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Статті в журналах з теми "CHC solver"
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Zhu, He, Stephen Magill, and Suresh Jagannathan. "A data-driven CHC solver." ACM SIGPLAN Notices 53, no. 4 (December 2, 2018): 707–21. http://dx.doi.org/10.1145/3296979.3192416.
Повний текст джерела
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DE ANGELIS, EMANUELE, FABIO FIORAVANTI, ALBERTO PETTOROSSI, and MAURIZIO PROIETTI. "Solving Horn Clauses on Inductive Data Types Without Induction." Theory and Practice of Logic Programming 18, no. 3-4 (July 2018): 452–69. http://dx.doi.org/10.1017/s1471068418000157.
Повний текст джерелаАнотація:
AbstractWe address the problem of verifying the satisfiability of Constrained Horn Clauses (CHCs) based on theories of inductively defined data structures, such as lists and trees. We propose a transformation technique whose objective is the removal of these data structures from CHCs, hence reducing their satisfiability to a satisfiability problem for CHCs on integers and booleans. We propose a transformation algorithm and identify a class of clauses where it always succeeds. We also consider an extension of that algorithm, which combines clause transformation with reasoning on integer constraints. Via an experimental evaluation we show that our technique greatly improves the effectiveness of applying the Z3 solver to CHCs. We also show that our verification technique based on CHC transformation followed by CHC solving, is competitive with respect to CHC solvers extended with induction.
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Faella, Marco, and Gennaro Parlato. "Reachability Games Modulo Theories with a Bounded Safety Player." Proceedings of the AAAI Conference on Artificial Intelligence 37, no. 5 (June 26, 2023): 6330–37. http://dx.doi.org/10.1609/aaai.v37i5.25779.
Повний текст джерелаАнотація:
Solving reachability games is a fundamental problem for the analysis, verification, and synthesis of reactive systems. We consider logical reachability games modulo theories (in short, GMTs), i.e., infinite-state games whose rules are defined by logical formulas over a multi-sorted first-order theory. Our games have an asymmetric constraint: the safety player has at most k possible moves from each game configuration, whereas the reachability player has no such limitation. Even though determining the winner of such a GMT is undecidable, it can be reduced to the well-studied problem of checking the satisfiability of a system of constrained Horn clauses (CHCs), for which many off-the-shelf solvers have been developed. Winning strategies for GMTs can also be computed by resorting to suitable CHC queries. We demonstrate that GMTs can model various relevant real-world games, and that our approach can effectively solve several problems from different domains, using Z3 as the backend CHC solver.
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Mordvinov, Dmitry A. "Property-Directed Inference of Relational Invariants." Modeling and Analysis of Information Systems 26, no. 4 (December 27, 2019): 550–71. http://dx.doi.org/10.18255/1818-1015-2019-4-550-571.
Повний текст джерелаАнотація:
Property Directed Reachability (PDR) is an efficient and scalable approach to solving systems of symbolic constraints also known as Constrained Horn Clauses (CHC). In the case of non-linear CHCs, which may arise, e.g., from relational verification tasks, PDR aims to infer an inductive invariant for each uninterpreted predicate. However, in many practical cases this reasoning is not successful, as invariants should be derived for groups of predicates instead of individual predicates. The article describes a novel algorithm that identifies these groups automatically and complements the existing PDR technique. The key feature of the algorithm is that it does not require a possibly expensive synchronization transformation over the system of CHCs. We have implemented the algorithm on top of a up-to-date CHC solver Spacer. Our experimental evaluation shows that for some CHC systems, on which existing solvers diverge, our tool is able to discover relational invariants.
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Gheorghiu, Călin-Ioan. "Chebfun Solutions to a Class of 1D Singular and Nonlinear Boundary Value Problems." Computation 10, no. 7 (July 8, 2022): 116. http://dx.doi.org/10.3390/computation10070116.
Повний текст джерелаАнотація:
The Chebyshev collocation method implemented in Chebfun is used in order to solve a class of second order one-dimensional singular and genuinely nonlinear boundary value problems. Efforts to solve these problems with conventional ChC have generally failed, and the outcomes obtained by finite differences or finite elements are seldom satisfactory. We try to fix this situation using the new Chebfun programming environment. However, for tough problems, we have to loosen the default Chebfun tolerance in Newton’s solver as the ChC runs into trouble with ill-conditioning of the spectral differentiation matrices. Although in such cases the convergence is not quadratic, the Newton updates decrease monotonically. This fact, along with the decreasing behaviour of Chebyshev coefficients of solutions, suggests that the outcomes are trustworthy, i.e., the collocation method has exponential (geometric) rate of convergence or at least an algebraic rate. We consider first a set of problems that have exact solutions or prime integrals and then another set of benchmark problems that do not possess these properties. Actually, for each test problem carried out we have determined how the Chebfun solution converges, its length, the accuracy of the Newton method and especially how well the numerical results overlap with the analytical ones (existence and uniqueness).
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DE ANGELIS, EMANUELE, FABIO FIORAVANTI, ALBERTO PETTOROSSI, and MAURIZIO PROIETTI. "Predicate Pairing for program verification." Theory and Practice of Logic Programming 18, no. 2 (December 4, 2017): 126–66. http://dx.doi.org/10.1017/s1471068417000497.
Повний текст джерелаАнотація:
AbstractIt is well-known that the verification of partial correctness properties of imperative programs can be reduced to the satisfiability problem for constrained Horn clauses (CHCs). However, state-of-the-art solvers for constrained Horn clauses (or CHC solvers) based onpredicate abstractionare sometimes unable to verify satisfiability because they look for models that are definable in a given class 𝓐 of constraints, called 𝓐-definable models. We introduce a transformation technique, calledPredicate Pairing, which is able, in many interesting cases, to transform a set of clauses into an equisatisfiable set whose satisfiability can be proved by finding an 𝓐-definable model, and hence can be effectively verified by a state-of-the-art CHC solver. In particular, we prove that, under very general conditions on 𝓐, the unfold/fold transformation rules preserve the existence of an 𝓐-definable model, that is, if the original clauses have an 𝓐-definable model, then the transformed clauses have an 𝓐-definable model. The converse does not hold in general, and we provide suitable conditions under which the transformed clauses have an 𝓐-definable modelif and only ifthe original ones have an 𝓐-definable model. Then, we present a strategy, called Predicate Pairing, which guides the application of the transformation rules with the objective of deriving a set of clauses whose satisfiability problem can be solved by looking for 𝓐-definable models. The Predicate Pairing (PP) strategy introduces a new predicate defined by the conjunction of two predicates occurring in the original set of clauses, together with a conjunction of constraints. We will show through some examples that an 𝓐-definable model may exist for the new predicate even if it does not exist for its defining atomic conjuncts. We will also present some case studies showing that Predicate Pairing plays a crucial role in the verification ofrelational properties of programs, that is, properties relating two programs (such as program equivalence) or two executions of the same program (such as non-interference). Finally, we perform an experimental evaluation of the proposed techniques to assess the effectiveness of Predicate Pairing in increasing the power of CHC solving.
