Wang, Chao; Xu, Zhijie; Lai, Canhai

The standard two-film theory (STFT) is a diffusion-based mechanism that can be used to describe gas mass transfer across liquid film. Fundamental assumptions of the STFT impose serious limitations on its ability to predict mass transfer coefficients. To better understand gas absorption across liquid film in practical situations, a multiphase computational fluid dynamics (CFD) model fully equipped with mass transport and chemistry capabilities has been developed for solvent-based carbon dioxide (CO 2) capture to predict the CO 2 mass transfer coefficient in a wetted wall column. The hydrodynamics is modeled using a volume of fluid method, and the diffusive andmore » reactive mass transfer between the two phases is modeled by adopting a one-fluid formulation. We demonstrate that the proposed CFD model can naturally account for the influence of many important factors on the overall mass transfer that cannot be quantitatively explained by the STFT, such as the local variation in fluid velocities and properties, flow instabilities, and complex geometries. The CFD model also can predict the local mass transfer coefficient variation along the column height, which the STFT typically does not consider.« less

Beyond the standard two-film theory: Computational fluid dynamics simulations for carbon dioxide capture in a wetted wall column

DOE PAGES

Wang, Chao; Xu, Zhijie; Lai, Canhai; ...

2018-03-27

The standard two-film theory (STFT) is a diffusion-based mechanism that can be used to describe gas mass transfer across liquid film. Fundamental assumptions of the STFT impose serious limitations on its ability to predict mass transfer coefficients. To better understand gas absorption across liquid film in practical situations, a multiphase computational fluid dynamics (CFD) model fully equipped with mass transport and chemistry capabilities has been developed for solvent-based carbon dioxide (CO 2) capture to predict the CO 2 mass transfer coefficient in a wetted wall column. The hydrodynamics is modeled using a volume of fluid method, and the diffusive andmore » reactive mass transfer between the two phases is modeled by adopting a one-fluid formulation. We demonstrate that the proposed CFD model can naturally account for the influence of many important factors on the overall mass transfer that cannot be quantitatively explained by the STFT, such as the local variation in fluid velocities and properties, flow instabilities, and complex geometries. The CFD model also can predict the local mass transfer coefficient variation along the column height, which the STFT typically does not consider.« less

ADIABATIC MASS LOSS IN BINARY STARS. II. FROM ZERO-AGE MAIN SEQUENCE TO THE BASE OF THE GIANT BRANCH

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

Ge, Hongwei; Chen, Xuefei; Han, Zhanwen

2015-10-10

In the limit of extremely rapid mass transfer, the response of a donor star in an interacting binary becomes asymptotically one of adiabatic expansion. We survey here adiabatic mass loss from Population I stars (Z = 0.02) of mass 0.10 M{sub ⊙}–100 M{sub ⊙} from the zero-age main sequence to the base of the giant branch, or to central hydrogen exhaustion for lower main sequence stars. The logarithmic derivatives of radius with respect to mass along adiabatic mass-loss sequences translate into critical mass ratios for runaway (dynamical timescale) mass transfer, evaluated here under the assumption of conservative mass transfer. Formore » intermediate- and high-mass stars, dynamical mass transfer is preceded by an extended phase of thermal timescale mass transfer as the star is stripped of most of its envelope mass. The critical mass ratio q{sub ad} (throughout this paper, we follow the convention of defining the binary mass ratio as q ≡ M{sub donor}/M{sub accretor}) above which this delayed dynamical instability occurs increases with advancing evolutionary age of the donor star, by ever-increasing factors for more massive donors. Most intermediate- or high-mass binaries with nondegenerate accretors probably evolve into contact before manifesting this instability. As they approach the base of the giant branch, however, and begin developing a convective envelope, q{sub ad} plummets dramatically among intermediate-mass stars, to values of order unity, and a prompt dynamical instability occurs. Among low-mass stars, the prompt instability prevails throughout main sequence evolution, with q{sub ad} declining with decreasing mass, and asymptotically approaching q{sub ad} = 2/3, appropriate to a classical isentropic n = 3/2 polytrope. Our calculated q{sub ad} values agree well with the behavior of time-dependent models by Chen and Han of intermediate-mass stars initiating mass transfer in the Hertzsprung gap. Application of our results to cataclysmic variables, as systems that must be stable against rapid mass transfer, nicely circumscribes the range in q{sub ad} as a function of the orbital period in which they are found. These results are intended to advance the verisimilitude of population synthesis models of close binary evolution.« less

Membrane-Mediated Extraction and Biodegradation of Volatile Organic Compounds From Air

DTIC Science & Technology

2005-01-01

side boundary-layer mass transfer resistance is a significant fraction of the total mass transfer resistance ( Raghunath , 1992). In some cases where...Sci. 59: 53–72. Raghunath , B., and S.–T. Hwang (1992). “Effect of boundary layer mass transfer resistance in the pervaporation of dilute organics

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.

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.

[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.

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.

Odorant transfer characteristics of white bread during baking.

PubMed

Onishi, Masanobu; Inoue, Michiko; Araki, Tetsuya; Iwabuchi, Hisakatsu; Sagara, Yasuyuki

2011-01-01

The potent odorants in the crust and crumb of white bread were identified and quantified by gas chromatography-mass spectrometry and gas chromatography/olfactometry. The weight loss ratio of the samples baked at 220 °C was controlled in the range of 0-28%. The odorants were classified into 5 types by the transfer characteristics: i) All amounts of odorant transferred from the crust to external space (type-I). ii) All transferred from the crust to the crumb and external space (type-II). iii) Certain amount remaining in the crust and the rest transferred to the crumb and external space (type-III). iv) All transferred from the crumb to external space (type-IV). v) Certain amount remaining in the crumb and the rest transferred to the crust and external space (type-V). The odorants of type-IV were not apparent after the crust had formed. The results indicate that the crust could be a barrier to prevent the odorants from being transferred to external space.

Advances in cryogenic engineering. Volume 27 - Proceedings of the Cryogenic Engineering Conference, San Diego, CA, August 11-14, 1981

NASA Astrophysics Data System (ADS)

Fast, R. W.

Applications of superconductivity are considered, taking into account MHD and fusion, generators, transformers, transmission lines, magnets for physics, cryogenic techniques, electrtronics, and aspects of magnet stability. Advances related to heat transfer in He I are discussed along with subjects related to theat transfer in He II, refrigeration of superconducting systems, refrigeration and liquefaction, dilution and magnetic refrigerators, refrigerators for space applications, mass transfer and flow phenomena, and the properties of fluids. Developments related to cryogenic applications are also explored, giving attention to bulk storage and transfer of cryogenic fluids, liquefied natural gas operations, space science and technology, and cryopumping. Topics related to cryogenic instrumentation and controls include the production and use of high grade silicon diode temperature sensors, the choice of strain gages for use in a large superconducting alternator, microprocessor control of cryogenic pressure, and instrumentation, data acquisition and reduction for a large spaceborne helium dewar. For individual items see A83-43221 to A83-43250

Development of a thermal-hydraulics experimental system for high Tc superconductors cooled by liquid hydrogen

NASA Astrophysics Data System (ADS)

Tatsumoto, H.; Shirai, Y.; Shiotsu, M.; Hata, K.; Kobayashi, H.; Naruo, Y.; Inatani, Y.; Kato, T.; Futakawa, M.; Kinoshita, K.

2010-06-01

A thermal-hydraulics experimental system of liquid hydrogen was developed in order to investigate the forced flow heat transfer characteristics in the various cooling channels for wide ranges of subcoolings, flow velocities, and pressures up to supercritical. A main tank is connected to a sub tank through a hydrogen transfer line with a control valve. A channel heater is located at one end of the transfer line in the main tank. Forced flow through the channel is produced by adjusting the pressure difference between the tanks and the valve opening. The mass flow rate is measured from the weight change of the main tank. For the explosion protection, electrical equipments are covered with a nitrogen gas blanket layer and a remote control system was established. The first cryogenic performance tests confirmed that the experimental system had satisfied with the required performances. The forced convection heat transfer characteristics was successfully measured at the pressure of 0.7 MPa for various flow velocities.

Simple control laws for low-thrust orbit transfers

NASA Technical Reports Server (NTRS)

Petropoulos, Anastassios E.

2003-01-01

Two methods are presented by which to determine both a thrust direction and when to apply thrust to effect specified changes in any of the orbit elements except for true anomaly, which is assumed free. The central body is assumed to be a point mass, and the initial and final orbits are assumed closed. Thrust, when on, is of a constant value, and specific impulse is constant. The thrust profiles derived from the two methods are not propellant-optimal, but are based firstly on the optimal thrust directions and location on the osculating orbit for changing each of the orbit elements and secondly on the desired changes in the orbit elements. Two examples of transfers are presented, one in semimajor axis and inclination, and one in semimajor axis and eccentricity. The latter compares favourably with a propellant-optimized transfer between the same orbits. The control laws have few input parameters, but can still capture the complexity of a wide variety of orbit transfers.

Learned Manipulation at Unconstrained Contacts Does Not Transfer across Hands

PubMed Central

Fu, Qiushi; Choi, Jason Y.; Gordon, Andrew M.; Jesunathadas, Mark; Santello, Marco

2014-01-01

Recent studies about sensorimotor control of the human hand have focused on how dexterous manipulation is learned and generalized. Here we address this question by testing the extent to which learned manipulation can be transferred when the contralateral hand is used and/or object orientation is reversed. We asked subjects to use a precision grip to lift a grip device with an asymmetrical mass distribution while minimizing object roll during lifting by generating a compensatory torque. Subjects were allowed to grasp anywhere on the object’s vertical surfaces, and were therefore able to modulate both digit positions and forces. After every block of eight trials performed in one manipulation context (i.e., using the right hand and at a given object orientation), subjects had to lift the same object in the second context for one trial (transfer trial). Context changes were made by asking subjects to switch the hand used to lift the object and/or rotate the object 180° about a vertical axis. Therefore, three transfer conditions, hand switch (HS), object rotation (OR), and both hand switch and object rotation (HS+OR), were tested and compared with hand matched control groups who did not experience context changes. We found that subjects in all transfer conditions adapted digit positions across multiple transfer trials similar to the learning of control groups, regardless of different changes of contexts. Moreover, subjects in both HS and HS+OR group also adapted digit forces similar to the control group, suggesting independent learning of the left hand. In contrast, the OR group showed significant negative transfer of the compensatory torque due to an inability to adapt digit forces. Our results indicate that internal representations of dexterous manipulation tasks may be primarily built through the hand used for learning and cannot be transferred across hands. PMID:25233091

Quantifying solute transport processes: are chemically "conservative" tracers electrically conservative?

USGS Publications Warehouse

Singha, Kamini; Li, Li; Day-Lewis, Frederick D.; Regberg, Aaron B.

2012-01-01

The concept of a nonreactive or conservative tracer, commonly invoked in investigations of solute transport, requires additional study in the context of electrical geophysical monitoring. Tracers that are commonly considered conservative may undergo reactive processes, such as ion exchange, thus changing the aqueous composition of the system. As a result, the measured electrical conductivity may reflect not only solute transport but also reactive processes. We have evaluated the impacts of ion exchange reactions, rate-limited mass transfer, and surface conduction on quantifying tracer mass, mean arrival time, and temporal variance in laboratory-scale column experiments. Numerical examples showed that (1) ion exchange can lead to resistivity-estimated tracer mass, velocity, and dispersivity that may be inaccurate; (2) mass transfer leads to an overestimate in the mobile tracer mass and an underestimate in velocity when using electrical methods; and (3) surface conductance does not notably affect estimated moments when high-concentration tracers are used, although this phenomenon may be important at low concentrations or in sediments with high and/or spatially variable cation-exchange capacity. In all cases, colocated groundwater concentration measurements are of high importance for interpreting geophysical data with respect to the controlling transport processes of interest.

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.

Modeling, Fabrication and Characterization of Scalable Electroless Gold Plated Nanostructures for Enhanced Surface Plasmon Resonance

NASA Astrophysics Data System (ADS)

Jang, Gyoung Gug

The scientific and industrial demand for controllable thin gold (Au) film and Au nanostructures is increasing in many fields including opto-electronics, photovoltaics, MEMS devices, diagnostics, bio-molecular sensors, spectro-/microscopic surfaces and probes. In this study, a novel continuous flow electroless (CF-EL) Au plating method is developed to fabricate uniform Au thin films in ambient condition. The enhanced local mass transfer rate and continuous deposition resulting from CF-EL plating improved physical uniformity of deposited Au films and thermally transformed nanoparticles (NPs). Au films and NPs exhibited improved optical photoluminescence (PL) and surface plasmon resonance (SPR), respectively, relative to batch immersion EL (BI-EL) plating. Suggested mass transfer models of Au mole deposition are consistent with optical feature of CF-EL and BI-EL films. The prototype CF-EL plating system is upgraded an automated scalable CF-EL plating system with real-time transmission UV-vis (T-UV) spectroscopy which provides the advantage of CF-EL plating, such as more uniform surface morphology, and overcomes the disadvantages of conventional EL plating, such as no continuous process and low deposition rate, using continuous process and controllable deposition rate. Throughout this work, dynamic morphological and chemical transitions during redox-driven self-assembly of Ag and Au film on silica surfaces under kinetic and equilibrium conditions are distinguished by correlating real-time T-UV spectroscopy with X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM) measurements. The characterization suggests that four previously unrecognized time-dependent physicochemical regimes occur during consecutive EL deposition of silver (Ag) and Au onto tin-sensitized silica surfaces: self-limiting Ag activation; transitory Ag NP formation; transitional Au-Ag alloy formation during galvanic replacement of Ag by Au; and uniform morphology formation under controlled hydraulic conditions. A method to achieve the time-resolved optical profile of EL Au plating was devised and provided a new transitional EL Au film growth model which validated mass transfer model prediction of the deposited thickness of ≤100 nm thin films. As a part of the project, validation of mass transfer model, a spectrophotometric method for quantitative analysis of metal ion is developed that improves the limit of detection comparable to conventional instrumental analysis. The present work suggests that modeling, fabrication and characterization of this novel CF-EL plating method is performed to achieve an ultimate purpose: developing a reliable, inexpensive wet chemical process for controlled metal thin film and nanostructure fabrication.

Online monitoring of coffee roasting by proton transfer reaction time-of-flight mass spectrometry (PTR-ToF-MS): towards a real-time process control for a consistent roast profile.

PubMed

Wieland, Flurin; Gloess, Alexia N; Keller, Marco; Wetzel, Andreas; Schenker, Stefan; Yeretzian, Chahan

2012-03-01

A real-time automated process control tool for coffee roasting is presented to consistently and accurately achieve a targeted roast degree. It is based on the online monitoring of volatile organic compounds (VOC) in the off-gas of a drum roaster by proton transfer reaction time-of-flight mass spectrometry at a high time (1 Hz) and mass resolution (5,500 m/Δm at full width at half-maximum) and high sensitivity (better than parts per billion by volume). Forty-two roasting experiments were performed with the drum roaster being operated either on a low, medium or high hot-air inlet temperature (= energy input) and the coffee (Arabica from Antigua, Guatemala) being roasted to low, medium or dark roast degrees. A principal component analysis (PCA) discriminated, for each one of the three hot-air inlet temperatures, the roast degree with a resolution of better than ±1 Colorette. The 3D space of the three first principal components was defined based on 23 mass spectral profiles of VOCs and their roast degree at the end point of roasting. This provided a very detailed picture of the evolution of the roasting process and allowed establishment of a predictive model that projects the online-monitored VOC profile of the roaster off-gas in real time onto the PCA space defined by the calibration process and, ultimately, to control the coffee roasting process so as to achieve a target roast degree and a consistent roasting.

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.

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.

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.

Early and Long-term Undernutrition in Female Rats Exacerbates the Metabolic Risk Associated with Nutritional Rehabilitation*

PubMed Central

Lizárraga-Mollinedo, Esther; Fernández-Millán, Elisa; García-San Frutos, Miriam; de Toro-Martín, Juan; Fernández-Agulló, Teresa; Ros, Manuel; Álvarez, Carmen; Escrivá, Fernando

2015-01-01

Human studies have suggested that early undernutrition increases the risk of obesity, thereby explaining the increase in overweight among individuals from developing countries who have been undernourished as children. However, this conclusion is controversial, given that other studies do not concur. This study sought to determine whether rehabilitation after undernutrition increases the risk of obesity and metabolic disorders. We employed a published experimental food-restriction model. Wistar female rats subjected to severe food restriction since fetal stage and controls were transferred to a moderately high-fat diet (cafeteria) provided at 70 days of life to 6.5 months. Another group of undernourished rats were rehabilitated with chow. The energy intake of undernourished animals transferred to cafeteria formula exceeded that of the controls under this regime and was probably driven by hypothalamic disorders in insulin and leptin signal transduction. The cafeteria diet resulted in greater relative increases in both fat and lean body mass in the undernourished rats when compared with controls, enabling the former group to completely catch up in length and body mass index. White adipose tissues of undernourished rats transferred to the high-lipid regime developed a browning which, probably, contributed to avoid the obesigenic effect observed in controls. Nevertheless, the restricted group rehabilitated with cafeteria formula had greater accretion of visceral than subcutaneous fat, showed increased signs of macrophage infiltration and inflammation in visceral pad, dyslipidemia, and ectopic fat accumulation. The data indicate that early long-term undernutrition is associated with increased susceptibility to the harmful effects of nutritional rehabilitation, without causing obesity. PMID:26105051

Beyond the standard two-film theory: Computational fluid dynamics simulations for carbon dioxide capture in a wetted wall column

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

Wang, Chao; Xu, Zhijie; Lai, Canhai

The standard two-film theory (STFT) is a diffusion-based mechanism that can be used to describe gas mass transfer across liquid film. Fundamental assumptions of the STFT impose serious limitations on its ability to predict mass transfer coefficients. To better understand gas absorption across liquid film in practical situations, a multiphase computational fluid dynamics (CFD) model fully equipped with mass transport and chemistry capabilities has been developed for solvent-based carbon dioxide (CO2) capture to predict the CO2 mass transfer coefficient in a wetted wall column. The hydrodynamics is modeled using a volume of fluid method, and the diffusive and reactive massmore » transfer between the two phases is modeled by adopting a one-fluid formulation. We demonstrate that the proposed CFD model can naturally account for the influence of many important factors on the overall mass transfer that cannot be quantitatively explained by the STFT, such as the local variation in fluid velocities and properties, flow instabilities, and complex geometries. The CFD model also can predict the local mass transfer coefficient variation along the column height, which the STFT typically does not consider.« less

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.

Convection Heat and Mass Transfer in a Power Law Fluid with Non Constant Relaxation Time Past a Vertical Porous Plate in the Presence of Thermo and Thermal Diffusion

NASA Astrophysics Data System (ADS)

Olajuwon, B. I.; Oyelakin, I. S.

2012-12-01

The paper investigates convection heat and mass transfer in power law fluid flow with non relaxation time past a vertical porous plate in presence of a chemical reaction, heat generation, thermo diffu- sion and thermal diffusion. The non - linear partial differential equations governing the flow are transformed into ordinary differential equations using the usual similarity method. The resulting similarity equations are solved numerically using Runge-Kutta shooting method. The results are presented as velocity, temperature and concentration profiles for pseudo plastic fluids and for different values of parameters governing the prob- lem. The skin friction, heat transfer and mass transfer rates are presented numerically in tabular form. The results show that these parameters have significant effects on the flow, heat transfer and mass transfer.

In General, the Total Voltammetric Current from a Mixture of Redox-Active Substances will Not be the Sum of the Currents that Each Substance would Produce Independently at the Same Concentration as in the Mixture

NASA Technical Reports Server (NTRS)

Leventis, Nicholas; Oh, Woon Su; Gao, Xue-Rong; Rawashdeh, Abdel Monem M.

2003-01-01

At the potential range where both decamethylferrocene (dMeFc) and ferrocene (Fc) are oxidized with rates controlled by linear diffusion, electrogenerated Fc(+) radicals diffusing outwards from the electrode react quantitatively (K23 C=5.8 x 10(exp 8) with dMeFc diffusing towards the electrode and produce Fc and dMeFc. That reaction replaces dMeFc with Fc, whose diffusion coefficient is higher than that of dMeFc(+), and the total mass-transfer limited current from the mixture is increased by approximately 10%. Analogous observations are made when mass-transfer is controlled by convective-diffusion as in RDE voltammetry. Similar results have been obtained with another, and for all practical purposes randomly selected pair of redox-active substances, [Co(bipy)3](2+) and N - methylphenothiazine (MePTZ); reaction of MePTZ(+) with [Co(bipy)3](2+) replaces the latter with MePTZ, which diffuses faster and the current increases by approximately 20%. The experimental voltammograms have been simulated numerically and the role of (a) the rate constant of the homogeneous reaction; (b) the relative concentrations; and, (c) the diffusion coefficients of all species involved have been studied in detail. Importantly, it was also identified that within any given redox system the dependence of the mass-transfer limited current on the bulk concentrations of the redox-active species is expected to be non-linear. These findings are discussed in terms of their electroanalytical implications.

Online measurement of viscosity for biological systems in stirred tank bioreactors.

PubMed

Schelden, Maximilian; Lima, William; Doerr, Eric Will; Wunderlich, Martin; Rehmann, Lars; Büchs, Jochen; Regestein, Lars

2017-05-01

One of the most critical parameters in chemical and biochemical processes is the viscosity of the medium. Its impact on mixing, as well as on mass and energy transfer is substantial. An increase of viscosity with reaction time can be caused by the formation of biopolymers like xanthan or by filamentous growth of microorganisms. In either case the properties of fermentation broth are changing and frequently non-Newtonian behavior are observed, resulting in major challenges for the measurement and control of mixing and mass transfer. This study demonstrates a method for the online determination of the viscosity inside a stirred tank reactor. The presented method is based on online measurement of heat transfer capacity from the bulk medium to the jacket of the reactor. To prove the feasibility of the method, fermentations with the xanthan producing bacterium Xanthomonas campestris pv. campestris B100 as model system were performed. Excellent correlation between offline measured apparent viscosity and online determined heat transfer capacity were found. The developed tool should be applicable to any other process with formation of biopolymers and filamentous growth. Biotechnol. Bioeng. 2017;114: 990-997. © 2016 Wiley Periodicals, Inc. © 2016 Wiley Periodicals, Inc.

Insights in the Diffusion Controlled Interfacial Flow Synthesis of Au Nanostructures in a Microfluidic System.

PubMed

Kulkarni, Amol A; Sebastian Cabeza, Victor

2017-12-19

Continuous segmented flow interfacial synthesis of Au nanostructures is demonstrated in a microchannel reactor. This study brings new insights into the growth of nanostructures at continuous interfaces. The size as well as the shape of the nanostructures showed significant dependence on the reactant concentrations, reaction time, temperature, and surface tension, which actually controlled the interfacial mass transfer. The microchannel reactor assisted in achieving a high interfacial area, as well as uniformity in mass transfer effects. Hexagonal nanostructures were seen to be formed in synthesis times as short as 10 min. The wettability of the channel showed significant effect on the particle size as well as the actual shape. The hydrophobic channel yielded hexagonal structures of relatively smaller size than the hydrophilic microchannel, which yielded sharp hexagonal bipyramidal particles (diagonal distance of 30 nm). The evolution of particle size and shape for the case of hydrophilic microchannel is also shown as a function of the residence time. The interfacial synthesis approach based on a stable segmented flow promoted an excellent control on the reaction extent, reduction in axial dispersion as well as the particle size distribution.

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.

Nonlinear feedback guidance law for aero-assisted orbit transfer maneuvers

NASA Technical Reports Server (NTRS)

Menon, P. K. A.

1992-01-01

Aero-assisted orbit transfer vehicles have the potential for significantly reducing the fuel requirements in certain classes of orbit transfer operations. Development of a nonlinear feedback guidance law for performing aero-assisted maneuvers that accomplish simultaneous change of all the orbital elements with least vehicle acceleration magnitude is discussed. The analysis is based on a sixth order nonlinear point-mass vehicle model with lift, bank angle, thrust and drag modulation as the control variables. The guidance law uses detailed vehicle aerodynamic and the atmosphere models in the feedback loop. Higher-order gravitational harmonics, planetary atmosphere rotation and ambient winds are included in the formulation. Due to modest computational requirements, the guidance law is implementable on-board an orbit transfer vehicle. The guidance performance is illustrated for three sets of boundary conditions.

Unsteady heat transfer performance of heat pipe with axially swallow-tailed microgrooves

NASA Astrophysics Data System (ADS)

Zhang, R. P.

2017-04-01

A mathematical model is developed for predicting the transient heat transfer and fluid flow of heat pipe with axially swallow-tailed microgrooves. The effects of liquid convective heat transfer in the microgrooves, liquid-vapor interfacial phase-change heat transfer and liquid-vapor interfacial shear stress are accounted for in the present model. The coupled non-linear control equations are solved numerically. Mass flow rate at the interface is obtained from the application of kinetic theory. Time variation of wall temperature is studied from the initial startup to steady state. The numerical results are verified by experiments. Time constants for startup and shutdown operation are defined to determine how fast a heat pipe responds to an applied input heat flux, which slightly decreases with increasing heat load.

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.

Mass transfer constraints on the chemical evolution of an active hydrothermal system, Valles caldera, New Mexico

USGS Publications Warehouse

White, A.F.; Chuma, N.J.; Goff, F.

1992-01-01

Partial equilibrium conditions occur between fluids and secondary minerals in the Valles hydrothermal system, contained principally in the Tertiary rhyolitic Bandelier Tuff. The mass transfer processes are governed by reactive phase compositions, surface areas, water-rock ratios, reaction rates, and fluid residence times. Experimental dissolution of the vitric phase of the tuff was congruent with respect to Cl in the solid and produced reaction rates which obeyed a general Arrhenius release rate between 250 and 300??C. The 18O differences between reacted and unreacted rock and fluids, and mass balances calculations involving Cl in the glass phase, produced comparable water-rock ratios of unity, confirming the importance of irreversible reaction of the vitric tuff. A fluid residence time of approximately 2 ?? 103 years, determined from fluid reservoir volume and discharge rates, is less than 0.2% of the total age of the hydrothermal system and denotes a geochemically and isotopically open system. Mass transfer calculations generally replicated observed reservoir pH, Pco2, and PO2 conditions, cation concentrations, and the secondary mineral assemblage between 250 and 300??C. The only extraneous component required to maintain observed calcite saturation and high Pco2 pressures was carbon presumably derived from underlying Paleozoic limestones. Phase rule constraints indicate that Cl was the only incompatible aqueous component not controlled by mineral equilibrium. Concentrations of Cl in the reservoir directly reflect mass transport rates as evidenced by correlations between anomalously high Cl concentrations in the fluids and tuff in the Valles caldera relative to other hydrothermal systems in rhyolitic rocks. ?? 1992.

Impact of current speed on mass flux to a model flexible seagrass blade

NASA Astrophysics Data System (ADS)

Lei, Jiarui; Nepf, Heidi

2016-07-01

Seagrass and other freshwater macrophytes can acquire nutrients from surrounding water through their blades. This flux may depend on the current speed (U), which can influence both the posture of flexible blades (reconfiguration) and the thickness of the flux-limiting diffusive layer. The impact of current speed (U) on mass flux to flexible blades of model seagrass was studied through a combination of laboratory flume experiments, numerical modeling and theory. Model seagrass blades were constructed from low-density polyethylene (LDPE), and 1, 2-dichlorobenzene was used as a tracer chemical. The tracer mass accumulation in the blades was measured at different unidirectional current speeds. A numerical model was used to estimate the transfer velocity (K) by fitting the measured mass uptake to a one-dimensional diffusion model. The measured transfer velocity was compared to predictions based on laminar and turbulent boundary layers developing over a flat plate parallel to flow, for which K∝U0.5 and ∝U, respectively. The degree of blade reconfiguration depended on the dimensionless Cauchy number, Ca, which is a function of both the blade stiffness and flow velocity. For large Ca, the majority of the blade was parallel to the flow, and the measured transfer velocity agreed with laminar boundary layer theory, K∝U0.5. For small Ca, the model blades remained upright, and the flux to the blade was diminished relative to the flat-plate model. A meadow-scale analysis suggests that the mass exchange at the blade scale may control the uptake at the meadow scale.

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.

In silico ordinary differential equation/partial differential equation hemodialysis model estimates methadone removal during dialysis

PubMed Central

Linares, Oscar A; Schiesser, William E; Fudin, Jeffrey; Pham, Thien C; Bettinger, Jeffrey J; Mathew, Roy O; Daly, Annemarie L

2015-01-01

Background There is a need to have a model to study methadone’s losses during hemodialysis to provide informed methadone dose recommendations for the practitioner. Aim To build a one-dimensional (1-D), hollow-fiber geometry, ordinary differential equation (ODE) and partial differential equation (PDE) countercurrent hemodialyzer model (ODE/PDE model). Methodology We conducted a cross-sectional study in silico that evaluated eleven hemodialysis patients. Patients received a ceiling dose of methadone hydrochloride 30 mg/day. Outcome measures included: the total amount of methadone removed during dialysis; methadone’s overall intradialytic mass transfer rate coefficient, km; and, methadone’s removal rate, jME. Each metric was measured at dialysate flow rates of 250 mL/min and 800 mL/min. Results The ODE/PDE model revealed a significant increase in the change of methadone’s mass transfer with increased dialysate flow rate, %Δkm=18.56, P=0.02, N=11. The total amount of methadone mass transferred across the dialyzer membrane with high dialysate flow rate significantly increased (0.042±0.016 versus 0.052±0.019 mg/kg, P=0.02, N=11). This was accompanied by a small significant increase in methadone’s mass transfer rate (0.113±0.002 versus 0.014±0.002 mg/kg/h, P=0.02, N=11). The ODE/PDE model accurately predicted methadone’s removal during dialysis. The absolute value of the prediction errors for methadone’s extraction and throughput were less than 2%. Conclusion ODE/PDE modeling of methadone’s hemodialysis is a new approach to study methadone’s removal, in particular, and opioid removal, in general, in patients with end-stage renal disease on hemodialysis. ODE/PDE modeling accurately quantified the fundamental phenomena of methadone’s mass transfer during hemodialysis. This methodology may lead to development of optimally designed intradialytic opioid treatment protocols, and allow dynamic monitoring of outflow plasma opioid concentrations for model predictive control during dialysis in humans. PMID:26229501

Formation of black hole x-ray binaries in globular clusters

NASA Astrophysics Data System (ADS)

Kremer, Kyle; Chatterjee, Sourav; Rodriguez, Carl; Rasio, Frederic

2018-01-01

We explore the formation of mass-transferring binary systems containing black holes within globular clusters. We show that it is possible to form mass-transferring binaries with main sequence, giant, and white dwarf companions with a variety of orbital parameters in globular clusters spanning a large range in present-day properties. We show that the presence of mass-transferring black hole systems has little correlation with the total number of black holes within the cluster at any time. In addition to mass-transferring binaries retained within their host clusters at late times, we also examine the black hole and neutron star binaries that are ejected from their host clusters. These ejected systems may contribute to the low-mass x-ray binary population in the galactic field.

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.

Treatability study of the effluent containing reactive blue 21 dye by ozonation and the mass transfer study of ozone

NASA Astrophysics Data System (ADS)

Velpula, Priyadarshini; Ghuge, Santosh; Saroha, Anil K.

2018-04-01

Ozonation is a chemical treatment process in which ozone reacts with the pollutants present in the effluent by infusion of ozone into the effluent. This study includes the effect of various parameters such as inlet ozone dose, pH of solution and initial concentration of dye on decolorization of dye in terms CRE. The maximum CRE of 98.62% with the reaction rate constant of 0.26 min-1 is achieved in 18 minutes of reaction time at inlet ozone dose of 11.5 g/m3, solution pH of 11 and 30 mg/L of initial concentration of dye. The presence of radical scavenger (Tertiary Butyl Alcohol) suppressed the CRE from 98.62% to 95.4% at high pH values indicates that the indirect mechanism dominates due to the presence of hydroxyl radicals which are formed by the decomposition of ozone. The diffusive and convective mass transfer coefficients of ozone are calculated as 1.78 × 10-5 cm2/sec and 0.075 min-1. It is observed that the fraction of resistance offered by liquid is very much high compared to gas phase indicates that the ozonation is a liquid phase mass transfer controlled operation.

Quantifying energy and mass transfer in crop canopies: sensors for measurement of temperature and air velocity

NASA Technical Reports Server (NTRS)

Bugbee, B.; Monje, O.; Tanner, B.

1996-01-01

Here we report on the in situ performance of inexpensive, miniature sensors that have increased our ability to measure mass and energy fluxes from plant canopies in controlled environments: 1. Surface temperature. Canopy temperature measurements indicate changes in stomatal aperture and thus latent and sensible heat fluxes. Infrared transducers from two manufacturers (Exergen Corporation, Newton, MA; and Everest Interscience, Tucson, AZ, USA) have recently become available. Transducer accuracy matched that of a more expensive hand-held infrared thermometer. 2. Air velocity varies above and within plant canopies and is an important component in mass and energy transfer models. We tested commercially-available needle, heat-transfer anemometers (1 x 50 mm cylinder) that consist of a fine-wire thermocouple and a heater inside a hypodermic needle. The needle is heated and wind speed determined from the temperature rise above ambient. These sensors are particularly useful in measuring the low wind speeds found within plant canopies. 3. Accurate measurements of air temperature adjacent to plant leaves facilitates transport phenomena modeling. We quantified the effect of radiation and air velocity on temperature rise in thermocouples from 10 to 500 micrometers. At high radiation loads and low wind speeds, temperature errors were as large as 7 degrees C above air temperature.

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.

Pulse combustor with controllable oscillations

DOEpatents

Richards, George A.; Welter, Michael J.; Morris, Gary J.

1992-01-01

A pulse combustor having thermally induced pulse combustion in a continuously flowing system is described. The pulse combustor is fitted with at lease one elongated ceramic body which significantly increases the heat transfer area in the combustion chamber of the combustor. The ceramic body or bodies possess sufficient mass and heat capacity to ignite the fuel-air charge once the ceramic body or bodies are heated by conventional spark plug initiated combustion so as to provide repetitive ignition and combustion of sequentially introduced fuel-air charges without the assistance of the spark plug and the rapid quenching of the flame after each ignition in a controlled manner so as to provide a selective control over the oscillation frequency and amplitude. Additional control over the heat transfer in the combustion chamber is provided by employing heat exchange mechanisms for selectively heating or cooling the elongated ceramic body or bodies and/or the walls of the combustion chamber.

Integration of CuAAC Polymerization and Controlled Radical Polymerization into Electron Transfer Mediated "Click-Radical" Concurrent Polymerization.

