نتایج جستجو برای: activation enthalpy

تعداد نتایج: 433132  

ژورنال: مواد پرانرژی 2020

In this paper investigates an energetic imidazolium ionic liquid plasticizer (ILP)  effect on the degradation kinetics of nitrocellulose, which is a important component of double based solid propellants. For better comparison and evaluation, diethyl phthalate (DEP) plasticizer, which has a structure similar to ILP, was also evaluated. Heat of combustion analysis was performed to evaluate the en...

1997
C Michaelsen

In this paper we demonstrate the utility of differential scanning calorimetry for investigating the thermodynamics and kinetics of a broad range of thin film reactions. We begin by describing differential scanning calorimeters and the preparation of thin film samples. We then cite a number of examples that illustrate how enthalpies of crystallization, heats of formation and enthalpies of interf...

1999
R. Geursen I. Lahiri M. Dinu M. R. Melloch D. D. Nolte

The superlattice intermixing of arsenic-rich nonstoichiometric AlAs/GaAs quantum wells grown at lowsubstrate temperatures around 300 °C is enhanced by several orders of magnitude relative to diffusion in stoichiometric structures grown at ordinary substrate temperatures. The transient enhanced intermixing is attributed to a supersaturated concentration of group-III vacancies grown into the crys...

this thesis attempts to investigate the effects of prelistening activities on enhancing iranian efl learners` listening comprehension. the present study investigated ways in which learners` background knowledge could be activated in order to enhance their l2 listening comprehension by limiting the number of possible text interpretations prior to listening. the experiments conducted in this study examined the effect of prior knowledge and vocabulary teaching on iranian efl learners listening comprehension. the current study has two purposes: one is to investigate the effect of background knowledge on the second language listening comprehension of iranian intermediates and the other is to determine whether second language is facilitated by the introduction of unknown vocabularies in the form of prelistening activities. to conduct the study different instruments such as listening proficiency test and four listening tests such as pre and posttests were used and various statistical processes and techniques including paired-sample t-test, and analysis of variance (anova) were used. the findings of this study supported all three hypotheses tested. differences were found between the means of preteaching vocabulary variable, the background knowledge activation variable, and mean difference between these two strategies variable. subjects scored higher when the unknown words were taught in advance. likewise, subjects scored higher when they were asked some relevant questions about the topic than on those without them. there was, in addition, a significant difference between the means of preteaching vocabulary strategy and background knowledge activation strategy. in fact, preteaching vocabulary had a better effect in enhancing the students’ listening comprehension, in comparison to background knowledge activation strategy.

پایان نامه :دانشگاه آزاد اسلامی - دانشگاه آزاد اسلامی واحد تهران مرکزی - دانشکده زبانهای خارجی 1390

this thesis attempts to investigate the effects of prelistening activities on enhancing iranian efl learners` listening comprehension. the present study investigated ways in which learners` background knowledge could be activated in order to enhance their l2 listening comprehension by limiting the number of possible text interpretations prior to listening. the experiments conducted in this stud...

2006
JURAJ MAJZLAN

Abs t rac t -The persistence of many seemingly metastable mineral assemblages in sediments and soils is commonly attributed to their sluggish transformation to the stable-phase assemblage. Although undoubtedly kinetics plays a major role, this study shows that thermodynamic factors, particularly surface energy, significantly influence the free energy. Enthalpies of formation of boehmite samples...

2003
Mahendra P. Verma

A thermodynamic approach is presented to classify geothermal reservoir as vapor or liquid dominated. According to it, the vapor dominated reservoir has specific volume of fluid (i.e. combined vapor and liquid) greater than the critical volume of water whereas the liquid dominated reservoir has lesser specific volume. Enthalpy is not a conservative entity in a geothermal system. Apart from it, t...

Journal: :Journal of Thermal Analysis and Calorimetry 2022

Abstract Colloidal ferric oxide/aluminum nanothermite mixture was incorporated into ammonium percholorate (AP). Nanothermite particles experienced an increase in AP decomposition enthalpy by 120% using DSC. Decomposition kinetic study performed integral isoconversional models including Kissinger and KAS models. offered decrease activation energy 55 44% models, respectively. nanocomposite is run...

2003

A B S X R A C T Unpoisoned sartorius muscles of Rana temporaria were stimulated tetanically in isometric contractions lasting up to 20 s at 0~ The observed enthalpy (heat + work) production and the chemical changes in these contractions were measured, and a comparison was made between the observed enthalpy and the enthalpy that could be explained by the chemical changes. Like earlier workers, w...

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