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Sun, Jintao, Qi Chen, Baoming Zhao, Caohui Guo, Jianyu Liu, Mingming Zhang, and Decai Li. "Temperature-dependent ion chemistry in nanosecond discharge plasma-assisted CH4 oxidation." Journal of Physics D: Applied Physics 55, no. 13 (January 4, 2022): 135203. http://dx.doi.org/10.1088/1361-6463/ac45ac.
Повний текст джерелаАнотація:
Abstract Ion chemistry with temperature evolution in weakly ionized plasma is important in plasma-assisted combustion and plasma-assisted catalysis, fuel reforming, and material synthesis due to its contribution to plasma generation and state transition. In this study, the kinetic roles of ionic reactions in nanosecond discharge (NSD) plasma-assisted temperature-dependent decomposition and oxidation of methane are investigated by integrated studies of experimental measurements and mathematical simulations. A detailed plasma chemistry mechanism governing the decomposition and oxidation processes in a He/CH4/O2 combustible mixture is proposed and studied by including a set of electron impact reactions, reactions involving excited species, and ionic reactions. A zero-dimensional model incorporating the plasma kinetics solver ZDPlasKin and the combustion chemical kinetics solver CHEMKIN is used to calculate the time and temperature evolution of the ion density. Uncertainty analysis of ionic reactions on key species generation is conducted by using different referenced data, and insignificant sensitivity is found. The numerical model is consistent with experimental data for methane consumption and generation of major species including CO, CO2, and H2. By modeling the temporal evolution of key ions, it is observed that O2 + presents the largest concentration in the discharge stage, followed by CH4 +, CH3 +, and CH2 +, which is in accordance with the traditional ion chemistry in hydrocarbon flames and agrees well with molecular-beam mass spectrometer investigations. The path flux shows that the concentrations of key species, including electrons, O, OH, H, O(1D), O2(a1Δg), O2 +, CH3 +, and CH4 +, change within 1–2 orders of magnitude and that the transition from a homogeneous state to a contracted/constricted state does not occur. The path flux and sensitivity analysis reveal the significant roles of cations in the stimulation of active radical generation, including CH, O, OH, and O(1D), thus accelerating methane oxidation. This work provides a deep insight into the ion chemistry of temperature-dependent plasma-assisted CH4 oxidation.
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Zhou, Wenjun, Xi Qin, Ming Lv, Lifeng Qiu, Zhongjiang Chen, and Fan Zhang. "Design of Plasmonic Photonic Crystal Fiber for Highly Sensitive Magnetic Field and Temperature Simultaneous Measurement." Micromachines 14, no. 9 (August 29, 2023): 1684. http://dx.doi.org/10.3390/mi14091684.
Повний текст джерелаАнотація:
A high-sensitivity plasmonic photonic crystal fiber (PCF) sensor is designed and a metal thin film is embedded for achieving surface plasmon resonance (SPR), which can detect the magnetic field and temperature simultaneously. Within the plasmonic PCF sensor, the SPR sensing is accomplished by coating both the upper sensing channel (Ch1) and the lower sensing channel (Ch2) with gold film. In addition, the temperature-sensitive medium polydimethylsiloxane (PDMS) is chosen to fill in Ch1, allowing the sensor to respond to the temperature. The magnetic field-sensitive medium magnetic fluid (MF) is chosen to fill in Ch2, allowing this sensor to respond to the magnetic field. During these processes, this proposed SPR-PCF sensor can achieve dual-parameter sensing. The paper also investigates the electrical field characteristics, structural parameters and sensing performance using COMSOL. Finally, under the magnetic field range of 50–130 Oe, this sensor has magnetic field sensing sensitivities of 0 pm/Oe (Ch1) and 235 pm/Oe (Ch2). In addition, this paper also investigates the response of temperature. Under the temperature range of 20–40 °C, Ch1 and Ch2 have temperature sensitivities of −2000 pm/°C and 0 pm/°C, respectively. It is noteworthy that the two sensing channels respond to only a single physical parameter; this sensing performance is not common in dual-parameter sensing. Due to this sensing performance, it can be found that the magnetic field and temperature can be detected by this designed SPR-PCF sensor simultaneously without founding and calculating a sensing matrix. This sensing performance can solve the cross-sensitivity problem of magnetic field and temperature, thus reducing the measurement error. Since it can sense without a matrix, it further can solve the ill-conditioned matrix and nonlinear change in sensitivity problems in dual-parameter sensing. These excellent sensing capabilities are very important for carrying out multiparameter sensing in complicated environments.
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Vieira, Bernardo C., Fabrício V. Andrade, and Antônio O. Fernandes. "Framework for Generating Configurable SAT Solvers." Journal of Integrated Circuits and Systems 6, no. 1 (December 27, 2011): 50–59. http://dx.doi.org/10.29292/jics.v6i1.338.
Повний текст джерелаАнотація:
The state-of-the-art SAT solvers usually share the same core techniques, for instance: the watched literals structure, conflict clause recording and non-chronological backtracking. Nevertheless, they might differ in the elimination of learnt clauses, as well as in the decision heuristic. This article presents a framework for generating configurable SAT solvers. The proposed framework is composed of the following components: a Base SAT Solver, a Perl Preprocessor, XML files (Solver Description and Heuristics Description files) to describe each heuristic as well as the set of heuristics that the generated solver uses. This solvers may use several techniques and heuristics such as those implemented in BerkMin, and in Equivalence Checking of Dissimilar Circuits, and also in Minisat. In order to demonstrate the effectiveness of the proposed framework, this article also presents three distinct SAT solver instances generated by the framework to address a complex and challenging industry problem: the Combinational Equivalence Checking problem (CEC).The first instance is a SAT solver that uses BerkMin and Dissimilar Circuits core techniques except the learnt clause elimination heuristic that has been adapted from Minisat; the second is another solver that combines BerkMin and Minisat decision heuristics at run-time; and the third is yet another SAT solver that changes the database reducing heuristic at run-time. The experiments demonstrate that the first SAT solver generated is a faster solver than state-of-the-art SAT solver BerkMin for several instances as well as for Minisat in almost every instance.
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Webb, Penny. "A way to solve problems." Child Care 14, no. 3 (March 2, 2017): 4–5. http://dx.doi.org/10.12968/chca.2017.14.3.4.
Повний текст джерелаДисертації з теми "CHC solver"
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Negus, Charles H. "An Interactive Chemical Equilibrium Solver for the Personal Computer." Thesis, Virginia Tech, 1997. http://hdl.handle.net/10919/36826.
Повний текст джерелаАнотація:
The Virginia Tech Equilibrium Chemistry (VTEC) code is a keyboard interactive, user friendly, chemical equilibrium solver for use on a personal computer. The code is particularly suitable for a teaching / learning environment. For a set of reactants at a defined thermodynamic state given by a user, the program will select all species in the JANAF thermochemical database which could exist in the products. The program will then calculate equilibrium composition, flame temperature, and other thermodynamic properties for many common cases. Examples in this thesis show VTEC's ability to predict chemical equilibrium compositions and flame temperature for selected reactions, and demonstrate how VTEC can substitute for and aid in the design of lab experiments, and identify trends in parametric studies.