PubMed

Xue, Wentao; Wang, Jie; Wen, Ming; Chen, Gaojian; Zhang, Weidong

2017-03-01

The successful chain-growth copper(I)-catalyzed azide-alkyne cycloaddition (CuAAC) polymerization employing Cu(0)/pentamethyldiethylenetriamine (PMDETA) and alkyl halide as catalyst is first investigated by a combination of nuclear magnetic resonance, gel-permeation chromatography, and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. In addition, the electron transfer mediated "click-radical" concurrent polymerization utilizing Cu(0)/PMDETA as catalyst is successfully employed to generate well-defined copolymers, where controlled CuAAC polymerization of clickable ester monomer is progressed in the main chain acting as the polymer backbone, the controlled radical polymerization (CRP) of acrylic monomer is carried out in the side chain. Furthermore, it is found that there is strong collaborative effect and compatibility between CRP and CuAAC polymerization to improve the controllability. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Robustness analysis of an air heating plant and control law by using polynomial chaos

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

Colón, Diego; Ferreira, Murillo A. S.; Bueno, Átila M.

2014-12-10

This paper presents a robustness analysis of an air heating plant with a multivariable closed-loop control law by using the polynomial chaos methodology (MPC). The plant consists of a PVC tube with a fan in the air input (that forces the air through the tube) and a mass flux sensor in the output. A heating resistance warms the air as it flows inside the tube, and a thermo-couple sensor measures the air temperature. The plant has thus two inputs (the fan's rotation intensity and heat generated by the resistance, both measured in percent of the maximum value) and two outputsmore » (air temperature and air mass flux, also in percent of the maximal value). The mathematical model is obtained by System Identification techniques. The mass flux sensor, which is nonlinear, is linearized and the delays in the transfer functions are properly approximated by non-minimum phase transfer functions. The resulting model is transformed to a state-space model, which is used for control design purposes. The multivariable robust control design techniques used is the LQG/LTR, and the controllers are validated in simulation software and in the real plant. Finally, the MPC is applied by considering some of the system's parameters as random variables (one at a time, and the system's stochastic differential equations are solved by expanding the solution (a stochastic process) in an orthogonal basis of polynomial functions of the basic random variables. This method transforms the stochastic equations in a set of deterministic differential equations, which can be solved by traditional numerical methods (That is the MPC). Statistical data for the system (like expected values and variances) are then calculated. The effects of randomness in the parameters are evaluated in the open-loop and closed-loop pole's positions.« less

Thermal Enhancement of Silicon Carbide (SiC) Power Electronics and Laser Bars: Statistical Design Optimization of a Liquid-Cooled Power Electronic Heat Sink

DTIC Science & Technology

2015-08-01

Forced Convective Heat Transfer Across a Pin Fin Micro Heat Sink”, International Journal of Heat and Mass Transfer 48 (2005) 3615-3627. 3. Cao...from Pin Fins Situated in an Oncoming Longitudinal Flow Which Turns to Crossflow”, International Journal of Heat and Mass Transfer, Vol. 25 No. 5...Flow Forced Convection”, International Journal of Heat and Mass Transfer, Vol. 39, No. 2, pp. 311-317, 1996. 11. Khan, W., Culham, J., and Yovanovich

Smooth information flow in temperature climate network reflects mass transport

NASA Astrophysics Data System (ADS)

Hlinka, Jaroslav; Jajcay, Nikola; Hartman, David; Paluš, Milan

2017-03-01

A directed climate network is constructed by Granger causality analysis of air temperature time series from a regular grid covering the whole Earth. Using winner-takes-all network thresholding approach, a structure of a smooth information flow is revealed, hidden to previous studies. The relevance of this observation is confirmed by comparison with the air mass transfer defined by the wind field. Their close relation illustrates that although the information transferred due to the causal influence is not a physical quantity, the information transfer is tied to the transfer of mass and energy.

A Numerical Analysis of the Transient Response of an Ablation System Including Effects of Thermal Nonequilibrium, Mass Transfer and Chemical Kinetics. Ph.D Thesis - Virginia Polytechnic Inst. and State Univ.

NASA Technical Reports Server (NTRS)

Clark, R. K.

1972-01-01

The differential equations governing the transient response of a one-dimensional ablative thermal protection system undergoing stagnation ablation are derived. These equations are for thermal nonequilibrium effects between the pyrolysis gases and the char layer and kinetically controlled chemical reactions and mass transfer between the pyrolysis gases and the char layer. The boundary conditions are written for the particular case of stagnation heating with surface removal by oxidation or sublimation and pyrolysis of the uncharred layer occurring in a plane. The governing equations and boundary conditions are solved numerically using the modified implicit method (Crank-Nicolson method). Numerical results are compared with exact solutions for a number of simplified cases. The comparison is favorable in each instance.

Characterization of metal adsorption kinetic properties in batch and fixed-bed reactors.

PubMed

Chen, J Paul; Wang, Lin

2004-01-01

Copper adsorption kinetic properties in batch and fixed-bed reactors were studied in this paper. The isothermal adsorption experiments showed that the copper adsorption capacity of a granular activated carbon (Filtrasorb 200) increased when ionic strength was higher. The presence of EDTA diminished the adsorption. An intraparticle diffusion model and a fixed-bed model were successfully used to describe the batch kinetic and fixed-bed operation behaviors. The kinetics became faster when the solution pH was not controlled, implying that the surface precipitation caused some metal uptake. The external mass transfer coefficient, the diffusivity and the dispersion coefficient were obtained from the modeling. It was found that both external mass transfer and dispersion coefficients increased when the flow rate was higher. Finally effects of kinetic parameters on simulation of fixed-bed operation were conducted.

Modeling the influence of coupled mass transfer processes on mass flux downgradient of heterogeneous DNAPL source zones

NASA Astrophysics Data System (ADS)

Yang, Lurong; Wang, Xinyu; Mendoza-Sanchez, Itza; Abriola, Linda M.

2018-04-01

Sequestered mass in low permeability zones has been increasingly recognized as an important source of organic chemical contamination that acts to sustain downgradient plume concentrations above regulated levels. However, few modeling studies have investigated the influence of this sequestered mass and associated (coupled) mass transfer processes on plume persistence in complex dense nonaqueous phase liquid (DNAPL) source zones. This paper employs a multiphase flow and transport simulator (a modified version of the modular transport simulator MT3DMS) to explore the two- and three-dimensional evolution of source zone mass distribution and near-source plume persistence for two ensembles of highly heterogeneous DNAPL source zone realizations. Simulations reveal the strong influence of subsurface heterogeneity on the complexity of DNAPL and sequestered (immobile/sorbed) mass distribution. Small zones of entrapped DNAPL are shown to serve as a persistent source of low concentration plumes, difficult to distinguish from other (sorbed and immobile dissolved) sequestered mass sources. Results suggest that the presence of DNAPL tends to control plume longevity in the near-source area; for the examined scenarios, a substantial fraction (43.3-99.2%) of plume life was sustained by DNAPL dissolution processes. The presence of sorptive media and the extent of sorption non-ideality are shown to greatly affect predictions of near-source plume persistence following DNAPL depletion, with plume persistence varying one to two orders of magnitude with the selected sorption model. Results demonstrate the importance of sorption-controlled back diffusion from low permeability zones and reveal the importance of selecting the appropriate sorption model for accurate prediction of plume longevity. Large discrepancies for both DNAPL depletion time and plume longevity were observed between 2-D and 3-D model simulations. Differences between 2- and 3-D predictions increased in the presence of sorption, especially for the case of non-ideal sorption, demonstrating the limitations of employing 2-D predictions for field-scale modeling.

CFD Application to Flow-Accelerated Corrosion in Feeder Bends

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

Pietralik, John M.; Smith, Bruce A.W.

2006-07-01

Feeder piping in CANDU{sup R} plants experiences a thinning degradation mechanism called Flow-Accelerated Corrosion (FAC). The piping is made of carbon steel and has high water flow speeds. Although the water chemistry is highly alkaline with room-temperature pH in a range of 10.0-10.5, the piping has FAC rates exceeding 0.1 mm/year in some locations, e.g., in bends. One of the most important parameters affecting the FAC rate is the mass transfer coefficient for convective mass transport of ferrous ions. The ions are created at the pipe wall as a result of corrosion, diffuse through the oxide layer, and are transportedmore » from the oxide-layer/water interface to the bulk water by mass transport. Consequently, the local flow characteristics contribute to the highly turbulent convective mass transfer. Plant data and laboratory experiments indicate that the mass transfer step dominates FAC under feeder conditions. In this study, the flow and mass transfer in a feeder bend under operating conditions were simulated using the Fluent{sup TM} computer code. Because the flow speed is very high, with the Reynolds numbers in a range of several millions, and because the geometry is complex, experiments in a 1:1 scale were conducted with the main objective to validate flow simulations. The experiments measured pressure at several key locations and visualized the flow. The flow and mass transfer models were validated using available friction-factor and mass transfer correlations and literature experiments on mass transfer in a bend. The validation showed that the turbulence model that best predicts the experiments is the realizable k-{epsilon} model. Other two-equation turbulence models, as well as one-equation models and Reynolds stress models were tried. The near-wall treatment used the non-equilibrium wall functions. The wall functions were modified for surface roughness when necessary. A comparison of the local mass transfer coefficient with measured FAC rate in plant specimens shows very good agreement. Visualization experiments indicate secondary flows in the bends. No boundary layer separation was observed in experiments or in simulations. (authors)« less

Control and Automation of Fluid Flow, Mass Transfer and Chemical Reactions in Microscale Segmented Flow

NASA Astrophysics Data System (ADS)

Abolhasani, Milad

Flowing trains of uniformly sized bubbles/droplets (i.e., segmented flows) and the associated mass transfer enhancement over their single-phase counterparts have been studied extensively during the past fifty years. Although the scaling behaviour of segmented flow formation is increasingly well understood, the predictive adjustment of the desired flow characteristics that influence the mixing and residence times, remains a challenge. Currently, a time consuming, slow and often inconsistent manual manipulation of experimental conditions is required to address this task. In my thesis, I have overcome the above-mentioned challenges and developed an experimental strategy that for the first time provided predictive control over segmented flows in a hands-off manner. A computer-controlled platform that consisted of a real-time image processing module within an integral controller, a silicon-based microreactor and automated fluid delivery technique was designed, implemented and validated. In a first part of my thesis I utilized this approach for the automated screening of physical mass transfer and solubility characteristics of carbon dioxide (CO2) in a physical solvent at a well-defined temperature and pressure and a throughput of 12 conditions per hour. Second, by applying the segmented flow approach to a recently discovered CO2 chemical absorbent, frustrated Lewis pairs (FLPs), I determined the thermodynamic characteristics of the CO2-FLP reaction. Finally, the segmented flow approach was employed for characterization and investigation of CO2-governed liquid-liquid phase separation process. The second part of my thesis utilized the segmented flow platform for the preparation and shape control of high quality colloidal nanomaterials (e.g., CdSe/CdS) via the automated control of residence times up to approximately 5 minutes. By introducing a novel oscillatory segmented flow concept, I was able to further extend the residence time limitation to 24 hours. A case study of a slow candidate reaction, the etching of gold nanorods during up to five hours, served to illustrate the utility of oscillatory segmented flows in assessing the shape evolution of colloidal nanomaterials on-chip via continuous optical interrogation at only one sensing location. The developed cruise control strategy will enable plug'n play operation of segmented flows in applications that include flow chemistry, material synthesis and in-flow analysis and screening.

Detection of metal-transfer mode in GMAW

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

Johnson, J.A.; Carlson, N.M.; Smartt, H.B.

1989-01-01

One of the requirements of a sensing system for feedback control of gas metal arc welding (GMAW) is the capability to detect information about the metal-transfer mode. Because the operating boundary for the desired transfer mode, expressed as a function of mass input and heat input, may vary due to conditions beyond the control of the system, a means of determining the transfer mode during welding is necessary. A series of sensing experiments is performed during which the ultrasonic emissions, audio emissions, welding current fluctuations, and welding voltage fluctuations are recorded as a function of the transfer mode. In addition,more » high speed movies (5000 frame/s) of the droplet formation and detachment are taken synchronously with the sensing data. An LED mounted in the camera is used to work the film at the beginning and end of the data acquisition period. A second LED is pulsed at a 1 kHz rate and the pulses are recorded on film and with the sensor data. Thus events observed on the film can be correlated with the sensor data. Data acquired during globular transfer, spray transfer, and stiff spray or streaming transfer are observed to correlate with droplet detachment and arc shorting. The audio, current, and voltage data can be used to discriminate among these different transfer modes. However, the current and voltage data are also dependent on the characteristics of the welding power supply. 4 refs., 5 figs.« less

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.

Accreting Black Hole Binaries in Globular Clusters

NASA Astrophysics Data System (ADS)

Kremer, Kyle; Chatterjee, Sourav; Rodriguez, Carl L.; Rasio, Frederic A.

2018-01-01

We explore the formation of mass-transferring binary systems containing black holes (BHs) within globular clusters (GC). We show that it is possible to form mass-transferring BH binaries with main sequence, giant, and white dwarf companions with a variety of orbital parameters in GCs spanning a large range in present-day properties. All mass-transferring BH binaries found in our models at late times are dynamically created. The BHs in these systems experienced a median of ∼30 dynamical encounters within the cluster before and after acquiring the donor. Furthermore, we show that the presence of mass-transferring BH systems has little correlation with the total number of BHs within the cluster at any time. This is because the net rate of formation of BH–non-BH binaries in a cluster is largely independent of the total number of retained BHs. Our results suggest that the detection of a mass-transferring BH binary in a GC does not necessarily indicate that the host cluster contains a large BH population.

Influence of Wind Pressure on the Carbonation of Concrete

PubMed Central

Zou, Dujian; Liu, Tiejun; Du, Chengcheng; Teng, Jun

2015-01-01

Carbonation is one of the major deteriorations that accelerate steel corrosion in reinforced concrete structures. Many mathematical/numerical models of the carbonation process, primarily diffusion-reaction models, have been established to predict the carbonation depth. However, the mass transfer of carbon dioxide in porous concrete includes molecular diffusion and convection mass transfer. In particular, the convection mass transfer induced by pressure difference is called penetration mass transfer. This paper presents the influence of penetration mass transfer on the carbonation. A penetration-reaction carbonation model was constructed and validated by accelerated test results under high pressure. Then the characteristics of wind pressure on the carbonation were investigated through finite element analysis considering steady and fluctuating wind flows. The results indicate that the wind pressure on the surface of concrete buildings results in deeper carbonation depth than that just considering the diffusion of carbon dioxide. In addition, the influence of wind pressure on carbonation tends to increase significantly with carbonation depth. PMID:28793462

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.

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

Influence of Wind Pressure on the Carbonation of Concrete.

PubMed

Zou, Dujian; Liu, Tiejun; Du, Chengcheng; Teng, Jun

2015-07-24

Carbonation is one of the major deteriorations that accelerate steel corrosion in reinforced concrete structures. Many mathematical/numerical models of the carbonation process, primarily diffusion-reaction models, have been established to predict the carbonation depth. However, the mass transfer of carbon dioxide in porous concrete includes molecular diffusion and convection mass transfer. In particular, the convection mass transfer induced by pressure difference is called penetration mass transfer. This paper presents the influence of penetration mass transfer on the carbonation. A penetration-reaction carbonation model was constructed and validated by accelerated test results under high pressure. Then the characteristics of wind pressure on the carbonation were investigated through finite element analysis considering steady and fluctuating wind flows. The results indicate that the wind pressure on the surface of concrete buildings results in deeper carbonation depth than that just considering the diffusion of carbon dioxide. In addition, the influence of wind pressure on carbonation tends to increase significantly with carbonation depth.

Application of mass spectrometry based electronic nose and chemometrics for fingerprinting radiation treatment

NASA Astrophysics Data System (ADS)

Gupta, Sumit; Variyar, Prasad S.; Sharma, Arun

2015-01-01

Volatile compounds were isolated from apples and grapes employing solid phase micro extraction (SPME) and subsequently analyzed by GC/MS equipped with a transfer line without stationary phase. Single peak obtained was integrated to obtain total mass spectrum of the volatile fraction of samples. A data matrix having relative abundance of all mass-to-charge ratios was subjected to principal component analysis (PCA) and linear discriminant analysis (LDA) to identify radiation treatment. PCA results suggested that there is sufficient variability between control and irradiated samples to build classification models based on supervised techniques. LDA successfully aided in segregating control from irradiated samples at all doses (0.1, 0.25, 0.5, 1.0, 1.5, 2.0 kGy). SPME-MS with chemometrics was successfully demonstrated as simple screening method for radiation treatment.

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...

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.

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.

Prospective Controlled Study of Buttock Fat Transfer Using Ultrasound and Photographic Measurements

PubMed Central

2016-01-01

Background: Buttock fat transfer is now the preferred method for gluteal augmentation. However, its efficacy has not been well-documented using measurements. Methods: Twenty-five consecutive patients underwent buttock fat transfer performed by the author. Twenty-one patients returned for measurements ≥3 months after surgery (inclusion rate, 84%). A separate group of 25 patients undergoing cosmetic surgery without buttock fat transfer served as controls. All patients underwent superwet liposuction using total intravenous anesthesia and no prone positioning. A closed filtration system was used to collect the fat. Subcutaneous fat thickness was assessed using ultrasound imaging. Measurements were made on standardized photographs. The data were controlled for change in body mass index. Clinical data were also evaluated. Results: The mean fat volume injected per buttock was 287 mL (range, 70–550 mL). Ultrasound measurements detected a significant increase in the subcutaneous fat thickness (P ≤ 0.001), with mean increments of 0.66 cm for the right buttock and 0.86 cm for the left buttock and no significant change for control patients. The mean calculated fat retention, based on the measured surface area injected, was 66%. Photographic measurements of buttock projection revealed a significant increase in treated patients (P < 0.01) and no significant change in control patients. There were no clinical complications at either recipient or donor sites and no evidence of oily cysts on ultrasound examinations. Conclusions: Photographic and ultrasound measurements, and clinical findings, confirm that buttock fat transfer effectively and safely increases buttock projection. PMID:27579222

No transfer between conditions in balance training regimes relying on tasks with different postural demands: Specificity effects of two different serious games.

PubMed

Naumann, Tim; Kindermann, Stefan; Joch, Michael; Munzert, Jörn; Reiser, Mathias

2015-03-01

Despite the increasing use of video games involving whole body movements to enhance postural control in health prevention and rehabilitation, there is no consistent proof that training effects actually transfer to other balance tasks. The present study aimed to determine whether training effects on two different video-game-based training devices were task-specific or could be transferred to either postural control in quiet stance or to performance on the other device. 37 young healthy adults were split into three groups: two intervention groups that trained for 30min on either the Nintendo(®) Wii Fit Balance Board or the MFT Challenge Disc(®) three times per week for 4 weeks and a control group that received no training. All games require participants to control virtual avatars by shifting the center of mass in different directions. Both devices differ in their physical properties. The Balance Board provides a stable surface, whereas the Challenge Disc can be tilted in all directions. Dependent variables were the game scores on both devices and the center of pressure (COP) displacements measured via force plate. At posttest, both intervention groups showed significant increases in performance on the trained games compared to controls. However, there were no relevant transfer effects to performance on the untrained device and no changes in COP path length in quiet stance. These results suggest that training effects on both devices are highly specific and do not transfer to tasks with different postural demands. Copyright © 2015 Elsevier B.V. All rights reserved.

Earth tides, global heat flow, and tectonics

USGS Publications Warehouse

Shaw, H.R.

1970-01-01

The power of a heat engine ignited by tidal energy can account for geologically reasonable rates of average magma production and sea floor spreading. These rates control similarity of heat flux over continents and oceans because of an inverse relationship between respective depth intervals for mass transfer and consequent distributions of radiogenic heat production.

Detection heart failures (HF) biomarkers by proton transfer reaction - mass spectrometry and ion mobility spectrometry

NASA Astrophysics Data System (ADS)

Shaltaeva, Y. R.; Vasilev, V. K.; Yakovlev, D. Y.; Kopylov, F. Iu; Syrkin, A. L.; Chomakhidze, P. Sh; Bykova, A. A.; Malinovskaya, L. K.; Skorokhod, A. I.

2016-10-01

Exhaled breath contains 1% of volatile organic compounds. The concentration of individual biomarkers in hundreds of volatile organic compounds lies within the range ppm- ppb. In compare with control group the concentrations of acetone, acetic acid, ethanol, propylene biomarkers is significantly higher in HF-PEF group.

Sequential cryogen spraying for heat flux control at the skin surface

NASA Astrophysics Data System (ADS)

Majaron, Boris; Aguilar, Guillermo; Basinger, Brooke; Randeberg, Lise L.; Svaasand, Lars O.; Lavernia, Enrique J.; Nelson, J. Stuart

2001-05-01

Heat transfer rate at the skin-air interface is of critical importance for the benefits of cryogen spray cooling in combination with laser therapy of shallow subsurface skin lesions, such as port-wine stain birthmarks. With some cryogen spray devices, a layer of liquid cryogen builds up on the skin surface during the spurt, which may impair heat transfer across the skin surface due to relatively low thermal conductivity and potentially higher temperature of the liquid cryogen layer as compared to the spray droplets. While the mass flux of cryogen delivery can be adjusted by varying the atomizing nozzle geometry, this may strongly affect other spray properties, such as lateral spread (cone), droplet size, velocity, and temperature distribution. We present here first experiments with sequential cryogen spraying, which may enable accurate mass flux control through variation of spray duty cycle, while minimally affecting other spray characteristics. The observed increase of cooling rate and efficiency at moderate duty cycle levels supports the above described hypothesis of isolating liquid layer, and demonstrates a novel approach to optimization of cryogen spray devices for individual laser dermatological applications.

An experimental and modeling study of grain-scale uranium desorption from field-contaminated sediments and the potential influence of microporosity on mass-transfer

NASA Astrophysics Data System (ADS)

Stoliker, D.; Liu, C.; Kent, D. B.; Zachara, J. M.

2012-12-01

The aquifer below the 300-Area of the Hanford site (Richland, WA, USA) is plagued by a persistent plume of dissolved uranium (U(VI)) in excess of the Environmental Protection Agency drinking water maximum contamination level even after the removal of highly contaminated sediments. The aquifer sediments in the seasonally saturated lower vadose zone act as both a source and sink for uranium during stage changes in the nearby Columbia River. Diffusion limitation of uranium mass-transfer within these sediments has been cited as a potential cause of the plume's persistence. Equilibrium U(VI) sorption is a strong function of variable chemical conditions, especially carbonate, hydrogen, and uranyl ion activities. Field-contaminated sediments from the site require up to 1,000 hours to reach equilibrium in static batch reactors. Increases in U(VI) concentrations over longer time-scales result from changes in chemical conditions, which drive reactions with sediments that favor U(VI) desorption. Grain-scale U(VI) sorption/desorption rates are slow, likely owing to diffusion of U(VI) and other solutes through intra-granular pore domains. In order to improve understanding of the impact of intra-granular diffusion and chemical reactions controlling grain-scale U(VI) release, experiments were conducted on individual particle size fractions of a <8 mm composite of field-contaminated, lower vadose zone sediments. For each size fraction, equilibrium U(VI) sorption/desorption in static batch reactors was well-described by surface complexation models over a range of chemical conditions applicable to the field site. Desorption rates from individual size fractions in flow-through batch reactors, examined under a single set of constant chemical conditions with multiple stop-flow events, were similar for all size fractions <2 mm. Kinetic U(VI) desorption in flow-through batch reactors was modeled using a multi-rate surface complexation approach, where sorption/desorption rates were assumed to be proportional to the displacement from equilibrium and multiple diffusion domains were described with a two-parameter lognormal distribution of mass-transfer rate coefficients. Parameters describing mass transfer were the same for all size fractions <2 mm but differed for the largest (2-8 mm) size fraction. The evolution of pH, along with dissolved cation and carbonate concentrations, was modeled using equilibrium cation exchange, rate-limited calcite dissolution, aerobic respiration, and silica dissolution. Desorption and chemical reaction models calibrated with individual size fractions predicted U(VI) and chemical composition as a function of time for the bulk sediment sample. Volumes of pores less than 2.4 nm, quantified using nitrogen adsorption-desorption isotherms, were the same for all size fractions < 2 mm, nearly double that of the 2-8 mm size fraction. Similarity in the observed pore volumes and multi-rate mass-transfer parameters across all size fractions <2 mm suggest the importance of pores in this size class in controlling slow grain-scale U(VI) desorption rates. Models like these provide a means for testing the influence of grain-scale mass-transfer on the persistence of U(VI) plume at the site.

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.

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.

Experimental investigation of 20 K two-stage layered active magnetic regenerative refrigerator

NASA Astrophysics Data System (ADS)

Park, Inmyong; Jeong, Sangkwon

2015-12-01

The performance of a two-stage layered AMRR is experimentally investigated. The test apparatus includes two-stage layered AMRs, low temperature superconducting (LTS) magnet which generates maximum magnetic field of 4 T, and the helium gas flow system. The helium compressor with the tandem rotary valve is employed to generate the oscillating flow of the helium gas minimizing the pressure swing effect. The mass flow rate of working fluid is controlled separately at the first and second stages of the AMR by solenoid valves. The mass flow rate of the AMRs is measured by the mass flow meter and the cryogenic hot-film sensor which is calibrated at cryogenic temperature range from 20 K to 77 K. In order to reduce the heat leak by shuttle heat transfer of the working fluid, void volumes have been implemented and connected to the cold ends of the AMR1 and AMR2. The temperature span of the AMR is recorded as 52 K and the performance of the AMR with the variation of the mass flow rate is analysed. The results show that the mass flow rate and the heat leak due to the shuttle heat transfer by oscillating working fluid are crucial factors in the AMR performance.

Design of passive interconnections in tall buildings subject to earthquake disturbances to suppress inter-storey drifts

NASA Astrophysics Data System (ADS)

Yamamoto, K.; Smith, MC

2016-09-01

This paper studies the problem of passive control of a multi-storey building subjected to an earthquake disturbance. The building is represented as a homogeneous mass chain model, i.e., a chain of identical masses in which there is an identical passive connection between neighbouring masses and a similar connection to a movable point. The paper considers passive interconnections of the most general type, which may require the use of inerters in addition to springs and dampers. It is shown that the scalar transfer functions from the disturbance to a given inter-storey drift can be represented as complex iterative maps. Using these expressions, two graphical approaches are proposed: one gives a method to achieve a prescribed value for the uniform boundedness of these transfer functions independent of the length of the mass chain, and the other is for a fixed length of the mass chain. A case study is presented to demonstrate the effectiveness of the proposed techniques using a 10-storey building model. The disturbance suppression performance of the designed interconnection is also verified for a 10-storey building model which has a different stiffness distribution but with the same undamped first natural frequency as the homogeneous model.

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.

Coherent transfer of orbital angular momentum to excitons by optical four-wave mixing.

PubMed

Ueno, Y; Toda, Y; Adachi, S; Morita, R; Tawara, T

2009-10-26

We demonstrate the coherent transfer of optical orbital angular momentum (OAM) to the center of mass momentum of excitons in semiconductor GaN using a four-wave mixing (FWM) process. When we apply the optical vortex (OV) as an excitation pulse, the diffracted FWM signal exhibits phase singularities that satisfy the OAM conservation law, which remain clear within the exciton dephasing time (approximately 1ps). We also demonstrate the arbitrary control of the topological charge in the output signal by changing the OAM of the input pulse. The results provide a way of controlling the optical OAM through carriers in solids. Moreover, the time evolution of the FWM with OAM leads to the study of the closed-loop carrier coherence in materials.

Evaporation heat transfer of carbon dioxide at low temperature inside a horizontal smooth tube

NASA Astrophysics Data System (ADS)

Yoon, Jung-In; Son, Chang-Hyo; Jung, Suk-Ho; Jeon, Min-Ju; Yang, Dong-Il

2017-05-01

In this paper, the evaporation heat transfer coefficient of carbon dioxide at low temperature of -30 to -20 °C in a horizontal smooth tube was investigated experimentally. The test devices consist of mass flowmeter, pre-heater, magnetic gear pump, test section (evaporator), condenser and liquid receiver. Test section is made of cooper tube. Inner and outer diameter of the test section is 8 and 9.52 mm, respectively. The experiment is conducted at mass fluxes from 100 to 300 kg/m2 s, saturation temperature from -30 to -20 °C. The main results are summarized as follows: In case that the mass flux of carbon dioxide is 100 kg/m2 s, the evaporation heat transfer coefficient is almost constant regardless of vapor quality. In case of 200 and 300 kg/m2 s, the evaporation heat transfer coefficient increases steadily with increasing vapor quality. For the same mass flux, the evaporation heat transfer coefficient increases as the evaporation temperature of the refrigerant decreases. In comparison of heat transfer correlations with the experimental result, the evaporation heat transfer correlations do not predict them exactly. Therefore, more accurate heat transfer correlation than the previous one is required.

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.

Development of a general equation to determine the transfer factor feed-to-meat for radiocesium on the basis of the body mass of domestic animals

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

Nalezinski, S.; Ruehm, W.; Wirth, E.

1996-05-01

Transfer factors from feed to meat (5{sub {integral}}), taken from literature for monogastric animals and ruminants have been correlated to their corresponding animal body mass (m{sub b}). Taking all data into account, a close relationship between both transfer factor and body mass becomes evident, yielding a regression function of (T{sub {integral}} = 8.0 x m{sub b}{sup {minus}0.91}) (r = -0.97). For monogastric animals (including poultry), the corresponding relationships are T{sub {integral}} = 1.9 x m{sub b}{sup {minus}0.72} (r = 0.78). The equations offer the opportunity to estimate the transfer factor for individual animals more precisely taking individual body masses intomore » account. They are of interest for animals, on which no or only poor data concerning radiocesium transfer factors are available. The determination of radiocesium transfer factors are reduced to a simple weighing process. 17 refs., 1 fig., 2 tabs.« less

Bioturbation and dissolved organic matter enhance contaminant fluxes from sediment treated with powdered and granular activated carbon.

PubMed

Kupryianchyk, D; Noori, A; Rakowska, M I; Grotenhuis, J T C; Koelmans, A A

2013-05-21

Sediment amendment with activated carbon (AC) is a promising technique for in situ sediment remediation. To date it is not clear whether this technique sufficiently reduces sediment-to-water fluxes of sediment-bound hydrophobic organic chemicals (HOCs) in the presence of bioturbators. Here, we report polychlorobiphenyl (PCB) pore water concentrations, fluxes, mass transfer coefficients, and survival data of two benthic species, for four treatments: no AC addition (control), powdered AC addition, granular AC addition and addition and subsequent removal of GAC (sediment stripping). AC addition decreased mass fluxes but increased apparent mass transfer coefficients because of dissolved organic carbon (DOC) facilitated transport across the benthic boundary layer (BBL). In turn, DOC concentrations depended on bioturbator activity which was high for the PAC tolerant species Asellus aquaticus and low for AC sensitive species Lumbriculus variegatus. A dual BBL resistance model combining AC effects on gradients, DOC facilitated transport and biodiffusion was evaluated against the data and showed how the type of resistance differs with treatment and chemical hydrophobicity. Data and simulations illustrate the complex interplay between AC and contaminant toxicity to benthic organisms and how differences in species tolerance affect mass fluxes from sediment to the water column.

Dynamics and control of high area-to-mass ratio spacecraft and its application to geomagnetic exploration

NASA Astrophysics Data System (ADS)

Luo, Tong; Xu, Ming; Colombo, Camilla

2018-04-01

This paper studies the dynamics and control of a spacecraft, whose area-to-mass ratio is increased by deploying a reflective orientable surface such as a solar sail or a solar panel. The dynamical system describing the motion of a non-zero attitude angle high area-to-mass ratio spacecraft under the effects of the Earth's oblateness and solar radiation pressure admits the existence of equilibrium points, whose number and the eccentricity values depend on the semi-major axis, the area-to-mass ratio and the attitude angle of the spacecraft together. When two out of three parameters are fixed, five different dynamical topologies successively occur through varying the third parameter. Two of these five topologies are critical cases characterized by the appearance of the bifurcation phenomena. A conventional Hamiltonian structure-preserving (HSP) controller and an improved HSP controller are both constructed to stabilize the hyperbolic equilibrium point. Through the use of a conventional HSP controller, a bounded trajectory around the hyperbolic equilibrium point is obtained, while an improved HSP controller allows the spacecraft to easily transfer to the hyperbolic equilibrium point and to follow varying equilibrium points. A bifurcation control using topologies and changes of behavior areas can also stabilize a spacecraft near a hyperbolic equilibrium point. Natural trajectories around stable equilibrium point and these stabilized trajectories around hyperbolic equilibrium point can all be applied to geomagnetic exploration.

Mass transfer cycles in cataclysmic variables

NASA Technical Reports Server (NTRS)

King, A. R.; Frank, J.; Kolb, U.; Ritter, H.

1995-01-01

It is well known that in cataclysmic variables the mass transfer rate must fluctuate about the evolutionary mean on timescales too long to be directly observable. We show that limit-cycle behavior can occur if the radius change of the secondary star is sensitive to the instantaneous mass transfer rate. The only reasonable way in which such a dependence can arise is through irradiation of this star by the accreting component. The system oscillates between high states, in which irradiation causes slow expansion of the secondary and drives an elevated transfer rate, and low states, in which this star contracts.

Accretion Structures in Algol-Type Interacting Binary Systems

NASA Astrophysics Data System (ADS)

Peters, Geraldine

The physics of mass transfer in interacting binaries of the Algol type will be investigated through an analysis of an extensive collection of FUV spectra from the FUSE spacecraft, Kepler photometry, and FUV spectra from IUE and ORFEUS-SPAS II. The Algols range from close direct impact systems to wider systems that contain prominent accretion disks. Several components of the circumstellar (CS) material have been identified, including the gas stream, splash/outflow domains, a high temperature accretion region (HTAR), accretion disk, and magnetically-controlled flows (cf. Peters 2001, 2007, Richards et al. 2010). Hot spots are sometimes seen at the site where the gas stream impacts the mass gainer's photosphere. Collectively we call these components of mass transfer "accretion structures". The CS material will be studied from an analysis of both line-of-sight FUV absorption features and emission lines. The emission line regions will be mapped in and above/below the orbital plane with 2D and 3D Doppler tomography techniques. We will look for the presence of hot accretion spots in both the Kepler photometry of Algols in the Kepler fields and phase-dependent flux variability in the FUSE spectra. We will also search for evidence of microflaring at the impact site of the gas stream. An abundance study of the mass gainer will reveal the extent to which CNO-processed material from the core of the mass loser is being deposited on the primary. Analysis codes that will be used include 2D and 3D tomography codes, SHELLSPEC, light curve analysis programs such as PHOEBE and Wilson-Devinney, and the NLTE codes TLUSTY/SYNSPEC. This project will transform our understanding of the mass transfer process from a generic to a hydrodynamical one and provide important information on the degree of mass loss from the system which is needed for calculations of the evolution of Algol binaries.

