Numerical Stability with Help from Entropy: Solving a Set of 13 Moment Equations for Shock Tube Problem

2019 ◽  
Vol 44 (1) ◽  
pp. 43-69 ◽  
Author(s):  
Carl Philipp Zinner ◽  
Hans Christian Öttinger

Abstract The shock structures of a 13 moment generalized hydrodynamics system of rarefied gases are simulated. These are first order hyperbolic equations derived from the Boltzmann equation. The investigated moment system stands out due to having an entropy evolution. In addition, a particular interest arises from the fact that the equations not only contain nonconservative products, but also provide the key to solving this mathematical and numerical issue by means of a simple substitution utilizing the physical entropy evolution. The apparent success of this method warrants investigation and provides a new perspective and starting point for finding general approaches to nonconservative products and irreversible processes. Furthermore, the system shows physically accurate results for low Mach numbers and is able to reveal the nonequilibrium entropy profile across a shock wave.

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Wesley Fussner ◽  
Mai Gehrke ◽  
Samuel J. van Gool ◽  
Vincenzo Marra

Abstract We provide a new perspective on extended Priestley duality for a large class of distributive lattices equipped with binary double quasioperators. Under this approach, non-lattice binary operations are each presented as a pair of partial binary operations on dual spaces. In this enriched environment, equational conditions on the algebraic side of the duality may more often be rendered as first-order conditions on dual spaces. In particular, we specialize our general results to the variety of MV-algebras, obtaining a duality for these in which the equations axiomatizing MV-algebras are dualized as first-order conditions.


2020 ◽  
Vol 2020 (9) ◽  
Author(s):  
Kirill Krasnov ◽  
Yuri Shtanov

Abstract We describe a new perturbation theory for General Relativity, with the chiral first-order Einstein-Cartan action as the starting point. Our main result is a new gauge-fixing procedure that eliminates the connection-to-connection propagator. All other known first-order formalisms have this propagator non-zero, which significantly increases the combinatorial complexity of any perturbative calculation. In contrast, in the absence of the connection-to-connection propagator, our formalism leads to an effective description in which only the metric (or tetrad) propagates, there are only cubic and quartic vertices, but some vertex legs are special in that they cannot be connected by the propagator. The new formalism is the gravity analog of the well-known and powerful chiral description of Yang-Mills theory.


1988 ◽  
Vol 03 (04) ◽  
pp. 953-1021 ◽  
Author(s):  
RICCARDO D’AURIA ◽  
PIETRO FRÉ ◽  
MARIO RACITI ◽  
FRANCO RIVA

Using a theorem by Bonora-Pasti and Tonin on the existence of a solution for D=10N=1 Bianchi identities in the presence of a Lorentz Chern Simons term, we find an explicit parametrization of the superspace curvatures. Our solution depends only on one free parameter which can be reabsorbed in a field redefinition of the dilaton and of the gravitello. We emphasize that the essential point which enables us to obtain a closed form for the curvature parametrizations and hence for the supersymmetry transformation rules is the use of first order formalism. The spin connection is known once the torsion is known. This latter, rather than being identified with Hµνρ as it is usually done in the literature, is related to it by a differential equation which reduces to the algebraic relation Hµνρ = - 3Tµνρ e4/3σ only at γ1=0 (γ1 being proportional to κ/g2). The solution of the Bianchi identities exhibited in this paper corresponds to a D=10 anomaly free supergravity (AFS). This theory is unique in first order formalism but corresponds to various theories in second order formalism. Indeed the torsion equation is a differential equation which, in order to be solved must be supplemented with boundary conditions. One wonders whether supplemented with a judicious choice of boundary conditions for the torsion equation, AFS yields all the interaction terms found in the effective theory of the heterotic string (ETHS). In this respect two remarks are in order. Firstly it appears that solving the torsion equation iteratively with Tµνρ = -1/3Hµνρ e-4/3σ as starting point all the terms of ETHS except those with a ζ(3) coefficient show up. (Whether the coefficient agree is still to be checked.) Secondly, as shown in this paper the rheonomic solution of the super Poincaré Bianchi identities is unique. Hence additional interaction terms can be added to the Lagrangian only by modifying the rheonomic parametrization of the [Formula: see text]-curvature. The only assumption made in our paper is that [Formula: see text] has at most ψ∧ψ∧V components (sector (1,2)). Correspondingly the only room left for a modification of the present theory is the addition of a (0, 3) part in the rheonomic parametrization of [Formula: see text]. When this work was already finished a conjecture was published by Lechner Pasti and Tonin that such a generalization of AFS might exist and be responsible for the ζ(3) missing term. Indeed if we were able to solve the [Formula: see text]-Bianchi with this new (0, 3)-part then the torsion equation would be modified via new terms which, in second order formalism, lead to additional gravitational interactions. The equation of motion of Anomaly Free Supergravity can be worked out from the Bianchi identities: we indicate through which steps. The corresponding Lagrangian could be constructed with the standard procedures of the rheonomy approach. In this paper we limit ourselves to the bosonic sector of such a Lagrangian and we show that it can indeed be constructed in such a way as to produce the relation between Hµνρ and Tµνρ as a variational equation.


