Dynamic critical behaviour and scaling
Oezoguz, B.E.
2001-01-01
Traditionally the scaling is the property of dynamical systems at thermal equilibrium. In second order phase transitions scaling behaviour is due to the infinite correlation length around the critical point. In first order phase transitions however, the correlation length remains finite and a different type of scaling can be observed. For first order phase transitions all singularities are governed by the volume of the system. Recently, a different type of scaling, namely dynamic scaling has attracted attention in second order phase transitions. In dynamic scaling, when a system prepared at high temperature is quenched to the critical temperature, it exhibits scaling behaviour. Dynamic scaling has been applied to various spin systems and the validity of the arguments are shown. Firstly, in this thesis project the dynamic scaling is applied to 4-dimensional using spin system which exhibits second order phase transition with mean-field critical indices. Secondly, it is shown that although the dynamic is quite different, first order phase transitions also has a different type of dynamic scaling
Antonov, N V; Kapustin, A S
2012-01-01
Critical behaviour of the dynamical Potts model, subjected to vivid turbulent mixing, is studied by means of the renormalization group. The advecting velocity field is modelled by Kraichnan’s rapid-change ensemble: Gaussian statistics with a given pair correlator 〈vv〉∝δ(t − t′) k −d−ξ , where k is the wave number, d is the dimension of space and 0 < ξ < 2 is an arbitrary exponent. The system exhibits different types of infrared scaling behaviour, associated with four infrared attractors of the renormalization group equations. In addition to the known asymptotic regimes (equilibrium Potts model and passive scalar field), the existence of a new, strongly non-equilibrium type of critical behaviour (universality class) is established, where the self-interaction of the order parameter and the turbulent mixing are equally important. The corresponding critical dimensions and the regions of stability for all the regimes are calculated in the leading order of the double expansion in ξ and ε = 6 − d. Special attention is paid to the effects of compressibility of the fluid, because they lead to interesting crossover phenomena. (paper)
Nonuniversal critical behaviour in a model for charge density wave dynamics
Ritala, R.K.; Hertz, J.A.
1986-02-01
We have studied short range fluctuations around the infinite-range model of charge density wave (CDW) dynamics. We find that the inhomogeneity of the local field, which is neglected in the infinite-range approximation has a dramatic effect on the transition. In the Bethe approximation the critical behaviour is nonuniversal. In particular, the current exponent is ζ = 3/2 log(z-1)/[log(z)]+log(1+f/J)], where z is the number of neighbors, f the pinning strength, and J the elastic coupling. (orig.)
Dekker, H.
1980-01-01
It is shown how to solve the master equation for a Markov process including a critical point by means of successive approximations in terms of a small parameter. A critical point occurs if, by adjusting an externally controlled quantity, the system shows a transition from normal monostable to bistable behaviour. The fundamental idea of the theory is to separate the master equation into its proper irreducible part and a corrective remainder. The irreducible or zeroth order stochastic approximation will be a relatively simple Fokker-Planck equation that contains the essential features of the process. Once the solution of this irreducible equation is known, the higher order corrections in the original master equation can be incorporated in a systematic manner. (Auth.)
Critical fatigue behaviour in brittle glasses
Unknown
Abstract. The dynamic fatigue fracture behaviour in different glasses under various sub-threshold loading conditions are analysed here employing an anomalous diffusion model. Critical dynamical behaviour in the time-to-fracture and the growth of the micro-crack sizes, similar to that observed in such materials in the case.
Fokkelman, Michiel; Balcıoğlu, Hayri E.; Klip, Janna E.; Yan, Kuan; Verbeek, Fons J.; Danen, Erik H. J.; van de Water, Bob
2016-01-01
Cancer cells migrate from the primary tumour into surrounding tissue in order to form metastasis. Cell migration is a highly complex process, which requires continuous remodelling and re-organization of the cytoskeleton and cell-matrix adhesions. Here, we aimed to identify genes controlling aspects of tumour cell migration, including the dynamic organization of cell-matrix adhesions and cellular traction forces. In a siRNA screen targeting most cell adhesion-related genes we identified 200+ genes that regulate size and/or dynamics of cell-matrix adhesions in MCF7 breast cancer cells. In a subsequent secondary screen, the 64 most effective genes were evaluated for growth factor-induced cell migration and validated by tertiary RNAi pool deconvolution experiments. Four validated hits showed significantly enlarged adhesions accompanied by reduced cell migration upon siRNA-mediated knockdown. Furthermore, loss of PPP1R12B, HIPK3 or RAC2 caused cells to exert higher traction forces, as determined by traction force microscopy with elastomeric micropillar post arrays, and led to considerably reduced force turnover. Altogether, we identified genes that co-regulate cell-matrix adhesion dynamics and traction force turnover, thereby modulating overall motility behaviour. PMID:27531518
Dynamic behaviour of lagoon ecosystems
Cioffi, F.
2008-01-01
The dynamic behaviour of primary producers in coastal lagoons due to change of external control parameters, phosphorous external load and maximum tidal flow rate, is investigated by using a eutrophication model. The eutrophication model allows the simulation of the temporal evolution of the concentration of the following species: a) in the water column: dissolved oxygen, vegetal organic carbon, particulate and dissolved organic carbon, dissolved phosphorous and hydrogen sulphide; b) in sediments: dissolved oxygen, particulate and dissolved organic carbon, dissolved and adsorbed phosphorous, hydrogen sulphide. The vegetal organic carbon is distinguished in three components related to the main groups of primary producers, namely eel grass, macro algae and microalgae, having different modalities of nutrient uptake and kinetics parameters depending on the S/V ratio. Diagrams representing the ecosystems dynamic response to the changes of the control parameters were constructed by simulations. The response diagrams suggest the existence of regime shifts which border different ecosystem stability ranges, characterized by the dominance of a specific group of primary producers and by different ecosystem vulnerability at summer water anoxia. A catastrophic bifurcation or abrupt regime shift, evidenced by Poincare sections obtained mapping, at a prefixed time period, the values of the concentration of the species, occurs for a critical value of the control parameter and manifests itself as an abrupt change of the dominant species from eel grass to macro algae. An analogous abrupt change from eel grass to macro algae occurs for a critical value of the tidal flowrate assumed as control parameter in simulations conducted for an assigned value of external phosphorous load.
Dynamic behaviour of CANDU reactor
Subramanian, M.G.; Srikantiah, G.; Pai, M.A.
1976-01-01
Understanding of the dynamic behaviour of a reactor system in a power station is essential for evolving control stragies as well as design modifications. The dynamic behaviour of Rajasthan Atomic Power Station is studied. Mathematical models for the reactor, the steam generator and the steam drum with the natural circulation loop are developed from physical principles like conservation of mass, momentum and energy. Each of these models is then simulated on a digital computer to obtain the characteristics during transients. The models are then combined to yield a dynamic mathematical model of the system comprising the reactor, the steam generator and the steam drum and this results in a nonlinear model. Using this model, responses of the system for various disturbances like step change in the area of the steam valve, step change in the temperature of feed water are obtained and are discussed. These models could be used to devise new control laws using optimal control theory or to evaluate the performance of existing control schemes. (author)
Electric arc behaviour in dynamic magnetic fields
Put'ko, V.F.
2000-01-01
The behaviour of an electric arc in different time-dependent (dynamic) magnetic fields was investigated. New possibilities were found for spatial and energy stabilisation of a discharge, for intensifying heat exchange, extending the electric arc and distributed control of electric arc plasma. Rotating, alternating and travelling magnetic fields were studied. It was found that under the effect of a relatively low frequency of variations of dynamic magnetic fields (f 1000 Hz) the arc stabilised at the axis of the discharge chamber, the pulsation level decreased and discharge stability increased. The borders between these two arc existence modes were formed by a certain critical field variation frequency the period of which was determined by the heat relaxation time of the discharge. (author)
'Critical' behaviour of weakly bound systems
Lassaut, M.; Lombard, R.J.; Bulboaca, I.
1995-11-01
The class of 3-dimensional finite range or similar potentials λW(r) is discussed, depending on a strength constant λ. The behaviour of the eigenvalue E as function of λ-λ c is studied, where λ c is the critical value at the transition from 0 → 1 bound state. For the l=0 case, E α (λ-λ c ) 2 was found, whereas the relationship is linear for l≥1. Treating l as a continuous parameter in the radial Schroedinger equation, the evolution of the power-law between l=0 and l=1 is given. Besides spherically symmetric scalar potentials, the case of a repulsive scalar potential combined with a spin-orbit component of the Thomas form is also discussed. (author)
Integrating human behaviour dynamics into flood disaster risk assessment
Aerts, J. C. J. H.; Botzen, W. J.; Clarke, K. C.; Cutter, S. L.; Hall, J. W.; Merz, B.; Michel-Kerjan, E.; Mysiak, J.; Surminski, S.; Kunreuther, H.
2018-03-01
The behaviour of individuals, businesses, and government entities before, during, and immediately after a disaster can dramatically affect the impact and recovery time. However, existing risk-assessment methods rarely include this critical factor. In this Perspective, we show why this is a concern, and demonstrate that although initial efforts have inevitably represented human behaviour in limited terms, innovations in flood-risk assessment that integrate societal behaviour and behavioural adaptation dynamics into such quantifications may lead to more accurate characterization of risks and improved assessment of the effectiveness of risk-management strategies and investments. Such multidisciplinary approaches can inform flood-risk management policy development.
Critical dynamics of an interacting magnetic nanoparticle system
Hansen, Mikkel Fougt; Jonsson, P.E.; Nordblad, P.
2002-01-01
Effects of dipole-dipole interactions on the magnetic relaxation have been investigated for three Fe-C nanoparticle samples with volume concentrations of 0.06, 5 and 17 vol%. While both the 5 and 17 vol% samples exhibit collective behaviour due to dipolar interactions, only the 17 vol% sample dis...... displays critical behaviour close to its transition temperature. The behaviour of the 5 vol% sample can be attributed to a mixture of collective and single-particle dynamics....
Dynamic behaviour of suction caissons
Liingaard, M.
2006-12-15
Offshore wind energy is a promising source of energy in the near future, and is rapidly becoming competitive with other power generating technologies. The continuous improvement in wind turbine technology means that the wind turbines have increased tremendously in both size and performance during the last 25 years. In order to reduce the costs, the overall weight of the wind turbine components is minimized, which means that the wind turbine structures become more flexible and thus more sensitive to dynamic excitation. Since the first resonance frequency of the modern offshore wind turbines is close to the excitation frequencies of the rotor system, it is of outmost importance to be able to evaluate the resonance frequencies of the wind turbine structure accurately as the wind turbines increase in size. In order to achieve reliable responses of the wind turbine structure during working loads it is necessary to account for the possibilities of dynamic effects of the soil-structure interaction. The aim of this thesis is to evaluate the dynamic soil-structure interaction of foundations for offshore wind turbines, with the intention that the dynamic properties of the foundation can be properly included in a composite structure-foundation system. The work has been focused on one particular foundation type; the suction caisson. The frequency dependent stiffness (impedance) of the suction caisson has been investigated by means of a three-dimensional coupled Boundary Element/Finite Element model, where the soil is simplified as a homogenous linear viscoelastic material. The dynamic stiffness of the suction caisson is expressed in terms of dimensionless frequencydependent coefficients corresponding to the different degrees of freedom. Comparisons with known analytical and numerical solutions indicate that the static and dynamic behaviour of the foundation are predicted accurately with the applied model. The analysis has been carried out for different combinations of the
Caring behaviours directly and indirectly affect nursing students' critical thinking.
Chen, Shu-Yueh; Chang, Hsing-Chi; Pai, Hsiang-Chu
2018-03-01
The purpose of this study was to determine the effect of caring behaviours on critical thinking and to examine whether self-reflection mediates the effect of caring on critical thinking. We also tested whether caring behaviours moderated the relationship between self-reflection and critical thinking. For this descriptive, correlational, cross-sectional study, we recruited 293 fifth-year nursing students from a junior college in southern Taiwan. Data were collected in 2014 on critical thinking, caring behaviours and self-reflection with insight using the Taiwan Critical Thinking Disposition Inventory, a Chinese version of the Caring Assessment Report Evaluation Q-sort, and a Chinese version of the Self-Reflection and Insight Scale, respectively. Relationships among variables were analysed by structural equation modelling, with the partial least squares method and Sobel test. The results showed that caring behaviours significantly positively affected critical thinking (β = 0.56, t = 12.37, p critical thinking (β = 0.34, t = 6.48, p critical thinking. Caring behaviours did not, however, moderate the relationship between self-reflection (β = 0.001, t = 0.021, p > 0.05) and critical thinking. Caring behaviours directly affect self-reflection with insight and critical thinking. In addition, caring behaviours also indirectly affect critical thinking through self-reflection and insight. © 2017 Nordic College of Caring Science.
Harmonic dynamical behaviour of thallous halides
The next is the deformation dipole model (DDM) of Karo and Hardy. [19] and rigid shell ... that the most realistic model for complete harmonic dynamical behaviour of the ..... metals, Ph.D. Thesis (Banaras Hindu University, 1971) Unpublished.
Slow dynamics at critical points: the field-theoretical perspective
Gambassi, Andrea
2006-01-01
The dynamics at a critical point provides a simple instance of slow collective evolution, characterised by aging phenomena and by a violation of the fluctuation-dissipation relation even for long times. By virtue of the universality in critical phenomena it is possible to provide quantitative predictions for some aspects of these behaviours by field-theoretical methods. We review some of the theoretical results that have been obtained in recent years for the relevant (universal) quantities, such as the fluctuation-dissipation ratio, associated with the non-equilibrium critical dynamics
Dynamic contraction behaviour of pneumatic artificial muscle
Doumit, Marc D.; Pardoel, Scott
2017-07-01
The development of a dynamic model for the Pneumatic Artificial Muscle (PAM) is an imperative undertaking for understanding and analyzing the behaviour of the PAM as a function of time. This paper proposes a Newtonian based dynamic PAM model that includes the modeling of the muscle geometry, force, inertia, fluid dynamic, static and dynamic friction, heat transfer and valve flow while ignoring the effect of bladder elasticity. This modeling contribution allows the designer to predict, analyze and optimize PAM performance prior to its development. Thus advancing successful implementations of PAM based powered exoskeletons and medical systems. To date, most muscle dynamic properties are determined experimentally, furthermore, no analytical models that can accurately predict the muscle's dynamic behaviour are found in the literature. Most developed analytical models adequately predict the muscle force in static cases but neglect the behaviour of the system in the transient response. This could be attributed to the highly challenging task of deriving such a dynamic model given the number of system elements that need to be identified and the system's highly non-linear properties. The proposed dynamic model in this paper is successfully simulated through MATLAB programing and validated the pressure, contraction distance and muscle temperature with experimental testing that is conducted with in-house built prototype PAM's.
Magnetocaloric effect and its implementation in critical behaviour ...
Model; manganites; magnetization; magnetocaloric effect; critical exponent. 1. Introduction. Large number of magnetocaloric effect (MCE) materials have attracted much ... external magnetic field, which is advantageous for applica- tion as magnetic ... of the magnetic phase transition and critical behaviour can be obtained by ...
Scaling and critical behaviour in nuclear fragmentation
Campi, X.
1990-09-01
These notes review recent results on nuclear fragmentation. An analysis of experimental data from exclusive experiments is made in the framework of modern theories of fragmentation of finite size objects. We discuss the existence of a critical regime of fragmentation and the relevance of scaling and finite size scaling
Dynamic behaviour of “Collapsible” concrete
Caverzan Alessio
2015-01-01
Full Text Available In this work a particular cement composite material for protection of structures and infrastructures against accidental actions, such as blast or impact, has been investigated. An experimental procedure has been developed in order to assess static and dynamic behaviour of energy absorbing cementitious composites. The granular cementitious composite has been studied focusing attention to compressive strength, high deformation and energy dissipation capacity which are important characteristics for an absorber material. An experimental characterization of the material behaviour under compressive static and dynamic loadings has been carried out. Different deformation velocities have been studied in order to define the material behaviour in a wide range of strain rates. The velocity range up to 0.1 m/s is investigated by means of a universal servo-hydraulic MTS 50 kN testing machine. Some preliminary results have been reported and discussed in the present work.
Critical dynamics in associative memory networks
Maximilian eUhlig
2013-07-01
Full Text Available Critical behavior in neural networks is characterized by scale-free avalanche size distributions and can be explained by self-regulatory mechanisms. Theoretical and experimental evidence indicates that information storage capacity reaches its maximum in the critical regime. We study the effect of structural connectivity formed by Hebbian learning on the criticality of network dynamics. The network endowed with Hebbian learning only does not allow for simultaneous information storage and criticality. However, the critical regime is can be stabilized by short-term synaptic dynamics in the form of synaptic depression and facilitation or, alternatively, by homeostatic adaptation of the synaptic weights. We show that a heterogeneous distribution of maximal synaptic strengths does not preclude criticality if the Hebbian learning is alternated with periods of critical dynamics recovery. We discuss the relevance of these findings for the flexibility of memory in aging and with respect to the recent theory of synaptic plasticity.
Critical Behaviour of a Two-Dimensional Random Antiferromagnet
Als-Nielsen, Jens Aage; Birgeneau, R. J.; Guggenheim, H. J.
1976-01-01
A neutron scattering study of the order parameter, correlation length and staggered susceptibility of the two-dimensional random antiferromagnet Rb2Mn0.5Ni0.5F4 is reported. The system is found to exhibit a well-defined phase transition with critical exponents identical to those of the isomorphou...... pure materials K2NiF4 and K2MnF4. Thus, in these systems, which have the asymptotic critical behaviour of the two-dimensional Ising model, randomness has no measurable effect on the phase-transition behaviour....
Lambda phage genetic switch as a system with critical behaviour
Vohradský, Jiří
2017-01-01
Roč. 431, OCT 27 2017 (2017), s. 32-38 ISSN 0022-5193 R&D Projects: GA MŠk(CZ) LM2015055 Institutional support: RVO:61388971 Keywords : Critical behaviour * Phage lambda * Genetic networks Subject RIV: EE - Microbiology, Virology OBOR OECD: Microbiology Impact factor: 2.113, year: 2016
Notes on scaling and critical behaviour in nuclear fragmentation
Campi, X.; Krivine, H.
1994-01-01
The relevance of the concepts of scaling and critical behaviour in nuclear fragmentation is discussed. Experimental results are reviewed to check whether the signals of a percolation or liquid-gas phase transition manifest themselves in the data. (author). 45 refs., 10 figs., 2 tabs
Critical behaviour in very pure Ni-Ta systems
Oddou, J.L.; Berthier, J.; Peretto, P.
1978-01-01
The authors use the perturbed angular correlation technique to follow the behaviour of the magnetic hyperfine field on 181 Ta in nickel in the critical region of the matrix. Contrary to what is expected, it is observed that the critical exponent associated to the hyperfine field is different from the critical exponent associated to the bulk magnetization. Because the concentrations of the various impurities are very low, the authors think that the explanation of the phenomenon is to be found in the framework of a one-impurity model interacting with the surrounding spins via an isotropic exchange energy
Simulating the evolution of industries using a dynamic behavioural model
Kunc, Martin
2004-01-01
Investment decisions determine that not only the evolution of industries is hard to forecast with certainty but also industries may have different dynamic behaviour and evolutionary paths. In this paper we present a behavioural framework to simulate the evolution of industries. Two factors determine the dynamic behaviour of an industry: managerial decision-making and the interconnected set of resources. Managerial decision-making significantly affects the dynamic behaviour of firms. Bounded r...
Resetting dynamic behaviour of pipework systems
Gaudin, M.
1997-01-01
Resetting models is applied to electricity generating plant pipework systems. A frequency approach to the problem is made in an original way thanks to the use of precise dynamic rigidity matrices. The method assumes two kinds of unknown: the usually processed mechanical characteristics (Young's Modulus, density etc.) and new resetting parameters acting on the dynamic behaviour of unknown connections. As the latter have a very wide range of possible variation, they benefit from a change of variable which allows the assumptions formulated to be complied with. The minimized cost function is based on a error in load. The frequencies required for building it are automatically selected thanks to different tests on measurements. Minimization uses a sensitivity technique linked with a method of least standard squares. The method has been programmed in Fortran 90 within the CIRCUS code and tried out on various examples which were simulated and sound effects cases as well as an actual case. (author)
The dynamical behaviour of SS 433
Collins, G.W. II
1985-01-01
In this paper a dynamical formalism is developed for describing the motion of a distorted object moving under the influence of the gravitational fields present in a close binary system. The object is assumed to be centred about one of the components and to have a form or shape sustained by axial forces such as rotation in addition to tides generated by the companion. Although such a shape will not be temporally constant, the moments of inertia are expressible in terms of the canonical coordinates of the problem and vary in a periodic manner. The dynamical behaviour of this 'elastic' body can be expressed in terms of periodic motion analogous to that found in a rigid body. The details of the resultant motion in turn places constraints on the nature of the components of the system. (author)
On Critical Behaviour in Systems of Hamiltonian Partial Differential Equations.
Dubrovin, Boris; Grava, Tamara; Klein, Christian; Moro, Antonio
2015-01-01
We study the critical behaviour of solutions to weakly dispersive Hamiltonian systems considered as perturbations of elliptic and hyperbolic systems of hydrodynamic type with two components. We argue that near the critical point of gradient catastrophe of the dispersionless system, the solutions to a suitable initial value problem for the perturbed equations are approximately described by particular solutions to the Painlevé-I (P[Formula: see text]) equation or its fourth-order analogue P[Formula: see text]. As concrete examples, we discuss nonlinear Schrödinger equations in the semiclassical limit. A numerical study of these cases provides strong evidence in support of the conjecture.
Pawlus Dorota
2017-12-01
Full Text Available The paper presents the dynamic response of annular three-layered plate subjected to loads variable in time. The plate is loaded in the plane of outer layers. The plate core has the electrorheological properties expressed by the Bingham body model. The dynamic stability loss of plate with elastic core is determined by the critical state parameters, particularly by the critical stresses. Numerous numerical observations show the influence of the values of viscosity constant and critical shear stresses, being the Bingham body parameters, on the supercritical viscous fluid plate behaviour. The problem has been solved analytically and numerically using the orthogonalization method and finite difference method. The solution includes both axisymmetric and asymmetric plate dynamic modes.
Dynamic trapping near a quantum critical point
Kolodrubetz, Michael; Katz, Emanuel; Polkovnikov, Anatoli
2015-02-01
The study of dynamics in closed quantum systems has been revitalized by the emergence of experimental systems that are well-isolated from their environment. In this paper, we consider the closed-system dynamics of an archetypal model: spins driven across a second-order quantum critical point, which are traditionally described by the Kibble-Zurek mechanism. Imbuing the driving field with Newtonian dynamics, we find that the full closed system exhibits a robust new phenomenon—dynamic critical trapping—in which the system is self-trapped near the critical point due to efficient absorption of field kinetic energy by heating the quantum spins. We quantify limits in which this phenomenon can be observed and generalize these results by developing a Kibble-Zurek scaling theory that incorporates the dynamic field. Our findings can potentially be interesting in the context of early universe physics, where the role of the driving field is played by the inflaton or a modulus field.
Liao, C-M; You, S-H; Cheng, Y-H
2015-01-01
Influenza poses a significant public health burden worldwide. Understanding how and to what extent people would change their behaviour in response to influenza outbreaks is critical for formulating public health policies. We incorporated the information-theoretic framework into a behaviour-influenza (BI) transmission dynamics system in order to understand the effects of individual behavioural change on influenza epidemics. We showed that information transmission of risk perception played a crucial role in the spread of health-seeking behaviour throughout influenza epidemics. Here a network BI model provides a new approach for understanding the risk perception spread and human behavioural change during disease outbreaks. Our study allows simultaneous consideration of epidemiological, psychological, and social factors as predictors of individual perception rates in behaviour-disease transmission systems. We suggest that a monitoring system with precise information on risk perception should be constructed to effectively promote health behaviours in preparation for emerging disease outbreaks.
Critical dynamics in population vaccinating behavior.
Pananos, A Demetri; Bury, Thomas M; Wang, Clara; Schonfeld, Justin; Mohanty, Sharada P; Nyhan, Brendan; Salathé, Marcel; Bauch, Chris T
2017-12-26
Vaccine refusal can lead to renewed outbreaks of previously eliminated diseases and even delay global eradication. Vaccinating decisions exemplify a complex, coupled system where vaccinating behavior and disease dynamics influence one another. Such systems often exhibit critical phenomena-special dynamics close to a tipping point leading to a new dynamical regime. For instance, critical slowing down (declining rate of recovery from small perturbations) may emerge as a tipping point is approached. Here, we collected and geocoded tweets about measles-mumps-rubella vaccine and classified their sentiment using machine-learning algorithms. We also extracted data on measles-related Google searches. We find critical slowing down in the data at the level of California and the United States in the years before and after the 2014-2015 Disneyland, California measles outbreak. Critical slowing down starts growing appreciably several years before the Disneyland outbreak as vaccine uptake declines and the population approaches the tipping point. However, due to the adaptive nature of coupled behavior-disease systems, the population responds to the outbreak by moving away from the tipping point, causing "critical speeding up" whereby resilience to perturbations increases. A mathematical model of measles transmission and vaccine sentiment predicts the same qualitative patterns in the neighborhood of a tipping point to greatly reduced vaccine uptake and large epidemics. These results support the hypothesis that population vaccinating behavior near the disease elimination threshold is a critical phenomenon. Developing new analytical tools to detect these patterns in digital social data might help us identify populations at heightened risk of widespread vaccine refusal. Copyright © 2017 the Author(s). Published by PNAS.
Investigation of fused silica dynamic behaviour
Malaise, F.; Chevalier, J.M.; Bertron, I.; Malka, F.
2006-01-01
The survivability of the fused silica shields to shrapnel impacts is a key factor for the affordable operation of the intense laser irradiation future facility Laser Mega Joule (LMJ). This paper presents experimental data and computational modelling for LMJ fused silica upon shock wave loading and unloading. Gas-gun flyer plate impact and explosively driven tests have been conducted to investigate the dynamic behaviour of this material. Hugoniot states and the Hugoniot Elastic Limit of LMJ fused silica have been obtained. These experimental data are useful for determining some constitutive model constants of the 'Crack-Model', a continuum tensile and compressive failure model with friction based. This model has been improved by taking into account nonlinear elasticity. The numerical results obtained by performing computations of the previous tests and some ballistic impact tests are discussed. The numerical comparisons with the experimental data show good agreement. Further developments to simulate the permanent densification and the solid-to-solid phase transformation of fused silica are required. (authors)
Avoided critical behavior in dynamically forced wetting.
Snoeijer, Jacco H; Delon, Giles; Fermigier, Marc; Andreotti, Bruno
2006-05-05
A solid object can be coated by a nonwetting liquid since a receding contact line cannot exceed a critical speed. In this Letter we study the dynamical wetting transition at which a liquid film gets deposited by withdrawing a vertical plate out of a liquid reservoir. It has recently been predicted that this wetting transition is critical with diverging time scales and coincides with the disappearance of stationary menisci. We demonstrate experimentally and theoretically that the transition is due to the formation of a solitary wave, well below the critical point. As a consequence, relaxation times remain finite at threshold. The structure of the liquid deposited on the plate involves a capillary ridge that does not trivially match the Landau-Levich film.
Quench dynamics across quantum critical points
Sengupta, K.; Powell, Stephen; Sachdev, Subir
2004-01-01
We study the quantum dynamics of a number of model systems as their coupling constants are changed rapidly across a quantum critical point. The primary motivation is provided by the recent experiments of Greiner et al. [Nature (London) 415, 39 (2002)] who studied the response of a Mott insulator of ultracold atoms in an optical lattice to a strong potential gradient. In a previous work, it had been argued that the resonant response observed at a critical potential gradient could be understood by proximity to an Ising quantum critical point describing the onset of density wave order. Here we obtain numerical results on the evolution of the density wave order as the potential gradient is scanned across the quantum critical point. This is supplemented by studies of the integrable quantum Ising spin chain in a transverse field, where we obtain exact results for the evolution of the Ising order correlations under a time-dependent transverse field. We also study the evolution of transverse superfluid order in the three-dimensional case. In all cases, the order parameter is best enhanced in the vicinity of the quantum critical point
Effects of mixing and stirring on the critical behaviour
Antonov, N V; Hnatich, Michal; Honkonen, Juha
2006-01-01
Stochastic dynamics of a nonconserved scalar order parameter near its critical point, subject to random stirring and mixing, is studied using the field-theoretic renormalization group. The stirring and mixing are modelled by a random external Gaussian noise with the correlation function ∼δ(t - t')k 4-d-y and the divergence-free (due to incompressibility) velocity field, governed by the stochastic Navier-Stokes equation with a random Gaussian force with the correlation function ∝ δ(t-t')k 4-d-y' . Depending on the relations between the exponents y and y' and the space dimensionality d, the model reveals several types of scaling regimes. Some of them are well known (model A of equilibrium critical dynamics and linear passive scalar field advected by a random turbulent flow), but there are three new non-equilibrium regimes (universality classes) associated with new nontrivial fixed points of the renormalization group equations. The corresponding critical dimensions are calculated in the two-loop approximation (second order of the triple expansion in y, y' and ε = 4 - d)
Critical magnetic behaviour in one and two dimensions
Koebler, U.; Hoser, A.
2007-01-01
Critical magnetic data of magnets in which the phase transition is driven by one-dimensional (1D) or two-dimensional (2D) interactions are examined. Characteristic for 1D (2D) phase transitions is that only the longitudinal (in plane) correlation length diverges. The transverse (inter-layer) interactions are then not relevant although they may be finite. The condition for 1D (2D) phase transitions is that the ratio of transverse (inter-layer) to longitudinal (in plane) interactions is below some threshold value. This threshold defines the bandwidth of the 1D (2D) universality class. On the other hand, three-dimensional (3D) magnetic Bragg scattering relies on a finite transverse (inter-layer) correlation length. If this correlation length is relatively long the spin structure appears 3D. For materials with a pure spin moment the dimensionality can now conveniently be inferred from the universal power function by which the order parameter approaches saturation at the stable fixed point T=0. Using this criterion it is concluded that the critical behaviour of 2D magnets is essentially of the 2D Ising type but for 1D magnets of the 3D Ising type. Slight deviations from the ideal model exponents are, however, frequently observed. Universality for T->0 is not of the Ising type in the investigated magnets with a 3D spin
Dynamical Response near Quantum Critical Points.
Lucas, Andrew; Gazit, Snir; Podolsky, Daniel; Witczak-Krempa, William
2017-02-03
We study high-frequency response functions, notably the optical conductivity, in the vicinity of quantum critical points (QCPs) by allowing for both detuning from the critical coupling and finite temperature. We consider general dimensions and dynamical exponents. This leads to a unified understanding of sum rules. In systems with emergent Lorentz invariance, powerful methods from quantum field theory allow us to fix the high-frequency response in terms of universal coefficients. We test our predictions analytically in the large-N O(N) model and using the gauge-gravity duality and numerically via quantum Monte Carlo simulations on a lattice model hosting the interacting superfluid-insulator QCP. In superfluid phases, interacting Goldstone bosons qualitatively change the high-frequency optical conductivity and the corresponding sum rule.
Dynamic behaviour of prestressed concrete bridges
Javor, T.
1982-01-01
The paper presents the results of experimental research of dynamic effects on prestressed concrete bridges in dynamic load tests using testing vehicles. The bridges were passed over in both directions at various speeds also running over an artificial unevenness to produce impact loads. From investigated bridges are shown the dynamic quantities such as dynamic coefficients, natural frequency, logarithmical decrement of damping, etc. (orig.) [de
The dynamic behaviour of a railway mine vehicle
van Manen, P.; Brickle, B.V.
1983-06-01
The paper describes a mathematical model of a railway mine vehicle which is capable of predicting its dynamic behaviour in response to track inputs. The predictions of the model have been compared with the results of tests carried out on a new high speed mine vehicle and the correlation shown is good. The model yields frequency response information for the vehicle and may be used to simulate dynamic behaviour in response to track irregularities. (4 refs.)
Static and Dynamic Criticality: Are They Different?
Cullen, D E; Clouse, C J; Procassini, R; Little, R C
2003-01-01
Let us start by stating that this paper does not contain anything new. It only contains material that has been known for decades, but which is periodically forgotten. As such this paper is intended merely to refresh people's memories. We will also mention that this paper is an example of the occasional discrepancy between textbook methodologies and real world applications, in the sense that the conclusions reached here contradict what it says in most textbooks, i.e., most textbooks incorrectly interpret the methods presented here, particularly with respect to the use of importance sampling to maintain population control. This paper is not intended as a general tutorial on criticality calculations. It is intended only to clarify the accuracy of various methods for solving criticality problems, such as a true time dependent dynamic calculation, versus an alpha or K static calculation. In particular, we address the long standing controversy between users of the TART code [1] with the dynamic method, and users of the MCNP code [2] with the alpha static method. In this paper we will prove which methods are accurate and inaccurate
Behaviour of Soil Subjected to Dynamic Loads
Bødker, L.
1998-01-01
foundations, and hence it is necessary to know the deformation properties for the soil at very low strain level. The main topic of the project is to increase the knowledge of the behaviour of Danish soils at small strain levels and to extend the laboratory facilities to deal with testing at small strains....... The soil behaviour at very small strain levels is non-linear, and the most common testing technique for this situation is the resonant column technique. One of the aims of this project is to install, check, get familiar with and perform tests on different kinds of Danish soils in a new Drnevich...... Longitudinal-Torsional Resonant Column apparatus placed at the Soil Mechanics Laboratory at Aalborg University. Another, but quite new technique for small strain testing to determine the maximum shear modulus, Gmax, is the bender element technique, and as part of the project this technique has also been...
Dynamic behaviour of a CAREM type reactor
Abbate, P.; Doval, A.
1990-01-01
As complement to CAREM reactor design studies, behaviour analysis were made in a non-stationary regime, with the aim of developing plant systems and determining process variables variation ranges, characteristic of normal operating conditions, specifying alarm values for different variables, as well as for operating policies. Transient accidental scenes analysis were made, concluding that reactor characteristics provide security, maintaining the core integrity. (Author) [es
Dynamical systems examples of complex behaviour
Jost, Jürgen
2005-01-01
Our aim is to introduce, explain, and discuss the fundamental problems, ideas, concepts, results, and methods of the theory of dynamical systems and to show how they can be used in speci?c examples. We do not intend to give a comprehensive overview of the present state of research in the theory of dynamical systems, nor a detailed historical account of its development. We try to explain the important results, often neglecting technical re?nements 1 and, usually, we do not provide proofs. One of the basic questions in studying dynamical systems, i.e. systems that evolve in time, is the construction of invariants that allow us to classify qualitative types of dynamical evolution, to distinguish between qualitatively di?erent dynamics, and to studytransitions between di?erent types. Itis also important to ?nd out when a certain dynamic behavior is stable under small perturbations, as well as to understand the various scenarios of instability. Finally, an essential aspect of a dynamic evolution is the transformat...
Moment-to-moment dynamics of ADHD behaviour
Aase Heidi
2005-08-01
Full Text Available Abstract Background The behaviour of children with Attention-Deficit / Hyperactivity Disorder is often described as highly variable, in addition to being hyperactive, impulsive and inattentive. One reason might be that they do not acquire complete and functional sequences of behaviour. The dynamic developmental theory of ADHD proposes that reinforcement and extinction processes are inefficient because of hypofunctioning dopamine systems, resulting in a narrower time window for associating antecedent stimuli and behaviour with its consequences. One effect of this may be that the learning of behavioural sequences is delayed, and that only short behavioural sequences are acquired in ADHD. The present study investigated acquisition of response sequences in the behaviour of children with ADHD. Methods Fifteen boys with ADHD and thirteen boys without, all aged between 6–9 yr, completed a computerized task presented as a game with two squares on the screen. One square was associated with reinforcement. The task required responses by the computer mouse under reinforcement contingencies of variable interval schedules. Reinforcers were cartoon pictures and small trinkets. Measures related to response location (spatial dimension and to response timing (temporal dimension were analyzed by autocorrelations of consecutive responses across five lags. Acquired response sequences were defined as predictable responding shown by high explained variance. Results Children with ADHD acquired shorter response sequences than comparison children on the measures related to response location. None of the groups showed any predictability in response timing. Response sequencing on the measure related to the discriminative stimulus was highly related to parent scores on a rating scale for ADHD symptoms. Conclusion The findings suggest that children with ADHD have problems with learning long sequences of behaviour, particularly related to response location. Problems with
Dynamic behaviour of the high confinement mode of fusion plasmas
Zohm, H.
1995-05-01
This paper describes the dynamic behaviour of the High Confinement mode (H-mode) of fusion plasmas, which is one of the most promising regimes of enhanced energy confinement in magnetic fusion research. The physics of the H-mode is not yet fully understood, and the detailed behaviour is complex. However, we establish a simple physics picture of the phenomenon. Although a first principles theory of the anomalous transport processes in a fusion plasma has not yet been given, we show that within the picture developed here, it is possible to describe the dynamic behaviour of the H-mode, namely the dynamics of the L-H transition and the occurrence of edge localized modes (ELMs). (orig.)
Dynamical behaviour at the Onset of Chaos
Anania, G
1988-09-15
Power-law divergence of nearby trajectories on the Feigenbaum attractor is discussed in terms of the algebraic index ..beta.. A statistical analysis is performed by following a multifractal approach. As a result, a fluctuating spectrum h(..beta.. is found, whose complete characterization requires the introduction of a generalized ''multispectral'' analysis. A simple model of period-doubling is extensively discussed, allowing to clarify many details of the related problems. A similar approach is expected to work in generic transitions towards chaotic behaviour.
Dynamical critical phenomena in driven-dissipative systems.
Sieberer, L M; Huber, S D; Altman, E; Diehl, S
2013-05-10
We explore the nature of the Bose condensation transition in driven open quantum systems, such as exciton-polariton condensates. Using a functional renormalization group approach formulated in the Keldysh framework, we characterize the dynamical critical behavior that governs decoherence and an effective thermalization of the low frequency dynamics. We identify a critical exponent special to the driven system, showing that it defines a new dynamical universality class. Hence critical points in driven systems lie beyond the standard classification of equilibrium dynamical phase transitions. We show how the new critical exponent can be probed in experiments with driven cold atomic systems and exciton-polariton condensates.
Static and dynamic behaviour of antiferromagnetic linear chains
Henkens, L.S.J.M.
1977-01-01
This thesis deals with an experimental study of the static and dynamic behaviour of s=1/2 heisenberg antiferromagnetic linear chains in the temperature range of 0,05K 4 , CuSeO 4 .5H 2 O, and CuBeF 4 .5H 2 O, all of which are isomorphic salts
Functional coordination of muscles underlying changes in behavioural dynamics.
Vernooij, Carlijn A; Rao, Guillaume; Perdikis, Dionysios; Huys, Raoul; Jirsa, Viktor K; Temprado, Jean-Jacques
2016-06-10
The dynamical systems approach addresses Bernstein's degrees of freedom problem by assuming that the neuro-musculo-skeletal system transiently assembles and dismantles its components into functional units (or synergies) to meet task demands. Strikingly, little is known from a dynamical point of view about the functioning of the muscular sub-system in this process. To investigate the interaction between the dynamical organisation at muscular and behavioural levels, we searched for specific signatures of a phase transition in muscular coordination when a transition is displayed at the behavioural level. Our results provide evidence that, during Fitts' task when behaviour switches to a different dynamical regime, muscular activation displays typical signatures of a phase transition; a reorganisation in muscular coordination patterns accompanied by a peak in the variability of muscle activation. This suggests that consistent changes occur in coordination processes across the different levels of description (i.e., behaviour and muscles). Specifically, in Fitts' task, target size acts as a control parameter that induces a destabilisation and a reorganisation of coordination patterns at different levels of the neuro-musculo-skeletal system.
Dynamic behaviour of rotary lip seal
El gadari M.
2014-01-01
Full Text Available We report on the dynamic behavior of a rotary lip seal by considering the interaction between lip, film and shaft roughness assumed to have a periodic form. The nonlinearities of stiffness and viscosity of the film are taken into account in a mass-spring-dumper model. Using the harmonic balance method, analytical prediction of the lip displacement is obtained, the frequency response is provided and the effect of the shaft undulation on the amplitude jumps of the lip displacement and on the film thickness fluctuations are discussed. The results have direct applications in reducing leakage that may occur between a smooth lip seal and a rough shaft.
Is Environmental Training Critical to Environmental Sustainability Behaviour
OT Aladesanmi
2014-09-01
Full Text Available In the past few decades, concern for the environment has increased significantly with evidences of change in perception of people's values and attitudes towards the environment. This study presents the results of a survey carried out among postgraduate students undergoing training in environmental and non-environmental fields with the aim of comparing their environmental sustainable behaviour. The purpose of the study was to evaluate the impact of environmental training on the postgraduate students? awareness, perceptions and behaviours with focus on the attitudes of the respondents towards environmental sustainability, and how these attitudes affect their behaviour. A purposive sampling method was used to obtain data using a semi-structured questionnaire. The respondents comprised of 50 and 47 postgraduate students undergoing training in environmental and non-environmental respectively. The data was subjected to statistical analysis using SPSS. The results of the study revealed that most of the students in environmental fields readily transferred the knowledge acquired in their training to a sustainable behaviour. DOI: http://dx.doi.org/10.3126/ije.v3i3.11083 International Journal of Environment Vol.3(3 2014: 241-251
Critical Thresholds in Earth-System Dynamics
Rothman, D.
2017-12-01
The history of the Earth system is a story of change. Some changesare gradual and benign, but others, especially those associated withcatastrophic mass extinction, are relatively abrupt and destructive.What sets one group apart from the other? Here I hypothesize thatperturbations of Earth's carbon cycle lead to mass extinction if theyexceed either a critical rate at long time scales or a critical sizeat short time scales. By analyzing 31 carbon-isotopic events duringthe last 542 million years, I identify the critical rate with a limitimposed by mass conservation. Further analysis identifies thecrossover timescale separating fast from slow events with thetimescale of the ocean's homeostatic response to a change in pH. Theproduct of the critical rate and the crossover timescale then yieldsthe critical size. The modern critical size for the marine carboncycle is roughly similar to the mass of carbon that human activitieswill likely have added to the oceans by the year 2100.
Effects of surface and bulk transverse fields on critical behaviour of ferromagnetic films
Saber, A.; Lo Russo, S.; Mattei, G.
2002-02-01
The influence of surface and bulk transverse fields on the critical behaviour of a ferromagnetic Ising film is studied using the effective field theory based on a single-site cluster method. Surface exchange enhancement is considered and a critical value is obtained. The dependence of the critical uniform transverse field on film thickness, phase diagrams in the fields, critical surface transverse field versus the bulk one, and exchange coupling ratio are presented. (author)
Dynamic of radionuclides behaviour in forest soils
Ruehm, W.; Steiner, M.; Wirth, E.; Dvornik, A.; Zhuchenko, T.A.; Kliashtorin, A.; Rafferty, B.; Shaw, G.; Kuchma, N.
1996-01-01
Within the research project ECP-5, the dynamics of radionuclides in automorphic forest soils within the 30-km-zone of Chernobyl and of hydromorphic forest soils in Belarus have been investigated. In upland forest soils, the lower layers of the organic horizons are characterized by the highest residence times for radiocesium and represent the largest pool for all radionuclides investigated. According to a preliminary estimate, radiocesium is more mobile compared to 125 Sb, which in turn migrates faster than 60 Co, 144 Ce, and 154 Eu. 106 Ru shows the lowest mobility. With regard to radiocesium, hydromorphic soils exhibit migration rates and transfer factors from soil to trees, which by far exceed those in automorphic soils. Based on a two-component quasi-diffusional model the average bias of 137 Cs in mesotrophic swamp soils was predicted. The activity concentrations of U, Pu, and Cs suggest that U and Pu were originally deposited as hot particles and that U is naturally accumulated in organic horizons
Dynamic behaviour of FBR fuel pin bundles
Martin, P.H.; Van Dorsselaere, J.P.; Ravenet, A.
1990-01-01
A programme of shock tests on a fast neutron reactor subassembly model (SPX1 geometry) including a complete bundle of fuel pins (dummy elements) is being carried out in the BELIER test facility at Cadarache. The purpose of these tests is: to determine the distribution of dynamic forces applied to the fuel rod clads under the impact conditions encountered in a reactor during a earthquake; to reduce as much as possible the conservatism of the methods presently used for the calculation of those forces. The test programme, now being completed, consists of the following steps: impacts on the mock-up in air with an non-compact bundle (situation of the subassembly at beginning of life (BOL) with clearances within the bundle); impacts under the same conditions but with fluid (water) in the subassembly; impacts on the mock-up in air and with a compacted bundle (simulating the conditions of an end-of-life (EOL) bundle with no clearance within the bundle). The accelerations studied in these tests cover the range encountered in design calculations for the subassembly frequencies in beam mode. (author)
Dynamical analysis of critical assembly CC-1
Aleman Fernandez, J.R.
1990-01-01
The computer code CC-1, elaborated for the analysis of transients in Critical Assemblies is described. The results by the program are compared with the ones presented in the Safety Report for the Critical Assembly of ''La Quebrada'' Nuclear Research Centre (CIN). 7 refs
Investigations into the dynamic behaviour of finned tube heat exchangers
Sandbrink, J.; Stegemann, D.
1981-01-01
Atmospheric disturbances due to thunder storms, side wind effects on the shell or ground inversion can impair the heat dissipation of a cooling tower. These effects react on the overall power plant, which is reflected in the varied electrical output. This uncontrolled behaviour has been investigated in detail for the case of a boiling water reactor nuclear power station with indirect natural draught dry cooling and compared with controlled performance. A computer model, which has been checked out by means of experimental investigations on three different types of tube, is presented to describe the dynamic behaviour of finned tube heat exchangers. (orig.) [de
Dynamics of quantum discord in a quantum critical environment
Xi Zhengjun; Li Yongming; Lu Xiaoming; Sun Zhe
2011-01-01
We study the dynamics of quantum discord (QD) of two qubits independently coupled to an Ising spin chain in a transverse field, which exhibits a quantum phase transition. For this model, we drive the corresponding Kraus operators, obtain the analytic results of QD and compare the dynamics of QD with the dynamics of relative entropy of entanglement nearby the critical point. It is shown that the impact of the quantum criticality environment on QD can be concentrated in a very narrow region nearby the critical point, so it supplies an efficient way to detect the critical points. In the vicinity of the critical point, the evolution of QD is shown to be more complicated than that of entanglement. Furthermore, we find that separable states can also be used to reflect the quantum criticality of the environment.
Apparent anomalous critical behaviour of superfluid helium 4 in porous medium
Maynard, R.; Deutscher, G.
1989-01-01
The anomalous critical exponents of the superfluid 4 He density in silica aerogels is analysed by a simple model where the distribution of pore size is assumed to be very broad. The strong modification of the critical behaviour is related to the structure of the aerogels skeleton which is discussed in terms of a percolation or alternatively a hierarchical sponge model
Numerical investigations of the dynamic behaviour of the DCB sample
Stoeckl, H.
1985-11-01
Expericence with the wedge-loaded double cantilever beam (DCB) sample has shown that a reliable numerical simulation of measurements of the stress intensity factor is made very difficult. One tries to predict the effects associated with the occurring complications quantitatively and to interpret the dynamic behaviour of the sample as the effects of various waveforms. The problem of stability of crack propagation is discussed using a criterion provided by Cotterell. (HP) [de
Classically dynamical behaviour of single particle in heavy nuclei
Gu Jianzhong; Zhuo Yizhong; Wu Xizhen
1998-01-01
A detailed analysis of the classically dynamical behaviour of a nucleon in heavy nuclei in terms of the TCSM (two-center shell model) is presented. Poincare section is a convenient and reliable criterion to judge the regularity (or chaoticity) of a classical system. The numerical calculations in this work are carried out for a nucleon in 238 U. The Poincare section map and the Poincare surface of section for different conditions are presented
Simulation model of dynamical behaviour of reactor fuel assemblies
Planchard, J.
1994-01-01
This report briefly describes the homogenized dynamical equations of a tube bundle placed in a perfect irrotational fluid, on case of small displacements. This approach can be used to study the mechanical behaviour of fuel assemblies of PWR reactor submitted to earthquake or depressurization blow-down. The numerical calculations require to define the added mass matrix of the fuel assemblies, for which the principle of computation is presented. (author). 14 refs., 4 figs
Non-monotonic behaviour in relaxation dynamics of image restoration
Ozeki, Tomoko; Okada, Masato
2003-01-01
We have investigated the relaxation dynamics of image restoration through a Bayesian approach. The relaxation dynamics is much faster at zero temperature than at the Nishimori temperature where the pixel-wise error rate is minimized in equilibrium. At low temperature, we observed non-monotonic development of the overlap. We suggest that the optimal performance is realized through premature termination in the relaxation processes in the case of the infinite-range model. We also performed Markov chain Monte Carlo simulations to clarify the underlying mechanism of non-trivial behaviour at low temperature by checking the local field distributions of each pixel
Dynamical behaviour of the coupled diffusion map lattice
Wei Wang; Cerdeira, H.A.
1993-10-01
In this paper we report the dynamical study of a coupled diffusive map lattice with the coupling between the elements only through the bifurcation parameter of the mapping function. The diffusive process of the lattice from an initially random distribution state to a homogeneous one and the stable range of the diffusive homogeneous attractor are discussed. For various coupling strengths we find that there are several types of spatio-temporal structures. In addition, the evolution of the lattice into chaos is studied and a largest Lyapunov exponent is used to characterize the dynamical behaviour. (author). 22 refs, 9 figs
Children: a critical link for changing driving behaviour
O' Brien, C. [York Univ., Toronto, ON (Canada)
2001-08-01
Sustainable transportation is a pressing issue, according to Transport Canada, the National Round Table on the Environment and the Economy, the Centre for Sustainable Transportation and several others. To meet Canada's commitment to reducing the carbon dioxide emissions by 20 per cent by 2005, reducing the number of kilometres driven seems to be the only viable solution. Improving air quality by reducing the use of cars will lessen the negative impact in children. Some of the strategies proposed include compact, mixed-use communities, user fees, increased use of public transit are combined with a requirement for greater public education and awareness. Several studies have demonstrated that increased knowledge of an issue alone does not lead to changes in behaviour. One strategy recommended is called social marketing, by fostering changes in norms, providing prompts, obtaining public commitments and the removal of barriers. Raising the profile of children in sustainable transportation makes parents more receptive to information about child-friendly transportation. Some of the impacts of cars on children are: traffic fatalities, less than 50 per cent of children now walk to school, the average physical activity guidelines for children are not met in two thirds of children, obesity, reduced independent mobility of children, emotional distress following an involvement in a traffic accident and more. Some programs such as Way to Go, Walking School Bus, and Active and Safe Routes to School have been implemented in many communities and were found to be successful and additional funding to these programs might be more efficient than conventional education programs to alter behaviour toward sustainable transportation. Get the children to influence their parents. 25 refs., 4 figs.
Thermal behaviour in dynamic recrystallisation. Application for iron base alloys
Belkebir, A.; Kobylanski, A.
1995-01-01
A constitutive relationship for predicting the flow stress with dynamic recrystallization were proposed. The approach is based on a phenomenological formalism of the law θ-ε where θ correspond to the work-hardening rate at constant strain rate and temperature. The equations proposed were justified by the experimental data collected by hot compression test of low-alloy steels. The model can be used to estimate the critical strain for the onset of dynamic recrystallization. (orig.)
Dynamic Hazards In Critical Infrastructure Of State
Ostrowska Teresa
2015-06-01
Full Text Available The authors are interested in some aspects of a development project entitled “The methodology of risk assessment for the purposes of crisis management system RP (ID 193751”. The project funded by the National Research and Development Centre under the Competition 3/2012 (security and defense. As part of the project the following items were reviewed and analyzed: materials related to the Government Security Centre, already completed and available products of the project ID 193751, and literature relating to, among other things, crisis management, critical infrastructure, business continuity, security, and threats. The basic emphasis of the article is focused on the resource-critical infrastructure interpretation of the state, whereby the state is perceived as a complex administrative structure in which, on the basis of external and internal interactions of resources, the risk of threats measurement is done.
Zhai, Liang-Jun; Wang, Huai-Yu; Yin, Shuai
2018-04-01
The conventional Kibble-Zurek scaling describes the scaling behavior in the driven dynamics across a single critical region. In this paper, we study the driven dynamics across an overlapping critical region, in which a critical region (Region A) is overlaid by another critical region (Region B). We develop a hybridized Kibble-Zurek scaling (HKZS) to characterize the scaling behavior in the driven process. According to the HKZS, the driven dynamics in the overlapping region can be described by the critical theories for both Region A and Region B simultaneously. This results in a constraint on the scaling function in the overlapping critical region. We take the quantum Ising chain in an imaginary longitudinal field as an example. In this model, the critical region of the Yang-Lee edge singularity and the critical region of the ferromagnetic-paramagnetic phase transition overlap with each other. We numerically confirm the HKZS by simulating the driven dynamics in this overlapping critical region. The HKZSs in other models are also discussed.
Phase transitions and critical behaviour for charged black holes
Carlip, S; Vaidya, S
2003-01-01
We investigate the thermodynamics of a four-dimensional charged black hole in a finite cavity in asymptotically flat and asymptotically de Sitter spaces. In each case, we find a Hawking-Page-like phase transition between a black hole and a thermal gas very much like the known transition in asymptotically anti-de Sitter space. For a 'supercooled' black hole - a thermodynamically unstable black hole below the critical temperature for the Hawking-Page phase transition - the phase diagram has a line of first-order phase transitions that terminates in a second-order point. For the asymptotically flat case, we calculate the critical exponents at the second-order phase transition and find that they exactly match the known results for a charged black hole in anti-de Sitter space. We find strong evidence for similar phase transitions for the de Sitter black hole as well. Thus many of the thermodynamic features of charged anti-de Sitter black holes do not really depend on asymptotically anti-de Sitter boundary conditions; the thermodynamics of charged black holes is surprisingly universal
Martin, Solange; Gaspard, Albane
2017-01-01
Beyond broad policy declarations, the implementation of ecological transition - which consists mainly in curbing consumption of energy and raw materials in our societies - requires substantial behavioural change at the collective, but also, quite obviously, the individual level. Yet, though there is general consensus around the principle of embarking on the path to transition, things get more complicated when it comes to changing our practices and habits. Can we act on individual behaviour and collective dynamics in respect of this particular aim of ecological transition, and, if so, how are we to go about it? Solange Martin and Albane Gaspard have examined this question for the French Environment and Energy Management Agency (ADEME) and offer us the fruit of their labours here. They show, for example, how the social and human sciences help to understand behaviour both at the individual level and in its collective dimensions, and they outline different possible lines of action to modify it. But, given the entanglement between various levels, it is essential, if we are to act effectively on behaviour, to combine approaches, tools and actors, and to analyse and understand social practices thoroughly before implementing political projects or measures
Critical quench dynamics in confined systems.
Collura, Mario; Karevski, Dragi
2010-05-21
We analyze the coherent quantum evolution of a many-particle system after slowly sweeping a power-law confining potential. The amplitude of the confining potential is varied in time along a power-law ramp such that the many-particle system finally reaches or crosses a critical point. Under this protocol we derive general scaling laws for the density of excitations created during the nonadiabatic sweep of the confining potential. It is found that the mean excitation density follows an algebraic law as a function of the sweeping rate with an exponent that depends on the space-time properties of the potential. We confirm our scaling laws by first order adiabatic calculation and exact results on the Ising quantum chain with a varying transverse field.
Self-regulated dynamical criticality in human ECoG
Guillermo eSolovey
2012-07-01
Full Text Available Mounting experimental and theoretical results indicate that neural systems are poised near a critical state. In human subjects, however, most evidence comes from functional MRI studies, an indirect measurement of neuronal activity with poor temporal resolution. Electrocorticography (ECoG provides a unique window into human brain activity: each electrode records, with high temporal resolution, the activity resulting from the sum of the local field potentials of sim 10^5 neurons. We show that the human brain ECoG recordings display features of self-regulated dynamical criticality: dynamical modes of activation drift around the critical stability threshold, moving in and out of the unstable region and equilibrating the global dynamical state at a very fast time scale. Moreover, the analysis also reveals differences between the resting state and a motor task, associated with increased stability of a fraction of the dynamical modes.
Dynamic space charge behaviour in polymeric DC cables
Rasmussen, Claus Nygaard; Holbøll, Joachim; Henriksen, Mogens
2002-01-01
The use of extruded insulation for DC cables involves a risk of local electric field enhancement, caused by a space charge build-up within the dielectric. In this work, the theory of charge generation and transport in polymers is applied in a numerical computer model in order to predict...... the formation and transport of space charges in a polymeric dielectric. The model incorporates the processes of field assisted electron-hole pair generation from impurity atoms, trapping and charge injection at the electrodes. Its aim has been to study the field- and temperature dependent dynamic behaviour...
Lu, Z X
2013-01-01
Using the usual mean-field theory approximation, the critical behaviour (i.e. the Curie temperature T c and the critical surface transverse field Ω sc ) in a multiple-surface-layer ferroelectric thin film is studied on the basis of the spin- 1/2 transverse Ising model. The dependence of the Curie temperature T c on the surface transverse field Ω s and the surface layer number N s are discussed in detail. Meanwhile the dependence of the critical surface transverse field Ω sc on the surface layer number N s is also examined. The numerical results indicate that the critical behaviour of ferroelectric thin films is obviously affected by modifications of the surface transverse field Ω s and surface layer number N s .
