16 results on '"Sub critical"'
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2. Measurement of reactivity in a source driven deep sub-critical system using neutron noise methods.
- Author
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Kumar, Rajeev, Degweker, S.B., Roy, Tushar, Singh, K.P., Samanta, Sudipta, Bajpai, Shefali, Ray, Nirmal, Yakub Ali, M., Patel, Tarun, Shukla, Mayank, and Sinha, Amar
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NEUTRON transport theory , *REACTIVITY (Fission reactors) , *ACCELERATOR-driven systems , *DATA analysis , *AUTOCORRELATION (Statistics) - Abstract
Measurement of reactivity in deep sub critical system using neutron noise method is challenging due to the modal effect. This paper addresses the issue of modal effect in such system in a new and better way. The measurements were carried out in the ADS experimental facility BRAHMMA commissioned recently at Bhabha Atomic Research Centre (BARC), India. The BRAHMMA assembly is a deep sub critical system having multiplication factor (K eff ) ∼ 0.9. The data analysis was carried out using two commonly used neutron noise techniques namely the Feynman alpha and the auto correlation function methods. The modal effect was eliminated by placing the neutron detectors at strategically chosen locations in the core. The detector locations were decided on the basis of the detailed modal analysis of the core. The modal analysis and calculations of the kinetic parameters of the core were carried out using a diffusion theory code. The measured reactivity was found to be in good agreement with the theoretical estimate. [ABSTRACT FROM AUTHOR]
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- 2017
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3. Measurement of sub-critical reactivity in a heavy water reactor by neutron noise methods using a time stamping data acquisition system.
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Kumar, Rajeev, Degweker, S.B., Singh, K.P., and Ali, M. Yakub
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REACTIVITY (Fission reactors) , *HEAVY water reactors , *NEUTRONS , *DATA acquisition systems , *NUCLEAR physics experiments - Abstract
Experiments were performed to measure the sub critical reactivity in a zero power heavy water moderated reactor by neutron noise methods. The measurements were carried out using a time stamping data acquisition system developed for this purpose. This system has the advantage that it gives the complete time history of the detected neutron pulse train and a single set of data so acquired can be used for analysis by any of the noise techniques. The data obtained in the course of the experiments were analyzed using two commonly used neutron noise techniques namely the Feynman alpha and the auto correlation function methods. Noise analysis in heavy water reactors is more cumbersome than in light water reactors due to an overlap of the prompt neutron and delayed neutron time scales and consequently an unavoidable contribution from delayed neutrons and photo neutrons. Measurements were done at various levels of sub criticality by varying the moderator level height. The measured sub-critical reactivities were found to be in good agreement with theoretical estimates. [ABSTRACT FROM AUTHOR]
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- 2016
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4. Phenomenological reduced-order modeling of subcritical combustion in cryogenic rocket engines: an application to the prediction of high-frequency combustion instabilities
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Guillaume Storck, Sébastien Ducruix, Luc-Henry Dorey, Marie Théron, DMPE, ONERA, Université Paris Saclay [Palaiseau], ONERA-Université Paris-Saclay, Laboratoire d'Énergétique Moléculaire et Macroscopique, Combustion (EM2C), CentraleSupélec-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), and Centre National d’Études Spatiales [Paris] (CNES)
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[PHYS]Physics [physics] ,Materials science ,business.product_category ,business.industry ,02 engineering and technology ,Combustion ,01 natural sciences ,7. Clean energy ,010305 fluids & plasmas ,Reduced order ,Physics::Fluid Dynamics ,[SPI]Engineering Sciences [physics] ,020401 chemical engineering ,Rocket ,0103 physical sciences ,Sub critical ,0204 chemical engineering ,Aerospace engineering ,business - Abstract
International audience; The set of equations governing reacting two-phase flows in liquid-propellant rocket engines is simplified and linearized around a steady base flow. In the particular case of a liquid/gas coaxial injector, models for the atomization, evaporation and combustion source terms are derived from a simplified physical description of both the oxidizer liquid core and spray. The resulting equations are projected onto a modal basis, leading to a quasi-linear dynamic description of the evolution of the system. In this paper, detailed model reduction focuses on the evaporation of polydisperse sprays and on the propagation of acoustic waves within the gas.
