Home About us Contact
|
Home About us Contact | ||
|
|
||
Propagation Mechanism (propagation + mechanism)
Selected AbstractsPropagation mechanisms for the Madden-Julian OscillationTHE QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY, Issue 569 2000Adrian J. Matthews Abstract The Madden-Julian Oscillation (MJO) is examined using 20-years of outgoing long-wave radiation and National Centers for Environmental Prediction/National Center for Atmospheric Research re-analysis data. Two mechanisms for the eastward propagation and regeneration of the convective anomalies are suggested. The first is a local mechanism operating over the warm-pool region. At the phase of the MJO with a dipole structure to the convection anomalies, there is enhanced tropical convection over the eastern Indian Ocean and reduced convection over the western Pacific. Over the equatorial western Indian Ocean, the equatorial Rossby wave response to the west of the enhanced convection includes a region of anomalous surface divergence associated with the anomalous surface westerlies and pressure ridge. This lends to suppress ascent in the boundary layer and shuts off the deep convection, eventually leading to a convective anomaly of the opposite sign. Over the Indonesian sector, the equatorial Kelvin wave response to the east of the enhanced convection includes a region of anomalous surface convergence into the anomalous equatorial surface easterlies and pressure trough, which will tend to favour convection in this region. The Indonesian sector is also influenced by an equatorial Rossby wave response (of opposite sign) to the west of die reduced convection over the western Pacific, which also has a region of anomalous surface convergence associated with its anomalous equatorial surface easterlies and pressure trough. Hence, convective anomalies of either sign tend to erode themselves from the west and initiate a convective anomaly of opposite sign via their equatorial Rossby wave response, and expand to the east via their equatorial Kelvin wave response. The second mechanism is global, involving an anomaly completing a circuit of the equator. Enhanced convection over the tropical western Pacific excites a negative mean-sea-level pressure (m.s.l.p.) anomaly which radiates rapidly eastward as a dry equatorial Kelvin wave at approximately 35 m s,1 over the eastern Pacific. It is blocked by the orographic barrier of the Andes and Central America for several days before propagating through the gap at Panama. After rapidly propagating as a dry equatorial Kelvin wave over the Atlantic, the m.s.l.p. anomaly is delayed further by the East African Highlands before it reaches the Indian Ocean and coincides with the development of enhanced convection at the start of the next MJO cycle. [source] Architectural Methodology Based on Intentional Configuration of BehaviorsCOMPUTATIONAL INTELLIGENCE, Issue 1 2001François Michaud Intelligence has been an object of study for a long time. Different architectures try to capture and reproduce these aspects into artificial systems (or agents), but there is still no agreement on how to integrate them into a general framework. With this objective in mind, we propose an architectural methodology based on the idea of intentional configuration of behaviors. Behavior-producing modules are used as basic control components that are selected and modified dynamically according to the intentions of the agent. These intentions are influenced by the situation perceived, knowledge about the world, and internal variables that monitor the state of the agent. The architectural methodology preserves the emergence of functionality associated with the behavior-based paradigm in the more abstract levels involved in configuring the behaviors. Validation of this architecture is done using a simulated world for mobile robots, in which the agent must deal with various goals such as managing its energy and its well-being, finding targets, and acquiring knowledge about its environment. Fuzzy logic, a topologic map learning algorithm, and activation variables with a propagation mechanism are used to implement the architecture for this agent. [source] Microdimensional Polyaniline: Fabrication and Characterization of Dynamics of Charge Propagation at Microdisk ElectrodesELECTROANALYSIS, Issue 17 2004Karolina Caban Abstract We describe fabrication of microdimensional polyanilne films in a controlled manner by voltammetric potential cycling or controlled potential electrolysis on platinum microdisk electrodes. The film grows in a form of hemispherical microdeposits, and its size largely exceeds the size of a Pt microdisk. Consequently, the film covers both the Pt substrate as well as the surrounding glass seal. Since the adhering polyaniline layer is conducting, the latter situation may lead to an increase in the effective electrode surface area. The lateral growth of polyaniline films outside the microdisk has also been demonstrated by performing diagnostic voltammetric experiments with use of a double microdisk set-up in which independent polarization of each disk is feasible. Microelectrode-based chronocoulometry, that involves an uncomplicated well-defined reduction potential step starting from the emeraldine (conducting) form and ending at leucoemeraldine (nonconducting) form, yields (upon application of a sufficiently short pulse) a well-defined linear response of charge versus square root of time that