Data collapse and critical dynamics in neuronal avalanche data
Butler, Thomas; Friedman, Nir; Dahmen, Karin; Beggs, John; Deville, Lee; Ito, Shinya
2012-02-01
The tasks of information processing, computation, and response to stimuli require neural computation to be remarkably flexible and diverse. To optimally satisfy the demands of neural computation, neuronal networks have been hypothesized to operate near a non-equilibrium critical point. In spite of their importance for neural dynamics, experimental evidence for critical dynamics has been primarily limited to power law statistics that can also emerge from non-critical mechanisms. By tracking the firing of large numbers of synaptically connected cortical neurons and comparing the resulting data to the predictions of critical phenomena, we show that cortical tissues in vitro can function near criticality. Among the most striking predictions of critical dynamics is that the mean temporal profiles of avalanches of widely varying durations are quantitatively described by a single universal scaling function (data collapse). We show for the first time that this prediction is confirmed in neuronal networks. We also show that the data have three additional features predicted by critical phenomena: approximate power law distributions of avalanche sizes and durations, samples in subcritical and supercritical phases, and scaling laws between anomalous exponents.
Universal Critical Dynamics in High Resolution Neuronal Avalanche Data
Friedman, Nir; Ito, Shinya; Brinkman, Braden A. W.; Shimono, Masanori; DeVille, R. E. Lee; Dahmen, Karin A.; Beggs, John M.; Butler, Thomas C.
2012-05-01
The tasks of neural computation are remarkably diverse. To function optimally, neuronal networks have been hypothesized to operate near a nonequilibrium critical point. However, experimental evidence for critical dynamics has been inconclusive. Here, we show that the dynamics of cultured cortical networks are critical. We analyze neuronal network data collected at the individual neuron level using the framework of nonequilibrium phase transitions. Among the most striking predictions confirmed is that the mean temporal profiles of avalanches of widely varying durations are quantitatively described by a single universal scaling function. We also show that the data have three additional features predicted by critical phenomena: approximate power law distributions of avalanche sizes and durations, samples in subcritical and supercritical phases, and scaling laws between anomalous exponents.
Ferdinand, A; Probst, A-C; Birringer, R; Michels, A; Kaul, S N
2014-01-01
We report on how nanocrystal size affects the critical behaviour of the rare-earth metal Gd near the ferromagnetic-to-paramagnetic phase transition. The asymptotic critical behaviour of the coarse-grained polycrystalline sample (with an average crystallite size of L≅100 μm) is that of a (pure) uniaxial dipolar ferromagnet, as is the case with single crystal Gd, albeit the width of the asymptotic critical region (ACR) is reduced. As the grain size approaches ∼30 nm, the ACR is so narrow that it could not be accessed in the present experiments. Inaccessibly narrow ACR for L ∼ 30 nm and continuous increase in the width of the ACR as L decreases from 16 to 9.5 nm basically reflect a crossover to the random uniaxial dipolar fixed point caused by the quenched random exchange disorder prevalent at the internal interfaces (grain boundaries). (paper)
Quantum critical dynamics for a prototype class of insulating antiferromagnets
Wu, Jianda; Yang, Wang; Wu, Congjun; Si, Qimiao
2018-06-01
Quantum criticality is a fundamental organizing principle for studying strongly correlated systems. Nevertheless, understanding quantum critical dynamics at nonzero temperatures is a major challenge of condensed-matter physics due to the intricate interplay between quantum and thermal fluctuations. The recent experiments with the quantum spin dimer material TlCuCl3 provide an unprecedented opportunity to test the theories of quantum criticality. We investigate the nonzero-temperature quantum critical spin dynamics by employing an effective O (N ) field theory. The on-shell mass and the damping rate of quantum critical spin excitations as functions of temperature are calculated based on the renormalized coupling strength and are in excellent agreement with experiment observations. Their T lnT dependence is predicted to be dominant at very low temperatures, which will be tested in future experiments. Our work provides confidence that quantum criticality as a theoretical framework, which is being considered in so many different contexts of condensed-matter physics and beyond, is indeed grounded in materials and experiments accurately. It is also expected to motivate further experimental investigations on the applicability of the field theory to related quantum critical systems.
Critical and post-critical behaviour of two-degree-of-freedom flutter-based generators
Pigolotti, Luca; Mannini, Claudio; Bartoli, Gianni; Thiele, Klaus
2017-09-01
Energy harvesting from flow-induced vibrations is a recent research field, which considers a diverse range of systems, among which two-degree-of-freedom flutter-based solutions were individuated as good candidates to obtain high energy performance. In the present work, numerical linear analyses and wind-tunnel tests were conducted on a flat-plate sectional model. The aim is to identify some design guidelines for generators exploiting the classical-flutter instability, through the investigation of the critical condition and the response during the post-critical regime. Many sets of governing parameters of interest from the energy-harvesting point of view were considered, including high levels of heaving damping to simulate the operation of a conversion apparatus. In particular, eccentricity of the elastic centre and small downstream mass unbalance can be introduced as solutions aiming at optimal operative ranges. The collected results suggest the high potentiality of flutter-based generators, and a significant enhancement of performance can be envisaged. Moreover, they contribute to improve the knowledge of the flutter excitation mechanism and to widen the dataset of measurements in the post-critical regime.
Entanglement dynamics in critical random quantum Ising chain with perturbations
Huang, Yichen, E-mail: ychuang@caltech.edu
2017-05-15
We simulate the entanglement dynamics in a critical random quantum Ising chain with generic perturbations using the time-evolving block decimation algorithm. Starting from a product state, we observe super-logarithmic growth of entanglement entropy with time. The numerical result is consistent with the analytical prediction of Vosk and Altman using a real-space renormalization group technique. - Highlights: • We study the dynamical quantum phase transition between many-body localized phases. • We simulate the dynamics of a very long random spin chain with matrix product states. • We observe numerically super-logarithmic growth of entanglement entropy with time.
The U(1)-Higgs model: critical behaviour in the confining-Higgs region
Alonso, J.L.; Azcoiti, V.; Campos, I.; Ciria, J.C.; Cruz, A.; Iniguez, D.; Lesmes, F.; Piedrafita, C.; Rivero, A.; Tarancon, A.; Badoni, D.; Fernandez, L.A.; Munoz Sudupe, A.; Ruiz-Lorenzo, J.J.; Gonzalez-Arroyo, A.; Martinez, P.; Pech, J.; Tellez, P.
1993-01-01
We study numerically the critical properties of the U(1)-Higgs lattice model, with fixed Higgs modulus, in the region of small gauge coupling where the Higgs and confining phases merge. We find evidence for a first-order transition line that ends in a second-order point. By means of a rotation in parameter space we introduce thermodynamic magnitudes and critical exponents in close resemblance with simple models that show analogous critical behaviour. The measured data allow us to fit the critical exponents finding values in agreement with the mean-field prediction. The location of the critical point and the slope of the first-order line are accurately measured. (orig.)
Classically dynamical behaviour of a nucleon in heavy nuclei
Gu Jianzhong; Zhao Enguang; Zong Hongshi; Zhuo Yizhong; Wu Xizhen
1998-01-01
Within the framework of the two-center shell model the classically dynamical behaviour of a nucleon in heavy nuclei is investigated systematically with the change of nuclear shape parameters for the first time. It is found that as long as the nucleonic energy 0is appreciably higher than the height of the potential barrier there is a good quantum-classical correspondence of nucleonic regular (chaotic) motion. Thus, Bohigas, Giannoni and Schmit conjecture is confirmed once again. We find that the difference between the potential barrier for prolate nuclei and that for oblate ones is reponsible for the energy-dependence difference between the nucleonic chaotic dynamics for prolate nuclei and that for oblate ones. In addition, it is suggested that nuclear dissipation is shape-dependent, and strong nuclear dissipation can be expected for medium or large separations in the presence of a considerable neck deformation built on a pronounced octupole-like deformation, which provides us a dynamical understanding of nuclear shape dependence of nuclear dissipation. (orig.)
On the oscillatory dynamical behaviour of epidemic spreading in fractal media
Bab, M A; Albano, E V
2008-01-01
We present numerical evidence that dynamical physical processes that develop a time-dependent characteristic length, and take place in fractal media exhibiting spatial discrete scale invariance (DSI) with fundamental scaling ratio b, may become coupled to the topology of the fractal leading to the observation of time DSI. The hallmark of time DSI is the observation of a log-periodic modulation of the dynamic or kinetic observables, which is characterized by a well-defined fundamental time scaling ratio (τ). Both fundamental scaling ratios are linked according to b = τ 1/z , where z is the dynamic exponent characteristic of the physical process. Specifically, we have studied the epidemic behaviour of the contact process (CP) in Sierpinski Carpets. The CP exhibits second-order irreversible phase transitions between an active regime and an absorbing state where the system is trapped without any escape possibility. We observed that relevant dynamic observables, such as the number of active sites, the survival probability of the epidemics and the mean square displacement of the epidemic from the origin (R 2 (t)), exhibit log-periodic modulations. By fitting the data we evaluate the fundamental time scaling ratio for various fractals and the corresponding dynamic exponents. Since, at criticality, one has that R 2 (t) ∼ t 2/z , an independent estimation of the dynamic exponent can be performed, in excellent agreement with results obtained by using the conjectured relationship for the fundamental scaling ratios b and τ
On the oscillatory dynamical behaviour of epidemic spreading in fractal media
Bab, M A; Albano, E V [Instituto de Investigaciones FisicoquImicas Teoricas y Aplicadas (INIFTA), Facultad de Ciencias Exactas, UNLP, CONICET, Casilla de Correo 16, Sucursal 4 (1900) La Plata (Argentina)
2008-02-01
We present numerical evidence that dynamical physical processes that develop a time-dependent characteristic length, and take place in fractal media exhibiting spatial discrete scale invariance (DSI) with fundamental scaling ratio b, may become coupled to the topology of the fractal leading to the observation of time DSI. The hallmark of time DSI is the observation of a log-periodic modulation of the dynamic or kinetic observables, which is characterized by a well-defined fundamental time scaling ratio ({tau}). Both fundamental scaling ratios are linked according to b = {tau}{sup 1/z}, where z is the dynamic exponent characteristic of the physical process. Specifically, we have studied the epidemic behaviour of the contact process (CP) in Sierpinski Carpets. The CP exhibits second-order irreversible phase transitions between an active regime and an absorbing state where the system is trapped without any escape possibility. We observed that relevant dynamic observables, such as the number of active sites, the survival probability of the epidemics and the mean square displacement of the epidemic from the origin (R{sup 2}(t)), exhibit log-periodic modulations. By fitting the data we evaluate the fundamental time scaling ratio for various fractals and the corresponding dynamic exponents. Since, at criticality, one has that R{sup 2}(t) {approx} t{sup 2/z}, an independent estimation of the dynamic exponent can be performed, in excellent agreement with results obtained by using the conjectured relationship for the fundamental scaling ratios b and {tau}.
Assessment of the dynamic behaviours of the ITER Vacuum Vessel
Blocki, J., E-mail: jacek.blocki@f4e.europa.eu [Fusion for Energy, Josep Pla 2, Torres Diagonal Litoral B3, 08019 Barcelona (Spain); Combescure, D. [Fusion for Energy, Josep Pla 2, Torres Diagonal Litoral B3, 08019 Barcelona (Spain); Mazzone, G. [ITER Organization, Route de Vinon sur Verdon, 13115 Saint Paul Lez Durance (France)
2013-10-15
Highlights: ► The cyclic symmetry structure with special boundary conditions has been analyzed. ► Results based on the FE solid model and on the FE shell model have been compared. ► The effect of the missing mass contained has been checked. -- Abstract: The dynamic behaviour of the ITER Vacuum Vessel (VV) under seismic loads will be assessed by carrying out the modal analysis and then by applying the response spectrum method which describes earthquake motions. The effect of the missing mass is included in this last analysis. Numerical results are based on two different Finite Element (FE) models and on three different methods by which natural frequencies and mode shapes are defined. It means, it is applied the cyclic symmetry method, the component mode synthesis method and the 360° FE model of the VV. Comparisons between obtained results for the different models and methods are presented.
Dynamical behaviour of the firing in coupled neuronal system
Wei Wang; Perez, G.; Cerdeira, H.A.
1993-03-01
The time interval sequences and the spatio-temporal patterns of the firings of a coupled neuronal network are investigated in this paper. For a single neuron stimulated by an external stimulus I, the time interval sequences show a low frequency firing of bursts of spikes, and reversed period-doubling cascade to a high frequency repetitive firing state as the stimulus I is increased. For two neurons coupled to each other through the firing of the spikes, the complexity of the time interval sequences becomes simple as the coupling strength increases. A network with large numbers of neurons shows a complex spatio-temporal pattern structure. As the coupling strength increases, the numbers of phase locked neurons increase and the time interval diagram shows temporal chaos and a bifurcation in the space. The dynamical behaviour is also verified by the Lyapunov exponent. (author). 17 refs, 6 figs
Knoeri, Christof; Wäger, Patrick A.; Stamp, Anna; Althaus, Hans-Joerg; Weil, Marcel
2013-01-01
Emerging technologies such as information and communication-, photovoltaic- or battery technologies are expected to increase significantly the demand for scarce metals in the near future. The recently developed methods to evaluate the criticality of mineral raw materials typically provide a ‘snapshot’ of the criticality of a certain material at one point in time by using static indicators both for supply risk and for the impacts of supply restrictions. While allowing for insights into the mechanisms behind the criticality of raw materials, these methods cannot account for dynamic changes in products and/or activities over time. In this paper we propose a conceptual framework intended to overcome these limitations by including the dynamic interactions between different possible demand and supply configurations. The framework integrates an agent-based behaviour model, where demand emerges from individual agent decisions and interaction, into a dynamic material flow model, representing the materials' stocks and flows. Within the framework, the environmental implications of substitution decisions are evaluated by applying life-cycle assessment methodology. The approach makes a first step towards a dynamic criticality assessment and will enhance the understanding of industrial substitution decisions and environmental implications related to critical metals. We discuss the potential and limitation of such an approach in contrast to state-of-the-art methods and how it might lead to criticality assessments tailored to the specific circumstances of single industrial sectors or individual companies. - Highlights: ► Current criticality assessment methods provide a ‘snapshot’ at one point in time. ► They do not account for dynamic interactions between demand and supply. ► We propose a conceptual framework to overcomes these limitations. ► The framework integrates an agent-based behaviour model with a dynamic material flow model. ► The approach proposed makes
Inga E. Larsson
2011-01-01
Full Text Available Patient participation is an important basis for nursing care and medical treatment and is a legal right in many Western countries. Studies have established that patients consider participation to be both obvious and important, but there are also findings showing the opposite and patients often prefer a passive recipient role. Knowledge of what may influence patients' participation is thus of great importance. The aim was to identify incidents and nurses' behaviours that influence patients' participation in nursing care based on patients' experiences from inpatient somatic care. The Critical Incident Technique (CIT was employed. Interviews were performed with patients (=17, recruited from somatic inpatient care at an internal medical clinic in West Sweden. This study provided a picture of incidents, nurses' behaviours that stimulate or inhibit patients' participation, and patient reactions on nurses' behaviours. Incidents took place during medical ward round, nursing ward round, information session, nursing documentation, drug administration, and meal.
Christiaan G. Joubert
2017-04-01
Full Text Available Background: Motivation for this study was found in concern expressed by civil aviation organisations that specialists in the air navigation services provider sector require appropriate and beneficial organisational leadership to encourage, enable and manage transformation within this highly structured setting. Also, academic research puts emphasis on a need for investigations of the roles, expectations and requirements of followers in the leadership–followership relationship. Followers’ experiences and expectations of leadership behaviours in an air navigation service provider (ANSP organisation were investigated and served as orientation and setting applicable to this study. Aim: The aim of the research was to identify and understand how follower experiences and expectations of leadership behaviours in a safety-critical commercial environment can affect leadership training and growth. The above-mentioned motivated this investigation of leadership traits and behaviours within an explicit context and from a follower’s viewpoint. Setting: The setting for the study was twenty two Air Traffic and Navigation Services Company sites where followers’ experiences and expectations of leadership behaviours in an air navigation service provider (ANSP organisation were investigated and served as orientation and setting applicable to this study. Methods: An ethnographic case study research style was adopted and followed because it allowed for an all-inclusive, holistic narrative report and interpretation. The samples for the quantitative and qualitative components of this study were parallel and methods employed addressed different aspects of the phenomenon, which allowed for a mixed methods research design. A one-way causality in the research design was observed because traits of followers that might influence leaders’ behaviours were excluded. Data were collected by means of a Leader Trait and Behaviour Questionnaire completed by participants
Lichtwarck-Aschoff, Anna; van Geert, Paul
2004-01-01
In this article we discussed a dynamic systems view on social behaviour in adolescence. Social behaviour is defined as a self-organizing attractor landscape, based on a network of proximal (i.e., direct) causes. In some cases, social development is disturbed, leading to problematic behaviour in
Intrinsic motivation, norms and environmental behaviour : The dynamics of overarching goals
Steg, L.; Lindenberg, S.M.; Keizer, K.
2016-01-01
The understanding, prediction, and encouragement of pro-environmental behaviour (i.e., behaviour that impacts the environment as little as possible) depend to a large extent on understanding the motivational dynamics of pro-environmental behaviour. In this review paper, we discuss the state of the
An effective field study of the magnetic properties and critical behaviour at the surface Ising film
Bengrine, M.; Benyoussef, A.; Ez-Zahraouy, H.; Mhirech, F.
1998-09-01
The influence of corrugation and disorder at the surface on the critical behaviour of a ferromagnetic spin-1/2 Ising film is investigated using mean-field theory and finite cluster approximation. It is found that the critical surface exponent β 1 follows closely the one of a perfect surface, in the two cases: corrugated surface and random equiprobable coupling surface. However, in the case of flat surface with random interactions the surface critical exponent β 1 depends on the concentration p of the strong interaction for p>p c =0,5, while for p≤p c , such critical exponent is independent on the value of p and is equal to the one of the perfect surface. Moreover, in the case of corrugated surface, the effective exponent for a layer z, β eff J(z,n), is calculated as a function of the number of steps at the surface. (author)
Critical behaviour of SU(n) quantum chains and topological non-linear σ-models
Affleck, I.; British Columbia Univ., Vancouver
1988-01-01
The critical behaviour of SU(n) quantum ''spin'' chains, Wess-Zumino-Witten σ-models and grassmanian σ-models at topological angle θ = π (of possible relevance to the quantum Hall effect) is reexamined. It is argued that an additional Z n symmetry is generally necessary to stabilize the massless phase. This symmetry is not present for the σ-models for n>2 and is only present for certain representations of ''spin'' chains. (orig.)
Anomalous quantum critical spin dynamics in YFe2Al10
Huang, K.; Tan, C.; Zhang, J.; Ding, Z.; MacLaughlin, D. E.; Bernal, O. O.; Ho, P.-C.; Baines, C.; Wu, L. S.; Aronson, M. C.; Shu, L.
2018-04-01
We report results of a muon spin relaxation (μ SR ) study of YFe2Al10 , a quasi-two-dimensional (2D) nearly ferromagnetic metal in which unconventional quantum critical behavior is observed. No static Fe2 + magnetism, with or without long-range order, is found down to 19 mK. The dynamic muon spin relaxation rate λ exhibits power-law divergences in temperature and magnetic field, the latter for fields that are too weak to affect the electronic spin dynamics directly. We attribute this to the proportionality of λ (ωμ,T ) to the dynamic structure factor S (ωμ,T ) , where ωμ≈105-107s-1 is the muon Zeeman frequency. These results suggest critical divergences of S (ωμ,T ) in both temperature and frequency. Power-law scaling and a 2D dissipative quantum XY model both yield forms for S (ω ,T ) that agree with neutron scattering data (ω ≈1012s-1 ). Extrapolation to μ SR frequencies agrees semiquantitatively with the observed temperature dependence of λ (ωμ,T ) , but predicts frequency independence for ωμ≪T , in extreme disagreement with experiment. We conclude that the quantum critical spin dynamics of YFe2Al10 is not well understood at low frequencies.
Perski, Olga; Blandford, Ann; West, Robert; Michie, Susan
2017-06-01
"Engagement" with digital behaviour change interventions (DBCIs) is considered important for their effectiveness. Evaluating engagement is therefore a priority; however, a shared understanding of how to usefully conceptualise engagement is lacking. This review aimed to synthesise literature on engagement to identify key conceptualisations and to develop an integrative conceptual framework involving potential direct and indirect influences on engagement and relationships between engagement and intervention effectiveness. Four electronic databases (Ovid MEDLINE, PsycINFO, ISI Web of Knowledge, ScienceDirect) were searched in November 2015. We identified 117 articles that met the inclusion criteria: studies employing experimental or non-experimental designs with adult participants explicitly or implicitly referring to engagement with DBCIs, digital games or technology. Data were synthesised using principles from critical interpretive synthesis. Engagement with DBCIs is conceptualised in terms of both experiential and behavioural aspects. A conceptual framework is proposed in which engagement with a DBCI is influenced by the DBCI itself (content and delivery), the context (the setting in which the DBCI is used and the population using it) and the behaviour that the DBCI is targeting. The context and "mechanisms of action" may moderate the influence of the DBCI on engagement. Engagement, in turn, moderates the influence of the DBCI on those mechanisms of action. In the research literature, engagement with DBCIs has been conceptualised in terms of both experience and behaviour and sits within a complex system involving the DBCI, the context of use, the mechanisms of action of the DBCI and the target behaviour.
Holmes, Dave; Murray, Stuart J
2011-04-01
Drawing on the works of Erving Goffman and Michel Foucault, this article presents part of the results of a qualitative study conducted in a forensic psychiatry setting. For many years, behaviour modification programmes (BMPs) have been subjected to scrutiny and harsh criticism on the part of researchers, clinicians and professional organizations. Nevertheless, BMPs continue to be in vogue in some 'total' institutions, such as psychiatric hospitals and prisons. Discourse analysis of mute evidence available in situ was used to critically look at behaviour modification programmes. Compelling examples of behaviour modification care plans are used to illustrate our critical analysis and to support our claim that BMPs violate both scientific and ethical norms in the name of doing 'what is best' for the patients. We argue that the continued use of BMPs is not only flawed from a scientific perspective, but constitutes an unethical approach to the management of nursing care for mentally ill offenders. Nurse managers need to be aware that BMPs violate ethical standards in nursing. As a consequence, they should overtly question the use of these approaches in psychiatric nursing. © 2011 The Authors. Journal compilation © 2011 Blackwell Publishing Ltd.
Kwan, Bethany M; Bryan, Angela D; Sheeran, Paschal
2018-01-25
Exercise behaviour change involves multiple experiences with success and failure. The Model of Action Phases (MAP) offers a dynamic account of how success and failure influence both immediate evaluations and future decisions and actions. However, predictions from the MAP have not been formally tested. A longitudinal daily diary study was used to examine how post-behaviour evaluations of exercise success and failure influence subsequent exercise intentions and behaviour. Participants (N = 104) set exercise goals, and then kept a daily online exercise diary for four weeks. Participants self-reported exercise behaviour, affective response to exercise, self-evaluations after success or failure at following through on intentions to exercise, and intentions to exercise in the next week. Multilevel modelling revealed significant within- and between-participant relationships among post-behaviour evaluations, intentions and subsequent behaviour. Findings supported MAP-derived predictions about how success and failure at exercise are associated with feelings about exercise and the self, and inform subsequent exercise intentions and behaviour. Positive post-behaviour evaluations of success or failure may stabilise positive intentions and aid maintenance of exercise behaviour. Implications of these MAP-based findings for intervention design are discussed.
Quantum Critical Point revisited by the Dynamical Mean Field Theory
Xu, Wenhu; Kotliar, Gabriel; Tsvelik, Alexei
Dynamical mean field theory is used to study the quantum critical point (QCP) in the doped Hubbard model on a square lattice. The QCP is characterized by a universal scaling form of the self energy and a spin density wave instability at an incommensurate wave vector. The scaling form unifies the low energy kink and the high energy waterfall feature in the spectral function, while the spin dynamics includes both the critical incommensurate and high energy antiferromagnetic paramagnons. We use the frequency dependent four-point correlation function of spin operators to calculate the momentum dependent correction to the electron self energy. Our results reveal a substantial difference with the calculations based on the Spin-Fermion model which indicates that the frequency dependence of the the quasiparitcle-paramagnon vertices is an important factor. The authors are supported by Center for Computational Design of Functional Strongly Correlated Materials and Theoretical Spectroscopy under DOE Grant DE-FOA-0001276.
Quantum critical point revisited by dynamical mean-field theory
Xu, Wenhu; Kotliar, Gabriel; Tsvelik, Alexei M.
2017-03-01
Dynamical mean-field theory is used to study the quantum critical point (QCP) in the doped Hubbard model on a square lattice. The QCP is characterized by a universal scaling form of the self-energy and a spin density wave instability at an incommensurate wave vector. The scaling form unifies the low-energy kink and the high-energy waterfall feature in the spectral function, while the spin dynamics includes both the critical incommensurate and high-energy antiferromagnetic paramagnons. We use the frequency-dependent four-point correlation function of spin operators to calculate the momentum-dependent correction to the electron self-energy. By comparing with the calculations based on the spin-fermion model, our results indicate the frequency dependence of the quasiparticle-paramagnon vertices is an important factor to capture the momentum dependence in quasiparticle scattering.
Quantum critical point revisited by dynamical mean-field theory
Xu, Wenhu; Kotliar, Gabriel; Rutgers University, Piscataway, NJ; Tsvelik, Alexei M.
2017-01-01
Dynamical mean-field theory is used to study the quantum critical point (QCP) in the doped Hubbard model on a square lattice. We characterize the QCP by a universal scaling form of the self-energy and a spin density wave instability at an incommensurate wave vector. The scaling form unifies the low-energy kink and the high-energy waterfall feature in the spectral function, while the spin dynamics includes both the critical incommensurate and high-energy antiferromagnetic paramagnons. Here, we use the frequency-dependent four-point correlation function of spin operators to calculate the momentum-dependent correction to the electron self-energy. Furthermore, by comparing with the calculations based on the spin-fermion model, our results indicate the frequency dependence of the quasiparticle-paramagnon vertices is an important factor to capture the momentum dependence in quasiparticle scattering.
The complex dynamics of wishful thinking: the critical positivity ratio.
Brown, Nicholas J L; Sokal, Alan D; Friedman, Harris L
2013-12-01
We examine critically the claims made by Fredrickson and Losada (2005) concerning the construct known as the "positivity ratio." We find no theoretical or empirical justification for the use of differential equations drawn from fluid dynamics, a subfield of physics, to describe changes in human emotions over time; furthermore, we demonstrate that the purported application of these equations contains numerous fundamental conceptual and mathematical errors. The lack of relevance of these equations and their incorrect application lead us to conclude that Fredrickson and Losada's claim to have demonstrated the existence of a critical minimum positivity ratio of 2.9013 is entirely unfounded. More generally, we urge future researchers to exercise caution in the use of advanced mathematical tools, such as nonlinear dynamics, and in particular to verify that the elementary conditions for their valid application have been met. PsycINFO Database Record (c) 2013 APA, all rights reserved.
Post Critical Behaviour of a Simple Non-Linear System in a Cross Wind
Náprstek, Jiří; Pospíšil, Stanislav
2011-01-01
Roč. 18, 3/4 (2011), s. 193-201 ISSN 1802-1484 R&D Projects: GA AV ČR(CZ) IAA200710902; GA ČR(CZ) GA103/09/0094 Institutional research plan: CEZ:AV0Z20710524 Keywords : limit cycles * dynamic stability * post-critical effects * non-linear dynamics Subject RIV: JN - Civil Engineering
Dynamical behaviour of gaseous halo in a disk galaxy
Ikeuchi, S.; Habe, A.
1981-01-01
Assuming that the gas in the halo of a disk galaxy is supplied from the disk as a hot gas, the authors have studied its dynamical and thermal behaviour by means of a time dependent, two-dimensional hydrodynamic code. They suppose the following boundary conditions at the disk. (i) The hot gas with the temperature Tsub(d) and the density nsub(d) is uniform at r=4-12 kpc in the disk and it is time independent. (ii) This hot gas rotates with the stellar disk in the same velocity. (iii) This hot gas can escape freely from the disk to the halo. These conditions will be verified if the filling factor of hot gas is so large as f=0.5-0.8, as proposed by McKee and Ostriker (1977). The gas motion in the halo has been studied for wider ranges of gas temperature and its density at the disk than previously studied. At the same time, the authors have clarified the observability of various types of gaseous haloes and discuss the roles of gaseous halo on the evolution of galaxies. (Auth.)
SALLY, Dynamic Behaviour of Reactor Cooling Channel by Point Model
Reiche, Chr.; Ziegenbein, D.
1981-01-01
1 - Nature of the physical problem solved: The dynamical behaviour of a cooling channel is calculated. Starting from an equilibrium state a perturbation is introduced into the system. That may be an outer reactivity perturbation or a change in the coolant velocity or in the coolant temperature. The neutron kinetics is treated in the framework of the one-point model. The cooling channel consists of a cladded and cooled fuel rod. The temperature distribution is taken into account as an array above a mesh of radial zones and axial layers. Heat transfer is considered in radial direction only, the thermodynamical coupling of the different layers is obtained by the coolant flow. The thermal material parameters are considered to be temperature independent. Reactivity feedback is introduced by means of reactivity coefficients for fuel, canning, and coolant. Doppler broadening is included. The first cooling cycle can be taken into account by a simple model. 2 - Method of solution: The integration of the point kinetics equations is done numerically by the P11 scheme. The system of temperature equations with constant heat resistance coefficients is solved by the method of factorization. 3 - Restrictions on the complexity of the problem: Given limits are: 10 radial fuel zones, 25 axial layers, 6 groups of delayed neutrons
Yin, T.; Tyas, A.; Plekhov, O.; Terekhina, A.; Susmel, L.
2015-01-01
Highlights: • The proposed method is successful in estimating dynamic strength of metals. • The critical distance varies as the loading/strain/displacement rate increases. • The reference strength varies as the loading/strain/displacement rate increases. • This method is recommended to be used with safety factors larger than 1.25. - Abstract: In the present study the linear-elastic Theory of Critical Distances (TCD) is reformulated to make it suitable for predicting the strength of notched metallic materials subjected to dynamic loading. The accuracy and reliability of the proposed reformulation of the TCD was checked against a number of experimental results generated by testing, under different loading/strain rates, notched cylindrical samples of aluminium alloy 6063-T5, titanium alloy Ti–6Al–4V, aluminium alloy AlMg6, and an AlMn alloy. To further validate the proposed design method also different data sets taken from the literature were considered. Such an extensive validation exercise allowed us to prove that the proposed reformulation of the TCD is successful in predicting the dynamic strength of notched metallic materials, this approach proving to be capable of estimates falling within an error interval of ±20%. Such a high level of accuracy is certainly remarkable, especially in light of the fact that it was reached without the need for explicitly modelling the stress vs. strain dynamic behaviour of the investigated ductile metals
Semi-analytical approach to modelling the dynamic behaviour of soil excited by embedded foundations
Bucinskas, Paulius; Andersen, Lars Vabbersgaard
2017-01-01
The underlying soil has a significant effect on the dynamic behaviour of structures. The paper proposes a semi-analytical approach based on a Green’s function solution in frequency–wavenumber domain. The procedure allows calculating the dynamic stiffness for points on the soil surface as well...... are analysed. It is determined how simplification of the numerical model affects the overall dynamic behaviour. © 2017 The Authors. Published by Elsevier Ltd....
Review of the dynamic behaviour of sports balls during normal and oblique impacts
Haron, Muhammad Adli; Jailani, Azrol; Abdullah, Nik Ahmad Faris Nik; Ismail, Rafis Suizwan; Rahim, Shayfull Zamree Abd; Ghazali, Mohd Fathullah
2017-09-01
In this paper are review of impact experiment to study the dynamic behaviour of sports ball during oblique and normal impacts. In previous studies, the investigation was done on the dynamic behaviour of a sports ball during oblique and normal impacts from experimental, numerical, and theoretical viewpoints. The experimental results are analysed and compared with the theories, in order to understand the dynamics behaviours based on the phenomenological occurrence. Throughout the experimental studies previously, there are results of dynamics behaviours examined by many researchers such as the coefficient of restitution, tangential coefficient, local deformation, dynamic impact force, contact time, angle of impact (inbound and rebound), spin rate of the ball, ball stiffness and damping coefficient which dependable of the initial or impact velocity.
Chen Yan; Chen Yong; Zhang Kezhi
2009-01-01
We study the dynamic behaviour of Bose-Einstein condensates with two- and three-atom interactions in optical lattices with analytical and numerical methods. It is found that the steady-state relative population displays tuning-fork bifurcation when the system parameters are changed to certain critical values. In particular, the existence of the three-body interaction not only transforms the bifurcation point of the system but also greatly affects the macroscopic quantum self-trapping behaviours associated with the critically stable steady-state solution. In addition, we investigated the influence of the initial conditions, three-body interaction, and the energy bias on the macroscopic quantum self-trapping. Finally, by applying the periodic modulation on the energy bias, we observed that the relative population oscillation exhibits a process from order to chaos, via a series of period-doubling bifurcations.
Network Randomization and Dynamic Defense for Critical Infrastructure Systems
Chavez, Adrian R. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Martin, Mitchell Tyler [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Hamlet, Jason [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Stout, William M.S. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Lee, Erik [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)
2015-04-01
Critical Infrastructure control systems continue to foster predictable communication paths, static configurations, and unpatched systems that allow easy access to our nation's most critical assets. This makes them attractive targets for cyber intrusion. We seek to address these attack vectors by automatically randomizing network settings, randomizing applications on the end devices themselves, and dynamically defending these systems against active attacks. Applying these protective measures will convert control systems into moving targets that proactively defend themselves against attack. Sandia National Laboratories has led this effort by gathering operational and technical requirements from Tennessee Valley Authority (TVA) and performing research and development to create a proof-of-concept solution. Our proof-of-concept has been tested in a laboratory environment with over 300 nodes. The vision of this project is to enhance control system security by converting existing control systems into moving targets and building these security measures into future systems while meeting the unique constraints that control systems face.
Nonequilibrium dynamic critical scaling of the quantum Ising chain.
Kolodrubetz, Michael; Clark, Bryan K; Huse, David A
2012-07-06
We solve for the time-dependent finite-size scaling functions of the one-dimensional transverse-field Ising chain during a linear-in-time ramp of the field through the quantum critical point. We then simulate Mott-insulating bosons in a tilted potential, an experimentally studied system in the same equilibrium universality class, and demonstrate that universality holds for the dynamics as well. We find qualitatively athermal features of the scaling functions, such as negative spin correlations, and we show that they should be robustly observable within present cold atom experiments.
Critical bifurcation surfaces of 3D discrete dynamics
Michael Sonis
2000-01-01
Full Text Available This paper deals with the analytical representation of bifurcations of each 3D discrete dynamics depending on the set of bifurcation parameters. The procedure of bifurcation analysis proposed in this paper represents the 3D elaboration and specification of the general algorithm of the n-dimensional linear bifurcation analysis proposed by the author earlier. It is proven that 3D domain of asymptotic stability (attraction of the fixed point for a given 3D discrete dynamics is bounded by three critical bifurcation surfaces: the divergence, flip and flutter surfaces. The analytical construction of these surfaces is achieved with the help of classical Routh–Hurvitz conditions of asymptotic stability. As an application the adjustment process proposed by T. Puu for the Cournot oligopoly model is considered in detail.
Phase dynamics of low critical current density YBCO Josephson junctions
Massarotti, D., E-mail: dmassarotti@na.infn.it [Dipartimento di Fisica, Università degli Studi di Napoli Federico II, Via Cinthia, 80126 Napoli (Italy); CNR-SPIN UOS Napoli, Complesso Universitario di Monte Sant’Angelo, Via Cinthia, 80126 Napoli (Italy); Stornaiuolo, D. [Dipartimento di Fisica, Università degli Studi di Napoli Federico II, Via Cinthia, 80126 Napoli (Italy); Rotoli, G. [Dipartimento di Ingegneria Industriale e dell’Informazione, Seconda Università di Napoli, Via Roma 29, 81031 Aversa (CE) (Italy); Carillo, F. [Nest, Scuola Normale Superiore, Piazza San Silvestro 12, 56126 Pisa (Italy); Galletti, L. [Dipartimento di Fisica, Università degli Studi di Napoli Federico II, Via Cinthia, 80126 Napoli (Italy); CNR-SPIN UOS Napoli, Complesso Universitario di Monte Sant’Angelo, Via Cinthia, 80126 Napoli (Italy); Longobardi, L. [Dipartimento di Ingegneria Industriale e dell’Informazione, Seconda Università di Napoli, Via Roma 29, 81031 Aversa (CE) (Italy); American Physical Society, 1 Research Road, Ridge, NY 11961 (United States); Beltram, F. [Nest, Scuola Normale Superiore, Piazza San Silvestro 12, 56126 Pisa (Italy); Tafuri, F. [CNR-SPIN UOS Napoli, Complesso Universitario di Monte Sant’Angelo, Via Cinthia, 80126 Napoli (Italy); Dipartimento di Ingegneria Industriale e dell’Informazione, Seconda Università di Napoli, Via Roma 29, 81031 Aversa (CE) (Italy)
2014-08-15
Highlights: • We study the phase dynamics of YBaCuO Josephson junctions using various tools. • We derive information on the dissipation in a wide range of transport parameters. • Dissipation in such devices can be described by a frequency dependent damping model. • The use of different substrates allows us to tune the shell circuit. - Abstract: High critical temperature superconductors (HTS) based devices can have impact in the study of the phase dynamics of Josephson junctions (JJs) thanks to the wide range of junction parameters they offer and to their unconventional properties. Measurements of current–voltage characteristics and of switching current distributions constitute a direct way to classify different regimes of the phase dynamics and of the transport, also in nontrivial case of the moderately damped regime (MDR). MDR is going to be more and more common in JJs with advances in nanopatterning superconductors and synthesizing novel hybrid systems. Distinctive signatures of macroscopic quantum tunneling and of thermal activation in presence of different tunable levels of dissipation have been detected in YBCO grain boundary JJs. Experimental data are supported by Monte Carlo simulations of the phase dynamics, in a wide range of temperatures and dissipation levels. This allows us to quantify dissipation in the MDR and partially reconstruct a phase diagram as guideline for a wide range of moderately damped systems.
Knoeri, Christof; Wäger, Patrick A; Stamp, Anna; Althaus, Hans-Joerg; Weil, Marcel
2013-09-01
Emerging technologies such as information and communication-, photovoltaic- or battery technologies are expected to increase significantly the demand for scarce metals in the near future. The recently developed methods to evaluate the criticality of mineral raw materials typically provide a 'snapshot' of the criticality of a certain material at one point in time by using static indicators both for supply risk and for the impacts of supply restrictions. While allowing for insights into the mechanisms behind the criticality of raw materials, these methods cannot account for dynamic changes in products and/or activities over time. In this paper we propose a conceptual framework intended to overcome these limitations by including the dynamic interactions between different possible demand and supply configurations. The framework integrates an agent-based behaviour model, where demand emerges from individual agent decisions and interaction, into a dynamic material flow model, representing the materials' stocks and flows. Within the framework, the environmental implications of substitution decisions are evaluated by applying life-cycle assessment methodology. The approach makes a first step towards a dynamic criticality assessment and will enhance the understanding of industrial substitution decisions and environmental implications related to critical metals. We discuss the potential and limitation of such an approach in contrast to state-of-the-art methods and how it might lead to criticality assessments tailored to the specific circumstances of single industrial sectors or individual companies. Copyright © 2013 Elsevier B.V. All rights reserved.
Ising critical behaviour in the one-dimensional frustrated quantum XY model
Granato, E.
1993-06-01
A generalization of the one-dimensional frustrated quantum XY model is considered in which the inter and intra-chain coupling constants of the two infinite XY (planar rotor) chains have different strengths. The model can describe the superconductor-insulator transition due to charging effects in a ladder of Josephson junctions in a magnetic field with half a flux quantum per plaquette. From a fluctuation-effective action, this transition is expected to be in the universality class of the two-dimensional classical XY-Ising model. The critical behaviour is studied using a Monte Carlo transfer matrix applied to the path-integral representation of the model and a finite-size-scaling analysis of data on small system sizes. It is found that, unlike the previous studied case of equal inter and intra-chain coupling constants, the XY and Ising-like excitations of the quantum model decouple for large interchain coupling, giving rise to pure Ising model critical behaviour for the chirality order parameter in good agreement with the results for the XY-Ising model. (author). 18 refs, 4 figs
Unstable dynamics, nonequilibrium phases, and criticality in networked excitable media
Franciscis, S. de; Torres, J. J.; Marro, J.
2010-01-01
Excitable systems are of great theoretical and practical interest in mathematics, physics, chemistry, and biology. Here, we numerically study models of excitable media, namely, networks whose nodes may occasionally be dormant and the connection weights are allowed to vary with the system activity on a short-time scale, which is a convenient and realistic representation. The resulting global activity is quite sensitive to stimuli and eventually becomes unstable also in the absence of any stimuli. Outstanding consequences of such unstable dynamics are the spontaneous occurrence of various nonequilibrium phases--including associative-memory phases and one in which the global activity wanders irregularly, e.g., chaotically among all or part of the dynamic attractors--and 1/f noise as the system is driven into the phase region corresponding to the most irregular behavior. A net result is resilience which results in an efficient search in the model attractor space that can explain the origin of some observed behavior in neural, genetic, and ill-condensed matter systems. By extensive computer simulation we also address a previously conjectured relation between observed power-law distributions and the possible occurrence of a ''critical state'' during functionality of, e.g., cortical networks, and describe the precise nature of such criticality in the model which may serve to guide future experiments.
General Critical Properties of the Dynamics of Scientific Discovery
Bettencourt, L. M. A. (LANL); Kaiser, D. I. (MIT)
2011-05-31
Scientific fields are difficult to define and compare, yet there is a general sense that they undergo similar stages of development. From this point of view it becomes important to determine if these superficial similarities can be translated into a general framework that would quantify the general advent and subsequent dynamics of scientific ideas. Such a framework would have important practical applications of allowing us to compare fields that superficially may appear different, in terms of their subject matter, research techniques, typical collaboration size, etc. Particularh' important in a field's history is the moment at which conceptual and technical unification allows widespread exchange of ideas and collaboration, at which point networks of collaboration show the analog of a percolation phenomenon, developing a giant connected component containing most authors. Here we investigate the generality of this topological transition in the collaboration structure of scientific fields as they grow and become denser. We develop a general theoretical framework in which each scientific field is an instantiation of the same large-scale topological critical phenomenon. We consider whether the evidence from a variety of specific fields is consistent with this picture, and estimate critical exponents associated with the transition. We then discuss the generality of the phenomenon and to what extent we may expect other scientific fields — including very large ones — to follow the same dynamics.
Measurement and analysis on dynamic behaviour of parallel-plate assembly in nuclear reactors
Chen Junjie; Guo Changqing; Zou Changchuan
1997-01-01
Measurement and analysis on dynamic behaviour of parallel-plate assembly in nuclear reactors have been explored. The electromagnetic method, a new method of measuring and analysing dynamic behaviour with the parallel-plate assembly as the structure of multi-parallel-beams joining with single-beam, has been presented. Theoretical analysis and computation results of dry-modal natural frequencies show good agreement with experimental measurements
Dynamic shifting in thalamocortical processing during different behavioural states.
Nicolelis, Miguel A L; Fanselow, Erika E
2002-01-01
Recent experiments in our laboratory have indicated that as rats shift the behavioural strategy employed to explore their surrounding environment, there is a parallel change in the physiological properties of the neuronal ensembles that define the main thalamocortical loop of the trigeminal somatosensory system. Based on experimental evidence from several laboratories, we propose that this concurrent shift in behavioural strategy and thalamocortical physiological properties provides rats with...
Sanlı, Ceyda; Saitoh, Kuniyasu; Luding, Stefan; van der Meer, Devaraj
2014-09-01
When a densely packed monolayer of macroscopic spheres floats on chaotic capillary Faraday waves, a coexistence of large scale convective motion and caging dynamics typical for glassy systems is observed. We subtract the convective mean flow using a coarse graining (homogenization) method and reveal subdiffusion for the caging time scales followed by a diffusive regime at later times. We apply the methods developed to study dynamic heterogeneity and show that the typical time and length scales of the fluctuations due to rearrangements of observed particle groups significantly increase when the system approaches its largest experimentally accessible packing concentration. To connect the system to the dynamic criticality literature, we fit power laws to our results. The resultant critical exponents are consistent with those found in densely packed suspensions of colloids.
Static and Dynamic Verification of Critical Software for Space Applications
Moreira, F.; Maia, R.; Costa, D.; Duro, N.; Rodríguez-Dapena, P.; Hjortnaes, K.
Space technology is no longer used only for much specialised research activities or for sophisticated manned space missions. Modern society relies more and more on space technology and applications for every day activities. Worldwide telecommunications, Earth observation, navigation and remote sensing are only a few examples of space applications on which we rely daily. The European driven global navigation system Galileo and its associated applications, e.g. air traffic management, vessel and car navigation, will significantly expand the already stringent safety requirements for space based applications Apart from their usefulness and practical applications, every single piece of onboard software deployed into the space represents an enormous investment. With a long lifetime operation and being extremely difficult to maintain and upgrade, at least when comparing with "mainstream" software development, the importance of ensuring their correctness before deployment is immense. Verification &Validation techniques and technologies have a key role in ensuring that the onboard software is correct and error free, or at least free from errors that can potentially lead to catastrophic failures. Many RAMS techniques including both static criticality analysis and dynamic verification techniques have been used as a means to verify and validate critical software and to ensure its correctness. But, traditionally, these have been isolated applied. One of the main reasons is the immaturity of this field in what concerns to its application to the increasing software product(s) within space systems. This paper presents an innovative way of combining both static and dynamic techniques exploiting their synergy and complementarity for software fault removal. The methodology proposed is based on the combination of Software FMEA and FTA with Fault-injection techniques. The case study herein described is implemented with support from two tools: The SoftCare tool for the SFMEA and SFTA
Neural correlates of dynamically evolving interpersonal ties predict prosocial behaviour
Johannes Jacobus Fahrenfort
2012-03-01
Full Text Available There is a growing interest for the determinants of human choice behaviour in social settings. Upon initial contact, investment choices in social settings can be inherently risky, as the degree to which the other person will reciprocate is unknown. Nevertheless, people have been shown to exhibit prosocial behaviour even in one-shot laboratory settings where all interaction has been taken away. A logical step has been to link such behaviour to trait empathy-related neurobiological networks. However, as a social interaction unfolds, the degree of uncertainty with respect to the expected payoff of choice behaviour may change as a function of the interaction. Here we attempt to capture this factor. We show that the interpersonal tie one develops with another person during interaction - rather than trait empathy - motivates investment in a public good that is shared with an anonymous interaction partner. We examined how individual differences in trait empathy and interpersonal ties modulate neural responses to imposed monetary sharing. After, but not before interaction in a public good game, sharing prompted activation of neural systems associated with reward (striatum, empathy (anterior insular cortex [AIC] and anterior cingulate cortex [ACC] as well as altruism and social significance (posterior superior temporal sulcus [pSTS]. Although these activations could be linked to both empathy and interpersonal ties, only tie-related pSTS activation predicted prosocial behaviour during subsequent interaction, suggesting a neural substrate for keeping track of social relevance.
The dynamics of consumer behaviour. On habit, discontent, and other fish to fry.
Scholderer, Joachim; Trondsen, Torbjørn
2008-11-01
Recent research has drawn attention to the role of past behaviour and habit in the overall structure of consumer behaviour. We argue that in cross-sectional data past behaviour and habit must be confounded with present beliefs and attitudes when the behaviour in question has been enacted numerous times before. To disentangle the effects, longitudinal data were collected from a large panel of Norwegian consumers (effective N=4184) in 1996, 2000, and 2004. Cross-lagged panel analysis indicated that higher consumption of traditional seafood led to increasingly negative evaluations of the product supply. These negative evaluations, in turn, prompted substitution of traditional seafood with newly available, processed seafood products and an increasing dominance of aqua-cultured species. The theoretical discussion focuses on the inability of static models of consumer behaviour (in particular, the theory of planned behaviour) to capture such dynamic effects. Marketing and policy implications related to the changing structure of the seafood market are outlined.
Critical behaviour of continuous phase transitions with infinitely many absorbing states
Hua Dayin; Wang Lieyan; Chen Ting
2006-01-01
A lattice gas model is proposed for the A 2 + 2B 2 → 2B 2 A reaction system with particle diffusion. In the model, A 2 dissociates in the random dimer-filling mechanism and B 2 dissociation is in the end-on dimer-filling mechanism. A reactive window appears and the system exhibits a continuous phase transition from a reactive state to a covered state with infinitely many absorbing states. When the diffusion of particle A and AB is included, there are still infinitely many absorbing states for the continuous phase transition, but it is found that the critical behaviour changes from the directed percolation (DP) class to the pair contact process with diffusion (PCPD) class
Dynamical behaviour of neuronal networks iterated with memory
Melatagia, P.M.; Ndoundam, R.; Tchuente, M.
2005-11-01
We study memory iteration where the updating consider a longer history of each site and the set of interaction matrices is palindromic. We analyze two different ways of updating the networks: parallel iteration with memory and sequential iteration with memory that we introduce in this paper. For parallel iteration, we define Lyapunov functional which permits us to characterize the periods behaviour and explicitly bounds the transient lengths of neural networks iterated with memory. For sequential iteration, we use an algebraic invariant to characterize the periods behaviour of the studied model of neural computation. (author)
Wang Lin
2015-01-01
Full Text Available Ti-5553 alloy is a near-beta titanium alloy with high strength and high fracture toughness. In this paper, the dynamic behaviour and shock-induced martensite phase transformation of Ti-5553 alloy with alpha/beta phases were investigated. Split Hopkinson Pressure Bar was employed to investigate the dynamic properties. Microstructure evolutions were characterized by Scanning Electronic Microscopy and Transmission Electron Microscope. The experimental results have demonstrated that Ti-5553 alloy with alpha/beta phases exhibits various strain rate hardening effects, both failure through adiabatic shear band. Ti-5553 alloy with Widmannstatten microstructure exhibit more obvious strain rate hardening effect, lower critical strain rate for ASB nucleation, compared with the alloy with Bimodal microstructures. Under dynamic compression, shock-induced beta to alpha” martensite transformation occurs.
Brymer, Eric; Davids, Keith
2013-01-01
This paper proposes how the theoretical framework of ecological dynamics can provide an influential model of the learner and the learning process to pre-empt effective behaviour changes. Here we argue that ecological dynamics supports a well-established model of the learner ideally suited to the environmental education context because of its…
Dynamic behaviour of AA 2024 under blast loading : experiments and simulations
Mediavilla Varas, J.; Soetens, F.; van der Meulen, Ronald; Kroon, E.; Aanhold, van J.E.; Soetens, F.; Katgerman, L.
2010-01-01
The dynamic behaviour of AA2024-T3 is investigated. Dynamic tensile tests using a servo-hydraulic and a light weight shock testing machine (LSM) have been performed. The servo-hydraulic test machine proves to be more reliable and reaches higher strain rates. Neither test revealed any strain rate
Choreographies and Behavioural Contracts on the Way to Dynamic Updates
Mario Bravetti
2014-11-01
Full Text Available We survey our work on choreographies and behavioural contracts in multiparty interactions. In particular theories of behavioural contracts are presented which enable reasoning about correct service composition (contract compliance and service substitutability (contract refinement preorder under different assumptions concerning service communication: synchronous address or name based communication with patient non-preemptable or impatient invocations, or asynchronous communication. Correspondingly relations between behavioural contracts and choreographic descriptions are considered, where a contract for each communicating party is, e.g., derived by projection. The considered relations are induced as the maximal preoders which preserve contract compliance and global traces: we show maximality to hold (permitting services to be discovered/substituted independently for each party when contract refinement preorders with all the above asymmetric communication means are considered and, instead, not to hold if the standard symmetric CCS/pi-calculus communication is considered (or when directly relating choreographies to behavioral contracts via a preorder, no matter the communication mean. The obtained maximal preorders are then characterized in terms of a new form of testing, called compliance testing, where not only tests must succeed but also the system under test (thus relating to controllability theory, and compared with classical preorders such as may/must testing, trace inclusion, etc. Finally, recent work about adaptable choreographies and behavioural contracts is presented, where the theory above is extended to update mechanisms allowing choreographies/contracts to be modified at run-time by internal (self-adaptation or external intervention.
Cristescu, C.P.; Mereu, B.; Stan, Cristina; Agop, M.
2009-01-01
Experimental investigations and theoretical analysis on the dynamics of a metal-oxide semiconductor heterostructure used as nonlinear capacity in a series RLC electric circuit are presented. A harmonic voltage perturbation can induce various nonlinear behaviours, particularly evolution to chaos by period doubling and torus destabilization. In this work we focus on the change in dynamics induced by a sinusoidal driving with constant frequency and variable amplitude. Theoretical treatment based on the microscopic mechanisms involved led us to a dynamic system with a piecewise behaviour. Consequently, a model consisting of a nonlinear oscillator described by a piecewise second order ordinary differential equation is proposed. This kind of treatment is required by the asymmetry in the behaviour of the metal-oxide semiconductor with respect to the polarization of the perturbing voltage. The dynamics of the theoretical model is in good agreement with the experimental results. A connection with El Naschie's E-infinity space-time is established based on the interpretation of our experimental results as evidence of the importance of the golden mean criticality in the microscopic world.
Dynamic market behaviour of autonomous network based power systems
Jokic, A.; Wittebol, E.H.M.; Bosch, van den P.P.J.
2006-01-01
Dynamic models of real-time markets are important since they lead to additional insights of the behavior and stability of power system markets. The main topic of this paper is the analysis of real-time market dynamics in a novel power system structure that is based on the concept of autonomous
Aero dynamical and mechanical behaviour of the Savonius rotor
Aouachria, Z. [Batna Univ., (Algeria). Applied Energetic Physics Laboratory
2009-07-01
Although the Savonius wind turbine is not as efficient as the traditional Darrieus wind turbine, its rotor design has many advantages such as simple construction; acceptance of wind from all directions; high starting torque; operation at relatively low speed; and easy adaptation to urban sites. These advantages may outweigh its low efficiency and make it suitable for small-scale power requirements such as pumping and rural electrification. This paper presented a study of the aerodynamic behaviour of a Savonius rotor, based on blade pressure measurements. A two-dimensional analysis method was used to determine the aerodynamic strengths, which leads to the Magnus effect and the generation of the vibrations on the rotor. The study explained the vibratory behaviour of the rotor and proposed an antivibration system to protect the machine. 14 refs., 1 tab., 9 figs.
Dynamic behaviour of a typical PHWR under earthquake load conditions
Fischer, U.; Brandt, K.; Krutzik, N.J.
1984-01-01
The paper deals with dynamic calculations for a PHWR reactor building founded on rock and on a base isolation system. The zero period accelerations, displacements, mode shapes and the floor response spectra of both calculations are compared. (Author) [pt
Behaviour of steel arch supports under dynamic effects of rockbursts
Horyl, P.; Šňupárek, Richard
2007-01-01
Roč. 116, č. 3 (2007), s. 119-128 ISSN 0371-7844 Institutional research plan: CEZ:AV0Z30860518 Keywords : steel arch support * rockbursts * dynamic loading Subject RIV: DH - Mining , incl. Coal Mining
Benato, Alberto; Stoppato, Anna; Bracco, Stefano
2014-01-01
Highlights: • Two procedures aimed at simulating the dynamic behaviour of power plants are compared. • They both are aimed at predicting the residual life of plant devices. • A single pressure gas-steam combined plant has been modelled. • A good correspondence has been found despite the different approaches used. - Abstract: The deregulated energy market and the increasing quota of electrical capacity covered by non-predictable renewable sources require strongly irregular and discontinuous operation of thermoelectric plants to satisfy users demand and compensate the variability of renewable sources. As a consequence, due to thermo-mechanical fatigue, creep and corrosion, a lifetime reduction of the most critical components occurs. The availability of a procedure able to predict the residual life of plant devices is necessary to assist the management decisions about power plants’ operation and maintenance scheduling. The first step of this procedure is the capability of simulating the plant behaviour versus time by evaluating the trends of the main thermodynamic parameters that describe the plant operation during different transient periods. In this context, the main contribution of the present paper is to propose a complete procedure able to simulate the plant dynamic behaviour and estimate the residual life reduction of some components. Indeed, two different models, developed by two different research groups, of the same single pressure heat recovery steam generator unit are presented and utilized to characterize the dynamic behaviour of the above mentioned power plant. The main thermodynamic variables during different transient operation conditions are predicted and good correspondence between the two methods is obtained. It can be also noted that, when the geometry and size of the devices are considered, the thermal inertia related to heat exchangers tubes, pipes and other physical masses causes a delay in the system response. Moreover, a residual life
Manstead, Antony S R
2011-09-01
In this paper, I reflect on past papers published in the British Journal of Social Psychology (BJSP) that have played a role in the development of the theory of reasoned action (TRA) and the theory of planned behaviour (TPB). I focus on seven papers that fall into five categories: (1) those that critique the TRA/TPB for taking insufficient account of social factors; (2) those that critique the models on the grounds that many social behaviours are 'habitual'; (3) those that critically examine the construct of perceived behavioural control; (4) those that argue for the importance of affective factors, which appear to be overlooked in the TRA/TPB; and (5) those that argue for the importance of studying the role of moderating factors and interaction effects in the TRA/TPB. I conclude that BJSP's traditional focus on criticism and theory development is one that benefits the journal and the field. ©2011 The British Psychological Society.
Einstein-Friedmann equation, nonlinear dynamics and chaotic behaviours
Tanaka, Yosuke; Nakano, Shingo; Ohta, Shigetoshi; Mori, Keisuke; Horiuchi, Tanji
2009-01-01
We have studied the Einstein-Friedmann equation [Case 1] on the basis of the bifurcation theory and shown that the chaotic behaviours in the Einstein-Friedmann equation [Case 1] are reduced to the pitchfork bifurcation and the homoclinic bifurcation. We have obtained the following results: (i) 'The chaos region diagram' (the p-λ plane) in the Einstein-Friedmann equation [Case 1]. (ii) 'The chaos inducing chart' of the homoclinic orbital systems in the unforced differential equations. We have discussed the non-integrable conditions in the Einstein-Friedmann equation and proposed the chaotic model: p=p 0 ρ n (n≥0). In case n≠0,1, the Einstein-Friedmann equation is not integrable and there may occur chaotic behaviours. The cosmological constant (λ) turns out to play important roles for the non-integrable condition in the Einstein-Friedmann equation and also for the pitchfork bifurcation and the homoclinic bifurcation in the relativistic field equation. With the use of the E-infinity theory, we have also discussed the physical quantities in the gravitational field equations, and obtained the formula logκ=-10(1/φ) 2 [1+(φ) 8 ]=-26.737, which is in nice agreement with the experiment (-26.730).