2020 ◽  
Vol 7 (2) ◽  
pp. 120-123
Author(s):  
Jerzy Jaskuła ◽  
Marek Siuta

The aim: Incidents with large number of casualties present a major challenge for the emergency services. Incident witnesses are always the first on scene. Authors aim at giving them an algorithm arranging the widely known first aid rules in such way, that the number of potential fatalities before the services’ arrival may be decreased. Material and methods: The authors’ main aim was creating an algorithm for mass casualty incident action, comprising elements not exceeding first aid skill level. Proceedings have been systematized, which led to creation of mass casualty incident algorithm. The analysis was based on the subject matter literature, legal acts and regulations, statistical data and author’s personal experience. Results: The analysis and synthesis of data from various sources allowed for the creation of Simple Emergency Triage (SET) algorithm. It has been proven – on theoretical level – that introducing an organized way of proceeding in mass casualty incident on the first aid level is justified. Conclusions: The SET algorithm presented in the article is of an implemental character. It may be a supplement to basic first aid skills. Algorithm may also be the starting point for further empirical research aimed at verifying its effectiveness.


1997 ◽  
Vol 12 (31) ◽  
pp. 2353-2366 ◽  
Author(s):  
Alberto Accardi ◽  
Andrea Belli

We study the most general renormalization transformations for the first-order formulation of the Yang–Mills theory. We analyze, in particular, the trivial sector of the BRST cohomology of two possible formulations of the model: the standard one and the extended one. The latter is a promising starting point for the interpretation of the Yang–Mills theory as a deformation of the topological BF theory. This work is a necessary preliminary step towards any perturbative calculation, and completes some recently obtained results.


2018 ◽  
Vol 42 (2) ◽  
pp. 176-190 ◽  
Author(s):  
Anat Toder-Alon ◽  
Frédéric F. Brunel

Purpose The purpose of this paper is to investigate how peer-to-peer word-of-mouth (PPWOM) conversations evolve over time because of the dynamic social nature of the community in which they take place. Design/methodology/approach This study analyzed PPWOM conversations in an online community website for new and expectant mothers. Two data collection phases were undertaken during a four-year period. In phase I, messages were collected for a one-month period from five different bulletin boards (i.e. cross-sectional data) and at two points in time (i.e. semi-longitudinal). In phase II, a full longitudinal study was conducted, and the complete text of all messages of a newly formed bulletin board was captured for a nine-month period. The corpus of messages was examined in line with the basic tools of ethnomethodology and conversation analysis. Findings This research developed a typology of PPWOM genres and showed that these genres change over the community lifespan. The findings confirmed that the levels of social cohesiveness and the interaction communicative motives are the main factors that distinguish different PPWOM genres. Research limitations/implications This research has offered a new perspective into the study of PPWOM, and hopefully it will serve as a starting point for a broader dialogue regarding the social context in which PPWOM is exchanged. Originality/value In contrast to traditional word-of-mouth research, this study demonstrated that PPWOM conversations go much beyond the exchange of functional information, and instead serve numerous social and emotional goals.


Author(s):  
Barış Yetkin

This study examines the orientalist influences in the media. Studies that determine the orientalist elements in media content in Turkey are not sufficient. In order to eliminate this deficiency, it was determined as the starting point of the research whether the orientalist stereotypes are still valid today and whether they contain epistemic violence. Based on this problem, some of the advertisements used in tourism promotion in the last 20 years within the framework of the official state policies of the Republic of Turkey are selected. Historical understanding and analytical thinking are adopted. In this direction, cultural context research is conducted using comparative case studies. It is aimed to find out whether the situation defined as self-orientalism in tourism promotion advertisements coincides with Western orientalist stereotypes. Thus, it is desired to provide a new perspective to researchers working on this subject and to present meta-analysis data.


2019 ◽  
Vol 11 (4) ◽  
pp. 863-881 ◽  
Author(s):  
Mahamudul Hasan

Purpose The purpose of this study is to propose and develop a new perspective in Islamic Marketing by Integrating Islamic Marketing principles and the conventional Social Marketing discipline. Design/methodology/approach This is a conceptual study that is based on academic contributions gathered from the works of key academicians of Islamic Marketing and Social Marketing discipline. The author also presents personal viewpoints regarding the discipline. Conventional social marketing practices in various Muslim and non-Muslim countries have been studied with theoretical discussions. A critical approach has been applied in this study to assimilate Islamic marketing principles with existing social marketing theories. Findings The author proposes a distinct discipline of Islamic Marketing, which is termed as Islamic Social Marketing. The new discipline has been compared with conventional social marketing framework and practices to demonstrate its distinctive features. The critical analysis and discussion exhibit that the proposed new discipline has both similarities and dissimilarities with present social marketing theories and practices. Originality/value This study contributes to Islamic Marketing discipline by proposing a unique field that has been termed as “Islamic Social Marketing”. Although many studies have been conducted on Islamic marketing, the analysis of social marketing in light of Islamic Marketing principles remains clearly in a vacuum-like situation. The current research work is a starting point for academic discussions on this issue that can provide guidelines to develop social marketing intervention programs for Muslim-dominated societies and assist Islamic value-driven social marketing practitioners.


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