Admissibility Region for Rarefaction Shock Waves in Dense Gases

In the vapour phase and close to the liquid–vapour saturation curve, fluids made of complex molecules are expected to exhibit a thermodynamic region in which the fundamental derivative of gasdynamic G is negative. In this region, non-classical gasdynamic phenomena such as rarefaction shock waves are physically admissible, namely they obey the second law of thermodynamics and fulfil the speed-orienting condition for mechanical stability. Previous studies have demonstrated that the thermodynamic states for which rarefaction shock waves are admissible are however not limited to the G <0 region. In this paper, the conditions for admissibility of rarefaction shocks are investigated. This results in the definition of a new thermodynamic region – the rarefaction shocks region – which embeds the G <0 region. The rarefaction shocks region is bounded by the saturation curve and by the locus of the states connecting double-sonic rarefaction shocks, i.e. shock waves in which both the pre-shock and post-shock states are sonic. Only one double-sonic shock is shown to be admissible along a given isentrope, therefore the double-sonic states can be connected by a single curve in the volume–pressure plane. This curve is named the double sonic locus. The influence of molecular complexity on the shape and size of the rarefaction shocks region is also illustrated by using the van der Waals model; these results are confirmed by very accurate multi-parameter thermodynamic models applied to siloxane fluids and are therefore of practical importance in experiments aimed at proving the existence of rarefaction shock waves in the single-phase vapour region as well as in future industrial applications operating in the non-classical regime

Maximum Intensity of Rarefaction Shock Waves for Dense Gases

Modern thermodynamic models indicate that fluids consisting of complex molecules may display non-classical gasdynamic phenomena such as rarefaction shock waves (RSWs) in the vapour phase. Since the thermodynamic region in which non-classical phenomena are physically admissible is finite in terms of pressure, density and temperature intervals, the intensity of RSWs is expected to exhibit a maximum for any given fluid. The identification of the operating conditions leading to the RSW with maximum intensity is of paramount importance for the experimental verification of the existence of non-classical phenomena in the vapour phase and for technical applications taking advantage of the peculiarities of the non-classical regime. This study investigates the conditions resulting in an RSW with maximum intensity in terms of pressure jump, wave Mach number and shock strength. The upstream state of the RSW with maximum pressure drop is found to be located along the double-sonic locus formed by the thermodynamic states associated with an RSW having both pre- and post-shock sonic conditions. Correspondingly, the maximum-Mach thermodynamic and maximum-strength loci locate the pre-shock states from which the RSW with the maximum wave Mach number and shock strength can originate. The qualitative results obtained with the simple van der Waals model are confirmed with the more complex Stryjek–Vera–Peng–Robinson, Martin–Hou and Span–Wagner equations of state for selected siloxane and perfluorocarbon fluids. Among siloxanes, which are arguably the best fluids for experiments aimed at the generation and measurement of an RSW, the state-of-the-art Span–Wagner multi-parameter equation of state predicts a maximum wave Mach number close to 1.026 for D6 (dodecamethylcyclohexasiloxane, [O-Si-(CH3)2]6). Such value is well within the capacity of the measurement system of a newly built experimental set-up aimed at the first-ever demonstration of the existence of RSWs in dense vapours

An empirical evaluation of prediction by partial matching in assembly assistance systems

Industrial assistive systems result from a multidisciplinary effort that integrates IoT (and Industrial IoT), Cognetics, and Artificial Intelligence. This paper evaluates the Prediction by Partial Matching algorithm as a component of an assembly assistance system that supports factory workers, by providing choices for the next manufacturing step. The evaluation of the proposed method was performed on datasets collected within an experiment involving trainees and experienced workers. The goal is to find out which method best suits the datasets in order to be integrated afterwards into our context-aware assistance system. The obtained results show that the Prediction by Partial Matching method presents a significant improvement with respect to the existing Markov predictors

Fluxul tehnologic şi analiza fizico-chimică a brânzei din lapte de capră obţinută prin metode tradiţionale într-o unitate de capacitate mică din judeţul Iaşi, România

The aim of the current paper is to present the traditional homemade technological flow utilised for obtaining goat cheese into a small range unit from IaşiCounty, Romania and to realise an analyse upon the product’s physical-chemical features. Regarding physical-chemical characteristics, the current paper aimed to study the following parameters: fat content, moisture content and acidity of goat cheese. At the end of the study we can affirm that goat cheese homemade obtained into a small range unit from IaşiCounty, Romania, fulfilled all the demandsrequired by the Romanian legislation, being a traditionally made product. The quality of the product is a very good one, being recorded superior values to thoseimposed by nowadays standards, for all the analysed physical-chemical indicators

Femtosecond laser ablation and structuring of a hard bi-layered coating

We studied surface modification of a bi-layered coating (Al2O3/TiAlN/steel) induced by fs laser with single and multi-pulse irradiation. The laser pulses (λ=775 nm, τ=200 fs) were generated by a Ti:sapphire laser. The single pulse threshold fluence for ablation of the top Al2O3 layer was Dath =0.56 Jcm-2. Single pulse actions with fluence increased up to 16.47 Jcm-2 caused widening of ablated area without significant change of the TiAlN layer underneath. In case of multipulse irradiation, periodical surface structures (LIPSS) were induced on the TiAlN layer surface. The average periodicity of created LIPSS was 600 nm.Physical chemistry 2012 : 11th international conference on fundamental and applied aspects of physical chemistry; Belgrade (Serbia); 24-28 September 201

Arguing with behavior influence: A model for web-based group decision support systems

In this work, we propose an argumentation-based dialogue model designed for Web-based Group Decision Support Systems, that considers the decision-makers' intentions. The intentions are modeled as behavior styles which allow agents to interact with each other as humans would in face-to-face meetings. In addition, we propose a set of arguments that can be used by the agents to perform and evaluate requests, while considering the agents' behavior style. The inclusion of decision-makers' intentions intends to create a more reliable and realistic process. Our model proved, in different contexts, that higher levels of consensus and satisfaction are achieved when using agents modeled with behavior styles compared to agents without any features to represent the decision-makers' intentions.- (undefined

Evaluating taxonomic inflation: towards evidence-based species delimitation in Eurasian vipers (Serpentes: Viperinae)

International audienceThe designation of taxonomic units has important implications for the understanding and conservation ofbiodiversity. Eurasian vipers are a monophyletic group of viperid snakes (Serpentes, Viperinae), currently comprising fourgenera (Daboia, Macrovipera, Montivipera and Vipera) and up to 40 species. Taxonomic units have been described usinga wide variety of methods and criteria, and consequently, considerable controversy still surrounds the validity of somecurrently listed species. In order to promote a consensus- and evidence-based taxonomy of Eurasian vipers, we analysedpublished mitochondrial and nuclear DNA sequences for this group to reconstruct phylogenetic relationships among currentlyrecognized viper species.We also compiled information on external morphology to assess their morphological distinctiveness.Phylogenetic inference based on mtDNA sequences shows contrasting levels of divergence across genera and species andidentifies several instances of non-monophyly in described species. Nuclear DNA sequences show extremely low levels ofgenetic variation, with a widespread pattern of allele sharing among distant species, and even among genera. Revision ofmorphological data shows that most species designations rely on scalation traits that overlap extensively among species ofthe same genus. Based on our combined assessment, we recognize 15 taxa as valid species, three taxa which likely representspecies complexes, 17 taxa of doubtful validity as species, and five taxa for which species status is maintained but furtherresearch is highly recommended to assess taxonomic arrangements. We stress the need to implement integrative taxonomicapproaches for the recognition of evidence-based taxonomic units in Eurasian viper