The 1976 NASA Lewis Chemical Equilibrium Code (CEC76) from which VTEC has been adapted uses Lagrangian multipliers to minimize free energy. CEC76 was written for mainframe computer use. Later versions of CEC76, adapted for personal computer use are available for a fee and have a very minimal user interface.Master of Science
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Guérineau, Olivier. "Contribution à l'étude de la combustion supersonique : stabilisation de flammes par ondes de choc." Châtenay-Malabry, Ecole centrale de Paris, 1997. http://www.theses.fr/1997ECAP0530.
Повний текст джерелаАнотація:
La combustion supersonique est bien adaptée à la propulsion des véhicules hypersoniques aérobies. Le statoréacteur àcombustion supersonique (superstatoréacteur) surclasse les systèmes plus classiques (turboreacteur, statoreacteur à combustion subsonique) lorsque le Mach de vol dépasse 7. La conception des foyers à combustion supersonique pose des problèmes fondamentaux et techniques difficiles. Des questions spécifiques posées par l'accrochage par une onde de choc au sein d'un mélange hydrogène-air. Une cinétique réactionnelle complexe est sélectionnée puis utilisée. Elle rend compte des principaux phénomènes caractérisant la combustion de l'hydrogène dans l'air : temps d'allumage, limites d'explosibilité d'un mélange stœchiométrique. Un code volumes finis, résolvant les équations de Navier-Stokes réactives, est adapté aux calculs de combustion supersonique. Les méthodes numériques employées sont exposées : en particulier la description des flux d'Euler par des solveurs approchés de Riemann (méthode de Roe, méthode des courbes de choc, flux d'Osher). Ces méthodes précises se sont cependant révélées délicates à utiliser du fait de la raideur du système. Deux configurations principales de calcul ont été dégagées d'une étude bibliographique des expériences et calculs de combustion faisant intervenir des chocs. Une étude numérique de l'allumage d'une flamme hydrogène-air derrière un disque de mach est présentée pour la première fois. Elle permet d'affirmer que les ondes observées dans les expériences précédemment citées sont des ondes de choc, et non pas des ondes de détonation. La position du disque de mach dépend de la modélisation employée au cours des calculs. La seconde configuration est celle d'un dièdre plonge dans un écoulement prémélangé air-hydrogène d'un nombre de Mach de 3. Les résultats prouvent que des détonations obliques fortes peuvent être stables, cette configuration constituant un mode d'accrochage envisageable pour une flamme. Ils montrent de plus les limites de la théorie classique des polaires de détonation aux hypothèses trop simplificatrices (propriétés thermodynamiques constantes). Enfin un calcul reprenant la première configuration à une température plus élevée met en évidence l'analogue de la réflexion de Mach pour des ondes de détonation. Ces études montrent qu'un tel système peut-être instable. Ces études concernant des situations pouvant se produire au sein de la chambre de combustion d'un superstatoréacteur, mettent en évidence des phénomènes dont il faut tenir compte.
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Chauvat, Yann. "Le phénomène de "carbuncle" : analyse d'une pathologie des schémas numériques à capture de choc." Toulouse, ENSAE, 2005. http://www.theses.fr/2005ESAE0015.
Повний текст джерелаАнотація:
Les calculs numériques d’écoulements supersoniques faisant intervenir des chocs forts, par des schémas à capture de choc, sont parfois affectés par une anomalie dont l'origine est encore mal comprise, le « carbuncle », qui se manifeste par une configuration complexe de chocs faibles et forts. Cette pathologie des schémas à capture de choc intervient dans des conditions physiques et numériques analysées dans cette thèse. La plupart des utilisateurs de schémas numériques se contentent de supprimer cette solution parasite par l’ajout de dissipation numérique au risque de dégrader la résolution des couches limites. De plus, cet ajout n’a aucune justification mathématique. Le premier but de cette thèse est d’analyser et de comprendre le phénomène de «carbuncle» et d'identifier les paramètres qui affectent son apparition. Les analyses de stabilité développées pour comprendre le phénomène de «carbuncle » sont détaillées. En particulier, l’analyse de stabilité matricielle de Dumbser et al. (2004), qui donne un critère sur la stabilité d’un schéma numérique, est utilisée pour montrer qu’il est possible de stabiliser un schéma instable en contrôlant finement la structure numérique du choc. De plus, une nouvelle analyse de stabilité, basée sur la méthode multimodale de Trefethen et al. (1993), est appliquée à l’étude des phénomènes transitoires d’apparition du « carbuncle ». Ces différentes approches concourent à démontrer que l'origine du phénomène de « carbuncle » réside dans la forme monodimensionnelle du flux numérique.
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Masurel, Eve. "Absorption sélective des goudrons issus de la gazéification : application au laveur Venturi d'une unité de cogénération biomasse." Thesis, Université de Lorraine, 2015. http://www.theses.fr/2015LORR0096.
Повний текст джерелаАнотація:
Parmi les procédés de conversion de la biomasse, la gazéification à l’air présente l’avantage d’un rendement de conversion électrique attractif, en particulier pour les petites puissances. Cependant, l’élimination des goudrons générés reste un verrou à lever pour permettre l’émergence industrielle du procédé de gazéification. Le traitement par absorption est considérée comme technologiquement mature mais le choix du solvant de lavage, sa gestion et l’optimisation du laveur représentent un élément crucial. Afin de mettre en avant les solvants envisageables, une méthodologie rapide et robuste de choix de solvant basée sur une analyse multicritère a été développée. La comparaison de plus d’une centaine de solvants conventionnels a permis de mettre en avant deux solvants. Afin d’étudier des performances de ces solvants, un pilote de lavage de type Venturi (laveur compact présentant une aire interfaciale importante et peu de risque d’encrassement) a été dimensionné et caractérisé. L’étude expérimentale sur gaz réel a permis d’une part d’étudier l’évolution de la charge en goudron dans le solvant et d’autre part de mesurer les efficacités de traitement des solvants sur le benzène, le naphtalène, l’anthracène et le pyrène. Ces données expérimentales ont ensuite été utilisées afin de valider la modélisation du laveur Venturi effectuée dans l’optique d’une optimisation et d’une extrapolation à l’échelle industrielle de l’unité de lavage. Afin d’estimer le coût de traitement en €/MWh, le dimensionnement des équipements à l’échelle industrielle a été effectué pour les deux solvants dans différents cas de figure afin d’effectuer leur évaluation technico-économiqueAmong biomass conversion processes, air gasification has the advantage of an attractive electrical conversion yield, especially for small powers. However, the elimination of the generated tar remains a lock to lift to allow the industrial emergence of the gasification process. The treatment by absorption is considered to be technologically mature but the choice of cleaning solvent, its management and the optimization of the scrubber represent a crucial element. In order to highlight possible solvents, a fast and robust solvents screening methodology based on a multi-criteria analysis was developed. Comparison of more than 100 of conventional solvents allowed to forward two solvents. To investigate performance of these solvents, a pilot scale Venturi scrubber (compact scrubber with a large Interfacial area and low risk fouling risk) has been designed and characterized. The experimental study on real raw gas allowed to study the evolution of the tar loading factor in the solvent and to measure treatment efficiencies of solvents on benzene, naphthalene, anthracene and pyrene. These experimental data were then used to validate the modelling of the Venturi scrubber in the context of optimization and extrapolation on the industrial scale of the washing unit. In order to estimate the cost of treatment in €/ MWh, the sizing of the equipment on an industrial scale has been made for two solvents in different cases in order to process to a technico-economical evaluation
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Rios, de Anda Agustin. "Influence of the solvent sorption, additivation, and chemical modification on the molecular mobility dynamics of Polyamide 6,6 amorphous phase and its consequences on the tensile and impact strength properties of this polymer." Thesis, Lyon 1, 2012. http://www.theses.fr/2012LYO10259/document.
