Estimation of the Rate of Hydrogen Penetration in a Welded API 5L Steel Pipe

2008 ◽  
Vol 273-276 ◽  
pp. 500-505
Author(s):  
Gabriel Plascencia ◽  
David Jaramillo ◽  
Felipe Hernández ◽  
Jorge Luis González
Keyword(s):  
Penetration Rate ◽  
Mechanical Damage ◽  
Electric Arc ◽  
Steel Pipe ◽  
Simple Diffusion ◽  
Rate Of Penetration ◽  
Ultrasonic Measurements ◽  
Hydrogen Penetration ◽  
Simple Diffusion Model ◽  
Damage To The Material

Hydrogen embrittlement is a common problem for the integrity of oil conducting pipes. In this work, we estimate the rate of hydrogen penetration into an API 5L steel pipe welded by electric arc. The hydrogen penetration was estimated by means of data taken from ultrasonic measurements. As expected, the steel pipe becomes more brittle as the hydrogen penetration rate does so. A simple diffusion model was developed. The model confirms the strong dependency between the rate of penetration and the mechanical damage to the material.

Behavior of Unsteady Turbulent Starting Round Jets

2012 ◽  
Vol 134 (6) ◽  
Author(s):  
Neerav Abani ◽  
Jaal B. Ghandhi
Keyword(s):  
High Speed ◽  
Penetration Rate ◽  
Injection Rate ◽  
Injection Velocity ◽  
Time Varying ◽  
Velocity Change ◽  
Rate Of Penetration ◽  
Round Jets ◽  
The Difference ◽  
Sudden Decrease

Turbulent starting jets with time-varying injection velocities were investigated using high-speed schlieren imaging. Two solenoid-controlled injectors fed a common plenum upstream of an orifice; using different upstream pressures and actuation times, injection-rate profiles with a step increase or decrease in injection velocity were tested. The behavior of the jet was found to be different depending on the direction of the injection-velocity change. A step increase in injection velocity resulted in an increased rate of penetration relative to the steady-injection case, and a larger increase in injection velocity resulted in an earlier change in the tip-penetration rate. The step-increase data were found to be collapsed by scaling the time by a convective time scale based on the tip location at the time of the injection-velocity change and the difference in the injection velocities. A sudden decrease in injection velocity to zero was found to cause a deviation from the corresponding steady-pressure case at a time that was independent of the initial jet velocity, i.e., it was independent of the magnitude of the injection-velocity change. Two models for unsteady injection from the literature were tested and some deficiencies in the models were identified.

scholarly journals A Simple Diffusion Model for Psychometric Analyses

2019 ◽  
Author(s):  
Udo Boehm ◽  
Maarten Marsman ◽  
Han van der Maas ◽  
Gunter Maris
Keyword(s):  
Diffusion Model ◽  
Functional Form ◽  
Response Times ◽  
Simple Diffusion ◽  
Regression Framework ◽  
Psychometric Analyses ◽  
Computer Based ◽  
Simple Diffusion Model ◽  
Source Of Information ◽  
Latent Regression

The emergence of computer-based assessments has made response times, in addition to response accuracies, available as a source of information about test takers’ latent abilities. The predominant approach to jointly account for response times and accuracies are statistical models. Substantive approaches such as the diffusion model, on the other hand, have been slow to gain traction due to their unwieldy functional form. In the present work we show how a single simplifying assumption yields a highly tractable diffusion model. This simple diffusion model is straightforward to analyse using Gibbs sampling and can be readily extended with a latent regression framework. We demonstrate the superior computational efficiency of our model compared to the standard diffusion model in a simulation study and showcase the theoretical merit of our model in an example application.

Effect of external and phase hardening on the hydrogen penetration rate in ferrite

1965 ◽  
Vol 7 (4) ◽  
pp. 221-223
Author(s):  
V. A. Gol'tsov ◽  
P. V. Gel'd ◽  
M. M. Steinberg
Keyword(s):  
Penetration Rate ◽  
Phase Hardening ◽  
Hydrogen Penetration

A Simple Diffusion Model of Surface Modification by Plasma

1997 ◽  
Vol 159 (2) ◽  
pp. 405-416 ◽  
Author(s):  
V. I. Dimitrov ◽  
J. D'Haen ◽  
G. Knuyt ◽  
C. Quaeyhaegens ◽  
L. M. Stals
Keyword(s):  
Surface Modification ◽  
Diffusion Model ◽  
Simple Diffusion ◽  
Simple Diffusion Model

A model of potassium ion efflux during exercise of skeletal muscle

1979 ◽  
Vol 236 (1) ◽  
pp. R83-R90 ◽  
Author(s):  
Y. Hazeyama ◽  
H. V. Sparks
Keyword(s):  
Time Course ◽  
Ion Pump ◽  
K Uptake ◽  
Direct Stimulation ◽  
Nernst Equation ◽  
Vasoactive Agent ◽  
Simple Diffusion ◽  
Pump Activity ◽  
Stimulation Period ◽  
Simple Diffusion Model

Potassium (K+) is a vasoactive agent and is released from muscle cells during exercise. A simple diffusion model does not predict the time course of K+ efflux during exercise, which decreases as the exercise progresses. We constructed a mathematical model using the concept of an active Na+-K+ ion pump to account for the decreased efflux during and uptake after exercise. Passive fluxes are calculated by the Nernst equation. Active fluxes are constrained to balance these passive fluxes at rest. The pump activity increases as either extracellular K+ or intracellular Na+ concentration increases. To test the model, the venous K+ efflux profile was simulated for direct stimulation (4/s) of the anterior calf mus cles of dogs. The model simulated the K+ release during the stimulation period and [K+] undershoot after the stimulation. The active Na+-K+ ATPase transport concept used in the model was further tested by observing K+ efflux after administration of ouabain. Ouabain infusion decreased K+ uptake during exercise slightly and abolished [K+] undershoot after the stimulation. These experimental data were matched by the model only if a discontinuous effect of ouabain is assumed. This suggests that ouabain may more completely block the sensitivity of the pump to intracellular [Na+] than to extracellular [K+].