V-ONSET: Introducing turbulent multiphase flow facility focusing on Lagrangian interfacial transfer dynamics

NASA Astrophysics Data System (ADS)

Salibindla, Ashwanth; Masuk, Ashik Ullah Mohammad; Ni, Rui

2017-11-01

We have designed and constructed a new vertical water tunnel, V-ONSET, to investigate interfacial mass, momentum and energy transfer between two phases in a Lagrangian frame. This system features an independent control of mean flow and turbulence level. The mean flow opposes the rising/falling velocity of the second phase, ``suspending'' the particles and increasing tracking time in the view area. Strong turbulence is generated by shooting 88 digitally-controlled water jets into the test section. The second phase, either bubbles or oil droplets, can be introduced into the test section through a capillary island. In addition to this flow control system, V-ONSET comes with a 3D two-phase visualization system, consisting of high-speed cameras, two-colored LED system, and in-house Lagrangian particle tracking algorithm. This enables us to acquire the Lagrangian evolution of both phases and the interfacial transfer dynamics in between, paving the way for new closure models for two-phase simulations. Financial support for this project was provided by National Science Foundation under Grant Number: 1653389 and 1705246.

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.

V3885 Sagittarius: A Comparison With a Range of Standard Model Accretion Disks

NASA Technical Reports Server (NTRS)

Linnell, Albert P.; Godon, Patrick; Hubeny, Ivan; Sion, Edward M; Szkody, Paula; Barrett, Paul E.

2009-01-01

A chi-squared analysis of standard model accretion disk synthetic spectrum fits to combined Far Ultraviolet Spectroscopic Explorer and Space Telescope Imaging Spectrograph spectra of V3885 Sagittarius, on an absolute flux basis, selects a model that accurately represents the observed spectral energy distribution. Calculation of the synthetic spectrum requires the following system parameters. The cataclysmic variable secondary star period-mass relation calibrated by Knigge in 2006 and 2007 sets the secondary component mass. A mean white dwarf (WD) mass from the same study, which is consistent with an observationally determined mass ratio, sets the adopted WD mass of 0.7M(solar mass), and the WD radius follows from standard theoretical models. The adopted inclination, i = 65 deg, is a literature consensus, and is subsequently supported by chi-squared analysis. The mass transfer rate is the remaining parameter to set the accretion disk T(sub eff) profile, and the Hipparcos parallax constrains that parameter to mas transfer = (5.0 +/- 2.0) x 10(exp -9) M(solar mass)/yr by a comparison with observed spectra. The fit to the observed spectra adopts the contribution of a 57,000 +/- 5000 K WD. The model thus provides realistic constraints on mass transfer and T(sub eff) for a large mass transfer system above the period gap.

Research on Volume Measurement System of Weights with Hydrostatic Technique

NASA Astrophysics Data System (ADS)

Wang, Jian; Ren, Xiaoping; Yao, Hong; Cai, Changqing; Zhang, Yue; Zhong, Ruilin; Ding, Jing'an

According to Annex B.7.4 of OIML R111-1, equipment for measuring volume of weights mass ranging from 1 kg to 20 kg including three methods of hydrostatic comparison is described. The equipment consists of a robot arm for transferring weights, a liquid bath, a mass comparator with 26.1 kg of maximum capacity and 1 mg of readability, glass housing, two weight exchangers including in air and in liquid, two weight holders including in air and in liquid, and a controller. The equipment will enable to perform automatically volume measurements.

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 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.

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.

IMPLICATIONS FOR THE FORMATION OF BLUE STRAGGLER STARS FROM HST ULTRAVIOLET OBSERVATIONS OF NGC 188

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

Gosnell, Natalie M.; Mathieu, Robert D.; Geller, Aaron M.

We present results of a Hubble Space Telescope (HST) far-ultraviolet (FUV) survey searching for white dwarf (WD) companions to blue straggler stars (BSSs) in open cluster NGC 188. The majority of NGC 188 BSSs (15 of 21) are single-lined binaries with properties suggestive of mass-transfer formation via Roche lobe overflow, specifically through an asymptotic giant branch star transferring mass to a main sequence secondary, yielding a BSS binary with a WD companion. In NGC 188, a BSS formed by this mechanism within the past 400 Myr will have a WD companion that is hot and luminous enough to be directlymore » detected as a FUV photometric excess with HST. Comparing expected BSS FUV emission to observed photometry reveals four BSSs with WD companions above 12,000 K (younger than 250 Myr) and three WD companions with temperatures between 11,000 and 12,000 K. These BSS+WD binaries all formed through recent mass transfer. The location of the young BSSs in an optical color–magnitude diagram (CMD) indicates that distance from the zero-age main sequence does not necessarily correlate with BSS age. There is no clear CMD separation between mass transfer-formed BSSs and those likely formed through other mechanisms, such as collisions. The seven detected WD companions place a lower limit on the mass-transfer formation frequency of 33%. We consider other possible formation mechanisms by comparing properties of the BSS population to theoretical predictions. We conclude that 14 BSS binaries likely formed from mass transfer, resulting in an inferred mass-transfer formation frequency of approximately 67%.« less

VOLATILIZATION OF ALKYLBENZENES FROM WATER.

USGS Publications Warehouse

Rathbun, R.E.; Tai, D.Y.

1985-01-01

Volatilization is a physical process of importance in determining the fate of many organic compounds in streams and rivers. This process is frequently described by the conceptual-two-film model. The model assumes uniformly mixed water and air phases separated by thin films of water and air in which mass transfer is by molecular diffusion. Mass-transfer coefficients for the water and air films are related to an overall mass-transfer coefficient for volatilization through the Henry's law constant.

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.

Theoretical models for supercritical fluid extraction.

PubMed

Huang, Zhen; Shi, Xiao-Han; Jiang, Wei-Juan

2012-08-10

For the proper design of supercritical fluid extraction processes, it is essential to have a sound knowledge of the mass transfer mechanism of the extraction process and the appropriate mathematical representation. In this paper, the advances and applications of kinetic models for describing supercritical fluid extraction from various solid matrices have been presented. The theoretical models overviewed here include the hot ball diffusion, broken and intact cell, shrinking core and some relatively simple models. Mathematical representations of these models have been in detail interpreted as well as their assumptions, parameter identifications and application examples. Extraction process of the analyte solute from the solid matrix by means of supercritical fluid includes the dissolution of the analyte from the solid, the analyte diffusion in the matrix and its transport to the bulk supercritical fluid. Mechanisms involved in a mass transfer model are discussed in terms of external mass transfer resistance, internal mass transfer resistance, solute-solid interactions and axial dispersion. The correlations of the external mass transfer coefficient and axial dispersion coefficient with certain dimensionless numbers are also discussed. Among these models, the broken and intact cell model seems to be the most relevant mathematical model as it is able to provide realistic description of the plant material structure for better understanding the mass-transfer kinetics and thus it has been widely employed for modeling supercritical fluid extraction of natural matters. Copyright © 2012 Elsevier B.V. All rights reserved.

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

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.

Method for removing metal vapor from gas streams

DOEpatents

Ahluwalia, R.K.; Im, K.H.

1996-04-02

A process for cleaning an inert gas contaminated with a metallic vapor, such as cadmium, involves withdrawing gas containing the metallic contaminant from a gas atmosphere of high purity argon; passing the gas containing the metallic contaminant to a mass transfer unit having a plurality of hot gas channels separated by a plurality of coolant gas channels; cooling the contaminated gas as it flows upward through the mass transfer unit to cause contaminated gas vapor to condense on the gas channel walls; regenerating the gas channels of the mass transfer unit; and, returning the cleaned gas to the gas atmosphere of high purity argon. The condensing of the contaminant-containing vapor occurs while suppressing contaminant particulate formation, and is promoted by providing a sufficient amount of surface area in the mass transfer unit to cause the vapor to condense and relieve supersaturation buildup such that contaminant particulates are not formed. Condensation of the contaminant is prevented on supply and return lines in which the contaminant containing gas is withdrawn and returned from and to the electrorefiner and mass transfer unit by heating and insulating the supply and return lines. 13 figs.

Method for removing metal vapor from gas streams

DOEpatents

Ahluwalia, R. K.; Im, K. H.

1996-01-01

A process for cleaning an inert gas contaminated with a metallic vapor, such as cadmium, involves withdrawing gas containing the metallic contaminant from a gas atmosphere of high purity argon; passing the gas containing the metallic contaminant to a mass transfer unit having a plurality of hot gas channels separated by a plurality of coolant gas channels; cooling the contaminated gas as it flows upward through the mass transfer unit to cause contaminated gas vapor to condense on the gas channel walls; regenerating the gas channels of the mass transfer unit; and, returning the cleaned gas to the gas atmosphere of high purity argon. The condensing of the contaminant-containing vapor occurs while suppressing contaminant particulate formation, and is promoted by providing a sufficient amount of surface area in the mass transfer unit to cause the vapor to condense and relieve supersaturation buildup such that contaminant particulates are not formed. Condensation of the contaminant is prevented on supply and return lines in which the contaminant containing gas is withdrawn and returned from and to the electrorefiner and mass transfer unit by heating and insulating the supply and return lines.

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.

A carbon dioxide stripping model for mammalian cell culture in manufacturing scale bioreactors.

PubMed

Xing, Zizhuo; Lewis, Amanda M; Borys, Michael C; Li, Zheng Jian

2017-06-01

Control of carbon dioxide within the optimum range is important in mammalian bioprocesses at the manufacturing scale in order to ensure robust cell growth, high protein yields, and consistent quality attributes. The majority of bioprocess development work is done in laboratory bioreactors, in which carbon dioxide levels are more easily controlled. Some challenges in carbon dioxide control can present themselves when cell culture processes are scaled up, because carbon dioxide accumulation is a common feature due to longer gas-residence time of mammalian cell culture in large scale bioreactors. A carbon dioxide stripping model can be used to better understand and optimize parameters that are critical to cell culture processes at the manufacturing scale. The prevailing carbon dioxide stripping models in literature depend on mass transfer coefficients and were applicable to cell culture processes with low cell density or at stationary/cell death phase. However, it was reported that gas bubbles are saturated with carbon dioxide before leaving the culture, which makes carbon dioxide stripping no longer depend on a mass transfer coefficient in the new generation cell culture processes characterized by longer exponential growth phase, higher peak viable cell densities, and higher specific production rate. Here, we present a new carbon dioxide stripping model for manufacturing scale bioreactors, which is independent of carbon dioxide mass transfer coefficient, but takes into account the gas-residence time and gas CO 2 saturation time. The model was verified by CHO cell culture processes with different peak viable cell densities (7 to 12 × 10 6  cells mL -1 ) for two products in 5,000-L and 25,000-L bioreactors. The model was also applied to a next generation cell culture process to optimize cell culture conditions and reduce carbon dioxide levels at manufacturing scale. The model provides a useful tool to understand and better control cell culture carbon dioxide profiles for process development, scale up, and characterization. Biotechnol. Bioeng. 2017;114: 1184-1194. © 2016 Wiley Periodicals, Inc. © 2016 Wiley Periodicals, Inc.

Field data and numerical simulation of btex concentration trends under water table fluctuations: Example of a jet fuel-contaminated site in Brazil

NASA Astrophysics Data System (ADS)

Teramoto, Elias Hideo; Chang, Hung Kiang

2017-03-01

Mass transfer of light non-aqueous phase liquids (LNAPLs) trapped in porous media is a complex phenomenon. Water table fluctuations have been identified as responsible for generating significant variations in the concentration of dissolved hydrocarbons. Based on field evidence, this work presents a conceptual model and a numerical solution for mass transfer from entrapped LNAPL to groundwater controlled by both LNAPL saturation and seasonal water table fluctuations within the LNAPL smear zone. The numerical approach is capable of reproducing aqueous BTEX concentration trends under three different scenarios - water table fluctuating within smear zone, above the smear zone and partially within smear zone, resulting in in-phase, out-of-phase and alternating in-phase and out-of-phase BTEX concentration trend with respect to water table oscillation, respectively. The results demonstrate the model's applicability under observed field conditions and its ability to predict source zone depletion.

Mathematical Modeling of Decarburization in Levitated Fe-Cr-C Droplets

NASA Astrophysics Data System (ADS)

Gao, Lei; Shi, Zhe; Yang, Yindong; Li, Donghui; Zhang, Guifang; McLean, Alexander; Chattopadhyay, Kinnor

2018-04-01

Using carbon dioxide to replace oxygen as an alternative oxidant gas has proven to be a viable solution in the decarburization process, with potential for industrial applications. In a recent study, the transport phenomena governing the carbon dioxide decarburization process through the use of electromagnetic levitation (EML) was examined. CO2/CO mass transfer was found to be the principal reaction rate control step, as a result gas diffusion has gained significant attention. In the present study, gas diffusion during decarburization process was investigated using computational fluid dynamics (CFD) modeling coupled with chemical reactions. The resulting model was verified through experimental data in a published paper, and employed to provide insights on phenomena typically unobservable through experiments. Based on the results, a new correction of the Frössling equation was presented which better represents the mass transfer phenomena at the metal-gas interface within the range of this research.

Aroma barrier properties of sodium caseinate-based films.

PubMed

Fabra, Maria José; Hambleton, Alicia; Talens, Pau; Debeaufort, Fréderic; Chiralt, Amparo; Voilley, Andrée

2008-05-01

The mass transport of six different aroma compounds (ethyl acetate, ethyl butyrate, ethyl hexanoate, 2-hexanone, 1-hexanol, and cis-3-hexenol) through sodium caseinate-based films with different oleic acid (OA)/beeswax (BW) ratio has been studied. OA is less efficient than BW in reducing aroma permeability, which can be attributed to its greater polarity. Control film (without lipid) and films prepared with 0:100 OA/BW ratio show the lowest permeability. OA involves a decrease in aroma barrier properties of the sodium caseinate-based films due to its plasticization ability. Preferential sorption and diffusion occurs through OA instead of caseinate matrix and/or BW. The efficiency of sodium caseinate-based films to retain or limit aroma compound transfers depend on the affinity of the volatile compound to the films, which relates physicochemical interaction between volatile compound and film. Specific interactions (aroma compound-hydrocolloid and aroma compound-lipid) induce structural changes during mass transfer.

Ceramic membrane microfilter as an immobilized enzyme reactor.

PubMed

Harrington, T J; Gainer, J L; Kirwan, D J

1992-10-01

This study investigated the use of a ceramic microfilter as an immobilized enzyme reactor. In this type of reactor, the substrate solution permeates the ceramic membrane and reacts with an enzyme that has been immobilized within its porous interior. The objective of this study was to examine the effect of permeation rate on the observed kinetic parameters for the immobilized enzyme in order to assess possible mass transfer influences or shear effects. Kinetic parameters were found to be independent of flow rate for immobilized penicillinase and lactate dehydrogenase. Therefore, neither mass transfer nor shear effects were observed for enzymes immobilized within the ceramic membrane. Both the residence time and the conversion in the microfilter reactor could be controlled simply by regulating the transmembrane pressure drop. This study suggests that a ceramic microfilter reactor can be a desirable alternative to a packed bed of porous particles, especially when an immobilized enzyme has high activity and a low Michaelis constant.

On Study of Application of Micro-reactor in Chemistry and Chemical Field

NASA Astrophysics Data System (ADS)

Zhang, Yunshen

2018-02-01

Serving as a micro-scale chemical reaction system, micro-reactor is characterized by high heat transfer efficiency and mass transfer, strictly controlled reaction time and good safety performance; compared with the traditional mixing reactor, it can effectively shorten reaction time by virtue of these advantages and greatly enhance the chemical reaction conversion rate. However, problems still exist in the process where micro-reactor is used for production in chemistry and chemical field, and relevant researchers are required to optimize and perfect the performance of micro-reactor. This paper analyzes specific application of micro-reactor in chemistry and chemical field.

Simulation of mercury capture by sorbent injection using a simplified model.

PubMed

Zhao, Bingtao; Zhang, Zhongxiao; Jin, Jing; Pan, Wei-Ping

2009-10-30

Mercury pollution by fossil fuel combustion or solid waste incineration is becoming the worldwide environmental concern. As an effective control technology, powdered sorbent injection (PSI) has been successfully used for mercury capture from flue gas with advantages of low cost and easy operation. In order to predict the mercury capture efficiency for PSI more conveniently, a simplified model, which is based on the theory of mass transfer, isothermal adsorption and mass balance, is developed in this paper. The comparisons between theoretical results of this model and experimental results by Meserole et al. [F.B. Meserole, R. Chang, T.R. Carrey, J. Machac, C.F.J. Richardson, Modeling mercury removal by sorbent injection, J. Air Waste Manage. Assoc. 49 (1999) 694-704] demonstrate that the simplified model is able to provide good predictive accuracy. Moreover, the effects of key parameters including the mass transfer coefficient, sorbent concentration, sorbent physical property and sorbent adsorption capacity on mercury adsorption efficiency are compared and evaluated. Finally, the sensitive analysis of impact factor indicates that the injected sorbent concentration plays most important role for mercury capture efficiency.

An Adaptable Multiple Power Source for Mass Spectrometry and other Scientific Instruments

DOE PAGES

Lin, Tzu-Yung; Anderson, Gordon A.; Norheim, Randolph V.; ...

2015-09-18

Power supplies are commonly used in the operation of many types of scientific equipment, including mass spectrometers and ancillary instrumentation. A generic modern mass spectrometer comprises an ionization source, such as electrospray ionization (ESI), ion transfer devices such as ion funnels and multipole ion guides, and ion signal detection apparatus. Very often such platforms include, or are interfaced with ancillary elements in order to manipulate samples before or after ionization. In order to operate such scientific instruments, numerous direct current (DC) channels and radio frequency (RF) signals are required, along with other controls such as temperature regulation. In particular, DCmore » voltages in the range of ±400 V, along with MHz range RF signals with peak-to-peak amplitudes in the hundreds of volts range are commonly used to transfer ionized samples under vacuum. Additionally, an ESI source requires a high voltage (HV) DC source capable of producing several thousand volts and heaters capable of generating temperatures up to 300°C. All of these signals must be properly synchronized and managed in order to carry out ion trapping, accumulation and detection.« less

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.

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.

OPTRAN- OPTIMAL LOW THRUST ORBIT TRANSFERS

NASA Technical Reports Server (NTRS)

Breakwell, J. V.

1994-01-01

OPTRAN is a collection of programs that solve the problem of optimal low thrust orbit transfers between non-coplanar circular orbits for spacecraft with chemical propulsion systems. The programs are set up to find Hohmann-type solutions, with burns near the perigee and apogee of the transfer orbit. They will solve both fairly long burn-arc transfers and "divided-burn" transfers. Program modeling includes a spherical earth gravity model and propulsion system models for either constant thrust or constant acceleration. The solutions obtained are optimal with respect to fuel use: i.e., final mass of the spacecraft is maximized with respect to the controls. The controls are the direction of thrust and the thrust on/off times. Two basic types of programs are provided in OPTRAN. The first type is for "exact solution" which results in complete, exact tkme-histories. The exact spacecraft position, velocity, and optimal thrust direction are given throughout the maneuver, as are the optimal thrust switch points, the transfer time, and the fuel costs. Exact solution programs are provided in two versions for non-coplanar transfers and in a fast version for coplanar transfers. The second basic type is for "approximate solutions" which results in approximate information on the transfer time and fuel costs. The approximate solution is used to estimate initial conditions for the exact solution. It can be used in divided-burn transfers to find the best number of burns with respect to time. The approximate solution is useful by itself in relatively efficient, short burn-arc transfers. These programs are written in FORTRAN 77 for batch execution and have been implemented on a DEC VAX series computer with the largest program having a central memory requirement of approximately 54K of 8 bit bytes. The OPTRAN program were developed in 1983.

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.

Heat Transfer of Confined Impinging Air-water Mist Jet

NASA Astrophysics Data System (ADS)

Chang, Shyy Woei; Su, Lo May

This paper describes the detailed heat transfer distributions of an atomized air-water mist jet impinging orthogonally onto a confined target plate with various water-to-air mass-flow ratios. A transient technique was used to measure the full field heat transfer coefficients of the impinging surface. Results showed that the high momentum mist-jet interacting with the water-film and wall-jet flows created a variety of heat transfer contours on the impinging surface. The trade-off between the competing influences of the different heat transfer mechanisms involving in an impinging mist jet made the nonlinear variation tendency of overall heat transfer against the increase of water-to-air mass-flow ratio and extended the effective cooling region. With separation distances of 10, 8, 6 and 4 jet-diameters, the spatially averaged heat transfer values on the target plate could respectively reach about 2.01, 1.83, 2.43 and 2.12 times of the equivalent air-jet values, which confirmed the applicability of impinging mist-jet for heat transfer enhancement. The optimal choices of water-to-air mass-flow ratio for the atomized mist jet required the considerations of interactive and combined effects of separation distance, air-jet Reynolds number and the water-to-air mass-flow ratio into the atomized nozzle.

Adiabatic Mass Loss Model in Binary Stars

NASA Astrophysics Data System (ADS)

Ge, H. W.

2012-07-01

Rapid mass transfer process in the interacting binary systems is very complicated. It relates to two basic problems in the binary star evolution, i.e., the dynamically unstable Roche-lobe overflow and the common envelope evolution. Both of the problems are very important and difficult to be modeled. In this PhD thesis, we focus on the rapid mass loss process of the donor in interacting binary systems. The application to the criterion of dynamically unstable mass transfer and the common envelope evolution are also included. Our results based on the adiabatic mass loss model could be used to improve the binary evolution theory, the binary population synthetic method, and other related aspects. We build up the adiabatic mass loss model. In this model, two approximations are included. The first one is that the energy generation and heat flow through the stellar interior can be neglected, hence the restructuring is adiabatic. The second one is that he stellar interior remains in hydrostatic equilibrium. We model this response by constructing model sequences, beginning with a donor star filling its Roche lobe at an arbitrary point in its evolution, holding its specific entropy and composition profiles fixed. These approximations are validated by the comparison with the time-dependent binary mass transfer calculations and the polytropic model for low mass zero-age main-sequence stars. In the dynamical time scale mass transfer, the adiabatic response of the donor star drives it to expand beyond its Roche lobe, leading to runaway mass transfer and the formation of a common envelope with its companion star. For donor stars with surface convection zones of any significant depth, this runaway condition is encountered early in mass transfer, if at all; but for main sequence stars with radiative envelopes, it may be encountered after a prolonged phase of thermal time scale mass transfer, so-called delayed dynamical instability. We identify the critical binary mass ratio for the onset of dynamical time scale mass transfer; if the ratio of donor to accretor masses exceeds this critical value, the dynamical time scale mass transfer ensues. The grid of criterion for all stars can be used to be the basic input as the binary population synthetic method, which will be improved absolutely. In common envelope evolution, the dissipation of orbital energy of the binary provides the energy to eject the common envelope; the energy budget for this process essentially consists of the initial orbital energy of the binary and the initial binding energies of the binary components. We emphasize that, because stellar core and envelope contribute mutually to each other's gravitational potential energy, proper evaluation of the total energy of a star requires integration over the entire stellar interior, not the ejected envelope alone as commonly assumed. We show that the change in total energy of the donor star, as a function of its remaining mass along an adiabatic mass-loss sequence, can be calculated. This change in total energy of the donor star, combined with the requirement that both remnant donor and its companion star fit within their respective Roche lobes, then circumscribes energetically possible survivors of common envelope evolution. It is the first time that we can calculate the accurate total energy of the donor star in common envelope evolution, while the results with the old method are inconsistent with observations.

The influence of spent household batteries to the organic fraction of municipal solid wastes during composting.

PubMed

Komilis, Dimitrios; Bandi, Dimitra; Kakaronis, Georgios; Zouppouris, Georgios

2011-06-01

The objective of this work was to investigate the potential transfer of 9 heavy metals from spent household batteries (zinc-carbon and alkaline-manganese batteries) to the organic fraction of municipal solid wastes during active composting. Six runs were performed including one control and 2 replications. Eleven types of alkaline and non-alkaline batteries were added at 3 different levels to the organic fraction of municipal solid wastes, namely at percentages equal to 0.98% w/w (low), 5.2% w/w (medium) and 10.6% w/w (high). Experiments were performed in 230 l insulated plastic aerobic bioreactors under a dynamic air flow regime for up to 60 days. Iron, copper and nickel masses contained in the organic fraction of the wastes were found significantly higher in the high level runs compared to the corresponding masses in the control. No metal transfer was obtained in the low and medium level runs. Metal mass balance closures ranged from 51% to 176%. Metals' concentrations in the leachates were below 10 mg l⁻¹ for most metals, except iron, while an increasing concentration trend versus time was measured in the leachates of the high level runs. In all cases, the contents of 5 regulated heavy metals in all end products were below the Hellenic limits. Copyright © 2011 Elsevier B.V. All rights reserved.

Of Magic Carpets, Rolling Snowballs, and Sleeping Dragons: an Energetics-based Classification for Hillslope/channel Interactions

NASA Astrophysics Data System (ADS)

Grant, G.; Cashman, K.; O'Connor, J.

2007-12-01

Interactions between hillslopes and channels can include a diverse range of geophysical processes, including debris flows, landslides, water floods, and volcanic flows. Each has its own characteristic time-energy trajectory. In some cases the energy of an event increases as it propagates through a landscape, primarily through the addition of mass and momentum; examples of these"rolling snowball" include the initiation and runout phases of volcanic lahars, avalanches, and debris flows. In other cases, loss of both mass and momentum from a moving body or fluid causes the energy of an event to dissipate with distance, similar to the unwinding of a rug; examples of these "magic carpets" include the depositional phases of lahars, pyroclastic flows, lava flows, and debris flows. Both snowballs and carpets leave distinctive imprints or tracks on the landscape that reflect the resultant mass flux from hill slope to channel. The efficiency of this mass transfer depends on the width and slope of the receiving channel and the rheological properties of the transported material. At one extreme, the channel easily accommodates mass flux from the slope, sometimes accompanied by fractionation into constituent phases. At the other extreme, mass from the hill slope can inundate and block the channel; these "sleeping dragons" modulate subsequent mass transfer down channel by changing the channel profile and bed properties. They also have the potential to "wake up" suddenly as mass failure and/or outbreak floods. Hazard prediction requires that the time-energy trajectory of each type of event be assessed; here we suggest some first order controls.

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.

Theoretical analysis for condensation heat transfer of binary refrigerant mixtures with annular flow in horizontal mini-tubes

NASA Astrophysics Data System (ADS)

Zhang, Hui-Yong; Li, Jun-Ming; Sun, Ji-Liang; Wang, Bu-Xuan

2016-01-01

A theoretical model is developed for condensation heat transfer of binary refrigerant mixtures in mini-tubes with diameter about 1.0 mm. Condensation heat transfer of R410A and R32/R134a mixtures at different mass fluxes and saturated temperatures are analyzed, assuming that the phase flow pattern is annular flow. The results indicate that there exists a maximum interface temperature at the beginning of condensation process for azeotropic and zeotropic mixtures and the corresponding vapor quality to the maximum value increases with mass flux. The effects of mass flux, heat flux, surface tension and tube diameter are analyzed. As expected, the condensation heat transfer coefficients increase with mass flux and vapor quality, and increase faster in high vapor quality region. It is found that the effects of heat flux and surface tension are not so obvious as that of tube diameter. The characteristics of condensation heat transfer of zeotropic mixtures are consistent to those of azeotropic refrigerant mixtures. The condensation heat transfer coefficients increase with the concentration of the less volatile component in binary mixtures.

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 cosolvents are discussed.

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.

Initiator and Photocatalyst-Free Visible Light Induced One-Pot Reaction: Concurrent RAFT Polymerization and CuAAC Click Reaction.

PubMed

Wang, Jie; Wang, Xinbo; Xue, Wentao; Chen, Gaojian; Zhang, Weidong; Zhu, Xiulin

2016-05-01

A new, visible light-catalyzed, one-pot and one-step reaction is successfully employed to design well-controlled side-chain functionalized polymers, by the combination of ambient temperature revisible addtion-fragmentation chain transfer (RAFT) polymerization and click chemistry. Polymerizations are well controlled in a living way under the irradiation of visible light-emitting diode (LED) light without photocatalyst and initiator, using the trithiocarbonate agent as iniferter (initiator-transfer agent-terminator) agent at ambient temperature. Fourier transfer infrared spectroscopy (FT-IR), NMR, and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS) data confirm the successful one-pot reaction. Compared to the reported zero-valent metal-catalyzed one-pot reaction, the polymerization rate is much faster than that of the click reaction, and the visible light-catalyzed one-pot reaction can be freely and easily regulated by turning on and off the light. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

A Review of Microbubble and its Applications in Ozonation

NASA Astrophysics Data System (ADS)

Shangguan, Yufei; Yu, Shuili; Gong, Chao; Wang, Yue; Yang, Wangzhen; Hou, Li-an

2018-03-01

Ozonation has been demonstrated to be an effective technology for the oxidation of organic matters in water treatment. But the low solubility and low mass transfer efficiency limit the application. Microbubble technology has the potential of enhancing gas-liquid mass transfer efficiency, thus it can be applied in ozonation process. The applications of microbubble ozonation have shown advantages over macro bubble ozonation in mass transfer and reaction rate. Microbubble ozonation will be a promising treatment both in water and wastewater treatment.

Determination of the dried product resistance variability and its influence on the product temperature in pharmaceutical freeze-drying.

PubMed

Scutellà, Bernadette; Trelea, Ioan Cristian; Bourlès, Erwan; Fonseca, Fernanda; Passot, Stephanie

2018-07-01

During the primary drying step of the freeze-drying process, mass transfer resistance strongly affects the product temperature, and consequently the final product quality. The main objective of this study was to evaluate the variability of the mass transfer resistance resulting from the dried product layer (R p ) in a manufacturing batch of vials, and its potential effect on the product temperature, from data obtained in a pilot scale freeze-dryer. Sublimation experiments were run at -25 °C and 10 Pa using two different freezing protocols: with spontaneous or controlled ice nucleation. Five repetitions of each condition were performed. Global (pressure rise test) and local (gravimetric) methods were applied as complementary approaches to estimate R p . The global method allowed to assess variability of the evolution of R p with the dried layer thickness between different experiments whereas the local method informed about R p variability at a fixed time within the vial batch. A product temperature variability of approximately ±4.4 °C was defined for a product dried layer thickness of 5 mm. The present approach can be used to estimate the risk of failure of the process due to mass transfer variability when designing freeze-drying cycle. Copyright © 2018 Elsevier B.V. All rights reserved.

Large Advanced Space Systems (LASS) computer-aided design program additions

NASA Technical Reports Server (NTRS)

Farrell, C. E.

1982-01-01

The LSS preliminary and conceptual design requires extensive iteractive analysis because of the effects of structural, thermal, and control intercoupling. A computer aided design program that will permit integrating and interfacing of required large space system (LSS) analyses is discussed. The primary objective of this program is the implementation of modeling techniques and analysis algorithms that permit interactive design and tradeoff studies of LSS concepts. Eight software modules were added to the program. The existing rigid body controls module was modified to include solar pressure effects. The new model generator modules and appendage synthesizer module are integrated (interfaced) to permit interactive definition and generation of LSS concepts. The mass properties module permits interactive specification of discrete masses and their locations. The other modules permit interactive analysis of orbital transfer requirements, antenna primary beam n, and attitude control requirements.

Direct fabrication of gas diffusion cathode by pulse electrodeposition for proton exchange membrane water electrolysis

NASA Astrophysics Data System (ADS)

Park, Hyanjoo; Choe, Seunghoe; Kim, Hoyoung; Kim, Dong-Kwon; Cho, GeonHee; Park, YoonSu; Jang, Jong Hyun; Ha, Don-Hyung; Ahn, Sang Hyun; Kim, Soo-Kil

2018-06-01

Pt catalysts for water electrolysis were prepared on carbon paper by using both direct current and pulse electrodeposition. Controlling the mass transfer of Pt precursor in the electrolyte by varying the deposition potential enables the formation of various Pt particle shapes such as flower-like and polyhedral particles. Further control of the deposition parameters for pulse electrodeposition resulted in changes to the particle size and density. In particular, the upper potential of pulse was found to be the critical parameter controlling the morphology of the particles and their catalytic activity. In addition to the typical electrochemical measurements, Pt samples deposited on carbon paper were used as cathodes for a proton exchange membrane water electrolyser. This single cell test revealed that our Pt particle samples have exceptional mass activity while being cost effective.

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 weariness under vibration action are attributable to infringements of normal mass transfer between the inhaled air and blood. The opportunity of use of the received laws is discussed for assessment of influence of gravitational fields on intensity mass transfer in capillaries of biosystems also.

Chemical reaction fouling model for single-phase heat transfer

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

Panchal, C.B.; Watkinson, A.P.

1993-08-01

A fouling model was developed on the premise that the chemical reaction for generation of precursor can take place in the bulk fluid, in the thermalboundary layer, or at the fluid/wall interface, depending upon the interactive effects of flu id dynamics, heat and mass transfer, and the controlling chemical reaction. The analysis was used to examine the experimental data for fouling deposition of polyperoxides produced by autoxidation of indene in kerosene. The effects of fluid and wall temperatures for two flow geometries were analyzed. The results showed that the relative effects of physical parameters on the fouling rate would differmore » for the three fouling mechanisms; therefore, it is important to identify the controlling mechanism in applying the closed-flow-loop data to industrial conditions.« less

Acoustically enhanced boiling heat transfer on a heated surface containing open microchannels

NASA Astrophysics Data System (ADS)

Boziuk, Thomas R.; Smith, Marc K.; Glezer, Ari

2011-11-01

Acoustic actuation is used to enhance boiling heat transfer on a submerged heated surface containing an array of open microchannels by controlling the formation and evolution of vapor bubbles and inhibiting the instability that leads to film boiling at the critical heat flux. The effect of actuation at millimeter and micrometer scales is investigated with emphasis on the behavior of bubble nucleation, growth, contact-line motion, condensation, and detachment. The results show that microchannels control the location of boiling and reduce the mean surface superheat. In addition, acoustic actuation increases the heat flux at a given surface temperature and leads to a significant increase in the critical heat flux, a reduction of the vapor mass above the surface, and the breakup of low-frequency vapor slug formation. Supported by ONR.

A Method of Efficient Inclination Changes for Low-thrust Spacecraft

NASA Technical Reports Server (NTRS)

Falck, Robert; Gefert, Leon

2002-01-01

The evolution of low-thrust propulsion technologies has reached a point where such systems have become an economical option for many space missions. The development of efficient, low trip time control laws has received an increasing amount of attention in recent years, though few studies have examined the subject of inclination changing maneuvers in detail. A method for performing economical inclination changes through the use of an efficiency factor is derived front Lagrange's planetary equations. The efficiency factor can be used to regulate propellant expenditure at the expense of trip time. Such a method can be used for discontinuous-thrust transfers that offer reduced propellant masses and trip-times in comparison to continuous thrust transfers, while utilizing thrusters that operate at a lower specific impulse. Performance comparisons of transfers utilizing this approach with continuous-thrust transfers are generated through trajectory simulation and are presented in this paper.