Analysis of construction dynamic plan using fuzzy critical path method
Kurij Kazimir V.
2014-01-01
Full Text Available Critical Path Method (CPM technique has become widely recognized as valuable tool for the planning and scheduling large construction projects. The aim of this paper is to present an analytical method for finding the Critical Path in the precedence network diagram where the duration of each activity is represented by a trapezoidal fuzzy number. This Fuzzy Critical Path Method (FCPM uses a defuzzification formula for trapezoidal fuzzy number and applies it on the total float (slack time for each activity in the fuzzy precedence network to find the critical path. The method presented in this paper is very effective in determining the critical activities and finding the critical paths.
Guilford, Tim; Wynn, Russell; McMinn, Miguel; Rodríguez, Ana; Fayet, Annette; Maurice, Lou; Jones, Alice; Meier, Rhiannon
2012-01-01
Using combined miniature archival light and salt-water immersion loggers, we characterise the year-round individual at-sea movements of Europe's only critically endangered seabird, the Balearic shearwater Puffinus mauretanicus, for the first time. Focusing on the non-breeding period, we show that all of the 26 breeding birds tracked from their breeding site on Mallorca in the Mediterranean Sea successfully made a 2–4 month migration into the Atlantic Ocean, where they utilised well-defined core areas off Portuguese and French coasts. As well as identifying high-risk areas in the Atlantic, our results confirm that breeding birds spend most of the year concentrated around productive waters of the Iberian shelf in the western Mediterranean. Migration phenology appeared largely unrelated to the subsequent (distinctly synchronous) breeding attempt, suggesting that any carry-over effects were compensated for during a long pre-laying period spent over winter in the Mediterranean. Using the light and salt-water immersion data alone we were also able to characterise the pattern of pre-laying visits to the colony in considerable detail, demonstrating that breeding pairs appear to coordinate their over-day visits using a high frequency of night-time visits throughout the winter. Our study shows that geolocation technology is a valuable tool for assessing the spatial distribution of risks to this critically endangered species, and also provides a low-impact method for remotely observing the detailed behaviour of seabird species that may be sensitive to disturbance from traditional study methods. PMID:22470471
Eva Barreira
2014-01-01
Full Text Available External Thermal Insulation Composite Systems (ETICS are often used in Europe. Despite its thermal advantages, low cost, and ease of application, this system has serious problems of biological growth causing the cladding defacement. Recent studies pointed that biological growth is due to high values of surface moisture content, which mostly results from the combined effect of exterior surface condensation, wind-driven rain, and drying process. Based on numerical simulation, this paper points the most critical parameters involved in hygrothermal behaviour of ETICS, considering the influence of thermal and hygric properties of the external rendering, the effect of the characteristics of the façade, and the consequences of the exterior and interior climate on exterior surface condensation, wind-driven rain, and drying process. The model used was previously validated by comparison with the results of an “in situ” campaign. The results of the sensitivity analyses show that relative humidity and temperature of the exterior air, atmospheric radiation, and emissivity of the exterior rendering are the parameters that most influence exterior surface condensation. Wind-driven rain depends mostly on horizontal rain, building’s height, wind velocity, and orientation. The drying capacity is influenced by short-wave absorbance, incident solar radiation, and orientation.
On the critical parameters that regulate the deformation behaviour of tooth enamel.
Xie, Zonghan; Swain, Michael; Munroe, Paul; Hoffman, Mark
2008-06-01
Tooth enamel is the hardest tissue in the human body with a complex hierarchical structure. Enamel hypomineralisation--a developmental defect--has been reported to cause a marked reduction in the mechanical properties of enamel and loss of dental function. We discover a distinctive difference in the inelastic deformation mechanism between sound and hypomineralised enamels that is apparently controlled by microstructural variation. For sound enamel, when subjected to mechanical forces the controlling deformation mechanism was distributed shearing within nanometre thick protein layer between its constituent mineral crystals; whereas for hypomineralised enamel microcracking and subsequent crack growth were more evident in its less densely packed microstructure. We develop a mechanical model that not only identifies the critical parameters, i.e., the thickness and shear properties of enamels, that regulate the mechanical behaviour of enamel, but also explains the degradation of hypomineralised enamel as manifested by its lower resistance to deformation and propensity for catastrophic failure. With support of experimental data, we conclude that for sound enamel an optimal microstructure has been developed that endows enamel with remarkable structural integrity for durable mechanical function.
Mechanical and dynamic mechanical behaviour of novel glass ...
M Rajesh
the intra-ply woven fabric hybridization enhances impact and damping properties of the composite ... Keywords. Intra-ply hybrid; natural fibre; mechanical properties; dynamic mechanical analysis; vibration; .... analysis test is conducted in nitrogen environment over a ..... Mnson J A and Jolliet O 2001 Life cycle assessment of.
Relationship dynamics and sexual risk behaviour of male partners of ...
A few men also admitted to being motivated by material and financial benefits from sex workers who they perceived as being rich and this was one factor that helped them sustain the relationships. These findings offer insights into the complex relationship dynamics within high risk sexual partnerships. However, the findings ...
Analysis of static and dynamic pile-soil-jacket behaviour
Azadi, Mohammad Reza Emami
1998-12-31
In the offshore industry, recent extreme storms, severe earthquakes and subsidence of the foundation of jacket platforms have shown that new models and methods must take into account the jacket- pile-soil foundation interaction as well as the non-linear dynamic performance/loading effects. This thesis begins with a review of the state of art pile-soil interaction model, recognizing that most existing pile-soil models have been established based on large diameter pile tests on specific sites. The need for site independent and mechanistic pile-soil interaction models led to the development of new (t-z) and (p-y) disk models. These are validated using the available database from recent large diameter pile tests in the North Sea and Gulf of Mexico. The established static disk models are applied for non-linear static analysis of the jacket-pile-soil system under extreme wave loading. Dynamic pile-soil interaction is studied and a new disk-cone model is developed for the non-linear and non-homogeneous soils. This model is applied to both surface and embedded disks in a soil layer with non-linear properties. Simplified non-linear as well as more complex analysis methods are used to study the dynamic response of the jacket platform under extreme sea and seismic loading. Ductility spectra analysis is introduced and used to study the dynamic performance of the jacket systems near collapse. Case studies are used to illustrate the effects of structural, foundation failure characteristics as well as dynamic loading effects on the overall performance of the jacket-pile-soil systems near ultimate collapse. 175 refs., 429 figs., 70 tabs.
The threshold of coexistence and critical behaviour of a predator-prey cellular automaton
Arashiro, Everaldo; Tome, Tania
2007-01-01
We study a probabilistic cellular automaton to describe two population biology problems: the threshold of species coexistence in a predator-prey system and the spreading of an epidemic in a population. By carrying out mean-field approximations and numerical simulations we obtain the phase boundaries (thresholds) related to the transition between an active state, where prey and predators present a stable coexistence, and a prey absorbing state. The numerical estimates for the critical exponents show that the transition belongs to the directed percolation universality class. In the limit where the cellular automaton maps into a model for the spreading of an epidemic with immunization we observe a crossover from directed percolation class to the dynamic percolation class. Patterns of growing clusters related to species coexistence and spreading of epidemic are shown and discussed
Symmetric dynamic behaviour of a superconducting proximity array with respect to field reversal
Lankhorst, M; Poccia, N
2017-01-01
As the complexity of strongly correlated systems and high temperature superconductors increases, so does also the essential complexity of defects found in these materials and the complexity of the supercurrent pathways. It can be therefore convenient to realize a solid-state system with regular supercurrent pathways and without the disguising effects of disorder in order to capture the essential characteristics of a collective dynamics. Using a square array of superconducting islands placed on a normal metal, we observe a state in which magnetic field-induced vortices are frozen in the dimples of the egg crate potential by their strong repulsion interaction. In this system a dynamic vortex Mott insulator transition has been previously observed. In this work, we will show the symmetric dynamic behaviour with respect to field reversal and we will compare it with the asymmetric behaviour observed at the dynamic vortex Mott transition. (paper)
Contribution to control of robotics structures and dynamic behaviour
Gilliot, Jean-Marie
1990-01-01
The scope of this thesis is the simulation of the dynamics of complex rigid multi-body systems involved in robotics, in order to control them. In the first stage, methods for obtaining equations and models required for simulation and control purposes are proposed and discussed: - determination of constraint equations using the jacobian matrices, - elaboration of direct and inverse dynamics of manipulators. The second part of this thesis deals with the different concepts and components involved in the setting of simulation systems for Robotics Application Programs: models, emulators and the software development environment. The control algorithms are then introduced as a particular class of robotics application programs. A simulator has been developed, allowing the calculation and the visualisation of robot motions, driven by generalized torques. Some examples of control programs generating such control torques are then presented to illustrate the use of the simulator. (author) [fr
Behaviour of soil-cement specimens in unconfined dynamic compression
Davies, J.; Fendukly, L. M.
1994-06-01
The response of the cement-stabilized red marl to dynamic loading in compression has been investigated over a range of cement contents and curing times. Specimens were subjected to different stress levels below unconfined compressive strength, at a frequency of 5 Hz, and a fatigue relationship for the material was developed. The value of resilient modulus was found to be greater than the modulus of elasticity for the same cement content and curing time.
Dynamic behaviour of pump-turbine runner: From disk to prototype runner
Huang, X X; Egusquiza, E; Valero, C; Presas, A
2013-01-01
In recent decades, in order to increase output power of hydroelectric turbomachinery, the design head and the flow rate of the hydraulic turbines have been increased greatly. This has led to serious vibratory problems. The pump-turbines have to work at various operation conditions to satisfy the requirements of the power grid. However, larger hydraulic forces will result in high vibration levels on the turbines, especially, when the machines operate at off-design conditions. Due to the economic considerations, the pump-turbines are built as light as possible, which will change the dynamic response of the structures. According to industrial cases, the fatigue damage of the pump-turbine runner induced by hydraulic dynamic forces usually happens on the outer edge of the crown, which is near the leading edges of blades. To better understand the reasons for this kind of fatigue, it is extremely important to investigate the dynamic response behaviour of the hydraulic turbine, especially the runner, by experimental measurement and numerical simulation. The pump-turbine runner has a similar dynamic response behaviour of the circular disk. Therefore, in this paper the dynamic response analyses for circular disks with different dimensions and disk-blades-disk structures were carried out to better understand the fundamental dynamic behaviour for the complex turbomachinery. The influences of the pattern and number of blades were discussed in detail
Rigorous lower bound on the dynamic critical exponent of some multilevel Swendsen-Wang algorithms
Li, X.; Sokal, A.D.
1991-01-01
We prove the rigorous lower bound z exp ≥α/ν for the dynamic critical exponent of a broad class of multilevel (or ''multigrid'') variants of the Swendsen-Wang algorithm. This proves that such algorithms do suffer from critical slowing down. We conjecture that such algorithms in fact lie in the same dynamic universality class as the stanard Swendsen-Wang algorithm
Dynamic analysis of nonlinear behaviour in inertial actuators
Borgo, M Dal; Tehrani, M Ghandchi; Elliott, S J
2016-01-01
Inertial actuators are devices typically used to generate the control force on a vibrating structure. Generally, an inertial actuator comprises a proof-mass suspended in a magnetic field. The inertial force due to the moving mass is used to produce the secondary force needed to control the vibration of the primary structure. Inertial actuators can show nonlinear behaviour, such as stroke saturation when driven at high input voltages. If the input voltage is beyond their limit, they can hit the end stop of the actuator casing and saturate. In this paper, the force generated by an inertial actuator is measured experimentally and numerical simulations of a linear piecewise stiffness model are carried out and compared with the results of analytical methods. First, a numerical model for a symmetric bilinear stiffness is derived and a parametric study is carried out to investigate the change of the end stop stiffness. In addition, the variation of the amplitude of the excitation is considered and a comparison is made with the analytical solution using the harmonic balance method. Finally, experimental measurements are carried out and the results are compared with simulated data to establish the accuracy of the model. (paper)
Catalytic properties and dynamic behaviour of uranium complexes
Le Marechal, J.F.
1986-01-01
The catalytic properties of organometallic uranium III and IV compounds in solution as well as reaction mechanisms are studied. The structure in solution of CpUCl 3 L 2 (L=THF, HMPA, OPPh 3 , OP(OR) 3 ) is investigated. When L=HMPA, the complex exists in two isomers in equilibrium with the L ligands either in trans or mer-cis configuration. The isomerization (Ea=92 kJ mol -1 ) as well as the bimolecular exchange with an outer sphere ligand L are observable in 1 H and 31 P NMR, and quantified with the spin saturation transfer technique in several solvents and at different temperatures between 230 and 330 K. This property is extended to other ligands. The compound U(AlH 4 ) 3 is synthetized. This compound catalyses the hydroalumination of olefins by LiAlH 4 with a very good anti-Markovnikov regioselectivity. A simple mechanism for this reaction is suggested. The reactions of the organoaluminates products with several reactants (D 2 O, I 2 , CH 2 O, Allyl-Br...) has been shown to be a powerful synthetic tool. Some specific alkenes and alkynes exhibit an interesting behaviour as dimerization or β-alkyl elimination which is easily interpreted by our mechanism [fr
Dynamical behaviour of natural convection in closed loops
Ehrhard, P.
1988-04-01
A one dimensional model is presented together with experiments, which describe the natural convective flow in closed loops heated at the bottom and cooled in the upper semicircle. Starting from a single loop, mechanical and thermal coupling with a second loop is discussed. The experiments and the theoretical model both concurrently demonstrate that the investigated natural convection is clearly influenced by non-linear effects. Beside the variety of stable steady flows there are extensive subcritical ranges of convective flow. In these parameter ranges subcritical instabilities of the steady state flow could occur in the presence of finite amplitude disturbances. However, the supercritical, global unstable range is characterized by chaotic histories of the variables of state. Non-symmetric heating generates an imperfect bifurcation out of the steady solution with zero velocity in the loop. This effect stabilizes the flow in the preferred direction. The flow in the opposite direction only remains stable in a small isolated interval of the heating parameter. Furthermore the calculations with the model equations demonstrate that a stable periodic behaviour of the flow is possible in a small parameter window. However, it has not been possible to verify this particular effect in the experiments conducted to date. (orig./GL) [de
Degli Esposti, M.; Giardinà, C.; Graffi, S.; Isola, S.
2001-01-01
We consider the zero-temperature dynamics for the infinite-range, non translation invariant one-dimensional spin model introduced by Marinari, Parisi and Ritort to generate glassy behaviour out of a deterministic interaction. It is argued that there can be a large number of metastable (i.e.,
Dynamic behaviours and control of fractional-order memristor-based ...
Dynamics of fractional-order memristor circuit system and its control are investigated in this paper. With the help of stability theory of fractional-order systems, stability of its equilibrium points is analysed. Then, the chaotic behaviours are validated using phase portraits, the Lyapunov exponents and bifurcation diagrams with ...
Comparison of brief dynamic and cognitive-behavioural therapies in avoidant personality disorder
Emmelkamp, Paul M. G.; Benner, Ank; Kuipers, Antoinette; Feiertag, Guus A.; Koster, Harrie C.; van Apeldoorn, Franske J.
Background There is a paucity of controlled trials examining the effectiveness of individual psychotherapy in personality disorders, especially in patients with cluster C disorders. Aims To compare the effectiveness of brief dynamic therapy and cognitive-behavioural therapy as out-patient treatment
Veldhuis, G.A.; Korzilius, H.P.L.M.
2017-01-01
Research has shown that many individuals have difficulties solving tasks that involve a principal component of dynamic systems: accumulation. They incorrectly assume that the behavioural pattern of a stock resembles that of its flows and vice versa. This has become known as correlation heuristic
Veldhuis, G.A.; Korzilius, H.
2016-01-01
Research has shown that many individuals have difficulties solving tasks that involve a principal component of dynamic systems: accumulation. They incorrectly assume that the behavioural pattern of a stock resembles that of its flows and vice versa. This has become known as correlation heuristic
Dynamic behaviour of non-uniform Bernoulli-Euler beams subjected ...
This paper investigates the dynamics behaviour of non-uniform Bernoulli-Euler beams subjected to concentrated loads ravelling at variable velocities. The solution technique is based on the Generalized Galerkin Method and the use of the generating function of the Bessel function type. The results show that, for all the ...
Schilders, W.H.A.; Meijer, P.B.L.; Ciggaar, E.
2008-01-01
In this paper we discuss the use of the state-space modelling MOESP algorithm to generate precise information about the number of neurons and hidden layers in dynamic neural networks developed for the behavioural modelling of electronic circuits. The Bartels–Stewart algorithm is used to transform
Analysis of the dynamic behaviour of tanks filled with a liquid
Ousset, Y.; Marquand, D.
1983-01-01
The construction of nuclear power plants sets the problem of the resistance of fuel storage tank to seisms. The presence of fluid changes sensitively the dynamic behaviour of the tank, what involves to take it into account. The CETIM choosed the method of integral equations to solve the problem of the calculation of the added mass matrix [Msub(A)] [fr
Al Shahrani, Abdullah; Yazdipour, Nima; Dehghan-Manshadi, Ali; Gazder, Azdiar A.; Cayron, Cyril; Pereloma, Elena V.
2013-01-01
The effect of deformation temperature and strain rate on the dynamic recrystallisation (DRX) behaviour of X70 pipeline steel was investigated. DRX parameters such as the critical and peak stresses and strains as well as the deformation activation energy were determined in the temperature range between 925 °C and 1125 °C for strain rates of 0.1, 1 and 5 s −1 . The relationship between the peak stresses and strains with the Zener–Hollomon parameter was determined. The dynamically recrystallised volume fraction was computed as a function of the different temperatures and strain rates. The APRGE software was applied for the first time on electron back-scattering diffraction data of dynamically recrystallised microstructures in order to reconstruct the prior austenite from the as-quenched martensite phase. The dynamically recrystallised flow stress curves and microstructure were also predicted using cellular automata modelling. The results show an earlier onset of DRX with a decrease in strain rate or an increase in deformation temperature. The dynamically recrystallised grain size is also found to decrease with an increase in strain rate and a lowering of deformation temperature
Design features affecting dynamic behaviour of fast reactor cores
Kayser, G.; Gouriou, A.
1981-06-01
The study of dynamic response of an LMFBR to normal and accidental transients needs first of all a simulation code taking into account all the important effects. The DYN-1 code aims at this target. It represents with a sufficiently accurate meshing the core in a 20 geometry for the thermal and reactivity effects, while the kinetics of this core are calculated with a point model. The primary pool, secondary loops, steam generator are also represented, as well as the control and protective systems. We give a short description of this code. Simpler codes are sometimes good enough for parametric studies
Nonlinear dynamics and chaotic behaviour of spin wave instabilities
Rezende, S M; Aguiar, F.M. de.
1986-09-01
Recent experiments revealed that spin wave instabilities driven by microwave fields, either parallel or transverse to the static magnetic field, display chaotic dynamics similar to other physical systems. A theory based on the coupled nonlinear equations of motion for two spin wave modes is presented which explains most features of the experimental observations. The model predicts subharmonic routes to chaos that depend on the parameter values. For certain parameters the system exhibits a Feigenbaum scenario characteristic of one-dimensional maps. Other parameters lead to different subharmonic routes indicative of multidimensional behavior, as observed in some experiments.
Elk, E.P. van; Borman, P.C.; Kuipers, J.A.M.; Versteeg, G.F.
1999-01-01
The dynamic behaviour and stability of single-phase reacting systems has been investigated thoroughly in the past and design rules for stable operation are available from literature. The dynamic behaviour of gas-liquid processes is considerably more complex and has received relatively little
Elk, van E.P.; Borman, P.C.; Kuipers, J.A.M.; Versteeg, G.F.
1999-01-01
The dynamic behaviour and stability of single-phase reacting systems has been investigated thoroughly in the past and design rules for stable operation are available from literature. The dynamic behaviour of gas–liquid processes is considerably more complex and has received relatively little
Boumans, I.J.M.M.; Hofstede, G.J.; Bolhuis, J.E.; Boer, de I.J.M.; Bokkers, E.A.M.
2016-01-01
Understanding behavioural dynamics in pigs is important to assess pig welfare in current intensive pig production systems. Agent-based modelling (ABM) is an approach to gain insight into behavioural dynamics in pigs, but its use in applied ethology and animal welfare science has been limited so far.
Dynamic Diversity: Toward a Contextual Understanding of Critical Mass
Garces, Liliana M.; Jayakumar, Uma M.
2014-01-01
Through an analysis of relevant social science evidence, this article provides a deeper understanding of critical mass, a concept that has become central in litigation efforts related to affirmative action admissions policies that seek to further the educational benefits of diversity. We demonstrate that the concept of critical mass requires an…
Sensitivity Analysis of the Critical Speed in Railway Vehicle Dynamics
Bigoni, Daniele; True, Hans; Engsig-Karup, Allan Peter
2013-01-01
-axle Cooperrider bogie, in order to study the sensitivity of the critical speed with respect to suspension parameters. The importance of a certain suspension component is expressed by the variance in critical speed that is ascribable to it. This proves to be useful in the identification of parameters for which...
Quantum Dynamical Behaviour in Complex Systems - A Semiclassical Approach
Ananth, Nandini [Univ. of California, Berkeley, CA (United States)
2008-01-01
One of the biggest challenges in Chemical Dynamics is describing the behavior of complex systems accurately. Classical MD simulations have evolved to a point where calculations involving thousands of atoms are routinely carried out. Capturing coherence, tunneling and other such quantum effects for these systems, however, has proven considerably harder. Semiclassical methods such as the Initial Value Representation (SC-IVR) provide a practical way to include quantum effects while still utilizing only classical trajectory information. For smaller systems, this method has been proven to be most effective, encouraging the hope that it can be extended to deal with a large number of degrees of freedom. Several variations upon the original idea of the SCIVR have been developed to help make these larger calculations more tractable; these range from the simplest, classical limit form, the Linearized IVR (LSC-IVR) to the quantum limit form, the Exact Forward-Backward version (EFB-IVR). In this thesis a method to tune between these limits is described which allows us to choose exactly which degrees of freedom we wish to treat in a more quantum mechanical fashion and to what extent. This formulation is called the Tuning IVR (TIVR). We further describe methodology being developed to evaluate the prefactor term that appears in the IVR formalism. The regular prefactor is composed of the Monodromy matrices (jacobians of the transformation from initial to finial coordinates and momenta) which are time evolved using the Hessian. Standard MD simulations require the potential surfaces and their gradients, but very rarely is there any information on the second derivative. We would like to be able to carry out the SC-IVR calculation without this information too. With this in mind a finite difference scheme to obtain the Hessian on-the-fly is proposed. Wealso apply the IVR formalism to a few problems of current interest. A method to obtain energy eigenvalues accurately for complex
Linking animal population dynamics to alterations in foraging behaviour
Nabe-Nielsen, Jacob; Sibly, Richard; Tougaard, Jakob
Background/Question/Methods The survival of animal populations is strongly influenced by the individuals’ ability to forage efficiently, yet there are few studies of how populations respond when disturbances cause animals to deviate from their natural foraging behavior. Animals that respond...... that are increasingly exposed to noise from ships, wind turbines, etc. In the present study we investigate how the dynamics of the harbor porpoise population (Phocoena phocoena) in the inner Danish waters is influenced by disturbances using an agent- based simulation model. In the model animal movement, and hence...... the animals’ ability to forage efficiently and to sustain their energy intake, is influenced by noise emitted from wind turbines and ships. The energy levels in turn affect their survival. The fine-scale movements of the simulated animals was governed by a spatial memory, which allowed the model to produce...
The effect of grain size on dynamic tensile extrusion behaviour
Park Leeju
2015-01-01
Full Text Available Dynamic tensile extrusion (DTE tests were conducted on coarse grained and ultrafine grained (UFG OFHC Cu, Interstitial free (IF Steel, and pure Ta. Equal channel angular pressing (ECAP of 16passes with Bc for Cu, IF Steel and 4 passes for Ta was employed to fabricated UFG materials. DTE tests were carried out by launching the sphere samples (Dia. 7.62 mm to the conical extrusion die at a speed of ∼500 m/sec. The fragmentation behavior of the soft-recovered fragments were examined and compared with each other. The DTE fragmentation behavior of CG and UFG was numerically simulated by the LS-DYNA FEM code.
Grundmann, U.; Rohde, U.; Naumann, B.
1985-01-01
Studies on theoretical simulation of the dynamic behaviour of the AST-500 type reactor primary coolant system are summarized. The first version of a dynamic model in the form of the DYNAST code is described. The DYNAST code is based on a one-dimensional description of the primary coolant circuit including core, draught stack, and intermediate heat exchanger, a vapour dome model, and the point model of neutron kinetics. With the aid of the steady-state computational part of the DYNAST code, studies have been performed on different steady-state operating conditions. Furthermore, some methodological investigations on generalization and improvement of the dynamic model are considered and results presented. (author)
Kretov, D A
2005-01-01
We used molecular dynamics (MD) simulations to study the density and the temperature behaviour of a flexible polyethylene (PE) subjected to various heating conditions and to investigate the PE chain conformational changes in a water solvent. First, we have considered the influence of the heating process on the final state of the polymeric system and the sensitivity of its thermodynamic characteristics (density, energy, etc.) for different heating regimes. For this purpose three different simulations were performed: fast, moderate, and slow heating. Second, we have investigated the PE chain conformational dynamics in water solvent for various simulation conditions and various configurations of the environment. From the obtained results we have got the pictures of the PE dynamical motions in water. We have observed a protein-like behaviour of the PE chain, like that of the DNA and the proteins in water, and have also estimated the rates of the conformational changes. For the MD simulations we used the optimized...
Dynamical soil-structure interactions: influence of soil behaviour nonlinearities
Gandomzadeh, Ali
2011-01-01
The interaction of the soil with the structure has been largely explored the assumption of material and geometrical linearity of the soil. Nevertheless, for moderate or strong seismic events, the maximum shear strain can easily reach the elastic limit of the soil behavior. Considering soil-structure interaction, the nonlinear effects may change the soil stiffness at the base of the structure and therefore energy dissipation into the soil. Consequently, ignoring the nonlinear characteristics of the dynamic soil-structure interaction (DSSI) this phenomenon could lead to erroneous predictions of structural response. The goal of this work is to implement a fully nonlinear constitutive model for soils into a numerical code in order to investigate the effect of soil nonlinearity on dynamic soil structure interaction. Moreover, different issues are taken into account such as the effect of confining stress on the shear modulus of the soil, initial static condition, contact elements in the soil-structure interface, etc. During this work, a simple absorbing layer method based on a Rayleigh/Caughey damping formulation, which is often already available in existing Finite Element softwares, is also presented. The stability conditions of the wave propagation problems are studied and it is shown that the linear and nonlinear behavior are very different when dealing with numerical dispersion. It is shown that the 10 points per wavelength rule, recommended in the literature for the elastic media is not sufficient for the nonlinear case. The implemented model is first numerically verified by comparing the results with other known numerical codes. Afterward, a parametric study is carried out for different types of structures and various soil profiles to characterize nonlinear effects. Different features of the DSSI are compared to the linear case: modification of the amplitude and frequency content of the waves propagated into the soil, fundamental frequency, energy dissipation in
Wilson, Susan C.; Lockwood, Peter V.; Ashley, Paul M.; Tighe, Matthew
2010-01-01
This article provides a critical review of the environmental chemistry of inorganic antimony (Sb) in soils, comparing and contrasting findings with those of arsenic (As). Characteristics of the Sb soil system are reviewed, with an emphasis on speciation, sorption and phase associations, identifying differences between Sb and As behaviour. Knowledge gaps in environmentally relevant Sb data for soils are identified and discussed in terms of the limitations this imposes on understanding the fate, behaviour and risks associated with Sb in environmental soil systems, with particular reference to mobility and bioavailability. - A critical and comparative review of Sb and As chemistry and associations in soil systems identifies research directions needed for better understanding of risks.
Static and dynamic wetting behaviour of ionic liquids.
Delcheva, Iliana; Ralston, John; Beattie, David A; Krasowska, Marta
2015-08-01
Ionic liquids (ILs) are a unique family of molecular liquids ('molten salts') that consist of a combination of bulky organic cations coupled to inorganic or organic anions. The net result of steric hindrance and strong hydrogen bonding between components results in a material that is liquid at room temperature. One can alter the properties of ionic liquids through chemical modification of anion and cation, thus tailoring the IL for a given application. One such property that can be controlled or selected is the wettability of an IL on a particular solid substrate. However, the study of wetting of ionic liquids is complicated by the care required for accurate and reproducible measurement, due to both the susceptibility of the IL properties to water content, as well as to the sensitivity of wettability measurements to the state of the solid surface. This review deals with wetting studies of ILs to date, including both static and dynamic wetting, as well as issues concerning line tension and the formation of precursor and wetting films. Copyright © 2014 Elsevier B.V. All rights reserved.
Critical Dynamics : The Expansion of the Master Equation Including a Critical Point
Dekker, H.
1980-01-01
In this thesis it is shown how to solve the master equation for a Markov process including a critical point by means of successive approximations in terms of a small parameter. A critical point occurs if, by adjusting an externally controlled quantity, the system shows a transition from normal
Off-criticality behaviour of the Blume-Capel quantum chain as a check of Zamolodchikov's conjecture
Gehlen, G. v.
1989-07-01
Using finite-size numerical calculations, we study the off-criticality behaviour of the Blume-Capel quantum chain in the neighbourhood of the c=7/10 tricritical Ising point. Moving from the tricritical point in the (1/10, 1/10)- and (3/5, 3/5)-directions into the disordered region, we find masses and thresholds in agreement with the structure proposed by Zamolodchikov from conformal field theory. Moving in the opposite directions, the spectrum is degenerate between the Z 2 -even and Z 2 -odd sectors, suggesting an underlying supersymmetry. The free-particle energy momentum relation and the scaling properties off criticality are checked. (orig.)
Arno Steinacher
Full Text Available Bipolar Disorders affect a substantial minority of the population and result in significant personal, social and economic costs. Understanding of the causes of, and consequently the most effective interventions for, this condition is an area requiring development. Drawing upon theories of Bipolar Disorder that propose the condition to be underpinned by dysregulation of systems governing behavioural activation or approach motivation, we present a mathematical model of the regulation of behavioural activation. The model is informed by non-linear, dynamical principles and as such proposes that the transition from "non-bipolar" to "bipolar" diagnostic status corresponds to a switch from mono- to multistability of behavioural activation level, rather than an increase in oscillation of mood. Consistent with descriptions of the behavioural activation or approach system in the literature, auto-activation and auto-inhibitory feedback is inherent within our model. Comparison between our model and empirical, observational data reveals that by increasing the non-linearity dimension in our model, important features of Bipolar Spectrum disorders are reproduced. Analysis from stochastic simulation of the system reveals the role of noise in behavioural activation regulation and indicates that an increase of nonlinearity promotes noise to jump scales from small fluctuations of activation levels to longer lasting, but less variable episodes. We conclude that further research is required to relate parameters of our model to key behavioural and biological variables observed in Bipolar Disorder.
Steinacher, Arno; Wright, Kim A
2013-01-01
Bipolar Disorders affect a substantial minority of the population and result in significant personal, social and economic costs. Understanding of the causes of, and consequently the most effective interventions for, this condition is an area requiring development. Drawing upon theories of Bipolar Disorder that propose the condition to be underpinned by dysregulation of systems governing behavioural activation or approach motivation, we present a mathematical model of the regulation of behavioural activation. The model is informed by non-linear, dynamical principles and as such proposes that the transition from "non-bipolar" to "bipolar" diagnostic status corresponds to a switch from mono- to multistability of behavioural activation level, rather than an increase in oscillation of mood. Consistent with descriptions of the behavioural activation or approach system in the literature, auto-activation and auto-inhibitory feedback is inherent within our model. Comparison between our model and empirical, observational data reveals that by increasing the non-linearity dimension in our model, important features of Bipolar Spectrum disorders are reproduced. Analysis from stochastic simulation of the system reveals the role of noise in behavioural activation regulation and indicates that an increase of nonlinearity promotes noise to jump scales from small fluctuations of activation levels to longer lasting, but less variable episodes. We conclude that further research is required to relate parameters of our model to key behavioural and biological variables observed in Bipolar Disorder.
Reactor Dynamics Experiments with a Sub-Critical Assembly
Miley, G.H.; Yang, Y.; Wu, L.; Momota, H.
2004-01-01
A resurgence in use of nuclear power is now underway worldwide. However due to the shutdown of many university research reactors , student laboratories must rely more heavily on use of sub-critical assemblies. Here a driven sub-critical is described that uses a cylindrical Inertial Electrostatic Confinement (IEC) device to provide a fusion neutron source. The small IEC neutron source would be inserted in a fuel element position, with its power input controlled externally at a control panel. This feature opens the way to use of the critical assembly for a number of transient experiments such as sub-critical pulsing and neutron wave propagation. That in turn adds important new insights and excitement for the student teaching laboratory
Schikorr, W.M.
2001-01-01
The neutron kinetic and the reactor dynamic behavior of Accelerator Driven Systems (ADS) is significantly different from those of conventional power reactor systems currently in use for the production of power. It is the objective of this study to examine and to demonstrate the intrinsic differences of the kinetic and dynamic behavior of accelerator driven systems to typical plant transient initiators in comparison to the known, kinetic and dynamic behavior of critical thermal and fast reactor systems. It will be shown that in sub-critical assemblies, changes in reactivity or in the external neutron source strength lead to an asymptotic power level essentially described by the instantaneous power change (i.e. prompt jump). Shutdown of ADS operating at high levels of sub-criticality, (i.e. k eff ∼0.99), without the support of reactivity control systems (such as control or safety rods), may be problematic in case the ability of cooling of the core should be impaired (i.e. loss of coolant flow). In addition, the dynamic behavior of sub-critical systems to typical plant transients such as protected or unprotected loss of flow (LOF) or heat sink (LOH) transients are not necessarily substantially different from the plant dynamic behavior of critical systems if the reactivity feedback coefficients of the ADS design are unfavorable. As expected, the state of sub-criticality and the temperature feedback coefficients, such as Doppler and coolant temperature coefficient, play dominant roles in determining the course and direction of plant transients. Should the combination of these safety coefficients be very unfavorable, not much additional margin in safety may be gained by making a critical system only sub-critical (i.e. k eff ∼0.95). A careful optimization procedure between the selected operating level of sub-criticality, the safety reactivity coefficients and the possible need for additional reactivity control systems seems, therefore, advisable during the early
NONE
1982-01-01
The purpose of the meeting was to review and discuss the effects induced by changes in some design characteristics on overall performances and transient behaviour of fast reactor cores. The main topics discussed in the four technical sessions were: National Review Presentations. Identification of the key issues to be considered in the following sessions; Effects of design changes on performance characteristics. Kinetics models and codes; Evaluation and interpretation of reactivity coefficients. Kinetics calculations for restrained and free-standing cores; Comparison of the dynamic behaviour of homogeneous and heterogeneous cores.
1982-01-01
The purpose of the meeting was to review and discuss the effects induced by changes in some design characteristics on overall performances and transient behaviour of fast reactor cores. The main topics discussed in the four technical sessions were: National Review Presentations. Identification of the key issues to be considered in the following sessions; Effects of design changes on performance characteristics. Kinetics models and codes; Evaluation and interpretation of reactivity coefficients. Kinetics calculations for restrained and free-standing cores; Comparison of the dynamic behaviour of homogeneous and heterogeneous cores
Nonlinear Dynamics and Nucleation Kinetics in Near-Critical Liquids
Patashinski, Alexander Z.; Ratner, Mark A.; Pines, Vladimir
1996-01-01
The objective of our study is to model the nonlinear behavior of a near-critical liquid following a rapid change of the temperature and/or other thermodynamic parameters (pressure, external electric or gravitational field). The thermodynamic critical point is manifested by large, strongly correlated fluctuations of the order parameter (particle density in liquid-gas systems, concentration in binary solutions) in the critical range of scales. The largest critical length scale is the correlation radius r(sub c). According to the scaling theory, r(sub c) increases as r(sub c) = r(sub 0)epsilon(exp -alpha) when the nondimensional distance epsilon = (T - T(sub c))/T(sub c) to the critical point decreases. The normal gravity alters the nature of correlated long-range fluctuations when one reaches epsilon approximately equal to 10(exp -5), and correspondingly the relaxation time, tau(r(sub c)), is approximately equal to 10(exp -3) seconds; this time is short when compared to the typical experimental time. Close to the critical point, a rapid, relatively small temperature change may perturb the thermodynamic equilibrium on many scales. The critical fluctuations have a hierarchical structure, and the relaxation involves many length and time scales. Above the critical point, in the one-phase region, we consider the relaxation of the liquid following a sudden temperature change that simultaneously violates the equilibrium on many scales. Below T(sub c), a non-equilibrium state may include a distribution of small scale phase droplets; we consider the relaxation of such a droplet following a temperature change that has made the phase of the matrix stable.
Bulk properties and near-critical behaviour of SiO2 fluid
Green, Eleanor C. R.; Artacho, Emilio; Connolly, James A. D.
2018-06-01
Rocky planets and satellites form through impact and accretion processes that often involve silicate fluids at extreme temperatures. First-principles molecular dynamics (FPMD) simulations have been used to investigate the bulk thermodynamic properties of SiO2 fluid at high temperatures (4000-6000 K) and low densities (500-2240 kg m-3), conditions which are relevant to protoplanetary disc condensation. Liquid SiO2 is highly networked at the upper end of this density range, but depolymerises with increasing temperature and volume, in a process characterised by the formation of oxygen-oxygen (Odbnd O) pairs. The onset of vaporisation is closely associated with the depolymerisation process, and is likely to be non-stoichiometric at high temperature, initiated via the exsolution of O2 molecules to leave a Si-enriched fluid. By 6000 K the simulated fluid is supercritical. A large anomaly in the constant-volume heat capacity occurs near the critical temperature. We present tabulated thermodynamic properties for silica fluid that reconcile observations from FPMD simulations with current knowledge of the SiO2 melting curve and experimental Hugoniot curves.
The dynamics of aerosol behaviour and fate within spruce canopies
Ould-Dada, Zitouni
1996-01-01
The current work was intended to provide data on aerosol inputs to forest ecosystems and their subsequent fate. The background to the project was the Chernobyl accident which highlighted the importance of forests and other semi-natural ecosystems as a link in the transfer of radioactivity to man. In the aftermath of the Chernobyl accident, forests were identified as a specific type of semi-natural ecosystem for which radioecological data were almost completely absent within the countries of the European Union. Information on radionuclide behaviour and transfer in forest ecosystems was therefore needed to establish and test radiological assessment models which can be used to evaluate the likely contribution to radiological dose-to-man contaminated forests may make. The objective of this study was thus to provide data on dry deposition, resuspension and field loss of aerosols to forest canopies, in particular those of Norway spruce (Picea abies), from wind tunnel experiments conducted with small scale 'model' canopies. An aerosol generation system was developed to produce aerosol particles in the size range of 0.13-1.37 μm (VMD). Particle size distributions can be controlled within desired limits and with sufficient stability over time allowing the technique to be suitable for use in extended aerosol deposition studies. A full scale dry deposition experiment using 0.82 μm (VMAD) uranium particles was performed in the wind tunnel using Norway spruce saplings of approximately 45 cm height. Deposition velocities (V g ) were obtained and these were related to meteorological measurements (wind speed, friction velocity, turbulence intensity) inside the wind tunnel and LAI of the canopy. The latter was divided into five horizontal layers and both horizontal and vertical variations in deposition were assessed. A V g value of 0.497 cm s -1 was obtained for the canopy as a whole with the highest and lowest fluxes of 2.85 x 10 -8 and 8.14 x 10 -9 μgU cm -2 s -1 occurring at
Blume, Steffen O P; Sansavini, Giovanni
2017-12-01
Complex dynamical systems face abrupt transitions into unstable and catastrophic regimes. These critical transitions are triggered by gradual modifications in stressors, which push the dynamical system towards unstable regimes. Bifurcation analysis can characterize such critical thresholds, beyond which systems become unstable. Moreover, the stochasticity of the external stressors causes small-scale fluctuations in the system response. In some systems, the decomposition of these signal fluctuations into precursor signals can reveal early warning signs prior to the critical transition. Here, we present a dynamical analysis of a power system subjected to an increasing load level and small-scale stochastic load perturbations. We show that the auto- and cross-correlations of bus voltage magnitudes increase, leading up to a Hopf bifurcation point, and further grow until the system collapses. This evidences a gradual transition into a state of "critical coupling," which is complementary to the established concept of "critical slowing down." Furthermore, we analyze the effects of the type of load perturbation and load characteristics on early warning signs and find that gradient changes in the autocorrelation provide early warning signs of the imminent critical transition under white-noise but not for auto-correlated load perturbations. Furthermore, the cross-correlation between all voltage magnitude pairs generally increases prior to and beyond the Hopf bifurcation point, indicating "critical coupling," but cannot provide early warning indications. Finally, we show that the established early warning indicators are oblivious to limit-induced bifurcations and, in the case of the power system model considered here, only react to an approaching Hopf bifurcation.
Toward Control of Universal Scaling in Critical Dynamics
2016-01-27
program that aims to synergistically combine two powerful and very successful theories for non-linear stochastic dynamics of cooperative multi...RESPONSIBLE PERSON 19b. TELEPHONE NUMBER Uwe Tauber Uwe C. T? uber , Michel Pleimling, Daniel J. Stilwell 611102 c. THIS PAGE The public reporting burden...to synergistically combine two powerful and very successful theories for non-linear stochastic dynamics of cooperative multi-component systems, namely
Jianyi Zhang
2017-07-01
anticipated that the expansion was induced by elastic recovery to a limited extent, while the shrinkage was primarily due to the solidification during storage. It was also found that, for all powders considered, the powder compressibility and the elastic recovery depended significantly on the particle breakage tendency: a decrease in the particle breakage tendency led to a slight decrease in the powder compressibility and a significant drop in immediate elastic recovery. This implies that the particle breakage tendency is a critical material attribute in controlling the compression behaviour of pharmaceutical powders.
Critical Dynamics of Burst Instabilities in the Portevin-Le Chatelier Effect
D'Anna, Gianfranco; Nori, Franco
2000-01-01
We investigate the Portevin-Le Chatelier effect (PLC), by compressing Al-Mg alloys in a very large deformation range, and interpret the results from the viewpoint of phase transitions and critical phenomena. The system undergoes two dynamical phase transitions between intermittent (or ''jerky'') and ''laminar'' plastic dynamic phases. Near these two dynamic critical points, the order parameter 1/τ of the PLC effect exhibits large fluctuations, and ''critical slowing down'' (i.e., the number τ of bursts, or plastic instabilities, per unit time slows down considerably)
Deriving Behaviour of Hodgkin Huxley model with fever dynamics: A computational study
Hasan ESKALEN
2017-10-01
Full Text Available A single neuron can be modeled by the set of differential equations. Hodgkin-Huxley (HH model, the one of the most famous neuron model, can be considered as a dynamical system with four independent variables. Here we studied to reduce the number of differential equation required for conductance based HH model under strong inhibitory noise. Exponential Integrate and Fire (EIF model, one independent variable, is used as a reduced model of HH model by using current-voltage (I-V curve of the original model. The required reduction parameters are determined from this curve. The behaviour of HH model and its reduced EIF (rEIF model are in good agreement in sub-threshold level. Above-threshold behaviour of reduced EIF model and original model compared in terms of threshold voltage under strong inhibitory noise. Our numerical simulations clearly show that sub-threshold behaviour of HH model perfectly reduced to rEIF model.
Spin dynamics in Tb studied by critical neutron scattering
Dietrich, O. W.; Als-Nielsen, Jens Aage
1971-01-01
The inelasticity of the critical neutron scattering in Tb was measured at and above the Neel temperature. In the hydrodynamic region the line width Gamma (q=0, kappa 1)=C kappa z1, with z=1.4+or-0.1 and c=4.3+or-0.3 meVAAz. This result deviates from the conventional theory, which predicts...
Moioli, Renan C; Vargas, Patricia A; Husbands, Phil
2012-09-01
Oscillatory activity is ubiquitous in nervous systems, with solid evidence that synchronisation mechanisms underpin cognitive processes. Nevertheless, its informational content and relationship with behaviour are still to be fully understood. In addition, cognitive systems cannot be properly appreciated without taking into account brain-body- environment interactions. In this paper, we developed a model based on the Kuramoto Model of coupled phase oscillators to explore the role of neural synchronisation in the performance of a simulated robotic agent in two different minimally cognitive tasks. We show that there is a statistically significant difference in performance and evolvability depending on the synchronisation regime of the network. In both tasks, a combination of information flow and dynamical analyses show that networks with a definite, but not too strong, propensity for synchronisation are more able to reconfigure, to organise themselves functionally and to adapt to different behavioural conditions. The results highlight the asymmetry of information flow and its behavioural correspondence. Importantly, it also shows that neural synchronisation dynamics, when suitably flexible and reconfigurable, can generate minimally cognitive embodied behaviour.
Bediou, J.
1993-01-01
Simulation of the dynamical behaviour of the EDF turbogenerator groups is based on developments concerning bearing behaviour and shaft line dynamics. A provisional model for the ARABELLE turbine dynamic behaviour is derived. The detailed representation of all the components allows for a fine analysis of the different effects and the evaluation of the stresses transmitted to the structure in anomalistic operating conditions
SALLY - a computer programme for the calculation of the dynamical behaviour of a cooling channel
Reiche, C.; Ziegenbein, D.
1978-12-01
This report describes the mathematical-physical fundamentals and provides a user's manual as well as some test examples for the programme SALLY. SALLY is suitable for the calculation of the dynamical behaviour of a cooling channel under following conditions: point-kinetics, heat transfer in the fuel in radial direction only, reactivity feedback, simple model of the first cooling cycle. Reactivity, coolant inlet temperature or coolant velocity can be disturbed. (author)
Design factors affecting dynamic behaviour of fast reactor cores. UK review paper
Brindley, K W [National Nuclear Corporation Ltd., Risley, Warrington (United Kingdom); Perks, M A [United Kingdom Atomic Energy Authority, Risley, Warrington (United Kingdom)
1982-01-01
This paper summarises the consideration that has been given in the UK to the following factors that affect the dynamic behaviour of fast reactor cores: fuel design - Pu/u homogeneity, fuel expansion, fuel-clad gaps, uranium fraction. Structural response - CR supports, diagrid, sub-assembly bowing sodium expansion coefficients - low void cores including heterogenous cores. Calculational methods and models are outlined and some experimental results are discussed. (author)
Dynamics and Control of Distillation Columns - A Critical Survey
Sigurd Skogestad
1997-07-01
Full Text Available Distillation column dynamics and control have been viewed by many as a very mature or even dead field. However, as is discussed in this paper significant new results have appeared over the last 5-10 years. These results include multiple steady states and instability in simple columns with ideal thermodynamics (which was believed to be impossible, the understanding of the difference between various control configurations and the systematic transformation between these, the feasibility of using the distillate-bottom structure, for control (which was believed to be impossible, the importance of flow dynamics for control studies, the fundamental problems in identifying models from open-loops responses, the use of simple regression estimators to estimate composition from temperatures, and an improved general understanding of the dynamic behavior of distillation columns which includes a better understanding of the fundamental difference between internal and external flow, simple formulas for estimating the dominant time constant, and a derivation of the linearizing effect of logarithmic transformations. These issues apply to all columns, even for ideal mixtures and simple columns with only two products. In addition, there have been significant advances for cases with complex thermodynamics and complex column configurations. These include the behavior and control of azeotropic distillation columns, and the possible complex dynamics of nonideal mixtures and of interlinked columns. However, both for the simple and more complex cases there are still a number of areas where further research is needed.
Kawasaki dynamics with two types of particles : critical droplets
Hollander, den W.Th.F.; Nardi, F.R.; Troiani, A.
2012-01-01
This is the third in a series of three papers in which we study a two-dimensional lattice gas consisting of two types of particles subject to Kawasaki dynamics at low temperature in a large finite box with an open boundary. Each pair of particles occupying neighboring sites has a negative binding
Kawasaki dynamics with two types of particles : critical droplets
Hollander, den W.Th.F.; Nardi, F.R.; Troiani, A.
2012-01-01
This is the third in a series of three papers in which we study a two-dimensional lattice gas consisting of two types of particles subject to Kawasaki dynamics at low temperature in a large ¿nite box with an open boundary. Each pair of particles occupying neighboring sites has a negative binding
Fatigue behaviour of core-spun yarns containing filament by means of cyclic dynamic loading
Esin, S.; Osman, B.
2017-10-01
The behaviour of yarns under dynamic loading is important that leads to understand the growth characteristics which is exposed to repetitive loadings during usage of fabric made from these yarns. Fabric growth is undesirable property that originated from low resilience characteristics of fabric. In this study, the effects of the filament fineness and yarn linear density on fatigue behaviour of rigid-core spun yarns were determined. Cotton covered yarns containing different filament fineness of polyester (PET) draw textured yarns (DTY) (100d/36f, 100d/96f, 100d/144f, 100d/192f and 100d/333f) and yarn linear densities (37 tex, 30 tex, 25 tex and 21 tex) were manufactured by using a modified ring spinning system at the same spinning parameters. Repetitive loads were applied for 25 cycles at levels between 0.1 and 3 N. Dynamic modulus and dynamic strain of yarn samples were analyzed statistically. Results showed that filament fineness and yarn linear density have significance effect on dynamic modulus and dynamic strain after cyclic loading.
Static states and dynamic behaviour of charges: observation and control by scanning probe microscopy
Ishii, Masashi
2010-01-01
This paper reviews charges that locally functionalize materials. Microscopic analyses and operation of charges using various scanning probe microscopy (SPM) techniques have revealed static, quasi-static/quasi-dynamic and dynamic charge behaviours. Charge-sensitive SPM has allowed for the visualization of the distribution of functionalized charges in electronic devices. When used as bit data in a memory system, the charges can be operated by SPM. The behaviour of quasi-static/quasi-dynamic charges is discussed here. In the data-writing process, spatially dispersive charges rather than a fast injection rate are introduced, but the technical problems can be solved by using nanostructures. Careful charge operations using SPM should realize a memory with a larger density than Tbit/inch 2 . Dynamic charges have been introduced in physical analyses and chemical processes. Although the observable timescale is limited by the SPM system response time of the order of several seconds, dynamics such as photon-induced charge redistributions and probe-assisted chemical reactions are observed. (topical review)
Static states and dynamic behaviour of charges: observation and control by scanning probe microscopy
Ishii, Masashi, E-mail: ISHII.Masashi@nims.go.j [National Institute for Materials Science (NIMS), 1-2-1 Sengen, Tsukuba, Ibaraki 305-0047 (Japan)
2010-05-05
This paper reviews charges that locally functionalize materials. Microscopic analyses and operation of charges using various scanning probe microscopy (SPM) techniques have revealed static, quasi-static/quasi-dynamic and dynamic charge behaviours. Charge-sensitive SPM has allowed for the visualization of the distribution of functionalized charges in electronic devices. When used as bit data in a memory system, the charges can be operated by SPM. The behaviour of quasi-static/quasi-dynamic charges is discussed here. In the data-writing process, spatially dispersive charges rather than a fast injection rate are introduced, but the technical problems can be solved by using nanostructures. Careful charge operations using SPM should realize a memory with a larger density than Tbit/inch{sup 2}. Dynamic charges have been introduced in physical analyses and chemical processes. Although the observable timescale is limited by the SPM system response time of the order of several seconds, dynamics such as photon-induced charge redistributions and probe-assisted chemical reactions are observed. (topical review)
Dynamic behaviour of dc double anode plasma torch at atmospheric pressure
Tu, X; Cheron, B G; Yan, J H; Cen, K F
2007-01-01
An original dc double anode plasma torch which provides a long-time and highly stable atmospheric plasma jet has been devised for the purpose of hazardous waste treatment. The arc fluctuations and dynamic behaviour of the argon and argon-nitrogen plasma jets under different operating conditions have been investigated by means of classical tools, such as the statistic method, fast Fourier transform (FFT) and correlation analysis. In our experiments, the takeover mode is identified as the fluctuation characteristic of the argon plasma jet while the restrike mode is typical in the argon-nitrogen plasma dynamic behaviour. In the case of pure argon, the FFT and correlation calculation results of electrical signals exhibit the only characteristic frequency of 150 Hz, which originates from the torch power and is independent of any change in the operating conditions. It indicates that the nature of fluctuations in an argon plasma jet is mainly induced by the undulation of the tri-phase rectified power supply. In contrast, besides the same low frequency bulk fluctuation, the dynamic behaviour of the argon-nitrogen plasma jet at high frequency (4.1 kHz) is ascribed to the rapid motion of both arc roots on the anode surface. In addition, it is found that each arc root attachment is rather diffused than located at a fixed position on the anode wall in the argon plasma jet, while constricted arc roots occur when nitrogen is added into argon as the plasma working gas
The Dynamics of Agile Practices for Safety-Critical Software Development
Nielsen, Peter Axel; Tordrup Heeager, Lise
2017-01-01
This short paper reports from a case study of the agile development of safety-critical software. It utilizes a framework of dynamic relationships between agile practices with the purpose of demonstrating the utility of the framework to understand a case in its context, and it shows significant...... dynamics. The study is concluded by pointing at which further research on the framework is required to use the framework in managing the agile development of safety-critical software....
Critical properties of Sudden Quench Dynamics in the anisotropic XY Model
Guo, Hongli; Liu, Zhao; Fan, Heng; Chen, Shu
2010-01-01
We study the zero temperature quantum dynamical critical behavior of the anisotropic XY chain under a sudden quench in a transverse field. We demonstrate theoretically that both quench magnetic susceptibility and two-particle quench correlation can be used to describe the dynamical quantum phase transition (QPT) properties. Either the quench magnetic susceptibility or the derivative of correlation functions as a function of initial magnetic field $a$ exhibits a divergence at the critical poin...
Angel Ric
Full Text Available The analysis of positional data in association football allows the spatial distribution of players during matches to be described in order to improve the understanding of tactical-related constraints on the behavioural dynamics of players. The aim of this study was to identify how players' spatial restrictions affected the exploratory tactical behaviour and constrained the perceptual-motor workspace of players in possession of the ball, as well as inter-player passing interactions. Nineteen professional outfield male players were divided into two teams of 10 and 9 players, respectively. The game was played under three spatial constraints: a players were not allowed to move out of their allocated zones, except for the player in possession of the ball; b players were allowed to move to an adjacent zone, and; c non-specific spatial constraints. Positional data was captured using a 5 Hz interpolated GPS tracking system and used to define the configuration states of players for each second in time. The configuration state comprised 37 categories derived from tactical actions, distance from the nearest opponent, distance from the target and movement speed. Notational analysis of players in possession of the ball allowed the mean time of ball possession and the probabilities of passing the ball between players to be calculated. The results revealed that the players' long-term exploratory behaviour decreased and their short-term exploration increased when restricting their space of interaction. Relaxing players' positional constraints seemed to increase the speed of ball flow dynamics. Allowing players to move to an adjacent sub-area increased the probabilities of interaction with the full-back during play build-up. The instability of the coordinative state defined by being free from opponents when players had the ball possession was an invariant feature under all three task constraints. By allowing players to move to adjacent sub-areas, the
SSI on the Dynamic Behaviour of a Historical Masonry Building: Experimental versus Numerical Results
Francesca Ceroni
2014-11-01
Full Text Available A reliable procedure to identify the dynamic behaviour of existing masonry buildings is described in the paper, referring to a representative case study: a historical masonry palace located in Benevento (Italy. Since the building has been equipped with a permanent dynamic monitoring system by the Department of Civil Protection, some of the recorded data, acquired in various operating conditions, have been analysed with basic instruments of the Operational Modal Analysis in order to identify the main eigenfrequencies and vibration modes of the structure. The obtained experimental results have been compared to the numerical outcomes provided by three detailed Finite Element (FE models of the building. The influence of Soil-Structure Interaction (SSI has been also introduced in the FE model by a sub-structure approach where concentrated springs were placed at the base of the building to simulate the effect of soil and foundation on the global dynamic behaviour of the structure. The obtained results evidence that subsoil cannot a priori be disregarded in identifying the dynamic response of the building.
Peak load-impulse characterization of critical pulse loads in structural dynamics
Abrahamson, G.R.; Lindberg, H.E.
1975-01-01
In presenting the characterization scheme, some general features are described first. A detailed analysis is given for the rigid-plastic system of one degree of freedom to illustrate the calculation of critical load curves in terms of peak load and impulse. This is followed by the presentation of critical load curves for uniformly loaded rigid-plastic beams and plates and for dynamic buckling of cylindrical shells under uniform lateral loads. The peak load-impulse characterization of critical pulse loads is compared with the dynamic load factor characterization, and some aspects of the history of the peak load-pulse scheme are presented. (orig./HP) [de
Chen, Yi; Zhang, Guangfeng; Li, Yiyang
2013-01-01
A spatial approach that incorporates three economic components and one environmental factor has been developed to evaluate the dynamic behaviours of the rural areas at a provincial level. An artificial fish swarm algorithm with variable population size (AFSAVP) is proposed for the spatial problem......, and the results have shown that the modelling method based on GDP data can assess the spatial dynamic behaviours and can be taken as an operational tool for the policy planners....
Critical behaviour of magnetic thin film with Heisenberg spin-S model
Masrour, R.; Hamedoun, M.; Bouslykhane, K.; Hourmatallah, A.; Benzakour, N.; Benyoussef, A.