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- 2020
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5. Application of the respiratory 'critical care-sub-critical care-rehabilitation integrated management model' in severe stroke associated pneumonia
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Kai Wang, Li-Jun Ma, Cheng Jianjian, Hu Xingang, and Xue-Lin Wang
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Male ,Pulmonary and Respiratory Medicine ,Respiratory Therapy ,medicine.medical_specialty ,Time Factors ,Stroke-associated pneumonia ,Critical Care ,Severe stroke ,Patient satisfaction ,Humans ,Medicine ,Sub critical ,Respiratory system ,Integrated management ,APACHE ,Aged ,lcsh:RC705-779 ,APACHE II ,business.industry ,Stroke Rehabilitation ,lcsh:Diseases of the respiratory system ,Pneumonia ,Severe pneumonia ,Respiratory “Critical Care-Sub-critical Care-Rehabilitation Integrated Management Model” ,Length of Stay ,Middle Aged ,medicine.disease ,Stroke ,Intensive Care Units ,Patient Satisfaction ,Emergency medicine ,Feasibility Studies ,Female ,Blood Gas Analysis ,business ,Research Article ,Care rehabilitation - Abstract
Background This study aimed to explore the feasibility of applying the respiratory “critical care-sub-critical care-rehabilitation integrated management model” in severe stroke-associated pneumonia and evaluate its effect. Methods From January to September 2018, 24 patients with severe stroke-associated pneumonia, who were admitted to the Respiratory Intensive Care Unit of the Respiratory and Critical Care Medicine Department of Henan Provincial People’s Hospital, were randomly divided into two groups: integrated management group and control group. According to the admission criteria of the respiratory “critical care-sub-critical care-rehabilitation integrated model” prescribed by the above-mentioned hospital, patients were grouped. The professional respiratory therapy team participated in the whole treatment. The acute physiology and chronic health evaluation II (APACHE II) score, clinical pulmonary infection score (CPIS) and oxygenation index of these two groups were dynamically observed, and the average hospital stay, 28-day mortality and patient satisfaction were investigated. Results Patients in the integrated management group and control group were similar before treatment (P > 0.05). After treatment, the main indicators, the APACHE II score, CPIS score and oxygenation index, were significantly different between the integration group and control group (P P < 0.05). However, the 28-day mortality wasn’t significantly different (P > 0.05). Conclusions For patients with severe stroke-associated pneumonia, it was feasible to implement the respiratory “critical care-sub-critical care-rehabilitation integrated management model”, which could significantly improve the treatment effect, shorten average hospitalization days and improve patient/family satisfaction.