Traveltime-based descriptions of transport and mixing in heterogeneous domains

NASA Astrophysics Data System (ADS)

Luo, Jian; Cirpka, Olaf A.

2008-09-01

Modeling mixing-controlled reactive transport using traditional spatial discretization of the domain requires identifying the spatial distributions of hydraulic and reactive parameters including mixing-related quantities such as dispersivities and kinetic mass transfer coefficients. In most applications, breakthrough curves (BTCs) of conservative and reactive compounds are measured at only a few locations and spatially explicit models are calibrated by matching these BTCs. A common difficulty in such applications is that the individual BTCs differ too strongly to justify the assumption of spatial homogeneity, whereas the number of observation points is too small to identify the spatial distribution of the decisive parameters. The key objective of the current study is to characterize physical transport by the analysis of conservative tracer BTCs and predict the macroscopic BTCs of compounds that react upon mixing from the interpretation of conservative tracer BTCs and reactive parameters determined in the laboratory. We do this in the framework of traveltime-based transport models which do not require spatially explicit, costly aquifer characterization. By considering BTCs of a conservative tracer measured on different scales, one can distinguish between mixing, which is a prerequisite for reactions, and spreading, which per se does not foster reactions. In the traveltime-based framework, the BTC of a solute crossing an observation plane, or ending in a well, is interpreted as the weighted average of concentrations in an ensemble of non-interacting streamtubes, each of which is characterized by a distinct traveltime value. Mixing is described by longitudinal dispersion and/or kinetic mass transfer along individual streamtubes, whereas spreading is characterized by the distribution of traveltimes, which also determines the weights associated with each stream tube. Key issues in using the traveltime-based framework include the description of mixing mechanisms and the estimation of the traveltime distribution. In this work, we account for both apparent longitudinal dispersion and kinetic mass transfer as mixing mechanisms, thus generalizing the stochastic-convective model with or without inter-phase mass transfer and the advective-dispersive streamtube model. We present a nonparametric approach of determining the traveltime distribution, given a BTC integrated over an observation plane and estimated mixing parameters. The latter approach is superior to fitting parametric models in cases wherein the true traveltime distribution exhibits multiple peaks or long tails. It is demonstrated that there is freedom for the combinations of mixing parameters and traveltime distributions to fit conservative BTCs and describe the tailing. A reactive transport case of a dual Michaelis-Menten problem demonstrates that the reactive mixing introduced by local dispersion and mass transfer may be described by apparent mean mass transfer with coefficients evaluated by local BTCs.

Improved ion optics for introduction of ions into a 9.4-T Fourier transform ion cyclotron resonance mass spectrometer

DOE PAGES

Chen, Yu; Leach, Franklin E.; Kaiser, Nathan K.; ...

2015-01-19

Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometry provides unparalleled mass accuracy and resolving power.[1],[2] With electrospray ionization (ESI), ions are typically transferred into the mass spectrometer through a skimmer, which serves as a conductance-limiting orifice. However, the skimmer allows only a small fraction of incoming ions to enter the mass spectrometer. An ion funnel, originally developed by Smith and coworkers at Pacific Northwest National Laboratory (PNNL)[3-5] provides much more efficient ion focusing and transfer. The large entrance aperture of the ion funnel allows almost all ions emanating from a heated capillary to be efficiently captured and transferred, resulting inmore » nearly lossless transmission.« less

Analysis of air-, moisture- and solvent-sensitive chemical compounds by mass spectrometry using an inert atmospheric pressure solids analysis probe.

PubMed

Mosely, Jackie A; Stokes, Peter; Parker, David; Dyer, Philip W; Messinis, Antonis M

2018-02-01

A novel method has been developed that enables chemical compounds to be transferred from an inert atmosphere glove box and into the atmospheric pressure ion source of a mass spectrometer whilst retaining a controlled chemical environment. This innovative method is simple and cheap to implement on some commercially available mass spectrometers. We have termed this approach inert atmospheric pressure solids analysis probe ( iASAP) and demonstrate the benefit of this methodology for two air-/moisture-sensitive chemical compounds whose characterisation by mass spectrometry is now possible and easily achieved. The simplicity of the design means that moving between iASAP and standard ASAP is straightforward and quick, providing a highly flexible platform with rapid sample turnaround.

Stability analysis of electrical powered wheelchair-mounted robotic-assisted transfer device.

PubMed

Wang, Hongwu; Tsai, Chung-Ying; Jeannis, Hervens; Chung, Cheng-Shiu; Kelleher, Annmarie; Grindle, Garrett G; Cooper, Rory A

2014-01-01

The ability of people with disabilities to live in their homes and communities with maximal independence often hinges, at least in part, on their ability to transfer or be transferred by an assistant. Because of limited resources and the expense of personal care, robotic transfer assistance devices will likely be in great demand. An easy-to-use system for assisting with transfers, attachable to electrical powered wheelchairs (EPWs) and readily transportable, could have a significant positive effect on the quality of life of people with disabilities. We investigated the stability of our newly developed Strong Arm, which is attached and integrated with an EPW to assist with transfers. The stability of the system was analyzed and verified by experiments applying different loads and using different system configurations. The model predicted the distributions of the system's center of mass very well compared with the experimental results. When real transfers were conducted with 50 and 75 kg loads and an 83.25 kg dummy, the current Strong Arm could transfer all weights safely without tip-over. Our modeling accurately predicts the stability of the system and is suitable for developing better control algorithms to enhance the safety of the device.

Syngas fermentation to biofuel: evaluation of carbon monoxide mass transfer and analytical modeling using a composite hollow fiber (CHF) membrane bioreactor.

PubMed

Munasinghe, Pradeep Chaminda; Khanal, Samir Kumar

2012-10-01

In this study, the volumetric mass transfer coefficients (Ka) for CO were examined in a composite hollow fiber (CHF) membrane bioreactor. The mass transfer experiments were conducted at various inlet gas pressures (from 5 to 30 psig (34.5-206.8 kPa(g))) and recirculation flow rates (300, 600, 900, 1200 and 1500 mL/min) through CHF module. The highest Ka value of 946.6 1/h was observed at a recirculation rate of 1500 mL/min and at an inlet gas pressure of 30 psig(206.8 kPa(g)). The findings of this study confirm that the use of CHF membranes is effective and improves the efficiency CO mass transfer into the aqueous phase. Copyright © 2012 Elsevier Ltd. All rights reserved.

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.

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.

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.

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.

The awakening of a classical nova from hibernation.

PubMed

Mróz, Przemek; Udalski, Andrzej; Pietrukowicz, Paweł; Szymański, Michał K; Soszyński, Igor; Wyrzykowski, Łukasz; Poleski, Radosław; Kozłowski, Szymon; Skowron, Jan; Ulaczyk, Krzysztof; Skowron, Dorota; Pawlak, Michał

2016-09-29

Cataclysmic variable stars-novae, dwarf novae, and nova-likes-are close binary systems consisting of a white dwarf star (the primary) that is accreting matter from a low-mass companion star (the secondary). From time to time such systems undergo large-amplitude brightenings. The most spectacular eruptions, with a ten-thousandfold increase in brightness, occur in classical novae and are caused by a thermonuclear runaway on the surface of the white dwarf. Such eruptions are thought to recur on timescales of ten thousand to a million years. In between, the system's properties depend primarily on the mass-transfer rate: if it is lower than a billionth of a solar mass per year, the accretion becomes unstable and the matter is dumped onto the white dwarf during quasi-periodic dwarf nova outbursts. The hibernation hypothesis predicts that nova eruptions strongly affect the mass-transfer rate in the binary, keeping it high for centuries after the event. Subsequently, the mass-transfer rate should significantly decrease for a thousand to a million years, starting the hibernation phase. After that the nova awakes again-with accretion returning to the pre-eruption level and leading to a new nova explosion. The hibernation model predicts cyclical evolution of cataclysmic variables through phases of high and low mass-transfer. The theory gained some support from the discovery of ancient nova shells around the dwarf novae Z Camelopardalis and AT Cancri, but direct evidence for considerable mass-transfer changes prior, during and after nova eruptions has not hitherto been found. Here we report long-term observations of the classical nova V1213 Cen (Nova Centauri 2009) covering its pre- and post-eruption phases and precisely documenting its evolution. Within the six years before the explosion, the system revealed dwarf nova outbursts indicative of a low mass-transfer rate. The post-nova is two orders of magnitude brighter than the pre-nova at minimum light with no trace of dwarf nova behaviour, implying that the mass-transfer rate increased considerably as a result of the nova explosion.

Coaxial ion trap mass spectrometer: concentric toroidal and quadrupolar trapping regions.

PubMed

Peng, Ying; Hansen, Brett J; Quist, Hannah; Zhang, Zhiping; Wang, Miao; Hawkins, Aaron R; Austin, Daniel E

2011-07-15

We present the design and results for a new radio-frequency ion trap mass analyzer, the coaxial ion trap, in which both toroidal and quadrupolar trapping regions are created simultaneously. The device is composed of two parallel ceramic plates, the facing surfaces of which are lithographically patterned with concentric metal rings and covered with a thin film of germanium. Experiments demonstrate that ions can be trapped in either region, transferred from the toroidal to the quadrupolar region, and mass-selectively ejected from the quadrupolar region to a detector. Ions trapped in the toroidal region can be transferred to the quadrupole region using an applied ac signal in the radial direction, although it appears that the mechanism of this transfer does not involve resonance with the ion secular frequency, and the process is not mass selective. Ions in the quadrupole trapping region are mass analyzed using dipole resonant ejection. Multiple transfer steps and mass analysis scans are possible on a single population of ions, as from a single ionization/trapping event. The device demonstrates better mass resolving power than the radially ejecting halo ion trap and better sensitivity than the planar quadrupole ion trap.

Numerical investigation of influence on heat transfer characteristics to pneumatically conveyed dense phase flow by selecting models and boundary conditions

NASA Astrophysics Data System (ADS)

Zheng, Y.; Liu, Q.; Li, Y.

2012-03-01

Solids moving with a gas stream in a pipeline can be found in many industrial processes, such as power generation, chemical, pharmaceutical, food and commodity transfer processes. A mass flow rate of the solids is important characteristic that is often required to be measured (and controlled) to achieve efficient utilization of energy and raw materials in pneumatic conveying systems. The methods of measuring the mass flow rate of solids in a pneumatic pipeline can be divided into direct and indirect (inferential) measurements. A thermal solids' mass flow-meter, in principle, should ideally provide a direct measurement of solids flow rate, regardless of inhomogeneities in solids' distribution and environmental impacts. One key issue in developing a thermal solids' mass flow-meter is to characterize the heat transfer between the hot pipe wall and the gas-solids dense phase flow. The Eulerian continuum modeling with gas-solid two phases is the most common method for pneumatic transport. To model a gas-solid dense phase flow passing through a heated region, the gas phase is described as a continuous phase and the particles as the second phase. This study aims to describe the heat transfer characteristics between the hot wall and the gas-solids dense phase flow in pneumatic pipelines by modeling a turbulence gas-solid plug passing through the heated region which involves several actual and crucial issues: selections of interphase exchange coefficient, near-wall region functions and different wall surface temperatures. A sensitivity analysis was discussed to identify the influence on the heat transfer characteristics by selecting different interphase exchange coefficient models and different boundary conditions. Simulation results suggest that sensitivity analysis in the choice of models is very significant. The simulation results appear to show that a combination of choosing the Syamlal-O'Brien interphase exchange coefficient model and the standard k-ɛ model along with the standard wall function model might be the best approach, by which, the simulation data seems to be closest to the experimental results.

Numerical Investigation for Strengthening Heat Transfer Mechanism of the Tube-Row Heat Exchanger in a Compact Thermoelectric Generator

NASA Astrophysics Data System (ADS)

Zhang, Zheng; Chen, Zijian; Liu, Hongwu; Yue, Hao; Chen, Dongbo; Qin, Delei

2018-04-01

According to the basic principle of heat transfer enhancement, a 1-kW compact thermoelectric generator (TEG) is proposed that is suitable for use at high temperatures and high flow speeds. The associated heat exchanger has a tube-row structure with a guide-plate to control the thermal current. The heat exchanger has a volume of 7 L, and the TEG has a mass of 8 kg (excluding the thermoelectric modules (TEMs)). In this paper, the heat transfer process of the tube-row exchanger is modeled and analyzed numerically; and the influences of its structure on the heat transfer and temperature status of the TEMs are investigated. The results show that use of the thin - wall pipes and increase of surface roughness inside the pipes are effective ways to improve the heat transfer efficiency, obtain the rated surface temperature, and make the TEG compact and lightweight. Furthermore, under the same conditions, the calculated results are compared with the data of a fin heat exchanger. The comparison results show that the volume and mass of the tube-row heat exchanger are 19% and 33% lower than those of the fin type unit, and that the pressure drop is reduced by 16%. In addition, the average temperature in the tube-row heat exchanger is increased by 15°C and the average temperature difference is increased by 19°C; the tube-row TEG has a more compact volume and better temperature characteristics.

Flash crystallization kinetics of methane (sI) hydrate in a thermoelectrically-cooled microreactor.

PubMed

Chen, Weiqi; Pinho, Bruno; Hartman, Ryan L

2017-09-12

The crystallization kinetics of methane (sI) hydrate were investigated in a thermoelectrically-cooled microreactor with in situ Raman spectroscopy. Step-wise and precise control of the temperature allowed acquisition of reproducible data within minutes, while the nucleation of methane hydrates can take up to 24 h in traditional batch reactors. The propagation rates of methane hydrate (from 3.1-196.3 μm s -1 ) at the gas-liquid interface were measured for different Reynolds' numbers (0.7-68.9), pressures (30.0-80.9 bar), and sub-cooling temperatures (1.0-4.0 K). The precise measurement of the propagation rates and their subsequent analyses revealed a transition from mixed heat-transfer-crystallization-rate-limited to mixed heat-transfer-mass-transfer-crystallization-rate-limited kinetics. A theoretical model, based on heat transfer, mass transfer, and intrinsic crystallization kinetics, was derived for the first time to understand the non-linear relationship between the propagation rate and sub-cooling temperature. The molecular diffusivity of methane within a stagnant film (ahead of the propagation front) was discovered to follow Stokes-Einstein, while calculated Hatta (0.50-0.68), Lewis (128-207), and beta (0.79-116) numbers also confirmed that the diffusive flux influences crystal growth. Understanding methane hydrate crystal growth is important to the atmospheric, oceanic, and planetary sciences and to energy production, storage, and transportation. Our discoveries could someday advance the science of other multiphase, high-pressure, and sub-cooled crystallizations.

Low body mass index compromises live birth rate in fresh transfer in vitro fertilization cycles: a retrospective study in a Chinese population.

PubMed

Cai, Jiali; Liu, Lanlan; Zhang, Junwen; Qiu, Huiling; Jiang, Xiaoming; Li, Ping; Sha, Aiguo; Ren, Jianzhi

2017-02-01

To evaluate the effects of low body mass index (BMI) on in vitro fertilization (IVF) outcomes in fresh transfer cycles. Retrospective cohort study. University-affiliated hospital. A total of 4,798 cycles with conventional stimulation and fresh transfer in a single IVF center during the period 2013-2014. Low BMI (<18.5 kg/m 2 ) was defined according to World Health Organization guidelines, and cycles within a normal weight range (18.5-24.9 kg/m 2 ) were used as reference. None. Live birth rate per fresh embryo transfer. Low BMI was associated with reduced live birth rates and increased miscarriage rates compared with normal weight, controlling for important covariates known to influence IVF outcomes. Patient age was the most potent confounder, causing a 10.5% reduction in the odds ratio (OR) for live birth between the groups compared. When an interaction term (age × BMI) was introduced, the OR for live birth was reduced in cycles of those aged ≥35 years compared with cycles of those aged 28-34 years, whereas the change in OR between cycles in those aged <28 and cycles in those aged 28-34 years was insignificant. Low BMI is associated with negative outcomes in fresh transfer cycles, especially for women of advanced age. Copyright © 2016 American Society for Reproductive Medicine. Published by Elsevier Inc. All rights reserved.

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.

Numerical Investigation for Strengthening Heat Transfer Mechanism of the Tube-Row Heat Exchanger in a Compact Thermoelectric Generator

NASA Astrophysics Data System (ADS)

Zhang, Zheng; Chen, Zijian; Liu, Hongwu; Yue, Hao; Chen, Dongbo; Qin, Delei

2018-06-01

According to the basic principle of heat transfer enhancement, a 1-kW compact thermoelectric generator (TEG) is proposed that is suitable for use at high temperatures and high flow speeds. The associated heat exchanger has a tube-row structure with a guide-plate to control the thermal current. The heat exchanger has a volume of 7 L, and the TEG has a mass of 8 kg (excluding the thermoelectric modules (TEMs)). In this paper, the heat transfer process of the tube-row exchanger is modeled and analyzed numerically; and the influences of its structure on the heat transfer and temperature status of the TEMs are investigated. The results show that use of the thin - wall pipes and increase of surface roughness inside the pipes are effective ways to improve the heat transfer efficiency, obtain the rated surface temperature, and make the TEG compact and lightweight. Furthermore, under the same conditions, the calculated results are compared with the data of a fin heat exchanger. The comparison results show that the volume and mass of the tube-row heat exchanger are 19% and 33% lower than those of the fin type unit, and that the pressure drop is reduced by 16%. In addition, the average temperature in the tube-row heat exchanger is increased by 15°C and the average temperature difference is increased by 19°C; the tube-row TEG has a more compact volume and better temperature characteristics.

Process for operating equilibrium controlled reactions

DOEpatents

Nataraj, Shankar; Carvill, Brian Thomas; Hufton, Jeffrey Raymond; Mayorga, Steven Gerard; Gaffney, Thomas Richard; Brzozowski, Jeffrey Richard

2001-01-01

A cyclic process for operating an equilibrium controlled reaction in a plurality of reactors containing an admixture of an adsorbent and a reaction catalyst suitable for performing the desired reaction which is operated in a predetermined timed sequence wherein the heating and cooling requirements in a moving reaction mass transfer zone within each reactor are provided by indirect heat exchange with a fluid capable of phase change at temperatures maintained in each reactor during sorpreaction, depressurization, purging and pressurization steps during each process cycle.

Advanced Propulsion for Geostationary Orbit Insertion and North-South Station Keeping

NASA Technical Reports Server (NTRS)

Oleson, Steven R.; Myers, Roger M.; Kluever, Craig A.; Riehl, John P.; Curran, Francis M.

1995-01-01

Solar electric propulsion (SEP) technology is currently being used for geostationary satellite station keeping to increase payload mass. Analyses show that advanced electric propulsion technologies can be used to obtain additional increases in payload mass by using these same technologies to perform part of the orbit transfer. In this work three electric propulsion technologies are examined at two power levels for an Atlas 2AS class spacecraft. The on-board chemical propulsion apogee engine fuel is reduced to allow the use of electric propulsion. A numerical optimizer is used to determine the chemical burns which will minimize the electric propulsion transfer time. Results show that for a 1550 kg Atlas 2AS class payload, increases in net mass (geostationary satellite mass less wet propulsion system mass) of 150 to 800 kg are possible using electric propulsion for station keeping, advanced chemical engines for part of the transfer, and electric propulsion for the remainder of the transfer. Trip times are between one and four months.

Mechanism and kinetics of the loss of poorly soluble drugs from liposomal carriers studied by a novel flow field-flow fractionation-based drug release-/transfer-assay.

PubMed

Hinna, Askell Hvid; Hupfeld, Stefan; Kuntsche, Judith; Bauer-Brandl, Annette; Brandl, Martin

2016-06-28

Liposomes represent a versatile drug formulation approach e.g. for improving the water-solubility of poorly soluble drugs but also to achieve drug targeting and controlled release. For the latter applications it is essential that the drug remains associated with the liposomal carrier during transit in the vascular bed. A range of in vitro test methods has been suggested over the years for prediction of the release of drug from liposomal carriers. The majority of these fail to give a realistic prediction for poorly water-soluble drugs due to the intrinsic tendency of such compounds to remain associated with liposome bilayers even upon extensive dilution. Upon i.v. injection, in contrast, rapid drug loss often occurs due to drug transfer from the liposomal carriers to endogenous lipophilic sinks such as lipoproteins, plasma proteins or membranes of red blood cells and endothelial cells. Here we report on the application of a recently introduced in vitro predictive drug transfer assay based on incubation of the liposomal drug carrier with large multilamellar liposomes, the latter serving as a biomimetic model sink, using flow field-flow fractionation as a tool to separate the two types of liposomes. By quantifying the amount of drug remaining associated with the liposomal drug carrier as well as that transferred to the acceptor liposomes at distinct times of incubation, both the kinetics of drug transfer and release to the water phase could be established for the model drug p-THPP (5,10,15,20-tetrakis(4-hydroxyphenyl)21H,23H-porphine). p-THPP is structurally similar to temoporfin, a photosensitizer which is under clinical evaluation in a liposomal formulation. Mechanistic insights were gained by varying the donor-to-acceptor lipid mass ratio, size and lamellarity of the liposomes. Drug transfer kinetics from one liposome to another was found rate determining as compared to redistribution from the outermost to the inner concentric bilayers, such that the overall process could be adequately described by a single 1st order kinetic model. By varying the donor-to-acceptor lipid mass ratio in the range 1:1 to 1:10, a correlation was established between donor-to-acceptor-lipid mass ratio and transfer kinetics, which is regarded essential for scaling to physiological lipid mass ratios. By applying the assay to a series of structurally related model compounds of different bilayer affinity, transfer and release kinetics were established over the whole expected range of liposome bilayer associated drugs in terms of water solubility and lipophilicity. A very rapid transfer and considerable release from liposomes to the water phase was observed for the more water-soluble compounds Sudan II (clogP 5.45) and Sudan III (clogP 6.83). For the more lipophilic compounds, the rate of transfer from the donor liposomes followed the rank order Sudan IV (fastest)>Oil Red O>Sudan Black>p-THPP (slowest). For an equimolar donor-to-acceptor lipid mass ratio, half-lifes of transfer in the range of 12min (Sudan IV) up to 1.5h (p-THPP) were determined. In essence, the results presented here allow for both, mechanistic insights and predictions of drug loss from liposomal carriers upon exposure to biological sinks, which appear more realistic than the commonly employed in vitro release tests. Copyright © 2016 Elsevier B.V. All rights reserved.

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.

The quantitative impact of the mesopore size on the mass transfer mechanism of the new 1.9μm fully porous Titan-C18 particles. I: analysis of small molecules.

PubMed

Gritti, Fabrice; Guiochon, Georges

2015-03-06

Previous data have shown that could deliver a minimum reduced plate height as small as 1.7. Additionally, the reduction of the mesopore size after C18 derivatization and the subsequent restriction for sample diffusivity across the Titan-C18 particles were found responsible for the unusually small value of the experimental optimum reduced velocity (5 versus 10 for conventional particles) and for the large values of the average reduced solid-liquid mass transfer resistance coefficients (0.032 versus 0.016) measured for a series of seven n-alkanophenones. The improvements in column efficiency made by increasing the average mesopore size of the Titan silica from 80 to 120Å are investigated from a quantitative viewpoint based on the accurate measurements of the reduced coefficients (longitudinal diffusion, trans-particle mass transfer resistance, and eddy diffusion) and of the intra-particle diffusivity, pore, and surface diffusion for the same series of n-alkanophenone compounds. The experimental results reveal an increase (from 0% to 30%) of the longitudinal diffusion coefficients for the same sample concentration distribution (from 0.25 to 4) between the particle volume and the external volume of the column, a 40% increase of the intra-particle diffusivity for the same sample distribution (from 1 to 7) between the particle skeleton volume and the bulk phase, and a 15-30% decrease of the solid-liquid mass transfer coefficient for the n-alkanophenone compounds. Pore and surface diffusion are increased by 60% and 20%, respectively. The eddy dispersion term and the maximum column efficiency (295000plates/m) remain virtually unchanged. The rate of increase of the total plate height with increasing the chromatographic speed is reduced by 20% and it is mostly controlled (75% and 70% for 80 and 120Å pore size) by the flow rate dependence of the eddy dispersion term. Copyright © 2015 Elsevier B.V. All rights reserved.

Nuclear electric power for multimegawatt orbit transfer vehicles

NASA Astrophysics Data System (ADS)

Casagrande, R. D.

Multimegawatt nuclear propulsion is an attractive option for orbit transfer vehicles. The masses of these platforms are expected to exceed the capability of a single launch from Earth necessitating assembly in space in a parking orbit. The OTV would transfer the platform from the parking orbit to the operational orbit and then return for the next mission. Electric propulsion is advantageous because of the high specific impulse achieved by the technology, 1000 to 5000 s and beyond, to reduce the propellant required. Nuclear power is attractive as the power system because of the weight savings over solar systems in the multimegawatt regime, and multimegawatts of power are required. A conceptual diagram is shown of an OTV with a command control module using electric thrusters powered from an SP-100 class nuclear reactor power system.

The calculating study of the moisture transfer influence at the temperature field in a porous wet medium with internal heat sources

NASA Astrophysics Data System (ADS)

Kuzevanov, V. S.; Garyaev, A. B.; Zakozhurnikova, G. S.; Zakozhurnikov, S. S.

2017-11-01

A porous wet medium with solid and gaseous components, with distributed or localized heat sources was considered. The regimes of temperature changes at the heating at various initial material moisture were studied. Mathematical model was developed applied to the investigated wet porous multicomponent medium with internal heat sources, taking into account the transfer of the heat by heat conductivity with variable thermal parameters and porosity, heat transfer by radiation, chemical reactions, drying and moistening of solids, heat and mass transfer of volatile products of chemical reactions by flows filtration, transfer of moisture. The algorithm of numerical calculation and the computer program that implements the proposed mathematical model, allowing to study the dynamics of warming up at a local or distributed heat release, in particular the impact of the transfer of moisture in the medium on the temperature field were created. Graphs of temperature change were obtained at different points of the graphics with different initial moisture. Conclusions about the possible control of the regimes of heating a solid porous body by the initial moisture distribution were made.

Electrochemically controlled iron isotope fractionation

NASA Astrophysics Data System (ADS)

Black, Jay R.; Young, Edward D.; Kavner, Abby

2010-02-01

Variations in the stable isotope abundances of transition metals have been observed in the geologic record and trying to understand and reconstruct the physical/environmental conditions that produced these signatures is an area of active research. It is clear that changes in oxidation state lead to large fractionations of the stable isotopes of many transition metals such as iron, suggesting that transition metal stable isotope signatures could be used as a paleo-redox proxy. However, the factors contributing to these observed stable isotope variations are poorly understood. Here we investigate how the kinetics of iron redox electrochemistry generates isotope fractionation. Through a combination of electrodeposition experiments and modeling of electrochemical processes including mass-transport, we show that electron transfer reactions are the cause of a large isotope separation, while mass transport-limited supply of reactant to the electrode attenuates the observed isotopic fractionation. Furthermore, the stable isotope composition of electroplated transition metals can be tuned in the laboratory by controlling parameters such as solution chemistry, reaction overpotential, and solution convection. These methods are potentially useful for generating isotopically-marked metal surfaces for tracking and forensic purposes. In addition, our studies will help interpret stable isotope data in terms of identifying underlying electron transfer processes in laboratory and natural samples.

An investigation on near wall transport characteristics in an adiabatic upward gas-liquid two-phase slug flow

NASA Astrophysics Data System (ADS)

Zheng, Donghong; Che, Defu

2007-08-01

The near-wall transport characteristics, inclusive of mass transfer coefficient and wall shear stress, which have a great effect on gas-liquid two-phase flow induced internal corrosion of low alloy pipelines in vertical upward oil and gas mixing transport, have been both mechanistically and experimentally investigated in this paper. Based on the analyses on the hydrodynamic characteristics of an upward slug unit, the mass transfer in the near wall can be divided into four zones, Taylor bubble nose zone, falling liquid film zone, Taylor bubble wake zone and the remaining liquid slug zone; the wall shear stress can be divided into two zones, the positive wall shear stress zone associated with the falling liquid film and the negative wall shear stress zone associated with the liquid slug. Based on the conventional mass transfer and wall shear stress characteristics formulas of single phase liquid full-pipe turbulent flow, corrected normalized mass transfer coefficient formula and wall shear stress formula are proposed. The calculated results are in good agreement with the experimental data. The shear stress and the mass transfer coefficient in the near wall zone are increased with the increase of superficial gas velocity and decreased with the increase of superficial liquid velocity. The mass transfer coefficients in the falling liquid film zone and the wake zone of leading Taylor bubble are lager than those in the Taylor bubble nose zone and the remaining liquid slug zone, and the wall shear stress associated falling liquid film is larger than that associated the liquid slug. The mass transfer coefficient is within 10-3 m/s, and the wall shear stress below 103 Pa. It can be concluded that the alternate wall shear stress due to upward gas-liquid slug flow is considered to be the major cause of the corrosion production film fatigue cracking.

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 increases from 298.7 to 323.15 K.

On-line monitoring of volatile organic compounds at pptv levels by means of proton-transfer-reaction mass spectrometry (PTR-MS) medical applications, food control and environmental research

NASA Astrophysics Data System (ADS)

Lindinger, W.; Hansel, A.; Jordan, A.

1998-02-01

A proton transfer reaction mass spectrometer (PTR-MS) system has been developed which allows for on-line measurements of trace components with concentrations as low as a few pptv. The method is based on reactions of H3O+ ions, which perform non-dissociative proton transfer to most of the common volatile organic compounds (VOCs) but do not react with any of the components present in clean air. Medical applications by means of breath analysis allow for monitoring of metabolic processes in the human body, and examples of food research are discussed on the basis of VOC emissions from fruit, coffee and meat. Environmental applications include investigations of VOC emissions from decaying biomatter which have been found to be an important source for tropospheric acetone, methanol and ethanol. On-line monitoring of the diurnal variations of VOCs in the troposphere yield data demonstrating the present sensitivity of PTR-MS to be in the range of a few pptv. Finally, PTR-MS has proven to be an ideal tool to measure Henry's law constants and their dependencies on temperature as well as on the salt content of water.

EFFECTS OF MOVEABLE PLATFORM TRAINING IN PREVENTING SLIP-INDUCED FALLS IN OLDER ADULTS

PubMed Central

Parijat, Prakriti; Lockhart, Thurmon E

2011-01-01

Identifying effective interventions is vitalin preventing slip-induced fall accidents in older adults. The purpose of the current study was to evaluate the efficacy of moveable platform training in improving recovery reactions and reducing fall frequency in older adults. Twenty-four older adults were recruited and randomly assigned to two groups (training and control). Both groups underwent three sessions including baseline slip, training, and transfer of training on a slippery surface. Both groups experienced two slips on a slippery surface, one during the baseline and the other (after two weeks) during the transfer of training session. In the training session, the training group underwent twelve simulated slips using a moveable platform while the control group performed normal walking trials. Kinematic, kinetic, and EMG data were collected during all the sessions. Results indicated a reduced incidence of falls in the training group during the transfer of training trial as compared to the control group. The training group was able to transfer proactive and reactive control strategies learned during training to the second slip trial. The proactive adjustments include increased center-of-mass velocity and transitional acceleration after training. Reactive adjustments include reduction in muscle onset and time to peak activations of knee flexors and ankle plantarflexors, reduced ankle and knee coactivation, reduced slip displacement, and reduced time to peak knee flexion, trunk flexion, and hip flexion velocities. In general, the results indicated a beneficial effect of perturbation training in reducing slip severity and recovery kinematics in healthy older adults. PMID:22134467

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.

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 microalgal growth with small bubbles in a raceway pond with swing gas aerators.

PubMed

Yang, Zongbo; Cheng, Jun; Liu, Jianzhong; Zhou, Junhu; Cen, Kefa

2016-09-01

A novel swing gas aerator was developed to generate small bubbles for improving the mass transfer coefficient and microalgal growth rate in a raceway pond. A high-speed photography system (HSP) was used to measure the bubble diameter and generation time, and online precise dissolved oxygen probes and pH probes were used to measure the mass transfer coefficient and mixing time. Bubble generation time and diameter decreased by 21% and 9%, respectively, when rubber gas aerators were swung in the microalgae solution. When water pump power and gas aeration rate increased in a raceway pond with swing gas aerators and oscillating baffles (SGAOB), bubble generation time and diameter decreased but solution velocity and mass transfer coefficient increased. The mass transfer coefficient increased by 25% and the solution velocity increased by 11% when SGAOB was used, and the microalgal biomass yield increased by 18%. Copyright © 2016 Elsevier Ltd. All rights reserved.

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.

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.

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.

Trophic Transfer of Arsenic from an Aquatic Insect to Terrestrial Insect Predators.

PubMed

Mogren, Christina L; Walton, William E; Parker, David R; Trumble, John T

2013-01-01

The movement of energy and nutrients from aquatic to terrestrial ecosystems can be substantial, and emergent aquatic insects can serve as biovectors not only for nutrients, but also for contaminants present in the aquatic environment. The terrestrial predators Tenodera aridifolia sinensis (Mantodea: Mantidae) and Tidarren haemorrhoidale (Araneae: Theridiidae) and the aquatic predator Buenoa scimitra (Hemiptera: Notonectidae) were chosen to evaluate the efficacy of arsenic transfer between aquatic and terrestrial environments. Culex tarsalis larvae were reared in either control water or water containing 1000 µg l(-1) arsenic. Adults that emerged from the control and arsenic treatments were fed to the terrestrial predators, and fourth instar larvae were fed to the aquatic predator reared in control or arsenic contaminated water. Tenodera a. sinensis fed arsenic-treated Cx. tarsalis accumulated 658±130 ng g(-1) of arsenic. There was no significant difference between control and arsenic-fed T. haemorrhoidale (range 142-290 ng g(-1)). Buenoa scimitra accumulated 5120±406 ng g(-1) of arsenic when exposed to arsenic-fed Cx. tarsalis and reared in water containing 1000 µg l(-1) arsenic. There was no significant difference between controls or arsenic-fed B. scimitra that were not exposed to water-borne arsenic, indicating that for this species environmental exposure was more important in accumulation than strictly dietary arsenic. These results indicate that transfer to terrestrial predators may play an important role in arsenic cycling, which would be particularly true during periods of mass emergence of potential insect biovectors. Trophic transfer within the aquatic environment may still occur with secondary predation, or in predators with different feeding strategies.

Modeling pH-zone refining countercurrent chromatography: a dynamic approach.