Повний текст джерелаАнотація:
Ce travail s’inscrit dans le projet de développement des réservoirs essence pour voitures à partir des formulations Polyamide 6,6 (PA6,6). Le PA6,6 est un bon candidat pour des applications techniques car il possède des bonnes propriétés thermomécaniques rapportés à son poids. Ces formulations doivent montrer des bonnes propriétés barrière aux essences classiques, aux biofuels (essence contenant de l’éthanol) et aussi à l’eau qui est présente dans l’atmosphère, tout en ayant une bonne tenue aux chocs.Les enjeux scientifiques sont la meilleure compréhension des interactions entre le PA6,6 et des solvants purs de polarités et tailles différentes mais aussi des mélanges ternaires composés d’éthanol, toluène et isooctane à différentes concentrations et qui modélisent les biofuels. On veut aussi étudier l’effet de ces solvants sur la température de transition vitreuse Tg qui est la signature de la mobilité moléculaire de la phase amorphe. Ensuite, l’effet de l’additivation ou de l’ajout des co-monomères sur les propriétés barrière et mécaniques, notamment les propriétés choc, a été étudié. Dans ce travail nous avons pu décrire comment la nature d’un solvant conditionne sa sorption et son effet plastifiant dans le PA6,6. On a aussi observé que la nature et les interactions interchaînes de la matrice polymère conditionnent aussi la prise en solvants. De plus, une approche thermodynamique a été proposée pour étudier et comprendre la sorption de mélanges ternaires éthanol-toluène-isooctane et leur effet plastifiant dans le PA6,6. On a aussi montré que les propriétés mécaniques du PA6,6 dépendent ou sont liées à l’état de mobilité moléculaire de la phase amorphe de ce polymèreThis work forms part of a project aimed to develop Polyamide 6,6(PA6,6)-based automotive fuel tanks. PA6,6 is a good candidate for technical applications since it possesses good thermo-mechanical properties compared to its weight. These formulations must exhibit good impermeable properties to classic gasoline, to biofuels (gasoline containing ethanol), and to water which is found in the atmosphere, while keeping good impact behavior.The scientific issues are the better understanding of PA6,6-solvent interactions in the case of a series of solvents having different sizes and polarities and also for a set of ternary mixtures composed of ethanol, toluene, and isooctane at various concentrations that model biofuels. The effect of these solvents on the glass transition temperature Tg (molecular mobility signature) was assessed. The effect of additivating or chemically-modifying PA6,6 on the impact and barrier properties of the polymer was studied.In this work, it was described how the nature of a solvent conditions its sorption and its plasticizing effect on PA6,6. It was also observed that the PA6,6 inter-chain interactions also condition the solvent sorption. Moreover, a thermodynamic approach describing the sorption and plasticizing effects of ternary mixtures in PA6,6 was considered and developed. It was also observed that PA6,6 mechanical properties depend or are related to the amorphous phase molecular mobility state
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Zebiri, Boubakr. "Étude numérique des interactions onde de choc / couche limite dans les tuyères propulsives Shock-induced flow separation in an overexpanded supersonic planar nozzle A parallel high-order compressible flows solver with domain decomposition method in the generalized curvilinear coordinates system Analysis of shock-wave unsteadiness in conical supersonic nozzles." Thesis, Normandie, 2020. http://www.theses.fr/2020NORMIR06.
Повний текст джерелаАнотація:
La nécessité d’une meilleure compréhension du mécanisme d’entrainement pour l’instabilité à basse fréquence observée dans un écoulement dans une tuyère sur-détendue a été discutée. Le caractère instable de l’onde de choc/couche limite reste un défi pratique important pour les problèmes des écoulements dans les tuyères. De plus, pour une couche limite turbulente incidente donnée, ce type d’écoulement présente généralement des mouvements de choc à basse fréquence plus élevées qui sont moins couplés aux échelles de temps de la turbulence en amont. Cela peut être bon du point de vue d’un expérimentateur, en raison de difficultés à mesurer des fréquences plus élevées, mais c’est plus difficile d’un point de vue calcul numérique en raison de la nécessité d’obtenir des séries temporelles plus longues pour résoudre les mouvements à basse fréquence. En excellent accord avec les résultats expérimentaux, une série de calcul LES de très longue durée a été réalisée, il a été clairement démontré l’existence de mouvements énergétiques à basse fréquence et à large bande près du point de séparation. Des efforts particuliers ont été faits pour éviter tout forçage à basse fréquence en amont, et il a été explicitement démontré que les oscillations de choc à basse fréquence observées n’étaient pas liées à la génération de turbulence d’entrée, excluant la possibilité d’un artefact numérique. Différentes méthodes d’analyse spectrales, et en décomposition en mode dynamique ont été utilisées pour montrer que les échelles de temps impliquées dans un tel mécanisme sont environ deux ordres de grandeur plus grandes que les échelles de temps impliquées dans la turbulence de la couche limite, ce qui est cohérent avec les mouvements de basse fréquence observés. En outre, ces échelles de temps se sont avérées être fortement modulées par la quantité de flux inversé à l’intérieur de la bulle de séparation. Ce scénario peut, en principe, expliquer à la fois l’instabilité des basses fréquences et sa nature à large bandeThe need for a better understanding of the driving mechanism for the observed low-frequency unsteadiness in an over-expanded nozzle flows was discussed. The unsteady character of the shock wave/boundary layer remains an important practical challenge for the nozzle flow problems. Additionally, for a given incoming turbulent boundary layer, this kind of flow usually exhibits higher low-frequency shock motions which are less coupled from the timescales of the incoming turbulence. This may be good from an experimenter’s point of view, because of the difficulties in measuring higher frequencies, but it is more challenging from a computational point of view due to the need to obtain long time series to resolve low-frequency movements. In excellent agreement with the experimental findings, a very-long LES simulation run was carried out to demonstrate the existence of energetic broadband low-frequency motions near the separation point. Particular efforts were done in order to avoid any upstream low-frequency forcing, and it was explicitly demonstrated that the observed low-frequency shock oscillations were not connected with the inflow turbulence generation, ruling out the possibility of a numerical artefact. Different methods of spectral analysis and dynamic mode decomposition have been used to show that the timescales involved in such a mechanism are about two orders of magnitude larger than the time scales involved in the turbulence of the boundary layer, which is consistent with the observed low-frequency motions. Furthermore, those timescales were shown to be strongly modulated by the amount of reversed flow inside the separation bubble. This scenario can, in principle, explain both the low-frequency unsteadiness and its broadband nature
Книги з теми "CHC solver"
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Ri shi yu shi cha. Beijing: Ke xue chu ban she, 2011.
