The Kinetic Study of H2S Formation and Desorption on the S/Pt(111) Surface by Computer Simulation

2003 ◽  
Vol 10 (05) ◽  
pp. 745-750 ◽  
Author(s):  
A. Z. Moshfegh ◽  
K. H. Zakeri
Keyword(s):  
Experimental Data ◽  
Activation Energy ◽  
Computer Simulation ◽  
Random Walk ◽  
Kinetic Study ◽  
Maximum Amount ◽  
Effect Of Temperature ◽  
Desorption Rate ◽  
Mechanism Of Formation ◽  
Maximum Value

In this investigation, we have studied the kinetics and mechanism of formation and desorption of H 2 S on the Pt (111) surface using a kinetic random walk model. The effect of temperature on the H 2 S formation was studied in the range of 85–150 K. It was observed that a maximum amount of H 2 S is formed at 90 K and the amount is reduced at higher temperatures. H 2 S production yield as a function of time at different initial sulfur coverage ranging from 0.02 to 0.33 ML (1 ML ≃ 1 × 1015 atoms/cm 2) was also examined. It was obvious that as the initial S coverage increases, the rate of H 2 S formation rapidly increases and reaches a maximum value and then declines gradually. Furthermore, according to our simulated TPD spectra, for β = 1 K/s the maximum desorption rate occurs at Tp = 107.2 K . In addition, analysis of simulated TPD spectra of H 2 S desorption showed in an activation energy of H 2 S desorption Ed = 27.2 kcal/mol . Finally, the obtained simulated results were compared with the experimental data reported very recently, showing excellent agreement.

Modelling of Rheological Behaviour of Pulps and Purées from Fresh and Frozen-Thawed Murta (Ugni molinae Turcz) Berries

2012 ◽  
Vol 8 (3) ◽  
Author(s):  
Kong S. Ah-Hen ◽  
Antonio Vega-Gálvez ◽  
Nelson O. Moraga ◽  
Roberto Lemus-Mondaca
Keyword(s):  
Experimental Data ◽  
Activation Energy ◽  
Rapid Change ◽  
Correlation Coefficients ◽  
Rheological Behaviour ◽  
Type Equation ◽  
Effect Of Temperature ◽  
Rheological Models ◽  
Temperature Activation ◽  
Ugni Molinae

Abstract The rheological behaviour of purées and pulps from fresh and frozen-thawed murta (Ugni molinae Turcz) berries was studied at 30, 45, 60 and 75 °C. The Mitschka method was shown to be applicable to the murta berries, with its products showing non-Newtonian pseudoplastic behaviour. Rheological models as Ostwald-de Waele, Herschel-Bulkley, Bingham, Casson and Mizrahi-Berk fitted the experimental data with high values for correlation coefficients. Effect of temperature was evaluated using an Arrhenius-type equation. Compared to the murta pulp, the fresh or frozen-thawed murta purées had higher apparent viscosity at any shear rate and would undergo a more rapid change in viscosity with temperature. Activation energy for fresh and frozen-thawed purées were 22.335 kJ mol-1 (R2 = 0.9225), and 16.478 kJ mol-1 (R2 = 0.9654) respectively, while for fresh and frozen-thawed pulp Ea values of 8.967 kJ mol-1 (R2 = 0.9618) and 6.943 kJ mol-1 (R2 = 0.9773) were determined respectively.

scholarly journals Modelling of DHA Production from S. Limacinum ouc88: fed-batch perspectives

2021 ◽  
Vol 2049 (1) ◽  
pp. 012076
Author(s):  
B Contreras ◽  
D Basto ◽  
G Gelves
Keyword(s):  
Experimental Data ◽  
Computer Simulation ◽  
Docosahexaenoic Acid ◽  
Industrial Processes ◽  
Mathematical Approach ◽  
Fed Batch ◽  
Batch Mode ◽  
Maximum Value ◽  
Schizochytrium Limacinum ◽  
Dha Production

Abstract Biotechnology and its need to improve industrial processes have shown the need for techniques that allow processes optimization. Computer simulation offers the advantage of determining production prospects without significant resources and experimentation time. That is why a kinetic study of DHA (docosahexaenoic acid) production from Schizochytrium limacinum OUC88 was developed in this investigation. Based on the above, a mathematical approach to simulate DHA production in a fed-batch model is proposed in this work, using Matlab software. The experimental data for determining kinetic parameters were taken from previous investigations, and a simulated DHA level in the fed-batch mode of 150 g/L was reached. On the contrary, the simulated results in batch mode present only a maximum value of 30 g/L, demonstrating the effectiveness of the fed-batch implementation with perspectives on improving processes.