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- 2020
6. Failed self-reformation of a sub-critical fast magnetosonic shock in collisionless plasma
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Mark E Dieckmann, Rolf Walder, Q. Moreno, Doris Folini, Xavier Ribeyre, Emmanuel d'Humières, V. T. Tikhonchuk, Centre de Recherche Astrophysique de Lyon (CRAL), École normale supérieure de Lyon (ENS de Lyon)-Université Claude Bernard Lyon 1 (UCBL), and Université de Lyon-Université de Lyon-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)
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Physics ,Nuclear and High Energy Physics ,010504 meteorology & atmospheric sciences ,sub-critical shock ,proto-shock ,Astrophysics::High Energy Astrophysical Phenomena ,fast magnetosonic waves ,collisionless plasma ,Mechanics ,Plasma ,Condensed Matter Physics ,01 natural sciences ,Shock (mechanics) ,Nuclear Energy and Engineering ,Physics::Plasma Physics ,[SDU]Sciences of the Universe [physics] ,Physics::Space Physics ,0103 physical sciences ,Perpendicular ,Astrophysics::Solar and Stellar Astrophysics ,Sub critical ,010306 general physics ,Astrophysics::Galaxy Astrophysics ,0105 earth and related environmental sciences ,self-reformation - Abstract
International audience; We study with a 1D particle-in-cell (PIC) simulation the evolution of a subcritical perpendicular fast magnetosonic shock. The shock propagates at 1.5 times the fast magnetosonic speed. Some upstream protons are reflected by the shock's electric potential. They form a beam which carries less energy than those that are reflected magnetically by super-critical shocks. The beam triggers the growth of a fast magnetosonic solitary wave upstream of the shock, which reflects the beam protons back to the shock. Extracting the momentum and energy of this beam allows the solitary wave to grow into a proto-shock that is trailed by a short downstream region. Protons from the shock-reflected proton beam increase the density of the plasma between the shock and the proto-shock reducing its potential difference relative to both surrounding structures. Bulk protons, which cross the proto-shock, react to the decreased potential jump. The plasma behind the proto-shock accelerates and so does the shock. The trailing end of the proto-shock speeds up in order to continue reflecting the beam protons and eventually it catches up with its front; the proto-shock collapses and the self-reformation fails. A more energetic proton beam could decrease the potential jump across the shock, let it collapse and replace it with the proto-shock.
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- 2019
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7. A priori bounds and multiplicity of positive solutions for p-Laplacian Neumann problems with sub-critical growth
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Benedetta Noris, Francesca Colasuonno, Alberto Boscaggin, Boscaggin A., Colasuonno F., and Noris B.
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Pure mathematics ,a priori estimate ,Neumann boundary condition ,General Mathematics ,010102 general mathematics ,existence and multiplicity ,Mathematics::Analysis of PDEs ,Multiplicity (mathematics) ,shooting method ,01 natural sciences ,010101 applied mathematics ,Shooting method ,Mathematics - Analysis of PDEs ,quasilinear elliptic equation ,FOS: Mathematics ,p-Laplacian ,A priori and a posteriori ,Sub critical ,0101 mathematics ,35J92, 35A24, 35B05, 35B09, 35B45 ,Analysis of PDEs (math.AP) ,Mathematics - Abstract
Let $10 \mbox{ in } \Omega, \quad \partial_\nu u = 0 \mbox{ on } \partial\Omega. \] We suppose that $f(0)=f(1)=0$ and that $f$ is negative between the two zeros and positive after. In case $\Omega$ is a ball, we also require that $f$ grows less than the Sobolev-critical power at infinity. We prove a priori bounds of radial solutions, focusing in particular on solutions which start above 1. As an application, we use the shooting technique to get existence, multiplicity and oscillatory behavior (around 1) of non-constant radial solutions., Comment: 26 pages, 3 figures
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- 2018
8. Extraction of bioactive compounds from sesame (Sesamum indicum L.) defatted seeds using water and ethanol under sub-critical conditions
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Alfonsina Ester Andreatta, Marcela Lilian Martinez, Alexis Velez, Damian Maestri, and Romina Mariana Bodoira