STRUCTURAL AND MAGNETIC PROPERTIES OF SINGLE CRYSTAL RARE EARTH Gd-Y SUPERLATTICES

1985 ◽  
Vol 56 ◽  
Author(s):  
J. Kwo ◽  
D. B. McWhan ◽  
M. Hong ◽  
E. M. Gyorgy ◽  
F. J. DiSalvo
Keyword(s):  
Rare Earth ◽  
Single Crystal ◽  
Magnetic Ordering ◽  
X Ray Diffraction ◽  
Simple Diffusion ◽  
X Ray ◽  
Composition Modulation ◽  
Strain Modulation ◽  
Simple Diffusion Model ◽  
Magnetization Behavior

AbstractHigh quality single crystal rare earth Gd-Y superlattices with wavelength varying from 8to 42 atomic layers were grown by the recently developed metal molecular beam epitaxy technique. The crystallinity and coherence of the superlattices were examined by X-ray diffraction, and the profiles of composition modulation and strain modulation were determined from a quantitative analysis based on a simple diffusion model for the Gd-Y interfaces. The sharp boundaries achieved in these metallic superlattices are approaching those in semiconductor superlattices. The various in-plane magnetization behavior at low fieldsamong superlattices of different wavelengths suggests the possible presence of new magnetic ordering structures as caused by the artificial modulation.

The influence of sperm concentration, length of the gamete co-culture and the evolution of different sperm parameters on the in vitro fertilization of prepubertal goat oocytes

Zygote ◽  
2010 ◽  
Vol 18 (4) ◽  
pp. 345-355 ◽  
Author(s):  
M.J. Palomo ◽  
T. Mogas ◽  
D. Izquierdo ◽  
M.T. Paramio
Keyword(s):  
Acrosome Reaction ◽  
Penetration Rate ◽  
Sperm Concentration ◽  
Semen Parameters ◽  
Oxygen Species ◽  
Vitro Fertilization ◽  
Rate Of Penetration ◽  
Sperm Penetration ◽  
Kinetics Of

SummaryThe aims of the present study were: (1) to evaluate the influence of sperm concentration (ranging from 0.5 × 106 to 4 × 106 spermatozoa/ml) and length of the gamete co-incubation time (2, 4, 6, 8, 10, 12, 16, 20, 24 or 28 h) on in vitro fertilization (IVF), assessing the sperm penetration rate; (2) to investigate the kinetics of different semen parameters as motility, viability and acrosome status during the co-culture period; and (3) to analyse the effect of the presence of cumulus–oocytes complexes (COCs) on these parameters. To achieve these objectives, several experiments were carried out using in vitro matured oocytes from prepubertal goats. The main findings of this work are that: (1) in our conditions, the optimum sperm concentration is 4 × 106 sperm/ml, as this sperm:oocyte ratio (approximately 28,000) allowed us to obtain the highest penetration rate, without increasing polyspermy incidence; (2) the highest percentage of viable acrosome-reacted spermatozoa is observed between 8–12 h of gamete co-culture, while the penetration rate is maximum at 12 h of co-incubation; and (3) the presence of COCs seems to favour the acrosome reaction of free spermatozoa on IVF medium, but not significantly. In conclusion, we suggest that a gamete co-incubation for 12–14 h, with a concentration of 4 × 106 sperm/ml, would be sufficient to obtain the highest rate of penetration, reducing the exposure of oocytes to high levels of reactive oxygen species produced by spermatozoa, especially when a high sperm concentration is used to increase the caprine IVF outcome.

A simple diffusion model showing anomalous scaling

2008 ◽  
Vol 15 (8) ◽  
pp. 082308 ◽  
Author(s):  
G. Rowlands ◽  
J. C. Sprott
Keyword(s):  
Diffusion Model ◽  
Anomalous Scaling ◽  
Simple Diffusion ◽  
Simple Diffusion Model

scholarly journals Complex genetic patterns in human arise from a simple range-expansion model over continental landmasses

2017 ◽  
Author(s):  
Ricardo Kanitz ◽  
Elsa G Guillot ◽  
Sylvain Antoniazza ◽  
Samuel Neuenschwander ◽  
Jérôme Goudet
Keyword(s):  
East Africa ◽  
Isolation By Distance ◽  
Null Model ◽  
Real Data ◽  
Modern Human ◽  
Initial Population ◽  
Simple Diffusion ◽  
Simple Diffusion Model ◽  
Approximate Bayesian ◽  
Expansion Model

AbstractAlthough it is generally accepted that geography is a major factor shaping human genetic differentiation, it is still disputed how much of this differentiation is a result of a simple process of isolation-by-distance, and if there are factors generating distinct clusters of genetic similarity. We address this question using a geographically explicit simulation framework coupled with an Approximate Bayesian Computation approach. Based on six simple summary statistics only, we estimated the most probable demographic parameters that shaped modern human evolution under an isolation by distance scenario, and found these were the following: an initial population in East Africa spread and grew from 4000 individuals to 5.7 million in about 132 000 years. Subsequent simulations with these estimates followed by cluster analyses produced results nearly identical to those obtained in real data. Thus, a simple diffusion model from East Africa explains a large portion of the genetic diversity patterns observed in modern humans. We argue that a model of isolation by distance along the continental landmasses might be the relevant null model to use when investigating selective effects in humans and probably many other species.

Sign in / Sign up

Export Citation Format

Share Document