Effect of ionizing radiation on the kinetics of hydrogenation on the Ni-MgO mixed catalyst

1982 ◽  
Vol 47 (7) ◽  
pp. 1780-1786 ◽  
Author(s):  
Rostislav Kudláček ◽  
Jan Lokoč
Keyword(s):  
Experimental Data ◽  
Activation Energy ◽  
Liquid Phase ◽  
Ionizing Radiation ◽  
Oxide Catalyst ◽  
Absorbed Dose ◽  
Hydrogenation Rate ◽  
Solution Composition ◽  
Mixed Catalyst ◽  
Kinetics Of

The effect of gamma pre-irradiation of the mixed nickel-magnesium oxide catalyst on the kinetics of hydrogenation of maleic acid in the liquid phase has been studied. The changes of the hydrogenation rate are compared with the changes of the adsorbed amount of the acid and with the changes of the solution composition, activation energy, and absorbed dose of the ionizing radiation. From this comparison and from the interpretation of the experimental data it can be deduced that two types of centers can be distinguished on the surface of the catalyst under study, namely the sorption centres for the acid and hydrogen and the reaction centres.

An homogeneous growth model of gallium arsenide epitaxial layers from the gas phase

1989 ◽  
Vol 54 (11) ◽  
pp. 2933-2950
Author(s):  
Emerich Erdös ◽  
Petr Voňka ◽  
Josef Stejskal ◽  
Přemysl Klíma
Keyword(s):  
Experimental Data ◽  
Gallium Arsenide ◽  
Kinetic Study ◽  
Gas Phase ◽  
Growth Model ◽  
Epitaxial Layers ◽  
Inhomogeneous Model ◽  
Homogeneous Models ◽  
Active Centres

This paper represents a continuation and ending of the kinetic study of the gallium arsenide formation, where a so-called inhomogeneous model is proposed and quantitatively formulated in five variants, in which two kinds of active centres appear. This model is compared both with the experimental data and with the previous sequence of homogeneous models.

The Effect of Temperature Fluctuation on the Formation of Billet Surface Defect in the Initial Solidification Area

2010 ◽  
Vol 148-149 ◽  
pp. 163-167
Author(s):  
Xiao Li Jin ◽  
Zuo Sheng Lei ◽  
Kang Deng ◽  
Zhong Ming Ren
Keyword(s):  
Continuous Casting ◽  
Temperature Fluctuation ◽  
Surface Defects ◽  
Casting Process ◽  
Effect Of Temperature ◽  
Billet Surface ◽  
Maximum Value ◽  
Key Factor ◽  
Oscillation Marks ◽  
Initial Solidification

The heat transfer in steel continuous casting process under mold oscillation was calculated, and temperature fluctuation phenomena was found in the initial solidification area, the maximum value was approximate 16 °C. The effect of different continuous casting parameters on temperature fluctuation were analyzed, and the temperature fluctuation was considered to be a key factor to the formation of oscillation marks. The Index of Temperature Fluctuation(ITF) was proposed to predict the effect of temperature fluctuation on the formation of billet surface defects.

scholarly journals Kinetics and thermodynamic properties related to the drying of 'Cabacinha' pepper fruits

2016 ◽  
Vol 20 (2) ◽  
pp. 174-180 ◽  
Author(s):  
Hellismar W. da Silva ◽  
Renato S. Rodovalho ◽  
Marya F. Velasco ◽  
Camila F. Silva ◽  
Luís S. R. Vale
Keyword(s):  
Experimental Data ◽  
Activation Energy ◽  
Free Energy ◽  
Thermodynamic Properties ◽  
Gibbs Free Energy ◽  
Removal Rate ◽  
Effective Diffusion ◽  
Drying Time ◽  
Three Samples ◽  
Different Temperatures

ABSTRACT The objective of this study was to determine and model the drying kinetics of 'Cabacinha' pepper fruits at different temperatures of the drying air, as well as obtain the thermodynamic properties involved in the drying process of the product. Drying was carried out under controlled conductions of temperature (60, 70, 80, 90 and 100 °C) using three samples of 130 g of fruit, which were weighed periodically until constant mass. The experimental data were adjusted to different mathematical models often used in the representation of fruit drying. Effective diffusion coefficients, calculated from the mathematical model of liquid diffusion, were used to obtain activation energy, enthalpy, entropy and Gibbs free energy. The Midilli model showed the best fit to the experimental data of drying of 'Cabacinha' pepper fruits. The increase in drying temperature promoted an increase in water removal rate, effective diffusion coefficient and Gibbs free energy, besides a reduction in fruit drying time and in the values of entropy and enthalpy. The activation energy for the drying of pepper fruits was 36.09 kJ mol-1.