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Tai yang dian chi ji qi ying yong. [Peking]: Guo fang gong ye chu ban she, 1985.
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3
Comandante Che: Guerrilla soldier, commander, and strategist, 1956-1967. University Park, Pa: Pennsylvania State University Press, 2003.
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Rencontres du Vietnam (2nd 1995 Hô CHI Minh City, Vietnam). The sun and beyond: Proceedings of the second Rencontres du Vietnam, Hô Chi Minh City, Vietnam, October 22-28, 1995. Gif-sur Yvette, France: Editions Frontières, 1996.
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Osborne, Mary Pope. Mo fa xiao che. Taibei Shi: Yuan liu chu ban shi ye gu fen you xian gong si, 2002.
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Amberson, Mary Margaret McAllen. A brave boy and a good soldier: John C.C. Hill and the Texas expedition to Mier. Austin: Texas State Historical Association, 2006.
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Bo mo tai yang dian chi guan jian ke xue he ji shu: Key science and technology of thin film solar cells. Shanghai: Shanghai ke xue ji shu chu ban she, 2013.
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Ying Han Han Ying tai yang dian chi ci hui: English-Chinese Chinese-English vocabulary of solar cell. [Peking]: Neng yuan chu ban she, 1986.
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Myeyeryakova, Vyera, and Viktor Starodubov. CNC Metal-cutting Machines. ru: INFRA-M Academic Publishing LLC., 2015. http://dx.doi.org/10.12737/5721.
Повний текст джерелаАнотація:
In the manual various ways of control of metal-cutting machines are considered, the principles of construction and possibility of systems of ChPU are given. Features of configurations and designs of machines with ChPU are presented,
ways of expansion of their technological capabilities, increases of productivity, accuracy and reliability.
The tasks solved during the training of managing directors of programs, feature of technological preparation, mathematical calculations and control unitary enterprise are considered. Programming bases for machines about ChPU, methods of adjusting are given,
features of technological service and repair. It is intended for students of the higher educational institutions which are trained in the directions 151900 "Design-technology ensuring machine-building productions" (qualification — the bachelor) and 151000
"Technological machines and the equipment" (qualification — the bachelor) on a preparation profile "Metal-cutting machines and complexes", and also for preparation in lyceums, technical schools, on special courses of CNC operators, members of repair crews, technologists-programmers.
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Chu ci yu shang gu li shi wen hua yan jiu: Zhongguo gu dai tai yang xun huan wen hua jie mi. Jinan: Qi Lu shu she, 1998.
Знайти повний текст джерелаЧастини книг з теми "CHC solver"
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Gurfinkel, Arie. "Program Verification with Constrained Horn Clauses (Invited Paper)." In Computer Aided Verification, 19–29. Cham: Springer International Publishing, 2022. http://dx.doi.org/10.1007/978-3-031-13185-1_2.
Повний текст джерелаАнотація:
AbstractMany problems in program verification, Model Checking, and type inference are naturally expressed as satisfiability of a verification condition expressed in a fragment of First-Order Logic called Constrained Horn Clauses (CHC). This transforms program analysis and verification tasks to the realm of first order satisfiability and into the realm of SMT solvers. In this paper, we give a brief overview of how CHCs capture verification problems for sequential imperative programs, and discuss CHC solving algorithm underlying the Spacer engine of SMT-solver Z3.
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Blicha, Martin, Konstantin Britikov, and Natasha Sharygina. "The Golem Horn Solver." In Computer Aided Verification, 209–23. Cham: Springer Nature Switzerland, 2023. http://dx.doi.org/10.1007/978-3-031-37703-7_10.
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AbstractThe logical framework of Constrained Horn Clauses (CHC) models verification tasks from a variety of domains, ranging from verification of safety properties in transition systems to modular verification of programs with procedures. In this work we present Golem, a flexible and efficient solver for satisfiability of CHC over linear real and integer arithmetic. Golem provides flexibility with modular architecture and multiple back-end model-checking algorithms, as well as efficiency with tight integration with the underlying SMT solver. This paper describes the architecture of Golem and its back-end engines, which include our recently introduced model-checking algorithm TPA for deep exploration. The description is complemented by extensive evaluation, demonstrating the competitive nature of the solver.
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Zlatkin, Ilia, and Grigory Fedyukovich. "Maximizing Branch Coverage with Constrained Horn Clauses." In Tools and Algorithms for the Construction and Analysis of Systems, 254–72. Cham: Springer International Publishing, 2022. http://dx.doi.org/10.1007/978-3-030-99527-0_14.
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AbstractState-of-the-art solvers for constrained Horn clauses (CHC) are successfully used to generate reachability facts from symbolic encodings of programs. In this paper, we present a new application to test-case generation: if a block of code is provably unreachable, no test case can be generated allowing to explore other blocks of code. Our new approach uses CHC to incrementally construct different program unrollings and extract test cases from models of satisfiable formulas. At the same time, a CHC solver keeps track of CHCs that represent unreachable blocks of code which makes the unrolling process more efficient. In practice, this lets our approach to terminate early while guaranteeing maximal coverage. Our implementation called Horntinuum exhibits promising performance: it generates high coverage in the majority of cases and spends less time on average than state-of-the-art.
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Fedyukovich, Grigory, and Gidon Ernst. "Bridging Arrays and ADTs in Recursive Proofs." In Tools and Algorithms for the Construction and Analysis of Systems, 24–42. Cham: Springer International Publishing, 2021. http://dx.doi.org/10.1007/978-3-030-72013-1_2.
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AbstractWe present an approach to synthesize relational invariants to prove equivalences between object-oriented programs. The approach bridges the gap between recursive data types and arrays that serve to represent internal states. Our relational invariants are recursively-defined, and thus are valid for data structures of unbounded size. Based on introducing recursion into the proofs by observing and lifting the constraints from joint methods of the two objects, our approach is fully automatic and can be seen as an algorithm for solving Constrained Horn Clauses (CHC) of a specific sort. It has been implemented on top of the SMT-based CHC solver AdtChc and evaluated on a range of benchmarks.
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Garcia-Contreras, Isabel, V. K. Hari Govind, Sharon Shoham, and Arie Gurfinkel. "Fast Approximations of Quantifier Elimination." In Computer Aided Verification, 64–86. Cham: Springer Nature Switzerland, 2023. http://dx.doi.org/10.1007/978-3-031-37703-7_4.
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AbstractQuantifier elimination (qelim) is used in many automated reasoning tasks including program synthesis, exist-forall solving, quantified SMT, Model Checking, and solving Constrained Horn Clauses (CHCs). Exact qelim is computationally expensive. Hence, it is often approximated. For example, Z3 uses “light” pre-processing to reduce the number of quantified variables. CHC-solver Spacer uses model-based projection (MBP) to under-approximate qelim relative to a given model, and over-approximations of qelim can be used as abstractions.In this paper, we present the QEL framework for fast approximations of qelim. QEL provides a uniform interface for both quantifier reduction and model-based projection. QEL builds on the egraph data structure – the core of the EUF decision procedure in SMT – by casting quantifier reduction as a problem of choosing ground (i.e., variable-free) representatives for equivalence classes. We have used QEL to implement MBP for the theories of Arrays and Algebraic Data Types (ADTs). We integrated QEL and our new MBP in Z3 and evaluated it within several tasks that rely on quantifier approximations, outperforming state-of-the-art.