2009-01-01
The magnetic properties of a ferromagnetic thin film of face centered cubic (FCC) lattice with Heisenberg spin-S are examined using the high-temperature series expansions technique extrapolated with Pade approximations method. The critical reduced temperature of the system τ c is studied as function of thickness of the film and the exchange interactions in the bulk, and within the surfaces J b , J s and J perpendicular respectively. A critical value of surface exchange interaction above which surface magnetism appears is obtained. The dependence of the reduced critical temperature on the film thickness L has been investigated.
A dynamic Monte Carlo study of anomalous current voltage behaviour in organic solar cells
Feron, K.; Fell, C. J.; Zhou, X.; Belcher, W. J.; Dastoor, P. C.
2014-01-01
We present a dynamic Monte Carlo (DMC) study of s-shaped current-voltage (I-V) behaviour in organic solar cells. This anomalous behaviour causes a substantial decrease in fill factor and thus power conversion efficiency. We show that this s-shaped behaviour is induced by charge traps that are located at the electrode interface rather than in the bulk of the active layer, and that the anomaly becomes more pronounced with increasing trap depth or density. Furthermore, the s-shape anomaly is correlated with interface recombination, but not bulk recombination, thus highlighting the importance of controlling the electrode interface. While thermal annealing is known to remove the s-shape anomaly, the reason has been not clear, since these treatments induce multiple simultaneous changes to the organic solar cell structure. The DMC modelling indicates that it is the removal of aluminium clusters at the electrode, which act as charge traps, that removes the anomalous I-V behaviour. Finally, this work shows that the s-shape becomes less pronounced with increasing electron-hole recombination rate; suggesting that efficient organic photovoltaic material systems are more susceptible to these electrode interface effects
Theoretical study of laser feedback interferometry for dynamical material's behaviour studies
Le-Barbier, Laura
2017-01-01
The purpose of this thesis is to study the feasibility of optical feedback interferometry (OFI) for measuring velocities for dynamical material's behaviour studies. Dynamical material's behaviour studies permit to analyse the shocked material when subjects to shocks (laser shocks, isentropic compression, projectiles, etc.). In these conditions, we seek to measure velocities up to 10 km/s. The OFI technique is regularly used as an embedded system to measure slow velocities in various fields. However, very few studies have been performed for determining velocities measurement limits for this system. As a matter of fact, the optical feedback induces nonlinear effects into the laser's cavity: it disrupts the laser's emitted optical power. Depending on the optical feedback strength, the laser can show chaotic behaviour, then it is no longer possible to get the information for the target's velocity or displacement regarding the signal. In this study, we have been developing mathematical models and performing a wide range of numerical simulations to study the performances and the limits of the OFI technique. We have been also studying the influence of the targets reflectivity, the length and the modulation frequency of the external cavity. (author) [fr
Oraby, Tamer; Thampi, Vivek; Bauch, Chris T
2014-04-07
Mathematical models that couple disease dynamics and vaccinating behaviour often assume that the incentive to vaccinate disappears if disease prevalence is zero. Hence, they predict that vaccine refusal should be the rule, and elimination should be difficult or impossible. In reality, countries with non-mandatory vaccination policies have usually been able to maintain elimination or very low incidence of paediatric infectious diseases for long periods of time. Here, we show that including injunctive social norms can reconcile such behaviour-incidence models to observations. Adding social norms to a coupled behaviour-incidence model enables the model to better explain pertussis vaccine uptake and disease dynamics in the UK from 1967 to 2010, in both the vaccine-scare years and the years of high vaccine coverage. The model also illustrates how a vaccine scare can perpetuate suboptimal vaccine coverage long after perceived risk has returned to baseline, pre-vaccine-scare levels. However, at other model parameter values, social norms can perpetuate depressed vaccine coverage during a vaccine scare well beyond the time when the population's baseline vaccine risk perception returns to pre-scare levels. Social norms can strongly suppress vaccine uptake despite frequent outbreaks, as observed in some small communities. Significant portions of the parameter space also exhibit bistability, meaning long-term outcomes depend on the initial conditions. Depending on the context, social norms can either support or hinder immunization goals.
Masugi-Tokita, M; Yoshida, T; Kageyama, S; Kawata, M; Kawauchi, A
2018-03-01
Metabotropic glutamate receptor subtype 7 (mGluR7) is one of the group III mGluRs, which are negatively coupled to adenylate cyclase via Gi/Go proteins and localised to presynaptic active zones of the mammalian central nervous system. We previously reported that mGluR7 is essential for intermale aggression and amygdala-dependent fear learning. To elucidate the role of mGluR7 in the neuroendocrine system, we performed biochemical analyses and found a significant reduction of testosterone levels in mGluR7 knockout (KO) mice. Testosterone replacement restored intermale aggressive behaviour in castrated wild-type mice to the level of gonadally intact wild-type mice. However, given the same dosage of testosterone replacement, mGluR7 KO mice showed almost no aggressive behaviour. These results indicate that reduction of plasma testosterone is unrelated to the deficit in intermale aggression in mGluR7 KO mice. Social investigating behaviour of intact mGluR7 KO mice also differed from that of wild-type mice; e.g. the KO mice showing less frequent anogenital sniffing and more frequent grooming behaviour. Testosterone replacement increased anogenital sniffing and grooming behaviour in castrated mGluR7 KO mice, while the differences were still present between castrated wild-type mice and KO mice after both underwent testosterone replacement. These results imply that reduction of plasma testosterone may partially inhibit social investigating behaviours in intact mGluR7 KO mice. Furthermore, castrated mGluR7 KO mice have smaller seminal vesicles than those of castrated wild-type mice, although seminal vesicle weights were normal in intact mice. These observations suggest that, besides testicular testosterone, some other hormone levels may be dysregulated in mGluR7 KO mice, and indicate a critical role of mGluR7 in the endocrine system. Taken together, our findings demonstrate that mGluR7 is essential for the regulation of the endocrine system, in addition to innate behaviours
Sumner, Isaiah; Iyengar, Srinivasan S
2007-10-18
We have introduced a computational methodology to study vibrational spectroscopy in clusters inclusive of critical nuclear quantum effects. This approach is based on the recently developed quantum wavepacket ab initio molecular dynamics method that combines quantum wavepacket dynamics with ab initio molecular dynamics. The computational efficiency of the dynamical procedure is drastically improved (by several orders of magnitude) through the utilization of wavelet-based techniques combined with the previously introduced time-dependent deterministic sampling procedure measure to achieve stable, picosecond length, quantum-classical dynamics of electrons and nuclei in clusters. The dynamical information is employed to construct a novel cumulative flux/velocity correlation function, where the wavepacket flux from the quantized particle is combined with classical nuclear velocities to obtain the vibrational density of states. The approach is demonstrated by computing the vibrational density of states of [Cl-H-Cl]-, inclusive of critical quantum nuclear effects, and our results are in good agreement with experiment. A general hierarchical procedure is also provided, based on electronic structure harmonic frequencies, classical ab initio molecular dynamics, computation of nuclear quantum-mechanical eigenstates, and employing quantum wavepacket ab initio dynamics to understand vibrational spectroscopy in hydrogen-bonded clusters that display large degrees of anharmonicities.
Function of dynamic models in systems biology: linking structure to behaviour.
Knüpfer, Christian; Beckstein, Clemens
2013-10-08
Dynamic models in Systems Biology are used in computational simulation experiments for addressing biological questions. The complexity of the modelled biological systems and the growing number and size of the models calls for computer support for modelling and simulation in Systems Biology. This computer support has to be based on formal representations of relevant knowledge fragments. In this paper we describe different functional aspects of dynamic models. This description is conceptually embedded in our "meaning facets" framework which systematises the interpretation of dynamic models in structural, functional and behavioural facets. Here we focus on how function links the structure and the behaviour of a model. Models play a specific role (teleological function) in the scientific process of finding explanations for dynamic phenomena. In order to fulfil this role a model has to be used in simulation experiments (pragmatical function). A simulation experiment always refers to a specific situation and a state of the model and the modelled system (conditional function). We claim that the function of dynamic models refers to both the simulation experiment executed by software (intrinsic function) and the biological experiment which produces the phenomena under investigation (extrinsic function). We use the presented conceptual framework for the function of dynamic models to review formal accounts for functional aspects of models in Systems Biology, such as checklists, ontologies, and formal languages. Furthermore, we identify missing formal accounts for some of the functional aspects. In order to fill one of these gaps we propose an ontology for the teleological function of models. We have thoroughly analysed the role and use of models in Systems Biology. The resulting conceptual framework for the function of models is an important first step towards a comprehensive formal representation of the functional knowledge involved in the modelling and simulation process
Bulsara, Adi R.; Lindner, John F.; In, Visarath; Kho, Andy; Baglio, Salvatore; Sacco, Vincenzo; Ando, Bruno; Longhini, Patrick; Palacios, Antonio; Rappel, Wouter-Jan
2006-01-01
Recently, we have shown the emergence of oscillations in overdamped undriven nonlinear dynamic systems subject to carefully crafted coupling schemes and operating conditions. Here, we summarize experimental results obtained on a system of N=3 coupled ferromagnetic cores, the underpinning of a 'coupled-core fluxgate magnetometer' (CCFM); the oscillatory behaviour is triggered when the coupling constant exceeds a threshold value (bifurcation point), and the oscillation frequency exhibits a characteristic scaling behaviour with the 'separation' of the coupling constant from its threshold value, as well as with an external target DC magnetic flux signal. The oscillations, which can be induced at frequencies ranging from a few Hz to high-kHz, afford a new detection scheme for weak target magnetic signals. We also present the first (numerical) results on the effects of a (Gaussian, exponentially correlated) noise floor on the spectral properties of the system response
Bulsara, Adi R. [Space and Naval Warfare Systems Center San Diego, Code 2363, 53560 Hull Street, San Diego, CA 92152-5001 (United States)]. E-mail: bulsara@spawar.navy.mil; Lindner, John F. [Physics Department, College of Wooster, Wooster, OH 44691 (United States); In, Visarath [Space and Naval Warfare Systems Center San Diego, Code 2363, 53560 Hull Street, San Diego, CA 92152-5001 (United States); Kho, Andy [Space and Naval Warfare Systems Center San Diego, Code 2363, 53560 Hull Street, San Diego, CA 92152-5001 (United States); Baglio, Salvatore [Dipartimento di Ingegneria Elettrica Elettronica e dei Sistemi, Universita degli Studi di Catania, Viale A. Doria 6, 95125 Catania (Italy); Sacco, Vincenzo [Dipartimento di Ingegneria Elettrica Elettronica e dei Sistemi, Universita degli Studi di Catania, Viale A. Doria 6, 95125 Catania (Italy); Ando, Bruno [Dipartimento di Ingegneria Elettrica Elettronica e dei Sistemi, Universita degli Studi di Catania, Viale A. Doria 6, 95125 Catania (Italy); Longhini, Patrick [Nonlinear Dynamics Group, Department of Mathematics, San Diego State University, San Diego, CA 92182 (United States); Palacios, Antonio [Nonlinear Dynamics Group, Department of Mathematics, San Diego State University, San Diego, CA 92182 (United States); Rappel, Wouter-Jan [Physics Department, University of California at San Diego, La Jolla, CA 929093 (United States)
2006-04-17
Recently, we have shown the emergence of oscillations in overdamped undriven nonlinear dynamic systems subject to carefully crafted coupling schemes and operating conditions. Here, we summarize experimental results obtained on a system of N=3 coupled ferromagnetic cores, the underpinning of a 'coupled-core fluxgate magnetometer' (CCFM); the oscillatory behaviour is triggered when the coupling constant exceeds a threshold value (bifurcation point), and the oscillation frequency exhibits a characteristic scaling behaviour with the 'separation' of the coupling constant from its threshold value, as well as with an external target DC magnetic flux signal. The oscillations, which can be induced at frequencies ranging from a few Hz to high-kHz, afford a new detection scheme for weak target magnetic signals. We also present the first (numerical) results on the effects of a (Gaussian, exponentially correlated) noise floor on the spectral properties of the system response.
A new experimental setup to characterize the dynamic mechanical behaviour of ballistic yarns
Chevalier, C; Kerisit, C; Faderl, N; Klavzar, A; Boussu, F; Coutellier, D
2016-01-01
Fabrics have been widely used as part of ballistic protections since the 1970s and the development of new ballistic solutions made from fabrics need numerical simulations, in order to predict the performance of the ballistic protection. The performances and the induced mechanisms in ballistic fabrics during an impact depend on the weaving parameters and also on the inner parameters of the yarns used inside these structures. Thus, knowing the dynamic behaviour of yarn is essential to determine the ballistic behaviour of fabrics during an impact. Two major experimental devices exist and are used to test ballistic yarns in a dynamic uniaxial tension. The first one corresponds to the Split Hopkinson Tensile Bars device, which is commonly used to characterize the mechanical properties of materials in uniaxial tension and under high loading. The second one is the transversal impact device. The real conditions of ballistic impact can be realized with this device. Then, this paper deals with a new experimental setup developed in our laboratory and called the ‘tensile impact test for yarn’ (TITY) device. With this device, specific absorbed energy measurements of para-aramid yarns (336 Tex, Twaron ™ , 1000 filaments) have been carried out and revealed that static and dynamic properties of para-aramid are different. (paper)
Kretov, D.A.; Kholmurodov, Kh.T.
2005-01-01
We used molecular dynamics (MD) simulations to study the density and the temperature behaviour of a flexible polyethylene (PE) subjected to various heating conditions and to investigate the PE chain conformational changes in a water solvent. First, we have considered the influence of the heating process on the final state of the polymeric system and the sensitivity of its thermodynamic characteristics (density, energy, etc.) for different heating regimes. For this purpose three different simulations were performed: fast, moderate, and slow heating. Second, we have investigated the PE chain conformational dynamics in water solvent for various simulation conditions and various configurations of the environment. From the obtained results we have got the pictures of the PE dynamical motions in water. We have observed a protein-like behaviour of the PE chain, like that of the DNA and the proteins in water, and have also estimated the rates of the conformational changes. For the MD simulations we used the optimized general-purpose DL P OLY code and the generic DREIDING force field. The MD simulations were performed on the parallel computers and special-purpose MDGRAPE-2 machine
Papageorgiou, George Nathaniel
2005-01-01
In the face of limited energy reserves and the global warming phenomenon, Europe is undergoing a transition from rapidly depleting fossil fuels to renewable unconventional energy sources. During this transition period, energy shortfalls will occur and energy prices will be increasing in an oscillating manner. As a result of the turbulence and dynamicity that will accompany the transition period, energy analysts need new appropriate methods, techniques and tools in order to develop forecasts for the behaviour of energy markets, which would assist in the long term strategic energy planning and policy analysis. This paper reviews energy market behaviour as related to policy formation, and from a dynamic point of view through the use of ''systems thinking'' and ''system dynamics'' principles, provides a framework for modelling the energy production and consumption process in relation to their environment. Thereby, effective energy planning can be developed via computerised simulation using policy experimentation. In a demonstration model depicted in this paper, it is shown that disasters due to attractive policies can be avoided by using simple computer simulation. (Author)
Donovan, Sarah-Louise; Salmon, Paul M; Horberry, Timothy; Lenné, Michael G
2018-01-01
Safety leadership is an important factor in supporting safe performance in the workplace. The present case study examined the role of safety leadership during the Bingham Canyon Mine high-wall failure, a significant mining incident in which no fatalities or injuries were incurred. The Critical Decision Method (CDM) was used in conjunction with a self-reporting approach to examine safety leadership in terms of decisions, behaviours and actions that contributed to the incidents' safe outcome. Mapping the analysis onto Rasmussen's Risk Management Framework (Rasmussen, 1997), the findings demonstrate clear links between safety leadership decisions, and emergent behaviours and actions across the work system. Communication and engagement based decisions featured most prominently, and were linked to different leadership practices across the work system. Further, a core sub-set of CDM decision elements were linked to the open flow and exchange of information across the work system, which was critical to supporting the safe outcome. The findings provide practical implications for the development of safety leadership capability to support safety within the mining industry. Copyright © 2017 Elsevier Ltd. All rights reserved.
Moment-to-moment dynamics of ADHD behaviour in South African children
Meyer Anneke
2006-03-01
Full Text Available Abstract Background The behaviour of children with Attention-Deficit/Hyperactivity Disorder is characterized by low predictability of responding. Low behavioural predictability is one way of operationalizing intra-individual ADHD-related variability. ADHD-related variability may be caused by inefficient behavioural selection mechanisms linked to reinforcement and extinction, as suggested by the recently published dynamic developmental theory (DDT of ADHD. DDT argues that ADHD is a basic neurobehavioural disorder, caused by dysfunctioning dopamine systems. For establishing ADHD as a neurobehavioural disorder, findings from studies conducted in Western countries should be replicated in other cultural populations. The present study replicated the study conducted in Norway, with children from the Limpopo province in the Republic of South Africa. Methods Boys and girls, aged 6–9 yr, from seven ethnic groups participated. Scores by teachers on the Disruptive Behavior Disorders rating scale defined participation in either ADHD-hyperactive/impulsive (-HI, ADHD-predominantly inattentive (-PI, or ADHD-combined (-C groups. Children below the 86th percentile were matched on gender and age and comprised the non-ADHD group. The children completed a computerized game-like task where mouse clicks on one of two squares on the screen resulted in delivery of a reinforcer according to a variable interval schedule of reinforcement. Reinforcers were cartoon pictures presented on the screen together with a sound. Predictability of response location and timing were measured in terms of explained variance. Results Overall, the results replicated findings from Norway. Specifically, the ADHD-C group showed significantly lower predictability of responding than the non-ADHD group, while the ADHD-HI and the ADHD-PI groups were in-between. In accordance with the previous study, response location, but not response timing, was a sensitive behavioural measure. There were no
The critical behaviour of self-dual Z(N) spin systems - Finite size scaling and conformal invariance
Alcaraz, F.C.
1986-01-01
Critical properties of a family of self-dual two dimensional Z(N) models whose bulk free energy is exacly known at the self-dual point are studied. The analysis is performed by studing the finite size behaviour of the corresponding one dimensional quantum Hamiltonians which also possess an exact solution at their self-dual point. By exploring finite size scaling ideas and the conformal invariance of the critical infinite system the critical temperature and critical exponents as well as the central charge associated with the underlying conformal algebra are calculated for N up to 8. The results strongly suggest that the recently constructed Z(N) quantum field theory of Zamolodchikov and Fateev (1985) is the underlying field theory associated with these statistical mechanical systems. It is also tested, for the Z(5) case, the conjecture that these models correspond to the bifurcation points, in the phase diagram of the general Z(N) spin model, where a massless phase originates. (Author) [pt
± J D-vector spin glass phase diagram and critical behaviour
Coutinho, S.; Lyra, M.L.
1988-01-01
The phase diagram and the correlation length exponents of the ± J D-Vector Spin-Glass model are studied in the framework of the real space mean field renormalization group method. The boundary between the spin-glass (SG) and the ferromagnetic (F) phases is obtained from the renormalization flow equations and shows a reentrant behaviour over the SG region. This re-entrance increases smoothly with the coordination number. Analytical expressions for the thermal and the correlation length exponents are calculated straight forwardly for all fixed points and figures are presented and compared with availables results from other methods and data. (author) [pt
The TNO Vehicle Dynamics Database (VDD): a tool for comparision of vehicle dynamics behaviour
Kleuskens, R.J.A.
1996-01-01
TNO has started a database containing data of vehicle dynamics properties of passenger cars, based on the results of eight objective ISO driving tests. From this database, car manufacturers and their suppliers can get the required information for design and marketing purposes in a fast and
Voltage Imaging of Waking Mouse Cortex Reveals Emergence of Critical Neuronal Dynamics
Scott, Gregory; Fagerholm, Erik D.; Mutoh, Hiroki; Leech, Robert; Sharp, David J.; Shew, Woodrow L.
2014-01-01
Complex cognitive processes require neuronal activity to be coordinated across multiple scales, ranging from local microcircuits to cortex-wide networks. However, multiscale cortical dynamics are not well understood because few experimental approaches have provided sufficient support for hypotheses involving multiscale interactions. To address these limitations, we used, in experiments involving mice, genetically encoded voltage indicator imaging, which measures cortex-wide electrical activity at high spatiotemporal resolution. Here we show that, as mice recovered from anesthesia, scale-invariant spatiotemporal patterns of neuronal activity gradually emerge. We show for the first time that this scale-invariant activity spans four orders of magnitude in awake mice. In contrast, we found that the cortical dynamics of anesthetized mice were not scale invariant. Our results bridge empirical evidence from disparate scales and support theoretical predictions that the awake cortex operates in a dynamical regime known as criticality. The criticality hypothesis predicts that small-scale cortical dynamics are governed by the same principles as those governing larger-scale dynamics. Importantly, these scale-invariant principles also optimize certain aspects of information processing. Our results suggest that during the emergence from anesthesia, criticality arises as information processing demands increase. We expect that, as measurement tools advance toward larger scales and greater resolution, the multiscale framework offered by criticality will continue to provide quantitative predictions and insight on how neurons, microcircuits, and large-scale networks are dynamically coordinated in the brain. PMID:25505314
Critical Behaviour of Pure and Site-Random Two Dimensional Antiferromagnets
Birgenau, R. J.; Als-Nielsen, Jens Aage; Shirane, G.
1977-01-01
Quasielastic neutron scattering studies of the static critical behavior in the two-dimensional antiferromagnets K2NiF4, K2MnF4, and Rb2Mn0.5Ni0.5F4 are reported. For T......Quasielastic neutron scattering studies of the static critical behavior in the two-dimensional antiferromagnets K2NiF4, K2MnF4, and Rb2Mn0.5Ni0.5F4 are reported. For T...
Miguel, António F.
2016-09-01
Walking is the most basic form of transportation. A good understanding of pedestrian's dynamics is essential in meeting the mobility and accessibility needs of people by providing a safe and quick walking flow [1]. Advances in the dynamics of pedestrians in crowds are of great theoretical and practical interest, as they lead to new insights regarding the planning of pedestrian facilities, crowd management, or evacuation analysis. Nicola Bellomo's et al. article [2] is a very timely review of the related research on modelling approaches, computational simulations, decision-making and crisis response. It also includes an attempt to accurately define commonly used terms, as well as a critical analysis of crowd dynamics and safety problems. As noted by the authors, ;models and simulations offer a virtual representation of real dynamics; that are essential to understand and predict the ;behavioural dynamics of crowds; [2]. As a physicist, I would like to put forward some additional theoretical and practical contributions that could be interesting to explore, regarding the perspective of physics on about human crowd dynamics (panic as a specific form of behaviour excluded).
Poirier, Marc; Gagnon, Martin; Tahan, Antoine; Coutu, André; Chamberland-lauzon, Joël
2017-01-01
In this paper, we present the application of cyclostationary modelling for the extrapolation of short stationary load strain samples measured in situ on hydraulic turbine blades. Long periods of measurements allow for a wide range of fluctuations representative of long-term reality to be considered. However, sampling over short periods limits the dynamic strain fluctuations available for analysis. The purpose of the technique presented here is therefore to generate a representative signal containing proper long term characteristics and expected spectrum starting with a much shorter signal period. The final objective is to obtain a strain history that can be used to estimate long-term fatigue behaviour of hydroelectric turbine runners.
The Impact of Speed of Play in Gambling on Psychological and Behavioural Factors: A Critical Review.
Harris, Andrew; Griffiths, Mark D
2018-06-01
Conceptually, there is a common association between gambling games with fast speeds of play and problem gambling. This relationship however, is largely correlational in nature, which comes at the expense of carefully controlled empirical investigation. Research that does exist aimed towards investigating the impact of gambling speeds on psychological and behavioural factors, is in its relative infancy, and the research possesses disparate methodologies and variables of interest. The aims of the current review is therefore to evaluate and summarise the existing body of evidence relating to speed of play in gambling, as well as discuss how this evidence can be used to inform harm minimisation approaches aimed at facilitating self-control during gambling. Eleven studies were selected for review based on the inclusion criteria, comprising nine experimental and two qualitative studies (one self-report focus group study and one observational study). There was a consistent finding across studies that games with faster speeds of play were preferred and rated as more exciting for all gamblers, ranging from non-problem to problem gamblers. Of concern, was the repeated finding that fast games are particularly appealing to those suffering with a gambling problem. Behavioural results were more inconsistent across studies, though the general trend supports the notion that games with faster speeds of play encourage more wagers, longer game play, and caused players, particularly problem gamblers, to experience difficulty in ceasing gambling. The implications of these findings for gambling policy, harm minimisation approaches, and future research are discussed.
Intellectual Disabilities, Challenging Behaviour and Referral Texts: A Critical Discourse Analysis
Nunkoosing, Karl; Haydon-Laurelut, Mark
2011-01-01
The texts of referrals written by workers in residential services for people with learning difficulties constitute sites where contemporary discourses of intellectual disabilities are being constructed. This paper uses Critical Discourse Analysis to examine referrals made to a Community Learning Disability Team (CLDT). The study finds referral…
Study on non-universal critical behaviour in Ising model with defects
Guimaraes, L.G.
1986-01-01
One-dimensional quantum analogous of two-dimensional Ising models with line and step type linear defects are studied. The phenomenological renormalization group was approached using conformal invariance for relating critical exponent N sup(*) sub(H). Aiming to obtain the Hamiltonian diagonal, Lanczos tridiagonal method was used. (H.C.K.)
Damgaard, Mads; Bayat, Mehdi; Andersen, Lars Vabbersgaard
2014-01-01
The fatigue life of offshore wind turbines strongly depends on the dynamic behaviour of the structures including the underlying soil. To diminish dynamic amplification and avoid resonance, the eigenfrequency related to the lowest eigenmode of the wind turbine should not coalesce with excitation f...
Abidin, Norhaslinda Zainal; Zaibidi, Nerda Zura; Zulkepli, Jafri Hj
2015-10-01
Obesity is a medical condition where an individual has an excessive amount of body fat. There are many factors contributing to obesity and one of them is the sedentary behaviour. Rapid development in industrialization and urbanization has brought changes to Malaysia's socioeconomic, especially the lifestyles of Malaysians. With this lifestyle transition, one of the impact is on weight and obesity. How does sedentary behaviour have an impact on the growth of Malaysian population's weight and obesity? What is the most effective sedentary behaviour preventing strategy to obesity? Is it through reduction in duration or frequency of sedentary behaviour? Thus, the aim of this paper is to design an intervention to analyse the effect of decreasing duration and frequency of sedentary behaviour on the population reversion trends of average weight (AW), average body mass index (ABMI), and prevalence of overweight and obesity (POVB). This study combines the different strands of sub-models comprised of nutrition, physical activity and body metabolism, and then synthesis these knowledge into a system dynamics of weight behaviour model, namely SIMULObese. Findings from this study revealed that Malaysian's adults spend a lot of time engaged in sedentary behaviour and this resulted in weight gain and obesity. Comparing between frequency and duration of sedentary behaviour, this study reported that reduced in duration or time spend in sedentary behaviour is a better preventing strategy to obesity compared to duration. As a summary, this study highlighted the importance of decreasing the frequency and duration of sedentary behaviour in developing guidelines to prevent obesity.
Achieving dynamic behaviour and thermal expansion in the organic solid state via co-crystallization.
Hutchins, Kristin M; Groeneman, Ryan H; Reinheimer, Eric W; Swenson, Dale C; MacGillivray, Leonard R
2015-08-01
Thermal expansion involves a response of a material to an external stimulus that typically involves an increase in a crystallographic axis (positive thermal expansion (PTE)), although shrinking with applied heat (negative thermal expansion (NTE)) is known in rarer cases. Here, we demonstrate a means to achieve dynamic molecular motion and thermal expansions in organic solids via co-crystallizations. One co-crystal component is known to exhibit dynamic behaviour in the solid state while the second, when varied systematically, affords co-crystals with linear thermal expansion coefficients that range from colossal to nearly zero. Two co-crystals exhibit rare NTE. We expect the approach to guide the design of molecular solids that enable predesigned motion related to thermal expansion processes.
The behaviour of a vehicle’s suspension system on dynamic testing conditions
Mihon, L.; Lontiş, N.; Deac, S.
2018-01-01
The paper presents a car suspension’s behaviour on dynamic testing conditions through theoretical and mathematical simulation on specific model, on the single traction wheel, according to the real vehicle and by experiment on the test bench by reproducing the road’s geometry and vehicle’s speed and measuring the acceleration and damping response of the suspension system on that wheel. There are taking in consideration also the geometry and properties of the tyre-wheel model and physical wheel’s properties. The results are important due to the suspension’s model properties which allows to extend the theory and applications to the whole vehicle for improving the vehicle’s dynamics.
Gaudin, M [Electricite de France (EDF), Direction des Etudes et Recherches, 92 - Clamart (France)
1998-12-31
Resetting models is applied to electricity generating plant pipework systems. A frequency approach to the problem is made in an original way thanks to the use of precise dynamic rigidity matrices. The method assumes two kinds of unknown: the usually processed mechanical characteristics (Young`s Modulus, density etc.) and new resetting parameters acting on the dynamic behaviour of unknown connections. As the latter have a very wide range of possible variation, they benefit from a change of variable which allows the assumptions formulated to be complied with. The minimized cost function is based on a error in load. The frequencies required for building it are automatically selected thanks to different tests on measurements. Minimization uses a sensitivity technique linked with a method of least standard squares. The method has been programmed in Fortran 90 within the CIRCUS code and tried out on various examples which were simulated and sound effects cases as well as an actual case. (author). 128 refs.
Brittle versus ductile behaviour of nanotwinned copper: A molecular dynamics study
Pei, Linqing; Lu, Cheng; Zhao, Xing; Zhang, Liang; Cheng, Kuiyu; Michal, Guillaume; Tieu, Kiet
2015-01-01
Nanotwinned copper (Cu) exhibits an unusual combination of ultra-high yield strength and high ductility. A brittle-to-ductile transition was previously experimentally observed in nanotwinned Cu despite Cu being an intrinsically ductile metal. However, the atomic mechanisms responsible for brittle fracture and ductile fracture in nanotwinned Cu are still not clear. In this study, molecular dynamics (MD) simulations at different temperatures have been performed to investigate the fracture behaviour of a nanotwinned Cu specimen with a single-edge-notched crack whose surface coincides with a twin boundary. Three temperature ranges are identified, indicative of distinct fracture regimes, under tensile straining perpendicular to the twin boundary. Below 1.1 K, the crack propagates in a brittle fashion. Between 2 K and 30 K a dynamic brittle-to-ductile transition is observed. Above 40 K the crack propagates in a ductile mode. A detailed analysis has been carried out to understand the atomic fracture mechanism in each fracture regime
Gaudin, M. [Electricite de France (EDF), Direction des Etudes et Recherches, 92 - Clamart (France)
1997-12-31
Resetting models is applied to electricity generating plant pipework systems. A frequency approach to the problem is made in an original way thanks to the use of precise dynamic rigidity matrices. The method assumes two kinds of unknown: the usually processed mechanical characteristics (Young`s Modulus, density etc.) and new resetting parameters acting on the dynamic behaviour of unknown connections. As the latter have a very wide range of possible variation, they benefit from a change of variable which allows the assumptions formulated to be complied with. The minimized cost function is based on a error in load. The frequencies required for building it are automatically selected thanks to different tests on measurements. Minimization uses a sensitivity technique linked with a method of least standard squares. The method has been programmed in Fortran 90 within the CIRCUS code and tried out on various examples which were simulated and sound effects cases as well as an actual case. (author). 128 refs.
Empowering people to change occupational behaviours to address critical global issues.
Ikiugu, Moses N; Westerfield, Madeline A; Lien, Jamie M; Theisen, Emily R; Cerny, Shana L; Nissen, Ranelle M
2015-06-01
The greatest threat to human well-being in this century is climate change and related global issues. We examined the effectiveness of the Modified Instrumentalism in Occupational Therapy model as a framework for facilitating occupational behaviour change to address climate change and related issues. Eleven individuals participated in this mixed-methods single-subject-design study. Data were gathered using the Modified Assessment and Intervention Instrument for Instrumentalism in Occupational Therapy and Daily Occupational Inventories. Quantitative data were analyzed using two- and three-standard deviation band methods. Qualitative data were analyzed using heuristic phenomenological procedures. Occupational performance changed for five participants. Participants' feelings shifted from frustration and helplessness to empowerment and a desire for action. They felt empowered to find occupation-based solutions to the global issues. Occupation-based interventions that increase personal awareness of the connection between occupational performance and global issues could empower people to be agents for action to ameliorate the issues.
Park, Jae Sung; Shekar, Ashwin; Graham, Michael D.
2018-01-01
The dynamics of the turbulent near-wall region is known to be dominated by coherent structures. These near-wall coherent structures are observed to burst in a very intermittent fashion, exporting turbulent kinetic energy to the rest of the flow. In addition, they are closely related to invariant solutions known as exact coherent states (ECS), some of which display nonlinear critical layer dynamics (motions that are highly localized around the surface on which the streamwise velocity matches the wave speed of ECS). The present work aims to investigate temporal coherence in minimal channel flow relevant to turbulent bursting and critical layer dynamics and its connection to the instability of ECS. It is seen that the minimal channel turbulence displays frequencies very close to those displayed by an ECS family recently identified in the channel flow geometry. The frequencies of these ECS are determined by critical layer structures and thus might be described as "critical layer frequencies." While the bursting frequency is predominant near the wall, the ECS frequencies (critical layer frequencies) become predominant over the bursting frequency at larger distances from the wall, and increasingly so as Reynolds number increases. Turbulent bursts are classified into strong and relatively weak classes with respect to an intermittent approach to a lower branch ECS. This temporally intermittent approach is closely related to an intermittent low drag event, called hibernating turbulence, found in minimal and large domains. The relationship between the strong burst and the instability of the lower branch ECS is further discussed in state space. The state-space dynamics of strong bursts is very similar to that of the unstable manifolds of the lower branch ECS. In particular, strong bursting processes are always preceded by hibernation events. This precursor dynamics to strong turbulence may aid in development of more effective control schemes by a way of anticipating dynamics
Modelling human behaviour in a bumper car ride using molecular dynamics tools: a student project
Buendía, Jorge J.; Lopez, Hector; Sanchis, Guillem; Pardo, Luis Carlos
2017-05-01
Amusement parks are excellent laboratories of physics, not only to check physical laws, but also to investigate if those physical laws might also be applied to human behaviour. A group of Physics Engineering students from Universitat Politècnica de Catalunya has investigated if human behaviour, when driving bumper cars, can be modelled using tools borrowed from the analysis of molecular dynamics simulations, such as the radial and angular distribution functions. After acquiring several clips and obtaining the coordinates of the cars, those magnitudes are computed and analysed. Additionally, an analogous hard disks system is simulated to compare its distribution functions to those obtained from the cars’ coordinates. Despite the clear difference between bumper cars and a hard disk-like particle system, the obtained distribution functions are very similar. This suggests that there is no important effect of the individuals in the collective behaviour of the system in terms of structure. The research, performed by the students, has been undertaken in the frame of a motivational project designed to approach the scientific method for university students named FISIDABO. This project offers both the logistical and technical support to undertake the experiments designed by students at the amusement park of Barcelona TIBIDABO and accompanies them all along the scientific process.
Adamides, E. D.; Papachristos, G.; Pomonis, N.
2012-01-01
Purpose – The purpose of this paper is to show how a critical realist paradigmatic stance and its associated research methodology can contribute to supply‐chain research by providing explanations for specific supply‐chain‐ and logistics‐related dynamic phenomena. / Design/methodology/approach – Initially, the case for a critical realist research paradigm is made, and then a retroductive pluralistic research methodology is used for demonstrating its application. Starting from an observation in...
The magnetic flux dynamics in the critical state of one-dimensional discrete superconductor
Ginzburg, S.L.; Nakin, A.V.; Savitskaya, N.E.
2006-01-01
We give a theoretical description of avalanche-like dynamics of magnetic flux in the critical state of discrete superconductors using a one-dimensional model of a multijunction SQUID. We show that the system under consideration demonstrates the self-organized criticality. The avalanches of vortices manifest themselves as jumps of the total magnetic flux in the sample. The sizes of these jumps have a power-law distribution. We argue that similarities in the behavior of discrete and usual type-II superconductors allows to extend our results for description of avalanche-like dynamics in type-II superconductors with strong pinning
Quantum critical behaviour of the plateau-insulator transition in the quantum Hall regime
Visser, A de; Ponomarenko, L A; Galistu, G; Lang, D T N de; Pruisken, A M M; Zeitler, U; Maude, D
2006-01-01
High-field magnetotransport experiments provide an excellent tool to investigate the plateau-insulator phase transition in the integral quantum Hall effect. Here we review recent low-temperature high-field magnetotransport studies carried out on several InGaAs/InP heterostructures and an InGaAs/GaAs quantum well. We find that the longitudinal resistivity ρ xx near the critical filling factor ν c ∼ 0.5 follows the universal scaling law ρ xx (ν, T) ∝ exp(-Δν/(T/T 0 ) κ ), where Δν = ν-ν c . The critical exponent κ equals 0.56 ± 0.02, which indicates that the plateau-insulator transition falls in a non-Fermi liquid universality class
Roelich, Katy; Dawson, David A.; Purnell, Phil; Knoeri, Christof; Revell, Ruairi; Busch, Jonathan; Steinberger, Julia K.
2014-01-01
Highlights: • We present a method to analyse material criticality of infrastructure transitions. • Criticality is defined as the potential for, and exposure to, supply disruption. • Our method is dynamic reducing the probability of lock-in to at-risk technologies. • We show that supply disruption potential is reducing but exposure is increasing. - Abstract: Decarbonisation of existing infrastructure systems requires a dynamic roll-out of technology at an unprecedented scale. The potential disruption in supply of critical materials could endanger such a transition to low-carbon infrastructure and, by extension, compromise energy security more broadly because low carbon technologies are reliant on these materials in a way that fossil-fuelled energy infrastructure is not. Criticality is currently defined as the combination of the potential for supply disruption and the exposure of a system of interest to that disruption. We build on this definition and develop a dynamic approach to quantifying criticality, which monitors the change in criticality during the transition towards a low-carbon infrastructure goal. This allows us to assess the relative risk of different technology pathways to reach a particular goal and reduce the probability of being ‘locked in’ to currently attractive but potentially future-critical technologies. To demonstrate, we apply our method to criticality of the proposed UK electricity system transition, with a focus on neodymium. We anticipate that the supply disruption potential of neodymium will decrease by almost 30% by 2050; however, our results show the criticality of low carbon electricity production increases ninefold over this period, as a result of increasing exposure to neodymium-reliant technologies
A Langevin model for fluctuating contact angle behaviour parametrised using molecular dynamics.
Smith, E R; Müller, E A; Craster, R V; Matar, O K
2016-12-06
Molecular dynamics simulations are employed to develop a theoretical model to predict the fluid-solid contact angle as a function of wall-sliding speed incorporating thermal fluctuations. A liquid bridge between counter-sliding walls is studied, with liquid-vapour interface-tracking, to explore the impact of wall-sliding speed on contact angle. The behaviour of the macroscopic contact angle varies linearly over a range of capillary numbers beyond which the liquid bridge pinches off, a behaviour supported by experimental results. Nonetheless, the liquid bridge provides an ideal test case to study molecular scale thermal fluctuations, which are shown to be well described by Gaussian distributions. A Langevin model for contact angle is parametrised to incorporate the mean, fluctuation and auto-correlations over a range of sliding speeds and temperatures. The resulting equations can be used as a proxy for the fully-detailed molecular dynamics simulation allowing them to be integrated within a continuum-scale solver.
Dynamic modelling of high speed ballasted railway trakcs: Analysis of the behaviour
Gallego, I.; Rivas, A.; Sanchez-Cambronero, S.; Lajara, J.
2016-07-01
The aim of the paper is to present a numerical model for a ballasted railway track that includes the dynamic effect of a moving train load and predicts the values of the vertical stiffness of the infrastructure. This model is therefore deemed to be a tool for the evaluation of the state of the track during service situations as well as a predictive model of the behaviour of the system. Consequently, it will be very useful when sizing the cross section of a new railway line is required.The main modelling tool is the finite element method. In regard to this, the application of damping elements to avoid the elastic wave reflection on the boundaries of the numerical domain will be studied. The proposed dynamic analysis consider the change in time of the value of the train load, but not the change in position along the tracks.In the end, a set of suggestions for the numerical model with moving loads will be summarize aiming for the mitigation of the unusual behaviour of the contact surface between the ballast and the sleepers. (Author)
Firm Size, a Self-Organized Critical Phenomenon: Evidence from the Dynamical Systems Theory
Chandra, Akhilesh
This research draws upon a recent innovation in the dynamical systems literature called the theory of self -organized criticality (SOC) (Bak, Tang, and Wiesenfeld 1988) to develop a computational model of a firm's size by relating its internal and the external sub-systems. As a holistic paradigm, the theory of SOC implies that a firm as a composite system of many degrees of freedom naturally evolves to a critical state in which a minor event starts a chain reaction that can affect either a part or the system as a whole. Thus, the global features of a firm cannot be understood by analyzing its individual parts separately. The causal framework builds upon a constant capital resource to support a volume of production at the existing level of efficiency. The critical size is defined as the production level at which the average product of a firm's factors of production attains its maximum value. The non -linearity is inferred by a change in the nature of relations at the border of criticality, between size and the two performance variables, viz., the operating efficiency and the financial efficiency. The effect of breaching the critical size is examined on the stock price reactions. Consistent with the theory of SOC, it is hypothesized that the temporal response of a firm breaching the level of critical size should behave as a flicker noise (1/f) process. The flicker noise is characterized by correlations extended over a wide range of time scales, indicating some sort of cooperative effect among a firm's degrees of freedom. It is further hypothesized that a firm's size evolves to a spatial structure with scale-invariant, self-similar (fractal) properties. The system is said to be self-organized inasmuch as it naturally evolves to the state of criticality without any detailed specifications of the initial conditions. In this respect, the critical state is an attractor of the firm's dynamics. Another set of hypotheses examines the relations between the size and the
Molecular dynamics simulation of a binary mixture near the lower critical point
Pousaneh, Faezeh; Edholm, Olle, E-mail: oed@kth.se [Theoretical Biological Physics, Department of Theoretical Physics, Royal Institute of Technology (KTH), AlbaNova University Center, SE-106 91 Stockholm (Sweden); Maciołek, Anna [Institute of Physical Chemistry, Polish Academy of Sciences, Kasprzaka 44/52, 01-224 Warsaw (Poland); Max-Planck-Institut für Intelligente Systeme, Heisenbergstrasse 3, D-70569 Stuttgart (Germany)
2016-07-07
2,6-lutidine molecules mix with water at high and low temperatures but in a wide intermediate temperature range a 2,6-lutidine/water mixture exhibits a miscibility gap. We constructed and validated an atomistic model for 2,6-lutidine and performed molecular dynamics simulations of 2,6-lutidine/water mixture at different temperatures. We determined the part of demixing curve with the lower critical point. The lower critical point extracted from our data is located close to the experimental one. The estimates for critical exponents obtained from our simulations are in a good agreement with the values corresponding to the 3D Ising universality class.
Effect of composition on the high rate dynamic behaviour of tungsten heavy alloys
Latif Kesemen
2015-01-01
Full Text Available Tungsten heavy alloys are currently used as kinetic energy penetrators in military applications due to their high density and superior mechanical properties. In the literature, quasi-static properties of different tungsten heavy alloys based on W-Ni-Cu and W-Ni-Fe ternary systems are well documented and presented. However, comparison of the dynamic behaviour of these alloys in terms of the correlation between quasi-static mechanical characterization and dynamical properties is lacking. In the present study, dynamic properties of tungsten heavy alloys having different binder phase compositions (90W-7Ni-3Cu and 90W-8Ni-2Fe at different projectile velocities were investigated. The examined and tested alloys were produced through the conventional powder metallurgy route of mixing, cold compaction and sintering. Mechanical characterization of these alloys was performed. In the ballistic tests, cylindrical tungsten heavy alloys with L/D ratio of 3 were impacted to hardened steel target at different projectile velocities. After the ballistic tests, deformation characteristics of test specimens during dynamic loading were evaluated by comparing the change of length and diameter of the specimens versus kinetic energy densities. The study concluded that 90W-8Ni-2Fe alloy has better perforation characteristics than 90W-7Ni-3Cu alloy.
Solvable lattice models with minimal and nonunitary critical behaviour in two dimensions
Riggs, H.; Chicago Univ., IL
1989-01-01
The exact local height probabilities found by Forrester and Baxter for a series of solvable lattice models in two dimensions are written in terms of nonunitary Virasoro characters and modifications of unitary A 1 (1) affine Lie algebra characters directly related to nonunitary but rational-level A 1 (1) characters. The relation between these results and a rational-level GKO decomposition is given. The off-critical lattice origin of the Virasoro characters and the role of the embedding diagram null vectors in the CTM eigenspace is described. Suggestions for the definition of rational and nonunitary models corresponding to arbitrary G/H cosets are given. (orig.)
Franco Mantovani
2017-06-01
Full Text Available Objectives: Premature ejaculation (PE is a sexual disorder characterised by excessive rapidity of orgasm. It is defined as either primary (60%, present since the onset of sexual activity, or secondary (40%, manifesting later in life. To date, dapoxetine is the only preparation approved for the on-demand treatment of PE. However, side effects, costs associated with the treatment of chronic PE, drug dependence and its variable effectiveness leads to a not insignificant drop-out rate. Dynamic rehabilitative/behavioural therapy may be a viable therapeutic option, working alongside pharmacological treatment, as long as the participation and involvement of both the individual and the couple is optimal. Materials and methods: 18 patients were enrolled, aged between 25 and 55 (mean: 40, all with primary PE, free of comorbidities and with their partners involved. Six patients were prescribed 30 mg dapoxetine two hours before sexual relations for 3 months (group A; 6 patients began the dynamic rehabilitative treatment (group B; 6 other couples were assigned to pharmacological treatment in association with dynamic rehabilitative behavioural treatment for 3 months (group C. Division of subjects was carried out by simple randomisation, excluding patients with a short frenulum, phimosis, ED, chronic prostatitis or experiencing results from previous treatment. Results: Outcomes of treatment were evaluated at the end of the 3 months of treatment and 3 months after discontinuing treatment. In Group A 75% of patients were cured at 3 months and 25% at 6 months. In Group B 25% patients were cured at 3 months and 25% at 6 months. In Group C 75% of patients were cured 3 months and 50% at 6 months. "Cured" means a Premature Ejaculation Diagnostic Tool (PEDT score reduced from an average of 12 to an average of 6 and Intravaginal Ejaculation Latency Time (IELT values from < 1 to > 6 minutes. Conclusions: the integration of pharmacological treatment with dynamic
Gauge dependence of the critical dynamics at the superconducting phase transition
M.Dudka
2007-01-01
Full Text Available The critical dynamics of superconductors in the charged regime is reconsidered within field-theory. For the dynamics, the Ginzburg-Landau model with complex order parameter coupled to the gauge field suggested earlier [Lannert et al. Phys. Rev. Lett. 92, 097004 (2004] is used. Assuming relaxational dynamics for both quantities, the renormalization group functions within one loop approximation are recalculated for different choices of the gauge. A gauge independent result for the divergence of the melectric conductivity is obtained only at the weak scaling fixed point unstable in one loop order where the timescales of the order parameter and the gauge field are different.
Volchenkov, D.
2009-01-01
Stochastic counterparts of nonlinear dynamics are studied by means of nonperturbative functional methods developed in the framework of quantum field theory (QFT). In particular, we discuss fully developed turbulence, including leading corrections on possible compressibility of fluids, transport through porous media, theory of waterspouts and tsunami waves, stochastic magnetohydrodynamics, turbulent transport in crossed fields, self-organized criticality, and dynamics of accelerated wrinkled flame fronts advancing in a wide canal. This report would be of interest to the broad auditorium of physicists and applied mathematicians, with a background in nonperturbative QFT methods or nonlinear dynamical systems, having an interest in both methodological developments and interdisciplinary applications. (author)
Volchenkov, D. [Bielefeld Univ., Center of Excellence Cognitive Interaction Technology (CITEC) (Germany)
2009-03-15
Stochastic counterparts of nonlinear dynamics are studied by means of nonperturbative functional methods developed in the framework of quantum field theory (QFT). In particular, we discuss fully developed turbulence, including leading corrections on possible compressibility of fluids, transport through porous media, theory of waterspouts and tsunami waves, stochastic magnetohydrodynamics, turbulent transport in crossed fields, self-organized criticality, and dynamics of accelerated wrinkled flame fronts advancing in a wide canal. This report would be of interest to the broad auditorium of physicists and applied mathematicians, with a background in nonperturbative QFT methods or nonlinear dynamical systems, having an interest in both methodological developments and interdisciplinary applications. (author)
Decelerating defects and non-ergodic critical behaviour in a unidirectionally coupled map lattice
Ashwin, Peter; Sturman, Rob
2003-01-01
We examine a coupled map lattice (CML) consisting of an infinite chain of logistic maps coupled in one direction by inhibitory coupling. We find that for sufficiently strong coupling strength there are dynamical states with 'decelerating defects', where defects between stable patterns (with chaotic temporal evolution and average spatial period two) slow down but never stop. These defects annihilate each other when they meet. We show for certain states that this leads to a lack of convergence (non-ergodicity) of averages taken from observables in the system and conjecture that this is typical for the system
A dynamic model to explain hydration behaviour along the lanthanide series
Duvail, M.; Spezia, R.; Vitorge, P.
2008-01-01
An understanding of the hydration structure of heavy atoms, such as transition metals, lanthanides and actinides, in aqueous solution is of fundamental importance in order to address their solvation properties and chemical reactivity. Herein we present a systematic molecular dynamics study of Ln 3+ hydration in bulk water that can be used as reference for experimental and theoretical research in this and related fields. Our study of hydration structure and dynamics along the entire Ln 3+ series provides a dynamic picture of the CN behavioural change from light (CN=9 predominating) to heavy (CN=8 predominating) lanthanides consistent with the exchange mechanism proposed by Helm, Merbach and co-workers. This scenario is summarized in this work. The hydrated light lanthanides are stable TTP structures containing two kinds of water molecules: six molecules forming the trigonal prism and three in the centre triangle. Towards the middle of the series both ionic radii and polarizabilities decrease, such that first-shell water-water repulsion increases and water-cation attraction decreases. This mainly applies for molecules of the centre triangle of the nine-fold structure. Thus, one of these molecules stay in the second hydration sphere of the lanthanide for longer average times, as one progresses along the lanthanide series. The interchange between predominantly CN=9 and CN=8 is found between Tb and Dy. Therefore, we propose a model that determines the properties governing the change in the first-shell coordination number across the series, confirming the basic hypothesis proposed by Helm and Merbach. We show that it is not a sudden change in behaviour, but rather that it results from a statistical predominance of one first hydration shell structure containing nine water molecules over one containing eight. This is observed progressively across the series. (O.M.)
A non-critical string approach to black holes, time and quantum dynamics
Ellis, John R.; Nanopoulos, Dimitri V.
1994-01-01
We review our approach to time and quantum dynamics based on non-critical string theory, developing its relationship to previous work on non-equilibrium quantum statistical mechanics and the microscopic arrow of time. We exhibit specific non-factorizing contributions to the {\
Euler Strut: A Mechanical Analogy for Dynamics in the Vicinity of a Critical Point
Bobnar, Jaka; Susman, Katarina; Parsegian, V. Adrian; Rand, Peter R.; Cepic, Mojca; Podgornik, Rudolf
2011-01-01
An anchored elastic filament (Euler strut) under an external point load applied to its free end is a simple model for a second-order phase transition. In the static case, a load greater than the critical load causes a Euler buckling instability, leading to a change in the filament's shape. The analysis of filament dynamics with an external point…
The asymptotic behaviour of a critical point reactor in the absence of a controller
Bansal, N.K.; Borgwaldt, H.
1976-11-01
A method is presented to calculate the first and second moments of neutron and precursor populations for a critical reactor system described by point kinetic equations and possessing inherent reactivity fluctuations. The equations have been linearised on the assumption that the system has a large average neutron population and that the amplitude of reactivity fluctuations is sufficiently small. The reactivity noise is assumed to be band limited white with a corner frequency higher than all the time constants of the system. Explicit expressions for the exact time development of the moments have been obtained for the case of a reactor without reactivity feedback and with one group of delayed neutrons. It is found that the expected values of the neutron and delayed neutron precursor numbers tend asymptotically to stationary values, whereas the mean square deviations increase linearly with time at an extremely low rate. (orig.) [de
Critical dynamics a field theory approach to equilibrium and non-equilibrium scaling behavior
Täuber, Uwe C
2014-01-01
Introducing a unified framework for describing and understanding complex interacting systems common in physics, chemistry, biology, ecology, and the social sciences, this comprehensive overview of dynamic critical phenomena covers the description of systems at thermal equilibrium, quantum systems, and non-equilibrium systems. Powerful mathematical techniques for dealing with complex dynamic systems are carefully introduced, including field-theoretic tools and the perturbative dynamical renormalization group approach, rapidly building up a mathematical toolbox of relevant skills. Heuristic and qualitative arguments outlining the essential theory behind each type of system are introduced at the start of each chapter, alongside real-world numerical and experimental data, firmly linking new mathematical techniques to their practical applications. Each chapter is supported by carefully tailored problems for solution, and comprehensive suggestions for further reading, making this an excellent introduction to critic...
Phase transitions, nonequilibrium dynamics, and critical behavior of strongly interacting systems
Mottola, E.; Bhattacharya, T.; Cooper, F.
1998-01-01
This is the final report of a three-year, Laboratory Directed Research and Development project at Los Alamos National Laboratory. In this effort, large-scale simulations of strongly interacting systems were performed and a variety of approaches to the nonequilibrium dynamics of phase transitions and critical behavior were investigated. Focus areas included (1) the finite-temperature quantum chromodynamics phase transition and nonequilibrium dynamics of a new phase of matter (the quark-gluon plasma) above the critical temperature, (2) nonequilibrium dynamics of a quantum fields using mean field theory, and (3) stochastic classical field theoretic models with applications to spinodal decomposition and structural phase transitions in a variety of systems, such as spin chains and shape memory alloys
Phase transitions, nonequilibrium dynamics, and critical behavior of strongly interacting systems
Mottola, E.; Bhattacharya, T.; Cooper, F. [and others
1998-12-31
This is the final report of a three-year, Laboratory Directed Research and Development project at Los Alamos National Laboratory. In this effort, large-scale simulations of strongly interacting systems were performed and a variety of approaches to the nonequilibrium dynamics of phase transitions and critical behavior were investigated. Focus areas included (1) the finite-temperature quantum chromodynamics phase transition and nonequilibrium dynamics of a new phase of matter (the quark-gluon plasma) above the critical temperature, (2) nonequilibrium dynamics of a quantum fields using mean field theory, and (3) stochastic classical field theoretic models with applications to spinodal decomposition and structural phase transitions in a variety of systems, such as spin chains and shape memory alloys.
Optimal system size for complex dynamics in random neural networks near criticality
Wainrib, Gilles, E-mail: wainrib@math.univ-paris13.fr [Laboratoire Analyse Géométrie et Applications, Université Paris XIII, Villetaneuse (France); García del Molino, Luis Carlos, E-mail: garciadelmolino@ijm.univ-paris-diderot.fr [Institute Jacques Monod, Université Paris VII, Paris (France)
2013-12-15
In this article, we consider a model of dynamical agents coupled through a random connectivity matrix, as introduced by Sompolinsky et al. [Phys. Rev. Lett. 61(3), 259–262 (1988)] in the context of random neural networks. When system size is infinite, it is known that increasing the disorder parameter induces a phase transition leading to chaotic dynamics. We observe and investigate here a novel phenomenon in the sub-critical regime for finite size systems: the probability of observing complex dynamics is maximal for an intermediate system size when the disorder is close enough to criticality. We give a more general explanation of this type of system size resonance in the framework of extreme values theory for eigenvalues of random matrices.
Optimal system size for complex dynamics in random neural networks near criticality
Wainrib, Gilles; García del Molino, Luis Carlos
2013-01-01
In this article, we consider a model of dynamical agents coupled through a random connectivity matrix, as introduced by Sompolinsky et al. [Phys. Rev. Lett. 61(3), 259–262 (1988)] in the context of random neural networks. When system size is infinite, it is known that increasing the disorder parameter induces a phase transition leading to chaotic dynamics. We observe and investigate here a novel phenomenon in the sub-critical regime for finite size systems: the probability of observing complex dynamics is maximal for an intermediate system size when the disorder is close enough to criticality. We give a more general explanation of this type of system size resonance in the framework of extreme values theory for eigenvalues of random matrices
Experimental research project on the dynamic behaviour of Garigliano N.P.P
Sano, Tito; Vitiello, Edmondo
1988-01-01
The Garigliano N.P.P., 150 MW electric and 500 MW thermic, was built from 1961- to 1964. During 1980 it was shut down and thereafter the decommissioning procedure was started. In 1984 ENEA-DISP sponsored a preliminary study for a program of on-site experimental research on the Garigliano plant as part of a more general research program on seismic safety margin assessments. This paper presents the main conclusions of this preliminary study. For the research concerning the dynamic behaviour, some features have been pointed out: a) The Garigliano N.P.P. gives the opportunity to get some results on the soil-structure interaction in the interesting case of soft-soil (indefinite layer). b) The interaction structure-soil-structure can be tested between reactor building and turbine that are separated by an expansion-joint (extending in the mat too). c) The spherical steel containment has no other structural connections with the inner reinforced concrete structure than at the foundation level and therefore it may give clean experimental results on the dynamic behaviour of the containment alone. d) The H/B (height/base) ratio of the reactor building is sufficiently low to obtain translational modes of the structure. The research program is subdivided into many phases. The ones concerning the overall structure behaviour are as following: 1) Excitation by underground explosions. 2) Excitation by actuators on the mat using as reaction mass a concrete slab (ad hoc built aside). The latter is also used to compare the dynamic foundation response with and without micropiles. 3) Excitation by shakers inside the reactor building (at the top of the concrete structure). 4) Impact tests on the external R.C. wall of the turbine building. Others phases of research program are related to the tests of aged components on site and on shaking table (up to failure load). At the end of this paper an outline of the first experiment (excitation by explosion) and some results are presented. (author)
Non-linear quantum critical dynamics and fluctuation-dissipation ratios far from equilibrium
Zamani, Farzaneh [Max Planck Institute for the Physics of Complex Systems, Nöthnitzer Str. 38, 01187 Dresden (Germany); Max Planck Institute for Chemical Physics of Solids, Nöthnitzer Str. 40, 01187 Dresden (Germany); Ribeiro, Pedro [CeFEMA, Instituto Superior Tcnico, Universidade de Lisboa, Av. Rovisco Pais, 1049-001 Lisboa (Portugal); Russian Quantum Center, Novaya Street 100 A, Skolkovo, Moscow Area, 143025 (Russian Federation); Kirchner, Stefan, E-mail: stefan.kirchner@correlated-matter.com [Center for Correlated Matter, Zhejiang University, Hangzhou, Zhejiang 310058 (China)
2016-02-15
Non-thermal correlations of strongly correlated electron systems and the far-from-equilibrium properties of phases of condensed matter have become a topical research area. Here, an overview of the non-linear dynamics found near continuous zero-temperature phase transitions within the context of effective temperatures is presented. In particular, we focus on models of critical Kondo destruction. Such a quantum critical state, where Kondo screening is destroyed in a critical fashion, is realized in a number of rare earth intermetallics. This raises the possibility of experimentally testing for the existence of fluctuation-dissipation relations far from equilibrium in terms of effective temperatures. Finally, we present an analysis of a non-interacting, critical reference system, the pseudogap resonant level model, in terms of effective temperatures and contrast these results with those obtained near interacting quantum critical points. - Highlights: • Critical Kondo destruction explains the unusual properties of quantum critical heavy fermion compounds. • We review the concept of effective temperatures in models of critical Kondo destruction. • We compare effective temperatures found near non-interacting and fully interacting fixed points. • A comparison with non-interacting quantum impurity models is presented.