DOM Products: Activation Energy Estimation and Reliability Assessment

2013 ◽  
Vol 470 ◽  
pp. 781-784 ◽  
Author(s):  
Chien Yi Huang ◽  
Yueh Hsun Lin ◽  
Eric Huang
Keyword(s):  
Experimental Data ◽  
Activation Energy ◽  
Subjective Experience ◽  
Reliability Assessment ◽  
Life Time ◽  
Service Condition ◽  
Energy Estimation ◽  
Failure Data ◽  
Scientific Approach ◽  
Temperature Scenario

A scientific approach is proposed in this research to investigate a disk on module (DOM) product's activation energy based on experimental data that eliminates subjective experience. This study considers multiple temperature conditions to enhance the accuracy of activation energy estimation. In order to ensure the consistency of failure mode in each temperature scenario, the slopes of Weibul probability plots obtained from the failure data are calculated followed by an examination for parallelism. The estimated life time under normal service condition differs from the results obtained using the industrial standard given activation energy by approximately 42%.

Diffusion Coefficients of Interest for the Simulation of Heat Treatment in Rare-Earth Transition Metal Magnets

2012 ◽  
Vol 727-728 ◽  
pp. 163-168 ◽  
Author(s):  
Marcos Flavio de Campos
Keyword(s):  
Experimental Data ◽  
Heat Treatment ◽  
Activation Energy ◽  
Rare Earth ◽  
Transition Metal ◽  
Impurity Atom ◽  
Diffusion Coefficients ◽  
Arrhenius Equation ◽  
Atom Diffusion ◽  
Essential Input

In the case of the modeling of sintering and heat treatments, the diffusion coefficients are an essential input. However, experimental data in the literature about diffusion coefficients for rare-earth transition metal intermetallics is scarce. In this study, the available data concerning diffusion coefficients relevant for rare-earth transition metal magnets are reviewed and commented. Some empirical rules are discussed, for example the activation energy is affected by the size of the diffusing impurity atom. Diffusion coefficients for Dy, Nd and Fe into Nd2Fe14B are given according an Arrhenius equation D=D0exp (-Q/RT). For Dy diffusion into Nd2Fe14B, Q 315 kJ/mol and D08 . 10-4m2/s.

scholarly journals Photocatalytic Degradation of Textile Dyeing Wastewater Using Titanium Dioxide and Zinc Oxide

2008 ◽  
Vol 5 (2) ◽  
pp. 219-223 ◽  
Author(s):  
Abbas J. Attia ◽  
Salih H. Kadhim ◽  
Falah H. Hussein
Keyword(s):  
Activation Energy ◽  
Zinc Oxide ◽  
Titanium Dioxide ◽  
Photocatalytic Degradation ◽  
Irradiation Time ◽  
Effect Of Temperature ◽  
Dyeing Wastewater ◽  
Textile Dyeing ◽  
Textile Factory ◽  
Textile Dyeing Wastewater

Photodegradation of a real textile dyeing wastewater taken from Hilla textile factory in Babylon Governorate, Iraq have been investigated. Photocatalytic degradation was carried out over suspensions of titanium dioxide or zinc oxide under ultraviolet irradiation. Photodegradation percentage was followed spectrophometrically by the measurements of absorbance at λmax equal to 380 nm. The rate of photodegradation increased linearly with time of irradiation when titanium dioxide or zinc oxide was used. A maximum color removal of 96% was achieved after irradiation time of 2.5 hours when titanium dioxide used at 303K and 82% color reduction was observed when zinc oxide used for the same period and at the same temperature. The effect of temperature on the efficiency of photodegradation of dyestuff was also studied. The activation energy of photodegradation was calculated and found to be equal to 21 ± 1 kJ mol-1 on titanium dioxide and 24 ± 1 kJ mol-1 on zinc oxide.

scholarly journals Optimal Strategies for Prudent Investors

1998 ◽  
Vol 01 (04) ◽  
pp. 473-486 ◽  
Author(s):  
Roberto Baviera ◽  
Michele Pasquini ◽  
Maurizio Serva ◽  
Angelo Vulpiani
Keyword(s):  
Growth Rate ◽  
Random Walk ◽  
Exponential Growth ◽  
Optimal Strategies ◽  
Maximum Amount ◽  
Exponential Growth Rate ◽  
One Dimensional ◽  
Economic Level ◽  
Random Walk With Drift ◽  
Analytical Expressions

We consider a stochastic model of investment on an asset in a stock market for a prudent investor. she decides to buy permanent goods with a fraction α of the maximum amount of money owned in her life in order that her economic level never decreases. The optimal strategy is obtained by maximizing the exponential growth rate for a fixed α. We derive analytical expressions for the typical exponential growth rate of the capital and its fluctuations by solving an one-dimensional random walk with drift.

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