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Oppermann, Hermann, and Matthias Hutter. "Au/Sn Solder." In Handbook of Wafer Bonding, 119–38. Weinheim, Germany: Wiley-VCH Verlag GmbH & Co. KGaA, 2012. http://dx.doi.org/10.1002/9783527644223.ch7.
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Clarke, Sue. "The Illustrator as Visual Problem Solver." In A Companion to Illustration, 199–228. Hoboken, NJ, USA: John Wiley & Sons, Inc., 2019. http://dx.doi.org/10.1002/9781119185574.ch9.
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Bradley, Andrew M. "A Hybrid Multithreaded Direct Sparse Triangular Solver." In 2016 Proceedings of the Seventh SIAM Workshop on Combinatorial Scientific Computing, 13–22. Philadelphia, PA: Society for Industrial and Applied Mathematics, 2016. http://dx.doi.org/10.1137/1.9781611974690.ch2.
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Gardi, Frédéric, Thierry Benoist, Julien Darlay, Bertrand Estellon, and Romain Megel. "Toward an Optimization Solver Based on Neighborhood Search." In Mathematical Programming Solver Based on Local Search, 53–64. Hoboken, NJ, USA: John Wiley & Sons, Inc., 2014. http://dx.doi.org/10.1002/9781118966464.ch3.
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Faella, Marco, and Gennaro Parlato. "Reasoning About Data Trees Using CHCs." In Computer Aided Verification, 249–71. Cham: Springer International Publishing, 2022. http://dx.doi.org/10.1007/978-3-031-13188-2_13.
Повний текст джерелаАнотація:
AbstractReasoning about data structures requires powerful logics supporting the combination of structural and data properties. We define a new logic called Mso-D(Monadic Second-Order logic with Data) as an extension of standard Mso on trees with predicates of the desired data logic. We also define a new class of symbolic data tree automata (Sdtas) to deal with data trees using a simple machine. Mso-D and Sdtas are both Turing-powerful, and their high expressiveness is necessary to deal with interesting data structures. We cope with undecidability by encoding Sdta executions as a system of CHCs (Constrained Horn Clauses), and solving the resulting system using off-the-shelf solvers. We also identify a fragment of Mso-D whose satisfiability can be effectively reduced to the emptiness problem for Sdtas. This fragment is very expressive since it allows us to characterize a variety of data trees from the literature, solving certain infinite-state games, etc. We implement this reduction in a prototype tool that combines an Mso decision procedure over trees (Mona) with a CHC engine (Z3), and use this tool to conduct several experiments, demonstrating the effectiveness of our approach across different problem domains.
Тези доповідей конференцій з теми "CHC solver"
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Zhu, He, Stephen Magill, and Suresh Jagannathan. "A data-driven CHC solver." In PLDI '18: ACM SIGPLAN Conference on Programming Language Design and Implementation. New York, NY, USA: ACM, 2018. http://dx.doi.org/10.1145/3192366.3192416.
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Tong, Timothy, Mohsen Abou-Ellail, Yuan Li, and Karam R. Beshay. "Numerical Computation of Reacting Flow in Porous Burners With an Extended CH4-Air Reaction Mechanism." In ASME 2004 Heat Transfer/Fluids Engineering Summer Conference. ASMEDC, 2004. http://dx.doi.org/10.1115/ht-fed2004-56012.
Повний текст джерелаАнотація:
The present paper presents, numerical computations for flow, heat transfer and chemical reactions in an axisymmetric inert porous burner. The porous media re-radiate the heat absorbed from the gaseous combustion products by convection and conduction. In the present work, the porous burner species mass fraction source terms are computed from an ‘extended’ reaction mechanism, controlled by chemical kinetics of elementary reactions. The porous burner has mingled zones of porous/nonporous reacting flow, i.e. the porosity is not uniform over the entire domain. Therefore, it has to be included inside the partial derivatives of the transport governing equations. Finite-difference equations are obtained by formal integration over control volumes surrounding each grid node. Up-wind differencing is used to insure that the influence coefficients are always positive to reflect the real effect of neighboring nodes on a typical central node. Finite-difference equations are solved, iteratively, for U, V, p’ (pressure correction), enthalpy and species mass fractions, utilizing a grid of (60×40) nodes. The sixty grid nodes in the axial direction are needed to resolve the detailed structure of the thin reaction zone inside the porous media. The porous burner uses a premixed CH4-air mixture, while its radiating characteristics are computed numerically, using a four-flux radiation model. Sixteen species are included, namely CH4, CH3, CH2, CH, CH2O, CHO, CO, CO2, O2, O, OH, H2, H, H2O, HO2, H2O2, involving 49 chemical reaction equations. It was found that 900 iterations are sufficient for complete conversion of the computed results with errors less than 0.1%. The computed temperature profiles of the gas and the solid show that, heat is conducted from downstream to the upstream of the reaction zone. Most stable species, such as H2O, CO2, H2, keep increasing inside the reaction zone staying appreciable in the combustion products. However, unstable products, such as HO2, H2O2 and CH3, first increase in the preheating region of the reaction zone, they are then consumed fast in the post-reaction zone of the porous burner. Therefore, it appears that their important function is only to help the chemical reactions continue to their inevitable completion of the more stable combustion products.
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Tong, Timothy W., Mohsen M. M. Abou-Ellail, Yuan Li, and Karam R. Beshay. "Numerical Simulation of Reacting Flows in Radiant Porous Burners." In ASME 2005 Summer Heat Transfer Conference collocated with the ASME 2005 Pacific Rim Technical Conference and Exhibition on Integration and Packaging of MEMS, NEMS, and Electronic Systems. ASMEDC, 2005. http://dx.doi.org/10.1115/ht2005-72008.
Повний текст джерелаАнотація:
The present paper presents, numerical computations for flow, heat transfer and chemical reactions in an axisymmetric inert porous burner. The porous media re-radiate the heat absorbed from the gaseous combustion products by convection and conduction. In the present work, the porous burner species mass fraction source terms are computed from an ‘extended’ reaction mechanism, controlled by chemical kinetics of elementary reactions. The porous burner has mingled zones of porous/nonporous reacting flow, i.e. the porosity is not uniform over the entire domain. Therefore, it has to be included inside the partial derivatives of the transport governing equations. Finite-difference equations are obtained by formal integration over control volumes surrounding each grid node. Up-wind differencing is used to insure that the influence coefficients are always positive to reflect the real effect of neighboring nodes on a typical central node. Finite-difference equations are solved, iteratively, for U, V, p’ (pressure correction), enthalpy and species mass fractions, utilizing a fine grid of (80×60) nodes. The eighty grid nodes in the axial direction are needed to resolve the detailed structure of the thin reaction zone inside the porous media. The radial grid is extended inside the annular solid wall of the porous burner, to compute the wall temperature. The porous burner uses a premixed CH4-air mixture, while its radiating characteristics are computed numerically, using a four-flux radiation model. Sixteen species are included, namely CH4, CH3, CH2, CH, CH2O, CHO, CO, CO2, O2, O, OH, H2, H, H2O, H2O, H2O2, involving 49 chemical reaction equations. It was found that 1000 iterations are sufficient for complete conversion of the computed results with errors less than 0.1%. The computed temperature profiles of the gas and the solid show that, heat is conducted from downstream to the upstream of the reaction zone. Most stable species, such as H2O, CO2, H2, keep increasing inside the reaction zone staying appreciable in the combustion products. However, unstable products, such as HO2, H2O2 and CH3, first increase in the preheating region of the reaction zone, they are then consumed fast in the post-reaction zone of the porous burner. Therefore, it appears that their important function is only to help the chemical reactions continue to their inevitable completion of the more stable combustion products.