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DEFATTED SESAME SEEDS ,SUB-CRITICAL CONDITIONS ,INGENIERÍAS Y TECNOLOGÍAS ,01 natural sciences ,Antioxidants ,Analytical Chemistry ,Sesamum ,Pressure range ,chemistry.chemical_compound ,0404 agricultural biotechnology ,Flavonols ,Sub critical ,Scavenging ,chemistry.chemical_classification ,Chromatography ,Ethanol ,biology ,010401 analytical chemistry ,Extraction (chemistry) ,WATER/ETHANOL MIXTURES ,Water ,04 agricultural and veterinary sciences ,General Medicine ,biology.organism_classification ,040401 food science ,0104 chemical sciences ,Ingeniería Química ,Kinetics ,chemistry ,High pressure ,Seeds ,Otras Ingeniería Química ,PRESSURIZED LIQUID EXTRACTION ,BIOACTIVE COMPOUNDS ,ANTIOXIDANT ACTIVITY ,Food Science - Abstract
Sesame seeds contain a vast array of lignans and phenolic compounds having important biological properties. An optimized method to obtain these seed components was designed by using water and ethanol at high pressure and temperature conditions. The maximum concentrations of lignans, total phenolics, flavonoids and flavonols compounds were achieved at 220 °C extraction temperature and 8 MPa pressure, using 63.5% ethanol as co-solvent. Under these conditions, the obtained sesame extracts gave the best radical scavenging capacity. Kinetic studies showed a high extraction rate of phenolic compounds until the first 50 min of extraction, and it was in parallel with the highest scavenging capacity. The comparison of our results with those obtained under conventional extraction conditions (normal pressure, ambient temperature) suggests that recovery of sesame bioactive compounds may be markedly enhanced using water/ethanol mixtures at sub-critical conditions. Fil: Bodoira, Romina Mariana. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto Multidisciplinario de Biología Vegetal. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Instituto Multidisciplinario de Biología Vegetal; Argentina Fil: Velez, Alexis. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Bahia Blanca. Planta Piloto de Ingeniería Química (I). Grupo Vinculado al Plapiqui - Investigación y Desarrollo en Tecnología Química; Argentina Fil: Andreatta, Alfonsina Ester. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Bahia Blanca. Planta Piloto de Ingeniería Química (I). Grupo Vinculado al Plapiqui - Investigación y Desarrollo en Tecnología Química; Argentina. Universidad Tecnológica Nacional; Argentina Fil: Martinez, Marcela Lilian. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto Multidisciplinario de Biología Vegetal. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Instituto Multidisciplinario de Biología Vegetal; Argentina Fil: Maestri, Damian. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto Multidisciplinario de Biología Vegetal. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Instituto Multidisciplinario de Biología Vegetal; Argentina
- Published
- 2017
9. Hydrogen Embrittlement and Sub-Critical Crack Growth in Hydride Forming Metals
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A.G. Varias
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Materials science ,Mechanics of Materials ,Hydride ,Materials Science (miscellaneous) ,Metallurgy ,TJ1-1570 ,Sub critical ,Mechanical engineering and machinery ,Environmental stress fracture ,Hydrogen embrittlement - Published
- 2005
10. Influencia de la microestructura en el comportamiento en fatiga de aceros perlíticos
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S. Fernandez, Mar Toledano, and Rodolfo Rodríguez
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Mechanical property ,Materials science ,Manufacturing process ,Fatiga ,Pearlitic steel ,Trefilado ,Microestructura ,Microstructure ,Industrial and Manufacturing Engineering ,Fatigue crack propagation ,lcsh:TP785-869 ,lcsh:Clay industries. Ceramics. Glass ,Mechanics of Materials ,Ceramics and Composites ,Forensic engineering ,Linear relation ,Sub critical ,Composite material ,Paris Law ,Ley de Paris ,Acero perlítico ,Stress intensity factor ,Fatigue ,Cold Drawing - Abstract
This article accounts the relationship between the microstructure of pearlitic steels (influenced by the cold-drawn manufacturing process) and the growing rate of sub critical cracks, produced by a cyclic-constant amplitude load. The microstructural study is performed in two levels: the pearlitic colony (first level) and the pearlitic lamellar microstructure (second microstructural level). The analysis of the fatigue behaviour was focused on the region II of the fatigue crack propagation regime, in which the crack growing rate per cicle, da/dN, is controlled by the amplitude of the stress intensity range, as described by Paris law. The enhancement of the fatigue behaviour, in the stable growing zone, is related with the progressive orientation of the pearlitic colonies in the cold drawing direction, showing a linear relation