First Estimates of Nonuniform Electrolyte on Seawater Corrosion Parameters

2008 ◽  
Author(s):  
V. G. DeGiorgi ◽  
J. G. Michopoulos
Keyword(s):  
Electrochemical Corrosion ◽  
Physical Parameters ◽  
Corrosion Prevention ◽  
Concentric Cylinder ◽  
Electrolyte Conductivity ◽  
Seawater Corrosion ◽  
Computational Work ◽  
Corrosion Cell ◽  
Future Work ◽  
Electrolyte Characteristics

All metals corrode with exposure to electrolytes. This is a fact of life experienced by owners of marine platforms and structures throughout the world. Computational modeling methodologies have been applied to evaluate and design corrosion prevention systems. All computational work to date makes similar assumptions of a uniform electrolyte. This is a valid assumption for structures in large volumes of constantly refreshing electrolyte in which the constitutive characteristics of the electrolyte can be approximated by a uniform mixture. There is experimental evidence that this assumption is not valid for smaller volumes. The need for a more general solution which is valid in these smaller enclosed spaces is being driven by future designs that place corrosion prevention systems in these areas. The sensitivity of solutions on variations in electrolyte conductivity is unknown. In this work preliminary results are presented that demonstrate the need to take into account the spatial variation in electrolyte characteristics for small enclosed volumes of electrolyte. Two geometries (a gap between plates and a two material concentric cylinder corrosion cell) are used to demonstrate the differences between uniform and spatial varying electrolyte. Future work is outlined which will take into account more physical parameters related to electrochemical corrosion.

THERMODYNAMIC AND MAGNETOHYDRODYNAMIC ANALYSIS OF BLOOD FLOW CONSIDERING ROTATION OF MICRO-PARTICLES OF BLOOD

2013 ◽  
Vol 13 (01) ◽  
pp. 1350013 ◽  
Author(s):  
J. C. MISRA ◽  
S. CHANDRA ◽  
G. C. SHIT ◽  
P. K. KUNDU
Keyword(s):  
Blood Flow ◽  
Differential Equations ◽  
Surface Velocity ◽  
Physical Parameters ◽  
Axial Distance ◽  
Micro Particles ◽  
Flow And Heat Transfer ◽  
Computational Work ◽  
Blood Flow Dynamics ◽  
Graphical Presentation

Flow and heat transfer of blood under the action of an external magnetic field are analyzed in this paper. The flow is considered to take place in a channel that is bounded by stretchable walls. The surface velocity of the channel is assumed to vary linearly with axial distance. The microrotation of the micro-particles of blood is taken into account by treating blood as a micropolar fluid. The governing partial differential equations are transformed into a system of ordinary differential equations and then solved numerically by developing a suitable finite difference technique. Computational work has been carried out in order to have an estimate of the velocity, microrotation, and the temperature of the fluid for different values of various physical parameters of interest in the present study of blood flow dynamics. Different physiological aspects are discussed via graphical presentation of the computed results.

scholarly journals Experiment study on the corrosion resistance of the surface metamorphic layer of grinding

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Xiaoliang Shi ◽  
Shichao Xiu ◽  
Xiao Liu
Keyword(s):  
Corrosion Resistance ◽  
Electrochemical Impedance ◽  
Electrochemical Corrosion ◽  
Surface Corrosion ◽  
Corrosion Cell ◽  
Grinding Mechanism ◽  
Large Phase ◽  
The Common ◽  
Large Clusters ◽  
Grinding Hardening

AbstractWorkpiece will face corrosive problems during its application after the manufacturing process. As the common final process, grinding can generate special metamorphic layer on the surface of workpiece and change the initial corrosion resistance of workpiece. In order to study the corrosion resistance of workpiece after grinding process, the paper carries on combining experiment of grinding and electrochemical corrosion. The characteristic of corrosion resistance of grinding is revealed based on the association of grinding mechanism and electrochemical theory. The corrosion potential of workpiece after grinding is higher than matrix, which shows the grinding surface is difficult to begin to corrode. Electrochemical impedance spectroscopy (EIS) shows the grinding surface has large phase angle, impedance and capacitance characteristic because the metamorphic layer of grinding has good obstructive ability. They reveal that grinding improves the surface corrosion resistance of workpiece. Then the mechanism of the corrosion resistance of grinding is revealed. The special grain boundary formed in grinding with much C element, large clusters and complex shape prolongs the corrosion channel, which reduces the corrosive speed. While, the sensitive hardening structure generated in grinding hardening with much free energy is easy to form the corrosion cell, which will accelerate the corrosion.