PubMed

Kotland, Alexis; Chollet, Sébastien; Autret, Jean-Marie; Diard, Catherine; Marchal, Luc; Renault, Jean-Hugues

2015-04-24

A model based on mass transfer resistances and acid-base equilibriums at the liquid-liquid interface was developed for the pH-zone refining mode when it is used in countercurrent chromatography (CCC). The binary separation of catharanthine and vindoline, two alkaloids used as starting material for the semi-synthesis of chemotherapy drugs, was chosen for the model validation. Toluene/CH3CN/water (4/1/5, v/v/v) was selected as biphasic solvent system. First, hydrodynamics and mass transfer were studied by using chemical tracers. Trypan blue only present in the aqueous phase allowed the determination of the parameters τextra and Pe for hydrodynamic characterization whereas acetone, which partitioned between the two phases, allowed the determination of the transfer parameter k0a. It was shown that mass transfer was improved by increasing both flow rate and rotational speed, which is consistent with the observed mobile phase dispersion. Then, the different transfer parameters of the model (i.e. the local transfer coefficient for the different species involved in the process) were determined by fitting experimental concentration profiles. The model accurately predicted both equilibrium and dynamics factors (i.e. local mass transfer coefficients and acid-base equilibrium constant) variation with the CCC operating conditions (cell number, flow rate, rotational speed and thus stationary phase retention). The initial hypotheses (the acid-base reactions occurs instantaneously at the interface and the process is mainly governed by mass transfer) are thus validated. Finally, the model was used as a tool for catharanthine and vindoline separation prediction in the whole experimental domain that corresponded to a flow rate between 20 and 60 mL/min and rotational speeds from 900 and 2100 rotation per minutes. Copyright © 2015 Elsevier B.V. All rights reserved.

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 misalignments. Sufficiently high injection rates alter the structure of the secondary flows and significantly improve the cooling performance.

Demonstration of Single Axis Combined Attitude Control and Energy Storage Using Two Flywheels

NASA Technical Reports Server (NTRS)

Kenny, Barbara H.; Jansen, Ralph; Kascak, Peter; Dever, Timothy; Santiago, Walter

2004-01-01

The energy storage and attitude control subsystems of the typical satellite are presently distinct and separate. Energy storage is conventionally provided by batteries, either NiCd or NiH, and active attitude control is accomplished with control moment gyros (CMGs) or reaction wheels. An overall system mass savings can be realized if these two subsystems are combined using multiple flywheels for simultaneous kinetic energy storage and momentum transfer. Several authors have studied the control of the flywheels to accomplish this and have published simulation results showing the feasibility and performance. This paper presents the first experimental results showing combined energy storage and momentum control about a single axis using two flywheels.

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.

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

Visualization of natural convection heat transfer on a sphere

NASA Astrophysics Data System (ADS)

Lee, Dong-Young; Chung, Bum-Jin

2017-12-01

Natural convection heat transfer phenomena on spheres were investigated by adopting mass transfer experiments based on analogy concept. The diameters of spheres were varied from 0.01 m to 0.12 m, which correspond to the Rayleigh numbers of 1.69×108-2.91×1011. The measured mass transfer coefficients agreed well with the existing correlations. The copper electroplating patterns on the spheres visualized the local heat transfer depending on angular distance. The streak plating patterns were observed on the upper part of the sphere, resulting from the wavy flow patterns caused by the instability.

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.

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 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.

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.

Applications of a new mass-driver concept

NASA Technical Reports Server (NTRS)

Oneill, G. K.

1981-01-01

A description of the operating principles and requirements of a novel mass-driver concept is presented. The design obtains acceleration of payload bucket coils by means of transverse focussing from strong, off-axis restoring forces that are produced by drive coils operating in a 'pull-only' mode. The concept offers the unprecedented possibility of operating high-performance mass-drivers entirely within the limitations of existing commercial switching devices, such as silicon-controlled rectifiers, spark gaps, vacuum-triggered arcs or vacuum mechanical switches. Representative applications of the concept described are: (1) a large-diameter magnetic lunar launcher for payloads having autonomous maneuvering; (2) an intermediate-diameter launcher with long operational life; and (3) a reaction engine for orbit transfer of large, massive objects.

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.

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.

Energy transfer and energy absorption in photon interactions with matter revisited: A step-by-step illustrated approach

NASA Astrophysics Data System (ADS)

Abdel-Rahman, W.; Podgorsak, E. B.

2010-05-01

A clear understanding of energy transfer and energy absorption in photon interactions with matter is essential for the understanding of radiation dosimetry and development of new dosimetry techniques. The concepts behind the two quantities have been enunciated many years ago and described in many scientific papers, review articles, and textbooks. Data dealing with energy transfer and energy absorption as well as the associated mass energy transfer coefficient and the mass energy absorption coefficient are readily available in web-based tabular forms. However, tables, even when available in detailed and easy to access form, do not lend themselves to serve as visual aid to promote better understanding of the dosimetric quantities related to energy transfer and energy absorption as well as their relationship to the photon energy and absorber atomic number. This paper uses graphs and illustrations, in addition to well-known mathematical relationships, to guide the reader in a systematic manner through the various stages involved in the derivation of energy absorbed in medium and its associated quantity, the mass energy absorption coefficient, from the mass attenuation coefficient.

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.

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…

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 particles much smaller than the sound wavelength. Good agreement between experiment and the theory of Yarin et al. is demonstrated. The time-averaged heat and mass transfer rates over a sphere surface are greatest at the sphere's equator and least at its poles in the experiment as predicted by the theory (the ultrasonic standing wave spans the vertical axis passing through the poles). The measured distribution of the mass transfer rate over the sphere surface also agrees with the theoretical predictions, which shows that in strong acoustic fields sublimation (or evaporation) results from the acoustic streaming.

Coordinative structuring of gait kinematics during adaptation to variable and asymmetric split-belt treadmill walking - A principal component analysis approach.

PubMed

Hinkel-Lipsker, Jacob W; Hahn, Michael E

2018-06-01

Gait adaptation is a task that requires fine-tuned coordination of all degrees of freedom in the lower limbs by the central nervous system. However, when individuals change their gait it is unknown how this coordination is organized, and how it can be influenced by contextual interference during practice. Such knowledge could provide information about measurement of gait adaptation during rehabilitation. Able-bodied individuals completed an acute bout of asymmetric split-belt treadmill walking, where one limb was driven at a constant velocity and the other according to one of three designed practice paradigms: serial practice, where the variable limb belt velocity increased over time; random blocked practice, where every 20 strides the variable limb belt velocity changed randomly; random practice, where every stride the variable limb belt velocity changed randomly. On the second day, subjects completed one of two different transfer tests; one with a belt asymmetry close to that experienced on the acquisition day (transfer 1; 1.5:1), and one with a greater asymmetry (transfer 2; 2:1) . To reduce this inherently high-dimensional dataset, principal component analyses were used for kinematic data collected throughout the acquisition and transfer phases; resulting in extraction of the first two principal components (PCs). For acquisition, PC1 and PC2 were related to sagittal and frontal plane control. For transfer 1, PC1 and PC2 were related to frontal plane control of the base of support and whole-body center of mass. For transfer 2, PC1 did not have any variables with high enough coefficients deemed to be relevant, and PC2 was related to sagittal plane control. Observations of principal component scores indicate that variance structuring differs among practice groups during acquisition and transfer 1, but not transfer 2. These results demonstrate the main kinematic coordinative structures that exist during gait adaptation, and that control of sagittal plane and frontal plane motion are perhaps a trade-off during acquisition of a novel asymmetric gait pattern. Copyright © 2018 Elsevier B.V. All rights reserved.

The chemical evolution of a travertine-depositing stream: Geochemical processes and mass transfer reactions

USGS Publications Warehouse

Lorah, Michelle M.; Herman, Janet S.

1988-01-01

This field study focuses on quantitatively defining the chemical changes occurring in Falling Spring Creek, a travertine-depositing stream located in Alleghany County, Virginia. The processes of CO2outgassing and calcite precipitation or dissolution control the chemical evolution of the stream. The observed chemical composition of the water was used with the computerized geochemical model WATEQF to calculate aqueous speciation, saturation indices, and CO2 partial pressure values. Mass balance calculations were performed to obtain mass transfers of CO2 and calcite. Reaction times, estimated from stream discharge, were used with the mass transfer results to calculate rates of CO2, outgassing and calcite precipitation between consecutive sampling points. The stream, which is fed by a carbonate spring, is supersaturated with respect to CO2 along the entire 5.2-km flow path. Outgassing of CO2 drives the solution to high degrees of supersaturation with respect to calcite. Metabolic uptake of CO2 by photosynthetic plants is insignificant, because the high supply rate of dissolved carbon dioxide and the extreme agitation of the stream at waterfalls and rapids causes a much greater amount of inorganic CO2 outgassing to occur. Calcite precipitation is kinetically inhibited until near the crest of a 20-m vertical waterfall. Calcite precipitation rates then reach a maximum at the waterfall where greater water turbulence allows the most rapid escape of CO2. Physical evidence for calcite precipitation exists in the travertine deposits which are first observed immediately above the waterfall and extend for at least 1.0 km below the falls. Net calcite precipitation occurs at all times of the year but is greatest during low-flow conditions in the summer and early fall.

Effects of high-pressure process on kinetics of leaching oil from soybean powder using hexane in batch systems.

PubMed

Uhm, Joo Tae; Yoon, Won Byong

2011-08-01

Mass transfer models of leaching oil from soybean (Glycine max) flour with hexane after high-pressure process (HPP) treatment were developed. High pressure (450 MPa) was applied to the soybean flour (mean diameter of flour particle: 365 μm) for 30 min before leaching the oil components in the solvent. The ratio of solvent (volume, mL) to soybean flour (mass, g), such as 1:10 and 1:20, was employed to characterize the effect of solvent ratio on the leaching rate in the batch type of extraction process. Ultraviolet absorbance at 300 nm was used to monitor the extraction rate. Saturation solubility (C(AS)) was determined to be 21.73 kg/m³. The mass transfer coefficients (k) were determined based on the 1st- and 2nd-order kinetic models. The 2nd kinetic model showed better fit. The HPP treatment showed a higher extraction rate and yield compared to the control, while the amount of solvent did not affect the extraction rate and yield. The scanning electron microscope showed that HPP-treated soybean particles included more pores than the untreated. The pores observed in the HPP-treated soybean flours might help increase the mass transfer rate of solvent and solute in the solid matrix. High-pressure processing can help increase the extraction rate of oil from the soybean flour operated in batch systems. The conventional solid to solvent ratio (1:20) used to extract oil composition from the plant seed did not help increase the amount of oil extracted from the soybean flour. © 2011 Institute of Food Technologists®

An overview of challenges in modeling heat and mass transfer for living on Mars.

PubMed

Yamashita, Masamichi; Ishikawa, Yoji; Kitaya, Yoshiaki; Goto, Eiji; Arai, Mayumi; Hashimoto, Hirofumi; Tomita-Yokotani, Kaori; Hirafuji, Masayuki; Omori, Katsunori; Shiraishi, Atsushi; Tani, Akira; Toki, Kyoichiro; Yokota, Hiroki; Fujita, Osamu

2006-09-01

Engineering a life-support system for living on Mars requires the modeling of heat and mass transfer. This report describes the analysis of heat and mass transfer phenomena in a greenhouse dome, which is being designed as a pressurized life-support system for agricultural production on Mars. In this Martian greenhouse, solar energy will be converted into chemical energy in plant biomass. Agricultural products will be harvested for food and plant cultivation, and waste materials will be processed in a composting microbial ecosystem. Transpired water from plants will be condensed and recycled. In our thermal design and analysis for the Martian greenhouse, we addressed the question of whether temperature and pressure would be maintained in the appropriate range for humans as well as plants. Energy flow and material circulation should be controlled to provide an artificial ecological system on Mars. In our analysis, we assumed that the greenhouse would be maintained at a subatmospheric pressure under 1/3-G gravitational force with 1/2 solar light intensity on Earth. Convection of atmospheric gases will be induced inside the greenhouse, primarily by heating from sunlight. Microclimate (thermal and gas species structure) could be generated locally around plant bodies, which would affect gas transport. Potential effects of those environmental factors are discussed on the phenomena including plant growth and plant physiology and focusing on transport processes. Fire safety is a crucial issue and we evaluate its impact on the total gas pressure in the greenhouse dome.

Determination of pollutant diffusion coefficients in naturally formed biofilms using a single tube extractive membrane bioreactor

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

Zhang, S.F.; Splendiani, A.; Freitas dos Santos, L.M.

A novel technique has been used to determine the effective diffusion coefficients for 1,1,2-trichloroethane (TCE), a nonreacting tracer, in biofilms growing on the external surface of a silicone rubber membrane tube during degradation of 1,2-dichloroethane (DCE) by Xanthobacter autotrophicus GJ10 and monochlorobenzene (MCB) by Pseudomonas JS150. Experiments were carried out in a single tube extractive membrane bioreactor (STEMB), whose configuration makes it possible to measure the transmembrane flux of substrates. A video imaging technique (VIT) was employed for in situ biofilm thickness measurement and recording. Diffusion coefficients of TCE in the biofilms and TCE mass transfer coefficients in the liquidmore » films adjacent to the biofilms were determined simultaneously using a resistances-in-series diffusion model. It was found that the flux and overall mass transfer coefficient of TCE decrease with increasing biofilm thickness, showing the importance of biofilm diffusion on the mass transfer process. Similar fluxes were observed for the nonreacting tracer (TCE) and the reactive substrates (MCB or DCE), suggesting that membrane-attached biofilm systems can be rate controlled primarily by substrate diffusion. The TCE diffusion coefficient in the JS150 biofilm appeared to be dependent on biofilm thickness, decreasing markedly for biofilm thicknesses of >1 mm. The values of the TCE diffusion coefficients in the JS150 biofilms <1-mm thick are approximately twice those in water and fall to around 30% of the water value for biofilms >1-mm thick.« less

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.

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.

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.

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.

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.

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.

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.

JPRS report: Science and technology. Central Eurasia

NASA Astrophysics Data System (ADS)

1995-02-01

Translated articles cover the following topics: laser-controlled rotary microwave waveguide junction; optical pulse-phase modulation of semiconductor laser; amplitude-phase distortions of light beam obliquely propagating through ground layer of troposphere; antenna arrays with ultrafast beam scanning; materials for a walk on moon; textile-wood-coal briquette path to capitalism; and development of automated system for scientific research and design of heat and mass transfer processes.

THE QUASI-ROCHE LOBE OVERFLOW STATE IN THE EVOLUTION OF CLOSE BINARY SYSTEMS CONTAINING A RADIO PULSAR

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

Benvenuto, O. G.; De Vito, M. A.; Horvath, J. E., E-mail: adevito@fcaglp.unlp.edu.ar, E-mail: foton@iag.usp.br

We study the evolution of close binary systems formed by a normal (solar composition), intermediate-mass-donor star together with a neutron star. We consider models including irradiation feedback and evaporation. These nonstandard ingredients deeply modify the mass-transfer stages of these binaries. While models that neglect irradiation feedback undergo continuous, long-standing mass-transfer episodes, models including these effects suffer a number of cycles of mass transfer and detachment. During mass transfer, the systems should reveal themselves as low-mass X-ray binaries (LMXBs), whereas when they are detached they behave as binary radio pulsars. We show that at these stages irradiated models are in amore » Roche lobe overflow (RLOF) state or in a quasi-RLOF state. Quasi-RLOF stars have radii slightly smaller than their Roche lobes. Remarkably, these conditions are attained for an orbital period as well as donor mass values in the range corresponding to a family of binary radio pulsars known as ''redbacks''. Thus, redback companions should be quasi-RLOF stars. We show that the characteristics of the redback system PSR J1723-2837 are accounted for by these models. In each mass-transfer cycle these systems should switch from LMXB to binary radio pulsar states with a timescale of approximately one million years. However, there is recent and fast growing evidence of systems switching on far shorter, human timescales. This should be related to instabilities in the accretion disk surrounding the neutron star and/or radio ejection, still to be included in the model having the quasi-RLOF state as a general condition.« less

Fission of actinide nuclei using multi-nucleon transfer reactions

NASA Astrophysics Data System (ADS)

Léguillon, Romain; Nishio, Katsuhisa; Hirose, Kentaro; Orlandi, Riccardo; Makii, Hiroyuki; Nishinaka, Ichiro; Ishii, Tetsuro; Tsukada, Kazuaki; Asai, Masato; Chiba, Satoshi; Ohtsuki, Tsutomu; Araki, Shohei; Watanabe, Yukinobu; Tatsuzawa, Ryotaro; Takaki, Naoyuki

2014-09-01

We are promoting a campaign to measure fission-fragment mass distributions for neutron-rich actinide nuclei populated by transfer reactions from their ground state up to an excitation energy of several tens MeV. We thus obtain the excitation energy dependence of the mass distribution. The experiment was carried out at the 20 MV JAEA tandem facility at Tokai. We report on the data obtained in the direct reaction 18 O + 232 Th . Transfer-channels and excitation energies of the fissioning nuclei were identified using silicon dE-E detectors located at forward angle. Two fission fragments were detected in coincidence using multi-wire proportional counters. Fission fragment masses were determined by kinematic consideration. We obtained the fission fragment mass distributions for 13 nuclei from actinium to uranium and some fission barrier heights. We are promoting a campaign to measure fission-fragment mass distributions for neutron-rich actinide nuclei populated by transfer reactions from their ground state up to an excitation energy of several tens MeV. We thus obtain the excitation energy dependence of the mass distribution. The experiment was carried out at the 20 MV JAEA tandem facility at Tokai. We report on the data obtained in the direct reaction 18 O + 232 Th . Transfer-channels and excitation energies of the fissioning nuclei were identified using silicon dE-E detectors located at forward angle. Two fission fragments were detected in coincidence using multi-wire proportional counters. Fission fragment masses were determined by kinematic consideration. We obtained the fission fragment mass distributions for 13 nuclei from actinium to uranium and some fission barrier heights. Present study is supported by the Ministry of Education, Culture, Sports, Science and Technology of Japan.

Carbon bed mercury emissions control for mixed waste treatment.

PubMed

Soelberg, Nick; Enneking, Joe

2010-11-01

Mercury has various uses in nuclear fuel reprocessing and other nuclear processes, and so it is often present in radioactive and mixed (radioactive and hazardous) wastes. Compliance with air emission regulations such as the Hazardous Waste Combustor (HWC) Maximum Achievable Control Technology (MACT) standards can require off-gas mercury removal efficiencies up to 99.999% for thermally treating some mixed waste streams. Test programs have demonstrated this level of off-gas mercury control using fixed beds of granular sulfur-impregnated activated carbon. Other results of these tests include (1) the depth of the mercury control mass transfer zone was less than 15-30 cm for the operating conditions of these tests; (2) MERSORB carbon can sorb mercury up to 19 wt % of the carbon mass; and (3) the spent carbon retained almost all (98.3-99.99%) of the mercury during Toxicity Characteristic Leachability Procedure (TCLP) tests, but when even a small fraction of the total mercury dissolves, the spent carbon can fail the TCLP test when the spent carbon contains high mercury concentrations.

Post-Dryout Heat Transfer to a Refrigerant Flowing in Horizontal Evaporator Tubes

NASA Astrophysics Data System (ADS)

Mori, Hideo; Yoshida, Suguru; Kakimoto, Yasushi; Ohishi, Katsumi; Fukuda, Kenichi

Studies of the post-dryout heat transfer were made based on the experimental data for HFC-134a flowing in horizontal smooth and spiral1y grooved (micro-fin) tubes and the characteristics of the post-dryout heat transfer were c1arified. The heat transfer coefficient at medium and high mass flow rates in the smooth tube was lower than the single-phase heat transfer coefficient of the superheated vapor flow, of which mass flow rate was given on the assumption that the flow was in a thermodynamic equilibrium. A prediction method of post-dryout heat transfer coefficient was developed to reproduce the measurement satisfactorily for the smooth tube. The post dryout heat transfer in the micro-fin tube can be regarded approximately as a superheated vapor single-phase heat transfer.

Experimental evaluation of a neural-oscillator-driven active mass damper system

NASA Astrophysics Data System (ADS)

Iba, Daisuke; Hongu, Junichi

2014-03-01

This paper proposes a new active dynamic absorber control system for high-rise buildings using a neural oscillator and a map, which estimates the amplitude level of the oscillator, and shows some experimental results by using an apparatus, which realizes the proposed control algorithm. The proposed system decides the travel distance and direction of the auxiliary mass of the dynamic absorber using the output of oscillator, which is the filtering result of structure acceleration responses by the property of the oscillator, and Amplitude-Phase map (AP-map) for estimation of the structural response in specific frequency between synchronization region, and then, transfer the auxiliary mass to the predetermined location by using a position controller. In addition, the developed active dynamic absorber system is mounted on the top of the experimental single degree of freedom structure, which represents high-rise buildings, and consists of the auxiliary mass, a DC motor, a ball screw, a microcomputer, a laser displacement sensor, and an acceleration sensor. The proposed AP-map and the algorithm to determine the travel direction of the mass using the oscillator output are embedded in the microcomputer. This paper starts by illuminating the relation among subsystems of the proposed system with reference to a block diagram, and then, shows experimental responses of the whole system excited by earthquakes to confirm the validity of the proposed system.

Vitrified-warmed embryo transfer is associated with mean higher singleton birth weight compared to fresh embryo transfer.

PubMed

Beyer, Daniel Alexander; Griesinger, Georg

2016-08-01

To test for differences in birth weight between singletons born after IVF with fresh embryo transfer vs. vitrified-warmed 2PN embryo transfer (vitrification protocol). Retrospective analysis of 464 singleton live births after IVF or ICSI during a 12 year period. University hospital. Fresh embryo transfer, vitrified-warmed 2PN embryo transfer (vitrification protocol). Birth weight standardized as a z-score, adjusting for gestational week at delivery and fetal sex. As a reference, birth weight means from regular deliveries from the same hospital were used. Multivariate regression analysis was used to investigate the relationship between the dependent variable z-score (fetal birth weight) and the independent predictor variables maternal age, weight, height, body mass index, RDS prophylaxis, transfer protocol, number of embryos transferred, indication for IVF treatment and sperm quality. The mean z-score was significantly lower after fresh transfer (-0.11±92) as compared to vitrification transfer (0.72±83) (p<0.001). Multivariate regression analysis indicated that only maternal height and maternal body mass index, but not type of cryopreservation protocol, was a significant predictor of birth weight. In this analysis focusing on 2PN oocytes, vitrified-warmed embryo transfer is associated with mean higher birth weight compared to fresh embryo transfer. Maternal height and body mass index are significant confounders of fetal birth weight and need to be taken into account when studying birth weight differences between ART protocols. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.

Steady boundary layer slip flow along with heat and mass transfer over a flat porous plate embedded in a porous medium.

PubMed

Aziz, Asim; Siddique, J I; Aziz, Taha

2014-01-01

In this paper, a simplified model of an incompressible fluid flow along with heat and mass transfer past a porous flat plate embedded in a Darcy type porous medium is investigated. The velocity, thermal and mass slip conditions are utilized that has not been discussed in the literature before. The similarity transformations are used to transform the governing partial differential equations (PDEs) into a nonlinear ordinary differential equations (ODEs). The resulting system of ODEs is then reduced to a system of first order differential equations which was solved numerically by using Matlab bvp4c code. The effects of permeability, suction/injection parameter, velocity parameter and slip parameter on the structure of velocity, temperature and mass transfer rates are examined with the aid of several graphs. Moreover, observations based on Schmidt number and Soret number are also presented. The result shows, the increase in permeability of the porous medium increase the velocity and decrease the temperature profile. This happens due to a decrease in drag of the fluid flow. In the case of heat transfer, the increase in permeability and slip parameter causes an increase in heat transfer. However for the case of increase in thermal slip parameter there is a decrease in heat transfer. An increase in the mass slip parameter causes a decrease in the concentration field. The suction and injection parameter has similar effect on concentration profile as for the case of velocity profile.

Steady Boundary Layer Slip Flow along with Heat and Mass Transfer over a Flat Porous Plate Embedded in a Porous Medium

PubMed Central

Aziz, Asim; Siddique, J. I.; Aziz, Taha

2014-01-01

In this paper, a simplified model of an incompressible fluid flow along with heat and mass transfer past a porous flat plate embedded in a Darcy type porous medium is investigated. The velocity, thermal and mass slip conditions are utilized that has not been discussed in the literature before. The similarity transformations are used to transform the governing partial differential equations (PDEs) into a nonlinear ordinary differential equations (ODEs). The resulting system of ODEs is then reduced to a system of first order differential equations which was solved numerically by using Matlab bvp4c code. The effects of permeability, suction/injection parameter, velocity parameter and slip parameter on the structure of velocity, temperature and mass transfer rates are examined with the aid of several graphs. Moreover, observations based on Schmidt number and Soret number are also presented. The result shows, the increase in permeability of the porous medium increase the velocity and decrease the temperature profile. This happens due to a decrease in drag of the fluid flow. In the case of heat transfer, the increase in permeability and slip parameter causes an increase in heat transfer. However for the case of increase in thermal slip parameter there is a decrease in heat transfer. An increase in the mass slip parameter causes a decrease in the concentration field. The suction and injection parameter has similar effect on concentration profile as for the case of velocity profile. PMID:25531301

In situ magnetic resonance measurement of conversion, hydrodynamics and mass transfer during single- and two-phase flow in fixed-bed reactors.

PubMed

Gladden, L F; Alexander, P; Britton, M M; Mantle, M D; Sederman, A J; Yuen, E H L

2003-01-01

In recent years there has been increasing interest in applying magnetic resonance (MR) techniques in areas of engineering and chemical technology. The science that underpins many of these applications is the physics and chemistry of transport and reaction processes in porous materials. Key to the exploitation of MR methods will be our ability to demonstrate that MR yields information that cannot be obtained using conventional measurement techniques in engineering research. This article describes two case studies that highlight the power of MR to give new insights to chemical engineers. First, we demonstrate the application of MR techniques to explore both mass transfer and chemical conversion in situ within a fixed bed of catalyst, and we then use these data to identify the rate-controlling step of the chemical conversion. Second, we implement a rapid imaging technique to study the stability of the gas-liquid distribution in the low- and high-interaction two-phase flow regimes in a trickle-bed reactor.

Incorporating both physical and kinetic limitations in quantifying dissolved oxygen flux to aquatic sediments

USGS Publications Warehouse

O'Connor, B.L.; Hondzo, Miki; Harvey, J.W.

2009-01-01

Traditionally, dissolved oxygen (DO) fluxes have been calculated using the thin-film theory with DO microstructure data in systems characterized by fine sediments and low velocities. However, recent experimental evidence of fluctuating DO concentrations near the sediment-water interface suggests that turbulence and coherent motions control the mass transfer, and the surface renewal theory gives a more mechanistic model for quantifying fluxes. Both models involve quantifying the mass transfer coefficient (k) and the relevant concentration difference (??C). This study compared several empirical models for quantifying k based on both thin-film and surface renewal theories, as well as presents a new method for quantifying ??C (dynamic approach) that is consistent with the observed DO concentration fluctuations near the interface. Data were used from a series of flume experiments that includes both physical and kinetic uptake limitations of the flux. Results indicated that methods for quantifying k and ??C using the surface renewal theory better estimated the DO flux across a range of fluid-flow conditions. ?? 2009 ASCE.

Field data and numerical simulation of btex concentration trends under water table fluctuations: Example of a jet fuel-contaminated site in Brazil.

PubMed

Teramoto, Elias Hideo; Chang, Hung Kiang

2017-03-01

Mass transfer of light non-aqueous phase liquids (LNAPLs) trapped in porous media is a complex phenomenon. Water table fluctuations have been identified as responsible for generating significant variations in the concentration of dissolved hydrocarbons. Based on field evidence, this work presents a conceptual model and a numerical solution for mass transfer from entrapped LNAPL to groundwater controlled by both LNAPL saturation and seasonal water table fluctuations within the LNAPL smear zone. The numerical approach is capable of reproducing aqueous BTEX concentration trends under three different scenarios - water table fluctuating within smear zone, above the smear zone and partially within smear zone, resulting in in-phase, out-of-phase and alternating in-phase and out-of-phase BTEX concentration trend with respect to water table oscillation, respectively. The results demonstrate the model's applicability under observed field conditions and its ability to predict source zone depletion. Copyright © 2017 Elsevier B.V. All rights reserved.

Rejuvenation of Spent Media via Supported Emulsion Liquid Membranes

NASA Technical Reports Server (NTRS)

Wiencek, John M.

2002-01-01

The overall goal of this project is to maximize the reuseability of spent fermentation media. Supported emulsion liquid membrane separation, a highly efficient extraction technique, is used to remove inhibitory byproducts during fermentation; thus, improving the yield while reducing the need for fresh water. The key objectives of this study are: Develop an emulsion liquid membrane system targeting low molecular weight organic acids which has minimal toxicity on a variety of microbial systems; Conduct mass transfer studies to allow proper modeling and design of a supported emulsion liquid membrane system; Investigate the effect of gravity on emulsion coalescence within the membrane unit; Access the effect of water re-use on fermentation yields in a model microbial system; Develop a perfusion-type fermentor utilizing a supported emulsion liquid membrane system to control inhibitory fermentation byproducts; Work for the coming year will focus on the determination of toxicity of various solvents, selection of the emulsifying agents, as well as characterizing the mass transfer of hollow-fiber contactors.

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 this closed chemical system, mass transfer from rock to vein was achieved through the fluid, in a dissolution-transport-precipitation process, possibly stress-assisted. To investigate the modalities of mass transfer towards this second vein type, LIBS profiles were performed in the rock matrix, taking Li concentration as a proxy for cookeite distribution. Cookeite is highly concentrated (40-70 vol%) in regularly spaced veins, and the LIBS profiles show that cookeite is evenly distributed in the rock matrix comprised between two veins. The absence of diffusion profiles suggests that the characteristic diffusion length for Li, Al and Si is greater than or equal to the distance separating two cookeite veins (3-6 cm). This is in agreement with characteristic diffusion lengths calculated from both grain boundary and pore fluid diffusion coefficients, for the estimated duration of the peak of metamorphism. Concerning mass transfer driving forces, phyllosilicates have very different morphologies in the rock matrix (fibers) compared to veins (euhedral crystals): fluid-mineral interfacial energy may be maximal in the small matrix pores, which can maintain higher cookeite solubility than in fluid-filled open spaces. Therefore, as soon as veins open, chemical potential gradients may develop and drive cookeite transfer from rock matrix to veins.

Carbon transfer from magnesia-graphite ladle refractories to ultra-low carbon steel

NASA Astrophysics Data System (ADS)

Russo, Andrew Arthur

Ultra-low carbon steels are utilized in processes which require maximum ductility. Increases in interstitial carbon lower the ductility of steel; therefore, it is important to examine possible sources of carbon. The refractory ladle lining is one such source. Ladle refractories often contain graphite for its desirable thermal shock and slag corrosion resistance. This graphite is a possible source of carbon increase in ultra-low carbon steels. The goal of this research is to understand and evaluate the mechanisms by which carbon transfers to ultra-low carbon steel from magnesia-graphite ladle refractory. Laboratory dip tests were performed in a vacuum induction furnace under an argon atmosphere to investigate these mechanisms. Commercial ladle refractories with carbon contents between 4-12 wt% were used to investigate the effect of refractory carbon content. Slag-free dip tests and slag-containing dip tests with varying MgO concentrations were performed to investigate the influence of slag. Carbon transfer to the steel was controlled by steel penetrating into the refractory and dissolving carbon in dip tests where no slag was present. The rate limiting step for this mechanism is convective mass transport of carbon into the bulk steel. No detectable carbon transfer occurred in dip tests with 4 and 6 wt%C refractories without slag because no significant steel penetration occurred. Carbon transfer was controlled by the corrosion of refractory by slag in dip tests where slag was present.

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.

OVERALL MASS TRANSFER COEFFICIENT FOR POLLUTANT EMISSIONS FROM SMALL WATER POOLS UNDER SIMULATED INDOOR ENVIRONMENTAL CONDITIONS

EPA Science Inventory

Small chamber tests were conducted to experimentally determine the overall mass transfer coefficient for pollutant emissions from still water under simulated indoor-residential or occupational-environmental conditions. Fourteen tests were conducted in small environmental chambers...

Acrylonitrile-Butadiene Rubber (NBR) Prepared via Living/Controlled Radical Polymerization (RAFT).

PubMed

Kaiser, Andreas; Brandau, Sven; Klimpel, Michael; Barner-Kowollik, Christopher

2010-09-15

In the current work we present results on the controlled/living radical copolymerization of acrylonitrile (AN) and 1,3-butadiene (BD) via reversible addition fragmentation chain transfer (RAFT) polymerization techniques. For the first time, a solution polymerization process for the synthesis of nitrile butadiene rubber (NBR) via the use of dithioacetate and trithiocarbonate RAFT agents is described. It is demonstrated that the number average molar mass, $\\overline M _{\\rm n} $, of the NBR can be varied between a few thousand and 60 000 g · mol(-1) with polydispersities between 1.2 and 2.0 (depending on the monomer to polymer conversion). Excellent agreement between the experimentally observed and the theoretically expected molar masses is found. Detailed information on the structure of the synthesized polymers is obtained by variable analytical techniques such as infrared spectroscopy (IR), nuclear magnetic resonance (NMR) spectroscopy, differential scanning calorimetry, and electrospray ionization-mass spectrometry (ESI-MS). Copyright © 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Effective Jet Properties for the Prediction of Turbulent Mixing Noise Reduction by Water Injection

NASA Technical Reports Server (NTRS)

Kandula, Max; Lonergan, Michael J.

2007-01-01

A one-dimensional control volume formulation is developed for the determination of jet mixing noise reduction due to water injection. The analysis starts from the conservation of mass, momentum and energy for the control volume, and introduces the concept of effective jet parameters (jet temperature, jet velocity and jet Mach number). It is shown that the water to jet mass flow rate ratio is an important parameter characterizing the jet noise reduction on account of gas-to-droplet momentum and heat transfer. Two independent dimensionless invariant groups are postulated, and provide the necessary relations for the droplet size and droplet Reynolds number. Results are presented illustrating the effect of mass flow rate ratio on the jet mixing noise reduction for a range of jet Mach number and jet Reynolds number. Predictions from the model show satisfactory comparison with available test data on supersonic jets. The results suggest that significant noise reductions can be achieved at increased flow rate ratios.

Factors affecting the outcome of "endometrial scratch" in women with recurrent implantation failure.