Chen Sen; Wu Yican; Jin Ming; Chen Zhibin; Bai Yunqing; Zhao Zhumin
2014-01-01
Accelerator Driven Sub-critical System (ADS) has particular neutronics behaviors compared with the critical system. Prompt jump approximation point reactor kinetics equations taken external source into account have been deduced using an approach of prompt jump approximation. And the relationship between injection reactivity and power ampliation has been achieved. In addition, based on the RELAP5 code the prolong development of point reactor kinetics code used into assessing sub-critical system have been promoted. Different sub-criticality (k eff = 0.90, 0.95, 0.97, 0.98 and 0.99) have been assessed in preliminary design of a type of natural circulation cooling sub-critical reactor under conditions of reactivity injection +1 β in one second. It shows that the external source prompt transient approximation method has an accurate solution after injecting reactivity around short time and has a capacity to solve the dynamic equation, and the sub-critical system has an inner stability while the deeper sub-criticality the less impact on the sub-critical system. (authors)
The walking behaviour of pedestrian social groups and its impact on crowd dynamics.
Mehdi Moussaïd
Full Text Available Human crowd motion is mainly driven by self-organized processes based on local interactions among pedestrians. While most studies of crowd behaviour consider only interactions among isolated individuals, it turns out that up to 70% of people in a crowd are actually moving in groups, such as friends, couples, or families walking together. These groups constitute medium-scale aggregated structures and their impact on crowd dynamics is still largely unknown. In this work, we analyze the motion of approximately 1500 pedestrian groups under natural condition, and show that social interactions among group members generate typical group walking patterns that influence crowd dynamics. At low density, group members tend to walk side by side, forming a line perpendicular to the walking direction. As the density increases, however, the linear walking formation is bent forward, turning it into a V-like pattern. These spatial patterns can be well described by a model based on social communication between group members. We show that the V-like walking pattern facilitates social interactions within the group, but reduces the flow because of its "non-aerodynamic" shape. Therefore, when crowd density increases, the group organization results from a trade-off between walking faster and facilitating social exchange. These insights demonstrate that crowd dynamics is not only determined by physical constraints induced by other pedestrians and the environment, but also significantly by communicative, social interactions among individuals.
Björn, Annika; Pudas-Tähkä, Sanna-Mari; Salanterä, Sanna; Axelin, Anna
2017-10-01
To evaluate the impact of video education on critical care nurses' knowledge and skills in using a behavioural pain assessment tool for intensive care patients and to explore the nurses' experiences with video education. Forty-eight nurses in one intensive care unit watched an educational video on the use of the Critical-Care Pain Observation Tool, then assessed pain in two patients with the tool and took a knowledge test. The researcher made parallel pain assessments. Interrater reliability of patients' pain assessment between nurses and the researcher was determined to examine nurses' skills in using the tool after education. Twenty nurses were interviewed about their experiences with the video education. Interviews were analysed with deductive thematic analysis. The knowledge test scores indicated that the nurses learned the principles of how to use the tool. The interrater reliability of pain assessments reached a moderate level of agreement during the painful procedure, with a weighted kappa coefficient value of 0.48, CL [0.37, 0.58]. The nurses perceived video education positively, but requested additional interaction. Video education is useful in teaching the principles of using a pain assessment tool. Additional clinical training is required for nurses to reach adequate skills in using the tool. Copyright © 2017 Elsevier Ltd. All rights reserved.
A study on physics parameters and flux behaviour for a fast critical facility using ''Baker'' model
Abu-Leilah, M.M.; Hussein, A.Z.; Gaafar, M.A.; Hamouda, I.F.
1983-01-01
Comparative study was performed to emphasize the effects of using different nuclear data systems and methods on the various parameters of the fast reactor. Multigroup libraries as 11 (ANL-5800) and 26 (BNAB-64) energy group systems of nuclear data constants were used in the present work. The calculations were carried out for both infinite dilution (self-shielding factor F= 1) and self-shielded cross sections. Various computer codes were elaborated and derived to meet the conditional requirements for such calculations. The important output of these calculations are the neutron spectra, neutron balance, fission and capture rate distributions, critical mass, breeding ratio in each region and total breeding ratio of the reactor. Five different cases of study were considered employing two systems of constants, infinite dilution and self-shielded cross-sections and treating stainless steel of the reactor as to be substituted by iron. Moreover, calculations have been concerned for averaged one group nuclear data constants which were condensed from the 11 and 26 group systems. Comparisons of the multigroup results with those of the group were made. The condensation process for averaging to one group was done to estimate the effect of such physical simplification on the calculated parameters. The present work results have been compared with many published works. Fair agreements are obtained, which varified the consistance and completeness of the methods implemented and used
Terrorism in Australia: factors associated with perceived threat and incident-critical behaviours.
Stevens, Garry; Agho, Kingsley; Taylor, Melanie; Barr, Margo; Raphael, Beverley; Jorm, Louisa
2009-03-27
To help improve incident preparedness this study assessed socio-demographic and socio-economic predictors of perceived risk of terrorism within Australia and willingness to comply with public safety directives during such incidents. The terrorism perception question module was incorporated into the New South Wales Population Health Survey and was completed by a representative sample of 2,081 respondents in early 2007. Responses were weighted against the New South Wales population. Multivariate analyses indicated that those with no formal educational qualifications were significantly more likely (OR = 2.10, 95%CI:1.32-3.35, p terrorism risk perception and concerns regarding potential impacts. The pattern of concern and response among those of migrant background may reflect secondary social impacts associated with heightened community threat, rather than the direct threat of terrorism itself. These findings highlight the need for terrorism risk communication and related strategies to address the specific concerns of these sub-groups as a critical underpinning of population-level preparedness.
Terrorism in Australia: factors associated with perceived threat and incident-critical behaviours
Raphael Beverley
2009-03-01
Full Text Available Abstract Background To help improve incident preparedness this study assessed socio-demographic and socio-economic predictors of perceived risk of terrorism within Australia and willingness to comply with public safety directives during such incidents. Methods The terrorism perception question module was incorporated into the New South Wales Population Health Survey and was completed by a representative sample of 2,081 respondents in early 2007. Responses were weighted against the New South Wales population. Results Multivariate analyses indicated that those with no formal educational qualifications were significantly more likely (OR = 2.10, 95%CI:1.32–3.35, p Conclusion Low education level is a risk factor for high terrorism risk perception and concerns regarding potential impacts. The pattern of concern and response among those of migrant background may reflect secondary social impacts associated with heightened community threat, rather than the direct threat of terrorism itself. These findings highlight the need for terrorism risk communication and related strategies to address the specific concerns of these sub-groups as a critical underpinning of population-level preparedness.
Terrorism in Australia: factors associated with perceived threat and incident-critical behaviours
Stevens, Garry; Agho, Kingsley; Taylor, Melanie; Barr, Margo; Raphael, Beverley; Jorm, Louisa
2009-01-01
Background To help improve incident preparedness this study assessed socio-demographic and socio-economic predictors of perceived risk of terrorism within Australia and willingness to comply with public safety directives during such incidents. Methods The terrorism perception question module was incorporated into the New South Wales Population Health Survey and was completed by a representative sample of 2,081 respondents in early 2007. Responses were weighted against the New South Wales population. Results Multivariate analyses indicated that those with no formal educational qualifications were significantly more likely (OR = 2.10, 95%CI:1.32–3.35, p terrorism risk perception and concerns regarding potential impacts. The pattern of concern and response among those of migrant background may reflect secondary social impacts associated with heightened community threat, rather than the direct threat of terrorism itself. These findings highlight the need for terrorism risk communication and related strategies to address the specific concerns of these sub-groups as a critical underpinning of population-level preparedness. PMID:19323842
Characterization of fluid dynamic behaviour and channel wall effects in microtube
Celata, G.P.; Cumo, M.; McPhail, S.; Zummo, G.
2006-01-01
Sometimes contradictory results available for fluid flow in micropipes show that much is yet to be verified in microfluid dynamics. In this study the influence of channel wall roughness and of channel wall hydrophobicity on adiabatic flow in circular microchannels is investigated, varying in diameter from 70 μm to 326 μm. The hydrodynamic behaviour of water in smooth tubes down to 30 μm inner diameter (ID) is also ascertained. Within the current experimental accuracy it is found that the classical Hagen-Poiseuille law for friction factor vs. Reynolds number is respected for all diameters measured and Re > 300. With degassed water, no effect of slip flow due to hydrophobic channel walls was noted even at 70 μm ID, which might suggest that the liquid slip flow phenomenon is associated with local desorption of dissolved gases on the hydrophobic surface, as reported elsewhere in the literature. For roughened glass channels, an increase in Darcy friction factor above 64/Re was observed only at the smallest diameter measured, 126 μm. Although the roughness levels of these channels were up to 10 times coarser than the untreated, smooth glass tubes, probably the higher factor was caused by actual deformation of channel circularity, rather than increased friction at the rougher wall, as similar behaviour was observed in a Teflon tube, also of imperfect circularity of cross-section. For all experiments, no anticipated transition to turbulent flow was observed, which means that the transitional Reynolds number was always found between Re ∼ 2000 and Re ∼ 3000. Finally, an introduction to the importance of viscous dissipation in microchannels is added, with quantitative indications of its influence on hydrodynamic properties. It is put forward as being an alternative to pressure measurements in the characterization of the behaviour of microscopic flow
Martin eEgelhaaf
2012-12-01
Full Text Available Insects such as flies or bees, with their miniature brains, are able to control highly aerobatic flight manoeuvres and to solve spatial vision tasks, such as avoiding collisions with obstacles, landing on objects or even localizing a previously learnt inconspicuous goal on the basis of environmental cues. With regard to solving such spatial tasks, these insects still outperform man-made autonomous flying systems. To accomplish their extraordinary performance, flies and bees have been shown by their characteristic behavioural actions to actively shape the dynamics of the image flow on their eyes (optic flow. The neural processing of information about the spatial layout of the environment is greatly facilitated by segregating the rotational from the translational optic flow component through a saccadic flight and gaze strategy. This active vision strategy thus enables the nervous system to solve apparently complex spatial vision tasks in a particularly efficient and parsimonious way. The key idea of this review is that biological agents, such as flies or bees, acquire at least part of their strength as autonomous systems through active interactions with their environment and not by simply processing passively gained information about the world. These agent-environment interactions lead to adaptive behaviour in surroundings of a wide range of complexity. Animals with even tiny brains, such as insects, are capable of performing extraordinarily well in their behavioural contexts by making optimal use of the closed action–perception loop. Model simulations and robotic implementations show that the smart biological mechanisms of motion computation and visually-guided flight control might be helpful to find technical solutions, for example, when designing micro air vehicles carrying a miniaturized, low-weight on-board processor.
Co-percolation to tune conductive behaviour in dynamical metallic nanowire networks.
Fairfield, J A; Rocha, C G; O'Callaghan, C; Ferreira, M S; Boland, J J
2016-11-03
Nanowire networks act as self-healing smart materials, whose sheet resistance can be tuned via an externally applied voltage stimulus. This memristive response occurs due to modification of junction resistances to form a connectivity path across the lowest barrier junctions in the network. While most network studies have been performed on expensive noble metal nanowires like silver, networks of inexpensive nickel nanowires with a nickel oxide coating can also demonstrate resistive switching, a common feature of metal oxides with filamentary conduction. However, networks made from solely nickel nanowires have high operation voltages which prohibit large-scale material applications. Here we show, using both experiment and simulation, that a heterogeneous network of nickel and silver nanowires allows optimization of the activation voltage, as well as tuning of the conduction behavior to be either resistive switching, memristive, or a combination of both. Small percentages of silver nanowires, below the percolation threshold, induce these changes in electrical behaviour, even for low area coverage and hence very transparent films. Silver nanowires act as current concentrators, amplifying conductivity locally as shown in our computational dynamical activation framework for networks of junctions. These results demonstrate that a heterogeneous nanowire network can act as a cost-effective adaptive material with minimal use of noble metal nanowires, without losing memristive behaviour that is essential for smart sensing and neuromorphic applications.
Effect of graphene oxide nano filler on dynamic behaviour of GFRP composites
Pujar, Nagabhushan V.; Nanjundaradhya, N. V.; Sharma, Ramesh S.
2018-04-01
Nano fillers like Alumina oxide, Titanium oxide, Carbon nano tube, Nano clay have been used to improve the mechanical and damping properties of fiber reinforced polymer composites. In the recent years Graphene oxide nano filler is receiving considerable attention for its outstanding properties. Literature available shows that Graphene oxide nano filler can be used to improve the mechanical properties. The use of Graphene oxide in vibration attenuation by enhancing the passive damping in fiber reinforced polymer composite has not been fully explored. The objective of this work is to investigate the dynamic behaviour of Glass fiber-reinforced composite embedded with Graphene oxide nano filler. Graphene oxide is dispersed in epoxy resin with various concentration (0.1%, 0.5% and 1%wt) using ultra-sonification process. Composite laminates were made using the traditional hand-lay-up followed by vacuum bag process. Experimental modal analysis using traditional `strike method' is used to evaluate modal parameters using FFT analyzer and Data Acquisition System. Experiments were carried out for two different fiber orientations viz 0 ➙ & 45 ➙ and two boundary conditions (Free-Free and Cantilever). The modal parameters such as natural frequency, mode shape, damping ratio were studied. This research work demonstrates the vibration damping behaviour with incorporation of Graphene oxide and provides a basic understanding of the damping characteristics in design and manufacture of high performance composites.
Llacer, Jorge [EC Engineering Consultants, LLC, Los Gatos, CA (United States)]. E-mail: jllacer@home.com; Solberg, Timothy D. [Department of Radiation Oncology, University of California, Los Angeles, CA (United States)]. E-mail: Solberg@radonc.ucla.edu; Promberger, Claus [BrainLAB AG, Heimstetten (Germany)]. E-mail: promberg@brainlab.com
2001-10-01
This paper presents a description of tests carried out to compare the behaviour of five algorithms in inverse radiation therapy planning: (1) The Dynamically Penalized Likelihood (DPL), an algorithm based on statistical estimation theory; (2) an accelerated version of the same algorithm; (3) a new fast adaptive simulated annealing (ASA) algorithm; (4) a conjugate gradient method; and (5) a Newton gradient method. A three-dimensional mathematical phantom and two clinical cases have been studied in detail. The phantom consisted of a U-shaped tumour with a partially enclosed 'spinal cord'. The clinical examples were a cavernous sinus meningioma and a prostate case. The algorithms have been tested in carefully selected and controlled conditions so as to ensure fairness in the assessment of results. It has been found that all five methods can yield relatively similar optimizations, except when a very demanding optimization is carried out. For the easier cases, the differences are principally in robustness, ease of use and optimization speed. In the more demanding case, there are significant differences in the resulting dose distributions. The accelerated DPL emerges as possibly the algorithm of choice for clinical practice. An appendix describes the differences in behaviour between the new ASA method and the one based on a patent by the Nomos Corporation. (author)
Modelling of the dynamical behaviour of LWR internals by homogeneization methods
Brochard, D.; Lepareux, M.; Gibert, R.J.; Delaigue, D.; Planchard, J.
1987-01-01
The upper plenum of the internals of PWR, the steam generator bundle, the nuclear reactor core, may be schematically represented by a beam bundle immersed in a fluid. The dynamical study of such a system needs to take into account fluid structure interaction. A refined modelisation at the scale of the tubes can be used but leads to a very important size of problem difficult to solve even on the biggest computers. The homogeneization method allows to have an approximation of the fluid structure interaction for the global behaviour of the bundle. It consists in replacing the heterogeneous physical medium (tubes and fluid) by an equivalent homogeneous medium whose characteristics are determined from the resolution of a set of problems on the elementary cell. The aim of this paper is to present the main steps of the determination of this equivalent medium in the case of small displacements (acoustic behaviour of the fluid) and in using displacement variables for both fluid and tubes. Then some precisions about the implementation of this method in computer codes will be given. (orig.)
Dynamic behaviour of high-pressure natural-gas flow in pipelines
Gato, L.M.C.; Henriques, J.C.C.
2005-01-01
The aim of the present study is the numerical modelling of the dynamic behaviour of high-pressure natural-gas flow in pipelines. The numerical simulation was performed by solving the conservation equations, for one-dimensional compressible flow, using the Runge-Kutta discontinuous Galerkin method, with third-order approximation in space and time. The boundary conditions were imposed using a new weak formulation based on the characteristic variables. The occurrence of pressure oscillations in natural-gas pipelines was studied as a result of the compression wave originated by the rapid closure of downstream shut-off valves. The effect of the partial reflection of pressure waves was also analyzed in the transition between pipes of different cross-sectional areas
Modification to 200 MW(e) CANDU for improved dynamic behaviour
Chamany, B.F.; Murthy, L.G.K.; Ray, R.N.
1976-01-01
Rajasthan Atomic Power Station is inherently suitable for base load operation. Its control philosophy is based on turbine following the reactor. However, due to load fluctuations and inherent limitation of the control system, there had been considerable number of outages of the station. This limitation is further enhanced by improper choice of the operating pressure range of the boilers. Besides, existing fuel design does not permit thermal cycling and hence there is no use in attempting to make the reactor follow the turbine. Design modifications have been suggested for incorporation in the further 200 MW(e) systems. The method adopted is complete decoupling of the reactor from the load. Dynamic behaviour of the station with the suggested modifications and its comparison with the existing situation has been brought out. (author)
Dynamic behaviour of high-pressure natural-gas flow in pipelines
Gato, L.M.C. [Department of Mechanical Engineering, Instituto Superior Tecnico, Technical University of Lisbon, Av. Rovisco Pais, 1049-001 Lisbon (Portugal)]. E-mail: lgato@mail.ist.utl.pt; Henriques, J.C.C. [Department of Mechanical Engineering, Instituto Superior Tecnico, Technical University of Lisbon, Av. Rovisco Pais, 1049-001 Lisbon (Portugal)]. E-mail: jcch@mail.ist.utl.pt
2005-10-01
The aim of the present study is the numerical modelling of the dynamic behaviour of high-pressure natural-gas flow in pipelines. The numerical simulation was performed by solving the conservation equations, for one-dimensional compressible flow, using the Runge-Kutta discontinuous Galerkin method, with third-order approximation in space and time. The boundary conditions were imposed using a new weak formulation based on the characteristic variables. The occurrence of pressure oscillations in natural-gas pipelines was studied as a result of the compression wave originated by the rapid closure of downstream shut-off valves. The effect of the partial reflection of pressure waves was also analyzed in the transition between pipes of different cross-sectional areas.
Hieu Nguyen
2011-01-01
Full Text Available Abstract The changes of dynamical behaviour of a single fullerene molecule inside an armchair carbon nanotube caused by the structural Peierls transition in the nanotube are considered. The structures of the smallest C20 and Fe@C20 fullerenes are computed using the spin-polarized density functional theory. Significant changes of the barriers for motion along the nanotube axis and rotation of these fullerenes inside the (8,8 nanotube are found at the Peierls transition. It is shown that the coefficients of translational and rotational diffusions of these fullerenes inside the nanotube change by several orders of magnitude. The possibility of inverse orientational melting, i.e. with a decrease of temperature, for the systems under consideration is predicted.
The dynamics of absence behaviour: Interrelations between absence from class and absence in class
Jonasson, Charlotte
2011-01-01
Abstract: Background: Studies of absence in educational settings have primarily been concerned with the causes for and results of student absence. However, recent research has argued that distinguishing between different forms of absence could be important. In consequence, studying the way in whi...... in the social practice of students, teachers and school managers. Evaluations of both absence from class and absence in class are important for understanding how absence behaviour can be identified and prevented....... performance. It is helpful to describe these findings using theoretical frameworks from sociology and psychology: specifically, spill-over theory and symbolic capital theory. Conclusions: This study has demonstrated how different forms of absence become dynamically interrelated through ongoing negotiations...
Sanli, Ceyda; Saitoh, K.; Luding, Stefan; van der Meer, Roger M.
2014-01-01
When a densely packed monolayer of macroscopic spheres floats on chaotic capillary Faraday waves, a coexistence of large scale convective motion and caging dynamics typical for glassy systems is observed. We subtract the convective mean flow using a coarse graining (homogenization) method and reveal
Hu, Dao-chun [College of Mechanical and Electrical Engineering, Nanjing University of Aeronautics and Astronautics, Nanjing 210016 (China); College of Mechanical and Electrical Engineering, Taizhou Vocational & Technical College, Taizhou 318000 (China); Chen, Ming-he, E-mail: meemhchen@nuaa.edu.cn [College of Mechanical and Electrical Engineering, Nanjing University of Aeronautics and Astronautics, Nanjing 210016 (China); Wang, Lei; Cheng, Hu [College of Mechanical Engineering, Taizhou University, Taizhou 318000 (China)
2016-01-01
High speed stamping process is used to high strength and high electrical conductivity phosphor bronze with extremely high strain rates more than 10{sup 3} s{sup −1}. This study on the dynamic tensile behaviour and deformational mechanism is to optimise the high speed stamping processes and improve geometrical precision in finished products. Thus, the tensile properties and deformation behaviour of C5191 phosphor bronze under quasi-static tensile condition at a strain rate of 0.001 s{sup −1} by electronic universal testing machine, and dynamic tensile condition at strain rate of 500, 1000 and 1500 s{sup −1} by split Hopkinson tensile bar (SHTB) apparatus were studied. The effects of strain rate and the deformation mechanism were investigated by means of SEM and TEM. The results showed that the yield strength and tensile strength of C5191 phosphor bronze under high strain rates deformation increased by 32.77% and 11.07% respectively compared with quasi-static condition, the strain hardening index increases from 0.075 to 0.251, and the strength of the material strain rates sensitivity index change from 0.005 to 0.022, which presented a clear sensitive to strain rates. Therefore, it is claimed that the dominant deformation mechanism was changed by the dislocation motion under different strain rates, and the ability of plastic deformation of C5191 phosphor bronze increased due to the number of movable dislocations increased significantly, started multi-line slip, and the soft effect of adiabatic temperature rise at the strain rate ranging from 500 to 1500 s{sup −1}.
Abuzairi, Tomy [Graduate School of Science and Technology, Shizuoka University, Hamamatsu 432-8561 (Japan); Department of Electrical Engineering, Faculty of Engineering, Universitas Indonesia, Depok 16424 (Indonesia); Okada, Mitsuru [Department of Engineering, Shizuoka University, Hamamatsu 432-8561 (Japan); Bhattacharjee, Sudeep [Department of Physics, Indian Institute of Technology, Kanpur 208016 (India); Nagatsu, Masaaki, E-mail: nagatsu.masaaki@shizuoka.ac.jp [Graduate School of Science and Technology, Shizuoka University, Hamamatsu 432-8561 (Japan); Department of Engineering, Shizuoka University, Hamamatsu 432-8561 (Japan); Research Institute of Electronics, Shizuoka University, Hamamatsu 432-8561 (Japan)
2016-12-30
Highlights: • Spatio-temporal behaviors of capillary APPJs are studied for various substrates. • Plasma irradiation area depended on the substrate conductivity and permittivity. • Surface irradiation area was significantly broadened in polymer-like substrate. • Effect of applying a substrate bias on the APPJ irradiation area was investigated. - Abstract: An experimental study on the dynamic behaviour of microcapillary atmospheric pressure plasma jets (APPJs) with 5 μm tip size for surfaces of different conductivity is reported. Electrical and spatio-temporal characteristics of the APPJs are monitored using high voltage probe, current monitor and high speed intensified charge couple device camera. From these experimental results, we presented a simple model to understand the electrical discharge characteristics of the capillary APPJs with double electrodes, and estimated the velocity of the ionization fronts in the jet and the electron density to be 3.5–4.2 km/s and 2–7 × 10{sup 17} m{sup −3}. By analyzing the dynamics of the microcapillary APPJs for different substrate materials, it was found that the surface irradiation area strongly depended on the substrate conductivity and permittivity, especially in the case of polymer-like substrate, surface irradiation area was significantly broadened probably due to the repelling behaviour of the plasma jets from the accumulated electrical charges on the polymer surface. The effect of applying a substrate bias in the range from −900 V to +900 V on the plasma irradiation onto the substrates was also investigated. From the knowledge of the present results, it is helpful for choosing the substrate materials for microscale surface modification.
Abuzairi, Tomy; Okada, Mitsuru; Bhattacharjee, Sudeep; Nagatsu, Masaaki
2016-01-01
Highlights: • Spatio-temporal behaviors of capillary APPJs are studied for various substrates. • Plasma irradiation area depended on the substrate conductivity and permittivity. • Surface irradiation area was significantly broadened in polymer-like substrate. • Effect of applying a substrate bias on the APPJ irradiation area was investigated. - Abstract: An experimental study on the dynamic behaviour of microcapillary atmospheric pressure plasma jets (APPJs) with 5 μm tip size for surfaces of different conductivity is reported. Electrical and spatio-temporal characteristics of the APPJs are monitored using high voltage probe, current monitor and high speed intensified charge couple device camera. From these experimental results, we presented a simple model to understand the electrical discharge characteristics of the capillary APPJs with double electrodes, and estimated the velocity of the ionization fronts in the jet and the electron density to be 3.5–4.2 km/s and 2–7 × 10"1"7 m"−"3. By analyzing the dynamics of the microcapillary APPJs for different substrate materials, it was found that the surface irradiation area strongly depended on the substrate conductivity and permittivity, especially in the case of polymer-like substrate, surface irradiation area was significantly broadened probably due to the repelling behaviour of the plasma jets from the accumulated electrical charges on the polymer surface. The effect of applying a substrate bias in the range from −900 V to +900 V on the plasma irradiation onto the substrates was also investigated. From the knowledge of the present results, it is helpful for choosing the substrate materials for microscale surface modification.
Coherent inflationary dynamics for Bose-Einstein condensates crossing a quantum critical point
Feng, Lei; Clark, Logan W.; Gaj, Anita; Chin, Cheng
2018-03-01
Quantum phase transitions, transitions between many-body ground states, are of extensive interest in research ranging from condensed-matter physics to cosmology1-4. Key features of the phase transitions include a stage with rapidly growing new order, called inflation in cosmology5, followed by the formation of topological defects6-8. How inflation is initiated and evolves into topological defects remains a hot topic of debate. Ultracold atomic gas offers a pristine and tunable platform to investigate quantum critical dynamics9-21. We report the observation of coherent inflationary dynamics across a quantum critical point in driven Bose-Einstein condensates. The inflation manifests in the exponential growth of density waves and populations in well-resolved momentum states. After the inflation stage, extended coherent dynamics is evident in both real and momentum space. We present an intuitive description of the quantum critical dynamics in our system and demonstrate the essential role of phase fluctuations in the formation of topological defects.
msiDBN: A Method of Identifying Critical Proteins in Dynamic PPI Networks
Yuan Zhang
2014-01-01
Full Text Available Dynamics of protein-protein interactions (PPIs reveals the recondite principles of biological processes inside a cell. Shown in a wealth of study, just a small group of proteins, rather than the majority, play more essential roles at crucial points of biological processes. This present work focuses on identifying these critical proteins exhibiting dramatic structural changes in dynamic PPI networks. First, a comprehensive way of modeling the dynamic PPIs is presented which simultaneously analyzes the activity of proteins and assembles the dynamic coregulation correlation between proteins at each time point. Second, a novel method is proposed, named msiDBN, which models a common representation of multiple PPI networks using a deep belief network framework and analyzes the reconstruction errors and the variabilities across the time courses in the biological process. Experiments were implemented on data of yeast cell cycles. We evaluated our network construction method by comparing the functional representations of the derived networks with two other traditional construction methods. The ranking results of critical proteins in msiDBN were compared with the results from the baseline methods. The results of comparison showed that msiDBN had better reconstruction rate and identified more proteins of critical value to yeast cell cycle process.
Pasqualini, D.; Witkowski, M.
2005-12-01
The Critical Infrastructure Protection / Decision Support System (CIP/DSS) project, supported by the Science and Technology Office, has been developing a risk-informed Decision Support System that provides insights for making critical infrastructure protection decisions. The system considers seventeen different Department of Homeland Security defined Critical Infrastructures (potable water system, telecommunications, public health, economics, etc.) and their primary interdependencies. These infrastructures have been modeling in one model called CIP/DSS Metropolitan Model. The modeling approach used is a system dynamics modeling approach. System dynamics modeling combines control theory and the nonlinear dynamics theory, which is defined by a set of coupled differential equations, which seeks to explain how the structure of a given system determines its behavior. In this poster we present a system dynamics model for one of the seventeen critical infrastructures, a generic metropolitan potable water system (MPWS). Three are the goals: 1) to gain a better understanding of the MPWS infrastructure; 2) to identify improvements that would help protect MPWS; and 3) to understand the consequences, interdependencies, and impacts, when perturbations occur to the system. The model represents raw water sources, the metropolitan water treatment process, storage of treated water, damage and repair to the MPWS, distribution of water, and end user demand, but does not explicitly represent the detailed network topology of an actual MPWS. The MPWS model is dependent upon inputs from the metropolitan population, energy, telecommunication, public health, and transportation models as well as the national water and transportation models. We present modeling results and sensitivity analysis indicating critical choke points, negative and positive feedback loops in the system. A general scenario is also analyzed where the potable water system responds to a generic disruption.
Dynamic Recrystallization Behavior and Critical Conditions of SiCp/A1-Cu Composite
HAO Shiming
2017-08-01
Full Text Available Using the Gleeble-1500D simulator, the high temperature plastic deformation behavior of 40%SiCP/Al-Cu composite were investigated at 350-500℃ with the strain rate of 0.01-10 s-1. The stress-strain curves were obtained during the tests. The critical conditions of dynamic recrystallization for onset of DRX during deformation of 40%SiCP/Al-Cu composite was obtained by computation of the strain hardening rate (θ from initial stress-strain data and introduction of the inflection point criterion of ln θ-ε curves and the minimum value criterion of (-∂(ln θ/∂ε-ε curves. The results indicate that the softening mechanism of the dynamic recrystallization is a feature of high-temperature flow stress strain curves of the composites, and the peak stress increases with the decrease of deformation temperature or the increase of strain rate. The inflection point in the ln θ-ε curve appears, and the minimum value of the (-∂(ln θ/∂ε-ε curve is presented when the critical state is attained for this composite. The critical strain decreases with the decrease of strain rate and the increase of deformation temperature. There is linear relationship between critical strain and peak strain, i.e. εc=0.528εp. The predicting model of critical strain is described by the function of εc=4.58×10-3Z0.09. Electron microscopic analysis show that the dynamic recrystallization occurs when the strain is 0.06 (T=400℃, ε=10 s-1, and the dynamic recrystallization grains fully grow up when the strain is 0.2.
Critical current densities and vortex dynamics in FeTexSe1-x single crystals
Taen, T.; Tsuchiya, Y.; Nakajima, Y.; Tamegai, T.
2010-01-01
The critical current density and the normalized relaxation rate are reported in FeTe 0.59 Se 0.41 single crystal. Critical current density is of order of 10 5 A/cm 2 , which is comparable to that in Co-doped BaFe 2 As 2 . In low temperature and low field region, the vortex dynamics of this system is well defined by the collective creep theory, which is quite similar to Co-doped BaFe 2 As 2 reported before. We also discuss the origin of the anomaly in the field dependence of the relaxation rate.
Wang Lin; Wang Yangwei; Xu Xin; Liu Chengze
2015-01-01
Ti-5553 alloy is a near-beta titanium alloy with high strength and high fracture toughness. In this paper, the dynamic behaviour and shock-induced martensite phase transformation of Ti-5553 alloy with alpha/beta phases were investigated. Split Hopkinson Pressure Bar was employed to investigate the dynamic properties. Microstructure evolutions were characterized by Scanning Electronic Microscopy and Transmission Electron Microscope. The experimental results have demonstrated that Ti-5553 alloy...
Kwasniok, Frank
2013-11-01
A time series analysis method for predicting the probability density of a dynamical system is proposed. A nonstationary parametric model of the probability density is estimated from data within a maximum likelihood framework and then extrapolated to forecast the future probability density and explore the system for critical transitions or tipping points. A full systematic account of parameter uncertainty is taken. The technique is generic, independent of the underlying dynamics of the system. The method is verified on simulated data and then applied to prediction of Arctic sea-ice extent.
Dynamical simulation of a linear sigma model near the critical point
Wesp, Christian; Meistrenko, Alex; Greiner, Carsten [Institut fuer Theoretische Physik, Goethe-Universitaet Frankfurt, Max-von-Laue-Strasse 1, D-60438 Frankfurt (Germany); Hees, Hendrik van [Frankfurt Institute for Advanced Studies, Ruth-Moufang-Strasse 1, D-60438 Frankfurt (Germany)
2014-07-01
The intention of this study is the search for signatures of the chiral phase transition. To investigate the impact of fluctuations, e.g. of the baryon number, on the transition or a critical point, the linear sigma model is treated in a dynamical 3+1D numerical simulation. Chiral fields are approximated as classical fields, quarks are described by quasi particles in a Vlasov equation. Additional dynamic is implemented by quark-quark and quark-sigma-field interaction. For a consistent description of field-particle interactions, a new Monte-Carlo-Langevin-like formalism has been developed and is discussed.
A nonlinear dynamical system approach for the yielding behaviour of a viscoplastic material.
Burghelea, Teodor; Moyers-Gonzalez, Miguel; Sainudiin, Raazesh
2017-03-08
A nonlinear dynamical system model that approximates a microscopic Gibbs field model for the yielding of a viscoplastic material subjected to varying external stresses recently reported in R. Sainudiin, M. Moyers-Gonzalez and T. Burghelea, Soft Matter, 2015, 11(27), 5531-5545 is presented. The predictions of the model are in fair agreement with microscopic simulations and are in very good agreement with the micro-structural semi-empirical model reported in A. M. V. Putz and T. I. Burghelea, Rheol. Acta, 2009, 48, 673-689. With only two internal parameters, the nonlinear dynamical system model captures several key features of the solid-fluid transition observed in experiments: the effect of the interactions between microscopic constituents on the yield point, the abruptness of solid-fluid transition and the emergence of a hysteresis of the micro-structural states upon increasing/decreasing external forces. The scaling behaviour of the magnitude of the hysteresis with the degree of the steadiness of the flow is consistent with previous experimental observations. Finally, the practical usefulness of the approach is demonstrated by fitting a rheological data set measured with an elasto-viscoplastic material.
Zinszner Jean-Luc
2015-01-01
Full Text Available Ceramic materials are commonly used as protective materials particularly due to their very high hardness and compressive strength. However, the microstructure of a ceramic has a great influence on its compressive strength and on its ballistic efficiency. To study the influence of microstructural parameters on the dynamic compressive behaviour of silicon carbides, isentropic compression experiments have been performed on two silicon carbide grades using a high pulsed power generator called GEPI. Contrary to plate impact experiments, the use of the GEPI device and of the lagrangian analysis allows determining the whole loading path. The two SiC grades studied present different Hugoniot elastic limit (HEL due to their different microstructures. For these materials, the experimental technique allowed evaluating the evolution of the equivalent stress during the dynamic compression. It has been observed that these two grades present a work hardening more or less pronounced after the HEL. The densification of the material seems to have more influence on the HEL than the grain size.
Ngamkhanong, C.; Kaewunruen, S.; Remennikov, A. M.
2017-10-01
As the crosstie beam in railway track systems, the prestressed concrete sleepers (or railroad ties) are principally designed in order to carry wheel loads from the rails to the ground. Their design takes into account static and dynamic loading conditions. It is evident that prestressed concrete has played a significant role as to maintain the high endurance of the sleepers under low to moderate repeated impact loads. In spite of the most common use of the prestressed concrete sleepers in railway tracks, there have always been many demands from rail engineers to improve serviceability and functionality of concrete sleepers. For example, signalling, fibre optic, equipment cables are often damaged either by ballast corners or by tamping machine. There has been a need to re-design concrete sleeper to cater cables internally so that they would not experience detrimental or harsh environments. Accordingly, this study will investigate the effects of through hole or longitudinal hole on static and dynamic behaviours of concrete sleepers under rail shock loading. The modified compression field theory for ultimate strength design of concrete sleepers will be highlighted in this study. The outcome of this study will enable the new design and calculation methods for prestressed concrete sleepers with holes and web opening that practically benefits civil, track and structural engineers in railway industry.
Garcia Cristobal
2018-01-01
Full Text Available Vibrations are responsible for a considerable number of accidents in aircrafts, bridges and other civil engineering structures. Therefore, there is a need to reduce the vibrations on structures made of composite materials. Delamination is a particularly dangerous failure mode for composite materials because delaminated composites can lose up to 60% of their strength and stiffness and still remain unchanged. One of the methods to suppress vibrations and preventing delamination is to incorporate nanofibers into the composite laminates. The aim of the present work is to investigate how nylon nanofibers affect the dynamic behaviour and delamination resistance of glass fibre reinforced polymer (GFRP composites. Experiments and numerical simulations using finite element modelling (FEM analysis are used to estimate the natural frequencies, the damping ratio and inter-laminar strength in GFRP composites with and without nylon nanofibers. It is found that the natural frequencies of the nylon nano-modified composites do not change significantly as compared to the traditional composites. However, nano-modified composites demonstrated a considerable increase in damping ratio and inter-laminar shear strength due to the incorporation of nylon nanofibers. This work contributes to the knowledge about the mechanical and dynamic properties of glass fibre reinforced polymer (GFRP composites with nylon nanofibers.
Anderson, Isobel
2011-01-01
This paper examines the role of guidance for practitioners in the evidence-policy-practice relationship through a critical reflection of the process of developing evidence-informed guidance for housing practitioners working in the area of antisocial behaviour in Scotland. The paper applies theoretical models for the use of evidence in policy and…
Simulation Based Exploration of Critical Zone Dynamics in Intensively Managed Landscapes
Kumar, P.
2017-12-01
The advent of high-resolution measurements of topographic and (vertical) vegetation features using areal LiDAR are enabling us to resolve micro-scale ( 1m) landscape structural characteristics over large areas. Availability of hyperspectral measurements is further augmenting these LiDAR data by enabling the biogeochemical characterization of vegetation and soils at unprecedented spatial resolutions ( 1-10m). Such data have opened up novel opportunities for modeling Critical Zone processes and exploring questions that were not possible before. We show how an integrated 3-D model at 1m grid resolution can enable us to resolve micro-topographic and ecological dynamics and their control on hydrologic and biogeochemical processes over large areas. We address the computational challenge of such detailed modeling by exploiting hybrid CPU and GPU computing technologies. We show results of moisture, biogeochemical, and vegetation dynamics from studies in the Critical Zone Observatory for Intensively managed Landscapes (IMLCZO) in the Midwestern United States.
A power law of order 1/4 for critical mean field Swendsen-Wang dynamics
Long, Yun; Ning, Weiyang; Peres, Yuval
2014-01-01
The Swendsen-Wang dynamics is a Markov chain widely used by physicists to sample from the Boltzmann-Gibbs distribution of the Ising model. Cooper, Dyer, Frieze and Rue proved that on the complete graph K_n the mixing time of the chain is at most O(\\sqrt{n}) for all non-critical temperatures. In this paper the authors show that the mixing time is \\Theta(1) in high temperatures, \\Theta(\\log n) in low temperatures and \\Theta(n^{1/4}) at criticality. They also provide an upper bound of O(\\log n) for Swendsen-Wang dynamics for the q-state ferromagnetic Potts model on any tree of n vertices.
Baartman, Jantiene E. M.; van Gorp, Wouter; Temme, Arnaud J. A. M.; Schoorl, Jeroen M.
Landscape evolution models (LEMs) simulate the three-dimensional development of landscapes over time. Different LEMs have different foci, e.g. erosional behaviour, river dynamics, the fluvial domain, hillslopes or a combination. LEM LAPSUS is a relatively simple cellular model operating on
Wang, Qian; Qin, Pinquan; Wang, Wen-ge
2015-10-01
Based on an analysis of Feynman's path integral formulation of the propagator, a relative criterion is proposed for validity of a semiclassical approach to the dynamics near critical points in a class of systems undergoing quantum phase transitions. It is given by an effective Planck constant, in the relative sense that a smaller effective Planck constant implies better performance of the semiclassical approach. Numerical tests of this relative criterion are given in the XY model and in the Dicke model.
Analysis of critical neutron- scattering data from iron and dynamical scaling theory
Als-Nielsen, Jens Aage
1970-01-01
Experimental three- axis spectrometer data of critical neutron- scattering data from Fe are reanalyzed and compared with the recent theoretical prediction by P. Resibois and C. Piette. The reason why the spin- diffusion parameter did not obey the prediction of dynamical scaling theory is indicated....... Double- axis spectrometer data have previously been interpreted in terms of a non- Lorentzian susceptibility. It is shown that with proper corrections for the inelasticity of the scattering the data are consistent with a Lorentzian form of susceptibility....
Dynamical effects and the critical behavior of random-field systems (invited)
Shapir, Y.
1985-01-01
A variety of phenomena is observed experimentally in random-field (RF) systems realized by the application of an external field to diluted antiferromagnets. At low temperatures, infinitely long hysteretic effects are manifested by the history dependence of the final states: long-range order is observed if the field is applied after cooling, while domain states are reached when field cooled. While no indications for critical fluctuations are detected in 2-D systems, scaling behavior, for both the correlation length and the specific heat, is observed in 3-D systems over an intermediate range of temperatures. The related critical properties seem to be well described by the corresponding ones in the 2-D pure Ising model. The renormalization-group approach, which yields for the equilibrium critical exponents their values of the pure model in d-2 dimensions, is reviewed. A generalization of the dimensional-reduction approach, which accounts self-consistently for renormalized responses of the RF system, is presented. The dynamical effects are implicitly incorporated through the variation in the critical response between the local and the global regimes, associated with short- and long-time scales, respectively. In both regimes the lower critical dimension is found to be d = 2 in accordance with stability arguments. The short-time critical behavior indicates a dimensional reduction by one for the 3-D thermal exponents, in agreement with the experimental results
Dynamical effects and the critical behavior of random-field systems
Shapir, Y.
1985-01-01
A variety of phenomena is observed experimentally in random-field (RF) systems realized by the application of an external field to diluted antiferromagnets. At low temperatures, infinitely long hysteretic effects are manifested by the history dependence of the final states: long-range order is observed if the field is applied after cooling, while domain states are reached when field cooled. While no indications for critical fluctuations are detected in 2-D systems, scaling behavior, for both the correlation length and the specific heat, is observed in 3-D systems over an intermediate range of temperatures. The related critical properties seem to be well described by the corresponding ones in the 2-D pure Ising model. The renormalization-group approach, which yields for the equilibrium critical exponents their values of the pure model in d-2 dimensions, is reviewed. A generalization of the dimensional-reduction approach, which accounts self-consistently for renormalized responses of the RF system, is presented. The dynamical effects are implicitly incorporated through the variation in the critical response between the local and the global regimes, associated with short- and long-time scales, respectively. In both regimes the lower critical dimension is found to be d = 2 in accordance with stability arguments. The short-time critical behavior indicates a dimensional reduction by one for the 3-D thermal exponents, in agreement with the experimental results. 37 references
A simulation analysis to characterize the dynamics of vaccinating behaviour on contact networks.
Perisic, Ana; Bauch, Chris T
2009-05-28
Human behavior influences infectious disease transmission, and numerous "prevalence-behavior" models have analyzed this interplay. These previous analyses assumed homogeneously mixing populations without spatial or social structure. However, spatial and social heterogeneity are known to significantly impact transmission dynamics and are particularly relevant for certain diseases. Previous work has demonstrated that social contact structure can change the individual incentive to vaccinate, thus enabling eradication of a disease under a voluntary vaccination policy when the corresponding homogeneous mixing model predicts that eradication is impossible due to free rider effects. Here, we extend this work and characterize the range of possible behavior-prevalence dynamics on a network. We simulate transmission of a vaccine-preventable infection through a random, static contact network. Individuals choose whether or not to vaccinate on any given day according to perceived risks of vaccination and infection. We find three possible outcomes for behavior-prevalence dynamics on this type of network: small final number vaccinated and final epidemic size (due to rapid control through voluntary ring vaccination); large final number vaccinated and significant final epidemic size (due to imperfect voluntary ring vaccination), and little or no vaccination and large final epidemic size (corresponding to little or no voluntary ring vaccination). We also show that the social contact structure enables eradication under a broad range of assumptions, except when vaccine risk is sufficiently high, the disease risk is sufficiently low, or individuals vaccinate too late for the vaccine to be effective. For populations where infection can spread only through social contact network, relatively small differences in parameter values relating to perceived risk or vaccination behavior at the individual level can translate into large differences in population-level outcomes such as final size
Dynamic critical phenomena in two-dimensional fully frustrated Coulomb gas model with disorder
Zhang Wei; Luo Mengbo
2008-01-01
The dynamic critical phenomena near depinning transition in two-dimensional fully frustrated square lattice Coulomb gas model with disorders was studied using Monte Carlo technique. The ground state of the model system with disorder σ=0.3 is a disordered state. The dependence of charge current density J on electric field E was investigated at low temperatures. The nonlinear J-E behavior near critical depinning field can be described by a scaling function proposed for three-dimensional flux line system [M.B. Luo, X. Hu, Phys. Rev. Lett. 98 (2007) 267002]. We evaluated critical exponents and found an Arrhenius creep motion for field region E c /2 c . The scaling law of the depinning transition is also obtained from the scaling function
Valdes Diaz, G.; Rodriguez-Calvo, S.; Perez-Gramatges, A.; Rapado-Paneque, M.; Fernandez-Lima, F. A.; Ponciano, C. R.; Silveira, E. F. . E-mail. apgram@instec.cu
2007-01-01
Ionising radiation used for sterilisation can have an effect on the physico-chemical properties of pharmaceutically relevant excipient systems, affecting therefore the stability of the formulation. The effect of gamma irradiation on the phase behaviour (cloud point - CP) and critical micelle concentration (CMC) of aqueous solutions of Triton X-100, used as a model nonionic surfactant, is investigated in this paper. Micellar solutions irradiated with ?-rays in a dose range between 0 and 70 kGy, including the sterilisation range of pharmaceutical preparations, were analysed using mass spectrometry. Results show a slight shift in molecular mass distribution of ethoxylated surfactant, which indicates degradation of polyethoxylated chains by water radical attacks. This fact, combined with the formation of cross-linked species, is considered to be responsible for the decrease observed in CP and CMC values of micellar solutions at all absorbed doses. There is no spectroscopic evidence of radiation damage to aromatic ring or hydrocarbon tail of surfactant. Models based on Flory-Huggins theory were employed to estimate CP from changes in mass distribution and to obtain cross-linking fractions. (Author)
R. Sepe
2017-01-01
Full Text Available The aim of the proposed research activity is to investigate the mechanical behaviour of a part of aerospace horizontal stabilizer, made of composite materials and undergoing static loads. The prototype design and manufacturing phases have been carried out in the framework of this research activity. The structural components of such stabilizer are made of composite sandwich panels (HTA 5131/RTM 6 with honeycomb core (HRH-10-1/8-4.0; the sandwich skins have been made by means of Resin Transfer Moulding (RTM process. In order to assess the mechanical strength of this stabilizer, experimental tests have been performed. In particular, the most critical inflight recorded aerodynamic load has been experimentally reproduced and applied on the stabilizer. A numerical model, based on the Finite Element Method (FEM and aimed at reducing the experimental effort, has been preliminarily developed to calibrate amplitude, direction, and distribution of an equivalent and simpler load vector to be used in the experimental test. The FEM analysis, performed by using NASTRAN code, has allowed modelling the skins of the composite sandwich plates by definition of material properties and stack orientation of each lamina, while the honeycomb core has been modelled by using an equivalent orthotropic plate. Numerical and experimental results have been compared and a good agreement has been achieved.
Morton, David W.; Lui, Matthew P.W.; Young, Colin L.
2003-01-01
Previously, the investigation of the (gas + liquid) critical properties of (alkanol + alkane) mixtures has focussed on (primary alkanol + straight chain alkane) mixtures. The experimental data available for (alkanol + alkane) mixtures, which include secondary or tertiary alcohols and/or branched chain alkanes, are extremely limited. This work extends the existing body of data on (alkanol + alkane) mixtures to include mixtures containing these components. Here the (gas + liquid) critical temperatures of 29 {alkanol (C 2 -C 5 ) + alkane (C 5 -C 12 )} mixtures are reported. All the (gas + liquid) critical lines for the binary mixtures studied are continuous, indicating they obey either Type I or Type II phase behaviour
Molecular dynamics study of vacancy-like defects in a model glass : static behaviour
Delaye, J. M.; Limoge, Y.
1993-10-01
The possibility of defining vacancy-like defects in a Lennard-Jones glass is searched for in a systematic manner. Considering different relaxation levels of the same system, as well as different external pressures, we use a Molecular Dynamics simulation method, to study at constant volume or external pressure, the relaxation of a “piece” of glass, after the sudden removal of an atom. Three typical kinds of behaviour can be observed: the persistence of the empty volume left by the missing atom, its migration by clearly identifiable atomic jumps and the dissipation “on the spot”. A careful analysis of the probabilities of these three kinds of behaviour shows that a meaningful definition of vacancy-like defects can be given in a Lennard-Jones glass. Dans cet article, nous nous penchons de façon systématique sur la possibilité de définir des défauts de type lacunaire dans un verre de Lennard-Jones, à différents niveaux de relaxation et de pression, par une méthode de simulation numérique en dynamique moléculaire à volume ou à pression constants. Le défaut est créé en supprimant un atome et en suivant la réponse du système. Nous observons trois comportements typiques : la persistance sur place du “trou” laissé par l'atome supprimé, sa migration par des sauts atomiques clairement identifiés et enfin sa dissipation sur place. Une analyse détaillée de ces trois comportements montre qu'il est possible dans un verre de Lennard-Jones de définir des défauts de type lacunaire.
Isothermal and dynamic oxidation behaviour of Mo-W doped carbon-based coating
Mandal, Paranjayee; Ehiasarian, Arutiun P.; Hovsepian, Papken Eh.
2015-10-01
The oxidation behaviour of Mo-W doped carbon-based coating (Mo-W-C) is investigated in elevated temperature (400-1000 °C). Strong metallurgical bond between Mo-W-C coating and substrate prevents any sort of delamination during heat-treatment. Isothermal oxidation tests show initial growth of metal oxides at 500 °C, however graphitic nature of the as-deposited coating is preserved. The oxidation progresses with further rise in temperature and the substrate is eventually exposed at 700 °C. The performance of Mo-W-C coating is compared with a state-of-the-art DLC(Cr/Cr-WC/W:C-H/a:C-H) coating, which shows preliminary oxidation at 400 °C and local delamination of the coating at 500 °C leading to substrate exposure. The graphitisation starts at 400 °C and the diamond-like structure is completely converted into the graphite-like structure at 500 °C. Dynamic oxidation behaviour of both the coatings is investigated using Thermo-gravimetric analysis carried out with a slow heating rate of 1 °C/min from ambient temperature to 1000 °C. Mo-W-C coating resists oxidation up to ˜800 °C whereas delamination of DLC(Cr/Cr-WC/W:C-H/a:C-H) coating is observed beyond ˜380 °C. In summary, Mo-W-C coating provides improved oxidation resistance at elevated temperature compared to DLC(Cr/Cr-WC/W:C-H/a:C-H) coating.
Luzyanin, I.D.; Khavronin, V.P.
1984-01-01
Results are presented of an experimental investigation of the behaviour of the nonlinear dynamic susceptibility in the phase transition region the cubic, weakly anisotropic ferromagnetics CdCr 2 S 4 and CdCr 2 Se 4 . It is shown that above the Curie point Tsub(C) two temperature regions, a scaling and anomalous, can be distinguished which involve critical phenomena of different nature. In the scaling region which corresponds to 4πchisub(0)) < or approximately 25, the behaviour found for the linear and nonlinear susceptibilities are in satisfactory agreement with the theoretical predictions based on similarity considerations. The anomalous region is directly adjacent to Tsub(C). In this region phenomena are observed which are not consistent with current concepts regarding the nature of second order phase transitions e.g. hysteresis with respect to magnetic field, a ''residual'' second order signal which persists a long time after switching off of the external stationary field and an anomalous behavioUr of the susceptibility at low frequencies. The resemblence of the phenomena observed in the anomalous region with those occurring in spin glasses is noted
The effects of temperature and strain rate on the dynamic flow behaviour of different steels
Lee, W.-S.; Liu, C.-Y.
2006-01-01
A compressive type split-Hopkinson pressure bar is utilized to compare the impact plastic behaviour of three steels with different levels of carbon content. S15C low carbon steel, S50C medium alloy heat treatable steel (abbreviated hereafter to medium carbon steel) and SKS93 tool steel with a high carbon and low alloy content (abbreviated hereafter to high carbon steel) are tested under strain rates ranging from 1.1 x 10 3 s -1 to 5.5 x 10 3 s -1 and temperatures ranging from 25 to 800 deg. C. The effects of the carbon content, strain rate and temperature on the mechanical responses of the three steels are evaluated. The microstructures of the impacted specimens are studied using a transmission electron microscope (TEM). It is found that an increased carbon content enhances the dynamic flow resistance of the three steels. Additionally, the flow stress increases with strain and strain rate in every case. A thermal softening effect is identified in the plastic behaviour of the three steels. The activation energy, ΔG * , varies as a function of the strain rate and temperature, but is apparently insensitive to the carbon content level. The present study identifies maximum ΔG * values of 58 kJ/mol for the S15C low carbon steel, 54.9 kJ/mol for the S50C medium carbon steel, and 56.4 kJ/mol for the SKS93 high carbon steel. A Zerilli-Armstrong BCC constitutive model with appropriate coefficients is applied to describe the high strain rate plastic behaviours of the S15C, S50C and SKS93 steels. The errors between the calculated stress and the measured stress are found to be less than 5%. The microstructural observations reveal that the dislocation density and the degree of dislocation tangling increase with increasing strain rate in all three steels. Additionally, the TEM observations indicate that a higher strain rate reduces the size of the dislocation cells. The annihilation of dislocations occurs more readily at elevated temperatures. The square root of the dislocation
Knopoff, Damián A.
2016-09-01
The recent review paper [4] constitutes a valuable contribution on the understanding, modeling and simulation of crowd dynamics in extreme situations. It provides a very comprehensive revision about the complexity features of the system under consideration, scaling and the consequent justification of the used methods. In particular, macro and microscopic models have so far been used to model crowd dynamics [9] and authors appropriately explain that working at the mesoscale is a good choice to deal with the heterogeneous behaviour of walkers as well as with the difficulty of their deterministic identification. In this way, methods based on the kinetic theory and statistical dynamics are employed, more precisely the so-called kinetic theory for active particles [7]. This approach has successfully been applied in the modeling of several complex dynamics, with recent applications to learning [2,8] that constitutes the key to understand communication and is of great importance in social dynamics and behavioral sciences.
Dynamic behaviour of solvent contactors in fuel reprocessing plants- an analysis
Raju, R P; Siddiqui, H R [Nuclear Waste Management Group, Bhabha Atomic Research Centre, Mumbai (India); Murthy, K K; Kansra, V P [Fuel Reprocessing Group, Bhabha Atomic Research Centre, Mumbai (India)
1994-06-01
Fuel reprocessing plants carry out separation of useful fissile and fertile materials from spent nuclear fuels by isolating highly radioactive fission products using solvent extraction method. In the fuel reprocessing step of nuclear fuel cycle, optimisation of process parameters in the PUREX flowsheet design is of great importance particularly on account of the need to realize high degree of recovery of fissile and fertile materials and to ensure proper control on concentrations of fissile element in process streams for avoidance of criticality. In counter-current solvent contactors of PUREX flowsheet there are a variety of processes conditions which may cause plutonium accumulations that requires attention to ascertain safe Pu concentrations within the contactors. A study was carried out using the PUREX process mathematical model Solvent Extraction Program Having Interacting Solutes (SEPHIS) for pulsed solvent contactors in PREFRE-1, Tarapur and PREFRE-2, Kalpakkam flowsheets for optimising the process parameters in plutonium purification cycles. The study was extended to predict the behaviour of contactors handling plutonium bearing solutions under certain anticipated deviations in the process parameters. Modifications wherever necessary were carried out to the original SEPHIS code. This paper discusses the results obtained during this analysis. (author). 2 figs., 2 tabs.