Initial Modeling of Material Phase Driven Localized Corrosion

2011 ◽  
Author(s):  
Stephanie A. Wimmer ◽  
Virginia G. DeGiorgi
Keyword(s):  
Electrochemical Corrosion ◽  
Corrosion Damage ◽  
Electrochemical Potential ◽  
Localized Corrosion ◽  
Metallic Material ◽  
Polarization Response ◽  
Electrochemical Response ◽  
Corrosion Cell ◽  
Individual Grains ◽  
Single Material

Localized corrosion often occurs when regions of a single material demonstrate a difference in electrochemical potential. Cathodic and anodic regions can develop in a component comprised of a single material. This variation is one cause of localized corrosion damage. This phenomenon of localized anode and cathode regions is well documented but not well understood. In this work the authors are examining variations in electrochemical response of individual grains within a metallic material. The objective is to determine if the distinct electrochemical response associated with austenite and ferrite phases in steel are sufficient to create a localized electrochemical corrosion cell. In this paper the authors present the first of a series of models that capture localized electrochemical corrosion driven by variations in grain polarization response.

Mass-transfer enhancement via chaotic laminar flow within a droplet

1999 ◽  
Vol 379 ◽  
pp. 319-331 ◽  
Author(s):  
MICHELLE D. BRYDEN ◽  
HOWARD BRENNER
Keyword(s):  
Mass Transfer ◽  
Velocity Ratio ◽  
Immiscible Liquid ◽  
Bubble Velocity ◽  
Physical Parameters ◽  
Fluid Viscosity ◽  
Concentric Cylinder ◽  
Bulk Fluid ◽  
Spherical Droplet ◽  
Vorticity Vector

The Stokes flow occurring within a non-neutrally buoyant spherical droplet translating by buoyancy through an immiscible liquid which is undergoing simple shear is shown to be chaotic under many circumstances for which the droplet translates by buoyancy through the entraining fluid. This flow is easily produced, for example, when the droplet rises (or falls) through the annular space of a vertical concentric-cylinder Couette viscometer or through a vertical Poiseuille flow. The parameters studied include: (i) droplet/bulk fluid viscosity ratio; (ii) shear strength/bubble rise velocity ratio; and (iii) the angle between the translational bubble velocity vector and the vorticity vector characterizing the undisturbed shear. Streamlines existing within a droplet that translates perpendicular to this vorticity vector are shown to be non-chaotic for all choices of physical parameters. Other relative orientations frequently contain chaotic trajectories. When solute initially dissolved within the droplet is extracted into the bulk fluid, the resulting overall mass-transfer coefficient (calculated via generalized Taylor dispersion theory) quantifying the extraction rate at asymptotically long times is shown to be significantly higher in the chaotic flow case.

Some Results of the Spectroscopic Study of Four Close Binary Systems of Early Spectral Types

1965 ◽  
Vol 5 ◽  
pp. 120-130
Author(s):  
T. S. Galkina
Keyword(s):  
Spectroscopic Study ◽  
Spectral Type ◽  
Spectroscopic Investigation ◽  
Binary Systems ◽  
Quantitative Information ◽  
Close Binary ◽  
Physical Parameters ◽  
Absorption And Emission ◽  
Close Binary Systems ◽  
Quantitative Estimates

It is necessary to have quantitative estimates of the intensity of lines (both absorption and emission) to obtain the physical parameters of the atmosphere of components.Some years ago at the Crimean observatory we began the spectroscopic investigation of close binary systems of the early spectral type with components WR, Of, O, B to try and obtain more quantitative information from the study of the spectra of the components.

Present status of radio astrometry with baselines ≤ 35 km

1978 ◽  
Vol 48 ◽  
pp. 175-178 ◽  
Author(s):  
K. J. Johnston
Keyword(s):  
Present Status ◽  
Future Work

A summary of results for radio astrometry with baselines ≤ 35 km and priorities for future work are given.

A theory of contamination in electron microscopes by surface diffusion

1978 ◽  
Vol 36 (1) ◽  
pp. 116-117
Author(s):  
J.T. Fourie
Keyword(s):  
Electron Beam ◽  
Surface Diffusion ◽  
High Vacuum ◽  
Ultra High Vacuum ◽  
Physical Parameters ◽  
Carbon Compounds ◽  
Hydrocarbon Molecules ◽  
Electron Microscopes ◽  
Primary Electrons ◽  
Long Chain

Contamination in electron microscopes can be a serious problem in STEM or in situations where a number of high resolution micrographs are required of the same area in TEM. In modern instruments the environment around the specimen can be made free of the hydrocarbon molecules, which are responsible for contamination, by means of either ultra-high vacuum or cryo-pumping techniques. However, these techniques are not effective against hydrocarbon molecules adsorbed on the specimen surface before or during its introduction into the microscope. The present paper is concerned with a theory of how certain physical parameters can influence the surface diffusion of these adsorbed molecules into the electron beam where they are deposited in the form of long chain carbon compounds by interaction with the primary electrons.