PubMed

Coughlan, Carol; Yuan, Xi; Demirol, Aygul; Ledger, William; Li, Tin Chiu

2014-01-01

To examine factors affecting the outcome of the endometrial scratch in women with recurrent implantation failure. A total of 57 eligible patients with a history of recurrent implantation failure underwent an endometrial biopsy in the luteal phase of the menstrual cycle in the month immediately preceding the embryo transfer cycle. The comparative group consisted of a retrospective cohort of 66 women with recurrent implantation failure but without endometrial biopsy. There were no significant differences between the intervention and control groups in terms of age, follicle-stimulating hormone (FSH), free androgen index, anti-Müllerian hormone, body mass index, the number of embryos transferred, and the number of embryo transfer cycles. The clinical pregnancy rate in the intervention group (53%) was significantly (p < 0.001) higher than that of the control group (15%). The only predictive factor was FSH. Women with FSH < or =10 IU/L had a pregnancy rate of 57.8%, significantly (p < 0.05) higher than that (20%) of women with FSH >10 IU/L. Women with a normal FSH are more likely to derive benefit from endometrial scratch.

Evaporation Kinetics of Polyol Droplets: Determination of Evaporation Coefficients and Diffusion Constants

NASA Astrophysics Data System (ADS)

Su, Yong-Yang; Marsh, Aleksandra; Haddrell, Allen E.; Li, Zhi-Ming; Reid, Jonathan P.

2017-11-01

In order to quantify the kinetics of mass transfer between the gas and condensed phases in aerosol, physicochemical properties of the gas and condensed phases and kinetic parameters (mass/thermal accommodation coefficients) are crucial for estimating mass fluxes over a wide size range from the free molecule to continuum regimes. In this study, we report measurements of the evaporation kinetics of droplets of 1-butanol, ethylene glycol (EG), diethylene glycol (DEG), and glycerol under well-controlled conditions (gas flow rates and temperature) using the previously developed cylindrical electrode electrodynamic balance technique. Measurements are compared with a model that captures the heat and mass transfer occurring at the evaporating droplet surface. The aim of these measurements is to clarify the discrepancy in the reported values of mass accommodation coefficient (αM, equals to evaporation coefficient based on microscopic reversibility) for 1-butanol, EG, and DEG and improve the accuracy of the value of the diffusion coefficient for glycerol in gaseous nitrogen. The uncertainties in the thermophysical and experimental parameters are carefully assessed, the literature values of the vapor pressures of these components are evaluated, and the plausible ranges of the evaporation coefficients for 1-butanol, EG, and DEG as well as uncertainty in diffusion coefficient for glycerol are reported. Results show that αM should be greater than 0.4, 0.2, and 0.4 for EG, DEG, and 1-butanol, respectively. The refined values are helpful for accurate prediction of the evaporation/condensation rates.

Mathematical model of compact type evaporator

NASA Astrophysics Data System (ADS)

Borovička, Martin; Hyhlík, Tomáš

2018-06-01

In this paper, development of the mathematical model for evaporator used in heat pump circuits is covered, with focus on air dehumidification application. Main target of this ad-hoc numerical model is to simulate heat and mass transfer in evaporator for prescribed inlet conditions and different geometrical parameters. Simplified 2D mathematical model is developed in MATLAB SW. Solvers for multiple heat and mass transfer problems - plate surface temperature, condensate film temperature, local heat and mass transfer coefficients, refrigerant temperature distribution, humid air enthalpy change are included as subprocedures of this model. An automatic procedure of data transfer is developed in order to use results of MATLAB model in more complex simulation within commercial CFD code. In the end, Proper Orthogonal Decomposition (POD) method is introduced and implemented into MATLAB model.

Long-term mass transfer and mixing-controlled reactions of a DNAPL plume from persistent residuals

NASA Astrophysics Data System (ADS)

Liu, Yuan; Illangasekare, Tissa H.; Kitanidis, Peter K.

2014-02-01

Understanding and being able to predict the long-term behavior of DNAPL (i.e., PCE and TCE) residuals after active remediation has ceased have become increasingly important as attention at many sites turns from aggressive remediation to monitored natural attenuation and long-term stewardship. However, plume behavior due to mass loading and reactions during these later phases is less studied as they involve large spatial and temporal scales. We apply both theoretical analysis and pore-scale simulations to investigate mass transfer from DNAPL residuals and subsequent reactions within the generated plume, and, in particular, to show the differences between early- and late-time behaviors of the plume. In the zone of entry of the DNAPL entrapment zone where the concentration boundary layer in the flowing groundwater has not fully developed, the pore-scale simulations confirm the past findings based on laboratory studies that the mass transfer increases as a power-law function of the Peclét number, and is enhanced due to reactions in the plume. Away from the entry zone and further down gradient, the long-term reactions are limited by the available additive and mixing in the porous medium, thereby behave considerably differently from the entry zone. For the reaction between the contaminant and an additive with intrinsic second-order bimolecular kinetics, the late-time reaction demonstrates a first-order decay macroscopically with respect to the mass of the limiting additive, not with respect to that of the contaminant. The late-time decay rate only depends on the intrinsic reaction rate and the solubility of the entrapped DNAPL. At the intermediate time, the additive decays exponentially with the square of time (t2), instead of time (t). Moreover, the intermediate decay rate also depends on the initial conditions, the spatial distribution of DNAPL residuals, and the effective dispersion coefficient.

Experimental Study on Flow Boiling of Deionized Water in a Horizontal Long Small Channel

NASA Astrophysics Data System (ADS)

Huang, Qian; Jia, Li; Dang, Chao; Yang, Lixin

2018-04-01

In this paper, an experimental investigation on the flow boiling heat transfer in a horizontal long mini-channel was carried out. The mini-channel was with 2 mm wide and 1 mm deep and 900 mm long. The material of the mini-channel was stainless. The working fluid was deionized water. The experiments were conducted with the conditions of inlet pressure in the range of 0.2 0.5 MPa, mass flux in the range of 196.57-548.96 kg/m2s, and the outlet vapor quality in the range of 0.2 to 1. The heat flux was in the range of 292.86 kW/m2 to 788.48 kW/m2, respectively. The influences of mass flux and heat flux were studied. At a certain mass flow rate, the local heat transfer coefficient increased with the increase of the heat flux. If dry-out occurred in the mini-channel, the heat transfer coefficient decreased. At the same heat flux, the local heat transfer coefficient would depend on the mass flux. It would increase with the mass flux in a certain range, and then decrease if the mass flux was beyond this range. Experimental data were compared with the results of previous studies. Flow visualization and measurements were conducted to identify flow regime transitions. Results showed that there were eight different kinds of flow patterns occurring during the flow boiling. It was found that flow pattern had a significant effect on heat transfer.

A Transfer of Training Study of Control Loader Dynamics

NASA Technical Reports Server (NTRS)

Cardullo, Frank M.; Stanco, Anthony A.; Kelly, Lon C.; Houck, Jacob A.; Grube, Richard C.

2011-01-01

The control inceptor used in a simulated vehicle is an important part in maintaining the fidelity of a simulation. The force feedback provided by the control inceptor gives the operator important cues to maintain adequate performance. The dynamics of a control inceptor are typically based on a second order spring mass damper system with damping, force gradient, breakout force, and natural frequency parameters. Changing these parameters can have a great effect on pilot or driver control of the vehicle. The neuromuscular system has a very important role in manipulating the control inceptor within a vehicle. Many studies by McRuer, Aponso, and Hess have dealt with modeling the neuromuscular system and quantifying the effects of a high fidelity control loader as compared to a low fidelity control loader. Humans are adaptive in nature and their control behavior changes based on different control loader dynamics. Humans will change their control behavior to maintain tracking bandwidth and minimize tracking error. This paper reports on a quasi-transfer of training experiment which was performed at the NASA Langley Research Center. The quasi transfer of training study used a high fidelity control loader and a low fidelity control loader. Subjects trained in both simulations and then were transferred to the high fidelity control loader simulation. The parameters for the high fidelity control loader were determined from the literature. The low fidelity control loader parameters were found through testing of a simple computer joystick. A disturbance compensatory task is employed. The compensatory task involves implementing a simple horizon out the window display. A disturbance consisting of a sum of sines is used. The task consists of the subject compensating for the disturbance on the roll angle of the aircraft. The vehicle dynamics are represented as 1/s and 1/s2. The subject will try to maintain level flight throughout the experiment. The subjects consist of non-pilots to remove any effects of pilot experience. First, this paper discusses the implementation of the disturbance compensation task. Second, the high and low fidelity parameters used within the experiment are presented. Finally, an explanation of results from the experiments is presented.

Modeling Degradation Product Partitioning in Chlorinated-DNAPL Source Zones

NASA Astrophysics Data System (ADS)

Boroumand, A.; Ramsburg, A.; Christ, J.; Abriola, L.

2009-12-01

Metabolic reductive dechlorination degrades aqueous phase contaminant concentrations, increasing the driving force for DNAPL dissolution. Results from laboratory and field investigations suggest that accumulation of cis-dichloroethene (cis-DCE) and vinyl chloride (VC) may occur within DNAPL source zones. The lack of (or slow) degradation of cis-DCE and VC within bioactive DNAPL source zones may result in these dechlorination products becoming distributed among the solid, aqueous, and organic phases. Partitioning of cis-DCE and VC into the organic phase may reduce aqueous phase concentrations of these contaminants and result in the enrichment of these dechlorination products within the non-aqueous phase. Enrichment of degradation products within DNAPL may reduce some of the advantages associated with the application of bioremediation in DNAPL source zones. Thus, it is important to quantify how partitioning (between the aqueous and organic phases) influences the transport of cis-DCE and VC within bioactive DNAPL source zones. In this work, abiotic two-phase (PCE-water) one-dimensional column experiments are modeled using analytical and numerical methods to examine the rate of partitioning and the capacity of PCE-DNAPL to reversibly sequester cis-DCE. These models consider aqueous-phase, nonaqueous phase, and aqueous plus nonaqueous phase mass transfer resistance using linear driving force and spherical diffusion expressions. Model parameters are examined and compared for different experimental conditions to evaluate the mechanisms controlling partitioning. Biot number, a dimensionless number which is an index of the ratio of the aqueous phase mass transfer rate in boundary layer to the mass transfer rate within the NAPL, is used to characterize conditions in which either or both processes are controlling. Results show that application of a single aqueous resistance is capable to capture breakthrough curves when DNAPL is distributed in porous media as low-saturation ganglia, while diffusion within the DNAPL should be considered for larger NAPL pools. These results offer important insights to the monitoring and interpretation of bioremediation strategies employed within DNAPL source zones.

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.

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)

Applications of aerospace technology in biology and medicine

NASA Technical Reports Server (NTRS)

Rouse, D. J.

1983-01-01

Utilization of NASA technology and its application to medicine is discussed. The introduction of new or improved commercially available medical products and incorporation of aerospace technology is outlined. A biopolar donor-recipient model of medical technology transfer is presented to provide a basis for the methodology. The methodology is designed to: (1) identify medical problems and NASA technology that, in combination, constitute opportunities for successful medical products; (2) obtain the early participation of industry in the transfer process; and (3) obtain acceptance by the medical community of new medical products based on NASA technology. Two commercial transfers were completed: the ocular screening device, a system for quick detection of vision problems in preschool children, and Porta-Fib III, a hospital monitoring unit. Two institutional transfers were completed: implant materials testing, the application of NASA fracture control technology to improve reliability of metallic prostheses, and incinerator monitoring, a quadrupole mass spectrometer to monitor combustion products of municipal incinerators. Mobility aids for the blind and ultrasound diagnosis of burn depth are also studied.

Biomass drying in a pulsed fluidized bed without inert bed particles

DOE PAGES

Jia, Dening; Bi, Xiaotao; Lim, C. Jim; ...

2016-08-29

Batch drying was performed in the pulsed fluidized bed with various species of biomass particles as an indicator of gas–solid contact efficiency and mass transfer rate under different operating conditions including pulsation duty cycle and particle size distribution. The fluidization of cohesive biomass particles benefited from the shorter opening time of pulsed gas flow and increased peak pressure drop. The presence of fines enhanced gas–solid contact of large and irregular biomass particles, as well as the mass transfer efficiency. A drying model based on two-phase theory was proposed, from which effective diffusivity was calculated for various gas flow rates, temperaturemore » and pulsation frequency. Intricate relationship was discovered between pulsation frequency and effective diffusivity, as mass transfer was deeply connected with the hydrodynamics. Effective diffusivity was also found to be proportional to gas flow rate and drying temperature. In conclusion, operating near the natural frequency of the system also favored drying and mass transfer.« less

Biochemicals from food waste and recalcitrant biomass via syngas fermentation: A review.

PubMed

Wainaina, Steven; Horváth, Ilona Sárvári; Taherzadeh, Mohammad J

2018-01-01

An effective method for the production of value-added chemicals from food waste and lignocellulosic materials is a hybrid thermal-biological process, which involves gasification of the solid materials to syngas (primarily CO and H 2 ) followed by fermentation. This paper reviews the recent advances in this process. The special focus is on the cultivation methods that involve the use of single strains, defined mixed cultures and undefined mixed cultures for production of carboxylic acids and higher alcohols. A rate limiting step in these processes is the low mass transfer between the gas and the liquid phases. Therefore, novel techniques that can enhance the gas-liquid mass transfer including membrane- and trickle-bed bioreactors were discussed. Such bioreactors have shown promising results in increasing the volumetric mass transfer coefficient (k L a). High gas pressure also influences the mass transfer in certain batch processes, although the presence of impurities in the gas would impede the process. Copyright © 2017 Elsevier Ltd. All rights reserved.

Heat and mass transfer analysis of unsteady MHD nanofluid flow through a channel with moving porous walls and medium

NASA Astrophysics Data System (ADS)

Zubair Akbar, Muhammad; Ashraf, Muhammad; Farooq Iqbal, Muhammad; Ali, Kashif

2016-04-01

The paper presents the numerical study of heat and mass transfer analysis in a viscous unsteady MHD nanofluid flow through a channel with porous walls and medium in the presence of metallic nanoparticles. The two cases for effective thermal conductivity are discussed in the analysis through H-C model. The impacts of the governing parameters on the flow, heat and mass transfer aspects of the issue are talked about. Under the patronage of small values of permeable Reynolds number and relaxation/contraction parameter, we locate that, when wall contraction is together with suction, flow turning is encouraged close to the wall where the boundary layer is shaped. On the other hand, when the wall relaxation is coupled with injection, the flow adjacent to the porous walls decreased. The outcome of the exploration may be beneficial for applications of biotechnology. Numerical solutions for the velocity, heat and mass transfer rate at the boundary are obtained and analyzed.

DETECTION OF WHITE DWARF COMPANIONS TO BLUE STRAGGLERS IN THE OPEN CLUSTER NGC 188: DIRECT EVIDENCE FOR RECENT MASS TRANSFER

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

Gosnell, Natalie M.; Mathieu, Robert D.; Geller, Aaron M.

2014-03-01

Several possible formation pathways for blue straggler stars have been developed recently, but no one pathway has yet been observationally confirmed for a specific blue straggler. Here we report the first findings from a Hubble Space Telescope Advanced Camera for Surveys/Solar Blind Channel far-UV photometric program to search for white dwarf companions to blue straggler stars. We find three hot and young white dwarf companions to blue straggler stars in the 7 Gyr open cluster NGC 188, indicating that mass transfer in these systems ended less than 300 Myr ago. These companions are direct and secure observational evidence that these blue straggler starsmore » were formed through mass transfer in binary stars. Their existence in a well-studied cluster environment allows for observational constraints of both the current binary system and the progenitor binary system, mapping the entire mass transfer history.« less

Improving microalgal growth with reduced diameters of aeration bubbles and enhanced mass transfer of solution in an oscillating flow field.

PubMed

Yang, Zongbo; Cheng, Jun; Lin, Richen; Zhou, Junhu; Cen, Kefa

2016-07-01

A novel oscillating gas aerator combined with an oscillating baffle was proposed to generate smaller aeration bubbles and enhance solution mass transfer, which can improve microalgal growth in a raceway pond. A high-speed photography system (HSP) was used to measure bubble diameter and generation time, and online precise dissolved oxygen probes and pH probes were used to measure mass-transfer coefficient and mixing time. Bubble diameter and generation time decreased with decreased aeration gas rate, decreased orifice diameter, and increased water velocity in the oscillating gas aerator. The optimized oscillating gas aerator decreased bubble diameter and generation time by 25% and 58%, respectively, compared with a horizontal tubular gas aerator. Using an oscillating gas aerator and an oscillating baffle in a raceway pond increased the solution mass-transfer coefficient by 15% and decreased mixing time by 32%; consequently, microalgal biomass yield increased by 19%. Copyright © 2016 Elsevier Ltd. All rights reserved.

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

Sorption and reemission of formaldehyde by gypsum wallboard. Report for June 1990-August 1992

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

Chang, J.C.S.

1993-01-01

The paper gives results of an analysis of the sorption and desorption of formaldehyde by unpainted wallboard, using a mass transfer model based on the Langmuir sorption isotherm. The sorption and desorption rate constants are determined by short-term experimental data. Long-term sorption and desorption curves are developed by the mass transfer model without any adjustable parameters. Compared with other empirically developed models, the mass transfer model has more extensive applicability and provides an elucidation of the sorption and desorption mechanism that empirical models cannot. The mass transfer model is also more feasible and accurate than empirical models for applications suchmore » as scale-up and exposure assessment. For a typical indoor environment, the model predicts that gypsum wallboard is a much stronger sink for formaldehyde than for other indoor air pollutants such as tetrachloroethylene and ethylbenzene. The strong sink effects are reflected by the high equilibrium capacity and slow decay of the desorption curve.« less

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.

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.

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.

EVERY INTERACTING DOUBLE WHITE DWARF BINARY MAY MERGE

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

Shen, Ken J.

2015-05-20

Interacting double white dwarf (WD) binaries can give rise to a wide variety of astrophysical outcomes ranging from faint thermonuclear and Type Ia supernovae to the formation of neutron stars and stably accreting AM Canum Venaticorum systems. One key factor affecting the final outcome is whether mass transfer remains dynamically stable or instead diverges, leading to the tidal disruption of the donor and the merger of the binary. It is typically thought that for low ratios of the donor mass to the accretor mass, mass transfer remains stable, especially if accretion occurs via a disk. In this Letter, we examinemore » low mass ratio double WD binaries and find that the initial phase of hydrogen-rich mass transfer leads to a classical nova-like outburst on the accretor. Dynamical friction within the expanding nova shell shrinks the orbit and causes the mass transfer rate to increase dramatically above the accretor's Eddington limit, possibly resulting in a binary merger. If the binary survives the first hydrogen-rich nova outbursts, dynamical friction within the subsequent helium-powered nova shells pushes the system even more strongly toward merger. While further calculations are necessary to confirm this outcome for the entire range of binaries previously thought to be dynamically stable, it appears likely that most, if not all, interacting double WD binaries will merge during the course of their evolution.« less

Overexpression and deletion of phospholipid transfer protein reduce HDL mass and cholesterol efflux capacity but not macrophage reverse cholesterol transport[S

PubMed Central

Kuwano, Takashi; Bi, Xin; Cipollari, Eleonora; Yasuda, Tomoyuki; Lagor, William R.; Szapary, Hannah J.; Tohyama, Junichiro; Millar, John S.; Billheimer, Jeffrey T.; Lyssenko, Nicholas N.; Rader, Daniel J.

2017-01-01

Phospholipid transfer protein (PLTP) may affect macrophage reverse cholesterol transport (mRCT) through its role in the metabolism of HDL. Ex vivo cholesterol efflux capacity and in vivo mRCT were assessed in PLTP deletion and PLTP overexpression mice. PLTP deletion mice had reduced HDL mass and cholesterol efflux capacity, but unchanged in vivo mRCT. To directly compare the effects of PLTP overexpression and deletion on mRCT, human PLTP was overexpressed in the liver of wild-type animals using an adeno-associated viral (AAV) vector, and control and PLTP deletion animals were injected with AAV-null. PLTP overexpression and deletion reduced plasma HDL mass and cholesterol efflux capacity. Both substantially decreased ABCA1-independent cholesterol efflux, whereas ABCA1-dependent cholesterol efflux remained the same or increased, even though preβ HDL levels were lower. Neither PLTP overexpression nor deletion affected excretion of macrophage-derived radiocholesterol in the in vivo mRCT assay. The ex vivo and in vivo assays were modified to gauge the rate of cholesterol efflux from macrophages to plasma. PLTP activity did not affect this metric. Thus, deviations in PLTP activity from the wild-type level reduce HDL mass and ex vivo cholesterol efflux capacity, but not the rate of macrophage cholesterol efflux to plasma or in vivo mRCT. PMID:28137768

Interaction between Convection and Heat Transfer in Crystal Growth

NASA Technical Reports Server (NTRS)

1998-01-01

Crystals are integral components in some of our most sophisticated and rapidly developing industries. Single crystals are solids with the most uniform structures that can be obtained on an atomic scale. Because of their structural uniformity, crystals can transmit acoustic and electromagnetic waves and charged particles with essentially no scattering or interferences. This transparency, which can be selectively modified by controlled additions of impurities known as dopants, is the foundation of modern electronic industry. It has brought about widespread application of crystals in transistors, lasers, microwave devices, infrared detectors, magnetic memory devices, and many other magnets and electro-optic components. The performance of a crystal depends strongly on its compositional homogeneity. For instance, in modern microcircuitry, compositional variations of a few percent (down to a submicron length scale) can seriously jeopardize predicted yields. Since crystals are grown by carefully controlled phase transformations, the compositional adjustment in the solid is often made during growth from the nutrient. Hence, a detailed understanding of mass transfer in the nutrient is essential. Moreover, since mass transfer is often the slowest process during growth, it is usually the rate limiting mechanism. Crystal growth processes are usually classified according to the nature of the parent phase. Nevertheless, whether the growth occurs by solidification from a melt (melt growth), nucleation from a solution (solution growth), condensation from a vapor (physical vapor transport) or chemical reaction of gases (chemical vapor deposition), the parent phase is a fluid. As is with most non-equilibrium processes involving fluids, liquid or vapor, fluid motion plays an important role, affecting both the concentration and temperature gradients at the soli-liquid interface.

Trophic Transfer of Arsenic from an Aquatic Insect to Terrestrial Insect Predators

PubMed Central

Mogren, Christina L.; Walton, William E.; Parker, David R.; Trumble, John T.

2013-01-01

The movement of energy and nutrients from aquatic to terrestrial ecosystems can be substantial, and emergent aquatic insects can serve as biovectors not only for nutrients, but also for contaminants present in the aquatic environment. The terrestrial predators Tenodera aridifolia sinensis (Mantodea: Mantidae) and Tidarren haemorrhoidale (Araneae: Theridiidae) and the aquatic predator Buenoa scimitra (Hemiptera: Notonectidae) were chosen to evaluate the efficacy of arsenic transfer between aquatic and terrestrial environments. Culex tarsalis larvae were reared in either control water or water containing 1000 µg l−1 arsenic. Adults that emerged from the control and arsenic treatments were fed to the terrestrial predators, and fourth instar larvae were fed to the aquatic predator reared in control or arsenic contaminated water. Tenodera a. sinensis fed arsenic-treated Cx. tarsalis accumulated 658±130 ng g−1 of arsenic. There was no significant difference between control and arsenic-fed T. haemorrhoidale (range 142–290 ng g−1). Buenoa scimitra accumulated 5120±406 ng g−1 of arsenic when exposed to arsenic-fed Cx. tarsalis and reared in water containing 1000 µg l−1 arsenic. There was no significant difference between controls or arsenic-fed B. scimitra that were not exposed to water-borne arsenic, indicating that for this species environmental exposure was more important in accumulation than strictly dietary arsenic. These results indicate that transfer to terrestrial predators may play an important role in arsenic cycling, which would be particularly true during periods of mass emergence of potential insect biovectors. Trophic transfer within the aquatic environment may still occur with secondary predation, or in predators with different feeding strategies. PMID:23826344

Modeling aerosol suspension from soils and oceans as sources of micropollutants to air.

PubMed

Qureshi, Asif; MacLeod, Matthew; Hungerbühler, Konrad

2009-10-01

Soil and marine aerosol suspension are two physical mass transfer processes that are not usually included in models describing fate and transport of environmental pollutants. Here, we review the literature on soil and marine aerosol suspension and estimate aerosol suspension mass transfer velocities for inclusion in multimedia models, as a global average and on a 1 x 1 scale. The yearly, global average mass transfer velocity for soil aerosol suspension is estimated to be 6 x 10(-10)mh(-1), approximately an order of magnitude smaller than marine aerosol suspension, which is estimated to be 8 x 10(-9)mh(-1). Monthly averages of these velocities can be as high as 10(-7)mh(-1) and 10(-5)mh(-1) for soil and marine aerosol suspension, respectively, depending on location. We use a unit-world multimedia model to analyze the relevance of these two suspension processes as a mechanism that enhances long-range atmospheric transport of pollutants. This is done by monitoring a metric of long-range transport potential, phi-one thousand (phi1000), that denotes the fraction of modeled emissions to air, water or soil in a source region that reaches a distance of 1000 km in air. We find that when the yearly, globally averaged mass transfer velocity is used, marine aerosol suspension increases phi1000 only fractionally for both emissions to air and water. However, enrichment of substances in marine aerosols, or speciation between ionic and neutral forms in ocean water may increase the influence of this surface-to-air transfer process. Soil aerosol suspension can be the dominant process for soil-to-air transfer in an emission-to-soil scenario for certain substances that have a high affinity to soil. When a suspension mass transfer velocity near the maximum limit is used, soil suspension remains important if the emissions are made to soil, and marine aerosol suspension becomes important regardless of if emissions are made to air or water compartments. We recommend that multimedia models designed to assess the environmental fate and long-range transport behavior of substances with a range of chemical properties include both aerosol suspension processes, using the mass transfer velocities estimated here.

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.

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.

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.

Measurement of momentum transfer due to adhesive forces: on-ground testing of in-space body injection into geodesic motion.

PubMed

Bortoluzzi, D; Benedetti, M; Baglivo, L; De Cecco, M; Vitale, S

2011-12-01

In the frame of many scientific space missions, a massive free-falling object is required to mark a geodesic trajectory, i.e., to follow inside a spacecraft an orbit that is determined only by the planetary gravity field. The achievement of high-purity geodesic trajectories sets tight design constraints on the reference sensor that hosts and controls the reference body. Among these, a mechanism may be required to cage the reference body during the spacecraft launch and to inject it into the geodesic trajectory once on-orbit. The separation of the body from the injection mechanism must be realized against the action of adhesion forces, and in the worst case this is performed dynamically, relying on the body's inertia through a quick retraction of the holding finger(s). Unfortunately, this manoeuvre may not avoid transferring some momentum to the body, which may affect or even jeopardize the subsequent spacecraft control if the residual velocity is too large. The transferred momentum measurement facility (TMMF) was developed to reproduce representative conditions of the in-flight dynamic injection and to measure the transferred momentum to the released test mass. In this paper, we describe the design and development of the TMMF together with the achieved measurement performance.

Controls of the U.S. Virtual Water Transfer Network

NASA Astrophysics Data System (ADS)

Garcia, S.; Mejia, A.

2017-12-01

A complex interplay of human and natural factors shape the economic geography of the U.S., operating through socioeconomic forces that drive the consumption, production, and exchange of commodities. The virtual water content of a commodity represents the water embedded in its production. This work investigates the controls of national bilateral transfers of the virtual water transfer network (VWTN), through a gravity-type spatial interaction model. We use a probabilistic model to predict the binary network and investigate whether the gravity model can explain the topological properties of the empirical weighted network. In general, the gravity model relates transfer flows to the mass of the trading regions and their geographical distance. We hypothesize that properties of the nodes such as population, employment, and availability of land, together with the Euclidean distance between two trading regions, capture the main drivers of the national VWTN. The results from the model are then compared to the empirical weighted network to verify its ability to model the structure of this self-organized system. The proposed empirical model provides insight into the processes that underlie the formation of the VWTN. It can be a promising tool to study how flows are affected by changes in the generating conditions due to shocks and/or stresses.

Fluid management in the optimization of space construction

NASA Technical Reports Server (NTRS)

Snyder, Howard

1990-01-01

Fluid management impacts strongly on the optimization of space construction. Large quantities of liquids are needed for propellants and life support. The mass of propellant liquids is comparable to that required for the structures. There may be a strong dynamic interaction between the stored liquids and the space structure unless the design minimizes the interaction. The constraints of cost and time required optimization of the supply/resupply strategy. The proper selection and design of the fluid management methods for: slosh control; stratification control; acquisition; transfer; gauging; venting; dumping; contamination control; selection of tank configuration and size; the storage state and the control system can improve the entire system performance substantially. Our effort consists of building mathematical/computer models of the various fluid management methods and testing them against the available experimental data. The results of the models are used as inputs to the system operations studies. During the past year, the emphasis has been on modeling: the transfer of cryogens; sloshing and the storage configuration. The work has been intermeshed with ongoing NASA design and development studies to leverage the funds provided by the Center.

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.

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...

Smoothed particle hydrodynamics method for evaporating multiphase flows.

PubMed

Yang, Xiufeng; Kong, Song-Charng

2017-09-01

The smoothed particle hydrodynamics (SPH) method has been increasingly used for simulating fluid flows; however, its ability to simulate evaporating flow requires significant improvements. This paper proposes an SPH method for evaporating multiphase flows. The present SPH method can simulate the heat and mass transfers across the liquid-gas interfaces. The conservation equations of mass, momentum, and energy were reformulated based on SPH, then were used to govern the fluid flow and heat transfer in both the liquid and gas phases. The continuity equation of the vapor species was employed to simulate the vapor mass fraction in the gas phase. The vapor mass fraction at the interface was predicted by the Clausius-Clapeyron correlation. An evaporation rate was derived to predict the mass transfer from the liquid phase to the gas phase at the interface. Because of the mass transfer across the liquid-gas interface, the mass of an SPH particle was allowed to change. Alternative particle splitting and merging techniques were developed to avoid large mass difference between SPH particles of the same phase. The proposed method was tested by simulating three problems, including the Stefan problem, evaporation of a static drop, and evaporation of a drop impacting a hot surface. For the Stefan problem, the SPH results of the evaporation rate at the interface agreed well with the analytical solution. For drop evaporation, the SPH result was compared with the result predicted by a level-set method from the literature. In the case of drop impact on a hot surface, the evolution of the shape of the drop, temperature, and vapor mass fraction were predicted.

Transfer Kinetics at the Aqueous/Non-Aqueous Phase Liquid Interface. A Statistical Mechanic Approach

NASA Astrophysics Data System (ADS)

Doss, S. K.; Ezzedine, S.; Ezzedine, S.; Ziagos, J. P.; Hoffman, F.; Gelinas, R. J.

2001-05-01

Many modeling efforts in the literature use a first-order, linear-driving-force model to represent the chemical dissolution process at the non-aqueous/aqueous phase liquid (NAPL/APL) interface. In other words, NAPL to APL phase flux is assumed to be equal to the difference between the solubility limit and the "bulk aqueous solution" concentrations times a mass transfer coefficient. Under such assumptions, a few questions are raised: where, in relation to a region of pure NAPL, does the "bulk aqueous solution" regime begin and how does it behave? The answers are assumed to be associated with an arbitrary, predetermined boundary layer, which separates the NAPL from the surrounding solution. The mass transfer rate is considered to be, primarily, limited by diffusion of the component through the boundary layer. In fact, compositional models of interphase mass transfer usually assume that a local equilibrium is reached between phases. Representing mass flux as a rate-limiting process is equivalent to assuming diffusion through a stationary boundary layer with an instantaneous local equilibrium and linear concentration profile. Some environmental researchers have enjoyed success explaining their data using chemical engineering-based correlations. Correlations are strongly dependent on the experimental conditions employed. A universally applicable theory for NAPL dissolution in natural systems does not exist. These correlations are usually expressed in terms of the modified Sherwood number as a function of Reynolds, Peclet, and Schmidt numbers. The Sherwood number may be interpreted as the ratio between the grain size and the thickness of the Nernst stagnant film. In the present study, we show that transfer kinetics at the NAPL/APL interface under equilibrium conditions disagree with approaches based on the Nernst stagnant film concept. It is unclear whether local equilibrium assumptions used in current models are suitable for all situations.A statistical mechanic framework has been chosen to study the transfer kinetic processes at the microscale level. The rationale for our approach is based on both the activation energy of transfer of an ion and its velocity across the NAPL/APL interface. There are four major energies controlling the interfacial NAPL dissolution kinetics: (de)solvation energy, interfacial tension energy, electrostatic energy, and thermal fluctuation energy. Transfer of an ion across the NAPL/APL interface is accelerated by the viscous forces which can be described using the averaged Langevin master equation. The resulting energies and viscous forces were combined using the Boltzmann probability distribution. Asymptotic time limits of the resulting kinetics lead to instantaneous local equilibrium conditions that contradict the Nernst equilibrium equation. The NAPL/APL interface is not an ideal one: it does not conserve energy and heat. In our case the interface is treated as a thin film or slush zone that alters the thermodynamic variables. Such added zone, between the two phases, is itself a phase, and, therefore, the equilibrium does not occur between two phases but rather three. All these findings led us to develop a new non-linearly coupled flow and transport system of equations which is able to account for specific chemical dissolution processes and precludes the need for empirical mass-transfer parameters. Work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract W-7405-Eng-48.

Phase separated membrane bioreactor: Results from model system studies

NASA Astrophysics Data System (ADS)

Petersen, G. R.; Seshan, P. K.; Dunlop, E. H.

The operation and evaluation of a bioreactor designed for high intensity oxygen transfer in a microgravity environment is described. The reactor itself consists of a zero headspace liquid phase separated from the air supply by a long length of silicone rubber tubing through which the oxygen diffuses in and the carbon dioxide diffuses out. Mass transfer studies show that the oxygen is film diffusion controlled both externally and internally to the tubing and not by diffusion across the tube walls. Methods of upgrading the design to eliminate these resistances are proposed. Cell growth was obtained in the fermenter using Saccharomyces cerevisiae showing that this concept is capable of sustaining cell growth in the terrestial simulation.

Communication: Site-selective bond excision of adenine upon electron transfer

NASA Astrophysics Data System (ADS)

Cunha, T.; Mendes, M.; Ferreira da Silva, F.; Eden, S.; García, G.; Limão-Vieira, P.

2018-01-01

This work demonstrates that selective excision of hydrogen atoms at a particular site of the DNA base adenine can be achieved in collisions with electronegative atoms by controlling the impact energy. The result is based on analysing the time-of-flight mass spectra yields of potassium collisions with a series of labeled adenine derivatives. The production of dehydrogenated parent anions is consistent with neutral H loss either from selective breaking of C-H or N-H bonds. These unprecedented results open up a new methodology in charge transfer collisions that can initiate selective reactivity as a key process in chemical reactions that are dominant in different areas of science and technology.

Phase separated membrane bioreactor - Results from model system studies

NASA Technical Reports Server (NTRS)

Petersen, G. R.; Seshan, P. K.; Dunlop, E. H.