The dynamics of marginality and self-organized criticality as a paradigm for turbulent transport
Newman, D.E.; Carreras, B.A.; Diamond, P.H.; Hahm, T.S.
1995-01-01
A general paradigm, based on the concept of self-organized criticality (SOC), for turbulent transport in magnetically confined plasmas has been recently suggested as an explanation for some of the apparent discrepancies between most theoretical models of turbulent transport and experimental observations of the transport in magnetically confined plasmas. This model describes the dynamics of the transport without relying on the underlying local fluctuation mechanisms. Computations based on a cellular automata realization of such a model have found that noise driven SOC systems can maintain average profiles that are linearly stable (submarginal) and yet are able to sustain active transport dynamics. It is also found that the dominant scales in the transport dynamics in the absence of sheared flow are system scales rather than the underlying local fluctuation scales. The addition of sheared flow into the dynamics leads to a large reduction of the system-scale transport events and a commensurate increase in the fluctuation-scale transport events needed to maintain the constant flux. The dynamics of these models and the potential ramifications for transport studies are discussed
Diversity in the dynamical behaviour of a compartmentalized programmable biochemical oscillator.
Weitz, Maximilian; Kim, Jongmin; Kapsner, Korbinian; Winfree, Erik; Franco, Elisa; Simmel, Friedrich C
2014-04-01
In vitro compartmentalization of biochemical reaction networks is a crucial step towards engineering artificial cell-scale devices and systems. At this scale the dynamics of molecular systems becomes stochastic, which introduces several engineering challenges and opportunities. Here we study a programmable transcriptional oscillator system that is compartmentalized into microemulsion droplets with volumes between 33 fl and 16 pl. Simultaneous measurement of large populations of droplets reveals major variations in the amplitude, frequency and damping of the oscillations. Variability increases for smaller droplets and depends on the operating point of the oscillator. Rather than reflecting the stochastic kinetics of the chemical reaction network itself, the variability can be attributed to the statistical variation of reactant concentrations created during their partitioning into droplets. We anticipate that robustness to partitioning variability will be a critical challenge for engineering cell-scale systems, and that highly parallel time-series acquisition from microemulsion droplets will become a key tool for characterization of stochastic circuit function.
SACS2: Dynamic and Formal Safety Analysis Method for Complex Safety Critical System
Koh, Kwang Yong; Seong, Poong Hyun
2009-01-01
Fault tree analysis (FTA) is one of the most widely used safety analysis technique in the development of safety critical systems. However, over the years, several drawbacks of the conventional FTA have become apparent. One major drawback is that conventional FTA uses only static gates and hence can not capture dynamic behaviors of the complex system precisely. Although several attempts such as dynamic fault tree (DFT), PANDORA, formal fault tree (FFT) and so on, have been made to overcome this problem, they can not still do absolute or actual time modeling because they adapt relative time concept and can capture only sequential behaviors of the system. Second drawback of conventional FTA is its lack of rigorous semantics. Because it is informal in nature, safety analysis results heavily depend on an analyst's ability and are error-prone. Finally reasoning process which is to check whether basic events really cause top events is done manually and hence very labor-intensive and timeconsuming for the complex systems. In this paper, we propose a new safety analysis method for complex safety critical system in qualitative manner. We introduce several temporal gates based on timed computational tree logic (TCTL) which can represent quantitative notion of time. Then, we translate the information of the fault trees into UPPAAL query language and the reasoning process is automatically done by UPPAAL which is the model checker for time critical system
Traore, Yannick L; Fumakia, Miral; Gu, Jijin; Ho, Emmanuel A
2018-03-01
In this study, we investigated the viscoelastic and mechanical behaviour of polyvinyl alcohol films formulated along with carrageenan, plasticizing agents (polyethylene glycol and glycerol), and when loaded with nanoparticles as a model for potential applications as microbicides. The storage modulus, loss modulus and glass transition temperature were determined using a dynamic mechanical analyzer. Films fabricated from 2% to 5% polyvinyl alcohol containing 3 mg or 5 mg of fluorescently labeled nanoparticles were evaluated. The storage modulus and loss modulus values of blank films were shown to be higher than the nanoparticle-loaded films. Glass transition temperature determined using the storage modulus, and loss modulus was between 40-50℃ and 35-40℃, respectively. The tensile properties evaluated showed that 2% polyvinyl alcohol films were more elastic but less resistant to breaking compared to 5% polyvinyl alcohol films (2% films break around 1 N load and 5% films break around 7 N load). To our knowledge, this is the first study to evaluate the influence of nanoparticle and film composition on the physico-mechanical properties of polymeric films for vaginal drug delivery.
Digital signal processing for velocity measurements in dynamical material's behaviour studies
Devlaminck, Julien; Luc, Jerome; Chanal, Pierre-Yves
2014-01-01
In this work, we describe different configurations of optical fiber interferometers (types Michelson and Mach-Zehnder) used to measure velocities during dynamical material's behaviour studies. We detail the algorithms of processing developed and optimized to improve the performance of these interferometers especially in terms of time and frequency resolutions. Three methods of analysis of interferometric signals were studied. For Michelson interferometers, the time-frequency analysis of signals by Short-Time Fourier Transform (STFT) is compared to a time-frequency analysis by Continuous Wavelet Transform (CWT). The results have shown that the CWT was more suitable than the STFT for signals with low signal-to-noise, and low velocity and high acceleration areas. For Mach- Zehnder interferometers, the measurement is carried out by analyzing the phase shift between three interferometric signals (Triature processing). These three methods of digital signal processing were evaluated, their measurement uncertainties estimated, and their restrictions or operational limitations specified from experimental results performed on a pulsed power machine. (authors)
Modelling Dynamic Behaviour and Spall Failure of Aluminium Alloy AA7010
Ma'at, N.; Nor, M. K. Mohd; Ismail, A. E.; Kamarudin, K. A.; Jamian, S.; Ibrahim, M. N.; Awang, M. K.
2017-10-01
A finite strain constitutive model to predict the dynamic deformation behaviour of Aluminium Alloy 7010 including shockwaves and spall failure is developed in this work. The important feature of this newly hyperelastic-plastic constitutive formulation is a new Mandel stress tensor formulated using new generalized orthotropic pressure. This tensor is combined with a shock equation of state (EOS) and Grady spall failure. The Hill’s yield criterion is adopted to characterize plastic orthotropy by means of the evolving structural tensors that is defined in the isoclinic configuration. This material model was developed and integration into elastic and plastic parts. The elastic anisotropy is taken into account through the newly stress tensor decomposition of a generalized orthotropic pressure. Plastic anisotropy is considered through yield surface and an isotropic hardening defined in a unique alignment of deviatoric plane within the stress space. To test its ability to describe shockwave propagation and spall failure, the new material model was implemented into the LLNL-DYNA3D code of UTHM’s. The capability of this newly constitutive model were compared against published experimental data of Plate Impact Test at 234m/s, 450m/s and 895m/s impact velocities. A good agreement is obtained between experimental and simulation in each test.
Catchment organisation, free energy dynamics and network control on critical zone water flows
Zehe, E.; Ehret, U.; Kleidon, A.; Jackisch, C.; Scherer, U.; Blume, T.
2012-04-01
as that these flow structures organize and dominate flows of water, dissolved matter and sediments during rainfall driven conditions at various scales: - Surface connected vertical flow structures of anecic worm burrows or soil cracks organize and dominated vertical flows at the plot scale - this is usually referred to as preferential flow; - Rill networks at the soil surface organise and dominate hillslope scale overland flow response and sediment yields; - Subsurface pipe networks at the bedrock interface organize and dominate hillslope scale lateral subsurface water and tracer flows; - The river net organizes and dominates flows of water, dissolved matter and sediments to the catchment outlet and finally across continental gradients to the sea. Fundamental progress with respect to the parameterization of hydrological models, subscale flow networks and to understand the adaptation of hydro-geo ecosystems to change could be achieved by discovering principles that govern the organization of catchments flow networks in particular at least during steady state conditions. This insight has inspired various scientists to suggest principles for organization of ecosystems, landscapes and flow networks; as Bejans constructural law, Minimum Energy Expenditure , Maximum Entropy Production. In line with these studies we suggest that a thermodynamic/energetic treatment of the catchment is might be a key for understanding the underlying principles that govern organisation of flow and transport. Our approach is to employ a) physically based hydrological model that address at least all the relevant hydrological processes in the critical zone in a coupled way, behavioural representations of the observed organisation of flow structures and textural elements, that are consistent with observations in two well investigated research catchments and have been tested against distributed observations of soil moisture and catchment scale discharge; to simulate the full concert of hydrological
HOW BOXERS DECIDE TO PUNCH A TARGET: EMERGENT BEHAVIOUR IN NONLINEAR DYNAMICAL MOVEMENT SYSTEMS
Robert Hristovski
2006-07-01
Full Text Available Previous research has shown how dynamical systems theory provides a relevant framework for investigating decision-making behavior in sport. The aim of this study was to adopt concepts and tools from nonlinear dynamics in examining effects of boxer-target distance and perceived punching efficiency on emergent decision-making during a typical practice task in boxing. Results revealed the existence of critical values of scaled distances between boxers and targets for first time appearance and disappearance of a diverse range of boxing actions including jabs, hooks and uppercuts. Reasons for the diversity of actions were twofold: i abrupt (qualitative changes in the number of the possible punches, i.e. motor solutions to the hitting task; and ii, fine modification of the probabilities of selecting specific striking patterns. Boxers were able to exploit the emerging perception of strikeability, leading to a changing diversity of selected actions and a cascade of abrupt changes in the perceptual-motor work space of the task. Perceived efficiency of a punching action by the participants also changed as a function of the scaled distance to a target and was correlated with the probability of occurrence of specific boxing actions. Accordingly, scaled distance-dependent perceived efficiency seems an important perceptual constraint in the training task of punching a heavy bag in boxers
Lenci, Stefano; Rega, Giuseppe; Ruzziconi, Laura
2013-06-28
The dynamical integrity, a new concept proposed by J.M.T. Thompson, and developed by the authors, is used to interpret experimental results. After reviewing the main issues involved in this analysis, including the proposal of a new integrity measure able to capture in an easy way the safe part of basins, attention is dedicated to two experiments, a rotating pendulum and a micro-electro-mechanical system, where the theoretical predictions are not fulfilled. These mechanical systems, the former at the macro-scale and the latter at the micro-scale, permit a comparative analysis of different mechanical and dynamical behaviours. The fact that in both cases the dynamical integrity permits one to justify the difference between experimental and theoretical results, which is the main achievement of this paper, shows the effectiveness of this new approach and suggests its use in practical situations. The men of experiment are like the ant, they only collect and use; the reasoners resemble spiders, who make cobwebs out of their own substance. But the bee takes the middle course: it gathers its material from the flowers of the garden and field, but transforms and digests it by a power of its own. Not unlike this is the true business of philosophy (science); for it neither relies solely or chiefly on the powers of the mind, nor does it take the matter which it gathers from natural history and mechanical experiments and lay up in the memory whole, as it finds it, but lays it up in the understanding altered and digested. Therefore, from a closer and purer league between these two faculties, the experimental and the rational (such as has never been made), much may be hoped. (Francis Bacon 1561-1626) But are we sure of our observational facts? Scientific men are rather fond of saying pontifically that one ought to be quite sure of one's observational facts before embarking on theory. Fortunately those who give this advice do not practice what they preach. Observation and theory get
A simulation analysis to characterize the dynamics of vaccinating behaviour on contact networks
Bauch Chris T
2009-05-01
Full Text Available Abstract Background Human behavior influences infectious disease transmission, and numerous "prevalence-behavior" models have analyzed this interplay. These previous analyses assumed homogeneously mixing populations without spatial or social structure. However, spatial and social heterogeneity are known to significantly impact transmission dynamics and are particularly relevant for certain diseases. Previous work has demonstrated that social contact structure can change the individual incentive to vaccinate, thus enabling eradication of a disease under a voluntary vaccination policy when the corresponding homogeneous mixing model predicts that eradication is impossible due to free rider effects. Here, we extend this work and characterize the range of possible behavior-prevalence dynamics on a network. Methods We simulate transmission of a vaccine-prevetable infection through a random, static contact network. Individuals choose whether or not to vaccinate on any given day according to perceived risks of vaccination and infection. Results We find three possible outcomes for behavior-prevalence dynamics on this type of network: small final number vaccinated and final epidemic size (due to rapid control through voluntary ring vaccination; large final number vaccinated and significant final epidemic size (due to imperfect voluntary ring vaccination, and little or no vaccination and large final epidemic size (corresponding to little or no voluntary ring vaccination. We also show that the social contact structure enables eradication under a broad range of assumptions, except when vaccine risk is sufficiently high, the disease risk is sufficiently low, or individuals vaccinate too late for the vaccine to be effective. Conclusion For populations where infection can spread only through social contact network, relatively small differences in parameter values relating to perceived risk or vaccination behavior at the individual level can translate into large
A novel critical infrastructure resilience assessment approach using dynamic Bayesian networks
Cai, Baoping; Xie, Min; Liu, Yonghong; Liu, Yiliu; Ji, Renjie; Feng, Qiang
2017-10-01
The word resilience originally originates from the Latin word "resiliere", which means to "bounce back". The concept has been used in various fields, such as ecology, economics, psychology, and society, with different definitions. In the field of critical infrastructure, although some resilience metrics are proposed, they are totally different from each other, which are determined by the performances of the objects of evaluation. Here we bridge the gap by developing a universal critical infrastructure resilience metric from the perspective of reliability engineering. A dynamic Bayesian networks-based assessment approach is proposed to calculate the resilience value. A series, parallel and voting system is used to demonstrate the application of the developed resilience metric and assessment approach.
Classical dynamics of the Abelian Higgs model from the critical point and beyond
G.C. Katsimiga
2015-09-01
Full Text Available We present two different families of solutions of the U(1-Higgs model in a (1+1 dimensional setting leading to a localization of the gauge field. First we consider a uniform background (the usual vacuum, which corresponds to the fully higgsed-superconducting phase. Then we study the case of a non-uniform background in the form of a domain wall which could be relevantly close to the critical point of the associated spontaneous symmetry breaking. For both cases we obtain approximate analytical nodeless and nodal solutions for the gauge field resulting as bound states of an effective Pöschl–Teller potential created by the scalar field. The two scenaria differ only in the scale of the characteristic localization length. Numerical simulations confirm the validity of the obtained analytical solutions. Additionally we demonstrate how a kink may be used as a mediator driving the dynamics from the critical point and beyond.
Lee, Ming-Tsung; Vishnyakov, Aleksey; Neimark, Alexander V
2013-09-05
Micelle formation in surfactant solutions is a self-assembly process governed by complex interplay of solvent-mediated interactions between hydrophilic and hydrophobic groups, which are commonly called heads and tails. However, the head-tail repulsion is not the only factor affecting the micelle formation. For the first time, we present a systematic study of the effect of chain rigidity on critical micelle concentration and micelle size, which is performed with the dissipative particle dynamics simulation method. Rigidity of the coarse-grained surfactant molecule was controlled by the harmonic bonds set between the second-neighbor beads. Compared to flexible molecules with the nearest-neighbor bonds being the only type of bonded interactions, rigid molecules exhibited a lower critical micelle concentration and formed larger and better-defined micelles. By varying the strength of head-tail repulsion and the chain rigidity, we constructed two-dimensional diagrams presenting how the critical micelle concentration and aggregation number depend on these parameters. We found that the solutions of flexible and rigid molecules that exhibited approximately the same critical micelle concentration could differ substantially in the micelle size and shape depending on the chain rigidity. With the increase of surfactant concentration, primary micelles of more rigid molecules were found less keen to agglomeration and formation of nonspherical aggregates characteristic of flexible molecules.
Critical Domain Problem for the Reaction–Telegraph Equation Model of Population Dynamics
Weam Alharbi
2018-04-01
Full Text Available A telegraph equation is believed to be an appropriate model of population dynamics as it accounts for the directional persistence of individual animal movement. Being motivated by the problem of habitat fragmentation, which is known to be a major threat to biodiversity that causes species extinction worldwide, we consider the reaction–telegraph equation (i.e., telegraph equation combined with the population growth on a bounded domain with the goal to establish the conditions of species survival. We first show analytically that, in the case of linear growth, the expression for the domain’s critical size coincides with the critical size of the corresponding reaction–diffusion model. We then consider two biologically relevant cases of nonlinear growth, i.e., the logistic growth and the growth with a strong Allee effect. Using extensive numerical simulations, we show that in both cases the critical domain size of the reaction–telegraph equation is larger than the critical domain size of the reaction–diffusion equation. Finally, we discuss possible modifications of the model in order to enhance the positivity of its solutions.
Mittal, R.
2014-01-01
The understanding of the thermodynamic properties of solids has important applications in diverse areas like condensed matter physics, materials science, mineralogy, geophysics, etc. We have been extensively investigating anomalous thermodynamic properties of compounds using the techniques of inelastic neutron scattering and lattice dynamics. We would present some of the results from our recent studies. Studies of materials exhibiting anomalous thermal expansion are of interest due to their fundamental scientific importance and potential applications in ceramic, optical and electronic industry etc. We have studied the thermodynamic properties of negative thermal expansion (NTE) compounds ZrW 2 O 8 , HfW 2 O 8 , ZrMo 2 O 8 , ZrV 2 O 7 , HfV 2 O 7 , Zn(CN) 2 , Cu 2 O, Ag 2 O, Ag 3 Co(CN) 6 and Ag 3 Fe(CN) 6 . Our calculations predicted that large softening of the phonon spectrum involving librational and translational modes below 10 MeV would be responsible for anomalous thermal expansion behaviour. High pressure inelastic neutron scattering experiments carried by us on cubic ZrW 2 O 8 , ZrMo 2 O 8 and Zn(CN) 2 confirmed the phonon softening. Our studies indicate that unusual phonon softening of low energy modes is able to account for the thermal expansion behaviour in these compounds. Superionic conduction in fluorite-structured (anti-fluorite, Li 2 O) oxides (MO 2 , M= U, Th) have applications in energy storage, conversion and nuclear industry. The possible role of phonon in initiation of diffusion has been studied in Li 2 O. We found that in the superionic regime lithium atoms may exhibit macroscopic movement along (100) direction. The microscopic modeling or simulation is found to play a pivotal role in understanding the conduction processes at high temperatures in Li 2 O. We have also studied zircon structured compounds MSiO 4 (M=Zr, Hf, Th, U), RPO 4 , (R=rare earth atom). The compounds are known to transform to the scheelite (body centered tetragonal, I4 1 /a
Dynamical scaling and critical scattering in pure and disordered ferromagnets probed by NSE
Alba, M. [LLB, CEA-CNRS UMR12, CEA-Saclay, 91191 Gif/Yvette Cedex (France)]. E-mail: michel.alba@cea.fr; Pouget, S. [DRFMC/SPSMS, CEN-Grenoble, 17 rue des Martyrs, 38054 Grenoble (France); Fouquet, P. [ILL, 6 rue Jules Horowitz, 38042 Grenoble (France); Farago, B. [ILL, 6 rue Jules Horowitz, 38042 Grenoble (France); Pappas, C. [Hahn-Meitner Institut, Glienickerstr. 100, 14109 Berlin (Germany)
2007-07-15
We have studied the 3D Heisenberg ferromagnetic model system CdCr{sub 2} {sub x} In{sub 2-2} {sub x} S{sub 4} in the ferromagnetic and reentrant phases as a function of temperature and momentum transfer using neutron spin echo (NSE) spectroscopy. The results from the pure sample CdCr{sub 2}S{sub 4} are in excellent agreement with the predictions of the renormalization group theory. In the presence of disorder, we see the evolution from a simple critical ferromagnetic scattering with single fast relaxation times to a more complex slow dynamics characteristic of spin glasses.
A critical oscillation constant as a variable of time scales for half-linear dynamic equations
Řehák, Pavel
2010-01-01
Roč. 60, č. 2 (2010), s. 237-256 ISSN 0139-9918 R&D Projects: GA AV ČR KJB100190701 Institutional research plan: CEZ:AV0Z10190503 Keywords : dynamic equation * time scale * half-linear equation * (non)oscillation criteria * Hille-Nehari criteria * Kneser criteria * critical constant * oscillation constant * Hardy inequality Subject RIV: BA - General Mathematics Impact factor: 0.316, year: 2010 http://link.springer.com/article/10.2478%2Fs12175-010-0009-7
Finite-temperature spin dynamics in a perturbed quantum critical Ising chain with an E₈ symmetry.
Wu, Jianda; Kormos, Márton; Si, Qimiao
2014-12-12
A spectrum exhibiting E₈ symmetry is expected to arise when a small longitudinal field is introduced in the transverse-field Ising chain at its quantum critical point. Evidence for this spectrum has recently come from neutron scattering measurements in cobalt niobate, a quasi-one-dimensional Ising ferromagnet. Unlike its zero-temperature counterpart, the finite-temperature dynamics of the model has not yet been determined. We study the dynamical spin structure factor of the model at low frequencies and nonzero temperatures, using the form factor method. Its frequency dependence is singular, but differs from the diffusion form. The temperature dependence of the nuclear magnetic resonance (NMR) relaxation rate has an activated form, whose prefactor we also determine. We propose NMR experiments as a means to further test the applicability of the E₈ description for CoNb₂O₆.
Signals for the QCD phase transition and critical point in a Langevin dynamical model
Herold, Christoph; Bleicher, Marcus; Yan, Yu-Peng
2013-01-01
The search for the critical point is one of the central issues that will be investigated in the upcoming FAIR project. For a profound theoretical understanding of the expected signals we go beyond thermodynamic studies and present a fully dynamical model for the chiral and deconfinement phase transition in heavy ion collisions. The corresponding order parameters are propagated by Langevin equations of motions on a thermal background provided by a fluid dynamically expanding plasma of quarks. By that we are able to describe nonequilibrium effects occurring during the rapid expansion of a hot fireball. For an evolution through the phase transition the formation of a supercooled phase and its subsequent decay crucially influence the trajectories in the phase diagram and lead to a significant reheating of the quark medium at highest baryon densities. Furthermore, we find inhomogeneous structures with high density domains along the first order transition line within single events.
Dynamic data-driven integrated flare model based on self-organized criticality
Dimitropoulou, M.; Isliker, H.; Vlahos, L.; Georgoulis, M. K.
2013-05-01
Context. We interpret solar flares as events originating in active regions that have reached the self-organized critical state. We describe them with a dynamic integrated flare model whose initial conditions and driving mechanism are derived from observations. Aims: We investigate whether well-known scaling laws observed in the distribution functions of characteristic flare parameters are reproduced after the self-organized critical state has been reached. Methods: To investigate whether the distribution functions of total energy, peak energy, and event duration follow the expected scaling laws, we first applied the previously reported static cellular automaton model to a time series of seven solar vector magnetograms of the NOAA active region 8210 recorded by the Imaging Vector Magnetograph on May 1 1998 between 18:59 UT and 23:16 UT until the self-organized critical state was reached. We then evolved the magnetic field between these processed snapshots through spline interpolation, mimicking a natural driver in our dynamic model. We identified magnetic discontinuities that exceeded a threshold in the Laplacian of the magnetic field after each interpolation step. These discontinuities were relaxed in local diffusion events, implemented in the form of cellular automaton evolution rules. Subsequent interpolation and relaxation steps covered all transitions until the end of the processed magnetograms' sequence. We additionally advanced each magnetic configuration that has reached the self-organized critical state (SOC configuration) by the static model until 50 more flares were triggered, applied the dynamic model again to the new sequence, and repeated the same process sufficiently often to generate adequate statistics. Physical requirements, such as the divergence-free condition for the magnetic field, were approximately imposed. Results: We obtain robust power laws in the distribution functions of the modeled flaring events with scaling indices that agree well
Trave-Massuyes, L. [Centre National de la Recherche Scientifique (CNRS), 31 - Toulouse (France); Milne, R.
1995-12-31
We are interested in the monitoring and diagnosis of dynamic systems. In our work, we are combining explicit temporal models of the behaviour of a dynamic system with implicit behavioural models supporting model based approaches. This work is drive by the needs of and applied to, two gas turbines of very different size and power. In this paper we describe the problems of building systems for these domains and illustrate how we have developed a system where these two approaches complement each other to provide a comprehensive fault detection and diagnosis system. We also explore the strengths and weaknesses of each approach. The work described here is currently working continuously, on line to a gas turbine in a major chemical plant. (author) 24 refs.
Trave-Massuyes, L [Centre National de la Recherche Scientifique (CNRS), 31 - Toulouse (France); Milne, R
1996-12-31
We are interested in the monitoring and diagnosis of dynamic systems. In our work, we are combining explicit temporal models of the behaviour of a dynamic system with implicit behavioural models supporting model based approaches. This work is drive by the needs of and applied to, two gas turbines of very different size and power. In this paper we describe the problems of building systems for these domains and illustrate how we have developed a system where these two approaches complement each other to provide a comprehensive fault detection and diagnosis system. We also explore the strengths and weaknesses of each approach. The work described here is currently working continuously, on line to a gas turbine in a major chemical plant. (author) 24 refs.
Enemark, Søren; Santos, Ilmar F.
2016-01-01
In this work, the nonlinear dynamic behaviour of a vertical rigid rotor interacting with a flexible foundation by means of two passive magnetic bearings is quantified and evaluated. The quantification is based on theoretical and experimental investigation of the non-uniformity (anisotropy......) of the magnetic field and the weak nonlinearity of the magnetic forces. Through mathematical modelling the nonlinear equations of motion are established for describing the shaft and bearing housing lateral dynamics coupled via the nonlinear and non-uniform magnetic forces. The equations of motion are solved...
Quantum critical matter. Quantum phase transitions with multiple dynamics and Weyl superconductors
Meng, Tobias
2012-01-01
In this PhD thesis, the physics of quantum critical matter and exotic quantum state close to quantum phase transitions is investigated. We will focus on three different examples that highlight some of the interesting phenomena related to quantum phase transitions. Firstly, we discuss the physics of quantum phase transitions in quantum wires as a function of an external gate voltage when new subbands are activated. We find that at these transitions, strong correlations lead to the formation of an impenetrable gas of polarons, and identify criteria for possible instabilities in the spin- and charge sectors of the model. Our analysis is based on the combination of exact resummations, renormalization group techniques and Luttinger liquid approaches. Secondly, we turn to the physics of multiple divergent time scales close to a quantum critical point. Using an appropriately generalized renormalization group approach, we identify that the presence of multiple dynamics at a quantum phase transition can lead to the emergence of new critical scaling exponents and thus to the breakdown of the usual scaling schemes. We calculate the critical behavior of various thermodynamic properties and detail how unusual physics can arise. It is hoped that these results might be helpful for the interpretation of experimental scaling puzzles close to quantum critical points. Thirdly, we turn to the physics of topological transitions, and more precisely the physics of Weyl superconductors. The latter are the superconducting variant of the topologically non-trivial Weyl semimetals, and emerge at the quantum phase transition between a topological superconductor and a normal insulator upon perturbing the transition with a time reversal symmetry breaking perturbation, such as magnetism. We characterize the topological properties of Weyl superconductors and establish a topological phase diagram for a particular realization in heterostructures. We discuss the physics of vortices in Weyl
Omar, R.; Rani, M. N. Abdul; Yunus, M. A.; Mirza, W. I. I. Wan Iskandar; Zin, M. S. Mohd
2018-04-01
A simple structure with bolted joints consists of the structural components, bolts and nuts. There are several methods to model the structures with bolted joints, however there is no reliable, efficient and economic modelling methods that can accurately predict its dynamics behaviour. Explained in this paper is an investigation that was conducted to obtain an appropriate modelling method for bolted joints. This was carried out by evaluating four different finite element (FE) models of the assembled plates and bolts namely the solid plates-bolts model, plates without bolt model, hybrid plates-bolts model and simplified plates-bolts model. FE modal analysis was conducted for all four initial FE models of the bolted joints. Results of the FE modal analysis were compared with the experimental modal analysis (EMA) results. EMA was performed to extract the natural frequencies and mode shapes of the test physical structure with bolted joints. Evaluation was made by comparing the number of nodes, number of elements, elapsed computer processing unit (CPU) time, and the total percentage of errors of each initial FE model when compared with EMA result. The evaluation showed that the simplified plates-bolts model could most accurately predict the dynamic behaviour of the structure with bolted joints. This study proved that the reliable, efficient and economic modelling of bolted joints, mainly the representation of the bolting, has played a crucial element in ensuring the accuracy of the dynamic behaviour prediction.
L.Y. Yang
2014-07-01
Full Text Available During the drill-and-blast progress in rock tunnel excavation of great deep mine, rock fracture is evaluated by both blasting load and pre-exiting earth stress (pre-compression. Many pre-existing flaws in the rock mass, like micro-crack, also seriously affect the rock fracture pattern. Under blasting load with pre-compression, micro-cracks initiate, propagate and grow to be wing cracks. With an autonomous design of static-dynamic loading system, dynamic and static loads were applied on some PMMA plate specimen with pre-existing crack, and the behaviour of the wing crack was tested by caustics corroding with a high-speed photography. Four programs with different static loading modes that generate different pre-compression fields were executed, and the length, velocity of the blasting wing crack and dynamic stress intensity factor (SIF at the wing crack tip were analyzed and discussed. It is found that the behaviour of blasting-induced wing crack is affected obviously by blasting and pre-compression. And pre-compression, which is vertical to the direction of the wing crack propagation, hinders the crack propagation. Furthermore, the boundary constraint condition plays an important role on the behaviour of blasting induced crack during the experiment.
Moxon, D.
1966-01-01
A dynamics code is described that solves the two-group neutron diffusion equations simultaneously with the thermal and the hydraulic equations for an average channel of a water-cooled reactor. Other reactor channels can be represented as 'slaves', which have no feedback to the average channel. The fission power at any axial station in a slave channel is related to that in the average by prescribed time-dependent factors, and the hydraulic flow is determined from pressure-drop requirements dictated by the performance of the average channel. A finite difference model of the fuel element and can represents the behaviour of the fuel temperatures and surface heat flux. The representation of the hydraulic circuit has been made sufficiently general that the code is applicable to B.W.R., P.W.R. and pressure tube reactor designs. The code can be used to study transients resulting from imposed time variations in coolant flow, inlet enthalpy, system pressure, electrical torque supplied to the circulating pumps, (or alternatively, the angular velocity of the pump rotors,) moderator height, frictional resistances simulating blockages and control rod and fuel element insertions. The harmonic response can be obtained by injecting sinusoidal time variations until the starting transient has been damped out. Output includes axial distributions of the neutron fluxes, heat flux, coolant density and temperature, burn-but margin, and the fuel and can temperatures in both the average and the slave channels. The code was originally written in FORTRAN II for use on the IBM 7090. Computing times vary greatly with the problem and the desired accuracy but experience has shown that a computing time which is slower than real time by a factor thirty is adequate for a wide range of cases. The code has recently been converted to S2 and EGTRAN for use on the IBM 7030 and the English Electric Leo Marconi KDF 9 computers. (author)
Wilkinson, Simon R
2016-01-01
The major challenge for a clinician is integration of the wisdom available in the wide range of therapeutic paradigms available. I have found the principles guiding dialectic behaviour therapy (DBT; see Miller, Rathus, & Linehan, 2007, for applying DBT to adolescents) extremely useful in my practice running a general adolescent unit; similarly, the understanding of the different information processing and learning principles associated with each of the Type A and C attachment strategies, as understood in dynamic maturational model (DMM), has guided me through the dark corners of treatment. Specifically, how does DMM inform practice of DBT? As a 'DBTer' might say, 'Where is the wisdom in both points of view?' Nevertheless, DMM is not primarily about treatment. It concerns how different ways of adapting to developmental contingencies bias perceptual propensities, and hence the information available for reflective brain function. Recognition of these twists to knowing what is going on can then be used to inform a variety of therapeutic approaches. The purpose of this article is to look for the signposts in DBT and DMM which together help navigate the comprehensive approach necessary in complicated therapy. In the process, hopefully some more general principles for addressing discomfited adolescents arise for informing future practice. Although many steer shy of using personality disorder diagnoses for adolescents, clinicians are nevertheless addressing, directly or indirectly, the personality development of all adolescents in treatment, regardless of their classical axis I diagnoses, including both those with developing emotional instability and a group of avoidant over-controlled adolescents, which in Norway is growing in prominence. © The Author(s) 2014.
Cross-cultural patterns in dynamic ratings of positive and negative natural emotional behaviour.
Sneddon, Ian; McKeown, Gary; McRorie, Margaret; Vukicevic, Tijana
2011-02-18
Studies of cross-cultural variations in the perception of emotion have typically compared rates of recognition of static posed stimulus photographs. That research has provided evidence for universality in the recognition of a range of emotions but also for some systematic cross-cultural variation in the interpretation of emotional expression. However, questions remain about how widely such findings can be generalised to real life emotional situations. The present study provides the first evidence that the previously reported interplay between universal and cultural influences extends to ratings of natural, dynamic emotional stimuli. Participants from Northern Ireland, Serbia, Guatemala and Peru used a computer based tool to continuously rate the strength of positive and negative emotion being displayed in twelve short video sequences by people from the United Kingdom engaged in emotional conversations. Generalized additive mixed models were developed to assess the differences in perception of emotion between countries and sexes. Our results indicate that the temporal pattern of ratings is similar across cultures for a range of emotions and social contexts. However, there are systematic differences in intensity ratings between the countries, with participants from Northern Ireland making the most extreme ratings in the majority of the clips. The results indicate that there is strong agreement across cultures in the valence and patterns of ratings of natural emotional situations but that participants from different cultures show systematic variation in the intensity with which they rate emotion. Results are discussed in terms of both 'in-group advantage' and 'display rules' approaches. This study indicates that examples of natural spontaneous emotional behaviour can be used to study cross-cultural variations in the perception of emotion.
Dynamic behaviour of raft and pile foundations tests and computational models. Pt. 1
Betbeder, J.; Garnier, J.C.; Gauvain, J.; Jeandidier, C.
1981-01-01
Pile foundations are commonly used for many types of buildings where the bearing capacity of soil is poor. For nuclear power plants buildings, however, there seems to be a fairly general reluctancy to accept design on piles, as it is considered difficult to demonstrate the safety of these foundations with respect to earthquakes, due to the relative lack of validation of the currently available aseismic design methods. Being conscious that pile foundations might be worth considering for future nuclear sites in France and that the reliability of design methods should be backed by experimental data, ELECTRICITE DE FRANCE decided in 1978 to undertake a series of tests, aimed at assessing the validity of computational models for seismic behaviour of pile foundations and trying to define better models if necessary. These tests on reduced scale structure, including various types of raft and pile foundations and different kinds of dynamic excitation (harmonic, earthquake simulation, impulsive release of a static force) have been made at the NICE airport site. The present paper deals with the general description of the tests and the first part of interpretation work, limited to in-structure harmonic excitation and earthquake simulation tests analyzed by simple spring -dashpot analytical models. The two following papers (K5-6 and K5-7) are devoted to specialized topics in relation with the interpretation of tests, i-e ground motions analysis for earthquake simulation and research work on a new computational model. Although preliminary conclusions can be drawn from the results obtained so far, further work will be necessary to reach a conclusive assessment on this difficult subject. (orig.)
Effect of intermolecular force on the static/dynamic behaviour of M/NEM devices
Kim, Namjung; Aluru, N. R.
2014-12-01
Advances made in the fabrication of micro/nano-electromechanical (M/NEM) devices over the last ten years necessitate the understanding of the attractive force that arises from quantum fluctuations (generally referred to as Casimir effects) [Casimir H B G 1948 Proc. K. Ned. Akad. Wet. 51 793]. The fundamental mechanisms underlying quantum fluctuations have been actively investigated through various theoretical and experimental approaches. However, the effect of the force on M/NEM devices has not been fully understood yet, especially in the transition region involving gaps ranging from 10 nm to 1 μm, due to the complexity of the force. Here, we numerically calculate the Casimir effects in M/NEM devices by using the Lifshitz formula, the general expression for the Casimir effects [Lifshitz E 1956 Sov. Phys. JETP 2 73]. Since the Casimir effects are highly dependent on the permittivity of the materials, the Kramer-Kronig relation [Landau L D, Lifshitz E M and Pitaevskii L P 1984 Electrodynamics of Continuous Media (New York: Pergamon Press)] and the optical data for metals and dielectrics are used in order to obtain the permittivity. Several simplified models for the permittivity of the materials, such as the Drude and Lorentz models [Jackson J D 1975 Classical Electrodynamics (New York: Wiley)], are also used to extrapolate the optical data. Important characteristic values of M/NEM devices, such as the pull-in voltage, pull-in gap, detachment length, etc, are calculated for devices operating in the transition region. Our results show that accurate predictions for the pull-in behaviour are possible when the Lifshitz formula is used instead of the idealized expressions for Casimir effects. We expand this study into the dynamics of M/NEM devices, so that the time and frequency response of M/NEM devices with Casimir effects can be explored.
Effect of intermolecular force on the static/dynamic behaviour of M/NEM devices
Kim, Namjung; Aluru, N R
2014-01-01
Advances made in the fabrication of micro/nano-electromechanical (M/NEM) devices over the last ten years necessitate the understanding of the attractive force that arises from quantum fluctuations (generally referred to as Casimir effects) [Casimir H B G 1948 Proc. K. Ned. Akad. Wet. 51 793]. The fundamental mechanisms underlying quantum fluctuations have been actively investigated through various theoretical and experimental approaches. However, the effect of the force on M/NEM devices has not been fully understood yet, especially in the transition region involving gaps ranging from 10 nm to 1 μm, due to the complexity of the force. Here, we numerically calculate the Casimir effects in M/NEM devices by using the Lifshitz formula, the general expression for the Casimir effects [Lifshitz E 1956 Sov. Phys. JETP 2 73]. Since the Casimir effects are highly dependent on the permittivity of the materials, the Kramer–Kronig relation [Landau L D, Lifshitz E M and Pitaevskii L P 1984 Electrodynamics of Continuous Media (New York: Pergamon Press)] and the optical data for metals and dielectrics are used in order to obtain the permittivity. Several simplified models for the permittivity of the materials, such as the Drude and Lorentz models [Jackson J D 1975 Classical Electrodynamics (New York: Wiley)], are also used to extrapolate the optical data. Important characteristic values of M/NEM devices, such as the pull-in voltage, pull-in gap, detachment length, etc, are calculated for devices operating in the transition region. Our results show that accurate predictions for the pull-in behaviour are possible when the Lifshitz formula is used instead of the idealized expressions for Casimir effects. We expand this study into the dynamics of M/NEM devices, so that the time and frequency response of M/NEM devices with Casimir effects can be explored. (paper)
Cross-cultural patterns in dynamic ratings of positive and negative natural emotional behaviour.
Ian Sneddon
2011-02-01
Full Text Available Studies of cross-cultural variations in the perception of emotion have typically compared rates of recognition of static posed stimulus photographs. That research has provided evidence for universality in the recognition of a range of emotions but also for some systematic cross-cultural variation in the interpretation of emotional expression. However, questions remain about how widely such findings can be generalised to real life emotional situations. The present study provides the first evidence that the previously reported interplay between universal and cultural influences extends to ratings of natural, dynamic emotional stimuli.Participants from Northern Ireland, Serbia, Guatemala and Peru used a computer based tool to continuously rate the strength of positive and negative emotion being displayed in twelve short video sequences by people from the United Kingdom engaged in emotional conversations. Generalized additive mixed models were developed to assess the differences in perception of emotion between countries and sexes. Our results indicate that the temporal pattern of ratings is similar across cultures for a range of emotions and social contexts. However, there are systematic differences in intensity ratings between the countries, with participants from Northern Ireland making the most extreme ratings in the majority of the clips.The results indicate that there is strong agreement across cultures in the valence and patterns of ratings of natural emotional situations but that participants from different cultures show systematic variation in the intensity with which they rate emotion. Results are discussed in terms of both 'in-group advantage' and 'display rules' approaches. This study indicates that examples of natural spontaneous emotional behaviour can be used to study cross-cultural variations in the perception of emotion.
Aguzzi, Jacopo; Sbragaglia, Valerio; Tecchio, Samuele; Navarro, Joan; Company, Joan B.
2015-01-01
Light-intensity cycles drive the relentless motion of species in the oceans, and water column migrants may cyclically make contact with the seabed, hence influencing the temporal dynamism of benthic ecosystems. The influence of light on this process remains largely unknown to date. In this study, we focus on the occurrence of day-night changes in benthic communities on the western Mediterranean continental shelf (100 m depth) and slope (400 m depth) as a potential result of a behaviourally sustained benthopelagic coupling. We analysed fluctuations in species abundance based on trawling at hourly intervals over a 4-day period as a proxy of activity rhythms at the seabed. We also measured light in situ to assess how the depth-related decrease of its intensity influences species rhythms and the occurrence of the putative benthopelagic synchronisation. Temporal similarities in the catch patterns for different species were screened by dendrogram analysis. On the continental shelf, species performing diel migrations (i.e., over a 24 h period) that were either vertical (i.e., benthopelagic) or horizontal across depths (i.e., nektobenthic) clustered together separately from the more sedentary endobenthic and epibenthic species. At the same depth, waveform analysis showed a significant diurnal increase in the catch of water column species and benthic species at night. Such coupling was absent on the continental slope, where light intensity was several orders of magnitude lower than that on the shelf. Our data indicate that diel activity rhythms, which are well known for vertical pelagic migrators, are also evident in the benthos. We discuss the role of light as a major evolutionary driver shaping the composition and biodiversity of benthic communities via visual predation.
Computational multi-fluid dynamics predictions of critical heat flux in boiling flow
Mimouni, S.; Baudry, C.; Guingo, M.; Lavieville, J.; Merigoux, N.; Mechitoua, N.
2016-01-01
Highlights: • A new mechanistic model dedicated to DNB has been implemented in the Neptune_CFD code. • The model has been validated against 150 tests. • Neptune_CFD code is a CFD tool dedicated to boiling flows. - Abstract: Extensive efforts have been made in the last five decades to evaluate the boiling heat transfer coefficient and the critical heat flux in particular. Boiling crisis remains a major limiting phenomenon for the analysis of operation and safety of both nuclear reactors and conventional thermal power systems. As a consequence, models dedicated to boiling flows have being improved. For example, Reynolds Stress Transport Model, polydispersion and two-phase flow wall law have been recently implemented. In a previous work, we have evaluated computational fluid dynamics results against single-phase liquid water tests equipped with a mixing vane and against two-phase boiling cases. The objective of this paper is to propose a new mechanistic model in a computational multi-fluid dynamics tool leading to wall temperature excursion and onset of boiling crisis. Critical heat flux is calculated against 150 tests and the mean relative error between calculations and experimental values is equal to 8.3%. The model tested covers a large physics scope in terms of mass flux, pressure, quality and channel diameter. Water and R12 refrigerant fluid are considered. Furthermore, it was found that the sensitivity to the grid refinement was acceptable.
Computational multi-fluid dynamics predictions of critical heat flux in boiling flow
Mimouni, S., E-mail: stephane.mimouni@edf.fr; Baudry, C.; Guingo, M.; Lavieville, J.; Merigoux, N.; Mechitoua, N.
2016-04-01
Highlights: • A new mechanistic model dedicated to DNB has been implemented in the Neptune-CFD code. • The model has been validated against 150 tests. • Neptune-CFD code is a CFD tool dedicated to boiling flows. - Abstract: Extensive efforts have been made in the last five decades to evaluate the boiling heat transfer coefficient and the critical heat flux in particular. Boiling crisis remains a major limiting phenomenon for the analysis of operation and safety of both nuclear reactors and conventional thermal power systems. As a consequence, models dedicated to boiling flows have being improved. For example, Reynolds Stress Transport Model, polydispersion and two-phase flow wall law have been recently implemented. In a previous work, we have evaluated computational fluid dynamics results against single-phase liquid water tests equipped with a mixing vane and against two-phase boiling cases. The objective of this paper is to propose a new mechanistic model in a computational multi-fluid dynamics tool leading to wall temperature excursion and onset of boiling crisis. Critical heat flux is calculated against 150 tests and the mean relative error between calculations and experimental values is equal to 8.3%. The model tested covers a large physics scope in terms of mass flux, pressure, quality and channel diameter. Water and R12 refrigerant fluid are considered. Furthermore, it was found that the sensitivity to the grid refinement was acceptable.
Analytical description of critical dynamics for two-dimensional dissipative nonlinear maps
Méndez-Bermúdez, J.A.; Oliveira, Juliano A. de; Leonel, Edson D.
2016-01-01
The critical dynamics near the transition from unlimited to limited action diffusion for two families of well known dissipative nonlinear maps, namely the dissipative standard and dissipative discontinuous maps, is characterized by the use of an analytical approach. The approach is applied to explicitly obtain the average squared action as a function of the (discrete) time and the parameters controlling nonlinearity and dissipation. This allows to obtain a set of critical exponents so far obtained numerically in the literature. The theoretical predictions are verified by extensive numerical simulations. We conclude that all possible dynamical cases, independently on the map parameter values and initial conditions, collapse into the universal exponential decay of the properly normalized average squared action as a function of a normalized time. The formalism developed here can be extended to many other different types of mappings therefore making the methodology generic and robust. - Highlights: • We analytically approach scaling properties of a family of two-dimensional dissipative nonlinear maps. • We derive universal scaling functions that were obtained before only approximately. • We predict the unexpected condition where diffusion and dissipation compensate each other exactly. • We find a new universal scaling function that embraces all possible dissipative behaviors.
Learning and adaptation: neural and behavioural mechanisms behind behaviour change
Lowe, Robert; Sandamirskaya, Yulia
2018-01-01
This special issue presents perspectives on learning and adaptation as they apply to a number of cognitive phenomena including pupil dilation in humans and attention in robots, natural language acquisition and production in embodied agents (robots), human-robot game play and social interaction, neural-dynamic modelling of active perception and neural-dynamic modelling of infant development in the Piagetian A-not-B task. The aim of the special issue, through its contributions, is to highlight some of the critical neural-dynamic and behavioural aspects of learning as it grounds adaptive responses in robotic- and neural-dynamic systems.
The dynamics of consumer behaviour: On habit, discontent, and other fish to fry
Scholderer, Joachim; Trondsen, Torbjørn
2008-01-01
Recent research has drawn attention to the role of past behaviour and habit in the overall structure of consumer behaviour. We argue that in cross-sectional data past behaviour and habit must be confounded with present beliefs and attitudes when the behaviour in question has been enacted numerous...... supply. These negative evaluations, in turn, prompted substitution of traditional seafood with newly available, processed seafood products and an increasing dominance of aqua-cultured species. The theoretical discussion focuses on the inability of static models of consumer behaviour (in particular...... times before. To disentangle the effects, longitudinal data were collected from a large panel of Norwegian consumers (effective N=4184) in 1996, 2000, and 2004. Cross-lagged panel analysis indicated that higher consumption of traditional seafood led to increasingly negative evaluations of the product...
2013-03-01
This : study : examines : the : travel : behaviour : and : attitudes : of : recently : resettled : refugees : in : Chittenden : County, : Vermont, : with : particular : attention : to : distinctions : based : on : gender : and : age. : It : is : base...
Kozma, Robert; Freeman, Walter J
2017-01-01
Measurements of local field potentials over the cortical surface and the scalp of animals and human subjects reveal intermittent bursts of beta and gamma oscillations. During the bursts, narrow-band metastable amplitude modulation (AM) patters emerge for a fraction of a second and ultimately dissolve to the broad-band random background activity. The burst process depends on previously learnt conditioned stimuli (CS), thus different AM patterns may emerge in response to different CS. This observation leads to our cinematic theory of cognition when perception happens in discrete steps manifested in the sequence of AM patterns. Our article summarizes findings in the past decades on experimental evidence of cinematic theory of cognition and relevant mathematical models. We treat cortices as dissipative systems that self-organize themselves near a critical level of activity that is a non-equilibrium metastable state. Criticality is arguably a key aspect of brains in their rapid adaptation, reconfiguration, high storage capacity, and sensitive response to external stimuli. Self-organized criticality (SOC) became an important concept to describe neural systems. We argue that transitions from one AM pattern to the other require the concept of phase transitions, extending beyond the dynamics described by SOC. We employ random graph theory (RGT) and percolation dynamics as fundamental mathematical approaches to model fluctuations in the cortical tissue. Our results indicate that perceptions are formed through a phase transition from a disorganized (high entropy) to a well-organized (low entropy) state, which explains the swiftness of the emergence of the perceptual experience in response to learned stimuli.
Adnan naji jameel
2016-03-01
Full Text Available In this paper, the effect of wear in the fluid film journal bearings on the dynamic stability of rotor bearing system has been studied depending on the development of new analytical equations for motion, instability threshold speed and steady state harmonic response for rotor with offset disc supported by worn journal bearings. Finite element method had been used for modeling the rotor bearing system. The analytical model is verified by comparing its results with that obtained numerically for a rotor supported on the short bearings. The analytical and numerical results showed good agreement with about 8.5% percentage error in the value of critical speed and about 3.5% percentage error in the value of harmonic response. The results obtained show that the wear in journal bearing decrease the instability threshold speed by 2.5% for wear depth 0.02 mm and 12.5% for wear depth 0.04 mm as well as decrease critical speed by 4.2% and steady state harmonic response amplitude by 4.3% for wear depth 0.02 mm and decrease the critical speed by 7.1% and steady state harmonic response amplitude by 13.9% for wear depth 0.04 mm.
Non-critical string theory formulation of microtubule dynamics and quantum aspects of brain function
Mavromatos, Nikolaos E
1995-01-01
Microtubule (MT) networks, subneural paracrystalline cytosceletal structures, seem to play a fundamental role in the neurons. We cast here the complicated MT dynamics in the form of a 1+1-dimensional non-critical string theory, thus enabling us to provide a consistent quantum treatment of MTs, including enviromental {\\em friction} effects. We suggest, thus, that the MTs are the microsites, in the brain, for the emergence of stable, macroscopic quantum coherent states, identifiable with the {\\em preconscious states}. Quantum space-time effects, as described by non-critical string theory, trigger then an {\\em organized collapse} of the coherent states down to a specific or {\\em conscious state}. The whole process we estimate to take {\\cal O}(1\\,{\\rm sec}), in excellent agreement with a plethora of experimental/observational findings. The {\\em microscopic arrow of time}, endemic in non-critical string theory, and apparent here in the self-collapse process, provides a satisfactory and simple resolution to the age...
Tresser, Shachar; Dolev, Amit; Bucher, Izhak
2018-02-01
High-speed machinery is often designed to pass several "critical speeds", where vibration levels can be very high. To reduce vibrations, rotors usually undergo a mass balancing process, where the machine is rotated at its full speed range, during which the dynamic response near critical speeds can be measured. High sensitivity, which is required for a successful balancing process, is achieved near the critical speeds, where a single deflection mode shape becomes dominant, and is excited by the projection of the imbalance on it. The requirement to rotate the machine at high speeds is an obstacle in many cases, where it is impossible to perform measurements at high speeds, due to harsh conditions such as high temperatures and inaccessibility (e.g., jet engines). This paper proposes a novel balancing method of flexible rotors, which does not require the machine to be rotated at high speeds. With this method, the rotor is spun at low speeds, while subjecting it to a set of externally controlled forces. The external forces comprise a set of tuned, response dependent, parametric excitations, and nonlinear stiffness terms. The parametric excitation can isolate any desired mode, while keeping the response directly linked to the imbalance. A software controlled nonlinear stiffness term limits the response, hence preventing the rotor to become unstable. These forces warrant sufficient sensitivity required to detect the projection of the imbalance on any desired mode without rotating the machine at high speeds. Analytical, numerical and experimental results are shown to validate and demonstrate the method.
Towards the Verification of Safety-critical Autonomous Systems in Dynamic Environments
Adina Aniculaesei
2016-12-01
Full Text Available There is an increasing necessity to deploy autonomous systems in highly heterogeneous, dynamic environments, e.g. service robots in hospitals or autonomous cars on highways. Due to the uncertainty in these environments, the verification results obtained with respect to the system and environment models at design-time might not be transferable to the system behavior at run time. For autonomous systems operating in dynamic environments, safety of motion and collision avoidance are critical requirements. With regard to these requirements, Macek et al. [6] define the passive safety property, which requires that no collision can occur while the autonomous system is moving. To verify this property, we adopt a two phase process which combines static verification methods, used at design time, with dynamic ones, used at run time. In the design phase, we exploit UPPAAL to formalize the autonomous system and its environment as timed automata and the safety property as TCTL formula and to verify the correctness of these models with respect to this property. For the runtime phase, we build a monitor to check whether the assumptions made at design time are also correct at run time. If the current system observations of the environment do not correspond to the initial system assumptions, the monitor sends feedback to the system and the system enters a passive safe state.
Dynamic and thermal behaviour of quasi-particles in superfluid 3He-B. Ch. 10
Guenault, A.M.; Pickett, G.R.
1990-01-01
In superfluid 3 He-B, the quasi-particle gas is particularly accessible to experimental study of quasi-particle dynamics. The authors discuss some of their own experiments in this field. In section 2 the experimental methods are outlined briefly. Then experiments are introduced which can be made with vibrating-wire resonators. They can be used as detectors of the thermal background quasi-particles, which means that they can be used as thermometers. They can be used as quasiparticle sources, i.e. they can be used as heaters; and they can be used as detectors of directed quasi-particle beams, which leads to the possibility of the use of two wires together as source and detector in a beam spectrometer. This logical order is largely followed in this chapter. In section 3 the thermal behavior of the quasi-particle gas is discussed, including the use of the damping of a resonator as a thermometer, leading to experiments on boundary conductance and on bulk ballistic thermal transport. Section 4 covers the onset of dissipation in a strongly driven wire resonator, in particular the Landau critical velocity and pair-breaking effects, together with a discussion of supercritical dissipation. This leads, in section 5, to some early results of the ballistic quasi-particle galvanometer. This latter field is a rapidly developing one and some possible intriguing experiments for the future are discussed in section 6. (author). 30 refs.; 17 figs.; 1 tab
The Ramifications of Meddling with Systems Governed by Self-organized Critical Dynamics
Carreras, B. A.; Newman, D. E.; Dobson, I.
2002-12-01
Complex natural, well as man-made, systems often exhibit characteristics similar to those seen in self-organized critical (SOC) systems. The concept of self-organized criticality brings together ideas of self-organization of nonlinear dynamical systems with the often-observed near critical behavior of many natural phenomena. These phenomena exhibit self-similarities over extended ranges of spatial and temporal scales. In those systems, scale lengths may be described by fractal geometry and time scales that lead to 1/f-like power spectra. Natural applications include modeling the motion of tectonics plates, forest fires, magnetospheric dynamics, spin glass systems, and turbulent transport. In man-made systems, applications have included traffic dynamics, power and communications networks, and financial markets among many others. Simple cellular automata models such as the running sandpile model have been very useful in reproducing the complexity and characteristics of these systems. One characteristic property of the SOC systems is that they relax through what we call events. These events can happen over all scales of the system. Examples of these events are: earthquakes in the case of plate tectonic; fires in forest evolution extinction in the co evolution of biological species; and blackouts in power transmission systems. In a time-averaged sense, these systems are subcritical (that is, they lie in an average state that should not trigger any events) and the relaxation events happen intermittently. The time spent in a subcritical state relative to the time of the events varies from one system to another. For instance, the chance of finding a forest on fire is very low with the frequency of fires being on the order of one fire every few years and with many of these fires small and inconsequential. Very large fires happen over time periods of decades or even centuries. However, because of their consequences, these large but infrequent events are the important ones
Graziani, S.; Pagano, F.; Pitrone, N.; Umana, E.
2010-01-01
Ionic Polymer Polymer Composites (IP 2 Cs) are emerging materials used to realize motion actuators and sensors. In the former case a voltage input is able to cause the membrane to bend while in the latter case by bending an IP 2 C membrane, a voltage output is obtained. In this paper authors introduce a software tool able to estimate the dynamic behaviour for sensors based on IP 2 Cs working in air. In the proposed tool, geometrical quantities that rule the sensing properties of IP 2 C-based transducers are taken into account together with their dynamic characteristics. A graphical interface (GUI) has been developed in order to give a useful tool that allows the user to understand the behaviour and the role of the parameters involved in the transduction phenomena. The tool is based on the idea that a graphical user interface will allow persons not skilled in IP 2 C materials to observe their behaviour and to analyze their characteristics. This could greatly increase the interest of researchers towards this new class of transducers; moreover, it can support the educational activity of students involved in advanced academical courses.
Jacobs, W; Boonen, R; Sas, P; Moens, D
2012-01-01
Accurate prediction of the lifetime of rolling element bearings is a crucial step towards a reliable design of many rotating machines. Recent research emphasizes an important influence of external dynamic loads on the lifetime of bearings. However, most lifetime calculations of bearings are based on the classical ISO 281 standard, neglecting this influence. For bearings subjected to highly varying loads, this leads to inaccurate estimations of the lifetime, and therefore excessive safety factors during the design and unexpected failures during operation. This paper presents a novel test rig, developed to analyse the behaviour of rolling element bearings subjected to highly varying loads. Since bearings are very precise machine components, their motion can only be measured in an accurately controlled environment. Otherwise, noise from other components and external influences such as temperature variations will dominate the measurements. The test rig is optimised to perform accurate measurements of the bearing behaviour. Also, the test bearing is fitted in a modular structure, which guarantees precise mounting and allows testing different types and sizes of bearings. Finally, a fully controlled multi-axial static and dynamic load is imposed on the bearing, while its behaviour is monitored with capacitive proximity probes.
Tajik, M.; Ghasemizad, A.
2008-01-01
In this research, new physical fission reactor parameters which have very sensitive effects on the qualitative behavior of a reactor, are introduced. Therefore, the two, the nonlinear dynamics of two, three and four dimensional, considering almost the effective parameters are formulated for describing nuclear fission reactor systems. Using both analytical and numerical methods, the stability and instability of the given dynamical equations and the conditions of stability are studied in these systems. We have shown that the two parameters of the mean energy residence time in fuel and coolant and also their ratios have the most qualitative effects on the dynamical behaviour of a typical nuclear fission reactor. Increasing or decreasing of these parameters from a captain limit can lead to stability or un stability in a given system
Critical ionisation velocity and the dynamics of a coaxial plasma gun
Raadu, M.A.