is consistent with the linear effective diffusion as the predominant charge propagation mechanism. When describing the system kinetics in terms of the effective (apparent) diffusion coefficient, we expect this parameter to be on the level of 10,8,cm2 s,1 or lower. The relative changes in dynamics of charge transport are discussed with respect to the polyaniline film loading, the size of microdisk electrode, expansion of the active electrode area, and the choice of electrolyte (strong acid) anion. The results are consistent with the view that when Pt microelectrode is modified with PANI deposit exceeding the size of the microdisk substrate, it behaves in a way as if its surface area is effectively much larger than the geometric area of Pt microdisk. [source] Persistence of business cycles in multisector real business cycle modelsINTERNATIONAL JOURNAL OF ECONOMIC THEORY, Issue 3-4 2006Jess Benhabib E00; E3; O40 In this paper we explore whether the changing composition of output in response to technology shocks can play a significant role in the propagation of shocks over time. For this purpose we study two multisector real business cycle models, with two and three sectors. We find that, although the two-sector model requires a high intertemporal elasticity of substitution of consumption to match the various dynamic properties of US macroeconomic data, the three-sector model has a strong propagation mechanism under conventional parameterizations, as long as the factor intensities in the three sectors are different enough. [source] Measuring predictability: theory and macroeconomic applicationsJOURNAL OF APPLIED ECONOMETRICS, Issue 6 2001Francis X. Diebold We propose a measure of predictability based on the ratio of the expected loss of a short-run forecast to the expected loss of a long-run forecast. This predictability measure can be tailored to the forecast horizons of interest, and it allows for general loss functions, univariate or multivariate information sets, and covariance stationary or difference stationary processes. We propose a simple estimator, and we suggest resampling methods for inference. We then provide several macroeconomic applications. First, we illustrate the implementation of predictability measures based on fitted parametric models for several US macroeconomic time series. Second, we analyze the internal propagation mechanism of a standard dynamic macroeconomic model by comparing the predictability of model inputs and model outputs. Third, we use predictability as a metric for assessing the similarity of data simulated from the model and actual data. Finally, we outline several non-parametric extensions of our approach. Copyright © 2001 John Wiley & Sons, Ltd. [source] Enhancing therapeutic loading and delaying transport via molecular imprinting and living/controlled polymerizationAICHE JOURNAL, Issue 1 2010Asa D. Vaughan Abstract This work demonstrates for the first time molecular imprinting using a "living/controlled" polymerization (LCP) strategy to enhance template loading/affinity and delay release in weakly crosslinked gels. Two gel systems were studied: poly(DEAEM- co -HEMA- co -PEG200DMA) gels imprinted for diclofenac sodium and poly(MAA- co -EGDMA) gels imprinted for ethyl adenine-9-acetate. Experimental evidence confirms that template diffusion coefficients within imprinted gels can be heavily influenced by template binding affinity. Recognition studies revealed significant increases in template loading/affinity with large increases in loading for LCP, and dynamic template release studies showed that imprinting via LCP extends the template release profile by twofold over that of imprinting via conventional free-radical polymerization techniques and fourfold over the control network (less Fickian and toward zero-order release with a profile coefficient of 0.70). Analysis of reaction kinetics indicated that LCP with reversible termination events increases the chemically controlled chain propagation mechanism, and that binding sites are formed during this phase of the polymerization. © 2009 American Institute of Chemical Engineers AIChE J, 2010 [source] Preparation of molecularly imprinted polymer microspheres via atom transfer radical precipitation polymerizationJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 13 2009Baiyi Zu Abstract The first combined use of atom transfer radical polymerization (ATRP) and precipitation polymerization in the molecular imprinting field is described. The utilized polymerization technique, namely atom transfer radical precipitation polymerization (ATRPP), provides MIP microspheres with obvious molecular imprinting effects towards the template, fast template binding kinetics and an appreciable selectivity over structurally related compounds. The living chain propagation mechanism in ATRPP results in MIP spherical particles with diameters (number-average diameter Dn , 3 ,m) much larger than those prepared via traditional radical precipitation polymerization (TRPP). In addition, the MIP microspheres prepared via ATRPP have also proven to show significantly higher high-affinity binding site densities on their surfaces than the MIP generated via TRPP, while the binding association constants Ka and apparent maximum numbers Nmax of the high-affinity sites as well as the specific template bindings are almost the same in the two cases. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 3257,3270, 2009 [source] LAND PRICE, COLLATERAL AND ECONOMIC GROWTH,THE JAPANESE ECONOMIC REVIEW, Issue 4 2009MASAYA SAKURAGAWA This paper extends Kiyotaki and Moore's (1997) to an endogenous growth model and investigates the dynamic properties of a growing economy with binding credit constraint when land is used not only as an input of production but also as collateral. There exists a balanced growth path in an economy with binding credit constraint. In response to a once and for all productivity shock, the developed model shows the propagation mechanism among output, capital, bank credit and the land price in terms of the growth rate. The model's tractability allows us to derive interesting qualitative and quantitative findings on business cycles. [source] Dynamic effects of financial intermediation over the business cycleECONOMIC INQUIRY, Issue 1 2000CS Lehr This paper provides a empirical evidence that the financial intermediation disturbances can generate business cycles. We examine three countries whose financial sectors are fully developed but quite distinct in their institutional and regulatory circumstances; thus, we can infer whether financial intermediation disturbances differ across dissimilar financial environments. We find that the dynamic responses of output to financial intermediation shocks exhibit similar patterns in all cases studied. However, the various institutional and regulatory circumstances have generated different propagation mechanisms transmitting the financial disturbance to output in ways that lead the magnitudes of the responses to deviate across economies. [source] Victor Horsley's Contribution to Jacksonian EpileptologyEPILEPSIA, Issue 11 2005Mervyn J. Eadie Summary:,Purpose: To describe Victor Horsley's contribution to John Hughlings Jackson's understanding of the mechanisms involved in the generalization of convulsive epileptic seizures. Methods: I reviewed Horsley's writings and other relevant late 19th century medical literature. Results: Horsley's combination of strategically sited surgical lesions and cerebral cortex stimulation studies in experimental animals showed that, contrary to Hughlings Jackson's earlier belief, epileptic activity arising in one cerebral hemisphere had to spread to the contralateral hemisphere before bilateral convulsing could occur. Conclusions: On the basis of well-designed experiments, Horsley made a major contribution to the understanding of epileptic seizure propagation mechanisms. [source] Noninvasive dynamic imaging of seizures in epileptic patientsHUMAN BRAIN MAPPING, Issue 12 2009Louise Tyvaert Abstract Epileptic seizures are due to abnormal synchronized neuronal discharges. Techniques measuring electrical changes are commonly used to analyze seizures. Neuronal activity can be also defined by concomitant hemodynamic and metabolic changes. Simultaneous electroencephalogram (EEG)-functional MRI (fMRI) measures noninvasively with a high-spatial resolution BOLD changes during seizures in the whole brain. Until now, only a static image representing the whole seizure was provided. We report in 10 focal epilepsy patients a new approach to dynamic imaging of seizures including the BOLD time course of seizures and the identification of brain structures involved in seizure onset and discharge propagation. The first activation was observed in agreement with the expected location of the focus based on clinical and EEG data (three intracranial recordings), thus providing validity to this approach. The BOLD signal preceded ictal EEG changes in two cases. EEG-fMRI may detect changes in smaller and deeper structures than scalp EEG, which can only record activity form superficial cortical areas. This method allowed us to demonstrate that seizure onset zone was limited to one structure, thus supporting the concept of epileptic focus, but that a complex neuronal network was involved during propagation. Deactivations were also found during seizures, usually appearing after the first activation in areas close or distant to the activated regions. Deactivations may correspond to actively inhibited regions or to functional disconnection from normally active regions. This new noninvasive approach should open the study of seizure generation and propagation mechanisms in the whole brain to groups of patients with focal epilepsies. Hum Brain Mapp, 2009. © 2009 Wiley-Liss, Inc. [source] The modelling of multi-fracturing solids and particulate mediaINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 1 2004D. R. J. Owen Abstract Computational strategies in the context of combined discrete/finite element methods for effective modelling of large-scale practical problems involving multiple fracture and discrete phenomena are reviewed in the present work. The issues considered include: (1) Fracture criteria and propagation mechanisms within both the finite and discrete elements, together with mesh adaptivity procedures for discretization and introduction of fracture systems; (2) Detection procedures for monitoring contact between large numbers of discrete elements; (3) Interaction laws governing the response of contact pairs; (4) Parallel implementation; (5) Other issues, such as element methodology for near incompressible behaviour and generation of random packing of discrete objects. The applicability of the methodology developed is illustrated through selected practical examples. Copyright © 2004 John Wiley & Sons, Ltd. [source] | ||||||||||||||||||||||