1989-01-01

The operation and evaluation of a bioreactor designed for high intensity oxygen transfer in a microgravity environment is described. The reactor itself consists of a zero headspace liquid phase separated from the air supply by a long length of silicone rubber tubing through which the oxygen diffuses in and the carbon dioxide diffuses out. Mass transfer studies show that the oxygen is film diffusion controlled both externally and internally to the tubing and not by diffusion across the tube walls. Methods of upgrading the design to eliminate these resistances are proposed. Cell growth was obtained in the fermenter using Saccharomyces cerevisiae showing that this concept is capable of sustaining cell growth in the terrestrial simulation.

Model system studies with a phase separated membrane bioreactor

NASA Technical Reports Server (NTRS)

Petersen, G. R.; Seshan, P. K.; Dunlop, Eric H.

1989-01-01

The operation and evaluation of a bioreactor designed for high intensity oxygen transfer in a microgravity environment is described. The reactor itself consists of a zero headspace liquid phase separated from the air supply by a long length of silicone rubber tubing through which the oxygen diffuses in and the carbon dioxide diffuses out. Mass transfer studies show that the oxygen is film diffusion controlled both externally and internally to the tubing and not by diffusion across the tube walls. Methods of upgrading the design to eliminate these resistances are proposed. Cell growth was obtained in the fermenter using Saccharomyces cerevisiae showing that this concept is capable of sustaining cell growth in the terrestial simulation.

Complementary methods for the determination of dissolved oxygen content in perfluorocarbon emulsions and other solutions.

PubMed

Fraker, Christopher A; Mendez, Armando J; Stabler, Cherie L

2011-09-08

Perfluorocarbons (PFCs) are compounds with increased oxygen solubility and effective diffusivity, making them ideal candidates for improving oxygen mass transfer in numerous biological applications. Historically, quantification of the mass transfer characteristics of these liquids has relied on the use of elaborate laboratory equipment and complicated methodologies, such as in-line gas chromatography coupled with temperature-controlled glass fritted diffusion cells. In this work, we present an alternative method for the determination of dissolved oxygen content in PFC emulsions and, by extrapolation, pure PFCs. We implemented a simple stirred oxygen consumption microchamber coupled with an enzymatic reaction for the quantitative determination of oxygen by optical density measurements. Chambers were also custom fitted with lifetime oxygen sensors to permit simultaneous measurement of internal chamber oxygen levels. Analyzing the consumption of oxygen during the enzymatic reaction via recorded oxygen depletion traces, we found a strong degree of correlation between the zero-order reaction rate and the total measured oxygen concentrations, relative to control solutions. The values obtained were in close agreement with published values in the literature, establishing the accuracy of this method. Overall, this method allows for easy, reliable, and reproducible measurements of oxygen content in aqueous solutions, including, but not limited to PFC emulsions.

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.

Experimental and CFD-PBM Study of Oxygen Mass Transfer Coefficient in Different Impeller Configurations and Operational Conditions of a Two-Phase Partitioning Bioreactor.

PubMed

Moradkhani, Hamed; Izadkhah, Mir-Shahabeddin; Anarjan, Navideh

2017-02-01

In this work, gas dispersion in a two-phase partitioning bioreactor is analyzed by calculating volumetric oxygen mass transfer coefficient which is modeled using a commercial computational fluid dynamics (CFD), code FLUENT 6.2. Dispersed oxygen bubbles dynamics is based on standard "k-ε" Reynolds-averaged Navier-Stokes (RANS) model. This paper describes a three-dimensional CFD model coupled with population balance equations (PBE) in order to get more confirming results of experimental measurements. Values of k L a are obtained using dynamic gassing-out method. Using the CFD simulation, the volumetric mass transfer coefficient is calculated based on Higbie's penetration theory. Characteristics of mass transfer coefficient are investigated for five configurations of impeller and three different aeration flow rates. The pitched six blade type, due to the creation of downward flow direction, leads to higher dissolved oxygen (DO) concentrations, thereby, higher values of k L a compared with other impeller compositions. The magnitude of dissolved oxygen percentage in the aqueous phase has direct correlation with impeller speed and any increase of the aeration magnitude leads to faster saturation in shorter periods of time. Agitation speeds of 300 to 800 rpm are found to be the most effective rotational speeds for the mass transfer of oxygen in two-phase partitioning bioreactors (TPPB).

A novel inverse numerical modeling method for the estimation of water and salt mass transfer coefficients during ultrasonic assisted-osmotic dehydration of cucumber cubes.

PubMed

Kiani, Hosein; Karimi, Farzaneh; Labbafi, Mohsen; Fathi, Morteza

2018-06-01

The objective of this paper was to study the moisture and salt diffusivity during ultrasonic assisted-osmotic dehydration of cucumbers. Experimental measurements of moisture and salt concentration versus time were carried out and an inverse numerical method was performed by coupling a CFD package (OpenFOAM) with a parameter estimation software (DAKOTA) to determine mass transfer coefficients. A good agreement between experimental and numerical results was observed. Mass transfer coefficients were from 3.5 × 10 -9 to 7 × 10 -9  m/s for water and from 4.8 × 10 -9  m/s to 7.4 × 10 -9  m/s for salt at different conditions (diffusion coefficients of around 3.5 × 10 -12 -11.5 × 10 -12  m 2 /s for water and 5 × 10 -12  m/s-12 × 10 -12  m 2 /s for salt). Ultrasound irradiation could increase the mass transfer coefficient. The values obtained by this method were closer to the actual data. The inverse simulation method can be an accurate technique to study the mass transfer phenomena during food processing. Copyright © 2018 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.

From Vulcanian explosions to sustained explosive eruptions: The role of diffusive mass transfer in conduit flow dynamics

NASA Astrophysics Data System (ADS)

Mason, R. M.; Starostin, A. B.; Melnik, O. E.; Sparks, R. S. J.

2006-05-01

Magmatic explosive eruptions are influenced by mass transfer processes of gas diffusion into bubbles caused by decompression. Melnik and Sparks [Melnik, O.E., Sparks, R.S.J. 2002, Modelling of conduit flow dynamic during explosive activity at Soufriere Hills Volcano, Montserrat. In: Druitt, T.H., Kokelaar, B.P. (eds). The Eruption of Soufriere Hills Volcano, Montserrat, from 1995 to 1999. Geological Society, London, Memoirs, 21, 307-317] proposed two end member cases corresponding to complete equilibrium and complete disequilibrium. In the first case, diffusion is fast enough to maintain the system near equilibrium and a long-lived explosive eruption develops. In the latter case, pre-existing bubbles expand under conditions of explosive eruption and decompression, but diffusive gas transfer is negligible. This leads to a much shorter eruption. Here we develop this model to consider the role of mass transfer by investigating transient flows at the start of an explosive eruption triggered by a sudden decompression. The simulations reveal a spectrum of behaviours from sustained to short-lived highly non-equilibrium Vulcanian-style explosions lasting a few tens of seconds, through longer lasting eruptions that can be sustained for tens of minutes and finally to eruptions that can last hours or even days. Behaviour is controlled by a mass-transfer parameter, ω, which equals n*2/3D, where n* is the bubble number density and D is the diffusivity. The parameter ω is expected to vary between 10 - 5 and 1 s - 1 in nature and reflects a time-scale for efficient diffusion. The spectrum of model behaviours is consistent with variations in styles of explosive eruptions of silicic volcanoes. In the initial stages peak discharges occur over 10-20 s and then decline to low discharges. If a critical bubble overpressure is assumed to be the criterion for fragmentation then fragmentation may stop and start several times in the declining period causing several pulses of high-intensity discharge. For the cases of strong disequilibria, the fluxes can decrease to negligible values where other processes, such as gas escape through permeable magma, prevents explosive conditions becoming re-established so that explosive activity stops and dome growth can start. For cases closer to the equilibrium the eruption can evolve towards a quasi-steady sustained flow, never declining sufficiently for gas escape to become dominant.

Minimum fuel coplanar aeroassisted orbital transfer using collocation and nonlinear programming

NASA Technical Reports Server (NTRS)

Shi, Yun Yuan; Young, D. H.

1991-01-01

The fuel optimal control problem arising in coplanar orbital transfer employing aeroassisted technology is addressed. The mission involves the transfer from high energy orbit (HEO) to low energy orbit (LEO) without plane change. The basic approach here is to employ a combination of propulsive maneuvers in space and aerodynamic maneuvers in the atmosphere. The basic sequence of events for the coplanar aeroassisted HEO to LEO orbit transfer consists of three phases. In the first phase, the transfer begins with a deorbit impulse at HEO which injects the vehicle into a elliptic transfer orbit with perigee inside the atmosphere. In the second phase, the vehicle is optimally controlled by lift and drag modulation to satisfy heating constraints and to exit the atmosphere with the desired flight path angle and velocity so that the apogee of the exit orbit is the altitude of the desired LEO. Finally, the second impulse is required to circularize the orbit at LEO. The performance index is maximum final mass. Simulation results show that the coplanar aerocapture is quite different from the case where orbital plane changes are made inside the atmosphere. In the latter case, the vehicle has to penetrate deeper into the atmosphere to perform the desired orbital plane change. For the coplanar case, the vehicle needs only to penetrate the atmosphere deep enough to reduce the exit velocity so the vehicle can be captured at the desired LEO. The peak heating rates are lower and the entry corridor is wider. From the thermal protection point of view, the coplanar transfer may be desirable. Parametric studies also show the maximum peak heating rates and the entry corridor width are functions of maximum lift coefficient. The problem is solved using a direct optimization technique which uses piecewise polynomial representation for the states and controls and collocation to represent the differential equations. This converts the optimal control problem into a nonlinear programming problem which is solved numerically by using a modified version of NPSOL. Solutions were obtained for the described problem for cases with and without heating constraints. The method appears to be more robust than other optimization methods. In addition, the method can handle complex dynamical constraints.

Investigation of Control Inceptor Dynamics and Effect on Human Subject Performance

NASA Technical Reports Server (NTRS)

Stanco, Anthony A.; Cardullo, Frank M.; Houck, Jacob A.; Grube, Richard C.; Kelly, Lon C.

2013-01-01

The control inceptor used in a vehicle simulation is an important part of adequately representing the dynamics of the vehicle. The inceptor characteristics are typically based on a second order spring mass damper system with damping, force gradient, breakout force, and natural frequency parameters. Changing these parameters can have a great effect on pilot control of the vehicle. A quasi transfer of training experiment was performed employing a high fidelity and a low fidelity control inceptor. A disturbance compensatory task was employed which involved a simple horizon line disturbed in roll by a sum of sinusoids presented in an out-the-window display. Vehicle dynamics were modeled as 1/s and 1/s2. The task was to maintain level flight. Twenty subjects were divided between the high and the low fidelity training groups. Each group was trained to a performance asymptote, and then transferred to the high fidelity simulation. RMS tracking error, a PSD analysis, and a workload analysis were performed to quantify the transfer of training effect. Quantitative results of the experiments show that there is no significant difference between the high and low fidelity training groups for 1/s plant dynamics. For 1/s2 plant dynamics there is a greater difference in tracking performance and PSD; and the subjects are less correlated with the input disturbance function

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.

Mathematical Model of Two Phase Flow in Natural Draft Wet-Cooling Tower Including Flue Gas Injection

NASA Astrophysics Data System (ADS)

Hyhlík, Tomáš

2016-03-01

The previously developed model of natural draft wet-cooling tower flow, heat and mass transfer is extended to be able to take into account the flow of supersaturated moist air. The two phase flow model is based on void fraction of gas phase which is included in the governing equations. Homogeneous equilibrium model, where the two phases are well mixed and have the same velocity, is used. The effect of flue gas injection is included into the developed mathematical model by using source terms in governing equations and by using momentum flux coefficient and kinetic energy flux coefficient. Heat and mass transfer in the fill zone is described by the system of ordinary differential equations, where the mass transfer is represented by measured fill Merkel number and heat transfer is calculated using prescribed Lewis factor.

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.

Experimental study of the condensation heat transfer characteristics of CO2 in a horizontal microfin tube with a diameter of 4.95 mm

NASA Astrophysics Data System (ADS)

Son, Chang-Hyo; Oh, Hoo-Kyu

2012-11-01

The condensation heat transfer characteristics for CO2 flowing in a horizontal microfin tube were investigated by experiment with respect to condensation temperature and mass flux. The test section consists of a 2,400 mm long horizontal copper tube of 4.6 mm inner diameter. The experiments were conducted at refrigerant mass flux of 400-800 kg/m2s, and saturation temperature of 20-30 °C. The main experimental results showed that annular flow was highly dominated the majority of condensation flow in the horizontal microfin tube. The condensation heat transfer coefficient increases with decreasing saturation temperature and increasing mass flux. The experimental data were compared against previous heat transfer correlations. Most correlations failed to predict the experimental data. However, the correlation by Cavallini et al. showed relatively good agreement with experimental data in the microfin tube. Therefore, a new condensation heat transfer correlation is proposed with mean and average deviations of 3.14 and -7.6 %, respectively.

Generation of cloned mice and nuclear transfer embryonic stem cell lines from urine-derived cells.

PubMed

Mizutani, Eiji; Torikai, Kohei; Wakayama, Sayaka; Nagatomo, Hiroaki; Ohinata, Yasuhide; Kishigami, Satoshi; Wakayama, Teruhiko

2016-04-01

Cloning animals by nuclear transfer provides the opportunity to preserve endangered mammalian species. However, there are risks associated with the collection of donor cells from the body such as accidental injury to or death of the animal. Here, we report the production of cloned mice from urine-derived cells collected noninvasively. Most of the urine-derived cells survived and were available as donors for nuclear transfer without any pretreatment. After nuclear transfer, 38-77% of the reconstructed embryos developed to the morula/blastocyst, in which the cell numbers in the inner cell mass and trophectoderm were similar to those of controls. Male and female cloned mice were delivered from cloned embryos transferred to recipient females, and these cloned animals grew to adulthood and delivered pups naturally when mated with each other. The results suggest that these cloned mice had normal fertility. In additional experiments, 26 nuclear transfer embryonic stem cell lines were established from 108 cloned blastocysts derived from four mouse strains including inbreds and F1 hybrids with relatively high success rates. Thus, cells derived from urine, which can be collected noninvasively, may be used in the rescue of endangered mammalian species by using nuclear transfer without causing injury to the animal.

Generation of cloned mice and nuclear transfer embryonic stem cell lines from urine-derived cells

PubMed Central

Mizutani, Eiji; Torikai, Kohei; Wakayama, Sayaka; Nagatomo, Hiroaki; Ohinata, Yasuhide; Kishigami, Satoshi; Wakayama, Teruhiko

2016-01-01

Cloning animals by nuclear transfer provides the opportunity to preserve endangered mammalian species. However, there are risks associated with the collection of donor cells from the body such as accidental injury to or death of the animal. Here, we report the production of cloned mice from urine-derived cells collected noninvasively. Most of the urine-derived cells survived and were available as donors for nuclear transfer without any pretreatment. After nuclear transfer, 38–77% of the reconstructed embryos developed to the morula/blastocyst, in which the cell numbers in the inner cell mass and trophectoderm were similar to those of controls. Male and female cloned mice were delivered from cloned embryos transferred to recipient females, and these cloned animals grew to adulthood and delivered pups naturally when mated with each other. The results suggest that these cloned mice had normal fertility. In additional experiments, 26 nuclear transfer embryonic stem cell lines were established from 108 cloned blastocysts derived from four mouse strains including inbreds and F1 hybrids with relatively high success rates. Thus, cells derived from urine, which can be collected noninvasively, may be used in the rescue of endangered mammalian species by using nuclear transfer without causing injury to the animal. PMID:27033801

Modeling of adsorption dynamics at air-liquid interfaces using statistical rate theory (SRT).

PubMed

Biswas, M E; Chatzis, I; Ioannidis, M A; Chen, P

2005-06-01

A large number of natural and technological processes involve mass transfer at interfaces. Interfacial properties, e.g., adsorption, play a key role in such applications as wetting, foaming, coating, and stabilizing of liquid films. The mechanistic understanding of surface adsorption often assumes molecular diffusion in the bulk liquid and subsequent adsorption at the interface. Diffusion is well described by Fick's law, while adsorption kinetics is less understood and is commonly described using Langmuir-type empirical equations. In this study, a general theoretical model for adsorption kinetics/dynamics at the air-liquid interface is developed; in particular, a new kinetic equation based on the statistical rate theory (SRT) is derived. Similar to many reported kinetic equations, the new kinetic equation also involves a number of parameters, but all these parameters are theoretically obtainable. In the present model, the adsorption dynamics is governed by three dimensionless numbers: psi (ratio of adsorption thickness to diffusion length), lambda (ratio of square of the adsorption thickness to the ratio of adsorption to desorption rate constant), and Nk (ratio of the adsorption rate constant to the product of diffusion coefficient and bulk concentration). Numerical simulations for surface adsorption using the proposed model are carried out and verified. The difference in surface adsorption between the general and the diffusion controlled model is estimated and presented graphically as contours of deviation. Three different regions of adsorption dynamics are identified: diffusion controlled (deviation less than 10%), mixed diffusion and transfer controlled (deviation in the range of 10-90%), and transfer controlled (deviation more than 90%). These three different modes predominantly depend on the value of Nk. The corresponding ranges of Nk for the studied values of psi (10(-2)

A METHOD FOR ESTIMATING DISTRIBUTIONS OF MASS TRANSFER RATE COEFFICIENTS WITH APPLICATION TO PURGING AND BATCH EXPERIMENTS. (R825825)

EPA Science Inventory

Mass transfer between aquifer material and groundwater is often modeled as first-order rate-limited sorption or diffusive exchange between mobile zones and immobile zones with idealized geometries. Recent improvements in experimental techniques and advances in our understanding o...

An overview of recent applications of computational modelling in neonatology

PubMed Central

Wrobel, Luiz C.; Ginalski, Maciej K.; Nowak, Andrzej J.; Ingham, Derek B.; Fic, Anna M.

2010-01-01

This paper reviews some of our recent applications of computational fluid dynamics (CFD) to model heat and mass transfer problems in neonatology and investigates the major heat and mass-transfer mechanisms taking place in medical devices, such as incubators, radiant warmers and oxygen hoods. It is shown that CFD simulations are very flexible tools that can take into account all modes of heat transfer in assisting neonatal care and improving the design of medical devices. PMID:20439275

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.

Single-step azide introduction in proteins via an aqueous diazo transfer.

PubMed

van Dongen, Stijn F M; Teeuwen, Rosalie L M; Nallani, Madhavan; van Berkel, Sander S; Cornelissen, Jeroen J L M; Nolte, Roeland J M; van Hest, Jan C M

2009-01-01

The controlled introduction of azides in proteins provides targetable handles for selective protein manipulation. We present here an efficient diazo transfer protocol that can be applied in an aqueous solution, leading to the facile introduction of azides in the side chains of lysine residues and at the N-terminus of enzymes, e.g. horseradish peroxidase (HRP) and the red fluorescent protein DsRed. The effective introduction of azides was verified by mass spectrometry, after which the azido-proteins were used in Cu(I)-catalyzed [3 + 2] cycloaddition reactions. Azido-HRP retained its catalytic activity after conjugation of a small molecule. This modified protein could also be successfully immobilized on the surface of an acetylene-covered polymersome. Azido-DsRed was coupled to an acetylene-bearing protein allowing it to act as a fluorescent label, demonstrating the wide applicability of the diazo transfer procedure.

End-Functionalized Palladium SCS Pincer Polymers via Controlled Radical Polymerizations.

PubMed

Lye, Diane S; Cohen, Aaron E; Wong, Madeleine Z; Weck, Marcus

2017-07-01

A direct and facile route toward semitelechelic polymers, end-functionalized with palladated sulfur-carbon-sulfur pincer (Pd II -pincer) complexes is reported that avoids any post-polymerization step. Key to our methodology is the combination of reversible addition-fragmentation chain-transfer (RAFT) polymerization with functionalized chain-transfer agents. This strategy yields Pd end-group-functionalized materials with monomodal molar mass dispersities (Đ) of 1.18-1.44. The RAFT polymerization is investigated using a Pd II -pincer chain-transfer agent for three classes of monomers: styrene, tert-butyl acrylate, and N-isopropylacrylamide. The ensuing Pd II -pincer end-functionalized polymers are analyzed using 1 H NMR spectroscopy, gel-permeation chromatography, and elemental analysis. The RAFT polymerization methodology provides a direct pathway for the fabrication of Pd II -pincer functionalized polymers with complete end-group functionalization. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

The effect of velocity slip and multiple convective boundary conditions in a Darcian porous media with microorganism past a vertical stretching/shrinking sheet

NASA Astrophysics Data System (ADS)

Latiff, Nur Amalina Abdul; Yahya, Elisa; Ismail, Ahmad Izani Md.; Amirsom, Ardiana; Basir, Faisal

2017-08-01

An analysis is carried out to study the steady mixed convective boundary layer flow of a nanofluid in a Darcian porous media with microorganisms past a vertical stretching/shrinking sheet. Heat generation/absorption and chemical reaction effects are incorporated in the model. The partial differential equations are transformed into a system of ordinary differential equations by using similarity transformations generated by scaling group transformations. The transformed equations with boundary conditions are solved numerically. The effects of controlling parameters such as velocity slip, Darcy number, heat generation/absorption and chemical reaction on the skin friction factor, heat transfer, mass transfer and microorganism transfer are shown and discuss through graphs. Comparison of numerical solutions in the present study with the previous existing results in literature are made and comparison results are in very good agreement.

Experimental Measurements of Heat Transfer through a Lunar Regolith Simulant in a Vibro-Fluidized Reactor Oven

NASA Technical Reports Server (NTRS)

Nayagam, Vedha; Berger, Gordon M.; Sacksteder, Kurt R.; Paz, Aaron

2012-01-01

Extraction of mission consumable resources such as water and oxygen from the planetary environment provides valuable reduction in launch-mass and potentially extends the mission duration. Processing of lunar regolith for resource extraction necessarily involves heating and chemical reaction of solid material with processing gases. Vibrofluidization is known to produce effective mixing and control of flow within granular media. In this study we present experimental results for vibrofluidized heat transfer in lunar regolith simulants (JSC-1 and JSC-1A) heated up to 900 C. The results show that the simulant bed height has a significant influence on the vibration induced flow field and heat transfer rates. A taller bed height leads to a two-cell circulation pattern whereas a single-cell circulation was observed for a shorter height. Lessons learned from these test results should provide insight into efficient design of future robotic missions involving In-Situ Resource Utilization.

Turbulent heat transfer as a control of platelet ice growth in supercooled under-ice ocean boundary layers

NASA Astrophysics Data System (ADS)

McPhee, Miles G.; Stevens, Craig L.; Smith, Inga J.; Robinson, Natalie J.

2016-04-01

Late winter measurements of turbulent quantities in tidally modulated flow under land-fast sea ice near the Erebus Glacier Tongue, McMurdo Sound, Antarctica, identified processes that influence growth at the interface of an ice surface in contact with supercooled seawater. The data show that turbulent heat exchange at the ocean-ice boundary is characterized by the product of friction velocity and (negative) water temperature departure from freezing, analogous to similar results for moderate melting rates in seawater above freezing. Platelet ice growth appears to increase the hydraulic roughness (drag) of fast ice compared with undeformed fast ice without platelets. Platelet growth in supercooled water under thick ice appears to be rate-limited by turbulent heat transfer and that this is a significant factor to be considered in mass transfer at the underside of ice shelves and sea ice in the vicinity of ice shelves.

Investigating In-Situ Mass Transfer Processes in a Groundwater U Plume Influenced by Groundwater-River Hydrologic and Geochemical Coupling (Invited)

NASA Astrophysics Data System (ADS)

Zachara, J. M.

2009-12-01

The Hanford Integrated Field Research Challenge (IFRC) site is a DOE/BER-supported experimental and monitoring facility focused on multi-scale mass transfer processes (hanfordifc@pnl.gov). It is located within the footprint of a historic uranium (U) waste disposal pond that overlies a contaminated vadose zone and a 1 km+ groundwater U plume. The plume is under a regulatory clean-up mandate. The site is in hydraulic connectivity with the Columbia River that is located approximately 300 m distant. Dramatic seasonal variations in Columbia River stage cause 2m+ variations in water table and associated changes in groundwater flow directions and composition that are believed to recharge contaminant U to the plume through lower vadose zone pumping. The 60 m triangular shaped facility contains 37 monitoring wells equipped with down-hole electrical resistance tomography electrode and thermistor arrays, pressure transducers for continual water level monitoring, and specific conductance electrodes. Well spacings allow cross-hole geophysical interrogation and dynamic plume monitoring. Various geophysical and hydrologic field characterizations were performed during and after well installation, and retrieved sediments are being subjected to a hierarchal laboratory characterization process to support geostatistical models of hydrologic properties, U(VI) distribution and speciation, and equilibrium and kinetic reaction parameters for robust but tractable field-scale reactive transport calculations. Three large scale (10,000 gal+), non-reactive tracer experiments have been performed to evaluate groundwater flowpaths and velocities, facies scale mass transfer, and subsurface heterogeneity effects under different hydrologic conditions (e.g., flow vectors toward or away from the river). A passive monitoring experiment was completed during spring and summer of 2009 that documents spatially variable U(VI) release and plume recharge from the contaminated lower vadose zone during oscillating rising and falling water table events. A large scale injection experiment to evaluate in situ U(VI) desorption kinetics controlled by mass transfer is planned for the fall of 2009. The presentation will summarize key results from these different activities, and discuss their implications to improved plume forecasting and development of an effective groundwater remedy.

Microbial removal of alkanes from dilute gaseous waste streams: kinetics and mass transfer considerations.

PubMed

Barton, J W; Klasson, K T; Koran, L J; Davison, B H

1997-01-01

Treatment of dilute gaseous hydrocarbon waste streams remains a current need for many industries, particularly as increasingly stringent environmental regulations and oversight force emission reduction. Biofiltration systems hold promise for providing low-cost alternatives to more traditional, energy-intensive treatment methods such as incineration and adsorption. Elucidation of engineering principles governing the behavior of such systems, including mass transfer limitations, will broaden their applicability. Our processes exploit a microbial consortium to treat a mixture of 0.5% n-pentane and 0.5% isobutane in air. Since hydrocarbon gases are sparingly soluble in water, good mixing and high surface area between the gas and liquid phases are essential for biodegradation to be effective. One liquid-continuous columnar bioreactor was operated for more than 30 months with continued degradation of n-pentane and isobutane as sole carbon and energy sources. The maximum degradation rate observed in this gas-recycle system was 2 g of volatile organic compounds (VOC)/(m3.h). A trickle-bed bioreactor was operated continuously for over 24 months to provide a higher surface area (using a structured packing) with increased rates. Degradation rates consistently achieved were approximately 50 g of VOC/(m3.h) via single pass in this gas-continuous columnar system. Effective mass transfer coefficients comparable to literature values were also measured for this reactor; these values were substantially higher than those found in the gas-recycle reactor. Control of biomass levels was implemented by limiting the level of available nitrogen in the recirculating aqueous media, enabling long-term stability of reactor performance.

Long-term systemic myostatin inhibition via liver-targeted gene transfer in golden retriever muscular dystrophy.

PubMed

Bish, Lawrence T; Sleeper, Meg M; Forbes, Sean C; Morine, Kevin J; Reynolds, Caryn; Singletary, Gretchen E; Trafny, Dennis; Pham, Jennifer; Bogan, Janet; Kornegay, Joe N; Vandenborne, Krista; Walter, Glenn A; Sweeney, H Lee

2011-12-01

Duchenne muscular dystrophy (DMD) is a lethal, X-linked recessive disease affecting 1 in 3,500 newborn boys for which there is no effective treatment or cure. One novel strategy that has therapeutic potential for DMD is inhibition of myostatin, a negative regulator of skeletal muscle mass that may also promote fibrosis. Therefore, our goal in this study was to evaluate systemic myostatin inhibition in the golden retriever model of DMD (GRMD). GRMD canines underwent liver-directed gene transfer of a self-complementary adeno-associated virus type 8 vector designed to express a secreted dominant-negative myostatin peptide (n = 4) and were compared with age-matched, untreated GRMD controls (n = 3). Dogs were followed with serial magnetic resonance imaging (MRI) for 13 months to assess cross-sectional area and volume of skeletal muscle, then euthanized so that tissue could be harvested for morphological and histological analysis. We found that systemic myostatin inhibition resulted in increased muscle mass in GRMD dogs as assessed by MRI and confirmed at tissue harvest. We also found that hypertrophy of type IIA fibers was largely responsible for the increased muscle mass and that reductions in serum creatine kinase and muscle fibrosis were associated with long-term myostatin inhibition in GRMD. This is the first report describing the effects of long-term, systemic myostatin inhibition in a large-animal model of DMD, and we believe that the simple and effective nature of our liver-directed gene-transfer strategy makes it an ideal candidate for evaluation as a novel therapeutic approach for DMD patients.

Impact of sub-horizontal discontinuities and vertical heterogeneities on recharge processes in a weathered crystalline aquifer in southern India

NASA Astrophysics Data System (ADS)

Nicolas, Madeleine; Selles, Adrien; Bour, Olivier; Maréchal, Jean-Christophe; Crenner, Marion; Wajiduddin, Mohammed; Ahmed, Shakeel

2017-04-01

In the face of increasing demands for irrigated agriculture, many states in India are facing water scarcity issues, leading to severe groundwater depletion. Because perennial water resources in southern India consist mainly of crystalline aquifers, understanding how recharge takes place and the role of preferential flow zones in such heterogeneous media is of prime importance for successful and sustainable aquifer management. Here we investigate how vertical heterogeneities and highly transmissive sub-horizontal discontinuities may control groundwater flows and recharge dynamics. Recharge processes in the vadose zone were examined by analysing the propagation of an infiltration front and mass transfers resulting from the implementation of a managed aquifer recharge (MAR) structure. Said structure was set up in the Experimental Hydrogeological Park in Telangana (Southern India), a well-equipped and continuously monitored site, which is periodically supplied with surface water deviated from the nearby Musi river, downstream of Hyderabad. An initial volume balance equation was applied to quantify the overall inputs from the MAR structure into the groundwater system, which was confirmed using a chloride mass balance approach. To understand how this incoming mass is then distributed within the aquifer, we monitored the evolution of water volumes in the tank, and the resulting lateral propagation front observed in the surrounding borehole network. Borehole logs of temperature and conductivity were regularly performed to identify preferential flow paths. As a result we observed that mass transfers take place in the way of preferential lateral flow through the most transmissive zones of the profile. These include the interface between the lower portion of the upper weathered horizon (the saprolite) and the upper part of the underlying fissured granite, as well as the first flowing fractures. This leads to a rapid lateral transfer of recharge, which allows quick replenishment of aquifers but may have severe implications regarding groundwater quality, whether contaminants originate from diffuse sources (such as fertilizers), or a localized injection of polluted surface water. These findings confirm previous studies about the non-linear behaviour of hard rock aquifers (Guihéneuf et al., 2014) and recharge processes (Boisson et al., 2015; Alazard et al., 2015). Depending on water level conditions, the aquifer shifts from a regional flow system (when superficial more connected and weathered levels are saturated), to independent local flow systems (when only the lower lesser fractured portion is saturated). Thus recharge seems to be controlled by the existence of (i) vertical heterogeneities within the unsaturated zone and (ii) highly transmissive sub-horizontal discontinuities, both of which controlling groundwater flows and recharge dynamics.

Automated mass spectrometer analysis system

NASA Technical Reports Server (NTRS)

Giffin, Charles E. (Inventor); Kuppermann, Aron (Inventor); Dreyer, William J. (Inventor); Boettger, Heinz G. (Inventor)

1982-01-01

An automated mass spectrometer analysis system is disclosed, in which samples are automatically processed in a sample processor and converted into volatilizable samples, or their characteristic volatilizable derivatives. Each volatilizable sample is sequentially volatilized and analyzed in a double focusing mass spectrometer, whose output is in the form of separate ion beams all of which are simultaneously focused in a focal plane. Each ion beam is indicative of a different sample component or different fragments of one or more sample components and the beam intensity is related to the relative abundance of the sample component. The system includes an electro-optical ion detector which automatically and simultaneously converts the ion beams, first into electron beams which in turn produce a related image which is transferred to the target of a vilicon unit. The latter converts the images into electrical signals which are supplied to a data processor, whose output is a list of the components of the analyzed sample and their abundances. The system is under the control of a master control unit, which in addition to monitoring and controlling various power sources, controls the automatic operation of the system under expected and some unexpected conditions and further protects various critical parts of the system from damage due to particularly abnormal conditions.

Automated mass spectrometer analysis system

NASA Technical Reports Server (NTRS)

Boettger, Heinz G. (Inventor); Giffin, Charles E. (Inventor); Dreyer, William J. (Inventor); Kuppermann, Aron (Inventor)

1978-01-01

An automated mass spectrometer analysis system is disclosed, in which samples are automatically processed in a sample processor and converted into volatilizable samples, or their characteristic volatilizable derivatives. Each volatizable sample is sequentially volatilized and analyzed in a double focusing mass spectrometer, whose output is in the form of separate ion beams all of which are simultaneously focused in a focal plane. Each ion beam is indicative of a different sample component or different fragments of one or more sample components and the beam intensity is related to the relative abundance of the sample component. The system includes an electro-optical ion detector which automatically and simultaneously converts the ion beams, first into electron beams which in turn produce a related image which is transferred to the target of a vidicon unit. The latter converts the images into electrical signals which are supplied to a data processor, whose output is a list of the components of the analyzed sample and their abundances. The system is under the control of a master control unit, which in addition to monitoring and controlling various power sources, controls the automatic operation of the system under expected and some unexpected conditions and further protects various critical parts of the system from damage due to particularly abnormal conditions.

Does tidal capture produce cataclysmic variables?

NASA Technical Reports Server (NTRS)

Bailyn, Charles D.; Grindlay, Jonathan E.; Garcia, Michael R.

1990-01-01

It is shown that earlier estimates of the number of cataclysmic variables (CVs) to be expected from tidal capture in globular clusters may have been considerably too high, since many such binaries will result in unstable mass transfer, and thus not become CVs after all. In particular, CVs with white dwarf masses less than or obout 1.0 solar mass will be supressed. Such unstable mass transfer events may produce some of the cluster mass loss required to stabilize the cluster core. The smaller number of stable CVs predicted may suggest a reconsideration of the nature of some of the low-luminosity cluster X-ray sources.

Kinetic Study of Mass Transfer by Sodium Hydroxide in Nickel Under Free-convection Conditions /by Don R. Mosher and Robert A. Lad

NASA Technical Reports Server (NTRS)

Mosher, Don R; Lad, Robert A

1954-01-01

An investigation was conducted using static capsules fabricated from "L" nickel tubing to determine the effect of temperature level, temperature gradient, and test duration on corrosion and mass transfer by molten sodium hydroxide under free-convection conditions. A base temperature range from 1000 degrees to 1600 degrees F with temperature differences to 500 degrees was studied. The rate of mass transfer was found to be strongly dependent on both temperature level and gradient. The rate shows little tendency to decrease for test durations up to 200 hours, although the concentration of nickel in the melt approaches a limited value after 100 hours.