Electron Microscopy in the Study of Natural Phytoplankton Assemblages

1985 ◽  
Vol 43 ◽  
pp. 620-623
Author(s):  
Linda Sicko-Goad
Keyword(s):  
Electron Microscopy ◽  
Aquatic Environment ◽  
Size Range ◽  
Physical Parameters ◽  
Specific Information ◽  
Phytoplankton Assemblages ◽  
Phytoplankton Productivity ◽  
Ecosystem Effects ◽  
Time Of Year ◽  
Species Specific

Although the use of electron microscopy and its varied methodologies is not usually associated with ecological studies, the types of species specific information that can be generated by these techniques are often quite useful in predicting long-term ecosystem effects. The utility of these techniques is especially apparent when one considers both the size range of particles found in the aquatic environment and the complexity of the phytoplankton assemblages.The size range and character of organisms found in the aquatic environment are dependent upon a variety of physical parameters that include sampling depth, location, and time of year. In the winter months, all the Laurentian Great Lakes are uniformly mixed and homothermous in the range of 1.1 to 1.7°C. During this time phytoplankton productivity is quite low.

A New Numerical Model for Electron-Probe Analysis at High Depth Resolution

1996 ◽  
Vol 54 ◽  
pp. 490-491
Author(s):  
P.-F. Staub ◽  
C. Bonnelle ◽  
F. Vergand ◽  
P. Jonnard
Keyword(s):  
Electron Probe ◽  
Surface Segregation ◽  
Depth Distribution ◽  
Computing Time ◽  
Depth Resolution ◽  
Physical Parameters ◽  
Electron Probe Analysis ◽  
Interface Phases ◽  
Excitation Conditions ◽  
High Depth

Characterizing dimensionally and chemically nanometric structures such as surface segregation or interface phases can be performed efficiently using electron probe (EP) techniques at very low excitation conditions, i.e. using small incident energies (0.5<E0<5 keV) and low incident overvoltages (1<U0<1.7). In such extreme conditions, classical analytical EP models are generally pushed to their validity limits in terms of accuracy and physical consistency, and Monte-Carlo simulations are not convenient solutions as routine tools, because of their cost in computing time. In this context, we have developed an intermediate procedure, called IntriX, in which the ionization depth distributions Φ(ρz) are numerically reconstructed by integration of basic macroscopic physical parameters describing the electron beam/matter interaction, all of them being available under pre-established analytical forms. IntriX’s procedure consists in dividing the ionization depth distribution into three separate contributions:

A Phonomotor Approach to Apraxia of Speech Treatment

2020 ◽  
Vol 29 (4) ◽  
pp. 2109-2130
Author(s):  
Lauren Bislick
Keyword(s):  
Phase I ◽  
Treatment Effects ◽  
Single Case ◽  
Motor Planning ◽  
The Other ◽  
Multimodal Approach ◽  
Apraxia Of Speech ◽  
Duration Of Treatment ◽  
Treatment Gains ◽  
Future Work

Purpose This study continued Phase I investigation of a modified Phonomotor Treatment (PMT) Program on motor planning in two individuals with apraxia of speech (AOS) and aphasia and, with support from prior work, refined Phase I methodology for treatment intensity and duration, a measure of communicative participation, and the use of effect size benchmarks specific to AOS. Method A single-case experimental design with multiple baselines across behaviors and participants was used to examine acquisition, generalization, and maintenance of treatment effects 8–10 weeks posttreatment. Treatment was distributed 3 days a week, and duration of treatment was specific to each participant (criterion based). Experimental stimuli consisted of target sounds or clusters embedded nonwords and real words, specific to each participants' deficit. Results Findings show improved repetition accuracy for targets in trained nonwords, generalization to targets in untrained nonwords and real words, and maintenance of treatment effects at 10 weeks posttreatment for one participant and more variable outcomes for the other participant. Conclusions Results indicate that a modified version of PMT can promote generalization and maintenance of treatment gains for trained speech targets via a multimodal approach emphasizing repeated exposure and practice. While these results are promising, the frequent co-occurrence of AOS and aphasia warrants a treatment that addresses both motor planning and linguistic deficits. Thus, the application of traditional PMT with participant-specific modifications for AOS embedded into the treatment program may be a more effective approach. Future work will continue to examine and maximize improvements in motor planning, while also treating anomia in aphasia.

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