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Lu, Chao, Zhao Hu, Bei Xie, and Ning Zhang. "Quantum CFD Simulations for Heat Transfer Applications." In ASME 2020 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2020. http://dx.doi.org/10.1115/imece2020-23915.
Повний текст джерелаАнотація:
Abstract In this paper, computational heat transfer (CHT) equations were solved using the state-of-art quantum computing (QC) technology. The CHT equations can be discretized into a linear equation set, which can be possibly solved by a QC system. The linear system can be characterized by Ax = b. The A matrix in this linear system is a Hermitian matrix. The linear system is then solved by using the HHL algorithm, which is a quantum algorithm to solve a linear system. The quantum circuit requires an Ancilla qubit, clock qubits, qubits for b and a classical bit to record the result. The process of the HHL algorithm can be described as follows. Firstly, the qubit for b is initialized into the phase as desire. Secondly, the quantum phase estimation (QPE) is used to determine the eigenvalues of A and the eigenvalues are stored in clock qubits. Thirdly, a Rotation gate is used to rotate the inversion of eigenvalues and information is passed to the Ancilla bit to do Pauli Y-rotation operation. Fourthly, revert the whole processes to untangle qubits and measure all of the qubits to output the final results for x. From the existing literature, a few 2 × 2 matrices were successfully solved with QC technology, proving the possibility of QC on linear systems [1]. In this paper, a quantum circuit is designed to solve a CHT problem. A simple 2 by 2 linear equation is modeled for the CHT problem and is solved by using the quantum computing. The result is compared with the analytical result. This result could initiate future studies on determining the quantum phase parameters for more complicated QC linear systems for CHT applications.
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Amaral, Sergio, Tom Verstraete, Rene´ Van den Braembussche, and Tony Arts. "Design and Optimization of the Internal Cooling Channels of a HP Turbine Blade: Part I—Methodology." In ASME Turbo Expo 2008: Power for Land, Sea, and Air. ASMEDC, 2008. http://dx.doi.org/10.1115/gt2008-51077.
Повний текст джерелаАнотація:
This first paper describes the Conjugate Heat Transfer (CHT) method and its application to the performance and lifetime prediction of a high pressure turbine blade operating at a very high inlet temperature. It is the analysis tool for the aerothermal optimization described in a second paper. The CHT method uses three separate solvers: a Navier-Stokes (NS) solver to predict the non-adiabatic external flow and heat flux, a Finite Element Analysis (FEA) to compute the heat conduction and stress within the solid, and a 1D aero-thermal model based on friction and heat transfer correlations for smooth and rib-roughened cooling channels. Special attention is given to the boundary conditions linking these solvers and to the stability of the complete CHT calculation procedure. The Larson-Miller parameter model is used to determine the creep-to-rupture failure lifetime of the blade. This model requires both the temperature and thermal stress inside the blade, calculated by the CHT and FEA. The CHT method is validated on two test cases: a gas turbine rotor blade without cooling and one with 5 cooling channels evenly distributed along the camber line. The metal temperature and thermal stress distribution in both blades are presented and the impact of the cooling channel geometry on lifetime is discussed.
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Goormans-Francke, Colinda, Guy Carabin, and Charles Hirsch. "Mesh Generation for Conjugate Heat Transfer Analysis of a Cooled High Pressure Turbine Stage." In ASME Turbo Expo 2008: Power for Land, Sea, and Air. ASMEDC, 2008. http://dx.doi.org/10.1115/gt2008-50660.
Повний текст джерелаАнотація:
The presented work demonstrates the feasibility of quasi-automatic structured mesh generation for all details in the complex cooling system of an industrial high pressure turbine stage, as required by advanced Conjugate Heat Transfer (CHT) simulations. The grid generation software has been adapted in order to quasi-automatically mesh typical cooling configurations such as cooling passages, basins, inserts, solid bodies, cooling holes, slots, and rib turbulators. A multi-domain structured mesh with about 154 million grid points and 12,316 blocks has been generated for the turbine stage. It includes 1,000 cooling holes, over 250 rib turbulators and 150 pin fins for the turbine stage. In order to verify the CFD response to the grid properties, simulations were performed as a first step on the coarse grid level (of 21.8 million grid points) using the 3D flow solver package FINE™/Turbo. The conductivity equation was solved for the solid part of the computational domain using the same temporal discretization scheme as for the flow solver. Parallel, coupled fluid/solid calculations using the k-ε turbulence model were performed on three different configurations: nozzle guide vane alone, rotor-blade alone, and full stage. These results show the feasibility of this approach to mesh generation for use in CHT modeling of the complex configuration of cooled turbine stages.
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Ma, Ming, and Hamid Emami-Meybodi. "Diffusion-Based Multiphase Multicomponent Modeling of Cyclic Solvent Injection in Ultratight Reservoirs." In SPE Annual Technical Conference and Exhibition. SPE, 2022. http://dx.doi.org/10.2118/210480-ms.
Повний текст джерелаАнотація:
Abstract The cyclic solvent (gas) injection has been proved as an economical and effective method to enhance oil recovery in ultratight reservoirs such as shales. However, accurate modeling of cyclic solvent injection has been challenging due to the complex nature of fluid transport in nanopores. Most models are developed based on Darcy's and Fick's laws, which do not capture some critical transport phenomena within nanopores at elevated pressure. Accordingly, we propose a predictive model encapsulating the essential transport mechanisms for cyclic solvent injection in ultratight reservoirs. The model adopts the binary friction concept to incorporate friction between different molecules as well as molecules and pore walls. The Maxwell-Stefan approach is employed to account for the friction among species. The friction between molecules and pore walls is incorporated through partial viscosity and Knudsen diffusivity. A general driving force, chemical potential gradient, and the compressibility factor are used for the high-pressure non-ideal fluid mixture. The Peng-Robinson equation of state with confinement effect is used for the phase behavior calculations. The total flux consists of multicomponent molecular diffusion flux resulting from the chemical potential gradient and pressure diffusion flux driven by the pressure gradient. The governing equations for composition and pressure are solved implicitly using the finite difference method. The developed model is validated against analytical solutions and laboratory experiments. The primary production and solvent injection process are then simulated for a trinary oil (CH4, C4H10, and C12H26) and two solvent types, including CH4 and CO2. The results show that hydrocarbon components’ transport in the vapor phase is much higher than in the liquid phase. Accordingly, light and heavy components are produced at different fluxes during primary production because the vapor phase mainly consists of lighter components. For the single-cycle solvent injection cases, both CO2 and CH4 improve hydrocarbon recovery, with CO2 slightly performing better than CH4. This is attributed to CO2's ability to extract more heavy components into the vapor phase, producing more heavy components within the vapor phase. The recovery factor of heavy components of CO2 injection (3.40%) is higher than that of CH4 injection (3.21%). For multi-cycle solvent injection cases, CO2 injection can improve hydrocarbon recovery with a 2.77% increment, slightly better than multi-cyclic CH4 injection with a 2.73% increment. The injected CO2 can extract more heavy components near the fracture. However, the injected CH4 can penetrate deeper into the matrix to extract more light components within a more extensive region.