between the intersect parameter of the Paris law (mechanical property) and the alignment angle of the microstructure.Este artículo pretende poner de manifiesto la influencia que los cambios microestructurales inducidos en un acero hipoeutectoide mediante un proceso de trefilado, tienen sobre la velocidad de crecimiento de fisuras sub-críticas, desarrolladas por solicitación cíclica con amplitud de carga constante. El análisis microestructural ha sido realizado a dos niveles: la colonia perlítica (primer nivel) y la microestructura laminar de la perlita (segundo nivel microestructural). El análisis del comportamiento en fatiga se ha centrado en la región II del régimen de propagación de fisuras por fatiga, en donde la velocidad de crecimiento de fisuras, da/dN, está controlada por la amplitud del factor de intensidad de tensiones, K, según queda descrito por la ley de Paris. Los resultados obtenidos muestran que la mejora en el comportamiento en fatiga de los aceros, en la zona de crecimiento estable de la fisura, se relaciona con el alineamiento de las colonias perlíticas en la dirección del trefilado, encontrando una relación lineal entre la constante de proporcionalidad de la ley de Paris (propiedad mecánica) con el ángulo de alineación de la microestructura.
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- 2004
11. Experimental investigation of a flow around a sphere
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Vukman Bakić
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Physics ,laser-Doppler anemometry ,geography ,geography.geographical_feature_category ,Renewable Energy, Sustainability and the Environment ,K-epsilon turbulence model ,Turbulence ,lcsh:Mechanical engineering and machinery ,turbulence ,Reynolds number ,Mechanics ,Inlet ,grid ,Physics::Fluid Dynamics ,symbols.namesake ,Classical mechanics ,Flow (mathematics) ,symbols ,Sub critical ,Vector field ,sphere ,lcsh:TJ1-1570 ,tripwire - Abstract
This paper presents the experimental results for the flow around a sphere: a smooth sphere in flow with low inlet turbulence, a sphere with trip wire and a sphere in flow with high free stream turbulence, at sub critical Reynolds number. The mean velocity field and the turbulence quantities are obtained using laser-Doppler anemometry. Comparison of velocity field and turbulence character is tics for different flow configuration are given.
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- 2004
12. Uniform flow around a circular cylinder in the subcritical range - using the Self-induced angular Moment Method turbulence model
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Johansson, Jens and Nielsen, Mogens Peter
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Physics::Fluid Dynamics ,SMoM turbulence model ,Circular cylinder ,Sub critical - Abstract
The uniform flow around a circular cylinder at Reynolds number 1e5 is simulated in a three dimensional domain by means of the newly developed Self-induced angular Moment Method, SMoM, turbulence model. The global force coefficients, Strouhal number, pressure distributions and wall shear stress distributions are compared to experimental findings reported in literature. The SMoM turbulence model is found to provide maximum, minimum and time-mean pressure coefficient distributions in very good agreement with experimental findings.
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- 2013
13. Modified Model of Sub-Critical Size Cranial Defect in the Rabbit
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José D. Santos, Maria Helena Fernandes, J. M Marques, Pedro S. Gomes, M. I. Dias, C. Viegas, C. Zagalo, and S. C Cabrita
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Cranial defect ,Philosophy ,Cranial vault ,Sub critical ,Trephine defect ,Rabbit ,Anatomy ,Humanities - Abstract
En las ciencias medicas, cualquier modelo animal de experimentacion debe ser reproducible y ajustado al proposito de simular la respuesta fisiologica humana. En la investigacion de la respuesta a la lesion osea, cuando son utilizados sustitutos oseos, es de gran importancia el estudio de defectos que no logran sanar, a menos que sean tratados con terapia de ingenieria de tejidos. Este fracaso define el concepto de "defecto de tamano critico" (CDS) el cual tiene limites diferentes segun la especie animal utilizada y la ubicacion del defecto. Aunque se trata de un concepto basico, cuando el objetivo del estudio es investigar la interfaz hueso-biomaterial, es de primordial importancia obtener la maxima superficie de contacto que sea posible. Para ello, se propone una modificacion en el enfoque quirurgico del modelo clasico de defecto de tamano subcritico biparietal en la boveda de conejo.