1978-01-01
The dynamics of an ionising wave in a coaxial plasma gun with an azimuthal bias magnetic field is analysed in a theoretical model. Only the radial dependence is treated and instead of including a treatment of the energy balance two separate physical assumptions are made. In the first case it is assumed that the total internal electric field is given by the critical ionisation velocity condition and in the second that the ionisation rate is constant. For consistency wall sheaths are assumed to match the internal plasma potential to that of the walls. On the basis of momentum and particle balance the radial dependence of the electron density, current density, electric field and drift velocity are found. An electron source is required at the cathode and the relative contribution from ionisation within the plasma is deduced. The assumption that there are no ion sources at the electrodes leads to a restriction on the possible values of the axial electric field. (author)
Inhomogeneous quasi-adiabatic driving of quantum critical dynamics in weakly disordered spin chains
Rams, Marek M; Mohseni, Masoud; Campo, Adolfo del
2016-01-01
We introduce an inhomogeneous protocol to drive a weakly disordered quantum spin chain quasi-adiabatically across a quantum phase transition and minimize the residual energy of the final state. The number of spins that simultaneously reach the critical point is controlled by the length scale in which the magnetic field is modulated, introducing an effective size that favors adiabatic dynamics. The dependence of the residual energy on this length scale and the velocity at which the magnetic field sweeps out the chain is shown to be nonmonotonic. We determine the conditions for an optimal suppression of the residual energy of the final state and show that inhomogeneous driving can outperform conventional adiabatic schemes based on homogeneous control fields by several orders of magnitude. (paper)
A Dynamic Hydrology-Critical Zone Framework for Rainfall-triggered Landslide Hazard Prediction
Dialynas, Y. G.; Foufoula-Georgiou, E.; Dietrich, W. E.; Bras, R. L.
2017-12-01
Watershed-scale coupled hydrologic-stability models are still in their early stages, and are characterized by important limitations: (a) either they assume steady-state or quasi-dynamic watershed hydrology, or (b) they simulate landslide occurrence based on a simple one-dimensional stability criterion. Here we develop a three-dimensional landslide prediction framework, based on a coupled hydrologic-slope stability model and incorporation of the influence of deep critical zone processes (i.e., flow through weathered bedrock and exfiltration to the colluvium) for more accurate prediction of the timing, location, and extent of landslides. Specifically, a watershed-scale slope stability model that systematically accounts for the contribution of driving and resisting forces in three-dimensional hillslope segments was coupled with a spatially-explicit and physically-based hydrologic model. The landslide prediction framework considers critical zone processes and structure, and explicitly accounts for the spatial heterogeneity of surface and subsurface properties that control slope stability, including soil and weathered bedrock hydrological and mechanical characteristics, vegetation, and slope morphology. To test performance, the model was applied in landslide-prone sites in the US, the hydrology of which has been extensively studied. Results showed that both rainfall infiltration in the soil and groundwater exfiltration exert a strong control on the timing and magnitude of landslide occurrence. We demonstrate the extent to which three-dimensional slope destabilizing factors, which are modulated by dynamic hydrologic conditions in the soil-bedrock column, control landslide initiation at the watershed scale.
Soil non-linearity and its effect on the dynamic behaviour of offshore platform foundations
Madshus, Christian
1997-07-01
This thesis focuses on non-linear soil response to the type of cyclic loading experienced under offshore gravity base platform foundations. These loads are dominated by a cyclic component around the main wave frequency, which may well mobilize soil non-linearity under severe sea-states. Superimposed on this main component are lower level higher frequency loads caused by resonant oscillations of the platform. The thesis presents results of specially designed triaxial tests to simulate this loading condition. The tests simultaneously applied two cyclic load components at different frequencies and amplitudes. The measured soil response to each component has been isolated through a frequency domain separation. It was found that the soil responds to the superimposed high frequency low level component as if the soil had a cyclically time-varying stiffness. If the superimposed component does not lead to load reversals, this stiffness variation is controlled by the frequency and amplitude of the main load component and by the hysteretic non-linearity of the soil. If the superimposed component causes reversals, the influence of the hysteretic non-linearity on the stiffness variation is reduced. The higher the degree of reversal, the more this influence it taken over by the variation in the instantaneous unloading-reloading stiffness of the soil. It was also found that this type of two-frequency cyclic soil testing is generally superior over conventional single-frequency testing in the way it enforces the soil to reveal several of its inherent properties not deducible from ordinary tests. Benefits of analyzing non-linear response in the frequency domain is demonstrated throughout this thesis. The ability of various theoretical soil models to simulate the observed soil behaviour under two-frequency cyclic loading has, been investigated through numerical analyses. It was found that only those models that are based on kinematic hardening are able to reproduce what was observed
Konstantopoulos, Nikolaos; Trivellas, Panagiotis; Reklitis, Panagiotis
2007-12-01
According to many researchers of organizational theory, a great number of problems encountered by the manufacturing firms are due to their failure to foster innovative behaviour by aligning business strategy and structure. From this point of view, the fit between strategy and structure is essential in order to facilitate firms' innovative behaviour. In the present paper, we adopt Porter's typology to operationalise business strategy (cost leadership, innovative and marketing differentiation, and focus). Organizational structure is built on four dimensions (centralization, formalization, complexity and employees' initiatives to implement new ideas). Innovativeness is measured as product innovation, process and technological innovation. This study provides the necessary theoretical framework for the development of a dynamic simulation method, although the simulation of social events is a quite difficult task, considering that there are so many alternatives (not all well understood).
Weng Marc Lim
2018-01-01
Full Text Available The technology acceptance model (TAM is a prominent and parsimonious conceptual lens that is often applied for behavioural modelling in technology-mediated environments. However, TAM has received a great deal of criticism in recent years. This article aims to address some of the most pertinent issues confronting TAM through a rejoinder that offers dialectic antidotes—in the form of conceptual, methodological, and replication treatments—to support the continued use of TAM to understand the peculiarities of user interactions with technology in technology-mediated environments. In doing so, this article offers a useful response to a common but often inadequately answered question about how TAM can continue to be relevant for behavioural modelling in contemporary technology-mediated environments.
Banasiak, J.
2016-09-01
There has been a hierarchy of models of crowd behaviour. One can consider the crowd at the so called microscopic level, as a collection of individuals, and derive its description in the form of a (large) system of ordinary differential equations describing the position and velocity of each individual, in parallel to the Newton's description of matter, see e.g. [10]. Another possibility is to describe crowd, in analogy to fluid dynamics, by providing its density and velocity at a given point, see e.g. [11,12]. At the same time, it is recognized that crowd is 'living, social' system that is prone to exhibit rare, not easily predictable, behaviour in response to stress induced by the perception of danger, or of the action of specific agents, see e.g. [1,2]. This high probability of the occurrence of events that are far from average, makes the crowd behaviour similar to the processes with fat-tailed distribution of events. Such unlikely events have been metaphorically termed black swans in [14], or Lévy flights in [13]. While microscopic and macroscopic models can capture many features of crowd dynamics, including obstacles, see [3,8], such models are described by differential equations that inherently are local in space. At the same time, black swan events are often caused by non-local interactions such as self-organization, learning or adherence to some averaged group behaviour. It is known that such interactions are well described by mean field models best represented by integro-differential equations, such as the Boltzmann equation of the rarefied gas theory. This has made plausible to introduce crowd models at the intermediate, (meso) scale by describing the crowd by the one particle distribution function that gives the density of individuals at any particular state; that is, at a given point in the domain and moving with a specific velocity.
Quench dynamics near a quantum critical point: Application to the sine-Gordon model
De Grandi, C.; Polkovnikov, A.; Gritsev, V.
2010-01-01
We discuss the quench dynamics near a quantum critical point focusing on the sine-Gordon model as a primary example. We suggest a unified approach to sudden and slow quenches, where the tuning parameter λ(t) changes in time as λ(t)∼υt r , based on the adiabatic expansion of the excitation probability in powers of υ. We show that the universal scaling of the excitation probability can be understood through the singularity of the generalized adiabatic susceptibility χ 2r+2 (λ), which for sudden quenches (r=0) reduces to the fidelity susceptibility. In turn this class of susceptibilities is expressed through the moments of the connected correlation function of the quench operator. We analyze the excitations created after a sudden quench of the cosine potential using a combined approach of form-factors expansion and conformal perturbation theory for the low-energy and high-energy sector, respectively. We find the general scaling laws for the probability of exciting the system, the density of excited quasiparticles, the entropy and the heat generated after the quench. In the two limits where the sine-Gordon model maps to hard-core bosons and free massive fermions we provide the exact solutions for the quench dynamics and discuss the finite temperature generalizations.
Gralton, Anna; Sinclair, Mark; Purnell, Ken
2004-01-01
This paper reviews research literature on the impact of environmental education initiatives on learners' attitudes, beliefs and behaviours. The review focuses on initiatives involving learners of all ages and school-aged learners in particular. The review shows two things. There is some evidence that environmental education initiatives are…
The crossover from mean-field to 3D-Ising critical behaviour in a 3-component microemulsion
Seto, H.; Schwahn, D.; Yokoi, E.
1995-01-01
Density fluctuations and associated critical phenomena of water droplets in a water-in-oil microemulsion system have been studied, We have recently found a mean-field behavior in the ''near-critical region'', and this evidence suggested that a crossover from mean-field to non-mean-field behavior...
Toward an improved understanding of the role of transpiration in critical zone dynamics
Mitra, B.; Papuga, S. A.
2012-12-01
Evapotranspiration (ET) is an important component of the total water balance across any ecosystem. In subalpine mixed-conifer ecosystems, transpiration (T) often dominates the total water flux and therefore improved understanding of T is critical for accurate assessment of catchment water balance and for understanding of the processes that governs the complex dynamics across critical zone (CZ). The interaction between T and plant vegetation not only modulates soil water balance but also influences water transit time and hydrochemical flux - key factors in our understanding of how the CZ evolves and responds. Unlike an eddy covariance system which provides only an integrated ET flux from an ecosystem, a sap flow system can provide an estimate of the T flux from the ecosystem. By isolating T, the ecohydrological drivers of this major water loss from the CZ can be identified. Still, the species composition of mixed-conifer ecosystems vary and the drivers of T associated with each species are expected to be different. Therefore, accurate quantification of T from a mixed-conifer requires knowledge of the unique transpiration dynamics of each of the tree species. Here, we installed a sap flow system within two mixed-conifer study sites of the Jemez River Basin - Santa Catalina Mountains Critical Zone Observatory (JRB - SCM CZO). At both sites, we identified the dominant tree species and installed sap flow sensors on healthy representatives for each of those species. At the JRB CZO site, sap sensors were installed in fir (4) and spruce (4) trees; at the SCM CZO site, sap sensors were installed at white fir (4) and maple (4) and one dead tree. Meteorological data as well as soil temperature (Ts) and soil moisture (θ) at multiple depths were also collected from each of the two sites. Preliminary analysis of two years of sap flux rate at JRB - SCM CZO shows that the environmental drivers of fir, spruce, and maple are different and also vary throughout the year. For JRB fir
Wertelaers, P
2010-01-01
The current design foresees a central heat exchanger followed by a controlled post heater, for all ECAL. We discuss the scheme and try to assess its performance, from a Barrel viewpoint. This is based on computational work. The coolant transfer pipes play an essential role in building a dynamical model. After some studies on the behaviour of the cooling circuit itself, a strong yet simple controller is proposed. Then, the system with feedback control is scrutinized, with emphasis on disturbance rejection. The most relevant disturbances are cooling ripple, pipe heat attack, and electronics’ switching.
Juan, Tu; Rongjue, Wei; Guan, J. F.; Matula, T. J.; Crum, L. A.
2008-01-01
The dynamic behaviour of SonoVue microbubbles, a new generation ultrasound contrast agent, is investigated in real time with light scattering method. Highly diluted SonoVue microbubbles are injected into a diluted gel made of xanthan gum and water. The responses of individual SonoVue bubbles to driven ultrasound pulses are measured. Both linear and nonlinear bubble oscillations are observed and the results suggest that SonoVue microbubbles can generate strong nonlinear responses. By fitting the experimental data of individual bubble responses with Sarkar's model, the shell coating parameter of the bubbles and dilatational viscosity is estimated to be 7.0 nm·s·Pa
Dynamic behaviour of TM380 mild steel and Ti6Al4V alloy subjected to blast loading
Shoke, Lerato
2016-10-01
Full Text Available and Base Metals Development Network Conference 2016, 19-20 October 2016, KwaZulu Natal, Maharani Hotel Dynamic behaviour of TM380 mild steel and Ti6Al4V alloy subjected to blast loading L. Shoke,1* K. Mutombo2, I.M. Snyman1 and T. Sono1 1... Landwards Sciences, Defence Peace Safety and Security (DPSS), 2 Material Sciences and Manufacturing (MSM), Council for Scientific and Industrial Research (CSIR), Pretoria, South Africa Lshoke@csir.co.za Abstract This paper deals...
Cadoni Ezio
2015-01-01
Full Text Available The dynamic behaviour of armour steel in tension was investigated over a wide range of strain-rates on round specimens. The experiments were carried out by means of a Split Hopkinson Tensile Bar device and by a Hydro Pneumatic Machine. The target strain rate were set at the following six levels: 10−3, 5, 25, 100, 500 and 1000 s−1. Two material models were calibrated and used to replicate the experiments and to simulate blasting event on steel plate. Finally, the two responses are compared.
Cadoni, Ezio; Dotta, Matteo; Forni, Daniele; Riganti, Gianmario; Kaufmann, Hanspeter
2015-09-01
The dynamic behaviour of armour steel in tension was investigated over a wide range of strain-rates on round specimens. The experiments were carried out by means of a Split Hopkinson Tensile Bar device and by a Hydro Pneumatic Machine. The target strain rate were set at the following six levels: 10-3, 5, 25, 100, 500 and 1000 s-1. Two material models were calibrated and used to replicate the experiments and to simulate blasting event on steel plate. Finally, the two responses are compared.
Full Text Available 17890055 IRAK1: a critical signaling mediator of innate immunity. Gottipati S, Rao ...IRAK1: a critical signaling mediator of innate immunity. PubmedID 17890055 Title IRAK1: a critical signaling mediator
Muhammad Murtadha Othman
2017-06-01
Full Text Available With the advent of advanced technology in smart grid, the implementation of renewable energy in a stressed and complicated power system operation, aggravated by a competitive electricity market and critical system contingencies, this will inflict higher probabilities of the occurrence of a severe dynamic power system blackout. This paper presents the proposed stochastic event tree technique used to assess the sustainability against the occurrence of dynamic power system blackout emanating from implication of critical system contingencies such as the rapid increase in total loading condition and sensitive initial transmission line tripping. An extensive analysis of dynamic power system blackout has been carried out in a case study of the following power systems: IEEE RTS-79 and IEEE RTS-96. The findings have shown that the total loading conditions and sensitive transmission lines need to be given full attention by the utility to prevent the occurrence of dynamic power system blackout.
Yamada, Y.; Murase, S.; Wada, H.; Tachikawa, K.
1985-01-01
The effects of cold-working on high-field pinning behaviour at 1.8 K and 4.2 K have been studied for multifilamentary NbTi, NbTiHf and NbTiTa superconductors, which were subjected to cold-working, heat treatment and cold-working, in sequence. It is found that the cold-working, either before or after heat treatment, shifts the peak in pinning force density to a higher field, while the maximum pinning force value is first increased with increasing amount of cold-working, and then decreased. This result can not be predicted by existing pinning theories, and we conclude that for pinning behaviour induced by cold-working, not only the introduction of pinning centres but also their size and spacing must be taken into account. (author)
Quirijns, F.J.; Poos, J.J.; Rijnsdorp, A.D.
2008-01-01
Catch per unit effort (CPUE) is commonly used as an indicator for monitoring developments in stock size. To ensure proportionality between average CPUE and total stock size, two processes that should be accounted for are the degree of targeting behaviour of the fleet and the management-induced
The Dynamics of Chinese Face Mechanisms and Classroom Behaviour: A Case Study
Wu, Xiaoxin
2009-01-01
Research on cross-cultural psychology, anthropology and sociology reveals that the impact of face on social interactions is both pervasive and powerful in Asia. Face, however, has not gained general acceptance as an important theoretical concept in the literature on Asian (Chinese in particular) classroom behaviour and management. This article…
Effect of colored noise on the critical dynamics of the Time-Dependent Landau-Ginzburg Model A
Korutcheva, E.; Rubia, J. de la
1999-08-01
By using the dynamical renormalization-group method, we show that the introduction of an additive colored noise with weak long-range correlations in the Time-Dependent Landau-Ginzburg Model A, does not give perturbative corrections for the dynamical critical exponent at least up to order O(ε 2 ). This result differs for a system with random quenched impurities, where a similar type of impurity correlation leads to corrections even of order O(ε). (author)
Bucur Florina
2015-01-01
Full Text Available This study refers to an experimental and numerical evaluation of a polyurea coating layer influence on the dynamic behaviour of OL50 specimens. Mechanical quasi-static and dynamic tensile tests were performed in axial loading conditions, for 2 mm steel plate specimens. Several metallic specimens have been previously coated with 1.5 mm and 3 mm respectively thickness polyurea layer and tested in traction. The findings results indicate that the presence of polyurea changes the loading pattern of metallic material in the necking area. In terms of polyurea coated metal specimens fracture, there was clearly observed a change of fracture limit. One possible explanation of this phenomenon is the modification of triaxiality state in the necking zone, fact proven by the numerical simulations. Test results indicate that the presence of polyurea layer delays the necking onset phenomenon which precedes the OL50 metallic specimen fracture.
Dynamic behaviour of the icosahedral Al–Pd–Mn quasicrystal with a Griffith crack
Xiao-Fang, Wang; Ai-Yu, Zhu; Tian-You, Fan
2009-01-01
The dynamic response of an icosahedral Al–Pd–Mn quasicrystal with a Griffith crack to impact loading is investigated in this paper. The elastohydrodynamic model for the wave propagation and diffusion together with their interaction is adopted. Numerical results of stress, displacement and dynamic stress intensity factors are obtained by using the finite difference method. The effects of wave propagation, diffusion and phonon–phason coupling on the quasicrystal in the dynamic process are discussed in detail, where the phason dynamics is explored particularly. (condensed matter: structure, thermal and mechanical properties)
Duman, M. S.; Kaplan, E.; Cuvalcı, O.
2018-01-01
The present paper is based on experimental studies and numerical simulations on the surface fatigue failure of the PTFE-bronze layered journal bearings under real-time loading. ‘Permaglide Plain Bearings P10’ type journal bearings were experimentally tested under different real time dynamic loadings by using real time journal bearing test system in our laboratory. The journal bearing consists of a PTFE-bronze layer approximately 0.32 mm thick on the steel support layer with 2.18 mm thick. Two different approaches have been considered with in experiments: (i) under real- time constant loading with varying bearing widths, (ii) under different real-time loadings at constant bearing widths. Fatigue regions, micro-crack dispersion and stress distributions occurred at the journal bearing were experimentally and theoretically investigated. The relation between fatigue region and pressure distributions were investigated by determining the circumferential pressure distribution under real-time dynamic loadings for the position of every 10° crank angles. In the theoretical part; stress and deformation distributions at the surface of the journal bearing analysed by using finite element methods to determine the relationship between stress and fatigue behaviour. As a result of this study, the maximum oil pressure and fatigue cracks were observed in the most heavily loaded regions of the bearing surface. Experimental results show that PTFE-Bronze layered journal bearings fatigue behaviour is better than the bearings include white metal alloy.
Holmes, W R; Edelstein-Keshet, L; Carlsson, A E
2012-01-01
Patterns of waves, patches, and peaks of actin are observed experimentally in many living cells. Models of this phenomenon have been based on the interplay between filamentous actin (F-actin) and its nucleation promoting factors (NPFs) that activate the Arp2/3 complex. Here we present an alternative biologically-motivated model for F-actin-NPF interaction based on properties of GTPases acting as NPFs. GTPases (such as Cdc42, Rac) are known to promote actin nucleation, and to have active membrane-bound and inactive cytosolic forms. The model is a natural extension of a previous mathematical mini-model of small GTPases that generates static cell polarization. Like other modellers, we assume that F-actin negative feedback shapes the observed patterns by suppressing the trailing edge of NPF-generated wave-fronts, hence localizing the activity spatially. We find that our NPF-actin model generates a rich set of behaviours, spanning a transition from static polarization to single pulses, reflecting waves, wave trains, and oscillations localized at the cell edge. The model is developed with simplicity in mind to investigate the interaction between nucleation promoting factor kinetics and negative feedback. It explains distinct types of pattern initiation mechanisms, and identifies parameter regimes corresponding to distinct behaviours. We show that weak actin feedback yields static patterning, moderate feedback yields dynamical behaviour such as travelling waves, and strong feedback can lead to wave trains or total suppression of patterning. We use a recently introduced nonlinear bifurcation analysis to explore the parameter space of this model and predict its behaviour with simulations validating those results. (paper)
Christopher M Stone
Full Text Available The release of genetically-modified or sterile male mosquitoes offers a promising form of mosquito-transmitted pathogen control, but the insights derived from our understanding of male mosquito behaviour have not fully been incorporated into the design of such genetic control or sterile-male release methods. The importance of aspects of male life history and mating behaviour for sterile-male release programmes were investigated by projecting a stage-structured matrix model over time. An elasticity analysis of transient dynamics during sterile-male releases was performed to provide insight on which vector control methods are likely to be most synergistic. The results suggest that high mating competitiveness and mortality costs of released males are required before the sterile-release method becomes ineffective. Additionally, if released males suffer a mortality cost, older males should be released due to their increased mating capacity. If released males are of a homogenous size and size-assortative mating occurs in nature, this can lead to an increase in the abundance of large females and reduce the efficacy of the population-suppression effort. At a high level of size-assortative mating, the disease transmission potential of the vector population increases due to male releases, arguing for the release of a heterogeneously-sized male population. The female population was most sensitive to perturbations of density-dependent components of larval mortality and female survivorship and fecundity. These findings suggest source reduction might be a particularly effective complement to mosquito control based on the sterile insect technique (SIT. In order for SIT to realize its potential as a key component of an integrated vector-management strategy to control mosquito-transmitted pathogens, programme design of sterile-male release programmes must account for the ecology, behaviour and life history of mosquitoes. The model used here takes a step in this
Arthur, Ronan F; Gurley, Emily S; Salje, Henrik; Bloomfield, Laura S P; Jones, James H
2017-05-05
Human factors, including contact structure, movement, impact on the environment and patterns of behaviour, can have significant influence on the emergence of novel infectious diseases and the transmission and amplification of established ones. As anthropogenic climate change alters natural systems and global economic forces drive land-use and land-cover change, it becomes increasingly important to understand both the ecological and social factors that impact infectious disease outcomes for human populations. While the field of disease ecology explicitly studies the ecological aspects of infectious disease transmission, the effects of the social context on zoonotic pathogen spillover and subsequent human-to-human transmission are comparatively neglected in the literature. The social sciences encompass a variety of disciplines and frameworks for understanding infectious diseases; however, here we focus on four primary areas of social systems that quantitatively and qualitatively contribute to infectious diseases as social-ecological systems. These areas are social mixing and structure, space and mobility, geography and environmental impact, and behaviour and behaviour change. Incorporation of these social factors requires empirical studies for parametrization, phenomena characterization and integrated theoretical modelling of social-ecological interactions. The social-ecological system that dictates infectious disease dynamics is a complex system rich in interacting variables with dynamically significant heterogeneous properties. Future discussions about infectious disease spillover and transmission in human populations need to address the social context that affects particular disease systems by identifying and measuring qualitatively important drivers.This article is part of the themed issue 'Opening the black box: re-examining the ecology and evolution of parasite transmission'. © 2017 The Author(s).
Singh, K.K.; Goswami, P.
1984-08-01
Thermodynamics of a weakly interacting fermion-boson mixture has been worked out on the basis of the effective Hamiltonian derived in an earlier paper. Tricritical point behaviour is discussed in terms of the fields (T,μ 3 ,μ 4 ). For the degenerate phase of the mixture, the theory reproduces the classical Landau expansion near a tricritical point. For the non-degenerate phase, the theory differs materially from the Landau theory; it predicts tricritical exponents in agreement with those calculated by applying renormalization group theory to phenomenological models, and a slope for the upper line larger than that of the lambda-line in the chi-T plane. (author)
Dynamic Critical Rainfall-Based Flash Flood Early Warning and Forecasting for Medium-Small Rivers
Liu, Z.; Yang, D.; Hu, J.
2012-04-01
China is extremely frequent food disasters hit countries, annual flood season flash floods triggered by rainfall, mudslides, landslides have caused heavy casualties and property losses, not only serious threaten the lives of the masses, but the majority of seriously restricting the mountain hill areas of economic and social development and the people become rich, of building a moderately prosperous society goals. In the next few years, China will focus on prevention and control area in the flash flood disasters initially built "for the surveillance, communications, forecasting, early warning and other non-engineering measure based, non-engineering measures and the combinations of engineering measures," the mitigation system. The latest progresses on global torrential flood early warning and forecasting techniques are reviewed in this paper, and then an early warning and forecasting approach is proposed on the basis of a distributed hydrological model according to dynamic critical rainfall index. This approach has been applied in Suichuanjiang River basin in Jiangxi province, which is expected to provide valuable reference for building a national flash flood early warning and forecasting system as well as control of such flooding.
Dynamical susceptibility near a long-wavelength critical point with a nonconserved order parameter
Klein, Avraham; Lederer, Samuel; Chowdhury, Debanjan; Berg, Erez; Chubukov, Andrey
2018-04-01
We study the dynamic response of a two-dimensional system of itinerant fermions in the vicinity of a uniform (Q =0 ) Ising nematic quantum critical point of d - wave symmetry. The nematic order parameter is not a conserved quantity, and this permits a nonzero value of the fermionic polarization in the d - wave channel even for vanishing momentum and finite frequency: Π (q =0 ,Ωm)≠0 . For weak coupling between the fermions and the nematic order parameter (i.e., the coupling is small compared to the Fermi energy), we perturbatively compute Π (q =0 ,Ωm)≠0 over a parametrically broad range of frequencies where the fermionic self-energy Σ (ω ) is irrelevant, and use Eliashberg theory to compute Π (q =0 ,Ωm) in the non-Fermi-liquid regime at smaller frequencies, where Σ (ω )>ω . We find that Π (q =0 ,Ω ) is a constant, plus a frequency-dependent correction that goes as |Ω | at high frequencies, crossing over to |Ω| 1 /3 at lower frequencies. The |Ω| 1 /3 scaling holds also in a non-Fermi-liquid regime. The nonvanishing of Π (q =0 ,Ω ) gives rise to additional structure in the imaginary part of the nematic susceptibility χ″(q ,Ω ) at Ω >vFq , in marked contrast to the behavior of the susceptibility for a conserved order parameter. This additional structure may be detected in Raman scattering experiments in the d - wave geometry.
Critical insight into the influence of the potential energy surface on fission dynamics
Mazurek, K.; Schmitt, C.; Wieleczko, J. P.; Ademard, G.; Nadtochy, P. N.
2011-01-01
The present work is dedicated to a careful investigation of the influence of the potential energy surface on the fission process. The time evolution of nuclei at high excitation energy and angular momentum is studied by means of three-dimensional Langevin calculations performed for two different parametrizations of the macroscopic potential: the Finite Range Liquid Drop Model (FRLDM) and the Lublin-Strasbourg Drop (LSD) prescription. Depending on the mass of the system, the topology of the potential throughout the deformation space of interest in fission is observed to noticeably differ within these two approaches, due to the treatment of curvature effects. When utilized in the dynamical calculation as the driving potential, the FRLDM and LSD models yield similar results in the heavy-mass region, whereas the predictions can be strongly dependent on the Potential Energy Surface (PES) for medium-mass nuclei. In particular, the mass, charge, and total kinetic energy distributions of the fission fragments are found to be narrower with the LSD prescription. The influence of critical model parameters on our findings is carefully investigated. The present study sheds light on the experimental conditions and signatures well suited for constraining the parametrization of the macroscopic potential. Its implication regarding the interpretation of available experimental data is briefly discussed.
Critical current density, vortex dynamics, and phase diagram of single-crystal FeSe
Sun, Yue; Pyon, Sunseng; Tamegai, Tsuyoshi; Kobayashi, Ryo; Watashige, Tatsuya; Kasahara, Shigeru; Matsuda, Yuji; Shibauchi, Takasada
2015-10-01
We present a comprehensive study of the vortex pinning and dynamics in a high-quality FeSe single crystal which is free from doping-introduced inhomogeneities and charged quasiparticle scattering because of its innate superconductivity. The critical current density Jc is found to be almost isotropic and reaches a value of ˜3 ×104 A /cm2 at 2 K (self-field) for both H ∥c and a b . The normalized magnetic relaxation rate S (=∣d ln M /d ln t ∣ ) shows a temperature-insensitive plateau behavior in the intermediate temperature range with a relatively high creep rate (S ˜ 0.02 under zero field), which is interpreted in the framework of the collective creep theory. A crossover from the elastic to plastic creep is observed, while the fishtail effect is absent for both H ∥c and a b . Based on this observation, the origin of the fishtail effect is also discussed. Combining the results of Jc and S , the vortex motion in the FeSe single crystal is found to be dominated by sparse, strong pointlike pinning from nanometer-sized defects or imperfections. The weak collective pinning is also observed and proved in the form of large bundles. Besides, the vortex phase diagram of FeSe is also constructed and discussed.
Evolution of dynamic susceptibility in molecular glass formers-a critical assessment
Brodin, A; Gainaru, C; Porokhonskyy, V; Roessler, E A
2007-01-01
Dielectric, depolarized light scattering (LS) and optical Kerr effect (OKE) data are critically discussed in an attempt to achieve a common interpretation of the evolution of dynamic susceptibility in molecular glass formers at temperatures down to the glass transition T g . The so-called intermediate power-law, observed in OKE data below a certain temperature T x , is identified with the excess wing, long since known from dielectric spectroscopy, with a temperature-independent exponent. This is in contrast with several recent analyses that concluded a considerable temperature dependence of spectral shapes. We introduce a new approach to disentangle α-peak and excess wing contributions in the dielectric spectra, which allows for frequency-temperature superposition (FTS) of the α-process at all temperatures above T g . From the LS spectra we conclude, in particular, that FTS holds even at temperatures well above the melting point, i.e. in normal equilibrium liquids. Attempting to correlate the fragility and stretching, our conclusions are opposite to those made previously. Specifically, we observe that a high fragility is associated with a less stretched relaxation function
On evolutionary stability in predator–prey models with fast behavioural dynamics
Křivan, Vlastimil; Cressman, R.
2009-01-01
Roč. 11, č. 2 (2009), s. 227-251 ISSN 1522-0613 R&D Projects: GA AV ČR IAA100070601 Grant - others:National Center for Ecological Analysis and Synthesis(US) DEB-0553768 Institutional research plan: CEZ:AV0Z50070508 Keywords : adaptive foraging * evolutionarily stable strategies * G-function Subject RIV: EH - Ecology, Behaviour Impact factor: 1.692, year: 2009
Bell, Andrew H; Munoz, Douglas P
2008-10-01
Performance in a behavioural task can be influenced by both bottom-up and top-down processes such as stimulus modality and prior probability. Here, we exploited differences in behavioural strategy to explore the role of the intermediate and deep layers of the superior colliculus (dSC) in covert orienting. Two monkeys were trained on a predictive cued-saccade task in which the cue predicted the target's upcoming location with 80% validity. When the delay between cue and target onset was 250 ms, both monkeys showed faster responses to the uncued (Invalid) location. This was associated with a reduced target-aligned response in the dSC on Valid trials for both monkeys and is consistent with a bottom-up (i.e. involuntary) bias. When the delay was increased to 650 ms, one monkey continued to show faster responses to the Invalid location whereas the other monkey showed faster responses to the Valid location, consistent with a top-down (i.e. voluntary) bias. This latter behaviour was correlated with an increase in activity in dSC neurons preceding target onset that was absent in the other monkey. Thus, using the information provided by the cue shifted the emphasis towards top-down processing, while ignoring this information allowed bottom-up processing to continue to dominate. Regardless of the selected strategy, however, neurons in the dSC consistently reflected the current bias between the two processes, emphasizing its role in both the bottom-up and top-down control of orienting behaviour.
Borello, A.; Frangini, S.; Masci, D.
1989-06-01
Concerning the two commonly observed phenomena of localized corrosion of Inconel 600 in high temperature caustic environments normally encountered in steam generators of PWR nuclear reactors, the aim of this work is to investigate the intergranular and the stress corrosion cracking behaviour of two heats of Alloy 600, having different origin. In fact one heat was produced by Centro Sviluppo Materiali (CSM) in laboratory scale; the other one was manufactured by Deltacogne following conventional industrial practices. The evaluation of intergranular corrosion susceptibility has been performed by means of the modified Huey test and the Electrochemical Potentiokinetic Reactivation (EPR). The stress corrosion cracking susceptibility was determined by the slow strain rate technique. The results of the present study show that the CSM heat has a better behaviour than the Deltacogne one as for the stress corrosion cracking susceptibility. On the contrary, concerning the intergranular corrosion resistance, both used tests point out that the Deltacogne material has a lower susceptibility to this type of localized corrosion. The sensitization areas in the TTS diagram, depend, even for the same heat, on the type of the test used for the evaluation. (author)
Žunkovič, Bojan; Heyl, Markus; Knap, Michael; Silva, Alessandro
2018-03-01
We theoretically study the dynamics of a transverse-field Ising chain with power-law decaying interactions characterized by an exponent α , which can be experimentally realized in ion traps. We focus on two classes of emergent dynamical critical phenomena following a quantum quench from a ferromagnetic initial state: The first one manifests in the time-averaged order parameter, which vanishes at a critical transverse field. We argue that such a transition occurs only for long-range interactions α ≤2 . The second class corresponds to the emergence of time-periodic singularities in the return probability to the ground-state manifold which is obtained for all values of α and agrees with the order parameter transition for α ≤2 . We characterize how the two classes of nonequilibrium criticality correspond to each other and give a physical interpretation based on the symmetry of the time-evolved quantum states.
Lima, J. P. De; Gonçalves, L. L.
The critical dynamics of the isotropic XY-model on the one-dimensional superlattice is considered in the framework of the position space renormalization group theory. The decimation transformation is introduced by considering the equations of motion of the operators associated to the excitations of the system, and it corresponds to an extension of the procedure introduced by Stinchcombe and dos Santos (J. Phys. A18, L597 (1985)) for the homogeneous lattice. The dispersion relation is obtained exactly and the static and dynamic scaling forms are explicitly determined. The dynamic critical exponent is also obtained and it is shown that it is identical to the one of the XY-model on the homogeneous chain.
Feng Wei
2015-01-01
Full Text Available In hot precision forging helical gears, the dynamic recrystallization phenomena will occur, which affect the microstructure of the formed part and in turn decide their mechanical properties. To investigate the effect of deformation temperature on the dynamic recrystallization in hot precision forging helical gears, a three dimensional (3D finite element (FE model was created by coupling the thermo-mechanical model with the microstructure evolution model developed based on the hot compressive experimental data of 20CrMnTiH steel. The hot precision forging process was simulated and the effect laws of the deformation temperature on the microstructure evolution the formed part were investigated. The results show that the dynamic recrystallization volume fraction and the average grain sizes increased with the increasing deformation temperature and the higher deformation temperature is beneficial to dynamic recrystallization and grain refinement.
Dynamic behaviour of anchors in cracked and uncracked concrete: a progress report
Rodriguez, M.; Klingner, R.E.
1997-01-01
In early 1993, the US Nuclear Regulatory Commission began a research program at The University of Texas at Austin, dealing with the dynamic behavior of anchors in cracked and uncracked concrete. In this paper, the progress of that research program is reviewed. The test program is summarized, and work performed to date is reviewed, with emphasis on the dynamic and static behavior of single tensile anchors in uncracked concrete. General conclusions from that work are discussed, and future plans are presented. (orig.)
Mutoru, J W; Smith, W; O'Hern, C S; Firoozabadi, A
2013-01-14
Understanding the transport properties of molecular fluids in the critical region is important for a number of industrial and natural systems. In the literature, there are conflicting reports on the behavior of the self diffusion coefficient D(s) in the critical region of single-component molecular systems. For example, D(s) could decrease to zero, reach a maximum, or remain unchanged and finite at the critical point. Moreover, there is no molecular-scale understanding of the behavior of diffusion coefficients in molecular fluids in the critical regime. We perform extensive molecular dynamics simulations in the critical region of single-component fluids composed of medium-chain n-alkanes-n-pentane, n-decane, and n-dodecane-that interact via anisotropic united-atom potentials. For each system, we calculate D(s), and average molecular cluster sizes κ(cl) and numbers N(cl) at various cluster lifetimes τ, as a function of density ρ in the range 0.2ρ(c) ≤ ρ ≤ 2.0ρ(c) at the critical temperature T(c). We find that D(s) decreases with increasing ρ but remains finite at the critical point. Moreover, for any given τ critical point.
Belfroid, S.P.C.; Nennie, E.D.; Lewis, M.
2016-01-01
Piping structures are generally subjected to high dynamic loading due to multiphase forces. In particular subsea structures are very vulnerable as large flexibility is required to cope for instance with thermal stresses. The forces due to multiphase flow are characterized by a broadband spectrum
Belyazid, Salim; Kurz, Dani; Braun, Sabine; Sverdrup, Harald; Rihm, Beat; Hettelingh, Jean-Paul
2011-01-01
A dynamic model of forest ecosystems was used to investigate the effects of climate change, atmospheric deposition and harvest intensity on 48 forest sites in Sweden (n = 16) and Switzerland (n = 32). The model was used to investigate the feasibility of deriving critical loads for nitrogen (N) deposition based on changes in plant community composition. The simulations show that climate and atmospheric deposition have comparably important effects on N mobilization in the soil, as climate triggers the release of organically bound nitrogen stored in the soil during the elevated deposition period. Climate has the most important effect on plant community composition, underlining the fact that this cannot be ignored in future simulations of vegetation dynamics. Harvest intensity has comparatively little effect on the plant community in the long term, while it may be detrimental in the short term following cutting. This study shows: that critical loads of N deposition can be estimated using the plant community as an indicator; that future climatic changes must be taken into account; and that the definition of the reference deposition is critical for the outcome of this estimate. - Research highlights: → Plant community changes can be used to estimate critical loads of nitrogen. → Climate change is decisive for future changes of geochemistry and plant communities. → Climate change cannot be ignored in estimates of critical loads. → The model ForSAFE-Veg was successfully used to set critical loads of nitrogen. - Plant community composition can be used in dynamic modelling to estimate critical loads of nitrogen deposition, provided the appropriate reference deposition, future climate and target plant communities are defined.
Full Text Available 17959357 Toll like receptors and autoimmunity: a critical appraisal. Papadimitraki ...ml) Show Toll like receptors and autoimmunity: a critical appraisal. PubmedID 17959357 Title Toll like receptors and auto
On Equivalence between Critical Probabilities of Dynamic Gossip Protocol and Static Site Percolation
Ishikawa, Tetsuya; Hayakawa, Tomohisa
The relationship between the critical probability of gossip protocol on the square lattice and the critical probability of site percolation on the square lattice is discussed. Specifically, these two critical probabilities are analytically shown to be equal to each other. Furthermore, we present a way of evaluating the critical probability of site percolation by approximating the saturation of gossip protocol. Finally, we provide numerical results which support the theoretical analysis.
Morari, R.; Antropov, E.; Socrovisciuc, A.; Prepelitsa, A.; Zdravkov, V.I.; Tagirov, L.R.; Kupriyanov, M.Yu.; Sidorenko, A.S.
2009-01-01
Present work reports the result of the proximity effect investigation for superconducting Nb/CuNi-bilayers with the thickness of the ferromagnetic layer (Cu x Ni 1-x ) being in the sub-nanometer range. It was found a non-monotonic behavior of the critical temperature T c , i.e. its growth with the increasing of the ferromagnetic layer thickness dF, for the series of the samples with constant thickness of Nb layer, (d Nb = const). (authors)
Portoghese, C.C.P.; Buchmann, J.H.
1996-01-01
This paper is concerned with the degradation of separation factors occurred when groups of ultracentrifuges having different gas-dynamic behaviour are connected in parallel arrangements. Differences in the gas-dynamic behavior were traduced in terms of different tails pressures for the same operational conditions, that are feed flow rate, product pressure and cut number. A mathematical model describing the ratio of the tails flow rates as a function of the tails pressure ratios and the feed flow rate was developed using experimental data collected from a pair of different ultracentrifuges connected in parallel. The optimization of model parameters was made using Marquardt's algorithm. The model developed was used to simulate the separation factors degradation in some parallel arrangements containing more than two centrifuges. Te obtained results were compared with experimental data collected from different groups of ultracentrifuges. It was observed that the calculated results were in good agreement with experimental data. This mathematical model, which parameters were determined in a two-centrifuges parallel arrangement, is useful to simulate the effect of quantified gas-dynamic differences in the separation factors of groups containing any number of different ultracentrifuges and, consequently, to analyze cascade losses due to this kind of occurrence. (author)
Dompierre, F; Sabourin, M
2010-01-01
This paper presents the application of the two-way fluid-structure interaction method introduced by ANSYS to calculate the dynamic behaviour of a Francis turbine runner under operating condition. This time-dependant calculation directly takes into account characteristics of the flow and particularly the pressure fluctuations caused by the rotor-stator interaction. This formulation allows the calculation of the damping forces of the whole system implicitly. Thereafter, the calculated dynamic stress can be used for a fatigue analysis. A verification of the mechanical and fluid simulations used as input for the fluid-structure interaction calculation is first performed. Subsequently, a connection of these two independent simulations is made. A validation according to the hydraulic conditions is made with the measurements from the scale model testing. Afterwards, the static displacement of the runner under the hydraulic load is compared with the results of a classical static analysis for verification purposes. Finally, the natural frequencies deduced by the post-processing of the dynamic portion of the runner displacement with respect to time are compared with the natural frequencies obtained from a classical acoustic modal analysis. All comparisons show a good agreement with experimental data or results obtained with conventional methods.
An investigation of dynamic mechanical behaviour of Ti6Al4V titanium alloy at room temperature
Ran Chun
2016-01-01
Full Text Available To study the high strain rate shear behaviour of Ti6Al4V titanium alloy, a series of dynamic compression experiments has been performed by split Hopkinson pressure bar (SHPB using Flat Hat-shaped specimen at room temperature. Macro true shear stress-true strain curves were obtained under different strain rate loading conditions at room temperature. The effects of strain hardening and strain rate hardening on the dynamic mechanical properties of Ti6Al4V titanium alloy were discussed. Results indicate that a The higher the strain rate, the higher the flow stress, therefore, the material has obvious strain rate hardening effect, b It is ductile failure for Ti6Al4V titanium alloy under quasi-static loading condition, c For dynamical tests, the values for true shear stress increase with increasing true strain till the maximum true shear stress, on the contrary, the values for true shear stress decrease with increasing the true strain after the maximum true shear stress and d The flow stress increases with increasing the true strain under quasi-static loading condition during the plastic deformation.
Dompierre, F; Sabourin, M, E-mail: frederick.dompierre@power.alstom.co [Alstom Power Systems, Hydro 1350 chemin Saint-Roch, Sorel-Tracy (Quebec), J3R 5P9 (Canada)
2010-08-15
This paper presents the application of the two-way fluid-structure interaction method introduced by ANSYS to calculate the dynamic behaviour of a Francis turbine runner under operating condition. This time-dependant calculation directly takes into account characteristics of the flow and particularly the pressure fluctuations caused by the rotor-stator interaction. This formulation allows the calculation of the damping forces of the whole system implicitly. Thereafter, the calculated dynamic stress can be used for a fatigue analysis. A verification of the mechanical and fluid simulations used as input for the fluid-structure interaction calculation is first performed. Subsequently, a connection of these two independent simulations is made. A validation according to the hydraulic conditions is made with the measurements from the scale model testing. Afterwards, the static displacement of the runner under the hydraulic load is compared with the results of a classical static analysis for verification purposes. Finally, the natural frequencies deduced by the post-processing of the dynamic portion of the runner displacement with respect to time are compared with the natural frequencies obtained from a classical acoustic modal analysis. All comparisons show a good agreement with experimental data or results obtained with conventional methods.
Dynamic modeling of the tradeoff between productivity and safety in critical engineering systems
Cowing, Michelle M.; Elisabeth Pate-Cornell, M.; Glynn, Peter W.
2004-01-01
Short-term tradeoffs between productivity and safety often exist in the operation of critical facilities such as nuclear power plants, offshore oil platforms, or simply individual cars. For example, interruption of operations for maintenance on demand can decrease short-term productivity but may be needed to ensure safety. Operations are interrupted for several reasons: scheduled maintenance, maintenance on demand, response to warnings, subsystem failure, or a catastrophic accident. The choice of operational procedures (e.g. timing and extent of scheduled maintenance) generally affects the probabilities of both production interruptions and catastrophic failures. In this paper, we present and illustrate a dynamic probabilistic model designed to describe the long-term evolution of such a system through the different phases of operation, shutdown, and possibly accident. The model's parameters represent explicitly the effects of different components' performance on the system's safety and reliability through an engineering probabilistic risk assessment (PRA). In addition to PRA, a Markov model is used to track the evolution of the system and its components through different performance phases. The model parameters are then linked to different operations strategies, to allow computation of the effects of each management strategy on the system's long-term productivity and safety. Decision analysis is then used to support the management of the short-term trade-offs between productivity and safety in order to maximize long-term performance. The value function is that of plant managers, within the constraints set by local utility commissions and national (e.g. energy) agencies. This model is illustrated by the case of outages (planned and unplanned) in nuclear power plants to show how it can be used to guide policy decisions regarding outage frequency and plant lifetime, and more specifically, the choice of a reactor tripping policy as a function of the state of the
Werner, Gerhard
2013-01-01
The topic of this paper will be addressed in three stages: I will first review currently prominent theoretical conceptualizations of the neurobiology of consciousness and, where appropriate, identify ill-advised and flawed notions in theoretical neuroscience that may impede viewing consciousness as a phenomenon in the physics of brain. In this context, I will also introduce relevant facts that tend not to receive adequate attention in much of the current consciousness discourse. Next, I will review the evidence that accrued in the last decade that identifies the resting brain as being in a state of criticality. In the framework of state phase dynamics of statistical physics, this observational evidence also entails that the resting brain is poised at the brink of a second order phase transition. On this basis, I will in the third stage propose applying the framework of the Renormalization Group to viewing consciousness as a phenomenon in statistical physics. In physics, concepts of phase space transitions and the Renormalization Group are powerful tools for interpreting phenomena involving many scales of length and time in complex systems. The significance of these concepts lies in their accounting for the emergence of different levels of new collective behaviors in complex systems, each level with its distinct macroscopic physics, organization, and laws, as a new pattern of reality. In this framework, I propose to view subjectivity as the symbolic description of the physical brain state of consciousness that emerges as one of the levels of phase transitions of the brain-body-environment system, along the trajectory of Renormalization Group Transformations
Poverty alleviation strategies in eastern China lead to critical ecological dynamics.
Zhang, Ke; Dearing, John A; Dawson, Terence P; Dong, Xuhui; Yang, Xiangdong; Zhang, Weiguo
2015-02-15
Poverty alleviation linked to agricultural intensification has been achieved in many regions but there is often only limited understanding of the impacts on ecological dynamics. A central need is to observe long term changes in regulating and supporting services as the basis for assessing the likelihood of sustainable agriculture or ecological collapse. We show how the analyses of 55 time-series of social, economic and ecological conditions can provide an evolutionary perspective for the modern Lower Yangtze River Basin region since the 1950s with powerful insights about the sustainability of modern ecosystem services. Increasing trends in provisioning ecosystem services within the region over the past 60 years reflect economic growth and successful poverty alleviation but are paralleled by steep losses in a range of regulating ecosystem services mainly since the 1980s. Increasing connectedness across the social and ecological domains after 1985 points to a greater uniformity in the drivers of the rural economy. Regime shifts and heightened levels of variability since the 1970s in local ecosystem services indicate progressive loss of resilience across the region. Of special concern are water quality services that have already passed critical transitions in several areas. Viewed collectively, our results suggest that the regional social-ecological system passed a tipping point in the late 1970s and is now in a transient phase heading towards a new steady state. However, the long-term relationship between economic growth and ecological degradation shows no sign of decoupling as demanded by the need to reverse an unsustainable trajectory. Copyright © 2014 The Authors. Published by Elsevier B.V. All rights reserved.
Wilding, Andrew; Liu, Ruixia; Zhou, John L
2005-07-01
Through cross-flow filtration (CFF) with a 1-kDa regenerated cellulose Pellicon 2 module, the ultrafiltration characteristics of river organic matter from Longford Stream, UK, were investigated. The concentration of organic carbon (OC) in the retentate in the Longford Stream samples increased substantially with the concentration factor (cf), reaching approximately 40 mg/L at cf 15. The results of dissolved organic carbon (DOC) and colloidal organic carbon (COC) analysis, tracking the isolation of colloids from river waters, show that 2 mg/L of COC was present in those samples and good OC mass balance (77-101%) was achieved. Fluorescence measurements were carried out for the investigation of retentate and permeate behaviour of coloured dissolved organic materials (CDOM). The concentrations of CDOM in both the retentate and permeate increased with increasing cf, although CDOM were significantly more concentrated in the retentate. The permeation model expressing the correlation between log[CDOM] in the permeate and logcf was able to describe the permeation behaviour of CDOM in the river water with regression coefficients (r(2)) of 0.94 and 0.98. Dry weight analysis indicated that the levels of organic colloidal particles were from 49 to 71%, and between 29 and 51% of colloidal particles present were inorganic. COC as a percentage of DOC was found to be 10-16% for Longford Stream samples.
Modeling Dynamic Anisotropic Behaviour and Spall Failure in Commercial Aluminium Alloys AA7010
Mohd Nor, M. K.; Ma'at, N.; Ho, C. S.
2018-04-01
This paper presents a finite strain constitutive model to predict a complex elastoplastic deformation behaviour involves very high pressures and shockwaves in orthotropic materials of aluminium alloys. The previous published constitutive model is used as a reference to start the development in this work. The proposed formulation that used a new definition of Mandel stress tensor to define Hill's yield criterion and a new shock equation of state (EOS) of the generalised orthotropic pressure is further enhanced with Grady spall failure model to closely predict shockwave propagation and spall failure in the chosen commercial aluminium alloy. This hyperelastic-plastic constitutive model is implemented as a new material model in the Lawrence Livermore National Laboratory (LLNL)-DYNA3D code of UTHM's version, named Material Type 92 (Mat92). The implementations of a new EOS of the generalised orthotropic pressure including the spall failure are also discussed in this paper. The capability of the proposed constitutive model to capture the complex behaviour of the selected material is validated against range of Plate Impact Test data at 234, 450 and 895 ms-1 impact velocities.
Creep behaviour of polyurethanes applied in the offshore industry under dynamic service conditions
Aquino, Fabio G.; Sheldrake, Terry; Clevelario, Judimar; Pires, Fabio S. [Wellstream International S/A - Rio de Janeiro, RJ (Brazil)], e-mail: fabio.aquino@wellstream.com; Souza, Miguel L. [Newtech Ltda, Sao Carlos, SP (Brazil)
2011-07-01
The oil industry commonly uses flexible pipes to convey oil and gas from wells to platforms that move constantly due to weather and tidal conditions. In this scenario, polymeric components are required to transitioning between the flexible material of the pipelines to the rigid material of the platform; polyurethanes are versatile polymers suitable for performing such services. As this material is subjected to constant loading during working conditions, and it its durability is to be maintained for several decades, it is important to determine the material's creep properties that relate to deformation caused by constant loading, which can represent an indirect measurement of the material's lifetime. In this study, creep behaviour data on the polyurethane samples was collected and an asymmetrical and nonlinear behaviour was observed. Additionally the material presented a creep fracture line with points only above 150% of deformation, considerably exceeding maximum values for its service conditions, which is limited to 10% of deformation considering the worst loading case for design premises of the final artifact. (author)
Li, Cai; Lowe, Robert; Ziemke, Tom
2014-01-01
In this article, we propose an architecture of a bio-inspired controller that addresses the problem of learning different locomotion gaits for different robot morphologies. The modeling objective is split into two: baseline motion modeling and dynamics adaptation. Baseline motion modeling aims to achieve fundamental functions of a certain type of locomotion and dynamics adaptation provides a "reshaping" function for adapting the baseline motion to desired motion. Based on this assumption, a three-layer architecture is developed using central pattern generators (CPGs, a bio-inspired locomotor center for the baseline motion) and dynamic motor primitives (DMPs, a model with universal "reshaping" functions). In this article, we use this architecture with the actor-critic algorithms for finding a good "reshaping" function. In order to demonstrate the learning power of the actor-critic based architecture, we tested it on two experiments: (1) learning to crawl on a humanoid and, (2) learning to gallop on a puppy robot. Two types of actor-critic algorithms (policy search and policy gradient) are compared in order to evaluate the advantages and disadvantages of different actor-critic based learning algorithms for different morphologies. Finally, based on the analysis of the experimental results, a generic view/architecture for locomotion learning is discussed in the conclusion.
Cai eLi
2014-10-01
Full Text Available In this article, we propose an architecture of a bio-inspired controller that addresses the problem of learning different locomotion gaits for different robot morphologies. The modelling objective is split into two: baseline motion modelling and dynamics adaptation. Baseline motion modelling aims to achieve fundamental functions of a certain type of locomotion and dynamics adaptation provides a ``reshaping function for adapting the baseline motion to desired motion. Based on this assumption, a three-layer architecture is developed using central pattern generators (CPGs, a bio-inspired locomotor center for the the baseline motion and dynamic motor primitives (DMPs, a model with universal ``reshaping functions. In this article, we use this architecture with the actor-critic algorithms for finding a good ``reshaping function. In order to demonstrate the learning power of the actor-critic based architecture, we tested it on two experiments: 1 learning to crawl on a humanoid and, 2 learning to gallop on a puppy robot. Two types of actor-critic algorithms (policy search and policy gradient are compared in order to evaluate the advantages and disadvantages of different actor-critic based learning algorithms for different morphologies. Finally, based on the analysis of the experimental results, a generic view/architecture for locomotion learning is discussed in the conclusion.
Parizeau, Kate; Massow, Mike von; Martin, Ralph
2015-01-01
Highlights: • We combined household waste stream weights with survey data. • We examine relationships between waste and food-related practices and beliefs. • Families and large households produced more total waste, but less waste per capita. • Food awareness and waste awareness were related to reduced food waste. • Convenience lifestyles were differentially associated with food waste. - Abstract: It has been estimated that Canadians waste $27 billion of food annually, and that half of that waste occurs at the household level (Gooch et al., 2010). There are social, environmental, and economic implications for this scale of food waste, and source separation of organic waste is an increasingly common municipal intervention. There is relatively little research that assesses the dynamics of household food waste (particularly in Canada). The purpose of this study is to combine observations of organic, recyclable, and garbage waste production rates to survey results of food waste-related beliefs, attitudes, and behaviours at the household level in the mid-sized municipality of Guelph, Ontario. Waste weights and surveys were obtained from 68 households in the summer of 2013. The results of this study indicate multiple relationships between food waste production and household shopping practices, food preparation behaviours, household waste management practices, and food-related attitudes, beliefs, and lifestyles. Notably, we observed that food awareness, waste awareness, family lifestyles, and convenience lifestyles were related to food waste production. We conclude that it is important to understand the diversity of factors that can influence food wasting behaviours at the household level in order to design waste management systems and policies to reduce food waste
Parizeau, Kate, E-mail: kate.parizeau@uoguelph.ca [Department of Geography, University of Guelph, Guelph, ON (Canada); Massow, Mike von [School of Hospitality, Food, and Tourism Management, University of Guelph, Guelph, ON (Canada); Martin, Ralph [Plant Agriculture Department, University of Guelph, Guelph, ON (Canada)
2015-01-15
Highlights: • We combined household waste stream weights with survey data. • We examine relationships between waste and food-related practices and beliefs. • Families and large households produced more total waste, but less waste per capita. • Food awareness and waste awareness were related to reduced food waste. • Convenience lifestyles were differentially associated with food waste. - Abstract: It has been estimated that Canadians waste $27 billion of food annually, and that half of that waste occurs at the household level (Gooch et al., 2010). There are social, environmental, and economic implications for this scale of food waste, and source separation of organic waste is an increasingly common municipal intervention. There is relatively little research that assesses the dynamics of household food waste (particularly in Canada). The purpose of this study is to combine observations of organic, recyclable, and garbage waste production rates to survey results of food waste-related beliefs, attitudes, and behaviours at the household level in the mid-sized municipality of Guelph, Ontario. Waste weights and surveys were obtained from 68 households in the summer of 2013. The results of this study indicate multiple relationships between food waste production and household shopping practices, food preparation behaviours, household waste management practices, and food-related attitudes, beliefs, and lifestyles. Notably, we observed that food awareness, waste awareness, family lifestyles, and convenience lifestyles were related to food waste production. We conclude that it is important to understand the diversity of factors that can influence food wasting behaviours at the household level in order to design waste management systems and policies to reduce food waste.
Effects of wind farms on harbour porpoise behaviour and population dynamics
Nabe-Nielsen, Jacob; Tougaard, Jakob; Teilmann, Jonas
We developed an individual-based simulation model in order to study the cumulative impacts of wind farms and ship traffic on the long-term survival and population dynamics of the harbour porpoise (Phocoena phocoena) in Kattegat and the Belt Seas. The model is based on knowl- edge of the porpoises...... at distances >1 km. Our simulations suggest that operating wind farms and wind farms under construction do not affect the size or dynamics of the harbour porpoise population in Kattegat. Ship traffic may, in contrast, cause the population size to decrease....
Zhang, Zhenbo; Tao, N. R.; Mishin, Oleg V.