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Tarokh, A., A. A. Mohamad, and L. Jiang. "Non-Premixed CH4 Combustion in a Porous Medium." In ASME 2009 International Mechanical Engineering Congress and Exposition. ASMEDC, 2009. http://dx.doi.org/10.1115/imece2009-12945.
Повний текст джерелаАнотація:
Combustion process is the major contributor to the air pollution, such as CO, unburned hydrocarbon, soot and NOx, etc. Porous media can be a good candidate for improving the combustion efficiency and reducing pollution formation. Premixed combustion has been extensively investigated in the literature, experimentally and computationally. However, investigation of non-premixed combustion in porous media is limited in the open literature, which is the topic of this paper. The present work deals with the numerical modeling of methane/air non-premixed combustion in porous media. Physical problem that is considered here is fuel jet which is injected to the air in free flame case and injected into a porous medium, in the porous medium combustion case. The flow is assumed turbulent and standard k-ε model with standard wall functions is used in the simulation. The solid porous structure is assumed to be composed of alumina fiber material with temperature dependent heat conductivity. Discrete Ordinate method is used to solve radiative transport equations. The governing equations are solved using finite volume method. The results show that the combustion in porous media has superior combustion efficiency and significantly lower NOx and CO emissions compare to the free flame. This is due to the lower maximum temperature in porous media combustion. In comparison with the free flame case where the combustion zone is narrow and long, the results shows the combustion zone in porous media is shorter in axial and wider in radial direction.
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Gunson, M. R., M. C. Abrams, C. B. Farmer, L. L. Lowes, C. P. Rinsland, and R. Zander. "Results from the flight of the Atmospheric Trace Molecule Spectroscopy on the ATLAS-1 Space Shuttle Mission." In Optical Remote Sensing of the Atmosphere. Washington, D.C.: Optica Publishing Group, 1993. http://dx.doi.org/10.1364/orsa.1993.ma.4.
Повний текст джерелаАнотація:
During the ATLAS-1 space shuttle mission, the ATMOS experiment, a Fourier transform infrared spectrometer operating in solar occultation mode from on-orbit (Farmer, 1987), collected data through more than 90 orbital sunrises and sunsets at latitudes between 30°N and 55°S. The resulting high-resolution infrared solar absorption spectra from these observations have so far been analyzed for the vertical profiles of several species (O3, HNO3, ClNO3, HCl, HF, N2O, CH4 and H2O) of immediate importance as correlative measurements for other satellite instruments, such as those carried on the Upper Atmospheric Research Satellite. Results for these gases together with those of other species measured by ATMOS, such as the more abundant man-made chlorofluorocarbons (CFC-11, CFC-12, HCFC-22) are compared with similar measurements made by this instrument from data acquired during its first flight in April, 1985. In the period between these two flights, the halogenated gases are expected to have increased measurably in concentration due to the continued release of the halogenated source gases. These ATMOS data provide a simultaneous measurement of the increase in the tropospheric source gases as well as the halogen sink species, HCl and HF.
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Kim, Jong Won, Kyu Sung Sim, Hyun Myung Son, and Kwang Deog Jung. "Thermochemical Hydrogen Production Using Ni-Ferrite and CH4." In ASME 2003 International Solar Energy Conference. ASMEDC, 2003. http://dx.doi.org/10.1115/isec2003-44084.
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Hydrogen production by a 2-step water-splitting thermochemical cycle using metal oxides (ferrites) redox pairs and CH4 have been studied in this experiment. Reactions were performed in a two-step redox cycle in which the ferrites were reacted with CH4 at 700°C–800°C to produce CO, H2, and various reduced phases (reduction step); these were then reoxidized with water vapor to generate H2 in water-splitting step (oxidation step) at 600°C–700°C. The reduced forms of Ni-Fe2O3, Ni-FeO and Ni-Fe alloy from XRD, showed respectively different reactivity for H2 formation from H2O. These were oxidized to the ferrite phase to produce H2 in the water-splitting step at 600°C–700°C. In reduction reaction at 800°C, carbon deposition arise on surface of Ni-ferrite due to CH4 decomposition. This reduced phase containing carbon, which reacts with H2O at 600°C, produce H2, CO, and CO2. The amount of H2 evolved using reduced phase containing carbon was much than that of other phase.
Звіти організацій з теми "CHC solver"
1
Newell, J. D. Impact of the next generation solvent on DWPF CPC processing. Office of Scientific and Technical Information (OSTI), February 2013. http://dx.doi.org/10.2172/1063805.
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2
Townley, David, and Paul Gee. Combined Heat & Power Using the Infinia Concentrated Solar CHP PowerDish System. Fort Belvoir, VA: Defense Technical Information Center, August 2013. http://dx.doi.org/10.21236/ada607481.
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Ervin, Kelly, Karl Smink, Bryan Vu, and Jonathan Boone. Ship Simulator of the Future in virtual reality. Engineer Research and Development Center (U.S.), September 2022. http://dx.doi.org/10.21079/11681/45502.
Повний текст джерелаАнотація:
The Army’s modernization priorities include the development of augmented reality and virtual reality (AR/VR) simulations for enabling the regiment and increasing soldier readiness. The use of AR/VR technology at the U.S. Army Engineer Research and Development Center (ERDC) is also growing in the realm of military and civil works program missions. The ERDC Coastal and Hydraulics Laboratory (CHL) has developed a ship simulator to evaluate bay channels across the world; however, the current simulator has little to no physical realism in nearshore coastal regions (Figure 1). Thus, the ERDC team is researching opportunities to advance ship simulation to deliver the Ship Simulator of the Future (SSoF). The SSoF will be equipped with a VR mode and will more accurately resolve nearshore wave phenomena by ingesting precalculated output from a Boussinesq-type wave model. This initial prototype of the SSoF application is intended for research and development purposes; however, the technologies employed will be applicable to other disciplines and project scopes, including the Synthetic Training Environment (STE) and ship and coastal structure design in future versions.
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Newell, J., D. Peeler, T. Edwards, M. Hay, and M. Stone. DWPF FLOWSHEET STUDIES WITH SIMULANT TO DETERMINE THE IMPACT OF NEXT GENERATION SOLVENT ON THE CPC PROCESS AND GLASS FORMULATION. Office of Scientific and Technical Information (OSTI), June 2011. http://dx.doi.org/10.2172/1018485.
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