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.

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.

Recent innovations in edible and/or biodegradable packaging materials.

PubMed

Guilbert, S; Cuq, B; Gontard, N

1997-01-01

Certain newly discovered characteristics of natural biopolymers should make them a choice material to be used for different types of wrappings and films. Edible and/or biodegradable packagings produced from agricultural origin macromolecules provide a supplementary and sometimes essential means to control physiological, microbiological, and physicochemical changes in food products. This is accomplished (i) by controlling mass transfers between food product and ambient atmosphere or between components in heterogeneous food product, and (iii) by modifying and controlling food surface conditions (pH, level of specific functional agents, slow release of flavour compounds), it should be stressed that the material characteristics (polysaccharide, protein, or lipid, plasticized or not, chemically modified or not, used alone or in combination) and the fabrication procedures (casting of a film-forming solution, thermoforming) must be adapted to each specific food product and usage condition (relative humidity, temperature). Some potential uses of these materials (e.g. wrapping of various fabricated foods; protection of fruits and vegetables by control of maturation; protection of meat and fish; control of internal moisture transfer in pizzas), which are hinged on film properties (e.g. organoleptic, mechanical, gas and solute barrier) are described with examples.

High-resolution experiments on chemical oxidation of DNAPL in variable-aperture fractures

NASA Astrophysics Data System (ADS)

Arshadi, Masoud; Rajaram, Harihar; Detwiler, Russell L.; Jones, Trevor

2015-04-01

Chemical oxidation of dense nonaqueous-phase liquids (DNAPLs) by permanganate has emerged as an effective remediation strategy in fractured rock. We present high-resolution experimental investigations in transparent analog variable-aperture fractures to improve understanding of chemical oxidation of residual entrapped trichloroethylene (TCE) in fractures. Four experiments were performed with different permanganate concentrations, flow rates, and initial TCE phase geometry. The initial aperture field and evolving entrapped-phase geometry were quantified for each experiment. The integrated mass transfer rate from the TCE phase for all experiments exhibited three time regimes: an early-time regime with slower mass transfer rates limited by low specific interfacial area; an intermediate-time regime with higher mass transfer rates resulting from breakup of large TCE blobs, which greatly increases specific interfacial area; and a late-time regime with low mass transfer rates due to the deposition of MnO2 precipitates. In two experiments, mass balance analyses suggested that TCE mass removal rates exceeded the maximum upper bound mass removal rates derived by assuming that oxidation and dissolution are the only mechanisms for TCE mass removal. We propose incomplete oxidation by permanganate and TCE solubility enhancement by intermediate reaction products as potential mechanisms to explain this behavior. We also speculate that some intermediate reaction products with surfactant-like properties may play a role in lowering the TCE-water interfacial tension, thus causing breakup of large TCE blobs. Our quantitative experimental measurements will be useful in the context of developing accurate computational models for chemical oxidation of TCE in fractures.

Biomechanical analysis of materials handling manipulators in short distance transfers of moderate mass objects: joint strength, spine forces and muscular antagonism.

PubMed

Nussbaum, M A; Chaffin, D B; Baker, G

1999-12-01

Although often suggested as a control measure to alleviate musculoskeletal stresses, the use of mechanical assistance devices (i.e. manipulators) in load transfers has not been extensively studied. Without data describing the biomechanical effects of such devices, justification for decisions regarding implementation of such tools is difficult. An experimental study of two types of mechanical manipulators (articulated arm and overhead hoist) was conducted to determine whether biomechanical stresses, and hence injury risk, would be alleviated. Short distance transfers of loads with moderate mass were performed both manually and with manipulator assistance under a variety of task conditions. Using analysis and output from new dynamic torso models, strength demands at the shoulders and low back, lumbar spine forces, and lumbar muscle antagonism were determined. Strength requirements decreased significantly at both the shoulders and low back when using either manipulator in comparison with similar transfers performed manually. Peak spine compression and anterior-posterior (a-p) shear forces were reduced by about 40% on average, and these reductions were shown to be primarily caused by decreases in hand forces and resultant spinal moments. Two metrics of muscular antagonism were defined, and analysis showed that torso muscle antagonism was largest overall when using the hoist. The results overall suggest that hoist-assisted transfers, although better in reducing spine compression forces, may impose relatively higher demands on coordination and/or stability at extreme heights or with torso twisting motions. The relatively higher strength requirements and spine compression associated with the articulated arm may be a result of the high inertia of the system. Potential benefits of practice and training are discussed, and conclusions regarding implementation of mechanical manipulators are given.

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…

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...

HIGH-TEMPERATURE, SHORT-TIME SULFATION OF CALCIUM- BASED SORBENTS. 1. THEORETICAL SULFATION MODEL

EPA Science Inventory

A mathematical model for the sulfation of CaO is developed around the overlapping grain concept. The potential influence of high mass-transfer rates from simultaneous calcination of CaCO3 or Ca(OH)2 is incorporated in the mass-transfer coefficient for SO2 diffusion to the partic...

Henry’s Law Constant and Overall Mass Transfer Coefficient for Formaldehyde Emission from Small Water Pools under Simulated Indoor Environmental Conditions

EPA Science Inventory

The Henry’s law constant (HLC) and the overall mass transfer coefficient are both important parameters for modeling formaldehyde emissions from aqueous solutions. In this work, the apparent HLCs for aqueous formaldehyde solutions were determined in the concentration range from 0....

Sales Training: Effects of Spaced Practice on Training Transfer

ERIC Educational Resources Information Center

Kauffeld, Simone; Lehmann-Willenbrock, Nale

2010-01-01

Purpose: The benefits of spaced training over massed training practice are well established in the laboratory setting. In a field study design with sales trainings, the purpose of this paper is to investigate the effects of spaced compared with massed practice on transfer quantity and quality, sales competence, and key figures.…

Snap evaporation of droplets on smooth topographies.

PubMed

Wells, Gary G; Ruiz-Gutiérrez, Élfego; Le Lirzin, Youen; Nourry, Anthony; Orme, Bethany V; Pradas, Marc; Ledesma-Aguilar, Rodrigo

2018-04-11

Droplet evaporation on solid surfaces is important in many applications including printing, micro-patterning and cooling. While seemingly simple, the configuration of evaporating droplets on solids is difficult to predict and control. This is because evaporation typically proceeds as a "stick-slip" sequence-a combination of pinning and de-pinning events dominated by static friction or "pinning", caused by microscopic surface roughness. Here we show how smooth, pinning-free, solid surfaces of non-planar topography promote a different process called snap evaporation. During snap evaporation a droplet follows a reproducible sequence of configurations, consisting of a quasi-static phase-change controlled by mass diffusion interrupted by out-of-equilibrium snaps. Snaps are triggered by bifurcations of the equilibrium droplet shape mediated by the underlying non-planar solid. Because the evolution of droplets during snap evaporation is controlled by a smooth topography, and not by surface roughness, our ideas can inspire programmable surfaces that manage liquids in heat- and mass-transfer applications.

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".

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.

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.

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.

Influence of the liquid-phase mass transfer on the performance of a packed-bed bioreactor for wastewater treatment.

PubMed

Sarti, A; Vieira, L G; Foresti, E; Zaiat, M

2001-07-01

This paper reports on the influence of the liquid-phase mass transfer on the performance of a horizontal-flow, anaerobic, immobilized-biomass (HAIB) reactor treating low-strength wastewater. The HAIB reactor was subjected to liquid superficial velocities (vs) ranging from 10 to 50 cm h(-1), corresponding to hydraulic detention time (theta h) of 10-2 h. The best performance was achieved at an overall theta h of 3.3 h due to the interdependence of biochemical reactions and mass transfer mechanisms for process optimization. The HAIB reactor was provided with four intermediate sampling ports, and the values of v(s) were fixed to permit sampling at different ports corresponding to thetah of 2 h as vs increased. The chemical oxygen demand removal (COD) efficiencies increased from 68% to 82% with the increase of v(s) from 10 to 50 cm h(-1). It could be concluded that the performance of the HAIB reactor was improved significantly by increasing vs, thus decreasing the liquid-phase mass transfer resistance.

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.

Surfactant effects on alpha-factors in aeration systems.

PubMed

Rosso, Diego; Stenstrom, Michael K

2006-04-01

Aeration in wastewater treatment processes accounts for the largest fraction of plant energy costs. Aeration systems function by shearing the surface (surface aerators) or releasing bubbles at the bottom of the tank (coarse- or fine-bubble aerators). Surfactant accumulation on gas-liquid interfaces reduces mass transfer rates, and this reduction in general is larger for fine-bubble aerators. This study evaluates mass transfer effects on the characterization and specification of aeration systems in clean and process water conditions. Tests at different interfacial turbulence regimes show higher gas transfer depression for lower turbulence regimes. Contamination effects can be offset at the expense of operating efficiency, which is characteristic of surface aerators and coarse-bubble diffusers. Results describe the variability of alpha-factors measured at small scale, due to uncontrolled energy density. Results are also reported in dimensionless empirical correlations describing mass transfer as a function of physiochemical and geometrical characteristics of the aeration process.

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.

Relationship between mass-flux reduction and source-zone mass removal: analysis of field data.

PubMed

Difilippo, Erica L; Brusseau, Mark L

2008-05-26

The magnitude of contaminant mass-flux reduction associated with a specific amount of contaminant mass removed is a key consideration for evaluating the effectiveness of a source-zone remediation effort. Thus, there is great interest in characterizing, estimating, and predicting relationships between mass-flux reduction and mass removal. Published data collected for several field studies were examined to evaluate relationships between mass-flux reduction and source-zone mass removal. The studies analyzed herein represent a variety of source-zone architectures, immiscible-liquid compositions, and implemented remediation technologies. There are two general approaches to characterizing the mass-flux-reduction/mass-removal relationship, end-point analysis and time-continuous analysis. End-point analysis, based on comparing masses and mass fluxes measured before and after a source-zone remediation effort, was conducted for 21 remediation projects. Mass removals were greater than 60% for all but three of the studies. Mass-flux reductions ranging from slightly less than to slightly greater than one-to-one were observed for the majority of the sites. However, these single-snapshot characterizations are limited in that the antecedent behavior is indeterminate. Time-continuous analysis, based on continuous monitoring of mass removal and mass flux, was performed for two sites, both for which data were obtained under water-flushing conditions. The reductions in mass flux were significantly different for the two sites (90% vs. approximately 8%) for similar mass removals ( approximately 40%). These results illustrate the dependence of the mass-flux-reduction/mass-removal relationship on source-zone architecture and associated mass-transfer processes. Minimal mass-flux reduction was observed for a system wherein mass removal was relatively efficient (ideal mass-transfer and displacement). Conversely, a significant degree of mass-flux reduction was observed for a site wherein mass removal was inefficient (non-ideal mass-transfer and displacement). The mass-flux-reduction/mass-removal relationship for the latter site exhibited a multi-step behavior, which cannot be predicted using some of the available simple estimation functions.

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

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

Chiral behavior of K →π l ν decay form factors in lattice QCD with exact chiral symmetry

NASA Astrophysics Data System (ADS)

Aoki, S.; Cossu, G.; Feng, X.; Fukaya, H.; Hashimoto, S.; Kaneko, T.; Noaki, J.; Onogi, T.; Jlqcd Collaboration

2017-08-01

We calculate the form factors of the K →π l ν semileptonic decays in three-flavor lattice QCD and study their chiral behavior as a function of the momentum transfer and the Nambu-Goldstone boson masses. Chiral symmetry is exactly preserved by using the overlap quark action, which enables us to directly compare the lattice data with chiral perturbation theory (ChPT). We generate gauge ensembles at a lattice spacing of 0.11 fm with four pion masses covering 290-540 MeV and a strange quark mass ms close to its physical value. By using the all-to-all quark propagator, we calculate the vector and scalar form factors with high precision. Their dependence on ms and the momentum transfer is studied by using the reweighting technique and the twisted boundary conditions for the quark fields. We compare the results for the semileptonic form factors with ChPT at next-to-next-to-leading order in detail. While many low-energy constants appear at this order, we make use of our data of the light meson electromagnetic form factors in order to control the chiral extrapolation. We determine the normalization of the form factors as f+(0 )=0.9636 (36 )(-35+57) and observe reasonable agreement of their shape with experiment.

Global Modeling of Nebulae with Particle Growth, Drift, and Evaporation Fronts. I. Methodology and Typical Results

NASA Astrophysics Data System (ADS)

Estrada, Paul R.; Cuzzi, Jeffrey N.; Morgan, Demitri A.

2016-02-01

We model particle growth in a turbulent, viscously evolving protoplanetary nebula, incorporating sticking, bouncing, fragmentation, and mass transfer at high speeds. We treat small particles using a moments method and large particles using a traditional histogram binning, including a probability distribution function of collisional velocities. The fragmentation strength of the particles depends on their composition (icy aggregates are stronger than silicate aggregates). The particle opacity, which controls the nebula thermal structure, evolves as particles grow and mass redistributes. While growing, particles drift radially due to nebula headwind drag. Particles of different compositions evaporate at “evaporation fronts” (EFs) where the midplane temperature exceeds their respective evaporation temperatures. We track the vapor and solid phases of each component, accounting for advection and radial and vertical diffusion. We present characteristic results in evolutions lasting 2 × 105 years. In general, (1) mass is transferred from the outer to the inner nebula in significant amounts, creating radial concentrations of solids at EFs; (2) particle sizes are limited by a combination of fragmentation, bouncing, and drift; (3) “lucky” large particles never represent a significant amount of mass; and (4) restricted radial zones just outside each EF become compositionally enriched in the associated volatiles. We point out implications for millimeter to submillimeter SEDs and the inference of nebula mass, radial banding, the role of opacity on new mechanisms for generating turbulence, the enrichment of meteorites in heavy oxygen isotopes, variable and nonsolar redox conditions, the primary accretion of silicate and icy planetesimals, and the makeup of Jupiter’s core.

Electron transfer dissociation (ETD): The mass spectrometric breakthrough essential for O-GlcNAc protein site assignments – A study of the O-GlcNAcylated protein Host Cell Factor C1

PubMed Central

Myers, Samuel A.; Daou, Salima; Affar, El Bachir; Burlingame, AL

2014-01-01

The development of electron-based, unimolecular dissociation mass spectrometric methods, i.e. electron capture and electron transfer dissociation (ECD and ETD, respectively), has greatly increased the speed and reliability of labile post-translational modification (PTM) site assignment. The field of intracellular O-GlcNAc (O-linked N-acetylglucosamine) signaling has especially advanced with the advent of ETD mass spectrometry. Only within the last five years have proteomic-scale experiments utilizing ETD allowed the assignment of hundreds of O-GlcNAc sites within cells and subcellular structures. Our ability to identify and unambiguously assign the site of O-GlcNAc modifications using ETD is rapidly increasing our understanding of this regulatory glycosylation and its potential interaction with other PTMs. Here, we discuss the advantages of using ETD, complimented with collisional-activation mass spectrometry (CID/CAD), in a study of O-GlcNAc modified peptides of the extensively O-GlcNAcylated protein Host Cell Factor C1 (HCF-1). HCF-1 is a transcriptional co-regulator, forms a stable complex with O-GlcNAc transferase and is involved in control of cell cycle progression. ETD, along with higher energy collisional dissociation (HCD) mass spectrometry, was employed to assign the PTMs of the HCF-1 protein isolated from HEK293T cells. These include nineteen sites of O-GlcNAcylation, two sites of phosphorylation and two sites bearing dimethylarginine, and showcase the residue-specific, PTM complexity of this regulator of cell proliferation. PMID:23335398

Irradiation and Enhanced Magnetic Braking in Cataclysmic Variables

NASA Astrophysics Data System (ADS)

McCormick, P. J.; Frank, J.

1998-12-01

In previous work we have shown that irradiation driven mass transfer cycles can occur in cataclysmic variables at all orbital periods if an additional angular momentum loss mechanism is assumed. Earlier models simply postulated that the enhanced angular momentum loss was proportional to the mass transfer rate without any specific physical model. In this paper we present a simple modification of magnetic braking which seems to have the right properties to sustain irradiation driven cycles at all orbital periods. We assume that the wind mass loss from the irradiated companion consists of two parts: an intrinsic stellar wind term plus an enhancement that is proportional to the irradiation. The increase in mass flow reduces the specific angular momentum carried away by the flow but nevertheless yields an enhanced rate of magnetic braking. The secular evolution of the binary is then computed numerically with a suitably modified double polytropic code (McCormick & Frank 1998). With the above model and under certain conditions, mass transfer oscillations occur at all orbital periods.

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

Clausen, Drew; Wade, Richard A.; Kopparapu, Ravi Kumar

Binaries that contain a hot subdwarf (sdB) star and a main-sequence companion may have interacted in the past. This binary population has historically helped determine our understanding of binary stellar evolution. We have computed a grid of binary population synthesis models using different assumptions about the minimum core mass for helium ignition, the envelope binding energy, the common-envelope ejection efficiency, the amount of mass and angular momentum lost during stable mass transfer, and the criteria for stable mass transfer on the red giant branch and in the Hertzsprung gap. These parameters separately and together can significantly change the entire predictedmore » population of sdBs. Nonetheless, several different parameter sets can reproduce the observed subpopulation of sdB + white dwarf and sdB + M dwarf binaries, which has been used to constrain these parameters in previous studies. The period distribution of sdB + early F dwarf binaries offers a better test of different mass transfer scenarios for stars that fill their Roche lobes on the red giant branch.« less

Numerical investigation of saturated upward flow boiling of water in a vertical tube using VOF model: effect of different boundary conditions

NASA Astrophysics Data System (ADS)

Hasanpour, B.; Irandoost, M. S.; Hassani, M.; Kouhikamali, R.

2018-01-01

In this paper a numerical simulation of upward two-phase flow evaporation in a vertical tube has been studied by considering water as working fluid. To this end, the computational fluid dynamic simulations of this system are performed with heat and mass transfer mechanisms due to energy transfer during the phase change interaction near the heat transfer surface. The volume of fluid model in an available Eulerian-Eulerian approach based on finite volume method is utilized and the mass source term in conservation of mass equation is implemented using a user defined function. The characteristics of water flow boiling such as void fraction and heat transfer coefficient distribution are investigated. The main cause of fluctuations on heat transfer coefficient and volume fraction is velocity increment in the vapor phase rather than the liquid phase. The case study of this research including convective heat transfer coefficient and tube diameter are considered as a parametric study. The operating conditions are considered at high pressure in saturation temperature and the physical properties of water are determined by considering system's inlet temperature and pressure in saturation conditions. Good agreement is achieved between the numerical and the experimental values of heat transfer coefficients.

Numerical investigation of saturated upward flow boiling of water in a vertical tube using VOF model: effect of different boundary conditions

NASA Astrophysics Data System (ADS)

Hasanpour, B.; Irandoost, M. S.; Hassani, M.; Kouhikamali, R.

2018-07-01

In this paper a numerical simulation of upward two-phase flow evaporation in a vertical tube has been studied by considering water as working fluid. To this end, the computational fluid dynamic simulations of this system are performed with heat and mass transfer mechanisms due to energy transfer during the phase change interaction near the heat transfer surface. The volume of fluid model in an available Eulerian-Eulerian approach based on finite volume method is utilized and the mass source term in conservation of mass equation is implemented using a user defined function. The characteristics of water flow boiling such as void fraction and heat transfer coefficient distribution are investigated. The main cause of fluctuations on heat transfer coefficient and volume fraction is velocity increment in the vapor phase rather than the liquid phase. The case study of this research including convective heat transfer coefficient and tube diameter are considered as a parametric study. The operating conditions are considered at high pressure in saturation temperature and the physical properties of water are determined by considering system's inlet temperature and pressure in saturation conditions. Good agreement is achieved between the numerical and the experimental values of heat transfer coefficients.

The materials processing research base of the Materials Processing Center

NASA Technical Reports Server (NTRS)

Latanision, R. M.

1986-01-01

An annual report of the research activities of the Materials Processing Center of the Massachusetts Institute of Technology is given. Research on dielectrophoresis in the microgravity environment, phase separation kinetics in immiscible liquids, transport properties of droplet clusters in gravity-free fields, probes and monitors for the study of solidification of molten semiconductors, fluid mechanics and mass transfer in melt crystal growth, and heat flow control and segregation in directional solidification are discussed.

Space transfer concepts and analysis for exploration missions

NASA Technical Reports Server (NTRS)

1990-01-01

The progress and results are summarized for mission/system requirements database; mission analysis; GN and C (Guidance, Navigation, and Control), aeroheating, Mars landing; radiation protection; aerobrake mass analysis; Shuttle-Z, TMIS (Trans-Mars Injection Stage); Long Duration Habitat Trade Study; evolutionary lunar and Mars options; NTR (Nuclear Thermal Rocket); NEP (Nuclear Electric Propulsion) update; SEP (Solar Electric Propulsion) update; orbital and space-based requirements; technology; piloted rover; programmatic task; and evolutionary and innovative architecture.

Low Gravity Issues of Deep Space Refueling

NASA Technical Reports Server (NTRS)

Chato, David J.

2005-01-01

This paper discusses the technologies required to develop deep space refueling of cryogenic propellants and low cost flight experiments to develop them. Key technologies include long term storage, pressure control, mass gauging, liquid acquisition, and fluid transfer. Prior flight experiments used to mature technologies are discussed. A plan is presented to systematically study the deep space refueling problem and devise low-cost experiments to further mature technologies and prepare for full scale flight demonstrations.

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

A simple mathematical method to estimate ammonia emission from in-house windrowing of poultry litter.

PubMed

Ro, Kyoung S; Szogi, Ariel A; Moore, Philip A

2018-05-12

In-house windrowing between flocks is an emerging sanitary management practice to partially disinfect the built-up litter in broiler houses. However, this practice may also increase ammonia (NH 3 ) emission from the litter due to the increase in litter temperature. The objectives of this study were to develop mathematical models to estimate NH 3 emission rates from broiler houses practicing in-house windrowing between flocks. Equations to estimate mass-transfer areas form different shapes windrowed litter (triangular, rectangular, and semi-cylindrical prisms) were developed. Using these equations, the heights of windrows yielding the smallest mass-transfer area were estimated. Smaller mass-transfer area is preferred as it reduces both emission rates and heat loss. The heights yielding the minimum mass-transfer area were 0.8 and 0.5 m for triangular and rectangular windrows, respectively. Only one height (0.6 m) was theoretically possible for semi-cylindrical windrows because the base and the height were not independent. Mass-transfer areas were integrated with published process-based mathematical models to estimate the total house NH 3 emission rates during in-house windrowing of poultry litter. The NH 3 emission rate change calculated from the integrated model compared well with the observed values except for the very high NH 3 initial emission rate from mechanically disturbing the litter to form the windrows. This approach can be used to conveniently estimate broiler house NH 3 emission rates during in-house windrowing between flocks by simply measuring litter temperatures.

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).

Intrinsic kinetic parameters of substrate utilization by immobilized anaerobic sludge.

PubMed

Zaiat, M; Vieira, L G; Foresti, E

1997-01-20

This article presents a method for evaluating the intrinsic kinetic parameters of the specific substrate utilization rate (r) equation and discusses the results obtained for anaerobic sludge-bed samples taken from a horizontal-flow anaerobic immobilized sludge (HAIS) reactor. This method utilizes a differential reactor filled with polyurethane foam matrices containing immobilized anaerobic sludge which is subjected to a range of feeding substrate flow rates. The range of liquid superficial velocities thus obtained are used for generating data of observed specific substrate utilization rates (r(obs)) under a diversity of external mass transfer resistance conditions. The r(obs) curves are then adjusted to permit their extrapolation for the condition of no external mass transfer resistance, and the values determined are used as a test for the condition of absence of limitation of internal mass transfer. The intrinsic parameters r(max), the maximum specific substrate utilization rate, and K(s), the half-velocity coefficient, are evaluated from the r values under no external mass transfer resistance and no internal mass transfer limitation. The application of such a method for anaerobic sludge immobilized in polyurethane foam particles treating a glucose substrate at 30 degrees C resulted in intrinsic r(max) and K(s), respectively, of 0.330 mg chemical oxygen demand (COD) . mg(-1) volatile suspended solids (VSS) . h(-1) and 72 mg COD . L(-1). In comparison with the values found in the literature, intrinsic r(max) is significantly high and intrinsic K(s) is relatively low. (c) 1997 John Wiley & Sons, Inc.

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.

Electron Capture Supernovae from Close Binary Systems

NASA Astrophysics Data System (ADS)

Poelarends, Arend J. T.; Wurtz, Scott; Tarka, James; Cole Adams, L.; Hills, Spencer T.

2017-12-01

We present the first detailed study of the Electron Capture Supernova Channel (ECSN Channel) for a primary star in a close binary star system. Progenitors of ECSN occupy the lower end of the mass spectrum of supernova progenitors and are thought to form the transition between white dwarf progenitors and core-collapse progenitors. The mass range for ECSN from close binary systems is thought to be wider than the range for single stars, because of the effects of mass transfer on the helium core. Using the MESA stellar evolution code, we explored the parameter space of initial primary masses between 8 and 17 {M}⊙ , using a large grid of models. We find that the initial primary mass and the mass transfer evolution are important factors in the final fate of stars in this mass range. Mass transfer due to Roche lobe overflow during and after carbon burning causes the core to cool down so that it avoids neon ignition, even in helium-free cores with masses up to 1.52 {M}⊙ , which in single stars would ignite neon. If the core is able to contract to high enough densities for electron captures to commence, we find that, for the adopted Ledoux convection criterion, the initial mass range for the primary to evolve into an ECSN is between 13.5 and 17.6 {M}⊙ . The mass ratio, initial period, and mass-loss efficiency only marginally affect the predicted ranges.

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 biogeochemical exchange at the channel-floodplain interface and quantification of process associated with environmental flow and river restoration strategies.

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.

Advanced Heat/Mass Exchanger Technology for Geothermal and Solar Renewable Energy Systems

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

Greiner, Miles; Childress, Amy; Hiibel, Sage

2014-12-16

Northern Nevada has abundant geothermal and solar energy resources, and these renewable energy sources provide an ample opportunity to produce economically viable power. Heat/mass exchangers are essential components to any energy conversion system. Improvements in the heat/mass exchange process will lead to smaller, less costly (more efficient) systems. There is an emerging heat transfer technology, based on micro/nano/molecular-scale surface science that can be applied to heat/mass exchanger design. The objective is to develop and characterize unique coating materials, surface configurations and membranes capable of accommodating a 10-fold increase in heat/mass exchanger performance via phase change processes (boiling, condensation, etc.) andmore » single phase convective heat/mass transfer.« less

Experimental study on bubble dynamics and wall heat transfer arising from a single nucleation site at subcooled flow boiling conditions – Part 2: Data analysis on sliding bubble characteristics and associated wall heat transfer

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

Yooa, Junsoo; Estrada-Perez, Carlos E.; Hassan, Yassin A.

In this second of two companion papers presents an analysis of sliding bubble and wall heat transfer parameters measured during subcooled boiling in a square, vertical, upward flow channel. Bubbles were generated only from a single nucleation site for better observation of both the sliding bubbles’ characteristics and their impact on wall heat transfer through optical measurement techniques. Specific interests include: (i) bubbles departure and subsequent growth while sliding, (ii) bubbles release frequency, (iii) coalescence of sliding bubbles, (iv) sliding bubbles velocity, (v) bubbles size distribution and (vi) wall heat transfer influenced by sliding bubbles. Our results showed that slidingmore » bubbles involve two distinct growth behaviors: (i) at low mass fluxes, sliding bubbles grew fast near the nucleation site, subsequently shrank, and then grew again, (ii) as mass flux increased, however, sliding bubbles grew more steadily. The bubbles originating from the single nucleation site coalesced frequently while sliding, which showed close relation with bubbles release frequency. The sliding bubble velocity near the nucleation site consistently decreased by increasing mass flux, while the observation often became reversed as the bubbles slid downstream due to the effect of interfacial drag. The sliding bubbles moved faster than the local liquid (i.e., ur<0) at low mass flux conditions, but it became reversed as the mass flux increased. The size distribution of sliding bubbles followed Gaussian distribution well both near and far from the nucleation site. The standard deviation of bubble size varied insignificantly through sliding compared to the changes in mean bubble size. Lastly, the sliding bubbles enhanced the wall heat transfer and the effect became more noticeable as inlet subcooling/mass flux decreased or wall heat flux increased. Particularly, the sliding bubble characteristics such as bubble growth behavior observed near the nucleation site played a dominant role in determining the ultimate level of wall heat transfer enhancement within the test channel.« less

Experimental study on bubble dynamics and wall heat transfer arising from a single nucleation site at subcooled flow boiling conditions – Part 2: Data analysis on sliding bubble characteristics and associated wall heat transfer

DOE PAGES

Yooa, Junsoo; Estrada-Perez, Carlos E.; Hassan, Yassin A.

2016-04-28

In this second of two companion papers presents an analysis of sliding bubble and wall heat transfer parameters measured during subcooled boiling in a square, vertical, upward flow channel. Bubbles were generated only from a single nucleation site for better observation of both the sliding bubbles’ characteristics and their impact on wall heat transfer through optical measurement techniques. Specific interests include: (i) bubbles departure and subsequent growth while sliding, (ii) bubbles release frequency, (iii) coalescence of sliding bubbles, (iv) sliding bubbles velocity, (v) bubbles size distribution and (vi) wall heat transfer influenced by sliding bubbles. Our results showed that slidingmore » bubbles involve two distinct growth behaviors: (i) at low mass fluxes, sliding bubbles grew fast near the nucleation site, subsequently shrank, and then grew again, (ii) as mass flux increased, however, sliding bubbles grew more steadily. The bubbles originating from the single nucleation site coalesced frequently while sliding, which showed close relation with bubbles release frequency. The sliding bubble velocity near the nucleation site consistently decreased by increasing mass flux, while the observation often became reversed as the bubbles slid downstream due to the effect of interfacial drag. The sliding bubbles moved faster than the local liquid (i.e., ur<0) at low mass flux conditions, but it became reversed as the mass flux increased. The size distribution of sliding bubbles followed Gaussian distribution well both near and far from the nucleation site. The standard deviation of bubble size varied insignificantly through sliding compared to the changes in mean bubble size. Lastly, the sliding bubbles enhanced the wall heat transfer and the effect became more noticeable as inlet subcooling/mass flux decreased or wall heat flux increased. Particularly, the sliding bubble characteristics such as bubble growth behavior observed near the nucleation site played a dominant role in determining the ultimate level of wall heat transfer enhancement within the test channel.« less

The continuous assembly and transfer of nanoelements

NASA Astrophysics Data System (ADS)

Kumar, Arun

Patterned nanoelements on flexible polymeric substrates at micro/nano scale at high rate, low cost, and commercially viable route offer an opportunity for manufacturing devices with micro/nano scale features. These micro/nano scale now made with various nanoelement can enhance the device functionality in sensing and switching due to their improved conductivity and better mechanical properties. In this research the fundamental understanding of high rate assembly and transfer of nanoelements has been developed. To achieve this objective, three sub topics were made. In the first step, the use of electrophoresis for the controlled assembly of CNT's on interdigitated templates has been shown. The time scale of assembly reported is shorter than the previously reported assembly time (60 seconds). The mass deposited was also predicted using the Hamaker's law. It is also shown that pre-patterned CNT's could be transferred from the rigid templates onto flexible polymeric substrates using a thermoforming process. The time scale of transfer is less than one minute (50 seconds) and was found to be dependent on polymer chemistry. It was found that CNT's preferentially transfer from Au electrode to non-polar polymeric substrates (polyurethane and polyethylene terephalathate glycol) in the thermoforming process. In the second step, a novel process (Pulsed Electrophoresis) has been shown for the first time to assist the assembly of conducting polyaniline on gold nanowire interdigitated templates. This technique offers dynamic control over heat build-up, which has been a main drawback in the DC electrophoresis and AC dielectrophoresis as well as the main cause of nanowire template damage. The use of this technique allowed higher voltages to be applied, resulting in shorter assembly times (e.g., 17.4 seconds, assembly resolution of 100 nm). The pre-patterned templates with PANi deposition were subsequently used to transfer the nanoscale assembled PANi from the rigid templates to thermoplastic polyurethane using the thermoforming process. In the third step, a novel integration of high rate pulsed electrophoretic assembly with thermally assisted transfer in a roll-to-roll process has been shown. This technique allowed the whole assembly and transfer process to take place in only 30 seconds. Further, a processing window is developed to control the percent area coverage of PANi with the aid of the belt speed. Also shown is the effect of different types of polymer on the quality of transfer, and it concluded that the transfer is affected by the polymer chemistry.

The Application Design of Solar Radio Spectrometer Based on FPGA

NASA Astrophysics Data System (ADS)

Du, Q. F.; Chen, R. J.; Zhao, Y. C.; Feng, S. W.; Chen, Y.; Song, Y.

2017-10-01

The Solar radio spectrometer is the key instrument to observe solar radio. By programing the computer software, we control the AD signal acquisition card which is based on FPGA to get a mass of data. The data are transferred by using PCI-E port. This program has realized the function of timing data collection, finding data in specific time and controlling acquisition meter in real time. It can also map the solar radio power intensity graph. By doing the experiment, we verify the reliability of solar radio spectrum instrument, in the meanwhile, the instrument simplifies the operation in observing the sun.

Fire retardancy using applied materials

NASA Technical Reports Server (NTRS)

Feldman, R.

1971-01-01

An example of advanced technology transfer from the Little Joe, Surveyor, Comsat, re-entry and Apollo age to everyday fire protection needs is presented. Utilizing the principle of sublimation cooling for thermostatic temperature control, the material meets a wide range of fire retardancy and heat transmission control requirements. Properties vary from flexible tape for conduits and electrical cables to rigid coatings for column protection, with a broad spectrum of sublimation temperatures available. The material can be applied in the field or in the factory, utilizing mass production techniques, yielding a product that is reliable, effective, widely available and low in cost.

Tunable multiwalled nanotube resonator

DOEpatents

Jensen, Kenneth J; Girit, Caglar O; Mickelson, William E; Zettl, Alexander K; Grossman, Jeffrey C

2013-11-05

A tunable nanoscale resonator has potential applications in precise mass, force, position, and frequency measurement. One embodiment of this device consists of a specially prepared multiwalled carbon nanotube (MWNT) suspended between a metal electrode and a mobile, piezoelectrically controlled contact. By harnessing a unique telescoping ability of MWNTs, one may controllably slide an inner nanotube core from its outer nanotube casing, effectively changing its length and thereby changing the tuning of its resonance frequency. Resonant energy transfer may be used with a nanoresonator to detect molecules at a specific target oscillation frequency, without the use of a chemical label, to provide label-free chemical species detection.