2016-01-01
The microstructure, texture and mechanical properties have been studied in PM2000 compressed via dynamic plastic deformation to a strain of 2.1. It is found that dynamic plastic deformation results in a duplex 〈111〉 + 〈100〉 fibre texture and refines the initial microstructure by nanoscale lamellae...... in the deformed microstructure. This reduction is more pronounced in the 〈111〉-oriented regions. Orientation-dependent recrystallisation takes place in the recovered microstructure, leading to strengthening of the 〈111〉 fibre texture component at the expense of the 〈100〉 fibre texture component....
Analyses of the dynamic behaviour of nuclear installation under external loads
Alex, H.; Kaestle, H.J.; Kuntze, W.M.
1976-04-01
This paper demonstrates the dynamic analysis of a reactor building which is subject to earthquake loading. The purpose of this investigation is to calculate characteristic dynamical parameters at certain positions of the structure, such as floor time histories. Following the selection of a typical earthquake time history the reactor building is modelled with Finite Elements. The calculations are performed with the program system ASKA using Time History Modal Analysis. Prior to the response calculation the eigenvalue problem is solved. The results of the analysis, such as displacements, stresses and floor time histories will be discussed in view of the chosen earthquake excitation. (orig.) [de
Lovreglio, Ruggiero; Ronchi, Enrico; Maragkos, Georgios; Beji, Tarek; Merci, Bart
2016-11-15
The release of toxic gases due to natural/industrial accidents or terrorist attacks in populated areas can have tragic consequences. To prevent and evaluate the effects of these disasters different approaches and modelling tools have been introduced in the literature. These instruments are valuable tools for risk managers doing risk assessment of threatened areas. Despite the significant improvements in hazard assessment in case of toxic gas dispersion, these analyses do not generally include the impact of human behaviour and people movement during emergencies. This work aims at providing an approach which considers both modelling of gas dispersion and evacuation movement in order to improve the accuracy of risk assessment for disasters involving toxic gases. The approach is applied to a hypothetical scenario including a ship releasing Nitrogen dioxide (NO2) on a crowd attending a music festival. The difference between the results obtained with existing static methods (people do not move) and a dynamic approach (people move away from the danger) which considers people movement with different degrees of sophistication (either a simple linear path or more complex behavioural modelling) is discussed. Copyright © 2016 Elsevier B.V. All rights reserved.
Castano, Jorge; Gvirtzman, H.A.
1981-01-01
A model of digital computation is presented to simulate the primary system of heat transportation, moderator system and the associated systems for adjustment, regulation and control in the PHWR reactor at the Atucha-1 nuclear power plant. The model discusses in a concentrated way the different components and allows the study of the dynamical behaviour of the power plant facing disturbances with respect to a state of stationary regime. General considerations and description of the model are made. The method is described showing flow sheets, graphs and developing basic formulas, simulating a primary system, moderator and secondary system of the steam generator and the main system of regulation. Also an analysis of the results is made, for the case of disturbances which reduce or increase the power of the reactor by 10%. (V.B.) [es
R. Fargère
2012-01-01
Full Text Available Some interactions between the dynamic and tribological behaviour of geared transmissions are examined, and a number of experimental and simulation results are compared. A model is introduced which incorporates most of the possible interactions between gears, shafts and hydrodynamic journal bearings. It combines (i a specific element for wide-faced gears that includes the normal contact conditions between actual mating teeth, that is, with tooth shape deviations and mounting errors, (ii shaft finite elements, and (iii the external forces generated by journal bearings determined by directly solving Reynolds' equation. The simulation results are compared with the measurement obtained on a high-precision test rig with single-stage spur and helical gears supported by hydrodynamic journal bearings. The experimental and simulation results compare well thus validating the simulation strategy both at the global and local scales.
V.A. Bazhenov
2014-12-01
Full Text Available Authors in their works study vibroimpact system dynamic behaviour by numerical parametric continuation technique combined with shooting and Newton-Raphson’s methods. The technique is adapted to two-mass two-degree-of-freedom vibroimpact system under periodic excitation. Impact is simulated by nonlinear contact interaction force based on Hertz’s contact theory. Stability or instability of obtained periodic solutions is determined by monodromy matrix eigenvalues (multipliers based on Floquet’s theory. In the present paper we describe the state of problem of parameter continuation method using for nonlinear tasks solution. Also we give the short survey of numerous contemporary literature in English and Russian about parameter continuation method application for nonlinear problems. This method is applied for vibroimpact problem solving more rarely because of the difficulties connected with repeated impacts.
Kang An
2013-10-01
Full Text Available This paper presents a passive dynamic walking model based on knee-bend behaviour, which is inspired by the way human beings walk. The length and mass parameters of human beings are used in the walking model. The knee-bend mechanism of the stance leg is designed in the phase between knee-strike and heel-strike. q* which is the angular difference of the stance leg between the two events, knee-strike and knee-bend, is adjusted in order to find a stable walking motion. The results show that the stable periodic walking motion on a slope of r <0.4 can be found by adjusting q*. Furthermore, with a particular q* in the range of 0.12
Abate, G.; Massimino, M. R.; Maugeri, M.
2008-01-01
The deep investigation of soil-foundation interaction behaviour during earthquakes represent one of the key-point for a right seismic design of structures, which can really behave well during earthquake, avoiding dangerous boundary conditions, such as weak foundations supporting the superstructures. The paper presents the results of the FEM modeling of a shaking table test involving a concrete shallow foundation resting on a Leighton Buzzard sand deposit. The numerical simulation is performed using a cap-hardening elasto-plastic constitutive model for the soil and specific soil-foundation contacts to allow slipping and up-lifting phenomena. Thanks to the comparison between experimental and numerical results, the power and the limits of the proposed numerical model are focused. Some aspects of the dynamic soil-foundation interaction are also pointed out
Dynamic behaviour of 210Pb, 210Po and 137Cs in coastal and shelf environments
Zuo, Z.
1992-01-01
The continental margins of the southern North Sea and the northwestern Mediterranean Sea were chosen as the main subject areas for the study of some of the key processes operating in water and in sediment: chemical scavenging, particle transport, sediment resuspension and deposition. The dynamic
Imitation dynamics of vaccine decision-making behaviours based on the game theory.
Yang, Junyuan; Martcheva, Maia; Chen, Yuming
2016-01-01
Based on game theory, we propose an age-structured model to investigate the imitation dynamics of vaccine uptake. We first obtain the existence and local stability of equilibria. We show that Hopf bifurcation can occur. We also establish the global stability of the boundary equilibria and persistence of the disease. The theoretical results are supported by numerical simulations.
Mother-Infant Dyadic State Behaviour: Dynamic Systems in the Context of Risk
Coburn, Shayna S.; Crnic, Keith A.; Ross, Emily K.
2015-01-01
Dynamic systems methods offer invaluable insight into the nuances of the early parent-child relationship. This prospective study aimed to highlight the characteristics of mother-infant dyadic behavior at 12?weeks post-partum using state space grid analysis (total n?=?322). We also examined whether maternal prenatal depressive symptoms and…
The dynamic behaviour of man-wide vehicles with an automatic active tilting mechanism
Pauwelussen, J.P.
1999-01-01
The major advantage of a motorcycle with respect to a passenger car is the possibility of the driver to tilt during cornering and thereby maintaining stability whereas a passenger car will suffer from the risk of capsizing at high speed. This observation has lead Brink Dynamics to create and develop
Analysis of the tensile behaviour of zircaloy-4 in the region of dynamic strain aging
Dellaretti Filho, O.
1974-01-01
An analysis of the tensile behavior of Zircaloy 4, centering around the influence of dynamic strain aging and strain rate history, is presented. This analysis is based on techniques introduced by Jaoul-Crussard and Reed-Hill. An attempt is also made to assess the experimental errors that influence these methods. (author)
Dynamic Behaviour of a Population of Controlled-by-price Demand Side Resources
Sossan, Fabrizio; Han, Xue; Bindner, Henrik W.
2014-01-01
It is described that controlling or shedding by price the power consumption of a population of thermostatic loads introduces in the aggregate consumption dynamic effects th at cannot be disregarded if electrical flexible demand is meant to supply power system services. It is shown that inducing...
Nardi, Bernardo; Laurenzi, Sabrina; Di Nicolò, Marzia; Bellantuono, Cesario
2012-01-01
The aim of this study was to evaluate the efficacy of cognitive-behavioural therapy (CBT) in the prevention of post partum depression (PPD) in pregnant women at risk. PubMed, Medline, PsychInfo, Embase, and the Cochrane Library databases were searched from January 1991 to June 2011 to review studies on the efficacy of CBT in the prevention of PD. The literature analyzed recommends that depression in pregnancy requires an efficient management to provide mother's symptoms relief as well as to prevent PD. While several studies demonstrated the efficacy of CBT in the treatment of PD, only a few controlled studies focused on its efficacy in the prevention of PD in women identified at risk during pregnancy. The efficacy of CBT in preventing PD in pregnant women at risk is supported by only a few studies, presenting some methodological flaws. Better designed trials are needed to strongly support the efficacy of such psychotherapeutic preventive strategy in women at risk for PD.
Hausen, H.
1985-01-01
The differences between the irradiation environment of a fission reactor and that of a fusion reactor are respectively described in relation to the radiation damage found and expected in the two types of nuclear reactor. It is shown that the microstructure developing for instance in stainless steel alloys is almost invariant to whether the production rate of helium is high or low. The finding is valid up to neutron doses corresponding to about 60 dpa. For this reason, irradiation creep data obtained in fission reactors may be used, with caution, for predicting creep behaviour in fusion reactors.It was further recognized that irradiation creep performed with high energy particles from an accelerator, yields results which are comparable to those obtained in fission reactors. For this reason, simulation creep experiments are found to be valuable for the development of irradiation creep resistant materials using, for example, high energy electrons or protons. Such kind of experiments are performed in many laboratories. For irradiation doses larger than 60 dpa, predictions with respect to creep rates in fission and fusion reactors are difficult. In end-of-life tests, which concern swelling, ductility, tensile properties, rupture, fatigue and embrittlement, the presence of helium, due to its production rate being much higher in most materials exposed to 14 MeV neutrons than to fission neutrons, may be of great importance
The dynamic behaviour of rail vehicles operating at high speeds for manriding in British coal mines
Manen, P. van
1984-01-01
The behaviour of trains used at high speeds for transporting men along mine railways is examined using a number of mathematical models. These models predict the responses of different rail vehicles to typical irregularities in the track, and are used to examine the guidance, the ride, and the likelihood of derailment of the main classes of manriding trains used in British coal mines. The outcome of the modelling compares favourably with the results of tests carried out on actual vehicles. The investigation has shown that the safe speed at which trains may operate is ultimately restricted by the condition of the track, but changes in the design of the vehicles can lead to an improved performance. The use of conventional wheelsets, for example, can reduce flange wear significantly and so allow higher speeds to be reached. Guidelines for the design of vehicles intended for high speed use are included in this thesis. (36 refs.)
Perier-Muzet, Maxime; Bedecarrats, Jean-Pierre; Stouffs, Pascal; Castaing-Lasvignottes, Jean
2014-01-01
A heat powered thermoacoustic refrigerator consists in a thermoacoustic engine that produces acoustic work utilizing heat, coupled to a thermoacoustic cooler that converts this acoustic energy into cooling effect. These machines have already proved their capability in laboratory or in space refrigeration. Previous studies have also demonstrated the possibility of using concentrated solar energy as thermal energy sources for low power heat driven thermoacoustic refrigerators. As other solar refrigeration systems, even if the cooling demand generally increases with the intensity of the solar radiation, one of the major difficulties is to insure a frigorific power supply when there is no, or low, solar radiation. The aim of this work is to study a kW scale solar thermoacoustic refrigerator capable to reach temperatures of the industrial refrigeration domain. This refrigerator is combined with a latent cold storage in order to guarantee a sufficient cooling capacity to face to refrigeration loads in spite of the production fluctuations. A description of the studied prototype is done and the model developed to describe the transient behaviour of the main components of this machine is introduced. The results obtained with a simulation of one week with real solar radiations are presented and the behaviour and the energetic performances of the entire system are analysed. Finally the impact of the sizing of the cold storage system is discussed. With the best storage design, the system is capable to supply a cooling power of 400 W at a temperature equal or lower than −20 °C with an average Coefficient Of Performance of the solar thermoacoustic refrigerator equal to 21%
Rosa De Finis
2016-11-01
Full Text Available Stainless steels are the most exploited materials due to their high mechanical strength and versatility in producing different alloys. Although there is great interest in these materials, mechanical characterisation, in particular fatigue characterisation, requires the application of several standardised procedures involving expensive and time-consuming experimental campaigns. As a matter of fact, the use of Standard Test Methods does not rely on a physical approach, since they are based on a statistical evaluation of the fatigue limit with a fixed probabilistic confidence. In this regard, Infra-Red thermography, the well-known, non-destructive technique, allows for the development of an approach based on evaluation of dissipative sources. In this work, an approach based on a simple analysis of a single thermographic sequence has been presented, which is capable of providing two indices of the damage processes occurring in material: the phase shift of thermoelastic signal φ and the amplitude of thermal signal at twice the loading frequency, S2. These thermal indices can provide synergetic information about the mechanical (fatigue and fracture behaviour of austenitic AISI 316L and martensitic X4 Cr Ni Mo 16-5-1; since they are related to different thermal effects that produce damage phenomena. In particular, the use of φ and S2 allows for estimation of the fatigue limit of stainless steels at loading ratio R = 0.5 in agreement with the applied Standard methods. Within Fracture Mechanics tests, both indices demonstrate the capacity to localize the plastic zone and determine the position of the crack tip. Finally, it will be shown that the value of the thermoelastic phase signal can be correlated with the mechanical behaviour of the specific material (austenitic or martensitic.
Baumuratova, Tatiana; Dobre, Simona; Bastogne, Thierry; Sauter, Thomas
2013-01-01
Systems with bifurcations may experience abrupt irreversible and often unwanted shifts in their performance, called critical transitions. For many systems like climate, economy, ecosystems it is highly desirable to identify indicators serving as early warnings of such regime shifts. Several statistical measures were recently proposed as early warnings of critical transitions including increased variance, autocorrelation and skewness of experimental or model-generated data. The lack of automatized tool for model-based prediction of critical transitions led to designing DyGloSA – a MATLAB toolbox for dynamical global parameter sensitivity analysis (GPSA) of ordinary differential equations models. We suggest that the switch in dynamics of parameter sensitivities revealed by our toolbox is an early warning that a system is approaching a critical transition. We illustrate the efficiency of our toolbox by analyzing several models with bifurcations and predicting the time periods when systems can still avoid going to a critical transition by manipulating certain parameter values, which is not detectable with the existing SA techniques. DyGloSA is based on the SBToolbox2 and contains functions, which compute dynamically the global sensitivity indices of the system by applying four main GPSA methods: eFAST, Sobol's ANOVA, PRCC and WALS. It includes parallelized versions of the functions enabling significant reduction of the computational time (up to 12 times). DyGloSA is freely available as a set of MATLAB scripts at http://bio.uni.lu/systems_biology/software/dyglosa. It requires installation of MATLAB (versions R2008b or later) and the Systems Biology Toolbox2 available at www.sbtoolbox2.org. DyGloSA can be run on Windows and Linux systems, -32 and -64 bits. PMID:24367574
Baumuratova, Tatiana; Dobre, Simona; Bastogne, Thierry; Sauter, Thomas
2013-01-01
Systems with bifurcations may experience abrupt irreversible and often unwanted shifts in their performance, called critical transitions. For many systems like climate, economy, ecosystems it is highly desirable to identify indicators serving as early warnings of such regime shifts. Several statistical measures were recently proposed as early warnings of critical transitions including increased variance, autocorrelation and skewness of experimental or model-generated data. The lack of automatized tool for model-based prediction of critical transitions led to designing DyGloSA - a MATLAB toolbox for dynamical global parameter sensitivity analysis (GPSA) of ordinary differential equations models. We suggest that the switch in dynamics of parameter sensitivities revealed by our toolbox is an early warning that a system is approaching a critical transition. We illustrate the efficiency of our toolbox by analyzing several models with bifurcations and predicting the time periods when systems can still avoid going to a critical transition by manipulating certain parameter values, which is not detectable with the existing SA techniques. DyGloSA is based on the SBToolbox2 and contains functions, which compute dynamically the global sensitivity indices of the system by applying four main GPSA methods: eFAST, Sobol's ANOVA, PRCC and WALS. It includes parallelized versions of the functions enabling significant reduction of the computational time (up to 12 times). DyGloSA is freely available as a set of MATLAB scripts at http://bio.uni.lu/systems_biology/software/dyglosa. It requires installation of MATLAB (versions R2008b or later) and the Systems Biology Toolbox2 available at www.sbtoolbox2.org. DyGloSA can be run on Windows and Linux systems, -32 and -64 bits.
Golovchanskiy, I.A.; Pan, A.V.; Fedoseev, S.A.; Shcherbakova, O.V.; Dou, S.X.
2012-01-01
A pinning potential for vortices was introduced assuming plastic pinning of vortex lattice on chains of out-of-plane individual edge dislocations that form low-angle domain boundaries in high quality YBa 2 Cu 3 O 7 thin films. Using this pinning potential with the classical Kim-Anderson vortex creep approach a model for critical current dependence on field has been successfully developed. The model shows a plausible description of J c (B a ) over the entire field range. Electrical field criterion is incorporated providing the ability to compare measurements made with different criteria (including different measurement techniques). Applicability of this model has been verified by experimental data obtained by direct transport and magnetisation measurements on high quality films grown by pulsed laser deposition. Pinning potential obtained from the fitting procedure is consistent with theoretical predictions. The model showed that the effective pinning landscape changes under influence of external conditions.
Saghir, Shahid; Younis, Mohammad I.
2016-01-01
We present an investigation of the static and dynamic behavior of the nonlinear von-Karman plates when actuated by the nonlinear electrostatic forces. The investigation is based on a reduced order model developed using the Galerkin method, which rely on modeshapes and in-plane shape functions extracted using a finite element method. In this study, a fully clamped microplate is considered. We investigate the static behavior and the results are validated by comparison with the results calculated by a finite element model. The forced-vibration response of the plate is then investigated when the plate is excited by a harmonic AC load superimposed to a DC load. The dynamic behavior is examined near the primary resonance. The microplate shows a strong hardening behavior due to the cubic nonlinearity of mid-plane stretching. However, the behavior switches to softening as the DC load is increased.
Saghir, Shahid
2016-11-16
We present an investigation of the static and dynamic behavior of the nonlinear von-Karman plates when actuated by the nonlinear electrostatic forces. The investigation is based on a reduced order model developed using the Galerkin method, which rely on modeshapes and in-plane shape functions extracted using a finite element method. In this study, a fully clamped microplate is considered. We investigate the static behavior and the results are validated by comparison with the results calculated by a finite element model. The forced-vibration response of the plate is then investigated when the plate is excited by a harmonic AC load superimposed to a DC load. The dynamic behavior is examined near the primary resonance. The microplate shows a strong hardening behavior due to the cubic nonlinearity of mid-plane stretching. However, the behavior switches to softening as the DC load is increased.
Static and Dynamic Behaviour Assessment of the Trajan Arch by Means of New Monitoring Technologies
Petti, L.; Barone, F.; Mammone, A.; Giordano, G.
2017-08-01
An effective assessment of the static and dynamic structural behavior of historical monuments requires the development and validation of suitable adaptive structural models using high-quality experimental data acquired with an effectively continuous and distributed monitoring. Furthermore, the adaptive strategy allows an efficient evaluation of the health status and of the evolution along the time of a historical monument, providing relevant information to plan appropriate actions for its long-term preservation. The Trajan Arch in Benevento chosen as a case of study to develop and apply this new adaptive strategy in cultural heritage conservation. The paper, after a description of the innovative monitoring system, based on state-of-the-art mechanical sensors, presents and discusses the results of two tests, comparing the measurements with the predictions of an adaptive structural FEM model developed for the dynamical simulation of the Trajan Arch.
Dynamic behaviour of nominal and PACMAN bunches for different LHC crossing schemes
Herr, Werner
2005-01-01
To avoid unwanted beam-beam interactions, the two LHC beams cross at an angle in all experimental interaction regions. The choice of the crossing plane in the different areas has fundamental consequences on the effects of the long range beam-beam interaction. An alternating crossing scheme, i.e. horizontal and vertical crossing planes in the two high luminosity experiments, is presently foreseen to partly compensate and minimize first order effects on PACMAN bunches. Recent studies with a simplified model of the machine suggested that an alternating crossing scheme may be less favourable due to a reduced dynamic aperture. In this report I investigate this assertion with a detailed tracking study. The head on and long range beam-beam effects are taken into account as well as machine imperfections. The effects on the dynamic aperture of nominal and PACMAN bunches are evaluated.
The behaviour of PM10 and ozone in Malaysia through non-linear dynamical systems
Sapini, Muhamad Luqman [Pusat Pengajian Matematik, Fakulti Sains Komputer & Matematik Universiti Teknologi MARA Kampus Seremban, 70300 Negeri Sembilan (Malaysia); Rahim, Nurul Zahirah binti Abd [Pengajian Matematik, Fakulti Sains Komputer & Matematik Universiti Teknologi MARA Kampus Jasin, 77000 Melaka (Malaysia); Noorani, Mohd Salmi Md. [Pusat Pengajian Sains Matematik, Fakulti Sains & Teknologi Universiti Kebangsaan Malaysia, 43650 Selangor (Malaysia)
2015-10-22
Prediction of ozone (O3) and PM10 is very important as both these air pollutants affect human health, human activities and more. Short-term forecasting of air quality is needed as preventive measures and effective action can be taken. Therefore, if it is detected that the ozone data is of a chaotic dynamical systems, a model using the nonlinear dynamic from chaos theory data can be made and thus forecasts for the short term would be more accurate. This study uses two methods, namely the 0-1 Test and Lyapunov Exponent. In addition, the effect of noise reduction on the analysis of time series data will be seen by using two smoothing methods: Rectangular methods and Triangle methods. At the end of the study, recommendations were made to get better results in the future.
The role of cable stiffness in the dynamic behaviours of submerged floating tunnel
Muhammad Naik
2017-01-01
Full Text Available Submerged floating tunnel (SFT is a new solution for the transportation infrastructure through sea straits, fjords, and inland waters and can be a good alternative to long span suspension bridges and immersed tunnels. The mooring cables/anchors are main structural components to provide restoring capacity to the SFT. The time domain dynamic problem of SFT moored by vertical and inclined mooring cables/anchors is formulated. The dynamic analysis of SFT subjected to hydrodynamic and seismic excitations is performed. As the cable stiffness determines the deformation ability of SFT, therefore it becomes crucial to evaluate the effect of mooring cable stiffness on the response of SFT. The displacements and internal forces of SFT clearly specify that the vertical/tension leg mooring cables provide very small stiffness as compared to inclined mooring cables. In order to keep the SFT displacements within an acceptable limit, the effect of cable stiffness should be properly evaluated for practical design of SFT.
Scaling Behaviour of Different Polymer Models in Dissipative Particle Dynamics of Unentangled Melts
Posel, Zbyšek; Rousseau, B.; Lísal, Martin
2014-01-01
Roč. 40, č. 15 (2014), s. 1274-1289 ISSN 0892-7022 R&D Projects: GA ČR(CZ) GA13-02938S Grant - others:GA UJEP(CZ) 53222 15 0008 01; CNRS-ASRT(FR) 20206 Institutional support: RVO:67985858 Keywords : coarse-grain potential * dissipative particle dynamics * rouse model Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 1.133, year: 2014
Dynamic behaviour of magneto-acoustic emission in a grain-oriented steel
Stupakov, Alexandr; Perevertov, Oleksiy; Landa, Michal
2017-01-01
Roč. 426, Mar (2017), s. 685-690 ISSN 0304-8853 R&D Projects: GA ČR GB14-36566G; GA ČR GA13-18993S Institutional support: RVO:68378271 ; RVO:61388998 Keywords : magneto-acoustic emission * magnetization dynamics * Barkhausen noise * surface field measurement * magnetization waveform control Subject RIV: BM - Solid Matter Physics ; Magnetism OBOR OECD: Condensed matter physics (including formerly solid state physics, supercond.) Impact factor: 2.630, year: 2016
Cracked rotors. A survey on static and dynamic behaviour including modelling and diagnosis
Bachschmid, Nicolo; Pennacchi, Paolo; Tanzi, Ezio [Politecnico di Milano (Italy). Dept. of Mechanical Engineering
2010-07-01
Cracks can develop in rotating shafts and can propagate to relevant depths without affecting consistently the normal operating conditions of the shaft. In order to avoid catastrophic failures, accurate vibration analyses have to be performed for crack detection. The identification of the crack location and depth is possible by means of a model based diagnostic approach, provided that the model of the crack and the model of the cracked shaft dynamical behavior are accurate and reliable. This monograph shows the typical dynamical behavior of cracked shafts and presents tests for detecting cracks. The book describes how to model cracks, how to simulate the dynamical behavior of cracked shaft, and compares the corresponding numerical with experimental results. All effects of cracks on the vibrations of rotating shafts are analyzed, and some results of a numerical sensitivity analysis of the vibrations to the presence and severity of the crack are shown. Finally the book describes some crack identification procedures and shows some results in model based crack identification in position and depth. The book is useful for higher university courses in mechanical and energetic engineering, but also for skilled technical people employed in power generation industries. (orig.)
Hajj-Mohamad, M; Darwano, H; Duy, S Vo; Sauvé, S; Prévost, M; Arp, H P H; Dorner, S
2017-01-01
Pharmaceuticals are discharged to the environment from wastewater resource recovery facilities, sewer overflows, and illicit sewer connections. To understand the fate of pharmaceuticals, there is a need to better understand their sorption dynamics to suspended sediments (SS) and settled sediments (StS) in sewer systems. In this study, such sorption dynamics to both SS and StS were assessed using a batch equilibrium method under both static and dynamic conditions. Experiments were performed with natively occurring and artificially modified concentrations of sewer pharmaceuticals (acetaminophen, theophylline, carbamazepine, and a metabolite of carbamazepine) and caffeine. Differences in apparent distribution coefficients, K d,app , between SS and StS were related to differences in their organic carbon (OC) content, and the practice of artificially modifying the concentration. K d,app values of modified contaminant concentrations and high OC sediments were substantially higher. Pseudo-second order desorption rates for these mobile compounds were also quantified. Successive flushing events to simulate the addition of stormwater to sewer networks revealed that aqueous concentrations would not necessarily decrease, because the added water will rapidly return to equilibrium concentrations with the sediments. Sorption and desorption kinetics must be considered in addition to dilution, to avoid underestimating the influence of dilution on concentrations of pharmaceuticals discharged to the environment. Copyright Â© 2016 Elsevier Ltd. All rights reserved.
Investigation on the dynamic behaviour of a parabolic trough power plant during strongly cloudy days
Al-Maliki, Wisam Abed Kattea; Alobaid, Falah; Starkloff, Ralf; Kez, Vitali; Epple, Bernd
2016-01-01
Highlights: • A detailed dynamic model of a parabolic trough solar thermal power plant is done. • Simulated results are compared to the experimental data from the real power plant. • Discrepancy between model result and real data is caused by operation strategy. • The model strategy increased the operating hours of power plant by around 2.5–3 h. - Abstract: The objective of this study is the development of a full scale dynamic model of a parabolic trough power plant with a thermal storage system, operated by the Actividades de Construcción y Servicios Group in Spain. The model includes solar field, thermal storage system and the power block and describes the heat transfer fluid and steam/water paths in detail. The parabolic trough power plant is modelled using Advanced Process Simulation Software (APROS). To validate the model, the numerical results are compared to the measured data, obtained from “Andasol II” during strongly cloudy periods in the summer days. The comparisons show a qualitative agreement between the dynamic simulation model and the measurements. The results confirm that the thermal storage enables the parabolic trough power plant to provide a constant power rate when the storage energy discharge is available, despite significant oscillations in the solar radiation.
Host behaviour-parasite feedback: an essential link between animal behaviour and disease ecology.
Ezenwa, Vanessa O; Archie, Elizabeth A; Craft, Meggan E; Hawley, Dana M; Martin, Lynn B; Moore, Janice; White, Lauren
2016-04-13
Animal behaviour and the ecology and evolution of parasites are inextricably linked. For this reason, animal behaviourists and disease ecologists have been interested in the intersection of their respective fields for decades. Despite this interest, most research at the behaviour-disease interface focuses either on how host behaviour affects parasites or how parasites affect behaviour, with little overlap between the two. Yet, the majority of interactions between hosts and parasites are probably reciprocal, such that host behaviour feeds back on parasites and vice versa. Explicitly considering these feedbacks is essential for understanding the complex connections between animal behaviour and parasite ecology and evolution. To illustrate this point, we discuss how host behaviour-parasite feedbacks might operate and explore the consequences of feedback for studies of animal behaviour and parasites. For example, ignoring the feedback of host social structure on parasite dynamics can limit the accuracy of predictions about parasite spread. Likewise, considering feedback in studies of parasites and animal personalities may provide unique insight about the maintenance of variation in personality types. Finally, applying the feedback concept to links between host behaviour and beneficial, rather than pathogenic, microbes may shed new light on transitions between mutualism and parasitism. More generally, accounting for host behaviour-parasite feedbacks can help identify critical gaps in our understanding of how key host behaviours and parasite traits evolve and are maintained. © 2016 The Author(s).
Dynamic behaviour of Li batteries in hydrogen fuel cell power trains
Veneri, O.; Migliardini, F.; Capasso, C.; Corbo, P.
A Li ion polymer battery pack for road vehicles (48 V, 20 Ah) was tested by charging/discharging tests at different current values, in order to evaluate its performance in comparison with a conventional Pb acid battery pack. The comparative analysis was also performed integrating the two storage systems in a hydrogen fuel cell power train for moped applications. The propulsion system comprised a fuel cell generator based on a 2.5 kW polymeric electrolyte membrane (PEM) stack, fuelled with compressed hydrogen, an electric drive of 1.8 kW as nominal power, of the same typology of that installed on commercial electric scooters (brushless electric machine and controlled bidirectional inverter). The power train was characterized making use of a test bench able to simulate the vehicle behaviour and road characteristics on driving cycles with different acceleration/deceleration rates and lengths. The power flows between fuel cell system, electric energy storage system and electric drive during the different cycles were analyzed, evidencing the effect of high battery currents on the vehicle driving range. The use of Li batteries in the fuel cell power train, adopting a range extender configuration, determined a hydrogen consumption lower than the correspondent Pb battery/fuel cell hybrid vehicle, with a major flexibility in the power management.
Load bearing and deformation behaviour of dynamically loaded wide plate specimens
Julisch, P.; Haedrich, H.J.; Stadtmueller, W.; Sturm, D.
1989-01-01
For the testing of large-scale specimens, a 12 MN-High Loading Rate Tensile Testing Machine was designed and built at MPA Stuttgart. The aim was to determine the influence of high loading rates on the stress and strain behaviour of unwelded and welded components of ferritic and austenitic materials. This new generation of testing machines is driven by a propellant charge, and generates a maximum tensile force of 12 MN with a piston velocity of 25 m/s after a stroke of 20 mm, or a maximum velocity of 60 m/s after a stroke of 400 mm. In a first test programme, welded and unwelded wide plate specimens made of material X 6 CrNi 18 11 were tested at room temperature with different strain rates from 10 -3 /s to 63/s. In addition to a description of the 12 MN-High Loading Rate Tensile Testing Machine, the results of the high loading rate tensile tests performed will be presented and compared with quasistatically tested wide plate specimens. (orig.)
Lee, Woei-Shyan, E-mail: wslee@mail.ncku.edu.tw [Department of Mechanical Engineering, National Cheng Kung University, Tainan 701, Taiwan (China); Lin, Chi-Feng [National Center for High-Performance Computing, Hsin-Shi Tainan County 744, Taiwan (China); Chen, Tao-Hsing [Department of Mechanical Engineering, National Kaohsiung University of Applied Sciences, Kaohsiung 807, Taiwan (China); Chen, Hong-Wei [Department of Mechanical Engineering, National Cheng Kung University, Tainan 701, Taiwan (China)
2011-07-25
A compressive split-Hopkinson pressure bar and transmission electron microscope (TEM) are used to investigate the mechanical behaviour and microstructural evolution of Inconel 718 at strain rates ranging from 1000 to 5000 s{sup -1} and temperatures between -150 and 550 deg. C. The results show that the flow stress increases with an increasing strain rate or a reducing temperature. The strain rate effect is particularly pronounced at strain rates greater than 3000 s{sup -1} and a deformation temperature of -150 deg. C. A significant thermal softening effect occurs at temperatures between -150 and 25 deg. C. The microstructural observations reveal that the strengthening effect in deformed Inconel 718 alloy is a result primarily of dislocation multiplication. The dislocation density increases with increasing strain rate, but decreases with increasing temperature. By contrast, the dislocation cell size decreases with increasing strain rate, but increases with increasing temperature. It is shown that the correlation between the flow stress, the dislocation density and the dislocation cell size is well described by the Bailey-Hirsch constitutive equations.
Ayse Yarali
Full Text Available Associative learning relies on event timing. Fruit flies for example, once trained with an odour that precedes electric shock, subsequently avoid this odour (punishment learning; if, on the other hand the odour follows the shock during training, it is approached later on (relief learning. During training, an odour-induced Ca(++ signal and a shock-induced dopaminergic signal converge in the Kenyon cells, synergistically activating a Ca(++-calmodulin-sensitive adenylate cyclase, which likely leads to the synaptic plasticity underlying the conditioned avoidance of the odour. In Aplysia, the effect of serotonin on the corresponding adenylate cyclase is bi-directionally modulated by Ca(++, depending on the relative timing of the two inputs. Using a computational approach, we quantitatively explore this biochemical property of the adenylate cyclase and show that it can generate the effect of event timing on associative learning. We overcome the shortage of behavioural data in Aplysia and biochemical data in Drosophila by combining findings from both systems.
The dynamic gastric environment and its impact on drug and formulation behaviour.
Van Den Abeele, Jens; Rubbens, Jari; Brouwers, Joachim; Augustijns, Patrick
2017-01-01
Before being absorbed in the small intestine and/or colon, orally administered drugs inevitably need to pass through the stomach. Hence, it seems reasonable that the residence of a dosage form in the gastric environment, however brief it may be, may influence drug disposition further down the gastrointestinal tract and may potentially impact systemic exposure to a drug of interest. However, research efforts in the past mainly focused on drug disposition at the level of the intestine, i.e. the main site of absorption, hereby disregarding or oversimplifying the stomach's contribution to gastrointestinal drug disposition. In the first part of this review, the complexity of the stomach with regard to anatomy, physiology and gastric fluid composition is emphasized. Between-population differences in gastric functioning and physicochemical characteristics of gastric fluids are discussed. The second part of this review focuses on several of the processes to which a dosage form can be exposed during its passage through the stomach and the implications for gastrointestinal drug behaviour and systemic drug disposition. Finally, the influence of real-life dosing conditions on drug disposition is discussed in the context of the stomach. Copyright © 2016 Elsevier B.V. All rights reserved.
Dupont, J.F.
1979-03-01
The principal simplifications of a mathematical model for the simulation of behaviour dynamics of a two-phase flow with heat exchange are examined, as it appears in a steam generator. The theoretical considerations and numerical solutions permit the evaluation of the validity limits and the influence of these simplifications on the results. (G.T.H.)
Carmeliet, J.; Abeele, van den K.E.A.
2004-01-01
The non-linear quasi-static and dynamic elastic behaviour of Berea sandstone has been experimentally analysed showing hysteresis and a strong influence of moisture especially in the lower saturation range. It is shown that non-linear hysteretic response originates within the "bond system" of the
Clodualdo Aranas
2018-05-01
Full Text Available The double differentiation method overestimates the critical stress associated with the initiation of dynamic transformation (DT because significant amounts of the dynamic phase must be present in order for its effect on the work hardening rate to be detectable. In this work, an alternative method (referred to here as the free energy method is presented based on the thermodynamic condition that the driving force is equal to the total energy obstacle during the exact moment of transformation. The driving force is defined as the difference between the DT critical stress (measured in the single-phase austenite region and the yield stress of the fresh ferrite that takes its place. On the other hand, the energy obstacle consists of the free energy difference between austenite and ferrite, and the work of shear accommodation and dilatation associated with the phase transformation. Here, the DT critical stresses in a C-Mn steel were calculated using the free energy method at temperatures ranging from 870 °C to 1070 °C. The results show that the calculated critical stress using the present approach appears to be more accurate than the values measured by the double differentiation method.
Gómez, C. M.; Culebras, M.; Cantarero, A.; Redondo-Foj, B.; Ortiz-Serna, P.; Carsí, M.; Sanchis, M. J.
2013-06-01
Segmented polycarbonatediol polyurethane (PUPH) has been synthesized and modified with different amounts of graphite conductive filler (from 0 to 50 wt%). Thermal and dynamical thermal analysis of the composites clearly indicates changes in the polyurethane relaxations upon addition of graphite. Broadband dielectric spectroscopy has been used to study the dielectric properties of the (PUPH) and one composite in the frequency range from 10-2 to 107 Hz and in the temperature window of -140 to 170 °C. Relaxation processes associated with different molecular motions and conductivity phenomena (Maxwell-Wagner-Sillars and electrode polarization) are discussed and related to the graphite content.
El-Hafidi, Ali; Birame Gning, Papa; Piezel, Benoit; Fontaine, Stéphane
2017-10-01
Experimental and numerical methods to identify the linear viscoelastic properties of flax fibre reinforced epoxy (FFRE) composite are presented in this study. The method relies on the evolution of storage modulus and loss factor as observed through the frequency response. Free-free symmetrically guided beams were excited on the dynamic range of 10 Hz to 4 kHz with a swept sine excitation focused around their first modes. A fractional derivative Zener model has been identified to predict the complex moduli. A modified ply constitutive law has been then implemented in a classical laminates theory calculation (CLT) routine.
A Dynamic Behaviour Analysis on the Frequency Control Capability of Electric Vehicles
Zarogiannis, Athanasios; Marinelli, Mattia; Træholt, Chresten
2014-01-01
The paper presents results of a study on the dynamic response of Electric Vehicle’s (EV) when participating in frequency control of an islanded system. The following cases were considered: when there is no EV performing frequency control, when the EV participates in primary frequency control...... and when the EV participates in both primary and secondary frequency control. Different parameters are tested in various combinations, and their influence on frequency deviation as well as power and energy provided by the EV with vehicle-to-grid (V2G) capability is shown....
Trucu, Dumitru
2016-09-01
In this comprehensive review concerning the modelling of human behaviours in crowd dynamics [3], the authors explore a wide range of mathematical approaches spanning over multiple scales that are suitable to describe emerging crowd behaviours in extreme situations. Focused on deciphering the key aspects leading to emerging crowd patterns evolutions in challenging times such as those requiring an evacuation on a complex venue, the authors address this complex dynamics at both microscale (individual level), mesoscale (probability distributions of interacting individuals), and macroscale (population level), ultimately aiming to gain valuable understanding and knowledge that would inform decision making in managing crisis situations.
Design features affecting dynamic behaviour of fast reactor cores. Overview paper
Kayser, G.; Gouriou, A.
1982-01-01
The study of dynamic response of a LMFBR to normal and accidental transients needs first of all a simulation code taking into account all the important effects. The DYN-1 code aims at this target. It represents with a sufficiently accurate meshing the core in a 2D geometry for the thermal and reactivity effects, while the kinetics of this core are calculated with a point model. The primary pool, secondary loops, steam generator are also represented, as well as the control and protective systems. A schematic representation of this code applied to Super Phenix 1 is shown. Simpler codes are sometimes good enough for parametric studies. The dynamic studies of this plant are related to different situations which can be classified in the following groups: normal operation, the stability of the reactor in a steady state situation, or with power or frequency regulation; the normal transients from one power level to another (startup procedures); the incidental situations, with the protective shut-down systems operative (for instance loss of electric supply power); the hypothetical accidental situations without scram. The first three groups of problems arise necessarily in the study of each plant ; the last group is related to very hypothetical situations, the probability of which can be made very low by a high reliability of the shut-down system. Also the need to study them depends on this reliability and subsequently on the philosophy which the licensing authorities adopt
Dynamic behaviour of tantalum hydride supported on silica or MCM-41 in the metathesis of alkanes
Soignier, Sophie
2014-01-01
The metathesis of ethane and propane catalysed by tantalum hydride supported on silica or MCM-41 was studied under static and dynamic conditions. During the reaction, the rate decreased over time, indicating deactivation of the catalyst. The evolution of the catalytic system and surface species over time was monitored by various physico-chemical methods: FTIR, 13C NMR spectroscopy, elemental analysis and chemical reactivity. A carbonaceous deposit composed of unsaturated hydrocarbyl species was observed by 13C NMR. This deposit was responsible for poisoning of the catalyst. The deactivation of the catalyst proved more severe at higher temperatures and under static rather than dynamic conditions. A partial regeneration of the catalyst could be achieved during a series of repeated runs. Mechanistically, the deconvolution of the products\\' distribution over time indicated the occurrence of hydrogenolysis in the early stages of the reaction, while pure metathesis dominated later on. The hydrogen was supplied by the dehydrogenation of hydrocarbyl surface species involved in the deactivation process. © 2014 The Royal Society of Chemistry.
Model dynamic behaviour analysis with chaotic noise using fuzzy logic based control
Silva, Glauco Antonio Santos da
2002-01-01
This work presents an application of fuzzy control on dynamical system models. It has been observed that fuzzy controllers maybe used as a good alternative to the classical PI controller, once it incorporates human line behavior. Three implication relationships were used for the fussy controllers, namely, Mamdani Min, Larsen and Takagi-Sugeno. Performance comparisons were made aiming at achieving the best performance for each model used. The PI controller was used as a minimum standard, once it has been present in the industry for many years, giving acceptable performances and some degree of reliability . Two kinds of perturbations were introduced in the models to test the controllers: a ramp and chaotic perturbations. The first one is a monotonic, standard increase of an input parameter. The second one presents non-periodicity and irregularity in such a way to be quite rough to the controllers. The chaotic signal, as an analysis tool to dynamical systems, is an interesting contribution of this work. As a general conclusion it can be said the best performance, in this work, was achieved by the Takagi-Sugeno fuzzy controller. (author)
Dynamic Behaviour and Seismic Response of Ground Supported Cylindrical Water Tanks
Asha, Joseph; Glory, Joseph
2018-05-01
Liquid storage tank such as in water distribution systems, petroleum plants etc., constitute a vital component of life line systems. Reducing earthquake effects on liquid storage tanks, to minimize the environmental and economic impact of these effects, have always been an important engineering concern. In this paper, the dynamic behavior of cylindrical ground supported concrete water tanks with different aspect ratios is investigated using finite element software ANSYS. The natural frequencies and modal responses are obtained for impulsive and convective modes of vibration. The natural frequency of vibration of the tank is observed to be the lowest at maximum water depth. The fundamental impulsive frequency increases as water level reduces and for water level less than 1/3 of tank height, there is significantly no change in impulsive frequency. The effect of wall flexibility on dynamic behavior of the tank is investigated by performing the modal analysis of flexible and rigid tanks. For a partially filled tank, the results of the present study are of significant relevance. The response of the tank to the transient loading as horizontal ground motion of El Centro earthquake is studied for various water heights. As the height of water on the tank increases, the ultimate maximum seismic response parameters are also observed to be increased. The location of maximum hoop stress varies in accordance with the variations in input ground motion and water fill condition whereas shear and bending moment are maximum at the base.
Dynamic behaviour of tantalum hydride supported on silica or MCM-41 in the metathesis of alkanes
Soignier, Sophie; Saggio, Guillaume; Taoufik, Mostafa; Basset, Jean-Marie; Thivolle-Cazat, Jean
2014-01-01
The metathesis of ethane and propane catalysed by tantalum hydride supported on silica or MCM-41 was studied under static and dynamic conditions. During the reaction, the rate decreased over time, indicating deactivation of the catalyst. The evolution of the catalytic system and surface species over time was monitored by various physico-chemical methods: FTIR, 13C NMR spectroscopy, elemental analysis and chemical reactivity. A carbonaceous deposit composed of unsaturated hydrocarbyl species was observed by 13C NMR. This deposit was responsible for poisoning of the catalyst. The deactivation of the catalyst proved more severe at higher temperatures and under static rather than dynamic conditions. A partial regeneration of the catalyst could be achieved during a series of repeated runs. Mechanistically, the deconvolution of the products' distribution over time indicated the occurrence of hydrogenolysis in the early stages of the reaction, while pure metathesis dominated later on. The hydrogen was supplied by the dehydrogenation of hydrocarbyl surface species involved in the deactivation process. © 2014 The Royal Society of Chemistry.
Experimental Investigations on the Dynamic Behaviour of O-Type Wire-Cable Vibration Isolators
Hong-Xia Wang
2015-01-01
Full Text Available A series of periodic loading experiments were carried out on the O-type wire-cable vibration isolators. The isolators were loaded under shear, roll, and tension-compression loadings. When subjected to shear and roll loads, the restoring force-deformation curves generated by the isolators formed symmetric hysteresis loops. However, when the isolators were loaded with tension-compression loads, the isolator produced asymmetric hysteresis loops. It is found through the experiment that the dynamic characteristics of the isolator are determined by the loading amplitude as well as the geometric parameters of the isolator while they are almost independent of loading frequency within the testing frequency range. Based on the experimental data, the dynamic response of the isolator was modeled by a modified normalized Bouc-Wen model. The parameters of this model were identified through an identification procedure that does not involve any nonlinear iterative algorithms. Comparison between the identification results and the experimental data suggests that the identification method is effective. With the model and the identified parameters, the frequency response of an O-type wire-cable vibration isolator-mass system was evaluated. Typical nonlinear response behaviors were found when the isolator was used in tension-compression mode while the response appears to be similar to that of a linear system when the isolator was used in shear and roll mode.
Dynamic Behaviour of Different Types of Cable-Stayed Bridges Due to Earthquake Loads
Alireza Mirza Goltabar Roshan
2016-12-01
Full Text Available Construction of large-scale structures has been considered as one of the human's main achievements. With their suitable view and high economical aspects, High-strength steel cables have been developed for analysis and erection of cable-stayed bridges in light of high speed development in computer technology. This type of bridges, while providing different behavior due to cable flexibility, has been recognized as one of the most practical choices for mid to large span bridges. This paper studies the non-linear dynamic behavior of cable bridges and the effect of some parameters (such as cable arrangement and shape of pylon on them. For this purpose, CSI Bridge software with the direct integration method of dynamic analysis has been used and the behavior of structure under different earthquake components has been analyzed for various conditions of cable arrangements and pylon shapes. Results indicate that the most suitable behavior would be for cable bridges with H-shape pylons arranged in series and also with A-shape pylons in radial arrangement.
Systematic study of strangeness production and dynamic behaviour with the FOPI experiment at SIS-18
Zinyuk, Victoria
2016-05-10
This work is dedicated to the investigation of in-medium behaviour of strange particles. In-medium production and propagation of K{sup +} and K{sup -} mesons is studied with the FOPI apparatus in {sup 58}Ni + {sup 58}Ni collisions at the incident beam energy of E{sub beam}= 1.91 AGeV, i.e. near the strangeness production threshold energies. Weak in-plane 'anti-flow' with respect to protons and a slight 'squeeze-out' is found in the azimuthal emission pattern of K{sup +} mesons. K{sup -} mesons exhibit an isotropic emission pattern within large statistic uncertainties. The comparison to the predictions of two independent transport calculations, HSD and IQMD, suggests a weakly repulsive KN in-medium potential of U{sub KN}20±5 MeV and an attractive anti KN in-medium potential of U{sub K}{sup {sub -N}}=-40 ± 10 MeV. Production of K{sup +/-/0}, φ mesons and the Λ baryon at normal nuclear matter density is studied in π{sup -} + A reactions with C, Cu and Pb targets at incident beam momentum of p{sub π{sup -}}=1.7 GeV/c. Differences in the final state phase space distributions measured in heavy and light targets point to repulsion for K{sup +} and K{sup 0}{sub S} mesons in nuclear medium. The latter is solely attributed to the strong interaction. The corresponding comparison for K{sup -} mesons suggests a strong absorption in nuclear medium. Observed φ meson yields support the hypothesis of Z{sup α}-scaling of the production cross section.
A 3D City Model with Dynamic Behaviour Based on Geospatial Managed Objects
Kjems, Erik; Kolář, Jan
2014-01-01
of a geographic data representation of the world. The combination of 3D city models and real time information based systems though can provide a whole new setup for data fusion within an urban environment and provide time critical information preserving our limited resources in the most sustainable way. Using 3D......One of the major development efforts within the GI Science domain are pointing at real time information coming from geographic referenced features in general. At the same time 3D City models are mostly justified as being objects for visualization purposes rather than constituting the foundation...... occasions we have been advocating for a new and advanced formulation of real world features using the concept of Geospatial Managed Objects (GMO). This chapter presents the outcome of the InfraWorld project, a 4 million Euro project financed primarily by the Norwegian Research Council where the concept...
Trophic dynamics and fishery potentials of the Indian Occean - critical assessment
Dalal, S.G.; Parulekar, A.H.
A critical review of the status of the Indian Ocean marine fisheries reveals that the presently exploited annual catch is less than one third of the projected potentials as estimated from the biological productivity and exploratory fishery survey...
Melting behaviour of gold-platinum nanoalloy clusters by molecular dynamics simulations
Ong, Yee Pin; Yoon, Tiem Leong [School of Physics, Universiti Sains Malaysia, 11800 USM, Penang (Malaysia); Lim, Thong Leng [Faculty of Engineering and Technology, Multimedia University, Melaka Campus, 75450 Melaka (Malaysia)
2015-04-24
The melting behavior of bimetallic gold-platinum nanoclusters is studied by applying Brownian-type isothermal molecular dynamics (MD) simulation, a program modified from the cubic coupling scheme (CCS). The process begins with the ground-state structures obtained from global minimum search algorithm and proceeds with the investigation of the effect of temperature on the thermal properties of gold-platinum nanoalloy clusters. N-body Gupta potential has been employed in order to account for the interactions between gold and platinum atoms. The ground states of the nanoalloy clusters, which are core-shell segregated, are heated until they become thermally segregated. The detailed melting mechanism of the nanoalloy clusters is studied via this approach to provide insight into the thermal stability of the nanoalloy clusters.
Park, Miok [Korea Institute for Advanced Study, Seoul (Korea, Republic of); Park, Jiwon; Oh, Jae-Hyuk [Hanyang University, Department of Physics, Seoul (Korea, Republic of)
2017-11-15
Einstein-scalar-U(2) gauge field theory is considered in a spacetime characterized by α and z, which are the hyperscaling violation factor and the dynamical critical exponent, respectively. We consider a dual fluid system of such a gravity theory characterized by temperature T and chemical potential μ. It turns out that there is a superfluid phase transition where a vector order parameter appears which breaks SO(3) global rotation symmetry of the dual fluid system when the chemical potential becomes a certain critical value. To study this system for arbitrary z and α, we first apply Sturm-Liouville theory and estimate the upper bounds of the critical values of the chemical potential. We also employ a numerical method in the ranges of 1 ≤ z ≤ 4 and 0 ≤ α ≤ 4 to check if the Sturm-Liouville method correctly estimates the critical values of the chemical potential. It turns out that the two methods are agreed within 10 percent error ranges. Finally, we compute free energy density of the dual fluid by using its gravity dual and check if the system shows phase transition at the critical values of the chemical potential μ{sub c} for the given parameter region of α and z. Interestingly, it is observed that the anisotropic phase is more favored than the isotropic phase for relatively small values of z and α. However, for large values of z and α, the anisotropic phase is not favored. (orig.)
Ma Yuan; He Zhilong; Peng Xueyuan; Xing Ziwen
2012-01-01
The self-acting valve has a significant influence on the efficiency and reliability of the reciprocating compressor. In the trans-critical CO 2 cycle, the large density and high pressure difference across the valve cause serious bending and impact stresses in the valve, offering great challenges for successful valve design. Experimental investigation of the valve dynamics is required in order to design a self-acting valve with a high efficiency and long life span for the trans-critical CO 2 compressor. A semi-hermetic reciprocating compressor was developed for application in CO 2 refrigeration, and a test system was incorporated into the compressor performance test rig, with a focus on investigating the dynamics of the discharge valves. With the experimental results, the movement of the valve was discussed in detail for the trans-critical CO 2 compressor, allowing for the study of the thermodynamic performance of the compressor. While varying design parameters such as pressure ratio, valve lift, spring stiffness and compressor speed, the movement of the discharge valve in the reciprocating CO 2 compressor was measured in order to investigate the major factors that influence the valve dynamics. The average valve speed increased from 0.71 m/s to 0.81 m/s as the discharge pressure changed from 7.8 MPa to 12 MPa. The experimental methods and results discussed in this paper could provide useful information for both valve testing and the optimization of their reliability in trans-critical CO 2 compressors.
Seismic behaviour of geotechnical structures
F. Vinale
2002-06-01
Full Text Available This paper deals with some fundamental considerations regarding the behaviour of geotechnical structures under seismic loading. First a complete definition of the earthquake disaster risk is provided, followed by the importance of performing site-specific hazard analysis. Then some suggestions are provided in regard to adequate assessment of soil parameters, a crucial point to properly analyze the seismic behaviour of geotechnical structures. The core of the paper is centered on a critical review of the analysis methods available for studying geotechnical structures under seismic loadings. All of the available methods can be classified into three main classes, including the pseudo-static, pseudo-dynamic and dynamic approaches, each of which is reviewed for applicability. A more advanced analysis procedure, suitable for a so-called performance-based design approach, is also described in the paper. Finally, the seismic behaviour of the El Infiernillo Dam was investigated. It was shown that coupled elastoplastic dynamic analyses disclose some of the important features of dam behaviour under seismic loading, confirmed by comparing analytical computation and experimental measurements on the dam body during and after a past earthquake.
Computational Analysis of Static and Dynamic Behaviour of Magnetic Suspensions and Magnetic Bearings
Britcher, Colin P. (Editor); Groom, Nelson J.
1996-01-01
Static modelling of magnetic bearings is often carried out using magnetic circuit theory. This theory cannot easily include nonlinear effects such as magnetic saturation or the fringing of flux in air-gaps. Modern computational tools are able to accurately model complex magnetic bearing geometries, provided some care is exercised. In magnetic suspension applications, the magnetic fields are highly three-dimensional and require computational tools for the solution of most problems of interest. The dynamics of a magnetic bearing or magnetic suspension system can be strongly affected by eddy currents. Eddy currents are present whenever a time-varying magnetic flux penetrates a conducting medium. The direction of flow of the eddy current is such as to reduce the rate-of-change of flux. Analytic solutions for eddy currents are available for some simplified geometries, but complex geometries must be solved by computation. It is only in recent years that such computations have been considered truly practical. At NASA Langley Research Center, state-of-the-art finite-element computer codes, 'OPERA', 'TOSCA' and 'ELEKTRA' have recently been installed and applied to the magnetostatic and eddy current problems. This paper reviews results of theoretical analyses which suggest general forms of mathematical models for eddy currents, together with computational results. A simplified circuit-based eddy current model proposed appears to predict the observed trends in the case of large eddy current circuits in conducting non-magnetic material. A much more difficult case is seen to be that of eddy currents in magnetic material, or in non-magnetic material at higher frequencies, due to the lower skin depths. Even here, the dissipative behavior has been shown to yield at least somewhat to linear modelling. Magnetostatic and eddy current computations have been carried out relating to the Annular Suspension and Pointing System, a prototype for a space payload pointing and vibration
Building a foundation to study distributed information behaviour
Terry L. von Thaden
2007-01-01
Full Text Available Introduction. The purpose of this research is to assess information behaviour as it pertains to operational teams in dynamic safety critical operations. Method. In this paper, I describe some of the problems faced by crews on modern flight decks and suggest a framework modelled on Information Science, Human Factors, and Activity Theory research to assess the distribution of information actions, namely information identification, gathering and use, by teams of users in a dynamic, safety critical environment. Analysis. By analysing the information behaviour of crews who have accidents and those who do not, researchers may be able to ascertain how they (fail to make use of essential, safety critical information in their information environment. The ultimate goal of this research is to differentiate information behaviour among the distinct outcomes. Results. This research affords the possibility to discern differences in distributed information behaviour illustrating that crews who err to the point of an accident appear to practice different distributed information behaviour than those who do not. This foundation serves to operationalise team sense-making through illustrating the social practice of information structuring within the activity of the work environment. Conclusion. . The distributed information behaviour framework provides a useful structure to study the patterning and organization of information distributed over space and time, to reach a common goal. This framework may allow researchers and investigators alike to identify critical information activity in the negotiation of meaning in high reliability safety critical work, eventually informing safer practice. This framework is applicable to other domains.
Assessment of dynamic mechanical behaviour of reinforced concrete beams using a blast simulator
Peroni Marco
2015-01-01
Full Text Available Critical infrastructures may become the target of terrorist bombing attacks or may have to withstand explosive loads due to accidents. The impulsive load connected to explosions is delivered to the structure in a few milliseconds forcing it to respond or fail in a peculiar mode. With reference to the above scientific framework this work presents an innovative apparatus designed and developed at the European Laboratory for Structural Assessment to reproduce a blast pressure history without using explosives. This apparatus is practically a hybrid nitrogen-spring-driven actuator that accelerates masses of up to 100 kg to a maximum velocity of about 25 m/s that impact against the tested structure. The pressure-load history applied to the structure is modulated and reshaped using appropriate layers of elastic soft materials (such as polymeric foams placed between the specimen and the impacting masses. Specific instrumentation has extensively been utilised to investigate the blast simulator performance and to precisely measure the pressure loads applied to the specimen. A series of tests on real scale reinforced concrete beams/columns (250 × 250 × 2200 mm has been performed to efficiently assess the performance and potentiality of the new blast simulator. Results are under evaluation. In addition to the experimental work, a series of numerical simulations by means of the explicit FEM code EUROPLEXUS have been carried out to support and improve the equipment design.