- Published
- 2010
14. Super-Arrhenius dynamics for sub-critical crack growth in two-dimensional disordered brittle media
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Loïc Vanel, Sergio Ciliberto, Pierre-Philippe Cortet, Laboratoire de Physique de l'ENS Lyon (Phys-ENS), École normale supérieure - Lyon (ENS Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Centre National de la Recherche Scientifique (CNRS), and École normale supérieure de Lyon (ENS de Lyon)-Université Claude Bernard Lyon 1 (UCBL)
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Arrhenius equation ,05.70.Ln,62.20.Mk ,Materials science ,Condensed matter physics ,Slow crack growth ,Dynamics (mechanics) ,General Physics and Astronomy ,Effective temperature ,01 natural sciences ,Condensed Matter::Disordered Systems and Neural Networks ,010305 fluids & plasmas ,Physics::Geophysics ,Growth velocity ,Stress (mechanics) ,[PHYS.MECA.MEMA]Physics [physics]/Mechanics [physics]/Mechanics of materials [physics.class-ph] ,symbols.namesake ,Disordered systems ,Brittleness ,Fracture ,0103 physical sciences ,symbols ,[PHYS.COND.CM-MS]Physics [physics]/Condensed Matter [cond-mat]/Materials Science [cond-mat.mtrl-sci] ,Sub critical ,010306 general physics - Abstract
International audience; Taking into account stress fluctuations due to thermal noise, we study thermally activated irreversible crack growth in disordered media. The influence of material disorder on sub-critical growth of a single crack in two-dimensional brittle elastic material is described through the introduction of a gaussian rupture threshold distribution. We derive analytical predictions for crack growth velocity and material lifetime in agreement with direct numerical calculations. It is claimed that crack growth process is inhibited by disorder: velocity decreases and lifetime increases with disorder. More precisely, lifetime is shown to follow a super-Arrhenius law, with an effective temperature $\theta-\theta_d$, where $\theta$ is related to the thermodynamical temperature and $\theta_d$ to the disorder variance.
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- 2006
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15. RESPONSE OF VELOCITY TO A SUDDEN CHANGE OF BED ROUGHNESS IN SUB CRITICAL OPEN CHANNEL FLOW
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R Della Morte, Armando Carravetta, M. Greco. A. Carravetta, R. Della Morte, Carravetta, Armando, and DELLA MORTE, Renata
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Bed roughness ,Sub critical ,Geotechnical engineering ,Hydraulic roughness ,Geology ,Open-channel flow - Published
- 2004
16. Collapsing Sub-Critical Bubbles
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Greg W. Anderson
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Physics ,Nuclear and High Energy Physics ,Particle physics ,Phase transition ,High Energy Physics - Phenomenology ,High Energy Physics - Phenomenology (hep-ph) ,Bubble ,Electroweak interaction ,High Energy Physics::Phenomenology ,Nucleation ,Sub critical ,FOS: Physical sciences - Abstract
In the standard scenario, the electroweak phase transition is a first order phase transition which completes by the nucleation of critical bubbles. Recently, there has been speculation that the standard picture of the electroweak phase transition is incorrect. Instead, it has been proposed that throughout the phase transition appreciable amounts of both broken and unbroken phases of $SU(2)$ coexist in equilibrium. I argue that this can not be the case. General principles insure that the universe will remain in a homogenous state of unbroken $SU(2)$ until the onset of critical bubble production., 7 pages plus three figures. OHSTPY-HEP-T-92-016 A topdrawer file of the figures is appended to the end
- Published
- 1992
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